1000 MPa级热轧双相钢不同弛豫时间的热处理工艺

基于汽车轻量化原则,应用热轧+超快冷+弛豫热处理一体化工艺技术得到了1000 MPa级热轧双相钢,并研究了弛豫时间对试验钢组织和性能的影响。结果表明,随着弛豫时间的增加,试验钢中铁素体和马氏体组织的带状分布越明显,其中铁素体晶粒尺寸与体积分数均增加,屈服强度降低,伸长率增加;抗拉强度先增加后降低,是马氏体体积分数和碳含量综合作用的结果;屈强比减小,n值增加。弛豫时间影响两相的体积分数、晶粒大小和内部亚结构。弛豫时间为10 s时,试验钢的抗拉强度为1025 MPa、伸长率为17.5%、屈强比为0.48、n值为0.13,具有最优综合力学性能;综合考虑力学性能和生产效率,试验钢在该工艺技术条件下合适的弛豫时间为7~10 s。

Heat treatment process of 1000 MPa hot-rolled dual phase steel with different relaxation time

Based on the principle of automobile lightweight, a 1000 MPa hot-rolled dual phase steel was prepared by hot rolling, ultra fast cooling and relaxation heat treatment, and effect of relaxation time on microstructure and mechanical properties of the tested steel was studied. The results show that with the increase of relaxation time, the banded distribution of ferrite and martensite of the tested steel is more obvious, the ferrite grain size and volume fraction increase, the yield strength decreases and the elongation increases. The tensile strength first increases and then decreases, which is the result of the combined action of martensite volume fraction and carbon content. The yield ratio decreases, and the n value increases. The relaxation time affects the volume fraction, grain size and internal substructure of dual phase. When the relaxation time is 10 s, tensile strength, elongation, yield ratio and n value of the tested steel are 1025 MPa, 17.5%, 0.48 and 0.13, respectively, under which shows the best comprehensive properties. Considering the mechanical properties and production efficiency, the appropriate relaxation time of the tested steel under the process conditions is 7-10 s.