厚壁件埋弧焊中频感应加热焊后热处理的多场耦合数值模拟

发布时间：2018-05-01 20:39

  本文选题：埋弧焊 + 焊后热处理　； 参考：《青岛科技大学》2017年硕士论文

【摘要】：用中频感应加热技术对厚壁埋弧焊工件进行焊后热处理能够消除焊接过程中产生的残余应力,降低焊接结构变形或开裂的倾向。本文采取实验研究和数值模拟相结合的方法,对厚壁件埋弧焊接过程中以及焊前或焊后中频感应预热或热处理过程中工件的耦合温度和应力场进行分析,研究焊接和感应加热工艺参数对焊后和热处理后工件残余应力场的影响。首先利用ANSYS软件对埋弧焊焊接过程中厚板工件的温度和应力场进行了模拟计算。选用双椭球热源建立了厚板埋弧堆焊的热力耦合数值模型,利用“生死单元”法模拟了焊接过程中工件的瞬态温度变化情况,获得了厚板不同位置处温度随时间的变化曲线。利用弹塑性理论,模拟了焊接过程中的应力场及焊后残余应力分布情况,获得了不同方向残余应力的分布规律。结果表明,熔合区等效残余应力最大,热影响区次之,母材区最小,其最大数值分别为234 MPa、188 MPa和50 MPa。对工件焊接过程中的温度变化及焊后残余应力进行了实验测试,实验结果与模拟结果较为吻合。其次建立了电磁-热-应力耦合模型,模拟了中频感应热处理过程中厚板工件的电磁场、温度场及应力场,分析了感应加热热处理后残余应力的分布。结果表明,感应加热焊后热处理能明显降低焊接接头残余应力值,其中熔合区减小幅度最大。感应热处理后熔合区、热影响区和母材区的最大残余应力分别降低到142MPa、134 MPa和36 MPa。利用盲孔法对焊后和热处理后焊接接头的残余应力进行了测量,实验结果与模拟结果较为吻合。最后利用建立的电磁-热耦合数值模型,对大直径321不锈钢圆筒件的焊前感应预热瞬态温度场进行了模拟分析。研究了感应线圈中不同电流大小、频率以及不同感应加热方式作用下工件的温度分布情况,通过调节电流参数和感应加热作用方式使得感应预热后工件加热区温度达到120±10℃的预热工艺要求。结果表明,最佳感应预热工艺为采用频率为10 KHz、大小为750 A的感应电流,加热10 s后停止20 s的间隔加热模式。
[Abstract]:Post-welding heat treatment of thick wall submerged arc welding workpiece with medium frequency induction heating technology can eliminate the residual stress in welding process and reduce the tendency of deformation or cracking of welding structure. In this paper, the coupling temperature and stress field of thick wall parts during submerged arc welding and in the process of induction preheating or heat treatment with intermediate frequency before or after welding are analyzed by means of experimental study and numerical simulation. The effect of welding and induction heating process parameters on residual stress field of workpiece after welding and heat treatment was studied. At first, the temperature and stress field of plate during submerged arc welding are simulated by ANSYS software. A thermal-mechanical coupled numerical model of thick plate submerged arc surfacing welding was established by using double ellipsoid heat source. The transient temperature variation of workpiece during welding was simulated by "birth and death element" method, and the temperature variation curves at different positions of thick plate with time were obtained. The stress field in welding process and the distribution of residual stress after welding are simulated by using elastic-plastic theory, and the distribution of residual stress in different directions is obtained. The results show that the equivalent residual stress in the fusion region is the largest, the heat affected zone is the second, the base metal region is the smallest, and the maximum values are 234MPA ~ 188 MPa and 50 MPA, respectively. The temperature change and residual stress after welding are tested experimentally. The experimental results are in good agreement with the simulation results. The electromagnetic field, temperature field and stress field of medium frequency induction heat treatment are simulated, and the distribution of residual stress after induction heat treatment is analyzed. The results show that the residual stress of welded joints can be significantly reduced by induction heating post-welding heat treatment, and the fusion zone is the largest. After induction heat treatment, the maximum residual stresses of fusion zone, heat affected zone and base metal region are reduced to 142 MPA ~ 134 MPa and 36 MPA / a respectively. The residual stresses of welded joints after welding and heat treatment were measured by blind hole method. The experimental results are in good agreement with the simulation results. Finally, the transient temperature field of pre-welding induction preheating of large diameter 321 stainless steel cylinder is simulated and analyzed by using the electromagnetic and thermal coupling numerical model. The temperature distribution of the workpiece under the action of different current size, frequency and different induction heating mode in the induction coil is studied. By adjusting the current parameters and the action mode of induction heating, the temperature of the heating zone of the workpiece after induction preheating can reach 120 卤10 鈩，

本文编号：1830963