Influence of cooling rates and tempering on the mechanical properties of Mn-Mo-Ni low-alloy steels

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• 作者：LIU HuibinZHANG Hanqian
• 会议时间：2013-06-01
• 关键词：Mn-Mo-Ni low-alloy steel ; cooling rate ; tempering ; strength ; toughness
• 作者单位：Baoshan Iron & Steel Co.,Ltd.,Shanghai 201900,China
• 母体文献：第五届宝钢学术年会论文集
• 会议名称：第五届宝钢学术年会
• 会议地点：上海
• 主办单位：中国金属学会
• 语种：chi

摘要

The microstructure and mechanical properties of Mn-Mo-Ni low-alloy steels were investigated at different level of cooling rates and tempering conditions.The steel plates cooling at 40℃/s and 30℃/min,the rates corresponding to the surface and half thickness of heavy steel plate during water quenching,produced microstructure of auto-tempered martensite and bainite respectively.During tempering,the strength of steels quenched at the two different cooling rates lowered continuously along with increase in the tempering parameter,defined by T( 20 + log t) where T:temperature and t:holding time.But the rate of strength change scales with the degree to which the virgin microstructure deviates from equilibrium.The strength of martensitic steel decreased faster and finally close to that of bainitic steel.The ductility and toughness gradually improved during tempering,passed through a maximum value,and finally lowered.The level of maximum toughness was also found to depend on cooling rates of Mn-Mo-Ni steels.The high cooling rate with microstructure of auto-tempered martensite showed larger toughness and lower ductile-brittle transition temperature than low cooling rate with microstructure of bainite,because the former had finer precipitated cementite particles at quenching and slower coarsing rate during tempering.