The CrMo steel and the production mannered null mass which are superior in strength and low temperature

摘要

PROBLEM TO BE SOLVED: To provide forged Cr-Mo steel having high strength and excellent low-temperature toughness even in the case of thick-walled articles.;SOLUTION: Cr-Mo steel, having a composition containing 0.10 to 0.20% C, ≤0.40% Si, 0.10 to 1.00% Mn, 0.05 to 1.00% Ni, 2.00 to 3.50% Cr, 0.10 to 1.50% Mo, 0.10 to 0.40% V, 0.010 to 0.030% Nb, 0.005 to 0.015% Ti, 0.0005 to 0.0015% B and 0.005 to 0.010% N, is forged, heated to 900 to 980°C, water-cooled and then tempered at a temperature not lower than 600°C and below the Ac1 transformation point. Required strength can be satisfied, and low-temperature toughness capable of withstanding use in extreme cold districts can be secured. By this method, mechanical properties uniform in a wall-thickness direction can be obtained even in the case of extra thick steel forgings having a wall thickness ranging from 200 to 600 mm, and the reliability of large equipment, such as pressure vessels and casings for thermal power generation, can be greatly improved.;COPYRIGHT: (C)2005,JPO&NCIPI