Super-thick steel material for structure having excellent performance of surface portion nrl-dwt and method for manufacturing the same

By controlling the alloy composition and rolling process, an ultra-thick steel was manufactured, solving the problem of micro-cracks on the surface and achieving excellent NRL-DWT performance and resistance to brittle crack propagation, making it suitable for mass production of ultra-thick high-strength steel.

CN116113721BActive Publication Date: 2025-11-07POHANG IRON & STEEL CO LTD
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Patent Information

Application Number
CN202180052244.2
Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
Priority Date
2020-08-25
Filing Date
2021-08-23
Publication Date
2025-11-07
Estimated Expiration
2041-08-23

AI Technical Summary

Technical Problem

Existing technologies struggle to effectively control surface microcracks in ultra-thick, high-strength steels, resulting in poor performance of NRL-DWT, particularly in resistance to brittle crack propagation. Furthermore, large-scale tensile testing is costly and difficult to apply to mass production.

Method used

By controlling the alloy composition, rolling temperature, and reduction, an ultra-thick steel is manufactured, containing a specific range of C, Si, Al, Mn, Ni, Nb, Ti, and Cu elements. A finishing rolling temperature below 740℃ and a cooling rate of more than 3℃/second are used to suppress micro-cracks on the surface and ensure excellent NRL-DWT performance.

Benefits of technology

It achieves excellent NRL-DWT performance in ultra-thick steel without adding expensive alloying elements, with a yield strength of over 460MPa, a thickness of 80-100mm, an NDTT value below -70℃, and a microcrack density of less than 0.1 cracks/mm2, meeting the requirements for resistance to brittle crack propagation.

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Abstract

The present disclosure relates to a steel material for an ultra-thick structure having excellent surface portion NRL-DWT performance and a manufacturing method thereof, and more particularly to a steel material for an ultra-thick structure and a manufacturing method thereof, the steel material comprising, in weight %, C: 0.05 to 0.09 %, Si: 0.1 to 0.4 %, Al: 0.01 to 0.05 %, Mn: 1.8 to 2.0 %, Ni: 0.3 to 0.7 %, Nb: 0.015 to 0.040 %, Ti: 0.005 to 0.02 %, Cu: more than 0 % and 0.05 % or less, the balance of Fe and other inevitable impurities, and the number of micro cracks having a length of 50 μm or more per square millimeter in a region from a surface portion to 5 mm directly below the surface portion is 0.1 or less.
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