Structural high-strength thick steel plate excellent in brittle crack propagation stop characteristic and manufacturing method thereof

Abstract

Provided is a high-strength thick steel plate for structural use having a thickness of 50 mm or more and excellent brittle crack arrestability which can be preferably used for ships and a method for manufacturing the steel plate. The steel plate with excellent brittle crack arrestability has a metallographic structure mainly including a bainite phase, a texture in which the integration degree I of the RD / / (110) plane in a central portion in the thickness direction is 1.5 or more, and a Charpy fracture appearance transition temperature vTrs in a surface portion and the central portion in the thickness direction of -40°C or lower. Further, the steel plate preferably has the Charpy fracture appearance transition temperature and the integration degree I of the RD / / (110) plane in the central portion in the thickness direction satisfying the relational expression (1) below: vTrs 1 / 2 �¢ t - 12 × I RD / / 110 �¢ 1 / 2 �¢ t ‰¤ - 70 where vTrs (1 / 2t) : fracture appearance transition temperature (°C) in the central portion in the thickness direction and I RD / / (110) [1 / 2t] : integration degree of the RD / / (110) plane in the central portion in the thickness direction.

Description

technical field [0001] The present invention relates to a high-strength thick steel plate for structural use (high-strength thick steel plate) excellent in brittle crack arrestability (brittle crack arrestability) and a manufacturing method thereof, and particularly relates to a high-strength thick steel plate suitable for ships with a plate thickness of 50 mm or more . 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 toughness at the operating temperature (toughness), brittle crack propagation stop characteristics are required. [0003] Vessels such as container ships and bulk carriers use high-strength thick-walled materials for their outer plate (outer plate of ship'shull) in their structures, but recently, along with the increase in size of ship hulls, high-strength thick-walled materials have fur...

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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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