High-temperature device, in particular high-temperature melting device for melting, in particular a refractory metal or a refractory metal compound

Abstract

The invention relates to a high-temperature device (10), in particular a high-temperature melting device (12) for melting, in particular, a refractory metal or a refractory metal compound, comprising a first crucible (14), a second crucible (14), at least a third crucible (14), a cooling device (18) for cooling the at least one crucible (14), at least one heater (24) configured for heating a crucible contents (48), and a protective gas dispenser (37) for generating a protective gas atmosphere in the crucible (14), wherein the heater (24) is configured for parallel and / or serial heating of a crucible contents (48) consisting of the refractory metal or the refractory metal compound.

Description

[0001] The invention relates to a high-temperature melting device, in particular for melting a refractory metal or a refractory metal compound. According to a second aspect, the invention relates to a method for producing refractory metal particles, refractory metal carbide, or refractory metal boride.

[0002] Refractory metals include the chemical elements titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, and tungsten. These metals have a high melting point, meaning they have a melting point above that of platinum (1772°C). They are non-noble, meaning they have a negative standard potential with respect to the standard hydrogen electrode. They typically react with oxygen at high temperatures and are therefore difficult to process.

[0003] DE 44 20 496 A1 and DE 36 08 693 A1 disclose processes for the melt-metallurgical production of hard materials. In this process, the feedstocks are melted using a plasma flame and then dripped onto a rotating disk in their molten state. The melt ejected from the rotating crucible cools in flight. These cooling sections require voluminous, encapsulated equipment flushed with protective gas to prevent particles from sticking to the reactor walls and gas reactions. This adversely impacts operating process costs and investment requirements.

[0004] From the book "Hartstoffe undHartmetalle" by R. Kieffer et al., Springer-Verlag 1953, processes are also known in which the material to be melted is held in a graphite crucible. After melting, the melt is poured into, usually cooled, molds. For economic reasons, the graphite crucible is chosen to be as large as possible in order to keep the area of ​​contact between the melt and the surroundings as small as possible relative to the melt volume. A disadvantage of such processes is the potential contamination of the melt with carbon from the graphite crucible.

[0005] The invention is based on the object of reducing disadvantages in the prior art, in particular reducing energy consumption.

[0006] The invention solves the problem by a high-temperature melting device for melting in particular a refractory metal or a refractory metal compound, with (a) a first crucible, (b) a second crucible, (c) at least one third crucible, (d) a cooling device for cooling the at least one crucible, (e) at least one heater which is designed to heat a crucible content, and (f) a protective gas dispenser for generating a protective gas atmosphere in the crucible, (g) wherein the heater is designed for the parallel and / or serial heating of a crucible content consisting of the refractory metal or the refractory metal compound.

[0007] According to a second aspect, the invention solves the problem by a method for melting or producing refractory metals, refractory metal particles, or a refractory metal compound, in particular a refractory metal carbide or a refractory metal boride, comprising the steps of (a) introducing starting material made of refractory metal or at least one refractory metal compound, in particular tungsten, tungsten carbide, a mixture of tungsten and carbon, into at least three crucibles, the crucibles being open to the environment, as crucible contents, (b) cooling the crucibles, (c) positioning a heater relative to the crucibles, (d) heating the crucible contents by means of a heater to above 1772°C. Preferably, (e) no more than 3 grams per square centimeter of crucible surface and / or no more than starting material is introduced into each of the crucibles. Preferably, (f) the at least three crucibles are heated in parallel and / or serially.The crucible area is the projection of the crucible interior, preferably the active area of ​​the inside of the crucible, onto a horizontal plane. The definition of the active area is explained below.

[0008] An advantage of the invention is that the melt cannot generally be contaminated with graphite. Unlike previous industrial processes for producing refractory metals or refractory metal compounds, the crucible is not enlarged. Instead, three or more crucibles are used, heated serially and / or in parallel. Due to the short heating time achieved in this way, i.e., the time during which the heater heats the crucible contents, the inside of the crucible heats up so little that it does not melt. Contamination of the melt is thus avoided.

[0009] Another advantage is that high energy efficiency can often be achieved. The short heating time also results in minimal radiation losses. Radiation power increases quadruply with temperature (Stefan-Boltzmann law). At the high temperatures required to melt refractory metals, thermal radiation is therefore considerable. The shorter the time at which the high temperatures are present, the shorter the energy loss due to radiation.

[0010] Another advantage is that the use of three or more crucibles results in a comparatively small amount of crucible content in each crucible. This cools quickly after heating, so that a fine-grained structure can usually be obtained.

[0011] It may also be advantageous for each individual heating process during which the heater is in operation to be comparatively short. Preferably, the heater is operated continuously for a maximum of 20 seconds, in particular a maximum of 15 seconds, particularly preferably a maximum of 10 seconds, in particular a maximum of 8 seconds. The high-temperature melting device can therefore be easily operated in partial load mode.

[0012] In the context of the present description, a high-temperature device is understood in particular to be a device by means of which the crucible contents can be heated to at least 1772°C several times in succession in a reproducible manner. A high-temperature melting device is understood in particular to be a high-temperature device by means of which at least one refractory metal, in particular tungsten, can be melted. However, it is not necessary for the crucible contents to actually be melted. The high-temperature melting device can be a high-temperature reactor in which the crucible contents can be heated to a temperature of at least 1772°C, whereby the crucible contents do not melt. Preferably, the high-temperature melting device is designed to heat the crucible contents to at least 2000°C, in particular at least 2500°C, more preferably at least 3000°C, and most preferably at least 3422°C.

[0013] A crucible is understood, in particular, to be a structure designed to repeatedly hold the starting material to be melted, sublimated, or reacted, and the resulting product, in particular the melt, without destroying the crucible. Preferably, the crucible is graphite-free, at least on its surface facing the inside of the crucible.

[0014] A cooling device is understood to be a device by means of which the temperature of at least one crucible can be reduced to such an extent that the crucible remains undamaged. The cooling device is preferably designed to cool the at least one crucible using a cooling fluid, in particular a cooling liquid.

[0015] A protective gas is understood to be a gas or gas mixture that does not react with the crucible contents. In particular, the protective gas is non-oxidizing. The protective gas is preferably an inert gas, for example, a noble gas.

[0016] A heater is a device by which the crucible contents can be heated. The heater is preferably designed for flameless heating of the crucible contents. For example, the heater is a plasma heater, which could also be called a plasma torch, or a laser, such as a diode laser.

[0017] The feature that the heater is designed for parallel heating of the crucible contents is understood in particular to mean that the heater is designed such that two, three or more crucibles can be heated simultaneously at least at one time. The feature that the heater is designed for serial heating of the crucible contents is understood in particular to mean that the heater is arranged relative to at least two crucibles in such a way that first one crucible and then the other crucible can be heated by means of the heater. The feature that the heater is movable relative to at least two crucibles is understood in particular to mean that either the heater or the at least one crucible or the heater and the crucible are moved.

[0018] According to a preferred embodiment, the heater has at least one plasma head for generating a thermal plasma. Preferably, the heater has a second and at least one third plasma head.

[0019] A thermal plasma is defined as a plasma in which the ions and atoms are at such a high temperature that the plasma emits visible light. The plasma head is preferably designed to generate an arc.

[0020] For example, the plasma head is a tungsten inert gas torch (TIG torch). A tungsten inert gas torch has a thermal efficiency of over 94% and is therefore well suited for energy-efficient heating of the crucible contents.

[0021] The high-temperature device preferably comprises a positioning device configured to move at least a portion of the heater, in particular the at least one plasma head. For example, the positioning device is a robot or is configured for guided movement of the at least one plasma head. If the heater comprises a laser, the positioning device is preferably configured to guide the laser beam into one, two, or more crucibles.

[0022] According to a preferred embodiment, the heater is designed to heat the crucible contents to at least 1742°C, in particular at least 2000°C, particularly preferably at least 2500°C, particularly preferably at least 3000°C, particularly preferably at least 3422°C.

[0023] According to one embodiment, the crucibles are open to the environment. This means that the crucibles are not arranged in a gas-tight, particularly evacuatable, housing. Such a high-temperature device is particularly simple to construct and operate.

[0024] Alternatively, the crucible, heater, and positioning device can be housed in a gas-tight housing. The protective gas dispenser is then preferably designed to generate a protective gas atmosphere within the housing. The advantage of such a design is the presence of protective gas. It is possible, but not necessary, for the housing to be designed to be evacuatable and, for example, to be brought to an internal pressure of 10 hPa.

[0025] The crucible has a vertical dimension and is usually open vertically, i.e., at the top, so that the starting material can be poured into the crucible and the product removed. The longitudinal dimension runs in the direction in which the crucible has the greatest dimension relative to a horizontal cross-section. The width dimension runs in the direction perpendicular to the longitudinal direction and the vertical direction. If the cross-section is circular, the longitudinal direction can be chosen arbitrarily.

[0026] Preferably, the crucible has a cross-sectional area, particularly an active one, of no more than 5 cm2 with respect to a horizontal cross-section in the width direction. The small cross-sectional area allows for a small amount of starting material to be easily accommodated. This, in turn, enables rapid heating of the starting material and cooling of the product.

[0027] The active cross-sectional area is determined as follows: First, the active area on the inside of the crucible is determined, i.e. the area that is heated to at least 1772°C during operation. If the heater is a plasma heater, the active area is the area of ​​the inner surface of the crucible that borders the arc, i.e. that onto which charged particles of the plasma impinge. The active spatial area is the spatial area through which the connecting lines from any two points in the area lead. The active area is thus the convex hull of the active spatial area. The active cross-sectional area is the area of ​​the intersection of the active spatial area in the corresponding cross-section. The small, particularly active, cross-sectional area results in rapid heating of the starting material.

[0028] The crucible preferably has a clear width B, in particular an active cross-section, of at most 5 cm, in particular at most 2.5 cm. The depth of the crucible is preferably at most 5 cm, in particular at most 3 cm. The depth is preferably at least 0.25 cm, in particular 0.5 cm.

[0029] Preferably, the crucible is constructed of a thermal conductor, at least on a surface facing the crucible interior. Its thermal conductivity is preferably at least 60 mm 2 / s, in particular at least, particularly preferably at least 100 mm 2 / s. Alternatively or additionally, its thermal conductivity is at least 164 W / m*K, in particular 220 W / m*K. Copper, silver, or a copper- and / or silver-containing alloy have proven particularly suitable. Alternatively or additionally, the electrical conductivity of the thermal conductor is at least 19 megasiemens per meter, in particular at least 40 megasiemens per meter.

[0030] According to one embodiment, the crucible is at least twice as large in its longitudinal dimension, preferably at least five times as large, in particular at least ten times as large in its width. It is also possible for the crucible to be curved transversely to the width. For example, the crucible is arcuate, in particular circular, or at least partially spiral-shaped, transversely to the width.

[0031] According to one embodiment, the crucible has a length transverse to the width that is at least twice, in particular at least five times, and particularly preferably at least ten times, the inside width. For example, the crucible can be designed as a channel, for example, an arcuate, spiral, or meandering channel.

[0032] The positioning device is preferably designed to automatically move the heater, in particular the plasma head, along the crucible during heating. If the heater comprises a laser, the positioning device is preferably designed to automatically move the laser beam along the crucible during heating. The speed at which the plasma head or the laser beam is moved along the crucible is preferably at least 2.5 mm / s. It is advantageous if the speed is at most 250 mm / s.

[0033] It is advantageous if the high-temperature device comprises a plurality of crucibles arranged in a regular 2-dimensional array. A regular array is understood to be an array that exhibits at least one spatial symmetry, for example, translational or rotational symmetry.

[0034] It is advantageous if the crucible is formed as a recess in a plate. For example, the plate is made of copper, silver, or an alloy containing copper and / or silver. The plate can be made of a single material or multi-component. For example, the plate can have a coating, such as a thermally conductive material. Alternatively, the plate can be coated with or consist of a high-melting-point material.

[0035] According to a preferred embodiment, the high-temperature device comprises two or more plates, each of which has crucibles formed therein.

[0036] For example, the plate can consist, at least on its surface, of a plate material whose melting point is above 1500°C, in particular above 1770°C, particularly preferably above 1850°C, in particular above 2100°C, particularly preferably above 3000°C. It is advantageous if the plate consists at least partially of a thermal conductor, which preferably has a thermal conductivity of at least 100 W / m*K, in particular at least 150 W / m*K, for example at least 200 W / m*K, and is coated with the aforementioned plate material. This results in simple production combined with a long service life.

[0037] Preferably, at most 50 g, in particular at most 25 g, particularly preferably at most 10 g and / or at most 5 cm 3 , in particular at most 2.5 cm 3 , particularly preferably at most 1 cm 3 , of starting material are filled into the crucible.

[0038] The high-temperature device preferably has an introduction device for automatically introducing starting material into the crucible. The introduction device is preferably designed to introduce a predetermined amount, in particular a predetermined weight or a predetermined volume, of starting material into the crucible.

[0039] Preferably, the high-temperature device has a removal device for removing the product from the crucible.

[0040] It is advantageous if the high-temperature device is designed to automatically carry out a method comprising the steps of (i) introducing a starting material into the crucible, (ii) positioning the plasma heater and a crucible relative to one another such that the crucible interior is in a plasma jet region of the plasma torch, (iii) controlling the plasma heater so that a crucible content is melted and / or chemically reacts in the crucible and a product is formed, (iv) cooling the crucible, and optionally (v) removing the product from the crucible. For example, the high-temperature device has a control system designed to control the introduction device, the heater, and the positioning device.

[0041] If the heater comprises a laser, the high-temperature device is preferably designed to automatically carry out a method comprising the steps of (i) introducing a starting material into the crucible, (ii) positioning the laser beam of the heater and a crucible relative to one another so that the crucible interior can be heated by means of the laser beam, (iii) controlling the laser so that a crucible content is melted in the crucible and / or chemically reacts and a product is formed, (iv) cooling the crucible and optionally (v) removing the product from the crucible.

[0042] If the high-temperature device has a housing, it is advantageous if the introduction device has a lock for introducing the starting material and / or a lock for discharging the product. Alternatively or additionally, the introduction device can have a starting material storage device for the starting material, which is arranged within the housing. Alternatively or additionally, the removal device can have a product storage device, which is arranged within the housing.

[0043] Preferably, the high-temperature device is designed to control the heater, in particular the plasma heater, so that the starting material in the crucible is heated to a temperature that is above the melting temperature of the crucible material facing the crucible interior. However, cooling the crucible does not melt this material.

[0044] It is advantageous to select the starting material quantity so that, when the crucible contents melt, a molten droplet is formed whose surface is less than two-thirds, and especially less than half, in contact with the inside of the crucible. The smaller the starting material quantity, the stronger the surface tension relative to the weight, resulting in the formation of a molten droplet that is only partially in contact with the crucible. This reduces heat input into the crucible.

[0045] It is advantageous if the shielding gas dispenser has a trailing shoe. A trailing shoe is a device that prevents the shielding gas escaping from an outlet opening toward the crucible from mixing quickly with the ambient gas, or delays this mixing.

[0046] The method according to the invention preferably comprises the steps of filling the crucibles with starting material and / or removing the final product from the crucibles. Filling with starting material preferably comprises automatically removing the product from a starting material storage. Removing the product from the crucibles preferably comprises filling the product into a product storage.

[0047] The high-temperature device is particularly designed for continuous operation and / or production not only on a laboratory scale, but also on an industrial scale. In particular, the high-temperature device is designed for producing at least 3 kg and / or 15 mol of product per hour.

[0048] Preferably, the high-temperature device is designed to produce at least 10 tons per year, in particular at least 100 tons per year, particularly preferably at least 250 tons per year of fused tungsten carbide.

[0049] Due to scalability, an upper limit is only limited by the effort involved in manufacturing the high-temperature device and is, for example, 5000 t per year.

[0050] The high-temperature device preferably has a spectrometer. The spectrometer can be used to detect a temporal change in the spectrum of the light emitted by the crucible contents. The high-temperature device preferably comprises a control unit configured to automatically control the heater based on measurement data from the spectrometer. For example, the control unit is configured to automatically terminate heating if a deviation of the currently measured spectrum from a target spectrum is smaller than a predetermined threshold. The deviation is calculated, for example, as the mean square error of the current spectrum and the target spectrum.

[0051] The high-temperature device preferably has a pyrometer. The control unit is preferably designed to automatically control the heater based on measurement data from the pyrometer. For example, the control unit is designed to automatically shut down the heater if a predetermined target temperature is exceeded.

[0052] According to one embodiment, at least one crucible, in particular at least a majority of the crucibles, has a volume of at most 10 milliliters, in particular at most 5 milliliters.

[0053] The invention is explained in more detail below with reference to the accompanying drawings. Figure 1 in sub-figure 1a a schematic perspective view of a high-temperature device in the form of a high-temperature melting device according to a first embodiment of the invention for carrying out a method according to the invention and in sub-figure 1b a plasma head which is hidden in sub-figure 1a, Figure 2 a perspective view of a high-temperature device in the form of a high-temperature melting device according to a second embodiment of the invention for carrying out a method according to the invention, and Figure 3 a plan view of a schematic view a perspective view of a high-temperature device in the form of a high-temperature reactor according to a third embodiment of the invention for carrying out a method according to the invention.

[0054] Figure 1ashows a schematic perspective view of a high-temperature device 10 in the form of a high-temperature melting device 12, which has crucibles 14.n (n = 1, 2, -... N), namely a first crucible 14.1, a second crucible 14.2, and a third crucible 14.3. Furthermore, the high-temperature melting device can have additional crucibles, as in the present case. The crucibles 14.n are formed as recesses in a plate 16.1, which in this case is designed as a strip, and form a crucible interior 17. The plate 16.1 is made of copper, for example.

[0055] The high-temperature melting device 10 comprises a cooling device 18, which has, for example, a cooling fluid inlet 20 and a cooling fluid outlet 22. Cold cooling fluid, in particular a cooling liquid such as cooling water, flows through the cooling fluid inlet 20 into a cooling fluid chamber, which is in thermal contact with the plate 16.1 and thereby cools it. Heated cooling fluid leaves the cooling fluid chamber and is directed to a cooler (not shown), which cools the cooling fluid.

[0056] The high-temperature melting device 12 has a heater 24, which in this case is a plasma heater, and a plasma head 26 in the form of a TIG torch. The plasma head 26 is Figure 1b and is shown in Figure 1a covered by an optional trailing shoe 28.

[0057] The plasma head 26 has a tungsten electrode 30 surrounded by a shielding gas nozzle 30 through which a shielding gas 34 exits. The shielding gas 34 is, for example, a noble gas, in particular argon.

[0058] It is possible, but not necessary, for a shielding gas line 36 to open into the trailing shoe 28, by means of which additional shielding gas 34 can be introduced into the trailing shoe 28. The components of the high-temperature device 10 that are designed to supply the shielding gas 34 form a shielding gas dispenser 37, which also has a schematically drawn shielding gas source 39.

[0059] The tungsten electrode 30 is electrically contacted by means of a connecting line 38, which connects the tungsten electrode 30 to a control unit 40, which comprises a power source 41.

[0060] The plasma head 26 is attached to a positioning device 42, which—as in the present case—has a first linear axis 44.1 and a second linear axis 44.2 acting perpendicularly thereto. The first linear axis 44.1 moves the plasma head 26 in a direction R along which the crucibles 14.n are arranged one behind the other. By moving only the first linear axis 44.1, the plasma head 26 can thus be successively positioned over the crucibles 14.1, 14.2, and 14.3.

[0061] Figure 1c shows a cross-section in the width direction through the crucible 14.1. A clear width B is, for example, B = 1.5 ± 0.2 cm. A depth T is, for example, B = 1.5 ± 0.2 cm.

[0062] An arc 44 is shown schematically. It is in contact with the inner surface 46 of a crucible in an active region A a. The active region delimits an active cross-sectional area Qa, shown in dashed lines. In this case, the active cross-sectional area Qa is Qa = 1 cm 2 . A crucible volume 48 is shown schematically. The clear width B a of the active cross-sectional area Qa is greater than the clear width B of the crucible, since the crucible has a cross-section that increases slightly with height and, for example, is slightly conical. For example, B a = 1.05 cm.

[0063] Due to the surface tension, a schematically drawn melt droplet 47 forms during heating, the surface of which is less than two thirds in contact with the inside of the crucible.

[0064] The crucible contents 48 may, for example, consist of a mixture of tungsten and carbon, which reacts to form tungsten carbide upon heating. Alternatively, the crucible contents 48 may be tungsten or another refractory metal to be melted.

[0065] Figure 1d shows a schematic section through a crucible 14' according to an alternative embodiment. The crucible 14' has a longitudinal extent L, which can also be referred to as length L, which is greater than the width B, in particular at least twice as large. When heating the crucible contents 48, the heater 24 preferably moves along the longitudinal extent L.

[0066] The high-temperature melting device 10 has a second plate 16.2. Generally, the high-temperature melting device comprises 10 plates 16.j (j = 1,..., J), with the number of plates J in this case being J = 4. Each of the plates 16.j has m crucibles. For example, m = 20 can apply, as in the present case, but this is not necessary.

[0067] It is possible for each plate to have its own cooling device, but preferably the cooling device 18 is designed to cool all plates 16.j.

[0068] The plasma head 26 can also be positioned over the crucibles 14.m+1, 14.m+2,... of the second plate 16.2 by means of the positioning device 42.

[0069] Figure 2shows a second embodiment of a high-temperature device 10 according to the invention, which has plasma heads 26.k (k = 1, 2, ..., K). For example, the number of plasma heads K is K = 3 as in the embodiment shown, but it can also be two or more than 3. By means of the plasma heads 26.k, k crucibles can be heated in parallel. The crucibles 14.i of the crucibles 14.i shown in the figures Figure 1 and 2 The high-temperature devices 10 shown are open to the environment, which means that they are not enclosed in a gas-tight housing. However, it is also possible that the embodiments according to the Figures 1 and 2 have a housing that Figure 1a surrounding the components shown.

[0070] Using a schematically shown optional spectrometer 51, a spectrum of the light emitted by the crucible contents 48 is recorded and fed to the control unit 40, which terminates the heating process if the measured spectrum deviates from a predetermined target spectrum by less than a predetermined threshold value. The deviation is measured, for example, by the sum of the squares of the deviation between the measured spectrum and the target spectrum.

[0071] The temperature of the crucible contents 48 can be measured using an optional pyrometer 53. The pyrometer 53 is connected to the control unit 40. For example, the control unit 40 stops when a predetermined target temperature is reached.

[0072] Figure 3shows a third embodiment of a high-temperature device 10 according to the invention, in particular a high-temperature melting device 12, which has a housing 50 that includes the crucibles 14.i, the heater 24, in particular the plasma head 26, and the positioning device 42. The positioning device 42 is formed by a rotary drive that rotates the plate 16. The crucibles 14.i are arranged at the same distance A from a rotation axis D of the plate 16. By rotating the plate 16, each crucible can thus be positioned under the plasma head 26.

[0073] The high-temperature device 10 includes an introduction device 52 for automatically introducing starting material 54 into the respective crucible 14, in this case, into the crucible 14.N. The introduction device 52 may have a starting material storage 56 in which starting material 48 can be or is stored.

[0074] The high-temperature device 10 can also have a removal device 58, by means of which a product 60, which has been produced during heating of the crucible contents, can be removed from the respective crucible, in this case, the crucible 14.12. The removal device 58 can have a product storage 62 in which the product 60 can be stored.

[0075] Using an optional lock 66, which can also be called an insertion lock, starting material 54 can be introduced into the housing 50 and fed to the insertion device 52. Using a second lock 68, which is also optional, product 60 can be removed from the housing 50.

[0076] If a starting material reservoir 56 and a product reservoir 62 are present, then, within the scope of a method according to the invention, for example, starting material is poured into the starting material reservoir 56 and then the housing 50 is filled with protective gas. The starting material is then successively poured into crucibles, heated, and then stored in the product reservoir, before being removed. This way, little protective gas is required.

[0077] Exemplary embodiment of a method according to the invention: The crucibles 14.n of a high-temperature device 10 according to the invention are filled with powdered starting material 54 using a doctor blade of the introduction device 52. The starting material 54 is a mixture of 35 weight percent tungsten metal and 65 weight percent tungsten carbide. The starting material 54 has a grain size of < 500 µm, measured by sieve analysis. The three plasma heaters 24 are ignited in DC mode, and thus three crucibles 14.1, 14.2, and 14.3 are heated in parallel with a power of 2-3 kW per plasma heater 24 for 3-5 seconds.

[0078] The heaters 24 attached to the positioning device 42 then move to the next crucible. This process was repeated for all crucibles. During the reactions, a melt formed at approximately 2700°C, which solidified rapidly due to cooling. The product 60 produced in this way is so-called fused tungsten carbide. Product 60 was characterized by a high hardness of approximately 2400 HV0.1 and a finely feathered eutectic solidified structure. Each of the crucibles 14.n contained approximately 1g of product, which could be easily removed from the cavities after cooling. The yield compared to the initial weight was over 95%. Compared to the conventional induction process, approximately 30% electrical energy was saved. In another variant of Example 1, pure tungsten metal < 500µm was used as the raw material and melted without problems at approximately 3400°C. This resulted in spheroidal particles with a diameter of approximately 4mm. Reference symbol

[0079] 10 High-temperature device 48 Crucible contents 12 High-temperature melting device 50 Housing 14 crucible 51 spectrometer 16 plate 52 insertion device 17 Crucible interior 53 pyrometer 18 Cooling device 54 Source material 20 Cooling fluid inlet 56 Source material storage 22 Cooling fluid outlet 58 Removal device 24 heater, plasma heater 60 product 26 Plasma head 62 Product storage 28 drag shoe A Distance 30 Tungsten electrode A a active area 32 shielding gas nozzle B clear width of the crucible 34 protective gas B a clear width of the active 36 Shielding gas line cross-sectional area 37 Shielding gas dispenser D axis of rotation 38 connecting cable L Longitudinal extension 39 Shielding gas source n Counting index (crucible) 40 Control unit N Number of crucibles 41 Power source j Counting index (plate) 42 Positioning device J Number of plates 44 Linear axis Qa cross-sectional area 45 arc T Depth of the crucible 46 Crucible inside T a Depth of the active cross-sectional area 47 Melt drops

Claims

1. High-temperature device (10), in particular high-temperature melting device (12) for melting in particular a refractory metal or a refractory metal compound, with (a) a first crucible (14), (b) a second crucible (14), (c) at least one third crucible (14), (d) a cooling device (18) for cooling the at least one crucible (14), (e) at least one heater (24) which is designed to heat a crucible content (48), and (f) a protective gas dispenser (37) for generating a protective gas atmosphere in the crucible (14), (g) wherein the heater (24) is designed for the parallel and / or serial heating of a crucible content (48) consisting of the refractory metal or the refractory metal compound.

2. High-temperature device (10) according to one of the preceding claims, characterized in thatthe heater (24) (a) at least one plasma head (26) for generating a thermal plasma and (b) a positioning device (42) which is designed to move the plasma head (26) relative to at least one crucible (14).

3. High-temperature melting device (12) according to one of the preceding claims, characterized in that the crucibles (14) are open to the environment.

4. High-temperature melting device (12) according to claim 2, characterized in that (a) the heater (24) has a second plasma head (26) and at least one third plasma head (26), (b) the crucibles (14), the heater (24) and the positioning device (42) are accommodated in a gas-tight housing (50) and (c) the protective gas dispenser (37) is designed to generate a protective gas atmosphere in the housing (50).

5. High-temperature melting device (12) according to one of the preceding claims, characterized in that(a) the plasma heater (24) is an arc heater, in particular a tungsten inert gas burner, (b) the crucibles (14) have a cross-sectional area (Qa) of at most 5 cm 2 and / or a clear width (B, B a ) in cross-section of at most 5 cm, (c) the crucible (14) is constructed, at least on its surface facing a crucible interior (17), from a thermal conductor which (i) has an electrical conductivity of at least 19 megasiemens per meter, in particular at least 40 megasiemens per meter and / or (ii) a thermal conductivity of at least 60 mm 2 / s and / or (iii) has a thermal conductivity of at least 164 W / m*K.

6. High-temperature melting device (12) according to one of the preceding claims, characterized in that(a) the crucible (14) has a longitudinal extent (L) which is at least twice as large as a width extent which is perpendicular to the longitudinal extent (L), and (b) the positioning device (42) is designed to automatically move the plasma head (26) during heating of the crucible contents (48).

7. High-temperature melting device (12) according to one of the preceding claims, characterized in that at least one crucible (14) is formed as a recess in a plate (16), 8. High-temperature melting device (12) according to one of the preceding claims, characterized by(a) an introduction device (52) for automatically introducing starting material (54) into the crucible (14) and (b) a removal device for removing product from the crucible (14), (c) wherein the high-temperature melting device (12) is designed to automatically carry out a method comprising the steps of: (i) introducing a starting material into the crucible (14), (ii) positioning the plasma heater (24) and a crucible (14) relative to one another such that the crucible interior (17) is in a plasma jet region of the plasma heater (24), (iii) controlling the plasma heater (24) such that a crucible content in the crucible (14) is melted and / or chemically reacts and a product is formed, (iv) cooling the crucible (14) and (v) removing the product from the crucible (14).

9. High-temperature melting device (12) according to one of the preceding claims, characterized in that(a) the plasma heater (24) is controlled in such a way that starting material in the crucible (14) is heated to a temperature which is above a melting temperature of the crucible material which faces the crucible interior (17) and / or (b) an amount of starting material is selected in such a way that when the crucible contents (48) melt, a melt drop (47) is formed, the surface of which lies against the crucible interior (46) by less than two thirds, in particular less than half.

10. High-temperature melting device (12) according to one of the preceding claims, characterized in that it is designed to automatically carry out a method comprising the steps of: (i) filling crucibles (14) with starting material and / or (ii) removing the product from the crucible (14).

11. High-temperature melting device (12) according to one of the preceding claims, characterized in that the protective gas dispenser (37) has a trailing shoe (28).

12. High-temperature melting device (12) according to one of the preceding claims, characterized in that it is designed to produce at least 3 kg of refractory metal or a refractory metal compound per hour and / or at least 10 t / a, in particular at least 100 t / a, or 250 t / a of fused tungsten carbide.

13. High-temperature melting device (12) according to one of the preceding claims, characterized by (a) a spectrometer (51) and / or (b) a pyrometer (53) and (c) a control unit (40) which is designed to automatically control the heaters (24) as a function of measurement data from the spectrometer (51) and / or the pyrometer (53).

14. A method for producing refractory metal particles, refractory metal carbide or boride, comprising the steps of (a) introducing starting material made of refractory metal or at least one refractory metal compound, in particular tungsten, tungsten carbide, a mixture of tungsten and carbon into at least three crucibles (14), the crucibles (14) being open to the environment, as crucible contents (48), (b) cooling the crucibles (14), (c) positioning a heater (24) relative to the crucibles (14), (d) heating the crucible contents (48) by means of a heater (24) to above 1772°C, (e) wherein at most 3 grams per square centimeter of crucible area and / or at most 10 grams of starting material are introduced into the crucibles (14) in each case, and (f) at least three crucibles (14) are heated in parallel and / or in series.

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