Inspection of the residual curvature in an anisotropic electrical steel strip and reasons for its formation

The residual curvature of strips of anisotropic electrical steel (AES) is a defect of its geometry. This defect results in deterioration in magnetic properties of steel products in a transformer due to their stressed states. The residual curvature also leads to a slowdown in labor productivity during punching of items in automated lines. The main reason for the formation of a residual curvature in AES is attributed to a difference in elastic tensile stresses caused by the coating on different sides of a strip in the case of polythickness of the coating. The obtained minimal values of residual curvature are reached when the difference in the coating thickness on two sides of the strip is limited within 1 μm. The indicators of residual curvature are the bending radius (an absolute indicator) and the deviation of the free end of a vertically suspended specimen (a relative indicator). Laboratory techniques of determining the degree of bending and the methods of determining the residual curvature of the AES strip used at OOO VIZ-Stal’ are presented.