锻压技术

预应变对汽车双相钢材料成形性的影响

英文标题：Influence of pre-strain on formability of dual-phase steel material for automobile

作者：乔书杰张晓莹

分类号：TF76; TG142.1

出版年,卷(期):页码：2020,45(11):181-186

摘要：

双相钢在成形过程中的相变情况复杂，单独采用普通拉伸性能对其成形性进行评价的误差较大。选取DP780双相钢，根据实际的生产参数和实验条件，采用单向拉伸过程预应变的方式，对单轴拉伸试样实施不同大小的预应变（0%，5%，10%和15%），再进行拉伸实验，直至试样断裂失效，分别对预拉伸后材料的力学性能和加工硬化进行评价。结果可知：DP780双相钢具有良好的抗拉强度、高加工硬化指数和低屈强比的特征，但塑性较低，伸长率仅为20.7%；随着预应变的增大，屈服强度和抗拉强度均相应增大，但是抗拉强度的变化较小，预应变主要影响了DP780双相钢的伸长率；经过预拉伸的试样在继续拉伸的过程中，加工硬化指数n值在拉伸开始阶段降低至最小值后，随着拉伸的继续，n值缓慢增大，这与未经过预拉伸试样的n值的变化规律明显不同，预应变后DP780双相钢在拉伸过程中的加工硬化主要表现在大应变区。

The phase transformation of dual-phase steel is complicated during the forming process, and the error in evaluating its formability by ordinary tensile properties alone is relatively large. Therefore, for DP780 dual-phase steel, according to the actual production parameters and experimental conditions, different pre-strains (0%, 5%, 10% and 15%) were applied to uniaxial tensile samples, and the tensile tests were conducted until the samples broke. Then, the mechanical properties and work hardening of materials after pre-stretching were evaluated. The results show that DP780 dual-phase steel has the characteristics of good tensile strength, high work hardening index and low yield ratio, but the plasticity is low, and the elongation is only 20.7%. With the increasing of pre-strain, both yield strength and tensile strength increase correspondingly, but the change of tensile strength is small, and the pre-strain mainly affects the elongation of DP780 dual-phase steel. After the pre-stretched sample continues to be stretched, the value of work hardening index n decreases to the minimum value at the beginning of stretch. With the stretch continues, the n value slowly increases, which is obviously different from that of the tensile specimen without pre-stretching. Furthermore, the work hardening of DP780 dual-phase steel after pre-strain is mainly manifested in the large strain area.

基金项目：

教育部产学协同育人项目（201802048105）

乔书杰（1983-），女，硕士，讲师 E-mail：njlgdxhjy@163.com

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