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KR-20260068108-A - High-strength, high-toughness, low-temperature resistant hot-rolled H-shaped steel for floating crude oil storage vessels and method of manufacturing the same

KR20260068108AKR 20260068108 AKR20260068108 AKR 20260068108AKR-20260068108-A

Abstract

The present invention belongs to the field of metallurgy and rolling technology, and specifically, it relates to a high-strength, high-toughness, low-temperature resistant hot-rolled H-shaped steel for floating crude oil storage vessels and a method for manufacturing the same, wherein the chemical composition is, in weight percent, C: 0.07~0.11%, Si≤0.2%, Mn: 1.5~1.9%, V: 0.06~0.10%, Nb: 0.02~0.05%, Ni: 0.1~0.4%, B: 0.001~0.002%, Alt: 0.025~0.045%, P≤0.015%, S≤0.006%, N: 0.01~0.015%, O≤0.003%, and the remainder is Fe and unavoidable impurities. The H-shaped steel according to the present invention emphasizes lightweighting technology based on eco-friendly principles, reduces overall transportation costs of floating crude oil storage vessels, improves material utilization efficiency, achieves a 15-30% weight reduction target for the structure of floating crude oil storage vessels, and thereby provides product and technical support for steel structures for hull modules.

Inventors

  • 자오 페이린
  • 우 원젠
  • 정 리
  • 리 둥
  • 장 페이
  • 왕 젠쥔
  • 리 차오
  • 쑹 헝쥔
  • 류 차오
  • 한 원시
  • 쑹 위칭
  • 장 위안화

Assignees

  • 샨동 아이론 앤드 스틸 컴퍼니 리미티드

Dates

Publication Date
20260513
Application Date
20231116
Priority Date
20230922

Claims (10)

  1. High-strength, high-toughness, low-temperature resistant hot-rolled H-shaped steel for floating crude oil storage vessels, characterized by a chemical composition in weight percent of C: 0.07~0.11%, Si≤0.2%, Mn: 1.5~1.9%, V: 0.06~0.10%, Nb: 0.02~0.05%, Ni: 0.1~0.4%, B: 0.001~0.002%, Alt: 0.025~0.045%, P≤0.015%, S≤0.006%, N: 0.01~0.015%, O≤0.003%, and the remainder being Fe and unavoidable impurities.
  2. In paragraph 1, High-strength, high-toughness, low-temperature resistant hot-rolled H-shaped steel for floating crude oil storage vessels, characterized in that the flange thickness of the above H-shaped steel is less than 15 mm.
  3. In paragraph 1, A high-strength, high-toughness, low-temperature resistant hot-rolled H-shaped steel for floating crude oil storage vessels, characterized in that the yield strength of the above high-strength, high-toughness, low-temperature resistant hot-rolled H-shaped steel is 440 MPa or more, the tensile strength is 520 MPa or more, the elongation is 18% or more, and the impact energy at -60°C is 150 J or more.
  4. In paragraph 1, High-strength, high-toughness, low-temperature resistant hot-rolled H-shaped steel for floating crude oil storage vessels, characterized in that the matrix structure of the H-shaped steel is finely milled pearlite + proeutectoid ferrite and the grain size is controlled in the range of grades 9 to 11.
  5. A method for manufacturing high-strength, high-toughness, low-temperature resistant hot-rolled H-shaped steel for floating crude oil storage vessels, characterized by including the following steps: a molten iron pretreatment step → an electric furnace smelting step → a step of blowing argon into a ladle → an LF refining step → a VD degassing step → a step of continuously casting a rectangular billet → a step of slowly cooling the continuously cast billet in a slow cooling pit → a furnace heating step → a BD rough rolling step → a step of semi-continuous rolling using a compact type TM in a steel section line → cooling between stands + water cooling of the lower flange after rolling → a step of intensive slow cooling in a cooling bed.
  6. In paragraph 5, A manufacturing method characterized by the heating furnace temperature being 1190~1220℃ during the rolling process, the furnace time of the cast billet being 180~240 min, and the rough rolling being reciprocated rolling with 7~9 passes.
  7. In paragraph 5, A manufacturing method characterized by using continuous rolling for finishing rolling, a finishing rolling start temperature of 960 to 1000°C, water cooling between finishing rolling stands being completely open, and a finishing rolling finish temperature of 780 to 850°C.
  8. In paragraph 5, A manufacturing method characterized by performing a flipping operation using a flipping device between rough rolling and finishing rolling, and controlling the temperature of the rolled material to a range of 960 to 1000℃ after a temperature waiting of 20 to 50 seconds according to the temperature measurement result, and then introducing it into a finishing rolling mill to perform continuous rolling.
  9. In paragraph 5, A manufacturing method characterized by a reduction rate of 8% to 15% in the last pass of finishing rolling, and sufficient cooling after finishing rolling being advantageous for promoting the precipitation of carbonitrides of V and acting as a precipitation strengthening agent.
  10. In paragraph 5, A manufacturing method characterized by controlling the cleanliness of molten steel using LF + VD in the refining process, losing nitrogen content after VD degassing, performing nitrogen increase treatment according to N content to enhance the precipitation strengthening effect of VN, and maintaining the nitrogen content in the steel within the range of 0.01 to 0.015% by adding 20 to 50 m of manganese nitride-cored wire in the nitrogen increase method.

Description

High-strength, high-toughness, low-temperature resistant hot-rolled H-shaped steel for floating crude oil storage vessels and method of manufacturing the same This application claims priority to Chinese Patent Application No. 2023112308667, filed on September 22, 2023, with the title of the invention "High-strength, high-toughness, low-temperature resistant hot-rolled H-shaped steel for floating crude oil storage vessels and method for manufacturing the same," and incorporates the entire contents of the same by reference in this specification. The present invention belongs to the field of metallurgy and rolling technology, and specifically relates to a high-strength, high-toughness, low-temperature resistant hot-rolled H-shaped steel for floating crude oil storage vessels and a method for manufacturing the same. Floating oil storage vessels are advanced, large-scale offshore processing equipment designed to extract deep-sea oil and gas resources. They are capable of extracting, processing, storing, and transporting energy sources such as offshore oil and natural gas, and are referred to as "offshore oil processing plants." Unlike relatively fixed offshore oil platforms, floating oil storage vessels can not only extract oil and store and transport crude oil products but also serve as large-scale offshore oil production bases that integrate personnel accommodation and production command. They can rapidly reach designated locations to carry out oil and gas field development and possess unique advantages such as short construction cycles and excellent maneuverability, making them applicable to oil and gas field development operations in various waters around the world. As the development of oil and natural gas resources expands from open waters to complex regions such as deep sea and cryogenic areas, the production, storage, unloading, and transportation of floating crude oil storage vessels are facing increasingly complex operating conditions. Consequently, the manufacturing of large crude oil storage vessels places stricter demands on material sophistication; new materials and technologies must be used to minimize maintenance costs without requiring dry docking for repairs for 30 years or more. The manufacturing of the upper modules requires a large volume of hot-rolled H-shaped steel. With the rising standards, there is an urgent need for hot-rolled H-shaped steel with superior overall performance to replace current lower-grade H-shaped steel, thereby enabling weight reduction while ensuring higher stability and reliability. In order to adapt to the operating environments of complex regions, such as cryogenic regions, higher requirements are being placed on the low-temperature impact toughness of steel. The necessary H-shaped steel must have a strength of 420 MPa or higher, a low ductile-brittle transition temperature, and the material's low-temperature resistance must reach at least Grade E, or even Grade F. Consequently, as the production volume of floating crude oil storage vessels increases, the demand for hot-rolled H-shaped steel that combines high strength grades of 420 MPa or higher with low-temperature resistance performance is increasing accordingly. Currently, Chinese hot-rolled H-shaped steel manufacturers have already successively developed and commercialized H-shaped steels with a yield strength of over 355 MPa and Grade E low-temperature resistance. There are also differences in production methods across different production lines, and generally, they are produced by combining composite microalloying with the addition of Nb, V, and Ti with thermomechanical rolling. These differences in manufacturing methods by company and production line are reflected in patent applications. The invention patent of application number CN201510788520.8 disclosed a 420 MPa-grade high-strength low-yield ratio H-shaped steel and a method for manufacturing the same. The chemical composition of the H-shaped steel is, in weight percentage, C: 0.11~0.15%, Si: 0.20~0.35%, Mn: 1.35~1.50%, P≤0.035%, S≤0.025%, Cu: 0.25-0.30%, Cr: 0.40-0.45%, Ni: 0.20-0.30%, Nb: 0.20-0.30%, and the remainder is iron and trace impurities. The present invention is implemented such that the yield strength of the low-yield ratio H-shaped steel is greater than 427 MPa, the tensile strength is greater than 641 MPa, and the yield ratio is 0.64~0.67. The above invention is intended for use in specific high-corrosion-resistant environments by adding elements such as Ni, Nb, and Cu. However, due to the influence of Cu elements during the manufacturing process, the probability of cracks occurring in the H-shaped steel legs increases under high rolling finishing temperature conditions, so the yield is low as the material must be used after surface grinding. At the same time, the addition of Cr and Cu elements makes it easy for abnormal structures to occur, and the material does not show a distinct yielding phenomenon, making it difficult to ensure safe