不同预制孔加工方式CR550/980DP双相钢扩孔性能

Hole Expansion Performance of CR550/980DP under Prefabricated Holes Cutted by Various Processes

采用Zwick-Roell/Z100拉力试验机、SIGMA-HD场发射型扫描电镜等研究手段研究不同加工形式的预制孔对CR550/980DP双相钢扩孔性能的影响。结果表明:线切割预制孔扩孔性能最优,激光切割其次,冲孔最差。不同加工方式预制孔缘附近组织与基体组织间硬度差异是导致扩孔性能不同的主要原因。冲孔预制孔缘附近塑性变形明显;激光切割预制孔缘附近组织经历了类似于淬火工艺热处理的过程,组织中马氏体含量增加但淬硬程度有限,这主要是材料中碳含量较少的缘故。冲孔扩孔试样裂纹尖端塑性变形不明显,断裂类型为脆性断裂;激光切割扩孔试样裂纹尖端塑性变形明显,断裂类型为韧性断裂。

The influencing factors of CR550/980DP hole-expansion performance were studied by means of Zwick-Roell/Z100 ensile testing machine and SIGMA-HD field emission scanning electron microscope,which were caused by prefabricated holes using different processes.The results show that the wire-electrode cutting prefabricated hole resents the optimal performance,laser cutting is secondary,punching is the worst.The main reason for the difference in hole-expansion performance is the micro-hardness discrepancy between the edge and matrix,which owing to the prefabricated holes cut by different processes.The obvious plastic deformation is occurred on the punching prefabricated hole near the edge,while the microstructure in the laser cutting prefabricated hole near the edge goes through the heat-treatment similar to the quenching process,which leads to the increase of martensite.And its micro-hardness is not so high due to the lack of carbon in the dual phase steel.The crack tip on the punching hole-expansion specimens appeared the unconspicuous plastic deformation and brittle fracture is found,while the crack tip on the laser cutting hole-expansion specimens observed the obvious plasticity deformation and its mode of fracture is ductile.