超声波冲击处理对S355J2W+N耐候钢对接接头疲劳性能的影响

Effect of ultrasonic impact treatment on fatigue performance of butt joint of S355J2W+N weather resistant steel

针对焊接结构中因焊趾处几何结构突变引起的应力集中,导致焊接接头疲劳强度明显降低的问题,采用最佳超声波冲击处理参数,有效地提高了S355J2W+N耐候钢对接接头疲劳性能。首先采用气体保护焊对S355J2W+N耐候钢进行焊接试验,随后对其焊缝及热影响区进行超声波冲击处理。通过疲劳试验、 X射线应力测试试验、金相试验对超声波冲击处理和未处理的S355J2W+N焊接接头疲劳性能和组织进行测试和对比分析。结果表明,超声波冲击处理后的焊接接头在循环次数为1×107条件下,疲劳强度提高87.9%;超声波冲击处理使接头熔合区表层晶粒细化并形成塑性应变层,降低了其焊趾处因几何结构突变引起的应力集中,使表层残余拉应力变为压应力,影响深度至少纵深1.5 mm,有利于改善对接接头疲劳性能。

For welding structure caused by weld toe geometry mutations in stress concentration,caused the fatigue strength of welded joint was decreased obviously.The optimum parameters of the ultrasonic impact treatment was adopted which effectively improved the S355J2W+N weathering steel fatigue performance of butt joint.First,the S355J2W+N weather-resistant steel was welded by gas shielded welding,and then ultrasonic shock treatment was carried out on the weld and thermal impact zone.Through fatigue test,stress test by X-ray method and metallographic test,the fatigue performance and microstructure of ultrasonic shock treatment and untreated S355J2W+N welded joints were tested and compared.The results showed that the fatigue strength of the welded joint after ultrasonic shock treatment increased by 87.9%under the condition of 1×107cycles.Ultrasonic impact treatment made the joint fusion zone surface grain refinement and plastic strain layer formation,reduced the weld edge stress concentration caused by geometric structure mutation.It made the surface residual tensile stress to compressive stress,the influence depth of at least 1.5 mm depth,helped improve fatigue performance of butt joint.