铬对超高强冷轧双相钢相变和组织性能的影响

实验室成功试制C-Si-Mn-Cr-Nb系和C-Si-Mn-Nb系超高强双相钢,利用热膨胀仪研究了铬对超高强双相钢相变规律的影响,利用光学显微镜、SEM以及拉伸试验对双相钢的微观组织和力学性能进行检测。实验结果表明:铬使实验用钢的CCT曲线整体右移,抑制铁素体和珠光体的生成,对铁素体开始转变温度影响不大,升高铁素体的终止转变温度,降低贝氏体转变温度,提高奥氏体的淬透性,在相同的冷速条件下,铬的加入更容易得到铁素体+马氏体的双相组织;合金元素铬显著改善双相钢的显微组织,细化晶粒,双相钢的屈服强度从510 MPa升高到535 MPa,抗拉强度从1 080 MPa升高到1 145 MPa,抗拉强度的增幅高于屈服强度,在抗拉强度提高的同时,伸长率升高。

Effect of Cr on Transformation, Microstructure and Properties of Ultra-High Strength Cold-Rolled Dual Phase Steel

Abstract: C-Si-Mn-Cr-Nb and C-Si-Mn-Nb Ultra-high strength dual phase steels were piloted in laboratory. The effect of Cr on transformation of high strength cold rolled dual phase steels was analyzed by using the thermal dilatometer. Optical microscopy, scanning electron microscopy and the tensile tests were used to characterize the microstructures and to determine the mechanical properties. The results show that, the CCT curve of tested steel which had Cr was shift to right. Cr markedly retards ferrite and pearlite transformation, and markedly reduces the finish temperature of ferrite transformation and the transformation temperature of bainite and martensite, but had less effect on the start temperature of the ferrite transformation and increased the harden-ability of the austenite. The tested steel has the F+M more easily including Cr in the same cooling rate. Cr have the well influence on the microstructure of the dual phase steel, make the grain refinement , the yield strength was increased from 510MPa to 535MPa and the tensile strength was raised from 1080MPa to 1150 MPa, With the tensile strength increasing the elongation was raised.