预变形对X90管线钢显微组织和力学性能的影响

采用拉伸试验、冲击试验、光学显微镜(OM)、扫描电镜(SEM)、显微硬度测试仪等研究了0.5%~6%预拉伸变形对X90管线钢显微组织及力学性能的影响。结果表明:随着预拉伸变形量的增加,X90管线钢晶粒增大,位错塞积导致强度增加,均匀延伸率下降,呈现典型的加工硬化特点,抗拉强度的增幅要小于屈服强度,屈强比增大;随着变形量的增加冲击吸收功逐渐由291J减小至235J,冲击试样断口的韧窝减小,伴随第二相粒子析出;显微硬度中间层较边缘区增加少,预拉伸在6%时边缘显微硬度为325HV。X90管线钢的预拉伸在4%以内能保证管线钢的正常服役。

Effect of Pre-deformation on Microstructures and Mechanical Properties of X90 Pipeline Steel

The effects of microstructure and properties of 0.5%-6% pre-deformation on X90 highly defor-mable pipeline steel were investigated and analyzed by means of tensile test, impact test, optical microscopy (OM), scanning electron microscopy (SEM), and microhardness test. The experimental results demonstrated that with the increasing of pre-tension deformation, the grain size increased. Stacked dislocations resulted in the increase of strength and the decrease of uniform elongation, which presented a typical characteristic of work hardening. The tensile strength increased less than the yield strength, and the R_t/R_m increased. With the increase of the deformation, impact absorbing energy decreased from 291 J to 235 J gradually. Scanning electron microscopy showed that dimples decreased and a second phase emerged. The microhardness of middle layer increased less than the amount of edge area, and the microhardness attained 325HV with the pre-tension deformation of 6% in the edge. X90 pipeline steel whose pre-tension deformation was less than 4% could ensure normal service.