THICK STEEL PLATE HAVING GOOD ULTRALOW-TEMPERATURE TOUGHNESS

摘要

A thick steel plate that contains definite components in the steel, said thick steel plate satisfying the following requirements: the average roundness (A) of inclusions present in the steel, the equivalent circle diameter of said inclusions exceeding 1.0 µm, is not greater than 1.8; the volume fraction (V) of the retained austenite phase at -196°C is 2.0-12.0%; and value (B) represented by formula (1) is 1.3 or greater.