激光拼焊板焊接接头的机械性能及焊接过程变形行为研究

发布时间：2018-06-04 04:28

本文选题：激光焊接 + 拼焊板　；参考：《重庆大学》2015年硕士论文

【摘要】：焊接接头的力学性能决定了焊接件后续的加工性能和使用性能。焊接过程的特殊性,导致焊接后焊缝及其附近区域组织和性能发生变化,这些变化最终将对焊接接头的综合力学性能产生影响。其次,由于薄板焊接时自身发生屈曲,导致薄板发生波浪变形,即便是像激光焊接那样的高能量密度焊接方法也无法避免。薄钢板激光拼焊技术具有节省材料、焊接方便、设计灵活等优点,在制造业尤其在汽车业中得到广泛应用。目前,对不等厚薄板激光拼焊的需求日趋增加,但对该类板材焊接过程中的变形行为及焊接接头力学行为特征的认识仍然不足。本课题实验研究了不等厚薄板的激光对接拼焊板的力学性能,并结合有限元方法重点考察焊接件中存在的应力、应变及对变形的影响规律。首先,研究了厚度为1.7mm的HC340LAD+Z板和厚度为2.6mm的HSLA340+Z板激光对接拼焊板的焊接接头微观结构及力学性能;然后,建立了焊接热源模型,结合实验结果验证了热源模型的可靠性,紧接着考察了焊接过程对焊接热敏区分布的影响;最后,研究了激光焊接不等厚板的变形行为及形成机制。研究结果表明:1)不等厚薄板的激光对接焊接成型性良好,焊缝整体过渡平滑、外观美观。焊缝处主要由粗大板条状马氏体构成,其中主要夹杂着细小针状铁素体和粒状碳化物。热影响区内主要由珠光体构成,且相比于母材组织细化明显。激光焊接接头强度高于母材,焊缝具有一定的塑性变形能力;2)所建立的3D高斯热源模型符合该激光焊接热源,而且通过优化工艺参数使焊接热敏现象得到控制,改善了焊接接头的机械性能;3)在不等厚板的焊接过程中,受板厚尺度因素的影响导致焊缝区靠近厚板侧上、下表面的温差较大,以至于厚板侧上、下表面的应力差较大,最终,导致厚板发生了更大程度的变形。
[Abstract]:The mechanical properties of welded joints determine the processing performance and service performance of welded parts. The particularity of the welding process leads to the changes of the microstructure and properties of the weld and its adjacent areas after welding. These changes will eventually affect the comprehensive mechanical properties of the welded joints. Secondly due to the buckling of the thin plate during welding the wave deformation of the thin plate is caused even the high energy density welding method such as laser welding cannot be avoided. Laser welding technology for thin steel plate has the advantages of saving material, convenient welding, flexible design and so on. It is widely used in manufacturing industry, especially in automobile industry. At present, the demand for laser welding of unequal thickness and thin plate is increasing day by day, but the understanding of deformation behavior and mechanical behavior of welded joint in the welding process of this kind of plate is still insufficient. In this paper, the mechanical properties of laser butt welded plate with different thickness and thin plate are studied experimentally, and the stress, strain and its influence on deformation of welded parts are investigated with finite element method. Firstly, the microstructure and mechanical properties of laser butt welded HC340LAD Z plate with thickness of 1.7mm and HSLA340 Z plate with thickness of 2.6mm are studied, and then the model of welding heat source is established, and the reliability of the model is verified by the experimental results. Then the influence of welding process on the distribution of welding heat sensitive zone is investigated. Finally, the deformation behavior and formation mechanism of laser welded unequal thickness plate are studied. The results show that the laser butt welding of different thickness and thin plate is good, the overall transition of weld is smooth, and the appearance is beautiful. The weld is mainly composed of coarse strip martensite with fine acicular ferrite and granular carbides. The heat affected zone is mainly composed of pearlite, and the microstructure is more fine than that of the base metal. The 3D Gao Si heat source model based on the laser welding joint strength is higher than the base metal, and the welding seam has a certain plastic deformation ability. The 3D Gao Si heat source model accords with the laser welding heat source, and the welding heat sensitivity is controlled by optimizing the process parameters. The mechanical properties of welded joints have been improved. During the welding process of unequal thickness plates, the influence of plate thickness scale factors leads to the large temperature difference between the weld zone near the thick plate side and the lower surface, so that the stress difference between the upper side and the lower surface of the thick plate side is great, and finally, Resulting in a greater degree of deformation of the thick plate.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG456.7

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