Abstract
Microstructure analysis and hardness analysis has been carried out on cast steel for components of soil digging machines due to heat treatment of quench, and martemper. The presence of residual austenite causes wear resistance and reduced fracture strength in the earth quarry component to function as a support for the designed arm. In its manufacture, it uses metal casting technology and heat quenching treatments and templates in suitable cooling media, to meet standard requirements. The temperature treatment of austenite 875 °C temperature was held for 90 minutes, and then quenched with variations in the cooling media of water, oil, and salt bath. Furthermore, the martemper process at 425 °C for 90 minutes is cooled to air to room temperature. Microstructure testing and weight percent composition using SEM-EDX and Brihnell scale hardness test. The analysis shows that the hardness value (388 HB) of cast steel quenched in salt bath media is greater than ordinary water (299 HB) and oil (260 HB). However, after the martemper process the value of hardness drops to (342 HB) in the salt water medium, which remains larger than ordinary water (264 HB) and oil (233 HB). This is due to the faster cooling speed in brine and produces martensitic microstructure and residual austenite after being observed with SEM-EDX. The results of this study meet the quality requirements according to the JIS G5111 standard where the minimum hardness value is 222 HB, to be used as a component in excavator.
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