In this study, Taguchi method is used to find out the effect of micro alloying elements like vanadium, niobium and titanium on the

hardness and tensile strength of the normalized cast steel. Based on this method, plan of experiments were made by using orthogonal

arrays to acquire the data on hardness and tensile strength. The signal to noise ratio and analysis of variance (ANOVA) are used to

investigate the effect of these micro alloying elements on these two mechanical properties of the micro alloyed normalized cast steel. The

results indicated that in the micro alloyed normalized cast steel both these properties increases when compared to non-micro-alloyed

normalized cast steel. The effect of niobium addition was found to be significantly higher to obtain higher hardness and tensile strength

when compared to other micro alloying elements. The maximum hardness of 200HV and the maximum tensile strength of 780 N/mm2

were obtained in 0.05%Nb addition micro alloyed normalized cast steel. Micro-alloyed with niobium normalized cast steel have the finest

and uniform microstructure and fine pearlite colonies distributed uniformly in the ferrite. The optimum condition to obtain higher hardness

and tensile strength were determined. The results were verified with experiments.

Increasing the operating temperature and pressure of an automotive engine and reducing its weight can improve fuel efficiency and lower carbon dioxide emissions. These can be achieved by changing the engine piston material from conventional aluminum alloy to high-strength heat- resistant steel. American Iron and Steel Institute 4140 modified steels (AISI 4140 Mod.s), which have improved strength, oxidation resistance, and wear resistance at high temperature were developed by adjusting the AISI 4140 alloy compositions and optimizing the heat treatment process for automotive engine applications. In this study, the effects of modifying alloy compositions on the microstructure, mechanical properties (both at room and high temperatures), and oxidation of AISI 4140 Mod.s were investigated. Effective grain refinement occurred due to the influence of high-temperature stable carbide forming elements such as Mo, and V. The bainite structure changed to martensite structure under the influence Cr and Ni. As the Cr and W contents increased, the oxidation resistance was improved, and the oxide layer thickness decreased after 10 hours exposure at 500°C. The AISI 4140 Mod. exhibited a 35% improvement in room temperature strength, 70% improvement in high-temperature strength, and 40% improvement in high-temperature oxidation resistance compared to conventional AISI 4140.