TIG溶接によるAZ31マグネシウム合金の凝固割れ感受性

抄録

AZ31 magnesium alloy plate, which set up a Local Tensile Strain crack tester, were welded using both DC and AC pulsed TIG welding machine. Effect of pulse frequency on crack sensitivity of welded alloy were investigated. The longitudinal cracks appeared on center of the bead which became clear the solidification crack after the observation of fractured surface using SEM. In the case of AC welding, the cracks occurred low applied load compared with DC welding. This fact is explained that the size of molten pool on the AC welded is larger than that of the DC welding. Regardless of the welding methods, occurrence of the solidification crack have a tendency to depend on the pulse frequency, and it is recognized that the solidification crack sensitivity decreases with the frequency of 30 Hz. The length of solidification cracks have a tendency to depend on the grain size on the fusion zone. This phenomenon is possibly explained by the fact that cracks did not easily propagated on the fusion zone because the applied stress is dispersed in fine grain. The solidification cracks of TIG welded AZ31 magnesium alloy were occurred by restraint stress due to the deformation during welding process and could not recognized the influence of the segregation of compounds on the fusion zone.