终轧温度对超高强热轧双相钢组织性能的影响

摘要：基于汽车轻量化原则，利用热轧大压下+超快冷+弛豫制备得到1200MPa级热轧双相钢（DP），借助OM、SEM、TEM和室温拉伸等试验手段，研究了终轧温度对试验钢组织性能的影响。研究表明：随着终轧温度增加，铁素体体积分数和晶粒尺寸逐渐减小，马氏体的体积分数逐渐增加；抗拉强度增加，伸长率减小，强塑积减小，屈强比最低为0.56，n值最高为0.13。终轧温度对各相的体积分数、形貌、分布和析出行为有影响，组织中细小的铁素体晶粒、细化的马氏体板条束和弥散的析出相提高了材料的均匀变形能力，综合考虑轧机负荷、生产效率和力学性能，试验钢在该工艺条件下合适的终轧温度可取810～840℃。

Effect of finishing temperature on microstructure and mechanical properties of ultra high strength hot rolled dual phase steel

Based on the principle of automotive lightweight, the 1200MPa grade hot rolled dual phase steel was prepared by hot rolling with large reduction, ultra fast cooling and relaxation. The effect of finishing temperature on the microstructure and properties of the steel was studied by means of OM, SEM, TEM and tensile test. The results show that with the increase in finishing temperature, ferrite volume fraction, ferrite grain size, elongation and product of strength and elongation decrease while martensite volume fraction and tensile strength increase. The lowest yield strength ratio is 056, and the highest n value is 013. The volume fraction, morphology, distribution and precipitation behavior of the phases are affected by finishing temperature. The fine ferrite grains, fine martensitic lath bundles and dispersed precipitates in the microstructure improve the uniform deformation ability of the material. Considering the mill load, production efficiency and mechanical properties, the reasonable finishing temperature of the test steel should be 810-840℃ under current process conditions.