回火工艺对TMCP低合金海工钢Nb微合金化效果的影响

Influence of tempering process on Nb microalloying effect of TMCP low-alloy offshore engineering steel

采用光学显微镜、扫描电镜、透射电镜和万能拉伸试验机等研究了含Nb和无Nb两种成分低合金海工钢经控轧控冷(TMCP)及回火工艺处理后的组织与性能,研究了回火工艺对Nb微合金化效果的影响。结果表明:经TMCP工艺和回火工艺处理后,含Nb钢平均屈服强度分别为448 MPa和491 MPa,-40℃冲击吸收能量分别为272 J和289 J,而无Nb钢平均屈服强度分别为379 MPa和470 MPa,-40℃冲击吸收能量分别为118 J和300 J。回火后,无Nb钢屈服强度提高了91 MPa,而冲击韧性更是提高了1.5倍,与含Nb钢强度和韧性的差距均得到明显缩小。因此,回火工艺对无Nb钢强韧性的提高效果更明显,而对含Nb钢强韧性的提高较小。

Microstructure and properties of low-alloy offshore engineering steel with and without Nb after thermo-mechanically controlled processing(TMCP)and tempering treatment were studied by means of optical microscope,scanning electron microscopy,transmission electron microscopy and universal tensile testing machine,and the influence of tempering process on Nb microalloying effect was studied.The results show that after TMCP and tempering treatment,the average yield strength of the Nb-containing steel is 448 MPa and 491 MPa respectively,the impact absorbed energy at-40℃is 272 J and 289 J respectively,while the average yield strength of the Nb-free steel is 379 MPa and 470 MPa respectively,and the impact absorbed energy at-40℃is 118 J and 300 J respectively.After tempering,the yield strength of the Nb-free steel is increased by 91 MPa,and the impact toughness is increased by 1.5 times.The gap between the strength and toughness of the Nb-free steel and Nb-containing steel is significantly reduced.Therefore,the tempering process is more effective in improving the strength and toughness of the Nb-free steel,but less effective in improving the strength and toughness of the Nb-containing steel.