High-strength steel sheet with excellent low-temperature toughness

Abstract

The high-strength steel plate contains C: 0.08% to 0.15%, Mn: 0.80% to 1.60%, Ni: 3.00% to 4.50%, Cr: 0.50% to 1.00%, and Mo: 0.50% to 1.00%, in mass % , Al: 0.020% to 0.085%, N: 0.0020% to 0.0070%, B: 0.0005% to 0.0020%, the plate thickness tmm exceeds 200mm and is less than 300mm, in the chemical composition, Ts is 380 to 430, Ceq is 0.80 ~1.05, Ac1 is 580~647, x is 46~90, by area%, the total amount of martensite and bainite is 99%~100%, the tensile strength is 780MPa~930MPa, the central part of the plate thickness is The absorbed energy obtained by the Charpy impact test at ‑60°C is 69J or more.

Description

technical field [0001] The present invention relates to a high-strength steel sheet that is excellent in low-temperature toughness and has a large plate thickness. More specifically, it relates to a steel plate having a thickness of more than 200 mm, a tensile strength of 780 MPa or more, and an absorbed energy at -60° C. of the central part of the plate thickness of 69 J or more. The steel plate is suitable for structures such as marine structures, pressure vessels, penstocks, and large cranes for ships. Background technique [0002] Among the above-mentioned structures, in general, in order to ensure the safety of the structure, low-temperature toughness is required for the steel plate used as the base material. In recent years, the scale of structures has increased remarkably, and in such structures, steel plates with a large plate thickness and high strength tend to be used. [0003] The above-mentioned structures generally use high-strength steel plates of 780MPa clas...

AI Technical Summary

Problems solved by technology

[0010] As mentioned above, in the conventional method, if the thickness of the steel plate exceeds 200 mm, it is impossible to obtain a high-strength steel plate with a tensile strength of 780 MPa or more and excellent low-temperature toughness.

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