It is well known, that lamellar pearlite austenitization can lead to rapid spheroidisation of cementite. This phenomenon is the base for ASR process – Accelerated carbide Spheroidisation and Refinement. It is possible to obtain fully spheroidised structure from lamellar pearlite within minutes by partial austenitization and divorced pearlitic transformation. Moreover, such structure is significantly finer than spheroidised structure after conventional soft annealing. The size of carbide particles obtained by ASR process depends on the austenitization rate. This is an important fact, because various kinds of heating methods can be applied for steel heat treatment with heating rate differing by decade orders. This article describes cementite morphology during spheroidisation with respect to the austenitization kinetics.100CrMnSi6-4 with pearlitic structure was austenitized isothermally at different temperatures and continuously at different heating rate. Cementite lamellae fragmentation at interphase boundary perlite/austenite was examined by SEM after deep etching. Size and distribution of resulting cementite fragments was characterized. Austenitization kinetics was observed via dilatometric measurement.Keywords: Carbide spheroidisation, bearing steel, pearlite, austenitization.
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