Heavy steel plate for high-heat energy input soldering with excellent shortness fissure spread stop character

Abstract

The present invention provides a steel plate which still exhibits excellent HAZ toughness and remarkable brittle cracking propagation cessation characteristic even under high thermal input welding. The inventive thick steel plate is formed by properly regulating chemical ingredients and meets the thick steel plates of the following formulae (1) and (2), and includes an organization having an organization with more than 95 area % of bainite fraction, and dislocation density of the bainite (rho<1 / 2>) is 1.0*10<6> to 5.0*10<7> (m<-1>). [Ti] / [N] is not less than 1.5 but not more than 4.0 ... (1), X value is not less than 40 but not more than 160 ... (2), X value = 500[C]+32[Si]+8[Mn]-9[Nb]+14[Cu]+17[Ni]-5[Cr]- 25[Mo]-34[V], in the formula, [] represents contents of each element (mass%).

Description

technical field [0001] The present invention relates to a thick steel plate suitable for welded structures such as ships and marine structures, and in particular to a heat-affected zone (Heat Affected Zone: HAZ) after welding with high heat energy input, which has excellent toughness and brittle crack propagation stop characteristics. Excellent thick steel plate. Background technique [0002] In recent years, for example, container ships and the like have been increased in size, and thick steel plates having a plate thickness of 50 mm or more have been used. In order to efficiently weld such a thick steel plate, high heat input welding or ultra-high heat input welding (hereinafter represented by "high heat input welding") with a heat input of 40 kJ / mm or more is required. [0003] However, when high heat energy input welding is performed, the HAZ is heated to a high-temperature austenite region and then gradually cooled, so that the structure is coarsened, and the toughness...

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Problems solved by technology

However, in order to properly precipitate the V compound, a more complicated process is required, and it may not be directly related to the above-mentioned "tissue stabilization" solution

[0009] As mentioned above, although various technologies for making the brittle crack propagation stop properties good have been proposed so far, it is difficult to stably achieve the desired structure on an industrial scale. Desired to establish a technology that can stably realize the property of stopping the propagation of brittle cracks

In addition, in these techniques, no consideration is given to improving the HAZ toughness during welding with high heat energy input

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