Soft annealing is an important and time demanding part of bearing steel treatment process. The experimental program of accelerated carbide spheroidisation deals with significant shortening of the time necessary for producing steel microstructure consisting of ferritic matrix and globular carbides. Globular carbide particles and the grain size of the matrix are significantly smaller after accelerated carbide spheroidisation process in comparison with conventional long-duration soft annealing. This fact ensures finer martensitic structure after hardening and this shows that the microstructure and properties of final hardened product are dependent on previous spheroidisation annealing. Finer carbides in structure enhance hardness and facilitate carbide dissolution during austenitisation. This effect enables quenching temperature lowering. It reduces the energy demand of the quenching process and mitigates the risk of residual stresses and distortion. The main objective of the present research was to identify the effect of the initial size of carbides and prior austenite grains upon the final microstructure and hardness of induction-quenched 100CrMnSi6-4 bearing steel. Microstructure evolution and hardness were monitored during austenitisation, quenching and subsequent tempering. Microstructure and properties after accelerated treatment were compared with those after conventional long-duration treatment.Keywords: ASR, Accelerated Carbide Spheroidisation, Induction quenching, Bearing steel.
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