超声冲击处理对不同强度等级钢焊接残余应力的影响

Effect of ultrasonic impact treatment on welding residual stress of steel specimens with different strength grades

采用超声冲击处理Q390B和EQ70两种强度等级的多道焊试板,通过小孔法和X射线衍射法测试试板表面残余应力,采用轮廓法测试试板内部残余应力,对比试板焊态应力及超声冲击处理态应力。研究发现:超声冲击处理使两种强度等级试板焊缝表面残余应力由焊态拉伸应力全部转变为压缩应力,纵向应力下降幅度为800MPa左右,横向应力下降幅值约为400MPa~600MPa;超声冲击处理造成的表面压应力深度达2mm~3mm,对焊接应力的影响深度可以达到5mm~8mm;超声冲击处理对两种材料的表面应力有明显的调控作用,都可以使表面应力幅值出现大幅下降;超声冲击处理对超过5mm~8mm深度的焊接应力影响不大。

The multipass-welded specimens of Q390 B steel and EQ70 steel are treated with the ultrasonic impact treatment(UIT).The surface stresses of the specimens are measured by the hole-drilling(HD)method and the X-ray diffraction method(XRD).The internal stresses of the specimens are measured by the contour method(CM).The as-welded stresses are then compared with the after-UIT stresses.The investigated results show that UIT can transfer the as-welded tensile surface stresses to compressive stresses for specimens with different strength grades.The reduction of the longitudinal stress reaches about 800 MPa,and that of the transverse stress comes to 400 MPa~600 MPa.UIT can introduce large compressive stress in the treated surface with a depth of 2 mm~3 mm and has effects on the welding stress up to a depth of 5 mm~8 mm.It has not significant effects on the surface stress reduction amplitude for welded specimen with different strength grades,in addition,it has no significant effects on the magnitude and distributions of the internal stresses in the specimens beyond the depth of 5 mm~8 mm.