High-strength thick steel plate for construction having excellent characteristics for preventing diffusion of brittle cracks, and production method therefor

Abstract

Provided are: a high-strength thick steel plate for construction having excellent characteristics for preventing the diffusion of brittle cracks, said plate being used for ships and having a preferred plate thickness of at least 50 mm; and a method for producing the thick steel plate. The thick steel plate has excellent characteristics for preventing the diffusion of brittle cracks, characterized in that: the main constituent of the metal structure is bainite; the steel plate has an aggregate structure in which the density (I) in the RD / / (110) plane at the plate thickness center is at least 1.5; and the Charpy fracture appearance transition temperature (vTrs) at the surface and plate thickness center is not more than -40 DEG C. More preferably, the Charpy fracture appearance transition temperature (vTrs) at the plate thickness center, and the density (I) in the RD / / (110) plane satisfy formula (1). vTrs(1 / 2t) - 12 IRD / / (110)[1 / 2t] <= -70 ...(1), wherein, vTrs(1 / 2t) is the fracture appearance transition temperature at the plate thickness center ( DEG C), and IRD / / (110)[1 / 2t] is the density in the RD / / (110) plane at the plate thickness center.

Description

technical field [0001] The present invention relates to a high-strength thick steel plate (for structural use) excellent in brittle crack arrestability (brittle crack arrestability) and a manufacturing method thereof, and particularly relates to a plate suitable for use in ships with a thickness of High-strength thick steel plate above 50mm. Background technique [0002] For large structures such as ships, because brittle fracture accidents have a great impact on the economy and the environment, it is generally required to improve safety. For the steel used, the impact on the operating temperature Toughness and brittle crack propagation stop properties are required. [0003] Vessels such as container ships and bulk carriers use high-strength thick-walled materials as the outer plate of the ship's hull in their structures, but recently, along with the increase in the size of the hull, high-strength thick-walled materials have further progressed. Generally, the higher the st...

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Problems solved by technology

[0011] However, the steel materials with excellent brittle crack propagation stopping properties described in Patent Documents 1 and 2 obtain a specific structure by cooling only the surface layer of the steel material and then reheating, and applying processing during the reheating. It is difficult to control the scale, especially for thick-walled materials with a plate thickness greater than 50mm, which is a process with a large load on rolling and cooling equipment

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