轧后控冷工艺对75Cr1钢球化退火组织性能影响的研究

Research on the effect of controlled cooling process after rolling on spheroidizing annealing microstructure and mechanical properties of 75Crl steel

针对锯片用钢高强度、良好的韧性和耐腐蚀性能,以及较高的淬透性和热稳定性的性能要求,研究了热轧后控冷工艺对75Cr1钢球化退火后显微组织和力学性能的影响;采用电子探针显微分析仪(EPMA)和透射电镜(TEM)对实验钢热轧及球化退火后的显微组织进行了表征。结果表明:通过不同热轧控冷工艺,获得了片层状珠光体、珠光体+铁素体、珠光体+贝氏体3种热轧态组织实验钢板。当热轧后实验钢板组织为片层状珠光体时,球化退火后渗碳体颗粒分布均匀,钢板屈服强度和抗拉强度分别为473 MPa和556 MPa。当热轧组织中存在铁素体组织时,球化后渗碳体颗粒出现了聚集现象,晶粒尺寸增大,钢板强度降低。当热轧后实验钢板组织出现贝氏体时,缩短了球化过程中碳原子的扩散距离,获得了良好的球化组织,钢板的屈服强度和抗拉强度分别为553 MPa和638 MPa。对不同热轧组织钢板球化退火效果进行对比分析可知:将实验钢板的热轧终冷温度控制在约510℃时,产生贝氏体组织,相较于片层状珠光体组织以及铁素体+珠光体组织更易于获得良好的球化退火组织。

The effect of controlled cooling process after hot rolling on the microstructure and mechanical properties of 75Crl steel after spheroidizing annealing was invesgated to meet the requirements of high strength,good toughness,corrosion resistance,high hardenability and thermal stability for saw blade steel.Electron probe microanalyzer(EPMA)and transmission electron microscopy(TEM)were utilized to characterize the microstructure of the experimental steel after hot rolling and spheroidizing annealing.The results revealed that different controlled cooling processes after rolling produced three types microstructure of hot rolled experimental plates with lamellar pearlite,pearlite+ferrite and pearlite+bainite microstructure.When the microstructure of the experimental plate after hot rolling was lamellar pearlite,the cementite particles were evenly distributed after spheroidization annealing,and the yield strength and tensile strength were 473 MPa and 556 MPa,respectively.When there was ferrite in the hot rolling microstructure,the spheroidized cementite particles aggregated,the grain size increased and the strength of the plates decreased.When the microstructure of the experimental plate after hot rolling was bainite,the diffusion distance of carbon atoms in the spheroidizing process was shortened,and a good spheroidized microstructure was obtained.The yield strength and tensile strength after spheroidization annealing were 553 MPa and 638 MPa,respectively.A comparative analysis was conducted on the spheroidization annealing effects of plates with different hot rolled microstructures.It was observed that controlling the final cooling temperature at about 510 C during hot rolling resulted in a bainite microstructure whih facilitated obtaining a favorable spheroidized annealing microstructure compared to lamellar pearlite or ferrite+pearlite microstructures.