JPS648041B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a first chamber, mountable on the first chamber, having a device for converting a molten metal stream into initially liquid and then solid metal particles in a non-oxidizing atmosphere; The present invention relates to an apparatus for producing metal powder from molten metal, having an intermediate ladle with a closable bottom hole which can be discharged into the first chamber, and a melting device for charging the molten metal into the intermediate ladle.

Metal powder production apparatuses belong to the prior art in which an intermediate ladle is always mounted on the powder production chamber and in which the melting device for charging the intermediate ladle is an open induction furnace. However, this entails the risk of partial oxidation of the molten metal by oxygen in the air as well as absorption of undesired gases by the molten metal (West German Patent Publication No. 2459131).
No. Specification).

According to West German Patent Publication No. 1041652,
Vacuum induction melting devices with gate devices for mold casting or ingot casting are known. The mold does not have a bottom hole and is not useful for transporting molten metal to the metal powder manufacturing equipment. The mold has no lid and therefore must be cooled in the gate chamber until the metal is at least partially solidified. The mold cannot also be called an intermediate ladle.

West German Patent Publication No. 1182396 also in principle
A vacuum apparatus for producing mold castings is known, which is similar to that according to document 1041652. Molds are also useless for transporting molten metal to post-processing equipment;
There is also no shutter suitable for this purpose, which would be able to protect the mold contents against atmospheric influences during transport.

DE 2007803 A1 discloses an atomization device, in particular for atomizing aluminum. The melter is not equipped with a vacuum or protective gas chamber, nor is it equipped with a gating device. Rather,
The molten aluminum is charged via an open trough into an optionally open conveying device which conveys the molten metal to the installation, and in an atomization device the molten metal is atomized under protective gas.

Furthermore, another gas-tight chamber is arranged directly above the powder production chamber, in which the intermediate ladle and the melting device are located, so that there is protection both within the melting device and in the powder production chamber. Devices for the production of metal powders with which an atmosphere can be maintained belong to the prior art (DE 1558370 and DE 2308061). However, such metal powder manufacturing equipment must take into account that the metal powder manufacturing chamber already has a height dimension that is limited by the falling speed of the metal particles and the residence time until solidification. It has a considerable overall height. Generally, such chambers have the shape of a tower or a slender cylinder with a conical end. Moreover, such devices are uneconomical to operate, since the melting capacity of the melting device is significantly larger than the capacity of the downstream metal powder production chamber.

Finally, it should be noted that prior art also includes a metal powder manufacturing apparatus in which a dusty raw material is converted into droplets by continuous melting and atomized using, for example, a rotating disk (see German Patent Publication No. 2528999). ). Such devices are advantageously provided for high-value metals with very high purity requirements, but have only a small production capacity, which is limited by the drip-melting process.

The object of the invention is to provide a melting device in which the molten metal is protected against constant oxidation and/or gas absorption, has a relatively small overall height, and has a melting device according to the preamble of claim 1. It is an object of the present invention to provide a metal powder production device which can be used to additionally charge still another metal powder production chamber.

The solution to the problem set out is that in the metal powder production device according to the invention as described in the introduction, (a) the melting device is spatially separated from the first chamber, in order to maintain a non-oxidizing atmosphere; (b) the second chamber comprises at least one gate for the entry and exit of the intermediate ladle, and (c) the intermediate ladle configured as a transport vessel is enclosed by a second chamber for transport and powder production. and (d) a second chamber of the melting apparatus is provided with a lid for maintaining a non-oxidizing atmosphere during the discharge into the first chamber, and (d) a second chamber of the melter is provided with a lid for removing the lid for the intermediate ladle charging process. This is done by having a drive device.

According to the device of the invention, the connection between the metal powder production chamber and the melting device is removed, so that the melting device can be used for other purposes, for example for charging at least one further metal powder production chamber. This has the advantage that it can also be used. The molten metal can be transported over long distances by constructing the intermediate ladle not only as a pouring spout but also as a transport container combined with a device or a lid for maintaining a non-oxidizing atmosphere. However, it is possible to be protected against oxidation and/or gas absorption. At the same time, the overall length of the device is significantly reduced, so that the construction costs for assembling the device are also minimal.

The device of the invention can be used in conjunction with all methods of dividing continuous and discontinuous melt streams into individual metal particles. Examples of this include a spraying method in which molten metal is broken into fine droplets by one or several gas jets, an ultrasonic atomization method, and a centrifugal method in which molten metal is atomized by centrifugal force. .

The device according to the invention particularly preferably works with an intermediate ladle, the intermediate ladle having a metal jacket;
A ceramic lining forming a crucible, having a first insulating layer disposed between the crucible and the jacket, with vertical, open at the top distributed circumferentially between the crucible and the first insulating layer. A ceramic intermediate layer is arranged which has several shafts which are open but closed on the sides, into which a resistive heating element is inserted from above using an insulating holding device, the lower heatable part of the heating element being inserted. is arranged at a distance from the shaft wall, and the upper non-heatable portion is surrounded by an insulation holding device.

The intermediate ladle serves as a transport container. Such containers are often used, as the name already suggests, not only for transporting the molten metal between the point of production and the point of consumption of the molten metal, but also for the time determined by the time of extraction of the molten metal from the container. It is also useful for storing molten metal. In this case, the storage time becomes considerable, especially when the flow rate per unit time is small compared to the stored melt. This situation arises in particular when producing metal powder from molten metal. The production of powders from liquid metals by numerous methods and alternatives, as well as the equipment necessary for this, belongs to the prior art.

The transportation and storage of the molten metal presupposes the maintenance of a constant temperature profile until the entire molten metal is consumed. To omit heating after each mold, it is necessary to first superheat the molten metal, which heating must be all the more the worse the insulation of the transport container. However, overheating increases the risk of increased gas absorption and of external influences or wear of the container lining. Therefore, attempts are generally made to heat the transport container.

Heating by means of arc electrodes is limited by the considerable structural complexity of the container lid and is not practical in transport containers with lids. Induction heating of molten metal is similarly difficult. External induction coils are easy to install and use in practice, but presuppose at least a field-permeable window in the non-ferromagnetic jacket or jacket of the container. The internal induction coil is
This creates thermal engineering problems that have to be solved by intensive cooling with high energy losses, as well as insulation problems if the interior of the transport container is to be placed under vacuum. Resistance heating devices with heating conductors embedded in the lining or ceramic material are not suitable for many ceramic materials, which are problematic for the above purpose.
At temperatures above 1000°C it becomes increasingly conductive, creating insulation problems.

The disadvantage of the conventionally used total heating devices and heating methods is that they do not have a sufficiently large heat storage capacity. This has a disadvantageous effect unless the transport container can be connected to electrical conductors in general on the transport road. In the case of molten metals that can only be charged into a conveying vessel under vacuum and/or protective gas, the conveying vessel is electrically heated in a charging station located in the melting apparatus, which is generally accessible through a gate. The possibility of overheating is also completely eliminated. In such cases, only the time during which the transport container is ejected for heating is taken into account. Since there is no heating possibility during the remaining time of each cycle, there is a risk of cooling of the molten metal and the transport container.

In contrast, the invention begins with the fact that the lined crucible and the thermal insulation layer present between the crucible and the container jacket are dimensioned in a conventional manner. Therefore, a ceramic intermediate layer is additionally present, and a number of resistive heating bodies distributed circumferentially in the intermediate layer break the contact between the heated part of the resistive element and the intermediate layer. It is arranged as follows.
In this way, a temperature peak occurs at the location of the resistance heating element, and the intermediate layer also assumes a temperature above the temperature of the molten metal and significantly higher than the temperature of the metal jacket. Starting from the intermediate layer, the temperature drops precipitously into the jacket, an effect which is attributable to the correspondingly dimensioned insulation layer. The temperature gradient from the intermediate layer through the lining or crucible to the melt is significantly flattened due to the good thermal conductivity of the building component. Thermal energy therefore flows from the intermediate layer with the heating element to the molten metal, and vice versa from the molten metal to the intermediate layer.
In this case, the intermediate layer has the function of a hollow cylindrical heat storage, especially when it consists of a ceramic material with a high specific heat. The heat storage capacity per unit volume is
It can additionally be increased even more when using materials with high densities. high temperature bricks for supporting structures,
A large number of highly flame-resistant and insulating bricks having the necessary properties are available on the market.

increasing the available heat storage volume by housing the resistance heating element in the lateral closed shaft;
For example, the heat transfer to the crucible is improved compared to the known housing of the resistive heating element in a so-called knee cup.
Furthermore, the cylindrical inner surface of the intermediate layer facilitates renewal of the lining at specific time intervals. Due to the distance in each direction between the heating element and the shaft wall, insulation problems are avoided. By heating the molten metal while it is being consumed, its temperature can be kept at a fairly constant level. This is particularly important for the production of metal powders with a narrow particle size distribution spectrum by so-called gas atomization. The reason is that the amount of molten metal flowing out depends on its viscosity, which in turn depends on the temperature level. Particular attention should be paid to keeping all process parameters constant when producing sufficiently homogeneous metal powders.

The intermediate ladle according to the invention is provided in particular for the production of nickel powder from nickel matrix alloys, where pouring temperatures of 1550 DEG to 1650 DEG C. are required.

With regard to the narrow particle size distribution spectrum of the metal powder, it is particularly advantageous to equip the lid of the transport container with a gas connection for a source of compressed gas. Therefore, if the charging height increases in the vessel, by appropriately controlling the gas pressure above the melt, care can be taken to compensate for the hydrostatic pressure at the bottom or bottom hole of the vessel, so that the unit time A certain amount of molten metal flows out of the container.

Further advantageous embodiments of the device according to the invention emerge from the patent claims.

An embodiment of the device according to the invention will now be described in detail with reference to FIGS. 1 to 3: In the first chamber 1 shown in FIG. It is located.
This device is a compressed gas atomization device. The chamber 1 has an upper conical part 1a and a lower conical part 1 where metal powder accumulates.
It has a slender cylindrical shape with b. Room 1
Inside, a non-oxidizing atmosphere is created using a protective gas or a vacuum pump. Starting from the reference platform 3, the first chamber extends downwards.

Physically resting on the reference plastoform 3 is an intermediate ladle 4, which is designed as a transport container and can be connected in a vacuum-tight manner to the upper end of the chamber 1. The intermediate ladle 4 has a lid 5 with a manipulator pin 6.
At the junction of chamber 1 and intermediate ladle 4, this ladle has a closable bottom hole (FIG. 2), by means of which a thin metal jet can be discharged coaxially into chamber 1. The details of the spraying and coagulating methods are prior art and will not be discussed in detail.

The intermediate ladle 4 can be lifted by a crane truck 7, a wire winch 8 and a hanging tool 9 disposed thereon, and can run horizontally on a rail 10. The rail 10 runs from the first chamber 1 to the melting device 12
It communicates with the second chamber 11 where is located. The melting device consists of an inductively heated tilting crucible 13, which is moved from its melting position to the tilting device 13a.
can lean towards. A non-oxidizing atmosphere can likewise be created in the second chamber 11 by means of a protective gas and/or a vacuum.

The second chamber 11 is equipped with a gate 14, which is equipped with gate valves 15 and 16 at both ends. In the ceiling 17 of the gate 14 there is a drive 18 in the form of a manipulator for lifting the lid 5 for the loading process of the intermediate ladle 4.

In order to transport the intermediate ladle 4 into and out of the second chamber 11 by means of the gate valves 15 and 16, the intermediate ladle 4 is moved onto a transport trolley 1 which can run into the chamber 11 on rails 20.
It's listed on 9.

The operation of the illustrated apparatus is carried out as follows: First, a predetermined amount of metal or alloy 21 is melted in a tilting crucible 13. The intermediate ladle 4 is then advanced into the gate 14 using the transport trolley 9, after being appropriately preheated, and the gate is then evacuated. The lid 5 is then removed using the drive device 18 (manipulator) and after opening the gate valve 16 the intermediate ladle 4 enters the chamber 11. The tilting crucible 13 is then brought to position 13a and the intermediate ladle 4
The molten metal is charged into the molten metal. A pouring trough 22 is provided to facilitate casting.

After the charging process, the intermediate ladle 4 is sent back into the gate 14, where it is covered with a lid 5. Close the gate valve 16, fill the gate 14 with inert gas,
After opening the gate valve 15, the intermediate ladle 4 can be brought into the atmosphere again, where it can be received by the crane truck 7 using the lifting device 9 and transported into the first chamber 1 in the direction of the arrow 23. can. After discharging the intermediate ladle, or after converting the molten metal into metal powder, the intermediate ladle is returned in the direction of arrow 24 to the melting device 12, where the process is repeated.

FIG. 2 shows an intermediate ladle 4 with a closable bottom hole 32, which serves as a transport container. The intermediate ladle 4 has an approximately rotationally symmetrical cross section, i.e. the interfaces and contact surfaces of all important structural parts are as conical or cylindrical surfaces and as annular surfaces aligned concentrically with respect to an imaginary vertical axis. It is configured. A crucible 35 made of a lining and containing a molten metal 36 is arranged in a cylindrical jacket 33 made of iron, which has two support pins 34 at both diametrical ends. The crucible 35 is made of a brick made of high-value aluminum oxide or magnesium oxide and has a bottom hole 32 formed by a conical recess in the perforated brick 37 at the bottom. The perforated brick rests on a bottom plate 38 through which only the tapered protrusion of the perforated brick 37 passes.

The crucible 35 is first surrounded by an intermediate layer 39 which is likewise composed of individual high-temperature bricks and whose vertical boundary surfaces 40 and 41 are cylindrical surfaces. Inside the intermediate layer 39, distributed centrally and equidistantly on the circumference, there are several vertical shafts 42 of approximately square cross section, all laterally as well as downwardly closed. Precisely, the shaft wall 43 lies in a radial plane and the shaft wall 44 lies in a concentric cylindrical plane (FIG. 3).

In the shaft 42 there are an equal number of resistance heating bodies 45, which have a hairpin shape and are inserted with their thickened upper ends into an insulating holding device 46.
The thickening results in a largely non-heatable upper part, while the remainder of the resistance heating element can be heated to incandescent heat. Such resistance heating bodies are products listed in catalogs. From FIGS. 2 and 3, it can be seen that the resistance heating element 45
It is observed that the shaft walls 43 and 44 have sufficient distance from the shaft walls 43 and 44 on all sides. Using an insulating holding device 46, the resistance heating element is inserted from above into the shaft 42, which is slightly expanded at this point.

The outer end of the resistance heating element 45 is connected to a radial conducting wire 47.
and extends outwardly through the jacket 33, insulated by a vacuum bushing 48. From here, a connecting line 49 leads to the current supply. The jacket 33 has an annular flange 50 at its upper end from which a cylindrical protective collar 51 for the vacuum bushing 48 extends.
extends downward.

A lid 5 rests on the annular flange 50 via a packing 52 and a covering flange 53, the lid being provided with reinforcing ribs 55 in which conveying holes 56 are arranged. Below the lid 5 there is a cylindrical collar 57 and a recess 58 lined with a second heat insulating material 59 made of ceramic material. Lid 5
A gas connection pipe 60 that leads to a compressed gas source (argon), not shown, passes through it. Using compressed gas, the level of the molten metal 36 is controlled so that it is under pressure to compensate for the decrease in hydrostatic pressure when the molten metal level drops. In the branch of the gas connection 60 there is an overpressure valve 61 which is surrounded by a hollow manipulator pin 6 .

The second insulation 59 projects slightly downward into the intermediate layer 39 and directly into the annular upper boundary surface 6 of the crucible 35.
It hits 2. The intermediate layer 39 is surrounded by a first insulation material 64, which consists of an outer lining 65 made of a heat-insulating ceramic material and a heat-insulating fibreboard 66 made of, for example, kaolin wool and bent into a hollow cylinder. In this way, good thermal insulation of the intermediate layer 39 to the jacket 33 is achieved.

The jacket 33 has a support flange 67 at its lower edge.
, so that the intermediate ladle 4 can be supported on the base plate. A packing flange 68 is disposed concentrically on the inside of the support flange and is offset upwardly relative thereto, which flange is fixed in a vacuum-tight manner to the lower edge of a cylindrical collar 69. The packing flange 68 and the collar 69 delimit a cavity 70 which can be evacuated by a conduit 71 when the transport container rests on a corresponding packing surface, for example a packing flange of a metal powder production device.

The bottom hole 32 opens into the cavity 70 through a schematically illustrated slider 72 which is provided with a calibrated outlet hole 73 for the molten metal to be sprayed and an inlet hole 74 for the cleaning gas. In the illustrated end position of the slider 72, the outlet hole 73 is connected to the bottom hole 32 so that the molten metal can flow out in a precisely metered manner. In one slider position, the inlet hole 7
4 is closed. This inlet hole is connected via a conduit 75 and a valve 76 to a cleaning gas source 71 (argon), which is separably fixed to the intermediate ladle 4 and transported together with it;
Cleaning gas flow can be maintained through the inlet hole 74 into the crucible 35 when the slider 72 is moved to the right and is in the closed position. In this position, the inlet hole 74 is aligned with the bottom hole 32 so that some solidifying molten metal can be removed from the bottom hole by the flushing gas stream. Furthermore, between the slider 72 and the perforated brick 37 having the bottom hole 32,
A perforated plate 78 is present, which serves as a cradle for the slider 72. The entire slider arrangement is surrounded by a slider casing 79, which is also shown schematically.

[Brief explanation of the drawing]

The accompanying drawings show an embodiment of the invention, in which FIG. 1 is a schematic representation of a complete metal powder manufacturing apparatus, FIG. 2 is a vertical cross-sectional view of an intermediate ladle with a molten metal guiding device, and FIG. FIG. 2 is an enlarged partial view taken from a horizontal sectional view at 1/2 height of the ladle shown in the figure. 1...First chamber, 4...Middle ladle, 5...Lid, 1
1... Second chamber, 12... Melting device, 14... Gate, 18... Drive device, 33... Metal jacket, 35... Crucible, 36... Molten metal, 39... Ceramic intermediate layer, 42... Shaft, 43, 44
...Shaft wall, 45...Resistance heating element, 46...
Insulation holding device, 60... gas connection, 64... first heat insulating layer, 67... support flange, 68... packing flange, 70... void, 72... slider, 73... exit hole, 74... ...Entrance hole, 77...
Cleaning gas source.

Claims (1)

Claims: 1. A first chamber having a device for converting the molten metal stream into initially liquid and then solid metal particles in a non-oxidizing atmosphere, mountable on the first chamber; An apparatus for producing metal powder from molten metal, comprising an intermediate ladle with a closable bottom hole that can be discharged into a chamber, and a melting device for charging molten metal into the intermediate ladle, comprising: (a) (b) the melting device 12 is surrounded by a second chamber 11 for maintaining a non-oxidizing atmosphere, which is spatially separated from the first chamber 1;
The second chamber 11 is provided with at least one gate 14 for the entry and exit of the intermediate ladle 4, (c) the intermediate ladle 4 configured as a transport container is transported into and into the first chamber 1 serving for powder production. (d) the second chamber 11 of the melting device 12 is provided with a lid 5 for maintaining a non-oxidizing atmosphere during evacuation; An apparatus for producing metal powder from molten metal, characterized by comprising: 2 The drive device 18 for removing the lid 5 is connected to the gate 1
4. The device according to claim 1, wherein the device is arranged in a. 3 Intermediate ladle 4 is metal jacket 33, crucible 3
5, with a first insulating layer 64 disposed between the crucible 35 and the jacket, with vertical, upwardly distributed circumferentially distributed between the crucible 35 and the first insulating layer 64 A ceramic intermediate layer 39 is arranged with several shafts 42 which are open but closed at the sides, into which a resistive heating element 45 is inserted from above by means of an insulating holding device 46, and a resistive heating element 45 is inserted below the heating element. 2. Device according to claim 1, characterized in that the heatable part is arranged at a distance from the shaft walls (43, 44) and the upper non-heatable part is surrounded by an insulation retention device (46). 4. The device according to claim 3, wherein the intermediate layer 39 of the intermediate ladle 4 is made of the same material as the crucible 35. 5. The device according to claim 3, wherein the lid 5 of the intermediate ladle 4 is provided with a gas connection 60 for a cleaning gas source 77. 6. Device according to claim 3, in which the cleaning gas source 77 is firmly attached to the intermediate ladle 4. 7 The intermediate ladle has a bottom hole that can be closed by a slider, and the slider 72 has an outlet hole 73 for the molten metal 36.
and an inlet hole 74 for the cleaning gas, in which the outlet hole for the melt at one end position of the slider 72 and the inlet hole for the cleaning gas at the other end position respectively communicate with the interior of the crucible 35 . Apparatus according to scope 3 or 6. 8. The metal jacket 33 of the intermediate ladle 4 is provided with an outer support flange 67 and an inner packing flange 68 displaced upwardly relative to the support flange. 4. A device according to claim 3, which can be mounted in a gas-tight manner on a flange. 9 The packing flange 68 of the intermediate ladle 4 is connected to the bottom hole 3.
2 and the empty space 7 inside the packing flange.
9. A device according to claim 3 or 8, wherein 0 is evacuable.