论文部分内容阅读
两阶段控制轧制后,采用不同的冷却路径进行冷却,研究冷却路径对Nb-Ti微合金钢组织和性能及沉淀行为的影响.结果表明,超快冷+空冷冷却路径可获得细晶组织,晶粒平均尺寸约为7.76μm,屈服强度高达425 MPa,抗拉强度高达500 MPa.超快冷+炉冷试样中存在细小的沉淀粒子,沉淀粒子尺寸主要集中在2—7 nm,而超快冷+空冷试样中只存在少量球形沉淀粒子,轧后直接空冷可获得相间沉淀粒子.不同冷却路径获得的热轧板在700℃下退火300 s后,沉淀粒子发生明显的粗化;退火处理后,超快冷+炉冷试样的晶粒平均尺寸减小为6.47μm,相对于退火前,其屈服强度和抗拉强度分别增加50和30 MPa、强度的增加主要源于细晶强化.对于含0.03%Nb(质量分数)的Nb-Ti微合金钢,由于沉淀粒子的体积分数有限,因此细晶强化效果远高于沉淀强化效果,强度的变化与晶粒尺寸的变化具有很好的对应性.另外,加工硬化指数与晶粒尺寸密切相关.随着晶粒平均尺寸的增加使加工硬化指数增加.
After the two-stage controlled rolling, different cooling paths were used for cooling to study the effect of cooling path on microstructure and properties and precipitation behavior of Nb-Ti microalloyed steel. The results show that fine-grained microstructure can be obtained by ultra- The average grain size is about 7.76μm, the yield strength is as high as 425 MPa and the tensile strength is as high as 500 MPa. There are small precipitated particles in the ultra-fast cooling and furnace cooling samples. The size of the precipitated particles mainly concentrates at 2-7 nm, There were only a few spherical precipitates in the rapid cooling and air cooling samples, and the precipitated particles could be obtained by direct air cooling after rolling.After annealing at 700 ℃ for 300 s, the precipitated particles were obviously roughened by annealing After treatment, the average grain size of the ultra-cold + furnace-cooled samples was reduced to 6.47μm, and the yield strength and tensile strength increased by 50 and 30 MPa, respectively, compared with those before annealing. The increase in strength was mainly due to the grain refinement For Nb-Ti microalloyed steels containing 0.03% Nb (mass fraction), due to the limited volume fraction of precipitated particles, the fine grain strengthening effect is much higher than the precipitation strengthening effect, and the change of strength and the change of grain size are very good In addition, plus Hardening index is closely related to grain size. With the increase in the average size of the work-hardening exponent increases.