STUDY OF THE EFFECT OF RAPID CYCLIC AUTENITIZATION HEAT TREATMENT ON MILD STEEL TO OBTAIN ADVANCED HIGH STRENGTH STEEL QUALITY

• Main Author: Fikry Aryaditama Arrozi, Ihza
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/76428
• Institution: Institut Teknologi Bandung

Steel is one of the world's most important engineering and construction materials, used in various aspects of our lives. One type of carbon steel that is widely used in the construction industry is structural steel. The heat treatment that is generally applied is conventional heat treatment to achieve mechanical properties that are categorized as high-strength steels. In the last decade, there have been more rapid heat treatment methods that can be applied to produce good mechanical properties in mild steels. The method that can be used is rapid austenization. This method can produce steel that has the strength and toughness of mild steel. In this research, the effect of heating cycles on mechanical and microstructural properties was studied to produce high-strength steel using the rapid austenitization method. The rapid austenitization heat treatment was carried out at 1000oC with a heating time of 15 seconds and a residence time of 45 seconds. Variations were carried out with one cycle, two cycles, three cycles, and four repeated heating cycles. Conventional austenization with a residence time of 30 minutes was used as a comparison. The immersion hardening method using iced brine water was used in two austenitizing modes after the heating process. A series of experiments above were carried out to study the effect of heating cycles on microhardness, charpy impact energy, tensile strength, microstructure, and fracture surfaces. The tests included hardness, impact, and tensile tests, as well as metallographic observations using optical microscope and fractography using scanning electron microscope. The experimental results show an increase in hardness in each cycle with a maximum value of 482 HV in the fourth cycle, a trend of increasing impact energy with a maximum value of 35.8 J/cm2 in the third cycle, an increase in UTS with a maximum value of 1290 MPa in the second cycle, a trend of increasing elongation with a maximum value of 16.72% in the third cycle, and martensite microstructure and fibrous ductile fracture in each cycle. It was concluded that the heat-treated steel with varying numbers of heating cycles in this study had a good combination of strength and ductility to enter the high-strength steel category with a UTS range of 1107 MPa to 1290 MPa and an elongation of 12.96% to 16.72%.