The Use of Molybdenum Ore and Molybdenum Metal


Several decades ago, a strange thing occurred at a New Zealand pasture. That year, there was a farmer sowing clover and gramineae forages in the pasture. It is a poor harvest that the grass is short and small, even withered yellow. However, it is strange that there was a place of grass growing well in the withered meadow, which looked like a “green island” in the yellow sea from afar. The farmer was curious about it and finally discovered the secrets after a careful observation: there was a molybdenum ore factory beside the island; many workers who seeking a short cut went straight from there to the factory gate; molybdenum ore powder which was adhered to workers boots fell on the pasture made the grass grew well.

Why molybdenum ore can make grass grow well? After careful study, people found that molybdenum is the essential microelement for plant growth. The soil at that pasture was lack of molybdenum. Therefore, it was not surprised to see a place of well-growing grass after dropping little molybdenum ore powder. Some plant has a greater need of molybdenum, especially leguminous and gramineae. Human ommochrome also contains little molybdenum. In addition, there is also much molybdenum in kale and cabbage. Hence, it will be good for the eyes if you eat kale and cabbage often. However, if there is too much molybdenum in horned livestocks (such as cattle, sheep, etc.) feed, the stomach problems will occur easily.

Molybdenum is a hard silver-grey metal. It has a mohs hardness of 10.2 and a high melting point of 2620°C. Pure molybdenum has ductility, but it will be fragile when contains a small amount of impurities. Chemical properties of molybdenum are also very stable, which can’t be corroded by hydrochloric acid, hydrofluoric acid and alkaline liquid, but nitric acid, aqua regia or concentrated sulfuric acid. When heated to above 500 degrees, molybdenum will burn and turn into molybdenum trioxide. Molybdenum metal powder, the material of deep-processed products by powder metallurgy, is obtained by hydrogen reduction with ammonium paramolybdate or MoO3 Nanopowder made by calcination as raw materials.

Molybdenum metal is not widely used. It is mainly used to manufacture the anode and cathode of vacuum tube and the tungsten bracket of bulb. In 1927, people manufactured the ultra-pure metal molybdenum with a purity of 99.999%, which can be pulled into filaments used for integrated circuit wires. In addition, molybdenum metal is also used in manufacturing electrical discharge machine. In recent years, numerically controlled wire cutting machine in China is manufactured by means of cutting and electrical discharging with conductive metal molybdenum. Under inert gases protection, molybdenum wire and tungsten wire can be formulated into a high temperature resistance for measuring the temperature ranging from 1200 degrees to 1200 degrees.

In the chemical industry, Molybdenum compounds are used as a catalyst, penetrating agent and dyes. Molybdenum can form a complex heteropoly acid with phosphorus and silicon, including “phosphorus molybdenum blue” and “molybdenum blue”, with a special blue. In the analysis of steel, these two compounds are commonly used to measure the amount of silicon and phosphorus content (colorimetric analysis).

Molybdenum, about 90% is used to manufacture a variety of special steel. Molybdenum steel has good flexibility, impact ductility and high hardness, which can be used to make axles, armored plates and gun barrels. It can improve the mechanical properties of pig irons when adding a very small amount of molybdenum. The alloy of molybdenum and tungsten has good acid resistance, which is used to replace expensive platinum.

The Compounds of Molybdenum and Sulfur

Molybdenum disulfide is a dark gray powder, looks much like graphite. In recent years, China vigorously promotes using molybdenum disulfide as a solid lubricant in industry. According to the measurement, adding molybdenum disulfide into lubricant oil, the frictional resistance can reduce by a third. For example, adding about 3 percent molybdenum disulfide into vehicle chassis lube, the mileage can be increased from fifteen hundred kilometers to six thousand kilometers; cupola furnace blower uses grease lubrication originally, which you have to add oil once every two days, but after using molybdenum disulfide, it can switch well after just add the lubricant one time a year. The common lubricant, when increase mechanical pressure or fasten rotational speed, the frictional resistance increases, however, it is especially valuable that if use molybdenum disulfide, it will reduce the frictional resistance. Therefore, it is very suitable for those machines with close contact surface, large pressure and high speed rotation, such as using molybdenum disulfide instead of butter lubricated motor bearings, bearing temperature can drop from four to six degrees and save a 15% of electricity. Molybdenum disulfide has many advantages, including stable chemical properties, acid and alkali resistance, only dissolved in aqua regia and hot concentrated sulfuric acid, therefore, it is non-perishable when using. It can bear heat and cold and maintain good lubrication properties ranging from -60 °C to 400 °C.