SEAM WELDED PIPE WITH COATED FILM HAVING CORROSION RESISTANCE AND OXIDATION RESISTANCE TO FLUID AND ITS PRODUCTION

摘要

PURPOSE:To easily produce the title seam welded pipe by providing an Ni electroplated layer having an oxidized coated film on the inner peripheral surface of a relatively thin seam welded pipe except the part in the vicinity of a bead part, and separately coating an Ni chemical-plated layer on the surface in the vicinity of the bead part. CONSTITUTION:The Ni plated layer 3 is formed at least on one surface of a band steel having <=about 2mm thickness by electroplating, and a seam welded pipe 1 having relatively small diameter (<=about 30mm) is produced while positioning the electroplated layer 3 on the inner peripheral surface side. The seam welded pipe 1 is heated at about 500-600 deg.C for about 10-20min in an oxidizing atmosphere to form an oxidized coated film 3' on the surface of the Ni electroplated layer 3 on the inner peripheral surface. Pickling is carried out to remove the oxidized coated film 3' on the base steel part exposed to the surface close to the bead part 4 while leaving the oxidized coated film 3' on the surface of the Ni electroplated layer 3, the pipe is dipped in the heated chemical Ni plating soln., and the surface close to the bead part 4 is separately coated with an Ni chemical-plated layer 5. By this method, the seam welded pipe 1 with the coated film having corrosion resistance and oxidation resistance to a fluid is obtained.