Influence of hot rolling process on the microstructure and mechanical properties of a press hardening steel

In this article, microstructure and mechanical properties of a press hardening steel prepared with different rolling parameters are studied, and the effects of the rolling processes are analyzed. The results show that when the finishing rolling temperatures are 870°C and 900°C and the coiling temperature rises from 640°C to 700°C, the strength of the press hardening steel increases and the elongation decreases. The yield strength of the steel prepared with low finishing rolling temperature is high, but the tensile strength has little difference, and the elongation decreases quickly. The microstructures consist of ferrite and pearlite, but as the coiling temperature rises, the amount of the alloy-carbide precipitates in the ferrite, and grain boundary is reduced significantly. The interlamellar spacing of pearlite gradually becomes narrow and the density of dislocation lines in the ferrite increases slightly. The press hardening steel rolled at the finishing temperature of 900°C and coiled at 670°C has excellent balance of mechanical properties. The yield strength, ultimate tensile strength, and elongation are 370 MPa, 598 MPa, and 19 %, respectively. Copyright © 2017 by ASTM International.