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    冷轧压下率对退火态Cr-Mo系深冲双相钢组织与性能的影响

    Effect of Cold Rolling Reduction Rate on Microstructure and Properties of Annealed Cr-Mo Dual-Phase Deep Drawing Steel

    • 摘要: 在不同压下率(70%,75%,80%)下对4.00 mm厚热轧态Cr-Mo系深冲双相钢进行冷轧,再在860 ℃下保温3 min进行退火处理,研究了冷轧压下率对试验钢组织、拉伸性能和深冲成形性能的影响。结果表明:随着冷轧压下率增加,试验钢中铁素体晶粒细化,马氏体含量增加,γ织构〈111〉//ND(ND为轧制面法向)取向密度先降后升,γ织构分布由70%冷轧压下率时的集中变得分散。当冷轧压下率不大于75%时,试验钢中η织构554〈225〉与ε织构332〈113〉的强度不低于热轧态试验钢,说明不大于75%压下率的冷轧变形有助于形成与维持有利于深冲成形性能的织构。随着冷轧压下率增加,试验钢的抗拉强度提高,断后伸长率、塑性应变比和加工硬化指数降低,强塑积先升后降;当冷轧压下率为75%时强塑积最佳,塑性应变比和加工硬化指数适中,此时试验钢兼具较高强度与良好深冲成形性能。

       

      Abstract: A hot-rolled Cr-Mo dual-phase deep drawing steel with thickness of 4.00 mm was cold-rolled at different reduction rates (70%, 75%, and 80%), and annealed at 860 °C for 3 min. The effect of cold rolling reduction rate on the microstructure, tensile properties, and deep drawing formability of the test steel were investigated. The results show that with the increase of cold rolling reduction rate, the ferrite grains in the test steel were refined, the martensite content increased, the orientation density of γ texture 〈111〉//ND (ND was the normal direction of rolling surface) decreased first and then increased, and the distribution of γ texture evolved from a concentrated state at 70% cold rolling reduction rate to a more dispersed state. When the cold rolling reduction rate was no more than 75%, the intensity of η texture 554〈225〉and ε texture 332〈113〉of the test steel was not lower than that of hot rolled test steel, indicating that the cold rolling deformation with the reduction rate not more than 75% was helpful to form and maintain these textures which were beneficial to deep drawing formability. With the increase of cold rolling reduction rate, the tensile strength of the annealed test steel increased, the elongation after fracture, plastic strain ratio, and strain hardening exponent decreased, and the product of strength and plasticity first increased then decreased. When the cold rolling reduction rate was 75%, the product of strength and plasticity was the highest, the plastic strain and strain hardening exponent were moderate, indicating relatively high strength and good deep drawing formability of the steel.

       

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