Magnetic properties of matrix metal

Magnetic thickness measurement is affected by changes in the magnetic properties of the base metal (in practical applications, changes in the magnetic properties of low carbon steel can be considered slight). To avoid the influence of heat treatment and cold working factors, standard plates with the same properties as the base metal of the specimen should be used to calibrate the instrument; Calibration can also be performed using the test piece to be coated.

B Electrical properties of the base metal

The conductivity of the base metal has an impact on the measurement, and the conductivity of the base metal is related to its material composition and heat treatment method. Use standard plates with the same properties as the base metal of the specimen to calibrate the instrument.

C Thickness of base metal

Each instrument has a critical thickness of the base metal. Beyond this thickness, the measurement is not affected by the thickness of the base metal. The critical thickness values of this instrument are shown in Appendix 1.

D edge effect

This instrument is sensitive to sudden changes in the surface shape of the specimen. Therefore, measuring near the edge or inner corner of the specimen is unreliable.

E curvature

The curvature of the specimen has an impact on the measurement. This effect always increases significantly with the decrease of curvature radius. Therefore, measuring on the surface of bent specimens is unreliable.

Deformation of the F specimen

The probe will cause deformation of the soft cover layer specimens, so reliable data can be measured on these specimens.

G Surface roughness

The surface roughness of the base metal and cover layer has an impact on the measurement. The increase in roughness leads to a greater impact. Rough surfaces can cause systematic and accidental errors, and the number of measurements should be increased at different positions during each measurement to overcome these accidental errors. If the base metal is rough, several positions must be taken on uncoated base metal specimens with similar roughness to calibrate the zero point of the instrument; Or dissolve and remove the covering layer with a solution that does not corrode the base metal, and then calibrate the zero point of the instrument.