Effect of Tempering Temperature on the Organization and Properties of Mn-Cr-Ni-Mo Steel after Tempering
Taking Mn-Cr-Ni-Mo low carbon low alloy steel as the research object,based on the simulation of JMatPro software,the organiza-tion and properties under different tempering temperature conditions were investigated by taking the methods of organization analysis and per-formance testing.The results show that:the microstructure of the test steel after quenching is slaty bainite+polygonal massive ferrite+mar-tensite,and then by 600~700℃ high-temperature tempering,with the increase of the tempering temperature,martensite and bainite succes-sively and gradually transformed,the amount of carbide precipitation to enhance the phenomenon of grain refinement,the average grain size increases,and these changes in the organization lead to the reduction of the strength and hardness of the material and the increase in the im-pact toughness.Tempered at 640℃ secondary hardening phenomenon,resulting in an increase in strength,impact toughness is relatively slightly decreased,and in 0~-40 ℃ when the impact value is no significant change,to maintain a high strength-toughness match.Mn-Cr-Ni-Mo low carbon low alloy steel quenched at 910℃+640℃ tempering heat treatment process program is feasible to meet the test steel pro-duction of X60,X65 and X70 and other steel grade pipeline pipe technical requirements.This kind of production of multiple steel pipes of dif-ferent steel grades with a single steel grade is an important way to safeguard production management,reduce costs and improve efficiency,which helps to enhance the market competitiveness of pipeline pipe products.