Intercept direct measurement method of steel grain size

In order to solve the problem that it was difficult to evaluate the average grain size of two-phase or multi-phase structure in steel products, taking single-phase structure interstitial-free atomic steel as the test object, the number of intercept measurements in a single field of view was determined by image processing software, and a new method for determining the average grain size by intercept direct measurement method was developed, which was applied to the average grain size evaluation of DH590, 38MnVS, 400E steel and other materials containing two groups or multi-phase structures. The results show that the method of intercept direct measurement of average grain size of steel products was simple and feasible, with high inspection efficiency and low error rate. The measurement results were basically consistent with the measurement results of the cut-off point method in GB/T 6394—2017. The intercept direct measurement method was suitable for the measurement of the average grain size of the single-phase structure, and it was also suitable for the measurement of the average grain size of the two-phase or multi-phase structure.