2018 年 24 巻 57 号 p. 507-511
In general, the reinforcing bar of the CO2 arc welded joints, are using a steel backing material. However, the steel backing material melting and becomes integrated with the welded portion. For this reason, it is impossible to visually confirm the initial layer portion. Therefore, by painting a paint containing aluminum as a main component on the outside of the backing material, the paint discolored by welding heat input. By using this phenomenon, we propose that it can be visually confirmed. In the CO2 gas arc welded joint of the reinforcing bar, when the difference between thermally discolored width and root gap is less than 4.8 mm, it was found that the reinforcing bar end face was sufficiently integrated.