構造用鋼材溶接部近傍の引張衝撃値分布(第1報)

鋼種の影響

抄録

In order to investigate the distributions of impact value in the heat affected zcne of welded parts of various steel plates, many tensile impact specimens of which diameter is very small were taken out of there. Using these specimens, tensile impact values were measured at every one mm from fusion line to the unaffected base metal. The used steels are mild steel, high tension steels, steels for low temperature use and steels for machine parts. These steel plates were butt welded by CO₂-O₂ arc welding process. The results obtained are as follows.
1. The decrease of tensile impact value in the heat affected zone corresponds to the hardening of that zone which was cooled rapidly after welding. The more the hardening of the heat affected zone, the more the decrease of tensile impact value becomes remarkable On a 80 kg/mm² high tension steel and four kinds of steel for machine parts, the decrease of the impact value in the heat affected zone is remarkable. In comparison with the case of these hardenable steels, the decreases of impact value are not considerable on mild steel SS 41, 55 kg/mm² and 60 kg/mm² high tension steels, Mn-Si fine grained and 2.5%Ni steels. A 100 kg/mm² high tension steel is softened by suffering welding arc heat, and impact values in the heat affected zone showed higher value than those of unaffected base metal.
2. The higher the carbon content of steel plates, the more the decrease of impact value and increase of hardness in the heat affected zone become considerable.