METHOD OF COATING WELDED TUBES

摘要

Method of coating the seam of a welded tube with an adherent metal coating, including applying a nonadherent metal coating to the inside and outside of the welded seam, externally heating the seam area with the seam located in the lower portion of the tube to generally the melting temperature of the coating, then applying a fluid coolant to the external surface to freeze the outer coating while continuing heating to melt the coating on the inner surface and finally quenching. In one preferred embodiment, the tube is heated with an induction heater including a seam coil which first heats the seam area below the melting temperature of the coating and then heated with a full body coil. The coolant may be chilled water or other coolant which is sprayed onto the seam area.