含裂纹主蒸汽管球三通安全性分析及其焊接修复模拟

发布时间：2019-02-19 08:54

【摘要】：主蒸汽管球三通作为主蒸汽管路中的一种特殊结构,在主蒸汽管路中用来分配和改变介质的流动方向,由于球三通结构和功能的特殊性,使得其在管道领域发挥着重要的作用。考虑到主蒸汽管球三通在主蒸汽管路中的重要性以及其发生事故的危害性,本文采用数值模拟与安全评定相结合的方法,对主蒸汽管球三通在含裂纹和挖掉裂纹情况下的安全性进行分析与评定,分析了主蒸汽管球三通修复时的焊接温度场以及残余应力场,并进一步研究了焊接残余应力与工作载荷的耦合场,研究得出以下结论:(1)含裂纹主蒸汽管球三通在550℃、18.4MPa额定负荷下最小Von Mises应力为27.3MPa,分布于球体外表面以及主管外表面部分区域;裂纹两端处应力峰值达到511MPa。基于GB/T 19624-2004对含裂纹主蒸汽管球三通进行安全性评价,失效评定图与最大容许等效裂纹尺寸得出的结论一致,认为主蒸汽管球三通是不安全的。(2)挖掉裂纹主蒸汽管球三通在550℃、18.4MPa额定负荷下最小Von Mises应力为26.2MPa,分布于球体外表面;应力峰值为276MPa,相比于含裂纹情况下应力峰值降低了45.9%;按照GB/T 19624-2004对挖掉裂纹的主蒸汽管球三通进行安全评定,其结果是满足安全要求。(3)采用焊条电弧焊工艺修复裂纹缺陷,预热200℃时等效残余应力峰值为226MPa;预热250℃焊接时,等效残余应力峰值位于焊缝处且达到210MPa,比预热200℃时减小了 7.6%,等效残余应力分布与预热200℃时大体一致,均关于焊缝区域基本对称。(4)预热200℃和250℃两种焊接条件下的周向残余应力、轴向残余应力分布基本一致,在250℃预热条件下焊接,应力值有所减小,应力梯度降低;周向残余应力和轴向残余应力峰值随焊接电流的增大而增大,随焊接速度的增大而减小;提高焊接电流或降低焊接速度,轴向残余应力的增长小于周向残余应力的增长。(5)预热200℃焊接时残余应力与工作载荷的耦合应力峰值为292MPa,预热250℃焊接时残余应力与工作载荷的耦合应力峰值为275MPa。对球三通在200℃和250℃预热条件下进行焊接修复均能够保证球三通在550℃、18.4MPa的额定负荷下安全运行。
[Abstract]:As a special structure in the main steam pipeline, the main steam pipe ball three-way is used to distribute and change the flow direction of the medium in the main steam pipeline. Because of the particularity of the structure and function of the ball three-way, it plays an important role in the pipeline field. Considering the importance of the main steam pipe ball three-way in the main steam pipeline and the harmfulness of the accident, the method of combining numerical simulation with safety assessment is adopted in this paper. In this paper, the safety of the main steam tube ball three-way in the case of cracks and excavations is analyzed and evaluated. The welding temperature field and residual stress field of the main steam tube ball are analyzed during the repair of the main steam tube ball. The coupling field of welding residual stress and working load is further studied. The following conclusions are obtained: (1) the minimum Von Mises stress of the main steam pipe ball with cracks is 27.3 MPA at 550 鈩，

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