US1982959A - Method of refining alloys - Google Patents

Description

Patented 4, 1934 UNITED s'rA'rEs METHOD or name ALLOYS August Kuhlmann, Falls, N; Y., as-

signer to Electra Metallurgical Company, a corporation of West Virginia No Drawing.

tion June 4, 1932,

Appliea Serial No. 615,469

1 Claim. '(CI. 75-11) My invention relates to the refining of certain alloys containing aluminum, and refers more specifically to the removal of aluminum from such alloys by a novel refining process,

"8 The chief object of the invention is to provide a novel process whereby high aluminum alloys, such as those produced by thealuminum or alumino-thermic reduction of refractory corn- P unds of metals, be refined to low alumilu num'or aluminum free alloys effectively and efficiently.

In the production of metals and alloys from refractory ores and compounds by aluminum or alumino-thermic reduction, it is usually advan- 1'5 tageous to operate with a considerable excess of aluminum in order to efiect a good recovery of metal from the compound. When using such excess of aluminum; it is frequently difiicult to produce an alloy having a low aluminum conao tent, for some of the aluminum alloys with the metal or metals being reduced, or even forms metallic compounds therewith. The usual methods of refining out the excess of aluminum with oxygen-containing compounds are often uncerz's tain in result, and involve large losses of one or more of the alloying elements.

Ihave discovered that many high aluminum alloys may be refined and the aluminum content thereof lowered or even completely removed so if the molten alloy is treated with a metal sulphide selected from a group of metals which have less chemical aflinity for sulphur than has aluminum. I have further discovered that the I additions of metal sulphide may readily be'made as so as controllably to reduce the aluminum content to any desired amount without introdu a detrimental amount of sulphur into the alloy.

Thehighaluminumalloystowhichtheprocass is applicable include those ofall metalshav- .a'o'ing a lower chemical afilnity for sulphur than has aluminum. For instance, alloys containing iron, cobalt, nickel, copper, silver, boron, chromium, tungsten, molybdenum, silicon, tantalum,

columbium, uranium, and vanadium alloyed with 8. aluminum either singly or in various combinations are included.

,The metal sulphide used in the refining process may be any within the above definition; that H is, any metal sulphide is suitable wherein the so metallic constituent has a lower chemical aiilnity sulphur than has aluminum, such for examiron sulphide, or chromium sulphide. It

be dmirable to use a sulphide of on furnace conditions and temperatures.

like ferroboron, or chromium sulphide in the case of a chromium-boron alloy; but wherever the introduction of a foreign metal other than aluminum is.unobjectionable, sulphidesof metals other than the chief constituents of the alloy may be used. The choice of a particular sulphide will be governed mainly by the above requirementas to chemical affinity, by the desired constitution and purity of the refined product, and by considerations of cost.

The process of the invention may be carried out by smelting a mixture of the high aluminum alloy and the proper sulphide in an electric or other furnace. However. any method which brings the said alloy and the sulphide into reaction' may be considered as within the scope of the present invention; for instance, the high aluminum alloy may be refined directly as it is produced in the. reduction process, by treating the still molten alloy with a molten bath containing the desired sulphide.

The reaction between the metal sulphide and the aluminum contained in the high aluminum alloy being refined. results in the liberation of the metal constituent of the sulphide and in the g formation of aluminum sulphide. In general, no other fluxing agents are required, the aluminum sulphide forming a fluid slag. Other slag forming materials such as lime, silica, alumina, and the like may be present, however, and in limited as quantity are not detrimental :to the process. The proportion of metal sulphide to be employed will depend on the amount of aluminum it is desired to remove from the alloy. In general, a quantity of metal sulphide slightly less than the stoichiometrical amount shown by the following typical reactions should be employed.

Slightly less than the theoretical requirement is used, for in commercial furnaces some oxidation of aluminum by air is inevitable. However, when a sulphide is employed which may be ther- 100 mally decomposed at the furnace temperatures, such as, for instance, iron pyrites (Fess) somewhat more than the stoichiometrical requirement must be used, depending to a large degree As an example of the application of my invention the following is typical: 775 pounds of crude ferroboron containing 81.08%v of boron,

' 383896; of aluminum,.the remainder to make up beingmostlyi-ron. wassmeltedinanelec- 110 tric iurnace together-with 175' pounds oi. iron pyrites. The product contained 15.04% of boron, 1.09% 01' aluminum, 0.02% of sulphur, with the remainder substantially all iron. 01

the boron contained in the crude'ierroboron,

85% was recovered mtne refined alloy.

A further example is the following: 100 pounds ofcrude chromium-boron containing 23.25% of boron, 8.97% of aluminum, and the remainder chiefly chromiu'mywas smelted in an electric furnace together with -47 pounds of chromiumb0ron alloy, recoveries in refined alloy of as much as 90% of the boron contained in the crude alloy and of 86% of the chromium contained in the crude alloy and in the sulphide have beenoobtained.

I claim:

Method for removing a preponderant proportion of the aluminum from an alloy containing upwards of about 20% boron, upwards of about 8% aluminum, and the remainder metal of the group consisting 01' iron and chromium, which comprises melting said alloy and treating the melt with a sulfide of a metal of said group consisting of iron and chromium.

AUGUST M. KUHLMANN.