Effect of carbon content on the plastic flow of plain carbon steels at elevated temperatures

Abstract

The elevated-temperature plastic-flow behavior of plain carbon steels with a base composition of 0.8 Mn and 0.25 Si was examined as a function of carbon content in the range 0.005 to 1.54 wt pct at strain rates from 6 x 10-6 to 2 x 10-2 sec-1. Beyond 0.05 C the flow stress at a strain of 0.1 decreased with increasing carbon content at the rate of 13 MPa per pct carbon. However, the degree of softening depended on the strain level at which the flow stress was measured, because the increasing carbon content also decreased the rate of work hardening. The inferred increase in recovery processes with increasing carbon content is in agreement with the effects of carbon on diffusivity, elastic modulus, and lattice spacing, as well as the observed increase in grain growth with increasing carbon content. In the range 850 to 1300 °C (1562 to 2372 °F), the temperature dependence of the flow stress can be represented by σ= A exp (-BT) where A depends on carbon content and strain, and B depends primarily on strain rate. Extrapolation to higher temperatures yields the carbon-content dependence of the flow stress at the austenite solidus. © 1982 American Society for Metals and the Metallurgical Society of AIME.