アルミニウム合金の溶接法に関する二,三の検討

Abstract

Aluminum and aluminum alloys are usually welded by TIG or MIG welding, and the former may generally give less blowholes in deposited metal than the latter. But TIG welding has slow deposition rate, which causes a wider softened zone, and may lead to insufficient mechanical properties of welded joint. MIG welding gives higher welding speed and deeper penetration, but it is likely to form blowholes.This experiment was carried out to compare the static and dynamic mechanical properties of TIG and MIG welded joints.The following results are obtained;1) Tensile strength and ductility of MIG butt-and double-tee joints, which were welded with lower heat input than TIG welding, were superior to those of TIG joints.2) Fatigue strength at 107 cycles were : 9.1 Kg/mm2 for base metal, 8.0 Kg/mm2 for MIG butt-welded joint (reinforcement removed), 7.1 Kg/mm2 for TIG butt-welded joint (reinforcement removed), 5.5 Kg/mm2 for TIG double-tee joint, and 4.5 Kg/mm2 MIG double-tee joint.But the toe angle of fillet welds seemed to more affect the fatigue strength, because the higher fatigue strength was obtained by MIG double-tee joints with round-worked toe than by TIG joints.3) According to X-ray radiographs MIG deposited metal had more blowholes than TIG deposited metal, but microscopically many blowholes were observed in a boundary zone of passes by TIG deposited metal. Especially interdendritic cavities were also found in MIG deposited metal.