Method for improving fatigue characteristics of lap welded joints

摘要

PROBLEM TO BE SOLVED: To reduce residual stress effectively and efficiently in a weld joint for a steel sheet by using TIG arc and the like and heating a position close to the weld zone in the lower sheet of a lap joint to the extent that the melting of the sheet is avoided. SOLUTION: An upper 1 and a lower sheet 2 are superposed and fixed with a holding jig 3. Arc welding is performed to form a fillet welded joint in the weld zone 6. The heat source generating part 4 is capable of parallel displacement for the weld zone 6. As the heat source 5, TIG arc, plasma arc and laser beam are emitted. The heat source 5 moves parallelly to the weld zone 6 at a position close to the weld zone 6, namely, a position away from the weld ending part 7 by a distance (a), and is capable of heating that part locally. The output of the heat source 5 is adjusted to the extent that the melting of the lower sheet 2 is avoided. As a result, since the heat source is excellent in heat concentration, heat efficiency is improved, reducing residual stress efficiently and enhancing fatigue characteristic.