关键词: 高Cr热成形钢, 连续退火, 微观组织, 力学性能

Abstract: Hot rolling, cold rolling, continuous annealing (780-840 ℃ ) and flat die quenching ( 930 ℃ for 5 min ) tests were carried out on self-designed and lab prepared high Cr hot-stamping steel, and the effect of continuous annealing temperature on the microstructure and properties of the tested steel was studied. The results show that the microstructure of the hot-rolled steel is composed of lamellar pearlite and polygonal ferrite, and the cold-rolled steel is fibrous ferrite and pearlite with the yield strength of 857 MPa, the tensile strength of 953 MPa, and the total extension of only 3.66%. After continuous annealing at 780 ℃ and 800 ℃, the microstructure of the tested steel still retains the fibrous ferrite and pearlite, which affects the plasticity after subsequent quenching. When the continuous annealing temperature is 820 ℃ and 840 ℃, the microstructure of the tested steel is bainite and martensite, and the mechanical properties after subsequent quenching meet the requirements of the hot-stamping steel. Considering comprehensively, 820 ℃ is the optimal continuous annealing temperature, and the tensile strength of the annealed plate after flat die quenching is 1655 MPa, the yield strength is 1233 MPa, and the total extension is 6.87%.

Key words: high Cr hot-stamping steel, continuous annealing, microstructure, mechanical properties