**9. Manganese steels**

Manganese is less expensive and mostly acts as deoxidizers. The presence of manganese in alloy steel reduces the prone to the hot shortness. As a result of which, the alloy steel containing manganese can perform the hot work.

Besides, the absence of manganese in the steel may form FeS. FeS has low melting temperature. Ehen the steel sample is how rolled then due to the low melting temperature of the FeS it melted first. Thus the few places in steels containing FeS become slippery, and thus the hot-rolled samples may slip during rolling.

Mn and Ni both reduce the critical temperature and lowers the amount of carbon in eutectoid. Alloying steels containing more than 10% Mn become austenitic after slow cooling.

Hadfield Mn steel is a special type of steel (12% Mn) and has great abrasion resistance. If it is slow-cooled from 1750F, then a large brittle carbide forms surrounding the austenite grain. Ultimately forms the structure with low strength and ductility.


**Table 2.**

**51**

*Phase Transformation in Micro-Alloyed Steels DOI: http://dx.doi.org/10.5772/intechopen.91468*

is carburized to improve wear resistance.

volume fraction and a reduction in precipitate size.

**11. Tungsten steels**

**12. Conclusion**

Molybdenum is a little expensive alloying element. It has limited solubility in austenite and ferrite. As a result of which, it is a strong carbide former. Molybdenum is used in combination with Ni or Cr or both. Plain molybdenum steel

A lot of research has been done in the case of interphase precipitation. In matter molybdenum plays significant roles. Four steels were manufactured with identical composition, and Ti, V, Mo, and N content is added to investigate the effect of composition on interphase precipitation. Alloys were rapidly cooled from the single austenite phase field and isothermally transformed at 630°C and 650°C for 90 min. When Mo is added, then there is a significant reduction in the austenite to ferrite transformation kinetics, particularly in the case of V steels. Interphase precipitation was observed in all alloys at both transformation temperatures. In the case of the Ti-bearing steel, two types of precipitate were observed, namely, TiC (finer) and Ti2C (coarser), while for the V-bearing steels, VC (finer) and V4C3 (coarser) were observed. Where Mo was present in the alloy, it was found dissolved in all carbide types. The (Ti,Mo)C and (V,Mo)C were formed by classical planer interphase precipitation (PIP), while the (Ti,Mo)2C and (V,Mo)4C3, which had a much wider row spacing, were formed through curved interphase precipitation (CIP). Each adopted one variant of the Baker-Nutting orientation relationship. The Ti-micro-alloyed steels undergo the smallest precipitates of all the steels, which were approximately the same size irrespective of whether Mo was present in the alloy and irrespective of the transformation temperature. However, the addition of Mo to the V-bearing steels causes significant increase in precipitate

Tungsten is mainly popular for providing high temperature properties and hardenability. It is mainly a carbide former. Approximately 2–3% W is equivalent to

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

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

Strengthening mechanism can be done by precipitation forming and grain refining. Micro-alloy element hinders grain growth that causes grain refinement [13]. Precipitates forming on ferrite or austenite cause improvement of hardening or strengthening of steel. Phase transformation in some cases also causes strengthening of steels. In phase transformation, different micro-alloying elements appear to contribute considerably. Strengthening of steels can be done by different heat

1% Mo. Tungsten is mainly used in the tools industry (**Table 2**).

temperatures than steels containing the more soluble VCN.

traditional quenched and tempered steels is micro-alloyed steels.

**10. Molybdenum steels**

*Basic comparison of different types of micro-alloyed steels.*
