EP0260617B1 - Process and apparatus for preparing and finishing metallic materials - Google Patents

Abstract

Liquid metal undergoes rapid rotational motion in an induction field and utilizes the resultant centrifugal forces to extend the metal in the form of a rotating film, the film becoming progressively thinner, along a baffle surface located in the induction field. The liquid metal can then emerge through the baffle surface in the form of wires or can be reduced in size on a cylindrical impact wall and then cooled.

Description

The present invention relates to a method and a device for the production and further processing of metallic substances by directly acting on liquid metal with the centrifugal forces of a rotating induction field, which set the liquid metal in a rotationally symmetrical container wall in a rotating movement.

It is known to break up and cool liquid metals in such a way that finely divided metallic powders or wires are formed.

The rate of cooling determines the structure of the products produced; very high cooling rates even lead to glass-like, i.e. amorphous structures.

Various methods are known for achieving these goals. One of these methods is to allow the metal to be atomized or cooled to flow out of a mostly heated and pressurized crucible through a nozzle provided with a relatively small opening and then by means of gas jets or through rapidly rotating and mostly cooled plates, hollow spheres, Cut and cool cylinders etc. A combination of these methods has also been proposed.

Other processes provide for the rapid cooling of metals by introducing them into a liquid that is pressed perpendicularly against a container wall by centrifugal forces.

However, these known methods have the disadvantage that fast rotating components are required, which leads to unbalance and contamination problems at these high speeds.

These problems do not exist in the method described at the outset and known from FR-A-2391799, according to which the rotational movement of the liquid metal is inductively brought about and accordingly no moving parts are required. However, this known method has the disadvantage that the liquid metal is rotated in a tube which is closed at the bottom except for a small central opening nozzle and through which the metal must then also leave the tube. Because of this small nozzle, firstly, the yield is limited and secondly, this nozzle poses a risk of clogging and is subject to rapid abrasion wear. In addition, the liquid metal is pressed tubularly against the inner wall of the tube due to the centrifugal force during the rotational movement and thus hardly has the opportunity to escape through the axially arranged nozzle.

From the two publications FR-A-1205683 and FR-A-1106022 it is known to empty vessels filled with liquid metal by rotating the metal electromagnetically and pumping it out of the vessel by centrifugal forces.

From the document FR-A-2352612 it is also known to produce tubular products by inductively rotating liquid metal and deforming it into a tube along a cylindrical wall.

The present invention is based on the object of creating a new method and a new device starting from the method described at the outset which no longer have the known disadvantages and additionally offer better possibilities for utilization.

To achieve this object, a method according to claim 1 is proposed.

In cases where an even more extensive division or faster cooling of the products produced is desired, the products divided by the described inductive centrifugation can by known methods such as gas atomization and / or impact atomization on rotating objects or in liquids or in an inductive movement and cooling device can be further divided or cooled. A device according to claim 4 is proposed for carrying out the method. Further preferred embodiments of the method according to claim 1 and the device according to claim 4 are contained in the dependent claims.

In this way, the metal is subjected to a very large acceleration and, as a result, to a very large extent centrifugation and fragmentation. In individual cases, it may be appropriate to attach a further flat inductor under the flattened hyperboloid, such that the metal is further divided in the annular gap between the trumpet-shaped guide surface and the flat inductor. In order to protect the refractory lining of the inside of the diverging extension or extension, it is advantageous to provide cooling between this diverging guide surface and the inductors. This cooling can be so intense that a thin-strength metal layer approach is formed, which permanently protects these parts.

It has been found to be particularly advantageous not to mechanically rotate an impact surface, which rotates in the same sense or in the opposite sense as the flowing metal current, but rather to expose the metal particles themselves to a rapidly rotating induction field by means of inductors arranged on or around the impact surfaces. This method has the advantage of creating a system which, with no moving parts, results in an excellent cutting and cooling of the metals, so that the entire process can be carried out without problems under high vacuum.

Furthermore, it was found that, depending on the intended use of the product obtained, the bodies or liquids used for collecting or impacting can have the same direction of rotation as the inductively centrifuged metal stream, or can be rotated in the opposite direction to increase the impact effect or cooling effect.

Furthermore, it was found that the centrifugal force generated depends largely on the frequency of the electric current used, and that it is quenched during the production of very fine or very fast Products the application of frequencies of several 100 or several 1000 Hertz comes into question.

In the case of mass casting of metals such as aluminum, steel, etc., various proposals have been made to influence the casting speed by surrounding the spout with a traveling wave inductor, the electrical action of which is a controlled variable.

The application of this principle to very small spouts can lead to a substantial enlargement of the spout in the present method and thus to operational simplification. Within the scope of this invention it was found that a helicoid arrangement of the inductors can lead to an additional possibility of regulating the liquid metal flow and consequently the end effect, an upward helicoid induction field reducing the throughput and a downward helicoid induction field increasing the Throughput.

If the method is used correctly, such large centrifugal forces of the liquefied metal can be achieved that a tube can be continuously hurled onto a cylindrical impact wall, the wall thickness of which can reach from 1 mm to several centimeters. This tube can be drawn off continuously and then rolled as a tube. However, it can also be slit open, with a continuous metal strip being formed after straight bending, which can then be further shaped as a strip hot and / or cold. The separation of the continuously formed pipe cross-section can be facilitated by the fact that the cylindrical impact wall has a slightly tapered extension.

The method described so far essentially relates to a liquid metal stream which, apart from the rotating induction field, is exposed to its own gravity. But it was now in the frame According to this invention, it was found that the application of a rotating induction field to a quantity of metal simultaneously moving in the opposite direction to gravity leads to a substantial increase in the effect of the induction forces. In this way, control by means of flow nozzles can be dispensed with in many cases, whereby other control options can be used.

According to this aspect of the method, the metal is conveyed in a direction substantially opposite to gravity by inductors and at the same time subjected to a rotating induction field, such that the metal is set in a rapid rotating movement and is subjected to centrifugal forces driving upwards, upon leaving the Device largely divides the metal flow.

The device for practicing this further development of the method according to the invention advantageously essentially consists of a cone-shaped guide surface which is closed at the bottom and expanded at the top and which is provided with inductors in such a way that a rotating induction field is generated in the interior of the cone, so that the metal located in the cone is centrifuged and, due to the conical design, is simultaneously spirally conveyed upwards.

It has been found to be particularly advantageous to increase the divergence of the cone continuously, ie in the shape of a trumpet or in a leap, and to provide the guiding surface formed in this way with a plurality of inductors. These inductors can have the same rotational speed. However, it has proven to be particularly advantageous to design or feed the inductors in such a way that the rotational speed is increased from bottom to top. It has turned out to be particularly advantageous to provide the upper part of the guide surface with a hyperboloid-like or trumpet-shaped outlet shape.

It does not fall outside the scope of this invention to support the inductive rotary movement of the device or the conical guide surface with its possibly associated hyperboloid-like or trumpet-shaped exit shape by a mechanical rotary movement of these parts.

The diverging guide surface can also be placed at the top end opposite a flat inductor, such that an annular gap is created between the outlet and the flat inductor.

The lower part of the diverging container normally consists of a flat or chopped bottom, advantageously a substantially cylindrical intermediate jacket between the bottom and the conical part.

This lower part, in which the liquid metals to be treated are introduced from below or from above, is advantageously heated.

The lower conical and / or cylindrical part is advantageously provided with helicoidally directed and controllable inductors in such a way that the metal flowing into the lower part can be brought in a regulated form into the area of the strong centrifuging inductors attached around the conical part and can be further processed there .

As already mentioned, this system can be operated with or without a control nozzle. If you want to work with a control nozzle, it can convey the metal through the axis of the cone or the diverging guide surface to the bottom and allow the metal to escape in a controlled manner. In this case, the storage container is located above the system. This arrangement has the advantage of not influencing the centrifuging circuit.

In other cases it will be possible to remove the metal to be atomized from below e.g. through a U-tube into the bottom or into the cylindrical part.

In other cases it is possible to use the cylindrical part and / or part of the cone as an induction furnace form where the metal to be atomized is melted or brought to the desired temperature or kept.

The amount to be withdrawn can be regulated by the lowest inductors, which can have a helicoid effect.

Moreover, it was found that the inductors attached to the conical or hyperbolic surface can also have a downward or upward helicoid effect.

At least the parts of the described devices exposed to the inductors should preferably be made of non-magnetic or electrically non-conductive materials.

From the above it can be seen that the liquid metal to be treated which is introduced into the lower part of the device is possibly heated there and transported upwards and is subjected to centrifugal forces in the diverging part by strong inductors, which are possibly arranged in several planes, and by this the diverging guide surface is moved upwards in order to be centrifuged and atomized at high speed at the upper end of the cone or at its trumpet-shaped extension.

It has been found that this type of installation, in which the metal is moved against gravity, is also very suitable for producing very fine wires, e.g. forms the cone in the hyperboloid exit shape and provides this exit shape with grooves or ribs. The wire produced in this way can, as already described above, be immediately collected in liquid cooling containers.

The device according to the invention also makes it possible to spin or atomize in a targeted direction, which is very favorable in many applications, for example for application coatings. In this case, the upper part of the cone is provided with a cover and the cone itself in the direction of the one to be coated Provide products with one or more slits, which allow the finely divided metal used for atomization or coating to exit. The excess metal can be piped back to the bottom of the device. In this case it can be advantageous to position the system at an angle or horizontally.

It has been found to be particularly advantageous that the device is constructed in such a way that the parts exposed to the metal bath, such as the cone with or without a cylindrical lower part and possibly with a hyperbolic upper part, are easily removed from the others for reasons of quality of the metals to be atomized or for reasons of wear System parts such as inductors, possibly heating or cooling system can be installed and removed.

Figur 1:

eine erste Ausführungsform der Erfindung;

Figur 2:

eine zweite Ausführungsform der Erfindung;

Figur 3:

eine Variante der Ausführungsform gemäss Figur 2; und

Figur 3A:

Einzelheiten des oberen Teils der Leitfläche aus Figur 3.

.The invention is described in more detail below with the aid of a few exemplary embodiments and with reference to the figures, in which the same parts are provided with the same reference numbers. Show it:

Figure 1:

a first embodiment of the invention;

Figure 2:

a second embodiment of the invention;

Figure 3:

a variant of the embodiment according to Figure 2; and

Figure 3A:

Details of the upper part of the guide surface from FIG. 3.

.

The system according to FIG. 1 understands the crucible 1, which contains the metal 2, the temperature of which is regulated by the inductor 3. The metal flows, possibly conveyed by a slight overpressure, through the abrasion-resistant nozzle 4 provided with a small cylindrical bore, which is then directly extended by a trumpet-shaped or hyperboloidal refractory and abrasion-resistant guide surface 34. The entire surface of 34 is cooled with a liquid which is introduced in closed cooling coils at 35 and is discharged at 36. The quantity of metal stream entering the nozzle 4 is regulated by the helicoid inductors 5, at the same time a slight rotary movement of the metal jet can be generated. After the metal has entered the space delimited by the guide surface 34, the strong inductors 37 set the metal into a very rapid rotary movement, which is then further accelerated by flat inductors 38, such that the metal particles with a are thrown at very high speed against the cylindrical wall 40 cooled by the water nozzles 39. This wall 40 can be rotated in the ball bearing 41 by a drive device, not shown. However, if you want to carry out the atomization under vacuum, the wall 40 is tightly connected to a hood 42 and the entire closed system is evacuated via a nozzle 43. In this case, the metal thrown against the wall 40 can be further moved and distributed by the inductors 44 which are attached around the cylindrical wall 40. The metal particles generated collect in the lower funnel-shaped part 40a, from which they can be removed after opening a valve 45 and are fed directly to a compacting system after a possible intermediate heating.

If an even greater acceleration of the metal particles emerging under the guide surface 34 is to be achieved, a ring 47 provided with the flat inductors 46 can be attached under the diverging guide surface 34 such that an annular gap 48 is formed between the guide surface 34 and the ring 47 which the metal particles are accelerated even further. In order to avoid freezing of the metal in this annular gap 48, the ring 47 can be heated, e.g. through the inductors 46.

The direction of rotation of the entire system, excited by the inductors 37, 38 and possibly 46, should be the same in all cases. The impact wall 40 or the inductors 44 can, depending on the desired nature of the end product, either work in the same direction of rotation of the aforementioned inductors or act in the opposite direction.

When leaving the annular gap 47, the divided products can also be treated further, as described above.

A device similar to that shown in FIG. 1 can lead to the production of tubes, or after slitting the tubes, of flat products. In this case, the impact wall 40 is designed to be slightly tapered downwards. The funnel-shaped approach 4a is omitted. The cooling nozzles 39 are then designed to be so weak that the particles emerging from 48 weld themselves together, the inductors 44 ensuring a uniform distribution of the particles spun on. At high throughputs, the divided metal flow between the annular gap 48 and the impact wall 40 is cooled by cooling, preferably inert gas cooling.

This by spinning and welding together The tube of the individual particles is continuously pulled out by an extraction system (not shown) and then possibly rolled, for example in a planetary diagonal rolling mill. As already mentioned, the shaped tube can be slit open and then rolled and wound in the form of a continuous strip, possibly subsequently, warm and / or possibly cold.

While in the previously described embodiment the metal is centrifuged in a falling manner, in the following embodiments according to FIGS. 2 and 3 it is in a direction opposite to gravity, i.e. transported or centrifuged from bottom to top.

The system according to FIG. 2 understands the crucible 1, which contains the metal 2, the temperature of which is regulated by the inductor 3. The metal flows through a line 1a into a container 60 of the device, which may be designed as a cylindrical storage container heated by inductors 61 and is extended upwards by a fireproof and abrasion-resistant guide surface 62 which widens in a trumpet-like or hyperboloidal manner. All or at least the uppermost part of the guide surface 62 is cooled with a liquid which flows, for example, through cooling coils or is located in a closed space and is introduced through 63 and is discharged through 64. The cooling can also take place via atomizing nozzles. A measuring probe 65 ensures a constant level of the metal bath 66 in 60 by operating a stuffing rod 69 via the controller 67 and an actuator 68 and / or actuating the inductors 5 designed as an induction valve. A set of inductors is arranged along the underside of the guide surface 62. The metal is first accelerated more and more by inductor 70a and then by inductors 70b, 70c and 70d. These inductors can produce a simple rotary movement, but can also be designed helicoidally, for example the lower inductors 70a and 70b causing an upward helicoidal movement, and the upper inductors 70c and 70d can possibly act downwards in order to expose the metal to the centrifugal forces for as long as possible. It is also appropriate to apply increasing frequencies to the inductors from 70a to 70d. For example, in most cases it is sufficient to operate the inductor 70a at the mains frequency, ie at 50 Hertz, the inductor 70b at 200 Hertz, the inductor 70c at 1000 Hertz and the inductor 70d at 2000 Hertz to be operated advantageously. It can easily be seen that the metal leaves the guide surface 62 with very large centrifugal forces and consequently with very large atomization.

If an even greater acceleration of the metal particles leaving the guide surface 62 is desired, a ring 73 provided with the flat inductors 72 can be attached over the diverging guide surface 62 in such a way that an annular gap 74 is formed between the edge of the guide surface 62 and the ring 73 which the metal particles are accelerated even further. In order to avoid freezing of the metal in this annular gap, the ring 73 can be heated e.g. through the inductors 72.

As already mentioned, moving the device up and down relative to the impact wall 75 or vice versa can lead to a greater regularity of the product obtained.

The device can also be used to produce fine wires, in that the exit side of the guide surface is provided with ridges and / or ribs 76, where the desired amount of metal is collected and collected in a liquid-filled, possibly rotatable basin 77, a very rapid cooling of the generated rays and a large length of the wires produced is achieved (left side of Figure 2).

The system described can also be used to coat metal strips, which are either bent spirally or temporarily around a tube the system can be pulled through.

The entire system described above can be centrifuged. However, if you want to centrifuge in a certain direction, e.g. The system can be placed at an angle or horizontally for the production of thin wires or for further atomization by gas jets.

Another embodiment of the device according to FIG. 2 is shown in FIG. 3. This system was specially designed for one-sided centrifugation e.g. developed for coating purposes or for further atomization by gas jets. It also illustrates the possibility of feeding through an oven placed next to the system. The system shown in FIG. 3 operates on similar principles to the system shown in FIG. 2, with the difference that the centrifuged metal is thrown out through the opening or slot 81 or the openings or slots 81, 82 and 83 (see also FIG. 3A) and that the excess amount can be collected in a trough 84 and returned to the crucible via a return 85. As it exits through the slots, the already finely divided metal can be atomized and cooled further by gas nozzles 86 or can be passed on to a rolling mill. This device can also be closed with a lid at the top.

As illustrated in FIG. 3, the crucible 1 is located next to the centrifuging system and is connected to the storage container 60 via the line 87 according to the principle of communicating tubes.

The return 85 into the crucible 1 is preferably surrounded by a heating winding 88 in order to prevent premature solidification.

Since the gravitational forces are negligible compared to the centrifugal forces, the devices can also be set up horizontally or at an angle. This applies particularly to systems which, according to FIG. 3, have openings or slots in liquid metal strands emerging from the guide surfaces. The diverging or even cylindrical guide surface can then be closed on the side opposite the entry of the liquid metal.

In summary, it should be emphasized that all of the exemplary embodiments described above have the common feature that a liquid, full metal strand is deformed at the latest at the central entrance into the rotationally symmetrical guide surface by the centrifugal forces of the induction-induced rotational movement. This hollow, hurled metal strand then widens conically or trumpet-shaped along the inner guide surface under the action of centrifugal force, this guide surface being acted upon by a continuous liquid metal film, the thickness of which decreases in accordance with the increase in radius. The flow at the inlet of the guide surface and the frequency and intensity of the inductive rotating fields are matched to the dimension of the guide surface in such a way that the metal film at the exit edge of the guide surface is so thin that the metal film tears and is completely atomized.

Claims (25)

1. A method of producing and further processing metallic substances by direct action on liquid metal with the centrifugal forces of a rotating induction field which set the liquid metal in rotation inside a rotationally symmetric limiting wall, whereby the centrifugal forces are utilized for extending the metal in the form of a rotating film, becoming progressively thinner, along a baffle surface located in an induction field, and whereby the liquid metal is conveyed in the form of a complete metal billet into a tubular nozzle in which it is performed into a tubular billet by inductive centrifugal forces and then, along a baffle surface spreadung out conically or in a trumpet shape, is further formed in an inductive rotating field into a conical or trumpet-shaped film which becomes progressively thinner.
2. Method according to claim 1 characterized in that the liquid metal is lifted up out of a vessel in the direction opposite to the direction of its gravitational force by inductively induced centrifugal forces.
3. Method according to one of claims 1 or 2, characterized in that the rotating metal film, by ribs or slots shaped on or in the baffle surface, is formed in a wire or strip shape and is then cooled.
4. A device for performing the method according to one of the claims 1 to 3, consisting of a crucible (1), acting as a supply container for the liquid metal (2), a centrifuging device and electromagnetic inductors for rotating the liquid metal in the centrifuging device, wherein the centrifuging device consists of an axially symmetric baffle surface (34, 62), on the outer surface of which the inductor or inductors (38, 70) are arranged, wherein the crucible (1) is connected to the inside of the baffle surface (34, 62) by an axial connecting section, and wherein the baffle surface (34, 62) widens in a trumpet shape or hyperboloidally.
5. Device according to claim 4, characterized in that the connecting section consists of a tubular nozzle (4) which forms an axial outlet of the crucible (1) and which at the bottom merges into the baffle surface (4a, 34).
6. Device according to claim 5, characterized in that the nozzle (4) is surrounded by an inductor (5) which produces a rotary field controlling the flow.
7. Device according to claim 6, characterized in that the inductor (5) has several pole shoes (5a, 5b, 5c) which are arranged helicoidally around the nozzle (4).
8. Device according to laim 4, characterized in that the baffle surface (34, 62) is provided with a cooling system on the inductor side.
9. Device according to one of claims 4 or 6, characterized in that, oppostie the baffle surace (34, 62) opening in a trumpet shape, a flat axially symmetric inductor ring (47, 73) is provided which forms an annular discharge gap (48,74) with the outer edge of the baffle surface (34, 62).
10. Device according to claim 4, characterized in that several inductors (37, 38) are allocated to the baffle surface (34), which inductors (37, 38) induce variously orientated rotary fields which are adapted to the change in direction of the deflected metal particles.
11. Device according to one of claims 4, 5, 8, 10, characterized in that the trumpet-shaped baffle surface (62) extends upwards from the upper edge of a cylindrical vessel (60).
12. Device according to claim 11, characterized in that the crucible (1) is arranged above the vessel (60), and in that a connecting line (1a) extends axially through the baffle surface (62) between the crucible (1) and the vessel.
13. Device according to claim 11, characterized in that the crucible (1) is arranged next to the trumpet-shaped baffle surface (62) and is connected to the vessel (60) according to the principle of communicating pipes.
14. Device according to one of claims 11 to 13, characterized in that the vessel (60) is surrounded by a heating system (61).
15. Device according to one of claims 11 to 14, characterized by a neasuring probe (65) for measuring and regulating the level in the vessel.
16. Device according to one of claims 11 to 15, characterized in that the inductor (70) allocated to the baffle surface consists of several inductor stages (70a, 70b, 70c, 70d).
17. Device according to claim 16, characterized in that the inductor stages (70a, 70b, 70c, 70d), as the baffle surface (62) widens, can be fed with correspondingly higher current frequencies.
18. Device according to one of claims 4 to 10, characterized in that the baffle surface (34, 62) is arranged coaxially inside a cylindrical impact wall (40, 75).
19. Device according to claim 18, characterized in that the impact wall (40, 75), is subjected to the action of a cooling device (12, 39).
20. Device according to claim 18 or 19, characterized in that electromagnetic inductors (44) are arranged on the outside of the impact wall (40, 75), which electromagnetic inductors (44) exert an inductive rotary field on the metal particles flung onto the inside of the impact wall (40, 75).
21. Device according to one of clains 18 to 20, characterized in that the impact wall (40, 75) is rotatable about its longitudinal axis and about the axis of symmetry of the baffle surface (34, 62).
22. Device according to one of claims 18 to 21, characterized in that the impact wall (40, 75), together with a hood (42) and a collecting funnel (40a), form a vacuum-tight housing about the centrifuging device and the supply crucible (1).
23. Device according to one of claims 11 to 17, characterized in that the trumpet-shape baffle surface (62) has discharge slots (81, 82, 83) near the outer edge.
24. Device according to claim 23, characterized by a collecting channel (84) which is provided at the upper outer edge of the baffle surface (62) and is connected to the crucible (1) by a heated return (85).
25. Device according to one of claims 4 to 24, characterized in that compressed-gas discharge nozzles (86) directed towards the metal particles flung out of the baffle surface are provided at the outermost edge of the baffle surface (34, 62).

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