WO2024149839A1

WO2024149839A1 - Method and device for vacuum die casting

Info

Publication number: WO2024149839A1
Application number: PCT/EP2024/050587
Authority: WO
Inventors: Thomas NINKEL
Original assignee: Ninkel Thomas
Priority date: 2023-01-12
Filing date: 2024-01-11
Publication date: 2024-07-18
Also published as: DE102023100620B4; DE102023100620A1

Abstract

The invention relates to a vacuum die casting device for producing cast parts using a die casting machine which forms a cavity, comprising a casting chamber (1) with a closure piston (2) and a casting piston (6), a melt metering furnace (4), and a suction tube (3) for connecting the melt metering furnace (4) to the casting chamber (1). The closure piston (2) and the casting piston (6) can be moved between a base position and a final position, wherein the casting chamber (1) has at least two vacuum connections (5), and each vacuum connection (5) has a suction opening (7) for connecting to the casting chamber (1). The casting piston (6) covers at least regions and/or sections of the suction openings (7) of the at least two vacuum connections (5) in the final position. The invention additionally relates to a die casting machine comprising the vacuum die casting device, to a vacuum die casting method, and to cast parts produced according to the method.

Description

'Method and device for vacuum pressure casting'

The invention relates to a device and a method for vacuum die casting for producing cast parts, a die casting machine and cast parts according to the preamble of the independent claims.

The conventional cold chamber die casting process is one of the casting processes with rapid mold filling, in which a certain amount of molten metal is dosed into the casting chamber from above in contact with atmospheric air and is conveyed into the mold cavity or cavity with a high static pressure by the casting force acting on the casting piston surface. In the conventional cold chamber die casting process, oxide formation and the inclusion of fluids such as air and/or gases occur in all three casting phases, but mainly during the dosing and mold filling phase of the casting cycle, which lead to reduced casting quality.

In order to counteract these process-related contaminations and also to increase the mold filling capacity, die casting under vacuum has become established in the conventional cold chamber die casting process. A vacuum chamber located in the mold cavity supports The second phase begins by building up a negative pressure in the mold cavity and in the casting system, provided that the casting piston surface has exceeded the dosing opening in the casting chamber and a spatial separation between the casting system and the atmosphere is created.

In the most rudimentary form of vacuum die casting, the negative pressure is generated via a vent valve located on the mold. Due to the insufficient process time remaining after the pouring piston has passed over the dosing opening and the often limited venting cross-sections of the valves and the connecting channels to the mold, the mold cavity, the runner and the casting chamber can often only be partially evacuated sufficiently.

In order to make evacuation more efficient, vacuum systems with an additional vacuum connection to the casting chamber now exist. One such system is known from the publication WO 2006/056410 A1. Here, after sealing and separating the casting chamber space from the atmosphere, a first vacuum phase is carried out and after separating the casting chamber space from the first supply line to the vacuum system, a second or further vacuum phase is carried out. Several embodiments of the vacuum system are described, firstly as a version with a direct connection to the casting chamber with separation from the atmosphere only by the casting piston, as a version with a dosing channel and locking mechanism at the filling opening or as a version with a lockable dosing pot. The vacuum exposure time can be significantly improved above all by the version with a dosing channel and locking mechanism. Although the additional vacuum source located at the top of the casting chamber improves the active system vacuum, oxide formation always occurs during the dosing process, which inevitably leads to reduced material quality despite more efficient evacuation. Complete extraction of all gases and/or residual air in the casting system is also hardly technically possible. In order to enable the dosing process to take place in the absence of atmospheric air, the process known in the industry as "Vacural" is described in the document DE 30 41 340 C2. Since in this process the dosing process is initiated solely by the negative pressure created by the mold, the active vacuum level depends largely on the tightness of the system. Even the smallest leaks lead to a drop in the system vacuum.

The invention described in the publication DE 10 2007 060 418 B4 was developed to reduce oxide formation during dosing, to be independent of leaks in the mold, and to fully exploit all the advantages of the more effective vacuum effect through a vacuum connection to the casting chamber. The core feature is the locking of the casting chamber on the mold side using a locking piston, which means that the chamber vacuum remains independent of mold leaks. The dosing process via a suction pipe from the dosing furnace, which is introduced into the casting chamber via the vacuum source located at the top, leads to reduced oxide formation. The closed system in the casting chamber also means that hardly any heat gets outside the system boundaries, which leads to significantly higher thermal stability compared to the conventional or "vacural" die casting process. However, the process described in document DE 10 2007 060 418 B4 has its process-technical weaknesses, which do not allow a continuous and uninterrupted casting process.

The hermetic sealing of the casting chamber by the sealing piston creates an active vacuum level in the chamber of 20 mbar to 30 mbar. This enormous negative pressure leads to a strong suction effect during dosing, whereby liquid metal is sucked upwards in the form of melt splashes towards the vacuum connection with each new dosing process and there, due to the thermal difference between the cold connecting pipe and the liquid melt splashes between the casting chamber and the vacuum connection on the inside of the connecting pipe. After a few casting cycles, this leads to a large amount of solidified molten metal settling, completely blocking the vacuum suction point.

The active casting chamber vacuum and the associated suction effect are only interrupted when the casting piston completely passes over the vacuum connection opening in the casting chamber. After dosing has ended and at the start of the first phase, the filling level in the casting chamber is gradually increased by the horizontal movement of the casting piston towards the mold.

When the melt in the casting chamber spills over due to the movement of the casting piston, liquid metal again reaches the cold connecting pipe, which further accelerates the clogging of the connecting pipe. If too much molten metal has solidified on the inside of the connecting pipe, no further dosing is possible from this point onwards and the casting operation must be stopped. The connecting pipe must be replaced. The connecting pipe, which is repeatedly clogged with solidified melt at short intervals, leads to insufficient process consistency, which is why this process is not suitable for practical use in the existing hardware version.

In the process described in DE 10 2007 060 418 B4 with only a single vacuum connection, at the end of the advance of the casting piston in the casting chamber of the die casting machine above the remaining melt surface, the original vacuum deteriorates to the point where atmospheric pressure is partially reached. This means that oxide formation takes place on the remaining melt surface despite the initial vacuum.

There is therefore a great need for a device for vacuum die casting which is simple, fast, reliable and cost-effective. The invention also focuses on a simple, fast, reliable and cost-effective method for vacuum die casting to produce cast parts, which also has a high level of process stability. Furthermore, the cast parts should be cost-effective to produce, individually designed and adapted to requirements, and durable, long-lasting and error-free, in order to keep the production-related costs low. The invention therefore has the task of providing a device and a method for vacuum die casting to produce cast parts and a cast part in order to overcome the above-mentioned difficulties.

This object is achieved in a surprisingly simple but effective manner by a device and a method for vacuum die casting for producing cast parts, by a die casting machine and by a cast part according to the teaching of the independent claims.

According to the invention, a device for vacuum die casting is proposed for producing cast parts by means of a die casting machine forming a cavity, which comprises a casting chamber with a closure piston and a casting piston, a melt dosing furnace and a suction pipe for connecting the melt dosing furnace to the casting chamber, wherein the closure piston and the casting piston can be moved between a basic position and an end position. The device is characterized in that the casting chamber has at least two vacuum connections, wherein each vacuum connection has a suction opening for connection to the casting chamber, and that the casting piston in the end position covers the suction openings of the at least two vacuum connections at least in regions and/or sections, preferably completely. The basic idea of the invention is that before production begins, the device for vacuum die casting is tested for the required tightness and/or sealing in order to detect leaks in advance that could have a negative effect on the casting quality and/or the cast part to be produced. In order to carry out the test for the required tightness and/or sealing, it is necessary for the device for vacuum die casting to have at least two, preferably more, vacuum connections.

The device for vacuum die casting for producing cast parts using a die casting machine that forms a cavity comprises a casting chamber, a melt dosing furnace and a suction pipe. It is understandable to a person skilled in the art that the device for producing the cast parts additionally has a die casting machine, preferably operated using vacuum and/or negative pressure, which forms the cavity, and a preferably closed melt dosing furnace with melt. It is thus intended that the device is used on and/or with a die casting machine.

Any shape of the casting chamber is conceivable within the scope of the invention. The casting chamber is preferably elongated, narrow and/or tubular. The casting chamber preferably has a first end and a second end opposite the first end, as well as an upper end formed between the first and second ends and a lower end formed between the first and second ends, which is opposite the upper end. It is conceivable that the casting chamber is designed in one part or in several parts and has two, three, four, five, six, seven, eight, nine, ten or more identically or differently designed modules. Preferably, at least one of the modules, preferably several or all of them, comprises a suitably designed structure for fluid-tight, in particular gas- and/or air-tight, connection of these. According to the invention, the casting chamber has a closure piston, preferably on the mold side, and a casting piston, preferably self-sealing and/or self-sealing. The casting chamber is also preferably designed such that the casting piston is arranged in the area of the first end in the basic position and engages therein and that the closure piston is arranged in the area of the second end in the basic position and hermetically seals the casting chamber. The person skilled in the art knows how a cavity that meets the requirements is formed and can be designed, and how it can be connected to the casting chamber, preferably in the area of the second end thereof. It is therefore intended that the device is used on and/or with a die casting machine that forms a cavity.

Within the scope of the invention, it has been recognized as essential that the casting piston can be moved between a basic position, in which the suction openings of the vacuum connections are exposed and in which, when a vacuum and/or negative pressure is applied, the casting chamber can be filled with melt from the melt dosing furnace via the suction pipe, and an end position, in which the filling of the casting chamber with melt is complete. It has been recognized that in the end position the casting piston covers the suction openings of the vacuum connections as required and at least in areas and/or sections, preferably completely or essentially. Suitable measures and means are known to a person skilled in the art. It is conceivable that the displacement of the casting piston from the basic position to the end position only takes place after a melt dosing weight that meets the requirements and is appropriate for the casting to be produced has been reached. It is also conceivable that the casting piston is elongated, narrow and/or tubular. Preferably, the casting piston is designed to be self-sealing and/or self-sealing with the measures known to a person skilled in the art. It is understandable that the casting piston is sealed by the sealing device arranged in the region of the first end of the casting chamber. basic position into the end position arranged closer towards the second end of the casting chamber.

It is also essential that the closure piston is arranged in the basic position in the area of the second end and hermetically seals the casting chamber. The closure piston can preferably be moved from the basic position to the end position after or when the end position of the casting piston is reached, so that the casting chamber is opened and the melt in the casting chamber enters the cavity for producing the cast part.

The term "within the range" refers to a spatial arrangement. The term "substantially" means that there is only a minor, in particular insignificant, change, modification and/or deviation from the relevant conditions.

The term “covering” refers to the arrangement of at least a part of the pouring piston, in particular a pouring piston head and/or a push rod of the pouring piston, in front of the suction opening.

According to the invention, the casting chamber further has at least two, preferably three, four, five, six, seven, eight, nine, ten, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more, identically or differently designed vacuum connections for generating a vacuum and/or negative pressure in the casting chamber. According to the invention, each vacuum connection is immediately and directly connected to the casting chamber by means of a suction opening. Within the scope of the invention, the basic arrangement of the vacuum connections is arbitrary and is subject to expert skill. The vacuum connections are preferably grouped, adjacent, paired, next to one another and/or one behind the other in order to facilitate access to them in this way. More preferably, the vacuum connections are arranged on the upper front side of the casting chamber. The term "vacuum" refers to a space in which there is no matter, in particular no gas, no gas mixture and in particular no air. The term "negative pressure" refers to a gas pressure in a space that is lower than the ambient gas pressure of a gas outside the space. As a rule, the gas outside the space is air and the ambient gas pressure is the atmospheric gas pressure. The atmospheric gas pressure depends on the location; at sea level it is approximately 1 bar.

According to the invention, the preferably closed melt dosing furnace, which more preferably contains melt, is connected to the casting chamber via the suction pipe, which is made of a suitable material that meets the requirements. It is understandable to the person skilled in the art that the suction pipe opens into the casting chamber in such a way that the casting chamber can be filled with the melt dosing weight that meets the requirements and is determined according to the casting to be produced. The suction pipe is preferably arranged in the region of the first end, in the middle or in the region of the second end of the casting chamber. More preferably, the suction pipe is arranged on the lower end face of the casting chamber.

The term "melt" is known to a person skilled in the art and refers to flowable, compressible and/or meterable liquid material for producing the cast parts. The melt is preferably a metal melt.

Within the scope of the invention, it has been recognized that the interaction of the vacuum and/or the negative pressure generated ensures that the cast parts produced are low in pores, oxide-free, stress-free, heat-treatable, forgeable and/or weldable. In addition, the cast parts can be designed and adapted individually and according to requirements, as well as being durable. It has been recognized as essential to the invention that the vacuum and/or the negative pressure is maintained accordingly in order to provide high-quality melt for the production of the cast parts. The term "sealing" or "tightness" describes a measure of the tightness of the device with respect to a fluid, such as air, gas and/or a mixture. Preferably, the tightness and/or sealing is at least 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, 99.91%, 99.92%, 99.93%, 99.94%, 99.95%, 99.96%, 99.97%, 99.98% or 99.99%. Suitable means for determining the tightness and/or sealing are known to a person skilled in the art. It is understandable that the term sealing and/or tightness is a relative term, since there is no such thing as an absolutely tight device and/or parts thereof. In the context of the invention, sealing or tightness is therefore to be understood as always relating to predetermined and/or predefined framework conditions, whereby, understandably, fluid can enter or pass through the device for a short time. The possibility of such a short-term fluid entry or passage into the device is, however, of secondary importance. For a person skilled in the relevant field, it is therefore obvious that the design according to the invention is not intended to achieve absolute tightness. Rather, it is preferred that fluid entry or passage into the device is largely impeded. Even more preferably, fluid entry or passage into the device is completely impeded, so that absolute tightness can be achieved at least partially and/or briefly. Tightness can also be adapted to the requirements of the processes through design effort and/or appropriate use of materials, although this is associated with increased costs. Advantageously, the inventive design of the casting chamber with at least two vacuum connections therefore creates a cost-effective and reliable option.

By means of the device according to the invention and in particular the inventive design of the casting chamber with at least two, preferably more, vacuum connections, it is possible to At the start of production, the device is tested for tightness or sealing in accordance with the requirements in order to ensure the production of low-porosity, oxide-free, stress-free, heat-treatable, forgeable and/or weldable cast parts. Furthermore, the device makes it possible to produce the cast parts in a stable, error-free and low-maintenance manner in a simple, fast, reliable and cost-effective manner.

Advantageous developments of the invention, which can be implemented individually or in combination, are presented in the subclaims.

In a further development, it is conceivable that at least one of the vacuum connections, preferably several or all, can be heated. Preferably, at least one of the vacuum connections can be heated in a range from 200°C to 1,000°C, even more preferably from 400°C to 700°C, 500°C to 600°C or 550°C to 650°C. Further preferably, at least one of the vacuum connections is set to at least 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, 360°C, 380°C, 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 820°C, 840°C, 860°C, 880°C, 900°C, 920°C, 940°C, 960°C or 980°C. Suitable means, such as a heater and/or a heating element, are known to a person skilled in the art. The heating element is particularly preferably arranged around and/or at the end of the vacuum connection facing the casting chamber. In this way, it is possible for the liquid melt splashes that occur during melt dosing from the melt dosing furnace via the suction pipe into the casting chamber to impact on the heated inner wall of the vacuum connection and/or the suction opening, continue to maintain their liquid state and combine to form larger liquid drops and flow back into the casting chamber through their own gravity on the inner wall of the vacuum connection and/or the suction opening. This prevents deposits of melt on or in the vacuum connection and/or the Suction opening is reliably and sustainably avoided in order to prevent a deterioration in the quality of the castings to be produced due to the partial or complete blockage of the vacuum connections.

In a further development, it is conceivable that the device comprises a regulating and/or control unit, whereby the vacuum connections can be regulated and/or controlled separately or together. Suitable means, such as a sequence control, are known to a person skilled in the art. In this way, it is possible to prevent the liquid melt splashes described above that occur during melt dosing from the melt dosing furnace via the suction pipe into the casting chamber, with the resulting disadvantages in terms of the associated deterioration in the quality of the cast parts to be produced. In addition, individual or collective control of the vacuum connections is possible, with the associated advantages.

In a further development, it is conceivable that at least one of the vacuum connections, preferably several or all of them, has a sleeve, a sleeve body that encloses the sleeve at least in part and/or in sections, i.e. partially or completely, a sealing and/or closing sleeve disk, a cover, a closure plate, in particular a removable and/or openable closure plate, and/or a pin, in particular a pin with a projection. It is conceivable that the sleeve and/or the sleeve body each have a second end arranged in the area of the suction opening and a first end in the area of the cover and/or the sleeve disk and opposite the second end. Within the scope of the invention, it is therefore conceivable that the sleeve has the sleeve disk at the first end, i.e. at the end opposite the suction opening, preferably towards the cover. It is conceivable that a fastening means, such as a flange or a vacuum connection flange, is fastened to the cover or in the outer surface of the cover. closing plate closes the vacuum connection at the end. If the closing plate can be opened and/or removed, it is possible to clean, maintain and/or repair the interior of the vacuum connection. In particular, molten metal accumulated in the vacuum connection can be removed. The pin enables the simplified drainage of molten metal accumulated in the vacuum connection. This flows down the pin and drips back into the melting chamber under the influence of gravity. For this purpose, the pin is arranged centrally in the sleeve in the axial direction. The projection is preferably arranged in the circumferential direction at the end of the pin pointing in the direction of the melting chamber and is intended to preferably prevent or at least make it more difficult for molten metal to penetrate into the vacuum connection. In a preferred embodiment, the pin can be heated in order to keep the molten metal penetrating and/or having penetrated the vacuum connection in a liquid state. The embodiments and/or configurations described elsewhere in connection with the heatable vacuum connection also apply to the pin. Particularly preferably, the pin is hollow, with a heating element arranged in the cavity. Particularly preferably, the lid and the pin are designed as one piece. Preferably, insulation is arranged on top of the lid.

In one embodiment of the further development, it is conceivable that the sleeve disk is provided with at least one, preferably two, three, four, five or more identically or differently designed, at least in regions and/or sections, i.e. partially or completely, preferably laterally, at the top and/or at the bottom, circumferential gap or gaps, in particular an annular gap. The gap is preferably formed on the side of the sleeve disk on its underside and completely circumferentially. The gap is essential for generating a directed flow. In a further embodiment of the development, it is conceivable that the sleeve body has at least two, preferably three, four, five, six, seven, eight, nine, ten, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more, identically or differently designed layers, wherein at least one, preferably several or all, of the layers is heatable and/or insulating. It is conceivable that the layers of the sleeve body are arranged next to one another and/or one above the other. The sleeve body having at least two layers preferably partially or completely encloses the sleeve. It is also conceivable that at least one layer can be heated by means of a heater, preferably an electric heater or a heating element. The at least one heatable layer can preferably be set to any temperature and can be regulated and/or controlled. Further preferably, the at least one layer is heatable, adjustable and/or controllable in a range from 200°C to 1,000°C, even more preferably from 400°C to 700°C, 500°C to 600°C or 550°C to 650°C. More preferably, the at least one layer is heated to at least 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, 360°C, 380°C, 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 820°C, 840°C, 860°C, 880°C, 900°C, 920°C, 940°C, 960°C or 980°C, and can be regulated and/or controlled. It is also conceivable that several layers, which are arranged next to one another and/or one above the other, are designed to be insulating. The insulating layer is preferably arranged on the outside of the heatable layer. Suitable materials are known to a person skilled in the art. For example, it is conceivable that the sleeve body has an electrical heater on the outside, which is insulated at the top to the lid by the upper insulation, insulated at the sides by the further outer insulation and insulated at the bottom by the lower insulation. In a further development of the invention, it is conceivable that at least one vacuum connection, preferably all vacuum connections, comprises an internal heater. The internal heater is arranged inside the vacuum connection in such a way that the air sucked out through the vacuum connection flows along the circumference of the internal heater. The internal heater preferably comprises an electric heater, a heating element and/or a housing. The at least one internal heater is further preferably adjustable in temperature as desired and can be regulated and/or controlled. The internal heater is further preferably heatable and can be regulated and/or controlled in a range from 200°C to 1,000°C, even more preferably from 400°C to 700°C, 500°C to 600°C or 550°C to 650°C. Further preferably, the internal heating is set to at least 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, 360°C, 380°C, 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 820°C, 840°C, 860°C, 880°C, 900°C, 920°C, 940°C, 960°C or 980°C, and can be regulated and/or controlled. It is also conceivable that the internal heater is insulated by means of a layer. The layer is preferably arranged on the outside. Suitable materials are known to a person skilled in the art. The internal heater is particularly preferably arranged on and/or in a cover described elsewhere, with at least part of the internal heater at least partially protruding into a sleeve body described elsewhere, with a gap being formed between the circumference of the internal heater and the sleeve body. The air sucked out through the vacuum connection can flow through the gap along the circumference of the internal heater. An electric heater is particularly preferably arranged on the outside of the sleeve body, which is arranged at least partially opposite the internal heater.

In a further development, it is conceivable that the suction pipe, the sleeve, the sleeve disc, the sleeve body, the at least two layers of the sleeve body, the cover, the closure plate and/or the pin are at least partially made of at least one of any desired, The suction pipe, the sleeve, the sleeve disk, the sleeve body, the at least two layers of the sleeve body, the cover, the closure plate and/or the pin are preferably made partly or completely of a metal such as steel, stainless steel, preferably rustproof stainless steel, another metallic material such as tungsten, an alloy, preferably a hard metal alloy, and/or a mixture thereof, a coated material and/or ceramic. The internal heater described elsewhere, in particular the housing, is further preferably made partly or completely of a metal such as steel, stainless steel, preferably rustproof stainless steel, another metallic material such as tungsten, an alloy, preferably a hard metal alloy, and/or a mixture thereof, a coated material and/or ceramic. The alloy is particularly preferably an iron alloy, nickel alloy, chromium alloy, molybdenum alloy, vanadium alloy and/or manganese alloy. Even more preferably, the alloy is a tungsten alloy, in particular with a tungsten content of at least 90%. Further preferably, the suction pipe, the sleeve, the sleeve disk, the sleeve body, the at least two layers of the sleeve body, the lid, the closure plate and/or the pin are made of the same material. Preferably, the coated material and/or the ceramic is temperature-resistant up to 1,000°C and/or chemically inert to molten metal. Further preferably, the ceramic of the insulation, in particular the upper, lower, outer and/or top-seated insulation described elsewhere, has a fleece-like structure known to the person skilled in the art, and/or the ceramic of the insulation is heat-resistant. Suitable coatings are known to a person skilled in the art. These materials are characterized by their widely known and consistent material properties and, in particular due to their good availability on the market, make it possible to manufacture the device cost-effectively with the properties required. The term “at least 90% tungsten content” refers to a 90% share of the volume and/or weight of the component that is formed by tungsten atoms.

The term "nonwoven structure" refers to a structure formed from fibers by a disordered arrangement. The definitions and embodiments of the above terms are understood to apply to all aspects described below in this specification, unless otherwise specified.

According to the invention, a die casting machine comprising a device described elsewhere is further proposed.

According to the invention, a method for vacuum die casting for producing cast parts is further proposed, which comprises the following steps: a) providing a device described in detail elsewhere or a die casting machine described elsewhere comprising a casting chamber with at least two vacuum connections; and b) closing the device or the die casting machine; and c) moving a closure piston and a casting piston into a basic position; and d) generating and maintaining a vacuum and/or negative pressure in the casting chamber by means of the at least two vacuum connections, wherein the casting chamber is filled with a melt; and e) moving the casting piston from the basic position towards an end position and ending the vacuum and/or negative pressure of a first of the at least two vacuum connections; and f) further moving the casting piston from the basic position towards the end position and ending the vacuum and/or negative pressure of a second of the at least two vacuum connections; and g) reaching the end position of the casting piston and moving the closing piston from the basic position to an end position; and h) producing the casting.

In the first step a), the device or die casting machine according to the invention is prepared, as described in detail elsewhere. In the second step b), the device or die casting machine is then closed. In the next step c), a closure piston and a casting piston are each moved to a basic position. This means that the casting piston is arranged in the area of the first end of the casting chamber in the basic position and engages therein, and that the closure piston is arranged in the area of the second end of the casting chamber in the basic position and hermetically seals the casting chamber. In the next step d), a vacuum and/or a negative pressure is generated and maintained in the casting chamber, preferably via the suction opening of the at least two vacuum connections. The vacuum and/or the negative pressure causes a pulling force that causes a targeted metering of the melt via a suction pipe from the melt dosing furnace into the casting chamber. This fills the casting chamber with the melt. In the next step e), the pouring piston is moved from the basic position towards an end position, whereby the vacuum and/or the negative pressure of the first of the at least two vacuum connections is terminated at the same time, parallel to the advance of the pouring piston. This means that as soon as the pouring piston passes over the suction opening of the corresponding vacuum connection, preferably completely, the vacuum and/or the negative pressure at this vacuum connection is switched off. In the next step f), parallel to step e), the pouring piston is moved further from the basic position towards the end position, whereby the vacuum and/or the negative pressure of the second of the at least two vacuum connections is terminated at the same time, parallel to the advance of the pouring piston. This means that as soon as the pouring piston passes over the suction opening of the corresponding vacuum connection, preferably completely, the vacuum and/or the negative pressure is also switched off at this vacuum connection. In other words, the vacuum and/or the negative pressure of the respective vacuum connection is switched off one after the other as soon as the preferably self-sealing pouring piston has completely passed the suction opening of the respective vacuum connection. As a result, the vacuum and/or the negative pressure remains constant until the pouring chamber is completely filled, whereby the degassing of the melt takes place while avoiding the formation of oxide. It is understandable that step f) is repeated until the vacuum and/or the negative pressure at the other of the at least two vacuum connections has also ended. In the next step g), i.e. as soon as the last vacuum connection and its suction opening have been passed by the pouring piston and it has reached the end position, the closing piston is moved from the basic position to the end position. This allows the pouring piston to convey the melt into a cavity of the die casting mold in the next step h) in order to obtain the cast part to be produced.

Using the method according to the invention, it is possible to produce the low-porosity, oxide-free, stress-free, heat-treatable, forgeable and/or weldable cast parts in a simple, fast, reliable and cost-effective manner in a stable, error-free and low-maintenance manner. Furthermore, it is possible, particularly due to the inventive design of the casting chamber with at least two, preferably more, vacuum connections, to test the device for a tightness or sealing in accordance with the requirements before production begins in order to enable the production of improved cast parts.

In a further development, it is conceivable that the displacement of the casting piston in step e) only takes place after a melt dosing weight has been reached that complies with the requirements and is appropriate for the casting to be produced. This means that step e) is only carried out after the end of the melt dosing has been reached. In a further development, it is conceivable that after step h) step j) takes place: j) Opening the die casting machine and removing the casting.

A specialist will understand that step j) only takes place after the cooling time has elapsed.

It is further conceivable that step a) and before step b) are carried out by step a) as follows: a) checking the required tightness and/or sealing of at least one of the at least two vacuum connections and/or the device.

Step a l ) is important, as explained in detail elsewhere, in order to detect system leaks prior to the manufacture of the castings and in this way to obtain the castings described elsewhere in the appropriate quality. Preferably, the tightness and/or sealing of several or all vacuum connections is checked as required, whereby each vacuum connection is checked individually and step a l ) is repeated as often as necessary, or all vacuum connections and/or the entire device can be checked simultaneously. More preferably, the tightness and/or sealing is at least 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, 99.91%, 99.92%, 99.93%, 99.94%, 99.95%, 99.96%, 99.97%, 99.98% or 99.99%, at least for a short time. Suitable means for determining the tightness and/or sealing of the device are known to a person skilled in the art.

In a further development, it is conceivable that the checking of one of the at least two vacuum connections and/or the device in step a1) takes place at a negative pressure of 2 mbar to 70 mbar and/or for a duration of at least 10 seconds. Preferably, the checking takes place at a negative pressure of at least 5 mbar, 10 mbar, 15 mbar, 20 mbar, 25 mbar, 30 mbar, 35 mbar, 40 mbar, 45 mbar, 50 mbar,

55 mbar, 60 mbar, 65 mbar or 70 mbar. The check is preferably carried out for a duration of at least 10 seconds, preferably 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100 seconds. Within the scope of the invention, it has been found that checking a vacuum connection with a measured individual negative pressure in the range of 5 mbar to 30 mbar over a period of 60 seconds has delivered the best results in terms of efficiency and cost. Furthermore, it has been found that checking the device with a measured total negative pressure in the range of 5 mbar to 30 mbar over a period of 60 seconds has also delivered the best results in terms of efficiency and cost.

According to the invention, a cast part is also proposed, preferably produced according to the method described in detail elsewhere, wherein the cast part is low in pores, oxide-free, stress-free, heat-treatable, forgeable and/or weldable. The cast part is preferably made of a metal, a metal mixture, an alloy and/or a mixture thereof.

Further details, features and advantages of the invention emerge from the following description of the preferred embodiments in conjunction with the subclaims. The respective features can be implemented alone or in combination with one another. The invention is not limited to the embodiments. The embodiments are shown schematically in the figures. The same reference numbers in the individual figures designate the same or functionally identical elements or elements that correspond to one another in terms of their function.

In detail:

Fig. 1 is a side sectional view of a vacuum die casting apparatus according to the invention; Fig. 2 is a side sectional view of a first embodiment of a vacuum connection according to the invention;

Fig. 3 is a side sectional view of the device of Fig. 1, wherein a step of a method for vacuum die casting according to the invention is carried out on the device;

Fig. 4 is a side sectional view of the device of Fig. 1, wherein a step of a method for vacuum die casting according to the invention is carried out on the device;

Fig. 5 is a side sectional view of the device of Fig. 1, wherein a step of a method for vacuum die casting according to the invention is carried out on the device;

Fig. 6 is a side sectional view of the device of Fig. 1, wherein a step of a method for vacuum die casting according to the invention is carried out on the device;

Fig. 7 is a side sectional view of the device of Fig. 1, wherein a step of a method for vacuum die casting according to the invention is carried out on the device;

Fig. 8 is a side sectional view of the device of Fig. 1, wherein a step of a method for vacuum die casting according to the invention is carried out on the device;

Fig. 9 is a side sectional view of the device of Fig. 1, wherein a step of a method according to the invention is shown on the device. ßend process for vacuum die casting;

Fig. 10 is a side sectional view of the device of Fig. 1, wherein a step of a method for vacuum die casting according to the invention is carried out on the device;

Fig. 11 is a side sectional view of the device of Fig. 1, wherein a step of a method for vacuum die casting according to the invention is carried out on the device;

Fig. 12 is a side sectional view of the device of Fig. 1, wherein a step of a method for vacuum die casting according to the invention is carried out on the device;

Fig. 13 is a side sectional view of a second embodiment of a vacuum connection according to the invention;

Fig. 14 is a side sectional view of a third embodiment of a vacuum connection according to the invention;

Fig. 15 is a side sectional view of a fourth embodiment of a vacuum connector according to the invention;

Fig. 16 is a cross-sectional view of a device comprising three of the third embodiments of a vacuum connection according to the invention; and

Fig. 17 is a side sectional view of the device comprising three of the third embodiments of a vacuum connection according to the invention. The invention describes a device for improved vacuum die casting, which consists of a casting chamber 1 with at least two, three, four, five or more heated vacuum connections 5 arranged one behind the other and at the top, with a mold-side closure piston 2, with a self-sealing casting piston 6, with a ceramic suction pipe 3 and a melt dosing furnace 4.

The first embodiment of the vacuum connections 5 contained in the device is shown in Fig. 2 and is individually composed of a cover 8 made of stainless steel, on which a vacuum connection flange 14 is fastened, a ceramic sleeve 13, which closes off at the first end towards the cover 8 with a ceramic sleeve disk 15, a sleeve body 12 made of stainless steel, which has an electric heater 11 on the outside. The electric heater 11 is insulated at the top towards the cover 8 by the upper insulation 16, laterally by the outer insulation 9 and downwards by the lower insulation 10, whereby the insulation consists of ceramic heat-resistant flow material which is heat-resistant up to 1,000 °C. The ceramic sleeve disk 15 of each vacuum connection 5 contained in the device is provided with a circumferential annular gap at the sides, top and bottom.

An advantageous feature of the device shown in Fig. 1 to Fig. 12 is that the heated vacuum connections 5 can be set as desired for any temperature value in the temperature range from 400 °C to 700 °C, but at least to the solidus temperature of the melt in the range from 550 °C to 620 °C, whereby the liquid melt splashes occurring during melt metering from the melt metering furnace 4 via the ceramic suction pipe 3 into the casting chamber 1 impact the heated inner wall of the ceramic sleeve 13, continue to retain their liquid state and combine to form larger liquid drops and flow down the inner wall of the ceramic sleeve 13 into the casting chamber 1 due to their own gravity. An advantageous feature of the device shown in Fig. 1 to Fig. 12 is that the ceramic sleeve disk 15 and the annular gap running around the sides, top and bottom create a suction flow on the heated inner wall of the ceramic sleeve 13 during melt metering under the influence of vacuum, which carries the emerging liquid melt splashes with it, which impact on the inner wall of the heated ceramic sleeve 13, combine to form larger liquid drops and flow into the casting chamber 1 under their own gravity.

A further advantageous feature of the device shown in Fig. 1 to Fig. 12 is that the ceramic sleeve 13 and the ceramic sleeve disk 15 are made of the same ceramic material, which is temperature-resistant up to 1,000 °C and chemically inert to molten metal.

A further advantageous feature of the device shown in Fig. 1 to Fig. 12 is that the respective vacuum connections 5 are switched off one after the other by means of a sequence control analogous to the advance of the self-sealing pouring piston 6 as soon as the self-sealing pouring piston 6 has completely passed over the suction opening 7 of the respective vacuum connection 5. As a result, the vacuum remains constant until the pouring chamber 1 is completely filled, whereby the degassing of the melt takes place while avoiding the formation of oxide. This is shown in Fig. 8, Fig. 9, Fig. 10, Fig. 11 and Fig. 12.

An advantageous feature of the method shown in Fig. 3 to Fig. 7 is that vacuum tests can be carried out in several steps to detect system leaks before production begins. In the first step, the vacuum test is carried out for the entire system, whereby the vacuum is active for 30 seconds and then switched off, and the measured total negative pressure must be in the range of 5 mbar to 30 mbar over a period of 60 seconds. All vacuum connections are connected in the same way, see state Y as shown in Fig. 3. In the second step, the vacuum test is carried out for the individual vacuum connections 5, whereby the vacuum is active for 30 seconds and is then switched off and the measured negative pressure in the respective switched vacuum connection 5 must be in the range of 5 mbar to 30 mbar over a period of 60 seconds. Here, each vacuum connection 5 is switched individually and one after the other, see state Y as in Fig. 4, Fig. 5, Fig. 6, and Fig.

7. The vacuum test can be carried out manually or fully automatically for both the entire system and the individual vacuum connections 5 using the sequence control. The device can then be used to produce high-quality cast parts, as the functionality of the individual vacuum connections is ensured.

Fig. 13 shows a third embodiment of a vacuum connection 5 according to the invention. This corresponds in large parts to the vacuum connection shown in Fig. 2, wherein the cover 8 has a removable and/or openable closure cap 25. Furthermore, the cover

8 is held in its position by fixing screws 22. The closure cap 25 is held on the cover 8 by means of removable closure screws 24. If the closure cap 25 is open and/or removed, it is possible to clean, repair and/or maintain the vacuum connection 5 in a simple and quick manner, in particular it is possible to remove molten metal. Due to the end arrangement of the closure cap 25, the cover 8 is widened and designed and encloses a sleeve body 18 on one side at least partially on the outer surface. Furthermore, the vacuum connection flange 14 is arranged on the surface of the cover 8 above the sleeve 13. In addition, the ceramic sleeve disk and the lower insulation were omitted. A sleeve 17 made of non-oxidized metal is arranged between the electrical heater 11 and the outer insulation 9 and ensures an even heat distribution of the heat emitted by the heating element 11. The vacuum connection 5 is connected to the vacuum connection 5 by means of the Cover 8 is held on the device by mounting screws 23, with lock nuts 26 being arranged on the mounting screws 23 at the ends opposite the cover 8.

Fig. 14 shows a third embodiment of a vacuum connection 5 according to the invention. This corresponds in large parts to the vacuum connection shown in Fig. 13, with a pin 31 running in the axial direction with the closure cap 21 being arranged centrally in the sleeve body 18. The pin 31 is designed as one piece with the closure cap 21. At an end pointing in the direction of the casting chamber (not shown), a projection 32 is arranged on the pin 31, which is aligned around the pin 31 in the circumferential direction. The pin 31 is hollow, and an electric heater 19 is arranged in the hollow space. The cover 8 and the closure cap 21 are insulated at the top by an insulation 20 sitting on top. Molten metal spraying into the vacuum connection 5 is largely prevented from penetrating further by the projection 32 and can drip down the pin 32 under the influence of gravity like water on a stalactite and back into the casting chamber. The small proportions of the molten metal spraying into the vacuum connection 5 that pass through the projection 19 are kept in the liquid state by the heat emitted by heaters 11 and 19 and also flow past the projection 19 again under the influence of gravity and drip along the pin 18 into the casting chamber. In the third embodiment, the pin 18 is made of a tungsten alloy with at least 90% tungsten content.

Fig. 15 shows a fourth embodiment of a vacuum connection 5 according to the invention. This corresponds in large parts to the vacuum connection shown in Fig. 13. The vacuum connection 5 comprises an internal heater 28 arranged on the cover 8, in which an electric heater 27 is arranged. The internal heater 28 is arranged in the sleeve 18 in such a way that arranges that a gap is formed between the sleeve 18 and the internal heater 28.

Fig. 16 shows a cross-sectional view of a device comprising three of the third embodiments of a vacuum connection 5 according to the invention. The device comprises a casting chamber 1, in the outer surface of which electrical heaters 29, 30 are arranged at the end facing the casting chamber 1 or around the end of the vacuum connections 5 facing the casting chamber 1.

Fig. 17 shows a side sectional view of the device comprising three of the third embodiments of a vacuum connection 5 according to the invention. In addition to the parts already visible in Fig. 16, the device also comprises a ceramic suction pipe 3, a melt dosing furnace 4 and a self-sealing pouring piston 6.

List of reference symbols casting chamber closure piston ceramic suction pipe melt dosing furnace vacuum connections self-sealing casting piston suction openings cover outer insulation lower insulation electric heater sleeve body ceramic sleeve vacuum connection flange ceramic sleeve disc upper insulation metallic sleeve body hard metal/hard metal alloy sleeve electric heater top-mounted insulation closure cap fixing screw assembly screw closure screw closure cap lock nut electric heater internal heater electric heaters electric heaters 31 cones

32 ProjectionY Vacuum “On”

N Vacuum “Off”

Claims

Patent claims

1. Device for vacuum die casting for producing cast parts by means of a die casting machine forming a cavity, comprising a casting chamber (1) with a closure piston (2) and a casting piston (6), a melt dosing furnace (4) and a suction pipe (3) for connecting the melt dosing furnace (4) to the casting chamber (1), wherein the closure piston (2) and the casting piston (6) are displaceable between a basic position and an end position, characterized in that the casting chamber (1) has at least two vacuum connections (5), wherein each vacuum connection (5) has a suction opening (7) for connection to the casting chamber (1), and that the casting piston (6) in the end position covers the suction openings (7) of the at least two vacuum connections (5) at least in part and/or in part.

2. Device according to claim 1, characterized in that at least one of the vacuum connections (5) is heatable.

3. Device according to claim 1 or 2, characterized in that the device comprises a regulating and/or control unit, wherein the vacuum connections (5) can be regulated and/or controlled separately from one another or together.

4. Device according to one of claims 1 to 3, characterized in that at least one of the vacuum connections (5) comprises a sleeve (13, 18), a sleeve body (9, 10, 11, 12, 16, 17) enclosing the sleeve (13, 18), a sleeve disk (15), a cover (8), a closure cap (21, 25), in particular a removable and/or openable closure cap (21, 25), and/or a pin (31), in particular a pin (31) with a projection (32).

5. Device according to claim 4, characterized in that the sleeve disc (15) has at least one circumferential gap at least in part and/or in sections.

6. Device according to claim 4 or 5, characterized in that the sleeve body (9, 10, 1 1, 12, 16, 17) has at least two layers (9, 10, 1 1, 12, 16), wherein at least one of the layers is heatable (1 1) and/or insulating (9, 10, 16).

7. Device according to one of claims 2 to 6, characterized in that at least one of the vacuum connections (5) or at least one of the layers of the sleeve body (9, 10, 11, 12, 16, 17) can be heated in a range from 200°C to 1,000°C.

8. Device according to one of claims 1 to 7, characterized in that the suction pipe (3), the sleeve (13, 18), the sleeve body (9, 10, 11, 12, 16, 17), the sleeve disk (15), the cover (8), the closure plate (21, 25) and/or the pin (31) is at least partially made of a metal, such as steel, stainless steel, preferably rust-proof stainless steel, an alloy, in particular a hard metal alloy, or a mixture thereof, of a coated metal and/or of ceramic.

9. Die casting machine comprising a device according to one of claims 1 to 8.

10. Method for vacuum die casting for producing cast parts comprising the following steps: i) providing a device according to one of claims 1 to 8 or a die casting machine according to claim 9 comprising a casting chamber (1) with at least two vacuum connections (5); and j) closing the device or the die casting machine; and k) moving a closure piston (2) and a casting piston

(6) into a basic position; and l) generating and maintaining a vacuum and/or negative pressure in the casting chamber (1) by means of the at least two vacuum connections (5), wherein the casting chamber is filled with a melt; and m) moving the casting piston (6) from the basic position towards an end position and ending the vacuum and/or negative pressure of a first of the at least two vacuum connections (5); and n) further moving the casting piston (6) from the basic position towards the end position and ending the vacuum and/or negative pressure of a second of the at least two vacuum connections (5); and o) reaching the end position of the casting piston (6) and moving the closure piston (2) from the basic position into an end position; and p) producing the casting.

1 1. Method according to claim 10, wherein the displacement of the casting piston (6) in step e) takes place after reaching a melt dosing weight.

12. The method according to claim 10 or 11, wherein after step h) step j) takes place: j) Opening the die casting machine and removing the casting.

13. Method according to one of claims 10 to 12, wherein after step a) and before step b) step a l) takes place: a l) checking the tightness and/or sealing of at least one of the at least two vacuum connections (5) and/or the device.

14. The method according to claim 13, wherein the checking of one of the at least two vacuum connections (5) in step a l) is carried out at a negative pressure of 2 mbar to 70 mbar and/or for a duration of at least 10 seconds.

15. Cast part, preferably produced according to the method according to one of claims 10 to 14, wherein the cast part is low in pores, oxide-free, stress-free, heat-treatable, forgeable and/or weldable.