Patent ID: 7011343

Claim:
A hollow metal fitting for use in making a welded metal joint with reduced residual stresses, which fitting comprises A. an internal annular shoulder having an inner diameter; and B. an annular wall which (1) extends from the shoulder, (2) has a cylindrical inner surface, (3) has a cylindrical outer surface whose diameter is greater than the inner diameter of the shoulder, (4) defines with the shoulder a cylindrical socket having a common longitudinal axis with the annular wall, and (5) has an end surface connecting the cylindrical outer and inner surfaces, which end surface is chamfered so that the inner surface extends away from the shoulder, and beyond the outer surface, in the axial direction and so that the end surface, as viewed in a cross section taken along the longitudinal axis of the annular wall, is concave, with the chamfered end surface terminating, at the cylindrical inner surface of the annular wall, in an annular lip connected to an annular ring by thin, radially spaced bars which are parallel to the longitudinal axis.