超高强度弹簧钢冷变形性能及其仿真模拟

Cold deformation performance and its simulation of ultra-high strength spring steel

针对60Si2CrVAT超高强度弹簧钢实际冷卷成形工况,采用准静态拉伸试验和不同微观表征手段研究了经Q&T (Quenching&Tempering)和Q-I-Q-T(Quenching-Isthothermal-Quenching-Tempering)工艺热处理后试验钢的组织形貌及冷变形前后力学性能的差异,并利用Deform-3D有限元数值模拟软件分析了2种工艺参数下的弹簧钢在冷卷成形过程中的应力、应变等场量参数的变化特征,预测了其冷卷成形过程中的断裂损伤概率。结果表明,Q-I-Q-T工艺复相组织弹簧钢的塑性更好,冷变形后的断面收缩率和伸长率比Q&T工艺马氏体中温回火组织弹簧钢分别高出了65%和66%。模拟结果显示,不同组织状态下的超高强度弹簧钢在卷制过程中的等效应力和等效应变分布规律近似,但Q-I-Q-T工艺复相组织弹簧钢在卷制过程中产生的等效应力和等效应变值更小,产生断裂的概率更低。

According to the actual cold-coiling process of ultra-high strength spring steel, 60 Si2 CrVAT, the microstructure and the mechanical properties of the tested steel after Quenching&Tempering(Q&T) and Quenching-Isthothermal-Quenching-Tempering(Q-I-Q-T) heat treatment processes were studied by quasi-static tensile experiments and different micro-characterization methods. Then the Deform-3 D finite element numerical simulation software was used to simulate the variation characteristics of the field parameters such as the stress and the strain during cold-coiling process under two process parameters, and to predict the fracture damage probability during the process. Results of tensile test show that under the same strength conditions, the plasticity of the Q-I-Q-T treated spring steel with multiphase microstructure is better than that of the Q&T treated spring steel with medium temperature tempered martensite in which percentage reduction of area and the elongation increase 65% and 66% respectively. Results of simulation show that the change law of the equivalent stress and the equivalent strain is similar for the tested steel with two different microstructures during cold coiling process, but the Q-I-Q-T treated spring steel has lower values of the equivalent stress and the equivalent strain during the process, and has lower probability of breakage.