异种轻质合金激光焊接工艺研究
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摘要
本文主要进行了TC4钛合金与L3工业纯铝的异种金属板材激光搭接焊研究。
TC4和铝之间的焊接属于异种金属焊接范畴。但TC4钛合金和铝激光焊接除一般异种金属焊接时容易出现的问题外,还有其特殊的地方如:熔点、激光吸收率相差大等,因此对其焊接性进行了分析。
由于钛合金与铝对激光的吸收率相差大,因此,采用搭接方式,利用钛对激光的良好的吸收,将其置于铝板之上,依靠热传导提高铝板温度,随着温度升高铝板对激光吸收率大幅增加,从而实现焊接过程。
试验采用1.5mm厚度的钛合金板材与1.0mm铝板,采用光斑直径为0.3mm,离焦量为0的激光束,改变激光功率与焊速等参数进行多次试验。通过拉伸试验、显微组织及硬度分析对表面形貌、显微组织、力学性能及SEM进行分析研究。
借用熔合比概念,估算了铝在焊缝中的含量,铝含量随线能量的增加而增加,结合扫描照片及能谱分析,分析了焊缝中金属间化合物的形成原因:激光焊接中焊缝冷却速度很快,熔池存在时间很短,由于试验采用搭接接头,铝板位于钛合金板的下部,所以铝没有足够的时间到达焊缝上部。而且熔池中铝与钛的熔合主要依靠对流,扩散很少,激光焊接具有很大的深宽比,焊缝形状呈钉型,铝板则位于钉尖位置,面积很窄,熔池中金属液体流动阻力大,因此铝很难到达焊缝上部,而在焊缝底部富集。所以焊缝底部铝含量要远远高于10%,而形成金属间化合物。
硬度分析与能谱分析结果都证明了金属间化合物的存在。接头拉伸试验表明,在功率为1.2kw,焊速为1.2m/min,线能量为1.0kJ/cm的条件下能够获得满足性能要求的接头。
根据显微组织照片及扫描电镜,分析了焊接中各种缺陷及产生的原因,包括气孔、裂纹与焊缝中的偏析。
Dissimilar metal plates laser welding of TC4 Ti alloy to L3 industrial pure Al are researched in this thesis.
Welding between TC4 and Al categorize into dissimilar metal welding.But TC4/Al welding have their specific characteristic, such as their melting point and laser absorptivity are different greatly, besides general dissimilar metal welding problem. So we analyze their weldability.
Because the difference between Ti alloy and Al's laser absorptivity is great, we adopt lap joint and make use of the great laser absorption of Ti, and put it on the Al plate,increase Al plate temperature by thermal conductivity.with temperature increasing,laser absorptivity of Al is increasing,so welding joint is formed.
We adopt 1.5mm Ti alloy plates and 1.0 mm Al plates, and the laser beam characteristic we use is 0.3mm spot diameter, 0 defocusing amount. We carry on several experiments by changing laser power and welding speed, and by tensile testing, microstructure and hardness analysis.We respectively research their surface profile, microstructure , mechanical characteristic and SEM pictures.
We evaluate Al content in welding by formula of penetration ratio, and the result show Al content increase with heat input increasing. Combining the picture of SEM and energy spectrum analysis, we know intermetallic composites forming in the welding: fast cooling speed in laser welding, short existing time of molten pool, and Al have no enough time to diffuse to welding above ,because Al plate lay under Ti alloy plate in lap welding. In addition, they mainly rely not on diffusion, but convection in Al/Ti molten pool, and large depth-to-width ratio, tack shape welding; Aluminum plates are located in the narrowest position. The aluminum is difficult to reach to the front of the weld and stays at the bottom because of the large liquid metal flow resistance in the weld pool, so the content of aluminum in the bottom of weld is far more than ten percent and they are eventually coming into being intermetallic compounds.
Both hardness analysis and energy spectrum analysis prove the existence of tntermetallic compounds. Tensile testing demonstrates it can get the meet capability joint on the conditions of power 1.2kw, weld speed 1.2m/min and energy input 1.0kJ/cm.
Based on pictures of microstructure and SEM, we analyze varied weld flaw and resulting causes, including gas pores, cracks and segregation in the welding.
TC4和铝之间的焊接属于异种金属焊接范畴。但TC4钛合金和铝激光焊接除一般异种金属焊接时容易出现的问题外,还有其特殊的地方如:熔点、激光吸收率相差大等,因此对其焊接性进行了分析。
由于钛合金与铝对激光的吸收率相差大,因此,采用搭接方式,利用钛对激光的良好的吸收,将其置于铝板之上,依靠热传导提高铝板温度,随着温度升高铝板对激光吸收率大幅增加,从而实现焊接过程。
试验采用1.5mm厚度的钛合金板材与1.0mm铝板,采用光斑直径为0.3mm,离焦量为0的激光束,改变激光功率与焊速等参数进行多次试验。通过拉伸试验、显微组织及硬度分析对表面形貌、显微组织、力学性能及SEM进行分析研究。
借用熔合比概念,估算了铝在焊缝中的含量,铝含量随线能量的增加而增加,结合扫描照片及能谱分析,分析了焊缝中金属间化合物的形成原因:激光焊接中焊缝冷却速度很快,熔池存在时间很短,由于试验采用搭接接头,铝板位于钛合金板的下部,所以铝没有足够的时间到达焊缝上部。而且熔池中铝与钛的熔合主要依靠对流,扩散很少,激光焊接具有很大的深宽比,焊缝形状呈钉型,铝板则位于钉尖位置,面积很窄,熔池中金属液体流动阻力大,因此铝很难到达焊缝上部,而在焊缝底部富集。所以焊缝底部铝含量要远远高于10%,而形成金属间化合物。
硬度分析与能谱分析结果都证明了金属间化合物的存在。接头拉伸试验表明,在功率为1.2kw,焊速为1.2m/min,线能量为1.0kJ/cm的条件下能够获得满足性能要求的接头。
根据显微组织照片及扫描电镜,分析了焊接中各种缺陷及产生的原因,包括气孔、裂纹与焊缝中的偏析。
Dissimilar metal plates laser welding of TC4 Ti alloy to L3 industrial pure Al are researched in this thesis.
Welding between TC4 and Al categorize into dissimilar metal welding.But TC4/Al welding have their specific characteristic, such as their melting point and laser absorptivity are different greatly, besides general dissimilar metal welding problem. So we analyze their weldability.
Because the difference between Ti alloy and Al's laser absorptivity is great, we adopt lap joint and make use of the great laser absorption of Ti, and put it on the Al plate,increase Al plate temperature by thermal conductivity.with temperature increasing,laser absorptivity of Al is increasing,so welding joint is formed.
We adopt 1.5mm Ti alloy plates and 1.0 mm Al plates, and the laser beam characteristic we use is 0.3mm spot diameter, 0 defocusing amount. We carry on several experiments by changing laser power and welding speed, and by tensile testing, microstructure and hardness analysis.We respectively research their surface profile, microstructure , mechanical characteristic and SEM pictures.
We evaluate Al content in welding by formula of penetration ratio, and the result show Al content increase with heat input increasing. Combining the picture of SEM and energy spectrum analysis, we know intermetallic composites forming in the welding: fast cooling speed in laser welding, short existing time of molten pool, and Al have no enough time to diffuse to welding above ,because Al plate lay under Ti alloy plate in lap welding. In addition, they mainly rely not on diffusion, but convection in Al/Ti molten pool, and large depth-to-width ratio, tack shape welding; Aluminum plates are located in the narrowest position. The aluminum is difficult to reach to the front of the weld and stays at the bottom because of the large liquid metal flow resistance in the weld pool, so the content of aluminum in the bottom of weld is far more than ten percent and they are eventually coming into being intermetallic compounds.
Both hardness analysis and energy spectrum analysis prove the existence of tntermetallic compounds. Tensile testing demonstrates it can get the meet capability joint on the conditions of power 1.2kw, weld speed 1.2m/min and energy input 1.0kJ/cm.
Based on pictures of microstructure and SEM, we analyze varied weld flaw and resulting causes, including gas pores, cracks and segregation in the welding.
引文
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[2] Ripple P. Laser beam welding with robots in the automotive industry. Proc ECLAT’94, 5th European Conference on Laser Treatment of Materials, DVS, 1994: 151～164
[3] Mazumder J. Laser welding. State of the art review. JOM, 1982, (7):16～24
[4] Mazumder J. Laser beam welding. ASM Handbook, ASM International,1993,12: 262～269
[5] Kujanpaa V P, David S A. Proc ICALEO’86,1986: 63
[6]何康生,曹雄夫编著.异种金属焊接.北京:机械工业出版社, 1986: 10~15
[7]赵鹏飞,康慧. Al-Ti异种合金真空钎焊的研究.材料工程,2001, 4: 25～28
[8]庞铭,虞钢,刘兆等. K418与42CrMo异种金属的激光穿透焊接.中国激光,2006, 33(8): 1122～1126
[9]柳绪静,刘黎明,王恒等.铝镁异种金属激光-TIG复合热源焊焊接性分析.焊接学报, 2005, 26(8): 31～34
[10] F. Wagner, I. Zerner, M. Kreimeyer, et al. Chara cterization and Properties of Dissimilar Metal Combinations of Fe/Al and Ti/Al-Sheet Materials. 20th International Congress on Applications of Lasers & Electro-Optics, ICALEO. Florida, USA, 2001: 1301
[11]宋敏霞,赵熹华,郭伟.钛合金与其它金属材料扩散连接研究现状与发展,焊接, 2005, 1: 5
[12] T. A. Mai, A. C. Spowage. Characterisation of dissimilar joints in laser welding of steel–kovar,copper–steel and copper–aluminium.Materials Science and Engineering A 374. 2004: 224～233
[13] A. Costa, L. Quintino, R. M. Miranda. Microstructural aspects of laser dissimilar welds of hard metals to steels. JOURNAL OF LASER APPLICATIONS Volume 16, 2004,12(4): 206～211
[14] Hongwei Shen, Mool C. Gupta. Nd: YAG Laser Welding of Copper to Stainless Steel. 2001international laser process conference, 2001
[15]美国金属学会.焊接与钎焊.金属手册.北京:机械工业出版社, 1994: 198
[16]何小东,张建勋,裴怡等.航空用钛合金激光焊和TIG焊残余应力测试.焊接, 2003 (10): 26～29
[17]梁春雷,李晓延,巩水利等. TC4钛合金薄板激光焊接头疲劳性能研究.材料工程,2006,4: 48～51
[18]朱秀军,熊建钢,黄安国等.钛合金TC4的激光焊接.电焊机,2004,34(9):13～16
[19]姚伟,巩水利,陈俐.钛合金激光穿透焊的焊缝成形(Ⅰ) .焊接学报, 2004, 25(4): 119～112
[20] P. S. Liu, W. A. Baeslack, J. Hurley. Dissimilar alloy laser beam welding of titanium: Ti-6Al-4V to beta-C. Welding Journal, 1994, 73(8): 7～16
[21] Z. Li,S. L. Gobbi. Laser welding for lightweight structures. Journal of Materials Processing Technology, 1997, 70(5): 137～144
[22] T. Shinoda, K. Matsunaga, T.Akaishi. Laser welding of titanium alloy. Journal of Light Metal Welding and Construction, 1990, 28(2): 1～8
[23] T. Shinoda, K. Matsunaga, T. Akaishi. Solidification cracking of beta titanium alloy inlaser welding. Journal of Light Metal Welding and Construction, 1990, 28(7): 291～297
[24] J. Dos Santos, G. am, F. Torster. et al Properties of power beam welded steels, Al- and Ti- alloys: Significance of strength mismatch. Welding in the world, 2000, 44(60): 42～64
[25] S.H. Wang, M. D. Wei, L. W. Tsay. Tensile properties of LBW welds in Ti–6Al–4V alloy at evaluated temperatures below 450℃. Materials Letters, 2003, 57:1815～1823
[26] Zhang Li, S. L. Gobbi, I. Norris, S Zolotovsky, K. H. Richter. Laser welding techniques for titanium alloy sheet. Journal of materials processing technology, 1997, 65: 203～208
[27] P. E. Denny and E. A. Metzbower. Laser beam welding of titanium. Welding Journal 1989, 68(8): 342～346
[28] A. C. Woloszyn, D. S. Howse, N. Sekhar et al. Development of procedures for low porosity Nd:YAG laser welding of 3.25 and 6.35mm thickness titanium alloy. TWI report, 2003: 763
[29]朱宏,金忠华.铝及铝合金激光焊接技术的研究现状.电子工艺技术. 1997. 7:129
[30]宋东风,胡绳荪,马力.铝合金激光焊接技术的发展现状.电焊机, 2004.9, 34(9): 1～3
[31] Shida Tomohiko. CO2 laser welding of aluminum alloys(1)-welding of aluminum alloy using CO2 laser beam in combination with MIG arc. Welding Research Ahroad. 1997. 43(5): 36～41
[32] Walduck R, Biffin J. Plasma arc augmented laser welding.Welding & Metal Fabrication, 1994, (4): 172～176
[33]许良红,田志凌,彭云等.高强铝合金的激光-MIG复合焊接的试验研究.稀有金属, 2005, 29(5): 773～779
[34]赵敬东.钛合金焊接的常见缺陷及其预防.焊接学报, 2000,(5): 56
[35]李亚江.特殊及难焊材料的焊接.北京:化学工业出版社, 2003: 153～167
[36] Patterson R A, Martin P L, Damkroger B K, Christodoulou L. Titanium Aluminide: Electron beam weldability. Welding Journal, 1990, 69(1): 39～44
[37] Patterson R A, Damkroger B K. Weldability of gamma titanium aluminide in weldability of Materials. Proceedings of symposium on weldability of materials, 1990, 10:259～267
[38]杜汉斌,沈剑平,邬美华等.钛合金激光未穿透焊气孔形成的机理研究.宇航材料工艺, 2006, 3: 51～54
[39]钱九红.航空航天用新型钛合金的研究发展及应用.稀有金属, 2000, 24(3): 218~222
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