The invention discloses low-temperature high-
toughness hot rolled H-shaped steel with the yield strength being 500MPa and a preparation method thereof. The low-temperature high-
toughness hot rolled H-shaped steel with the yield strength being 500MPa comprises, by
mass, 0.10-0.16% of C, 0.25-0.45% of Si, 0.70-1.55% of Mn, 0-0.030% of P, 0-0.025% of S, 0.015-0.035% of Nb, 0.0010-0.0025% of B, and the balance Fe and inevitable impurities. The production technology process of the steel comprises the following steps of
continuous casting slab heating, rough rolling, universal rolling, saw
cutting and
sizing, and heat treatment. According to the low-temperature high-
toughness hot rolled H-shaped steel with the yield strength being 500MPa and the preparation method thereof, after conventional technology rolling, saw
cutting and
sizing based on the components, the production technology including subcritical
quenching and
tempering is applied to the H-shaped steel, tempered sorbites, ferrites which are arranged in an approximately equiaxial distribution mode, and fine
carbide distributed on the H-shaped steel in a dispersion mode are obtained, the effects that the yield strength of the H-shaped steel is not lower than 500MPa, and the longitudinal ballistic work at the temperature of -60 DEG C is averagely larger than 49J are achieved, and the extremely-low ductile-brittle
transition temperature is realized.