Pengaruh Austemper Temperatur Quench 350 0C dan 400 0C dengan Variasi Holding Time 1,5 Jam, 2 Jam dan 2,5 Jam terhadap Kekerasan dan Struktur Mikro besi Cor Kelabu Paduan 0,5 % Kromium (Cr) dan 0,6 % Tembaga (Cu)

Abstract

Like steels, gray cast iron is alloying of iron (Fe) and carbon. This cast iron is one of cast iron that used in a lot of applications because the properties is benefical like easy to made, the competitive productions cost, etc. But the mechanics properties of gray cast iron is not as high as steels. The mechanical properties of gray cast iron is influenced by microstructures like matrix fase and the graphites. That microstructures is determined by cooling rate, heat treatment and alloys.There are a lot of application of gray cast irons and they are needed which have high strength. So, because of that the gray cast irons are added by other alloys , Copper (Cu) and Chromium (Cr) then they are gave austemper heat treatment. In this research, The Writer evaluated the effect of Chromium (Cr) and Copper (Cu) addition which have given austempered heat treatment to the microstructures and hardness of gray cast iron. The alloys percentage addition are 0,5 % chromium and 0,6 % copper. While the austemper process is used 350 0C and 400 0C temperature. The means is used for austemper process is salt bath and using three variations holding time, 1,5 hour; 2 hour; 2,5 hour. The experiment used Brinell Hardness experiment and metalography. The results of this experiment are : the increasing of hardness value and appearing of new matrix, bainit matrix. The highest hardness value is got at 350 0C salt bath temperature with two hour holding time ( 319 HBN ). The hardness is increased 44 % to non austempered ( 221 HBN ). Keywords : gray cast iron, austemper, chromium, copper, bainit