The Effect of Cooling Rates on Vanadium Microalloyed Steel

The predominant application of vanadium is for alloying of steel to obtain fine dispersion of carbide/nitride/ carbonitride precipitates for achieving high strength with adequate ductility. It amounts to about 85% of the total consumption, a share that appears rather stable over time. The remaining part goes to chemicals and to alloying of titanium. World-wide about 65% of vanadium for alloying of steel is used in microalloyed structural steels, whereas the remaining35% is used in V-alloyed steels, such as high speed and tools steels, high temperature low alloy steels, etc. The strengthening effect of microalloying additions may be produced by the dispersion strengthening effect of fine microalloyed precipitates or by grain refinement, i.e. inhibition of grain growth by carbonitride particles, or by a combination of these two effects [1]. In order to maintain fine austenite grain size prior to transformat-ion, particles that remain undissolved in austenite, or particles that will precipitate during hot rolling are required [2]. To produce very fine precipitates that are responsible for dispersion strengthening (i.e. particles that are2-5 nm in diameter), it is necessary that these should be freshly precipitated during or after transf-ormation to ferrite.