Investigating the effects of short time austenitizing and cooling rate on pearlitic microstructure and mechanical properties of a hot rolled plain eutectoid carbon steel

In this research, the effects of transformation temperature, time and cooling rate during continuous and isothermal heat treatment processes on microstructure evolutions and mechanical properties of a hot rolled plain eutectoid steel rod were investigated. Austenitizing was performed at the temperatures of 850 and 950 °C for 5 min. Cooling rate was selected between 7 and 26 °C/s for the continuous cooling and isothermal cooling was conducted in a salt bath furnace at the temperature range of 520 and 560 °C. The results showed that the finest pearlite microstructure and a good combination of strength and ductility were achieved by isothermal heat treatment at 560 °C. On the other hand, continuous cooling from 850 °C at the rate of 26 °C/s resulted in an adequate tensile strength (1040 MPa) and substantial increase in the ductility (elongation: 21% and reduction area: 51%).