Patent Application
20240351103
The invention relates to a changing system for a tundish unit of an atomization installation for atomizing metal melts for powder-metallurgy purposes. The invention furthermore relates to a tundish unit for such a changing system, an atomization installation, and a method for atomizing metal melt.
An atomization installation or powder atomization installation is an installation which produces powder from liquid metal with the aid of atomizing in a protective gas atmosphere. This powder is then separated from the gas and post-treated.
A device for producing metal powder is known from DE 41 29 991 C1. The known device has a storage container for the molten starting material, at least one exchangeable sprue, at least one atomization installation, and at least one falling shaft arranged underneath it for the solidification of the produced metal powder. A chamber enclosing the storage container and the sprue is arranged on the falling shaft. In order to be able to exchange the sprue or funnels more easily, the chamber has a closable lateral opening in the area of the sprue, on which a lock chamber is placed for the insertion of at least one sprue. A carriage alternately movable into the chamber and completely movable back into the lock chamber is arranged on guardrails, on the lower side of which a number of atomization nozzles corresponding to the number of the sprues is fastened. The sprues are placeable on the carriage from above. The falling shaft is provided with a coupling device, which establishes a gas-tight connection between falling shaft and atomization installation after the positioning of the coaxial assembly, consisting of sprue and atomization nozzle, above the falling shaft.
In this device, the sprue is to be exchangeable in a simple manner without venting the remaining part of the device and in addition exact positioning of sprue and atomization nozzle is to be possible.
In the method according to DE 41 42 991 C1, one sprue is always located in a working position while the other sprue is preheated. It is thus possible to bring the sprues to an optimum working temperature before use. The removal and the exchange of the sprues from the chamber takes place in pairs in each case, for which purpose the method has to be interrupted, of course.
Further prior art is known from the publications DE 33 11 343 A1, DE 35 339 64 C1, DE 40 113 92 A1, DE 100 44 364 C1, DE 197 38 682 A1, WO 2018/189708 A1, and CN 109641276 A.
Of course, the exchange of the casting nozzles and/or sprues is necessary from time to time for reasons of wear. If a redundant sprue is provided, as in the method according to DE 41 29 991 C1, an interruption of the atomization process is necessary after a comparatively short time in order to introduce further atomization assemblies into the system. The operation of the atomization installation can only be resumed when at least one of the atomization assemblies has reached operating temperature again under protective gas atmosphere.
The invention is therefore based on the object of providing a changing system of the type mentioned at the outset which enables quasi-continuous operation of a manufacturing installation.
In particular, it is possible by way of the changing system according to the invention to provide metal melts for a metal powder in a quasi-continuous method.
According to one aspect of the invention, a changing system for a tundish unit of an atomization installation for atomizing metal melts, in particular for powder-metallurgy purposes, is provided, wherein the changing system comprises at least one chamber for accommodating at least one first tundish unit in a working position, wherein the chamber has at least one connection to a charging device, preferably in the form of a casting device, and at least one connection to an atomization tower or an atomization shaft, wherein the changing system furthermore comprises means for providing at least one second tundish unit in a readiness position within the changing system and at least one changing station designed as a lock chamber for accommodating and/or introducing and/or removing at least one third tundish unit and a displacement system, which is designed so that the introduction and/or removal of at least one tundish unit can take place while a tundish unit is located in the working position.
In order to enable quasi-continuous atomizing, the tundish unit or atomization unit located in the working position can be filled continuously with liquid metal. Since it is necessary due to the service life of the nozzle to provide multiple tundish units in which the atomizing can take place, organizing multiple tundish units in a changing system is provided according to the invention. According to the invention, at least three, but preferably four tundish units are provided in the changing system. One tundish unit can thus always be in operation while further tundish units are currently being refitted or preheated, in order to later be able to be exchanged for the tundish unit located in the working position.
The pouring of the melt into the tundish unit and the operation of the tundish unit (also designated as an atomization unit) takes place in a protective gas atmosphere.
In order that an exchange of the tundish units can take place under protective gas atmosphere, the changing system according to the invention comprises at least one changing station designed as a lock chamber for accommodating and/or introducing and/or removing at least one tundish unit.
The displacement system of the changing system according to the invention is preferably designed so that the introduction and/or removal of at least one tundish unit can take place while a second and/or further tundish unit is located in a readiness position.
The at least one changing station can be connected, for example, via a lateral opening to the chamber.
Both the changing station and the chamber can preferably be evacuated and can be flooded with inert gas or protective gas.
In one embodiment of the changing system according to the invention, it is provided that the changing system has a plurality of changing stations, each of which laterally adjoins the chamber and of which at least one, preferably all are designed as lock chambers.
In a particularly preferred variant of this changing system, it is provided that a total of four changing stations are provided, which are each connected laterally to the chamber arranged approximately in the middle. The changing stations can form a displacement cross with the chamber, for example. Each changing station preferably forms a type of cloister, which extends radially from the center of the chamber. One tundish unit can be arranged in the working position in the center of the chamber, for example. One tundish unit can be preheated in the readiness position in each of two changing stations, whereas one tundish unit can be exchanged in one changing station.
In a second exemplary embodiment according to the invention, the changing station comprises a turntable arranged in the chamber, which accommodates a plurality of tundish units. These tundish units can be rotatable from a working position into multiple readiness positions.
In one expedient embodiment of the changing system according to the invention, which comprises a turntable, at least one media coupling, which is connectable to a media coupling design complementary of a tundish unit, can be assigned to the position of a tundish unit on the turntable. A media supply for power, cooling water, inert gas, etc. is preferably connected to the media coupling.
Additionally or alternatively, at least one media coupling can be provided in each changing station, which is connectable to a media coupling design complementary of a tundish unit.
At least one changing station is expediently designed so it can be evacuated.
At least one changing station can be connectable to the chamber via at least one vacuum gate valve or disconnectable from the chamber via the vacuum gate valve.
Preferably, all changing stations can be blocked off gas-tight with respect to the chamber and evacuated. It is thus possible to flood the changing station with air comparatively rapidly before the removal of a tundish unit.
The connections to the charging device and to the atomization tower or the atomization shaft are preferably designed as vacuum gate valves. For example, a vacuum induction casting device, to which the changing station is connectable in a gas-tight manner, can be provided as a charging device.
At least one of the changing stations is preferably designed as a heating station for preheating at least one tundish unit.
The displacement system according to the invention can comprise linear guides, on which or at which the tundish units are movably arranged. For example, guide rails can be provided as linear guides, which can be designed as sliding guides or for accommodating movable undercarriages of the tundish units.
The subject matter of the invention is furthermore a tundish unit for use with a changing system of the above-described type, which comprises a tundish vessel that accommodates a sprue and a casting nozzle, having means for heating and/or cooling the sprue and/or the casting nozzle and having at least one media coupling, which is designed complementary to at least one media coupling of the changing system.
The tundish unit can have skids or at least one sliding guide in the lower side of a nozzle plate. Alternatively, the tundish unit can have a movable undercarriage, which is designed complementary to the displacement system of the changing system.
To ensure adequate leak-tightness between a nozzle plate of the tundish unit and an atomization shaft gate valve, for example, it can be provided that the tundish container is vertically movable relative to the undercarriage, in order to establish a vacuum-tight connection to the atomization process chamber, for example, to an atomization tower or to an atomization shaft, in the working position of the tundish unit. The entry of interfering gas into the atomization shaft process chamber is thus reliably prevented. The vertical mobility of the tundish container relative to the undercarriage causes the seal to be engaged and disengaged.
The tundish unit can be raised and lowered via pneumatic cylinders operated by inert gas within the displacement system. In order to ensure the leak-tightness between nozzle plate and atomization shaft gate valve, the tundish unit is lowered into the working position.
Alternatively, it can be provided that the tundish unit is spring mounted on an undercarriage such that it interacts with a hold-down device of the changing system in the working position. The relevant station in the chamber can be equipped with a hold-down device operated by a cylinder. The tundish unit is then pressed by the hold-down device on the atomization shaft gate valve. By virtue of the spring mounting of the tundish unit, it can independently detach itself from the atomization shaft gate valve upon lifting off of the hold-down device.
Instead of a movable undercarriage, the tundish unit can have at least one sliding guide, which interacts with corresponding guide means of the displacement system.
The tundish unit preferably comprises at least one sealing means on the lower side of a nozzle plate of the casting nozzle, which interacts with a sealing surface of an atomization shaft gate valve. The sealing means can be embodied, for example, as a sliding seal or friction seal. Alternatively, an inclination of the displacement system or a linear guide can be provided so that the tundish unit seats itself by its intrinsic weight on the sealing surface of the atomization shaft gate valve via this inclination during positioning.
According to a further aspect of the invention, an atomization installation having a changing system and multiple tundish units of the above-described type is provided.
The atomization installation can comprise at least one first atomization tower, which is connectable in a gas-tight manner to a connection of the chamber of the changing system.
In a particularly advantageous variant of the atomization installation according to the invention, it is provided that it comprises at least one second atomization tower, wherein the changing system is alternately connectable to the first or second atomization tower.
A further aspect of the invention relates to a method for atomizing metal melt to form a metal powder in an atomization installation having a changing system for multiple tundish units, wherein the method comprises a supply of molten metal from a vacuum induction casting device as a charging device into a first tundish unit in a working position within the changing system and the atomizing of the melt through a casting nozzle of the tundish unit into an atomization tower or atomization shaft arranged underneath, while at least one second tundish unit is preheated in a readiness position and at least one third tundish unit is removed from the changing system or introduced therein.
The method expediently comprises the use of a changing system of the above-described type and preferably the use of at least one tundish unit of the above-described type.
Controlling the supply of the molten metal as a function of the metal level in the tundish unit located in the working position can be provided in the method. The liquid level can be detected by means of a laser distance measurement in this case, for example.
The invention will be explained hereinafter on the basis of several exemplary embodiments with reference to the appended drawings.
In the figures:
The atomization installation 1 shown in
The atomizing of the liquid metal is carried out using a tundish unit 7 shown by way of example in
A graphite heater, the resistance heating elements 13 of which are embedded in the refractory lining 11, is provided within the refractory lining 11 of the tundish container 10. The casting nozzle 9 is also partially enclosed by a refractory lining 11, in which resistance heating elements 13 are also embedded, which cause nozzle heating. The tundish unit 7 comprises a gas nozzle 28, which is connected on both sides to an inert gas supply 14. The molten metal exiting from the casting nozzle 9 is atomized by means of the inert gas supplied via the gas nozzle 28 in the atomization tower 3 of the atomization installation 1 to form a powder.
In the described exemplary embodiment, the tundish container 10 comprises a movable undercarriage, which is only indicated in the drawing. Via the wheels 15 of the tundish container 10, it can be moved on rails 16 of the changing system 2. The tundish container 10 furthermore comprises a ring space 17, to which cooling water can be applied and which forms a cooling jacket, via which the sprue 8 can be cooled as needed. The cooling jacket prevents undesirable co-heating of the process chamber.
Reference is made hereinafter to
The changing system 2 comprises four changing stations 22, which are each designed as lock chambers and are connected to lateral openings of the chamber 18. The changing stations 22 can each be blocked off in a vacuum-tight or gas-tight manner relative to the chamber 18 via changing gate valves 23. The changing stations 22, which can be completely evacuated and have corresponding connections to a vacuum system, are accessible via removable covers 24. The covers 24 are arranged tightly closable on corresponding openings 25 on the changing stations 22.
The changing stations 22 are arranged in a cross relative to the chamber 18, which has a circular cross section in the described exemplary embodiment, so that each changing station 22 extends with an angular interval of 90° relative to the adjacent changing station 22 on the circumference of the chamber 18. As already mentioned above, rails 16 (see
The tundish units 7 are introduced via a crane (not shown) through the openings 25 into the changing stations 22, which are each also designed as a heating station for preheating the tundish units 7 and are each equipped with corresponding media couplings.
The changing stations 22 are equipped over the entire length with replaceable refractory radiation shields. The changing stations 22 can each be evacuated separately via vacuum pumps and can alternately be flooded with inert gas (argon or nitrogen) or with air. The number of the changing stations 22 results from the required heating time of the refractory lining 11 of the tundish container 7 to a temperature between 1700 and 1800° C. From a temperature of approximately 300° C., the heating of the tundish units 7 can only take place under inert gas, since otherwise the graphite of the tundish container heater would combust. The energy and media supply of the tundish units 7 takes place by means of high pressure hoses for inert gas. The power supply and thermocouple lines are embodied as cables. Cooling water is supplied by means of hoses.
Electric cylinders or direct drives having variable settable speed and distance measurement systems are provided for the linear movement and positioning of the tundish units 7 within the changing system 2.
The tundish unit 7 arranged in the chamber 18 in
Before the cover 24 of the relevant changing station 22 can be opened (the changing station 22 is already shown in the open state in the figure), the changing station 22 is evacuated and flooded with air. After completed changing process, the cover 24 is closed again, it is evacuated, flooded with inert gas, and a temperature-controlled heating process is started. At least two tundish units 7 are each located in a holding position in the other changing stations 22. The heating process takes place in a temperature-controlled manner. As already mentioned above, one tundish unit 7 is located in the working position, i.e., in the atomizing position.
The exemplary embodiment according to
As already mentioned above, a seal between the nozzle plate 12 and the vacuum gate valve 21 is required upon the movement of a tundish unit 7 into the working position. The vacuum gate valve 21 represents the lower connection 20 of the chamber 18. Such a seal can take place by means of corresponding sliding seals or friction seals between the nozzle plate, on the one hand, and a sealing surface to the vacuum gate valve 21, on the other hand.
Alternatively, it can be provided that the tundish unit 7 is vertically movable and can be lowered into a working position, so that a sealing means on the nozzle plate and/or on the atomization gate valve flange can be engaged with one another here. The tundish unit 7 can be raised and lowered, for example, via pneumatic cylinders operated by inert gas within the rail system. In order to ensure the leak-tightness between the nozzle plate 12 and the vacuum gate valve 21, the tundish unit 7 is lower during the positioning. An alternative embodiment of the tundish unit 7 provides that the tundish unit 7 is spring mounted on wheels and is held in the working position by a hold-down device (not shown) in a sealed position. The hold-down device presses the nozzle plate 12 onto a flange of the vacuum gate valve 21. Upon lifting off of the hold-down device, the tundish unit 7 can automatically detach from the vacuum gate valve 21.
As schematically shown in
The atomization towers 3 are water cooled. Moreover, they can additionally be equipped with electrical water preheating.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 208 605.5 | Aug 2021 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/071787 | 8/3/2022 | WO |
