PROBLEM TO BE SOLVED: To improve the accuracy of the measurement result of a spheroidization ratio by preventing a plurality of adjacent carbide particles from being erroneously recognized as one carbide particle when using a computer to automatically measure a spheroidization ratio of carbide in a steel material.;SOLUTION: A method for measuring a spheroidization ratio of carbide in a steel material includes the steps of: performing binarizing processing of converting each of pixels included in image data of a measurement object surface subjected to etching treatment, into a white pixel or a black pixels (S5); detecting a black pixel group surrounding white pixels to form a ring, as an outline of one carbide particle on the image data subjected to binarizing processing (S7); computing a degree of circularity of the detected outline of the carbide particle (S8); and computing the sum total of areas of regions surrounded with outlines of carbide particles, the degrees of circularity of which are 0.5 or higher, and the sum total of areas of regions surrounded with outlines of carbide particles, the degrees of circularity of which are lower than 0.5, and using these sum totals to compute a spheroidization ratio (S10).;COPYRIGHT: (C)2014,JPO&INPIT
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