| 摘要 |
The present invention addresses the problem, in relation to spot welding of steel plates having a tensile strength of 750 to 2500 MPa in which the toughness is liable to be insufficient and a sufficient CTS is difficult to ensure, of ensuring a sufficiently high joint strength, in particular CTS, in a stable manner; and providing a highly reliable spot-welding joint in which CTS has been ensured in a stable manner. In this spot-welding joint, the P-concentration is measured at a pitch of 1 mum in a rectangular planar region that measures 100 mum × 100 mum, is perpendicular to the plate surface, and is centered on a point located 100 mum inward from the end part of a nugget in a direction parallel to the plate surface to obtain a measured value of the P-concentration for each of the 100 × 100 measurement points; and the average values of the measured values of the P-concentration of 20 adjacent measurement points, from amongst the 100 × 100 measurement points, arranged in a row along the direction parallel to the plate surface are repeatedly calculated while shifted by one point at a time, thereby obtaining 81 × 100 average values. In this case, the number of average values exceeding a value equal to twice the average P-concentration is 0 to 100. |
