Structural ultra-thick steel having excellent resistance to brittle crack propagation, and production method therefor

Abstract

The present invention provides structural ultra-thick steel having excellent resistance to brittle crack propagation and a production method therefor. Provided according to the present invention are: structural ultra-thick steel, which has excellent resistance to brittle crack propagation, comprises 0.02-0.10 wt% of C, 0.8-2.5 wt% of Mn, 0.05-1.5 wt% of Ni, 0.005-0.1 wt% of Nb, and 0.005-0.1 wt% of Ti with the remainder being Fe and other inevitable impurities, and has microstructures including one structure selected from the group consisting of a single-phase structure of ferrite, a single-phase structure of bainite, a complex-phase structure of ferrite and bainite, a complex-phase structure of ferrite and pearlite, and a complex-phase structure of ferrite, bainite, and pearlite; and a production method therefor. According to one aspect of the present invention, ultra-thick structural steel, which has excellent resistance to brittle crack propagation and has excellent yield strength and an excellent impact transition temperature in the center, can be obtained.

Description

technical field [0001] The invention relates to an ultra-thick steel material for structure with excellent brittle crack growth resistance and a manufacturing method thereof. Background technique [0002] Recently, in the design of structures used in the fields of ships, marine, construction, and civil engineering at home and abroad, it is necessary to develop ultra-thick steel with high strength characteristics. [0003] When a structure is designed using high-strength steel, the weight of the structure can be reduced, which is not only economically beneficial, but also facilitates processing and welding work because the thickness of the steel plate can be reduced. [0004] Generally, for high-strength steel, due to the reduction of the total reduction rate in the manufacture of ultra-thick steel, the central part cannot be deformed sufficiently, so that the structure of the central part becomes coarse, resulting in an increase in hardenability and the formation of bainite,...

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Problems solved by technology

[0008] However, although these techniques help to refine the microstructure of the surface layer, they cannot solve the problem of a decrease in impact toughness due to the coarsening of the microstructure in the center, and therefore cannot be used as a fundamental measure for brittle crack growth resistance.

[0009] Also, the technology itself significantly reduces productivity when applied to usual mass-production systems, so it may be difficult to commercialize this technology

[0010] In addition, when adding a large amount of elements such as Ni that contribute to the improvement of toughness, the resistance to brittle crack growth can be improved, but since the Ni element is an expensive element, it is difficult to apply it commercially in terms of manufacturing costs.

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