PURPOSE: To prevent rust formation on a part to be welded before welding and the formation of oxidized coating due to heat in welding, by applying an aqueous composition prepared by dissolving an acrylic resin or the like in an aqueous solution containing a solvent and having a pH value of 7 or higher on the part to be welded and its periphery of a steel material.
CONSTITUTION: 5W30wt% acrylic resin or short-oil alkyl resin that contains free carboxyl groups or sulfonic groups and has an oil length of 40% or less and 2W 15wt% solvent (e.g. methanol) compatible with water are mixed in 60W90wt% aqueous solution that contains 1W5wt% ammonia or lower amine and has a pH value of 9 or less to prepare the surface-treating agent comprising the aqueous composition. Subsequently, the surface-treating agent is applied on the part to be welded and its periphery of a steel material.
EFFECT: Adherence of spatters in welding can be prevented by the above-mentioned treatment, and after welding, even if the surface-treating agent remains on the surface of steel material, it is possible to apply a coating on the surface as it is.
KOBAYASHI HARUO
KIRIO TADASHI
TOGAWA HIDEO
MATSUMURA YUUSUKE
HOTSUTA TAKEMICHI
HIDA MICHIAKI
SUZUKI SHIGEYOSHI
TAIHO KOGYO CO LTD