Study On The Arc Characteristic And Process Of CMT Technique To Ultrathin Aluminum Alloy

When using conventional MIG welding method to weld aluminum and aluminum alloy sheet, due to the characteristics of fast heat transmission, great linear expansion coefficient and easy oxidized., there will be defects such as great deformation, weld porosity and leakage on them. For welding the ultra-thin aluminum alloy below 0.5 mm, TIG, laser welding, micro-arc plasma welding methods cann`t get good joint. Using the advantage technology called CMT short for Cold Metal Transfer, with lower welding heat input, which is good for welding thin aluminum alloy with high efficiency and high quality. The research on CMT technology is mostly on the applicability of CMT technology and study on dissimilar metal brazing technology. There is seldom research on welding ultrathin aluminum alloy sheet.This article is based on reading massive domestic and foreign researches on the CMT welding technology. Use the TPS2700 CMT welding machine and KUKA KR16 automatic welding robot to establish the automatic CMT welding system. Use 0.3mm aluminum alloy as test material. Establish CMT welding signal acquisition system with high-speed cameras, hanover welding quality analyzer to adjust parameters: I-boost, I-sc-wait, I-sc2 for studying the influence of three parameters on the stability of CMT arc and the voltage and current density distribution, the mechanism of CMT waveform control was mastered.Research shows that: reduce the value of I-boost properly could cut down the welding heat input, but when the arc energy cut down, the arc instability and weld formation are getting poor. I-sc-wait assist to add the welding heat input, In the case of other variate unchanged, increasing I-sc-wait could enhance the stability of welding, but if the value of I-sc-wait is oversize, the arc overshoot phenomenon would happen, lead to get the bad weld formation. I-sc2 effects the arc stability when arc relight, by reason of exist the arc inertial effect, if I-sc2 setting is oversize, the arc energy when arc relight is too large.In the design of welding waveform for ultra-thin aluminum alloy, I-boost is set at low level, ensure that low energy input. On the basis of ensure getting suitable weld formation, raise I-sc-wait to replenish the welding heat input. Set the I-sc2 lower than 40 A to avoid the problem of poor formation when arc relight because of arc inertial effect. Through the analysis of arc shape and the voltage and current density distribution, the consequence shows that the design of CMT waveform can both reduce the welding energy and guarantee arc stability. At the welding speed of 1.1 m/min, I-boost is 8A, I-sc-wait is 40 A, I-sc2 is 30 A, process good weld formation.