EFFECT OF CARBON AND NITROGEN-CONTENT ON DYNAMIC STRAIN-AGING IN LOW-CARBON STEELS

Three different carbon steels, namely ASTM 516 Gr70 PVQ plate, G40.21 350 WT plate and G40.21 350 AT plate, were tensile tested at temperatu res from ambient to 623 K over a range of strain rates (1.48 x 10(-5)- 1.48 x 10(-3) s(-1)). Particular attention was paid to behaviour that was indicative of dynamic strain aging, namely (i) serrated yielding. (ii) negative strain rate dependence of the ultimate tensile strength and (iii) increase of the ultimate tensile strength measured at elevat ed temperatures compared with that measured at ambient temperature. Th e three steels displayed different strain aging behaviours and these d ifferences are discussed in terms of their respective nitrogen and car bon contents.