Welded tubes are produced from a strip that is rolled formed and welded. Welded sizes up to and including 5” O.D. are certified to ASTM A -249/A-269 (average wall). This specification also ensures that tensile, yield and elongation tests have been performed, in addition to flaring, flanging, hardness, flattening and hydrostatic or non-destructive electrical tests.
Welded and Drawn Tubing available size range of .202” O.D. to 8” O.D. and wall thickness of .015” to 1” Cold-rolled strip in long coils is rolled to a tube form, then passed under the welding head, which melts the edges of the open seam to form a fusion weld. No filler metal or flux is used, and the weld bead is of the same analysis as the parent metal. All tubing is carefully inspected for weld porosity or other damaging faults before being approved for redrawing.
The welded tubing is then cold drawn in exactly the same way as seamless. As it undergoes repeated cold drawing and annealing it takes on the appearance and qualities of seamless tubing. The weld can be detected only by etching or by microscopic examination. Cold work and annealing cause the weld area to recrystallize with ductility and mechanical properties that are equivalent to the parent metal.
Cold Worked and Annealed Tubing -?available in a size range of 5/8” O.D. to 4” O.D. and wall thickness of .035” to .120” This manufacturing method starts in the same manner as welded and drawn tubing. Cold-rolled strip is rolled into tube form and fusion welded without the addition of filler metal. It is then selectively cold worked in the weld area and given a full solution anneal, causing this area to recrystallize. With this controlled processing, the strength, ductility and corrosion resistance of the weld area is equal or superior to the parent metal. This similarity between parent and weld zone structures gives cold worked, annealed tubing uniformity and makes it ideally suitable for condenser tube or other heat exchange applications. Cold worked annealed tubing meets the requirements of ASTM A-249 and tolerances of ASTM A -450. Required minimum mechanical properties – 75,000 psi tensile strength, 30,000 psi yield strength and 35% elongation – are met in both the base metal and the weld area.