US2500912A - Method of making alloys - Google Patents

Description

Patented Mar. 14, 1950 METHOD OF MAKING ALLOYS John J. McLaughlin, Chicago, Ill., assignor to Crimora Research and Development Corporation, Crimora, Va, a corporation of Virginia No Drawing. Application December 20, 1944, Serial No. 569,097

1 Claim.

This invention relates to a method of making alloys, and has particular reference to the introduction of manganese into magnesium or magnesium alloys having a relatively low melting point.

One aim of the invention is to reduce the time required to perform the alloying operation.

Another aim is to substantially reduce the amount of external heat that is required to fuse the metals and produce a homogeneous alloy.

Still another aim is to employ heat resulting from an exothermic reaction, for melting the manganese used in making the desired alloy.

A further aim is to form the manganese into a mass or briquette with material, capable of causing an exothermic reaction, for producing suflicient heat to melt the manganese, to the end that it will fuse and be mixed thoroughly with the other components of the desired alloy.

Other aims and objects of the invention will appear in the following description.

The method applies principally to the production of alloys containing high percentages of magnesium, which have many desirable properties and useful purposes. In accordance with the invention, such an alloy can be formed by first melting a batch of magnesium or magnesium alloy and then adding manganese, in the form of briquettes, which also contain materials capable of producing an exothermic reaction that is started when the briquettes are immersed in and subjected to the temperature of the molten magnes um.

The briquettes are preferably formed by mixing finely divided or powdered manganese, such as is obtained by the electrolytic recovery process, with a powdered oxide of manganese, such as MnOz, and powdered magnesium. Other oxides of manganese, such as MnO, and MnzOs and M11304 can be used. Also, aluminum in powdered form can be used as a substitute for or in combination with magnesium. The oxide of manganese and the magnesium or aluminum are used to efiect the exothermic reaction, the amounts depending upon the rate at which it is desired that the reaction shall take place and other factors, such as the desired, final temperature of the fused batch.

When manganese dioxide and magnesium are used, the magnesium content should be more than half of the oxide content, so that no man- I ganous oxide (MnO) will be formed and cause a corresponding loss of manganese. If aluminum is used instead of magnesium and it is desired that no appreciable amount be added to the melt, the aluminum should be stoichiometrically equivalent to the MnOz or other oxidizing agent used. In either case, the amount of oxidizing agent employed should be suificient to provide available oxygen of from 1% to 5% of the weight of the briquettes, employin either aluminum or magnesium, or both.

The constitutents of the briquettes should be thoroughly mixed and then pressed sufficiently to provide a density sufiicient to make them sink readily in the molten bath of magnesium. For example, a pressure of the order of 10.000 pounds per square inch should be used to compress manganese briquettes. The MnOz should be as free from silica as possible, since the presence of silicon is detrimental to the efiicient alloying of manganese with magnesium. If desired, a pure manganese dioxide can be used. It can be prepared from electrolytic manganese by dissolving nitric acid and decomposing the nitrate to produce a gray, hard dense manganese dioxide.

When briquettes are prepared in which about 5% to nearly 10% of the total manganese present is in the form of MnOz, the balance existing in the form of manganese metal, and such briquettes are introduced into a melted mass comprisin principally magnesium, a metal efiiciency of 90% or better may be obtained. Total percentages of manganese of the order of about 0.5% may be readily introduced into magnesium in this manner; but greatly increased amounts, up to 5% may be added easily, if desired. The briquettes may be prepared in any suitable size to facilitate handling. Briquettes of general disc shape three inches in diameter and approximately one inch in thickness have been found suitable for the purpose.

As an example of the process, manganese was fused with a 40 pound batch of magnesium alloy containing about 6% aluminum and 3% zinc. The 40 pound batch was melted in an iron pot under a chloride flux and heated to approximately 700 C. Approximately one-third of a pound of previously prepared briquettes were introduced, said briquettes containing 25% powdered magnesium, 5% manganese dioxide and metallic manganese of 65 mesh. The briquettes sank into the molten metal and dissolved with a vigorous convective motion of the molten metal but with no excessive spitting or boiling. The mass was permitted to cool to allow separation of impurities, such as iron, and it was found, on analysis, that the manganese content of the alloy was approximately 56%, which corresponded to more than of the total added manganese.

The process may be practiced in other ways and with other percentages of manganese and briquettes having percentages of materials other than those given in the specific example. When the process was carried on. in the same manner as given in the example, but employing loriquette containing 10% of manganese dioxide, the mass boiled rather violently but in a controlled manner. In an open vessel, the reaction was impractically violent when the briquettes contained 20% manganese dioxide and quite an incendiary effect was obtained when the briquettes contained as much as 50% manganese dioxide.

The method may be carried out also by introducing the desired amount of manganese, for example, from 0.1% to 5%, into pure magnesium, the total weight of briquettes being calculated to the proper amount of manganese, and the resulting product then alloyed with other elements such as zinc, aluminum, copper and the like, by introducin the same in the manner customarily used in making magnesium alloys. It has been found, however, that if the briquettes are added to the otherwise completed alloy, iron and other impurities can be removed more effectively than when the manganese is added to the magnesium and the other alloying elements subsequently added.

Other oxidizers than MnOz or oxides of manganese can be used. For example, nitrates, especially sodium and potassium nitrate can be used. Also, it is contemplated that chlorates and perchlorates can be employed. If any chlorine is evolved it would tend to clean up the metal. In addition, permanganate and diehromate can he used. It is further contemplated that cerium metals canbe used as a substitute for magnesium or aluminum to react with the oxidizer for producing the exothermic reaction.

Since certain changes can be made without departing from the spirit and scope of this inventicn, it is intended that all matter contained in the description thereof shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

The method of adding manganese to an alloy of magnesium, zinc and aluminum containing a high percentage of magnesium, the steps which comprise melting the alloy; and introducing into the molten hath exothermic strongly coherent briquettes containing from 5% to 10% manganese dioxide, approximately magnesium, and the balance, manganese powder.

JOHN J. McLAUGHLIN.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 778,345 Weber Dec. 27, 1904 906,009 Goldschmidt Dec. 8', 1908 2,250,687 Zeppelin July 29, 1941 2,267,862 Hanawalt et al. Dec. 1941 2,337,314 Deppeler Dec. 21, 1943 FOREIGN PATENTS Number Country Date 20,604 Great Britain A. D. 1905 185,749 Great Britain Sept. '7, 1922 115,655 Australia July 31, 1942