| 摘要 |
PURPOSE:To form an impact resistant film having good close adhesiveness without requiring painting pretreatment, in a preheating process at the time of the application of powder paint to the surface of a steel material, by performing said process in a temp. range substantially generating no oxide film. CONSTITUTION:At first, a steel material 5 is rapidly heated in a temp. range preventing the thickness of the oxide film generated on the surface of the steel material from exerting effect on the destruction of a film, for example, in a range of about 180-220 deg.C in a preheating apparatus 1. Powder painting is immediately applied to a painting machine 2 before the oxide film is grown and powder paint is melted by the holding heat of the steel material 5 to form a film. Subsequently, the steel material is fed in a post-heating furnace 3 to be heated and held to a temp. range completing the curing reaction of the film in the furnace 3. After the curing of the film, the steel material is cooled through a cooling apparatus 4 to be used for a steel pipe or a reinforcing bar.
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