Thick steel plate and manufacturing method thereof

Abstract

The present invention provides a thick steel plate excellent in large heat input welding characteristics and material homogeneity in the steel plate and a manufacturing method thereof. A thick steel plate containing C: 0.030 to 0.080%, Si: 0.01 to 0.10%, Mn: 1.20 to 2.40%, P: 0.008% or less, S: 0.0005 to 0.0040%, and Al: 0.005 to 0.005%. 0.080%, Nb: 0.003-0.040%, Ti: 0.003-0.040%, N: 0.0030-0.0100%, B: 0.0003-0.0030%, further containing Cu, Ni, Cr, Mo, V, Ca, Zr, REM as needed One or two or more of them, the balance being Fe and unavoidable impurities, and the variation range of Vickers hardness (HV) in the sheet thickness direction and sheet width direction: ΔHV is 30 or less. A manufacturing method comprising heating a raw steel material with the above-mentioned composition to a temperature of 1000-1300°C, performing hot rolling, and then carrying out under the condition that the impact pressure of the jet stream on the surface of the steel plate is 1 MPa or more immediately before accelerated cooling Descaling, followed by accelerated cooling.

Description

technical field [0001] The invention relates to a thick steel plate suitable for various steel structures such as ships, marine structures, buildings, and steel pipes, especially for large heat input welding, and a manufacturing method thereof. Background technique [0002] Steel structures used in the fields of ships, marine structures, buildings, steel pipes, and the like are generally finished into structures of desired shapes by joining them by welding. Therefore, from the viewpoint of ensuring safety, these structures are required to ensure the properties of the welded part, mainly the joint strength and joint toughness, in addition to the properties of the base material that are the basis of the steel used, that is, strength, toughness, and elongation. Also excellent. [0003] In addition, in recent years, the above-mentioned ships and steel structures tend to be larger, so the steel materials used are also expected to be higher in strength and thicker, and on the oth...

AI Technical Summary

Problems solved by technology

However, the influence of the high heat input welding countermeasures represented by patent documents 5 and 6 on the homogeneity of the steel plate material has not yet been verified.

Images