JPS5591936A - Heat treatment method for steel pipe - Google Patents

Abstract

PURPOSE:To uniformly heat the whole steel pipe, by applying heat insulating paint on a specific point of pipe end part, at the time of heating the steel pipe in a heating furnace. CONSTITUTION:The steel pipe 1 is heated in the heating furnace 3 for the purpose of uniformalization of quality, level up and elimination of weak point at manufacturing time. On this occasion, the pipe end part 4 is superheated at a higher temperature than the central part of the pipe 1 and on the contrary, quality uniformalization of the pipe 1 is retarded. At this time, the heat insulating paint 15, such as thermet, boiler paint etc, is applied in a fixed extent of the part 4 of the pipe 1. Application limits or thickness etc. of the heat insulating paint is determined suitably by the kind of paint, heating temperature, dimension of the pipe 1 etc. Also, application on both inside and outside faces or only one face of the part 4, is determined by the condition at that time. Thus, the pipe 1 heated the whole body uniformly, is taken out from the furnace 3 and is annealed sending to annealing vessel and then the steel pipe having superior characteristics uniformly, is obtained.