水中溶接部の気孔生成について : 気孔生成に及ぼす水圧の影響

概要

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The effect of water pressure on formation of porosity in underwater gravity welding were investigated within the range of 0 to 6kgf/(cm)^2 (gauge). The ilmenite type, high titanium oxide type and iron powder iron oxide type electrodes of 4mm in diameter and SM41 steel base metals of 6 and 9mm in thickness are used. Main results are summerized as follows : (1) The porosity is formed in weld metal, when water pressure is over about 0.5kgf/(cm)^2. The porosity increases with an increasing of water pressure. (2) The porosity (A type) in weld metal obtained under water-pressure of 0.5 to 3kgf/(cm)^2 is caused by the concentrated hydrogen in front of the solidification front. (3) The porosity (B type) is observed in weld metal obtained under water-pressure of 3 to 6kgf/(cm)^2 and the special solidification lines are often generated around porosity. The porosity is caused by bubble formed in molten metal, which is catched by the progressing solidification front. (4) The special solidification line is formed by a repetition of growth of bubble at the progressing solidification front and escape of bubble from there. (5) Changes of porosity shape and porosity formation mechanism with water pressure are caused by concentration of hydrogen in molten metal, which is greatly increased with water pressure.
1981-12-05