New approach for the quantification of microstructures in nonoriented electrical steels

An original method for the estimation of effective average grain size and effective aspect ratio in nonhomogeneous microstructures and a parameter describing the homogeneity of microstructure are presented. The principal types of microstructure for nonoriented electrical steels under investigation are defined. The coefficients of homogeneity for equiaxed and columnar microstructures are calculated. It is shown that the coefficient of homogeneity is independent of the shape of the grains. fective average grain size of the nonhomogeneous microstructures is calculated as a weighted sum of the average grain sizes of homogeneous grain groups. The aspect ratio of the microstructure is also calculated by this weighted sum approach. A correlation is found between the mechanical properties and the proposed quantitative characterisation of the microstructure of the nonoriented electrical steel.