Metal founding – Process – Shaping a forming surface
Patent
1982-02-17
1984-06-12
Hampilos, Gus T.
Metal founding
Process
Shaping a forming surface
164 6, 164 15, 164526, 106 382, B22C 902
Patent
active
044535864
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of producing frozen casting moulds or cores of a granular material and a binder in a mould chamber or a core box, comprising the use of a freezable binder which is in a gas or liquid state at positive temperatures calculated in .degree. C.
The specification of the U.S. Pat. No. 4,150,704 teaches a method in which the mould sand is admixed with a controlled quantity of water which after moulding is frozen to ice in a certain depth from the surface that is caused to contact molten metal e.g. by placing a layer of so-called dry ice or spraying liquid nitrogen on the surface. This gives a very strong mould surface which retains its strength and shape until the surface of the metal has solidified. As the metal gives off its heat, the water melts and evaporates so that the mould begins collapsing without the use of mechanical means. Practically no smoke is developed in the casting process, and the mould sand can be reused right away.
An article in the Russian magazine Liteinoe Proizvodsto, 1975, no. 5, p. 21-22, describes the freezing of a sand mould containing 3 to 7% water by means of a coolant that circulates through the evaporator in a cooling system and through the mould.
Freezing of the added water is by nature a rather slow process, and consequently it takes a relatively long time from the moment when the moulding process is finished until the mould has frozen deep enough to be able to resist the effect of molten metal for a sufficiently long time, and this in turn causes the overall mould production to become considerably more time-consuming than the conventional mould manufacturing processes.
The object of the invention is to overcome this drawback of the known embodiments of the present method, and this object is achieved in that the binder has been frozen before the moulding process or is rapidly brought down below its freezing point during said process in that at least one of the tools and/or materials that the binder, which itself may have been precooled, is caused to contact in the moulding process, has been cooled in advance. In this embodiment part or the entire necessary cooling may have been effected in advance, i.e. before the moulding process, so that the molten metal may be poured into the mould immediately after the termination of the moulding process. This provides for such a great production rate that the method may be used in connection with fast working automatic machines for the production of casting moulds with or without cores, e.g. of the type disclosed in the applicants' Danish patent specification No. 87 462 to obtain the high operation rate of this machine.
When the binder has been frozen before the moulding process, it may be expedient that additionally at least one of the tools and/or materials which the binder is caused to contact in the moulding process or in the mould and which may contain a binder previously used, has been cooled below the freezing point of the binder or to a temperature slightly above said freezing point.
Furthermore, the mould binder may have been cooled before the mould manufacturing process so that it is present in the form of fine, dendritic particles, e.g. snow, in the mould material, and a compression during the moulding process may entail that the binder obtains part of or its entire binding capacity depending upon the temperature conditions at the time of the mould manufacturing process.
The mould binder used may also have been cooled before the mould manufacturing process so that it is present in the form of a finely divided powdered material, e.g., ice in the mould material, and a compression during the moulding process may entail that the binder obtains part of or its entire binding capacity depending upon the temperature conditions at the time of the mould manufacturing process.
When a suitable mixture of granular material and snow or broken ice is compressed in a mould box, the snow or the ice may thus be caused to bind the grains of the material together to impart a cohesive force to the mould or the core suf
REFERENCES:
patent: 4150704 (1979-04-01), Hoult
patent: 4243093 (1981-01-01), Nieman
Derwent's Abstract No. 74607c/42, SU718 215 Published 1980, Feb. 28, Gruzman, V. M.
Patent Abstracts of Japan, Abstract of JP 55-1905 Published Jan. 9, 1980, Jiyunsaka Nakashima.
Jespersen Emil
Singh Bakshi B.
Dansk Industri Syndikat A/S
Hampilos Gus T.
Seidel Richard K.
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