Specialized metallurgical processes – compositions for use therei – Compositions – Loose particulate mixture containing metal particles
Patent
1988-03-09
1989-11-14
McDowell, Robert
Specialized metallurgical processes, compositions for use therei
Compositions
Loose particulate mixture containing metal particles
75 68R, 75256, 420528, 420590, C22C 105
Patent
active
048804622
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention is concerned with a rapidly dissolving additive for molten metal, a process for the preparation of said additive and its use for the introduction of alloying elements into metals.
In the production of metal alloys, in practice the alloying elements are usually added in solid form to a molten metal bath. Thus, for example, aluminium is alloyed with magnesium in order to achieve improved strengths, with silicon in order to improve the castability and the strength and with manganese and chromium in order to increase the strength and corrosion resistance. Furthermore, a whole series of further alloying elements are known for the purpose of influencing alloying properties. Under current general practice alloying elements, in particular the alloying metal, which has a higher melting point in comparison with the base metal, is added in the form of a pre-alloy in order to achieve a rapid dissolving. The disadvantage of this pre-alloying is the limited content of alloying metal. Thus, for example the standard prealloys for aluminium alloying contain, besides aluminium, only a maximum of 20% of silicon, up to 20% of chromium or up to 50% of manganese. Thus, up to 4 times the amount of aluminium must be added to the alloying element; this results in higher transport costs, storage costs, energy consumption and the like. In order at least partly to avoid these disadvantages, it is known from U.S. Pat. No. 3,592,637 to use mixtures of aluminium or silicon powder with powders of alloying metals or alloying metal alloys in briquet form. Thus, for example, alloying briquets with 25% aluminium and 75% of the metals chromium, manganese and iron are commercially available. The disadvantages of such alloying agent are the proportion of alloying element being limited to 75% and the low speed of dissolving. British Patent Specification No. 2,112,020 also describes similar mixtures in which a part of the aluminium is replaced by chloride or fluoride salts. Commercially available tablets containing chromium, manganese and iron also have only a limited speed of dissolving.
Therefore, it is an object of the present invention to provide an additive for metal melts which does not display the mentioned disadvantages of the prior art but which, also in the case of higher concentrations of alloying metal, makes possible a complete and rapid dissolving in a molten base metal.
SUMMARY OF THE INVENTION
Thus, according to the present invention, there is provided a rapidly dissolving additive for molten metal which contains 2 to 50% by weight of a component A, consisting of an alkali metal aluminium fluoride and/or of an alkali metal aluminium fluoridecontaining salt mixture, and 50 to 98% by weight of a component B, which consists of at least one alloying metal, this alloying metal being different from the base metal to be alloyed, the components A and B being present intimately mixed.
DETAILED DISCLOSURE
We have, surprisingly, found that the additives according to the present invention, even in the case of higher contents of alloying metal than correspond to the prior art, possess an unexpectedly high speed of dissolving with simultaneous complete utilisation of the alloying metal.
The rapidly dissolving additive for molten metals according to the present invention consists of 2 to 50% by weight of component A and 50 to 98% by weight of component B.
As component A, there can be used an alkali metal aluminium fluoride and/or an alkali metal aluminium fluoride-containing salt mixture provided that, in the case of the use of the additive according to the present invention, unacceptable amounts of impurities are not introduced into the base metal. Furthermore, the melting point of the salt or of the salt mixture should not lie above that of the base metal. Instead of an alkali metal aluminium fluoride, there can also preferably be used a mixture of an alkali metal fluoride and aluminium fluoride. As preferred alkali metal aluminium fluoride-containing salt mixtures, there are to be under
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patent: 3941588 (1976-03-01), Dremann
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McDowell Robert
SKW Trostberg Aktiengesellschaft
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