TS590 approx 980 MPa Grade Low-Carbon Equivalent Type Galvannealed Sheet Steel with Superior Spot-Weldability

摘要

High strength galvannealed (GA) sheet steels have been developed for the improvement of weight reduction, crashworthiness and anti-corrosion properties of an auto body. In general, the strengthening of GA steel can be realized through the addition of alloy elements although Zn coating properties and spot weldability are affected at the same time. In this paper, the mechanical properties and spot weldability of newly developed 590-980 MPa GA steels are described. Excellent mechanical properties and crashworthiness comparable to those of dual phase steel have been obtained by adding Mo, Ti and Nb which are suitable alloying elements for strengthening the steels processed with continuous galvanizing line. Spot weldability, especially in terms of ductility ratio, has been remarkably enhanced through the reduction of carbon equivalent.