Q&P工艺对22MnB5钢微观组织及力学性能的影响

Effect of Q&P process on microstructure and mechanical properties of 22MnB5 steel

利用光学显微镜、拉伸试验机、扫描电镜、XRD和EBSD等手段对22MnB5钢的微观组织及力学性能进行了表征,并重点分析了一步法Q&P工艺处理后的22MnB5钢中残留奥氏体含量及残留奥氏体中碳含量与力学性能的关系。结果表明:采用一步法Q&P工艺,可以获得抗拉强度超过1400 MPa,伸长率超过15%的超高强度22MnB5钢板。随着淬火温度从240℃升高至300℃,22MnB5钢的组织由马氏体转变为马氏体+残留奥氏体复相组织,试样中的残留奥氏体含量逐渐增加。相同配分温度延长配分时间,残留奥氏体含量呈现先增加后降低趋势。不同热处理工艺下残留奥氏体中的平均碳含量为1.49wt%。采用一步法Q&P热处理工艺可以使残留奥氏体中富集碳,提高残留奥氏体稳定性,强塑积可以达到22.14 GPa獉%。

Microstructure and mechanical properties of 22MnB5 steel were characterized by means of optical microscope(OM),universal tensile testing machine,scanning electron microscope(SEM),X-ray diffraction(XRD)and electron backscattered diffraction(EBSD).The relationship between the volume fraction of retained austenite,the carbon in retained austenite and the mechanical properties of 22MnB5 steel treated by one-step Q&P process were analyzed.The results show that an ultra-high-strength 22MnB5 steel sheet with tensile strength over 1400 MPa and elongation over 15%can be obtained using the one-step Q&P process.As the quenching temperature is increased from 240℃to 300℃,the microstructure of 22MnB5 steel can be changed from martensite to martensite+retained austenite complex,and the volume fraction of retained austenite in the specimen is increased gradually.With extending partitioning time at the same partitioning temperature,the volume fraction of retained austenite increases first and then decreases.The average carbon content in retained austenite under different heat treatment processes is 1.49wt%.The one-step Q&P heat treatment process can enrich carbon in the retained austenite,improve the stability of the retained austenite,and the product of strength and elongation can reach 22.14 GPa·%.