The microstructure and mechanical properties of the steels with different coiling temperature were studied by utilizing scanning electron microscopy (SEM) and transmission electron microscope (TEM). The results show that with the increase of coiling temperature, the tensile strength gradually decreases, while the yield strength increases first and then decreases, and the elongation increases continuously. At coiling temperature 350 ℃, the experimental steel shows the best mechanical properties with tensile strength at 1253 MPa, yield strength at 1099 MPa and the elongation of 13%, while the Charpy impact energy is 102 J at-20℃. The main reason is that when the coiling temperature is slightly lower than martensite transformation temperature (Ms), the main microstructure of the tested steel is the fine and interlocking lath bainite and martensite. This microstructure can effectively block the dislocation motion to improve the strength. The large angle grain boundary can hinder the crack growth, and the thin film M/A between the laths can increase the plasticity and toughness of the materials.%利用扫描电镜(SEM)和透射电镜(TEM)等仪器研究卷取温度对高Ti微合金热轧高强钢显微组织和力学性能的影响.研究结果表明:随着卷取温度的升高,抗拉强度不断减小,屈服强度先增加再减小,伸长率不断增大.当350℃卷取时,试验钢拥有良好的综合力学性能,即抗拉强度为1253 MPa,屈服强度为1099 MPa,伸长率为13%,-20℃冲击功为102 J.这是因为该卷取温度略低于Ms点,试验钢显微组织由大量板条贝氏体(细小且交织)、少量马氏体和针状铁素体组成,这种显微组织能有效阻碍位错运动,从而提高强度.同时大角度晶界能够阻碍裂纹扩展,再加上板间的薄膜M/A,保证了材料的塑性和韧性.
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