Fatigue Strength Improvement of Low Carbon Steel through Carburizing Process with Coconut Shell Charcoal

Abstract

The fatigue strength of low carbon steel is a limitation that is often considered in machine construction, especially in rotating component parts. Low carbon steel has special properties that are soft, good welding and good machining, as well as relatively inexpensive prices but have low fatigue strength. For this reason, in this study, a carburizing process was carried out with the media of coconut shell charcoal as a source of carbon and shell powder as a catalyst. The addition of carbon using the carburizing method is relatively easy and does not require a large cost because the materials used are abundant in nature. The carburization process was carried out at 950°C for 4 hours. Furthermore, mechanical properties were tested with hardness, tensile testing and fatigue testing. The carburization process with charcoal media is expected to increase hardness, tensile strength and fatigue strength. Fatigue testing is carried out by the reverse bending method with a load varying 70%, 60%, 50% and 45% of the tensile strength of the material. In addition, microstructure examination and fault surface observation are also carried out to analyze the phenomenon of changes in material structure due to carburization. The hardness value of ST37 steel before carburizing ie 118 HRB increased to 127 HRB after undergoing carburizing treatment. Tensile test results also experienced an increase in which the initial tensile strength value of ST37 steel by 356.66 MPa increased to 541.15 MPa after the carburizing process. Likewise in fatigue testing, the fatigue limit has increased significantly, where the ST37 steel fatigue limit before the carburizing pack is at a stress level of 161 MPa. After experiencing the carburizing pack process the ST37 steel fatigue limits are at a voltage level of 232 MPa.