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1、上海交通大学硕士学位论文2219铝合金TIG焊接性研究姓名：吴龙飞申请学位级别：硕士专业：材料加工工程指导教师：吴毅雄;杨学勤20070801同样焊接条件下形成的焊接接头在-196低温下的抗拉强度、伸长率高于室温条件下。与焊后直接进行拉伸性能测试的接头相比， 同样焊接条件下形成的焊接接头经人工时效后其抗拉强度有所提高，但试样整体的伸长率有所下降。弯曲性能和冲击韧性都随焊接规范的增强而增加。焊接接头在-196低温条件下的冲击韧性低于室温。经室温拉伸后的接头试样呈现宏观脆性断裂。焊接接头室温、低温拉伸试样均断裂于熔合区，其断裂机理为准解理与沿晶混合型断裂，焊缝部位室温冲击断裂属微孔缩聚型，焊缝部位
2、低温冲击的断裂机理主要为准解理断裂。 关键词：2219 铝合金，焊接性，气孔敏感性，裂纹敏感性，力学性能，TIG 焊接 Weldability of 2219 Aluminum Alloy in TIG Welding ABSTRACTWeldability of 2219 Aluminum Alloy in TIG Welding ABSTRACT Researches were performed on the weldability and TIG welding technique of 2219 alloy boards with 6mm in thickness, which ha
3、ve been selected as the tank material of the roll booster of a new-type rocket. The purpose of the research is to give support to the validity verification of the manufactural project of the roll booster, in which 2219 alloy and TIG method have been selected, and to provide essential technique to th
4、e trial- manufacture of the roll booster. Influences of welding parameters on the width of weld were found by experiments. The results showed that in backing welding, duty cycle, frequency, argon flow and height of arc would be 20%, 100Hz, 15L/min, 6.5mm, while in cosmetic welding would be 40%, 80Hz
5、, 18L/min and 6.0mm. Pore tendency of 2219 alloy was tested in different welding conditions. The results revealed that there would be substandard chain pores in the joints whatever with purging by acetone before welding or without purging, however almost no pores with scraping. To reduce the pores i
6、n joint, welding with stronger welding condition would be beneficial. In the same welding condition , few differences of pore sensitivity were found between 2219 and 2A14 alloy, and so were the differences between the filler wire of ER2319 and H703. Researches on crack tendency of 2219 alloy was per
7、formed on rigidly fixed butt joints and intercrossed lap joints. No crack generated in the rigidly fixed butt joints. In the intercrossed lap joints, fine and isometric grains were found, and solidification crack went along the eutectic gridding composed of(Al) and CuAl2 phases. Tests revealed that
8、specimens with 6mm in thickness are more tendentious to crack than those with 3mm in thickness, and welding joints with filler wire ER2319 are more tendentious to solidification crack than those with H703. Lower current intensity has less tendency to crack. Few differences of crack tendency were fou
9、nd between SW-TIG(Square-Wave TIG) welding and VP-TIG(Variable-Polarity TIG) welding. Mechanical properties of welding joints in different welding conditions were tested. The results showed that tensile strength, elongation percentage, strength ratio increase when stronger welding condition is appli
10、ed. No much differences of tensile strength were found between SW-TIG welding joints and VP-TIG welding joints, or between with filler wire ER2319 and H703. Joints welded on both sides with three passes have higher strength than those welded on single side with two passes. The joints showed higher s
11、trength and elongation percentage at -196 than at room temperature. After proper artificial aging process, the strength of joints increases, while the elongation percentage decreases. Bending property and impact property of the joints increase when stronger welding condition is taken. The inspection
12、 suggested brittle fracture of the joints, which had broke along the fusion zone in the tensile test at room and lower temperature, with the mechanism of the combination of quasi-cleavage and intercrystalline fracture. The fracture face of the sample from the weld impacted at room temperature showed
13、 characteristics of microvoid accumulation fracture, however the one impacted at -196 indicated the mechanism of the combination of quasi-cleavage and intercrystalline fracture. Keywords： 2219 aluminum alloy， weldability， pore tendency， crack tendency， mechanical property，TIG welding 1 上海交通大学上海交通大学
14、学位论文原创性声明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：吴龙飞 日期： 2007 年 8 月 8 日 2 上海交通大学上海交通大学 学位论文版权使用授权书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交论文的复印件和电子版，允许论文被查阅和借阅。
15、 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。 保密保密，在 年解密后适用本授权书。 本学位论文属于 不保密不保密。 （请在以上方框内打“” ） 学位论文作者签名：吴龙飞 指导教师签名：吴毅雄 日期： 2007 年 8 月 8 日 日期： 2007 年 8 月 8 日 上海交通大学硕士学位论文 1第一章 绪论 1.1 本文研究的目的和意义 随着航天技术的发展，我国新一代5m箭体直径的大型运载火箭已正式进入研制阶段。3.35m直径模块助推器是该火箭的动力部件之一。根据该助推器的总体研制方案，其贮箱主体材料
16、为2219铝合金，其中部分结构确定选用T6态的2219合金并采用方波TIG焊接方法。 2219铝合金作为火箭贮箱制造材料在国外已得到了成功的应用，大约从70年代起，在美国2219合金作为贮箱材料全面取代2014，一直延续至今仍在广泛使用。然而，我国自70年代开始成功制造运载火箭以来，贮箱材料均选用了2A14（T6态）铝合金。多年以来，这种合金在火箭贮箱制造中显露出的高焊接裂纹倾向性始终没有得到根本解决。再加上新一代大型运载火箭以液氢-液氧为燃料，2A14合金的低温力学性能也难以适应这种新的要求。因而该合金在新一代火箭贮箱的制造中将被2219合金全面取代。 目前，国内尚缺乏对2219合金在火箭贮箱制造方面的焊接性研究，国外在这方面的研究结果也未见公布。由于贮箱属于一种复杂的焊接结构，其箱体材料的可焊性如何，直接关系到贮箱的技术性能、研制周期、生产成本和使用可靠性，因而有必要对其进行研究。 本课题旨在通过对新一代运载火箭3.35m直径模块助推器研制方案中选用的厚度为6mm的2219（T6态）铝合金板进行焊接试验与测
