The chemical composition of AISI 5120 steel is 0.21%C-0.24%Si-0.89%Mn-1.25%Cr in weight
percent. The specimens for dilatometric tests were machined to thin plates of 10×3×1 mm3
from a
hot-rolled bar. The dilatometric tests were carried out to obtain the phase transformation kinetic
data. For heat transfer coefficients during oil-quenching, a ring specimen of SUS 304 steel, whose
Microstructure of 5160 alloy steel austenitized at 830 ºC, isothermally transformed at 677 ºC for 30 seconds and water quenched after etching with 2% nital (left), 4% picral (center) and 10% sodium metabisulfite (right).