EP1448331B1 - Method for producing die-cast parts and a die casting device - Google Patents

Abstract

The invention relates to a method for producing die-cast parts, in particular wheel rims or wheels for vehicles, in addition to a diecasting device therefor. To produce high quality wheel rims or wheels, the starting materials are heated in stages in a casting cell and are transferred in a semi-solid form to a die casting machine, where they are formed into die-cast parts.

Description

The invention relates to a method and a device for the production of die-cast parts, in particular of parts of aluminum or magnesium materials. The invention particularly relates the production of rims or wheels for the vehicle industry.

Rims or wheels for vehicles, especially motor vehicles, are today after the low-pressure casting process made of aluminum materials. It acts These are usually simply controlled low-pressure casting machines with high manual Working interest. Every machine requires an operator who can handle both the high temperatures the molten metal and the exhaust gases of the casting process is exposed. The demolding of the cast parts is expensive.

Many hand operations affect part quality and casting cycle time a bike is 7 to 12 minutes. Design changes condition the manufacture new forms.

The manufacturer (Niederdruckgiesser) buys the required aluminum alloy in bar form and melts them in melting furnaces next to the low-pressure casting machine, i.e. The quality can also vary from machine to machine.

A procedure. for the casting of motor vehicle wheels, aluminum, magnesium or Like. Light metals in low-pressure casting, consisting essentially of a crucible for keeping the melt hot, a mold arranged above the crucible as well as an emanating from the mold, the lid of the crucible protruding and protruding into the melt riser, which by pouring The metal consumed in the molded part is charged into the casting machine according to DE-C-3619525. It is characterized in that before each casting a metal block (Ingot) of a casting weight substantially corresponding mass in the gas space introduced above the bath level of the casting machine and before or after the Pulling or ejecting the casting introduced into the bath of the casting machine becomes.

It is well known, parts of aluminum or magnesium materials by Die casting from the melt or semi-solid, cut bolts (SSM method or thixomolding). So far, however, it has not been possible to develop economically alternative methods for such heavily loaded parts.

Thus, DE-C-195 38 243 discloses a method for producing a semi-molten one Thixogiess casting material in the thixogistic material, comprising an outer layer portion with dendrites around an outer periphery of a Main body section around, is subjected to a heat treatment to a semi-molten casting material with coexistent solid and liquid phases to create. Here are the dendrites, resp. Dendrite fragments by elevation the temperature of the outer layer portion with respect to the main body portion in transformed spherical solid phases, and the outer layer portion in a semi-molten State brought. By using skin effects is too fast Heating the main body can be prevented. Such a step-by-step process to heat up is expensive and requires several Induktionsheizschritte with different Frequencies (services).

In US-PS 5 638 889 a casting method with a casting device is disclosed. The Warming the billets takes place in a heating device of the casting immediately in front of the mold. The heating of the billets is multi-level with in accordance with accordingly high cycle times.

EP-A-710 515 describes a thixocasting process of wheels with a rheocast alloy and a device for this, in which a robot is used.

The invention is therefore based on the object, a process for the preparation of To develop die cast parts, in particular of wheels or rims for vehicles, with which the disadvantages of the prior art can be overcome. In particular, should produce high quality wheels and the like with reduced effort become. The environmental impact should be significantly reduced, in conjunction with improved working conditions.

The solution of the problem is solved with the features of claim 1. Advantageous Embodiments are disclosed in the subclaims.

In a previously known as such Druckgiesseinrichtung with supply and heating devices for the casting material, a die casting machine, handling equipment and control devices are integrated heaters, which are also a gradual Heating bolts of aluminum materials outside the die casting machine allow (possibly also of magnesium materials), which then without appreciable Contact the ambient air into the die casting machine.

After die casting or pressure forming, the castings undergo further training of the process in a special process cooled and outsourced and indeed much faster than usual. Characteristic of heating up is that with high, constant energy input is started and the energy input then after reaching of the thixotropic microstructure in the metal area is reduced.

Significant advantages of the method according to the invention are that it is fully automated executable, the handling of liquid metal is eliminated, including the appropriate smelting furnaces and potential hazards. Exhaust gases, etc. arrive not in direct contact with operators and the environment. The cycle time per wheel decreases to about 1 minute.

Another object of the invention is to provide a casting device according to claim 4 for carrying out the method. The casting equipment is considered automated Casting cell formed and has variable shapes and inserts of the forms, wherein ejector elements are provided which are at the same time functional elements.

Fig. 1:

eine Giesszelle

Fig. 2:

einen festen Formrahmen in perspektivischer Darstellung

Fig. 3:

einen Formenrahmen im Teilschnitt

The invention will be described below in an embodiment with reference to a drawing. In the drawing shows the

Fig. 1:

a casting cell

Fig. 2:

a solid form frame in perspective view

3:

a mold frame in partial section

The casting cell includes a die casting machine 1 with a mold, a converter for the heating system 2, a monitor 3, a removal robot 5 for parts removal with a control unit 5, a loading robot 6 for Slugzuführung with control unit. 7 and a spray robot 8 with control unit 9. Also provided are facilities mold temperature control 10, cooling stations 11 and 13, electrical, e.g. inductive heating units 12 for heating Slugs (bolts), a device for parts inspection ago a conveyor belt 16 for the discharge of non-quality parts and another Conveyor 15 for discharging the good parts. Provided are still a metal supply (Sluglager 17), an automatic cleaning station 18 and a manual cleaning station 20 for Giessteile, a balance 19 and a repair area 21st

The die casting machine 1 are fed directly to slugs or bolts or portions previously were heated in the heating units 12. You can directly and under exclusion of air in the Giesskammer the die casting machine 1 are transferred. When using magnesium materials (but also useful for aluminum materials), the heated slugs in closed Containers supplied by robot 6 of the casting chamber of the die casting machine 1. The Containers are closed with a lid so that the slugs are already heated in these be and upon reaching the desired temperature from the heating unit 12 to the casting chamber without Protective gas can be supplied. The container is provided with a lid which can be lifted off can be or is hinged to the container. For the eventual provision of molten portions, the lid or the bottom of the container can also with a additional and closable opening for a pressure or vacuum emptying provided be. The container may be rather flat or tall and narrow. A complete Adaptation of the container to the shape of the material portion is not required, although a As low as possible air volume in the closed container is advantageous. In particular, should only a small air gap between the lid and the material surface (portion) be given. A achievable by shaping and weight of the lid tightness is usually sufficient. In semi-solid materials, the emptying of the container is simply over the edge of the container. Alternatively, the supply of the bolts also directly from a heated staging space / supply channel out, which may also be directly connected to the casting chamber can, if necessary, during the transfer, the temperature can be increased even more can. In the case of aluminum materials, e.g. preferably an alloy no. A357 (Al-Si7Mg0.6) used to quench and outsource the cast parts with less Time required (T5 treatment). The heating before casting takes place gradually. This can be divided into three areas. A high-power warming at the beginning, a "cooking" after reaching the thixotropic structure in the mantle area of the bolt and in a Homogenization for final setting of globulithic structure in the starting material.

Here, an Al bolt of 5 to 6 "diameter initially with a constant high energy heated to about 550 to 570 ° C, with the difference in temperature to the Innem of the bolt up c. 20 ° C is. Subsequently, the energy input is drastically reduced in a very short time, held for a very short time ("cooking") and then increased again and held again until a temperature of about 585 ° C is reached and the temperature difference to about 2 to 3 degrees has sunk. For bolts up to 4 "diameter, the procedure can be simplified so far be that step of lowering the energy input slower and for a longer time can be done evenly.

The individual bolts can also be "packaged" in foil before heating, preferably in an aluminum foil to avoid oxide formation, etc. Likewise Shielding gas can be used to prevent the oxide formation.

The starting material of the slugs is a homogeneously distributed, fine-grained material Consider, which by the heating process a uniformly distributed, globular microstructure with Komfeinheiten about 50-100 microns forms. The latter is for e.g. qualitatively high-quality wheels or rims, which are produced according to an SSM procedure should, required.

It is no longer liquid material to handle. All exhaust gases are sucked off and the spray form optimized so far that no residual spray is disposed of got to. Flue gas generation is almost impossible.

The molds and casting tools have a modular structure, so cost-effective per type of wheel and simply exchangeable mold packages are given. A quick change for the respective shaping part of the forms is possible.

The mold in the die casting machine 1 is e.g. two-part or three-part and variable use. Since the rim bed per wheel dimension remains unchanged, only two have Mold plates can be adapted to different front design. These can still Inserts that consist of a cheap and less high-strength material. Thus, the life of such inserts can be adapted to the required number of shots and only the basic form must be made of high-strength material.

Furthermore, the mold plates can contain slide inserts, which in defined areas adjustable heights and widths in front design (depending on tire and rim dimensions) allow, so not for each dimension an extra shape is needed.

Special scrapers allow easy demolding even in complicated shapes or undercuts. These scrapers are arranged so that after a Formöffnungshub is moved by a Ausstosshub up, with contour parts / slide also be moved transversely to the Entformungsrichtung and released from the casting can.

According to a further embodiment, the mold for the manufacture of a vehicle wheel of eg aluminum materials on a solid mold frame 30 with a mold centering 31 and moldings or slide 32 and cooling coils. The fixed mold frame 30 is connected in a conventional manner with the casting chamber 34. He also has part-specific core elements for holes in the hub 36 of the wheel 35, which can serve as ejector elements of the wheel 35 at the same time. Thus, no additional ejectors are needed, but functional parts are used which are already required for other tasks (here as a core element). The filling of the casting mold takes place from the hub 36 of the wheel 35 and between the hub surface and the gate 37 of the casting chamber 34 there is arranged as insert a filter 38 supported on the hub 36, which serves primarily to seal the oxide skins of the SSM to be pressed. Bolzens withhold, resp. rip open and crush. The screen 38 is a stamped part made of aluminum or steel and perforated according to the hub surface. The bolts, not shown, are heated and supplied O ₂ -arm. The filling in the mold cavity is weitgehenst dry, ie without lubricant. Due to the sieve can be dispensed with a shearing knife for the oxide skin of the bolt.

Casting chamber 34 and casting piston of the die casting machine 1 are preferably made a ceramic material to avoid the use of lubricants and sprays to be able to.

Compared to the previous casting direction of the visible surface of the wheel 35 ago significantly lower material returns and the hub itself becomes a press residue. The remains of the screen 38 are doing with the machining of the Removed hub surface (the sieve 38 is made of steel, so can the aluminum-steel shavings e.g. used in steelmaking). The visible surface of the wheel 35 is already poured close to the final contour.

The moldings or slide 32 are with, not shown, drives and guides provided to ensure a retraction and extension of the moldings or slide 32.

Almost perpendicular to the support plane of the fixed mold frame 30 are surfaces for locking the slider 32 is provided. Furthermore, surfaces for locking the Slider 32 is provided, which is parallel to the said support plane on the slider 32 or the mold parts are arranged. Also almost perpendicular to the above Support level are other surfaces for combined counter locking and mold centering intended.

Corresponding counter-contours are formed in the movable mold frame 33.

The surfaces for locking the slider 32 are preferably located on the or in the fixed mold frame 30 and more preferably in a line. The surfaces to Form centering are independent of the number of moldings or slide 32 formumlaufend.

The forces acting during casting thus be in the fixed mold frame 30 on the Areas for combined centering and counter locking on the right and left of Slider 32 distributed - force and force transfer are thus approximately on a line and are easier to control.

The molds or sliders 32 are suitable for the common range of wheel sizes (e.g. from 13 "to 22") and can be arranged in a single set of mold frames 30, 33 become.

reference numeral

1

die casting machine

2

inverter

3

monitor

4

removal robot

5

control unit

6

loading robot

7

control unit

8th

spray robot

9

control unit

10

mold tempering

11

cooling station

12

heating unit

13

cooling station

14

parts control

15

conveyor belt

16

conveyor belt

17

Sluglager

18

cleaning station

19

Libra

20

cleaning station

21

repair area

30

solid shape frame

31

guide

32

pusher

33

movable mold frame

34

casting chamber

35

wheel

36

hub

37

bleed

38

scree

Claims (8)

1. A method for manufacturing diecast parts, in particular wheels or rims for motor vehicles, via casting, wherein the parent materials are supplied and heated in the form of billets or slugs, wherein the heated parent materials exhibit a globulithic microstructure, are supplied in a semi-solid form to a diecasting machine (1), and cast or molded with the application of high pressures, characterized in that the heated parent materials are supplied to the diecasting machine (1) largely under hermetic seal, and the cycle time measures approx. 1 minute.
2. The method according to claim 1, characterized in that the parent materials are heated in stages.
3. The method according to claim 1 or 2, characterized in that the diecast parts are subsequently cooled to at least 180°C, and the cast parts can be aged for a shorter time (T5).
4. A casting device for manufacturing diecast parts, in particular rims or wheels for motor vehicles with a casting device containing a diecasting machine (1), heating devices (12) for heating the parent materials, and handling devices, in particular robots (4, 6, 7) for handling the parent materials and diecast parts, characterized in that the casting device is designed as an automated casting cell having variable molds and mold inserts, wherein ejection elements are provided that simultaneously are functional elements during the casting process.
5. The casting device according to claim 4, characterized in that the material of an insert is adjusted to the required number of shots.
6. The casting device according to claim 4, characterized in that the mold comprises a fixed and movable mold frame (30, 33), incorporating modular molded parts or sliders (32) arranged on guides.
7. The casting device according to claim 4 or 6, characterized in that the molded parts or sliders (32) can be arranged in the mold frame (30, 33) for specific part sizes.
8. The casting device according to at least one of claims 4 to 7, characterized in that the casting chamber and piston of the diecasting machine (1) consist of a ceramic material.

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