| 摘要 |
PURPOSE:To enable the sharp improvement of a detect finding sensitivity, by a method wherein a defect finding is performed as a steel material surface, positioned facing and opposite to a scanning coil, is gradually cooled to a given temperature rather than a magnetic transformation temperature. CONSTITUTION:A profile roller 53 is pivotably secured to an axis 53b mounted in a direction perpendicular to a conveyance direction of a billet 1 and at support plates 53a hung at the upstream side and downstream side of the conveyance direction of the billet 1 and from an under surface of a fixing plate 5. When the roller 53 is brought into rolling contact with the surface of the billet 1, a probe body 52 is designed to be positioned at a given height from the surface of the billet 1. As the billet 1 is conveyed, the surface of the billet 1, positioned facing and opposite to a scanning coil 55, is gradually cooled to a given depth (about 2mm.) and below a magnetic transformation temperature with a cooling water jetted through two nozzles 56, 56, and with this an operation to find a surface defect is performed. |
