PURPOSE: To decrease the welding defects in welding for making a large diameter steel pipe, by performing the multielectrode submerged arc welding using composite core wires for a high CaF2 fused flux contg. limited amts. of components and using a preceding electrode as a DC power source.
CONSTITUTION: The multielectrode submerged arc welding using a fused flux consisting, by weight, of 5W25% SiO2, 0.5W15% MnO, 5W25% CaO, 5W20% MgO, 2W20% Al2O3, 2W10% TiO2, 1W5% BaO, 20W60% CaF2, and if necessary 0.1W15% B2O3 and the balance impurities, and satisfying (CaO+MgO)/SiO2= 1.5W3.0, using composite core wires for 1 or ≥2 pieces of electrodes and using a DC power source for the preceding electrode is used for welding for forming a large diameter steel pipe. The reason for limiting the components lies in that CaF2 is effective in decreasing the content of the oxygen in the weld metal and if it is contained more than the upper limit, satisfactory beads are unobtainable. B2O3 is necessary for the formation of uniform and fine ferrite, and when it is contained more than the upper limit, cracking arises. If the value of (CaO+MgO)/SiO2 is below the lower limit, the arc is unstable and if above the upper limit, the workability is poor.
MIYAMOTO MASAO
ADACHI SEIZOU
KUSUMI YOSHIZOU
WADA HISANORI
KOMIZO HIROICHI
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| JPS55114471A | 1980-09-03 |