回火温度对1100 MPa级高强钢组织与性能的影响

研究了920 ℃水淬+不同温度回火后1100 MPa级高强钢的显微组织和力学性能。结果表明:回火温度为250 ℃时,所得到的力学性能最佳,抗拉强度、屈服强度、硬度、断后伸长率和冲击吸收能量分别为1423 MPa、1220 MPa、446 HV5、14.2%和56 J。随回火温度的升高,抗拉强度、屈服强度、硬度值整体呈现下降的趋势,冲击吸收能量先减小后增加。回火温度为150 ℃时,组织为回火马氏体和ε碳化物,析出的ε碳化物呈细长杆状。回火温度上升到250 ℃之后,马氏体板条稍有粗化,ε碳化物长大。随回火温度继续升高,板条马氏体逐渐转变为等轴铁素体,ε碳化物也会转变为渗碳体并逐渐球化粗化。

Effect of tempering temperature on microstructure and properties of 1100 MPa grade high-strength steel

Microstructure and mechanical properties of 1100 MPa grade high-strength steel after water quenching at 920 ℃ and tempering at different temperatures were studied. The results show that when the tempering temperature is 250 ℃, the tested steel obtains the optimum mechanical properties, the tensile strength, yield strength, hardness, elongation after fracture and impact absorbed energy are 1423 MPa, 1220 MPa, 446 HV5, 14.2% and 56 J, respectively. With the increase of tempering temperature, the tensile strength, yield strength and hardness show a downward trend as a whole, and the impact absorbed energy first decreases and then increases. When the tempering temperature is 150 ℃, the microstructure is composed of tempered martensite and slender rod-shape precipitated ε carbides. After the tempering temperature rises to 250 ℃, the martensite laths are slightly coarsened, and the ε carbides grow up. With further increase of tempering temperature, the lath martensite gradually transforms to equiaxed ferrite, the ε carbides also transform to cementite and gradually spheroidize and coarsen.