Method of producing welded tube with excellent corrosion-resistant inner surface

Abstract

Disclosed is a method of producing a welded steel tube with excellent inner surface corrosion resistance, in which at least one surface of a steel strip is coated with a first plate layer made of at least one of nickel, cobalt and alloys based on the metals, the plated steel strip is formed into a welded tube with the plated surface being inside, a film-forming material of at least one of tin and tin-based alloys is inserted into the inside of the welded tube and is then heat-treated at a temperature not lower than the melting point of the film-forming material by passing the tube through a continuous heating furnace having a non-oxidizing gas atmosphere therein so that the film forming material as inserted into the welded tube is fused and spread over the first plate layer to form a second plate layer thereon, and the tube is finally cooled. The welded steel tube of the present invention is free from cracks, pin holes, overplated spots and peeling of the plate layer and therefore has excellent corrosion resistance.

Dependencies are inferred from the claim text.