Molybdenum is a transition metal (refers to the "D" block of the periodic table), or more strictly, "a transition metal as "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell". (source Wikipedia). In its pure form, molybdenum metal is a soft, silvery white metal which has one of the highest melting points of all elements. The melting point of molybdenum is 2,623 °C (4,753 °F), which is 2,000°F higher than the melting point of steel. It is also 1,000°F higher than the melting point of most rocks. Though it has the fifth highest melting point of all of the elements, it has the lowest coefficient of thermal expansion, making it a highly sought after component in high temperature applications.
Though molybdenum has a very high melting point, it oxidizes readily at temperatures in excess of 760°C. When exposed to air at this temperature, an oxide layer sublimes as the base metal reacts with oxygen, resulting in an oxidation process that resembles smoke. When properly controlled, the oxide can be recovered and reduced again to reclaim its molybdenum content. To avoid oxidation loss however, molybdenum is often utilized in inert or vacuum environments.
The largest use of molybdenum is as an alloy in the production of steel and stainless steel where it improves the strength and hardness of the alloyed metals. Ultra high strength steels with up to 8% contained molybdenum can withstand pressures up to 300,000 pounds per square inch. It also improves the strength of steel at elevated temperatures. In the United States, steel production consumes approximately 60% of manufactured molybdenum. In alloy applications, molybdenum content varies from 0.5% to 8%, dependent upon desired characteristics. Overall, iron and steel account for more that 78% of the worlds molybdenum consumption.