Pearlitic Lamellae Spheroidisation During Austenitization and Subsequent Temperature Hold

Typical processing routes for bearing steels include a soft annealing stage. The purpose of this procedure is to obtain a microstructure containing globular carbides in ferritic matrix. A newly developed process called ASR (Accelerated Spheroidisation and Refinement) cuts the carbide spheroidisation times several fold, producing considerably finer globular carbides than conventional soft annealing. Finer microstructure also leads to more homogeneous and finer structure after final hardening process. The present paper explores process of the accelerated spheroidisation (ASR) in steel 100CrMnSi6-4 with initial pearlitic structure. Cementite lamellae morphology was observed in different stages of austenitization. The heat treatment was performed using induction heating in quenching dilatometer. There was analysed influence of austenitization temperature and austenitization time on spheroidisation. Hardness and carbide morphology was observed. Deep etching was used to reveal evolution of cementitic lamellae fragmentation. It is favourable process especially in induction treatment of small parts.