论文总字数：23172字

摘 要

异种钢焊接接头在实际中被广泛的运用.由于焊接接头两端材料抗拉强度、线膨胀系数、焊接性能的差异，又由于焊接工艺的影响,焊接接头的性能往往会低于两侧母材的性能。在高温服役条件下，经常会在焊接处产生很多孔洞和微观裂纹。这些缺陷会聚集形成宏观裂纹，则会对设备运行增加很多风险。考虑到设备的经济性和可操作性，工业上往往会采用补焊的方法来延长焊接接头的寿命，即将焊接接头出现裂纹缺陷的部分采用机械手段清除，然后再对清除部分进行焊接修补。但是补焊过程会给原接头性能和完整性评估等方面带来很大的影响，所以补焊过程渐渐成为压力容器和管道结构完整性的重要考虑部分。

本文利用有限元软件ABAQUS顺次耦合的焊接残余应力计算程序，对P91/12Cr1MoV异种钢焊接接头的焊接残余应力分布情况以及补焊形式对焊接残余应力分布的影响进行了模拟研究。

通过建立有限元模型，首先进行热分析，将得到的所有节点温度输入到结果文件作为力分析的预定义场，然后在力分析过程中，从前面得到的预定义场中读取各节点的温度进行差值计算，从而得到残余应力场。从而得到以下结论：

1.接头在焊接熔合线附近产生的残余应力较大，最大应力峰值出现在靠近管壁外侧P91母材热影响区；在原来最大应力处补焊之后，在补焊热影响区的残余应力最大，而且分布不均匀。

2.增加补焊长度可以有效地减小焊接接头残余应力，可以选择较大的补焊长度，选择较大的焊接线能量，焊后可以采用热处理或增加焊接过渡层等方法来减少其焊接残余应力。

3.补焊宽度对焊接接头残余应力影响不大，可以不予以考虑；增加补焊层数会使残余应力分布更加分散由原来的“单波峰”变为“双波峰”，会对接头完整性有不利影响。

4.整体补焊的强度要高于局部补焊，如果实际情况允许，尽量采用整体补焊的形式。

关键词：补焊形式 异种钢焊接接头 补焊长度 补焊宽度 整体补焊

ABSTRACT

The dissimilar steel welded joints has been widely used in practice. Due to differences in tensile strength, linear expansion coefficient and welding performance of the welded joints at both ends, but also due to the impact of the welding process, the properties of welded joints on both sides tend to be lower than the performance of the base material. In the high-temperature service conditions, there are many holes and micro-cracks in In the welding place. These defects will Gather to form macroscopic crack if we could not deal with them, the risk of the running of the equipment would be increase. Given the economic and operability of the equipment, people often adopt the method of repair welding to prolong the life of the welded joint in industry , and the crack defects which has been generated In the welded joint would be cleared by mechanical means. Then repair the areas by welding . But the repair welding process will affect the performance of the original joint, integrity evaluation etc. so repair welding process has been gradually become an important consideration of the pressure vessel and piping structural.

In this paper, the finite element software ABAQUS progressive coupling welding residual stress calculation program has been used. We simulated the distribution of Welding residual stress of P91/12Cr1MoV weld joints of dissimilar steel, and we also simulated the effects of repair welding form on the distribution of welding residual stress. Choosing a different welding length, width, and repair welding layers, analyzed the changes of the residual steels along the P91 fusion line side heat affected zone in order to provide a reference for the Optimization of repair welding process.

By building the finite element model, the thermal was analyzed firstly, to set the predefined field for force analysis ,node temperature was input to the file. Then during the force analysis, read the temperature of each node to do deviation calculation on the base of the former predefined field, and the residual stress field is obtained. The conclusions are as follows:

1. Near the weld fusion line of the joint, the residual stress is larger. And in the P91 parent metal heat affected zone, the maximum stress peak is Close to the outsides of the tube wall, after the repair welding of the original maximum stress point , the maximum residual stress appeared at the heat affected zone of the repair welding and unevenly distributed .

2. increase the breadth of welding can effectively reduce the residual stress of welded joints , you can choose a larger welding length , choose a larger welding energy , if you want to reduce the residual stress after welding, you can using the heat treatment or increase the welding transition layer.

3. The width of the repair welding have little effect on the residual stress of welded joints, so this factor could be ignored. Increase the number of layers makes the distribution of residual stress more diffuse, and turns the Single wave to dual wave .This would have an adverse effect on the Joint integrity.

4. The strength of the overall repair welding is higher than the local repair welding, if the actual circumstances permit, we should adopt the overall repair welding as far as possible .

Key words: repair welding form; weld joints of dissimilar steel; repair welding Length; repair welding width; overall repair welding

目录

摘要 I

ABSTRACT Ⅱ

第一章 绪论 1

1.1 引言 1

1.2 异种钢焊接接头材料的选用 1

1.3 有限元分析软件在分析焊接应力中的应用和发展 2

1.4 本课题研究重点与内容 3

第二章 补焊过程对P91/12Cr1MoV接头残余应力的影响 6

2.1常见补焊类型及补焊对接头残余应力影响 6

2.1.1 补焊几何尺寸对残余应力的影响 7

2.1.2 补焊工艺过程对残余应力的影响 8

2.2 P91/12Cr1MoV焊接接头有限元模拟 9

2.2.1 材料参数 9

2.2.2有限元模型 10

2.2.3有限元模拟结果与分析 12

第三章 结论与展望 25

3.1 主要结论 24

3.2 展望 24

参考文献 27

致 谢 30

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