| 摘要 |
PURPOSE:To provide a steel plate having enhanced suitability for phosphate treatment and excellent corrosion resistance after painting imparted thereto obtained by a method wherein laser rays with high energy density is irradiated to a surface of the steel plate and a surface layer thereof is activated. CONSTITUTION:To a surface of the steel plate, especially, a pickled or a polished surface of the steep plate, laser rays such as pulse laser or the like with an energy density of 0.05J/cm<2> or more is irradiated for a short time. Then, by said laser rays irradiation, only a surface layer up to 10mu or less of the surface of the steel plate is modified as well as activated. As the result, excellent suitability for phosphate treatment and corrosion resistance after painting are imparted to the surface of the steel plate. Further, in order to continuously treat a surface of a steel strip running at a high speed, high frequency pulse repeating laser is effective. |
