The manufacture of tubes or pipes of steel covered products of the polymer, with heating, coating and hardening is carried out on the lengths of tube support lacking

摘要

Lengths of polymer-coated tubing are continuously produced from steel strip by roll-forming and welding at a fast rate of speed. The welded tubing is sized, cleaned and heated to raise its temperature to that desired for applying a polymeric coating. After coating, the tubing is heated to a desired baking temperature and then cooled. The tubing is unsupported from a location upstream of the coating station until cooled. Elongated endless belts grip the tubing over a longitudinal distance of at least about 2 feet and pull the tubing in a controlled manner to maintain the tubing in precise spatial location throughout its heating, coating and baking.