【作者】 石磊；

【导师】 高洪明；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2006， 硕士

【摘要】 Plasma-MIG焊可以看作是等离子弧焊与熔化极气体保护焊(MIG)两种方法的结合。这种方法焊接铝合金时相对于MIG焊具有气孔少、晶粒细小等优点。本文设计了喷嘴式Plasma-MIG焊枪。在焊枪设计中采用环形喷嘴作为等离子阳极、对产热点直接水冷等方法,使焊枪的性能大大提高,不仅增大了其电流承载能力,而且明显提高了易损件的使用寿命。并在此焊枪基础上建立了Plasma-MIG焊接试验系统。分析了铝合金焊接气孔的形成机理,并设计正交试验方案研究送丝速度、MIG电压、等离子电流、焊接速度、离子气流量、保护气流量等参数及实验误差对焊缝气孔的影响。结果表明,离子气流量对气孔影响显著,焊接速度和MIG电压对气孔影响较大。在此综合分析的基础上,得出实现低气孔焊接的最佳工艺参数范围。利用上述得出的工艺参数对10mm厚5A06铝合金进行对焊,对焊缝进行X射线无损检测,只检测到极少的气孔;测试了接头的力学性能,其强度、韧性相对于MIG双道焊均有所提高;并对其断口和微观组织进行了分析。另外对10mm厚5A06铝合金进行了高熔敷率焊接研究,得出在不影响其接头强度、韧性的情况下,送丝速度可达14.5m/min,熔敷率达到了80g/min。更多还原

【Abstract】 Plasma-MIG welding process, which is superior over regular metal-inter- gas arc welding (MIG) process on the aspects of reducing porosity and achieving finer grains in welding aluminum alloys, can be regarded as a synthesis of plasma welding and gas-metal-arc welding (MIG).In this study, a nozzle-plasma-MIG welding torch, in which the nozzle acted as the plasma anode and the vital parts were directly cooled with water, was designed and had the improvements on the current capacity and life of the quick wearing parts. Moreover, an experimental system of plasma-MIG welding process was set up on the ground of the torch.The mechanism of porosity formation in welding Al-alloy was analyzed and the influences of welding process parameters consisting of wire speed、wire potential、plasma current、welding speed、plasma gas flow rate and shielding gas flow rate on the porosity were studied through an orthogonal experimental scheme taking into account experimental error at the same time. The experimental results demonstrate that the influences of plasma gas flow is remarkable, the weld speed and wire potential take the second place. According to the synthetical analysis, the optimum plasma-MIG process specification of little porosity welding was obtained.In this paper, 10 mm thick 5A06 aluminum alloy was butt welded with the above plasma-MIG welding process parameters, X-ray was adopted to nondestructively test the welding seams and very little porosity was inspected; the tensile strength and toughness of the Plasma-MIG welding were both higher than that of the two-pass MIG welding by comparing the mechanical properties of welded joints, and the fracture and the microstructure were also analyzed. In addition, the high melting rate welding of 10 mm thick 5A06 aluminum alloy was also studied, the wire feed rate and the melting rate come to 14.5m/min and 80g/min respectively on the premise that the tensile strength and the toughness of the weld meeted the requirements.更多还原