Abstract
Metallographic analysis of the primary austenitic grain of carbon steels after various thermal treatment is carried out. Two methods are examined in detail: the ASTM recommended procedure and the recently proposed method based on stochastic simulations of convex space filling systems. The difference between the profile size and 3D grain size estimates based on the profile and intercept counts occurring in heterogenous grain structures and to certain degree also in structures with mild size dispersion is removed in the latter case. An attention is given also to the possibilities to separate the components of the heterogeneous grain structures.

Key words
carbon steels, duplex grain structures, grain size estimation, primary austenitic grain, w-s diagram

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