PENGARUH VARIASI TEMPERATUR DAN HOLDING TIME DENGAN MEDIA QUENCHING OLI MESRAN SAE 40 TERHADAP STRUKTUR MIKRO DAN KEKERASAN BAJA ASSAB 760

The purpose of this study was (1) Determine the influence of temperature variation with quenching media Mesran SAE 40 oil to microstructure and hardness of carbon steel ASSAB 760, (2) Knowing the effect of holding time variation with quenching media Mesran SAE 40 oil to microstructure and hardness of carbon steel ASSAB 760, (3) Knowing the interaction of temperature variation and holding time variation with quenching media Mesran SAE 40 oil to microstructure and hardness of carbon steel ASSAB 760. This research uses experimental methods. Objects in this study is ASSAB 760 medium carbon steel, the product of the Associated Swedish Steels AB (Assab Steels) Stockholm, Sweden, with the chemical content of 0.50% C, 0.60% Mn, 0.30% Si and 0.04 S %. Data analysis techniques in this study using descriptive data analysis results graphically illustrate the tables, histograms, graphics, and images of microstructures. As an input parameter in analyzing the data include: temperature variation (800 °C, 840 °C, and 880 °C), holding time variation(15 minutes, 25 minutes, and 35 minutes), microstructure, and hardness. The results showed a change in the level of hardness and the microstructure formed. From the hardness test results obtained the highest level of hardness in the specimen temperature 800 °C with holding time of 35 minutes 27.66 HRC consecutive lows towards the specimen temperature of 840 °C with holding time 35 min and temperature of specimens 880 °C with holding time of 35 minutes 24.33 HRC, 840 °C specimen temperature and holding time 25 minutes at 24 HRC, the specimen temperature of 880 °C with holding time of 25 minutes 23.33 HRC, specimen temperature of 840 °C with holding time of 15 minutes 22.33 HRC, the specimen temperature 800 °C with holding time 25 minutes at 22 HRC, the specimen temperature of 880 °C with holding time of 15 minutes 21.33 HRC, specimen temperature of 800 °C with holding time of 15 minutes 19.33 HRC, and the lowest rate is specimens of raw material 8 HRC . Microstructure test shows microstructure of raw materials consists of ferrite and pearlite with impartial large crystals form and in accordance with the carbon content of 0.50 % and in the group of the hardening specimens with quenching media Mesran SAE 40 oil, new microstructure is obtained martensite is the main structure in increasing steel hardness . From the research it can be concluded that the variation of temperature and holding time variation with quenching media Mesran SAE 40 oil can change the microstructure and increases hardness of steel ASSAB 760 with the highest hardness value of the specimen temperature of 800 °C with holding time of 35 minutes 27.66 HRC