International Journal of Advanced Science and Technology Vol.132 (2019), pp.35-46 http://dx.doi.org/10.33832/ijast.2019.132.05 ISSN: 2207-6360 IJAST Copyright ⓒ 2019 NADIA EFFECT OF QUENCHING AND TEMPERING ON MICRO STRUCTURE AND MECHANICAL PROPERTIES IN LATERITE STEEL ^ Desiran Sembiring 1 , Djoko Setyo Widodo 2 and Bintang Adjiantoro 3 1 PhD Candidate Faculty of Mechanical Engineering Program of Technology University of Malaysia 2 PhD Candidate Faculty of Mechanical Engineering Program Technology University of Malaysia and Lecture at Universitas Krinadwipayana Jakarta, Indonesia 3 Metallurgical Research Center LIPI, Serpong PUSPIPTEK Complex 1 desmuham@gmail.com, 2 djokosetyowidodo@gmail.com, 3 bintangadjiantoro@yahoo.co.id Abstract— The need for high armor material has an impact on the use of laterite steel as an armor material. Therefore the increase of the mechanical properties in laterite steel needs to be done. One way to improve mechanical properties in steel is through quenching and tempering. The variables used in this study are variations in cooling media (water, oil, and air) and tempering temperatures (0°C, 100°C, and 200°C). This study used the experimental method using metallographic observations under optical microscopy, hardness value using Rockwell hardness method, tensile strength values using tensile testing machines and standard ASTM E8, as well as impact resistance values using the Charpy type impact testing machine and ASTM E23 standard. The results showed that specimens from quenching with medium water at a tempering temperature of 100°C had the highest average hardness and tensile strength. This is due to the relatively high content of martensite. The highest impact resistance is owned by specimens from quenching oil followed by tempering at 100°C. In some specimens, there was a secondary hardening event or an increase in hardness after the tempering process and tempered martensite embrittlement event namely the impact resistance value which actually decreased after going through the tempering process. Keywords— quenching, tempering, microstructure, mechanical properties, laterite steel 1. INTRODUCTION The need for bullet-proof material that is light in bullet-proof vehicles is very necessary in order to improve the ability of vehicle mobility and also the efficiency of fuel consumption. Steel has long been used as an armor material. Steel was chosen because of its good mechanical properties and easy characterization. In addition, the availability of steel which is quite large and easy for machinery to process a steel material that is often chosen as bulletproof material (Beny, 2010). ^ Received: July 1, 2019 Reviewed: October 15, 2019 Accepted: November 11, 2019