**11. Tungsten steels**

Tungsten is mainly popular for providing high temperature properties and hardenability. It is mainly a carbide former. Approximately 2–3% W is equivalent to 1% Mo. Tungsten is mainly used in the tools industry (**Table 2**).

For achieving high strength and toughness, fine grain structure is essential in steels. To produce such microstructure, a carefully controlled high temperature processing of steels must be done. Hot working alone cannot refine the coarse or nonuniform grain. For example, grain coarsening behavior of laboratory heats of C-Si-Mn base steels varies with the concentration of Al, V, Ti, or Nb micro-alloy addition. Thus, steels containing the very insoluble TiN coarsen at much higher temperatures than steels containing the more soluble VCN.

The main strengthening mechanisms of micro-alloyed steels are grain refinement and precipitation [12]. It can be done by high temperature-controlled process and by adding proper alloying elements. Nowadays an economical alternative of the traditional quenched and tempered steels is micro-alloyed steels.
