Q690厚板对接焊残余应力评估及其对焊接接头断裂性能的影响

Evaluation of residual stress and its influence on fracture performance of Q690 thick plate butt welded joint

[目的]旨在研究高强钢厚板多层多道焊的复杂焊接残余应力,评估其对焊接接头断裂性能的影响。[方法]以75 mm厚Q690高强钢板为研究对象,制定多层多道对接焊工艺,完成对接接头的焊接,使用轮廓法获得中剖面的纵向残余应力,基于自主开发的高效热−弹−塑性有限元计算方法,再现厚板多层多道焊的热循环、微观组织演变等现象,将单轴拉伸试验与GTN损伤模型相结合,提出Q690高强钢板的GTN模型参数,分析金属母材及焊接接头试样的断裂特性和应力−应变曲线。[结果]采用所提方法预测的厚板对接接头熔池形状、金相体积分数都与试验测量基本吻合;考虑焊接固态相变和高强钢轧制初始应力的力学分析,得到的焊接残余应力与试验结果高度一致,并得到了横向残余应力分布;考虑焊接微观缺陷及横向残余应力,阐明了残余应力影响焊接接头断裂性能的力学机理。[结论]相关研究可为高强钢厚板焊接结构残余应力及断裂性能评估提供借鉴和指导。

[Objective]This study aims to investigate the complex welding residual stress of high-strength steel thick plate with multi-pass welding,and examines the influence of such stress on the fracture behavior of welded joints.[Methods]Taking 75 mm thick Q690 high-strength steel thick plate as the research object,multi-pass butt welding and a corresponding welding experiment are carried out,and the longitudinal residual stress on the middle cross section is then measured by the contour method after cooling.Based on effective thermal elastic-plastic FE computation,properties such as the thermal cycle and microstructure evolution during the multi-pass welding of thick steel plate are represented.The uniaxial tension test and GTN damage model are combined to obtain the parameters of GTN model for Q690 high-strength steel plate,which are then used to examine the fracture behavior and stress-strain curves of the base metal and welded joint specimens.[Results]The predicted shape of the weld pool and the content of the metallographic phase show good agreement with the measured data.After considering the solid phase transformation during welding and initial stress due to rolling,the longitudinal and transverse residual stresses are in good agreement with the measured results.Moreover,the fracture behavior of the welded joints is also investigated while considering welding micro defects and transverse residual stress,and the mechanical mechanism of welding residual stress is clarified.[Conclusion]The results of this study can provide valuable references for the evaluation of the residual stress and fracture behavior of welded joints in high-strength steel thick plate.