Low-carbon equivalent extra-thick high-toughness normalized steel plate for offshore wind power and manufacturing method of low-carbon equivalent extra-thick high-toughness normalized steel plate

By using low-carbon, high-manganese microalloying and full-process process control, the problems of low carbon equivalent and high and low temperature toughness of extra-thick steel plates for offshore wind power have been solved, achieving high strength and uniform performance of extra-thick steel plates and reducing production costs.

CN122279382APending Publication Date: 2026-06-26JIANGYIN XINGCHENG SPECIAL STEEL WORKS CO LTD
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Patent Information

Application Number
CN202610244829.9
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2026-03-02
Publication Date
2026-06-26

AI Technical Summary

Technical Problem

Existing technologies struggle to simultaneously achieve low carbon equivalent, good weldability, and high and low temperature toughness on 100-150mm thick steel plates used in offshore wind power. Furthermore, the properties are not uniform in the thickness direction, and the grains are coarse after normalizing heat treatment, making it difficult to balance strength and toughness.

Method used

By adopting a low-carbon, high-manganese micro-composite micro-alloying design, combined with full-process process control of smelting, heating, rolling and normalizing heat treatment, inclusions are reduced by smelting, grains are refined by rolling, and microstructure is optimized by normalizing treatment, thus achieving low carbon equivalent and high strength and low-temperature toughness of steel plates.

Benefits of technology

The steel plate has good weldability under low carbon equivalent, yield strength and tensile strength of 355MPa and 470~560MPa respectively, impact energy of ≥50J at -50℃, and uniform properties in the thickness direction, which meets the requirements of offshore wind power and reduces production costs.

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Abstract

The thickness of the steel plate ranges from 100 mm to 150 mm, the steel plate comprises, by weight, 0.12%-0.18% of C, 0.20%-0.40% of Si, 1.20%-1.60% of Mn, smaller than or equal to 0.020% of P and smaller than or equal to 0.005% of S, Ni, Mo and Cr are matched for trace hardening and tempering and Nb + V + Ti ternary composite microalloying, B is strictly controlled to be smaller than or equal to 0.0005%, and the carbon equivalent CEV is smaller than or equal to 0.43%. The yield strength of the steel plate is larger than or equal to 355 MPa, the tensile strength is 470-560 MPa, and the transverse and longitudinal Charpy impact energy unit value at the temperature of-50 DEG C is larger than or equal to 50 J. The manufacturing method comprises the steps of smelting and casting, continuous casting billet heating, rolling and normalizing heat treatment, wherein the rolling compression ratio is larger than or equal to 3.0, the reduction rate of the last three passes of rough rolling is larger than 9%, the finish rolling temperature of finish rolling is 780-820 DEG C, the normalizing temperature is 870-900 DEG C, and the heat preservation time coefficient is 1.5-2.5 min / mm. The problems that an extra-thick plate is insufficient in obdurability and uneven in thickness performance under the low carbon equivalent are solved, the welding performance is good, the production cost is low, and the ultra-thick plate is suitable for offshore wind power single-pile foundation structural parts and can be produced in batches.
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