一种宽回火时间窗口的10.9级螺栓钢组织和性能

Microstructure and properties of a grade 10.9 bolt steel with wide tempering time window

利用光学显微镜、扫描电镜、透射电镜、洛氏硬度等试验方法研究了一种钒微合金化Si-Mn-Cr系螺栓钢经870℃淬火+550℃不同时间回火后的微观组织、力学性能。结果表明,870℃淬火后试验钢为马氏体板条组织,经550℃分别回火40、60、80 min后,均为清晰的马氏体板条组织并伴有细小弥散的碳化物析出。当回火时间在40~80 min时,试验钢的抗拉强度在1081~1120 MPa范围内,屈服强度在993~1013 MPa范围内,断面收缩率在56.0%~56.3%范围内,力学性能稳定,试验钢的拉伸断口均有明显的缩颈现象,起裂源区均为细小韧窝伴有撕裂棱的韧性断裂,综合力学性能良好。因此研究的10.9级螺栓钢回火时间窗口宽泛,并且综合力学性能稳定,进而有利于扩大螺栓钢的使用范围。

Microstructure and mechanical properties of a vanadium microalloyed Si-Mn-Cr bolt steel after quenching at 870 ℃+tempering at 550 ℃ for different time were studied by means of optical microscope,scanning electron microscope,transmission electron microscope,and Rockwell hardness test.The results show that the microstructure of the tested steel after quenching at 870 ℃ is lath martensite,and the microstructure after tempering at 550 ℃ for 40,60 and 80 min,respectively,is clear martensie with accompaning by fine dispersed carbide precipitates.When the tempering time is 40-80 min,the tensile strength of the tested steel is 1081-1120 MPa,the yield strength is 993-1013 MPa,and the percentage reduction of area is 56.0%-56.3%,all of which are relatively stable,and the tensile fracture of the tested steel has obvious neck contraction phenomenon.The fracture source areas are all ductile fractures with small dimples and tearing edges,and the comprehensive mechanical properties are good.Therefore,the tempering time window of the 10.9 grade bolt steel is broad,and the comprehensive mechanical properties are stable,which is conducive to expanding the range of use of bolt steel.