High temperature deformation behavior of carbon steel in the austenite anddelta-ferrite regions

Stress-strain relations of carbon steels in the gamma, phase and delta phas e regions have been analyzed through the high temperature tensile tests at various temperatures from 1100 to 1450 degrees C and strain rates from 10(- 4) to 10(-2)/s using Gleeble system, During hot tensile test, a ceramic fib er tube was used to reduce the radial temperature gradient in the heated sp ecimen. The flow stresses of carbon steels varied not only with the test te mperatures and strain rates, but also with the process condition of cooling rate. The measured flow stress of delta phase was lower than that of gamma phase. The degree of strain hardening of delta phase was negligible compar ed with that of gamma phase. A simple constitutive equation, which takes in to account temperature, strain and strain rate, could successfully describe the measured flow stress of carbon steel by hot tensile test. The calculat ed flow stress was in good agreement with experimentally measured data.