Process for manufacturing diecast parts

Details Process for manufacturing diecast parts Process for manufacturing diecast parts

1996-11-18

2000-02-15

Reed Batten, Jr., J.

Metal founding

Process

Shaping liquid metal against a forming surface

106 3822, 106 3827, 164 65, 164 72, 164113, 164138, B22C 300, B22D 1714, B22D 1720

Patent

active

060241586

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a method for the production of diecastings from a light metal alloy. Diecasting methods for the production of light metal parts for all kinds of further use in industry, e.g. in the automotive industry or in the production of appliances, have been further developed in recent years, particularly with a view to producing large numbers of items at an economic price. One of such methods is referred to as squeezecasting which involves a subsequent compression in the actual mould, or the socalled MFT process developed by the applicant of the present invention and disclosed in DE-OS 23 23 426 and DE-PS 30 02 886, which has considerably contributed to accelerating the evacuation of the mould chamber. As a result, injection operations (commonly referred to as shots) can be performed faster, thus increasing the output figures.
Moreover, the production method has been improved with regard to parting compounds and lubricants for the mould interiors and also for the plunger, thus likewise increasing productivity.


BACKGROUND OF THE INVENTION

U.S. Pat. No. 5,076,344 for example discloses a process in which a molten standard aluminum alloy is fed to a casting or fill chamber through a suction tube. From there, the molten aluminum alloy is then charged into the casting chamber and into the evacuated chamber of a mould, by means of a piston. Inside said mould chamber, the concentration of the parting compound, an alkali halide, is 0.5 to 3% by weight, whereas in the casting chamber the concentration of this parting compound which simultaneously acts as a lubricant here, is between 2 to 7% by weight. The parting compound preferred in this process is an aqueous solution of potassium iodide. The parting compound which is applied to the mould and the plunger prevents the aluminum alloy from sticking to the walls of the mould chamber or the plunger piston, resp. and the casting chamber. The parting compound thus contributes to a continuous and smooth flow of the process.
The disadvantage involved in the use of alkali halides, particularly potassium iodide, is that this salt will corrode the steel-containing parts of the apparatus performing said process. Moreover, the feed process, which is effected via a suction tube, is awkward. Another problem associated with this prior art process is that the quality of the diecastings is impaired by gas inclusions as well as other impurities. The corrosion of the steel can lead to impurities in the metal alloy since corroded bits and particles may come off the steel surface.
Furthermore, the known processes are often complex, thus requiring a machine of likewise complex construction which in turn results in high maintenance costs--all of which makes these processes uneconomic.
Meanwhile, the industries further processing such light metal parts have come to expect additionally improved material properties such as higher strength, lower weights, thin walls, complex geometries, capability of being further processed such as weldability, heat treatability or the possibility of using modern connection technologies when assembling or installing and disassembling or removing such parts.


DISCLOSURE OF THE INVENTION

It is therefore the object of the present invention to provide a process which fulfills the abovementioned requirements. This object is accomplished according to the invention by a combination of the following features:
Primary alloys are used. These are of an invariable composition, with a limit placed on the proportions of copper, iron and zinc. Starting materials for such primary alloys are e.g. AlSi7Mg0.3 having a eutecticum content of approx. 35% and exhibiting high ductility and high fatigue strength, as well as eutectic or almost eutectic Al--Si alloys, various Al--Mg alloys and high-purity Mg alloys.
Before these alloys are introduced, they are subjected to a smelting treatment such as de-gassing and/or filtration.
The vacuum produced in the mould chamber is below 50 mbar when the molten alloy is introduced.
The parting compo

REFERENCES:
patent: 2045913 (1936-06-01), Hoy et al.
patent: 3008202 (1961-11-01), Bauer
patent: 4463793 (1984-08-01), Thurner
patent: 5076339 (1991-12-01), Smith
patent: 5076344 (1991-12-01), Fields et al.
Patent Abstracts of Japan, vol. 8, No. 249 (M-338) [1686], Nov. 15, 1994, & JP,A,59-125255, Fusou Keigoukin, Jul. 19, 1984.
Database WPI, Derwent Publications Ltd., London, G.B. AN 94-061685 XP002004092 & JP,A,06-015 406, Hitachi Funmatsu, Jan. 25, 1994.

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