冷轧超低碳BH钢连续退火及平整工艺

Continuous annealing and temper rolling process of ultra-low-carbon cold rolled bake-hardening steel

研究了连续退火均热段温度和平整工艺对冷轧超低碳BH钢的组织和力学性能的影响规律。结果表明,超低碳BH钢在740～850℃之间均能完成再结晶退火,且随着均热段温度的升高,BH钢的屈服强度和抗拉强度单调下降,n值单调上升;伸长率和r值先上升后下降,并同在820℃左右达到峰值;显微硬度也呈单调下降趋势。平整伸长率由0向1.8%增加过程中,钢板的强度呈下抛物线形变化;低于0.8%时会产生屈服平台;高于1.5%时,加工硬化加剧导致强度快速上升,屈服强度可在1.2%～1.5%之间达到最低值。

Effect of soaking temperature during continuous annealing and temper rolling on mechanical properties of ultra-low-carbon cold rolled bake-hardening steel was studied by using a hot-dip process simulator.The results show that re-crystallization occurs in the steel during soaking at 740~850 ℃.As the temperature increasing,yield strength,tension strength and micro-hardness of the BH steel monotonically decrease and its n value monotonically increases.At the same time,elongation and r value of the BH steel increases firstly to the peak value at 820 ℃ and then decreases.The steel strength varies with the temper rolling elongation.When the temper elongation varies from 0 % to 1.8 %,strength of the BH steel decreases firstly with the increase of the temper elongation to 1.2 % and then increases.The stress-strain curve exhibits a yield point elongation for the temper elongation less than 0.8%,and when the temper elongation more than 1.5 %,the strength increases sharply due to strain-hardening.The suggested values of temper elongation are 1.2 %~1.5 %,for which the lower strength and optimal formability of the BH steel can be obtained.