Process for the atomisation of molten metal to produce metal powders.

p0001The invention relates to a method for producing metallic particles from a metal melt, said metal melt discharged through a discharge nozzle as a jet of metal and the metal jet downstream acted upon by the dispensing nozzle in a sputtering zone with a feed-through through a nozzle means fluid is atomized by means of which the jet of metal to the metal particles becomes.

p0002The size or particle size distribution of the metallic particles produced by such a method is, inter alia, the cross section of the dispensing nozzle from the pressure with which the molten metal is passed conveyed by the dispensing, depending on the arrangement of the nozzle means relative to the dispensing nozzle and on other parameters which may optionally may be adjustable in order to adjust the particle size distribution of the metal particles as desired according to. this very much is the ratio of outputted through the dispensing nozzle metal to durchgeleitetem and outputted through the nozzle means fluid. In order to achieve a very fine particle size range, it is necessary, the amount of metal per unit time output by the dispensing nozzle, that is, the metal flow rate to decrease. This has so far been accomplished in that the cross section of the discharge nozzle is selected in accordance small. Here, however, results in lower limits for the cross section of the dispensing nozzle, which, for example, are caused by the fact that at too small output nozzle cross section by gravity no transport of the metal melt is possible through the dispensing nozzle through more, or that then also by the suction effect of the in the neighborhood dispensing nozzles provided means no transport of the molten metal from the delivery nozzle out is achieved more. Furthermore, there is at small cross-section of the dispensing nozzle to the risk of freezing of the metal beam or in the dispensing nozzle, so that it can come to a clogging of the dispensing nozzle. A clogged dispensing nozzle is however useless. Furthermore, a danger of clogging present in the molten metal melt foreign ingredients such Oxidschlacken results or the like in dispensing nozzles small cross section.

p0003The invention is therefore based on the object to provide a method of the aforementioned type, with which it is easily possible, metal particles of any desired particle spectrum and esp. to produce even a very fine grain spectrum easily.

p0004This object is inventively achieved in that the metal beam, the electromagnetic field of an electromagnetic field means flows through the region between the discharge nozzle and the atomization, the metal beam is changed by the electromagnetic field in its cross-section as compared to the procedure established by the dispensing outlet section. According to the invention it is thus possible to use a dispensing nozzle with a relatively large cross section, so that no transport problem of the molten metal through the discharge nozzle and through no freezing and / or clogging of the dispensing nozzle is given. The molten metal may therefore leave due to the effect of gravity as a laminar metal beam, the dispensing nozzle. The inventive method has the particular advantage that metal particles can be produced with it, which are present in a very fine particle size distribution, because the electro magnetic field induced change of the cross section of the metal beam or esp. Reduction of its cross section in the area of ​​atomizing the metal flow rate in relation to the nozzle means passing through atomizing fluid is correspondingly small, so that the inventive method is excellent in productivity.

p0005In the method, the metal beam can be accelerated by means of the electromagnetic field of the electromagnetic field means downstream to the dispensing nozzle, so that the speed of the concentrated metal beam the cross-section ratio of dispensing to constricted metal beam is correspondingly greater than the flow velocity of the metal beam through the dispensing therethrough. It is also possible that the metal beam is influenced by means of the electromagnetic field of the electromagnetic field in the dispensing means such that the adjacent to the inner surface of the dispensing zone of the metal jet is slowed down in comparison with its central zone. In any case, thus resulting in a narrowed metal beam, ie, a metal beam whose cross-section is small compared to the cross section of the dispensing nozzle. The dispensing nozzle may have any cross-sectional shape, ie they may have a round, an angular, oval or have any other solid or annular cross-section.

p0006According to the invention it is also possible to influence the exiting with a particular cross-section of the dispensing jet of metal by means of the electric magnetic field means so that the ratio of cross-sectional area of ​​the constricted metal beam is increased to its circumferential length. This can for instance. Be realized that a metal beam with a circular outlet cross-section by the action of the electric magnetic field means is shaped such that its cross-section forms a flat ellipse before the metal beam enters the atomization zone. Thereby, the engagement surface for the sputtering fluid is a hand extended and on the other hand reduces the required depth for the disintegration of the metal beam through the atomizing fluid. support or promote advantageously the solution of the invention is based, above task Both effects.

p0007When practical, it has been found if the metal jet downstream to a diameter between 5 and 20 mm, preferably 8 to 10 mm having discharge nozzle in a cross-section with a linear dimension of between about 0.5 and 4 mm, preferably between about 1 and 2 mm is concentrated.

p0008Of course, the dispensing nozzle also possess greater linear cross-sectional dimensions. The same applies to the linear dimensions of the narrowed metal beam. The latter dimensions should serve primarily to provide orders of magnitude; no way intended to limit the subject invention those dimensions.

p0009The concentrated jet of metal can be applied in the sputtering zone with a gaseous fluid, which may be air or an inert gas. Of course, any other gaseous fluid reach the application.

p0010Another possibility is to apply the concentrated jet of metal in the sputtering zone with a liquid.

p0011The inventive method is applicable to all metals that have magnetic properties, so that the output from the dispensing molten metal in the form of a metal beam in the electromagnetic field of which is arranged in the vicinity of the dispensing electromagnetic field apparatus can be narrowed in the manner of an insubstantial mold. The electromagnetic field device or the electromagnetic field must therefore be appropriate in size and properly oriented to narrow the laminar jet of molten metal accordingly. As molten metal molten aluminum or a copper melt is eg. Used. There are of course also other molten metals applicable, as has already been mentioned.

p0012Further details, features and advantages will become apparent from the following description of a diagrammatically illustrated embodiment of a device for carrying out the inventive method.

p0013The figure shows a piece-wise dispensing 10, which is drawn partially cut. Through the dispensing nozzle 10 flows through a metal beam 12 at a speed indicated by the arrow v1. Downstream after the dispensing nozzle 10 is an electric magnetic field means 14 is provided which is arranged coaxially to the discharge nozzle 10 and formed with a passage 16 for the metal beam 12th In the passage 16 of the electric magnetic field device 14, an electromagnetic field H is given. By the electromagnetic field H exiting from the dispensing nozzle 10 metal beam 12 12'eingeengt to a metal beam. The cross-section of the dispensing nozzle 10 is in the drawing with Q and the cross section of the narrowed metal beam 12 'is denoted by q. The cross-section Q may form excessively the cross-section Q correspond, ie for example a circular cross-section Q can be reduced to a circular cross-section q. However, it is also possible that the cross-section q to the cross-section Q differs, ie eg., a circular cross-section Q are transformed into an elliptical cross-section q. Here, preferably q <Q. According to the relationship of the cross section Q of the dispensing nozzle 10 to the cross-section q of said constricted metal beam 12 'is the speed v2 of the narrowed metal beam 12'grösser than the speed v1 of the metal beam 12 when flowing through the dispensing nozzle 10. The speed v2 of the concentrated metal beam 12 is indicated in the drawing as the speed v1 by an arrow.

p0014Downstream after the electric magnetic field means 14 is a nozzle device 18 is provided, which is directed against the constricted or reduced metal beam 12 '. Through the nozzle means 18, a fluid 20 'is directed so that the direction indicated by arrows fluid 20 the narrowed metal beam 12' against the narrowed metal beam 12 applied and the concentrated metal beam 12 'is atomized in the order specified by the nozzle means 18 atomizing zone 22 to metal particles. The metal particles are then cooled in a cooling zone 24 and can be collected accordingly.

p0015The electromagnetic field device 14 thus serves as insubstantial mold to fit 12 to narrow the exiting from the discharge nozzle 10 metal beam.