22MnB5钢热变形诱发相变及其对组织性能的影响

Hot Deformation Induced Phase Transformation of 22MnB5 Steel and Its Influence on Microstructure and Property

摘要:

利用Gleeble 3500热力试验机对22MnB5钢板在温度900~600 ℃、应变速率0.01~0.40 s-1条件下进行热拉伸，研究变形过程中的应力应变行为，并结合光镜、扫描电镜、X射线衍射仪和硬度测试仪分析试样的微观组织，探究热变形对相变的影响.结果表明：当温度为800 ℃，应变速率达到0.10 s-1后，变形将诱发铁素体相变；在700 ℃下热变形促进铁素体相变；在600 ℃下热变形将诱发贝氏体相变.在800~600 ℃热变形过程中，由于形变应变诱发或促进了奥氏体转变，22MnB5钢的变形抗力降低、延性提高，从而改善了成型性能；相应冲压件的强度在900~1 000 MPa.

关键词:硼钢; 热变形; 相变; 变形温度; 应变速率

Abstract:

Thermal tensile tests of 22MnB5 steel sheet were conducted with Gleeble 3500 thermomechanical simulator at temperatures of 900 ℃ to 600 ℃ and strain rates of 0.01 s-1 to 0.40 s-1, then stressstrain behaviors during deformation were analyzed. The microstructure was investigated by optical microscopy, scanning electron microscopy and Xray diffraction analyzer. The results show that, when the specimen is deformed at 800 ℃, the deformation induces ferrite transformation as the strain rate reaches 0.10 s-1; transformation to ferrite is promoted by the deformation at 700 ℃; and bainite, instead of ferrite, is induced accounting for deformation at 600 ℃. During the hot deformation process at the temperature range of 800~600 ℃, the decrease of deformation resistance and the increase of ductility lead to the improvement of formability for 22MnB5 steel, since the strain induces or promotes austenite transformation to other phases. Meanwhile, tensile strengthes are about 900~1 000 MPa.

Key words:boron steel; hot deforming; phase transformation; deformation temperature; strain rate