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以TMCP(Thermo Mechanical Control Process)实验获得的低成本热轧FB(Ferrite/Bainite)钢为研究对象,通过扩孔实验评价FB钢板的延伸凸缘性能,分析显微组织对延伸凸缘性能的影响,并对扩孔过程中FB钢的裂纹扩展行为进行探讨。结果表明:当贝氏体体积分数在19~25%时,热轧FB钢的抗拉强度不低于551 MPa、扩孔率不小于77%,力学性能和延伸凸缘性能综合起来比较良好;裂纹通过孔洞和微裂纹相互扩展、连接的方式进行;当裂纹扩展到硬相的贝氏体时,裂纹沿着铁素体和贝氏体的相界面绕过贝氏体,并切断铁素体继续扩展。
The low-cost hot-rolled Ferrite / Bainite (TMCP) steel obtained from the TMCP (Thermo Mechanical Control Process) experiment was taken as the research object. The extended flange performance of the FB steel plate was evaluated by the expanding hole test and the influence of the microstructure on the performance of the extended flange , And explored the crack propagation behavior of FB steel during reaming. The results show that when the volume fraction of bainite is between 19 and 25%, the tensile strength of hot rolled FB steel is not less than 551 MPa and the hole expanding ratio is not less than 77%. The mechanical properties and stretch flange performance are relatively good. The cracks propagate through holes and microcracks to each other and join together. When the crack propagates to the bainite in hard phase, the crack circumvents the bainite along the phase interface between ferrite and bainite and cuts off the ferrite Continue to expand.