| 摘要 |
<p>An object of the present invention is to provide a high strength welded joint manufactured by a method of resistance spot welding a sheet set of two or more steel sheets, with which segregation in a nugget and generation of a crack is reduced and thereby interface failure is prevented without reducing the hardness of the welded joint. In a welded joint manufactured by a method of resistance spot welding thin steel sheets, when the diameter of a nugget formed from the thin steel sheets is denoted by d, on a horizontal plane passing through a nugget surrounded by a corona bond, distribution of an amount of P in a region in the nugget surrounded by a closed curve at a distance d/100 from an end portion of a weld zone toward the inside of the nugget and a closed curve at a distance d/5 from the end portion of the weld zone toward the inside of the nugget is analyzed by area analysis, and the proportion of the region in terms of area in which the concentration m (mass %) of P is more than twice the concentration M (mass %) of P of a base metal composition is 5% or less.</p> |
