Development of new AC TIG welding power source and its improvement of productivity

CO2 emission control of vehicle became more and more strict. For example, the emission by automobile should be less than 95 g/km in EU by the end of 2021. Weight saving, such as using aluminum alloys instead of steel, is an effective method to comply the regulation. For joining those aluminum alloy parts, high efficiency and high quality welding process is required. Tungsten Inert Gas (TIG) welding process is a high quality welding process, but it has some disadvantages of lower deposition rate and shallow penetration. Especially, the penetration becomes shallow in aluminum alloys welding using Alternative Current (AC) TIG welding, because the arc shows poor concentration in the polarity of Electrode Positive (EP) than in the polarity of Electrode Negative (EN). Then new digital inverter controlled AC TIG welding power source has been developed. The power source has high speed current response to realize stable output at a range of 5 A to 500 A and AC frequency up to 500 Hz. As increasing AC frequency in the AC TIG welding process, the arc has become concentrated extremely. The concentrated arc has reduced the time from arc start to weld pool formation in fillet joint, and enabled high-quality thin plate edge welding of 0.2 mm thick JIS A 1050. Even in 100％ argon shielding gas, using AC-DC switching TIG welding with AC frequency of 500 Hz has penetrated to levels similar to the penetration depth by normal AC TIG welding with AC frequency of 300 Hz in 30％He-70％Ar gas. It has shown that AC-DC switching TIG has advantage to reduce production cost because expensive helium gas is not necessary to penetrate deeply. © 2020 Japan Light Metal Welding Association