H-SECTION STEEL AND METHOD OF PRODUCING THE SAME

摘要

An H-section steel has a predetermined chemical composition, in which a Mg-containing oxide having an equivalent circle diameter of 0.005 μm to 0.5 μm is contained at a total number density of 100 pieces/mm2 to 5000 pieces/mm2, a thickness of a flange is 100 mm to 150 mm, at a strength evaluation portion which is at a ⅙ position from a surface of the flange in a length direction and at a ¼ position from the surface in a thickness direction, a fraction of bainite in a steel structure is 80% or more, and the average prior austenite grain size is 70 μm or more, and at a toughness evaluation portion which is at a ½ position from the surface of the flange in the length direction and at a ¾ position from the surface of the flange in the thickness direction, the average prior austenite grain size in a steel structure is 200 μm or less.

主权项

1. An H-section steel comprising, as a chemical composition, by mass %:
C: 0.05% to 0.16%; Si: 0.01% to 0.50%; Mn: 0.70% to 2.00%; V: 0.01% to 0.20%; Al: 0.0001% to 0.10%; Ti: 0.003% to 0.030%; N: 0.0010% to 0.0200%; O: 0.0001% to 0.0100%; Mg: 0.0003% to 0.0050%; Ni: 0% to 0.50%; Cr: 0% to 0.50%; Cu: 0% to 0.50%; Mo: 0% to 0.30%; Nb: 0% to 0.010%; B: 0% to 0.0020%; Ca: 0% to 0.0050%; and a remainder of Fe and impurities, wherein a carbon equivalent Ceq obtained by the following Equation 1 is 0.30% to 0.50%; a Mg-containing oxide having an equivalent circle diameter of 0.005 μm to 0.5 μm at a total number density of 100 pieces/mm2 to 5000 pieces/mm2; a thickness of a flange is 100 mm to 150 mm; at a strength evaluation portion which is at a ⅙ position from a surface of the flange in a length direction and at a ¼ position from the surface in a thickness direction, a fraction of bainite in a steel structure is 80% or more, and an average prior austenite grain size is 70 μm or more; and at a toughness evaluation portion which is at a ½ position from the surface of the flange in the length direction and at a ¾ position from the surface of the flange in the thickness direction, the average prior austenite grain size in a steel structure is 200 μm or less,
Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15   Equation (1), wherein C, Mn, Cr, Mo, V, Ni, and Cu represent the amount of each element contained by mass % and the amount of an element not contained is 0.