Rectangular tube with two inward-bentside ends

摘要

The two opposing end side surfaces of the rectangular tube are bent inwards over a mandrel and thereby become sheared away from the top and bottom tube surfaces. Thereafter the protruding corners of these latter surfaces are cut off. The side ends are bent inwards by press rams with superimposed drawing dies. Further press rams cut away the protruding edges. Two tubes so treated and placed together end to end therefore have an intermediary wedge-shaped depression in which a weld is formed.