Ferrochrome Related Reading

chromium

Chromium is a lustrous gray metal with a density of 7.2, a melting point of 1857°C and a boiling point of 2672°C. It is ductile, but becomes hard and brittle when it contains impurities such as oxygen, hydrogen, carbon and nitrogen. The chemical properties of chromium are inactive, and it is stable to oxygen and water vapor at room temperature. Chromium starts to react with oxygen when the temperature is higher than 600 °C, but when an oxide film is formed on the surface, the reaction is slow. When heated to 1200 °C, The oxide film is destroyed and the reaction becomes faster again. At high temperatures, chromium reacts with nitrogen, carbon, and sulfur. Chromium can interact with fluorine at room temperature. Chromium is soluble in hydrochloric acid, sulfuric acid and perchloric acid, passivated after encountering nitric acid, and no longer reacts with acid. Chromium can form alloys with magnesium, titanium, tungsten, zirconium, vanadium, nickel, tantalum, and yttrium. Chromium and its alloys have strong corrosion resistance.

chromite

There are about 50 kinds of chromium-containing minerals found in nature, which belong to oxides, chromates and silicates. In addition, there are a few hydroxides, iodates, nitrides and sulfides. Among them, chromium nitride and chromium sulfide minerals are only found in meteorites. Chromium minerals with industrial value belong to chromium spinel minerals, and their chemical formula is (Mg, Fe2+) (Cr, Al, Fe3+) 2O4 or (Mg, Fe2+) O (Cr, Al, Fe3+) 2O3, Its Cr2O3 content is 18% to 62%.

Common chromium minerals are:

(1) Chromite, the chemical composition is (Mg, Fe) Cr2O4, between ferrous chromite (FeCr2O4, containing FeO 32.09%, Cr2O3 67.91%) and magnesium chromite (MgCr2O4, containing Mg 20.96%, Cr2O3 79.04%), both ferrochromite and magnesium chromite are usually referred to as chromite. Chromite is an equiaxed crystal system, the crystals are fine octahedrons, usually granular and dense massive aggregates, black in color, brown streaks, semi-metallic luster, hardness 5.5, density 4.2-4.8, weak magnetic. Chromite is a magmatic mineral produced in ultrabasic rocks. When the ore-bearing rock is damaged by weathering, chromite is often transferred into placer. Chromite is the most important mineral raw material for smelting chromium, and low-quality ore rich in iron can be used as advanced refractory material.

(2) Chromium-rich spar, also known as ferrochromium spinel or aluminum chromite, has a chemical composition of Fe(Cr, Al)2O4 and contains 32% to 38% of Cr2O3.

(3) Hard chromium spinel, the chemical composition is (Mg, Fe) (Cr, Al) 2O4, containing 32% to 50% of Cr2O3. Chromium-rich spar and hard chromium spinel have the same morphology, physical properties, origin, occurrence and use as chromite. The methods of industrial production of metallic chromium include aluminum reduction, silicon reduction, carbon reduction and electrolysis.