Mechanical Characterization of Ship Building Grade A Steel by Rapid Cooling in Different Liquid Media

ABSTRACT: Steel is an essential component used to build marine vessels due to its endurance of the sea’s harsh conditions, including corrosion and dynamic stresses, therefore, different grades of mild steel are used in shipbuilding. It provides the strength, ductility, and weldability necessary for structural integrity, consisting of carbon, manganese, etc., as alloying elements. In this research, different quenching media were employed to assess variations in mechanical properties. This process ultimately triggered alterations in the microstructure of the steel. Two types of media, such as vegetable oil (Canola) and Polyvinylpyrrolidone polymer (PVP), were studied in comparison with simple heat-treated steel. Mechanical characterization comprised of tensile testing, hardness and impact testing to evaluate major changes in strength and ductility. Furthermore, a microscope was used to interpret the microstructure. To guarantee consistency in testing, samples were prepared in accordance with ASTM guidelines. The yield strength of as-received steel was increased from 298 MPa to 358 MPa and 370 MPa because of rapid cooling action in PVP and oil, respectively. A significant increase in Ultimate tensile strength was achieved due to the variety of quenching media; however, ductility was seriously compromised because of the excessive hardness of the material. Impact energy analysis revealed a notable reduction, which is linked with degradation in toughness.