High-strength steel material having enhanced resistance to brittle crack propagation and break initiation at low temperature and method for manufacturing same

Abstract

An aspect of the present invention relates to a high-strength steel material, having enhanced resistance to brittle crack propagation and break initiation at a low temperature, which comprises in weight % 0.02-0.09% of C, 0.005-0.3% of Si, 0.5-1.7% of Mn, 0.001-0.035% of Sol.Al, 0.03% or less of Nb (not including 0%), 0.01% or less of V (not including 0%), 0.001-0.02% of Ti, 0.01-1.0% of Cu, 0.01-2.0% of Ni, 0.01-0.5% of Cr, 0.001-0.5% of Mo, 0.0002-0.005% of Ca, 0.001-0.006% of N, 0.02% or less of P (not including 0%), 0.003% or less of S (not including 0%) and 0.002% or less of O (not including 0%) with a balance of Fe, and inevitable impurities, satisfies relational expression (1) below, has a microstructure comprising polygonal ferrite and needle-shaped ferrite of the total of 50 area% or greater, and comprises 3.5 area % or less of a martensite-austenite (MA) composite. Relational expression (1): 5*C + Si + 10*sol.Al <= 0.6 (In relational expression (1), each symbol for the element is a value indicating each element content in weight %).

Description

technical field [0001] The present disclosure relates to a high-strength steel having excellent fracture initiation resistance and fracture propagation resistance at low temperatures, which can be suitably applied to steel for shipbuilding offshore structures, and a manufacturing method thereof. Background technique [0002] Due to the depletion of energy sources, the extraction of resources has gradually moved to deep sea areas or extremely cold areas, and accordingly, mining and storage facilities have increased in size and become more complex in structure. Therefore, the thickness of steel in these fields increases, and the steel is designed to have high strength. [0003] As the thickness of steel increases and high-strength steels have been developed, the addition of alloying elements increases. A large amount of alloying elements can cause the problem of toughness deterioration during the welding manufacturing process. [0004] The reason why the toughness of the wel...

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Problems solved by technology

[0007] However, since the structure has been designed to have a large size and the use environment has changed to a polar environment, there may be a problem that it may be difficult to sufficiently secure fracture initiation resistance and fracture propagation resistance at low temperatures by applying the above-mentioned conventional methods

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