THICK STEEL PLATE AND PRODUCTION METHOD FOR THICK STEEL PLATE

摘要

Provided are a steel plate having high tensile strength, high yield strength, and excellent low-temperature toughness and a method for manufacturing the steel plate.;A steel plate contains 0.04% to 0.15% C, 0.1% to 2.0% Si, 0.8% to 2.0% Mn, 0.025% or less P, 0.020% or less S, 0.001% to 0.100% Al, 0.010% to 0.050% Nb, and 0.005% to 0.050% Ti and further contains Cu, Ni, Cr, Mo, and N on a mass basis such that 0.5%≦Cu+Ni+Cr+Mo≦3.0% and 1.8≦Ti/N≦4.5 are satisfied, the remainder being Fe and inevitable impurities. The area fraction of polygonal ferrite is less than 10%. The effective grain size at the through-thickness center is 15 μm or less. The standard deviation of the effective grain size is 10 μm or less.

主权项

1. A steel plate containing 0.04% to 0.15% C, 0.1% to 2.0% Si, 0.8% to 2.0% Mn, 0.025% or less P, 0.020% or less S, 0.001% to 0.100% Al, 0.010% to 0.050% Nb, and 0.005% to 0.050% Ti on a mass basis, the steel plate further containing Cu, Ni, Cr, Mo, and N on a mass basis such that 0.5%≦Cu+Ni+Cr+Mo≦3.0% and 1.8≦Ti/N≦4.5 are satisfied, a remainder being Fe and inevitable impurities,
wherein an area fraction of polygonal ferrite is less than 10%, the effective grain size at the through-thickness center is 15 μm or less, and a standard deviation of the effective grain size is 10 μm or less.