STRUCTURAL HIGH TENSILE STEEL WITH REDUCED STRESS AGING BRITTLENESS

摘要

PURPOSE:To provide the titled structural high tensile steel almost free from the lowering of impact absorbing energy even after stress aging, that is, capable of preventing toughness deterioration due to the stress aging obtained by adding one or more of Ca, Mg to a steel added with V and N. CONSTITUTION:The above described high tensile steel is constituted from 0.12- 0.25% C, 0.05-1.0% Si, 0.5-2.0% Mn, 0.025% or less P, 0.01% or less S, 0.006-0.06% Al, 0.03-0.20% V, 0.010-0.03% N and 0.0005-0.0070% Ca or/and 0.0005-0.0070% Mg and the remainder of Fe. Because said steel contains a large amount of V and N, the reinforcing action due to V N precipitation is sufficiently developed, for example, if a cooling speed after hot rolling is slow. Therefore, the thick high tensile steel material can be produced from said steel.