KR101568504B1 - Steel plate for pressure vessel having excellent strength and toughness after post welding heat treatment and method for manufacturing the same - Google Patents
Steel plate for pressure vessel having excellent strength and toughness after post welding heat treatment and method for manufacturing the same Download PDFInfo
- Publication number
- KR101568504B1 KR101568504B1 KR1020130160816A KR20130160816A KR101568504B1 KR 101568504 B1 KR101568504 B1 KR 101568504B1 KR 1020130160816 A KR1020130160816 A KR 1020130160816A KR 20130160816 A KR20130160816 A KR 20130160816A KR 101568504 B1 KR101568504 B1 KR 101568504B1
- Authority
- KR
- South Korea
- Prior art keywords
- steel sheet
- toughness
- strength
- pwht
- less
- Prior art date
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 64
- 239000010959 steel Substances 0.000 title claims abstract description 64
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 24
- 238000010438 heat treatment Methods 0.000 title claims abstract description 16
- 238000000034 method Methods 0.000 title claims abstract description 12
- 238000003466 welding Methods 0.000 title description 9
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 16
- 229910001568 polygonal ferrite Inorganic materials 0.000 claims abstract description 14
- 239000012535 impurity Substances 0.000 claims abstract description 8
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 6
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 6
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 6
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 6
- 238000001816 cooling Methods 0.000 claims description 20
- 238000005098 hot rolling Methods 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 8
- 238000003303 reheating Methods 0.000 claims description 7
- 238000005096 rolling process Methods 0.000 claims description 5
- 230000001186 cumulative effect Effects 0.000 claims description 4
- 230000000694 effects Effects 0.000 description 14
- 230000000052 comparative effect Effects 0.000 description 13
- 229910045601 alloy Inorganic materials 0.000 description 7
- 239000000956 alloy Substances 0.000 description 7
- 239000000463 material Substances 0.000 description 6
- 229910001566 austenite Inorganic materials 0.000 description 5
- 239000013078 crystal Substances 0.000 description 3
- 230000006866 deterioration Effects 0.000 description 3
- 238000009628 steelmaking Methods 0.000 description 3
- 229910001563 bainite Inorganic materials 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000010899 nucleation Methods 0.000 description 2
- 230000006911 nucleation Effects 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010779 crude oil Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING 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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING 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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
본 발명은 PWHT 후 강도 및 인성이 우수한 압력용기용 강판 및 그 제조방법에 관한 것으로서, 본 발명의 일 실시형태는 중량%로, C: 0.05~0.2%, Si: 0.15~0.5%, Mn: 1.6%초과~2.0%이하, P: 0.030%이하, S: 0.030%이하, Al: 0.015~0.05%, Cr: 0.005~0.05%, Mo: 0.005~0.1%, V: 0.005~0.08%, Ti: 0.001~0.05%, Ni: 0.05~0.6%, Cu: 0.35%초과~0.65%이하, 잔부 Fe 및 기타 불가피한 불순물을 포함하며, 폴리고날 페라이트 + 베이나이틱 페라이트 혼합조직을 주상으로 포함하고, Cr, Mo, Ti 및 V 중 1종 이상을 포함하는 탄질화물을 부피분율로 0.02%이상 포함하는 미세조직을 갖는 PWHT 후 강도 및 인성이 우수한 압력용기용 강판 및 그 제조방법을 제공한다.
본 발명에 따르면, 600MPa급 이상의 강도를 가지면서 50시간에 이르는 용접 후 열처리(PWHT) 후에도 강도 및 인성이 열화되지 않아 우수한 기계적 물성을 확보할 수 있는 압력용기용 강판을 제공할 수 있다.The present invention relates to a steel sheet for a pressure vessel excellent in strength and toughness after PWHT and a method of manufacturing the steel sheet. The present invention provides a steel sheet for a pressure vessel, comprising 0.05 to 0.2% of C, 0.15 to 0.5% of Si, 0.001 to 0.05%, Mo: 0.005 to 0.1%, V: 0.005 to 0.08%, Ti: 0.001% or more 0.05 to 0.6% of Ni, more than 0.35% to 0.65% of Cu, and the balance of Fe and other unavoidable impurities, and contains polygonal ferrite + baynitic ferrite mixed structure as a main phase, Cr, Mo , A carbonitride containing a carbonitride containing at least one of Ti and V in a volume fraction of 0.02% or more, and having excellent strength and toughness after PWHT, and a process for producing the same.
According to the present invention, it is possible to provide a steel sheet for a pressure vessel that has strength of 600 MPa or more and does not deteriorate strength and toughness even after 50 hours of post-weld heat treatment (PWHT), thereby securing excellent mechanical properties.
Description
본 발명은 PWHT 후 강도 및 인성이 우수한 압력용기용 강판 및 그 제조방법에 관한 것으로서, 보다 상세하게는 석유화학 제조설비, 저장탱크, 열교환기, 반응로 및 응축기 등에 바람직하게 이용될 수 있는 용접 후 열처리(PWHT) 후 강도 및 인성이 우수한 압력용기용 강판 및 그 제조방법에 관한 것이다.
The present invention relates to a steel sheet for a pressure vessel excellent in strength and toughness after PWHT and a method of manufacturing the same, and more particularly, to a steel sheet for a pressure vessel excellent in strength and toughness after PWHT, Which is excellent in strength and toughness after heat treatment (PWHT), and a method for producing the same.
최근 석유의 품귀 현상 및 고유가 시대를 맞이하여 열악한 환경에서의 유전 개발이 활발해지는 추세에 따라 원유의 정제 및 저장용 강재에 대하여 후물화가 이루어지고 있다.
In recent years, due to the scarcity of petroleum and the trend of oil development in harsh environments due to the high oil price era, refining and storage steel for crude oil are being reused.
상기와 같은 강재의 후물화 이외에도 강재를 용접한 경우에 용접 후 구조물의 변형을 방지하고, 형상 및 치수를 안정시키기 위한 목적으로, 용접시 발생된 응력을 제거하기 위하여, 용접 후 열처리(PWHT, Post Weld Heat Treatment)를 행하게 된다. 그러나 장시간의 PWHT 공정을 행한 강재는 미세조직의 조대화로 인하여 인장강도가 저하되는 문제가 있다.
In order to prevent the deformation of the post-weld structure and to stabilize the shape and the dimension in the case of welding the steel material in addition to the post-welding of the steel material as described above, post-welding heat treatment (PWHT, Post Weld Heat Treatment). However, the steel material subjected to the PWHT process for a long time has a problem that the tensile strength is lowered due to the coarsening of the microstructure.
즉, 장시간 PWHT 후에는 기지조직(Matrix) 및 결정립계의 연화, 결정립 성장, 탄화물의 조대화 등에 따라 강도 및 인성이 동시에 저하되는 현상을 초래하게 된다.
That is, after the PWHT for a long time, strength and toughness are simultaneously lowered due to softening of matrix and grain boundaries, grain growth, coarsening of carbide, and the like.
상기 장시간 PWHT 열처리에 따른 물성의 저하를 방지하기 위한 대표적인 기술로는 특허문헌 1이 있다. 상기 기술은 중량%로,C: 0.05~0.20%,Si: 0.02~0.5%,Mn: 0.2~2.0%,Al: 0.005~0.10%, 잔부 Fe 및 불가피한 불순물로 이루어지고, 필요에 따라 Cu,Ni,Cr,Mo,V,Nb,Ti,B,Ca,희토류 원소 중 1종 또는 2종 이상을 추가로 포함하는 슬라브를 가열 및 열간압연한 후,실온으로 공냉하고,Ac1~Ac3 변태점에서 가열한 뒤 서냉하는 공정에 의해, PWHT 보증시간을 16시간까지 가능하게 하는 것에 관한 것이다.
As a typical technique for preventing deterioration of physical properties due to the above-described long-time PWHT heat treatment, JP-A-2001-328701 has been proposed. The above-described technique is characterized by comprising, by weight, 0.05 to 0.20% of C, 0.02 to 0.5% of Si, 0.2 to 2.0% of Mn, 0.005 to 0.10 of Al, balance Fe and unavoidable impurities, , A slab further comprising at least one of Cr, Mo, V, Nb, Ti, B, Ca and rare earth elements is heated and hot rolled, and then air-cooled at room temperature and heated at Ac1 to Ac3 transformation point To a PWHT guaranteed time of up to 16 hours by a slow cooling process.
그러나, 상기 기술에 나타난 PWHT 보증 시간은 후물화 및 용접부 조건이 가혹한 경우에는 매우 부족하며, 그 이상의 장시간 PWHT의 적용은 불가능한 문제점을 갖고 있다.
However, the PWHT guarantee time shown in the above-mentioned technique is very insufficient when the post-welding and welding conditions are severe, and it is impossible to apply the PWHT for a longer period of time.
따라서, 강재의 후물화 및 용접부 조건이 가혹하더라도 장시간의 PWHT 후에 강도와 인성이 저하되지 않는 PWHT에 대한 저항성이 큰 강재가 요구되고 있다.
Accordingly, there is a demand for a steel material having a high resistance to PWHT which does not deteriorate in strength and toughness after prolonged PWHT even if the post-treatment of the steel material and the welding conditions are severe.
본 발명은 장시간의 용접 후 열처리(PWHT) 후에도 강도와 인성의 저하를 방지할 수 있는 PWHT 후 강도 및 인성이 우수한 압력용기용 강판 및 그 제조방법을 제공하고자 하는 것이다.
An object of the present invention is to provide a steel sheet for a pressure vessel excellent in strength and toughness after PWHT which can prevent deterioration of strength and toughness even after a long post-welding heat treatment (PWHT), and a method of manufacturing the same.
본 발명의 일 실시형태는 중량%로, C: 0.05~0.2%, Si: 0.15~0.5%, Mn: 1.6%초과~2.0%이하, P: 0.030%이하, S: 0.030%이하, Al: 0.015~0.05%, Cr: 0.005~0.05%, Mo: 0.005~0.1%, V: 0.005~0.08%, Ti: 0.001~0.05%, Ni: 0.05~0.6%, Cu: 0.35%초과~0.65%이하, 잔부 Fe 및 기타 불가피한 불순물을 포함하며, 폴리고날 페라이트 + 베이나이틱 페라이트 혼합조직을 주상으로 포함하고, Cr, Mo, Ti 및 V 중 1종 이상을 포함하는 탄질화물을 부피분율로 0.02%이상 포함하는 미세조직을 갖는 PWHT 후 강도 및 인성이 우수한 압력용기용 강판을 제공한다.
An embodiment of the present invention is a ferritic stainless steel comprising 0.05 to 0.2% of C, 0.15 to 0.5% of Si, more than 1.6 to 2.0% of Mn, not more than 0.030% of P, not more than 0.030% of S, 0.001 to 0.05% of Cr, 0.005 to 0.05% of Cr, 0.005 to 0.1% of Mo, 0.005 to 0.08% of V, 0.001 to 0.05% of Ti, 0.05 to 0.6% of Ni, 0.35 to 0.65% of Cu, Fe and other unavoidable impurities, and contains a polygonal ferrite + baynitic ferrite mixed structure as a main phase and at least 0.02% by volume fraction of a carbonitride containing at least one of Cr, Mo, Ti and V A steel sheet for a pressure vessel excellent in strength and toughness after PWHT having a microstructure is provided.
본 발명의 다른 실시형태는 중량%로, C: 0.05~0.2%, Si: 0.15~0.5%, Mn: 1.6%초과~2.0%이하, P: 0.030%이하, S: 0.030%이하, Al: 0.015~0.05%, Cr: 0.005~0.05%, Mo: 0.005~0.1%, V: 0.005~0.08%, Ti: 0.001~0.05%, Ni: 0.05~0.6%, Cu: 0.35%초과~0.65%이하, 잔부 Fe 및 기타 불가피한 불순물을 포함하는 강 슬라브를 1050~1250℃에서 재가열하는 단계; 상기 재가열된 강 슬라브를 Ar3~Tnr 온도범위에서 누적압하율 30%이상으로 열간압연하여 열연강판을 얻는 단계; 상기 열연강판을 강판의 1/4 두께 기준으로 2~30℃/s의 냉각속도로 450~550℃까지 1차 냉각하는 단계; 상기 냉각된 열연강판을 (Ac1+30℃)~(Ac3-50℃)로 재가열하는 단계; 및 상기 재가열된 열연강판을 5~100℃/s의 냉각속도로 400℃이하까지 2차 냉각하는 단계를 포함하는 PWHT 후 강도 및 인성이 우수한 압력용기용 강판의 제조방법을 제공한다.
Another embodiment of the present invention is a ferritic stainless steel comprising 0.05 to 0.2% of C, 0.15 to 0.5% of Si, more than 1.6 to 2.0% of Mn, not more than 0.030% of P, not more than 0.030% of S, 0.001 to 0.05% of Cr, 0.005 to 0.05% of Cr, 0.005 to 0.1% of Mo, 0.005 to 0.08% of V, 0.001 to 0.05% of Ti, 0.05 to 0.6% of Ni, 0.35 to 0.65% of Cu, Reheating the steel slab containing Fe and other unavoidable impurities at 1050 to 1250 占 폚; Hot-rolling the reheated steel slab to a cumulative rolling reduction of 30% or more in a temperature range of Ar3 to Tnr to obtain a hot-rolled steel sheet; Cooling the hot-rolled steel sheet to 450 to 550 ° C at a cooling rate of 2 to 30 ° C / s based on 1/4 thickness of the steel sheet; Reheating the cooled hot-rolled steel sheet to (Ac1 + 30 占 폚) to (Ac3-50 占 폚); And secondarily cooling the reheated hot-rolled steel sheet to a temperature of 400 ° C or less at a cooling rate of 5 to 100 ° C / s. The present invention also provides a method for manufacturing a steel sheet for a pressure vessel excellent in strength and toughness after PWHT.
본 발명에 따르면, 600MPa급 이상의 강도를 가지면서 50시간에 이르는 용접 후 열처리(PWHT) 후에도 강도 및 인성이 열화되지 않아 우수한 기계적 물성을 확보할 수 있는 압력용기용 강판을 제공할 수 있다. 또한, 기존의 제조방법에 포함되는 노말라이징 열처리를 생략할 수 있어 보다 경제적으로 압력용기용 강판을 제조할 수 있다.
According to the present invention, it is possible to provide a steel sheet for a pressure vessel that has strength of 600 MPa or more and does not deteriorate strength and toughness even after 50 hours of post-weld heat treatment (PWHT), thereby securing excellent mechanical properties. In addition, the normalizing heat treatment included in the conventional manufacturing method can be omitted, and a steel sheet for a pressure vessel can be produced more economically.
이하, 본 발명을 설명한다. 하기 설명되는 합금조성의 %는 중량%를 의미한다.
Hereinafter, the present invention will be described. % Of the alloy composition described below means% by weight.
C: 0.05~0.2%C: 0.05 to 0.2%
C는 강도를 향상시키는 원소로서, 그 함량이 0.05% 미만에서는 기지 상의 자체적인 강도가 저하되고, 0.20%를 초과하는 경우에는 용접성 저하 등의 문제점이 있다. 따라서, 상기 C는 0.05~0.2%의 범위를 갖는 거서이 바람직하다.
C is an element for improving the strength. When the content is less than 0.05%, the strength of the matrix is deteriorated. When the content exceeds 0.20%, there is a problem of deterioration in weldability. Therefore, C is preferably in the range of 0.05 to 0.2%.
Si: 0.15~0.5%Si: 0.15-0.5%
Si는 탈산 및 고용강화에 효과적인 원소이며, 충격 천이 온도 상승효과를 위하여 첨가되는 원소이다. 이러한 효과를 달성하기 위해서는 0.15% 이상 첨가되어야 하나, 0.5%를 초과하여 첨가되는 경우에는 용접성이 저하되고 강판 표면에 산화 피막이 심하게 형성되는 문제점이 있다. 따라서, Si의 함량은 0.15~0.50%로 하는 것이 바람직하다.
Si is an effective element for deoxidation and solid solution strengthening, and is an element added for the effect of increasing the impact transition temperature. In order to achieve such an effect, 0.15% or more should be added, but when it is added in excess of 0.5%, the weldability is lowered and the oxide film is formed on the surface of the steel sheet. Therefore, the Si content is preferably 0.15 to 0.50%.
Mn: 1.6%초과~2.0%이하Mn: not less than 1.6% and not more than 2.0%
Mn은 강도를 확보하는데 유리한 원소이며, 상기 효과를 위해서, 1.6%를 초과하는 범위로 첨가되는 것이 바람직하다. 다만, 2.0%를 초과하는 경우에는 S와 함께 연신된 비금속 개재물인 MnS를 형성하여 상온 연신율 및 저온인성을 저하시키는 문제가 있다. 따라서, 상기 Mn은 1.6%초과~2.0%이하의 범위를 만족하는 것이 바람직하다.
Mn is an element which is advantageous for securing strength, and for the above effect, it is preferable that Mn is added in a range exceeding 1.6%. However, if it exceeds 2.0%, there is a problem that MnS which is a non-metallic inclusion drawn together with S is formed to lower the room temperature elongation and the low temperature toughness. Therefore, it is preferable that the Mn is satisfied in a range of more than 1.6% to 2.0% or less.
P: 0.030%이하P: not more than 0.030%
P는 제조공정중 불가피하게 함유되어 저온인성을 해치는 원소이므로, 가능한 그 함량을 낮게 제어하는 것이 바람직하다. 다만, 제강공정에서 상기 P를 매우 낮은 함량으로 제거하기 위해서는 과다한 비용이 소요되므로, 0.030%이하의 범위 내에서 관리하는 것이 바람직하다.
P is an element that is inevitably contained in the production process and deteriorates the low-temperature toughness, so it is preferable to control the content of P to be as low as possible. However, since excessive cost is required to remove the P in a very low content in the steelmaking process, it is preferable to control the P within a range of 0.030% or less.
S: 0.030%이하S: not more than 0.030%
S 역시 P와 더불어, 제조공정중 불가피하게 함유되어 저온인성에 악영향을 주는 원소이지만, P와 마찬가지로 제강공정에서 상기 S를 매우 낮은 함량으로 제거하기 위해서는 과다한 비용이 소요되므로, 0.030%이하의 범위 내에서 관리하는 것이 바람직하다.
S is also an element which is inevitably contained in the manufacturing process and adversely affects the low temperature toughness. However, as in the case of P, excessive cost is required to remove the S in a very low content in the steelmaking process. .
Al: 0.015~0.05%Al: 0.015 to 0.05%
Al은 상기 Si와 더불어 제강 공정에서 강력한 탈산제로 사용되는 원소이다. 다만, 상기 Al의 함량이 0.015% 미만인 경우에는 상기 탈산효과가 미미하며, 0.05%를 초과하는 경우에는 상기 탈산효과가 포화되어 제조원가가 상승하는 문제점이 있다. 따라서, 상기 Al은 0.015~0.05%의 범위를 만족하는 것이 바람직하다.
Al is an element that is used as a strong deoxidizer in the steelmaking process together with the Si. However, if the content of Al is less than 0.015%, the effect of deoxidation is insignificant. If the content of Al exceeds 0.05%, the deoxidation effect is saturated and the manufacturing cost increases. Therefore, it is preferable that the above Al satisfies a range of 0.015 to 0.05%.
Cr: 0.005~0.05%Cr: 0.005 to 0.05%
Cr은 탄질화물을 형성시켜 강도를 증가시키는 원소이며, 본 발명에서는 상기 강도 증가 효과를 위해서 0.005%이상 첨가되는 것이 바람직하다. 다만, 상기 Cr은 고가의 원소이어서 0.05%를 초과하여 첨가하는 경우에는 제조비용의 상승을 초래하므로, 상기 Cr은 0.005~0.05%의 범위를 갖는 것이 바람직하다.
Cr is an element which increases the strength by forming carbonitride. In the present invention, it is preferable that Cr is added in an amount of 0.005% or more for the purpose of increasing the strength. However, Cr is an expensive element, and when it is added in an amount exceeding 0.05%, the production cost is increased. Therefore, the Cr content is preferably in the range of 0.005 to 0.05%.
Mo: 0.005~0.1%Mo: 0.005 to 0.1%
Mo는 Cr과 마찬가지로, 강도 증가에 유효한 원소일 뿐만 아니라, 황화물에 의한 균열 발생을 방지하는 원소이다. 상기 효과를 위해서, 상기 Mo는 0.005%이상 첨가되어야 하나, Mo 역시 고가의 원소로서 제조비용의 상승을 초래하므로, 0.1% 이하로 함유되는 것이 바람직하다. 따라서, 상기 Mo는 0.005~0.1%의 범위를 갖는 것이 바람직하다.
Like Cr, Mo is not only an element effective for increasing the strength, but also an element preventing the occurrence of cracks due to sulfides. For the above effect, the Mo content should be 0.005% or more, but Mo is also an expensive element, leading to an increase in production cost, and therefore, it is preferable that the Mo content is 0.1% or less. Therefore, the Mo content is preferably in the range of 0.005 to 0.1%.
V: 0.005~0.08%V: 0.005 to 0.08%
V는 탄질화물을 형성시켜 강도 증가에 매우 유리한 원소이다. 상기 효과를 위해서, 상기 V는 0.005%이상 첨가되어야 하나, 고가인 관계로 0.08% 이하로 첨가하는 것이 바람직하다. 따라서, 상기 V는 0.005~0.08%의 범위를 갖는 것이 바람직하다.
V is a very favorable element for increasing the strength by forming carbonitride. For the above effect, the V should be added in an amount of 0.005% or more, but it is preferably added in an amount of 0.08% or less in view of the high cost. Therefore, it is preferable that V is in the range of 0.005 to 0.08%.
Ti: 0.001~0.05%Ti: 0.001 to 0.05%
Ti는 V와 마찬가지로 탄질화물을 형성시켜 강도를 증가시키는 중요한 원소이다. 상기 효과를 위해서, 상기 Ti는 0.001%이상 첨가되어야 하나, 0.05%를 초과하는 경우에는 연속주조 과정에서 조대한 석출물로 나타나 인성저하를 초래할 수 있다. 따라서, 상기 Ti는 0.001~0.05%의 범위를 갖는 것이 바람직하다.
Ti, like V, is an important element for increasing the strength by forming carbonitride. For the above effect, the Ti should be added in an amount of 0.001% or more, but if it exceeds 0.05%, the Ti may appear as a coarse precipitate in the continuous casting process, resulting in a decrease in toughness. Therefore, the Ti content is preferably in the range of 0.001 to 0.05%.
Ni: 0.05~0.6%Ni: 0.05 to 0.6%
Ni은 저온인성 향상에 가장 효과적인 원소로서, 상기 효과를 위해, 0.05%이상 첨가되는 것이 바람직하다. 다만, 상기 Ni는 고가의 원소이어서, 0.6%를 초과하는 경우에는 제조비용의 상승을 초래하므로, 상기 Ni는 0.05~0.6%의 범위를 갖는 것이 바람직하다.
Ni is the most effective element for improving the low-temperature toughness. For the above effect, it is preferable that Ni is added in an amount of 0.05% or more. However, since the Ni is an expensive element, when it exceeds 0.6%, the production cost is increased. Therefore, the Ni is preferably in the range of 0.05 to 0.6%.
Cu: 0.35%초과~0.65%이하Cu: more than 0.35% to less than 0.65%
Cu는 강도의 향상에 효과적인 원소로서, 상기 효과를 위해 0.35%를 초과하여첨가되는 것이 바람직하다. 다만, 상기 Cu는 고가의 원소로서 제조비용의 상승을 초래하므로 0.65%이하로 첨가하는 것이 바람직하다. 따라서, 상기 Cu는 0.35%초과~0.65%이하의 범위를 갖는 것이 바람직하다.
Cu is an element effective for improving the strength and is preferably added in an amount exceeding 0.35% for the above effect. However, since Cu is an expensive element, it leads to an increase in production cost, and therefore it is preferable to add Cu at 0.65% or less. Therefore, it is preferable that the Cu has a range of more than 0.35% to 0.65% or less.
본 발명의 나머지 성분은 Fe다. 다만, 통상의 제조과정에서는 원료 또는 주위 환경으로부터 의도되지 않는 불순물들이 불가피하게 혼입될 수 있으므로, 이를 배제할 수는 없다. 이들 불순물들은 통상의 제조과정의 기술자라면 누구라도 알 수 있는 것이기 때문에 그 모든 내용을 특별히 본 명세서에서 언급하지는 않는다.
The remainder of the present invention is Fe. However, in the ordinary manufacturing process, impurities which are not intended from the raw material or the surrounding environment may be inevitably incorporated, so that it can not be excluded. These impurities are not specifically mentioned in this specification, as they are known to any person skilled in the art of manufacturing.
한편, 본 발명이 제공하는 강판은 전술한 합금조성을 만족하는 동시에, 폴리고날 페라이트 + 베이나이틱 페라이트 혼합조직을 주상으로 포함하는 미세조직을 갖는 것이 바람직하며, 이를 통해 PWHT 후에도 우수한 강도 및 인성을 확보할 수 있다. 이 때, 상기 폴리고날 페라이트는 40~70면적%, 베이니틱 페라이트는 25~60면적%인 것이 바람직한데, 상기 폴리고날 페라이트가 40면적%이하이거나, 베이니틱 페라이트가 60면적%를 초과하는 경우에는 인성이 급격히 저하될 수 있으며, 상기 폴리고날 페라이트가 70면적%를 초과하거나, 베이니틱 페라이트가 25면적% 미만인 경우에는 우수한 강도를 확보하지 못하게 된다. 한편, 상기 베이니틱 페라이트는 애시큘라(accicular) 페라이트와 베이나이트를 포함하여 이루어질 수 있다. 더불어, 본 발명의 미세조직은 제조공정상 제2상조직이 불가피하게 형성될 수 있으며, 이 때 상기 제2상조직은 5면적%이하로 관리되는 것이 바람직하다. 상기 제2상조직은 펄라이트, 마르텐사이트, 도상 마르텐사이트 등의 미세조직을 포함할 수 있다.
On the other hand, the steel sheet provided by the present invention preferably has a microstructure containing the polygonal ferrite + bainite ferrite mixed structure as a main phase, satisfying the above-mentioned alloy composition, and thereby securing excellent strength and toughness even after PWHT can do. In this case, it is preferable that the polygonal ferrite is 40 to 70% by area and the bainitic ferrite is 25 to 60% by area. When the polygonal ferrite is 40% by area or less or the bainitic ferrite is more than 60% Toughness may be rapidly deteriorated. When the polygonal ferrite is more than 70% by area or the bainitic ferrite is less than 25% by area, excellent strength can not be secured. On the other hand, the bainitic ferrite may include an accicular ferrite and bainite. In addition, the microstructure of the present invention may inevitably be formed with a normal second phase structure, wherein the second phase structure is preferably controlled to 5% or less by area. The second phase structure may include microstructures such as pearlite, martensite, and graphite martensite.
또한, 본 발명의 강판은 Cr, Mo, Ti 및 V 중 1종 이상을 포함하는 탄질화물을 부피분율로 0.02%이상 포함하는 것이 바람직하며, 이를 통해 우수한 강도 및 저온인성을 확보할 수 있다. 상기 탄질화물은 다량 생성될수록 본 발명이 얻고자 하는 효과에 보다 유리하나, 제조공정상 5부피%를 초과하기는 어렵다.
In addition, the steel sheet of the present invention preferably contains 0.02% or more by volume of carbonitride containing at least one of Cr, Mo, Ti, and V, thereby securing excellent strength and low temperature toughness. The greater the amount of the carbonitride is, the more advantageous the effect to be obtained by the present invention is, but it is difficult to exceed 5% by volume of the carbonitrided product at the normal level.
이 때, 상기 탄질화물은 50nm이하의 크기를 갖는 것이 바람직한데, 이와 같이 미세한 탄질화물을 형성시킴으로써 PWHT 후에도 우수한 강도 및 인성을 확보할 수 있다. 만일 상기 탄질화물이 50nm를 초과하여 조대한 탄질화물로 형성되는 경우에는 오히려 강도 및 인성이 저하될 수 있다.
At this time, the carbonitride preferably has a size of 50 nm or less. By forming the fine carbonitride in this way, excellent strength and toughness can be secured even after PWHT. If the carbonitride is formed of coarse carbonitride in excess of 50 nm, the strength and toughness may be lowered.
전술한 바와 같이 제공되는 본 발명의 강판은 590~640℃에서 25~50시간 열처리 후, 600MPa이상의 우수한 인장강도를 확보할 수 있음과 동시에 -49℃에서의 충격인성이 50J이상으로서 높은 저온인성을 가질 수 있으며, 이를 통해 상기 기계적 물성이 요구되는 석유화학 제조설비, 저장탱크, 열교환기, 반응로 및 응축기 등에 바람직하게 적용될 수 있다.
The steel sheet of the present invention provided as described above has an excellent tensile strength of 600 MPa or more after heat treatment at 590 to 640 ° C for 25 to 50 hours and has an impact toughness of 50 J or more at -49 ° C, And can be suitably applied to a petrochemical production facility, a storage tank, a heat exchanger, a reaction furnace, and a condenser in which the mechanical properties are required.
이하, 본 발명의 제조방법에 대하여 설명한다.
Hereinafter, the production method of the present invention will be described.
우선, 전술한 합금조성을 만족하는 강 슬라브를 1050~1250℃에서 재가열한다. 상기 가열온도가 1050℃미만일 경우에는 용질원자의 고용이 어렵고, 1250℃를 초과하는 경우에는 오스테나이트 결정립 크기가 너무 조대하게 되어 강판의 물성을 저하시킨다.
First, the steel slab satisfying the alloy composition described above is reheated at 1050 to 1250 占 폚. When the heating temperature is lower than 1050 DEG C, solid solute atoms are difficult to solidify, and when the heating temperature exceeds 1250 DEG C, the austenite grain size becomes too coarse, thereby deteriorating the physical properties of the steel sheet.
이후, 상기 재가열된 강 슬라브를 Ar3~Tnr 온도범위에서 열간압연하여 열연강판을 얻는다. 상기 온도범위의 열간압연을 통해 오스테나이트를 팬케익화시켜 이후 얻어지는 폴리고날 페라이트와 베이니틱 페라이트를 미세화시킬 수 있으며, 이에 의해 우수한 강도와 인성을 동시에 확보할 수 있다. 상기 열간압연온도가 Tnr(오스테나이트 미재결정역과 재결정역의 경계온도)을 초과하는 경우에는 오스테나이트의 재결정으로 인해 결정립이 조대해지고 이에 따라 냉각 후에도 조대한 미세조직이 출현함에 따라 우수한 물성을 확보하기 곤란해진다. 반면, 상기 열간압연온도가 Ar3미만일 경우에는 낮은 온도로 인해 열간압연성이 곤란해질 수 있고, 이로 인해 품질 불량이 발생할 수 있다. 따라서, 상기 열간압연온도는 Ar3~Tnr의 범위를 갖는 것이 바람직하다. 한편, 상기 Tnr온도는 하기 식으로부터 계산이 가능하다.
Thereafter, the reheated steel slab is hot-rolled in the Ar3 to Tnr temperature range to obtain a hot-rolled steel sheet. The austenite can be pancake-formed by hot rolling in the temperature range described above, and the resulting polygonal ferrite and bainitic ferrite can be made finer, thereby ensuring excellent strength and toughness at the same time. When the hot rolling temperature exceeds Tnr (boundary temperature between the austenite non-recrystallized zone and the recrystallization zone), the crystal grains become coarse due to the recrystallization of austenite, and coarse microstructure appears after cooling, It becomes difficult. On the other hand, when the hot rolling temperature is lower than Ar 3, the hot rolling property may become difficult due to the low temperature, and thus quality defects may occur. Therefore, it is preferable that the hot rolling temperature has a range of Ar3 to Tnr. On the other hand, the Tnr temperature can be calculated from the following equation.
Tnr(℃) = 887+464×C+890×Ti+363×Al-357×Si+(732×V-230×V1/2)
Tnr (占 폚) = 887 + 464 占 C + 890 占 Ti + 363 占 Al-357 占 Si + (732 占 V-230 占 V1 / 2 )
나아가, 상기 열간압연시 누적압하율이 30%이상이 되도록 하는 것이 바람직한데, 상기 누적압하율이 30%미만일 경우에는 폴리고날 페라이트 및 베이니틱 페라이트의 핵생성 사이트가 부족하게 되어 결정립의 크기가 25㎛를 초과하는 수준으로 조대해질 수 있다.
Further, when the cumulative rolling reduction is less than 30%, the nucleation sites of the polygonal ferrite and the bainitic ferrite become insufficient, and the size of the crystal grains becomes 25 Lt; RTI ID = 0.0 > um. ≪ / RTI >
또한, 상기 열간압연시 패스당 10%이상의 압하율 가하는 것이 바람직한데, 이를 통해 압연방향으로 오스테나이트 조직을 연신시키면서 내부에 변형대를 형성하여 미세한 폴리고날 페라이트와 베이니틱 페라이트를 얻을 수 있다. 상기 패스당 압하율이 10%미만일 경우에도 폴리고날 페라이트 및 베이니틱 페라이트의 핵생성 사이트가 부족하게 되어 결정립의 크기가 조대해질 수 있다.
In addition, it is preferable that a reduction ratio of 10% or more is applied per pass during the hot rolling. By this, the austenite structure is stretched in the rolling direction to form a deformation band inside to obtain fine polygonal ferrite and bainitic ferrite. If the reduction ratio per pass is less than 10%, the nucleation sites of the polygonal ferrite and the bainitic ferrite may be insufficient and the grain size may become large.
이후, 상기와 같이 얻어진 열연강판을 강판의 1/4 두께 기준으로 2~30℃/s의 냉각속도로 450~550℃까지 1차 냉각한다. 상기 냉각속도가 2℃/s미만일 경우에는 페라이트의 결정립이 조대화지고 폴리고날 페라이트의 분율이 증가할 수 있으며, 30℃/s를 초과하는 경우에는 베이니틱 페라이트 또는 제2상조직의 분율이 증가하여 본 발명에서 얻고자하는 미세조직을 확보하기 곤란할 수 있다.
Thereafter, the hot-rolled steel sheet obtained as described above is first cooled to 450 to 550 占 폚 at a cooling rate of 2 to 30 占 폚 / s based on 1/4 thickness of the steel sheet. When the cooling rate is less than 2 DEG C / s, the crystal grains of the ferrite are coarse and the fraction of the polygonal ferrite is increased. When the cooling rate is more than 30 DEG C / s, the fraction of bainitic ferrite or the second phase structure is increased It may be difficult to secure the microstructure to be obtained in the present invention.
이어서, 상기 1차 냉각된 열연강판을 (Ac1+30℃)~(Ac3-50℃)로 재가열한다. 상기 재가열온도가 (Ac1+30℃)미만일 경우에는 인성 향상 효과가 충분하지 않고, (Ac3-50℃)를 초과할 경우에는 인성 향상 효과는 충분히 얻을 수 있으나 강도가 저하되는 단점이 있다.
Subsequently, the primary cooled hot-rolled steel sheet is reheated to (Ac1 + 30 deg. C) to (Ac3-50 deg. C). When the reheating temperature is lower than (Ac1 + 30 deg. C), the toughness improving effect is not sufficient. When the reheating temperature is higher than (Ac3-50 deg. C), the toughness improving effect is sufficiently obtained but the strength is lowered.
상기 재가열된 열연강판을 5~100℃/s의 냉각속도로 400℃이하까지 2차 냉각한다. 상기 냉각속도가 5℃/s미만일 경우에는 강도 및 인성 등의 기계적 물성이 열화될 수 있다. 상기 냉각속도는 빠를수록 본 발명이 얻고자 하는 효과를 향상시키나, 제조설비상의 한계로 인해 100℃/s를 초과하기는 어렵다.
The reheated hot-rolled steel sheet is secondarily cooled to a temperature of 400 ° C or less at a cooling rate of 5 to 100 ° C / s. If the cooling rate is less than 5 ° C / s, mechanical properties such as strength and toughness may be deteriorated. The faster the cooling rate, the better the effect to be obtained by the present invention, but it is difficult to exceed 100 ° C / s due to limitations in the production facility.
한편, 전술한 바와 같이 제공되는 본 발명의 제조방법에 따르면, 압력용기용 강재의 제조를 위해 기존에 사용되던 높은 온도에서의 노말라이징 열처리를 생략할 수 있어 보다 경제적으로 압력용기용 강판을 제조할 수 있다.
According to the manufacturing method of the present invention provided as described above, the normalizing heat treatment at a high temperature, which is conventionally used for manufacturing a steel material for a pressure vessel, can be omitted, and a steel sheet for a pressure vessel can be manufactured more economically .
이하, 실시예를 통해 본 발명을 보다 상세히 설명한다. 다만, 하기 실시예는 본 발명을 보다 상세히 설명하기 위한 예시일 뿐, 본 발명의 권리범위를 한정하지 않는다.
Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are only illustrative of the present invention in more detail and do not limit the scope of the present invention.
(실시예)(Example)
하기 표 1의 합금조성을 갖는 강 슬라브를 하기 표 2의 조건을 이용하여 열연강판을 제조하였다. 이 때, 미재결정역 열간압연은 760℃에서 행하였고, 1차 냉각정지온도는 500℃였으며, 열연강판의 재가열온도는 740℃, 2차 냉각속도는 20℃/s, 2차 냉각정지온도는 350℃였다. 단, 비교예 4의 경우에는 상기 열간압연 후 910℃에서 1.3×t+20분간 노말라이징 열처리한 후 공냉을 실시하였다(단, t는 강판 두께임). 상기와 같이 제조된 열연강판에 대하여 미세조직 및 탄질화물 분율을 관찰하고, 그 결과를 하기 표 2에 나타내었다. 추가적으로 표 3의 조건으로 용접을 행한 뒤 열처리(PWHT)를 행하고, 기계적 물성을 측정하여 그 결과를 하기 표 3에 나타내었다.
Hot-rolled steel sheets were prepared by using the steel slabs having the alloy compositions shown in the following Table 1 under the conditions shown in Table 2 below. The reheating temperature of the hot-rolled steel sheet was 740 ° C, the secondary cooling rate was 20 ° C / s, and the secondary cooling-stop temperature was 560 ° C. 350 ° C. However, in the case of Comparative Example 4, after the hot rolling, the steel sheet was subjected to a normalizing heat treatment at 910 ° C. for 1.3 × t + 20 minutes, followed by air cooling (where t is the thickness of the steel sheet). The microstructure and carbonitride fractions of the hot-rolled steel sheet thus prepared were observed, and the results are shown in Table 2 below. In addition, welding was performed under the conditions shown in Table 3, followed by heat treatment (PWHT), and mechanical properties were measured. The results are shown in Table 3 below.
(℃)Reheat temperature
(° C)
(%)Cumulative reduction rate
(%)
(℃/s)Primary cooling rate
(° C / s)
두께
(mm)Steel plate
thickness
(mm)
분율
(부피%)Carbonitride
Fraction
(volume%)
(℃)PWHT temperature
(° C)
(Hr)PWHT time
(Hr)
(MPa)Yield strength
(MPa)
(MPa)The tensile strength
(MPa)
(J)Shock Toughness (@ -49 ℃)
(J)
상기 표 1 내지 3에서 알 수 있듯이, 본 발명이 제안하는 합금조성 및 제조조건을 만족하는 발명예 1 내지 12의 경우에는 본 발명이 얻고자 하는 미세조직 및 탄질화물 분율을 확보함으로써 PWHT시간이 25~50시간에 이르게 되어도 강도와 인성이 매우 우수한 수준임을 알 수 있다.
As can be seen from Tables 1 to 3, in the case of Inventive Examples 1 to 12 satisfying the alloy composition and manufacturing conditions proposed by the present invention, by securing the microstructure and the fraction of the carbonitride to be obtained according to the present invention, It can be seen that strength and toughness are very good even after reaching ~ 50 hours.
반면, 비교예 1 내지 3의 경우에는 본 발명이 제안하는 합금조성 및 제조조건을 만족하지 않아 본 발명에서 얻고자 하는 미세조직과 탄질화물 분율을 확보할 수 없었으며, 이로 인해 PWHT 후 강도와 충격인성 모두 본 발명예에 비해 낮은 수준임을 알 수 있다.
On the other hand, in the case of Comparative Examples 1 to 3, since the alloy composition and the manufacturing conditions proposed by the present invention were not satisfied, the microstructure and the fraction of the carbonitride to be obtained in the present invention could not be secured, It can be seen that all of the humanities are lower than those of the present invention.
비교예 4는 일반 압연 및 냉각 조건을 적용한 경우로써, 이 또한 마찬가지로 본 발명이 얻고자 하는 미세조직과 탄질화물 분율을 확보하지 못하였으며, 이로 인해 PWHT 후 강도와 충격인성 모두 매우 낮은 수준임을 알 수 있다.Comparative Example 4 shows that when the general rolling and cooling conditions are applied, the microstructure and the fraction of the carbonitride to be obtained by the present invention can not be ensured, and both the strength and impact toughness after PWHT are very low have.
Claims (6)
40~70 면적%의 폴리고날 페라이트 + 25~60 면적%의 베이나이틱 페라이트 혼합조직을 주상으로 포함하고,
Cr, Mo, Ti 및 V 중 1종 이상을 포함하는 탄질화물을 부피분율로 0.02%이상 포함하는 미세조직을 갖는 PWHT 후 강도 및 인성이 우수한 압력용기용 강판.The steel sheet according to any one of claims 1 to 3, wherein the steel sheet contains 0.05 to 0.2% of C, 0.15 to 0.5% of Si, more than 1.6 to 2.0% of Mn, 0.030 to less than 0.05% of S, 0.030 to less than 0.05% 0.001 to 0.05% of Mo, 0.005 to 0.1% of Mo, 0.005 to 0.08% of V, 0.001 to 0.05% of Ti, 0.05 to 0.6% of Ni, more than 0.35 to 0.65% of Cu and the balance Fe and other unavoidable impurities In addition,
A polygonal ferrite having an area of 40 to 70 area% and a ferritic blend of 25 to 60 area%
A steel plate for a pressure vessel excellent in strength and toughness after PWHT having a microstructure containing at least 0.02% by volume of carbonitride containing at least one of Cr, Mo, Ti and V.
상기 탄질화물은 50nm이하의 원상당 직경을 갖는 PWHT 후 강도 및 인성이 우수한 압력용기용 강판.The method according to claim 1,
Wherein the carbonitride has a circle equivalent diameter of 50 nm or less and is excellent in strength and toughness after PWHT.
상기 강판은 590~640℃에서 25~50시간 열처리 후, 인장강도가 600MPa이상이고, -49℃에서의 충격인성이 50J이상인 PWHT 후 강도 및 인성이 우수한 압력용기용 강판.The method according to claim 1,
The steel sheet is excellent in strength and toughness after PWHT having a tensile strength of 600 MPa or more and an impact toughness of 50 J or more at -49 캜 after heat treatment at 590 to 640 캜 for 25 to 50 hours.
상기 재가열된 강 슬라브를 Ar3~Tnr 온도범위에서 누적압하율 30%이상으로 열간압연하여 열연강판을 얻는 단계;
상기 열연강판을 강판의 1/4 두께 기준으로 2~30℃/s의 냉각속도로 450~550℃까지 1차 냉각하는 단계;
상기 1차 냉각된 열연강판을 (Ac1+30℃)~(Ac3-50℃)로 재가열하는 단계; 및
상기 재가열된 열연강판을 5~100℃/s의 냉각속도로 400℃이하까지 2차 냉각하는 단계를 포함하며,
미세조직은 40~70 면적%의 폴리고날 페라이트 + 25~60 면적%의 베이나이틱 페라이트 혼합조직을 주상으로 포함하는 PWHT 후 강도 및 인성이 우수한 압력용기용 강판의 제조방법.The steel sheet according to any one of claims 1 to 3, wherein the steel sheet contains 0.05 to 0.2% of C, 0.15 to 0.5% of Si, more than 1.6 to 2.0% of Mn, 0.030 to less than 0.05% of S, 0.030 to less than 0.05% 0.001 to 0.05% of Mo, 0.005 to 0.1% of Mo, 0.005 to 0.08% of V, 0.001 to 0.05% of Ti, 0.05 to 0.6% of Ni, more than 0.35 to 0.65% of Cu and the balance Fe and other unavoidable impurities Reheating the steel slab at 1050 to 1250 占 폚;
Hot-rolling the reheated steel slab to a cumulative rolling reduction of 30% or more in a temperature range of Ar3 to Tnr to obtain a hot-rolled steel sheet;
Cooling the hot-rolled steel sheet to 450 to 550 ° C at a cooling rate of 2 to 30 ° C / s based on 1/4 thickness of the steel sheet;
Reheating the primary cooled hot-rolled steel sheet to (Ac1 + 30 占 폚) to (Ac3-50 占 폚); And
Cooling the reheated hot-rolled steel sheet to a temperature of 400 ° C or less at a cooling rate of 5 to 100 ° C / s,
Wherein the microstructure is excellent in strength and toughness after PWHT including a polygonal ferrite of 40 to 70 area% and a mixed ferrite structure of 25 to 60 area% as a main phase.
상기 열간압연시 패스당 10%이상의 압하율 가하는 PWHT 후 강도 및 인성이 우수한 압력용기용 강판의 제조방법.
The method of claim 5,
A method for producing a steel sheet for a pressure vessel, which is excellent in the strength and toughness after PWHT, which has a reduction ratio of 10% or more per pass in the hot rolling.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR1020130160816A KR101568504B1 (en) | 2013-12-20 | 2013-12-20 | Steel plate for pressure vessel having excellent strength and toughness after post welding heat treatment and method for manufacturing the same |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR1020130160816A KR101568504B1 (en) | 2013-12-20 | 2013-12-20 | Steel plate for pressure vessel having excellent strength and toughness after post welding heat treatment and method for manufacturing the same |
Publications (2)
Publication Number | Publication Date |
---|---|
KR20150073024A KR20150073024A (en) | 2015-06-30 |
KR101568504B1 true KR101568504B1 (en) | 2015-11-11 |
Family
ID=53518844
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
KR1020130160816A KR101568504B1 (en) | 2013-12-20 | 2013-12-20 | Steel plate for pressure vessel having excellent strength and toughness after post welding heat treatment and method for manufacturing the same |
Country Status (1)
Country | Link |
---|---|
KR (1) | KR101568504B1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN110527793A (en) * | 2019-09-06 | 2019-12-03 | 武汉科技大学 | A kind of heat treatment method improving low chromium type stainless steel welded joint low-temperature flexibility |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP3353333B1 (en) * | 2015-09-22 | 2020-07-08 | Tata Steel IJmuiden B.V. | A hot-rolled high-strength roll-formable steel sheet with excellent stretch-flange formability and a method of producing it |
KR101940880B1 (en) * | 2016-12-22 | 2019-01-21 | 주식회사 포스코 | Sour resistance steel sheet having excellent low temperature toughness and post weld heat treatment property, and method of manufacturing the same |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2011001620A (en) * | 2009-06-22 | 2011-01-06 | Jfe Steel Corp | High strength thick steel plate combining excellent productivity and weldability and having excellent drop weight characteristic after pwht, and method for producing the same |
JP2012122111A (en) | 2010-12-10 | 2012-06-28 | Jfe Steel Corp | Method for producing tmcp and tempering process type high-strength thick steel plate having both excellent productivity and weldability, and excellent in drop-weight characteristic after pwht |
-
2013
- 2013-12-20 KR KR1020130160816A patent/KR101568504B1/en active IP Right Grant
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2011001620A (en) * | 2009-06-22 | 2011-01-06 | Jfe Steel Corp | High strength thick steel plate combining excellent productivity and weldability and having excellent drop weight characteristic after pwht, and method for producing the same |
JP2012122111A (en) | 2010-12-10 | 2012-06-28 | Jfe Steel Corp | Method for producing tmcp and tempering process type high-strength thick steel plate having both excellent productivity and weldability, and excellent in drop-weight characteristic after pwht |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN110527793A (en) * | 2019-09-06 | 2019-12-03 | 武汉科技大学 | A kind of heat treatment method improving low chromium type stainless steel welded joint low-temperature flexibility |
Also Published As
Publication number | Publication date |
---|---|
KR20150073024A (en) | 2015-06-30 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
KR101322067B1 (en) | High strength steel sheet having excellent property after post weld heat treatment and method for manufacturing the same | |
KR101417231B1 (en) | Ultra heavy steel plate for pressure vessel with excellent low-temperature toughness and tensile property and manufacturing method of the same | |
KR101917453B1 (en) | Steel plate having excellent ultra low-temperature toughness and method for manufacturing same | |
KR101758497B1 (en) | Steel Plate For Pressure Vessel With Excellent PWHT Resistance And Manufacturing Method Thereof | |
KR101674775B1 (en) | Hot rolled steel using for oil country and tubular goods and method for producing the same and steel pipe prepared by the same | |
KR101778398B1 (en) | Pressure vessel steel plate having excellent property after post weld heat treatment and method for manufacturing the same | |
KR101536478B1 (en) | Pressure vessel steel with excellent low temperature toughness and sulfide stress corrosion cracking, manufacturing method thereof and manufacturing method of deep drawing article | |
KR101585724B1 (en) | A thick plate of pipeline with excellent DWTT at low temperature and YR ratio characteristics, and method of the same | |
KR20160079166A (en) | High strength structural steel having low yield ratio and good impact toughness and preparing method for the same | |
CN108474089B (en) | Thick steel plate having excellent low-temperature toughness and hydrogen-induced cracking resistance and method for manufacturing same | |
KR20160078624A (en) | Hot rolled steel sheet for steel pipe having excellent low-temperature toughness and strength and method for manufacturing the same | |
KR101253888B1 (en) | High strength steel sheet having excellent property after post weld heat treatment and method for manufacturing the same | |
KR101568504B1 (en) | Steel plate for pressure vessel having excellent strength and toughness after post welding heat treatment and method for manufacturing the same | |
KR102164107B1 (en) | High strength steel plate having superior elongation percentage and excellent low-temperature toughness, and manufacturing method for the same | |
KR101353858B1 (en) | Pressure vessel steel plate having excellent resustance property after post weld heat treatment and manufacturing method of the same | |
KR101560943B1 (en) | Hot rolled steel sheet having a good low temperature toughness and method for manufacturing the same | |
KR101858857B1 (en) | High-strength hot-rolled steel plate having high dwtt toughness at low temperature, and method for manufacturing the same | |
KR101786262B1 (en) | Hot-rolled thick steel plate having excellent strength and dwtt toughness at low temperature, and method for manufacturing the same | |
KR101795882B1 (en) | Steel sheet for pipe having excellent strength and toughness, method for manufacturing the same, and method for manufacturing welded steel pipe using the same | |
JP7197699B2 (en) | Steel material for pressure vessel excellent in resistance to hydrogen-induced cracking and its manufacturing method | |
KR101899736B1 (en) | Thick steel sheet having excellent low temperature toughness and resistance to hydrogen induced cracking, and method of manufacturing the same | |
KR20170075867A (en) | The steel sheet having high-strength and excellent heat affected zone toughness and method for manufacturing the same | |
KR101482341B1 (en) | Pressure vessel steel plate having excellent resustance property after post weld heat treatment and manufacturing method of the same | |
EP3889303A1 (en) | Steel plate for high temperature applications having excellent strength at high temperature and method for manufacturing the same | |
KR101507943B1 (en) | Line-pipe steel sheet and method for manufacturing the same |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
A201 | Request for examination | ||
E902 | Notification of reason for refusal | ||
E701 | Decision to grant or registration of patent right | ||
GRNT | Written decision to grant | ||
FPAY | Annual fee payment |
Payment date: 20181102 Year of fee payment: 4 |