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通过拉伸试验检测力学性能,用金相显微镜观察高强IF钢热轧态及退火态的纤维组织,并用透射电镜观察试验钢中的析出相粒子。在640℃终轧温度下,铁素体区轧制总压下率由60%升高到81%,高强热轧IF钢板的屈服强度为150～180 MPa,抗拉强度为312～321 MPa,屈强比为0.48～0.56,总伸长率为26.4%～31.2%,n值为0.22～0.23,而r值则由1.41降低到1.01,|Δr|则由0.625降低到0.133。结果表明,轧制总压下率对热轧高强IF钢的屈服强度、抗拉强度、总伸长率以及n值影响较小,但是对r值和平面各向异性值Δr的影响非常大。铁素体区轧制总压下率的增大使得高强IF钢热轧板中动态再结晶的驱动力增大,发生动态再结晶晶粒的数目增多,从而导致形变织构的减弱和后续退火再结晶驱动力的减小。同时,随着铁素体区轧制总压下率的增大,高强IF钢退火再结晶程度降低以及析出的粒子变细。
The mechanical properties were tested by tensile test, the hot-rolled and annealed fiber microstructures of high-strength IF steel were observed by optical microscope, and the precipitated particles in the test steel were observed by transmission electron microscope. Under the condition of 640 ℃ final rolling temperature, the total rolling reduction in ferrite zone increased from 60% to 81%. The yield strength of high strength hot rolled IF steel plate was 150-180 MPa and the tensile strength was 312-312 MPa. The yield ratio was 0.48-0.56, the total elongation was 26.4% -31.2%, the value of n was 0.22-0.23, while the value of r decreased from 1.41 to 1.01, || r | decreased from 0.625 to 0.133. The results show that the total rolling reduction has little effect on the yield strength, tensile strength, total elongation and n value of hot rolled high strength IF steel, but the effect of r and plane anisotropy value Δr is very large. The increase of the total rolling reduction in the ferrite zone leads to the increase of the dynamic recrystallization driving force in hot-rolled high IF steel sheets and the increase of the number of dynamic recrystallization grains, which leads to the weakened deformation texture and subsequent annealing Recrystallization driving force reduction. At the same time, with the increase of total rolling reduction in ferrite zone, the recrystallization degree of high strength IF steel decreases and the precipitated particles become finer.