高强铝合金T型接头激光焊接技术研究
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摘要
轻质高强、高弹性模量、高比强度和高比刚度的以铝锂合金为代表的高强铝合金是优秀的航空航天材料,焊接在提高材料利用率、减轻结构质量、降低成本方面具独具优势,尤其是高能量密度、高焊接精度和高焊接效率的激光焊。在飞机蒙皮、壁板等结构中,采用焊接代替传统的铆接工艺制造T型接头,减重效果显著。然而由于铝合金特性及T型接头结构特点,无论传统焊接还是先进的激光焊接都遇到了焊缝成形、气孔、变形等依靠单独焊接方式难以解决的问题。本文在激光焊的基础上成功将激光填丝焊用于3mm厚铝锂合金T型接头的焊接上,既充分发挥了激光焊的优势,也弥补了其不足。
首先,根据铝合金激光焊和填丝焊的焊接试验要求和T型接头的特点,优化与设计了定位装置、送丝装置及工装夹具,为工艺试验研究提供了装备条件。
其次,基于正交试验法设计了试验,研究了激光功率、焊接速度、焊接角度和偏移量四个主要的工艺参数对T型接头角焊缝界面结合、表面成形和底板熔深的影响。利用直观和极差分析试验结果发现,焊接角度和偏移量是影响T型接头焊缝成形的主要因素。对SUS304不锈钢T型接头激光焊接的工艺参数进行优化,当激光功率2000W、焊接速度2.5mm/min、焊接角度35。、偏移量0.5mm时,可以获得最佳的焊缝成形。之后,在优化的焊接工艺基础上进行了铝锂合金T型接头激光填丝焊,分析试验结果发现填丝焊极大的改善角焊缝成形和避免焊接热裂纹。
最后,研究了影响T型接头气孔的因素,分析发现焊接角度、焊接速度和材料中镁元素含量对气孔有较大的影响。对接头显微组织和力学性能研究发现：填丝焊使两侧焊缝组织相似且以等轴晶为主,提高了T型接头抗拉强度,还使得焊缝硬度分布更均匀,填丝焊由于增加了焊接热输入,焊缝硬度比激光焊焊缝硬度稍低,施焊顺序也会造成角焊缝硬度分布不同。焊后热处理工艺对消除铝合金激光焊接气孔有显著功效,使T型接头硬度分布更加均匀,但焊缝中心的显微硬度有所下降,母材的显微硬度相应提高。
研究成果有助于进一步推进T型接头激光焊接的发展和应用,同时为T型接头焊后处理消除焊缝气孔技术提供了参考依据,为后续进行T型接头两侧同步的双光束激光焊接研究打下了基础。
High strength aluminum alloy is one of the most important materials and finds extensive application in aerospace industry because of its light weight, superior strength-to-weight ratio, and high elastic modulus. Laser welding with high energy density can offer remarkable advantages over conventional fusion welding processes, such as minimal component distortion and high productivity, and is specifically suitable for joining aerospace structures. It is prominent to reduce weight that using welding crafts replace traditional rivet bond especially in the manufacturing of the aircraft skin, panel etc…However, due to the properties of aluminum alloy and the structural characteristics of T-joint, whether traditional TIG welding or advanced laser welding has to face with some problems in formation of weld, such as pores, cracks, deformation, which are difficult to solve by single way. In this paper, the fillet weld for T-joint of 3.0 mm thick 5A90 Al-Li alloy has been completed through laser welding with filling wire on the base of laser welding, which provides many advantages which are not found in either.
First of all, the position device, wire feeder and fixture which offer the equipment condition for craft investigation have been designed and optimized according to requirements of laser welding with filling wire tests and structural characteristics of T-joint.
In addition, the influences of welding parameters on fillet weld formation were investigated based on orthogonal tests. The results showed that the main factors affecting weld formation are welding angle and displace. With the results of orthogonal tests, laser-beam-welded T-joint parameter of SUS304 stainless steel was optimized, and the rules of parameters selection were set up. The optimal weld formation was obtained from validating trial. The laser welding with filling wire for T-joints of Al-Li alloy were carried out based on optimized parameters of laser welding, the results shows that the weld formation was improved greatly and hot cracks were avoided.
Finally, the influences of the pores for T-joint have been studied. Microstructures and mechanical properties of weld have been studied and analyzed as well. The results show that laser welding with filling wire in T-joint can complete good formations of weld which has similar organizations on both sides and has properties of grain-based and transition uniform. the tensile strength of joint with filling wire is increased nearly 20% than the joint by laser welding. Besides, the microhardness of Al-Li alloy weld bead is tended toward uniform and also affected by the welding sequence. The porosity and micro structure defect vanishes after heat-treatment technology at the cost of hardness decreases of the weld center.
The research results can help to advance the development and application of laser welding in T-joint, as well as provides a reference for eliminating the porosity in weld bead after welding. The results have also formed the basis of dual beam laser welding of T-joint for later studies.
首先,根据铝合金激光焊和填丝焊的焊接试验要求和T型接头的特点,优化与设计了定位装置、送丝装置及工装夹具,为工艺试验研究提供了装备条件。
其次,基于正交试验法设计了试验,研究了激光功率、焊接速度、焊接角度和偏移量四个主要的工艺参数对T型接头角焊缝界面结合、表面成形和底板熔深的影响。利用直观和极差分析试验结果发现,焊接角度和偏移量是影响T型接头焊缝成形的主要因素。对SUS304不锈钢T型接头激光焊接的工艺参数进行优化,当激光功率2000W、焊接速度2.5mm/min、焊接角度35。、偏移量0.5mm时,可以获得最佳的焊缝成形。之后,在优化的焊接工艺基础上进行了铝锂合金T型接头激光填丝焊,分析试验结果发现填丝焊极大的改善角焊缝成形和避免焊接热裂纹。
最后,研究了影响T型接头气孔的因素,分析发现焊接角度、焊接速度和材料中镁元素含量对气孔有较大的影响。对接头显微组织和力学性能研究发现：填丝焊使两侧焊缝组织相似且以等轴晶为主,提高了T型接头抗拉强度,还使得焊缝硬度分布更均匀,填丝焊由于增加了焊接热输入,焊缝硬度比激光焊焊缝硬度稍低,施焊顺序也会造成角焊缝硬度分布不同。焊后热处理工艺对消除铝合金激光焊接气孔有显著功效,使T型接头硬度分布更加均匀,但焊缝中心的显微硬度有所下降,母材的显微硬度相应提高。
研究成果有助于进一步推进T型接头激光焊接的发展和应用,同时为T型接头焊后处理消除焊缝气孔技术提供了参考依据,为后续进行T型接头两侧同步的双光束激光焊接研究打下了基础。
High strength aluminum alloy is one of the most important materials and finds extensive application in aerospace industry because of its light weight, superior strength-to-weight ratio, and high elastic modulus. Laser welding with high energy density can offer remarkable advantages over conventional fusion welding processes, such as minimal component distortion and high productivity, and is specifically suitable for joining aerospace structures. It is prominent to reduce weight that using welding crafts replace traditional rivet bond especially in the manufacturing of the aircraft skin, panel etc…However, due to the properties of aluminum alloy and the structural characteristics of T-joint, whether traditional TIG welding or advanced laser welding has to face with some problems in formation of weld, such as pores, cracks, deformation, which are difficult to solve by single way. In this paper, the fillet weld for T-joint of 3.0 mm thick 5A90 Al-Li alloy has been completed through laser welding with filling wire on the base of laser welding, which provides many advantages which are not found in either.
First of all, the position device, wire feeder and fixture which offer the equipment condition for craft investigation have been designed and optimized according to requirements of laser welding with filling wire tests and structural characteristics of T-joint.
In addition, the influences of welding parameters on fillet weld formation were investigated based on orthogonal tests. The results showed that the main factors affecting weld formation are welding angle and displace. With the results of orthogonal tests, laser-beam-welded T-joint parameter of SUS304 stainless steel was optimized, and the rules of parameters selection were set up. The optimal weld formation was obtained from validating trial. The laser welding with filling wire for T-joints of Al-Li alloy were carried out based on optimized parameters of laser welding, the results shows that the weld formation was improved greatly and hot cracks were avoided.
Finally, the influences of the pores for T-joint have been studied. Microstructures and mechanical properties of weld have been studied and analyzed as well. The results show that laser welding with filling wire in T-joint can complete good formations of weld which has similar organizations on both sides and has properties of grain-based and transition uniform. the tensile strength of joint with filling wire is increased nearly 20% than the joint by laser welding. Besides, the microhardness of Al-Li alloy weld bead is tended toward uniform and also affected by the welding sequence. The porosity and micro structure defect vanishes after heat-treatment technology at the cost of hardness decreases of the weld center.
The research results can help to advance the development and application of laser welding in T-joint, as well as provides a reference for eliminating the porosity in weld bead after welding. The results have also formed the basis of dual beam laser welding of T-joint for later studies.
引文
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[2]Hatch J E. Aluminum Properties and Physical Metallurgy[M]. Ohio, USA:ASM,1984:48-50.
[3]李红萍.铝合金在飞机上的应用[J].民用飞机设计与研究,2003(1)：18-22.
[4]《中国航空材料手册》编委会编.中国航空材料手册.第三卷：铝合金、镁合金[M].北京：中国标准出版社,2002：120-126.
[5]鲁隽.用先进结构和材料打造A380[J].国际航空,2004(1)：41-42.
[6]曹春晓.一代材料技术,一代大型飞机[J].航空学报,2008,29(3)：701-706.
[7]杨守杰,陆政,苏彬,等.铝锂合金研究进展[J].材料工程,2001,5：24-26.
[8]刘斌,陈铮铮,顾冰芳,等.铝锂合金的发展与应用[J].现代机械.2001,4：71-74.
[9]周昌荣,潘青林,朱朝明,等.新型铝锂合金的研究与发展[J].材料导报,2004,5(18)：30-32.
[10]黄兰萍,郑子樵,李世晨,等.铝锂合金的研究与应用[J].材料导报,2002,16(5)：22-23.
[11]刘静安.俄国铝合金研发现状与技术发展趋势[J].世界有色金属,2007,4：17-19.
[12]尹登峰,郑子樵.铝锂合金的研究开发的历史现状[J].材料导报,2003,2：21-22.
[13]潘复生,张丁非,等著.铝合金及应用[M].北京：化学工业出版社,2006：368-370.
[14]左铁钏,等.高强铝合金的激光加工[M].北京：国防工业出版社,2002：47-141.
[15]В.Л.罗沙著铝及铝合金的焊接[M].上海：上海科学技术出版社,1960：68-79.
[16]刘会杰,编著.焊接冶金与焊接性[M].北京：机械工业出版社,2007：124-140.
[17]任家烈,吴爱萍.先进材料的连接[M].机械工业出版社,2000：39-74.
[18]Messler Jr.Fbbert W. Bohnenstiehl, Scot.et al. A pressure-assisted approach for laser-beam weld-bonding Al alloy[J]. Structure for automobiles Assembly Automation.2004,24(4): 330-378.
[19]王家淳.激光焊接技术的发展与展望[J].激光技术,2001,25(1)：51-55.
[20]Z. Sun and M. Kuo. Bridging the joint gap wire feed laser welding[J]. Journal of Materials Precessing Technology,1999,187:213-222.
[21]李国华,蔡艳,高志国,等.航宇铝合金结构激光焊[J].航空制造技术,2007(7)：64-66.
[22]G. Sepold, T. C. Zuo, and C. Binroth. CO2 Laser beam welding aluminum alloys for transport systems[J]. Welding Research Supplement,2000(3):89-90.
[23]刘世永,孟德,黄德康.铝合金激光焊接的研究现状[J].机械工程材料,2004,6,28(9)：5-8.
[24]S. J. Katayama and Y. Yamaguchi. Effect of porosity and mechanical properties of CO2 laser welded aluminium alloy[J]. Welding Research Supplement,2005(5):70-73.
[25]齐向前,李玉昌,武建军等.铝合金激光焊接技术特性[J].焊接技术,2005,6,34(3)：30-32.
[26]郑启光,辜建辉,王涛,等.激光深熔焊接的熔池行为与焊接缺陷的研究[J].激光技术,2000,24(2)：90-94.
[27]E. J. Lavernia, T. S. Srivatsan, F. A. Mohamed. Review strength, deformation, fracture behaviour and ductility of aluminium-lithium alloy[J]. Journal of Materials Science.1990,25: 1137-1143.
[28]陈彦宾,曹丽杰.铝合金激光焊接研究现状[J].焊接,2001(3)：9-12.
[29]C. M. Allen. Laser Welding aluminium alloys[J]. TWI,2004:44-52.
[30]张盛海,陈铠,肖荣诗,等.高强铝合金T型接头激光焊接的研究现状[J].激光杂志2005(4)：45-48.
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