KR100928796B1 - Steel Fabrication Method for 600MPa Pressure Vessel with High Tensile Strength - Google Patents

Steel Fabrication Method for 600MPa Pressure Vessel with High Tensile Strength Download PDF

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KR100928796B1
KR100928796B1 KR1020020052572A KR20020052572A KR100928796B1 KR 100928796 B1 KR100928796 B1 KR 100928796B1 KR 1020020052572 A KR1020020052572 A KR 1020020052572A KR 20020052572 A KR20020052572 A KR 20020052572A KR 100928796 B1 KR100928796 B1 KR 100928796B1
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steel
weight
less
pressure vessel
toughness
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KR20040021117A (en
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장웅성
윤병현
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주식회사 포스코
재단법인 포항산업과학연구원
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium

Abstract

본 발명은 발전소의 보일러, 압력용기 등의 소재에 이용되는 인성이 우수한 600MPa급 압력용기용 강에 관한 것으로, 그 목적은 강도와 인성을 향상시키기 위하여 미량의 B, Ti등을 첨가하는데, 이러한 합급원소의 첨가효과를 높이기 위하여 노말라이징 열처리 후의 냉각속도를 최적화함으로써 인성이 우수한 인장강도 600MPa급 압력용기용 강의 제조방법을 제공하는데 있다.
The present invention relates to a 600MPa class pressure vessel steel with excellent toughness used in boilers, pressure vessels, etc. of power plants, and its purpose is to add a small amount of B, Ti, etc. to improve strength and toughness. The present invention provides a method for producing a 600MPa pressure vessel steel with excellent tensile strength by optimizing the cooling rate after normalizing heat treatment to increase the element addition effect.

상기 목적을 달성하기 위한 본 발명은 중량%로, C:0.08~0.16%, Si:0.1~0.4%, Mn:0.8~1.8%, Mo:0.2~0.8%, Ni:0.3~0.8%, B:0.0005~0.003%, Ti:0.005~0.025%, Al:0.01~0.08%, P:0.010%이하, S:0.010% 이하, N:0.010% 이하, 나머지 Fe 및 기타 불가피한 불순물로 조성되는 강 소재를 Ac3 ~ 930℃ 온도범위에서 노말라이징한 후 판 중심부에서 0.5~5℃/초 냉각속도로 상온까지 강제 공냉시키는 것을 포함하여 이루어지는 인성이 우수한 600MPa급 압력용기용 강의 제조방법을 그 기술적 요지로 한다.
The present invention for achieving the above object by weight, C: 0.08 ~ 0.16%, Si: 0.1 ~ 0.4%, Mn: 0.8 ~ 1.8%, Mo: 0.2 ~ 0.8%, Ni: 0.3 ~ 0.8%, B: Steel material composed of 0.0005 ~ 0.003%, Ti: 0.005 ~ 0.025%, Al: 0.01 ~ 0.08%, P: 0.010% or less, S: 0.010% or less, N: 0.010% or less, remaining Fe and other unavoidable impurities The technical gist of the 600MPa pressure vessel steel with excellent toughness, including forced air cooling at room temperature at a temperature of 0.5 to 5 ° C./sec at a plate center after normalizing at a temperature range of 3 to 930 ° C., shall be considered.

Description

인성이 우수한 인장강도 600ＭＰａ급 압력용기용 강의 제조방법{A Method of 600MPa Grade Tensile Strength Steel for Pressure Vessel Having Superior Toughness}A Method of 600MPa Grade Tensile Strength Steel for Pressure Vessel Having Superior Toughness

본 발명은 발전소의 보일러, 압력용기 등의 소재에 이용되는 Mn-Mo-Ni계 탄소강에 관한 것으로서, 보다 상세하게는 Mn-Mo-Ni계 강에 적절한 성분을 첨가하고 노말라이징 열처리과정에서 강제냉각을 적용함으로써 얻을 수 있는 인성이 우수한 600MPa급 압력용기용 강의 제조방법에 관한 것이다.
The present invention relates to Mn-Mo-Ni-based carbon steel used for materials such as boilers, pressure vessels of power plants, and more particularly, by adding an appropriate component to Mn-Mo-Ni-based steel and forced cooling in the normalized heat treatment process. It relates to a method for producing a 600MPa class pressure vessel steel with excellent toughness obtained by applying.

종래 Mn-Mo-Ni계 강인 A302C(ASTM규격)는 강의 5대 원소 이외에 Mo과 Ni이 첨가되고 Cr-Mo계 합금강과는 달리 템퍼링 열처리없이 노말라이징 열처리만을 거쳐 제조된 것으로서, 고온에서의 기계적 특성을 확보하여 중·고온용 압력용기의 소재로 사용된다.A302C (ASTM standard), a conventional Mn-Mo-Ni steel, is manufactured by only normalizing heat treatment without tempering heat, unlike Mo- and Ni-added steel and Cr-Mo alloy steel, in addition to the five major elements of steel. It is used as a material for medium and high temperature pressure vessels.

그러나, 사용환경이 더욱 가혹해지고 있는 현재의 상황에서, 상기 A302C강(ASTM 규격)을 노말라이징 열처리만 한 경우에는 소재의 물성이 발전설비의 설계요구치에 미치지 못하게 되는 경우가 종종 발생할 수 있다. However, in the present situation where the use environment is becoming more severe, when the normalized heat treatment of the A302C steel (ASTM standard) is performed, it may sometimes occur that the material properties of the material do not meet the design requirements of the power generation equipment.

따라서, 소재의 기계적 특성을 향상시킬 수 있는 방안이 요구되고 있는 실정이다.
Therefore, the situation is required to improve the mechanical properties of the material.

본 발명은 이러한 기술적 문제를 해결하기 위한 것으로, 강도와 인성을 향상시키기 위하여 미량의 B, Ti등을 첨가한다. 상기 첨가물 B, Ti를 탄화물과 질화물 형태로 미세하게 석출시키므로써 인장강도를 높이고, B을 모재에 고용시키므로써 인성을 향상시키게 되며, 이러한 합급원소의 첨가효과를 높이기 위하여 노말라이징 열처리 후의 냉각속도를 최적화함으로써 인성이 우수한 인장강도 600MPa급 압력용기용 강의 제조방법을 제공하는데, 그 목적이 있다.
The present invention is to solve this technical problem, to add a small amount of B, Ti and the like in order to improve the strength and toughness. By finely depositing the additives B and Ti in the form of carbides and nitrides to increase the tensile strength, and to solidify the B in the base material to improve toughness, and to increase the cooling effect after the normalizing heat treatment to increase the addition effect of these alloying elements. The purpose of the present invention is to provide a method for producing a 600MPa pressure vessel steel with excellent tensile strength by optimizing.

본 발명은 중량%로, C:0.08~0.16%, Si:0.1~0.4%, Mn:0.8~1.8%, Mo:0.2~0.8%, Ni:0.3~0.8%, B:0.0005~0.003%, Ti:0.005~0.025%, Al:0.01~0.08%, P:0.010%이하, S:0.010% 이하, N:0.010% 이하, 나머지 Fe 및 기타 불가피한 불순물로 조성되는 강을 Ac3 ~ 930℃ 온도범위에서 노말라이징한 후, 판 중심부에서 0.5~5℃/초 냉각속도로 상온까지 강제 공냉시키는 것을 포함하여 이루어지는 인성이 우수한 600MPa급 압력용기용 강의 제조방법에 관한 것이다. The present invention is in weight%, C: 0.08 to 0.16%, Si: 0.1 to 0.4%, Mn: 0.8 to 1.8%, Mo: 0.2 to 0.8%, Ni: 0.3 to 0.8%, B: 0.0005 to 0.003%, Ti : 0.005 ~ 0.025%, Al: 0.01 ~ 0.08%, P: 0.010% or less, S: 0.010% or less, N: 0.010% or less, steel composed of remaining Fe and other unavoidable impurities in the temperature range of A c3 ~ 930 ℃ After normalizing, the present invention relates to a method for producing a 600 MPa-class pressure vessel steel with excellent toughness, including forced air cooling to room temperature at a rate of 0.5 to 5 ° C./sec at a plate center.

이하, 본 발명을 상세히 설명한다.
Hereinafter, the present invention will be described in detail.

C:0.08~0.16중량%C: 0.08 to 0.16 weight%

C는 소재의 강도와 경도를 결정하는 중요한 원소로서, 그 함량이 0.08중량% 미만이면 강도 및 경도가 저하하고, 0.16중량% 보다 많으면 용접성이 나빠져 압력용기 제작이 어렵기 때문에, 그 함량을 0.08~0.16중량%로 제한하는 것이 바람직하다.
C is an important element that determines the strength and hardness of the material. If the content is less than 0.08% by weight, the strength and hardness are lowered. If it is more than 0.16% by weight, the weldability is poor and the pressure vessel is difficult to manufacture. It is preferable to limit to 0.16% by weight.

Si:0.1~0.4중량%Si: 0.1-0.4 wt%

Si는 제강중 산소를 제거하는 탈산제로서, 그 함량이 0.1중량% 미만이면 탈산효과가 불안정하고, 0.4중량% 보다 많으면 강도는 향상되나 인성이 나빠지므로, 그 함량을 0.1~0.4중량%로 제한하는 것이 바람직하다.
Si is a deoxidizer that removes oxygen in steelmaking. If the content is less than 0.1% by weight, the deoxidation effect is unstable, and if it is more than 0.4% by weight, the strength is improved but the toughness is deteriorated. Therefore, the content is limited to 0.1 to 0.4% by weight. It is preferable.

Mn:0.8~1.8중량%Mn: 0.8-1.8 wt%

Mn은 강도유지 및 열처리특성을 향상시키는 원소로서, 그 함량이 0.8중량% 미만이면 강도가 저하하고, 1.8중량% 보다 많으면 용접성에 중요한 영향을 미치는 탄소당량값이 높아져 용접성이 나빠지므로, 그 함량을 0.8~1.8중량%로 제한하는 것이 바람직하다.
Mn is an element that improves strength retention and heat treatment characteristics. If the content is less than 0.8% by weight, the strength decreases. If the content is more than 1.8% by weight, Mn increases the carbon equivalent value which has a significant effect on weldability. It is preferable to limit to 0.8 to 1.8% by weight.

Mo:0.2~0.8중량% Mo: 0.2-0.8 wt%                     

Mo은 고온강도를 높이고, 고온환경에서 장시간 사용시 발생하는 뜨임취성에 대한 저항성을 높이는 원소로, 이와 같은 효과를 얻기 위해서는 0.2중량% 이상 첨가해야 하지만, 그 함량이 0.8중량%보다 많으면 용접성이 나빠지므로, 그 함량을 0.2~0.8중량%로 제한하는 것이 바람직하다.
Mo is an element that increases the high temperature strength and increases the resistance to temporal brittleness generated during long time use in a high temperature environment. To achieve this effect, Mo should be added at least 0.2% by weight, but if the content is more than 0.8% by weight, the weldability is deteriorated. It is preferable to limit the content to 0.2 to 0.8% by weight.

Ni:0.3~0.8중량%Ni: 0.3-0.8 wt%

Ni은 고온강도를 높이고 인성을 향상시키는 원소로서, 0.3중량% 미만으로 첨가되는 경우에는 그 효과가 미미하고, 0.8중량% 보다 많이 첨가되면 용접성을 해치기 때문에, 그 함량을 0.3~0.8중량%로 제한하는 것이 바람직하다.
Ni is an element that increases the high temperature strength and improves toughness. When it is added at less than 0.3% by weight, the effect is insignificant, and when it is added at more than 0.8% by weight, Ni is limited to 0.3 to 0.8% by weight. It is desirable to.

B:0.0005~0.003중량%B: 0.0005-0.003 weight%

B은 본 발명강의 필수원소로서 극미량 첨가로도 강의 경화성을 증가시켜 용접성에 해로운 강화원소의 첨가량을 감소시킬 수 있으며, 그 함량이 0.0005중량% 미만인 경우에는 노말라이징 열처리시 그 효과가 미미하고, 0.003중량% 보다 많이 첨가되는 경우에는 결정립계 및 입내에 조대한 B 화합물이 형성되어 경화성 효과를 상실하고 인성을 저하시키므로, 그 함량을 0.0005~0.003중량%로 제한하는 것이 바람직하다.
B is an essential element of the present invention steel can be added to a very small amount to increase the hardenability of the steel to reduce the amount of reinforcing elements harmful to the weldability, if the content is less than 0.0005% by weight in normalizing heat treatment, the effect is insignificant, 0.003 In the case where more than% by weight is added, coarse B compounds are formed in the grain boundary and in the mouth, and thus, the hardenable effect is lost and the toughness is lowered. Therefore, the content is preferably limited to 0.0005 to 0.003% by weight.

Ti:0.005~0.025중량%Ti: 0.005% to 0.025% by weight

Ti는 B와 함께 본 발명의 필수원소로서 미량첨가에 의해 N과 결합하여 TiN을 형성하여 모재의 노말라이징 열처리시에는 오스테나이트 결정립을 미세화시키고 B과 N과의 결합을 억제하여 B의 경화성을 향상시키는데 효과적인 원소이다. 그 함량이 0.005중량% 미만에서는 효과가 없으며, 0.025중량%를 초과하면 조대석출물의 형성과 고용 Ti의 증대로 인성저하를 초래하므로, 그 함량을 0.005~0.025중량%로 제한하는 것이 바람직하다.
Ti is an essential element of the present invention together with B to form TiN by microaddition, thereby minimizing austenite grains during normalizing heat treatment of the base material, and inhibiting binding between B and N to improve the hardenability of B. Is an effective element. If the content is less than 0.005% by weight, it is ineffective, and if it exceeds 0.025% by weight, the toughness is reduced due to the formation of coarse precipitates and the increase of solid solution Ti. Therefore, the content is preferably limited to 0.005 to 0.025% by weight.

Al:0.01~0.08중량%Al: 0.01% to 0.08% by weight

Al은 탈산을 위해 반드시 첨가되어야 하며 질소와 결합하여 AlN을 형성함으로써 강의 조직을 미세화시키고 고용질소를 저감시켜 인성을 향상시키며, B의 질소와의 결합을 방지시켜 B의 경화성 효과를 높이는 원소로, 0.01중량% 미만 첨가되는 경우에는 그 효과가 미미하고, 0.08중량%를 초과하면 그 효과는 포화되고 개재물이 증가되므로, 그 함량을 0.01~0.08중량%로 제한하는 것이 바람직하다.
Al must be added for deoxidation and combines with nitrogen to form AlN to refine the structure of steel and reduce the solid solution nitrogen to improve toughness, and to prevent the bonding of B with nitrogen to increase the hardening effect of B, When less than 0.01% by weight is added, the effect is insignificant. If it is more than 0.08% by weight, the effect is saturated and inclusions are increased. Therefore, the content is preferably limited to 0.01 to 0.08% by weight.

P:0.010중량% 이하P: 0.010% by weight or less

P은 0.010중량%를 초과하여 첨가되면, 열처리하는 과정과 소재가 고온 사용환경에서 장시간 사용될 때 발생하는 뜨임취성 감수성을 높이기 때문에, 그 함량을 0.010중량% 이하로 제한하는 것이 바람직하다.
When P is added in excess of 0.010% by weight, it is preferable to limit the content to 0.010% by weight or less because the process of heat treatment and the temper brittleness generated when the material is used for a long time in a high temperature use environment are enhanced.

S:0.010중량% 이하S: 0.010% by weight or less

S은 0.010중량%를 초과하여 첨가되면, Mn과 MnS를 형성하여 충격인성을 저해 하고 고온강도를 해치므로, 그 함량을 0.010중량% 이하로 제한하는 것이 바람직하다.
When S is added in excess of 0.010% by weight, since Mn and MnS are formed to impair impact toughness and impair high temperature strength, it is preferable to limit the content to 0.010% by weight or less.

N:0.01중량% 이하N: 0.01 wt% or less

N은 Al, Ti, B 등과 결합하여 조직변태에 유용하게 작용하는 원소이지만, 0.01중량%를 초과하면 강 제조시 B와 결합하여 B의 경화성을 해치고 과잉의 고용질소는 용접부 인성저하를 초래하므로, 그 함량을 0.01중량% 이하로 제한하는 것이 바람직하다.

N is an element that is useful in tissue transformation by combining with Al, Ti, B, etc., but when it exceeds 0.01% by weight, N is combined with B when steel is manufactured to impair the hardenability of B, and excessive solid solution of nitrogen causes deterioration of the weld toughness. It is preferable to limit the content to 0.01% by weight or less.

상기의 화학조성 범위내로 조정한 강재를 노말라이징 열처리하고 강재의 두께에 따라서 일정시간 유지한 후, 냉각 테이블상에 설치한 강제공냉 장치를 이용하여 제어냉각을 실시한다.The steel material adjusted within the above-mentioned chemical composition range is subjected to normal heat treatment and maintained for a predetermined time according to the thickness of the steel material, and then controlled cooling is performed using a forced air cooling device installed on a cooling table.

상기 노말라이징 열처리온도는 Ac3~930℃ 온도범위로 하는데, 그 이유는 열처리 온도가 오스테나이트 변태온도보다 지나치게 높아지면(930℃초과) 오스테나이트 결정립이 조대화되어 기계적 성질이 저하되고, Ac3 온도 미만에서는 열처리 효과가 없기 때문이다.The normalizing heat treatment temperature is A c3 ~ 930 ℃ temperature range, the reason is that if the heat treatment temperature is higher than the austenite transformation temperature (over 930 ℃) austenitic grains are coarsened, mechanical properties are degraded, A c3 It is because there is no heat processing effect below temperature.

다음으로, 냉각조건은 판두께에 관계없이 강재 중심부에서의 냉각속도가 0.5~5℃/초가 되도록 조절하여 상온까지 냉각시키는 것이 바람직하다. 통상의 강재 는 별도의 강제냉각없이 자연 냉각되므로 강재의 두께에 따라 냉각속도가 달라지며 통상 0.1~0.5℃/초 전후의 냉각속도가 얻어진다. 노말라이징 온도에서 상온까지의 냉각속도가 0.5℃/초 미만이 되면 강제냉각의 효과가 없고 5℃/초 초과의 속도에서는 냉각속도에 따른 미세조직의 변화가 커지므로 재질 제어가 용이하지 않게 된다. 따라서 노말라이징 온도에서 상온까지의 냉각속도를 0.5~5℃/초 범위로 제한하는 것이 바람직하다.

Next, the cooling conditions are preferably cooled to room temperature by adjusting the cooling rate at the center of the steel to be 0.5 to 5 ° C / sec regardless of the plate thickness. Since ordinary steel naturally cools without forced cooling, the cooling rate varies depending on the thickness of the steel, and a cooling rate of about 0.1 to 0.5 ° C / sec is generally obtained. If the cooling rate from the normalizing temperature to room temperature is less than 0.5 ℃ / second, there is no effect of forced cooling, and at the speed of more than 5 ℃ / second, the microstructure changes according to the cooling rate is not easy to control the material. Therefore, it is preferable to limit the cooling rate from the normalizing temperature to room temperature in the range of 0.5 to 5 ° C / sec.

이하, 실시예를 통하여 본 발명을 상세히 설명한다.
Hereinafter, the present invention will be described in detail through examples.

[실시예]EXAMPLE

하기 표 1과 같이 조성된 발명재 및 종래재의 기계적 특성을 비교하기 위해, 두께 25mm인 소재들을 모두 900℃에서 1시간 유지한 후 냉각속도를 변화하는 방식으로 열처리하여 인장 및 충격시험을 실시하고, 그 결과를 하기 표2에 나타내었다. 비교재(1)은 발명재(3)과 동일한 조성의 강을 이용하여 강제냉각을 적용하지 않고 자연 공냉시킨 경우이며 비교재(2)는 발명재(3)과 동일한 조성의 강에 6℃/초의 과도한 강제냉각을 적용한 경우이다.
In order to compare the mechanical properties of the invention material and the prior art composition as shown in Table 1, all materials having a thickness of 25mm was maintained at 900 ℃ for 1 hour and then subjected to a tensile and impact test by heat treatment in a manner that changes the cooling rate, The results are shown in Table 2 below. The comparative material (1) is a case of naturally air cooling without applying forced cooling by using steel of the same composition as the invention material (3), and the comparative material (2) is 6 ° C / This is the case with excessive forced cooling of seconds.

구분division 성분(wt%)Component (wt%) CC SiSi PP SS MnMn MoMo NiNi BB AlAl TiTi NN 종래재Conventional 0.170.17 0.2730.273 0.0090.009 0.0030.003 1.411.41 0.5040.504 0.5840.584 ­­ 0.030.03 ­­ ­­ 발명재1Invention 1 0.1420.142 0.2510.251 0.0100.010 0.0030.003 1.401.40 0.4820.482 0.5450.545 0.00090.0009 0.0210.021 0.0070.007 0.00380.0038 발명재2Invention 2 0.1460.146 0.2530.253 0.0090.009 0.0030.003 1.381.38 0.4830.483 0.5500.550 0.00140.0014 0.0210.021 0.0100.010 0.00370.0037 발명재3Invention 3 0.1100.110 0.2530.253 0.0090.009 0.0030.003 1.391.39 0.5030.503 0.5480.548 0.00180.0018 0.020.02 0.0110.011 0.00340.0034 비교재1Comparative Material 1 0.1100.110 0.2530.253 0.0090.009 0.0030.003 1.391.39 0.5030.503 0.5480.548 0.00180.0018 0.020.02 0.0110.011 0.00340.0034 비교재2Comparative Material 2 0.1100.110 0.2530.253 0.0090.009 0.0030.003 1.391.39 0.5030.503 0.5480.548 0.00180.0018 0.020.02 0.0110.011 0.00340.0034

구분division 냉각속도 (℃/초)Cooling rate (℃ / sec) 항복강도 (kg/㎟)Yield strength (kg / ㎠) 인장강도 (kg/㎟)Tensile Strength (kg / ㎠) 연신율 (%)Elongation (%) 충격에너지(J)Impact energy (J) 상온(℃)Room temperature (℃) 0(℃)0 (℃) -20(℃)-20 (℃) 종래재Conventional 0.20.2 5252 6767 2020 15.415.4 9.19.1 7.17.1 발명재1Invention 1 1.01.0 5656 7777 2222 103.2103.2 89.189.1 58.058.0 발명재2Invention 2 1.01.0 5757 7676 2121 111.1111.1 100.0100.0 76.576.5 발명재3Invention 3 2.02.0 5959 7878 2121 122.3122.3 85.385.3 55.355.3 비교재1Comparative Material 1 0.20.2 5555 7070 2020 41.041.0 28.128.1 25.225.2 비교재2Comparative Material 2 6.06.0 6262 7979 1313 15.115.1 8.88.8 5.35.3

상기 표2에 나타난 바와 같이, 본 발명의 발명재(1)~(3)은 인장강도, 항복강도 및 연신율에 있어서 종래재와 비교재(1)에 비해 우수함을 알 수 있다. 특히, 충격인성은 종래재나 비교재에 비해 매우 우수한 것을 알 수 있다. 그러나, 과도한 강제냉각이 적용된 비교재(2)의 경우, 강도는 필요이상으로 증가되는 반면 인성은 오히려 저하되는 것을 알 수 있다.
As shown in Table 2, it can be seen that the inventive materials (1) to (3) of the present invention are superior to the conventional materials and the comparative material (1) in tensile strength, yield strength and elongation. In particular, it can be seen that the impact toughness is very excellent compared to the conventional materials and comparative materials. However, it can be seen that in the case of the comparative material 2 to which excessive forced cooling is applied, the strength is increased more than necessary while the toughness is lowered.

상기한 바와 같이 본 발명에 의하면, 강중에 B, Ti를 첨가하여 탄소함량을 낮추면서 동시에 노말라이징 열처리 시 강제냉각을 적용함으로써, 우수한 강도 및 충격인성을 갖는 압력용기용 강의 제조방법을 제공하는 효과가 있다.As described above, according to the present invention, by adding B and Ti to the steel to lower the carbon content and at the same time by applying forced cooling during the normalizing heat treatment, the effect of providing a method for producing a steel for pressure vessel having excellent strength and impact toughness There is.

Claims (1)

중량%로, C:0.08~0.16%, Si:0.1~0.4%, Mn:0.8~1.8%, Mo:0.2~0.8%, Ni:0.3~0.8%, B:0.0005~0.003%, Ti:0.005~0.025%, Al:0.01~0.08%, P:0.010%이하, S:0.010% 이하, N:0.010% 이하(0은 제외), 나머지 Fe 및 기타 불가피한 불순물로 조성되는 강을 Ac3 ~ 930℃ 온도범위에서 노말라이징한 후 강 중심부에서 0.5~5℃/초 냉각속도로 상온까지 강제 공냉시키는 것을 포함하여 이루어지는 인성이 우수한 600MPa급 압력용기용 강의 제조방법.By weight%, C: 0.08 to 0.16%, Si: 0.1 to 0.4%, Mn: 0.8 to 1.8%, Mo: 0.2 to 0.8%, Ni: 0.3 to 0.8%, B: 0.0005 to 0.003%, Ti: 0.005 to 0.025%, Al: 0.01 ~ 0.08 %, P: 0.010% or less, S: 0.010% or less, N: 0.010% or less (zero is not included), a steel that is the composition in balance of Fe and other unavoidable impurities, Ac 3 ~ 930 ℃ temperature Method for producing a 600MPa pressure vessel steel with excellent toughness, including forced air cooling to room temperature at 0.5 to 5 ℃ / sec cooling rate in the center of the steel after normalizing in the range.
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