| 摘要 |
PURPOSE:To enable the manufacture of low-alloy normalized forged steel having superior toughness at low temp. as the forged steel for thick-walled vessels by reducing Si and P content and adjusting Mn content to the specific value based on C content. CONSTITUTION:As the stock for thick-walled pressure vessels of a large size for chemical industry and nuclear power uses, the low-alloy normalized forged steel containing 0.01-0.10% C, <0.10% Si, 2.0-3.5% Mn, 0.008-0.025% Al, 0.0050-0.0150% N, <0.010% P, and <0.010% S and having the quantitative relation 10C+Mn=2.40-3.30% between C content and Mn content is used. By reducing P and Si content to the utmost and further forming a structure containing pro-eutectoid ferrite having low temper brittleness sensitivity, the low-alloy normalized forged steel for large-sized vessels excelling in toughness at low temp. can be obtained even in case of >=150mm thickness.
|
