nature

The atomic number of chromium is 24. The atomic weight is 51.996, and the outer electronic structure is 3d54s1. Melting point 1875 ℃, boiling point 2680 ℃. Density (20 ℃) 7.19g/cm3. The melting temperature of aluminum based chromium (Cr99%) is about 1830 ℃, and the density is about 7.2g/cm3. The melting temperature of electrolytic chromium (Cr99.9%) is about 1850 ℃, and the density is about 7.2g/cm3. Chromium is a brittle metal with a silver white color and a slight sky blue hue. Stable for oxygen, nitrogen, and humid air below 300 ℃. As the temperature increases, oxidation accelerates, but after the formation of an oxide film on the surface, the oxidation rate slows down. When the oxide film is destroyed at 1200 ℃, the oxidation rate accelerates. Therefore, chromium has antioxidant capacity below 1000 ℃. Cold hydrochloric acid, cold nitric acid, and sulfuric acid have weak effects on chromium and have acid resistance properties. Chromium and oxygen form oxides CrO, Cr2O3, and CrO3, with Cr2O3 being more stable. Chromium and carbon generate Cr4C, Cr7C3, and Cr3C2; Generate Cr2Si, Cr5Si3, CrSi, and CrSi2 with silicon. The silicides of chromium are more stable than carbides, and chromium forms CrN and Cr2N with nitrogen. Chromium and sulfur form CrS.

purpose

Chromium is a brittle metal that cannot be used as a metal material alone, but when combined with iron, nickel, cobalt, titanium, aluminum, copper and other alloys, it becomes an engineering material with heat resistance, thermal strength, wear resistance, and special properties. Metal chromium is used as an alloying agent in the production of various nickel or cobalt based high-temperature alloys, titanium alloys, aluminum based alloys, resistance alloys, and copper alloys. Part of it is used to produce stainless steel and heat-resistant steel. These materials are widely used in industries such as aviation, aerospace, nuclear reactors, automobiles, shipbuilding, chemicals, and military.