I. Overview of chromium salts

Chromium salt is one of the main series of inorganic chemical products in China, widely used in metallurgy, leather, pigments, dyes, spices, metal watch treatment, wood preservative, military and other industries, is listed as one of the most competitive eight kinds of resource raw material products.

Second, introduction to the application of chromium

Because chromium is hard and brittle, corrosion resistance and other excellent properties, it is widely used in metallurgy, chemical industry, cast iron, fire resistance and high precision technology and other fields.

1. Metallurgical industry

Chromium is hard, often mixed into steel to make both hard and corrosion-resistant alloy, mainly used to refine stainless steel, heat-resistant steel and various electric heating element materials. Stainless steel in the encounter with corrosive substances, its surface will form a fine and solid chromium oxide film, protect the internal metal does not continue to be corroded, some stainless steel even in the high temperature of 800℃, but also to maintain its excellent performance. Chrome steel is a good material for the manufacture of machinery, tanks and armored vehicles.

2. Chemical industry

Various chromium salts processed from chromite are the main raw materials in the chemical industry. Chromium salt is one of the main varieties of inorganic salt, in daily life is very widely used, mainly used in electroplating, tanning leather, printing and dyeing, medicine, fuel, catalyst, oxidant, matches and metal corrosion inhibitor and other aspects.

At the same time, chromium metal has been listed as one of the most important electroplating metals, in most cases, chromium plating layer is specially used as the most external coating of parts, chromium plating, the thinner the chromium layer, the more close to the surface of the metal, some barrels, the inner wall of the barrel, the chromium plating layer is only five thousandths of a millimeter thick, but after firing hundreds of shells, bullets, the chromium layer still exists. Without the physical properties provided by the chromium plating layer, the service life of most parts will be greatly shortened due to wear, corrosion and other reasons, and must be replaced or repaired frequently, so electroplated chromium is more and more widely used in many industrial manufacturing.

3, refractory materials and cast iron

Because the melting point of chromite is as high as 1900℃-2050℃, it can maintain the same volume at high temperatures and does not react with any slag. Therefore, it can be used as refractory materials, steel furnaces and non-ferrous metal smelting furnaces lining. Therefore, in terms of refractory materials, chromite is used to manufacture chrome bricks, chrome magnesia bricks and other special refractory materials.

In addition, chromium is also used in cast iron, such as chromium cast ductile iron has high strength, high elongation, high impact value and low hardness characteristics.

4. Other uses

In the automotive industry, chromium is also involved in the production of automotive brake pads.

Third, China's ancient chromium salt oxidation technology

The world-famous "eighth wonder of the world" - the second pit of the Terracotta Warriors and horses of Qin Shihuang has unearthed a number of bronze swords with a total of eight edges. Archaeologists measured with vernier calipers and found that the error of the eight edges is less than a hair, and 19 bronze swords have been unearthed.

The internal organization of these bronze swords is dense, the body of the sword is bright and smooth, the blade is finely ground, and the texture comes and goes without interleaving. They have slept under the loess for more than 2,000 years, and when they were unearthed, they were as bright as new and sharp. After testing, the researchers found that the surface of the sword has a layer of chromium salt compounds 10 microns thick. This discovery immediately caused a sensation in the world, because this chromium salt oxidation treatment method, only modern advanced technology, Germany in 1937, the United States in 1950 has invented and applied for a patent.