熱間圧延棒鋼の表面欠陥の自動探傷法
1971 年 57 巻 3 号 p. 601-613
詳細
1971 年 57 巻 3 号 p. 601-613
The fluorescent magnetic particle method is usually used for inspection of surface defects of hot rolled steel bars. However, in this method, the evaluation is not quantitative and the judgement of harmful defect depends on the skill of inspector, and moreover the inspection rate is very low.
To improve these drawbacks and to develope an automatic inspection in production line, the present autors have studied the eddy current inspection method and a new automatic magnetic inspection method using semi-conductor elements.
Some characteristics of eddy current test coil have been investigated and a high sensitive coil newly designed clearly detects a surface defect whose depth is 0.3 mm.
Eddy current inspection is suitable for detection of surface single or short defects such as shells and roll marks.
An automatic magnetic inspection method has been developed for detection of long defect. In this method Sony magnetodiode (SMD) is used to detect leakage flux from surface defect of bar which is magnetized by a. c. magnetic field.
The inspection system based on this new method is able to detect harmful seam and crack without descaling process. A seam of 0.1 mm depth is easily detected and inspection rate is 30-40 T/H for bars of 50-100 mm diameter.
This system is taking the place of fluorescent magnetic particle inspection method.
The combined method of eddy current inspection and leakage magnetic flux detection is possible to detect all kinds of surface defect in production line automatically.
