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研究了C--Mn--Mo--Cu--Nb--Ti--B系低碳微合金钢915℃淬火和490～640℃回火的调质工艺对钢的组织及力学性能的影响.用扫描电镜和透射电镜对实验钢的组织、析出物形态和分布以及断口形貌进行观察,采用X射线衍射仪分析钢中残余奥氏体的体积分数.结果表明:调质后,实验钢获得贝氏体、少量马氏体及残余奥氏体复相组织,贝氏体板条宽度只有250 nm,残余奥氏体的体积分数随着回火温度的升高而降低,经淬火与520℃回火后残余奥氏体的体积分数为2.1%.调质后析出物的数量激增,6～15 nm的析出物占70%以上.实验钢经过915℃淬火与520℃回火后,其屈服强度达到915 MPa,抗拉强度990 MPa,-40℃冲击功为95 J.细小的析出物及窄的板条提高了钢的强度.板条间有残余奥氏体存在,改善了实验钢的韧性.
The effects of quenching and tempering at 915 ℃ and tempering at 490 ~ 640 ℃ on the microstructure and mechanical properties of C - Mn - Mo - Cu - Nb - Ti - B low carbon microalloyed steel The morphology, distribution and fracture morphology of experimental steel were observed by SEM and TEM, and the volume fraction of retained austenite in steel was analyzed by X-ray diffractometer.The results showed that after quenching and tempering, the experimental steel Bainite, a small amount of martensite and residual austenite complex phase, the width of bainite lath is only 250 nm, the volume fraction of retained austenite decreases with increasing tempering temperature, quenched with 520 After tempering, the volume fraction of retained austenite is 2.1%, the amount of precipitates after quenching and tempering increases sharply, and the precipitates at 6-15 nm account for more than 70% .The experimental steels after quenching at 915 ℃ and tempering at 520 ℃ The yield strength reaches 915 MPa, the tensile strength is 990 MPa, and the impact energy at -40 ° C is 95 J. The small precipitates and the narrow slats increase the strength of the steel, and the residual austenite exists between the slats, improving the experimental steel Toughness.