经济型铁素体/贝氏体高扩孔钢的组织与性能

 通过TMCP工艺实验，研究了Si、Mn含量对低碳Si Mn钢显微组织、力学及成形性能的影响，探讨了铁素体/贝氏体双相钢(FB钢)在扩孔过程中的裂纹形成及扩展行为。研究结果表明，增加Si含量，实验钢中等轴铁素体的体积分数增加，扩孔性能得到改善；而增加Mn含量，实验钢的强度和韧性显著提高，但塑性和扩孔性能有所下降。FB钢中的裂纹扩展主要是以微孔聚集机制进行，当遇到贝氏体时，裂纹通过铁素体 贝氏体相界面并剪断铁素体进行扩展。合理选择Si、Mn含量和TMCP工艺参数，可以获得690 MPa级的经济型热轧FB高扩孔钢，扩孔率达到了95%，综合性能较好。

Microstructures and Properties of Ferrite/Bainite Dual-Phase Steels With High Hole-Expanding Ratio

The effects of Si and Mn contents on microstructure, mechanical properties and formability of low carbon Si Mn steels were studied, and the crack propagation of ferrite/bainite dual phase steel was also investigated. The results showed that the increase in Si content increases the volume fraction of equiaxed ferrite. However, the increase in Mn content increases both strength and ductility, but decreases elongation and hole expanding ratio. The crack of ferrite/bainite dual phase steel is formed by the mode of microvoid coalescence. When a microcrack meets the bainite,it mostly propagates along the phase interface between ferrite and bainite and by cutting off ferrite grains. The hot rolled ferrite/bainite dual phase steel, which has a hole expanding ratio of 95% and good property combination, could be produced by designing proper contents of Si and Mn as well as parameters of TMCP.