The Research Of Vanadium Oxide Direct Alloying To Make Non-quenched And Tempered Steel

At present, most of vanadium steel are smelted by ferrovanadium alloy in domesticiron and steel groups. Ferrovanadium alloy is obtained by using vanadium oxide and Fethrough a complicated process, which not only consumes large amounts of energy andraises the cost of steel, but also brings sever problems to the environment. The goal ofthis research is to develop an additive of vanadium oxide which can be directly fed andfast alloyed, and apply it in producing non-quenched and tempered steel. By using thisprocedure, the process for producing ferrovanadium alloy is omitted, so that theproduction cost and environment pollution can be reduced.In this study, the thermodynamic calculations of reaction of V2O5and reductant inlaboratory, the reasonable proportion of V2O5, reductant, additive and blinder inreductant piece were performed and the feasible way to add reductant into molten steelwas investigated. By design reasonable smelting process, non-quenched and temperedsteel containing vanadium was fabricated in laboratory and put into pilot test. Thevanadium yielding rate, metallographic phase, inclusions and mechanical property ofthe steel was investigated.It’s feasible for V2O5to be reduced by reductant piece in molten steel. By addingappropriate Fe powder and CaF2powder, high vanadium yielding rate can beobtained.Using Al+Mg, Si+C as reductant, the highest vanadium yielding rates canreach95.11%,98.17%respectively in laboratory.When using Al+Mg, Si+C as reductant, with the increase of Mg and C in reductantpiece, V yielding rate rises, grain of the obtained steel is refined, and yield strength isalso increased. At the same time, the adding of Mg and C also bring apparent increase toductility of steel. But when Mg is lower than37.5wt%, or C is lower than20wt%inthe reductant, the ductility does not change significantly.In pilot test, cored wire made by V2O5, reducing agent and additive was directlyput into molten steel. V was reduced from V2O5and directly alloying in steel. The obtained steel was forged or rolled, and it was found the inclusions are strip in steel. Theconclusion are mainly composed of MnS, SiO2, which means the composition and typesof inclusions are not transformed by reductant piece. After tensile failure, the formationdimple fracture is contented to inclusions, which would speed up the fracture failure ofmaterial. When using cored wire, the yielding rate can reach95%, and the tensilestrength is higher than785MPa.