METHOD AND APPARATUS FOR COATING THE SEAMS OF WELDED TUBES

摘要

The method for coating the seam of a welded tube (20) of this invention includes applying a mixture of the desired protective metal coating in powdered form and a liquid flux over the interna l surface of the welded seam with the welded seam located in a lower portion of the tube, then heating the welded seam to the melting temperature of the protective metal coating, melting the metal coating which flows over the seam forming an adherent metallurgical bond. The preferred apparatus includes a wand (86) which extends between the opposed edges (24) of the open seam tu be in the welding apparatus and extends axially through the tube to overlie the welded seam spaced from the welding apparatu s. The wand includes three conduits transmitting the powdered protective metal coating (88), liquid flux (94), and nonoxidizing g as (38) to the applicator which includes a nozzle (58) which atomizes and sprays the liquid flux over the internal surface of the seam and which combines with the powdered protective metal coating to form a paste. The preferred heating apparatus includes a first induction heater (100) adjacent the seam which preheats the seam and a full body coil (102) which heats the entire tube.