[SMM Science] what is South African chromium ore?

South African chromium ore is a kind of chromium ore made from chromium ore produced in South Africa. In the metallurgical industry, chromite is mainly used to produce ferrochromium and metal chromium. As an additive to steel, chromium ore chromium ferroalloy produces a variety of special steel with high strength, corrosion resistance, wear resistance, high temperature resistance and oxidation resistance, such as stainless steel, acid resistant steel, heat resistant steel, ball bearing steel, spring steel, tool steel and so on. Chromium has aerobic and iron-loving properties, and is more aerobic. Only when the fugacity of reduction and sulfur is high, chromium shows sulfur-loving property. Chromium is generally trivalent under the condition of endogenesis. The ion radius of Cr3+ at the sixth acid site is similar to that of Al3+Fe3+, so there can be a wide range of isomorphism between them. In addition, the elements that can be replaced by the isomorphism of chromium are Mn, Mg, Ni, Co, Zn and so on. Therefore, chromium is widely distributed in mafic silicate minerals and accessory minerals. Under the condition of strong oxidation of supergene band (alkaline medium), Cr3+ is oxidized to chromate ion in the form of Cr6+, which makes the inactive chromium ion migrate into soluble chromium anion. Ions with strong polarization (such as Cu, Pb, etc.) form insoluble chromium acid minerals. At present, more than 50 kinds of chromium-containing minerals have been found in nature, which belong to oxides, chromate and silicate, respectively. In addition, there are a small number of hydroxides, iodate, nitrides and sulfides. Among them, chromium nitride and chromium sulfide minerals are only found in meteorites. South African chromium ore sand, chemical composition (Mg, Fe) Cr2O4, is between ferrous chromite (FeCr2O4, contains FeO32.09%, Cr2O3 67.91) and magnesia chromite (MgCr2O4, contains MgO20.96%, Cr2O3 79.04%). Ferrochromite and magnesia chromite are usually referred to as chromite. Chromite is an equiaxed crystal system, the crystal is fine octahedral, usually granular and dense block aggregate, color black, stripe brown, semi-metallic luster, hardness 5.5, specific gravity 4.2 to 4.8, with weak magnetism. Chromite is a magmatic mineral, which occurs in ultrabasic rocks. When ore-bearing rocks are weathered and destroyed, chromite is often transferred into placer. Chromite is the most important mineral raw material for chromium smelting, and the inferior ore rich in iron can be used as high-grade refractories.