Spheroidisation is well studied process in steels with pearlitic structures. Bainite as initial microstructure for spheroidisation treatment is not so frequent. The article describes rapid carbide spheroidisation of bainitic structure of 51CrV4 spring steel. The experimental steel was treated in quenching dilatometer capable of rapid temperature changes. Isothermal austenitization was studied at different temperatures with respect to its kinetics and microstructural features. Special attention was paid to the morphology of growing austenite grains and carbide morphology during their dissolution in austenite. Rapid partial austenitization was repeatedly applied to achieve accelerated carbide spheroidisation. This phenomenon is known for pearlitic structures. The article shows that bainite can be spheroidised in similar way as pearlite. Accelerated carbide spheroidisation can be applied as replacement of conventional time-consuming spheroidisation annealing.
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