Evaluation of microstructures of variously heat treated carbon steel by magnetic coercivity measurement

The microstructures of variously heat treated 0.85% carbon steel were evaluated by magnetic coercivity measurement. Austenitizing, isothermal transformation, continuous cooling or spheroidization heat treatment was carried out to produce various microstructures. Microstructural parameters such as prior austenite grain size, phase and pearlite interlamellar spacing were measured along with coercivity to investigate the relationships between them. Prior austenite grain size had little effect on the measured coercivity. Coercivity was observed to be high in order of martensite, pearlite and ferrite phase. The linear decrease of coercivity with the increasing pearlite interlamellar spacing was found. Therefore, coercivity was suggested as a potential nondestructive evaluation parameter for assessing the microstructures - pearlite interlamellar spacing and kind of phase - of 0.85% carbon steel.