Effects of warm forming on deep drawability of a TRIP-aided dual-phase sheet steel

摘要

To improve the deep drawing of high-strength TRIP-aided dual-phase (TDP) sheet steel, Swift cup test of a 0.19C-1.54si-l.52Mn (mass%) TDP steel was investigated at temperatures between 20°C and 250°C. The steel exhibited a larger limiting drawingratio (LDR) than those of the conventional ferrite-bainite and ferrite-martensite dual-phase steels without retained austenite. Furthermore, the LDR was enhanced by warm drawing at about 150°C, at which the strain-induced transformation of the retainedaustenite particles is suppressed most. Such excellent deep drawability was caused by large local necking resistance due to "the transformation hardening" and "the stress relaxation" resulting from the strain-induced martensite transformation at the cupwall just above the punch bottom, as well as low drawing resistance of the shrinking flange.