ＭＡＧ溶接の溶接作業性と継手性能に及ぼすシールドガス組成の影響

Abstract

CO2 welding has been used more and more because of the properties of saving energy and obtaining higher efficiency, but now there grow requirements for further reduction of spatter, improvement of bead appearance, increase of welding speed and elevation of quality of weld metal. MIG welding seems to be suitable for these purposes, but it has fatal demerit that blowholes generate so often.It was thought that these requirements can be satisfied by combining of CO2 and MIG welding (MAG welding), so that an investigation was made about the effects of Ar-CO2 mixed gas welding on the usability and properties of weld.The results obtained are as follows:1) Generation of spatter becomes fewer when spray transfer occurs in MAG welding.2) Spray transfer occurs when ratio of Ar in shielding gas is more than 70%.3) It is necessary to make the ratio of Ar in shielding gas less than 85% so as to inhibit the generation of blowholes.4) Frequency of short cricuit increases according to increase of ratio of Ar, but as the ratio or Ar becomes over 85%, it decreases.5) Appearance of bead and mechanical properties of weld metal become better according to increase of Ar ratio in shielding gas.By these results, it was concluded that Ar-20%CO2 mixed gas was the best for MAG welding. And it was understood that Ar-20%CO2 MAG welding had merits of CO2 and MIG welding and furthermore, it had special features better than those two welding.Also, the electrode wires DD50A and DD50S were developed for MAG welding.