J. Phys. IV France
Volume 08, Numéro PR2, June 1998
Soft Magnetic Materials 13
Page(s) Pr2-725 - Pr2-728
Soft Magnetic Materials 13

J. Phys. IV France 08 (1998) Pr2-725-Pr2-728

DOI: 10.1051/jp4:19982169

Accuracy and repeatability of coating thickness measurements on non-oriented electrical steels using the magnetic induction method

M. Lindenmo and B. Lewin

European Electrical Steels, Surahammars Bruk, Box 201, 735 23 Surahammar, Sweden

The insulation coating often applied on non-oriented electrical steels is of importance in many ways. One of the most critical aspects of the coating is its thickness. It is therefore very important for good control of the coating thickness, to measure this parameter accurately and with good repeatability. This paper concentrates on the practical aspects of the magnetic induction method for coating thickness measurements, since this is the most common method with users of electrical steel. The investigation demonstrates that it is important to calibrate a magnetic induction instrument using a calibration standard with the same base metal permeability, thickness and surface roughness as the sample to be measured. Calibration foils used and wear of the measuring tip are other important factors. In view of the accuracy and repeatability of he method, the allowed range of measured coating thickness needs to be about ±0,5 µm for an average coating thickness of 1 µm.

© EDP Sciences 1998