Improving the formability of low carbon sheet steel by control of interstitial carbon content and temperature

Abstract

Several authors have shown a relationship between strain rate sensitivity and the formability of sheet metals. In this study it is shown that by cooling to subzero temperatures the strain rate sensitivity of low carbon sheet steel can be improved dramatically and that this increased strain rate sensitivity leads to improved formability. At laboratory strain rates the optimum conditions for improved formability, a temperature of ∼70 °C and an interstitial carbon content of ∼20 ppm, were determined experimentally. Optimization involves a tradeoff between strain rate sensitivity, strain hardening and fracture strain. Testing under these conditions leads to an improvement in formability of ∼13 pct.