【作者】 宋以国；

【导师】 郑玉峰；

【作者基本信息】 哈尔滨工程大学 ， 材料学， 2013， 博士

【摘要】 近年来，压水式反应堆和沸水堆带有贯穿件的焊接结构中发现了应力腐蚀裂纹，对核电运行造成了潜在的安全隐患，这已经引起了研究人员的重视。材料性能、腐蚀介质和应力状态是造成应力腐蚀裂纹的三个主要因素，尤其是在焊缝区附近产生的焊接残余应力较大，是导致焊接件中出现应力腐蚀裂纹的重要因素。采用数值模拟方法，对异种金属管板焊接结构进行残余应力的预测与评价，对于核反应堆中贯穿件的焊接具有重要意义。为了优化大型多焊缝管板结构的焊接工艺，本文利用焊接热传导、焊接热弹塑性有限元分析理论和ANSYS大型有限元分析软件，以同种金属管板结构焊接温度场和残余应力场的数值模拟为基础，提出了适用于有T型材的多焊缝管板结构焊接残余应力场数值模拟的有限元模型和热源加载方式、多层焊道的填充等计算方法，并分析了坡口角度、焊接顺序和焊缝相交处堆焊对焊接残余应力的影响。利用此有限元模型和计算方法对有T型材的低合金高强钢S690和SS316L不锈钢异种金属多焊缝管板结构的焊接温度场和残余应力场进行了数值模拟，并采用盲孔法对实际焊接件进行了表面残余应力测试，试验验证了有限元模型和计算方法在有T型材的多焊缝管板结构焊接残余应力场数值模拟与预测方面的适用性。研究结果表明，对于低合金高强钢管板焊接结构，坡口角度由40°增加到50°，在一定程度上改善了Von-Mises等效应力、切向和轴向残余应力分布；对径向残余应力分布的恶化作用并不明显。焊接顺序对等效应力以及径向、切向和轴向残余应力峰值有较大影响，两面交替焊优于其他焊接顺序。修正的两面交替焊与两面交替焊的等效应力以及径向、切向和轴向残余应力峰值基本相同。在实际的焊接操作中，大角度坡口可以保证焊透，减少焊接缺陷，而修正的两面交替焊可以减少焊件的翻转次数，提高工作效率。因此，从简化操作工艺，提高焊缝质量的角度出发，50°坡口角度和修正的两面交替焊是比较好的焊接工艺。模拟结果显示，对于有T型材的多焊缝管板焊接结构，焊缝相交处的堆焊层明显降低了环焊缝焊趾处的等效应力和轴向残余应力峰值；对径向和切向残余应力峰值影响较小。堆焊层还明显降低了焊缝相交处的等效应力和轴向残余应力峰值，并在一定程度上降低了切向残余应力峰值；只有径向残余应力峰值有所增加。因此，有T型材的多焊缝管板焊接结构，在所有焊缝完成后，在贯穿件与壳板环焊缝和T型材与壳板焊缝相交处采用奥氏体焊材堆焊，可以作为焊后释放残余应力的有效方法。为了验证有T型材的多焊缝管板焊接结构的有限元模型和计算方法，本文对低合金高强钢S690和SS316L不锈钢异种金属多焊缝管板结构进行了焊接残余应力的分析和测试，计算结果与实际测得的应力值吻合较好。焊接结构件的应力测试值基本反映了有限元模型计算得出的残余应力变化趋势，试验验证了数值模拟中采用的有限元模型和计算方法预测焊接结构残余应力分布的适用性。结合数值模拟与试验验证结果，获得了在坡口角度50°和修正的两面交替焊的焊接工艺条件下，低合金高强钢S690和SS316L不锈钢异种金属多焊缝管板结构焊接残余应力场的分布规律。环焊缝在壳板上的热影响区和焊趾处出现压应力区，贯穿件上的残余拉应力较小，测得的最大等效应力在环焊缝熔合区，距离环焊缝与壳板熔合线2mm处，为269MPa。更多还原

【Abstract】 Recently, some stress corrosion cracks (SCC) are found in the welding structures withthe nozzle in pressurized water reactors (PWR) and boiling water reactor (BWR). So moreattentions are paid to ensure safety of nuclear power operation. It is well known that threemajor factors, namely materials properties, caustic media and stress status, have largecontributions to SCC. It is recognized that the tensile residual stress on the surface of thewelding structure largely increases the risk of initiating SCC. It is very important for thewelding structure with the nozzle in the nuclear reactor to evaluate and predict the weldingresidual stresses in the dissimilar metal tube-plate welding structure (TPWS) by the numericalsimulation method.To optimize the welding technology of the large TPWS with multi-welds, this paper appliedthe welding thermal conduction, the welding thermal elastic-plastic analysis theory and theANSYS finite element analysis software, proposed the finite element model (FEM) and thealgorithm about heat source loading and the passes filled by the “birth and death” elementmethod, based on the numerical simulation of the TPWS in the temperature field and thewelding residual stresses field. They were suitable for the numerical simulation of thetube-plate welding structure with T-shape sections (TPWST) in the residual stresses field. Theeffect of the groove angle, the welding sequence and the overlaying on the intersection ofthree weld beads on the residual stresses was analyzed. The FEM and the algorithm wereapplied to simulate the temperature field and the residual stresses field of the low alloy highstrength steels S690and SS316L stainless steels dissimilar metal TPWST. The residualstresses on the surface of the welding specimen were measured by blind-hole method. Theapplicability of the FEM and the algorithm was verified by the experiment in the numericalsimulation and prediction of the welding residual stresses in the TPWST.To the low alloy high strength steels TPWS, the simulation results showed that, the grooveangle from40°to50°, the Von-Mises equivalent stress, hoop and axial residual stressdistribution was improved to some extent, while deterioration of the radial residual stressdistribution was not obvious. The welding sequence had great influence on the peak values ofthe equivalent stress, the radial, hoop and axial residual stress. The alternative welding sequence was better than the other. The equivalent stress, the radial, hoop and axial residualstress of the amended alternative welding sequence were almost same as these of thealternative welding sequence. In the actual welding operation, the large groove angle canensure penetration of the weld bead, and the amended alternative welding sequence madeturnover of the welding part reduce. To simplify the welding operation and improve the weldbead quality, it was good to apply the welding technology of the50°groove angle and theamended alternative welding sequence.The simulation results showed that, to the TPWST, the overlaying on the intersection ofthree weld beads decreased obviously the peak values of the equivalent stress and the axialresidual stress at the toes of the girth weld, and had the little effect on the peak values of theradial and hoop residual stress. The overlaying decreased obviously the peak values of theequivalent stress and the axial residual stress on the intersection of the weld beads, anddecreased the peak value of the hoop residual stress to some extent, but the peak value of theradial residual stress increased. So the austenitic overlaying on the intersection of the girthweld and the weld bead of T-shape sections was the effective method to reduce the weldingresidual stresses after welding to the TPWST. The overlaying was finished after all weldbeads.To verify the feasibility of the3D FEM and the algorithm of the S690and SS316Ldissimilar metal TPWST, this paper compared simulation results of the welding residualstresses with testing data, the both accorded each other. It showed that the FEM and thealgorithm can be used to predict the residual stress distribution of the TPWST and theapplicability of them was verified by the experiment. From the simulation results and test data,the residual stress distribution of the S690and SS316L dissimilar metal TPWST was knownwith the welding technology of50°groove angle and the amended alternative weldingsequence. The compression stress occurred on the heat affected zone and the toe of the girthweld on the plate. The low tensile stress occurred on the tube. The peak value of the residualtensile stress was on the girth weld close to the plate. The maximum value of the equivalentstress in measurement was269MPa, which was on the girth weld and2mm from the fusionline of the girth weld on the plate.更多还原