KR20130034727A - Alloy with low specific gravity and manufacturing method thereof - Google Patents
Alloy with low specific gravity and manufacturing method thereof Download PDFInfo
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Abstract
Description
본 발명은 경량 원소(Al, Si 등)를 첨가하여 비중을 7.0 g/㎤ 이하로 줄인 저비중강판용 합금 및 그 제조방법에 관한 것이다.
The present invention relates to an alloy for low specific gravity steel sheet having a specific gravity reduced to 7.0 g / cm 3 or less by adding lightweight elements (Al, Si, etc.) and a method of manufacturing the same.
기존의 차량용 강판으로는 TWIP강(800MPa 이상)이 주목받고 있었다. TWIP강의 조성은, C : 0.1~0.6 wt%, Al : 1.0~5.0 wt%, Mn : 15 ~ 30 wt% ,Si : 0.01 ~ 4.0 wt%의 고강도강 합금계로 이루어졌다.TWIP steel (800 MPa or more) was drawing attention as a conventional steel sheet for vehicles. The composition of the TWIP steel was made of a high strength steel alloy system of C: 0.1 to 0.6 wt%, Al: 1.0 to 5.0 wt%, Mn: 15 to 30 wt%, and Si: 0.01 to 4.0 wt%.
이러한 TWIP강은 다량의 Mn 첨가를 통한 잔류 오스테나이트의 높은 분율을 확보한 후, 열처리를 통한 TRIP효과 이용하여 베이나이트 조직을 이루어 인장 강도 800MPa 이상을 나타내었다.The TWIP steel obtained a high fraction of retained austenite through the addition of a large amount of Mn, and then formed a bainite structure using the TRIP effect through heat treatment, thereby exhibiting a tensile strength of 800 MPa or more.
또한, TWIP강은 일반강 대비 Mn의 함량이 매우 높다. Mn 함량이 첨가됨에 따라, 강의 고용강화 효과가 커지며 또한 소성변형이 슬립(Slip)이 아닌 쌍정(Twin)에 의해 발생한다. 쌍정의 발생은 고경계각 입계로서 전위(Dislocation)의 이동을 방해하여 가공경화 효과가 크게 나타나게 된다. 이를 통해 TWIP강은 인장강도 800MPa 이상과 연신율 50% 이상의 기계적 특징을 갖는 것이다. In addition, TWIP steel has a very high content of Mn compared to general steel. As the Mn content is added, the solid solution strengthening effect of the steel is increased, and plastic deformation is caused by twins rather than slips. The occurrence of twins is a high boundary grain boundary, which impedes movement of dislocations, resulting in a large work hardening effect. Through this, TWIP steel has mechanical properties of tensile strength of 800 MPa or more and elongation of 50% or more.
일반적으로 TWIP강은 고Mn 함유에 따라 고온에서 오스테나이트 단일상으로 존재하며, 일반강 대비 높은 층결함에너지 (20~30mJ/m2)로 인하여 상온에서의 오스테나이트 잔류 가능성이 높다. 따라서 TWIP강은 고온에서 균질화 처리 후, 열간 압연을 통해 오스테나이트내 잔류 응력을 형성하도록 한 후, 빠른 냉각을 통해 마르텐사이트 및 20 ~ 30% 정도의 잔류 오스테나이트를 형성한다. 그 이후 인성 확보를 위해 열처리 (750℃ 이상) 및 냉각을 통한 잔류 오스테나이트의 마르텐사이트 변태 및 탄화물을 형성하게 한다.Generally, TWIP steel exists as austenite single phase at high temperature due to high Mn content, and there is a high possibility of retaining austenite at room temperature due to higher layer defect energy (20-30mJ / m2) than general steel. Therefore, after the TWIP steel is homogenized at a high temperature, hot rolling is used to form residual stress in austenite, and then rapid cooling forms martensite and 20 to 30% of retained austenite. Thereafter, to ensure toughness, the martensite transformation and carbides of the retained austenite are formed through heat treatment (at least 750 ° C.) and cooling.
그러나 이러한 TWIP강은 고강도, 고연신의 기계적 특징을 나타내지만, Mn은 산화성이 강력한 합금 원소여서, 고 Mn 함량 첨가에 따른 주조성이 현저히 떨어진다. 또한 고 Mn 함유에 따른 ε-마르텐사이트(HCP구조)가 생성되기 쉬워, 제품 가공시 기계적 변형에 의한 ε-마르텐사이트가 생성되어 취화가 되는 경향이 있다.However, TWIP steels exhibit mechanical properties of high strength and high elongation, but Mn is an oxidatively strong alloying element, and castability is significantly reduced due to the addition of high Mn content. In addition, ε-martensite (HCP structure) due to high Mn content is easily generated, and ε-martensite due to mechanical deformation during product processing tends to be brittle.
TWIP강은 또한 지연파괴 현상이 발생하고 있다. 소성 변형 초기에는 가공성이 굉장히 우수 하지만, 가공 후 수소 취성에 의한 지연파괴 현상이 발생한다. 이를 위해 Al 원소 첨가 통하여 지연파괴를 늦추는 결과가 있지만, 이 역시 실험실 단위의 평가 결과이다.TWIP steel is also experiencing delayed failure. In the early stage of plastic deformation, workability is very good, but delayed fracture phenomenon occurs due to hydrogen embrittlement after processing. For this purpose, the delayed destruction is delayed by adding Al element, but this is also the result of laboratory evaluation.
따라서, TWIP강의 사용을 위해서는 주조성의 개선과 지연파괴 현상을 개선할 필요가 있었다.
Therefore, in order to use TWIP steel, it is necessary to improve castability and delay fracture phenomenon.
상기의 배경기술로서 설명된 사항들은 본 발명의 배경에 대한 이해 증진을 위한 것일 뿐, 이 기술분야에서 통상의 지식을 가진자에게 이미 알려진 종래기술에 해당함을 인정하는 것으로 받아들여져서는 안 될 것이다.
It should be understood that the foregoing description of the background art is merely for the purpose of promoting an understanding of the background of the present invention and is not to be construed as an admission that the prior art is known to those skilled in the art.
본 발명은 이러한 문제점을 해결하기 위하여 제안된 것으로, Al, Si, Cr 등의 경량 치환형 합금 원소의 첨가를 통한 Fe 대비 비중을 약 10% 이상 낮춘 저비중 강판 및 Mn을 다량 첨가하지 않은 저비중 자동차용 강판을 제공하는데 그 목적이 있다.
The present invention has been proposed to solve this problem, low specific gravity steel sheet and low specific gravity without adding a large amount of Mn lowering the specific gravity compared to Fe by the addition of lightweight substitutional alloy elements such as Al, Si, Cr The purpose is to provide a steel sheet for automobiles.
상기의 목적을 달성하기 위한 본 발명에 따른 저비중강판용 합금은, 주성분을 Fe로 하고, C : 0.2~0.5 wt%, Mn : 5~10 wt%, Al : 10~15 wt%, Si : 3 wt%이하(0은 불포함), Cr : 3 wt%이하(0은 불포함), Ni : 0.1~2 wt%, B : 0.005 wt%이하(0은 불포함) 및 기타 불가피한 불순물을 포함하는 조성으로 구성된다.Alloy for low specific gravity steel sheet according to the present invention for achieving the above object, the main component is Fe, C: 0.2 ~ 0.5 wt%, Mn: 5 ~ 10 wt%, Al: 10 ~ 15 wt%, Si: 3 Consists of a composition containing less than or equal to wt% (0 not included), less than 3 wt% of Cr (0 not included), 0.1 to 2 wt% of Ni, less than 0.005 wt% (0 not included) and other unavoidable impurities do.
상기 저비중강판용 합금의 조직은 "페라이트+오스테나이트" 또는 "페라이트" 조직일 수 있다.The structure of the alloy for low specific gravity steel sheet may be a "ferrite + austenite" or "ferrite" structure.
상기 저비중강판용 합금은 비중이 7.0 g/㎤ 이하(0은 불포함)일 수 있다.
The low specific gravity steel alloy may have a specific gravity of 7.0 g / cm 3 or less (0 is not included).
한편, 상기 저비중강판용 합금을 제조하기 위한 제조방법은, 청구항 1 조성의 합금 소재를 1100~1300℃에서 균질화처리하는 균질화단계; 900~1100℃에서 열간압연하는 성형단계; 압연된 소재를 급랭하는 냉각단계; 700~900℃에서 유지하는 재결정단계; 및 상기 재결정된 소재를 다단 냉간 압연하는 박판화단계;를 포함한다.On the other hand, the production method for producing an alloy for low specific gravity steel sheet, the homogenizing step of homogenizing the alloy material of the composition of claim 1 at 1100 ~ 1300 ℃; Forming step of hot rolling at 900 to 1100 ° C .; A cooling step of quenching the rolled material; Recrystallization step to maintain at 700 ~ 900 ℃; And a thinning step of cold rolling the recrystallized material in multiple stages.
상기 균질화단계는 1시간 동안 진행될 수 있으며, 상기 재결정단계는 5분~1시간 동안 진행될 수 있다.
The homogenization may be performed for 1 hour, and the recrystallization may be performed for 5 minutes to 1 hour.
상술한 바와 같은 구조로 이루어진 저비중강판용 합금 및 그 제조방법에 따르면, 인장강도 850MPa, 연신율 25% 를 나타내는 저비중 고강도강으로서, 비중이 약 10% 이상 감소하여 경량화 효과가 크다.According to the alloy for low specific gravity steel sheet having the above-described structure and a method for manufacturing the same, a low specific gravity high strength steel having a tensile strength of 850 MPa and an elongation of 25%, the specific gravity is reduced by about 10% or more, and the weight reduction effect is large.
종래의 TWIP강 대비 저 Mn, 고 Al 함량을 통해, Mn보다 주조성이 상대적으로 좋은 Al을 이용하여 제품 상용성이 향상된다.
Low Mn and high Al content compared to conventional TWIP steel, product compatibility is improved by using a relatively good castability than Mn.
도 1은 본 발명의 일 실시예에 따른 저비중강판용 합금의 제조과정을 나타낸 도면.1 is a view showing a manufacturing process of the alloy for low specific gravity steel sheet according to an embodiment of the present invention.
이하에서는 첨부된 도면을 참조하여 본 발명의 바람직한 실시 예에 따른 저비중강판용 합금 및 그 제조방법에 대하여 살펴본다.Hereinafter, with reference to the accompanying drawings looks at the alloy for low specific gravity steel according to a preferred embodiment of the present invention and a manufacturing method thereof.
본 발명의 저비중강판용 합금은, 주성분을 Fe로 하고, C : 0.2~0.5 wt%, Mn : 5~10 wt%, Al : 10~15 wt%, Si : 3 wt%이하(0은 불포함), Cr : 3 wt%이하(0은 불포함), Ni : 0.1~2 wt%, B : 0.005 wt%이하(0은 불포함) 및 기타 불가피한 불순물을 포함하는 조성으로 구성된다.In the low specific gravity steel alloy of the present invention, the main component is Fe, C: 0.2 to 0.5 wt%, Mn: 5 to 10 wt%, Al: 10 to 15 wt%, Si: 3 wt% or less (0 is not included) , Cr: 3 wt% or less (0 is not included), Ni: 0.1-2 wt%, B: 0.005 wt% or less (0 is not included) and other inevitable impurities.
본 발명의 저비중강판용 합금은 비중 7.0g/㎤ 이하를 달성하기 위해 Al을 10 wt% 이상 첨가하며, 고용강화 효과 통한 강도 확보 위해 Mn을 5 ~ 10wt% 을 첨가한다. 또한 열간 및 냉간 압연 시 발생되는 파괴의 원인이 되는 탄화물을 최대한 억제하기 위해 C를 0.2 내지 0.5wt% 첨가한다. 저비중 효과를 극대화 하기 위해 페라이트 안정화 원소인 Si과 Cr을 각각 3 wt% 이하로 제어하여 최종 비중을 6.7g/cm3으로 한다. 또한, 페라이트 안정화 원소인 Al, Si Cr의 첨가로 인한 고온상(오스테나이트) 확보의 어려움을 극복하기 위해 Ni을 0.1 ~ 2.0 wt%, B을 0.005 wt% 이하로 첨가한다.In the low specific gravity steel alloy of the present invention, Al is added in an amount of 10 wt% or more to achieve a specific gravity of 7.0 g / cm 3 or less, and Mn is added in an amount of 5 to 10 wt% to secure strength through a solid solution strengthening effect. In addition, C is added 0.2 to 0.5wt% in order to suppress the carbide which is the cause of breakdown during hot and cold rolling as much as possible. In order to maximize the low specific gravity effect, the final specific gravity is controlled to 6.7g / cm3 by controlling ferrite stabilizing elements Si and Cr to 3 wt% or less. In addition, in order to overcome the difficulty of securing a high temperature phase (austenite) due to the addition of Al and Si Cr, which are ferrite stabilizing elements, Ni is added in an amount of 0.1 to 2.0 wt% and B in an amount of 0.005 wt% or less.
제조방법으로는, 1200℃에서 약 1시간 균질화 처리 후, 950℃ 이상에서 열간 압연을 마무리 하여 급냉을 한다. 그 후 700℃에서 약 1시간 이내 유지 한 후 냉각한다. 그리고, 소재의 박판화를 위해 다단 냉간 압연을 시행한다.
As a manufacturing method, after homogenizing at 1200 degreeC for about 1 hour, hot rolling is finished at 950 degreeC or more, and quenching is performed. After that, it is maintained at 700 ° C. for about 1 hour and then cooled. Then, multi-stage cold rolling is performed to thin the material.
구체적으로, 조성에 있어서 탄소는 철강의 주요 경화 합금 원소로써, 일반적으로 탄소강은 0.2 wt% 이하로 제어한다. 본 합금계에서는 Al의 다량 첨가에 따른 오스테나이트 확보의 어려움을 피하기 위해 C을 0.2 ~ 0.5 wt%로 제한한다. 또한 C은 Al, Mn 첨가 시 (Fe,Mn)Al3C의 Perovskite 구조를 갖는 κ탄화물을 형성하며, 탄화물 제어 위해 위와 같이 탄소 함량을 제한한다.Specifically, in the composition, carbon is the main hard alloying element of steel, and in general, carbon steel is controlled to 0.2 wt% or less. In this alloy system, C is limited to 0.2 to 0.5 wt% in order to avoid difficulty in securing austenite due to the addition of a large amount of Al. In addition, C forms a κ carbide having a Perovskite structure of (Fe, Mn) Al 3 C upon addition of Al and Mn, and restricts the carbon content as described above for carbide control.
Al은 대표적은 산화물, 질화물, 탄화물 원소 및 페라이트 안정화 원소로써, 강중에 첨가하게 되면 주조 공정상에 산화물을 쉽게 형성하며, 조대한 AlN 계통의 질화물을 형성함으로써 강중의 파괴 거동에 영향을 준다. Al is typically an oxide, nitride, carbide element and ferrite stabilizing element. When added to steel, Al easily forms an oxide during the casting process and affects the fracture behavior of steel by forming a coarse AlN-based nitride.
또한, Al을 다량 첨가하게 되면 Mn과 결합하여 κ탄화물을 생성하여 강의 열간 또는 냉간 압연시의 제품 품질에 영향을 준다. Al 함량을 10 ~ 12 wt%로 제한하여 강의 비중을 약 7.0 g/cm3 이하로 유지할 수 있다. In addition, the addition of a large amount of Al combines with Mn to form κ carbide, which affects the product quality during hot or cold rolling of steel. By limiting the Al content to 10 to 12 wt%, the specific gravity of the steel can be maintained below about 7.0 g / cm3.
Mn은 대표적인 고용강화 및 오스테나이트 안정화 원소이다. 또한 Mn함량 증가 시 적층 결함 에너지 (Stacking fault energy)가 증가함에 따라 전위의 슬립에 의한 강의 변형이 일어나기 수월하다. 강의 잔류 오스테나이트를 확보하기 위해 Mn을 5 ~ 10 wt% 범위로 제한 한다. 이 조성 범위에서 잔류 오스테나이트는 약 5% 정도이다.Mn is a representative solid solution strengthening and austenite stabilizing element. In addition, as the stacking fault energy increases when the Mn content increases, it is easy to cause deformation of the steel due to slip of dislocations. Mn is limited to a range of 5 to 10 wt% to ensure residual austenite in the steel. Residual austenite in this composition range is about 5%.
Si은 페라이트 안정화 원소 및 비중을 낮추는 효과를 갖는다. 하지만 다량 첨가할 경우 강의 표면에 고온 산화층을 형성하여 가공시 파단 가능성이 높아진다. 따라서 함량을 3wt% 이하로 제한한다.
Si has the effect of lowering the ferrite stabilizing element and specific gravity. However, when a large amount is added, a high temperature oxide layer is formed on the surface of the steel to increase the possibility of breakage during processing. Therefore, the content is limited to 3wt% or less.
상기 범위내에서 제조된 저비중강판용 합금의 비중은 아래와 같다.Specific gravity of the alloy for low specific gravity steel sheet manufactured in the above range is as follows.
상기 합금계 중 가장 비중이 낮은 합금계는 4번이며, 비중은 6.3 g/cm3 수준이다. 그러나 이 조성은 1000℃ 이상에서 페라이트 단일상으로 열간 압연시 연신된 페라이트내 생성되는 탄화물로 인하여 강판의 취성이 증가하게 된다. The alloy system having the lowest specific gravity among the alloy systems is No. 4, and the specific gravity is about 6.3 g / cm 3. However, this composition increases the brittleness of the steel sheet due to the carbide produced in the ferrite drawn during hot rolling into a ferrite single phase at 1000 ℃ or more.
1번 조성은 1000℃ 기준으로 페라이트 약 78% 와 오스테나이트 약 18%로 구성되어 있으며, 그 외에 κ탄화물 등의 탄화물이 약 4% 정도 존재하게 된다. 이로 인해 열간 압연 시 탄화물 분포와 크기에 따라 취성 여부가 결정된다. 열간 압연 시 재료의 파단을 방지하기 위해 기지내 미세 나노 크기의 탄화물을 분포하며, 입계에 조대한 마이크로 크기의 탄화물을 억제할 필요가 있다.The first composition is composed of about 78% of ferrite and about 18% of austenite based on 1000 ° C. In addition, about 4% of carbide such as κ carbide is present. For this reason, brittleness is determined by the carbide distribution and size during hot rolling. In order to prevent fracture of the material during hot rolling, it is necessary to distribute fine nano-sized carbides in the matrix and to suppress coarse-sized carbides at grain boundaries.
B 첨가에 따른 금속간 화합물(Fe2B 등) 생성에 따른 취성 변화는 지배적이지 않으며, B 첨가 시 발생되는 보라이드(Boron nitride) 영향은 생성되는 분율이 탄화물과 비교하여 매우 적게 생성되므로 그 영향은 지배적이지 않다.The brittleness change due to the formation of intermetallic compounds (Fe2B, etc.) with addition of B is not dominant, and the effect of boride (Boron nitride) caused by addition of B is very small compared with carbides. Is not
1번 합금 조성에 대한 기대 효과는 인장강도 850MPa 과 연신율 25% 이상의 상온 기계적 성질을 갖으며, 비중이 6.85 g/㎤ 정도 나타내어 기존 고강도강 대비 약 12% 경량화 효과를 나타낼 수 있다.Expected effect on the alloy composition 1 has a mechanical strength of room temperature of more than 850MPa of elongation and 25% or more of elongation, and the specific gravity is about 6.85 g / cm 3, which can be about 12% lighter than the existing high strength steel.
도 1은 이러한 본 발명의 일 실시예에 따른 저비중강판용 합금의 제조과정을 나타낸 도면으로서, 저비중강판용 합금의 제조과정은, 청구항 1 조성의 합금 소재를 1100~1300℃에서 균질화처리하는 균질화단계; 900~1100℃에서 열간압연하는 성형단계; 압연된 소재를 급랭하는 냉각단계; 700~900℃에서 유지하는 재결정단계; 및 상기 재결정된 소재를 다단 냉간 압연하는 박판화단계;를 포함한다.1 is a view showing a manufacturing process of the alloy for low specific gravity steel sheet according to an embodiment of the present invention, the manufacturing process of the alloy for low specific gravity steel sheet, the homogenization step of homogenizing the alloy material of the composition of claim 1 at 1100 ~ 1300 ℃ ; Forming step of hot rolling at 900 to 1100 ° C .; A cooling step of quenching the rolled material; Recrystallization step to maintain at 700 ~ 900 ℃; And a thinning step of cold rolling the recrystallized material in multiple stages.
여기서, 상기 균질화단계는 1시간 동안 진행되도록 하며, 재결정단계는 5분~1시간 동안 진행되도록 할 수 있다.
Here, the homogenization step may be performed for 1 hour, and the recrystallization step may be performed for 5 minutes to 1 hour.
이러한 저비중강판용 합금 및 그 제조방법에 따르면, 인장강도 850MPa, 연신율 25% 를 나타내는 저비중 고강도강으로서, 비중이 약 10% 이상 감소하여 경량화 효과가 크다.According to such an alloy for low specific gravity steel and its manufacturing method, it is a low specific gravity high strength steel exhibiting a tensile strength of 850 MPa and an elongation of 25%.
또한, 종래의 TWIP강 대비 저 Mn, 고 Al 함량을 통해, Mn보다 주조성이 상대적으로 좋은 Al을 이용하여 제품 상용성이 향상된다.
In addition, through the low Mn, high Al content compared to the conventional TWIP steel, product compatibility is improved by using Al, which is relatively better castability than Mn.
본 발명은 특정한 실시예에 관련하여 도시하고 설명하였지만, 이하의 특허청구범위에 의해 제공되는 본 발명의 기술적 사상을 벗어나지 않는 한도 내에서, 본 발명이 다양하게 개량 및 변화될 수 있다는 것은 당 업계에서 통상의 지식을 가진 자에게 있어서 자명할 것이다.While the present invention has been particularly shown and described with reference to specific embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims It will be apparent to those of ordinary skill in the art.
Claims (6)
상기 저비중강판용 합금의 조직은 "페라이트+오스테나이트" 또는 "페라이트" 조직인 것을 특징으로 하는 저비중강판용 합금.The method according to claim 1,
The structure of the alloy for low specific gravity steel sheet is an alloy for low specific gravity steel, characterized in that the "ferrite + austenite" or "ferrite" structure.
상기 저비중강판용 합금은 비중이 7.0 g/㎤ 이하(0은 불포함)인 것을 특징으로 하는 저비중강판용 합금.The method according to claim 1,
The low specific gravity steel sheet alloy has a specific gravity of 7.0 g / cm 3 or less (0 is not included).
900~1100℃에서 열간압연하는 성형단계;
압연된 소재를 급랭하는 냉각단계;
700~900℃에서 유지하는 재결정단계; 및
상기 재결정된 소재를 다단 냉간 압연하는 박판화단계;를 포함하는 저비중강판용 합금의 제조방법.Claim 1 homogenization step of homogenizing the alloy material of the composition at 1100 ~ 1300 ℃;
Forming step of hot rolling at 900 to 1100 ° C .;
A cooling step of quenching the rolled material;
Recrystallization step to maintain at 700 ~ 900 ℃; And
A method of manufacturing an alloy for low specific gravity steel sheet comprising a; a thin plated step of cold rolling the recrystallized material in multiple stages.
상기 균질화단계는 1시간 동안 진행되는 것을 특징으로 하는 저비중강판용 합금의 제조방법.The method of claim 4,
The homogenization step is a method for producing an alloy for low specific gravity steel, characterized in that for 1 hour.
상기 재결정단계는 5분~1시간 동안 진행되는 것을 특징으로 하는 저비중강판용 합금의 제조방법.The method of claim 4,
The recrystallization step is a method for producing a low specific gravity steel alloy, characterized in that for 5 minutes to 1 hour.
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| WO2015099221A1 (en) * | 2013-12-26 | 2015-07-02 | 주식회사 포스코 | Steel sheet having high strength and low density and method of manufacturing same |
| EP3088546A4 (en) * | 2013-12-24 | 2016-12-07 | Posco | Lightweight steel sheet having excellent strength and ductility and method for manufacturing same |
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| EP3088546A4 (en) * | 2013-12-24 | 2016-12-07 | Posco | Lightweight steel sheet having excellent strength and ductility and method for manufacturing same |
| US10273556B2 (en) | 2013-12-24 | 2019-04-30 | Posco | Lightweight steel sheet having excellent strength and ductility and method for manufacturing same |
| WO2015099221A1 (en) * | 2013-12-26 | 2015-07-02 | 주식회사 포스코 | Steel sheet having high strength and low density and method of manufacturing same |
| CN106068333A (en) * | 2013-12-26 | 2016-11-02 | Posco公司 | High intensity low-gravity steel plate and manufacture method thereof |
| CN106068333B (en) * | 2013-12-26 | 2018-07-06 | Posco公司 | High intensity low-gravity steel plate and its manufacturing method |
| US10626476B2 (en) | 2013-12-26 | 2020-04-21 | Posco | High specific strength steel sheet and method for manufacturing same |
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