P91钢多层多道补焊残余应力数值分析

发布时间：2018-04-05 05:17

本文选题：P91钢　切入点：补焊　出处：《江苏科技大学》2017年硕士论文

【摘要】：P91钢(9Cr1Mo,V,Nb)是一种新型的马氏体耐热钢,在长期服役过程中往往会出现局部裂纹等问题。补焊具有操作简单、成本低和修复质量高等优点,从而成为修复耐热钢管缺陷的主要手段。补焊所产生的焊接残余应力往往是焊接接头裂纹产生的首要原因,因此,为确保补焊工艺的成功实施以及补焊部位的各项性能得到有效控制,必须对焊接残余应力进行全面系统的分析。传统的残余应力检测方法大多只能测量焊件表层残余应力,而焊接数值模拟能快速对不同焊接工艺参数下残余应力作出定量化描述。通过数值模拟的方法,可以全面了解影响残余应力分布规律的因素,为制定合理的焊接工艺和预测焊接残余应力提供指导依据。本文采用同质和异质两种填充材料对60mm厚P91钢进行补焊试验,采用小孔法对补焊后试件残余应力进行测量。基于热弹塑性理论,利用ANSYS建立P91钢多层多道补焊三维数值分析模型,计算了P91钢补焊的残余应力,并探究了补焊的残余应力分布特征,确定补焊的危险位置。结果表明:模拟结果和试验结果吻合较好,证明了模型的准确性。对于同质补焊,在焊接过程中,由于后序焊缝对前序焊缝具有热处理作用,每层焊缝表面的纵向应力峰值逐渐减小。焊接结束后,焊缝及其近缝区域表现出较高的纵向残余拉应力,峰值为532MPa,高于材料室温下屈服强度,离焊缝稍远处,纵向残余拉应力迅速降为压应力。横向拉应力较大值位于最后一层焊道先施焊侧,峰值为444MPa。Von-mises等效应力在起弧及熄弧端较大,达到屈服强度,沿厚度方向残余应力数值相对较小可以忽略。在坡口轮廓区域,纵向残余应力沿厚度方向呈增大趋势,峰值出现在距焊缝上表面5-7mm处,且后施焊侧坡口轮廓区域应力峰值较先焊侧大,峰值为589MPa。对于异质补焊,施焊后在焊缝及其附近区域表现出较大的纵向拉应力,应力峰值为482MPa,随着距焊缝中心距离增大,拉应力迅速降为压应力;横向拉应力较大值位于焊缝上表面两侧,峰值为333MPa;最高等效应力区位于上表面焊缝区域周围,峰值为470MPa,小于母材室温时屈服强度;在坡口轮廓区域,纵向残余应力随着补焊厚度的增加,呈先减小后增大趋势,且较大值位于焊缝的根部,峰值为424MPa。在真实服役条件下,残余应力整体有较大下降幅度,在坡口轮廓区域,纵向残余应力随着补焊厚度的增加而增大,较大应力区位于焊缝中部。
[Abstract]:P91 steel is a new type of martensite heat-resistant steel, which often has local cracks in the long service.Repair welding has the advantages of simple operation, low cost and high repair quality.Welding residual stress produced by welding is often the primary cause of welding joint cracks. Therefore, in order to ensure the successful implementation of the repair welding process and the effective control of the properties of the repair welding site,Welding residual stress must be comprehensively and systematically analyzed.Most of the traditional residual stress detection methods can only measure the residual stress in the surface layer of the welding piece, but the numerical simulation of welding can quickly quantify the residual stress under different welding process parameters.By means of numerical simulation, the factors affecting the distribution of residual stress can be fully understood, and the guidance basis for making reasonable welding process and predicting welding residual stress can be provided.In this paper, two filling materials, homogeneous and heterogeneous, are used to weld 60mm thick P91 steel, and the residual stress of post-weld specimens is measured by small hole method.Based on thermoelastic-plastic theory, a three-dimensional numerical analysis model of multi-layer and multi-pass repair welding for P91 steel was established by using ANSYS. The residual stress of P91 steel was calculated, and the distribution characteristics of residual stress were investigated, and the dangerous position of repair welding was determined.The results show that the simulation results are in good agreement with the experimental results, and the accuracy of the model is proved.For homogeneous repair welding, the longitudinal stress peak value of each layer of weld decreases gradually because of the heat treatment effect of the post-sequence weld on the pre-sequence weld during the welding process.At the end of welding, the longitudinal residual tensile stress of the weld and its near seam shows a relatively high peak value of 532 MPA, which is higher than the yield strength of the material at room temperature, and the longitudinal residual tensile stress decreases rapidly to compressive stress at a little distance from the weld.The larger transverse tensile stress is located at the first welding side of the last layer of welding pass, and the peak value of 444MPa.Von-mises equivalent stress is larger at the starting and extinguishing end of arc, reaching the yield strength, and the value of residual stress along the thickness direction is relatively small and can be neglected.In the groove contour region, the longitudinal residual stress increases along the thickness direction, and the peak value appears at 5-7mm from the upper surface of the weld, and the peak value of the stress in the groove profile region of the post-weld side is larger than that of the first welding side, and the peak value is 589 MPA.For heterogeneous welding, the longitudinal tensile stress is larger in the weld and its adjacent area after welding, the peak value of the stress is 482MPa, and the tensile stress decreases rapidly to compressive stress with the increase of distance from the center of the weld.The larger transverse tensile stress is located on both sides of the upper surface of the weld, the peak value is 333MPa, the maximum equivalent stress zone is located around the weld area of the upper surface, the peak value is 470MPa, which is smaller than the yield strength of the base metal at room temperature.The longitudinal residual stress decreases first and then increases with the increase of welding thickness, and the larger value is located at the root of the weld, and the peak value is 424 MPA.Under the real service condition, the residual stress decreases greatly. In the groove contour, the longitudinal residual stress increases with the increase of the welding thickness, and the larger stress zone is located in the middle of the weld.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG457.11

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