한국주조공학회

In this study, we investigated effect of austempering factors and Mn addition on mechanical properties of ADI with ferrite- bainite matrix by pearlite-bainite transformation treatment. Ductile cast iron specimens containing various of Mn were austenitized at 875℃ for 350 sec or 925℃ for 160 sec and then austempered at 300℃ or 400℃ for the various periods(5 to 30 min). Manganese increased pearlite volume fraction in as cast ductile cast iron. The obtained results are as follows ; 1) In austenitizing, hardness of sepecimens austenitized at 875℃ for 350 sec was higher than that of 925℃ for 160 sec. 2) In effect of austempering temperature, tensile strength and handness of specimens austempered at 300℃ was higher than that of 400℃. However, elongation had reverse tendency. 3) Increasing austempering time decreased hardness due to the increment of bainite and retained austenite fractions. However, toughness are increased.