PENGARUH AUSTEMPER TEMPERATUR QUENCH 3500C DAN 4000C DENGAN VARIASI HOLDING TIME 1,5 JAM, 2 JAM DAN 2,5 JAM TERHADAP KEKERASAN DAN STRUKTUR MIKRO BESI COR KELABU NON PADUAN

Abstract

Grey Cast iron is the most useful material in metal casting. It use in vital component of machine, like machine case, train brake, etc. The Grey cast iron was used because the material can faint the vibration of machine and it cheapest. But it has low mechanical properties. The mechanical properties of grey cast iron are influenced by cooling rate, heat treatment, liquid treatment and alloying. Some application of its materials need high strength grey cast iron. To improve it, we can give austemper heat treatment. In these research the effect of austemper has been evaluated. Base material non alloying was austenitized at 9500C for 1 h, and then austempered at quench temperature 3500C and 4000C with variation holding time 1,5 h, 2 h and 2,5 h. The Brinell hardness test and metallography examinations have been conducted to known of its effect. From Brinell hardness test is an improvement of hardness at quench temperature 3500C and holding time 1,5 h about 10,2% from 167 BHN to 184 BHN, at quench temperature 3500C/2 h is 25,7% from 167 BHN to 210 BHN, at temperature quench 3500C/2,5 h about is 10,2% from 167 BHN to 184 BHN, at 4000C/1,5 h 5,4% from 167 BHN to 176 BHN, at 4000C/2 h 16,8% from 167 BHN to 195 BHN and at 4000C/2,5 h 7,2% from 167 BHN to 179 BHN. However the microstructure of speciment are bainit with graphite type VII (flake) and type A on distribution graphite.