HC340LA钢冲压“桔皮”缺陷成因及措施

分析了340 MPa级冷轧低合金高强度钢“桔皮”缺陷钢板和正常钢板的微观组织结构和力学性能。结果表明,缺陷钢板的应力-应变曲线屈服点伸长率达到了3.73%,屈服延伸过大导致了所冲压的前风窗横梁连接板表面产生“桔皮”缺陷。在实验室采用对钢板预拉伸的方法模拟钢板工业化生产的平整与拉伸矫直工艺,随着预拉伸量的增加,试验样屈服平台的长度减少,当预拉伸量超过1.8%时,试验样的屈服平台消失。微观组织进一步分析显示,退火温度高导致钢板晶粒粗大和晶粒取向异常是冲压钢板 “桔皮”缺陷产生的根源。在连续退火工艺环节中合理控制平整和拉伸矫直工艺可以消除或者缩短试验钢屈服平台长度,并避免冲压件表面“桔皮”缺陷发生。

Causes and improvement measures of stamping orange peel defects of HC340LA steels

The microstructure and mechanical properties of the 340 MPa-grade cold-rolled high strength low alloy (HSLA) steels with and without orange peel defects were analyzed. The results show that the yield point elongation of the stress-strain curve of the defective steel plate reaches 3.73%. The yield extension is too large, which leads to the orange peel defect on the surface of the stamped front windshield beam connecting plate. In the laboratory, the technique of the pre-stretching of the steel sheets is used to simulate the skin pass and stretching straight process for the industrial production of the steel sheets. With the increasing the pre-deformation amount, the length of the yield platform of the sample decreases, and when the pre-tension amount exceeds 1.8%, the yielding platform of the sample disappears. Further analysis of the microstructure reveals that the high annealing temperature leads to the coarse grain size and the abnormal grain orientation, which is the root cause of the "orange peel" defect of the stamped steel plate. In the annealing process, the reasonable control of leveling and tension straightening can eliminate or shorten the length of the yield platform of the test steel and avoid the occurrence of orange peel defects on the stamping parts.