PURPOSE: To prevent the generation of the pressed flaw of ceramic oxidized scale on the surface of tube and to reduce the repair rate of the surface of tube of the final product by heating a billet after ceramic antioxidants are applied to the part where the surface flaw of billet is repaired with a grinder.
CONSTITUTION: A billet which consists of an austenitic stainless steel and to which billet inspection is executed after it is rolled with a billet mill is repaired by grinding. This repair with the grinder is performed until it is confirmed by PT inspection (Penetrate Test) that all the surface flaw is removed. Then, the antioxidants are applied to the repaired part by grinding and, after drying, the billet is heated and made into a tube.