| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-strength resistance spot welded joint by suppressing separation and rupture without causing softening by degrading segregation of a nugget on two or more plate assemblies and preventing generation of cracks.SOLUTION: When the diameter of a nugget structured by thin steel plates is d in a resistance spot welded joint of the thin steel plates, a distribution state of the quantity of P, which exists in a region within the nugget surrounded by a closed curve of a distance d/100 and a closed curve of a distance d/5 in a nugget internal direction from an end part of a melting part on a level surface of the nugget surrounded by a corona bond, is subjected to surface analysis. The resistance spot welded joint is characterized by that an area ratio in which the concentration m (mass%) of P exceeds twice the concentration M (mass%) of a base material composition is 5% or less. |
