Pengaruh Temperatur Austempering Terhadap Sifat Mekanis dan Struktur Mikro Austempered Ductile Iron

Abstract

The austempering process is a high performance heat treatment that, when appllied to Ductile Cast Iron it can improve the strength up to 100 % or more in combination with improvements the toughness of material Austempering process ductile cast iron whereby a material in the austenitic condition is quech in a hot liquid salt bath (KNO3 + NaNO2) at a temperature just above the martensite start of the material, held in the bath until the austenit of the material is fully transformed, and then cooled to room temperature. In this paper we wish the result is have a good combination between strength and toughness. To have a god combination there is a few variables that can use for austempering process that is the composition of ductile cast iron and the time of austempering process as a dependent variable and austempering temperature as an independent variable. Which is for an independent variable is variated to see the effect after austempering process. The temperature can be present for austempering process are 250 o C, 300 o C, and 350 o C. The result after austempering process are tested by tensile test, hardness test, and metallography. Afterwards it compared to see the effect after austempering and from that result we can conclude that the increase of the strength and hardness of ductile cast iron will be improvements when the temperature of austempering at low temperature (250 o C) is about 1098,57 N/mm2 and 501,9 for Brinell number and will decrease when the temperature austempering at high temperature (350 o C) for the srength is 914,56 N/mm2 dan 368,25 for brinell number the different after austemepring is because lot of bainite formed at low temperature. Key word : Austempering, Ductile cast iron, Tensile strength, Hardness