A shaped workpiece made of a plastic material, comprising a tubular part having a radial bore and an outer circumference, and a union having an end face surface, which abuttingly engages the circumference of the tubular part in a region of the radial bore and is fixedly connected therewith by welding, wherein the weld is affected by means separate from the end face surface of the union for supporting a portion of the outer circumference of the tubular part at least in the region of the radial bore and heating a circular region around the radial bore of the tubular part and the end face surface of the union by heat radiation after the end face surface of the union was brought into an abutting engagement with the outer circumference of the tubular part and, thereafter, pressing the two parts to each other.