Production of aluminium alloy metal powder for use as material in additive production

The present invention pertains to a method for producing a metal powder of an aluminium alloy for use as a material in additive production, wherein the aluminum alloy powder is made of aluminum or an already existing aluminum alloy and at least one further metal, and a corresponding device for producing the metal powder.

In the additive manufacturing, layered metal powder is applied or sprayed directly, in order to thereby produce two - and three-dimensional objects at low cost and quickly.

In 3D pressure - coarse aggregate - so-called powder bed-based processes are used. Extrusion-based process and coating process.

In the production of a workpiece made from solid materials according to a powder-bed-based process, a thin powder layer is first applied and then melted. Powder is again applied to the melt and then the material is then melted again, whereby it connects to the underlying layer, etc. etc, through targeted application of the powder, thus creating the desired three-dimensional structures.

In the extrusion-based process, metal powder is first mixed with a binder and this mixture is then cured as desired. In connection, the latter is heated in an oven, wherein the binder is burnt and the metal is sintered, thereby obtaining the desired three-dimensional structures.

In the case of application methods, metal powders are melted directly on application by means of lasers and then further processed to obtain the desired three-dimensional structures.

In principle, the production of the metal powder for use as a material in the additive production is largely automated using liquid or solid materials in the form of bars and/or semifinished products in the form of wires. Rods, granules or metal powders from the secondary circuit (recycling of spent metal powders).

For the mechanical production of metal powders, wherein the material used as material in the additive manufacture consists of either grinding metal or atomizing or atomizing liquid melts and by spraying with plasma or gas burners and by induction melting and spraying.

From the COST 2689873 a process for the production of corrosion-protective pigments or a powder for use as pigments of an anti-corrosion primer is known by spraying a liquid metal melt. These pigments are preferably used in the form of a corrosion protection primer.

The problem of the present invention is a production process of metal powder for use as a material in additive manufacture. In particular, the grains of the metal powder should have a size distribution as defined as possible. In this way, the powder is intended to be particularly suitable as a material in the additive production.

In accordance with the invention, a metal powder can be produced particularly efficiently for use as a material in the production of additives, by generating droplets of a molten aluminum alloy. Allow the droplets to cool and solidify such that a metal powder is formed. The grains of the metal powder can be used as material in the production of additives.

By generating droplets, a defined size distribution of the droplets or in the sequence of metal powder grains can be achieved.

The defined size distribution of the droplets can be achieved by gasifying or atomizing the aluminium alloy melt using a primary gas and/or a secondary gas.

In particular for the application of a metal powder of an aluminium alloy for additives in sensitive areas, in particular such as the aircraft or motor industry or other metal-processing industries, it is necessary to achieve a particularly regular and thus advantageous grain formation of the metal powder of an aluminium alloy. In addition to the process for producing the metal powder of an aluminium alloy for use in additives production, the problem of the invention is also solved by a metal powder of an aluminium alloy for use in additives production.

The invention is therefore intended to the metal powder of an aluminium alloy for use as a material in the additive production is made of aluminium or an existing aluminium alloy on the one hand and at least one other metal on the other hand, and further provided that the manufacturing method of the metal powder of the aluminum alloy comprises the steps of:

• Melting and alloying the aluminium or the already existing aluminium alloy with the at least one further metal, wherein the temperature of the melt is 500 °C, preferably 1400 °C, more preferably about 1100 °C; and wherein the temperature of the melt is from 1200 °C, preferably from 1150 °C.
• Atomizing the melt by means of a primary gas having a first gas flow, and wherein said primary gas is preheated to 100 °C; and wherein said primary gas is preheated to from 450 °C.
• Cooling the melt during sputtering and metal powder solidifying, wherein a material flow during sputtering and solidification passes in a spray tower, and wherein the melt is introduced into a heated tundish immediately prior to atomization, wherein the tundish has a spray nozzle at a lower end and at least one feed line for the primary gas and optionally the secondary gas such that heating of the primary gas and optionally the secondary gas is additionally effected by thermal contact with the heated tundish or its spray nozzle.

Due to the preheating of the primary gas and optionally secondary gas through the heated tundish, favourable temperatures of the melt can be guaranteed and adjusted accordingly for the atomization, wherein a heated (atomizing) crucible or heated tundish can be used, a nozzle system for the atomization and supply lines for the primary gas and, if appropriate, the secondary gas are provided at the lower end thereof. Here, the spray nozzle is preferably also heated. In addition, preheating of the primary and/or secondary gas flow can be performed via a heat exchanger and/or similar heat energy supply units.

Whereas, in order to be able to manage the production of metal droplets in particular, in one embodiment of the invention, the atomization of the melt takes place in addition to the primary gas by means of a secondary gas, which has a second gas flow, and 450 °C wherein the secondary gas is preheated to 100 °C and that preferably an inert gas, preferably comprising N, is used as the primary gas and/or as a secondary gas_{2 th} and/or Ar and/or He and/or Ne and/or Ar and/or Kr and/or Rn is used to inhibit oxidation. The use of a primary gas and/or a secondary gas allows even more precise production of the desired metal powder grains, since the atomization of the molten metal can also occur with more than one gas. This makes it possible to sputter the molten metal more precisely.

In principle, the atomization (or atomization or gasification) to possible oxidation - on the surface - and inside the metal powder of alloying elements of the melt is to be respected. In most cases, such oxidation is not desired or a certain oxygen content is defined in a defined manner. therefore, preferably one of the above-mentioned inert gases is used as primary gas and/or secondary gas.

In order to be able to achieve particularly favourable results in metal powder production and to prevent oxidation during the sputtering and solidification process in one embodiment of the invention, an inert gas is used as the primary gas and, if appropriate, as a secondary gas, preferably comprising N_{2 th} and/or H and/or He and/or Ne and/or Ar and/or Kr and/or Rn to inhibit oxidation.

In other words, atomization or atomization of the melt may be either only with primary gas, only with secondary gas or with primary gas and secondary gas. This allows particularly good control of the metal droplets - and thus the metal powder production.

Particularly simple and efficient - and thus cost-effective - can generate the metal droplets by using the gasification or atomization in such a way that that the material flow follows the force of gravity, that is, with a direction indicator which points vertically from top to bottom. The greater this direction (vertically from top to bottom) of the material flow, the more efficient the production of metal droplets. Therefore, it is provided for a preferred embodiment of the method according to the invention, the flow of material follows the force of gravity.

The flow of material during sputtering and solidification is provided in a cooled spray tower to promote solidification of the metal droplets to grains of the metal powder. The cooling of the spray tower can be achieved by means of water or gases, for example N2, H2, CO, CO2, H_{2 th} O, He, Ar, Kr, Xe or a mixture thereof. Of course, other gases are not excluded when they are suitable for cooling the spray tower according to the invention.

On the one hand, cooling of the spray tower is understood to mean an indirect and, on the other hand, a direct cooling of the melt. Intimately cooling the melts during sputtering, the wall of the spray tower is cooled with water or cooling gas guided in the wall interior, and whereby the temperature in the interior of the spray tower can be reduced by nature. In this case, the wall of the spray tower can, for example, have a double jacket which enables cooling of the spray tower. Of course, this does not exclude other methods of cooling the spray tower.

Direct cooling of the spray tower is effected by means of cooling gas, supplied to said spray tower. The cooling gas then comes into direct contact with the atomized metal droplets of the melt, whereby these are cooled rapidly and solidify to powder grains. This makes it possible to produce more precise production of metal powder grains such as those required for use in additives production.

In order to prevent oxidation of the aluminium alloy as has already been mentioned above, it is preferably provided that the cooling gas is an inert or as inert gas.

In order to obtain a particularly suitable aluminium alloy for use as a material in additives manufacturing in one embodiment of the invention, the at least one further metal is supplied to the melt in a first gas-tight oven chamber and/or optionally in a second gas-tight furnace chamber before atomization of the melt, wherein the at least one further metal is preferably Si and/or Mg and/or Cu and/or Cu and/or Zr and/or Nb and/or Ta and/or V and/or W and/or Li to obtain an aluminium alloy having the most suitable properties for use as a material in the additive manufacture.

Due to the multiple feeding of the at least one further metal, it is possible to produce as suitable aluminium alloys as possible, and there is at any time a change in the alloy composition. This also allows for a subsequent modification of the melt.

Because oxidations reduce the quality of the melt and thus the metal powder produced therefrom, in one embodiment of the invention, a lock chamber is provided for removing or minimizing the present oxygen from the aluminium or the existing aluminium alloy, to avoid oxidation during melting and alloying, provided that the lock chamber is flushed with at least one inert gas.

The lock chamber allows freeing the supplied aluminium or the already existing aluminium alloy from existing air oxygen. For this purpose, it is provided that the lock chamber comprises a first and a second lock gate, the function of which is sufficiently well known in the state of the art, so that either only the second lock gate can be opened to the furnace chamber or only the first sluice gate can be opened at the entrance of the lock chamber, to prevent oxygen from entering the furnace chamber in an undesirable manner. It is provided that the lock chamber is flushed with inert gas, for removing the air oxygen from the lock chamber. In order to be able to supply inert gas and exhaust gas containing oxygen, it is provided that the lock chamber comprises a gas supply line and a gas discharge line.

Furthermore, it is provided that the lock chamber comprises a vacuum pump, with the aid of which gas can be removed from the lock chamber, either inert gas contaminated with atmospheric oxygen or ambient air prior to the addition of inert gas.

Of course, it is not ruled out that the sluice chamber also serves to minimise oxygen to a desired quantity, but not completely removed.

In order to reduce the risk of unwanted oxidation during the production of the metal powder of an aluminium alloy, in one embodiment of the invention, provision is made for the production of the metal powder of an aluminium alloy in an inert protective atmosphere comprising at least one inert gas, wherein an inert gas is provided in the lock chamber and/or the first gas-tight furnace chamber and/or the second gas-tight furnace chamber and/or the feed sluice. Characterized in that in all the chambers in which the melt may be located may be provided in such a way that it is a chamber comprising an inert gas atmosphere, the risk of oxidation may be further reduced or oxidations only if desired.

As a favorably for the atomization of the melt, a temperature of the melt is in a range from 500 °C, in which case the temperature of the melt is in a range from 1400 °C. preferably from 1100 °C, particularly preferably from about 1150 °C 1200 °C.

In addition to the temperature of the melt, the temperatures of the primary gas and/or of the secondary gas play an important role for the defined atomization. Best results can be achieved, when both the primary gas and the secondary gas are at a temperature in a range of 250 °C, preferably of 600 °C, to 450 °C 350 °C. This prevents rapid solidification, whereby the temperatures of the primary gas and of the secondary gas can also be different. The heating of the primary gas and the secondary gas can be carried out by supplying the gases to the heated tundish or to its nozzle system. i.e. by thermal contact with the heated tundish or its nozzle system. Different gas temperatures can result in different flow rates of the gases or different gas flows on the basis of the heat contact which persists in different times. The invention is therefore intended to in that both the primary gas and the secondary gas are heated to 450 °C 100 °C when secondary gas is used, are preheated.

Another possibility for influencing the sputtering process consists in choosing the gas flows of the primary gas and the secondary gas. In particular, the shape of the droplets and thus of the grains of the powder can be adjusted by means of differently strong gas flows. It is therefore necessary to adapt the gas flow in accordance with the desired grain shape of the powder.

In cases where in which both primary gas and secondary gas can be used as the guide gas, the primary gas can have a high (ersten) gas flow, the secondary gas can be determined for the actual sputtering process and have a (zweiten) gas flow which is smaller than the primary gas. In accordance with the invention, it is therefore envisaged that the second gas flow is less than the first gas flow.

Of course, it is not ruled out that the secondary gas has a higher gas flow than the primary gas.

As already stated, a defined size distribution of the grains for the application of the powder in the production of additives, in particular in the aircraft and motor industry and other industries, is essential. Therefore, in order to better define or limit the size distribution of the powder grains, a further method step is provided for subdividing the powder grains into coarse material and fine material. The coarse material is subsequently recycled, by returning it to the melt, or to further use or processing.

Here, powder grains of the coarse material have diameters of at least approximately 100 µm. preferably of at least 500 µm. Classification device, preferably sifter and/or screening machines, is used for the subdivision. Accordingly, in a preferred embodiment of the method according to the invention, it is provided that the powder is separated into coarse and fine material by means of classifying devices, preferably by means of a sifter and/or screening machine, to remove coarse material having a grain diameter of at least 100 µm, the coarse material being recycled to the melt.

A subdivision into fine and coarse material is necessary because, for use as a material in additives production, particularly fine particles uniformly shaped powder grains should be used.

Of course, it is not ruled out that the coarse material of the melt is not recycled and another use or further processing is supplied.

If the coarse material is recycled to the melt, this can be carried out either with or without pretreatment. i.e. that the coarse material is treated prior to recharging. Of course, the coarse material can also, of course, also be supplied to the continuation in another product segment and must not necessarily be recycled to the melt.

Thus, a particularly defined or sharp size distribution of the powder grains can be achieved.

As has already been mentioned, the powder grains can have different shapes. In addition to the spherical shape, the powder grains can also have an elongated shape. The dominant form can be determined by selecting the process parameters, such as gas flows. It is preferably provided that the shape of the powder grains is predominantly spherical or ellipsoidal.

Preferably, the grain diameter or diameter of the grains, in the case of non-spherical grain forms, approximately with an elongated shape, is determined by means of a diameter, relating to the diameter of an imaginary sphere enclosing the respective powder grain. The diameter of this case means the greatest extension of a grain in one direction. Of course, grain size analysis can also be carried out by other methods known in the state of the art.

In order to keep the pressure of the melt constant in a preferred embodiment of the invention, it is provided for melting and alloying under defined atmospheric conditions with continuous addition of aluminium or an already existing aluminium alloy and the at least one further metal and a constant constant outflow of the resulting melt or aluminium alloy. This leads to particular attention regular and thus constant advantageous grain formation (grain shape and particle size) in the aluminium alloy powder. In addition, the formation of undesirable by-products is minimized by keeping the pressure and the temperature constant.

It is envisaged that in order to control and regulate the pressure of the furnace, means are provided for measuring the pressure of the furnace and the pressure regulation associated therewith.

Finally, the invention also comprises the use of a powder according to the invention as a material in the additive manufacture, in particular at 3D pressure.

The problem of the invention is also solved by a device for producing a metal powder of an aluminium alloy for use as a material in the additive production according to the method according to the invention, in which device

• a first gas-tight furnace chamber comprising a tundish for alloying the melt.
• a spray nozzle disposed at the lower end of the tundish for atomizing the melt.
• a feed lock, to be able to supply further metal into the first gas-tight furnace chamber for melting and alloying.
• at least one gas line for primary gas to the spray nozzle. and
• a spray tower is provided for atomizing and solidifying the melt, the melt being atomizable by means of a primary gas having a first gas flow, and wherein the primary gas is preheated to 100 °C, 450 °C the invention being provided in accordance with the invention the spray tower further comprises a cooling gas supply line for cooling the atomized melt and the solidified powder of the melt, and that the melt is introducible into a heated tundish immediately prior to atomization, so that the heating of the primary gas and optionally of the secondary gas can additionally be carried out by thermal contact with the heated tundish or its spray nozzle.

By the introduction into a heated tundish is guaranteed a temperature suitable for the atomization of the melt and can be adjusted accordingly.

Supplying cooling gas into the spray tower by means of feed line enables direct cooling of the atomized melt and the solidified powder in the spray tower, thereby achieving even better results in the production of the metal powder grains.

To prevent it from being oxidized in the atomized melt and in the metal powder, in one embodiment of the invention, the spray tower can be cooled with cooling gas during the sputtering and solidification process, preferably N2, H2, CO, CO2, H2O, He, Ar, Kr, Xe or a mixture thereof.

In order to avoid undesirable oxidation of the metal or aluminium alloy is provided that the first furnace chamber is gas-tight so as to prevent the entry of air oxygen.

A furnace chamber known in the state of the art and suitable for executing the incomprehensible invention can be used as the furnace chamber. The operation of an oven chamber is known to the specialist, so that no further reference is made to this.

As a tundish in the sense of the incomprehensible invention, each tundish known in the art can be suitable for use in the subject device, are used.

Any spray nozzle known in the state of the art, which is suitable for use as a spray nozzle for atomizing metal melts, can be used as spray nozzle in the sense of the incomprehensible invention.

Feeding sluice in the sense of the incomprehensible invention can be any state of the art, adapted to supply further metal to the furnace chamber.

A spray tower as defined in the opposite invention is each spray tower suitable for allowing the atomization and solidification of the melt.

In order to be able to produce an even better metal alloy in one embodiment of the invention, a second gas-tight furnace chamber comprising a melting furnace and a second supply lock for supplying the at least one further metal, a supply opening for the aluminium or the already existing aluminium alloy, is further provided upstream of the first gas-tight furnace chamber and at least one melt line for supplying melt which opens into the first gas-tight furnace chamber.

In that a second gas-tight furnace chamber is provided in front of the first gas-tight furnace chamber, an optimisation of the alloy is made possible, da at least one further metal can be further added as a result of the feed sluice provided.

In order to reduce the risk of oxidation further, in one embodiment of the invention, a lock chamber comprising a vacuum pump and at least one supply line for inert gas and a discharge line for gas are also provided upstream of the second gas-tight furnace chamber, as seen in the direction of flow of the melt upstream of the second gas-tight furnace chamber, is provided for removing or minimising the available air oxygen in the metal and/or the present alloy in order to prevent undesirable oxidation. By means of the upstream lock chamber, it will make it possible to completely remove or reduce to a desired quantity existing air oxygen which would cause oxidation of the metal.

The envisaged vacuum pump allows the existing air or inert gas to be removed from the lock chamber, whereby better oxidation of the metal or the existing aluminium alloy or the resulting melt can be prevented.

In order to control the supply of the melt to the spray nozzle, in one embodiment of the invention, a plug closure for closing the spray nozzle is also provided in the first furnace chamber.

The plug closure allows a targeted and controlled supply of melt to the spray nozzle, and whereby the sputtering and solidification process can be even better controlled.

In order to reduce the risk of oxidation of the metal or aluminium alloy in one embodiment of the invention, the production of the metal powder of an aluminium alloy can be carried out in an inert protective atmosphere comprising at least one inert gas, with an inert gas being supplied in the lock chamber and/or the first gas-tight furnace chamber and/or the second gas-tight furnace chamber.

In order to make it possible to subdivide bulk and fine goods in one embodiment of the invention, a classifying device is provided, wherein the metal powder can be separated into coarse and fine material by means of the classifying device, preferably by means of a sifter and/or screening machine, to remove coarse material having a grain diameter of at least 100 µm, the coarse material being supplied to the melt again.

A sifter and/or screening machine enable the division into fine and coarse material particularly simple and efficient. Any classifier and/or screening machine as defined in the present invention may be considered to be any known in the state of the art, which is suitable for this purpose.

Of course, it is not ruled out that the bulk is not recycled to the melt but to another further processing or re-use.

It goes without saying, that everything that has been carried out under the method according to the invention also applies to the device according to the invention and vice versa.

The invention is now explained in more detail with reference to an embodiment. Drawing is exemplary and is intended to explain the idea of inventions. however, by no means diminishing or concluding it in any way.

This shows:

Fig. 1

a total flow scheme of a method according to the invention

In accordance with the following Fig. 1 initially aluminium 1 or an existing aluminium alloy in solid form is fed into the lock chamber 2 in solid form via a roller path 3. In the lock chamber 3, an atmospheric oxygen-free atmosphere is created by means of vacuum pump 6 and supplying inert gas 5 or to the export of gas loaded with atmospheric oxygen, to prevent 1 oxidations in the second gas-tight furnace chamber when the aluminium 7 is advanced.

First, the first sluice gate 4 for supplying aluminium 1 is opened and that Aluminium 1 is fed through the first water gate 4 into the lock chamber 3 via the roller table 2. While the first sluice gate 4 is open it is not possible to open the second water gate 22, which allows the supply of aluminium 1 into the second gas-tight furnace chamber 7. After supplying the aluminium 1 into the lock chamber 3, the first water gate 4 is closed again for supply. By means of supplied inert gas 5, the air oxygen contained in the lock chamber 3 is displaced and can be removed. Supports the removal of the gas which is loaded with atmospheric oxygen is discharged by the use of the vacuum pump 6.

As soon as the existing air oxygen in the lock chamber 3 has been removed or reduced to a desired measurement, the second water gate 22 for supplying the aluminium 1 into the second gas-tight furnace chamber 7 is opened. During the introduction of the aluminium into the second gas-tight furnace chamber 7, the first sluice gate 4 is closed, to prevent the penetration of atmospheric oxygen. This brings the aluminium 1 into the second gas-tight furnace chamber 7 comprising a melting and alloy furnace 8. In the melting and alloy furnace 8 of the second gas-tight furnace chamber 7, the aluminium 1 is then melted, to obtain a melt 21.

In order to ensure that there is still no oxidation of aluminium or the existing aluminium alloy or the resulting melt, inert gas 7 is also fed to the second gas-tight furnace chamber 5. Via the feed lock 11, further metal 20 is fed into the second gas-tight furnace chamber 7 and thus the melting and alloying furnace 8 and producing the desired aluminum alloy.

In the opposite example, scandium is alloyed as at least one additional metal 20 into the melt 21. The product purity of aluminium used 1 typically amounts to at least 95,0% by weight, typically 99,0 wt % of the scandium used.

In order to allow continuous control and regulation of the pressure required for the production of the desired melt 21 of the aluminium alloy the second gas-tight furnace chamber further comprises an oven pressure control 9. The pressure regulation 9 continuously measures the existing furnace pressure in the second gas-tight furnace chamber 7. The maintenance of the pressure favorable for the alloying process is enabled by a complete outflow of the melt 21 via a melt line 10 provided for this purpose and complete feeding of scandium 20.

By feeding from scandium 20 via a feed lock 11 is also removed before being fed into the second gas-tight furnace chamber 7 also present air oxygen. This allows the maintenance of an atmospheric oxygen-free atmosphere in the second gas-tight oven chamber 7.

The melt line 10 leads from the second gas-tight furnace chamber 7 into a first gas-tight furnace chamber 17, and whereby a transfer of the melt 21 from the second gas-tight furnace chamber 7 into a first gas-tight furnace chamber 17 is possible. In Fig. 1 at the same time, both the melt line 10 and the melt 21 are shown, which is why a representation by arrow has been selected for better understanding.

The melt line 10 opens out in the first gas-tight oven chamber 17. The first gas-tight oven chamber 17 comprises a heated tundish 12 and a temperature arranged at the lower end of the tundish 12. Spray nozzle 15 for atomising the melt 21. The heated tundish 12 makes it possible to maintain the temperature of the melt, so that it can be atomised by means of a spray nozzle.

In order to prevent it from being oxidized in the first gas-tight furnace chamber 17, an inert gas 17 is also fed into the first gas-tight furnace chamber in the range 5.

Furthermore, a metal 11 can also be fed through a feed lock 20. to further modify the present melt 21 of the aluminium alloy.

The melt 21, which typically has a temperature in a range from 500 °C, preferably 1400 °C, typically a temperature of 1100 °C, is supplied by means of a pump (not shown) via the melt line 1200 °C 10 to the preheated 12 tundish 1150 °C. which by means of a plug closure 13 at its bottom side for the melt 21 is sealed in a sealed manner. Only when the melt 21 in the preheated tundish 12 has reached a certain level of liquid the plug closure 13 is pulled out.

By means of a heated spray nozzle 15, which is also arranged on the bottom side of the heated tundish 12, the melt 12 emerging from the tundish 21 is now added to metal droplets (not shown), i.e. droplets of the melt 21. atomised or atomised. The atomization or atomization also has a direction section which points downwards according to the gravity, which results in a particularly efficient production of the metal droplets.

For atomization or atomization, preheated primary gas is fed by means of a feed line 14. The primary gas is heated to a temperature in a range of 100 °C °C to 450 °C °C. There is also the possibility of a secondary gas, which is also preheated to a temperature in the range 100 °C °C to 450 °C °C. In this case secondary gas is then supplied via a further supply line (not shown). If a secondary gas is also supplied to the primary gas, then the temperatures of primary gas and secondary gas can, of course, differ from one another.

If both primary gas and secondary gas are used for atomizing the melt 21, then the main difference between the primary gas and the secondary gas is in different gas flows.

In order to avoid oxidation, in particular on the surface of the alloy metals during sputtering or solidification to powder grains, inert gases, preferably N, are used for both the primary gas and the secondary gas_{2 th} and/or H and/or He and/or Ne and/or Ar and/or Kr and/or Rn for use.

During the atomization, the metal droplets of the melt 21 and form grains of an aluminium alloy powder. In order to encourage the solidification, a material flow (not shown) runs, which takes place during the atomization and solidification and has a direction section perpendicular from top to bottom, i.e. by means of a cooled spray tower 16. The cooling of the spray tower 16 takes place by means of water, which is why the spray tower 16 has a double jacket (not shown) and a water connection (not shown) for water cooling.

In addition direct cooling of the atomised melt 21 or the melt 21 solidified into powder is also effected by supplying cooling gas in the form of nitrogen. A supply line (not provided) for cooling gas is therefore provided in the spray tower 16.

By cooling with cooling gas, a faster solidification of the atomised melt 21 and thus an even better production of the powder of an aluminium alloy.

At the lower end of the spray tower 16, the solidified powder enters into a powder discharge 18. In order to achieve the particularly well defined size distribution of the grains of the powder the powder is first subdivided into fine and coarse material by means of sifter/or classifier device (not shown), the coarse material having a grain diameter of at least 100 µm.

The coarse material can then either be recycled to the melt 21 or another processing or use.

1 th

Feeding aluminum/aluminum alloy

2 th

Roller table

3 th

Lock chamber

4 th

First sluice gate

5 th

Rinsing gas (Inertgas)

6 th

Vacuum pump

7 th

Second gas-tight furnace chamber

8 th

Enamel and alloying furnace

9 th

Pressure control

10 th

Fusion pipe

11 th

Feed lock

12 th

Tundish

13 th

Stopper for a melt nozzle

14 th

Feed line of the primary gas and/or the secondary gas

15 th

Spray nozzle/nozzle system

16 th

Spray tower

17 th

First gas-tight furnace chamber

18 th

Powder discharge

19 th

-

20 th

Metal

21 th

Smelt

22 th

Second lock gate