Steel sheet

Abstract

The invention provides a steel sheet which has the characteristics of low manufacturing cost, high production efficiency, base metal brittle crack propagation stop performance and excellent tenacity of a welding heat affected zone in high heat input welding. The steel sheet has prescribed chemical components: 0.30-0.40 mass% of a carbon equivalent, and -0.0015-+0.0015 mass% of SOLB. At 1 / 2 part of a sheet thickness, the weighted average DAVE of a grain size of a grain is 3.0-17.0 [mu] m; at 1 / 2 part of a sheet thickness, the weighted average DAVE of a grain size of a grain is 3.0-17.0 [mu] m; the area percentage of a surface (100) forming a angle within 15 DEG relative to a surface in a rolling direction is 2.0-20.0%; at 1 / 4 part of a sheet thickness, the total number density of circle diameter TiN particles, MnS particles and composite particles with 0.5-2.0 [mu] m equivalents is 20-200 / mm2; at 1 / 4 part of a sheet thickness, the number density of circle diameter oxide particle with 1-10 [mu] m equivalents is 20-200 / mm2, the sheet thickness being 10-35mm, and the yield stress being 300-500 MPa.

Description

technical field [0001] The present invention relates to a steel plate excellent in toughness of a welded heat-affected zone and excellent brittle crack propagation arrest performance of a base material when welded. Background technique [0002] For thick steel plates used in structures such as shipbuilding, construction, tanks, marine structures, and line pipes, in order to suppress brittle fracture of structures, performance to suppress brittle cracks from welded joints is required (hereinafter referred to as joint toughness) ). In addition, for the above-mentioned thick steel plate for structures, even if brittle fracture occurs at the welded joint, performance (hereinafter, crack arrestability) that can stop the propagation of brittle cracks in the base metal is also required. Especially in recent years, the development of oil fields in cold regions such as ice seas where there are large amounts of buried energy such as oil and natural gas has been active. Therefore, in ...

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Problems solved by technology

[0003] However, the above-mentioned fracture resistance generally tends to decrease significantly at extremely low temperatures.

In addition, in order to improve welding construction efficiency and reduce costs, it is required to apply high heat input welding that can be welded in a single pass. In this case, the joint toughness is prone to coarsening, so it will be further reduced.

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