高炭素鋼のガスシールドアーク溶接に関する研究(第3報)

溶接部の機械的性質に及ぼす母材Sの影響

抄録

Mainly mechanical properties of high carbon steel (0.65-0.70%C, 0.008-0.026%S) welds for narrow gap (gap; 10 mm) butt welding in the flat position (build up process; intermittent, continuous) and vertical position (continuous) have been investigated by CO₂+20%O₂ gas shielded arc welding.
The results obtained are as follows:
(1) In case of tensile tests of welded joints by butt welding in the flat position (intermittent), excellent tensile properties with break down in weld metal and base metal are obtained for 0.008%S base metal. Tensile properties decrease as sulphur contents increase from 0.014%S to 0.026%S and Fractured position are almost in heat affected zone. For different base metals, tensile properties of welded joints by continuous welding are lower than by intermittent welding and fractured position by continuous welding are almost in heat affected zone. In case of vertical welding, excellent tensile properties with break down in base metal are obtained for different base metals.
(2) In case of rotating bending fatigue tests of welded joints by butt welding in the flat position and vertical welding, excellent fatigue strength are obtained for 0.008%S, 0.020%S base metals. In case of welded joints in the flat position for 0.026% S base metal, low fatigue strength are obtained and fractured origin exists at intercrystalline crack in heat affected zone for continuous welding.