高强钢边部开裂影响因素研究

Influence of factors on edge crack of high strength steel

基于高强钢边部开裂的应变特点,利用单拉试样的胀形试验,研究了边部加工状态、冲裁间隙及材料化学成分等对高强钢边部开裂的影响。结果表明,双相钢DP780+Z边部开裂对边部加工状态较为敏感,冲裁的加工方式易产生边部毛刺和引起边部开裂,而线切割及铣削加工能很好的避免这一现象的发生;冲裁间隙也是影响边部开裂的重要因素,不同强度的高强钢对应的合理间隙值是不同的,DP590产生边部裂纹时,最大主应变对冲裁间隙较为敏感,而对于DP780来说,产生边部裂纹时的最大主应变对冲裁间隙敏感性较差,随着冲裁间隙的增大,最大主应变未有明显变化;对双相钢DP780+Z来说,选用高屈强比的材料成分,降低两相的强度差,可有效地降低裂纹扩展的速度。

Based on the strain characteristics of edge crack of high strength steel,the edge crack of high strength steel was studied by the bulge test,some influence factors were considered,such as the state of the edge,the blanking clearance and the material composition.The result shows that the edge crack of dual phase steel DP780 ＋ Z is more sensitive to the processing state of the side part,and the punching machining method is easy to produce the edge burr and to cause the edge cracking,while the wire-electrode cutting and milling can avoid the occurrence of this phenomenon. Blanking clearance is also an important factor to influence the edge crack,the corresponding reasonable clearance value of high strength steel with different strength is different,when the DP590 has edge crack,the maximum major strain is sensitive to stamping clearance. While for DP780,the maximum major strain is less sensitive to stamping clearance,with the increase of blanking clearance,the maximum major strain has no obvious change. Dual phase steel DP780 ＋ Z with high yield-to-strength ratio can be used to reduce the strength difference between two phases,which can effectively reduce the speed of edge cracking propagation.