Extra thick hot rolled h section steel and production method therefor

An extra thick hot rolled H section steel, containing, by mass, the following chemical components:

• 0.04-0.11% of C, 0.10-0.40% of Si, 0.40-1.00% of Mn, 0.40-1.00% of Cr, 0.10-0.40% of Cu, 0.020-0.060% of Nb, 0.040-0.100% of V, 0.010-0.025% of Ti, 0.010-0.030% of Al, 0.0060-0.0120% of N, not more than 0.015% of P, not more than 0.005% of S, not more than 0.0060% of O, and the balance Fe and trace residual elements, wherein 0.090%<Nb+V+Ti≤0.170%, 6.5≤(V+Ti)/N≤10.5, and the chemical components satisfy the condition of 0.30%≤CEV≤0.48% according to a calculation equation CEV=C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15,
• wherein at the part, one sixth of the width distance from an end portion and one quarter of the thickness from outer surface, of a flange of the H section steel, a microstructure contains, by area, 85-98% of acicular ferrite and the balance bainite or retained austenite, wherein the bainite content is not more than 2%, the length-width ratio of acicular ferrite is 2:1 to 5:1, and the ferrite has a grain width size of not more than 40 μm, and the difference of acicular ferrite contents in different zones through thickness of the flange is not more than 16%,
• wherein the H section steel has a flange thickness of 90 mm-150 mm, and
• wherein at the part, one sixth of the width distance from the end portion and one quarter of the thickness from outer surface, of the flange of the H section steel, the tensile yield strength at the room temperature is not less than 460 MPa, the tensile strength is not less than 540 MPa, an elongation after fracture is not less than 24.0%, the impact energy value at −20° C. is not less than 80 J, and the thickness-direction properties reach grade Z35.