in quenched and tempered state. This can be accomplished by structural refinement. One possible way to refine final quenched and tempered structure is refinement of the soft annealed structure before quenching. The article is devoted to accelerated carbide spheroidisation and refinement (ASR) and subsequent hardening of the 51CrV4 spring steel. Samples with different carbide size were prepared by conventional soft annealing in atmosphere furnace and ASR process by induction heating. Influence of the structural refinement on the properties of quenched and tempered state was studied.

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.

finer globular carbides than conventional soft annealing. The present paper explores the effect of the heating rate and temperature on the accelerated carbide spheroidisation process and on the resulting hardness. Accelerated spheroidisation was achieved by thermal cycling for several minutes around various temperatures close to the transformation temperature at various heating rates applied by induction heating.

kulistych o znacznie mniejszych rozmiarach w porównaniu do tych, jakie powstają w konwencjonalnym procesie wyżarzania zmiękczającego. Niniejsza praca analizuje wpływ szybkości grzania i temperatury na proces przyspieszonej sferoidyzacji węglików i na uzyskana twardość. Przyspieszona sferoidyzacje węglików uzyskano dzięki zastosowaniu cyklicznych zmian temperatury trwających kilka minut wokół określonych temperatur bliskich temperaturze przemiany za pomocą grzania indukcyjnego z różnymi prędkościami.

after conventional soft annealing. Apparently, structure after accelerated carbide spheroidisation is significantly finer than after long duration soft annealing – in terms of carbide particles and grain size. That enhances steel hardness and homogeneity of the structure in final state after hardening. Findings: Presented experiment deals with accelerated carbide spheroidisation of 100CrMnSi6-4 bearing steel during final stage of hot rolling. Main purpose is to achieve microstructure consisting of globular carbides and ferritic matrix directly after hot forming. Research limitations/implications: The combination of a suitable forming temperature, an appropriate amount of deformation and a possible reheating lead to globular carbide formation during austenite decomposition instead of cementite lamellae. Originality/value: Experiment results are promising for quenching and tempering in comparison with structure after conventional soft annealing with coarser. Finer ASR structure retains finer austenite grain at quenching temperature and higher dispersion strengthening.