Effect of warm rolling process on microstructures and tensile properties of 10 Mn steel

Abstract

The influence of warm rolling processes on the microstructures and tensile properties of 10 Mn steel was studied. Strength appeared to increase with the rolling temperature but strengthening mechanisms varied. The increase of warm rolling temperature from 250 °C to 600 °C leads to enhanced recrystallization in martensite during the intercritical annealing (IA) at 620 °C for 5 h. As a result, both ultimate tensile strength (UTS) and total elongation (TE) increase. However, the size of relatively coarse recrystallized austenite grains and the resultant yield strength (YS) remain almost constant in this temperature range. The further increase of rolling temperature to 700–800 °C causes a considerable amount of pearlite to be formed during the IA, and then martensite is formed after the IA, resulting in dramatical increases in both YS and UTS but at the great loss of ductility. The warm rolling at 600 °C with 63% thickness reduction can produce the steel with the best mechanical combination of 1.2 GPa UTS and 35% TE, due to the formation of many ultrafine austenite grains and strain-induced cementite precipitates. This demonstrates that the mechanical combination of non-V-alloyed medium Mn steel can be improved to an equivalent level of 0.7% V alloyed 10 Mn steel just via the economic strain-induced cementite precipitation.