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通过拉伸和冲击试验以及SEM、TEM和EBSD组织观察,研究了不同热处理工艺参数对3.5Ni钢显微组织和力学性能的影响。结果表明:3.5Ni钢在860℃保温1 h水淬后得到细小的板条马氏体(LM)加粒状贝氏体(GB)组织;570℃回火后,LM的板条变粗,GB中的M/A岛也溶解消失,基体上有大量渗碳体析出。随着回火温度的升高,板条继续合并长大,并且开始出现多边形铁素体,渗碳体也不断长大。回火温度为570~600℃时,低温韧性随回火温度的升高而增加,但是继续升高回火温度会使得低温韧性下降。研究表明:3.5Ni低温钢经860℃水淬+600℃回火的热处理可以获得最佳的力学性能。
The effects of different heat treatment parameters on the microstructure and mechanical properties of 3.5Ni steel were studied by tensile and impact tests and SEM, TEM and EBSD microstructures. The results show that the fine lath martensite (LM) plus granular bainite (GB) is obtained when the 3.5Ni steel is quenched at 860 ℃ for 1 h. After tempering at 570 ℃, the laths of LM become thicker and GB The M / A island also dissolves and disappears, and a large amount of cementite precipitates on the substrate. With the tempering temperature increases, slats continue to merge and grow, and began to appear polygonal ferrite, cementite also continue to grow. When the tempering temperature is from 570 ℃ to 600 ℃, the low temperature toughness increases with the increase of tempering temperature, but the continued increase of tempering temperature will cause the low temperature toughness to decrease. The results show that: 3.5Ni low temperature steel by 860 ℃ water quenching +600 ℃ tempering heat treatment can get the best mechanical properties.