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研究了回火温度对低合金调质钢力学性能和显微组织的影响。结果表明:淬火态为具有自回火析出物的板条马氏体,具有良好的强韧性配合;在250℃左右回火后片状碳化物析出量增加,提高了屈服强度;在400℃回火后在板条界析出碳化物薄壳,导致回火脆性现象;高温回火后板条形态仍普遍存在,局部区域的板条合并成铁素体块晶。在550℃以上回火析出大量纳米碳化物,渗碳体明显粗化.细晶强化和析出强化是实验钢的主要强化方式。在回火过程中组织演变及析出物性质直接影响拉伸曲线特征和n值。
The effect of tempering temperature on the mechanical properties and microstructure of low alloyed quenched and tempered steel was studied. The results show that the as-quenched state is lath martensite with self-tempering precipitates and has a good combination of strength and toughness. The amount of flake carbides precipitated after tempering at about 250 ℃ increases, and the yield strength increases. At 400 ℃ After the fire in the slab boundary carbide precipitates, resulting in temper brittleness phenomenon; high temperature tempering lath shape is still widespread, the local area of the lath merged into ferrite bulk crystal. A large amount of nano-carbides were precipitated at tempering above 550 ℃, and the cementite obviously coarsen.The fine-grain strengthening and precipitation strengthening are the main strengthening ways of experimental steel. Tectonic evolution and precipitation properties during tempering directly affect the characteristics of tensile curves and n values.