Molybdenum is one of the 90 naturally occurring elements. It has a body-centred cubic structure and is classed as a refractory metal because of its melting point of 2617 °C (2890 K).

Molybdenum minerals have long been known, but the element was discovered in 1778 by Carl Wilhelm Scheele. The metal was first isolated in 1781 by Peter Jacob Hjelm.

Molybdenum and molybdenum alloys are produced using either powder metallurgy or by a molten route (electron-beam or vacuum arc melting). Powder metallurgical processing has decisive advantages over the other methods and therefore is most widely used. The fine-grained microstructure resulting from powder metallurgy production results in easier further processing and improves the mechanical properties of the final product. Additionally, the powder route is the only production possibility for alloys such as molybdenum doped with La2O3 or Y2O3.

Manufacture of Semi-finished Products

The most important minerals for the extraction of molybdenum are molybdenite, (MoS2) and yellow lead ore or wulfenite (PbMoO4). The largest molybdenum deposits are located in North and South America and in China. Molybdenite occurs as a by-product of copper extraction in Chilean copper mines.

The ores mostly contain around 0.5 % MoS2 and must be separated from accompanying minerals by enrichment through a fl otation process. The concentrate is then roasted, converting the molybdenum sulphide into molybdenum trioxide. Impurities are removed from the roasted concentrate either by sublimation, or by chemical treatment. The raw materials for the production of molybdenum powder are ammonium molybdate and molybdenum trioxide.

Both materials are converted into molybdenum powder by a two-stage hydrogen reduction process, which gives fi ne-grained metal powder of high purity (≥ 99.97 %).

After screening and homogenisation, molybdenum powder is pressed into rods and plates of various geometries and dimensions. This takes place using either hydraulic presses with steel dies, or by isostatic pressing, in which a rubber bag is fi lled with powder for consolidating into a compact by water pressure acting on all sides.

Sintering then takes place, usually in hydrogen furnaces at temperatures in the range 1800 - 2200 °C (2073 - 2473 K). The mechanical strength and density of the pressed compact increases during the sintering process to reach the properties necessary for further processing to semi-fi nished products.

The sintered billets are then hot worked at temperatures in the range 1200 - 1500 °C (1473 - 1773 K) using processes such as extrusion, forging or rolling. As the degree of deformation increases the working temperature can be reduced. In this way forged parts, round bars, sheets, foils and ribbons are produced. Wires are manufactured from round bars by drawing.

Product Range and Guaranteed Chemical Composition

In addition to molybdenum of different purity levels, the alloys listed below are in production.

Material designationChemical composition
(information given in weight, %)
Mo (pure)≥ 99.97 % Mo *)
Mo-UHP (ultra high prity)≥ 99.9995 % Mo
TZMMo 0.5 % Ti 0.08 % Zr 0.01 - 0.04 % C
MHCMo 1.2 % Hf 0.1 % C
Lanthanated Mo (ML)MLMo 0.3 % La2O3
MLRMo 0.7 % La2O3 (R=Recrystallized)
MLSMo 0.7 % La2O3 (S=Stress relieved)
MoILQMo 0.03 % La2O3 (ILQ=Incandescent Lamp Quality)
Yttriated Mo (MY)Mo 0.47 % Y2O3 0.08 % CeO2
MoReMo5ReMo 5.0 % Re
Mo41ReMo 41.0 % Re
MoWMW70Mo 30.0 % W
MW50Mo 50.0 % W
R750Mo 30.0 ± 3.0 % Cu

*) metallische Reinheit ohne W / metallic purity without W