Method of unilateral coating of metal strip and apparatus therefor

<td>POLAND REPUBLIC ICE</td><td>PATENT DESCRIPTION</td><td> 124706</td>

<td></td><td>/ Additional patent to patent no</td><td></td>

<td></td><td>• Submitted: 17.03.77 (P. 196737)</td><td>Int. Cl³</td>

<td></td><td>Priority: 18.03.76 United States</td><td>C23C 1/00</td>

<td>OFFICE</td><td>America</td><td></td>

<td>PATEOTOWY</td><td>The application was announced: 02.01.78</td><td></td>

<td>PRL</td><td>Patent description published: 15.04.1985</td><td></td>

Inventor: —- Patented: Armco Steel Corporation, Middletown. (United States of America)

Method of one-sided coating of the metal strip and a device for one-sided coating of the metal strip and

The subject of the invention is a method of one-sided coating of a metal strip and a device for one-sided coating of a metal strip.

A known method of one-sided coating of a metal tape is that the tape is coated on one side with a protective, non-wetting coating layer. The tape is then coated in a hot bath, after which the protective layer is rinsed off or removed.¹⁰

A method of coating a metal strip is known from US Pat. No. 3,383,250, in which the cleaned strip is heated on both sides to the temperature at which coating is carried out, and then subjected to ¹⁵unilateral oxidation tape. The strip is then introduced into a molten metal bath where the non-oxidized side of the strip is coated.

tAnother method, the tape is coated into ³⁰bath on both sides and then the coating on one side of the tape is removed using a jet knife or an air nozzle. The residue of the coating metal is then removed by electrolysis.

Recently, electrolytic coating has been used to produce single-coated products. For this purpose, the coated tape is passed through a roller partially immersed in the electrolyte. The exposed side of the tape is coated with a layer of metal while the other side protected by the roller on which it is moved remains uncoated.

Although the desired products can be obtained by using the methods previously known, they have some disadvantages. The methods known hitherto are expensive, consist of more stages than ordinary coating in a hot bath and require the use of special equipment. The currently used screening techniques lead to the production of an uncoated surface of insufficient quality, unsuitable for applying a paint with a high degree of smoothness.

It is known from German Patent No. 2406939 to completely coat the surface of pipes and rods using the pressure of hot metal. However, this process cannot be used for one-sided coating of a metal strip.

Known metal strip coating devices include a bath housing a molten metal bath, rollers for introducing the belt into the metal bath, and rollers for removing the coated strip from the metal bath. A jet knife equipped with a narrow nozzle through which a high pressure gas stream is extracted is used to remove excess coating metal or to clean the surface of the strip from the coating metal. .

The tape according to the method of the invention

12470«

124 706 moves over the coating metal bath so that the bottom side of the tape to be coated with metal is in continuous contact with the meniscus formed on the surface of the coating metal bath, while the side of the strip to be coated with metal is maintained in an oxidized state, by restricting oxygen access to the tape before the tape contacts the coating metal bath meniscus. The coated strip is then torn off into the coating metal bath meniscus and excess metal coating the strip removed with a gas stream.

Preferably, the tape is guided at a distance of 9.9 mm above the surface of the coating metal bath. I l The surface of the belt is kept in a nonfcstleiHonyim * state by^?impregnating the tape with a protective atmosphere by coating the tape with a coating metal, after which the tape is brought into contact with the ambient atmosphere.

Preferably, the coated side of the strip is finished by exposure to air or to a non-oxidizing protective gas.

Preferably the surface of the strip is maintained in an oxidized state by surrounding the strip with a non-oxidizing protective atmosphere during the coating operation _vand finishing the tape.

Preferably, the coated and finished tape is exposed to the ambient atmosphere at a temperature above the limit temperature of oxide film formation on the uncoated side of the tape.

Alternatively, the coated and finished strip is cooled to a temperature below the limit temperature of oxide film formation on the uncoated side of the strip.

Preferably the belt path lowers towards the coating metal bath, after the meniscus is formed between the belt and the bath, maintaining a constant level of the coating metal bath.

• According to the solution for coating a metal strip comprising a tub containing a bath of molten coating metal and rollers guiding a coated strip and a jet knife for removing excess coating metal from the coated side of the strip, one guide roller is located above the coating metal bath and a contact zone of coated metal The coated tape is surrounded by a shield connected to the inlet with a source of a protective atmosphere.

Preferably, the single guide roller is positioned above the coating metal bath that leads the tape to contact the surface of the bath and discharges the tape in an upward direction.

Preferably, the cover has a top wall, a front wall, a rear wall and side walls extending into the metal bath, a front wall opening and an inlet opening connected to a source of a protective non-oxidizing atmosphere.

The cover walls completely surround the single guide roller, preventing ambient air from entering it.

Preferably, the device comprises a cooling cover, one end of which is sealed to the cover in the outlet area of ​​the cover, and the other end being provided with an outlet of the coated tape and an inlet connected to the source of the non-oxidizing protective layer.

The cooling cover has an inlet connected to a source of a protective non-oxidizing atmosphere and cooled rollers embedded in the cooling cover between which the tape passes.

The cooling cover has an inlet connected to a source of protective non-oxidizing atmosphere, at least one inlet of non-oxidizing atmosphere from the cooling cover, at least one heat exchanger cooling the exhausted non-hot atmosphere, and at least one outlet supplying a cooled atmosphere to the cooling cover. ,_; .

The other end of the cooling shroud has an outlet facing downwards reaching into a water bath, an inlet connected to a source of a non-oxidizing protective atmosphere, rollers guiding the tape through the cooling shroud, and includes a water bath ...

Preferably, the jet knife is located outside the shell.

Preferably, the device comprises baffles cooperating with a jet knife to remove gas from the uncoated side of the belt. Preferably, the jet knife is located within the sheath and is connected to a non-oxidizing protective atmosphere source.

Alternatively, two guide rollers are used.

In such a device there are two guide rollers above the coating metal bath, and the coating metal bath zone in contact with the coated tape is surrounded by a shield connected to the inlet with a protective atmosphere source.

Preferably, the two guide rollers are spaced apart, parallel to each other, such that the tape contacts the meniscus on the surface of the coating metal bath on the track between the rollers.

Preferably, the first roll of a pair of guide rollers is located at a greater distance from the bath surface than the second roller.

Preferably, the cover has a top wall, a front wall, a rear wall, side walls extending deep into the metal bath, an outlet of the coated tape and an inlet opening connected to a source of a protective non-oxidizing atmosphere.

Preferably, the front wall of the sheath is located between the first roller and the second roll and has an outlet opening through which the tape contacting the meniscus of the coating metal bath passes, the sheath surrounding the first roll. The jet knife is located outside the shield.

Preferably the device comprises a sealing block mounted on a bracket outside the front wall of the shield in the opening of the front wall in contact with the tape and partially closing the opening of the front wall.

In the alternative, three guide rollers are used. In such a device there are three guide rollers above the coating metal bath and the coating metal bath zone in contact with the coated tape is surrounded

124 706 with a shield connected to the outlet with a protective atmosphere source.

Preferably, the third guide roller located between the first guide roller and the second guide roller is closer to the bath surface than the other two guide rollers.

Preferably, the cover has a top wall, a front wall, a rear wall and side walls extending deep into the metal bath, an outlet of the coated tape and an inlet opening connected to a source of a non-oxidizing protective atmosphere. The cover walls surround all three rollers, protecting them from the effects of the ambient atmosphere.

Preferably, the jet knife is located within the sheath and is connected to a source of non-oxidizing protective atmosphere.

The device comprises a sealing block mounted on a bracket outside the front wall of the shield, in the opening of the front wall in contact with the tape and partially closing the opening of the front wall.

Preferably, the third roller is mounted along the bottom edge of the sealing block.

The method and apparatus can be used to produce metal strip coated on one side with hot metal coating baths such as cyan, cy / z alloys, aluminum, aluminum alloys, tin and lead alloys, lead and the like. The method and apparatus of the invention have been described for use in the production of an iron metal strip coated on one side with zinc or aluminum, these examples not limiting the scope of the invention.

One-sided coated tapes are used in the automotive, equipment and construction panels industries. The galvanized side of such a product has excellent corrosion resistance, while the non-galvanized side is characterized by excellent paint pleasure and can be easily welded using the spot method and the like.

In cases where it is desirable that only one side be protected against corrosion, it is understood that the one-side coated product should include a suitable coating to protect the coated metal and the uncoated side should be coated with high gloss paint or subjected to another finishing treatment.

The subject of the invention has been shown in the embodiment in the drawing, in which fig.

is a schematic diagram of a device for one-sided coating of a metal strip with two guide rollers in axial section, fig.

- the device in cross section along the line 2-2 in Fig. 1, Fig. 3 - section of the tape in contact with the meniscus of the coating metal, in axial section, Fig. 4 - section of the tape in contact with the concave meniscus of aluminum, in the axial section, Fig. 5 - a translation of the device embodiment with three guide rollers, in axial section, Fig. 5a - a fragment of the device according to Fig. 5, Fig. 6 - the device according to Fig. 5 in cross section, Fig. 7 - embodiment of the device with one guide roller, in axial section, Figs. 8, 9, 10 - solutions of the device according to Fig. 7 with a cross-sectional acid cleaning apparatus, Figs. 11 ^ 13, 14, 16, 17 - examples embodiment of the apparatus with one guide roller, in axial section, Fig. 16 - embodiment of the apparatus with three guide rollers, in axial section, Fig. 18 - a fragment of the device according to Fig. 17, in top view.

In all embodiments of the invention, a conventional strip treatment is applied prior to coating. For example, the belt can be cleaned in an oxidation-protected heater, annealed and cooled in a protective atmosphere at high temperature. The accuracy of the pretreatment of the strip is not a limitation of the invention as long as the appropriate temperature is maintained during the coating of the strip and the treated surface is clean and free of oxide. Suitable methods for preparing the tape are discussed, for example, in US Patent Nos. 2140893, 3320085, 3837790, and 3936543.

A first embodiment of the invention is shown in Figs. 1-3. The coating tub 1 shown in Fig. 1 contains a molten coating metal bath 2. The metal iron band, one side of which is coated, is shown in the drawing, in Fig. 3 the cover 4 is an extension of the usual cover (shown fragmentarily in Fig. 5) tape production apparatus. The cover 4 can be an integral part of the cover 5, or it can be attached to it in a gas-tight manner. Favorable sealing. non-gas-tight 6 is placed between the cover 4 and the cover 5. The seal 6 can be made in any convenient form. For example, nipple 6 is shown with two pairs of sealing roses 7-8 and 9-10.

The cover 4 consists of a front wall 4a, a back wall 4b, side walls 4c and 4d and a cover 4e. Figures 1 and 2 show that the front and rear⁴θ and the side walls reach for a bath 2 of molten metal. The front wall 4a has a V-shaped cut-out or opening 11, part of which extends above the bath 2 and marks the exit of the strip 3 from the cover 4. The opening 11 should have a width of⁴⁵ up to the width of the coated iron band. The tape 3 passes between the sealed rollers 9-10 and 7-8 to the roll 12 through the cover 4. From the roll 12, the tape moves to the roll 13 carrying the surface of the coated tape closer to the surface⁵⁰ than the '2a molten coating bath. From the roll 13, the belt passes through the opening 11 of the cover 4 to the roll 14 and from this place the molten metal coating bath rises and leaves. Rollers 12, 13 and 14 are attached in a known manner, which has not been⁵⁵ depicted in the figure.

The front wall 4a of the cover 4 may be provided with a support 15 housing an elongated, plate-like block 16 made of graphite or other suitable material serving as a seal for closing a larger part of the opening in the front wall of the cover. The graphite block 16 is raised and lowered within the support and is supported above or above on the coated surface of the iron-based metal strip 3.

It is important that the cover 4 is in the non-oxidizing atmosphere so that the surface of the strip 3 remains clean and free of oxide before coating. The casing 4 has an inlet 17 through which a non-oxidizing gas such as nitrogen, inert gases and the like is introduced. The non-oxidizing atmosphere in the enclosure 4 must be maintained at a slight overpressure such as the surrounding oxidizing atmosphere could not enter through the opening 11, in particular parts thereof 11a and 11b (see Fig. 2) not sealed with a seal 16. In a similar manner, it is preferable to use an inlet of a non-oxidizing atmosphere 18 between sealed pairs of rollers 7-8 and 9-10. In addition, it is preferable that in chamber 18a the non-oxidizing atmosphere is at a pressure slightly higher than the pressure in the casing 4 and higher than in the casing 5. The non-oxidizing atmosphere in the casing 5, which cannot be contaminated even when the apartment is closed during operation, is protected by casing 4 . Since the pressure of the non-oxidizing atmosphere in chamber 18a is higher than the pressure in the sheath 5, this can also prevent contamination of the atmosphere in the sheath 5 from sources coming from the outlet of the tape making apparatus. The coated side of the tape is finished with a jet knife 19.

The operations performed on the described device can be represented as follows. The metal strip 3 passing between and through rollers 7-8, 9-10, 12, 13 and 14 as indicated by arrows A (Fig. 1) can cause the formation of small wrinkles and waves on the surface 2a of the bath 2 of the molten coating metal. This causes the tangential side of the metal strip 3 to contact the molten coating metal. The meniscus, formed as a result of surface tension and wetting properties of the coating metal, coats the tape side continuously in contact with it. Meniscus 20 are shown in Figs. 1-3. Using the properties of meniscus 20 one can coat the tape 3 on one side without having to dip it in the bath 2. Thus, the tape 3 after passing through the roller 14 is coated on the side 3a and uncoated on the side 3b.

In Figs. 1-3, the thickness of the band 3, the distance of the rollers 13 and 14 from the surface 2a of the bath 2 and the height of the meniscus have been increased in proportion. The distance of the strip 3 from the surface 2a of the bath 2 enabling the formation and maintenance of a permanent coating meniscus varies depending on the coating metal used and its surface tension and wetting properties. Excellent results for most coating metals are obtained when a distance of about 0.8 ohms or less is maintained.

It is advantageous to place the roller 13 slightly higher above the surface 2a of the molten coating metal 2 and the rollers 14. Also in this case for the clarity of Figure 1 this difference has been exaggerated. The expected height difference is about 0.3 to 0.6 cm. The purpose of this height difference is to further protect against splashing or damage to the roller 14 by the roller 13 located below the nozzle 4 and therefore invisible to the operator.

The jet knife 19 can be positioned slightly below the axis of the roller 14. The distance in the jet knife is fixed to the axis of the roller 14 depends mainly on the diameter of the roller 14 and the speed of belt travel. It is important that the jet cutter does not blow through the contaminated atmosphere opening 11 or damage the meniscus 20. The jet cutter 19 can be positioned above roll 14 as shown by dashed line 19a. To ensure proper blasting, it is important that the cross profile of the strip 3 remains flat. For this purpose, it is preferred that the support roller (shown in dashed line 21) is attached opposite the jet knife 19a.

A further embodiment of the invention is shown in Fig. 5. In this solution, elements similar to the solution in Fig. 1 have the same numbers. The difference of the solution according to Fig. 5 is that an additional roller 22 is placed behind the cover 4a between the rollers 13 and 14. The roller 22 is attached by means of a suitable fastening device (not shown in the drawing) in such a way as to deflect the belt travel between the rollers 13 and 14 a bit down. This allows the rollers 13 and 14 to be slightly moved away from the surface 2a of the molten coating metal bath 2, which protects them against splashing or destructive metal coating. The length of roll 22 is slightly smaller than the width of the moving belt.

Similarly to Figs. 1-3, also in Fig. 5 the thickness of the strip 3, meniscus height 20 and distance of the rollers 13 and 14 from the surface 2a of the molten coating metal bath 2 have been exaggerated for image clarity 2. The deflection of the strip 3 by roll 22. The amount of deviation is usually about 6.6 - 1.3 cm, which allows the rollers 13 and 14 to be positioned at a greater distance from the bath surface 2a similar to the solution shown in figure 1. All other parts of the apparatus in Fig. 5 and the operations can be the same as shown in Fig. 1. The meniscus produced is talc itself as in Fig. 3. The same meniscus occurs using any suitable coating metal. However, while usually the meniscus is formed in the form shown in Fig. 3 it has been found that when used as aluminum coating metal the roll 22 can press the tape slightly lower to the surface 2a of the molten coating metal bath 2 because the aluminum forms the meniscus 23 shown in figure 4. Thus, when used as aluminum coating metal, the tape can move slightly closer to the surface of the molten coating bath, which ensures unilateral jpowflelkanliie. Shown in fig. 5 the solution can be modified by placing the roller 22 on the sealing block 16. This is shown in Figure 5a, in which the roller 22a (corresponding to the roller 22 in Figure 5) is rotatably mounted on the sealing block 16a (corresponding to the sealing block 16 in Figure 5) by ordinary devices (not shown). Roller 22a is attached along the lower edge of the sealing block 16a and contacts the uncoated side 3b of the strip 3 to achieve the same

124 706 as described with reference to roller 22 in Fig.

5. Also according to the invention, the roller 22 shown in Fig. 5 can be placed in the cover 4, which only requires the correct positioning of the rollers 13 and 14 in order to adapt them to the above change, δ

Figure 6 is similar to Figure 2 (similar parts are marked with similar numerical indices) is a cross-sectional view illustrating the front wall 4a of the cover 4 shown in Figure 1 or

5. Fig. 6 differs from Fig. 2 in that the bracket 15 and the graphite seal 16 are eliminated, and the gap forming the outlet of the nozz nozzle is lowered slightly above the strip 3 to reduce the outlet opening. Thus, in the solutions shown in Fig. 1 and 5, the graphite seal 16 and bracket 15 can be eliminated and then protection against the oxidant atmosphere entering through the face ensures that the sheath 4 maintains the non-oxidizing atmosphere under slight overpressure. ²⁰

A further embodiment of the invention is shown in Figure 7 where the coating vessel comprises a molten coating metal bath

25. The cover 26 forms a further part of the cover 27 for pretreatment of the belt. In addition, the nozzle may be an integral part of the pre-treatment cover 27 or may be blocked with it in a gas-tight manner. The seal 28 is located between the cover 26 and the cover 27. The seal can be made in any convenient form. For example, it can be two pairs of sealing rollers 29-30 and 31-32. The inlet of the non-oxidizing atmosphere can be placed between pairs of rollers. The cover 26 consists of a rear wall 26b and side walls 26c. front³⁵the rear and side walls are immersed in a bath of molten coating metal 25.

The metal band 3 is moved between rollers 31 and 32 and 29 and 30 forming a seal. The belt then passes over the roller 34 rotating in the opposite direction and through the roller 3i5 carrying the surface of the belt closer to the surface of the molten coating metal bath 25a. Roll 35 moves the coated tape up the coating bath 25, after which the tape leaves the shield &lt;26 through the outlet slot 36.

The casing 26 is protected by an inlet 27 of the non-oxidizing atmosphere, which is kept inside the casing by a slight overpressure so that the surrounding oxygen-containing atmosphere 50 does not enter the nozzle through the inlet opening 36. Sealing 28 and its inlet 33 for the non-oxidizing atmosphere meet the same meaning as described for the seal 6 and outlet 18 shown in Fig. 1. In addition, seal 28 and outlet 33 are particularly important when closing the cover 26. According to the example shown in Figure 7, the jet knife 38 is introduced through the cover

26. The jet knife operates using the same non-oxidizing gas as found in the nozzle.

The solution according to Fig. 7 differs from the solution shown in Figs. 1 and 5 in that all coating and finishing operations are carried out in the sheath 26 and in its protective, non-oxidizing atmosphere. Subjecting the metal iron band moving in the direction of the arrow B to the operations shown in Fig. 7, a small wave is formed on the surface 25a of the molten coating metal bath 25 resulting from the formation of meniscus 39 through the surface of the strip 3 which, passing through the roller 35, slides over the surface 25a of the molten metal bath undergoing continuous contact coating. Rollers 34 and 35 as well as jet knife 38 can be mounted with conventional clamping devices (not shown). The metal band after going up near the outlet 36 is coated on side 3a and uncoated on side 3b. The coated side is finished with a jet knife 38, placed in any position, provided that it does not damage the meniscus 39 and the upper surface 25a of the molten coating bath 25. If it is necessary to position the jet cutter 38 above the roll 35, at a distance such that this may cause twisting of the transverse profile of the strip 3, the roll can be retracted as described in Fig. 1 to ensure that the flat profile of the strip is maintained during the finishing operation.

In the described embodiments of the invention, the strip 3 is exposed to a narmalned atmosphere at a suitably elevated temperature at which visible amounts of oxide form on the uncoated surface of side 3b. During short-term exposure to external factors, a thin layer or oxide film is formed on the tape. The film adhering to the base metal consists mainly of FeO, then covered with FeaO mud₄and finally a layer of FeaO₃. If the temperature of the strip exposed to the oxidizing atmosphere is lower than about 556 ° C, the FeO layer does not form, which is the case e.g. when zinc is used as the molten coating metal. When aluminum is used as the molten coating metal, the strip temperature is above 550 ° C and a FeO layer is formed.

As previously mentioned, the oxide layer can be removed using an acid purification method. The term "acid purification method" was used intentionally to distinguish it from "acid digestion". The difference between purification and acid etching lies in the depth of acid action. Acid digestion refers to severe action to remove sediment from a generally finished product. The first phase of acid purification is a purely chemical process and consists in dissolving the oxide film. The oxide films dissolve and at different speeds. The dissolution rate of FejO &lt;is controlled because it dissolves slowly. Thin, porous oxide films can be removed using the phenomenon of acid penetration and action directly on the metallic substrate. The rate of removal of oxide can be increased in a number of ways. First of all, the rate of chemical reaction can be increased by increasing the temperature of the acid bath or by increasing the acid concentration. In addition, speed

124 706 oxide removal by acid penetration can be increased by applying an electric current. This increases the dissolution of the metal in the substrate and local surface disorders caused by the evolution of hydrogen.

The acid cleaning of the one-side coated metal strip poses a significant problem of such removal of oxide from the uncoated side of the iron strip, during which etching of the coated side is minimized. This condition decides that the electrolytic acid purification process is preferred.

The acid purification process entails a series of interrelated parameters forming a huge number of combinations of these parameters, each of which is suitable for the proper removal of visible oxide film from the uncoated side of the tape. The basic idea is to clean the acid with one-side coated metal tape.

The basic parameters of the acid purification process include the type of acid used, the distance of the electrode and tape, the time of immersion of the tape and the current density on the electrode. To reduce the precipitation of the coated side of the tape, it is preferred to use a dilute acid solution, generally at a concentration of 1% by volume or lower. The type of acid used depends on its effectiveness, price, availability and requirements for liquidation of pollution and requirements related to ventilation. Most common acids such as sulfuric, phosphoric, hydrochloric and nitric acid can be successfully used for this purpose. Sulfuric and phosphoric acids are slightly more favorable not only because of their effectiveness, but also because of their lower tendency to smoke.

If you want to minimize pickling and staining on the coated side, keep the acid temperature low (below about 38 ° C). The distance between the electrode and tape should be as small as possible to increase the efficiency of the process. The distance of the electrode is measured continuously to avoid contact with the tape. The immersion time of the tape should also be as short as possible, limited to the time needed to remove the oxide layer that is visible. Practically, however, the time of immersion of the belt depends on the size of the reactor and the speed of belt movement. What is needed is the smallest current density in a given installation. A current density of 0.21 to 6.43 A / cm is sufficient². A significant increase in current density is useless and non-electronic.

Figure 8 shows a modified galvanic chamber in which an acid purification operation can be performed. Fig. 8 shows a tank 40 containing a dilute acid bath 41. Tape 3 coated on the side 3a and with non-liviolevicillin on the sitlroinlie 3b prlzepuisBearing in the bath 41 via a roller 42 fitted in the usual way, which is not shown in the drawing. A block made of a reactive metal such as zinc is placed in a way so that it fits close to the uncoated side of the iron strip 3 and is held in this position by a suitable device, which is not shown in the drawing. The metal block 43 is electrically connected to the metal strip with an iron foundation through the element 44 and the roller 42. However, the glass does not increase⁵ The effect on the metal substrate is the rapid evolution of hydrogen on the uncoated surface of the belt 3, which helps to remove oxide from it. Hydrogen that also flashes out of block 43 made of reactive metal contributes to the removal of¹⁰ oxide from the uncoated surface of the tape 3b. Other reactive metals such as magnesium and aluminum may also be used.

In the tests, Ejarówmo O, 5P / o silicic acid and. Oj5P / o phosposic acid were used¹⁵ fora, like an acid bath 41 using it at 32 ° C. Tape 3 is coated on the side 3a with zinc, and on the side 3b with oxide formed as a result of exposing the tape at a temperature of about 480 ° C. "²⁰ coating operation in a protective atmosphere, on Jainain, conception. Workable and zinc (block 43 is placed at a distance of about 0.32 cm from the surface of the belt 3b. Oxide is removed from the surface 3b in about 3 seconds, with²⁵ the zinc coating side 3a of the tape remains intact.

Figure 9 shows another apparatus for cleaning and acid strip 3 coated on it₃₀ iraioo metal after isitaonlie 3a and itleinek after stmruie 3b. In this version, the vat 45 contains a dilute acid bath 46. The belt 3 is passed through a submerged roller 47 and the electrode 48 is placed in contact with the uncoated side of the belt₃₅ 36. The electrode and tape (via roller 47) are connected to the power source 49 with the supply lines 50 and 51 respectively.

It has been found that by using instead of connecting 51 a power source 49 with a roller 47 (known as a sliding contact lufo contact roller) to supply the current to the tape, a molten metal bath can be used, thus eliminating damage to the surface of the tape due to scratches or sparks. The guide wire 51 can be

4 $ connected to tub 1, as long as it is made of metal. This solution is exemplified in Fig. 1. Alternatively, the guide wire 51 can be connected to the electrode 51a immersed in a molten metal bath.

This solution is exemplified in Fig. 5. It is understood that the connection methods of Prism 51 as shown in Figs. 1 and 5 can be applied to all coating versions described when the se acid purification methods described in reference to Fig. 9 are used.

It was found that the solution presented in Fig.

9, in which the current is supplied from an external source 49 is more effective than the version shown in Fig. 8. The dissolution of iron • by the oxide layer increases with the evolution of hydrogen which accompanies the removal of oxide from the metal strip with an iron base 3. You can use or a source of direct or alternating current, with alternating current being more advantageous due to the fact that the pulsation of the current increases the speed of the acid purification process. The electrode 48 can be made of an electrically conductive and passive material relative to the diluted acid bath 46. Stainless steel is best for this purpose. Electrode 48 can also be made of other materials such as platinum and lead.

A diluted acid bath 46 containing 0.5% sulfuric acid at a temperature of about 32 ° C was used in the test. As a power source, a welding DC generator was used to supply current of about 11a amperes to the cathode strip 3 and the anode, made of stainless steel electrode 48. On page 3b of strip 3 there is an oxide film formed by exposing the strip to 482 ° G after coating in an oxygen-resistant atmosphere. The oxide film is removed in less than 6 seconds, which is accompanied by the rapid evolution of hydrogen on electrode 48 and the surface of the strip 3b. During immersion less than 4 seconds, no staining is observed on the zinc-coated side of tape 3a. During a dipping time of 6 seconds, a number of pitting and stains are observed on the zinc coated side of the tape. The stainless steel electrode is placed approximately 1.3 cm from the surface of the 3b side of the tape.

In other tests, a diluted acid bath 46 containing 0.5% sulfuric acid at 26.7 ° C was re-used, and stainless steel was again used as the electrode. Tape 3 is coated on page 3a with zinc and on page 3b with oxide formed by exposing the tape at a temperature of about 480 ° C after it leaves the protective atmosphere during coating to air. An AC source was used to provide current of approximately 9 amperes. The electrode 48 was placed about 2, δι cm from the tape surface 3b. Under these conditions, the oxide film is removed in about 2 seconds. No pitting is observed on the coated side of the strip 3a.

A variation of the version illustrated in Figure 9 is shown in Figure 16, in which the tape is again indexed 3, the zinc coated side is index 3a, and the non-coated side is index 3b. In this version, tape 3 is passed over roll 52, and the dilute acid bath 46 shown in Fig. 9 is replaced with a sponge 53 saturated with dilute acid.

The sponge 53 is mounted with a mounting device 54, which can be made of stainless steel or other material that is not chemically resistant or crushed under the influence of acid. The sponge 53 and handle 54 are connected to a power source 55 via a 56 lead. The tape is also connected to a power source via a roller 52 and a 57 lead. Alternating or direct current source can be used as current source 55. The inlet device 58 is located in the sponge holder 54 and is supplemented by it as acid.

The solution shown in Fig. 10 is advantageous because no special tank is needed and the sponge 53 is an oxide removal and cleaning device. Pay attention to the necessity of replacing the sponge if it is worn or if there are so many particles deposited on the sponge that it may cause the tape to be scratched 3.

After acid cleaning, the well-known rinsing and drying steps should be used to limit further acid action on both sides of the belts. Diluted acids, different from those listed above, are used for this purpose, the selection of the most advantageous of which is not difficult for a skilled person. Diluted acids may contain commonly used additives such as surfactants, inhibitors, anti-foaming agents and the like.

The steps of acid washing, rinsing and drying can be eliminated if one-sided coated iron itimist poisoistlarwli iSlia in a cooling atmosphere until the temperature of the belt decreases, in which there is no visible formation of oxide on the uncoated side.

This solution is shown in Fig. 11. The device shown in Fig. 11 is the same as in Fig. 7 and similar assemblies are marked with similar numerical symbols. The solution shown in Fig. 11 differs only from that shown in Fig. 7 "in that a cooling cover 59 has been added to the cover 26 near the outlet 36. The cooling cover 59 is provided with an outlet 60. The length of the cooling cover is chosen so that the time during which the tape 3 leaves it through the outlet 60 is sufficient to cool the tape to a temperature of about 156^{| About}C, i.e. to a temperature at which no visible amounts of oxide are formed on the uncoated side 3b of the belt.

Of course, the cooling cover 59 must be filled with a non-oxidizing atmosphere, which is introduced into the enclosure 59 through the outlet 36. If desired, the cooling cover 59 may be provided with an additional inlet 61 of the non-oxidizing atmosphere. In the case of the embodiment shown, the cooling cover 59 is shown simply by attaching it to the cover 26. It is understood that the cover portion 26e that is visible below the cover 59 and containing the outlet 36 can be eliminated. Except that the coated tape is allowed to cool in an atmosphere that protects against the formation of visible amounts of oxide on the uncoated side, the remaining operations in the version shown in Figure 11 are the same as those described with reference to Figure 7.

The length of the cooling jacket, in which the coated strip is allowed to cool to a temperature at which there is no noticeable oxide formation on the uncoated side, may be reduced if a device is used to accelerate the strip cooling process. Fig. 12 shows the solution completely identical to Fig. 7 and again similar fragments are marked with similar numerical indexes. In the solution presented in Fig. 12 a cooling cover 62 similar to the cover was used

124 706 shown in Fig. 11 and equipped, if necessary, with an additional inlet 64 of non-oxidizing atmosphere and outlet 63. The belt 3 passes between the cooled rollers 65 and 66 to lower the temperature of the belt, which allows shortening of the cooling cover 62. Also in this case it is possible to eliminate the portion 26e of the nozzle top wall 26d below the cooling cover 62 and containing the outlet 36.

Another solution for protecting the tape from the formation of visible amounts of oxide is shown in Figure 13. In this case the device is essentially the same as in Figure 7 and the coating operation is carried out in the same way. The cover 26 is provided with a cooling cover 67 provided with an outlet 68. A protective atmosphere is supplied to the cover 67 from the cover 26 and if necessary via an additional inlet 69. In this solution, part of the protective atmosphere is discharged through the inlet 70 to a heat exchanger schematically represented and marked by 71 and provided with a fan or the like. The cooled protective atmosphere from the heat exchanger is recycled to the cooling jacket 87 via outlet 72, which causes the cooled protective atmosphere to hit the belt 3. In order to increase the cooling efficiency, a second heat exchanger 73 inlet 74 and outlet 75 opposite the outlet 72 may be used. The use of opposite directed streams 7 and 75 is intended to ensure the flat configuration of the belt cross section 3. The use of heat exchangers 71 and 73 allows to shorten the cover 67 compared to the cover 59 shown in Fig. 111, because the cooling efficiency of the strip 3 increases.

Another device for cooling the strip is shown in Fig. 14. In this embodiment, the coating method and apparatus for this purpose are the same as those shown in Fig. 7, and similar fragments have been designated with similar face indexes. The solution shown in Fig. 14 is based on the idea that the one-sided coated tape can be cooled in a water bath without the formation of visible oxide film on the uncoated surface of the tape. The cover 76 is enlarged above the top wall 26d of the cover 26. A guide roller 77 is located in the upper part of the cover. The cover 78 is located below the surface of the water bath 79 in the respective tank 80. The tape 3 enters the cover 26 through the outlet 36 and leaves the cover 78 going to water bath 79. Using a submerged roller 81, the tape is passed through a water bath 79 and directed upwards to remove it from the water bath. Part 78 of the cover 76 is provided with a non-oxidizing outlet of the protective atmosphere 82 passing from the cover 76 and steam formed as a result of the strip 3 submerging in the water bath 79. The outlet 82 is provided with a control valve 82 and through the outlet the flow can be measured by counting symbol 84. Partitions 78a and 78b may be used to reduce backward diffusion of water vapor into shield 76. It is understood that the non-oxidizing protective atmosphere in the sheath 76 passes from the nozzle 26 through the outlet 36.

In all embodiments shown in Figs. 11-13, the protective atmosphere contained in the cooling jacket must be under a pressure that prevents atmospheric access from the surroundings through the outlet of the cooling jacket into its interior.

Figure 115 shows a modification of the solution of Figure 5 in that the coating and finishing operations are carried out in a protective atmosphere. To this end, the bath 85 is filled with a bath of molten coating metal 86. The shell 87 is connected or forms a whole with the pre-treatment shell 88 (shown fragmentarily). The seal can be placed between the cover 87 and the cover 88 fulfilling the same role as the seal 6 shown in figure 5. For illustrative purposes, the seal 89 is shown to be made of two pairs of sealed rollers 90-91 and 92-93, and an inlet of non-oxidizing atmosphere 94 between them, which performs the same function as the inlet 18 shown in Fig. 5. Iron metal band again marked with 3 is passed through the same way. the downwardly rotating roller 95 corresponding to the roller 12 shown in Fig. 5. The belt 3 is also passed under rollers 96, 97 and 98 serving the same role as the rollers 13, 14 and 22 shown in Fig. 5. The cover 87 is built of front wall 87a, rear wall 87b and side walls 87e. As shown in the sketch, the front, rear and side walls are partially immersed in a bath 86 of molten coating metal.

The cover 87d of the sheath 87 is provided with a non-luminous arbor 99, and a vitreous 100 through which the band 3 passes. The jet knife 101 is mounted in the sheath 87 and can be positioned in the sheath in any position provided it does not damage the meniscus 102. Attaching the roller or a jet cutter (which is not shown in the drawing) can be implemented as described in relation to Fig. 1 in relation to a jet cutter.

In the solution according to Fig. 15, the strip 3 is coated on side 3a and uncoated on side 3b. The solution of Fig. 15 differs from that of Fig. 5 mainly in that the coating and blasting operations are carried out in an atmosphere of the protective sheath 87 eliminating the block 16 needed for maintaining tightness in Fig. 5. The one-sided coated tape can be passed through outlet 100 into the surrounding atmosphere, after which it must be subjected to appropriate acid purification, rinsing and drying steps as described above. Optionally, the tape can be left in a protective atmosphere (until the temperature is lowered to a level where no oxide formation is observed on the uncoated side of the tape) using any of the devices shown in Figs. 11-14. In the solution presented in Fig. 15 it is possible to eliminate roll 98. The results obtained using this solution are similar to those obtained for the embodiment shown in figure 1, but both the coating and finishing step are carried out in a sheath.

Figure 16 shows a similar solution to that of Figure 7, giving similar parts of the apparatus similar numerical indexes. The coating operation in the version shown in Fig. 16 is the same as that described with reference to Fig. 7. Fig. 16 differs from Fig. 7 in that the front wall 25a of the shield 26 jesit is provided with an opening 103 having dimensions such that the jet knife 104 fits exactly to it in such a way that its rear part remains outside the cover. The opening 103 may be provided with a hinged closure 105 which, while the jet knife nozzle is in operation, remains on the lid of the dyszya 104, and when the jet knife is laid down for cleaning, closes the opening 103 to prevent oxidative atmosphere from entering through the opening 103 Additional attachment devices (not shown) can be used for the jet knife. The bore 103 may be equipped with a sealing washer (not shown) or other sealing device to protect the atmosphere in the nozzle from contaminating the ingress through the bore 103 or next to the jet knife with an oxidizing atmosphere. If the opening 103 is tightly fitted to the conical shape of the jet knife 104, such a sealing device may be an overpressure of the protective atmosphere contained in the shield 26. The solution shown in Fig. 16 can be applied to all versions described above in which the jet knife is housed in a sheath. This solution greatly facilitates periodic cleaning of the jet knife.

In all the described solutions, in which the knife is placed in a sheath, there may be a problem in some cases the formation of dust from the coating metal arising during the jet finishing operations of metal vapors. You can also come across the problem of coating metal impurities arising on the uncoated surface of the tape. Contamination with coating metal is the result of finishing operations during which they are entrained from the edge of the tape. Figs. 17 and 18 show a jet knife design eliminating these problems. For the purpose of exemplary representation in Figure 17, a coating apparatus identical to Figure 7 is shown indicating similar parts with similar numerical indices. It is understood that the nozzle of the structure shown in Figs. 17 and 18 can be applied in exactly the same way to the apparatus shown in Fig. 15 (with or without the use of a roller 98).

In Figures 17 and 18, the mouth of the slit 36 ​​of the sheath 26 surround on three sides a wall or a partition 106, 107 and 108. A jet knife 109 is mounted on the outside of the outlet guard 26, the end of which is extended by a partition 107. This arrangement of the parts and the use of non-oxidizing gas in the jet cutter 109, allows the zinc-coated side 3a of the strip 3 to be finished before being exposed to the surrounding air atmosphere. Coating metal dust or formed spot erosions are blown out of the uncoated side of belt 3b. If the environmental conditions allow it, another partition or vertex (which is not shown) can be passed through the vertex of the partition edge 106 through the edge 108. Such a vertex gives a gap through which the tape 3 can be moved. This vertex will eliminate any undesirable casting deviations that may occur during finishing. The system of baffles causes the uncoated side of the strip 3b to be blown away by dust of the coating metal or erosion and thus cleaned.

The bath temperature depends on the melting point of the metal used for the coating. The bath must be maintained at a temperature that guarantees that the coating metal will be molten and remain molten until the blasting process is complete. In contrast to the known methods of coating using a hot bath, during which, for coating on both sides, the tape is immersed in the bath used according to the present invention, the method of coating the tape on one side does not require a significant amount of heat. Practically, the bath temperature must be exactly the same as that required for good double-sided coating and must be kept as constant as possible to reduce the formation of impurities. A constant bath level must be maintained in all solutions described. To precisely set the bath level, methods known in the art such as a pneumatic displacement chamber or a mechanical displacement plug are used. Preferably, an automatic bath level control method is also used which is well known to those skilled in the art.

The volume of the molten metal coating bath may be less than the volume necessary in the known double-sided coating method with a hot bath. Because, according to the method of the invention, the time of contact of the strip with the bath is much shorter, the dissolution rate of the strip compared to the melting rate of the coating metal, which should be added to the bath will be such that the bath will not be saturated with iron, while it decreases or completely eliminates the process of creating impurities. This gives a defect-free coating.

The temperature of the metal band leaving the preparation cover upstream of the outlet cover depends on the coating metal used. The bath temperature must be high enough to prevent molten coating metal from running on the tape. Thus, the belt temperature cannot be so high as to cause

124 706 excessive mixing of the coating metal with the tape metal.

In all solutions, it is necessary to maintain a non-oxidizing atmosphere in the discharge cover. For this purpose, a non-oxidizing atmosphere containing nitrogen or an inert gas is used. The non-oxidizing atmosphere in the exhaust casing must be kept at a sufficient pressure that prevents the oxidizing atmosphere from entering the exhaust casing through its inlet. The same applies, of course, to the cooling cover, which is shown in Fig. Mn-tM. The sheath temperature must be maintained at a level comparable to that used in known double-sided coating methods. The temperature depends on the belt temperature and the percentage of hydrogen in the atmosphere in which the belt preparation is carried out.

The roller or rollers placed near the molten coating metal bath should have a surface that is not easily wetted by the molten coating metal. This makes it easier to remove the coating metal from the rollers that got on them as a result of accidental splashes. If desired, a roll or rollers positioned near the molten coating metal may be shaped such that unused parts outside the edge of the coated tape are slightly tapered away from the surface of the bath. This further facilitates belt guidance.

Solutions in which the finishing stream is obtained by means of non-oxidizing gas inside the exhaust casing (Fig. 7) have numerous advantages, such as the lack of coating wrinkles even at very low speeds, no effects caused by the action of oxygen on the bath surface, reduction of defects caused by pollution, deprived oxygen shield and effective elimination of slag formation on the surface. On the other hand, during this process, vapors and powder formed during the metal coating should be observed, and the possibility of staining the uncoated side of the tape with the metal coating.

The solution according to Figs. 17 and 18, in which the non-oxidizing finishing gas stream is used outside the chamber but before the belt comes into contact with air, is accompanied by all the above-mentioned advantages of using the finishing stream. This process reduces the accumulation of coating metal dust in the discharge cover, and excludes coating metal staining on the uncoated side of the tape. On the other hand, the non-oxidizing gas used in the finishing stream does not allow for overpressure in the discharge cover.

In the solution of Fig. 1, in which the finishing coating is applied in the atmosphere surrounding the enclosure, the finishing process does not create problems with coating metal slag, dust or staining. The consumption of non-oxidizing atmosphere is also limited. On the other hand, most of the advantages of a process in which the finishing is carried out in a non-oxidizing atmosphere in the wine outlet cover are not obtained. However, this drawback can be partly mitigated by the use of a non-oxidizing atmosphere such as a nitrogen atmosphere after the strip has been exposed to ambient air.

The solutions in which a single roll is used (Fig. 7) are characterized by the simplicity of the apparatus; reducing the problems associated with the shape of the tape and the length of time the tape contacts and the bath meniscus. To ensure the best conditions to prevent iron from entering the bath. When using a single roll, care should be taken to prevent zinc accumulation and the single roll, and the fact that the limited area of ​​the meniscus will require closing of the finishing stream to prevent tearing of the meniscus.

The use of a two-roller system allows finishing in air (as shown in Figure 1) or in an outlet cover as shown in Figure H5i. Longer contact of the meniscus with the tape makes the meniscus less easy to tear. Thus, a longer contact of the meniscus gives a greater opportunity for the iron to dissolve from the belt. The arrangement of two rollers is more complicated than apparatus with one roller and more attention should be paid to the shape of the tape.

The arrangement of the three rollers as shown in Figs. 5 and 15 shows all the advantages of a arrangement of two rollers, and is additionally characterized by an eyeliner for increasing the distance of large rollers from the bath surface. This system also has all the disadvantages of a two roll system, including the fact that the three roll system is an even more complicated apparatus, and that care should be taken not to immerse the middle roll or other damage to the tape, especially when coating a very wide tape.

EXAMPLE 1. Iron-colored metal strip caliber 28 is coated on one side with zinc using the coating apparatus and method shown in Fig. 1. At a belt speed of 123 m / min, the strip is led through the aperture of the cover. belt temperature about 466 ° C-471 ° C. The bath is maintained at 460 ° C.

The non-oxidizing, nitrogen-protective atmosphere is introduced into the discharge nozzle at a rate

19.6 m⁸/hour. The roller 12 turning downwards has a temperature of -2-3 ° C. There is 12-10 parts oxygen per million in the non-oxidizing atmosphere.

Jet knife 19 with a 0.76 mm slit section provides air at a pressure increased by 0.061 atmosphere. The nozzle is maintained at a height of about 115.2^cm above bath level, and positioned it up at an angle of about 2 ° or 3 °. Roll diameter 14 is 304.8 mm. The nozzle is kept at a distance of 4.9 mm from the coated side of the tape.

By carrying out the procedure described above on an iron-based metal band, a band coated on one side with zinc in the amount of 57.05 g / m².

In the usual quality tests including adhesion determination, zinc

124 706 the coating layer exhibits satisfactory features. The uncoated side of the tape is covered with a small oxide film and no zinc coating is observed on it. .

Example II A 28 gauge thick iron band is covered on one side with aluminum, using the coating apparatus and method shown in Fig. Ί. At a belt speed of 15.24 m / minute, the belt is introduced into the outlet of the discharge nozzle. I use a belt temperature close to 765 ° C. The molten coating metal bath is maintained at 688 ° C.

A non-oxidizing, nitrogen-protective atmosphere is introduced into the exhaust shroud at a rate of 8.4 mV hour. The roller 12 rotating downwards is kept at - 23.4 ° C. Less than 166 parts per million oxygen is registered in the atmosphere.

The jet nozzle 19 with a 0.76 mm slit section provides air at a pressure increased by 0.051 atmosphere. The nozzle is kept at a height of about 16 cm above the level of the bath and rises upwards at an angle of about 16 °. Roll diameter 14 is 304.8 mm. The nozzle is kept at a distance of about 3.2 mm to about 4.75 mm from the coated side of the tape.

As a result of the procedure described above on an iron tape, a one-sided coating of gliu is obtained in an amount of 57.9 * 5 g / m².

In the usual quality tests involving adhesion determination, the aluminum coating layer has satisfactory properties.

If desired, the oxide film can be removed by acid purification. The oxide coating adheres strongly and easily adopts painting preparation activities, such as phosphating. Under these conditions, the uncoated side of the tape coated with the oxide film exhibits satisfactory paint-receiving properties.

Finishing of the coated side was carried out using a jet knife. Of course, other well-known finishing methods such as asbestos wiping and the like can be used.