Vanadium - Transforming Possibilities

The Manufacture, Properties and Weldability of Vanadium-Containing Steels

Abstract:

This paper examines a range of aspects related to the production and use of vanadium containing steels. 

During continuous casting vanadium steels can exhibit high levels of hot ductility giving them low susceptiblity to transverse cracking, thus offering potential yield improvements. Furthermore, the range of cooling rates obtained during casting can lead to a precipitate particle size and distribution which are almost ideal for the production of Ti-V-N steels.

In the course of rolling, vanadium steels tend to recrystallise over a wide temperature range, leading to lower rolling loads than observed with other micro-alloyed steels, particularly as the temperature is reduced. In addition, the recrystallised austenite grain size is reasonably constant over a wide range of finish rolling temperature, resulting in relative insensitivity of properties and this grain size can be refined by controlled additions of Ti and N. Furthermore, if rolled at low temperature, in the two-phase region, steels containing vanadium alone can develop recovered microstructures containing both a high dislocation density and a precipitate size and distribution which lead to a combination of high strength and good toughness. Thus, by application of appropriate processing procedures including hot rolling, temperature controlled rolling, accelerated cooling and two-phase rolling a family of steels with a wide and controllable range of properties can be obtained. The properties of some of these steels are considered.

Vanadium steels are weldable over a range of heat inputs and exhibit the additional benefit that the incorporation of vanadium can give rise to advantageous heat affected zone microstructures, particularly at slower HAZ cooling rates, and this may lead to increasing use of such steels as heat inputs are increased. Results which demonstrate the effect of vanadium on RAZ toughness are presented.

Keywords:

vanadium microalloyed steel, HAZ toughness, weldability.

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