| 摘要 |
<p>PROBLEM TO BE SOLVED: To discriminate the existence of surface defects in a steel plate, especially periodical flaw, by suppressing to a minimum fouling level of an optical device, even in a very poor rolling environment. SOLUTION: In a process for manufacturing the steel plate by a hot rolling mill, this device is equipped with a case 3 installed on a properly high position over a running line of the steel plate 1, the optical device stored in the case 3, for irradiating the steel plate surface with light, and detecting reflected light reflected from the surface, and a surface defect detection device 7 for processing a detected signal outputted from the optical device, and detecting the surface defect. A slit 9a is formed on a part, where an optical path of the optical device exists on a blocked face of the case 3, facing the running line, and a shielding plate 10 is openably and closably installed in the case 3 relative to the slit 9a, and the shielding plate 10 is opened only at surface defect inspection time.</p> |
