Behavior in spheroidizing annealing and mechanical properties of medium carbon steel

The behavior in spheroidizing annealing and mechanical properties of controlled rolled and cooled (CRC) and conventional rolled (CR) medium carbon steel SWRCH35K were studied with two annealing cycles. One was the conventional intercritical annealing. The other was subcritical annealing, which involves heating to below A1 for several times. It was found that compared to intercritical annealing, spheroidization occurs more rapidly in subcritical process, with formation of finer and degenerated pearlite with many kinks and breaks. The higher spheroidization level and finer carbides make the steel having better ductility and cold formability. The rapid spheroidization in sub-critical process greatly reduce the energy, time and cost of spheroidization. However, rapid spheroidization can not be observed in intercritical process as the original fine pearlite is dissolved at the temperature above A1. The spheroidization of controlled rolled and cooled wire rod, in which there are a lot of degenerated pearlite, occurs more rapidly than that of conventional rolled wire rod, although in which fine pearlite is observed too.