The development of a588 modified laterite steel using thermomechanical and low-temperature tempering process for weather resistant steel

Abstract

Laterite Steel A-588 has the potential to be a high strength low alloy for Corten steel application. Laterite steel A-588 is developed through a thermomechanical process followed by a tempering process to obtain high strength and corrosion resistance. This study aims to determine the correlation between the addition of nickel content, the variation of the cooling rate during heat treatment to the mechanical properties, and the corrosion resistance of A-588 laterite steel. The Cu, Cr, Ni, P, and Si elements significantly impact microstructure transformation. Laterite Steel A-588 with nickel and thermo-mechanical process variation has been focused on in this research. Laterite steel with 0,42%, 1%, 2%, and 3% nickel varied was homogenized, hot rolled, and heat treated with three cooling variations by water, oil, and air. They are processed with 150 C tempering. Low tempering temperature caused fine carbide precipitation and phase transition of martensite to bainite. This resulted in bainite as the final microstructure, lath tempered martensite, carbide, and ferrite. 3% Ni with a fast cooling rate increased the tempered martensite and bainite phase formation. It allowed the strength and hardness to increase relatively, followed by decreased elongation and corrosion resistance caused by the galvanic reaction. Most optimal of mechanical properties determined at a sample with 2% nickel in a water medium (strength 1203 MPa, elongation 10%, hardness 404 BHN, corrosion rate 1,306 mpy).

Effect Nickel and Quench-Temper Process on Mechanical and Corrosion Properties of Astm A588 Waethering Steel

“…Tempering temperature, holding time, and cooling rate from the tempering temperature significantly affect steel's final properties. As the previous study, the low temperature (150 ℃) of the tempering process caused the fine carbide deposition and the phase transformation of martensite to bainite in small quantities, so it is no significant impact on strength and elongation [7]. Besides that, the influence of alloying elements on mechanical and corrosion behavior is convoluted.…”

“…Like the water quenched, austenite does not have enough time to transform into the ferrite phase. As a result, the final martensite is smaller than the martensite with oil cooling [7]. The tempered martensite was not visible (Fig.…”

“…Mo, Cr, and Ni are responsible for broadening the bainitic transformation region and obtaining bainitic fraction after quenching [14]. The presence of nickel shifts the CCT curve to the right, thus delaying the reaction of ferrite, pearlite, and bainite [7]. In this simulation, the addition of Ni will affect the formation of bainite with a range of cooling rates towards a slower cooling rate, which is around 0.6 ℃/s to 100 ℃/s.…”