Development of periodic defect detector for steel cold rolling mill using magnetic flux leakage testing method

Koshihara, Takahiro; JFE Steel Kabuhiki Kaisha Fukuyama Chiku Steel Kenkyujo; Japan

Koshihara, T.; JFE Steel Corporation; Japan
Matsufuji, Y.; JFE Steel Corporation; Japan
Yamawaki, M.; JFE Steel Corporation; Japan

ID: ECNDT-0082-2018
Download: PDF
Session: Surface Methods 2
Room: R2
Date: 2018-06-14
Time: 11:10 - 11:30

In cold rolling processes, roll defects on thin steel sheets cause problems as they can be seen clearly after the sheets are painted in the customer’s manufacturing processes. But, these defects are usually invisible since their height or depth is as small as normal surface roughness of steel sheets. Therefore, they can only be detected by human inspection after grinding the steel surface. However, it is necessary to stop the traveling steel sheet for this type of human inspection.

Against this background, the authors found that Magnetic Flux Leakage Testing (MFLT) is effective for detecting these kinds of roll defects. But there was challenges to install MFLT to cold rolling process. Firstly, thick steel plate is hard to magnetization. Then, roughness of cold rolled steel sheet shape makes it difficult to keep stable inspection.

The authors have developed a detector with new arrangement of sensor, magnetization coil to magnetize thick cold rolled steel sheet, and developed contact detection system to keep away from impact shock of collision of MFLT sensor against a steel sheet. Consequently, the authors have completed the installation of the automatic inspection equipment at the cold rolling process of West Japan Works(Fukuyama District) of JFE Steel Corp.