Influence of reduced protective gas pressure on the formation of temperature fields and penetration during laser welding of thin-walled shell structures from aluminum alloys

The regularities governing the formation of temperature fields and the geometric parameters of penetration during laser welding of thin-walled cylindrical shell–end element structures made of aluminum alloys were investigated. Three welding schemes were considered: welding of 7075 alloy in an argon atmosphere at a reduced pressure of 170–190 Pa and at atmospheric pressure (105 kPa), as well as welding of a dissimilar 5083–7075 joint in an argon atmosphere at reduced pressure. Laser welding was performed at a power of 400 W and a welding speed of 66.7 mm/s. The experimental investigations were combined with finite-element modeling of thermal processes using a calibrated volumetric conical heat-source model. It was determined that, for alloy 7075, the penetration depth increases to 1.0 mm while the weld width simultaneously decreases to 0.38–0.40 mm, whereas at atmospheric pressure these values are 0.47 and 0.60–0.67 mm, respectively. Experiments showed that, during welding at reduced pressure, the structure is heated to 38–40 °C at a distance of 2–3 mm from the fusion line. The results obtained show that reduced pressure can be an effective process parameter for localizing welding heating.