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1、上海交通大学 硕士学位论文 汽车用铝合金焊接工艺的研究 姓名：杨淑芳 申请学位级别：硕士 专业：材料加工工程 指导教师：楼松年 20040101 汽车用铝合金焊接工艺的研究 摘 要 本文针对汽车用铝合金的焊接性较差焊接时常有气孔裂纹等 缺陷出现对汽车车身常用的 6061 铝合金的焊接工艺进行了研究 为铝合金在汽车业中的应用提供了试验依据 对于扩大铝合金的应用 和推动轿车进一步轻量化具有重要的意义和实际应用价值 利用压板对接FISCO焊接裂纹试验气孔敏感性试验对 6061 铝合金的焊接性进行了分析研究了 6061 铝合金的焊接工艺得出 焊接接头成型较好的工艺参数对 6061 焊接接头的力学性能强
2、度 硬度和塑性 进行了测试 然后利用金相显微镜 X 射线能谱仪 EDX 先进测试手段对 6061 铝合金焊接接头及其附近区域的显微组织焊 缝的点成分进行了分析 6061 铝合金焊接性的分析结果表明6061 铝合金具有一定的结晶 裂纹敏感性而且比 3A21 铝合金的抗热裂性差利用 4043 焊丝作为 填充金属 6061 铝合金的焊缝热裂纹敏感性小 裂纹只产生于焊缝的 弧坑处弧坑处的裂纹既有纵向的又有横向的在 TIG 和 MIG 焊下 6061 铝合金的气孔敏感性较大焊接方法环境相对湿度试板表面 状态保护气体成分及焊接规范对 6061 铝合金的气孔敏感性有很大 的影响 焊缝中的气孔大致有三类 链状
3、气孔 密集气孔和单个气孔 控制各种水分的来源并采用合适的焊接规范可减小 6061 的气孔敏感 性此外在保护气氛中加入适量的氧化性气体也可减小 6061 的气 孔敏感性 6061 铝合金的焊接工艺试验表明 TIG 和 MIG 焊的工艺参数对焊 缝成形有明显的影响采用单种焊接方法TIGMIG 和激光焊得 到的焊缝熔深和熔宽均比激光-电弧复合焊的焊缝要小故激光-电弧 复合焊是一种很有潜力的焊接方法 6061 焊接接头力学性能与组织分析表明 6061 焊接接头的硬度 强度和塑性均低于母材的对应力学性能 且在距焊缝中心约 913mm 处的热影响区发生了软化 软化区产生的主要原因是该区强化相粒子 在焊接热
4、循环过程中发生了过时效产生聚集粗化经过一定的自然 时效接头的强度和延伸率有一定的恢复 关键词汽车6061 铝合金裂纹气孔焊接工艺显微组织 RESEARCH ABOUT THE WELDING TECHNOLOGY OF AUTOMOTIVE ALUMINIUM ALLOYS ABSTRACT The weldability of automotive aluminum alloys is not very good and deficiencies (such as porosity, hot cracking) often occur during welding. Therefore, t
5、he article explored the welding technology of 6061 aluminum alloy that is often used in car body. This research provides experiment data for the application of aluminum alloys in automotive industry. The work also has important practical value to the further use of aluminum alloys that will make aut
6、omotive lighter. The weldability of 6061 alloy was examined by means of FISCO to test welding crack susceptibility and tests of porosity sensibility. The welding technology of 6061 was studied to get suitable welding parameters. The mechanical properties of 6061 welded joint were also tested. In ord
7、er to make further research of the different performance between welded joint and base metal of 6061 alloy, the microstructure characteristics and point component of butt joint of 6061 alloy were studied by means of advanced test methods including optics microscope and energy dispersive X-ray microa
8、nalysis (EDX). Furthermore, the article also covered research of effects about different welding processes and parameters on 6061 alloy bead sizes. The analysis results indicate that 6061 alloy is characterized by the sensibility of crystal crack and hydrogen porosity. Under the same condition, 6061
9、 alloy is more susceptible to hot cracking than 3A21 alloy. While 4043 welding wire was used as the filler metal, low crack susceptibility was achieved and hot crack only emerged in arc crater. Crater crack appeared both longitudinal and horizontal. As far as 6061 alloys porosity susceptibility is c
10、oncerned, influencing factors include welding methods, relative humidity of the environment, surface state of test plate, composition of shielding gas and welding variables. There were three main types of porosity in welded joint, i.e. porosity of chains, intensive porosity and single porosity. It w
11、as found that to strictly control sources of moisture could effectively reduce the amount of porosity in the weld. In addition, 6061 alloys porosity susceptibility could be reduced by use of suitable welding variables and adding gas with oxidizability to the shielding atmosphere. The result of weldi
12、ng procedures test shows that welding parameters have great effect on weld shape. And hybrid welding of laser and electric arc can allow the weld with larger penetration and width compared to that seam welded by single welding method (such as TIG, MIG and YAG laser). So it is proved that the hybrid
13、welding process is ideal. The study of microstructure and properties of 6061 welding joint indicates that hardness, tensile strength and plasticity of the joint are lower than the relevant properties of base metal and the weakest point of welded joint is in the soften zone of HAZ, 913mm away from th
14、e weld center. It is formed due to the overaging of the main strengthening phase particle, which aggregates and coarsens during the influence of welding heat. After some extent of natural seasoning, tensile strength and plasticity of the joint are restored. KEY WORDSautomotive, 6061 alloy, hot crack
15、ing, porosity, welding technology, microstructure 上海交通大学 学位论文原创性声明 本人郑重声明所呈交的学位论文是本人在导师的指导下 独立进行研究工作所取得的成果除文中已经注明引用的内容外本 论文不包含任何其他个人或集体已经发表或撰写过的作品成果 对本 文的研究做出重要贡献的个人和集体均已在文中以明确方式标明 本人完全意识到本声明的法律结果由本人承担 学位论文作者签名杨淑芳 日期2 0 0 4 年 1 月 1 2 日 上海交通大学 学位论文版权使用授权书 本学位论文作者完全了解学校有关保留使用学位论文的规定 同意学校保留并向国家有关部门或机构送
16、交论文的复印件和电子版 允许论文被查阅和借阅 本人授权上海交通大学可以将本学位论文的 全部或部分内容编入有关数据库进行检索可以采用影印缩印或扫 描等复制手段保存和汇编本学位论文 保密在 年解密后适用本授权书 本学位论文属于 不保密 请在以上方框内打 学位论文作者签名杨淑芳 指导教师签名楼松年 日期2 0 0 4 年 1 月 1 2 日 日期2 0 0 4 年 1 月 1 2 日 上海交通大学硕士学位论文 - 1 - 第一章 前言 1.1 研究背景和目的 为适应现代社会的需要汽车正向着节能环保安全舒适智能低成 本及长寿命方向发展尤其是节能和环保更是关系人类可持续发展的重大问题 而解决能源和环保这两个问题最有效的措施是减轻汽车的重量以降低能耗 减少 污染提高燃油效率实现汽车轻量化的主要方法有修改结构设计缩小汽车 规格和采用新型材料1 2其中采用新型材料来降低汽车重量是最有潜力的用 高强度钢板来代替原先使用的普碳钢是汽车轻量化的一个重要手段35由于高 强钢比普碳钢强度高的多按等强度转换原则钢板的厚度就可削减这样大大 减少了钢材用量从而有效地降低了汽
