THE EFFECT OF HEAT TREATMENT AND CHEMICAL COMPOSITION ON THE HARDNESS AND THE MICROSTRUCTURE OF HIGH CARBON STEEL FOR GRINDING BALL APPLICATION

• Main Author: MUNIB FIKRY (NIM : 12508032), AHMAD
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/20850
• Institution: Institut Teknologi Bandung

High carbon steel is one type of steel which has carbon content over 0.5 % and usualy is used for the applications requiring high strength, high wear resistance, and high hardness for example in grinding ball application. Some methods to form grinding ball are through casting and forging. To improve the hardness of the steel which has been formed into grinding ball, the steel has to be heated to a certain temperature above its austenizing temperature, which can be derived from the phase diagram of the steel, then the steel need to <br /> <br /> <br /> be cooled using a specific quenchant. In this research the effect of quenchant variations, chemical composition of sampels, and austenizing temperature variations is studied. Austenizing process is conducted on two sampels of high carboon steel grinding ball that have different chemical composition namely sample X (0,82% C, 0,84% Mn, 0,56% Cr) and sample Y (0,5 wt% C, 0,95 wt% Mn, 0,52 <br /> <br /> <br /> wt% Cr), three temperature variations : 8500C, 9000C, dan 9500C in 60 minutes, then the samples are cooled using two quenchant variations : oil and the air. In order to examine the effect of those three variables, hardness and metallography testing are necessary. Some of the results obtained from the experiment are that the average of hardness of the samples quenched using oil is higher than that of the samples quenched using the air. Sample X achieves the highest hardness by heat treatment at the austenitization temperature of 9000C with the average hardness of 69,8 HRC using oil as quenchant, sample Y achieves the highest hardness by heat treatment at an austenitization temperature of 8500C with the average hardness of 64,6 HRC using oil as quenchant. The values of carbon equivalent of sample X and Y are 0,43 and 0,38 respectively. Quenching using oil yields martensite as dominant phase while quenching using the air yeild pearlite as dominant phase.