KR20220004220A - 7Ni steel plate and production process for LNG storage tank - Google Patents

7Ni steel plate and production process for LNG storage tank Download PDF

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KR20220004220A
KR20220004220A KR1020217040526A KR20217040526A KR20220004220A KR 20220004220 A KR20220004220 A KR 20220004220A KR 1020217040526 A KR1020217040526 A KR 1020217040526A KR 20217040526 A KR20217040526 A KR 20217040526A KR 20220004220 A KR20220004220 A KR 20220004220A
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이신 황
장롱 씨에
후이빈 우
송보 후어
펑청 장
빙쥔 장
칭춘 리
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난징 아이론 앤드 스틸 컴퍼니 리미티드
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    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C38/00Ferrous alloys, e.g. steel alloys
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    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00Microstructure comprising significant phases
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    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/008Martensite

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Abstract

본 발명은 철강 제련 기술 분야에 관한 것으로, LNG 저장탱크용 7Ni 강판 및 생산 공정을 제공한다. 이의 화학 성분 및 질량 백분율은 C: 0.02%~0.06%, Si: 0.20%~0.35%, Ni: 4.0%~8.0%, Mn: 0.3%~0.7%, P≤0.005%, S≤0.005%, Al: 0.03%~0.05%, Nb: 0.02%~0.05%, Cr: 0.2%~0.4%, 나머지는 Fe 및 불가피한 불순물이다. 강판의 인장 강도는 690~790Mpa, 항복 강도는 590~700MPa, 연신율은 ≥24%이고, -196℃에서의 횡방향 충격 에너지는 ≥100J이며, LNG를 저장하고 운송하는 압력용기 제조에 사용할 수 있다.The present invention relates to the field of steel smelting technology, and provides a 7Ni steel plate for an LNG storage tank and a production process. Its chemical composition and mass percentage are: C: 0.02%~0.06%, Si: 0.20%~0.35%, Ni: 4.0%~8.0%, Mn: 0.3%~0.7%, P≤0.005%, S≤0.005%, Al : 0.03%~0.05%, Nb: 0.02%~0.05%, Cr: 0.2%~0.4%, the remainder is Fe and unavoidable impurities. The tensile strength of the steel sheet is 690~790Mpa, the yield strength is 590~700MPa, the elongation is ≥24%, and the transverse impact energy at -196℃ is ≥100J, and it can be used to manufacture pressure vessels that store and transport LNG. .

Description

LNG 저장탱크용 7Ni 강판 및 생산 공정7Ni steel plate and production process for LNG storage tank

본 발명은 철강 제련 기술 분야에 관한 것으로, 보다 상세하게는 LNG 저장탱크용 7Ni 강판 및 생산 공정에 관한 것이다.The present invention relates to the field of steel smelting technology, and more particularly, to a 7Ni steel plate for an LNG storage tank and a production process.

경제가 발전함에 따라 환경 및 자원 문제가 여러 국가의 최우선 과제로 부상하고 있으며 청정, 무공해 및 고열량의 에너지원으로서 LNG는 점차 미래 에너지 사용에서 더 큰 비중을 차지할 것이다. 천연가스 사용 범위 확대는 중국이 에너지 구조를 최적화하고 생태 환경을 보호하는 중요한 수단이 되었다. 현재 국내외에서 LNG 저장, 운송 도구에 널리 사용되는 강판은 9Ni강이다. 중국은 Ni 빈국으로서, 비용 절감을 위해 성능 확보를 기반으로 Ni 함량을 줄이는 것은 중요한 방법 중 하나이다. 니켈 함량 절약형 7Ni강에 대한 연구는 아직 초기 단계이며, 현재 7Ni 강판에 대한 몇몇 특허가 보고되었다. 출원 번호 201711306269.2의 "초저온 환경용 니켈 절약형 7Ni강 및 이의 열처리 공정의 제작 방법"은 초저온 환경용 니켈 절약형 7Ni강 및 이의 열처리 공정을 개시하였으며, 7Ni강 성분은 Ni: 7.00%~7.60%, C: 0.02%~0.06%, Si: 0.03%~0.80%, Mn: 0.10%~0.90%, Cr: 0.30%~0.60%, 나머지는 Fe 및 불가피한 개재물이다. 상기 QLT 열처리를 채택한 7Ni강은 강한 가소성 조합과 우수한 저온인성을 가지며, 그 성능은 9Ni강에 상당한 수준에 도달하였다. 출원번호 201310285597.4의 "초저온 압력용기용 고니켈강 및 이의 제조 방법"에 언급된 강의 Ni 질량분율은 7.00~7.50%이며, 2회 담금질 + 템퍼링 공정을 채택하여 획득한 7Ni강판은 9Ni강을 대체하며 LNG 저장탱크 제조에 사용될 수 있다. 출원번호 201310494688.9의 "-196℃에서 사용 가능한 저Ni 고Mn 경제형 저온강 및 이의 제조 방법"에 언급된 강의 Mn 질량분율은 1.00%~1.50%, Ni 질량분율은 7.00%~8.00%이며, 2회 담금질 + 템퍼링 공정을 채택하여 획득한 Ni강은 -196℃에서 우수한 인성을 갖는다. 출원번호 201410369201.9 "저비용 초저온 니켈강 및 이의 제조 방법"은 노멀라이징 + 담금질 + 템퍼링 공정을 채택하여 -196℃에서 우수한 인성을 갖는 Ni강을 획득한다. 또한 UFC + TMCP 공정을 채택하여 압연 후 직접 강판을 마르텐사이트 변태 온도 이하로 신속하게 냉각시켜 오프라인 담금질 공정을 수행함으로써 열처리 공정을 간소화하고 7Ni 강판의 저온인성을 향상시킨다.As the economy develops, environmental and resource issues are emerging as top priorities for many countries, and as a clean, pollution-free and high-calorie energy source, LNG will increasingly account for a larger share of future energy use. Expanding the scope of natural gas use has become an important means for China to optimize its energy structure and protect its ecological environment. Currently, the steel sheet widely used for LNG storage and transportation tools at home and abroad is 9Ni steel. As a Ni poor country, China is one of the important ways to reduce the Ni content based on securing performance in order to reduce costs. Research on nickel content-saving 7Ni steel is still in its infancy, and several patents for 7Ni steel sheet have been reported. Application No. 201711306269.2, "Nickel-saving 7Ni steel for cryogenic environment and method for manufacturing heat treatment process thereof" discloses nickel-saving 7Ni steel for cryogenic environment and heat treatment process thereof, and the 7Ni steel component contains Ni: 7.00% to 7.60%, C: 0.02% to 0.06%, Si: 0.03% to 0.80%, Mn: 0.10% to 0.90%, Cr: 0.30% to 0.60%, the remainder is Fe and unavoidable inclusions. 7Ni steel adopting the QLT heat treatment has a strong combination of plasticity and excellent low-temperature toughness, and its performance has reached a significant level compared to 9Ni steel. The Ni mass fraction of steel mentioned in "High-nickel steel for cryogenic pressure vessel and manufacturing method thereof" of application number 201310285597.4 is 7.00-7.50%, and 7Ni steel sheet obtained by adopting two-time quenching + tempering process replaces 9Ni steel and LNG Can be used to manufacture storage tanks. The Mn mass fraction of the steel mentioned in "Low Ni, high Mn economical low-temperature steel usable at -196 ° C. and its manufacturing method" of Application No. 201310494688.9 is 1.00% to 1.50%, and the Ni mass fraction is 7.00% to 8.00%, twice Ni steel obtained by adopting quenching + tempering process has excellent toughness at -196°C. Application No. 201410369201.9 "Low-cost cryogenic nickel steel and manufacturing method thereof" adopts normalizing + quenching + tempering process to obtain Ni steel having excellent toughness at -196°C. In addition, by adopting the UFC + TMCP process, the steel sheet is quickly cooled to below the martensite transformation temperature after rolling, and the offline quenching process is performed to simplify the heat treatment process and improve the low-temperature toughness of the 7Ni steel sheet.

본 발명은 상기와 같은 기술적 문제점을 감안하여 종래 기술의 단점을 극복한 LNG 저장탱크용 7Ni 강판 및 생산 공정을 제공한다. LNG 저장 운송용 강의 성능 확보를 전제로 Ni의 함량을 최대한 줄여 경제적이고 실현 가능한 제조 방법을 제공한다.The present invention provides a 7Ni steel sheet for an LNG storage tank and a production process that overcomes the disadvantages of the prior art in consideration of the above technical problems. An economical and feasible manufacturing method is provided by reducing the Ni content as much as possible on the premise of securing the performance of steel for LNG storage and transportation.

상기 기술적 문제점을 해결하기 위하여, 본 발명은 LNG 저장탱크용 7Ni 강판을 제공한다. 이의 화학 성분 및 질량 백분율은 C: 0.02%~0.06%, Si: 0.20%~0.35%, Ni: 4.0%~8.0%, Mn: 0.3%~0.7%, P≤0.005%, S≤0.005%, Al: 0.03%~0.05%, Nb: 0.02%~0.05%, Cr: 0.2%~0.4%, 나머지는 Fe 및 불가피한 불순물이다.In order to solve the above technical problem, the present invention provides a 7Ni steel sheet for an LNG storage tank. Its chemical composition and mass percentage are: C: 0.02%~0.06%, Si: 0.20%~0.35%, Ni: 4.0%~8.0%, Mn: 0.3%~0.7%, P≤0.005%, S≤0.005%, Al : 0.03%~0.05%, Nb: 0.02%~0.05%, Cr: 0.2%~0.4%, the remainder is Fe and unavoidable impurities.

기술적 효과는 다음과 같다. 본 발명은 Nb, Cr 미세 합금 Ni 절약형 합금 설계를 채택하여, 노멀라이징 압연 + 2상 영역 담금질 + 템퍼링 생산 공정을 혁신하였으며, 압연 후 급속 냉각 과정을 생략하였다. 이는 에너지를 절약할 뿐만 아니라, 후속 담금질 공정의 원활한 진행을 위해 우수한 판형을 제공하였으며, 최종적으로 기계적 물성이 우수한 LNG 저장탱크용 강판을 획득하였다.The technical effects are as follows. The present invention adopts the Nb, Cr microalloy Ni-saving alloy design, and innovates the normalizing rolling + two-phase region quenching + tempering production process, and omits the rapid cooling process after rolling. This not only saves energy, but also provides an excellent plate shape for the smooth progress of the subsequent quenching process, and finally, a steel plate for an LNG storage tank with excellent mechanical properties was obtained.

본 발명에서 더욱 한정하는 기술적 해결책은 하기와 같다.The technical solution further limited in the present invention is as follows.

더 나아가, 두께는 8~30mm이다.Furthermore, the thickness is 8-30 mm.

본 발명의 다른 목적은 LNG 저장탱크용 7Ni 강판 생산 공정을 제공하는 것이다. 여기에는,Another object of the present invention is to provide a 7Ni steel plate production process for an LNG storage tank. Here,

화학 성분에 따라 원료를 제련하고, 진공 제련로에서 제련을 수행하며, 잉곳으로 주조한 후, 잉곳을 정사각형 주조편으로 단조하고, 통풍이 되지 않는 곳에서 공랭을 수행하는 주조편 제조 단계;Smelting the raw material according to the chemical composition, performing the smelting in a vacuum smelting furnace, after casting into an ingot, forging the ingot into a square slab, and a slab manufacturing step of performing air cooling in an unventilated place;

주조편을 1150~1250℃에서 2~3시간 동안 온도를 유지하고, 주조편에 대해 2단계 압연을 수행하며, 여기에서 조압연의 초기 압연 온도는 1000~1100℃이고, 총 압축비는 40%~60%이고, 마무리 압연의 초기 압연 온도는 850~900℃이고, 총 압축비는 40%~70%이고, 최종 압연 온도는 750~850℃이며, 그 후 공랭을 수행하는 노멀라이징 압연 단계; 및The slab is maintained at a temperature of 1150 to 1250 ℃ for 2-3 hours, and two-stage rolling is performed on the slab, wherein the initial rolling temperature of the rough rolling is 1000 to 1100 ℃, and the total compression ratio is 40% ~ 60%, the initial rolling temperature of the finish rolling is 850 ~ 900 ℃, the total compression ratio is 40% ~ 70%, the final rolling temperature is 750 ~ 850 ℃, then normalizing rolling step of performing air cooling; and

압연된 강판을 600~700℃에서 300℃ 이하로 담금질하며, 다시 500~580℃에서 템퍼링하고, 템퍼링 속도는 5~20℃/s이고, 온도 유지 시간은 0.5~2시간이고, 공랭을 수행하는 2상 영역 담금질 + 템퍼링 단계가 포함된다.The rolled steel sheet is quenched at 600~700℃ to 300℃ or lower, and again tempered at 500~580℃, the tempering rate is 5~20℃/s, the temperature holding time is 0.5~2 hours, and air cooling is performed. A two-phase zone quenching + tempering step is included.

전술한 LNG 저장탱크용 7Ni 강판 생산 공정에 있어서, 강판의 화학 성분 및 질량 백분율은 C: 0.05%, Si: 0.25%, Mn: 0.60%, Ni: 7.2%, P: 0.0045%, S: 0.0030%, Al: 0.038%, Cr: 0.28%, Nb: 0.043%, 나머지는 Fe 및 불가피한 불순물이다.In the above-described 7Ni steel sheet production process for an LNG storage tank, the chemical composition and mass percentage of the steel sheet is C: 0.05%, Si: 0.25%, Mn: 0.60%, Ni: 7.2%, P: 0.0045%, S: 0.0030% , Al: 0.038%, Cr: 0.28%, Nb: 0.043%, the remainder being Fe and unavoidable impurities.

화학 성분에 따라 원료를 제련하고, 진공 제련로에서 제련을 수행하며, 잉곳으로 주조한 후, 잉곳을 두께가 80mm인 정사각형 주조편으로 단조하고, 통풍이 되지 않는 곳에서 공랭을 수행하는 주조편 제조 단계;Smelting raw materials according to chemical composition, performing smelting in a vacuum smelting furnace, casting into an ingot, forging the ingot into a square slab with a thickness of 80 mm, and performing air cooling in a non-ventilated place. step;

주조편을 가열로에 이송하여 1156℃로 가열하고 2.6시간 동안 온도를 유지한 후 꺼내 압연을 수행하고, 주조편에 대해 2단 압연을 수행하며, 여기에서 조압연은 오스테나이트 완전 재결정 영역에서 압연하며, 초기 압연 온도는 1100℃, 압하량은 60%이고, 마무리 압연은 오스테나이트 미재결정 영역에서 압연하며, 초기 압연 온도는 900℃, 압하량은 63%이고, 최종 압연 온도는 790℃이며, 그 후 공랭을 수행하여 12mm 두께의 열간 압연 강판을 형성하는 노멀라이징 압연 단계; 및The slab is transferred to a heating furnace, heated to 1156° C., maintained at the temperature for 2.6 hours, taken out and rolled, and two-stage rolling is performed on the slab, where rough rolling is rolled in the austenite complete recrystallization region. The initial rolling temperature is 1100 ° C, the rolling reduction is 60%, the finish rolling is rolled in the austenite non-recrystallization region, the initial rolling temperature is 900 ° C, the rolling reduction is 63%, and the final rolling temperature is 790 ° C, Thereafter, normalizing rolling step of performing air cooling to form a hot-rolled steel sheet having a thickness of 12 mm; and

압연된 강판을 660℃에서 300℃ 이하로 담금질하고, 다시 560℃에서 템퍼링하며, 템퍼링 속도는 10℃/s이고, 1시간 온도를 유지하며 공랭을 수행하는 2상 영역 담금질 + 템퍼링 단계가 포함된다.The rolled steel sheet is quenched at 660 ° C. to 300 ° C. or less, and again tempered at 560 ° C., the tempering rate is 10 ° C / s, and the two-phase region quenching + tempering step is performed while maintaining the temperature for 1 hour. .

전술한 LNG 저장탱크용 7Ni 강판 생산 공정에 있어서, 강판의 화학 성분 및 질량 백분율은 C: 0.06%, Si: 0.23%, Mn: 0.55%, Ni: 7.3%, P: 0.0043%, S: 0.0031%, Al: 0.035%, Cr: 0.25%, Nb: 0.040%, 나머지는 Fe 및 불가피한 불순물이다.In the above-described 7Ni steel sheet production process for an LNG storage tank, the chemical composition and mass percentage of the steel sheet is C: 0.06%, Si: 0.23%, Mn: 0.55%, Ni: 7.3%, P: 0.0043%, S: 0.0031% , Al: 0.035%, Cr: 0.25%, Nb: 0.040%, the remainder being Fe and unavoidable impurities.

화학 성분에 따라 원료를 제련하고, 진공 제련로에서 제련을 수행하며, 잉곳으로 주조한 후, 잉곳을 두께가 80mm인 정사각형 주조편으로 단조하고, 통풍이 되지 않는 곳에서 공랭을 수행하는 주조편 제조 단계;Smelting raw materials according to chemical composition, performing smelting in a vacuum smelting furnace, casting into an ingot, forging the ingot into a square slab with a thickness of 80 mm, and performing air cooling in a non-ventilated place. step;

주조편을 가열로에 이송하여 1239℃로 가열하고 2.1시간 동안 온도를 유지한 후 꺼내 압연을 수행하고, 주조편에 대해 2단 압연을 수행하며, 여기에서 조압연은 오스테나이트 완전 재결정 영역에서 압연하며, 초기 압연 온도는 1100℃, 압하량은 60%이고, 마무리 압연은 오스테나이트 미재결정 영역에서 압연하며, 초기 압연 온도는 900℃, 압하량은 45%이고, 최종 압연 온도는 790℃이며, 그 후 공랭을 수행하여 18mm 두께의 열간 압연 강판을 형성하는 노멀라이징 압연 단계; 및The slab is transferred to a heating furnace, heated to 1239° C., maintained at the temperature for 2.1 hours, taken out and rolled, and two-stage rolling is performed on the slab, where rough rolling is rolled in the austenite complete recrystallization region. The initial rolling temperature is 1100 ℃, the rolling reduction is 60%, the finish rolling is rolled in the austenite non-recrystallization region, the initial rolling temperature is 900 ℃, the rolling reduction is 45%, the final rolling temperature is 790 ℃, After that, normalizing rolling step of performing air cooling to form a hot-rolled steel sheet having a thickness of 18 mm; and

압연된 강판을 66℃에서 300℃ 이하로 담금질하고, 다시 560℃에서 템퍼링하며, 템퍼링 속도는 10℃/s이고, 1시간 온도를 유지하며 공랭을 수행하는 2상 영역 담금질 + 템퍼링 단계가 포함된다.The rolled steel sheet is quenched at 66 ° C. to 300 ° C. or less, and again tempered at 560 ° C., the tempering rate is 10 ° C / s, and the two-phase zone quenching + tempering step is performed while maintaining the temperature for 1 hour. .

본 발명의 유익한 효과는 다음과 같다.Advantageous effects of the present invention are as follows.

(1) 본 발명에서 니켈은 비탄화물 형성원소로, γ상 영역을 확장할 수 있는 오스테나이트 형성 및 안정화 원소이며, 강도 저하 없이 저온인성을 향상시킬 수 있다. 니켈은 강의 CCT 곡선을 우측으로 이동시킬 수 있으므로, 임계 감소 담금질 속도를 낮춰 담금질성을 향상시킬 수 있다. 니켈은 저온인성을 개선하고 인성-취성 전이 온도를 낮추는 데 중요한 역할을 하므로, Ni는 본 발명의 가장 중요한 합금 원소이다.(1) In the present invention, nickel is a non-carbide forming element, an austenite forming and stabilizing element that can expand the γ-phase region, and can improve low-temperature toughness without lowering strength. Nickel can shift the CCT curve of the steel to the right, so the hardenability can be improved by lowering the critical reduction quenching rate. Since nickel plays an important role in improving low-temperature toughness and lowering the toughness-brittle transition temperature, Ni is the most important alloying element in the present invention.

(2) 본 발명에서 탄소는 강한 고용 강화 원소이자 강한 오스테나이트 안정화 원소로서 강판의 강도에 긍정적인 영향을 미치지만 인성, 가소성 및 용접 성능에는 부정적인 영향을 미친다. 따라서 저온 강판에 우수한 충격 인성 및 용접 성능을 부여하기 위해서는 탄소 함량을 비교적 낮은 범위로 제어해야 한다.(2) In the present invention, carbon as a strong solid solution strengthening element and a strong austenite stabilizing element has a positive effect on the strength of the steel sheet, but has a negative effect on toughness, plasticity and welding performance. Therefore, in order to impart excellent impact toughness and welding performance to the low-temperature steel sheet, it is necessary to control the carbon content in a relatively low range.

(3) 본 발명에서 망간은 주로 고용 강화의 역할을 하며, 탄소 함량 감소로 인한 강도 저하를 보완할 수 있다. 동시에 망간은 니켈과 마찬가지로 강의 상전이 온도를 낮출 수 있고, Mn/C 및 Mn/S를 적절히 증가시키는 것은 인성에 유리하다. 따라서 본 발명은 Mn을 주요한 합금 원소 중 하나로 사용한다.(3) In the present invention, manganese mainly plays a role of solid solution strengthening, and can compensate for the decrease in strength due to a decrease in carbon content. At the same time, manganese, like nickel, can lower the phase transition temperature of steel, and appropriately increasing Mn/C and Mn/S is beneficial for toughness. Therefore, the present invention uses Mn as one of the main alloying elements.

(4) 본 발명에서 규소는 고용 강화 원소이자 탈산 원소로서, 강재의 강도를 증가시키고 제강과정에서 유해 원소인 산소의 함량을 감소시킬 수 있다. 규소는 망간과 일정한 비율로 강재에 존재하여 망간 편석을 억제하는 것 외에도 결정계에서 인의 편석을 억제할 수 있다. 그러나 규소는 강재의 용접열 영향 영역의 저온인성을 저하시키므로 규소 함량은 0.15~0.3%로 제어한다.(4) In the present invention, silicon as a solid solution strengthening element and deoxidizing element can increase the strength of steel and reduce the content of oxygen, which is a harmful element in the steelmaking process. Silicon is present in steel in a certain ratio with manganese, and in addition to suppressing manganese segregation, it can suppress segregation of phosphorus in the crystal system. However, since silicon lowers the low-temperature toughness of the weld heat-affected region of steel, the silicon content is controlled to 0.15-0.3%.

(5) 본 발명에서 크롬의 첨가는 강판의 경화능을 향상시키고 강판의 강도를 개선할 수 있다. 미량의 Nb를 첨가하고 일정한 Nb/Si 범위를 제어하면, 강도 및 가소성에 무해할 뿐만 아니라, 넓고 두꺼운 판의 용접 성능 향상에 도움이 된다. S와 P는 강재의 유해 원소로 편석을 유발하기 쉽고 강재의 저온인성을 감소시키며 용접 시의 열간 균열의 민감도를 증가시킨다. 따라서 강재 중의 P 및 S 함량을 엄격하게 제어해야 한다.(5) The addition of chromium in the present invention can improve the hardenability of the steel sheet and improve the strength of the steel sheet. If a small amount of Nb is added and a certain Nb/Si range is controlled, it is not only harmless to strength and plasticity, but also helps to improve welding performance of wide and thick plates. S and P are harmful elements of steel, which are easy to cause segregation, reduce the low-temperature toughness of steel, and increase the sensitivity of hot cracking during welding. Therefore, the P and S content in the steel must be strictly controlled.

(6) 본 발명의 단면 조직은 페라이트 매트릭스 상에 마르텐사이트와 오스테나이트가 분포되어 있다. 기계적 성능 지표는 항복 강도가 590~700MPa, 인장 강도가 690~790MPa, 연신율이 ≥24%이고, -196℃에서 횡방향 충격 에너지는 ≥100J이다. (6) In the cross-sectional structure of the present invention, martensite and austenite are distributed on a ferrite matrix. The mechanical performance indicators are the yield strength of 590~700MPa, the tensile strength of 690~790MPa, the elongation ≥24%, and the transverse impact energy at -196℃ ≥100J.

도 1은 실시예 1의 금속 조직 사진이다.
도 2는 실시예 2의 금속 조직 사진이다.
1 is a photograph of the metal structure of Example 1.
2 is a photograph of the metal structure of Example 2.

실시예 1Example 1

본 실시예에서 제공하는 LNG 저장탱크용 7Ni 강판 및 생산 공정에 있어서, 강판의 화학 성분 및 질량 백분율은 C: 0.05%, Si: 0.25%, Mn: 0.60%, Ni: 7.2%, P: 0.0045%, S: 0.0030%, Al: 0.038%, Cr: 0.28%, Nb: 0.043%, 나머지는 Fe 및 불가피한 불순물이다.In the 7Ni steel sheet for LNG storage tank and the production process provided in this embodiment, the chemical composition and mass percentage of the steel sheet is C: 0.05%, Si: 0.25%, Mn: 0.60%, Ni: 7.2%, P: 0.0045% , S: 0.0030%, Al: 0.038%, Cr: 0.28%, Nb: 0.043%, the remainder being Fe and unavoidable impurities.

주조편 제조 단계: 화학 성분에 따라 원료를 제련하고, 진공 제련로에서 제련을 수행하며, 잉곳으로 주조한 후, 잉곳을 두께가 80mm인 정사각형 주조편으로 단조하고, 통풍이 되지 않는 곳에서 공랭을 수행한다.Casting slab manufacturing stage: smelting raw materials according to chemical composition, performing smelting in a vacuum smelting furnace, casting into ingots, forging the ingots into square slabs with a thickness of 80mm, and air cooling in a non-ventilated place carry out

노멀라이징 압연 단계: 주조편을 가열로에 이송하여 1156℃로 가열하고 2.6시간 동안 온도를 유지한 후 꺼내 압연을 수행하고, 주조편에 대해 2단 압연을 수행하며, 여기에서 조압연은 오스테나이트 완전 재결정 영역에서 압연하며, 초기 압연 온도는 1100℃, 압하량은 60%이고, 마무리 압연은 오스테나이트 미재결정 영역에서 압연하며, 초기 압연 온도는 900℃, 압하량은 63%이고, 최종 압연 온도는 790℃이며, 그 후 공랭을 수행하여 12mm 두께의 열간 압연 강판을 형성한다.Normalizing rolling step: The slab is transferred to a heating furnace, heated to 1156° C., maintained at the temperature for 2.6 hours, taken out and rolled, and two-stage rolling is performed on the slab, where rough rolling is complete austenite Rolling in the recrystallization region, the initial rolling temperature is 1100 ℃, the rolling reduction is 60%, the finish rolling is rolling in the austenite non-recrystallization region, the initial rolling temperature is 900 ℃, the rolling reduction is 63%, the final rolling temperature is 790 ° C., and then air cooling is performed to form a hot rolled steel sheet having a thickness of 12 mm.

2상 영역 담금질 + 템퍼링 단계: 압연된 강판을 660℃에서 300℃ 이하로 담금질하고, 다시 560℃에서 템퍼링하며, 템퍼링 속도는 10℃/s이고, 1시간 온도를 유지하며 공랭을 수행한다.Two-phase region quenching + tempering step: The rolled steel sheet is quenched at 660 ° C. to 300 ° C. or less, and again tempered at 560 ° C., the tempering rate is 10 ° C./s, and air cooling is performed while maintaining the temperature for 1 hour.

본 실시예에서 얻은 저온 강판은 관련 국가표준에 따라 검출을 수행하였으며, 그 결과를 표 1에 나타내었다.The low-temperature steel sheet obtained in this example was detected according to the relevant national standard, and the results are shown in Table 1.

표 1: 실시예 1 저온 강판 성능Table 1: Example 1 low temperature steel sheet performance

Figure pct00001
Figure pct00001

실시예 2Example 2

본 실시예에서 제공하는 LNG 저장탱크용 7Ni 강판 및 생산 공정에 있어서, 강판의 화학 성분 및 질량 백분율은 C: 0.06%, Si: 0.23%, Mn: 0.55%, Ni: 7.3%, P: 0.0043%, S: 0.0031%, Al: 0.035%, Cr: 0.25%, Nb: 0.040%, 나머지는 Fe 및 불가피한 불순물이다.In the 7Ni steel sheet for LNG storage tank and the production process provided in this embodiment, the chemical composition and mass percentage of the steel sheet are C: 0.06%, Si: 0.23%, Mn: 0.55%, Ni: 7.3%, P: 0.0043% , S: 0.0031%, Al: 0.035%, Cr: 0.25%, Nb: 0.040%, the remainder being Fe and unavoidable impurities.

주조편 제조 단계: 화학 성분에 따라 원료를 제련하고, 진공 제련로에서 제련을 수행하며, 잉곳으로 주조한 후, 잉곳을 두께가 80mm인 정사각형 주조편으로 단조하고, 통풍이 되지 않는 곳에서 공랭을 수행한다.Casting slab manufacturing stage: smelting raw materials according to chemical composition, performing smelting in a vacuum smelting furnace, casting into ingots, forging the ingots into square slabs with a thickness of 80mm, and air cooling in a non-ventilated place carry out

노멀라이징 압연 단계: 주조편을 가열로에 이송하여 1239℃로 가열하고 2.1시간 동안 온도를 유지한 후 꺼내 압연을 수행하고, 주조편에 대해 2단 압연을 수행하며, 여기에서 조압연은 오스테나이트 완전 재결정 영역에서 압연하며, 초기 압연 온도는 1100℃, 압하량은 60%이고, 마무리 압연은 오스테나이트 미재결정 영역에서 압연하며, 초기 압연 온도는 900℃, 압하량은 45%이고, 최종 압연 온도는 790℃이며, 그 후 공랭을 수행하여 18mm 두께의 열간 압연 강판을 형성한다.Normalizing rolling step: The slab is transferred to a heating furnace, heated to 1239° C., maintained at the temperature for 2.1 hours, and then taken out and rolled, and two-stage rolling is performed on the slab, where rough rolling is austenite complete Rolling in the recrystallization region, the initial rolling temperature is 1100 ℃, the rolling reduction is 60%, the finish rolling is rolling in the austenite non-recrystallization region, the initial rolling temperature is 900 ℃, the rolling reduction is 45%, the final rolling temperature is 790°C, and then air-cooling to form a hot-rolled steel sheet having a thickness of 18 mm.

2상 영역 담금질 + 템퍼링 단계: 압연된 강판을 660℃에서 300℃ 이하로 담금질하고, 다시 560℃에서 템퍼링하며, 템퍼링 속도는 10℃/s이고, 1시간 온도를 유지하며 공랭을 수행한다.Two-phase region quenching + tempering step: The rolled steel sheet is quenched at 660 ° C. to 300 ° C. or less, and again tempered at 560 ° C., the tempering rate is 10 ° C./s, and air cooling is performed while maintaining the temperature for 1 hour.

본 실시예에서 얻은 저온 강판은 관련 국가표준에 따라 검출을 수행하였으며, 그 결과를 표 2에 나타내었다.The low-temperature steel sheet obtained in this example was detected according to the relevant national standard, and the results are shown in Table 2.

표 2: 실시예 2 저온 강판 성능Table 2: Example 2 low temperature steel sheet performance

Figure pct00002
Figure pct00002

종래 기술과 비교하여 본 발명은 니켈 저감 합금 설계를 통해 노멀라이징 압연 + 2상 영역 담금질 + 템퍼링 생산 공정을 채택하고 성능 상에서 GB 3531-2014 저온 압력 용기용 강재 중 9Ni 표준에 완전히 도달하며 생산 비용이 크게 절감된다.Compared with the prior art, the present invention adopts normalizing rolling + two-phase zone quenching + tempering production process through nickel reduction alloy design, and in performance fully reaches 9Ni standard among GB 3531-2014 low-temperature pressure vessel steel materials, and the production cost is significantly higher savings are made

상기 실시예 이외에도, 본 발명에는 다른 실시예가 있을 수 있다. 동등한 대체 또는 동등한 변환에 의해 형성된 임의의 기술적 해결책은 모두 본 발명의 보호범위 내에 속한다.In addition to the above embodiments, the present invention may have other embodiments. Any technical solutions formed by equivalent substitution or equivalent transformation all fall within the protection scope of the present invention.

Claims (5)

LNG 저장탱크용 7Ni 강판에 있어서,
이의 화학 성분 및 질량 백분율은 C: 0.02%~0.06%, Si: 0.20%~0.35%, Ni: 4.0%~8.0%, Mn: 0.3%~0.7%, P≤0.005%, S≤0.005%, Al: 0.03%~0.05%, Nb: 0.02%~0.05%, Cr: 0.2%~0.4%, 나머지는 Fe 및 불가피한 불순물인 것을 특징으로 하는 LNG 저장탱크용 7Ni 강판.
In the 7Ni steel sheet for an LNG storage tank,
Its chemical composition and mass percentage are: C: 0.02%~0.06%, Si: 0.20%~0.35%, Ni: 4.0%~8.0%, Mn: 0.3%~0.7%, P≤0.005%, S≤0.005%, Al : 0.03%~0.05%, Nb: 0.02%~0.05%, Cr: 0.2%~0.4%, 7Ni steel sheet for LNG storage tank, the remainder being Fe and unavoidable impurities.
제1항에 있어서,
두께가 8~30mm인 것을 특징으로 하는 LNG 저장탱크용 7Ni 강판.
The method of claim 1,
7Ni steel sheet for LNG storage tank, characterized in that the thickness is 8 ~ 30mm.
LNG 저장탱크용 7Ni 강판 생산 공정에 있어서,
화학 성분에 따라 원료를 제련하고, 진공 제련로에서 제련을 수행하며, 잉곳으로 주조한 후, 잉곳을 정사각형 주조편으로 단조하고, 통풍이 되지 않는 곳에서 공랭을 수행하는 주조편 제조 단계;
주조편을 1150~1250℃에서 2~3시간 동안 온도를 유지하고, 주조편에 대해 2단계 압연을 수행하며, 여기에서 조압연의 초기 압연 온도는 1000~1100℃이고, 총 압축비는 40%~60%이고, 마무리 압연의 초기 압연 온도는 850~900℃이고, 총 압축비는 40%~70%이고, 최종 압연 온도는 750~850℃이며, 그 후 공랭을 수행하는 노멀라이징 압연 단계; 및
압연된 강판을 600~700℃에서 300℃ 이하로 담금질하며, 다시 500~580℃에서 템퍼링하고, 템퍼링 속도는 5~20℃/s이고, 온도 유지 시간은 0.5~2시간이고, 공랭을 수행하는 2상 영역 담금질 + 템퍼링 단계;를 포함하는 것을 특징으로 하는 LNG 저장탱크용 7Ni 강판 생산 공정.
In the 7Ni steel plate production process for an LNG storage tank,
Smelting the raw material according to the chemical composition, performing the smelting in a vacuum smelting furnace, after casting into an ingot, forging the ingot into a square slab, and a slab manufacturing step of performing air cooling in an unventilated place;
The slab is maintained at a temperature of 1150 to 1250 ℃ for 2-3 hours, and two-stage rolling is performed on the slab, wherein the initial rolling temperature of the rough rolling is 1000 to 1100 ℃, and the total compression ratio is 40% ~ 60%, the initial rolling temperature of the finish rolling is 850 ~ 900 ℃, the total compression ratio is 40% ~ 70%, the final rolling temperature is 750 ~ 850 ℃, then normalizing rolling step of performing air cooling; and
The rolled steel sheet is quenched at 600~700℃ to 300℃ or lower, and again tempered at 500~580℃, the tempering rate is 5~20℃/s, the temperature holding time is 0.5~2 hours, and air cooling is performed. 7Ni steel sheet production process for LNG storage tank, characterized in that it comprises; two-phase region quenching + tempering step.
제3항에 있어서,
강판의 화학 성분 및 질량 백분율은 C: 0.05%, Si: 0.25%, Mn: 0.60%, Ni: 7.2%, P: 0.0045%, S: 0.0030%, Al: 0.038%, Cr: 0.28%, Nb: 0.043%, 나머지는 Fe 및 불가피한 불순물이고,
화학 성분에 따라 원료를 제련하고, 진공 제련로에서 제련을 수행하며, 잉곳으로 주조한 후, 잉곳을 두께가 80mm인 정사각형 주조편으로 단조하고, 통풍이 되지 않는 곳에서 공랭을 수행하는 주조편 제조 단계;
주조편을 가열로에 이송하여 1156℃로 가열하고 2.6시간 동안 온도를 유지한 후 꺼내 압연을 수행하고, 주조편에 대해 2단 압연을 수행하며, 여기에서 조압연은 오스테나이트 완전 재결정 영역에서 압연하며, 초기 압연 온도는 1100℃, 압하량은 60%이고, 마무리 압연은 오스테나이트 미재결정 영역에서 압연하며, 초기 압연 온도는 900℃, 압하량은 63%이고, 최종 압연 온도는 790℃이며, 그 후 공랭을 수행하여 12mm 두께의 열간 압연 강판을 형성하는 노멀라이징 압연 단계; 및
압연된 강판을 660℃에서 300℃ 이하로 담금질하고, 다시 560℃ 에서 템퍼링하며, 템퍼링 속도는 10℃/s이고, 1시간 온도를 유지하며 공랭을 수행하는 2상 영역 담금질 + 템퍼링 단계;를 포함하는 것을 특징으로 하는 LNG 저장탱크용 7Ni 강판 생산 공정.
4. The method of claim 3,
The chemical composition and mass percentage of the steel sheet are: C: 0.05%, Si: 0.25%, Mn: 0.60%, Ni: 7.2%, P: 0.0045%, S: 0.0030%, Al: 0.038%, Cr: 0.28%, Nb: 0.043%, the remainder being Fe and unavoidable impurities,
Smelting raw materials according to chemical composition, performing smelting in a vacuum smelting furnace, casting into an ingot, forging the ingot into a square slab with a thickness of 80 mm, and performing air cooling in a non-ventilated place. step;
The slab is transferred to a heating furnace, heated to 1156° C., maintained at the temperature for 2.6 hours, taken out and rolled, and two-stage rolling is performed on the slab, where rough rolling is rolled in the austenite complete recrystallization region. The initial rolling temperature is 1100 ° C, the rolling reduction is 60%, the finish rolling is rolled in the austenite non-recrystallization region, the initial rolling temperature is 900 ° C, the rolling reduction is 63%, and the final rolling temperature is 790 ° C, After that, normalizing rolling step of performing air cooling to form a hot-rolled steel sheet having a thickness of 12 mm; and
Quenching the rolled steel sheet at 660 ° C. to 300 ° C. or less, and tempering again at 560 ° C., the tempering rate is 10 ° C./s, and two-phase region quenching + tempering step of performing air cooling while maintaining the temperature for 1 hour. 7Ni steel plate production process for LNG storage tank, characterized in that.
제3항에 있어서,
강판의 화학 성분 및 질량 백분율은 C: 0.06%, Si: 0.23%, Mn: 0.55%, Ni: 7.3%, P: 0.0043%, S: 0.0031%, Al: 0.035%, Cr: 0.25%, Nb: 0.040%, 나머지는 Fe 및 불가피한 불순물이고,
화학 성분에 따라 원료를 제련하고, 진공 제련로에서 제련을 수행하며, 잉곳으로 주조한 후, 잉곳을 두께가 80mm인 정사각형 주조편으로 단조하고, 통풍이 되지 않는 곳에서 공랭을 수행하는 주조편 제조 단계;
주조편을 가열로에 이송하여 1239℃로 가열하고 2.1시간 동안 온도를 유지한 후 꺼내 압연을 수행하고, 주조편에 대해 2단 압연을 수행하며, 여기에서 조압연은 오스테나이트 완전 재결정 영역에서 압연하며, 초기 압연 온도는 1100℃, 압하량은 60%이고, 마무리 압연은 오스테나이트 미재결정 영역에서 압연하며, 초기 압연 온도는 900℃, 압하량은 45%이고, 최종 압연 온도는 790℃이며, 그 후 공랭을 수행하여 18mm 두께의 열간 압연 강판을 형성하는 노멀라이징 압연 단계; 및
압연된 강판을 660℃에서 300℃ 이하로 담금질하고, 다시 560℃에서 템퍼링하며, 템퍼링 속도는 10℃/s이고, 1시간 온도를 유지하며 공랭을 수행하는 2상 영역 담금질 + 템퍼링 단계;를 포함하는 것을 특징으로 하는 LNG 저장탱크용 7Ni 강판 생산 공정.
4. The method of claim 3,
The chemical composition and mass percentage of the steel sheet are C: 0.06%, Si: 0.23%, Mn: 0.55%, Ni: 7.3%, P: 0.0043%, S: 0.0031%, Al: 0.035%, Cr: 0.25%, Nb: 0.040%, the remainder being Fe and unavoidable impurities,
Smelting raw materials according to the chemical composition, performing smelting in a vacuum smelting furnace, casting into an ingot, forging the ingot into a square slab with a thickness of 80 mm, and performing air cooling in a non-ventilated place. step;
The slab is transferred to a heating furnace, heated to 1239° C., maintained at the temperature for 2.1 hours, taken out and rolled, and two-stage rolling is performed on the slab, where rough rolling is rolled in the austenite complete recrystallization region. The initial rolling temperature is 1100 ℃, the rolling reduction is 60%, the finish rolling is rolled in the austenite non-recrystallization region, the initial rolling temperature is 900 ℃, the rolling reduction is 45%, the final rolling temperature is 790 ℃, After that, normalizing rolling step of performing air cooling to form a hot-rolled steel sheet having a thickness of 18 mm; and
Quenching the rolled steel sheet at 660 ° C. to 300 ° C. or lower, and tempering again at 560 ° C., the tempering rate is 10 ° C / s, and two-phase region quenching + tempering step of performing air cooling while maintaining the temperature for 1 hour; 7Ni steel plate production process for LNG storage tank, characterized in that.
KR1020217040526A 2019-05-27 2019-10-16 7Ni steel plate and production process for LNG storage tank KR20220004220A (en)

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