EP0656819B1 - Process and device for casting components - Google Patents

Abstract

PCT No. PCT/EP94/01813 Sec. 371 Date Mar. 16, 1995 Sec. 102(e) Date Mar. 16, 1995 PCT Filed Jun. 3, 1994 PCT Pub. No. WO94/29050 PCT Pub. Date Dec. 22, 1994The invention relates to a process and devices for casting components in metal alloys on the tilt casting principle in which a quantity of melt metered for casting is spread over a large gate cross section without turbulence from a melt container of the mould (30) into the mould (31) by rotating the casting device. To prevent the formation of oxide and weak structural points, the melt is taken from a metering furnace under a protective gas in a melt container connected to the mould and taken thence into the mould also under a protective gas. The melt hardens there under increased gas pressure on the feeder region of the casting, whereby its properties such as fine-grained, dense structure, high stability under load and accurately dimensioned surfaces are considerably improved.

Description

The invention relates to a method and an apparatus for casting Components, made of metal alloys according to the tilting principle according to the respective Generic term of independent claims 1, 3 and 15. When shaping components The liquid material state is a variety of different processes and devices known that more or less resemble a high quality Workpiece requirements with regard to freedom of design, Surface quality and in particular optimal material properties to reach. The main difficulties initially lie in the mold filling process, the initially compact melt volume divided and a large one Surface is exposed to the attack of the air atmosphere, which by appropriate Reactions lead to an impairment of the material quality. Molten metal alloys, their Alloy components have a high reactivity with the oxygen, Have nitrogen and water vapor in the air. It became like this early on sensitive alloys, for example the Durville tipping process applied.

DE-PS 377 683 proposes a method in which an elongated Casting vessel numerous castings are made in succession. During the casting process the melt container is erected, which limits one higher metallostatic pressure can be achieved. Here, however, the Atmosphere free access to the melt, so that especially as it progresses Easily drain oxide from the bath surface into the mold cavity can reach. A direct remains during the solidification of the casting There is a connection with the large melt reservoir in the casting container so that the solidification process is slowed down.

DE-PS 505 224 describes a method in which on a similar one Swing arranged casting container two molds are mounted, which alternate be filled with melt. Here, too, the air has free access to the melt pool with a large surface, so that the impurities present here can easily get into the mold.

DE-PS 21 64 755 describes a high-performance casting process for large series, in which the disadvantages of the aforementioned proposals largely could be eliminated. However, there is a high level of technical effort required, particularly in the event of malfunctions on a single mold everyone else with impaired.

The solidification process in the casting mold usually occurs through volume contraction and gas excretion cavities and pores in the component structure must be combated with considerable effort. The shrinking processes also locally lead to the formation of gaps between the cast wall and mold wall surfaces, which significantly affects the heat transfer, what also has negative repercussions on the structure quality and also Sink marks on the casting surface that make the component unusable do.

GB 2 080 714 A describes a method and an apparatus of the type described in the introduction. The device comprises a Pouring canister, which during the implementation of the process of a mold cavity through a channel with an elongated constriction is separated, with at least the after tilting in oxide skin located in a feeder head is washed into the casting will be. Through the formation of the constriction, the mold filling controlled in the sense of throttling, whereby a layered mold filling is not possible. In the constriction occur high flow velocities with turbulence and oxide turbulence on and there is a risk of leaching and metal lugs. The flow paths of the melt from the gate the channel with the constriction and the feeder head are in relation to the casting size very long and affect the Melt quality considerably due to reactions and temperature losses, which greatly reduces the mold filling and fluidity becomes.

The object of the present invention is, using novel methods and a new type of pouring device for high-quality component production to create necessary favorable conditions, both when filling the mold as well as during the solidification of the castings, at the same time a special one to enable rational manufacturing and thereby the disadvantages of the above Avoid procedures and devices. Turbulence and Distribution of the melt during mold filling can be avoided. After a Further tasks are the reactions of the alloy melt with the Gases of the atmosphere and the mold cavity are prevented. After a Another advanced task is preferably a sharp-contoured filling achieved and an optimally fine-grained and dense component structure during the Solidification process can be ensured.

Methods and a suitable device are used to achieve this object proposed with the features of the independent claims, here is a sealable container for the melt over a large gate cross-section with the cavity of a mold initially lying above the container connected.

The gate creates the direct connection between the casting container and the mold cavity and should be such that a throttling or Swirling of the melt when overflowing can be avoided. Its big Cross section based on the cross section of the cut mold cavity or the adjacent mold wall parts of the component can after a first Approach over 40%, especially over 50% of the latter cross-sectional areas be. The large cross section related to the cross section of the cut mold cavity or the cross section of the adjacent mold wall parts extends according to the invention over essentially the entire length of the latter areas. The gate communicates here each with the deepest parts of the mold cavity or the mold wall part before turning. Only their cross-sectional areas parallel to the gate cross-section are referred to as cut surfaces on which the relative dimensioning of the gate.

It is preferred to flush first with protective gas, then with a metered one Melt quantum filled under protective gas and sealed gastight, then the container with the mold is rotated about a horizontal axis so that the Melt is conveyed into the mold without leading tongues or splashes.

According to a method according to the invention will increase the Gas pressure - in particular Shielding gas pressure - during the Form filling process and / or the solidification process made. It is cheap here when the protective gas is recovered during the subsequent expansion becomes.

The process is peculiar to that for a casting process one corresponding to the gross volume of the melt quantity for a casting Quantity is poured into the casting tank during the casting process completely solidified, with only a small volume fraction of the melt, the the feeder volume forms, in the gate itself or, if necessary, in small quantities remains in the casting tank.

To avoid the oxidation processes, one is preferred Execution of the casting tank under protective gas with liquid Melt filled, the inert gas during the rotation of the Casting container with the mold is maintained.

According to an alternative embodiment to this, a quantity corresponding to the melting quantity becomes fixed metal volume introduced into the casting tank, first then the sealing connection between the casting container and the casting mold and the interior was purged with protective gas, whereupon the melt quantum is melted for a cast in the casting container. Otherwise runs the procedure unchanged. Here, too, the oxidation processes liquid phase effectively avoided.

To improve the structure, an increase in pressure of the protective gas is carried out during made of the solidification process, whereby the feed volume and thus the Use of metal can be reduced because of the overpressure on the melt level the otherwise usual metallostatic pressure of high-reaching feeders replaced.

To improve the castings is applied to alloys that are less prone to oxidation or are at risk of oxidation The use of protective gas is dispensed with, but otherwise the last one described Procedure with an increase in pressure in the interior of the casting container during the mold filling process and / or during the solidification process the same effects of reduced use of materials and one to bring about improved structure and surface quality of the casting.

Here it is possible according to alternative procedures, either that Introduce melt quantum in liquid form into the casting container, or in solid form and then melt in the casting tank. Otherwise the procedure is carried out unchanged from the aforementioned.

According to another method according to the invention for improving castings, those due to the alloys used and / or the shape The process becomes less prone to void formation and sink marks carried out without building up an overpressure, but in the gate and preferably in a part of the casting tank melt to the extent necessary stops after turning to create a metallostatic pressure.

Here, too, it is possible, according to alternative procedures, either to introduce the melt quantum in liquid form into the casting container, or in solid form and then melt in the casting container. Furthermore the method is carried out unchanged from the aforementioned.

According to the method according to the invention there is in particular the risk of contamination and the inclusions in the casting excluded in that Comparison to the adjacent component surface or the cut part of the mold cavity, a large gate cross section is provided, or that a compared to the size of the casting or the mold cavity in the direction of Long gating axis of rotation is provided. This results in a calm overflow, preferably completely under the bath level from the casting container into the casting mold, so that a faultless casting is created.

The gate with a large cross-section is with the pouring channel or barrel identical and at the same time represents the volume of feeder. It forms the immediate one Connection between the interior of the casting container and the mold cavity.

Further configurations are characterized by a number of significant advantages out. When transferring a metered amount of melt from a metering furnace in the casting container of the device under a protective gas atmosphere Oxidation of the melt effectively prevented. This is all the more important because during this process the pouring jet falls freely into the casting container, not a special one here as with conventional working methods intensive oxide skin formation with constant tearing off, washing in and swirling takes place in the melt. Then by the rotating movement of the device Form filling can begin due to the predetermined large gate cross sections particularly quiet and with low flow velocity Melt run on the principle of communicating tubes, what especially in connection with one that is also present in the mold cavity Protective gas atmosphere the risk of foam formation, which is known to Inclusions in the cast structure leads, effectively eliminated. It stays that way the melt front closed, d. H. it does not lead to the formation of leading ones Metal tongues or even splashes, so that even when casting as a common Dreaded cold run is avoided.

According to a preferred embodiment, it is provided that the mold cavity for an elongated component is aligned in the direction of the axis of rotation. This enables a wide melt front to be represented.

Another design is that the cores lie towards the casting container are arranged. As a result, the cut mold wall parts themselves reduced to end wall parts of the component to improve the quality.

For cast parts such as cylinder heads or cylinder crankcases of internal combustion engines surfaces with high quality standards a mold wall opposite to the gate.

The solidification should be carried out in a known manner, if necessary by heating and / or Cooling can be controlled so that it is the most distant from the casting tank Position of the component progresses towards the gate.

According to a preferred embodiment, a further overflow channel becomes parallel intended for gate, so that initially a gas or air volume compensation can take place to avoid foaming.

Due to the close coupling of the casting container to the mold cavity extremely short flow paths realized. The melt reaches the shortest route their final position, cools quickly and freezes. So the "channeling effect", that in conventional mold filling processes due to long-lasting After-flow or through-flow occurs in certain areas of the mold switched off.

These advantages also have further effects in the subsequent solidification process. First, the heat balance of the mold is eliminated pronounced channeling effects, the corresponding local overheating both in the casting and in the adjacent mold wall areas cause far less disturbed, so that a targeted control of the solidification is favored.

Furthermore, an increased, in particular variable, protective gas pressure during the solidification very special advantages. By a strong increase in gas pressure, mainly due to the melt level at the end of the mold filling acts below which the feed volume of the casting is, can Appropriate increase of the feed pressure is achieved and thus a substantial Sealing feed of the cast structure can be forced. At the same time, a vigorously pressing the cast part surfaces against the mold walls and through Prevention of the harmful gap formation an increased heat transfer causes.

This in turn shortens the solidification time and increases the sharpness of the contours as well as the dimensional accuracy of the castings. Beyond that, too the formation of alloys, especially in alloys with a wide solidification interval dreaded sink marks on the cast surface eliminated. Here the increase in gas pressure can far exceed that of conventional processes, e.g. B. low pressure casting process, possible pressures due to the limitation go to the comparatively small volume of a single cast. Through the additional use of the well-known swell sequence cooling (DE-PS 26 46 060) the improvements mentioned are optimal Way expanded. According to this, the application of a method is provided after the mold has been brought to a working temperature before filling and after filling the mold from the end zones to the feed zones cooling down to the end of solidification becomes.

Improvements can also be made in the use of inert gas. The application A protective gas pump not only allows the application of several bar pressure, it also allows for a subsequent pressure reduction Recovery of the protective gas. This way the losses stay up unavoidable leakage is limited.

When using alloys that are less strong in the molten state The gases in the atmosphere can react to the usually expensive shielding gas be dispensed with and instead an increase in pressure due to compressed air can be brought about, while all other advantages are retained.

Finally, the proposed methods offer ideal conditions for use in a casting cell sealed off from the outside world reliable prevention of foundry emissions.

For this, the use of a combined melting and dosing furnace according to DE-PS 20 41 588, which at the same time the problem of introducing charging material solves, of particular advantage. After that, a arranged gas-tight charging chamber with a charging body through which one quantified amount of melt conveyed into the casting or melt container can be.

Advantageous embodiments of the method and the device are in the Subclaims defined, the content of which is hereby incorporated by reference.

Fig. 1

zeigt einen Vertikalschnitt durch einen Gießbehälter mit einer Gießform entlang der Schnittlinie A-B nach Fig. 2;

Fig. 2

zeigt einen Vertikalschnitt durch einen Gießbehälter mit einer Gießform nach Fig. 1 senkrecht zur Drehachse;

Fig. 3

zeigt eine Gießzelle mit zur Durchführung erfindungsgemäßer Verfahren geeigneten Anlageteilen in systematischer Darstellung;

Fig. 4

zeigt einen Vertikalschnitt durch einen Gießbehälter mit einer Gießform durch die Drehachse in einer zweiten Ausführungsform.

The invention is described below on the basis of exemplary embodiments in conjunction with the drawing;

Fig. 1

shows a vertical section through a casting container with a casting mold along the section line AB of FIG. 2;

Fig. 2

shows a vertical section through a casting container with a casting mold of Figure 1 perpendicular to the axis of rotation.

Fig. 3

shows a casting cell with system parts suitable for performing methods according to the invention in a systematic representation;

Fig. 4

shows a vertical section through a casting container with a casting mold through the axis of rotation in a second embodiment.

In the exemplary embodiment according to FIG. 1, a casting mold 31 (mold) is with a mold cavity 1 through a mold cover plate 2, side parts 3, Cores 4 and a mold base plate 5 are formed. Under the mold base plate 5 there is a casting container 30 with a housing 6 and one Refractory lining 7, which is a melt quantum 8 metered for a casting contains. The melt quantum 8 is with the help of a not shown Dosing furnace in particular through the filling opening 9 with the closure 10 open filled under protective gas; then the shutter 10 is closed. A protective gas connection 11 is shown on the closure 10. Furthermore, the horizontal is in the direction of the longitudinal extent of Casting mold 31 and casting container 30 extending axis of rotation 12 of the casting device shown. As an opening within the mold base plate 5 is a Bleed 13 formed with a large cross section.

An arrow above the mold cover plate 2 symbolizes the direction of movement the same for demolding the finished component.

The mold 31 with the mold cavity 1 can also be seen in FIG. 2, those from the mold cover plate 2, side parts 3, cores 4 and the mold base plate 5 exists. In the base plate 5 are the gate 13 and a parallel further overflow channel 14 can be seen. On the casting container 30 is the housing 6, the refractory lining 7 and the contained therein for a casting metered melt quantum 8 recognizable.

By rotating the entire casting device about the axis of rotation 12 against the The melt flows clockwise through the gate 13 with a large cross section in a calm, turbulence-free flow into the mold cavity 1 and fills this in a few seconds. At the end of the rotary movement is the Pouring container 30 over the mold base plate 5. Now the internal pressure, in particular the protective gas pressure above that which solidifies in the mold cavity 1 Melt, the total volume of which also includes the required feeder volume, increased with the help of the pressure connection 11 and thus the sealing supply of the Casting improved. After the solidification is complete, the overpressure can rise to Normal pressure lowered, the mold opened and the sufficiently cooled Cast part can be removed. Then a new casting cycle begins.

Arrows to the side of the mold side parts 3 symbolize their direction of movement for demolding.

FIG. 3 shows a rotatable casting device 19 with a rotary drive 27 and a casting container 30 and a casting mold 31 connecting them Bracing means 32 shown within a casting cell 21. The axis of rotation 12 the pouring device is also shown. The casting container 30 is over a line 26 with a pump and storage system shown only symbolically 18, 28 connected. A metering furnace is located within the casting cell 21 15, which has an elastic gas-tight coupling 23 with the filling opening 9 of the casting container 30 is connected. The metering oven 15 is a Lock 22 connected to an area outside the casting cell 21. To the Lock 22 can alternatively be a charging device 16 for lumpy Feed material or a charging device 17 for liquid feed material connect. The casting cell comprises a further lock 22. Above the mold 31, a manipulator 20 for cores can be seen.

FIG. 4 shows a casting device consisting of a casting container 30 and a mold 31 shown.

The casting container 30 differs from that shown in FIG. 1 in that that it has no fill opening. However, it points within the refractory layer 7 means for heating 24. A solid metal quatum 25 is in the Casting container 30 used. Corresponds in cross section perpendicular to the axis of rotation 12 this pouring device shown in Figure 2.

The casting mold 31 essentially corresponds to that shown in FIG. 1. It comprises a mold cover plate 2, mold side parts 3 and one Mold base plate 5. However, means 29 for cooling are in the side parts shown. Cores 4 are used in the mold. The axis of rotation of the device is designated 12.

Claims (20)

1. A process of casting components of metal alloys in accordance with the tilting casting process in a casting mould (31) - especially in a permanent mould - which is provided with at least one ingate (13) which establishes an open connection between the mould cavity (1) of the casting mould (31) and the interior of a tiltable casting container (30) for the melt, with the casting container (30), in a position below the casting mould (31), being filled with an amount of melt (8) required for one casting operation, whereupon the casting container (30), together with the casting mould (31), is rotated around a horizontal axis of rotation (12) in such a way that the melt is conveyed via the ingate into the casting mould (31),
   characterised in

   that the mould cavity (1) is connected directly to the casting container (30) via the ingate (13),

   that the mould cavity (1), with its longitudinal axis, is aligned in the direction of the axis of rotation (12), with the ingate (13) extending substantially along the entire length of the mould cavity, with the melt flowing in through a large cross-section of the ingate relative to the gated cross-section of the mould cavity,

   that, prior to being rotated, the casting container (30) is closed so as to be gas-tight, and

   that, at least temporarily during the mould filling operation and the solidification process, the pressure in the interior of the casting container (30) is increased.
2. A process according to claim 1,
   characterised in

   that the casting container (30) is filled with a quantified metal quantity (25) in a solid form for one casting operation and closed so as to be gas-tight, whereupon the metal quantity (25) is melted to form the amount of melt required for one casting operation.
3. A process of casting components of metal alloys in accordance with the tilting casting process in a casting mould (31) - especially a permanent mould - which is provided with at least one ingate (13) which establishes an open connection between the mould cavity (1) of the casting mould (31) and the interior of a tiltable casting container (30) for the melt, with the casting container (30), in a position below the casting mould (31), being filled with an amount of melt (8) required for one casting operation, whereupon the casting container (30), together with the casting mould (31), is rotated around a horizontal axis of rotation (12) in such a way that melt is conveyed via the ingate into the casting mould (31),
   characterised in

   that the mould cavity (1) is connected directly to the casting container (30) via the ingate (13),

   that the mould cavity (1), with its longitudinal axis, is aligned in the direction of the axis of rotation (12), with the ingate (13) extending substantially along the entire length of the mould cavity, with the melt flowing in through a large cross-section of the ingate relative to the gated cross-section of the mould cavity,

   that, prior to being rotated, the casting container (30) is closed to be leak-proof, and

   that, at least in the ingate (13), part of the melt remains as feeder volume.
4. A process according to claim 3,
   characterised in

   that the casting container (30) is filled with a quantified metal quantity (25) in a solid form for one casting operation and closed so as to be leak-proof, whereupon the metal quantity (25) is melted to form the amount of melt required for one casting operation.
5. A process according to any one of claims 3 or 4,
   characterised in

   that part of the melt remains in the entire cross-section of the casting container (30) in the form of feeder volume.
6. A process according to any one of claims 3 or 4,
   characterised in

   that, at least temporarily for the duration of the mould filling operation and of the solidification process, the pressure in the interior of the casting container (30) is increased.
7. A process according to claim 1 or 3,
   characterised in

   that the casting container (30) for the melt is first flushed with inert gas, then filled under inert gas with the amount of liquid melt (8) required for one casting operation and closed so as to be gas-tight, whereupon the melt is conveyed into the casting mould (31) under inert gas.
8. A process according to claim 2 or 4,
   characterised in

   that, after having been closed so as to be gas-tight, the casting container (30) is flushed with inert gas and that the metal quantity (25) is melted to form the amount of melt required for one casting operation, whereupon the melt is conveyed into the casting mould (31) under inert gas.
9. A process according to any one of claims 7 or 8,
   characterised in

   that, at least temporarily for the duration of the mould filling operation and of the solidification process, the inert gas pressure in the interior of the casting container (30) is increased.
10. A process according to any one of claims 7 or 8,
    characterised in

    that after the mould filling operation or the solidification process, the inert gas used is recovered during the pressure-relieving process for re-use.
11. A process according to any one of claims 7 or 8,
    characterised in

    that, prior to being flushed with inert gas, the air contained in the casting container (30) is largely evacuated.
12. A process according to any one of claims 1 to 4,
    characterised in

    that a mould cavity (1) provided with cores (4), with said cores reaching as far as a component surface, is arranged in such a way that said cores (4) point towards the cross-sectional surface of the ingate.
13. A process according to any one of claims 1 to 4,
    characterised in

    that between the casting container (30) and the mould cavity (1), at the beginning of the casting operation, an exchange of gas takes place through at least one further overflow channel (14) in addition to the ingate (13).
14. A process according to claim 13,
    characterised in

    that the further overflow channel (14) extends substantially along the component length, parallel to the ingate (13).
15. A device for casting components of metal alloys in accordance with the tilting casting process in a casting mould (31) - especially a permanent mould - which is provided with at least one ingate (13) which establishes an open connection between the mould cavity (1) of the casting mould (31) and the interior of a tiltable casting container (30) for the melt, with the casting container (30) being movable into a position below the casting mould (31) and with the casting container (30) being tiltable together with the adjoining casting mould (31), having clamping means (32) between the casting mould (31) and the casting container (30) and having rotational driving means (27) for rotating the casting container (30) with the casting mould (31) around a horizontal axis (12), with the interior of the casting container (30) being adapted to the gross volume of an amount of melt required for one single component casting,
    characterised in

    that the ingate (13) constitutes a direct connection between the casting container (30) and the mould cavity (1),

    that the mould cavity (1), with its longitudinal axis, is aligned in the direction of the axis of rotation (12) and that the ingate (13) extends along substantially the entire length of the mould cavity/component length, so that the casting mould (31) comprises an ingate (13) with a large cross-section relative to the cross-section of the ingated mould cavities or component wall parts.
16. A device according to claim 15,
    characterised in

    that there are provided closing means (10) for closing the casting container in a gas-tight way, and pressure increasing means (18) for increasing the inner pressure in the casting container.
17. A device according to any one of claims 15 or 16,
    characterised in

    that the casting container (30) is connected to the mould cavity (1) of the casting mould (31) by at least one further overflow channel (14) in addition to the ingate.
18. A device according to claim 17,
    characterised in

    that the further overflow channel (14) substantially extends along the entire length of the mould cavity/component length, parallel to the ingate (13).
19. A device according to any one of claims 15 or 16,
    characterised in

    that the ingate (13) has a substantially uniform width which is smaller than its length.
20. A device according to any one of claims 15 or 16,
    characterised in

    that the casting container (30), together with a casting mould (31), is rotatable around a longitudinal axis positioned in the cross-sectional plane of the ingate (13).

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