BUILDING STEEL MATERIAL FOR LOW TEMPERATURE USE, EXCELLENT IN TOUGHNESS AT LOW TEMPERATURE IN BASE MATERIAL AND LARGE HEAT INPUT HAZ AND HAVING LOW YIELD RATIO AT LOW TEMPERATURE

摘要

PROBLEM TO BE SOLVED: To produce a building steel material with low yield ratio at low temp., having low yield ratio (YR≥80%) and high toughness at low temp., having high toughness at low temp. even in a large heat input HAZ(half-affected zone), and enabling new earthquake-resistant design. ;SOLUTION: This material is a building steel material excellent in toughness at low temp. in a large heat input HAZ as well as in a base material and having low yield ratio at low temp. This building steel material has a composition consisting of, by weight, 0.04-0.18% C, 0.05-0.4% Si, 0.6-1.7% Mn, 0.005-0.015% Ti, 0.055-0.08% sol.Al, ≤0.003% N, ≤0.002% S, ≤0.015% P, 0.001-0.003% Ca, and the balance Fe with inevitable impurities and satisfying Ti+sol.Al≥0.07% and also has a mixed structure composed essentially of ferrite and bainite.;COPYRIGHT: (C)1997,JPO