JP2013515861A - High-strength steel sheet with excellent post-weld heat treatment resistance and manufacturing method thereof - Google Patents
High-strength steel sheet with excellent post-weld heat treatment resistance and manufacturing method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 75
- 239000010959 steel Substances 0.000 title claims abstract description 75
- 238000010438 heat treatment Methods 0.000 title claims abstract description 35
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 16
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 13
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 12
- 229910052802 copper Inorganic materials 0.000 claims abstract description 10
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 9
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 9
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 9
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 7
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 7
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 7
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 7
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 7
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 7
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 6
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 6
- 239000000463 material Substances 0.000 claims description 15
- 239000013078 crystal Substances 0.000 claims description 14
- 238000001816 cooling Methods 0.000 claims description 13
- 239000000203 mixture Substances 0.000 claims description 12
- 238000005096 rolling process Methods 0.000 claims description 12
- 229910000859 α-Fe Inorganic materials 0.000 claims description 12
- 238000005098 hot rolling Methods 0.000 claims description 6
- 238000003303 reheating Methods 0.000 claims description 6
- 230000009467 reduction Effects 0.000 claims description 5
- 229910001562 pearlite Inorganic materials 0.000 claims description 4
- 230000001186 cumulative effect Effects 0.000 claims description 3
- 230000007423 decrease Effects 0.000 abstract description 12
- 238000003466 welding Methods 0.000 abstract description 8
- 230000007774 longterm Effects 0.000 abstract description 6
- 239000011651 chromium Substances 0.000 description 22
- 239000010955 niobium Substances 0.000 description 17
- 239000010949 copper Substances 0.000 description 16
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 15
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 12
- 239000011575 calcium Substances 0.000 description 12
- 238000005336 cracking Methods 0.000 description 12
- 229910052739 hydrogen Inorganic materials 0.000 description 12
- 239000001257 hydrogen Substances 0.000 description 12
- 230000000694 effects Effects 0.000 description 11
- 238000000034 method Methods 0.000 description 8
- 238000001953 recrystallisation Methods 0.000 description 8
- 239000010936 titanium Substances 0.000 description 8
- 239000011572 manganese Substances 0.000 description 7
- 239000011159 matrix material Substances 0.000 description 7
- 230000008569 process Effects 0.000 description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 5
- 230000006866 deterioration Effects 0.000 description 5
- 229910001566 austenite Inorganic materials 0.000 description 4
- 238000005728 strengthening Methods 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000003921 oil Substances 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- 238000009628 steelmaking Methods 0.000 description 3
- 230000008719 thickening Effects 0.000 description 3
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 2
- 229910001563 bainite Inorganic materials 0.000 description 2
- 229910001567 cementite Inorganic materials 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 238000009749 continuous casting Methods 0.000 description 2
- 239000010779 crude oil Substances 0.000 description 2
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 1
- 238000009863 impact test Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000011593 sulfur Substances 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
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
-
- 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
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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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
- C22C38/002—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
- C22C38/04—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
- C22C38/06—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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
-
- 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
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
-
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/004—Dispersions; Precipitations
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- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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- 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
- C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
長期間の溶接後熱処理(PWHT、Post Weld Heat Treatment、PWHT)を行っても強度及び靭性の低下が発生しないPWHT抵抗性に優れた鋼板を提供する。溶接後熱処理抵抗性に優れた高強度鋼板及びその製造方法は、重量%で、C:0.1〜0.3%、Si:0.15〜0.50%、Mn:0.6〜1.2%、P:0.035%以下、S:0.020%以下、Al:0.001〜0.05%、Cr:0.01〜0.35%、Mo:0.005〜0.2%、V:0.005〜0.05%、Nb:0.001〜0.05%、Ti:0.001〜0.05%、Ca:0.0005〜0.005%、Ni:0.05〜0.5%を含み、Cu:0.005〜0.5%、Co:0.005〜0.2%及びW:0.005〜0.2%からなる群より選択された1種以上、残りはFe及び不可避な不純物を含んでなる。 Provided is a steel sheet having excellent PWHT resistance in which a decrease in strength and toughness does not occur even after a long-term post-weld heat treatment (PWHT, Post Weld Heat Treatment, PWHT). A high-strength steel sheet having excellent heat treatment resistance after welding and a method for producing the same are in weight percent, C: 0.1 to 0.3%, Si: 0.15 to 0.50%, Mn: 0.6 to 1 .2%, P: 0.035% or less, S: 0.020% or less, Al: 0.001-0.05%, Cr: 0.01-0.35%, Mo: 0.005-0. 2%, V: 0.005 to 0.05%, Nb: 0.001 to 0.05%, Ti: 0.001 to 0.05%, Ca: 0.0005 to 0.005%, Ni: 0 1 containing 0.5 to 0.5% and selected from the group consisting of Cu: 0.005 to 0.5%, Co: 0.005 to 0.2% and W: 0.005 to 0.2% More than seeds, the rest comprises Fe and inevitable impurities.
Description
本発明は湿潤硫化水素環境での原油精製設備、貯蔵タンク、熱交換器、反応炉、凝縮器などに用いられる鋼板に関し、より詳細には、溶接後熱処理(PWHT、Post Weld Heat Treatment)でも強度と靭性に優れた鋼板及びその製造方法に関する。 The present invention relates to a steel sheet used in a crude oil refining facility, a storage tank, a heat exchanger, a reaction furnace, a condenser, etc. in a wet hydrogen sulfide environment, and more specifically, it is strong even after a post-weld heat treatment (PWHT). And a steel plate excellent in toughness and a method for producing the same.
最近、石油の品薄現象及び高油価時代を迎え、劣悪な環境の油田が活発に開発される傾向により、原油の精製及び貯蔵用鋼材に対して厚物化が行われている。 Recently, with the trend of oil shortage and high oil prices, oil fields with poor environment have been actively developed, and thickening has been performed on steel for refinement and storage of crude oil.
上記のような鋼材の厚物化の他にも、鋼材を溶接した場合に溶接後の構造物の変形を防止し、形状及び寸法を安定させる目的で、溶接時に発生した応力を除去するために溶接後熱処理(PWHT、Post Weld Heat Treatment)を行う。しかし、長期間のPWHT工程を行った鋼板は、その組織の粗大化によって鋼板の引張強度が低下するという問題がある。 In addition to the thickening of steel materials as described above, welding is performed to remove stress generated during welding for the purpose of preventing deformation of the structure after welding and stabilizing the shape and dimensions when welding steel materials. Post heat treatment (PWHT, Post Weld Heat Treatment) is performed. However, a steel sheet that has been subjected to a long-term PWHT process has a problem that the tensile strength of the steel sheet decreases due to the coarsening of the structure.
即ち、長期間のPWHT後には基地組織(Matrix)及び結晶粒界の軟化、結晶粒成長、炭化物の粗大化などにより強度及び靭性が同時に低下する現象が引き起こされる。 That is, after PWHT for a long period of time, a phenomenon in which strength and toughness simultaneously decrease due to softening of the matrix structure (Matrix) and crystal grain boundaries, crystal grain growth, coarsening of carbides, and the like.
上記長期間のPWHT熱処理による物性の低下を防止するための手段として、特許文献1では重量%で、C:0.05〜0.20%,Si:0.02〜0.5%,Mn:0.2〜2.0%,Al:0.005〜0.10%、必要に応じて、Cu、Ni、Cr、Mo、V、Nb、Ti、B、Ca、希土類元素のうち1種又は2種以上を含み、残部が鉄及び不可避な不純物からなるスラブを加熱及び熱間圧延した後、室温で空冷し、Ac1〜Ac3変態点で加熱し徐冷する工程により、16時間までPWHTを保持できるようにした。 As means for preventing deterioration of physical properties due to the above-mentioned long-term PWHT heat treatment, in Patent Document 1, the weight percentage is C: 0.05 to 0.20%, Si: 0.02 to 0.5%, Mn: 0.2 to 2.0%, Al: 0.005 to 0.10%, if necessary, one of Cu, Ni, Cr, Mo, V, Nb, Ti, B, Ca, rare earth elements or After heating and hot rolling a slab containing two or more types, the balance being iron and inevitable impurities, air cooling at room temperature, and maintaining at PWHT up to 16 hours by heating at the Ac1 to Ac3 transformation points and gradually cooling I was able to do it.
しかし、上記技術に示されたPWHT保持時間は、厚物化及び溶接部の条件が苛酷な場合には非常に不足し、それ以上の長期間のPWHTの適用は不可能であるという問題がある。 However, the PWHT holding time shown in the above technique is very short when the conditions for thickening and welding are severe, and there is a problem that it is impossible to apply PWHT for a longer period of time.
従って、鋼材の厚物化及び溶接部の条件の苛酷化に伴い、長期間のPWHT後にも強度と靭性が低下しないPWHTに対する抵抗性の大きい鋼材が求められている。 Accordingly, as the steel material becomes thicker and the conditions of the weld zone become severe, there is a demand for a steel material having high resistance to PWHT in which strength and toughness do not decrease even after long-term PWHT.
本発明の一側面は、長期間の溶接後熱処理(Post Weld Heat Treatment、PWHT)後にも強度と靭性が低下しない溶接後熱処理(PWHT)抵抗性に優れた高強度鋼板及びその製造方法を提供する。 One aspect of the present invention provides a high-strength steel sheet having excellent post-weld heat treatment (PWHT) resistance that does not decrease strength and toughness even after long-term post-weld heat treatment (PWHT) and a method for manufacturing the same. .
本発明は重量%で、C:0.1〜0.3%、Si:0.15〜0.50%、Mn:0.6〜1.2%、P:0.035%以下、S:0.020%以下、Al:0.001〜0.05%、Cr:0.01〜0.35%、Mo:0.005〜0.2%、V:0.005〜0.05%、Nb:0.001〜0.05%、Ti:0.001〜0.05%、Ca:0.0005〜0.005%、Ni:0.05〜0.5%を含み、Cu:0.005〜0.5%、Co:0.005〜0.2%及びW:0.005〜0.2%からなる群より選択された1種以上、残りはFe及び不可避な不純物を含み、上記組成は下記関係式を満たす溶接後熱処理抵抗性に優れた高強度鋼板を提供する。
Cu+Ni+Cr+Mo:1.5%以下
Cr+Mo:0.4%以下
V+Nb:0.1%以下
Ca/S:1.0以下
The present invention is weight percent, C: 0.1-0.3%, Si: 0.15-0.50%, Mn: 0.6-1.2%, P: 0.035% or less, S: 0.020% or less, Al: 0.001 to 0.05%, Cr: 0.01 to 0.35%, Mo: 0.005 to 0.2%, V: 0.005 to 0.05%, Nb: 0.001-0.05%, Ti: 0.001-0.05%, Ca: 0.0005-0.005%, Ni: 0.05-0.5%, Cu: 0.00 One or more selected from the group consisting of 005 to 0.5%, Co: 0.005 to 0.2%, and W: 0.005 to 0.2%, the remainder including Fe and inevitable impurities, The composition provides a high-strength steel sheet excellent in post-weld heat treatment resistance that satisfies the following relational expression.
Cu + Ni + Cr + Mo: 1.5% or less Cr + Mo: 0.4% or less V + Nb: 0.1% or less Ca / S: 1.0 or less
また、本発明は上記組成範囲を満たす鋼スラブを1050〜1250℃の温度範囲で再加熱する段階と、上記再加熱した鋼スラブをTnr〜Tnr+100℃の温度範囲で熱間圧延する段階と、上記熱間圧延した熱延鋼板を850〜950℃の温度範囲で、1.3×t+(10〜30分)(但し、tは鋼材の厚さ(mm)を意味する)間保持する熱処理段階と、上記熱処理した鋼板を0.1〜10℃/secの冷却速度で冷却する段階とを含む溶接後熱処理抵抗性に優れた高強度鋼板の製造方法を提供する。 Further, step present invention to hot rolling at the stage and a temperature range of the re-heated steel slab T nr ~T nr + 100 ℃ reheating the steel slab satisfying the above composition range in a temperature range of from 1,050 to 1250 ° C. And the above hot-rolled hot-rolled steel sheet is held at a temperature range of 850 to 950 ° C. for 1.3 × t + (10 to 30 minutes) (where t means the thickness (mm) of the steel material). Provided is a method for producing a high-strength steel plate having excellent post-weld heat treatment resistance, including a heat treatment step and a step of cooling the heat-treated steel plate at a cooling rate of 0.1 to 10 ° C / sec.
本発明によると、500MPa級以上の強度を有し、100時間に及ぶPWHT後にも強度及び靭性が劣化せず、耐水素誘起割れ性に優れた圧力容器用鋼板を提供することができる。 According to the present invention, it is possible to provide a steel plate for a pressure vessel that has a strength of 500 MPa class or more, does not deteriorate in strength and toughness even after 100 hours of PWHT, and has excellent resistance to hydrogen-induced cracking.
以下では、本発明について詳しく説明する。 Hereinafter, the present invention will be described in detail.
まず、本発明の組成範囲について詳しく説明する(以下、重量%)。 First, the composition range of the present invention will be described in detail (hereinafter, wt%).
炭素(C)の含量は0.1〜0.3%に限定することが好ましい。Cは強度を向上させる元素で、その含量が0.1%未満では基地相の強度が低下し、0.3%を超えると組織内に偏析が発生し、水素誘起割れの抵抗性を低下させるという問題点がある。 The content of carbon (C) is preferably limited to 0.1 to 0.3%. C is an element that improves the strength. If the content is less than 0.1%, the strength of the matrix phase decreases, and if it exceeds 0.3%, segregation occurs in the structure and decreases the resistance to hydrogen-induced cracking. There is a problem.
シリコン(Si)の含量は0.15〜0.50%に限定することが好ましい。Siは脱酸及び固溶強化に効果的な元素で、衝撃遷移温度の上昇効果のために添加される元素である。このような効果を達成するためには、0.15%以上添加されなければならず、0.5%を超えて添加されると、溶接性が低下し、鋼板表面に酸化皮膜がひどく形成されるという問題点がある。 The silicon (Si) content is preferably limited to 0.15 to 0.50%. Si is an element effective for deoxidation and solid solution strengthening, and is an element added for increasing the impact transition temperature. In order to achieve such an effect, 0.15% or more must be added. If it exceeds 0.5%, the weldability deteriorates and an oxide film is severely formed on the steel sheet surface. There is a problem that.
マンガン(Mn)の含量は0.6〜1.2%に限定することが好ましい。MnはSとともに延伸された非金属介在物であるMnSを形成して常温伸び率及び低温靭性を低下させるため、1.2%以下に管理することが好ましい。しかし、本発明の特性上、Mnが0.6%未満添加されると、適切な強度を確保することが困難であるため、その含量は0.6〜1.2%に限定する。 The manganese (Mn) content is preferably limited to 0.6 to 1.2%. Since Mn forms MnS which is a non-metallic inclusion stretched with S and lowers the room temperature elongation and the low temperature toughness, it is preferably controlled to 1.2% or less. However, if Mn is added in an amount of less than 0.6% due to the characteristics of the present invention, it is difficult to ensure an appropriate strength, so the content is limited to 0.6 to 1.2%.
アルミニウム(Al)の含量は0.001〜0.5%に限定することが好ましい。Alは上記Siとともに製鋼工程において強力な脱酸剤の一つであり、0.001%未満では上記脱酸効果がわずかで、0.05%を超えて添加されると、上記脱酸効果は飽和し、製造原価が上昇するという問題点がある。 The aluminum (Al) content is preferably limited to 0.001 to 0.5%. Al is one of the powerful deoxidizers in the steel making process together with Si. If less than 0.001%, the deoxidation effect is slight, and if added over 0.05%, the deoxidation effect is There is a problem that the manufacturing cost increases due to saturation.
リン(P)は低温靭性を阻害する元素で、製鋼工程で除去するのに多くの費用がかかるため、0.035%以下の範囲内で管理することが好ましい。 Phosphorus (P) is an element that inhibits low-temperature toughness, and it takes a lot of money to remove it in the steelmaking process. Therefore, it is preferable to manage it within a range of 0.035% or less.
硫黄(S)もPとともに低温靭性に悪影響を与える元素で、Pと同様に製鋼工程で除去するのに多くの費用がかかり得るため、0.020%以下の範囲内で管理することが好ましい。 Sulfur (S) is an element that adversely affects low-temperature toughness together with P, and it can be costly to remove in the steel making process in the same manner as P. Therefore, it is preferable to manage it within a range of 0.020% or less.
クロム(Cr)の含量は0.01〜0.35%に限定することが好ましい。Crは強度を増加させる元素で、本発明において、強度増加の効果のためには0.01%以上添加されなければならないが、高価の元素であるため、0.35%を超えて添加すると、製造費用の上昇をもたらし、0.35%以下に管理することが好ましい。 The content of chromium (Cr) is preferably limited to 0.01 to 0.35%. Cr is an element that increases the strength, and in the present invention, it must be added 0.01% or more for the effect of increasing the strength, but since it is an expensive element, if added over 0.35%, It causes an increase in manufacturing cost and is preferably controlled to 0.35% or less.
モリブデン(Mo)の含量は0.005〜0.2%に限定することが好ましい。MoはCrと同様に、強度増大に有効な元素である上、硫化物による割れの発生を防止する元素である。上記効果のためには0.005%以上添加されなければならないが、Moも高価の元素で、製造費用の上昇をもたらすため、0.2%以下に限定することが好ましい。 The molybdenum (Mo) content is preferably limited to 0.005 to 0.2%. Like Cr, Mo is an element effective for increasing the strength, and is an element that prevents the occurrence of cracks due to sulfides. For the above effect, 0.005% or more must be added. However, Mo is also an expensive element and causes an increase in manufacturing cost, so it is preferable to limit it to 0.2% or less.
バナジウム(V)の含量は0.005〜0.05%に限定することが好ましい。VはCr、Moのように強度の増大に効果的な元素である。従って、0.005%以上添加されなければ、強度増大の効果が図れないが、高価であるため、0.05%以下添加することが好ましい。 The vanadium (V) content is preferably limited to 0.005 to 0.05%. V is an element effective for increasing the strength, such as Cr and Mo. Accordingly, if 0.005% or more is not added, the effect of increasing the strength cannot be achieved, but it is expensive, so 0.05% or less is preferably added.
ニオビオム(Nb)の含量は0.001〜0.05%に限定することが好ましい。Nbはオーステナイトに固溶されてオーステナイトの硬化能を増大させ、基地(Matrix)と整合する炭窒化物(Nb(C,N))として析出されることで、強度を増加させる重要な元素である。その含量が0.001%以上添加されなければ上記効果が得られないが、多量添加すると、連鋳過程で粗大な析出物となり、水素誘起割れのサイト(site)の役割をすることがあるため、その含量は0.05%以下に制限することが好ましい。 The content of niobium (Nb) is preferably limited to 0.001 to 0.05%. Nb is an important element that increases the strength by being dissolved in austenite to increase the hardening ability of austenite and precipitated as carbonitride (Nb (C, N)) consistent with the matrix (Matrix). . The above effect cannot be obtained unless the content is 0.001% or more, but if added in a large amount, coarse precipitates may be formed in the continuous casting process, which may serve as sites for hydrogen-induced cracking. The content is preferably limited to 0.05% or less.
チタン(Ti)の含量は0.001〜0.05%に限定することが好ましい。TiはNbと同様に炭窒化物(Ti(C,N))として析出されることで、強度を増加させる重要な元素である。その含量が0.001%以上添加されなければ上記効果が得られないが、多量添加すると、連鋳過程で粗大な析出物となり、水素誘起割れのサイトの役割をすることがあるため、その含量は0.05%以下に制限することが好ましい。 The content of titanium (Ti) is preferably limited to 0.001 to 0.05%. Ti is an important element that increases the strength by being precipitated as carbonitride (Ti (C, N)) in the same manner as Nb. The above effect cannot be obtained unless the content is 0.001% or more. However, if added in a large amount, coarse precipitates may be formed in the continuous casting process, which may serve as a site for hydrogen-induced cracking. Is preferably limited to 0.05% or less.
カルシウム(Ca)の含量は0.0005〜0.005%に限定することが好ましい。CaはCaSに生成されてMnSの非金属介在物を抑制するために添加するが、そのためには0.0005%以上添加されなければならない。しかし、その含量が0.005%を超えると、鋼中に含有されたOと反応して非金属介在物であるCaOを生成するため、その上限値は0.005%に限定することが好ましい。 The calcium (Ca) content is preferably limited to 0.0005 to 0.005%. Ca is generated in CaS and added to suppress non-metallic inclusions of MnS. For this purpose, 0.0005% or more must be added. However, if its content exceeds 0.005%, it reacts with O contained in the steel to produce CaO which is a non-metallic inclusion, so the upper limit is preferably limited to 0.005%. .
ニッケル(Ni)の含量は0.05〜0.5%に限定することが好ましい。Niは低温靭性の向上に最も効果的な元素で、その含量が0.05%以上添加されなければ上記効果が得られないが、高価の元素で、製造費用の上昇をもたらすため、0.5%以下に添加することが好ましい。 The nickel (Ni) content is preferably limited to 0.05 to 0.5%. Ni is the most effective element for improving low-temperature toughness, and the above effect cannot be obtained unless the content is 0.05% or more. However, since it is an expensive element and causes an increase in manufacturing cost, 0.5% It is preferable to add to below%.
本発明は、上記組成にCu、Co及びWからなる群より選択された1種以上を含む。 The present invention includes one or more selected from the group consisting of Cu, Co and W in the above composition.
銅(Cu)の含量は0.005〜0.5%を添加することが好ましい。Cuは固溶強化又はe−Cu析出などによる基地組織(matrix)の強化によるPWHT熱処理後にも強度の劣化を防止し、基地強化及びリカバリー抑制を通じて強度及び靭性の劣化を防止する。但し、高価であるため、その含量を0.005〜0.5%の範囲内で添加することが好ましい。 The content of copper (Cu) is preferably 0.005 to 0.5%. Cu prevents strength deterioration even after PWHT heat treatment by strengthening the matrix structure by solid solution strengthening or e-Cu precipitation, and prevents strength and toughness deterioration by strengthening the base and suppressing recovery. However, since it is expensive, it is preferable to add the content within the range of 0.005 to 0.5%.
コバルト(Co)の含量は0.005〜0.2%を添加することが好ましい。Coは基地組織の軟化を防止するのに効果的な元素ではあるが、高価であるため、0.005〜0.2%の範囲内で添加することが好ましい。 The content of cobalt (Co) is preferably 0.005 to 0.2%. Co is an effective element for preventing the softening of the matrix structure, but is expensive, so it is preferably added in the range of 0.005 to 0.2%.
タングステン(W)の含量は0.005〜0.2%添加することが好ましい。WはWCを形成したり、セメンタイト(Cementite)析出分率を減少させ、セメンタイトの成長/凝集抑制を防止して強度及び靭性の劣化を防止することができるという特性を有するため、0.005%以上添加することが好ましい。但し、上記Wは高価であるため、0.005〜0.2%の範囲内で添加することがより好ましい。 The content of tungsten (W) is preferably 0.005 to 0.2%. W has the characteristics that it can form WC, decrease the cementite precipitation rate, prevent the growth / aggregation of cementite and prevent deterioration of strength and toughness, so 0.005% It is preferable to add more. However, since W is expensive, it is more preferable to add it in the range of 0.005 to 0.2%.
本発明の鋼材は圧力容器用鋼材として使用することができる。これを考慮すると、下記Cu、Ni、Cr、Mo、V、Nbなどの元素の含量は次の関係を満たすことが好ましい。
Cu+Ni+Cr+Mo:1.5%以下
Cr+Mo:0.4%以下
V+Nb:0.1%以下
Ca/S:1.0以下
The steel material of the present invention can be used as a steel material for pressure vessels. Considering this, it is preferable that the content of elements such as Cu, Ni, Cr, Mo, V, and Nb below satisfy the following relationship.
Cu + Ni + Cr + Mo: 1.5% or less Cr + Mo: 0.4% or less V + Nb: 0.1% or less Ca / S: 1.0 or less
即ち、Cu+Ni+Cr+Mo、Cr+Mo及びV+Nbの関係は、圧力容器用鋼材の基本規格(ASTM A20)においてそれぞれ制限している数値で、これにより、Cu+Ni+Cr+Mo含量は1.5%以下、Cr+Mo含量は0.4%以下、V+Nb含量は0.1%以下に制限する。但し、本発明の実施形態により含まれない合金元素は0と計算することができる。 That is, the relationship of Cu + Ni + Cr + Mo, Cr + Mo, and V + Nb is a numerical value restricted respectively in the basic standard (ASTM A20) of steel materials for pressure vessels, whereby the Cu + Ni + Cr + Mo content is 1.5% or less and the Cr + Mo content is 0.4%. Hereinafter, the V + Nb content is limited to 0.1% or less. However, alloy elements not included in the embodiment of the present invention can be calculated as zero.
また、Ca/S比は、MnS介在物を球状化させて水素誘起割れの抵抗性を向上させる必須構成比で、1.0を超えると、その効果が期待し難いため、その比率は1.0以下になるよう調節する。 Further, the Ca / S ratio is an essential component ratio for improving the resistance of hydrogen-induced cracking by spheroidizing MnS inclusions, and when it exceeds 1.0, it is difficult to expect the effect. Adjust to 0 or less.
残りはFe及び不可避な不純物からなる。 The remainder consists of Fe and inevitable impurities.
以下、本発明の微細組織について詳しく説明する。 Hereinafter, the microstructure of the present invention will be described in detail.
上記のような組成を有する鋼を、後述する過程により適した制御圧延及び熱処理をすると、その微細組織はフェライト又はフェライトとパーライトの混合組織からなることができ、上記組織内には低温組織が出来るだけ含まれないことが好ましいが、10%まではベイナイトが含まれてよい。組織を上述した形態に制御する理由は、本発明で対象とする水素誘起割れに対する抵抗性に優れ、適切な強度と靭性を持たせるためである。 When the steel having the above composition is subjected to controlled rolling and heat treatment more suitable for the process described later, the microstructure can be composed of ferrite or a mixed structure of ferrite and pearlite, and a low temperature structure can be formed in the structure. Is preferably not included, but up to 10% may include bainite. The reason why the structure is controlled to the above-described form is that it has excellent resistance to hydrogen-induced cracking, which is a target of the present invention, and has appropriate strength and toughness.
また、水素誘起割れの抵抗性を確保するためには、水素誘起割れに脆弱なバンド組織がどれだけ形成されたのかを示すバンディングインデックス(Banding Index)(ASTM E−1268により測定される)が0.25以下であることが好ましい。上記バンディングインデックス(Banding Index)値が0.25を超えると、その微細組織では水素誘起割れの抵抗性が急激に低下する。 Further, in order to ensure the resistance of hydrogen-induced cracking, a banding index (measured by ASTM E-1268) indicating how much a band structure vulnerable to hydrogen-induced cracking has been formed is 0. .25 or less is preferable. When the banding index value exceeds 0.25, the resistance of hydrogen-induced cracking rapidly decreases in the microstructure.
鋼板の厚さ方向の中心部(3/8〜5/8t、t:鋼板の厚さ)のフェライト結晶粒の平均サイズは50μm以下であることが好ましい。これは上記フェライト結晶粒のサイズが大き過ぎると、強度と靭性が低下する恐れがあるためである。結晶粒のサイズに対する下限はないが、本発明で対象とする鋼材では、大体5μm未満の結晶粒を得ることが困難であるため、結晶粒のサイズは5μm以上にしてもよい。 The average size of the ferrite crystal grains in the central portion (3/8 to 5 / 8t, t: thickness of the steel plate) in the thickness direction of the steel plate is preferably 50 μm or less. This is because if the size of the ferrite crystal grains is too large, the strength and toughness may decrease. Although there is no lower limit to the size of the crystal grains, it is difficult to obtain crystal grains of less than 5 μm with the steel material targeted by the present invention, so the crystal grain size may be 5 μm or more.
以下では、本発明の製造方法について詳しく説明する。 Below, the manufacturing method of this invention is demonstrated in detail.
本発明は、上記組成範囲を満たす鋼スラブを1050〜1250℃の温度範囲で再加熱する。上記再加熱温度が1050℃より低いと、溶質原子の固溶が困難で、1250℃を超えると、オーステナイト結晶粒のサイズが過度に粗大となり、鋼板の性質を阻害するためである。 In the present invention, a steel slab satisfying the above composition range is reheated in a temperature range of 1050 to 1250 ° C. When the reheating temperature is lower than 1050 ° C., it is difficult to dissolve the solute atoms. When the reheating temperature is higher than 1250 ° C., the size of the austenite crystal grains becomes excessively large, which impairs the properties of the steel sheet.
上記再加熱後、本発明では水素誘起割れの抵抗性を有するためのフェライト+パーライトの2相複合組織を有し、且つバンディングインデックス(Banding Index)(ASTM E−1268により測定)が0.25以下になるよう再結晶制御圧延、熱処理、PWHT熱処理が求められる。 After the reheating, the present invention has a ferrite + pearlite two-phase composite structure for resistance to hydrogen-induced cracking, and a banding index (measured by ASTM E-1268) is 0.25 or less. Recrystallization controlled rolling, heat treatment, and PWHT heat treatment are required.
再結晶制御圧延は、上記再加熱された鋼スラブを未再結晶以上の温度で熱間圧延を施すことで行う。上記未再結晶温度であるTnrは、下記式から計算することができる。 Recrystallization controlled rolling is performed by subjecting the reheated steel slab to hot rolling at a temperature higher than non-recrystallization. T nr which is the non-recrystallization temperature can be calculated from the following equation.
Tnr(℃)=887+464×C+890×Ti+363×Al−357×Si+(6446×Nb−644×Nb1/2)+(732×V−230×V1/2) Tnr (° C.) = 887 + 464 × C + 890 × Ti + 363 × Al-357 × Si + (6446 × Nb−644 × Nb 1/2 ) + (732 × V−230 × V 1/2 )
バンディングインデックス(Banding Index)(ASTM E−1268により測定)値を0.25以下にするには、再結晶制御圧延が最も重要な変数であり、再結晶制御圧延はTnr〜Tnr+100℃の温度範囲の区間で各圧延パス当たりに10%以上の圧下率を加えて、累積圧下率30%以上を付与することが好ましい。これは、上記累積圧下率が30%未満では、バンディングインデックス(Banding Index)値の0.25以下を期待することができないためである。また、再結晶制御圧延の温度を限定する理由も、バンディングインデックスを制御するためであり、結晶粒が粗大化しない状態でバンド組織を抑制するためである。より詳細には、温度が再結晶域基準温度(Tnr)より低いと、オーステナイトがパンケーキ化し、バンディングインデックスが高くなるため好ましくなく、逆に、温度が高すぎると、結晶粒のサイズが大きくなりすぎるため好ましくない。 In order to reduce the banding index (measured by ASTM E-1268) value to 0.25 or less, the recrystallization controlled rolling is the most important variable, and the recrystallization controlled rolling is performed between T nr and T nr + 100 ° C. It is preferable that a rolling reduction rate of 10% or more is added to each rolling pass in the temperature range to give a cumulative rolling reduction rate of 30% or more. This is because when the cumulative rolling reduction is less than 30%, it is not possible to expect a banding index value of 0.25 or less. Moreover, the reason for limiting the temperature of the recrystallization controlled rolling is to control the banding index and to suppress the band structure in a state where the crystal grains are not coarsened. More specifically, if the temperature is lower than the recrystallization zone reference temperature (T nr ), austenite is pancakeed and the banding index becomes high, which is not preferable. Conversely, if the temperature is too high, the size of the crystal grains becomes large. Since it becomes too much, it is not preferable.
以後、上記熱間圧延を行い、冷却された熱延鋼板を熱処理する。上記熱処理は850〜950℃の温度範囲で、1.3×t+(10〜30分)(但し、tは鋼材の厚さ(mm)を意味する)の条件で保持する。上記熱処理温度が850℃未満では、固溶溶質元素の再固溶が困難で、強度を確保することが困難となり、熱処理温度が950℃を超えると、結晶粒の成長が起きて低温靭性を阻害する。 Thereafter, the hot rolling is performed, and the cooled hot-rolled steel sheet is heat-treated. The heat treatment is held in the temperature range of 850 to 950 ° C. under the conditions of 1.3 × t + (10 to 30 minutes) (where t means the thickness (mm) of the steel material). If the heat treatment temperature is less than 850 ° C., it is difficult to re-dissolve the solid solution solute element and it is difficult to ensure the strength. If the heat treatment temperature exceeds 950 ° C., crystal grain growth occurs and inhibits low temperature toughness. To do.
上記熱処理保持時間を制約する理由は、上記保持時間が1.3×t+10分(tは鋼材の厚さ(mm)を意味する)より短いと、組織の均質化が困難で、1.3×t+30分(tは鋼材の厚さ(mm)を意味する)を超えると、生産性を阻害するためである。 The reason for limiting the heat treatment holding time is that when the holding time is shorter than 1.3 × t + 10 minutes (t means the thickness (mm) of the steel material), it is difficult to homogenize the structure. This is because when t + 30 minutes (t means the thickness (mm) of the steel material) is exceeded, productivity is hindered.
上記保持された鋼板を中心部の冷却速度を基準として0.1〜10℃/secで冷却する。それ以下の冷却速度では冷却中にフェライト結晶粒の粗大化が発生する恐れがあり、それ以上の冷却速度では過大な第2相(ベイナイト分率10%以上)が発生する可能性が高いためである。 The held steel sheet is cooled at 0.1 to 10 ° C./sec based on the cooling rate at the center. If the cooling rate is lower than that, ferrite crystal grains may be coarsened during cooling, and if the cooling rate is higher than that, an excessive second phase (more than 10% bainite fraction) is likely to occur. is there.
上記冷却速度は、鋼板中心部のフェライトの平均結晶粒のサイズを50μm以下に調整するためである。 The cooling rate is to adjust the average crystal grain size of ferrite in the center of the steel sheet to 50 μm or less.
上記熱処理工程を経て製造された本発明の鋼板は、圧力容器の製作時に付加される溶接工程により残留応力を除去するなどのためにPWHT処理が必要である。一般的に長期間のPWHT熱処理後には強度及び靭性の劣化が発生するが、上記本発明により製造された鋼板は、通常のPWHT温度条件である600〜640℃で、長期間(〜100時間)実施しても強度及び靭性の大きな低下なく溶接施工が可能であるという長所がある。特に、本発明の鋼板は、100時間のPWHT後にも450MPa以上の引張強度を有し、−50℃でのシャルピー衝撃エネルギー値が50J以上を満たす。 The steel sheet of the present invention manufactured through the above heat treatment process needs PWHT treatment in order to remove residual stress by a welding process added at the time of manufacturing the pressure vessel. Generally, deterioration of strength and toughness occurs after long-term PWHT heat treatment, but the steel sheet produced according to the present invention has a normal PWHT temperature condition of 600 to 640 ° C. and a long period (up to 100 hours). Even if it is carried out, there is an advantage that welding can be performed without a great decrease in strength and toughness. In particular, the steel sheet of the present invention has a tensile strength of 450 MPa or more even after 100 hours of PWHT, and satisfies a Charpy impact energy value at −50 ° C. of 50 J or more.
以下、本発明の実施例について詳しく説明する。但し、本発明は下記実施例に限定されない。 Examples of the present invention will be described in detail below. However, the present invention is not limited to the following examples.
下記表1には発明鋼と比較鋼の化学成分をそれぞれ示した。表1のような組成を有する鋼スラブを表2の鋼板厚、再加熱温度、圧延、熱処理及び冷却して鋼板を製造した。 Table 1 below shows the chemical components of the inventive steel and the comparative steel. Steel slabs having the composition shown in Table 1 were manufactured by manufacturing the steel plate thickness, reheating temperature, rolling, heat treatment and cooling shown in Table 2.
上記条件で製造された鋼板に対し、PWHTなどを下記表2のような条件で実施した後、降伏強度、引張強度、低温靭性及びクラックの長さ比(CLR、Crack Length Ratio、%)を調べ、その結果を下記表2に示した。 After the steel sheet manufactured under the above conditions is subjected to PWHT etc. under the conditions shown in Table 2 below, the yield strength, tensile strength, low temperature toughness, and crack length ratio (CLR, Crack Length Ratio,%) are examined. The results are shown in Table 2 below.
但し、低温靭性は、−50℃でVノッチを有する試片に対し、シャルピー衝撃試験を行って得たシャルピー衝撃エネルギー値で評価し、下記表2におけるクラックの長さ比(Crack Length Ratio、%)はNACE TM0277規格により測定したものである。 However, the low temperature toughness was evaluated by a Charpy impact energy value obtained by conducting a Charpy impact test on a specimen having a V notch at −50 ° C., and the crack length ratio (Crack Length Ratio,%) in Table 2 below. ) Is measured according to NACE TM0277 standard.
上記表1及び2の結果から分かるように、本発明の組成及製造条件を満たす発明鋼は、PWHT時間が50時間以上100時間になっても強度と靭性が低下しない。比較鋼は本発明の組成及び製造条件から外れるもので、発明鋼と比べると、PWHT時間が短い場合は、発明鋼と略同等の強度と靭性を示すが、PWHT時間が50時間以上と長くなるにつれ、発明鋼より強度と靭性が著しく劣化することが分かる。 As can be seen from the results in Tables 1 and 2 above, the strength and toughness of the invention steel satisfying the composition and production conditions of the present invention does not decrease even when the PWHT time is 50 hours or more and 100 hours. The comparative steel deviates from the composition and production conditions of the present invention. Compared with the inventive steel, when the PWHT time is short, it shows substantially the same strength and toughness as the inventive steel, but the PWHT time is as long as 50 hours or more. It can be seen that the strength and toughness of the steel according to the invention are significantly deteriorated.
特に、発明鋼では、100時間のPWHT後にも低温靭性値の低下が大きくないが、比較鋼では低温靭性値の低下がひどいことが分かる。 In particular, it can be seen that the low-temperature toughness value of the invention steel is not significantly reduced even after 100 hours of PWHT, but the low-temperature toughness value of the comparative steel is severely reduced.
一方、H2S(Sour Gas)ガス雰囲気下での水素誘起割れの抵抗性を示すCLR(Crack Length Ratio、%)は、発明鋼が抜群に優れていることが分かる。このように、発明鋼が、CLRにおいて優れる理由が、フェライト及びパーライトの複合組織で構成される微細組織の均質化の程度を示すバンディングインデックス(Banding Index)が0.25以下に低く制御されるためであることが本実施例により分かる。 On the other hand, CLR (Crack Length Ratio,%) indicating the resistance of hydrogen-induced cracking in an H 2 S (Sour Gas) gas atmosphere shows that the inventive steel is excellent. Thus, the reason why the inventive steel is superior in CLR is that the banding index indicating the degree of homogenization of the microstructure composed of the composite structure of ferrite and pearlite is controlled to be lower than 0.25. It can be seen from this example that this is true.
本発明は重量%で、C:0.1〜0.3%、Si:0.15〜0.50%、Mn:0.6〜1.2%、P:0.035%以下、S:0.020%以下、Al:0.001〜0.05%、Cr:0.01〜0.35%、Mo:0.005〜0.2%、V:0.005〜0.05%、Nb:0.001〜0.05%、Ti:0.001〜0.05%、Ca:0.0005〜0.005%、Ni:0.05〜0.5%を含み、Cu:0.005〜0.5%、Co:0.005〜0.2%及びW:0.005〜0.2%からなる群より選択された1種以上、残りはFe及び不可避な不純物を含み、上記組成は下記関係式を満たす溶接後熱処理抵抗性に優れた高強度鋼板を提供する。
Cu+Ni+Cr+Mo:1.5%以下
Cr+Mo:0.4%以下
V+Nb:0.1%以下
Ca/S:1.0以上
The present invention is weight percent, C: 0.1-0.3%, Si: 0.15-0.50%, Mn: 0.6-1.2%, P: 0.035% or less, S: 0.020% or less, Al: 0.001 to 0.05%, Cr: 0.01 to 0.35%, Mo: 0.005 to 0.2%, V: 0.005 to 0.05%, Nb: 0.001-0.05%, Ti: 0.001-0.05%, Ca: 0.0005-0.005%, Ni: 0.05-0.5%, Cu: 0.00 One or more selected from the group consisting of 005 to 0.5%, Co: 0.005 to 0.2%, and W: 0.005 to 0.2%, the remainder including Fe and inevitable impurities, The composition provides a high-strength steel sheet excellent in post-weld heat treatment resistance that satisfies the following relational expression.
Cu + Ni + Cr + Mo: 1.5% or less Cr + Mo: 0.4% or less V + Nb: 0.1% or less Ca / S: 1.0 or more
本発明の鋼材は圧力容器用鋼材として使用することができる。これを考慮すると、下記Cu、Ni、Cr、Mo、V、Nbなどの元素の含量は次の関係を満たすことが好ましい。
Cu+Ni+Cr+Mo:1.5%以下
Cr+Mo:0.4%以下
V+Nb:0.1%以下
Ca/S:1.0以上
The steel material of the present invention can be used as a steel material for pressure vessels. Considering this, it is preferable that the content of elements such as Cu, Ni, Cr, Mo, V, and Nb below satisfy the following relationship.
Cu + Ni + Cr + Mo: 1.5% or less Cr + Mo: 0.4% or less V + Nb: 0.1% or less Ca / S: 1.0 or more
また、Ca/S比は、MnS介在物を球状化させて水素誘起割れの抵抗性を向上させる必須構成比で、1.0未満の場合には、その効果が期待し難いため、その比率は1.0以上になるよう調節する。
Further, the Ca / S ratio is an essential component ratio for improving the resistance of hydrogen-induced cracking by spheroidizing MnS inclusions, and when the ratio is less than 1.0, the effect is difficult to expect. Adjust to 1.0 or higher .
Claims (7)
上記組成は下記関係式を満たす溶接後熱処理抵抗性に優れた高強度鋼板。
Cu+Ni+Cr+Mo:1.5%以下
Cr+Mo:0.4%以下
V+Nb:0.1%以下
Ca/S:1.0以下 C: 0.1-0.3%, Si: 0.15-0.50%, Mn: 0.6-1.2%, P: 0.035% or less, S: 0.020 % Or less, Al: 0.001 to 0.05%, Cr: 0.01 to 0.35%, Mo: 0.005 to 0.2%, V: 0.005 to 0.05%, Nb: 0 0.001 to 0.05%, Ti: 0.001 to 0.05%, Ca: 0.0005 to 0.005%, Ni: 0.05 to 0.5%, Cu: 0.005 to 0 One or more selected from the group consisting of 0.5%, Co: 0.005-0.2%, and W: 0.005-0.2%, the remainder including Fe and inevitable impurities,
The above composition is a high-strength steel sheet excellent in post-weld heat treatment resistance satisfying the following relational expression.
Cu + Ni + Cr + Mo: 1.5% or less Cr + Mo: 0.4% or less V + Nb: 0.1% or less Ca / S: 1.0 or less
上記組成は下記関係式を満たす鋼スラブを1050〜1250℃の温度範囲で再加熱する段階と、
上記再加熱した鋼スラブをTnr〜Tnr+100℃の温度範囲で熱間圧延する段階と、
上記熱間圧延した熱延鋼板を850〜950℃の温度範囲で、1.3×t+(10〜30分)(但し、tは鋼材の厚さ(mm)を意味する)間保持する熱処理段階と、
上記熱処理した鋼板を0.1〜10℃/secの冷却速度で冷却する段階と、を含む溶接後熱処理抵抗性に優れた高強度鋼板の製造方法。
Cu+Ni+Cr+Mo:1.5%以下
Cr+Mo:0.4%以下
V+Nb:0.1%以下
Ca/S:1.0以下 C: 0.1-0.3%, Si: 0.15-0.50%, Mn: 0.6-1.2%, P: 0.035% or less, S: 0.020 % Or less, Al: 0.001 to 0.05%, Cr: 0.01 to 0.35%, Mo: 0.005 to 0.2%, V: 0.005 to 0.05%, Nb: 0 0.001 to 0.05%, Ti: 0.001 to 0.05%, Ca: 0.0005 to 0.005%, Ni: 0.05 to 0.5%, Cu: 0.005 to 0 One or more selected from the group consisting of 0.5%, Co: 0.005-0.2%, and W: 0.005-0.2%, the remainder including Fe and inevitable impurities,
The above composition is a step of reheating a steel slab satisfying the following relational expression in a temperature range of 1050 to 1250 ° C .;
Hot rolling the reheated steel slab in a temperature range of T nr to T nr + 100 ° C .;
Heat treatment stage for holding the hot-rolled hot-rolled steel sheet in the temperature range of 850 to 950 ° C. for 1.3 × t + (10 to 30 minutes) (where t means the thickness (mm) of the steel material). When,
A step of cooling the heat-treated steel sheet at a cooling rate of 0.1 to 10 ° C./sec.
Cu + Ni + Cr + Mo: 1.5% or less Cr + Mo: 0.4% or less V + Nb: 0.1% or less Ca / S: 1.0 or less
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