铝合金超声波辅助电阻钎焊技术研究

发布时间：2018-05-24 19:20

本文选题：超声振动 + 电阻钎焊　；参考：《兰州理工大学》2017年硕士论文

【摘要】：电阻钎焊具有热量集中,加热时间短,热影响区小,变形和应力小的优点,广泛应用于电子、微型设备和小型医疗设备。文献报道,超声波的施加使电阻钎焊接头焊合率升高到85%。目前,电阻钎焊仍限于微型材料的焊接,并且对超声辅助电阻钎焊原理也没有相关研究。因此,本文以焊接较大尺寸的接头,探索超声辅助电阻钎焊原理为主要的研究目标,设计制作了超声辅助电阻钎焊装置,采用Al-Si-Mg合金钎料,在大气环境下对6063铝合金进行了超声辅助电阻钎焊。该装置结构简单,能提供瞬时低电压、大电流、精确焊接压力,减少超声波衰减,且该装置为国内首个超声辅助电阻钎焊装置,并获国家专利授权。本文研究了两步电阻钎焊工艺,并得到了最优工艺。研究中发现电阻钎焊过程中会发生爆破现象,而超声波可以消除爆破现象,超声方向和时间以及焊接接头几何形状会对爆破现象有影响。两步电阻钎焊方法使母材和钎料之间的界面形成了较大区域的冶金结合,从而改善了钎料和母材之间的连接条件。研究发现,爆破现象的产生是由于在电、热和力的作用下熔融钎料中的电流密度过高引起的。当超声振动移除两母材接触区域的氧化膜,并且超声时间不低于6s时,可消除爆破现象。本文采用非等尺寸的焊接接头,研究了接头中钎料的偏移现象。同时讨论了等尺寸和非等尺寸条件下Si元素的高速扩散以及火口裂纹的产生和防止机制。研究发现:由于上界面处电流密度大,产生的热量高,而且下界面处的散热能力强,因此,产生了钎料的偏移现象。在焊接电流持续作用于局部区域时,熔融钎料中的Si元素偏聚于界面处,并且沿着高扩散率通道(Al晶粒的晶界)向母材中高速扩散。当采用非等尺寸焊接接头时,Si的高速扩散只在电流密度大的区域产生。最长的扩散距离达到了958.3μm。在高温条件下,扩散的Si使母材产生了溶蚀孔洞,最后形成了火口裂纹。而超声振动可以防止局部区域的高温、Si元素的扩散以及溶蚀孔洞和火口裂纹等裂纹的产生。通过上述的分析,得出了不同接头尺寸和有无超声振动条件电阻钎焊机理,以及电流路径变化的机理图。
[Abstract]:Resistance brazing has the advantages of heat concentration, short heating time, small heat affected zone, small deformation and small stress, so it is widely used in electronic, micro-equipment and small medical equipment. It is reported that the application of ultrasonic wave can increase the soldering rate of resistance brazing joint to 85. At present, resistive brazing is still limited to the welding of micro materials, and the principle of ultrasonic assisted resistance brazing is not studied. Therefore, in order to weld large size joints and explore the principle of ultrasonic assisted resistance brazing, an ultrasonic assisted resistance brazing device is designed and fabricated, and Al-Si-Mg alloy filler metal is used. Ultrasonic assisted resistance brazing of 6063 aluminum alloy was carried out in atmospheric environment. The device is simple in structure, can provide instantaneous low voltage, high current, accurate welding pressure and reduce ultrasonic attenuation. It is the first ultrasonic assisted resistance brazing device in China and has been authorized by national patent. In this paper, the two-step resistance brazing process is studied, and the optimum process is obtained. It is found that blasting will occur in the process of resistance brazing while ultrasonic wave can eliminate the blasting phenomenon. The direction and time of ultrasonic and the geometry of welded joint will affect the blasting phenomenon. The two-step resistance brazing method makes the interface between the base metal and the filler metal form a large area of metallurgical bonding, thus improving the connection condition between the filler metal and the base metal. It is found that the blasting phenomenon is caused by the high current density in the molten solder under the action of electricity, heat and force. When ultrasonic vibration removes the oxide film in the contact area of the two base materials and the ultrasonic time is not less than 6 s, the blasting phenomenon can be eliminated. In this paper, the offset phenomenon of solder in the joint is studied by using non-equal size welded joint. At the same time, the high speed diffusion of Si element and the mechanism of crack generation and prevention are discussed under the condition of equal size and unequal size. It is found that because of the high current density at the upper interface, the high heat production and the strong heat dissipation capacity at the lower interface, the offset phenomenon of solder is produced. When the welding current continues to act on the local region, the Si element in the molten solder concentrates at the interface and diffuses at high speed along the grain boundary of the Al grain in the high diffusivity channel. The high speed diffusion of Si only occurs in the region with high current density when the non-equal size welded joints are used. The longest diffusion distance is 958.3 渭 m. At high temperature, the dispersed Si causes the dissolution of the base metal, and finally forms the crack at the mouth of the fire. The ultrasonic vibration can prevent the diffusion of Si element in the local region and the formation of cracks such as cavity and fire mouth. Through the above analysis, the mechanism of resistance brazing with or without ultrasonic vibration and the mechanism diagram of current path change are obtained.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG457.14

【参考文献】