TRIP800钢激光焊焊接接头的疲劳性能

Fatigue Performance of TRIP800 Steel Laser-welded Joint

对TRIP800钢以焊接速度为7mm/s,焊接功率为570 W,离焦量为-1mm进行激光焊接,焊接后的工件采用加载频率为8Hz、R=0的拉-拉循环加载的条件下,测定TRIP800钢激光焊后疲劳S-N曲线.得出其疲劳强度极限是σ-1=560 Mpa;通过对疲劳断口的扫描分析发现TRIP800钢板激光焊后宏观疲劳断口上有明显的三个区域,分别是疲劳源区、疲劳区和瞬断区.疲劳源开始于表面下的第二相处和表面的应力集中处,裂纹的扩展区为微孔聚集型断裂最终瞬断区发生纯剪切断裂.

For TRIP800 steel,the welding speed is 7 mm/s,the welding power is 570 W,and the defocusing amount is-1mm for laser welding.The workpiece after welding is loaded with the loading frequency of 8 Hz and R=0,the fatigue SN curve of TRIP800 steel after laser welding is determined.It is concluded that the fatigue strength limit is σ-1=560 Mpa.Through the scanning analysis of fatigue fracture,it is found that there are three obvious areas on the macro-fracture of TRIP800 steel plate after laser welding,which are fatigue source zone,fatigue zone and instantaneous fault zone.The fatigue source begins at the second phase below the surface and the stress concentration at the surface.The extended region of the crack is a pure shear fracture in the final instantaneous break region of the microporous aggregate fracture.