天津职业技术师范大学2013届本科生毕业论文
4 结论
本论文围绕等离子与电弧复合焊接低碳钢工艺研究理论研究这一主题，开展了粉末堆积等离子与CO2气体保护焊接夹具的制作，使这两种原本各有用途的焊接方法结合起来，对不同参数下的焊接件进行研究和分析，并获得了在不同因素下的高速摄像照片。取得了以下主要成果及结论：
1）研究了复合焊接过程， 首先对粉末堆积等离子焊接与CO2气体保护焊接的各自特点的研究分析，在已有专用夹具、实验的基础上，考虑在送粉率、焊接速度、粉末等离子电流及CO2气体保护焊电流不同的情况下，所得熔宽及焊件表面质量各不相同。
2）相对本实验，所得的最佳实验参数为第四组实验数据，即当送粉率为18g/min，焊接速度为4mm/s，等离子电流为100A，CO2气体保护焊电流为160A时，焊件的熔宽最大，为8.84mm,且焊缝成形规则边缘处过渡圆滑边，成形质量美观,表面质量最好；实验九，即当送粉率为24g/min，焊接速度为6mm/s，等离子电流为100A，CO2气体保护焊电流为80A时，焊件的熔宽最小，为4.18mm,且焊缝成形不规则，出现驼峰焊道与咬边等焊接缺陷,表面质量最差。
3）由取最大熔宽两组实验数据比较，即实验四，实验七知，焊接速度对焊件的表面质量影响最大。
4）由高速摄像装置可知，在焊接过程中，CO2气体保护焊首先对低碳钢进行焊接，而后，粉末等离子焊对焊缝进行表面强化处理，增加了焊件的表面质量。
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天津职业技术师范大学2013届本科生毕业论文
参考文献
[1] Brown D. The effect of electromagnetic stirring and mechanical vibration on arc welding[J]. Welding journal，1962，41(2)：41~50
[2] T seng C F, Savage W F. The effect of arc oscillation in either the transverse or
longitudinal direction has a beneficial effect on the fusion zone microstructure and tends to reduce Sensitivity to hot cracking[J]. Welding Journal，1971, 50(12)：777~785
[3] E.O.Correa; S.C.Costa; J.N.Santos, 2008, Journal of Materials Processing Technology, vol.198,: p.323~329.
[4] Munitz A, Cotler C, Shaham H, etal. Electron beam welding of magnesium AZ91D plates[J]. Welding Journal,2000, 79(7)：202~208.
[5] 柯鼎华.二氧化碳气体保护焊在供水管道上的应用 [ J]. 科技创新导报, 2008( 13). [6]卢振洋, 黄鹏飞,蒋观军, 等. 高速熔化极气体保护焊机理及工艺研究现状.焊接，2006, （6）: 16-20
[7] 霍晓敏,唐清山. 二氧化碳气体保护焊在薄板焊接中的应用 [ J]. 四川建筑科学研究, 2009( 6).
[8] 何明戟,朱志康,陈淑慧.等离子弧焊机的发展与前景[J].电焊机,2007,37(9):5-7. [9] 史耀武.材料焊接工程（上）[M].中国材料工程大典,第22卷.北京:化学工业出版社,2005.
[10] 陈科. 等离子弧焊接性能及其应用[J]. 造船技术. 1979(05)
[11] 肖春林,张翼鹏. 等离子弧焊接的特点及基本工作原理[J]. 科技信息(科学教研). 2008(08)
[12] 张幻. 等离子弧焊接工艺及应用[J]. 船海工程. 2008(01)
[13] 袁玉兰,王惜宝,朱冬妹,刘丹. 活化CO2气体保护焊的研究[J]. 焊管. 2006(01)
[14] 张红. 等离子弧填丝粉末堆焊设备的研究[D]. 天津大学 2007
[15] 周振丰,张文钺编.焊接冶金与金属焊接性[M]. 机械工业出版社, 1988
[16] 邱葭菲,王立. CO2气体保护焊焊接工艺设计及在工程机械中的应用[J]. 新技术新工艺. 2005(02)
[17] 金业全. 焊缝弧坑的成因及其控制[J]. 铁道机车车辆工人. 1998(08)
[18] 吕耀辉,刘存龙,向永华,姜祎,夏丹,徐滨士. 等离子弧焊接维修技术[A]. 第四届世界维修大会论文集[C]. 2008
[19] 沈阳机电学院焊接教研室“反极性弱等离子弧基本特性及其堆焊工艺与设备”研究小组. 反极性弱等离子弧基本特性及其堆焊工艺、设备的研究已获明显成效[J]. 沈阳工业大学学报. 1982(02)
[20] 陈全明，金属材料及强化技术．同济大学出版社.
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天津职业技术师范大学2013届本科生毕业论文
附录1：英文资料
Droplet transfer during conventional gas metal arc and plasma-gas
metal arc hybrid welding with Al 5183 ?ller metal
C.-H. Kim*, Y.-N. Ahn, K.-B. Lee
Welding and Joining Research Group, Korea Institute of Industrial Technology, 7-47
Songdo-dong, Incheon 406-840, Republic of Korea
Article history:Received 12 December 2011,Received in revised form 28 February 2012,Accepted 2 March 2012 Available online 9 March 2012.
Keywords:Welding,GMAW,Plasma-GMA,hybrid-welding,Dropl-et transfer,Al 5183 ?ller
Abstract:When welding with 5xxx series aluminium ?ller wires, explosion of droplets occurs during droplet transfer, which results in spatter formation. In plasma-GMA (gas metal arc) hybrid welding, the coaxial plasma arc surrounding the GMA enables more stable droplet transfer and lower GMA current. In this study, bead-on-plate welding tests were conducted using conventional GMA welding and plasma-GMA hybrid welding. Droplet transfer behaviours for both processes were observed using high-speed imaging, and droplet explosion behaviour was analysed under various welding conditions. In plasma-GMA welding, the droplet transfer was stabilized without in-flight explosion, even for high welding current and higher melting rate was achieved by the additional plasma
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天津职业技术师范大学2013届本科生毕业论文
arc.
1. Introduction
In GMA (gas metal arc) welding, a welding arc is established between the continuously fed filler wire and the base material. The filler wire is melted by the welding arc plasma and droplets of the melted alloy travel across the welding arc and into the weld pool.The thermal process that occurs during droplet formation and transfer was investigated by several researchers, and it was found that the droplets are overheated by the surrounding welding arc and that their temperatures are higher than the melting temperature of the filler metal [1-5]. Moreover, overheating of the droplets increases with the welding current. With Al filler wires containing Mg, such as the 5xxx series filler wire, high-vapour-pressure elements in the wire cause the in-flight explosion of droplets [6]. The plasma-GMA hybrid welding process was proposed in the 1970s [7-9]. In plasma-GMA hybrid welding, a gas metal arc is coaxially positioned inside a plasma arc established between A plasma nozzle and the base material.Heating from the surrounding plasma arc was found to stabilize the droplet transfer in GMA welding, even for low welding currents [10,11].In high current welding of Al alloy, the plasma arc can also supply additional heat to the base material and stabilize the droplet transfer without in-flight explosion but there have been few studies on the melting and droplet transfer behaviours for high current welding.
In this paper, droplet transfer behaviours were investigated during GMA and plasma-GMA hybrid welding of Al 5083 alloy with Al 5183 filler wire containing about 5% Mg. Through high-speed imaging, droplet transfer for each process was analysed and in-flight explosions under various welding conditions were observed.
2. Experimental setup
An Al 5083 plate with a thickness of 25 mm and an Al 5183 wire were used as the base and filler materials, respectively. Table 1 shows the typical chemical composition of Al 5083 and 5183 alloys. Torch arrangements for GMA and plasma-GMA hybrid welding are shown in Fig. 1. In GMA welding, an Ar 50%-He 50% mixture was supplied as the
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天津职业技术师范大学2013届本科生毕业论文
shielding gas at a flow rate of 40L/min. The diameters of the filler wires used were 1.2 mm, 1.6 mm, and 2.4mm, and a DC pulse current was applied. In plasma-GMA hybrid welding, Ar was used to serve three purpose-it was as the shielding, plasma, and GMA gas. Flow rates for the shielding, plasma, and GMA gas are 5 l/min, 15 l/min, and 10 l/min, respectively. A continuous-wave current was applied to obtain a plasma arc and a DC pulse current was applied for GMA. Tables 2 and 3 list the welding parameters for GMA and plasma-GMA hybrid welding.
A high-speed imaging system with a capture speed of 6000 frames per second was employed for observation of the droplet transfer behaviour. Band pass (808 nm) and neutral density(ND400) filters were used to obtain clear images, and a metal halide lamp was used for backlighting. ·
Table 1 Chemical composition of Al alloys (wt.%).
Al5083 Al5183
Si 0.4 0.08 Mn 0.4-0.1 0.70 Cr 0.05-0.25 0.15 Cu 0.1 0.02 Zn 0.25 0.10 Mg 4.0-4.9 4.9 Fe 0.4 0.2 Al Bal. Bal. 30