Optimisation of Quenching Temperature after Accelerated Carbide Spheroidisation in 100CrMnSi6-4 Bearing Steel

Hauserová Daniela - COMTES FHT a.s.

Current efforts to boost competitiveness and reduce time and energy demands in production lead to improved efficiency of existing processes and technologies.However, carbide spheroidisation is a time and energy consuming process owing to diffusion.Research into accelerated carbide spheroidisation processes has shown that lamellar pearlite may be globularised within minutes using heat treatment or thermomechanical processing.After the ASR process (Accelerated Spheroidisation and Refinement), the size of globular carbides as well as the final grain size are several times smaller than those obtained by conventional long-time soft annealing.Finer initial microstructures lead to finer final martensitic microstructures and enhanced properties of the steel upon quenching and tempering.In addition, finer microstructures obtained by accelerated spheroidising speed up the dissolution processes during austenitising. As a result, the quenching temperatures can be reduced.At lower quenching temperatures, less residual stress and distortion in final parts can be expected.In the present study, the effects of annealing techniques, i.e. long-time conventional soft annealing and accelerated carbide spheroidisation, upon the microstructure and properties of the quenched and tempered material have been explored.The temperature and time of austenitising 100CrMnSi6-4 bearing steel by induction have been optimised.

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