Metallurgical apparatus – Means for melting or vaporizing metal or treating liquefied... – By means introducing treating material
Patent
1994-09-14
1995-07-25
Kastler, Scott
Metallurgical apparatus
Means for melting or vaporizing metal or treating liquefied...
By means introducing treating material
266233, B22D 4100
Patent
active
054355273
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns an apparatus and a process for the late introduction of particulate alloy (powder or gain) when casting a liquid metal (in general cast iron).
DESCRIPTION OF RELATED ART
The invention is intended in particular for the discontinuous casting of shaped parts in series of medium and great length in moulds obtained by automatic machines.
It is known that it is advantageous to effect the late introduction of agents for the treatment of cast iron (nodulising and/or inoculating agents) to obtain a quality which is as reproducible as possible of cast parts of cast iron and a good yield on the part of the treatment agents used, in particular when the agent contains magnesium which is volatile and difficult to dissolve in the liquid cast iron.
The late introduction operation can be carried out in a casting ladle just prior to the casting operation, but that results in an inadequate yield and insufficient regularity in terms of quality of the cast parts.
It is also possible to use the "in mould" procedure which involves providing at the entrance of the casting mould a recess in which the treatment agent will be disposed in such a way that it is regularly dissolved by the cast iron in a molten condition as it passes into the mould. That procedure is effective but it is also long and difficult to carry into effect, and in particular the configuration of the geometry of the cast iron feed passages has to be carefully designed in order to avoid the possible entrainment of endogenous or exogenous inclusions within the cast part.
That procedure is preferably reserved for long runs which make it possible to amortize the cost of development of the mould.
The document FR 2 588 571 also discloses an apparatus in which the treatment agent is introduced by means of a gas under low pressure into a closed treatment chamber which is also under low pressure and in which liquid metal to be treated and cast is disposed. Such a pressurised arrangement permits good dissolution of the agents, in particular Mg, and the production of cast parts of high quality, but it raises problems in terms of operation (fouling, blockage of the vents or risers, untimely accumulation of undissolved agent etc . . . ) when there is a wish to carry out discontinuous casting operations in series.
A similar apparatus is known from the documents EP 30 220 or BE 639 410. The treatment agent is added by means of a carrier gas to the surface of the liquid cast iron which is set in motion in the form of a vortex within a chamber. In EP 30 220 it is preferable for said chamber to be closed by a sealing cover in order to improve the efficiency of use of the agent when it is volatile (for example if it contains magnesium). This apparatus which is used for discontinuous casting operations in series with a frequent interruption in the jet of metal between two casting operations suffers from the same type of disadvantages as discussed above and requires the presence of a chamber which is sealed under pressure to facilitate the introduction of the volatile agent and to improve its effectiveness and the quality of homogeneity of the casting operations.
It is known also that, to introduce a treatment agent into liquid cast iron, it is possible to use immersed lances in which the agent is propelled by a carrier gas, but that makes it necessary always to have a substantial minimum amount of liquid metal (residue) and in addition the carrier gas is a considerable source of cooling and therefore solidification of the liquid metal.
SUMMARY OF THE INVENTION
Confronted with those problems the applicants sought to provide an apparatus which is simple to use and easy to adapt in particular to discontinuous casting of small runs of parts with the late introduction of treatment agents, in particular those comprising volatile elements such as Mg and/or which are little soluble in liquid metal.
The applicants also sought to provide a process which improves the levels of efficiency of use of the treatment agent added and the degree of
REFERENCES:
patent: 4053146 (1977-10-01), Smartt et al.
patent: 4997167 (1991-03-01), Harma
patent: 5129629 (1992-07-01), Christensen
Japanese Patent Abstract No. 55-75856, Appl. No. 53-148540 Patent Abstracts of Japan, vol. 4, No. 116, Aug. 19, 1980.
Japanese Patent Abstract No. 55-75855, Appl. No. 53-148539 Patent Abstracts of Japan, vol. 4, No. 116, Aug. 19, 1980.
Kastler Scott
Pechiney Electrometallurgie
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