600 MPa级元宝梁用钢冲压开裂原因分析

Analysis on stamping crack of 600 MPa grade crossbeam steel

为解决元宝梁冲压开裂问题,用OM和SEM等仪器与ABAQUS有限元仿真软件对600 MPa级元宝梁用钢冲压开裂原因进行了分析.结果表明:600 MPa级元宝梁用钢化学成分、力学性能与冷弯性能均满足标准要求,金相组织为准多边形铁素体与少量珠光体的混合组织,不存在带状组织;开裂件断口形貌呈现出明显鱼骨状形貌,钢板中心分层,两侧分布起源于中心分层并沿同一方向扩展的三角形台阶状断口,不同形貌断口均属于韧性断裂,而断口整体形貌显示材料在断裂前没有发生缩颈过程.利用ABAQUS软件对"先冲压再压边工艺"与"先压边再冲压工艺"两种工况进行有限元分析,结果显示:先冲压再压边工艺边部应力集中更严重,边部节点应力超过了材料抗拉强度从而导致撕裂现象的发生;由"先冲压再压边工艺"改为"先压边再冲压工艺"后元宝梁冲压开裂率由50%降至0,材料边部变形均匀,未见缩颈与开裂现象发生.

In order to solve the problem of stamping cracking of crossbeam steel,the reasons of stamping cracking of 600 MPa grade crossbeam steel were revealed by using optical microscopy（OM）,scanning electron microscopy（SEM） and ABAQUS finite element simulation software. The results show that the chemical composition,mechanical properties and cold bending properties of 600 MPa grade crossbeam steel can meet the standard requirements,and the microstructure is composed of pseudo-polygonal ferrite and a small amount of pearlite,without banded structure. The fracture surface showed a fishbone-like morphology.The center of the steel plate was stratified. The triangular step-like fracture originated from the central crack and distributed by the two sides which extended in the same direction. The fracture of different morphologies exhibited a ductile mode. The whole fracture morphology suggested that no necking occurred before fracture.Two kinds of stamping working conditions were simulated by ABAQUS software. The results showed that the process of first stamping and then blank pressing induced great stress concentration in the edge of plate,and the node stress of plate edge exceeded the tensile strength,leading to the tearing phenomenon. The cracking rate of crossbeam was reduced from 50% to 0 when the stamping process changed from first stamping and then blank pressing to first blank pressing and then stamping. At this moment the edge deformation of the material was uniform,without any shrinkage and cracking.