Determination of Mo Content and Heat Treatment of 960 MPa Molybdenum-Containing Low-Carbon Steel

To obtain the best chemical composition and heat treatment of the high-strength low-carbon steel with 960 MPa yield strength,the effect of heat treatment on microstructure and mechanical properties of the tested steels with different Mo contents was investigated by microstructure analysis,mechanical property testing and impact fracture examination.The results show that the tempering resistant ability of the quenched steel increased with the increase of Mo content.The best heat treatment(quenching at 880 ℃ and temperting at 580 ℃) for the tested steel with optimal Mo content of 0.4wt% was determined.With this treatment the steel could get the yield strength 980 MPa,tensile strength 1 000 MPa,elongation 15.5%,average Charpy impact energy at -20 ℃ 52 J and the impact fracture surface had dimple characteristic.The microstructure was tempered sorbite,and the lath martensite was partly resolved.