Molybdenum and its applications
Carbon steels represent the by far largest volume of metallic materials used for a wide variety of applications such as general construction, automotive, energy transport, power generation and tooling. The carbon content in these steels ranges from nearly zero (IF steel) to approximately 2% (Ledeburite steel) according to the iron-carbon phase diagram. The largest volume of carbon steels comes as rolled products (flat and long products, SBQ) while smaller quantities are forged or directly cast (crosslink) into shape.
Molybdenum is used efficiently and economically in alloy steel & iron to:
- Control microstructure
- Improve hardenability
- Reduce temper embrittlement
- Resist hydrogen attack & sulphide stress cracking
- Increase elevated temperature strength
- Improve weldability, especially in high strength low alloy steels (HSLA)
Molybdenum alloying typically becomes relevant when yield strength of above 500 MPa is to be achieved and sometimes also for lower strength levels when heavy gages are being produced. The application of an additional heat treatment after hot forming allows producing microstructures with exceptional properties in terms of strength and toughness, and often requires Molybdenum alloying.
The applied molybdenum additions needed to meet the high end of the application properties are comparatively small in most cases. In fact, with the exception of High-Speed Steel (HSS) and Maraging Steel the Mo content often ranges between 0.2 and 0.5% and rarely exceeds 1%.