Method for continuously contact-coating one side only of a ferrous base metal strip with a molten coating metal
Abstract
Method and apparatus for producing a continuous metal band of ferrous base coated on one side only with a coating metal, the other side of the metal-free coating band remaining, the ferrous metal band having been treated to clean its surface and remove the oxide , the process of which comprises the phase of, providing a coating vessel containing a molten metal bath of the coating metal.

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Projected expiry passed 18 March 1997, 29.5 years ago.
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55 claims: 3 independent, 52 dependent
- 1REIVINDICACIONES 10. 15. 20. 25. 1. - Procedimiento y aparato para producir una banda conti nua metálica de base ferrosa revestida en un lado solamente con uil i I metal de revestimiento, permaneciendo el otro lado de la banda exen to de metal de revestimiento, habiéndose tratado la banda metálicí ferrosa para limpiar su superficie y eliminar el óxido, cuyo procedimiento comprende la fase de, proporcionar un recipiente de revestimiento que contiene un baño de metal fundido del metal de re-r vestimiento, y caracterizado por las fases de conducir la banda hasta una posición por encima de la superficie superior del baño de modo que las características de tensión superficial y humectabí lidad del metal fundido de revestimiento permitan la formación de un menisco en la superficie superior del baño en contacto con el lado de la banda encarado al baño;formar el menisco;mantener el menisco y continuamente el contacto del lado solamente de la band con el mismo;mantener al menos el lado de la banda en estado exen to de óxido al menos hasta que el lado se ha puesto inicialmente en contacto con el menisco, y dar acabado al lado revestido de la banda eliminando el exceso de metal de revestimiento de la misma.
- 2- Procedimiento según la reivindicación 1, caracterizado porque el metal fundido de revestimiento se elige de la clase | í consistente en zinc, aleaciones de zinc, aluminio, aleaciones alú.-:ί mínicas y aleaciones de plomo,
- 3- Procedimiento según las reivindicaciones 1 o 2, cara¿ I terizado porque comprende las fases de utilizar un solo rodillo para conducir la banda hasta la posición de formación del menisco con i respecto a la superficie del baño y utilizar el rodillo simple para conducir la banda revestida separándola de la superficie del baño después de revestido dicho lado. 30. 5. ίο. 15.
- 4- Procedimiento según las reivindicaciones 1 o 2, carao terizado porque comprende la fases de utilizar un primer y un seguk r do rodillos mantenidos en relación paralela haciendo que la banda ¡ pase alrededor de los mismos, y formando el menisco contra la banda en el tramo comprendido entre los rodillos.
- 5- Procedimiento según la reivindicación 1, caracterizado porque comprende las fases de mantener la banda en una atmósfera ¡ protectora antioxidante hasta que el lado se ha puesto en contacto con el menisco;retirar la banda revestida de la atmósfera haciéndola pasar a la atmósfera ambiente, y dar acabado con chorro al la·¡ do revestido de la ba n da con aire en la atmósfera ambiente. ¡
- 6- Procedimiento según la reivindicación 1, caracterizado porque comprende las fases de'manten o? la banda en una atmósfera protectora antioxidante hasta que el lado se ha puesto en contacto con el menisco, y dar acabado con chorro al lado revestido de la banda' con un gas protector antioxidante antes de exponer la banda a la atmósfera ambiente. 20. 25. 30.
- 7- Procedimiento según la reivindicación 6, caracterizado porque comprende las fases de mantener la banda en una atmósfera protectora antioxidante hasta que el lado se ha puesto en contacto! con el menisco, y conducir la banda revestida por un lado y acabada desde la atmósfera protectora hasta la atmósfera ambiente mientras la banda se mantiene a una temperatura suficientemente elevada para dar por resultado la formación de una película de óxido sobre el la do sin revestir. 8, - Procedimiento según la reivindicación 1, caracterizado porque comprende la fase de mantener la banda metálica ¿Le base fe- ΐ rrosa en una atmósfera protectora antioxidante a ti-avós de las eta-! pas de revestimiento y acabado y hasta que la banda se ha enfriado ! í a una temperatura necesaria para que no se forme una película de ó-¡ -44— 10. 15. 20. 25. xido sobre su lado sin revestir.
- 89. - Procedimiento según la reivindicación 1, caracterizad) porque comprende las fases de mantener la banda metálica de base ferrosa en una atmósferra protectoras antioxidante en todas las eta pas de revestimiento y acabado y someter la banda revestida por un lado a enfriamiento por agua antes de introducirla en la atmósfera ambiente.
- 910. - Procedimiento según la reivindicación 13, caracterizó do porque comprende las fases de mantener la banda en una atmósfera protectora antioxidante en todas las fases de revestimiento y acabado,
- 1011. - Procedimiento según la reivindicación 4, caracterizando porque comprende la fase de mantener la banda en una atmósfera protectora antioxidante en todas las fases de revestimiento y acabado.
- 1112. - Procedimiento según la reivindicación 4, caracterizando porque comprende la fase de deprimir el tramo de la banda hacia el baño de metal fundido del revestimiento.
- 1213. - Procedimiento según la reivindicación 5, caracteriza do porque comprende la fase de someter la banda revestida poi’ un la do a limpieza por ácido.
- 1314. - Procedimiento según la reivindicación 7, caracteriza do porque comprende la fase de someter la banda con la película de óxido sobre su lado sin revestir a limpieza por ácido.
- 1415. - Procedimiento según la reivindicación 14, caracteri-Í zado porque comprende la fase de proporcionar un baño de ácido diluido para dicha etapa de limpieza por ácido, conducir la banda re vestida por un lado y acabada a través del baño, proporcionar un electrodo de metal sacrificial adyacente al lado de la banda sin re. vestir dentro del baño de ácido y conectar eléctricamente el elee30. -455. 10. 15. 20. 25. trodo y la banda para eliminar la película de óxido del lado de la banda sin revestir. lo.- Procedimiento según la reivindicación 14, caracterizado porque comprende las fases de proporcionar un baño de ácido diluido para etapa de limpieza por ácido, conducir la banda revesI tida y acabada a través del baño;proporcionar un electrodo adya- ! cente al lado de la banda sin revestir dentro del baño y proporcio! nar medios para conectar la banda y el electrodo a través de una fuente de corriente. I I
- 1517. - Procedimiento según la reivindicación 14, caracterizado porque comprende la fase de hacer que el lado sin revestir de la banda revestida por un lado y acabada pase en contacto con una í J esponja que contiene una solución de ácido diluido, proporcionar me I dios para conéctar la banda y la esponja a través de una fuente ! de corriente eléctrica y suministrar continuamente la solución de ¡ ácido diluido a la esponja para eliminar de este modo la película de óxido del lado de la banda sin revestir.
- 1618. - Procedimiento según la reivindicación 8, caracteriza do porque comprende la fase de hacer que la banda revestida por un I lado y acabada pase . alrededor de rodillos refrigerados para acelerar el enfriamiento de la banda a una temperatura en la cual se for Γ me película de óxido sobre el lado sin revestir. | i
- 1719. - Procedimiento según la reivindicación 8, caracteriza) l do porque comprende la fase de impeler un gas antioxidante protector contra la banda revestida por un lado y acabada para acelerar el enfriamiento de la banda a una temperatura en la cual se forme película de óxido sobre el lado sin revestir. j
- 1820. - Procedimiento según la reivindicación 16, caracteri-! zado porque la fuente de corriente es una fuente de corriente alter na. I 30. -465. 21,- Procedimiento según ls. reivindicación 16, caracteriza do porque la fuente de corriente es una fuente de corriente conti-j· nua. 10.
- 1922. - Procedimiento según la reivindicación 16, caracteri-!· zado porque comprende la fase de proporcionar un segundo electrodo en el baño de metal fundido de revestimiento, conectando el segundo electrodo a la fuente de corriente, para conectar de este modo la banda de la fuente de corriente.
- 2023. - Procedimiento según la reivindicación 16, caracteri-* zado porque el recipiente de metal fundido de revestimiento es metálico y comprende la fase de conectar el recipiente a la fuente de corriente para conectar de este modo la banda a la fuente de oó rriente. 15. 24.- Procedimiento según la reivindicación 1, caracterizado porque comprende la fase de mantener el nivel del baño constante. 20. 25. 30. 25·- Aparato para la aplicación del procedimiento según las reivindicaciones 1 a 24, del tipo que comprende un recipiente que contiene un baño fundido de metal de revestimiento, caracterizado porque se constituye de medios para conducir la banda hasta j una posición con respecto a la superficie superior del baño de for ma que las características de tensión superficial y humectabilidaJ del metal fundido de revestimiento permitan la formación de un meJ nisco en la superficie superior del baño que se pone continuamente en contacto con un lado solamente de la banda encarado al baño revistiéndolo;medios de acabado para dar acabado al lado revestido de la banda, y medios para mantener por lo menos un lado de la ban da en estado exento de óxido al menos hasta que dicho lado se ha puesto en contacto con el menisco. 26,- Aparato según la reivindicación 25, caracterizado pot 5. 10. 15. 20. 25. que el metal fundido de revestimiento se elige de la clase consis. tente en zinc, aleaciones de zinc, aluminio, aleaciones de aluminio y aleaciones de plomo.
- 2127. - Aparato según la reivindicación 25, caracterizado porque los medios para conducir la banda se situán de tal modo qu;mantiene en la posición del menisco el lado de la banda que recibe el revestimiento a una distancia del nivel de la superficie superior del baño que puede alcanzar hasta aproximadamente 7,95 mm.
- 2228. - Aparato según la reivindicación 25, caracterizado porque los medios para conducir la banda hasta la posición citada con respecto a la superficies superior del baño comprenden, un so. lo rodillos alrededor del cual pasa la banda, situándose el rodillo simple para conducir la banda hacia la superficie superior del baño en contacto con el menisco y por lo tanto separándola después de la superficie superior del baño.
- 2329. - Aparato según la reivindicación 25, caracterizado porque los medios para conducir la banda hasta la citada posición con respecto a la superficie superior del baño comprenden un par de rodillos que mantienen una relación paralela y alrededor de los cuales pasa la banda, situándose de tal modo los rodillos del par que el menisco se pone en contacto con un lado de la banda en el tramo comprendido entre los mismos, conduciendo el primer rodillo del par a la banda hacia la superficie superior del baño e iniciad do el tramo, terminando el segundo rodillos de par el tramo y con duciendo la banda para separarla de la superficie superior del baño. . .··
- 2430. - Aparato según la reivindicación 25, caracterizado porque se disponen medios para mantener la banda en una atmósfera protectoras antioxidante que comprenden una caperuza adaptada al aparato de preparación de la banda, cuya caperuza tiene una parte 30. 5. 10. 15. 20. 25. superior y paredees delanteras, trasera y laterales que se introducen en el baño, teniendo la caperuza una salida para la banda metá lica de base ferrosa y medios para introducir la atmósfera protectora antioxidante en la caperuza a una presión positiva suficiente para evitar la entrada de la atmósfera ambiente en la caperuza a través de la salida.
- 2531. - Aparato según la reivindicación 25, caracterizado poir que comprende medios para mantener la banda revestida por un lado en una atmósfera protectora antioxidante hasta que la banda alcanza una temperatura a la cual no se forma película de óxido visible sobre el lado sin revestir de la banda.
- 2632. - Aparato según la reivindicación 28, caracterizado po que comprende medios para mantener la banda en una atmósfera protjej tora antioxidante que comprende una caperuza de revestimiento conec tada al aparato de preparación de la banda, cuya caperuza de reves timiento tiene una parte superior y paredes delantera trasera y la terales que se dirigen hacia abajo introducindose en el baño para dejar cerrado completamente el rodillo y separado de la atmósfera ambiente, teniendo la caperuza de revestimiento una salida para la banda de metal de base ferrosa y medios psra introducir dicha atmós fera protectora antioxidante en la caperuza de revestimiento a una presión positiva suficiente para evitar la entrada de atmósfera ambiente en la caperuza de revestimiento a través de la salida.
- 2733. - Aparato según la reivindicación 29, caracterizado por que el primer rodillo se sitúa a una distancia del nivel de la superficie superior del baño de aproximadamente 3,18 mm aproximadamente 6,35 mm mayor que la del segundo rodillo.
- 2834. - Aparato según la reivindicación 29, caracterizado pot que comprende, un tercer rodillo situado entre el primer y el segundo rodillos, cuyo tercer rodillo somete el tramo de la banda a de30. 5. 330. 15. 20. 25. flexión entre el primer y el segundo rodillos hacie dicho baño. 35.” Aparato según la reivindicación 29, caracterizado per que se dota de medios para mantener la banda en una atmósfera pro tectora antioxidante que comprende una caperuza de revestimiento conectada al aparato de preparación normal de la banda, cuya capé ruza de revestimiento tiene una parte superior y paredes delantera, trasera y laterales que se extienden hacia abajo introduciéndose en el baño, situándose la pared delantera de la caperuza entre el primer y el segundo rodillos con una salida a través déla cual ρε sa el tramo de la banda en contacto con el menisco, de modo que 3 caperuza de revestimiento deja encerrado el primer rodillo y la parte del tramo de la banda que se pone inicialmente en contacto con el menisco, y medios para introducir la atmósfera protectora antioxidante en la caperuza de revestimiento. 36.- Aparato según la reivindicación 29, caracterizado por que comprende medios para mantener la banda en una atmósfera pro tectora antioxidante, que comprende una caperuaa de revestimiento conectada al aparato de preparación normal de la banda, cuya cape ruza de revestimiento tiene una parte superior y paredes delanter. trasera y laterales que se extienden hacia abajo introduciéndose en el baño, de modo que la caperuza de revestimiento deja encerra dos el primer y el segundo rodillos separándolos déla atmósfera ambiente teniendo la caperuza de revestimiento una salida para la banda revestida por un lado y medios para introducir la atmósfera protectora antioxidante en la caperuza de revestimiento a una pre sión positiva suficiente para evitar la entrada de la atmósfera ambiente a través de la salida déla caperuza de revestimiento, 37·“ Aparato según la reivindicación 30, caracterizado pbr que los medios de acabado comprenden una cuchilla de chorro sitúa da a fuera de la campana de revestimiento. 30. -505. 10. 15. 20. 25.
- 2938. - Aparato según la reivindicación 30, caracterizado por que los medios de acabado comprenden una cuchilla de chorro situada en el interior de la caperuza de revestimiento y medios para d¿ tar a la cuchilla de chorro de un gas protector antioxidante.
- 3039. - Aparato según la reivindicación 30, caracterizado por que comprende medios para mantener la banda revestida por un lado en una atmósfera protectora sntioxidante hasta que la banda aleanza una temperatura en la cual no se forma película de óxido visible sobre el lado sin revestir de la banda.
- 3140. - Aparato según la reivindicación 32, caracterizado porque los medios de cabado presentan una cuchilla de chorro sitúa da en el interior de la caperuza de revestimiento y medios para proporcionar a la cuchilla de chorro un gas protector antioxidante.
- 3241. - Aparato según la reivindicación 32, caracterizado porque los medios de acabado presentan una cuchilla de chorro situada fuera de la caperuza de revestimiento en su salida j r medios para alimentar a la cuchilla de chorro un gas protector antioxidan te, por lo que el lado revestido de la banda recibe acabado por la cuchilla antes de quedar expuesto a la citada atmósfera.
- 3342. - Aparato según la reivindicación 32, caracterizado porque los medios de acabado presentan una cuchilla de chrro montá da de una forma desmontable a través de una abertura en la pared delantera de la caperuza de revestimiento para dar acabado al lade revestido de la banda dentro de la caperuza, y medios para alimentar a la cuchilla de chorro una atmósfera protectora antioxidante.
- 3443. - Aparato según la reivindicación 32, caracterizado porque comprende una caperuza de enfriamiento, cuya caperuza de en friamiento tiene un primer extremo conectado a la caperuza de revestimiento de una forma hermética al gas én su salida, teniendo li caperuza de enfriamiento un segundo extremo con una salida para la 30. 5. 10. 15. 20. 25. banda, y teniendo la caperuza de enfriamiento la longitud necesaria para que al recorrerla la banda haya alcanzado una temperatura en la cual no se forme una película de óxido visible, medios para mentener una atmósfera protectora antioxidante dentro de la caperuza de enfriamiento a una presión positiva de modo que la atmósfe ra del ambiente no penetre por la salida de la caperuza de enfria-f miento·
- 3544. - Aparato según la reivindicación 32, caracterizado porque presenta una caperuza de enfriamiento, cuya caperuza de en friamiento tiene un primer extremo conectado a la caperuza de revestimiento de una forma hermética al gas en dicha salida, tenien do la caperuza de enfriamiento un segundo extremo con una salida para la banda;medios para mantener una atmósfera protectora anti. xidante dentro de la caperuza de enfriamiento una presión positiv^. de modo que la atmósfera ambiente no penetre por la salida de la caperuza de enfriamiento, montándose rodillos refrigerados dentro de la caperuza de enfriamiento para el paso alrededor de los mismos de dicha banda revestida por un lado, por lo que la banda revestida por un lado alcanzará dentro de la caperuza de enfriamien to una temperatura a la cual no se forma película de óxido en su lado sin revestir.
- 3645. - Aparato según la reivindicación 32, caracterizado porque presenta una caperuza de enfriamiento, cuya caperuza de enfriamiento tiene un primer extremo conectado a la caperuza de reves timiento de una forma hermética al gas en su salida, teniendo la caperuza de enfriamiento un segundo extremo con una salida para la banda, medios para mantener una atmósfera protectora antioxidante dentro de la caperuza de enfriamiento a una presión positiva de mo do que no penetre atmósfera de ambiente por la salida de la caperu za de enfriamiento, medios para extraer la atmósfera protectora an 30. -525. 10. 15. 20. 25. tioxidante de la caperuza de enfriamiento, medios para enfriar la atmósfera extraída y para volver a introducir dicha atmósfera extraída en la caperuza de enfriamiento y contra una banda revestida por un lado que pasa a través de la misma, por lo que la banda revestida por un lado alcanzará, en el interior de la caperuza de enfriamiento, una temperatura a la cual no se forma película de óxido visible sobre su lado sin revestir. 46.- Aparato según la reivindicación 32, caracterizado porque comprende una caperuza de enfriamiento, cuya caperuza de eh friamiento tiene un primer extremo conectado a la caperuza de re vestimiento de una forma hermética al gas en su salida, teniendo la caperuza de enfriamiento un segundo extremo en forma de tobera vuelta hacia abajo, un baño de agua, introduciéndose la tobera en el baño de agua, medios para mantener la atmósfera protectora antioxidante dentro de la caperuza de enfriamiento, medios para con ducir la banda revestida por un lado a través de la caperuza de enfriamiento y el baño de agua para reducir la temperatura de la banda a un nivel en el cual no se forma película de óxido visible sobre au lado sin revestir. 47·- Aparato según la reivindicación 34, caracterizado porque se dota de medios para mantener la banda en una atmósfera protectora, antioxidante que comprende una caperuza de revestimien to conectada al aparato de preparación de la banda, cuya caperuza de revestimiento tiene una parte superior y paredes delanteras, tra sera y laterales que se dirigen hacia abajo introduciéndose en el baño, de modo que la caperuza de revestimiento comprende un primer, segundo y tercer rodillos separándolos de la atmósfera ambiente, teniendo la caperuza de revestimiento un extremo para la banda re-r vestida por un lado y medios para introducir la atmósfera protecto ra antioxidante en la caperuza de revestimiento a una presión posi. 30. -53' 5. 10. 15. 20. tiva suficiente para evitar la entrada de atmósfera ambiente a tra vés de la salida de la caperuza de revestimiento.
- 3748. - Aparato según la reivindicación 35, caracterizado porque se disponen medios para mantener la atmósfera protectora dentro de la caperuza de revestimiento a una presión positiva suficiente para evitar la entrada de atmósfera ambiente en la caperuza de revestimiento a través de la salida.
- 3849. - Aparato según la reivindicación 30, caracterizado porque el dispositivo de acabado comprende una cuchilla de chorro situada en el interior de la caperuza de revestimiento y medios para alimentar a la cuchilla de chorro un gas protector antioxidaii te. i
- 3950. - Aparato según la reivindicación 30, caracterizado porque se dispone medios para mantener la banda revestida por un lado en una atmósfera protectora antioxidante hasta que la banda alcanza una temperatura en la cual no se forma película de óxido visible sobre el lado sin revestir de la banda.
- 4051. - Aparato según la reivindicación 36, caracterizado porque el dispositivo de acabado presenta una cuchilla de chorro situada en el interior de la caperuza de revestimiento y medios ¡ para alimentar a la cuchilla de chorro un gas protector antioxidan te. 25. 52.- Aparato según la reivindicación 36, caracterizado porque el dispositivo de acabado presenta una cuchilla de chorro situada en el exterior de la caperuza de revestimiento en su extré mo de salida y medios para alimentar alia cuchilla de chorro un gas protector antioxidante por lo que el lado revestido de la banda recibe acabado por dicha cuchilla antes de exponerse a la atmós. T fera. 30. 53·- Aparato según la reivindicación 36, caracterizado -5410. 15. 20. 25. porque el dispositivo de acabado presenta una cuchilla de chorro montada de una forma desmontable a través de una abertura en la pa red frontal de la caperuza de revestimiento para dar acabado aliado revestido de la banda en el interior de la caperuza y medios pa ra alimentar a la cuchilla de chorro una atmósfera protectora antio xidante.
- 4154. - Aparato según la reivindicación 36, caracterizado porque se dota de una caperuza de enfriamiento, cuya caperuza de enfriamiento tiene un primer extremo conectado a la caperuza de re vestimiento de una forma hermética al gas én dicha salida, teniendo la caperuza de enfriamiento un segundo extremo con una salida para la banda, teniendo la caperuza de enfriamiento la longitud ne cesaría para que el recorrerla la banda haya alcanzado una tempera! tura en la cual no se forma película de óxido visible sobre la mis ma;medios para mantener una atmósfera protectora antioxidante den tro de la caperuza de enfriamiento a una presión positiva de modo que no penetre atmósfera ambiente por la salida de la caperuza de enfriamiento.
- 4255. - Aparato según la reivindicación 36, caracterizado pot que presenta una caperuza de enfriamiento, cuya caperuza de enfria miento tiene un primer extremo conectado a la caperuza de revestimiento de una forma hermética en su salida, teniendo la caperuza enfriamiento un segundo extremo con una salida para la banda, medios para mantener una atmósfera protectora antioxidante en el interior de la caperuza de enfriamiento a una presión positiva para que no penetre atmósfera ambiente a través de la salida de la caperuza de enfriamiento, montándose rodillos refrigerantes en el interior de la caperuza de enfriamiento para el paso de la banda revestida por una lado alrededor de los mismos, por lo que la banda revestida po:: un lado alcanzará en el interior de la caperuza de enfriamiento un£ 30. “555. 10. 15. 20. 25. temperatura en la cual no se forma película de óxido visible sobre su lado sin revestir. 56.- Aparato según la reivindicación 36, caracterizado porque se dispone una caperuza de enfriamiento, cuya caperuza de enfriamiento tiene un primer extremo conectado a la caperuza de r¿ vestimiento de una forma hermética al gas en su salida, teniendo la caperuza de enfriamiento un segundo extremo con una salida para la banda, medios para mantener una atmósfera protectora antioxidante en el interior de la caperuza de enfriamiento a una presión positi I va para que no penetre atmósfera ambiente por la salida de la capé, ruza de enfriamiento, y medios para extraer dicha atmósfera proteo, tora antioxidante de la caperuza de enfriamiento, enfriar la atmód. fera extraida y volver a introducir la atmósfera extraída enfriad?, en la caperuza de enfriamlsato y contra dicha banda revestida por i|n lado que pasa a través de la misma, por lo que la banda revestida por un lado alcanzará'dentro de la caperuza de enfriamiento una temperatura en la cual no se forma película de óxido visible en sr. lado sin revestir. 57·- Aparato según la reivindicación 36, caracterizado pdr 'que se dota de una caperuza de enfriamiento, cuya caperuza de enfriamiento tiene un primer extremo conectado a la caperuza de revestimiento de una forma hermética al gas en su salida, teniendo la caperuza de enfriamiento un segundo extremo en forma de tobera vuelta hacia abajo, un baño de agua, extendiéndose la tobera para introducirse en el baño de agua, medios para mantener la atmósfera protectora antioxidante en el interior de la caperuza de enfriamiento, medios para conducir la banda revestida por un lado a través de la caperuza de enfriamiento y el baño de agua con el fin de reducir la temperatura de la banda a un nivel en el que no se forma película de óxido visible sobre su lado sin revestir. 30. -56· 5. 10. 58, - Aparato según la reivindicación 41, caracterizado por que comprende medios deflectores asociados con la cuchilla de chorro que dirige el gas en sentido contrario al lado sin revestir de la banda para evitar la deposición de manchas de metal de revestimiento sobre dicho lado sin revestir.
- 4359. - Aparato según la reivindicación 35, caracterizado pot que comprende un tercer rodillo situado entre el primero y el seguh do rodillos y fuera de la caperuza de revestimiento, cuyo tercer rodillo se sitúa para someter a deflexión al tramo de la banda com prendido entre el primero y el segundo rodillo con dirección al ba ño. 15. 20. 25.
- 4460. - Aparato según la reivindicación 47, caracterizado por que el dispositivo de acabado presenta una cuchilla de chorro sitúa da en el interior de la caperuza de revestimiento y medios para alimentar a la cuchilla de chorro gas protector antioxidante.
- 4561. - Aparato según la reivindicación 47, caracterizado por que comprende medios para mantener la banda revestida por un lado en una atmósfera protectora antioxidante hasta que la banda alcanza una temperatura en la cual no se forma película de óxido visible sobre el lado sin revestir de la banda.
- 4662. - Aparato según la reivindicación 47, caracterizado por que el dispositivo de acabado por chorro comprende una cuchilla de chorro situada en el interior de la caperuza de revestimiento y me dios para alimentar a la cuchilla de chorro un gas protector anti£ xidante.
- 4763. - Aparato según la reivindicación 47, caracterizado por que el dispositivo de acabado comprende una cuchilla de chorro situada en el exterior de la caperuza de revestimiento en su salida y medios para proporcionar a la cuchilla de chorro un gas protector I antioxidante, por lo que el lado revestido de la banda acabado por 30. -575. 10. 15. 20. 25. la cuchilla antes de quedar expuesto a la atmósfera. 64·- Aparato según la reivindicación 47, caracterizado pol· que el dispositivo de acabado, comprende una cuchilla de chorro mok tada de una forma desmontable a través de una abertura en la pared frontal de la caperuza de revestimiento para dar acabado al lado revestido de la banda dentro de la caperuza, y medios para proporcionar a la cuchilla de chorro una atmósfera, antioxidante.
- 4865. - Aparato según la reivindicación 47, caracterizado por que presenta una caperuza de enfriamiento, cuya caperuza de enfria miento tiene un primer extremo conectado a la caperuza de revestimiento de una forma hermética en su extremo de salida, teniendo la caperuza de enfriamiento un segundo extremo con una salida para la banda, siendo la caperuza de enfriamiento de tal longitud que al ser recorrida por la banda, la banda habrá alcanzado una temperatu! ra en la cual no se forma película de óxido visible sobre la misma;medios para mantener una atmósfera protectora antioxidante dentro de la caperuza de enfriamiento a una presión positiva de modo que la atmósfera ambiente no penetre en la salida de la caperuza de enfriamiento,
- 4966. - Aparato según la reivindicación 47, caracterizado pol· que presenta una caperuza de enfriamiento, cuya caperuza de enfria miento tiene un primer extremo conectado a la caperuza de revestimiento de una forma hermética al gas en su salida, teniendo la caperuza de enfriamiento un segundo extremo con una salida para la bsn da, medios para mantener una atmósfera protectora antioxidante den tro de la caperuza de enfriamiento a una presión positiva para que no penetre atmósfera ambiente por la salida de la caperuza de enfiramiento, montándose rodillos regriegradores dentro de la caperuza de enfriami arito para el paso alrededor de los mismos de una banj da revestida por un lado, por lo que la banda revestida por un ladd 30. -585. 10. 15. 20. 25. alcanzará dentro de la caperuza de enfriamiento una temperatura er la cual no se forma película de óxido visible sobre su lado sin fe vestir.
- 5067. - Aparato según la reivindicación 47, caracterizado pea que presenta una caperuza de enfriamiento, cuya caperuza de enfrie miento tiene un primer extremo conectado a la caperuza de revestimiento de una forma hermética al gas en su salida, teniendo la caperuza de enfriamiento un segundo extremo en una salida para la banda, medios para mantener una atmósfera protectora antioxidante dentro de la caperuza de enfriamiento a una presión positiva para que no penetre atmósfera ambiente por el extremo de salida de la caperuza de enfriamiento, medios para extraer la atmósfera protectora antioxidante de la caperuza de enfriamiento, enfriar la atmós fera extraída y volver a introducir la atmósfera extraída enfriada en la caperuza de enfriamiento y contra la banda revestida por un lado que pasa a través de la misma, por lo que la banda revestida por un lado alcanzará dentro de la caperuza de enfriamiento una temperatura en la cual no se forma película de óxido visibles sobre su lado sin revestir.
- 5168. - Aparato según la reivindicación 47, caracterizado pot que presenta una caperuza de enfriamiento, cuya caperuza de enfria miento tiene un primer extremo conectado a la caperuza de revestimiento de una forma hermética al gas en su salida, teniendo la caperuza de enfriamiento un segundo extremo en forma de tobera vuelt hacia abajo, un baño de agua, penetrando la tobera en el baño de agua, para mantener dicha atmósfera protectora antioxidante dentro de la caperuza de enfriamiento, y medios para conducir la banda re· vestida por un lado a através de la caperuza de enfriamiento y el baño de agua para reducir la temperatura de la banda a un nivel en el cual no se forma película de óxido visible sobre su lado sin re 30. - 59vestir.
- 5269. - Aparato según la reivindicación 45, caracterizado pob que presenta un dispositivo de bloque de estanquidad montado de una forma desplazable sobre el exterior de la pared frontal de la cape ruza en la salida situado para ponerse en contacto con la banda y cerrar parcialmente la salida.
- 5370. - Aparato según la reivindicación 52, caracterizado por que comprende medios deflectores asociados con la cuchilla de chorro que dirige el gas desde la misma en sentido contrario al lado sin revestir de la banda para evitar la deposición de manchas de metal en el revestimiento sobre el lado sin revestir.
- 5471. - Aparato según la reivindicación 69, caracterizado porque comprendemedios para mantener la atmósfera protectora dentro de la caperuza de revestimiento a una presión positiva suficien te para evitar la entrada de atmósfera ambiente en la caperuza de revestimiento a través de la salida.
- 5572. - Aparato según la reivindicación 59, caracterizado porque comprende un dispositivo de bloque de estanquidad montado de una forma desplazable en el exterior de la pared delantera de 1 caperuza en la salida y situado para ponerse en contacto con la banda y cerrar parcialmente la salida. 73·- Aparato según la reivindicación 59, caracterizado porque comprende un dispositivo de bloque de estanquidad montado de una forma desplazable en el exterior de la pared frontal de la caperuza en la salida situada para cerrar parcialmente la salida, montándose el rodillo a lo largo del canto interior del dispositi vo de bloque de estanquidad. 74·- Aparato según la reivindicación 59, caracterizado I porque comprende medios deflectores asociados con la cuchilla de chorro que dirigen el gas desde la misma en sentido contrario al -Solado sin revestir de la banda para evitar de este modo la deposición de manchas de metal de revestimiento sobre el lado sin reves tir. 75·- Procedimiento y aparato para producir una banda con tínua metálica de base ferrosa, revestida en un lado solamente con metal de revestimiento, tal y como queda sustancialmente descrito en la presente Memoria y en los dibujos adjuntos. Esta Memoria consta de sesenta hojas, escritas a máquina por una sola cara. ARMCO STEEL CORPORATION 7 HOJAS ηθ 1 ASMCO STEEL CORPOSATION 7 HOJAS na 2 4e A Z2a <$ ESC ALA VARIABLE tí hml-ot? ARMCO STEEL CORPORATION 7 HOJAS nQ 3 ARMGO STEEL CORPORATION 7 HOJAS nC 4 ARMCO STEEL CORPORATION 7 HOJAS nQ 5 ,74 7E 26a — •65 /%> ~26¿ 733 Éb zs 77fes £S} ¿¿7 δ? α - -S£ £6 Itirhrñ Jttn É&U ;ííí £* ¿*n· tr >5^ n MAR. 1977 ABMCO STEEL CORPOBATION 7 hojas ηδ 6 ARMCO STEEL CORPORATION 7 HOJAS nQ 7 26a— 2€>b -¿7 -3/ 30 -f ) ( )—¿¿ ' ' ^0 33 -Z4 ¿a η?? ESCALA. VARIABLS ΐ 3 M». /E 7 ‘/2 5 w F -«*»<fee
Independent claims55
411 paragraphs in 6 sections, as filed
MINISTRY OF INDUSTRY AND INDUSTRIAL PROPERTY REGISTER
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<img file="ES456984A1_D0002.tif" />
SPAIN
PATENT OF INVENTION
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UNE A * 4
MOO. 3106
USE AS FIRST PAGE OF THE REPORT
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The present invention relates to a method and apparatus for continuously contact coating one side only of a ferrous base metal strip with a molten coating metal and, more particularly, relates to a method and device with which it is not necessary to immerse the strip in the molten coating metal bath.
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The method and apparatus described in the present invention may be employed to produce a ferrous-based metal strip provided on one side only with a coating of any metal suitable for hot-dip coating, such as zinc, zinc alloy, aluminum, aluminum alloy, lead-tin alloy, lead, and the like. Although the invention is not intended to be limited to the scope set forth in the description, By way of example and to illustrate the method and apparatus of the invention, the same will be described as used in the production of a ferrous-based metal strip coated on one side only with zinc or with aluminium.
In recent years, there has been increasing demand for ferrous-based metal strip coated with a protective metal on only one side, such as steel strip galvanized on one side. This product is particularly useful in industries such as the automotive, household appliance, and building panel industries. The galvanized side of said product offers excellent corrosion resistance while the uncoated side is characterized by excellent paintability and can be easily welded using spot welding or similar techniques, in those cases where protection against corrosion is required.
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corrosion on only one side of the product, it will be appreciated that a product coated on one side represents considerable savings in coating metal and also provides an uncoated side to which a gloss paint or other finish can be applied.
Prior to this invention, technicians have devised various ways to produce a ferrous-based metal strip coated on one side. In one process, the ferrous-based metal strip is coated on one side with a protective lacquer (i.e., a barrier layer that is not wetted by the coating metal). The strip is coated, traditionally by hot-dipping. The barrier layer is then scraped off or otherwise removed.
U.S. Patent No. 5,585,250 teaches a process whereby the metal strip is properly cleaned on both sides, its temperature raised to the plating temperature, and then it is caused to oxidize on one side only. The strip is then passed through a bath of molten plating metal which adheres to the unoxidized side only.
In another process, the strip is hot-dip coated on both sides, with as much of the coating as possible removed from one side using an air knife or air jet. The remaining coating metal on the side subjected to the air jet is then removed by an electrolytic stripping process.
Finally, electrolytic coating has been used to obtain a product coated on one side only. To this end, the strip to be coated passes around a roller partially immersed in an electrolyte. The exposed side
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-4th position of the band will have a metal coating deposited on it, while the other side of the band remains uncoated, protected by the roller around which it passes.
Although these various prior art practices can produce acceptable products, they are characterized by certain limitations. In general, prior art practices are expensive, require more production steps than conventional hot-dip coating, and require expensive special equipment. Currently employed masking techniques produce an uncoated surface of marginal quality for good finish paint applications.
Technicians have previously used a hot metal meniscus to completely cover your bars and rods, as indicated in German patent number:
06 939. The process described in this patent cannot be applied to the coating on one side of a ferrous-based metal strip.
The method and apparatus of the present invention permit rapid, continuous contact coating of only one side of a ferrous base metal strip with a molten coating metal. Coating thicknesses can be controlled as with any of the two-sided hot-dip coating methods. No roll assemblies are required in the molten metal, thereby eliminating material buildup and maintenance problems. The present invention can be implemented more cheaply and more easily than the one-side coating processes used on an industrial scale. Continuous coating lines of the in-line annealing type can be modified in such a way that
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an easy and inexpensive way to make a one-sided coated product according to the present invention and in fact with provisions for interchangeability of equipment, the same production line can be used to make a one-sided coated product or a double-sided coated product as desired. The quality of the product is superior to that obtained by other hot-dip methods with respect to coated or uncoated surfaces.
According to the invention, there is provided a process for producing a ferrous base metal strip coated with a coating metal on one side only, the other side of the strip remaining free of said coating metal, the ferrous base metal strip having been treated to bring it to the appropriate coating temperature and to leave its surface clean and free of oxide, which method comprises the steps of enabling a coating vessel containing a molten bath of said coating metal; conveying the strip to a position above the upper surface of the bath such that the surface tension and wettability characteristics of the molten coating metal allow the formation of a meniscus on the upper surface of the bath in contact with the side of the strip facing said bath; forming said meniscus; maintaining the meniscus and continuously contact coating said side only of the metal strip; maintaining the strip in a protective antioxidant atmosphere at least until said side of the strip has initially contacted the meniscus, and finishing the coated side of the strip by removing excess coating metal from the strip.
The apparatus according to the invention comprises a coating vessel containing a molten bath of coating metal 5.
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-β· arrangement, means for conveying a ferrous metal strip into a position relative to the upper surface of the bath such that the surface tension and wetting characteristics of the molten coating metal allow the formation of the meniscus on the upper surfaces of the bath which is continuously brought into contact with only one side of said strip fitted to the bath, coating it; finishing means for finishing the coated side of said strip, and means for maintaining the strip in a protective antioxidant atmosphere at least until the side of said strip has contacted the meniscus.
In a first embodiment, the strip is made to pass over the surface of the molten coating metal bath. The strip passes around a first roller and the surface of the strip to be coated is caused to pass close enough to the molten coating metal bath so that the surface tension and wettability characteristics of the coating metal allow the formation of a meniscus which continuously contacts and coats the strip surface. The initial coating of the strip surface is carried out inside a cap or nozzle provided with a protective anti-oxidant atmosphere. While the surface to be coated is still in contact with the molten metal meniscus of the coating, the strip is guided out of the cap or nozzle. Once out of the cap or nozzle, the strip passes around a second roller and is guided upward, separating it from the molten metal bath of the coating. The coated surface of the strip is finished by means of an air knife. Means are used to prevent the entry of an anti-oxidant atmosphere into the interior of the cap or nozzle. •7
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A second embodiment of the invention differs from the first only in the use of a third small roller between the first and second rollers and located outside the cap or nozzle. This third roller deflects the section of strip between the first and second rollers slightly downward, allowing the first and second rollers to be positioned at a slightly greater distance from the molten coating metal bath to prevent metal spatter or pickup by the rollers. The third, smaller roller will typically be shorter than the width of the strip being coated to prevent pickup of coating metal.
In a third embodiment, the surface of the strip to be coated is caused to pass sufficiently close to the surface of the molten metal bath to permit the formation of a coating meniscus by means of a single roll which drives the surface of the strip up to the meniscus and through<sub>s</sub>you see zz<sup>1</sup> from the same and then in an ascending direction separating it from the super i
surface of the molten metal coating bath. The coated surface is again finished by means of an air knife. In this mode, the single roller and the air knife are both located within a hood or nozzle filled with a protective atmosphere, and the blast finish is achieved with anti-oxidant or inert gas. In a similar manner, the first two embodiments described above may be provided with an enlarged protective cap or nozzle box housing the jet finishing means as well as the first and second rollers of the first embodiment and the first, second and third rollers of the second embodiment.
In those cases where the coated band is subjected
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to an anti-oxidant atmosphere while the strip is sufficiently hot to produce visible oxide on its uncoated side, the strip will then be subjected to acid cleaning, followed by rinsing and drying steps to remove visible oxide. This acid cleaning can be performed in several ways, as described later.
When coating and finishing operations are performed within a protective atmosphere, the necessary acid cleaning can be eliminated by holding the strip within a protective atmosphere until it cools to a temperature at which no visible oxide forms on its uncoated side when exposed to an oxidizing atmosphere. Means may be used to accelerate the cooling of the strip while it is still in a protective atmosphere, as will be described later.
Figure 1 is a semi-schematic and fragmentary elevation and cross-sectional view of a first embodiment of the coating apparatus and method of the present invention.
Item
Figure 2 is a cross-sectional view taken along section line 2-2 of Figure 1.
Figure 5 is a semi-schematic, fragmentary cross-sectional view illustrating the contact of the band with the molten lining metal meniscus.
Figure 4 is a fragmentary semi-schematic cross-sectional view, similar to Figure 5, but illustrating the type of meniscus that can be produced when aluminum is used as the molten cladding metal.
Figure 5 is a semi-schematic, fragmented cross-sectional view similar to Figure 1, and illustrates the
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another embodiment of the present invention.
Figure 5a is a fragmentary cross-sectional view illustrating the combination of the sealing block and third roller of Figure 5.
Figure 6 is a semi-schematic cross-sectional view, similar to Figure 2, and illustrates the lining apparatus of Figures 1 or 5 without the use of a sealing block.
Figure 7 is a semi-schematic, fragmentary cross-sectional view of another embodiment of the coating method and apparatus of the present invention.
Figure 8 is a semi-schematic, fragmentary cross-sectional view illustrating a first method and apparatus for acid cleaning.
Figure 9 is a semi-schematic, fragmentary cross-sectional view, similar to Figure 8, illustrating a second method and apparatus for acid cleaning.
Figure 10 is a fragmentary, semi-convoluted cross-sectional view illustrating a third method and apparatus for acid cleaning.
Figures 11 through 14 are schematic and fragmentary cross-sectional views similar to Figure 7 and illustrate various methods and means by which the strip may be maintained in a protective antioxidant atmosphere until it is cooled to the temperature necessary so that, when exposed to an oxidizing atmosphere, no visible rust will form on its uncoated side.
Figure 15 is a semi-schematic and fragmentary cross-sectional view illustrating another embodiment of the method and means of the present invention, similar to the embodiment of
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Figure 5, but in which the coating and finishing operations are kept within a protective atmosphere.
Figures 16 and 17 are semi-schematic, fragmentary cross-sectional views similar to Figure 7, illustrating alternate air knife arrangements.
Figure 18 is a fragmentary plan view of the apparatus of Figure 17.
All embodiments of the present invention require the use of strip preparation techniques of the same type prior to coating. For example, the strip may be cleaned in an anti-oxidant preheater, annealed and cooled in a protective atmosphere at elevated temperature, the precise nature of the strip preparation steps are not a limitation of the present invention as long as the strip is at the appropriate temperature at the time of coating and its surfaces are clean and free of oxide. Appropriate band preparation techniques can be found, for example, in U.S. Patents 2,110,895, 5,520,085, 5,857,790 and 5,956,545.
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A first embodiment of the present invention is illustrated in Figures 1 to 5. The coating vessel is indicated by reference 1 and contains a bath of molten coating metal 2. The ferrous base metal strip, one side of which is to be coated, is indicated by reference 5. The apparatus is provided with a cap or nozzle 4 which constitutes an extension of the cap (illustrated in a fragmentary manner by reference 5) of the conventional apparatus for preparing the strip. The nozzle 4 may form an integral part of the cap 5, or it may be connected to it in a gas-tight manner. Preferably, a gas-tight seal is formed indicated by a
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25« general mode by reference 6 between the nozzle 4 and the cap 5» The hermetic seal 6 can take any appropriate form. By way of example, the hermetic seal or sealing device 6 is illustrated as consisting of two pairs of sealing rollers 7-8 and 9-10.
The nozzle 4 comprises a front wall 4a, a rear wall 4b, side walls 4c and 4d and an upper part 4e.
It is evident from Figures 1 and 2 that the front, rear and side walls extend downward into the molten metal bath 2. The front wall 4a has a U-shaped notch or opening 11, one part of which extends above the bath 2 and defines an outlet for the strip 3 from the nozzle of the cap 4. The outlet 11 should be of sufficient width to allow the passage of the widest strip of ferrous base to be coated.
The band 3 passes between the sealing rollers 9“10 and 7-8 up to the roller 12 inside the nozzle 4. From the roller 12 the band passes to the roller IJ which puts the surface of the band to be coated close to the upper surface 2a<sup>! </sup>from the molten coating bath. From roller 13 the strip passes through the nozzle outlet 11 to roller 14 and from this roller it rises and is separated from the molten metal coating bath 2. Rollers 12, 13 and 14 are properly supported by normal means not illustrated.
The front wall 4a of the nozzle 4 may be provided with a support 15 intended to receive an elongated block of the panel type 16 of graphite or other suitable material which serves as a sealing device to close the major part of the nozzle outlet 11. The graphite block 16 can rise and fall freely within the support 15 and rests on the upper or uncoated surface of the Fe30 base metal strip.
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It is important that nozzle 4 be provided with an anti-oxidant atmosphere so that the surfaces of strip 3 remain clean and free of rust before coating. To this end, nozzle 4 has an inlet 17 through which a suitable anti-oxidant gas is introduced into the nozzle. Any suitable anti-oxidising gas comprising nitrogen, inert gases or the like may be used. The anti-oxidising atmosphere within the nozzle 4 must be maintained at a slight positive pressure so that the ambient oxidising atmosphere outside the nozzle cannot penetrate the nozzle through the nozzle outlet 11 and in particular through the parts 11a and 11b (see Figure 2) which are not closed by the sealing device 16. In a similar way, It is preferable to provide an inlet of anti-rust atmosphere 18 between the pairs of sealing rods 7"8 and 9-10. It is furthermore preferable that the anti-rust atmosphere in the auxiliary chamber 18a be at a pressure slightly above the pressure prevailing inside the nozzle 4 and higher than the pressure inside the cap 5. In this way it is ensured that the anti-rust atmosphere inside the cap 5 cannot be contaminated even during periods of detention of the apparatus while work is being performed inside the nozzle 4. Since the pressure of the anti-oxidant atmosphere inside the auxiliary chamber 18a is greater than the atmospheric pressure inside the cap 5, contamination of the atmosphere inside the cap 5 from sources at the inlet end of the normal strip preparation apparatus will also be prevented. Finally, the coated side of the coating 3 will be finished by means of an air knife 19, which will be explained in more detail later.
Having described the apparatus, its operation can be stated as follows: With the ferrous base metal strip 5 threaded between the rollers 7-8, 9-10, 12, 15 and 14 around the same, as illustrated, and moving in the direction of arrow A (figure 1), a small ripple can be formed on the upper surface 2a of the molten coating metal bath 2. In this way, contact is produced between the adjacent side of the ferrous base metal strip 5 and the molten metal of the coating and the surface tension characteristics t
and wettability of the coating metal will result in the formation of a meniscus which will be in continuous contact with the adjacent surface of the strip, coating it. The meniscus is represented by reference 20 in Figures 1 to 5. Thanks to the meniscus 20, continuous contact coating can be achieved on one side of the strip 5 only without the need to immerse the strip in bath 2. Thus, the band 5, as it rises from the roller 14, will have a coated side 5a and an uncoated side 5b.
Those skilled in the art will understand that in order to clearly demonstrate in Figures 1 to 5 the thickness of the strip 5, the distances of the rollers 15 and 14 from the upper surface 2a of the bath 2 and the height of the meniscus have been exaggerated. The distance of said surface of the strip 5 to be coated - from the upper surface 2a of the bath 2, which allows the formation and maintenance of a meniscus of re-<sup>1 </sup>coating, will vary depending on the cladding metal used and its surface tension and wettability characteristics. Excellent results have been achieved with most cladding metals when this distance is properly maintained at 7.94 mm.<sup>0</sup> less.
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15It is preferable that the roller 3 be positioned above the upper surface 2a of the molten metal coating bath 2 at a slightly greater height than the roller 14. Again, this height difference has been exaggerated for clarity in Figure 1. The invention encompasses an actual height difference in the range of about 0.125 in to about 0.25 in. The purpose of this height difference is simply to additionally ensure that no splashing or metal collection occurs by the roller 13, which is located below the nozzle 4 and is therefore not visible to the bath operator.
The air knife 19 may be positioned on or slightly below the centerline of the roller 14. The distance at which the air knife may be positioned below the centerline of the roller 14 will depend primarily on the roller diameter and the web speed. It is important that the air knife does not inject a contaminating atmosphere through the nozzle outlet 11 or disturb the meniscus 20. The air knife 19 may be positioned above
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of the roller 14, as illustrated by dotted lines at 19a. To ensure proper blast finishing, it is important that the cross-section of the web 5 remain flat. To this end, it is preferable to provide a support roller (illustrated by dashed lines at 21) opposite the air knife 19a.
Another embodiment of the present invention is illustrated in Figure 5. This embodiment is similar to the embodiment of Figure 1 and like parts are indicated by like reference numerals. The embodiment of Figure 5 differs only in the provision of the roller 22 located outside the nozzle and between the
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25rollers 13, 14. Roller 22 will be provided with appropriate biasing means (not shown) and is positioned to deflect the strip section 3 between rollers 15 and 14 slightly downwards. This will allow rollers 13 and 14 to be lifted slightly from the upper surface 2a of the molten metal bath.
lining 2 to ensure that no metal splashing or pick-up occurs on these rollers. Roller 22 should be slightly shorter than the width of strip 3. As in figures 13, the thickness of 1 i
band 3, the height of the meniscus 20 and the distance of the rollers 13 and 14 from the upper surface 2a of the molten investment metal bath 2 have been exaggerated in Figure 5 for clarity. The deflection induced in band 3 by the rod 22 has also been exaggerated. The magnitude of the deflection is contemplated within the order of approximately 6.25 to 12.70 mm, which allows the placement of the rollers 13 and 14 at a similar height from the upper surface 2a of the bath, greater than in the embodiment illustrated in Figure 1. In all other respects, the apparatus of Figure 5 and its operation can be practically identical to the apparatus of Figure 1. The meniscus formed is the same as that illustrated in Figure 3.
The meniscus will be the same with any suitable cladding metal. However, it has been found that when aluminum is used as the cladding metal, although the meniscus will normally have the shape illustrated in Figure 3, the roll 2 may actually depress the strip 3 slightly below the surface 2a of the molten cladding metal bath 2 because the aluminum forms a meniscus of the type illustrated at 23 in Figure 4. In this way, using aluminum as a molten metal coating, the strip can pass
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in fact slightly below the surface of the molten investment bath, achieving a coating on one side.
The embodiment of Figure 5 can be modified by holding the roller 22 on the sealing block 16. This is illustrated in Figure 5a» where the roller 22a (equivalent to the roller 22 of Figure 5) is held to rotate on the sealing block 16a (equivalent to the sealing block 16 of Figure 5) by means of a normal type (not illustrated). The roller 22a lies along the lower edge of the sealing block 16a and will contact the uncoated side 5b of the strip 5 for the same purpose as described with respect to the roller 22 in Figure 5. It is also within the scope of the invention to locate the roller 22 of Figure 5 within the nozzle 4, requiring only that proper positioning of the rollers 15 and 14 permit this change.
Figure 16 is similar to Figure 2 (the same reference numerals having been used to indicate like parts) and may be considered to be a cross-sectional view illustrating the front wall 4a of the nozzle 4 of Figure 1 or Figure 5. Figure 6 differs from Figure 2 in that the support 15 and the graphite sealing device 16 have been eliminated and the notch forming the nozzle outlet 11c has been reduced to a position immediately above it. band 5 to minimize the opening of the outlet.
In this way, in the embodiments of figures 1 and 5, the graphite sealing device 16 and the support 15 can be eliminated, preventing the entry of oxidising atmosphere through the outlet 11c, maintaining the antioxidant atmosphere inside the cap 4 at a slightly positive pressure.
Another embodiment of the present invention is illustrated in fig.
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Figure 7. A coating vessel 24 containing a bath of molten coating metal 25 is shown in Figure 7. A nozzle 26 is shown, which constitutes a fragmented continuation of the strip pretreatment cap shown at 27. In this case too, the nozzle may form an integral part of the pretreatment cap 27 or may be connected to it in a gas-tight manner. A sealing device, generally indicated by reference 28, is provided between the nozzle 26 and
and the cap 27. The sealing device may take any appropriate form and, for illustrative purposes, is again shown as comprising two pairs of sealing rollers 29, 30 and 31-32. An inlet for an anti-rust atmosphere may be located between the pairs of rollers, as indicated by reference 33. The cap 26 has a front wall 26a, a rear wall 26b and side walls, one of which is illustrated at 26c. The front, rear and side walls of the hood 26 extend downward into the molten coating metal bath 25.
The ferrous base metal strip is again indicated by reference numeral 3 and passes between rollers 31 and 32 and rollers 29 and 3θ of the sealing device. It then passes over the downward-facing roller 34 and around roller 35 which brings the surface of the strip to be coated proximate the upper surface 25a of the molten metal coating bath. Roller 35 then directs the coated strip upwards away from the molten coating metal bath 25 and the strip exits through nozzle 26 via an outlet slot 36.
The nozzle 26 is provided with an inlet 37 of atmos. I
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antioxidant atmosphere and the antioxidant atmosphere is maintained within the nozzle at a slightly positive pressure so that the ambient atmosphere containing oxygen outside the nozzle does not enter through the outlet slot 36. The sealing device 28 and its antioxidant atmosphere inlet 33 can serve the same purpose as described with respect to the sealing device 6 and inlet 18 in Figure 1. Again, the sealing device 28 and the inlet 33 are of particular importance during the stopping of the nozzle 26. In the embodiment of Figure 7, a jet blade 38 is provided inside the nozzle 26. The jet blade operates with antioxidant gas which may be the same as the antioxidant atmosphere inside the nozzle.
The operation of the embodiment of Figure 7 differs from the embodiments of Figures 1 and 5 mainly in the sense that the coating and finishing operations are carried out inside the nozzle 26 and in its protective anti-oxidant atmosphere. The ferrous base metal strip 3 being threaded in the manner illustrated in Figure 7 and moving in the direction of arrow B, a small ripple formed on the surface 25a of the molten metal bath and the coating 26 will also result in the formation of a meniscus 39 whereby the surface of the strip 3 facing the upper surface 25a of the molten metal bath will be continuously coated by contact as it passes around the roller 35. The mounting means (not shown) inside the nozzle 26 for the rollers 34 and 35 or for the jet blade 38 may be of the standard type. As the ferrous base metal strip ascends toward the exit slot 36, it will be coated on one side 3a and uncoated on the side 3b. The coated side will receive a finish
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with the jet blade 58 which, again, can be positioned in any position so long as it does not disturb the meniscus 59 and the upper surface 25a of the molten coating bath 25. If for convenience it is desired that the jet blade 58 be positioned above the roller 55 by a distance that would cause deformation of the cross-sectional shape of the strip 5, a support roller may be used, as described with respect to Figure 1, to ensure that the cross section of the strip remains flat during the finishing operation.
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In all of the embodiments described, the band 5 will be exposed to the ambient atmosphere while still at a temperature high enough to result in the formation of a visible oxide on its uncoated side 5b. For short exposure times, the visible oxide coating will be composed of thin oxide layers or films, the film adjacent to the base metal being composed primarily of FeO, covered by a film of Fe^O^ followed, in turn, by a layer of PegO^. If the strip temperature, when exposed to an oxidizing atmosphere, is below approximately 568°C, the PeO layer that normally forms when the molten cladding metal is zinc will not form. When the molten cladding metal is aluminum, the strip temperature will typically be above 5θθ°0 and an FeO layer will form.
The visible oxide layer can be removed by an acid cleaning process, as mentioned above.
The term cleaning process<sub>z</sub>a with acid is used in this process a..propos it o, to distinguish it from acid pickling. The distinction between cleaning and acid pickling is a matter of gravity.
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Acid pickling is usually used to refer to a rigorous treatment to remove scale from a semi-finished product. The first stage of an acid cleaning process is purely chemical and involves the dissolution of oxide films. Oxide films dissolve in different proportions, with the dissolution of Fe^O^ being the slowest process. Thin, porous oxide films can be removed by acid penetration and direct attack of the metal base. The rate of oxide removal can be increased in several ways. First, the rate of chemical reaction can be increased by raising the temperature of the acid bath or by increasing the acid concentration. In addition,
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The rate of penetration oxide removal can be increased by inducing an electric current. This increases the dissolution of the base metal and local surface agitation by hydrogen generation.
Acid cleaning of single-sided coated metal strip presents a unique problem in that it is desirable to remove oxide from the uncoated side of the ferrous-based metal strip while minimizing etching of the coated side. It has been determined that the use of an electrolytic acid cleaning process is preferable.
Acid cleaning involves a number of interrelated variables, resulting in an almost infinite number of specific combinations of these variables that can successfully remove the visible oxide film from the uncoated side of the strip. Nevertheless, basic guidelines can be established for the preferable acid cleaning of coated ferrous-based metal strip.
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on the one hand.
The basic variables of acid cleaning include the acid used, acid concentration, acid temperature, electrode-strip distance, strip immersion time, and current density through the electrode. To minimize attack on the coated side of the strip, it is preferable to use a dilute acid solution, usually a commercial acid of 1% by volume or less. The type of acid used will be determined by its effectiveness, cost, availability, pollution control requirements, and ventilation requirements. Common acids for this purpose include sulfuric, phosphoric, hydrochloric, and nitric acids. Sulfuric and phosphoric acids are slightly more effective, with sulfuric acid being preferred not only because of its effectiveness but also because of its lower tendency to form vapors.
The acid temperature should be kept low (below approximately 57°C) if chemical attack and spotting of the coated side of the strip is to be minimized, and the electrode-to-strip distance should be minimized to increase efficiency. However, the electrode distance will be determined by the continuous pitch line requirements necessary to avoid strip-electrode contact. Strip immersion time should also be kept to the minimum necessary to simply remove any visible oxide present. However, from a practical standpoint, strip immersion time will be determined by tank dimensions and strip speeds. In a given installation there must be a minimum current density. The range of 20 to 40 amps per square decimeter has proven to be totally)
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satisfactory. Increasing the current density much above the practical minimum would simply be a waste with no additional practical results.
Figure 8 illustrates a modified galvanic vessel whereby the acid cleaning step may be performed. In Figure 8, a vat 40 is illustrated containing a dilute acid bath 41. The strip 5 with its coated side 5a and uncoated side 5b is passed through the bath 41 around the roller 42 held within the bath by a standard type device (not shown).<sub>n</sub> block 45 of sacrificial metal (e.g., zinc) is positioned a short distance from the uncoated side 5b of the ferrous base metal strip 5 and is held in position by suitable support devices (not shown). The sacrificial metal block 45 is electrically connected to the ferrous base metal strip, as indicated by reference 44, by roller 42. Although the attack rate of the base metal does not increase, the rapid generation of hydrogen on the uncoated surface of strip 5 aids in oxide removal. Hydrogen is also generated in the sacrificial metal block 45 and rises to aid in oxide agitation on the uncoated strip surface 5b. Other sacrificial metals, including magnesium and aluminum, may be employed.
In actual experimental tests, 0.5 phi sulfuric and 0.5 phi phosphoric acids have been employed as the dilute acid bath 41 and maintained at a temperature of about 52°C. Strip 5 was coated on one side 5a with zinc and had an oxide layer on side 5b formed as a result of the strip being brought out of the protective atmosphere of the coating operation into air at a temperature of about 1
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482°C. A sacrificial zinc block 45 was used and held at a distance of approximately 3.18 mm from the surface of band 3b. The oxide layer was removed from surface 3b in approximately 5 seconds with no evidence of etching of the zinc layer on the band 3a side. |
Yo
Figure 9 illustrates another method and apparatus for acid cleaning a strip 3 having a hot metal coated side 3a and an oxide coated side 3b. In this embodiment, a tub 45 containing a dilute acid bath 46 is used. The strip 3 is passed around a roller.
submerged 4? and an electrode 48 is located adjacent to the side of the)
I uncoated band 5b. The electrode and the band (by the roller ί i
47) are connected to a current source 49, as in 5θ, and 51<sup>! </sup>respectively. It has also been found that instead of connecting connector 51 of the power source 49 to the roller 47<sup>1 </sup>(or in sliding contact or with contact rollers, as is known in this branch of the industry, the molten lining metal can be used to induce electric current to the strip eliminating possible surface damage of the strip by scratches or electric arcing. For this purpose, the conductor 51 from the current source 49 can be connected to
to the lining tank 1 when the lining tank is made of metal. As an example, this is illustrated in Figure 1. As a variant, the conductor 51 can be connected to
I i
an electrode 51a immersed in the coating metal bath
to melt. As an example, this is illustrated in Figure 5·' i
It will be understood that the connections of conductor 51 illustrated in Figures 1 and 5 could be used in any of the coating modalities described when acid cleaning of the type described with respect to Figure 5 is to be employed.
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ra 9.
The embodiment of Figure 9, in which a current is induced from an external source 49, has proven to be more effective than the embodiment of Figure 8. The dissolution of the iron below the oxide layer is accelerated by some generation of hydrogen to help remove the oxide and detach it from the ferrous base metal strip 3. The current source 49 may be alternating or direct current, with alternating current being preferable because the pulsation i of the current increases the rate of the acid cleaning process. The electrode 48 may be any suitable material that is conductive but not attacked by the dilute acid bath 46. Stainless steel is an excellent electrode material. Other materials such as platinum or even lead may be used for element 48.
In an actual experimental test the dilute acid bath 46 comprised 0.5% sulfuric acid maintained at a temperature of about 32°C. The power source 49 was a direct current welding generator providing a current flow of about 110 amperes with a band 3 constituting the cathode and an electrode 48 constituting a stainless steel anode. Strip 3 had an oxide layer on one side 3b formed by the strip upon exiting the protective antioxidant atmosphere of the air coating operation at a strip temperature of approximately 482°C. The oxide film was removed in less than 6 seconds with rapid hydrogen evolution at electrode 48 and the strip surface 3b. No staining of the zinc coating was observed on the 3a side of the strip at times ,
Immersion times of less than 4 seconds. A slight man- 25 5 was observed.
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etching and etching of zinc coating in times of immersion.
6-second sion. The stainless steel electrode was located approximately 12.70 mm from side 3b of the band.<sup>!</sup>
In another test the dilute acid bath 46 was again 0.5% sulfuric acid maintained at a temperature of about 26°C and the electrode was again stainless steel. Strip 5 had a zinc coating on side 3a and an oxide coating on side 3b formed by the strip as it exited the protective atmosphere of the coating operation into air at a strip temperature of about 482°C. The power source 49 was an alternating current source providing a current of approximately 9 amperes. The electrode 48 was held at a distance of approximately 25.4 mm from the surface of the strip 3b. Under these conditions the oxide film was removed in about two seconds. No etching of the zinc coating on the surface 3a of the strip was observed.
• YO
A variation of the embodiment of Figure 9 is illustrated in Figure 10 in which the band was indicated by nu¿ i
I go for reference 3 with its metal coating side 3¿
I and its oxide coated side 3b. In this embodiment, the strip j 3 passes over a support roller 52 and the bath 46 of Figure 9 has been replaced by a sponge loaded with dilute acid 53. The sponge 55 is held by a holding device 54 which may be made of stainless steel or other metal not attacked by the dilute acid used. The sponge 55 and its
I support 54 was connected to a current source 55, as indicated by reference 56. Band 3 was also connected to the current source by roller 52, as indicated by reference!
I rence 57 .Ea current source 55 can be a source of co4
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alternating or direct current. An input device 58 is used in the sponge holder 5^ by which acid replenishment can be achieved, the embodiment of Figure 10 being characterized by the advantage that no tub is required and the sponge 55 does not provide a rubbing rust removal action. Care should be taken to replace the sponge when necessary due to wear or accumulation of sufficient particles embedded in the sponge that could present a risk of scratches to the band 3.
All acid cleaning procedures described above can be followed by appropriate rinsing and drying steps (well known in the trade) to limit
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acid attack on both sides of the strip. Other suitable dilute acids than those listed above may be employed, and the preferred choice of dilute acid is well within the knowledge of the person skilled in the art. The dilute acids employed may comprise standard additives such as inhibitory surfactants, antifoaming agents, and the like, as is well known.
The acid cleaning, rinsing and drying phases can be eliminated if the ferrous base metal strip coated on one side is kept in a protective anti-oxidant atmosphere until t
that reaches a temperature low enough to avoid) i
the formation of a visible acid coating on its uncoated side. This method and apparatus are illustrated in Figure 11.
By way of example, the coating process and apparatus of Figure 11 is identical to that of Figure 7, so that similar parts are indicated with the same reference numbers. The embodiment of Figure 11 differs from the embodiment of Figure 7 only in that a cooling cap has been added.<sup>!</sup>
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-27ment 59 to the nozzle 26 in the outlet area of the nozzle 36, cooling cap 59 is provided with an outlet 60. The cooling cap is of such length that, at the moment
The
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as the strip 3 passes through the outlet of the cap 60, it will have cooled to a temperature of approximately 149°C i.e., a temperature at which no visible oxide will form on the uncoated side 3b of the strip. The cooling cap 59 will, of course, be provided with an antioxidative atmosphere which will enter the cap 59 through the outlet of the cap 60.
bera 36. If necessary, an additional inlet ) for the antioxidant atmosphere can be provided in the cooling cap 59, as indicated in reference 61. Although, for the purposes of illustrating the example, the cooling cap 59
cooling 59, this cap is illustrated simply added to the nozzle 26, it will be understood that the part 26e of the upper zone of the nozzle 26d located below the cap 59 and comprising the nozzle outlet 36, can be eliminated.
Except for keeping the coated band in a protective atmosphere until it has cooled sufficiently to prevent
I the formation of visible oxide on its uncoated side, the operation of the embodiment in Figure 11 is identical to that described with respect to Figure 7.
The length of the cooling cap required to keep the coated strip in a protective atmosphere until the strip reaches a temperature at which no visible oxide forms on its uncoated side can be reduced.
i litandomedios psra increase the cooling rate of the band. Figure 12 illustrates an embodiment virtually identical to Figure 7, so again, similar parts are illustrated with the same reference numerals. In Figure 1
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12, a cooling cap 62 similar to cap 59 of Fig. 11 is used and has an outlet 65 and an additional inlet 64 for anti-oxidant atmosphere, if deemed necessary. In this embodiment, the strip 5 may be passed around chilled rollers 65 and 66 which reduce the temperature of the strip, allowing the cooling cap 62 to be shortened. Again, the portion 26e of the upper region of the nozzle 26d, which lies below the cooling cap 62 and includes the outlet 56, can be eliminated.
Another way in which the strip can be protected from visible oxide formation is illustrated in Figure 15. Again, the apparatus is virtually identical to that of Figure 7 and the coating operation is carried out in the same manner. In this embodiment, the nozzle 26 is provided with a cooling cap 67 having an outlet 68. A protective atmosphere is formed in the hood 67 from the nozzle 26 and an additional inlet for said atmosphere can be provided, as indicated by reference 69, if deemed necessary.
In this embodiment, a portion of the protective atmosphere is drawn from the cooling hood through outlet 70 to a heat exchanger schematically indicated by reference 71 which incorporates a fan or similar device. The cooled protective atmosphere from heat exchanger 71 is reintroduced into the cooling hood. to 67 by the jet 72 which makes the cooled protective atmosphere fall on the band 5"To increase the cooling effect of the band, a second changer can be enabled t
heat exchanger 75 having an inlet 74 and a jet 75 diametrically opposite to jet 72. The provision of diametrically opposed jets 72 and 75 will ensure that the configuration is maintained.
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25» flat cross-section of the strip 5* The heat exchangers 71 and 75 allow a ©cutting of the cap 6?, if compared with the cap 59 of figure 11, since the cooling of the strip 5 is accelerated.
Another strip cooling device is illustrated in Figure 14. In this embodiment, once again, the coating process and apparatus for implementing it are identical to Figure 7, so like parts are indicated by the same reference numerals. The embodiment of the i
Figure 14 is based on the determination that a strip coated on one side can be cooled in a water bath without the shape i
tion of a visible oxide film on its uncoated side. For this purpose, a cap 76 is used which is directed upwards from the top 26d of the tub 26. At its upper end, the cap is provided with a guide roller 77 and ends in an outlet nozzle 78. The nozzle 78 is located below the surface of a water bath 79 in a suitable tub 80. The web 5 leaves the nozzle 26 through the nozzle outlet 36 and enters the cap 76. Inside the cap 76 the band passes around the guide roller 77 and
I leaves the nozzle 78 entering the water bath 79. The strip is guided through the water bath 79 and is directed upwards out of the water bath by means of a submerged roller 81. The nozzle part 7θ of the cap 76 is provided with an outlet 82 for the protective anti-oxidant atmosphere inside the cap 76 and the water vapor produced by the immersion of the strip in the water bath 79.
The outlet 82 is provided with a regulating valve 82 and the flow through the outlet 82 can be checked by an orifice meter (known in this branch of the industry) indicated by
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a general mode by reference 84. Deflectors 78a and 78b may be provided in the nozzle portion 78 to minimize back diffusion of water vapor into the hood 76. It will be understood that the protective anti-oxidant atmosphere within the hood 76 will come from the nozzle 26 through the nozzle outlet 36.
In all embodiments of Figures 11 to 13 the protective atmosphere within the cooling cap must be maintained at a pressure sufficient to prevent the entry of ambient oxidizing atmosphere into the cooling cap through the cooling cap outlet.
Figure 15 illustrates a modification of the embodiment of Figure 5 in which both coating and finishing operations are performed within a protective atmosphere. For this purpose, a molten metal vessel 85 contains a molten coating metal bath 86. A nozzle 87 is connected to or forms an integral part of the pretreatment cap (illustrated in fragmentary form at 88). Again, a dis. positive sealing, indicated in a general way by the reference 89, can be used between the nozzle 87 and the cap 88 serving the same purpose as the sealing device 6 of figure 5. Again, in order to expose a form of sealing device 89 that serves as an example, said device is illustrated as being composed of pairs of sealing rollers 90-91 and 92-93 with an inlet of antioxidant atmosphere 94 between them, serving the same purpose as the entry i
from figure 18 5· The ferrous base metal band is | í
indicated again by reference 3 and has to pass around a 95 direction change roller equivalent to 12 of ί
Figure 5· The band 3 also passes under rollers 96,<sup>1</sup>
-5197 and 98 are equivalent and serve the same purpose as rollers 13, 14 and 22 in Figure 5, respectively. The cap 87 has a front wall 87a, a rear wall
87b and side walls, one of which is indicated by reference 87c. These front, rear and side walls are partially introduced into the molten coating metal bath.
ment 86, as illustrated. The upper part 87d of the nozzle 87 is provided with an anti-oxidant atmosphere inlet 99 and an outlet 100 for the band 3. A jet blade 101 i
It is mounted inside the cap 87 and can be placed in any position inside the cap as long as it does not disturb the meniscus t
102. A backing roller or support roller or jet blade (not illustrated) may be provided for the jet blade 101 as described with respect to Figure 1.
The operation of the embodiment of Figure 15 is identical to that of Figure 5 and the strip 3 may be provided with a coated side 3a and an uncoated side 3b. The embodiment of Figure 15 differs from Figure 5 primarily in that both coating and finishing operations are performed within the nozzle 87 and its protective atmosphere, eliminating the need for the sealing block.
I of Figure 5 The strip coated on one side may pass through the nozzle outlet 100 into the ambient atmosphere, after which it will be subjected to appropriate acid cleaning, rinsing and drying as described above. Alternatively, the strip may be maintained in a protective atmosphere (until it reaches a temperature at which no visible oxide will form on its uncoated side 3b) by any of the means illustrated in Figures 11 to 14. In modality i
From figure 15, roller 98 would be eliminated. The result of this
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elimination would be a modality, similar to figure 1, but with both coating and finishing stages being carried out inside the nozzle.
Figure 16 illustrates an embodiment similar to Figure 7, and similar parts are indicated by the same reference numerals. The coating operation in the embodiment of Figure 16 is again identical to that described with respect to Figure 7. Figure 16 differs from Figure 7 in that the front wall 26a of the nozzle 26 is provided with an opening 103 sized to smoothly accept the jet blade 104 with its front end located within the nozzle 26 and its rear end directed away from the nozzle. The opening 103 may be provided with a hinged closure 105 which descends over the nozzle 104 when the nozzle is in place and which closes the opening 103 to prevent the entry of an oxidizing atmosphere through the opening 103 when the jet blade 104 is removed for cleaning. Additional support means (not shown) may be provided for the jet blade 104 and may be of a conventional nature. The opening 103 may be provided with a gasket (not shown) or other sealing device to prevent contamination of the protective atmosphere inside the nozzle by ΐ
an external oxidizing atmosphere passing through the opening<sup>1 </sup>103 and around the jet blade. If the opening 103 | is designed to fit the peripheral dimensions of the jet blade 104, the use of the dis-¡
I positive sealing by the positive pressure of the protective atmosphere maintained within the nozzle 26. The device of Figure 16 can be applied to any of the embodiments described above which have a jet blade i located within the nozzle. This device significantly facilitates30.
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mind the peripheral cleaning of the jet blade. j
In those coating modalities described j
In the case of previously described applications where the jet blade is located within the nozzle, under certain circumstances a problem may arise with the formation of coating metal dust from the coating metal vapor formed in the jet finishing operation. A problem may also arise with coating metal smearing on the uncoated surface of the strip. The coating metal spots are, again, the result of the finishing operation, the spots forming from the edges of the strip. Figures 17 and 18<sup>!</sup> Yo
illustrate a jet knife device that eliminates these problems. By way of example, Figure 17 illustrates a coating apparatus identical to that of Figure 7, where the parts ¡ i
similar ones are indicated by the same reference numbers. It is I
It will be understood that the nozzle arrangement of Figures 17 and 18 can be applied to the coating apparatus of Figure 15 (with or without roller 88) in exactly the same manner.
In figures 17 and 18, the exit slot 56 is the ¡ i
Hood 26 is enclosed on three sides by walls or baffles 106, 107 and 108. Jet blade 109 is mounted on the outside of nozzle 26 with its forward end directed through partition 107. With this arrangement, and without using gas<sup>1 </sup>rust preventer on the jet blade 109, the zinc coating on side 5a of the strip 5 will receive the finishing treatment before being exposed to the surrounding air atmosphere. Any metallic dust from the coating or stains formed will be removed without detriment to the uncoated side 5b of the strip. When ambient conditions warrant, another deflector
I (not illustrated) can be extended across the top edges-<sup>1</sup>
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of the baffles 106 and 108. The upper baffle will be provided with a slot through which the belt 3 can pass. The upper baffle can eliminate any drafts that might be created by the finishing action. The side of the baffle system opposite the uncoated side of the belt 3b is still open, allowing any metal coating dust or stains to be removed from the uncoated side of the belt 3b.
In all the coating methods and media described above, the bath temperature will depend on the molten investment metal used. The bath must be maintained at a sufficient temperature to ensure that the investment metal remains molten until finishing by means of the jet knife. Unlike conventional hot dip coating processes, where the strip to be coated (on both sides) is dipped into the bath, the one-sided coating processes of the present invention cannot rely on the strip itself to induce a significant amount of heat into the molten coating bath. The bath temperature should be ΐ
essentially the same as for good double-sided coating practice and should be kept as constant as possible to minimize the formation of impurities. In all the modalities described, particularly since they rely for their proper functioning on the formation of a meniscus, the bath level must be kept appropriately constant. To this end,
I must use a pneumatic displacement chamber or I plug
mechanical displacement to achieve precise adjustment of the bath level, as is known in this branch of industry. Automatic means of bath level control should preferably be used (as is also known in this branch of industry).
The molten investment metal bath may be heated in any normal manner including the use of electrical resistance elements, induction heating, dip tube heating and the like. Those skilled in the art will understand that the volume of the molten investment metal bath may be substantially less than that required in normal immersion coating processes.
hot (coating on both sides). As, according to the present-*
your invention, the contact of the strip with the bath is significantly reduced, the rate of dissolution of the strip when compared to the rate of molten lining metal required to enter the bath will be of such a nature that the bath cannot become saturated with iron and the formation of impurities is minimized or eliminated. This, in turn, will result in a defect-free lining. For this reason, it is preferable for the container for the molten investment metal to have an interior lining with a suitable ceramic material.
In all the modalities described above, the tea i
temperature of the ferrous-based metal strip, as it comes out of ¡ j
the normal pretreatment cap and penetrates the nozzle<sub>t</sub> i of the coating will again depend on the molten lining metal used and can be easily determined by one skilled in the art. The temperature of the strip must be high enough to avoid areas without any molten metal coating on it. For the same reason, the temperature of the strip must not be so high that excess alloying occurs between the lining metal and the base metal.
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In all embodiments, an oxidizing atmosphere must be maintained in the nozzle. Any suitable oxidizing atmosphere comprising nitrogen and an inert gas can be used for this purpose. The oxidizing atmosphere within the nozzle must be maintained at a pressure sufficient to prevent the oxidizing atmosphere from entering the nozzle through the nozzle outlet. The same thing must occur, of course, in a cooling cap, such as those described with respect to figures 11 to 14. The condensation point inside the nozzle i
should be maintained at a comparable level by allowing in procedural<sup>! </sup>ordinary coating processes (both sides). This level depends on the strip temperature and the percentage of hydrogen in the atmosphere during the strip preparation operation, as is known.
In all the embodiments described above, the roller or rollers located next to the molten coating metal bath should preferably be provided with a surface that is not easily wetted by the molten coating metal. This facilitates the removal of any coating metal from the rollers by accidental pick-up or splashing. If desired, the roll(s) next to the molten lining metal should be crowned or shaped appropriately so that the unused portions beyond the edges of the lining strip have a slightly tapered section away from the bath surfaces. This also facilitates strip guidance.
The present invention has been disclosed in various embodiments.<sub>to</sub> The choice of a modality or combination of modalities will depend on the number of factors that comprise the
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equipment already available, coating material used, the desired characteristics of the final coated product and other factors. Naturally, this choice is well within the knowledge of the person skilled in the art. For example, in the modalities described above in
In which jet finishing is carried out with an antioxidant gas inside the nozzle (e.g. the embodiment in Figure 7), a number of advantages are obtained. These advantages include the absence of waviness of the coating even at very low speeds; the absence of problems related to
two with oxide on the bath surface; a reduction in problems with defects such as stains or impurities; no oxide curtains are formed on the finished coating; and a virtual elimination of foaming is achieved. On the other hand, with this procedure the operator must monitor the formation of metallic vapors from the coating and the formation of dust and the possibility of metallic stains from the coating on the uncoated side of the strip.
In an embodiment as illustrated in Figures 17-18, where anti-oxidant jet finishing gas is used outside the chamber but before the strip is exposed to the ambient atmosphere, all of the above advantages of jet finishing are obtained. This procedure also reduces the problem of build-up of metal dust from the coating on the nozzle and eliminates staining.
I of coating metal on the uncoated side of the 1st ban-í da. On the other hand, the anti-oxidant gas used in jet finishing is not available to create a positive pressure in the nozzle.
In a modality illustrated in figure 5, where ί is
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It uses air finishing in an ambient atmosphere outside the nozzle. The finishing operation is exposed for ease of operation, and there will be no coating metal fumes, dust, or staining problems. It also reduces the consumption of anti-oxidant atmospheres. On the other hand, most of the advantages obtained when finishing is carried out with an antioxidant atmosphere inside the nozzle are not obtained by this procedure, although this drawback can be partially reduced by using an antioxidant atmosphere (for example nitrogen) after the band has been exposed to the atmosphere.
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ambient air atmosphere.
Those modalities that use a configuration
Single-roller models (e.g., Figure 7) are characterized by the simplicity of the apparatus. Minimizing problems with strip shape deficiencies and minimizing the contact length between the strip and the meniscus improves the likelihood of iron buildup in the bath. With the single-roller configuration, care must be taken to avoid zinc pick-up on the single roll, and the reduced meniscus area will require careful monitoring!
strict blast finishing to avoid interruption of the meniscus by the same.
The use of the double roller configuration allows finishing in air (as shown in Figure 1) or with the nozzle as shown in Figure 15. The longer contact time between the meniscus and the strip will cause the meniscus to
be interrupted less easily. For the same reason, this !
The longer meniscus contact provides a greater opportunity for iron dissolution from the strip. The double roller configuration is more complex from a viewing point.
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view of the device and greater care must be taken with regard to the shape of the band.
The triple roller configuration of Figure 5 and 15 offers all the advantages of the double roller configuration plus the ability to increase the roller spacing.
from the bath surface. This configuration also has all the disadvantages of the dual-roller configuration, along with the fact that it is even more complex in terms of apparatus design, and care must be taken to ensure that the intermediate roller does not score or otherwise damage the web, particularly when coating a very wide web.
EXAMPLE 1 !
A 28 gauge ferrous base metal strip is reviewed.<sub>z</sub> i tio on one side with zinc using the coating apparatus ¡ ί
and the procedure outlined above with respect to Figure 1.
At a speed of 12 m per minute the strip was introduced into the nozzle at a strip temperature of approximately 466 to 471°C. The bath temperature was maintained at 460°C.
A protective anti-oxidant atmosphere of nitrogen was introduced into the nozzle at a rate of 19.82 cubic meters per hour. A condensation point was recorded on the 12th direction change roller.
sation of -23°C, along with 120 ppm of oxygen. ¡ A
The jet nozzle 19 had a nozzle gap of 0.76 mm and was supplied with air at a propellant pressure of 0.63 kg/cm . The nozzle was held at a height J of approximately 152 mm above the bath level and was directed upwards at an angle of approximately 2 or 3°. The roller 14 had a diameter of 305 mm. The nozzle was
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fcenia at a distance of approximately 4.76 mm from the coated side of the band.
As a result of the procedure described above, the ferrous-based metal band received on one side a zinc coating having a layer weight of 57.95 gm/m . When subjected to classical quality tests, including
In terms of adhesion, the zinc coating proved to be excellent. The uncoated side of the strip had a light oxide film, and no zinc stains appeared.
EXAMPLE II
A metal base band was covered on one side.
28 gauge ferrous with aluminum, using the apparatus and coating procedure set forth in Figure 1. At a strip speed of 15 per minute, the strip was able to enter the nozzle at a temperature of approximately 704°C. The temperature of the molten coating bath was maintained at 690°C,
A protective nitrogen atmosphere was introduced into the nozzle at a flow rate of 8.49 cubic meters per hour. A dew point of -23°C was recorded at changeover roller 12, along with less than 100 ppm of oxygen.
The jet nozzle 19 had a nozzle gap of 0.76 mm and was supplied with air at a delivery pressure of ·
Yo
0.5 kg/cm . The nozzle was kept at a height of approx. l i
mind 101 mm above the bath level and was directed upwards at an angle of approximately 10°. The roller 14 had a diameter of 304.8 mm. The nozzle was held at a distance of approximately 3.18 mm to approximately 4.76 mm from the coated side of the strip.
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As a result of the above procedure, the ferrous base metal strip was provided on one side with an aluminum coating having a coating weight of 100g.
57.95 gm/m · When subjected to traditional quality tests, including adhesion tests, the aluminum coating proved to be excellent.
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Modifications of the invention may be made without departing from its spirit. For example, in both embodiments in which oxide film is formed on the uncoated side of the ferrous base metal strip, the oxide film does not have to be
I must be removed by acid cleaning. The oxide film j is adherent and readily accepts pretreatment;
, and for painting, for example phosphating, in these circumstances, ¡A
The uncoated side with a pre-treated oxide film demonstrates excellent painting properties.
In the modalities described above, the acabaq i
d or the coated side has been described with regard to the ¡ í
using a jet blade. Naturally, various other finishing techniques can be used, including asbestos-based cleaning agents and similar.
Having sufficiently described the nature of the invention, as well as the manner of carrying it out in practice, it should be noted that the provisions indicated above are susceptible to modifications in detail as long as they do not alter their fundamental principle.
Contents6
30 sheets
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37 members in 23 offices
Members37
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| NL7702760A | Netherlands (Kingdom of the) | A | |
| DE2712003A1 | Germany | A1 | |
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| PL196737A1 | Poland | A1 | |
| ES456984A1This record | Spain | A1 | |
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| US4082868A | United States of America | A | |
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| AU2304377A | Australia | A | |
| US4114563A | United States of America | A | |
| US4152471A | United States of America | A | |
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| NL178017C | Netherlands (Kingdom of the) | C |
Numbers
- Publication
- 456984
- Application
- 456984
Titles
- English
- PROCEDURE AND APPLIANCE TO PRODUCE A CONTINUOUS FERRY-BASED METALLIC BAND, COVERED ON ONE SIDE ONLY WITH COVER METAL.
Classification
- IPC, 2
- B05C9 02
- C23C2 00