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 0,3 % Kromium (Cr) dan 0,6 % Tembaga (Cu)

Abstract

Of all materials, gray cast iron is the most widely used. This is because it has a very low cost, is easily in large quantities, and is easy to machine. Some applications of its materials need high hardness gray cast iron. To improve its hardness number then the alloy of gray cast iron is aimed to know how far austemper affects the hardness number and microstructure of gray cast iron. Austempering process gray cast iron where by 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 The temperature can be present for austempering process are 350 oC, and 400 oC. and the holding time is 1.5 hour, 2 hour, 2.5 hour. From the analysis the hardness number 0n range 254 - 285 BHN. From the metalography can obtained that microstructure is bainite, pearlite, grafit, austenite. Key words : Gray Cast Iron, Hardness Number, Bainite Structur, Austempering.