Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1998-06-15
2000-08-22
Lin, Kuang Y.
Metal founding
Process
Shaping liquid metal against a forming surface
164133, B22D 1712
Patent
active
061056588
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process and a device for filling a casting mould with a molten metal.
The pouring of castings, whose diameter exceeds their axial length, e.g. dynamically-balanced castings such as light-alloy castings for vehicles, requires in most cases the use of a central downsprue, through which the molten metal flows into the centre of the shaped cavity of the casting mould. In addition, lateral and multiple in-gates are employed. Common to all of these processes is that the molten metal is delivered through a feed channel of relatively small diameter, approx. 30 mm to 50 mm. In order for the molten metal to be able to flow reliably from this downsprue to all areas of the shaped cavity of the casting mould before hardening, the molten fluid metal must be kept at a high temperature. This results in high build-up of heat in the feed region, the result of which in turn being a partial overheating of the casting mould in the downsprue region. Such overheating causes the downsprue linings to wear significantly, which reduces the service life of the casting mould. The high temperature of the molten metal, moreover, lengthens the cooling cycle, the result of which as a rule being the employment of expensive additional cooling procedures.
The object of the invention is to improve the filling of a casting mould with a molten metal so as to both reduce cycle times and improve casting quality.
Japanese reference JP 54 115 628 A discloses that molten metal is first fed decentrally into an annular chamber. The annular chamber is connected along its circumference to the shaped cavity of the casting mould in such a way that the molten metal flowing from the annular chamber into the shaped cavity can be evenly distributed along the circumference. This arrangement is supposed to reduce turbulent flow in the molten metal, which in turn reduces gas pocket development in the finished product. There remains the problem, however, that the molten metal flows relatively slowly into the shaped cavity, so that the molten, fluid metal must be maintained at a high temperature, which entails the aforementioned disadvantages.
It is proposed that this object can be achieved through the process and apparatus of the present invention.
SUMMARY OF THE INVENTION
The idea underlying the invention comprises that the molten metal be forced out of the annular chamber into the shaped cavity by means of a piston, that is housed inside the annular chamber so as to be able to slide. This arrangement ensures that further inflow of molten metal will be prevented at the end of the filling cycle. The molten metal is pushed by means of the piston, ahead of the latter and forced out of the annular chamber into the shaped cavity.
This arrangement allows molten metal delivery without turbulence, which reduces bubble development and so improves the quality of the casting. In addition, the annular, decentralized inflow of molten metal provides for the distribution of heat via the molten metal over the entire circumference of the annular chamber. The more even distribution of heat prevents localized overheating, which can lead to particularly strong wear on the casting mould. In addition, the faster inflow of molten metal, together with shorter flow distances for the molten metal inside the shaped cavity enable reduction of the temperature of the delivered molten metal. This permits a further reduction of wear as well as energy savings. Finally, the molten metal is permitted to harden more quickly, which, on the one hand, permits additional shortening of the overall cycle time as well as a reduction in dendritic growth, the result of which is improved mechanical characteristics following from shorter dendritic propagation.
The annular chamber is provided with at least one piston, which can be pressed into the volume contained inside the annular chamber. In this arrangement, this piston closes off the feed channel for the molten metal and pushes the molten metal remaining inside the annular chamber into the shaped
REFERENCES:
patent: 5263531 (1993-11-01), Drury et al.
patent: 5320160 (1994-06-01), Kato et al.
patent: 5527101 (1996-06-01), Kato et al.
patent: 5810068 (1998-09-01), Kato
patent: 5913353 (1999-06-01), Riley et al.
Giesserei Lexikon, Published by Ernst Brunhuber, 1983, Fachverlag Schiele & Schon GmbH, Berlin pp. 4-41. Basis: General Background on Casting Techniques.
BBS Kraftfahrzeugtechnik AG
Lin Kuang Y.
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