New Approach in Accelerated Carbide Spheroidisation of 100CrMnSi6-4 high-carbon chromium steel

Co-authors DLOUHÝ Jaromír, NOVÝ Zbyšek, ZRNÍK Jozef

Processing of high-carbon chromium steels often includes an annealing stage, at which initial lamellar pearlite should be transformed into ferrite with globular carbides. Carbide spheroidisation is a significant metallurgical process, which contributes to profound changes in microstructure and mechanical properties. The purpose of such treatment is to enhance machinability of the material or to condition the microstructure for subsequent hardening. Carbide spheroidising occurs through diffusion, which is a long-term and energy-demanding process. The holding times, sometimes up to tens of hours make soft annealing one of the most expensive heat treatment processes. The new process was newly designed at the company COMTES FHT shortens carbide spheroidising several times and therefore delivers considerable time and cost savings. The high-carbon chromium steels are not fit for further working unless soft-annealed. The purpose of this annealing process is to obtain globular carbides uniformly distributed in the matrix and to achieve overall softening. The present paper explores the effect of the newly-designed thermal schedules on the carbide spheroidisation behaviour, on the decrease in hardness in high-carbon chromium steel grade 100CrMnSi6-4 and on processing times.