Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1995-03-16
1997-05-06
Hail, III, Joseph J.
Metal founding
Process
Shaping liquid metal against a forming surface
164336, 164120, B22D 2300
Patent
active
056261802
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process of and device for casting components, with liquid metal being introduced into a cavity of a mould where it is consolidated. For forming components, starting from the liquid material condition, there is known a large number of different processes and devices which more or less meet the requirements to be complied with by high-quality workpiece in respect of shaping freedom, surface quality and especially optimum material properties. The main difficulties initially concern the operation of filling the mould wherein the initially compact melt volume is divided, with a large surface thereof being exposed to air atmosphere, which, due to certain reactions, leads to the material quality being adversely affected. Molten metal alloys whose alloying constituents react very strongly to oxygen, nitrogen and the water vapour of air are particularly affected. In consequence, the tilting casting method according to Durville for example was applied to sensitive alloys at an early stage.
DE-PS 377 683 proposes a process wherein numerous casings are produced one after the other from an oblong casting container. In the course of the casting operation, the melt container is erected, as a result of which a somewhat higher metallostatic pressure can be achieved. However, with this method, the atmosphere has free access to the melt, so that especially as the container empties, oxide can easily reach the mould cavity from the bath surface. During the solidification of the castings there remains a direct connection with the large melt volume in the casting container, so that the solidification process is slowed down.
DE-PS 505 224 describes a process wherein two moulds alternately filled with melt are mounted on a casting container arranged similarly to a swing. Again, the air has free access to the melt bath with its large surface, so that it is particularly easy for the existing impurities to enter the mould.
DE-PS 21 64 755 describes a high-performance casting process for large series wherein, admittedly, the disadvantages of the above proposals were largely eliminated, but it requires sophisticated, expensive equipment, and even if one single mould fails, the remaining parts are affected as well.
As a rule, during the solidification process, volume contractions and gas segregations cause the component structure to form shrinkholes and pores which have to be eliminated at great expense. The shrinking processes also, locally, lead to the formation of gaps between the surfaces of the casting wall and mould wall, which gaps greatly affect the heat transfer, which also has negative effects on the quality of the structure and leads to sink marks, thus rendering the component useless.
SUMMARY OF THE INVENTION
It is the object of the invention to use new types of processes and casting facilities to create the advantageous conditions required for producing high-quality components, both during the mould filling operation and also during solidification of the castings, and at the same time to permit particularly rational production and eliminate the disadvantages of the above-mentioned processes and devices. The purpose is to avoid turbulence and melt division during the mould filling operation. Furthermore, it is the object of the invention to prevent any reactions of the alloy melt with the gases of the atmosphere and of the mould cavity. Finally, the intention is, preferably, to achieve sharp contours during the filling process and to ensure an optimum fine-grained and dense component structure during the solidification process.
To achieve the objective there are proposed processes and a suitable device having the characteristics of the independent claims, with a sealable container for the melt being connected by a large ingate cross-section to the cavity of the mould which, initially, is positioned above the container.
The ingate constitutes the direct connection between the casting container and the mould cavity and shall be dimensioned in such a way as to avoid the
REFERENCES:
patent: 2233405 (1941-03-01), Fahlman
patent: 3333625 (1967-08-01), Fromson
patent: 3635791 (1972-01-01), Bly et al.
patent: 3863704 (1975-02-01), Kahn
patent: 4733714 (1988-03-01), Smith
patent: 5163500 (1992-11-01), Seaton et al.
Kahn Friedhelm
Kahn Joachim
Hail III Joseph J.
Herrick Randolph
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