EP0848652B1 - Process and device for filling a casting tool with a metal melt - Google Patents

Abstract

PCT No. PCT/DE96/01544 Sec. 371 Date Jun. 15, 1998 Sec. 102(e) Date Jun. 15, 1998 PCT Filed Aug. 14, 1996 PCT Pub. No. WO97/09137 PCT Pub. Date Mar. 13, 1997In order to fill a casting mould with a molten metal, the latter is caused to flow into through an annular chamber into the shaped cavity of a casting mould, such annular chamber discharging over the entire external periphery of the shaped cavity into the latter. The inflow of molten metal into the annular chamber is interrupted by means of a piston, which, being borne inside the annular chamber, is capable of sliding therein. The molten metal can be caused to flow across a large flow cross-section, which shortens the filling time even with reduced flow velocity.

Description

The invention relates to a method and an apparatus for Filling a casting tool with a molten metal according to the The preamble of claim 1 and claim 2.

When casting castings, their diameter in relation to axial length is large, e.g. B. in rotationally symmetrical castings, like alloy wheels for vehicles is used in most Cases used a central gate, in which the metal melt fed into the center of the mold cavity becomes. There are also side gates and multiple gates used. All of these methods have in common that the molten metal via a feed channel with a relative small diameter of about 30mm to 50mm is fed. So that the metal melt before solidification from this pour all parts of the mold cavity of the casting tool are reliable can flow is a high temperature of the molten Metal necessary. This means a high heat input in the Area of the feed and thus a partial overheating of the Casting tool in the gate area. This overheating has one heavy wear of the tool or the sprue bushings As a result, the service life of the casting tools is reduced become. The high temperature of the molten metal prolongs moreover, the cooling cycle, so that usually complex additional cooling measures must be used.

From JP 54 115 628 A, from which the invention is based, it is known, the metal melt initially decentralized to an annular chamber feed. The ring chamber is along its circumference with the Mold cavity of the casting tool connected so that the molten metal from the annular chamber into the mold cavity evenly can flow over the circumference. This is supposed to a smoother melt flow can be caused, the gas inclusions reduced on the finished product. However, that still exists Problem that the molten metal enters the mold cavity relatively slowly can flow, so that a high temperature continues of molten metal with the disadvantages described above necessary is.

The invention has for its object to fill the To improve casting tool with a molten metal so that shorter cycle times with an improved quality of the casting can be united.

According to the invention, this object is achieved by a method with the features of claim 1 and by a device with the features of claim 2.

Advantageous embodiments of the invention are in the on this Claims related subclaims specified.

The basic idea of the invention is to melt the metal from the annular chamber into the mold cavity through a To displace the piston, which is slidable within the annular chamber is stored. This ensures that in the end of the filling cycle the further supply of molten metal is prevented. The piston advances the molten metal and pushes them out of the ring chamber into the mold cavity inside.

The molten metal can therefore be supplied without turbulence, which reduces the formation of voids and the quality of the Casting is increased. Next is the circular decentralized Feeding the molten metal through the heat input the molten metal on the entire circumference of the annular chamber distributed. The more even distribution of heat input avoids local overheating, which leads to a particularly strong Lead wear of the casting tool. In addition, the faster supply of the molten metal and the shorter ones Flow paths of the molten metal in the mold cavity a reduction the temperature of the molten metal supplied. this means a further reduction in wear and a Saving energy. Finally, the molten metal solidify faster, which on the one hand results in an additional shortening the total cycle time and also the dendrite growth reduced, so that the casting better mechanical Has characteristic values due to smaller dendrite arm distances.

The annular chamber is provided with at least one piston which can be pressed into the volume of the annular chamber. This The piston closes the feed channel of the molten metal and presses the molten metal remaining in the ring chamber into the mold cavity.

The method and the device can preferably be used rotationally symmetrical castings are used, for example for the production of alloy wheels for vehicles.

The method and the device can be used with all known die casting processes, especially in low pressure casting machines, in back pressure casting machines, in press casting machines, with "squeeze" effect and with vacuum casting machines.

In the following, the invention is based on one in the drawing illustrated embodiment explained in more detail. The only Figure of the drawing shows the casting in axial section of a light alloy wheel for a vehicle, the right one Half the condition with the mold open and the left one Half shows the condition with the mold closed.

In the drawing is the manufacture of a light alloy wheel shown for a motor vehicle.

The casting tool consists of a steel mold that is assembled is made of a lower tool part 10, an upper one Tool part 12 with a central insert 14 and slides 16. The lower tool part 10 is fixed on a base plate 18 assembled. The upper tool part 12 and its central insert 14 can be moved vertically. If necessary, the upper tool part 12 also integrally formed with the central insert 14 his. Centrally through the base plate 18 and the lower tool part 10 a jack 20 is guided.

On the base plate 18, a retaining ring 22 is mounted, the lower tool part 10 coaxially encloses. The retaining ring 22 is radial to the outer circumference of the lower tool part 10 spaced so that between the outer circumference of the lower tool part 10 and an axially adjoining paragraph the base plate 18 on the one hand and the inner circumference of the retaining ring 22 on the other hand, a cylindrical annular chamber 24 is formed becomes. At the bottom, the annular chamber 24 is through the base plate 18 completed, with a fluid pressure channel 26 through the base plate 18 leads from below into the annular chamber 24. Down in the Annular chamber 24 is an annular piston 28 which supports the fills the entire horizontal cross section of the annular chamber 24 and has half the axial height of the annular chamber 24. The piston 28 is in the annular chamber 24 on its outer circumference and on its Inner circumference tightly guided. The piston 28 can by Pressurization via the fluid pressure channel 26 in the annular chamber 24 are pushed upwards. Alternatively, the piston 28 pushed up by several hydraulically operated jacks become.

A feed channel 30 leads through the retaining ring 22 above the Piston 28 in the annular chamber 24. The feed channel 30 extends radially through the retaining ring 22 and rises axially from the outside inside. An inflow pipe 32 which is acted upon by a pressure piston is frictional and tight with a dome-shaped Mouthpiece to the radially outer end of the feed channel 30 then inserted into the retaining ring.

The annular chamber 24 opens out at its upper end over its entire length Circumference and over their entire radial width in the mold cavity of the casting tool on its outer circumference. In the in the Drawing shown embodiment, in which the Casting is a vehicle wheel, the annular chamber 24 opens into the formed by the lower tool part 10 and the sliders 16 Area of the mold cavity that is the outer rim flange of the wheel forms.

The casting process is as follows:

First, the upper tool part 12 with the central insert is located 14 in the raised upper position and the piston 28 lies at the bottom in the annular chamber 24, as in the right one Half of the drawing is shown. Via the inflow pipe 32 and the molten metal is fed radially from the outside into the feed channel 30 the annular chamber 24 is fed above the piston 28. The molten metal fills the annular chamber 24 and the mold cavity of the lower one Tool part 10, so that in the lower tool part 10th sets a characteristic bottom depth of the molten metal. The amount of molten metal supplied in this way is dosed according to the shape and weight of the cast body.

Then the piston 28 is pushed up until it Inlet cross section of the feed channel 30 into the annular chamber 24 closes and the metal feed to the annular chamber 24 is interrupted. The piston 28 displaces itself in the annular chamber 24 volume of the molten metal located in the Mold cavity of the lower tool part 10. The piston 28 is located now shown in the left half of the drawing Position.

Then the upper tool part 12 and the central insert 14 moved down into the left half of the Position shown in the drawing. The doughy molten metal compacted and into the free tool cavities displaced, especially in the cavities that the rim well and form the inner rim flange.

As an alternative to lowering the upper tool part together 12 and the central insert 14 can also initially Central insert 14 are driven down so that the tool is closed in the hub area. Then that will upper tool part 12 moved down and displaced and compresses the molten metal in the area of the spokes.

The compression in the hub area is done by lifting the jack 20 from below into the middle hub area, in which the hub bore is inserted later.

The feed channel 30 preferably does not open out in a circular manner Cross section into the annular chamber 24, but widens when Open into the annular chamber 24 delta-shaped in the circumferential direction the annular chamber 24. This distributes the through the feed channel 30 molten metal flowing into the annular chamber 24 more evenly on both sides in the circumferential direction and one laminar flow of the molten metal as it flows into the Annulus 24 is favored.

Instead of a single feed channel 30, several can Feed channels are distributed over the circumference of the annular chamber 24 his.

The piston 28 can be a one-piece closed ring body be trained. It is also possible to use a piston 28 or to divide several radial joints, the thermal Take up extensions of the piston 28 in the circumferential direction.

The piston 28 can also be divided into several (preferably 2) coaxially nested and axially displaceable Ring body may be divided, which pressurized separately and can be moved. The outer ring body is first applied to close the feed channel 30 and interrupt the metal supply. The inner ring body serves to melt the metal from the annular chamber 24 into the To displace mold cavity and especially in the pouring area condense.

It is evident that the annulus 24 is not above hers entire circumference must flow freely into the mold cavity. Essential is that the largest possible inflow cross section exists between the annular chamber 24 and the mold cavity.

It can also be seen that the annular chamber 24 is not necessarily must open on the outer circumference of the mold cavity, but can also open out in a radially central region. Where the annular chamber 24 opens into the mold cavity is expedient set according to the shape of the cast body. The farther the annular chamber 24 is arranged radially outside, the larger the inflow cross section and the more effective the invention Benefits used.

The annular chamber 24 does not have to have a rotationally symmetrical shape, but can also take the form of a polygon, for example to have. In this case, the piston may be individual Piston body divided, which correspond to the individual polygon sides.

The method according to the invention can also be used for non-rotationally symmetrical ones Castings are used.

REFERENCE SIGN LIST

10th

lower tool part

12th

upper tool part

14

Central use

16

Slider

18th

Base plate

20th

Lifting stamp

22

Retaining ring

24th

Ring chamber

26

Fluid pressure channel

28

piston

30th

Feed channel

32

Inflow pipe

Claims (13)

1. A method for filling a casting tool with a metal melt, in which firstly the metal melt is supplied decentrally to an annular chamber, which communicates via at least the greater part of its periphery with the mould cavity of the casting tool, and then the metal melt flows out of this annular chamber into the mould cavity, characterised in that at the end of the filling cycle the supply of the metal melt into the annular chamber is interrupted by at least one piston displaceable in the annular chamber, whereby the piston displaces the metal melt out of the annular chamber into the mould cavity.
2. A device for filling a casting tool with a metal melt, having at least one supply duct (30) for the metal melt, which is disposed decentrally to the mould cavity of the casting tool and opens into an annular chamber(24), wherein the annular chamber (24), open over at least the larger part of its periphery, opens into the mould cavity, characterised in that at least one piston (28) is slidably mounted in the annular chamber (28) in such a manner that in its pushed-in position it closes the at least one supply duct (30).
3. A device according to Claim 2,
   characterised in that the piston (28), when pushed into the annular chamber (24), can displace the metal melt out of the annular chamber (24) into the mould cavity.
4. A device according to Claim 2 or 3,
   characterised in that the annular chamber (24) is disposed at the outer periphery of the mould cavity and is joined by the same shape to the outer contour of the mould cavity.
5. A device according to one of Claims 2 to 4, characterised in that the annular chamber (24), open over its entire periphery, opens into the mould cavity of the tool.
6. A device according to one of Claim 2 to 5, characterised in that the piston (28) is a body closed over the entire periphery of the annular chamber (24), the cross-sectional area of which is congruent with the cross-sectional area of the annular chamber (24).
7. A device according to one of Claims 2 to 6, characterised in that the piston (28) is divided by at least one radial joint.
8. A device according to one of Claims 2 to 7, characterised in that the piston (28) is divided into at least two piston members mounted coaxially in relation to one another and coaxially displaceably towards one another.
9. A device according to one of Claims 1 to 8, characterised in that the at least one supply duct (30), which widens in a delta shape in the peripheral direction of the annular chamber (24), opens into the annular chamber (24).
10. A device according to one of Claims 2 to 9, characterised in that the annular chamber (24) is constructed in the shape of a circular ring.
11. A device according to one of Claims 2 to 9, characterised in that the annular chamber (24) is constructed in the shape of a polygonal ring.
12. A device according to Claim 10 for the manufacture of rotationally symmetrical castings, in particular light alloy wheels for motor vehicles, characterised in that the annular chamber (24) and the piston (28) have the form of straight circular cylinders.
13. A device according to Claim 12 for the manufacture of light alloy wheels for motor vehicles, characterised in that the annular chamber (24) opens into the region of the mould cavity forming the outer rim bead.

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