水カーテン式水中ＭＩＧアーク溶接 ＩＩ 溶接金属の性質および強さに与える水圧の影響

Abstract

The effect of water pressure on chemical compositions and non-diffusible hydrogen content in weld metal was studied by use of high water. pressure simulator. The water curtain type MIG arc welding method was applied to the butt welding of mild steel under high pressure levels corresponding to water depth of 50 m and 90 m. The results obtained are as follows.1) In case the pure argon was used as a shielding gas, silicon, manganese and carbon content in weld metal were not affected with water depth. On the other hand, when oxygen was added to argon, these elements decreased with increasing of oxygen content and arc length under the constant water pressure and also decreased with increasing of water pressure under the constant oxygen content and the constant arc length.2) Non-diffusible hydrogen content in weld metal was not affected so much with increasing of water pressure and was in the range of 2.2-3.5 cc/100 g, which was very low level compared with the other wet welding method.3) Effect of root gap was dissimilar in plate thickness. For the single pass butt welding of 6 mm thick plate, the appropriate gap was 0 mm or 2-3 mm.4) The hardness in welds was not affected with water pressure. The hardness in weld metal decreased with increasing of oxygen content which affected the increase of molten metal and decrease of deoxidizes elements.5) Single pass and multi-pass butt welds, welded in down hand position under high water pressure, included no defect and passed not only in tensile test but also in 180°bending test.6) Good results were obtained in Charpy V-notch impact test of deposited metal welded. under water depth of 50 m. Oxygen addition to shielding gas was available for increasing the impact value.