X65管线钢管闪光对焊电热场和热力场耦合数值模拟及接头性能研究

发布时间：2018-03-05 11:25

本文选题：X65管线钢　切入点：闪光对焊　出处：《青岛科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：本论文通过试验研究和数值模拟相结合的方法,分析了X65管线钢管闪光对焊过程中的电、热和力三场耦合问题及接头缺陷的形成机理,为管道闪光对焊工艺在高级别管线钢管焊接中的应用提供了基础数据和理论指导。建立了闪光对焊接头的电、热和力多场耦合模型,对X65管线钢管闪光对焊过程中的电、热和力学行为进行了研究。在电热耦合模型中综合考虑了材料相变和温度对材料热物性的影响,利用“生死”单元法和单元实体分层加载模拟闪光烧损和产热问题,获得了X65管线钢管闪光对焊接头在闪光阶段的温度场分布规律和不同闪光速度条件下焊接接头的温度变化规律。在热力耦合模型中,利用刚粘塑性接触分析,模拟了闪光对焊顶锻阶段接头的变形,获得了焊接接头的应力应变曲线和不同顶锻留量条件下端面质点的位移变化规律。利用上述模型分析了焊接工艺参数对焊接接头热、力行为的影响,优化了X65管线钢管闪光对焊的工艺参数。对X65管线钢管闪光对焊焊接接头力学性能、显微组织分析和焊接缺陷形成机理进行了研究。接头的金相分析表明焊接的高热输入使接头焊缝区和部分热影响区的晶粒粗化,形成魏氏组织,降低了接头的冲击韧性。力学性能测试结果表明接头的显微组织变化是造成接头塑性和韧性差的主要因素,但由于接头处因顶锻压力形成了较高的位错密度,接头的抗拉强度反而较高。不恰当的焊接工艺易形成过烧、夹渣和灰斑缺陷,焊缝断口的灰斑缺陷内部和边缘的密集裂纹导致接头脆性解理断裂。
[Abstract]:In this paper, the coupling problem of electric, thermal and force fields and the forming mechanism of joint defects in the process of flash butt welding of X65 pipeline steel pipe are analyzed by means of the combination of experimental research and numerical simulation. This paper provides basic data and theoretical guidance for the application of pipeline flash butt welding technology in high grade pipeline steel pipe welding. The electric, thermal and force coupling models of flash butt welding joint are established, and the electric properties of X65 pipeline steel tube during flash butt welding are studied. The thermal and mechanical behaviors are studied. In the electrothermal coupling model, the effects of phase transition and temperature on the thermal properties of the material are considered synthetically. The "birth and death" element method and the layered loading of the element entity are used to simulate the flash burning loss and heat production. The temperature field distribution of flash butt welded joint of X65 pipeline steel pipe during flash stage and the temperature variation law of welded joint under different flash velocity are obtained. In the coupled thermodynamic model, rigid visco-plastic contact analysis is used. The deformation of the joint in the stage of flash butt welding is simulated, and the stress-strain curve of the welded joint and the law of displacement change of the end particle under different conditions are obtained. Using the above model, the heat of welding process parameters on the welded joint is analyzed. Under the influence of force behavior, the technological parameters of flash butt welding for X65 pipeline steel tube are optimized. The mechanical properties of X65 pipeline steel tube flash butt welding joint are studied. Microstructure analysis and welding defect formation mechanism were studied. Metallographic analysis of the joint shows that the high heat input results in the coarsening of the grain in the weld zone and part of the heat-affected zone of the joint and the formation of the Weiss structure. The mechanical properties test results show that the microstructure change of the joint is the main factor that causes the poor plasticity and toughness of the joint, but due to the high dislocation density of the joint due to the top forging force, However, the tensile strength of the joint is higher than that of the joint. The improper welding process is apt to form overburning, slag and gray spot defects, and the dense cracks inside and on the edge of the gray spot defect of the weld seam lead to brittle cleavage fracture of the joint.
【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG457.11

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