高强韧中锰钢CO_(2)气体保护焊接头的疲劳性能

Fatigue Properties of CO_(2) Gas Shielded Welded Joint of High Strength and Toughness Medium-Mn Steel

采用CO_(2)气体保护焊对30 mm厚高强韧中锰钢板进行对焊试验,通过圆棒拉压疲劳试验获得中锰钢焊接接头的应力幅-寿命曲线,测定了其高周疲劳极限并观察其断口形貌。结果表明:在应力比为-1、循环次数为10~7周次条件下,中锰钢焊接接头的高周疲劳极限为353 MPa;当中锰钢焊接接头焊缝中存在明显的焊接缺陷时,疲劳裂纹萌生于微观缺陷处,而当焊缝中无焊接缺陷时,疲劳裂纹萌生于试样表面熔合线位置,疲劳裂纹扩展区表面粗糙,存在着明显的二次裂纹,瞬断区表面存在大量均匀细小的韧窝。

The butt welding test of 30 mm thick high strength and toughness medium-Mn steel plate was carried out by CO_(2) gas shielded welding.The stress amplitude-life curves of medium-Mn steel welded joints were obtained by round bar tensile and compressive fatigue test.The high cycle fatigue limit was measured and its fracture morphology was observed.The results show that the high cycle fatigue limit of medium-Mn steel welded joint was 353 MPa at stress ratio of-1 and 10~7 cycles.When obvious welding defects existed in the medium-Mn steel welded joint,the fatigue crack initiated at the microscopic defects.When no welding defects existed in the weld,the fatigue crack initiated at the fusion line of the sample surface.The surface of the fatigue crack propagation zone was rough,and obvious secondary cracks existed.There were a large number of uniform and fine dimples on the surface of the transient fracture area.