ATOMIZATION OF METALS

Description

[0001] This invention relates to a device for gas atomizing a liquid metal or metal alloy stream.

[0002] The atomizing and spray depositing of a stream of liquid metal is well known for example from British Patent Specification No. 1262471, and our own British Patent Specifications Nos. 1379261 and 1472939. However, the control of the mass deposition of the metal on a deposition surface has always been a problem.

[0003] One proposal to improve the control of the mass distribution of the deposited layer of gas atomised of metal is set out in British Patent Specification No. 1455862 where it is proposed to oscillate the spray of atomized particles by the use of a primary set of gas jets for atomization and two sets of secondary jets which are rapidly switched on and off to impart an oscillatory motion to the spray of atomized metal.

[0004] An alternative proposal was disclosed in European Patent Publication No. 0127303A where individual gas jets were switched on and off to accomplish the function of both atomizing and oscillating the spray. However, we found both these methods very difficult to control. In the first proposal the use of secondary jets can result in excess cooling of the deposited metal meaning that subsequently arriving particles do not coalesce properly with the already deposited metal. In the second method the shape and properties (e.g. temperature) of the spray can change as individual jets are switched on and off which makes it extremely difficult to ensure uniform deposition and solidification conditions. We therefore proposed in European Patent Publication No. 225080 an improved device for imparting more controlled and precise movements to an atomized liquid stream of molten metal or metal alloy which involved tilting the actual atomizer on an axis so that the atomizing gas flow field remained the same but was moved to and fro by to and fro tilting of the atomizer. However, whilst such a device enables more controlled deposition, there can be inertia problems inherent in a mechanical to and fro tilting movement.

[0005] It is therefore an object of the present invention to provide an improved atomizing device and method of atomization.

[0006] According to the present invention there is provided apparatus for gas atomizing a stream of molten metal or metal alloy comprising:
   an atomizing device for receiving a supply of atomizing gas;
   an opening defined by the atomizing device through which the stream may be teemed;
   a rotor, supported by the atomizing device, and including an annular jet or a plurality of jets arranged about the opening through which atomizing gas may issue for atomizing the stream into a spray of droplets, in use, the atomizing gas issuing from the annular jet or plurality of jets forming an atomising gas flow field which would, when the rotor is stationary, surround the stream and be of asymmetric geometry with respect to the axis of the stream;
   means for moving the rotor relative to the atomizing device for varying the positional relationship of the asymmetric gas flow field relative to the stream whereby the asymmetry of the atomizing gas flow field may impart movement to the spray relative to the axis of the liquid stream whilst the overall geometry of the atomizing gas flow field remains substantially constant.

[0007] The invention also includes a method of moving a spray of atomized droplets of molten metal or metal alloy comprising the steps of passing a stream of molten metal or metal alloy through an opening in an atomizing device, providing the atomizing device with a rotor having an atomizing jet or jets arranged about the opening, supplying atomizing gas to the atomizing device whereby an atomizing gas flow field is formed which, when the rotor is stationary, surrounds the stream and is of asymmetric geometry with respect to the axis of the stream, directing the atomizing gas flow field at the stream to atomize the stream into a spray of droplets, and moving the rotor to vary the positional relationship of the atomizing gas flow field relative to the stream during atomization to impart movement to the spray whilst maintaining the overall geometry of the atomizing gas flow field substantially constant.

[0008] The improved method of the present invention does not involve the switching on and off of gas jets to move the spray. Instead, despite the proximity to the nozzle from which molten metal issues, we have devised a system whereby the spray is moved by moving the atomizing jets themselves possibly with the whole atomizing device tilting as well if desired. This has the following particular advantages over previous methods:

(a) on average the atomizing conditions can be kept more consistent because gas jets are not being switched on and off;

(b) the movement imparted is preferably a rotation or angular oscillation about the stream so that the spray can be moved very easily by varying movements of atomizing rotor(s) and, if desired, tilting the atomizer;

(c) the rate of movement can be easily varied by the speed of the rotor and, if required, the tilt of the atomizer;

(d) the speed of movement of the locus of the spray axis at any instant during deposition can be easily varied;

(e) some alloys, such as aluminium alloys, cast iron, tin and zinc alloys, tend to produce spray cones of relatively small angle of divergence and therefore the cooling of the particles in flight can be inhibited. When taken together with the relatively high local mass flux at the deposition surface this can result in excessive deposition temperatures. Spreading the spray by rotation or angular oscillation of the atomizer to cause corresponding movement of the gas field in accordance with the present invention will, in this case, result in more uniform and cooler deposition conditions. As a result the deposition rate could be increased;

(f) the main axis of the spray can be made to follow a wide range of pre-determined paths; e.g. a circular path, an elliptical path, etc. This is in contrast to our prior tilting method where the path of the spray is undertaking a to and fro movement along a straight line only. Therefore, the greater control over the spray movements and provides increased flexibility in operation;

(g) the rate of deposition can be increased because of the increased area over which the metal is deposited (ie. the increased size of the spray relative to the product). This is achieved because the metal will cool more quickly and therefore can be poured at a higher rate; and

(h) the quality of the deposit will improve in that the microstructure and porosity distribution will be more uniform.

[0009] Consequently, the apparatus and method of the present invention provides a very high degree of control over the atomizing device and the movement of the spray which previously has not been attainable. This enables the locus of the spray axis to be varied to suit the shape of deposit being produced or to control the deposition conditions and/or the profile of the spray on the surface of the collector.

[0010] In one form of the method of the invention the liquid stream is molten metal or metal alloy, the spray is directed at a substrate moving continuously through the spray and the spray is moved transverse to the direction of movement to achieve uniformity of thickness of deposition across the width of the substrate and is spread laterally in the direction of movement by the asymmetry of the gas flow field whereby strip, coated strip, plate or coated plate products may be formed.

[0011] The invention will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 is sectional side elevation of an atomizer of the closest prior art;

Figures 2a, 2b and 2c are diagrammatic perspective view of the formation of tube and bar deposits using the apparatus of figure 1 and the spray mass flux profile exemplified as applied to tube;

Figures 3a, 3b and 3c are diagrammatic views showing respectively, the side elevation of the formation of strip, a view on A-A in figure 3b, and the spray mass flux profile using atomizers of the prior art according to figure 1;

Figure 4 is a cross-section of a first embodiment of atomizing device in accordance with the invention;

Figure 5 is a cross-section of a second embodiment of atomizing device in accordance with the invention;

Figure 6 is a cross-section of a third embodiment of atomizing device in accordance with the invention;

Figures 7a and 7b are examples of spray profiles that can be achieved with the present invention;

Figures 8a, 8b and 8c are diagrammatic perspective views of the formation of tube and bar deposits using apparatus of the present invention in contrast to figures 2a and 2b and the spray mass flux profile exemplified as applied to tube;

Figures 9a, 9b and 9c are diagrammatic views of the invention showing respectively the side elevation of the foundation of strip in contrast to figure 3a, a view in the direction of arrow B, and the spray mass flux profile; and

Figures 10a and 10b, respectively, show the spray mass flux profile of a spray for forming strip using the tilting atomizing device of figure 1 and using the rotational device of the present invention in conjunction with tilting.

[0012] In the drawings illustrating the closest prior art an atomizing device (10) is positioned within an atomizer housing (11) and below the nozzle opening (12) of tundish (13). The atomizing device (10) includes a plenum chamber (14) and has atomizing gas jet openings (15). The atomizing device (10) is substantially annular in shape having a central opening (16) through which a stream (17) from the tundish (13) is arranged to pass. The atomizing device is supported within the housing (11) by diametrically opposed supports (18, 19) which project outwardly from the atomizing device (10) and is positioned sufficiently away from the bottom of the tundish (13) and has a central opening (16) dimensioned so that the atomizing device may be made to undergo a tilting motion. So that this tilting motion may be achieved the supports (18, 19) are mounted within respective bearings (20, 21) in the atomizer housing (11). One of the supports (18) also serves as a conduit (22) to supply atomizing gas to the plenum chamber (14).

[0013] The movement of the atomizing device (10) is effected by mechanical means consisting of a rotated cam and a cam follower held against the cam profile (not shown). The cam follower has a connecting arm (27) pivoted to it and extends to a pivotal connection (29) on a plate (30). The plate (30) is freely movable and is fixed to the support (19) at a position offset from the pivotal connection (29).

[0014] Accordingly, it will be understood that movement of the rotated cam is translated into movement of the atomizing device (10) via the cam follower connecting arm (27) and plate (30). The cam profile may be designed to define a predetermined degree of movement and the speed of rotation of the cam controls the speed of movement of the atomizing device. The to and fro tilting movement of the atomizing device imparts a corresponding scanning movement to the spray (31) since the atomizing device (10) carries with it the atomizing gas jet openings (15). Further details of this arrangement may be obtained from our aforementioned European Patent Publication No. 225080.

[0015] For examples of products formed using the apparatus of figure 1 reference may be had to figures 2a, 2b, and 2c. In those figures the spray (31) is shown scanning the deposition surface, either axially in the direction of arrow (32) in the formation of a tube (33) (figure 2a) or about the end of a bar deposit (34) which, as with the tube, is rotated in the direction of arrows (35) and moved axially in the direction of arrow (36) as shown in figure 2b.

[0016] When a spray is scanned across the bar end or along the rotating tube as shown in those figures, the locus of the spray axis (37) on the surface follows a to and fro linear path. It is therefore essential to ensure that the scanning frequency of the spray is sufficiently high that the resulting layer per revolution is effectively uniform. For example, as shown in figure 2c with respect to the formation of tube, the spray profile (38) defined about the locus of the spray axis must overlap to give uniform deposition for each revolution. However, in the formation of tube for example, as the required diameter of the deposit increases the ratio of scanning frequency to rotational speed increases, which can lead to mechanical design problems due to the inherent inertia of the tilting atomizer.

[0017] In figure 3a strip or plate (60) is shown being formed on a substrate (61) moving in the direction of arrow (62). But, in order to achieve maximum spray density whilst accommodating the maximum spray mass flux profile of a spray without defects consequential on too hot deposition (indicated by line (63) with respect to spray profiles (64), it is necessary to use two or more rows (65) of two or more atomized sprays (66) to produce strip with sufficiently uniform deposition conditions throughout the section even though the atomized sprays (66) scan transverse to the direction of movement as indicated by arrows (67).

[0018] In the tilting atomizer of figure 1 the spray cone generated by the atomizing device is always maintained, the tilting of the atomizer achieving to and fro movement of the spray cone, and the gas jets are used merely for atomization.

[0019] In the present invention the atomizing device may be tilted, but movement of the spray may be achieved without such motion. For example, in figure 4, a liquid stream (41) of molten metal or metal alloy is atomized by gas which is fed via pipes (42) to an atomiser body (43). The gas exits through orifices (44) arranged around the liquid stream (41) in a rotor (45) which is movable about the axis of the liquid stream (41) and may be arranged either to undertake angular oscillation to and fro about the stream or to undertake complete rotation about the stream. As can be seen from the figure, the size of the orifices (44) differ according to the circumferential position around the liquid stream in order to generate an asymmetric atomizing gas field. The rotor (45) is held in position by bearings (46) and (47), the gas leakage is prevented between the rotor (45) and the atomizer body (43) by suitable seals (48) and (49) as shown. The gas jets emerging from the orifices (44) atomize the liquid stream (41) to form the spray (50). The rotor (45) is movable about the stream (41) by means of a driven actuating means (51) such as a spur gear for example. On rotation or angular oscillation to and fro of the rotor the overall asymmetry of the atomizing gas field remains the same but because its position relative to the stream varies, the different asymmetrical positions of the gas flow field imparts rotation or an oscillation to the spray (50).

[0020] In figure 5 a similar apparatus is shown including a rotor (145) and similar reference numerals to those in figure 4 have been used in a one hundred series to indicate corresponding parts. However, in figure 5, instead of varying the size of orifice (144) about the circumference of the atomizing device the angles of attack of the emerging gas jets - indicated by references (152) - are varied about the circumference to produce the asymmetric spray pattern. If desired, combinations of figure 4 and figure 5 are possible, ie. varying the orifice size and the angles of attack.

[0021] In the embodiment of figure 6 an asymmetric atomizing gas field is produced by means of two rotors which are rotatable relative to each other and to the atomizer body. In figure 6 a liquid metal stream (241) passing through the atomizer body is atomized by an atomizing gas fed via pipes (242) to the atomizer body (243). The gas is received in a plenum chamber (253) and exists the atomizer body (243) through atomizing orifices (244). The orifices (244) are arranged in two circular arrays in two concentric rotors (254, 255) and are distributed about the stream (241) in order to atomize it. The size of the orifices in each rotor (254, 255) differ according to their circumferential position around the liquid stream in order to generate an asymmetric atomizing gas field. However, by using two rotors (254, 255) more flexibility in the control of the resultant spray shape is provided.

[0022] The inner rotor (254) is held in position by bearings (246) and (247) and the outer rotor (255) by bearings (256) and (257). Gas leakage is prevented between the rotors (254, 255) and the atomizer body (243) by suitable seals (248, 249 and 258). The atomizing gas jets emerging from the orifices (244) and atomize the liquid stream (241) to form a spray (250). The arrays of gas jets in the respective rotors (254, 255) may be focused at a single atomizing point relative to the stream or at an atomizing zone (259) where the stream (241) is broken up into a spray. The rotors (254, 255) are movable by means of respective bevel gears (260, 261). By synchronizing the two rotors (254, 255) the asymmetric gas flow field can be kept substantially constant and rotation or to and fro angular oscillation imparts movement to the spray whilst it retains its same cross-sectional shape determined by the gas flow field. However, by moving one rotor relative to the other the geometry of the gas flow field may be altered as well which provides increased flexibility.

[0023] If desired, the atomizer with a rotor or rotors for rotation and/or angular to and fro oscillation about the stream can be used in the tilting arrangement of figure 1 so that the atomizing device tilts and rotates or angularly oscillates simultaneously.

[0024] In use, referring to figures 7a and 7b if the pattern of the atomizing gas jets (300) emerging from respective orifices (44, 144, 244) is arranged such that the result is a conical jet the axis (301) of which is inclined at a small angle and relative to the axis (302) of rotation of the respective rotors, then the spray profile (303) will be symmetric about the conical jet axis (301) even though the gas field is asymmetric with respect to the atomizing device and particularly the main axis of the liquid stream (302) which, in this case, coincides with the rotor axis. If the rotor is angularly oscillated to and fro about the stream then the effective spray profile can be modified as indicated by the plan view (304) at the bottom of figure 7a.

[0025] In figure 7b the rotor is rotated to form the effective spray profile (305). Obviously, the actual spray profiles produced are a function of the gas jet pattern and the velocity profile applied to the respective rotor which may be angular oscillation or rotation.

[0026] In figures 8a, 8b, and 8c, the advantages of the present invention are illustrated in the formation of tube (400) and bar (401) deposits. In both cases there is a rotational and axial movement of the forming deposits (402) and (403) respectively as well as scanning movement of the sprays indicated by arrows (406). As opposed to the spray movement imparted solely by tilting the atomizer as disclosed in figures 2a, 2b, and 2c, the additional rotation or angular oscillation of the atomizing rotor causes the locus of the spray axis indicated by lines (404) and (405) in figures 8a and 8b respectively to be spread (or to have an effective wider spray profile (407) as indicated in figure 8c with reference to the formation of tube) which allows the scanning speed of the spray to be reduced whilst still achieving the necessary overlap to give uniform deposition. As the scanning speed is reduced more metal can be put down without having a detrimental effect on the desired properties of the finished deposit.

[0027] In figures 9a and 9b the production of strip or plate (410) is diagrammatically illustrated. In contrast to the tilting of figures 3a and 3b, the addition of rotation or angular oscillation to the atomizing rotor produces a spread uniformity illustrated by spray profile (411) of figure 9c, such that only one row of tilting atomizers (412) is required as opposed to two greatly simplifying the plant needed and possibly increasing the production rate. Of course, although rows of two atomizers have been disclosed in figures 3a and 9a, if a reduced width of strip or plate is required then a single atomizer may be sufficient in the present invention as opposed to two atomizers, one behind the other, previously required.

[0028] The contrasting spray profiles in the formation of strip are more clearly shown in figures 10a and 10b where the combination of rotation to tilting is demonstrated. In particular, the scanning of a spray by tilting the atomizer plus rotation has the advantage in strip production by spreading the spray laterally, by tilting, to obtain the correct uniformity of thickness and also longitudinally, by rotation. Thus, figure 10a shows a spray profile (420) achieve solely by tilting the atomizer to and fro whereas figure 10b shows a spray profile (421) with the addition of rotation or angular oscillation to achieve greater spread. This results in more uniform deposition conditions throughout the thickness of the strip which will reduce the amount of porosity in the bottom and top surfaces of the strip deposit (caused by low deposition rates at the edge of the spray). In the present invention there is less variation in deposition rate as the collector traverses under the spray and therefore porosity is reduced.

[0029] The method of rotation of the present invention will also have significant advantages in the production of tubes, billets and clad products, particularly for billets and tubes of large diameter. The reason for this is that the spray will cover a larger area, ie. have a larger 'footprint' and therefore it is easier to obtain complete coverage of the tube or the billet surface compared to the old method solely of tilting. Although the invention has been particularly described with a stream axis which passes through the centre of a rotatable atomizing device, the axis of rotation of atomizer or the axis of the jets could be different to axis of metal stream. In this arrangement the holes could be uniform whilst the geometry of the gas flow field and thus the spray would be asymmetric to the liquid stream. Further, the jets need not be arranged on a circle; for example, the jets could be in an elliptical arrangement and there could be one, two or more rotors. In the case of two rotors, these could be rotating in the same or opposite directions (or angularly oscillated in the same or opposite directions).

[0030] The above devices can also be used for producing gas atomized metal powders whereby the movement of the spray can impart improved cooling to the atomised particles.

Claims

1. Apparatus for gas atomizing a stream of molten metal or metal alloy comprising:
   an atomizing device for receiving a supply of atomizing gas;
   an opening defined by the atomizing device through which the stream may be teemed;
   a rotor, supported by the atomizing device, and including an annular jet or a plurality of jets arranged about the opening through which atomizing gas may issue for atomizing the stream into a spray of droplets, in use, the atomizing gas issuing from the annular jet or plurality of jets forming an atomising gas flow field which would, when the rotor is stationary, surround the stream and be of asymmetric geometry with respect to the axis of the stream;
   means for moving the rotor relative to the atomizing device for varying the positional relationship of the asymmetric gas flow field relative to the stream whereby the asymmetry of the atomizing gas flow field may impart movement to the spray relative to the axis of the liquid stream whilst the overall geometry of the atomizing gas flow field remains substantially constant.

2. Apparatus according to claim 1, wherein the atomizing rotor comprises a plurality of atomizing jets which vary in size about the rotor whereby an asymmetric gas flow field may be produced.

3. Apparatus according to claim 1, wherein there are a plurality of atomizing jets and the asymmetric gas flow field is produced by varying the angle of attack on the atomizing jets about the rotor.

4. Apparatus according to claim 1, wherein the asymmetric gas flow field is produced by the axis of the rotor being spaced from the axis of the stream.

5. Apparatus according to claim 1, wherein there are a plurality of atomizing jets and the asymmetric gas flow field is produced by the atomizing gas jets being positioned in the rotor asymmetrically with respect to its axis.

6. Apparatus according to claim 1, wherein the atomizing rotor comprises an annular atomizing jet and the asymmetric gas flow field is produced by the annular opening having a width or position in the rotor which varies about the rotor to provide the asymmetric gas flow field.

7. Apparatus according to claim 1, wherein there are two rotors each including an atomizing jet or jets for forming an asymmetric gas flow field with respect to the axis of the liquid stream and each being movable relative to the other and to the atomizing device whereby, in combination, the asymmetry of the gas flow field relative to the liquid stream may be varied.

8. Apparatus according to any one of the preceding claims further including means for tilting the atomizing device so that during atomization, the spray may be moved to and fro by tilting of the atomizing device.

9. Apparatus according to claim 1, comprising a plenum chamber formed within the atomizing device;
   means coupled to the atomizing device for supporting the atomizing device including an inlet path communicating the plenum chamber with an atomizing gas source; and,
   a plurality of atomizing gas jet openings formed in the rotor for directing atomizing gas onto the stream passing through the opening, the atomizing gas jet openings being positioned in a predetermined fixed relationship relative to one another so as to form the asymmetric atomizing gas flow field of predetermined geometry.

10. Apparatus according to claim 9, including control means operative to impart either angular oscillating movement to the rotor or complete rotation.

11. Apparatus according to claim 10, wherein the control means comprises a spur gear connecting with the rotor operative to move the rotor relative to the atomizing device.

12. Apparatus according to claim 1, including at least first and second rotors which are movable relative to each other and to the atomizing device and in which the overall geometry of the atomizing gas flow field remains substantially constant when the rotors are synchronized.

13. A method of moving a spray of atomized droplets of molten metal or metal alloy comprising the steps of passing a stream of molten metal or metal alloy through an opening in an atomizing device, providing the atomizing device with a rotor having an atomizing jet or jets arranged about the opening, supplying atomizing gas to the atomizing device whereby an atomizing gas flow field is formed which, when the rotor is stationary, surrounds the stream and is of asymmetric geometry with respect to the axis of the stream, directing the atomizing gas flow field at the stream to atomize the stream into a spray of droplets, and moving the rotor to vary the positional relationship of the atomizing gas flow field relative to the stream during atomization to impart movement to the spray whilst maintaining the overall geometry of the atomizing gas flow field substantially constant.

14. A method according to claim 13, further comprising tilting the atomizing device about an axis to impart to and fro movement to the asymmetric gas flow field.

15. A method according to claim 13, wherein the spray is directed at a substrate moving continuously through the spray, the spray is moved transverse to the direction of movement by tilting the atomizing device to and fro to achieve uniformity of thickness of deposition across the substrate and the spray is spread laterally in the direction of movement by varying the positional relationship of the asymmetric gas flow field to achieve uniformity of deposition in the direction of movement of the substrate whereby strip, coated strip, plate or coated plate products may be formed.

16. A method according to claim 13, 14 or 15, wherein metallic or ceramic particles are applied to the spray to be incorporated in a deposit formed on a collecting substrate.

17. A method according to any one of claims 13 to 16, wherein the movements of the spray are controlled to produce spray deposited ingots, bars, tubes, rings, rolls, conical shapes, forging and extrusion blanks, shapes for thixotropic deformation, laminated or coated products and metal matrix composites.

18. A method according to claim 13, wherein the stream is atomized by the application of an atomization gas issuing from at least two relatively rotatable rotors; and comprising the further step of varying the positional relationship and/or the asymmetry of the gas flow field relative to the stream during atomization to impart movement to the spray either maintaining the overall geometry of the atomizing gas flow field substantially constant by synchronizing the rotors or varying the asymmetry of the gas flow field by effecting relative movement between the rotors during atomizing.

19. A method according to claim 13, wherein the spray is allowed to cool and solidify in flight whereby metal powder is formed.

Ansprüche

1. Vorrichtung zur Gaszerstäubung eines Stroms geschmolzenen Metalls oder einer geschmolzenen Metallegierung

- mit einer Zerstäubereinrichtung für die Aufnahme einer Zufuhr von Zerstäubungsgas,

- mit einer Öffnung, die von der Zerstäubungseinrichtung gebildet wird und durch die der Strom gegossen werden kann,

- mit einem Rotor, der von der Zerstäubungseinrichtung getragen wird und eine Ringdüse oder eine Vielzahl von Düsen aufweist, die um die Öffnung herum angeordnet sind, durch welche im Einsatz Zerstäubungsgas zur Zerstäubung des Stroms in einen Tröpfchensprühnebel austreten kann, wobei das aus der Ringdüse oder der Vielzahl von Düsen austretende Gas ein zerstäubendes Gasstromfeld bildet, das, wenn der Rotor stationär ist, den Strom umgeben und eine asymmetrische Geometrie bezüglich der Achse des Stroms haben würde, und

- mit Einrichtungen zum Bewegen des Rotors relativ zur Zerstäubungseinrichtung, um die Lagebeziehung des asymmetrischen Gasstromfeldes bezüglich des Stroms zu verändern, wodurch die Asymmetrie des zerstäubenden Gasstromfeldes dem Sprühnebel bezüglich der Achse des Flüssigkeitsstroms eine Bewegung erteilen kann, während die Gesamtgeometrie des zerstäubenden Gasstromfelds im wesentlichen konstant bleibt.

2. Vorrichtung nach Anspruch 1, bei welcher der zerstäubende Rotor eine Vielzahl von Zerstäubungsdüsen aufweist, deren Größe sich um den Rotor herum ändert, wodurch ein asymmetrisches Gasstromfeld erzeugt werden kann.

3. Vorrichtung nach Anspruch 1, bei welcher eine Vielzahl von Zerstäuberdüsen vorhanden ist und das asymmetrische Gasstromfeld dadurch erzeugt wird, daß der Angriffswinkel an den Zerstäuberdüsen um den Rotor variiert wird.

4. Vorrichtung nach Anspruch 1, bei welcher das asymmetrische Gasstromfeld dadurch erzeugt wird, daß die Achse des Rotors im Abstand von der Achse des Stroms angeordnet ist.

5. Vorrichtung nach Anspruch 1, bei welcher eine Vielzahl von Zerstäuberdüsen vorgesehen sind und das asymmetrische Gasstromfeld dadurch erzeugt wird, daß die Zerstäubergasdüsen in dem Rotor asymmetrische bezüglich seiner Achse angeordnet sind.

6. Vorrichtung nach Anspruch 1, bei welcher der zerstäubende Rotor eine Zerstäuberringdüse aufweist und das asymmetrische Gasstromfeld durch die Ringöffnung erzeugt wird, die eine Breite oder Lage in dem Rotor hat, die sich um den Rotor herum ändert, um das asymmetrische Gasstromfeld zu erzeugen.

7. Vorrichtung nach Anspruch 1, bei welcher zwei Rotoren vorgesehen sind, von denen jeder eine Zerstäuberdüse oder Zerstäuberdüsen zur Bildung eines asymmetrischen Gasstromfelds bezüglich der Achse des Flüssigkeitsstroms hat und von denen jeder bezüglich des anderen und der Zerstäubereinrichtung bewegbar ist, wodurch in Kombination die Asymmetrie des Gasstromfelds bezüglich des Flüssigkeitsstroms variiert werden kann.

8. Vorrichtung nach einem der vorhergehenden Ansprüche, welche weiterhin Einrichtungen zum Kippen der Zerstäubereinrichtung aufweist, so daß während der Zerstäubung der Sprühnebel durch Kippen der Zerstäubervorrichtung vor- und zurückbewegt werden kann.

9. Vorrichtung nach Anspruch 1

- mit einer in der Zerstäubervorrichtung ausgebildeten Hauptkammer,

- mit einer mit der Zerstäubereinrichtung zum Tragen der Zerstäubereinrichtung gekoppelten Einrichtung, die einen Einlaßweg hat, der die Hauptkammer mit einer Zerstäubergasquelle in Verbindung setzt, und

- mit einer Vielzahl von Zerstäubergasdüsenöffnungen, die in dem Rotor ausgebildet sind, um Zerstäubergas auf den Strom zu richten, der durch die Öffnung hindurchgeht, wobei die Zerstäubergasdüsenöffnungen in einer vorgegebenen, feststehenden Beziehung bezüglich einander positioniert sind, wodurch das asymmetrische Zerstäubergasstromfeld mit vorgegebener Geometrie gebildet wird.

10. Vorrichtung nach Anspruch 9 mit einer Steuereinrichtung, die so arbeitet, daß dem Rotor entweder eine Winkeloszillationsbewegung oder eine vollständige Drehung erteilt wird.

11. Vorrichtung nach Anspruch 10, bei welcher die Steuereinrichtung ein Stirnradgetriebe aufweist, das mit dem Rotor in Verbindung steht und so arbeitet, daß der Rotor bezüglich der Zerstäubereinrichtung bewegt wird.

12. Vorrichtung nach Anspruch 1 mit wenigstens einem ersten und einem zweiten Rotor, die zueinander und zu der Zerstäubereinrichtung beweglich sind, wobei die Gesamtgeometrie des Zerstäubergasstromfelds im wesentlichen konstant bleibt, wenn die Rotoren synchronisiert sind.

13. Verfahren zum Bewegen eines Sprühnebels aus zerstäubten Tröpfchen geschmolzenen Metalls oder einer geschmolzenen Metallegierung, das die Schritte aufweist,

- einen Strom von geschmolzenem Metall oder geschmolzener Metallegierung durch eine Öffnung in einer Zerstäubereinrichtung hindurchzulassen,

- die Zerstäubervorrichtung mit einem Rotor zu versehen, der eine Zerstäuberdüse oder Zerstäuberdüsen aufweist, die um die Öffnung herum angeordnet sind,

- der Zerstäubereinrichtung Zerstäubergas zuzuführen, wodurch ein Zerstäubergasstromfeld gebildet wird, das, wenn der Rotor stationär ist, den Strom umgibt und bezüglich der Achse des Stroms eine asymmetrische Geometrie hat,

- das Zerstäubergasstromfeld an den Strom so zu richten, daß der Strom in einen Sprühnebel von Tröpfchen zerstäubt wird, und

- den Rotor so zu bewegen, daß die Lagebeziehung des Zerstäubergasstromfelds bezüglich des Stroms während des Zerstäubens verändert wird, um dem Sprühnebel eine Bewegung zu erteilen, während die Gesamtgeometrie des Zerstäubergasstromfelds im wesentlichen konstant gehalten wird.

14. Verfahren nach Anspruch 13, zu welchem weiterhin das Kippen der Zerstäubereinrichtung um eine Achse gehört, um dem asymmetrischen Gasstromfeld eine Hin- und Herbewegung zu erteilen.

15. Verfahren nach Anspruch 13, bei welchem der Sprühnebel gegen ein Substrat gerichtet wird, das sich kontinuierlich durch den Sprühnebel bewegt, wobei der Sprühnebel quer zur Bewegungsrichtung durch Hin- und Herkippen der Zerstäubereinrichtung bewegt wird, um eine gleichförmige Dicke der Abscheidung über dem Substrat zu erzielen, und der Sprühnebel seitlich in der Bewegungsrichtung auseinandergezogen wird, indem die Lagebeziehung des asymmetrischen Gasstromfelds verändert wird, um eine Gleichförmigkeit der Abscheidung in der Bewegungsrichtung des Substrats zu erzielen, um so Bandprodukte, beschichtete Bandprodukte, Plattenprodukte oder beschichtete Plattenprodukte herstellen zu können.

16. Verfahren nach Anspruch 13, 14 oder 15, bei welchem in den Sprühnebel metallische oder keramische Teilchen aufgegeben werden, damit sie in einer auf einem Sammelsubstrat gebildeten Abscheidung eingeschlossen werden.

17. Verfahren nach einem der Ansprüche 13 bis 16, bei welchem die Bewegungen des Sprühnebels so gesteuert werden, daß durch Sprühnebel abgeschiedene Barren, Stangen, Rohre, Ringe, Rollen, konische Formkörper, Schmiederohlinge und Extrusionsrohlinge, Formkörper für thixotrope Verformung, laminierte oder beschichtete Produkte und Metallmatrixverbundstoffe hergestellt werden.

18. Verfahren nach Anspruch 13, bei welchem der Strom durch Aufbringen eines Zerstäubergases zerstäubt wird, das aus wenigstens zwei relativ drehbaren Rotoren austritt, und das den weiteren Schritt aufweist, die Lagebeziehung und/oder die Asymmetrie des Gasstromfelds bezüglich des Stroms während der Zerstäubung zu variieren, um dem Sprühnebel eine Bewegung zu erteilen, entweder dadurch, daß die Gesamtgeometrie des Zerstäubergasstromfelds im wesentlichen konstant gehalten wird, indem die Rotoren synchronisiert werden, oder dadurch, daß die Asymmetrie des Gasstromfelds variiert wird, indem eine Relativbewegung zwischen den Rotoren während der Zerstäubung bewirkt wird.

19. Verfahren nach Anspruch 13, bei welchem der Sprühnebel im Flug abkühlen und sich verfestigen gelassen wird, wodurch Metallpulver gebildet wird.

Revendications

1. Appareil pour pulvériser un courant liquide de métal ou d'alliage de métaux à l'aide d'un gaz comprenant:
   un dispositif de pulvérisation destiné à être alimenté en gaz de pulvérisation;
   une ouverture définie par le dispositif de pulvérisation, à travers laquelle le courant peut être déversé;
   un rotor, supporté par le dispositif de pulvérisation, et comportant une buse annulaire ou une pluralité de buses disposées autour de l'ouverture à travers laquelle le gaz de pulvérisation peut passer pour pulvériser le courant en formant, pendant l'utilisation, un jet de gouttelettes, le gaz de pulvérisation provenant de la buse annulaire ou de la pluralité de buses constituant un flux de gaz de pulvérisation qui, lorsque le rotor est fixe, entoure le courant et présente une géométrie asymétrique par rapport à l'axe du courant;
   un moyen pour produire le mouvement du rotor par rapport au dispositif de pulvérisation et faire varier la relation de position existant entre le flux de gaz asymétrique et le courant, de façon que l'asymétrie du flux de gaz de pulvérisation puisse provoquer le déplacement du jet d'aspersion par rapport à l'axe du courant liquide, tandis que la géométrie globale du flux de gaz de pulvérisation demeure sensiblement constante.

2. Appareil selon la revendication 1, dans lequel le rotor de pulvérisation comprend une pluralité de buses de pulvérisation de dimensions variables disposées autour du rotor, de façon qu'un courant de gaz asymétrique puisse être produit.

3. Appareil selon la revendication 1, comportant une pluralité de buses de pulvérisation, le flux de gaz asymétrique étant produit par variation de l'angle d'attaque des buses de pulvérisation autour du rotor.

4. Appareil selon la revendication 1, dans lequel le flux de gaz asymétrique est produit par l'axe du rotor, qui est espacé de l'axe du courant.

5. Appareil selon la revendication 1, comportant une pluralité de buses de pulvérisation, le flux de gaz asymétrique étant produit par disposition des buses d'amenée de gaz de pulvérisation dans le rotor de façon asymétrique par rapport à son axe.

6. Appareil selon la revendication 1, dans lequel le rotor de pulvérisation comprend une buse de pulvérisation annulaire, le flux de gaz asymétrique étant produit par l'ouverture annulaire dont la largeur ou position dans le rotor varie autour de l'axe du rotor de façon à former le flux de gaz asymétrique.

7. Appareil selon la revendication 1, comportant deux rotors comprenant chacun une buse ou une pluralité de buses de pulvérisation pour former un flux de gaz asymétrique par rapport à l'axe du courant liquide, chacun pouvant être déplaçable par rapport à l'autre et par rapport au dispositif de pulvérisation de façon que, en association, il soit possible de faire varier l'asymétrie du flux de gaz par rapport au courant liquide.

8. Appareil selon l'une quelconque des revendications précédentes, comportant en outre des moyens pour basculer le dispositif de pulvérisation, de façon que pendant la pulvérisation, le jet d'aspersion puisse être déplacé alternativement par basculement du dispositif de pulvérisation.

9. Appareil selon la revendication 1, comprenant une chambre ou plenum formé à l'intérieur du dispositif de pulvérisation;
   des moyens couplés au dispositif de pulvérisation pour supporter le dispositif de pulvérisation, comportant un chemin d'admission faisant communiquer la chambre ou plenum avec une source de gaz de pulvérisation; et
   plusieurs ouvertures d'arrivée de gaz de pulvérisation formées dans le rotor, pour diriger le gaz de pulvérisation vers le courant liquide qui traverse l'ouverture, les ouvertures d'arrivée de gaz de pulvérisation étant placées dans une relation fixe prédéterminée les unes par rapport aux autres, de façon à former un flux de gaz de pulvérisation d'une géométrie prédéterminée.

10. Appareil selon la revendication 9, comportant des moyens de commande fonctionnant par mise en oeuvre soit d'un mouvement oscillant angulaire au rotor, soit d'une rotation complète.

11. Appareil selon la revendication 10, dans lequel les moyens de commande comprennent un engrenage à ergot se connectant avec le rotor, permettant de déplacer le rotor par rapport au dispositif de pulvérisation.

12. Appareil selon la revendication 1, comportant au moins un premier et un second rotors qui peuvent être déplacés l'un par rapport à l'autre, et par rapport au dispositif de pulvérisation, et dans lequel la géométrie globale du flux de gaz de pulvérisation reste sensiblement constante lorsque les rotors sont synchronisés.

13. Procédé de déplacement d'un jet d'aspersion de gouttelettes pulvérisées de métal ou d'alliage de métaux fondu comprenant les étapes consistant à faire passer un courant de métal ou d'alliage de métaux fondu par une ouverture située dans un dispositif de pulvérisation, à munir le dispositif de pulvérisation d'un rotor comportant une buse ou plusieurs buses de pulvérisation disposées autour de l'ouverture, à alimenter le dispositif de pulvérisation en gaz de pulvérisation de façon qu'un flux de gaz de pulvérisation soit formé, lequel, lorsque le rotor est fixe, entoure le courant liquide et présente une géométrie asymétrique par rapport à l'axe du courant liquide, à diriger le flux de gaz de pulvérisation vers le courant liquide pour atomiser le courant liquide et former un jet de gouttelettes, et à déplacer le rotor de façon à faire varier la relation de position existant entre le flux de gaz de pulvérisation et le courant liquide pendant la pulvérisation pour provoquer le mouvement du jet tout en maintenant sensiblement constante la géométrie globale du flux de gaz de pulvérisation

14. Procédé selon la revendication 13, comprenant en outre le basculement du dispositif de pulvérisation autour d'un axe afin de soumettre à un mouvement alternatif le flux de gaz asymétrique.

15. Procédé selon la revendication 13, dans lequel le jet d'aspersion est dirigé vers un substrat se déplaçant en continu dans le jet d'aspersion, le jet d'aspersion étant déplacé transversalement par rapport au sens du mouvement, en basculant le dispositif de pulvérisation alternativement, afin d'obtenir une uniformité d'épaisseur du dépôt sur le substrat, et le jet d'aspersion étant déplacé latéralement selon le sens du mouvement en faisant varier la relation de position existant entre le flux de gaz asymétrique pour obtenir une uniformité du dépôt selon le sens du mouvement du substrat de façon que des produits en bandes, en bandes revêtues, en plaques ou en plaques revêtues, puissent être formés.

16. Procédé selon la revendication 13, 14 ou 15, dans lequel des particules métalliques ou céramiques à incorporer dans un dépôt formé sur un substrat collecteur sont contenues dans le jet.

17. Procédé selon l'une quelconque des revendications 13 à 16, dans lequel les mouvements du jet d'aspersion sont contrôlés de façon à produire des dépôts par aspersion, sur lingots, barres, tubes, anneaux, rouleaux, formes coniques, des galettes forgées et extrudées, des formes pour déformation thixotropiques, des produits feuilletés ou revêtus, et des composites de matrices métalliques.

18. Procédé selon la revendication 13, dans lequel le courant liquide est pulvérisé par action d'un gaz de pulvérisation provenant au moins de deux rotors pouvant tourner de façon relative; et comprenant l'étape supplémentaire de variation de la relation de position et/ou de l'asymétrie du flux de gaz par rapport au courant liquide pendant la pulvérisation pour que le jet d'aspersion effectue un mouvement, soit en maintenant sensiblement constante la géométrie globale du flux de gaz de pulvérisation par synchronisation des rotors, soit par variation de l'asymétrie du flux de gaz en effectuant un mouvement relatif entre les rotors pendant la pulvérisation.

19. Procédé selon la revendication 13, dans lequel on opére de façon que le jet d'aspersion se refroidisse et se solidifie en vol et qu'une poudre métallique soit formée.

Drawing