GB520331A - Improvements in or relating to materials for use in the production of alloys containing chromium, and to the production of alloys therefrom - Google Patents

Abstract

520,331. Alloys. UDY, M. J. Sept. 15, 1938, Nos. 26984, 26985, 26986, and 26987. Convention dates, Sept. 23, 1937, Jan. 22, 1938, July 23, 1938, and Sept. 7, 1938. [Class 82 (i)] A reaction-mixture for use in the production of chromium alloys is made by oxidizing carbonbearing ferrochromium to a product low in carbon and containing iron and chronium in oxidzed forms, and mixing the oxidized product in the solid state with a solid non-carbonaceous reducing-agent such as silicon, aluminium, magnesium, or alloys thereof, including nickel silicide in the case where nickel is wanted in the final alloy. The ferro-chromium may be produced by reducing low-grade chromite with carbon in a submerged-are electric furnace and may be oxidized in molten or solid form. In the former case the melt is blown 'with air or oxidized by iron-oxide, preferably in the presence of a base such as lime, to produce a workable slag; in the latter case the ferrochromium, which may be saturated with carbon or contain carbon and silicon to facilitate grinding, is ground and roasted at above 1000‹C. if desired, with oxidation promoters' such as lime, baryta, strontia, soda-ash, sodium chlorate, nitrate, or bichromate, manganese-dioxide, chromium trioxide, or potash. In either case, the degree of oxidation may'be controlled to effect the desired carbon-elimination' or the desired ratio of chromous to chromic oxides, and more than one oxidation may be carried out after regrinding, if desired, to a finer comminution than that previously employed and at below 1000‹C. The chromium ratio of the oxidized product may be improved, if desired, by the process of Specification 437,008 to the point, if necessary, of the total exclusion of iron. The product is ground and mixed with the reducing- agent in finely-divided form, or the two materials are ground together; the mixture may be employed for the direct production of iron-alloys or may be added to a steel bath, or to cast-iron, being employed in briquetted or loose form or in bags or metal containers, if desired with the addition of sodium nitrate, bichromate, chlorate, iron oxide, or manganese: dioxide, and a further addition of lime to give, with the silica present or produced during the reaction, a slag having a lime-silica ratio, e.g., 'of approximately 1.5:1. The additional lime may be obtained from a basic slag with which the mixture may be placed in contact. Chromium steels of specific composition, and chromium-nickel steels containing specified amounts of manganese silicon, carbon, aluminium, vanadium, and copper, are referred to.