WO2022139204A1 - 표면품질 및 내 라멜라티어링 품질이 우수한 스팀드럼용 극후물 강재 및 그 제조방법 - Google Patents
표면품질 및 내 라멜라티어링 품질이 우수한 스팀드럼용 극후물 강재 및 그 제조방법 Download PDFInfo
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- WO2022139204A1 WO2022139204A1 PCT/KR2021/017415 KR2021017415W WO2022139204A1 WO 2022139204 A1 WO2022139204 A1 WO 2022139204A1 KR 2021017415 W KR2021017415 W KR 2021017415W WO 2022139204 A1 WO2022139204 A1 WO 2022139204A1
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- thick steel
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 80
- 239000010959 steel Substances 0.000 title claims abstract description 80
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 28
- 239000000463 material Substances 0.000 claims description 97
- 238000010438 heat treatment Methods 0.000 claims description 56
- 238000005242 forging Methods 0.000 claims description 50
- 230000009467 reduction Effects 0.000 claims description 32
- 238000000034 method Methods 0.000 claims description 29
- 238000005096 rolling process Methods 0.000 claims description 29
- 229910052799 carbon Inorganic materials 0.000 claims description 28
- 229910052804 chromium Inorganic materials 0.000 claims description 23
- 229910052750 molybdenum Inorganic materials 0.000 claims description 23
- 229910001566 austenite Inorganic materials 0.000 claims description 22
- 230000001186 cumulative effect Effects 0.000 claims description 22
- 229910052748 manganese Inorganic materials 0.000 claims description 22
- 229910052759 nickel Inorganic materials 0.000 claims description 20
- 229910052758 niobium Inorganic materials 0.000 claims description 18
- 229910052719 titanium Inorganic materials 0.000 claims description 16
- 229910052802 copper Inorganic materials 0.000 claims description 14
- 239000002244 precipitate Substances 0.000 claims description 14
- 239000002344 surface layer Substances 0.000 claims description 14
- 229910052782 aluminium Inorganic materials 0.000 claims description 13
- 239000012535 impurity Substances 0.000 claims description 13
- 229910052710 silicon Inorganic materials 0.000 claims description 12
- 229910052717 sulfur Inorganic materials 0.000 claims description 12
- 229910052720 vanadium Inorganic materials 0.000 claims description 12
- 229910052791 calcium Inorganic materials 0.000 claims description 11
- 238000005098 hot rolling Methods 0.000 claims description 11
- 229910052698 phosphorus Inorganic materials 0.000 claims description 10
- 238000003466 welding Methods 0.000 claims description 10
- 229910000859 α-Fe Inorganic materials 0.000 claims description 9
- 239000002245 particle Substances 0.000 claims description 8
- 238000001816 cooling Methods 0.000 claims description 7
- 239000011159 matrix material Substances 0.000 claims description 6
- 229910001562 pearlite Inorganic materials 0.000 claims description 5
- 239000002131 composite material Substances 0.000 claims description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 50
- 239000011651 chromium Substances 0.000 description 41
- 239000010949 copper Substances 0.000 description 38
- 239000011572 manganese Substances 0.000 description 38
- 239000010955 niobium Substances 0.000 description 29
- 239000010936 titanium Substances 0.000 description 24
- 230000000694 effects Effects 0.000 description 19
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 15
- 230000008569 process Effects 0.000 description 15
- 239000011575 calcium Substances 0.000 description 14
- 239000000047 product Substances 0.000 description 14
- 238000005266 casting Methods 0.000 description 13
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 12
- 229910045601 alloy Inorganic materials 0.000 description 11
- 239000000956 alloy Substances 0.000 description 11
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 10
- 239000000203 mixture Substances 0.000 description 10
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 8
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 8
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 8
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 8
- 239000011733 molybdenum Substances 0.000 description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 7
- 239000012467 final product Substances 0.000 description 7
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 6
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 6
- 230000007423 decrease Effects 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 238000001953 recrystallisation Methods 0.000 description 6
- 239000010703 silicon Substances 0.000 description 6
- 239000011593 sulfur Substances 0.000 description 6
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 6
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 5
- 230000007547 defect Effects 0.000 description 5
- 239000006104 solid solution Substances 0.000 description 5
- 238000005728 strengthening Methods 0.000 description 5
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 238000000227 grinding Methods 0.000 description 4
- 239000011574 phosphorus Substances 0.000 description 4
- 238000003303 reheating Methods 0.000 description 4
- 238000005204 segregation Methods 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 150000001247 metal acetylides Chemical class 0.000 description 3
- 230000001376 precipitating effect Effects 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- 239000011800 void material Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000003917 TEM image Methods 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000004615 ingredient Substances 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 238000009628 steelmaking Methods 0.000 description 2
- 238000005482 strain hardening Methods 0.000 description 2
- 238000005496 tempering Methods 0.000 description 2
- 239000002918 waste heat Substances 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910001208 Crucible steel Inorganic materials 0.000 description 1
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910000797 Ultra-high-strength steel Inorganic materials 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- 238000011179 visual inspection Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
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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
- C22C38/02—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
- C22C38/18—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
-
- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
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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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- 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
- C21D7/00—Modifying the physical properties of iron or steel by deformation
- C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
-
- 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
- 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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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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
- 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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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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
- 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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0273—Final recrystallisation annealing
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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
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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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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- 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
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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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
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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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
- C22C38/46—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
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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
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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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
Definitions
- the present invention relates to a steel material that can be used in petrochemical power plants and boilers, and a method for manufacturing the same, and more particularly, to an ultra-thick steel material for a steam drum with excellent surface quality and lamellar tearing resistance and a method for manufacturing the same it's about
- a boiler steam drum used in power generation facilities is a container that separates steam and water by storing the steam evaporated from the boiler under a constant pressure.
- Waste heat boilers are often used to utilize heat generated from chemical reactions or combustion reactions, and a steam drum is always required when a waste heat boiler is installed.
- the thickening of steel materials used for large-scale and large-capacity storage is continuously increasing. As the thickness of the steel increases, the total rolling reduction decreases, so the microstructure increases, and the material tends to deteriorate due to defects in the material such as inclusions or segregation. Therefore, in order to improve the internal and external soundness of steel, there is a trend to reduce the concentration of impurities such as non-metallic inclusions or segregation, or to limit cracks and voids in the surface and inside the material.
- Patent Document 1 related to this is a technology for applying a drop-down in the roughing process of thick plates. From the reduction ratio for each pass set to be close to the design allowable values (load and torque) of the rolling mill, the limit reduction ratio for each thickness at which plate engagement occurs is determined. The technology to determine the thickness of the roughing mill and to distribute the reduction ratio by adjusting the index of the thickness ratio for each pass in order to secure the target thickness of the roughing mill This provides a manufacturing method that can apply an average reduction ratio of about 27.5% in the final 3 passes of rough rolling based on 80mmt.
- the average reduction ratio of the entire thickness of the product is measured, and in the case of an extremely thick material having a maximum thickness of 233 mmt or more, it is technically difficult to apply a high strain to the center where the residual voids exist.
- One of the other methods of manufacturing ultra-thick products is to utilize a forging machine with a higher effective deformation amount per pass than a rolling mill.
- the casting slab extracted from the heating furnace is erected vertically to give the overall width forging reduction of 400mm or more, and the width forging pass is performed with the reduction amount within 2 passes, which is the condition within the buckling limit reduction amount of the width forging pass.
- surface defects may occur due to local strain concentration in the blast forging process.
- the defect propagates during the forging process and the surface quality in the product state after rolling may be further deteriorated.
- Patent Document 3 a material provided with a predetermined alloy composition is heated to 1200 to 1350° C., hot forging is performed with a cumulative rolling reduction of 25% or more, and heated to an Ac3 point or higher and 1200° C. or lower, and the cumulative rolling reduction is Hot-rolling to 40% or more, reheating to an Ac3 point or higher and 1050 °C or lower, quenching from a temperature of an Ac3 point or higher to a lower temperature of 350 °C or lower or an Ar3 point or lower, and tempering at a temperature of 450 °C to 700 °C It is disclosed that a thick high-strength steel sheet of 100 mmt or more having a yield strength of 620 MPa or more can be manufactured through the process of performing the
- the carbon equivalent (Ceq) and hardenability index (DI) are high, so it is not only vulnerable to surface cracks during casting, but also in the case of a steam drum steel manufactured by normalizing heat treatment The process conditions cannot be easily applied.
- the carbon equivalent (Ceq) and hardenability index (DI) are high, cracks in the surface layer of the cast slab are easily generated due to the generation of the hard structure in the surface layer during the secondary cooling process of steelmaking, and the cracks propagate during the forging process, so that the final product may deteriorate the surface quality of
- Patent Document 1 Korean Patent Publication No. 10-2012-0075246 (published on July 6, 2012)
- Patent Document 2 Korean Patent Publication No. 10-2012-0074039 (published on Jul. 5, 2012)
- Patent Document 3 Korean Patent Publication No. 10-2017-0095307 (published on August 22, 2017)
- an extremely thick steel material for a steam drum having excellent surface quality and lamellar tearing resistance and a method for manufacturing the same can be provided.
- the ultra-thick steel material according to an aspect of the present invention, by weight%, C: 0.2 to 0.3%, Si: 0.05 to 0.5%, Mn: 1.0 to 2.0%, Al: 0.005 to 0.1%, P: 0.01% or less, S: 0.015% or less, Nb: 0.001 to 0.02%, V: 0.001 to 0.03%, Ti: 0.001 to 0.03%, Cr: 0.01 to 0.3%, Mo: 0.01 to 0.12%, Cu: 0.01 to 0.4%, Ni: 0.05 to 0.4%, Ca: 0.0005 to 0.004%, the remaining Fe and other unavoidable impurities, Ceq according to the following relation 1 satisfies the range of 0.5 to 0.6, and an average particle size of 20 ⁇ m or less.
- the hard tissue fraction in the surface layer which is a region from the surface to 10 mm in the thickness direction, is 5 area% or less, and 3/8t to 5/8t (here, t means the thickness of the steel material (mm))
- the porosity of the central region, which is the region, is 0.1 mm 3 /g or less, and among the precipitates observed in the steel cross section after the post-welding heat treatment (PWHT), there may be more than 5 fine VC precipitates with a diameter of 5 to 15 nm per 1 ⁇ m 2 .
- [C], [Mn], [Cr], [Mo], [V], [Ni] and [Cu] are respectively C, Mn, Cr, Mo, V, Ni and It means the content (wt%) of Cu, and 0 is substituted if these components are not intentionally added.
- the thickness of the steel may be 133 ⁇ 250mm.
- the tensile strength of the steel may be 550 ⁇ 690 MPa.
- the thickness direction cross-sectional shrinkage (ZRA) of the steel material may be 35% or more.
- the maximum surface crack depth of the steel may be 0.1 mm or less (including 0).
- the method of manufacturing an ultra-thick steel material according to an aspect of the present invention in weight%, C: 0.2 to 0.3%, Si: 0.05 to 0.5%, Mn: 1.0 to 2.0%, Al: 0.005 to 0.1%, P: 0.01 % or less, S: 0.015% or less, Nb: 0.001 to 0.02%, V: 0.001 to 0.03%, Ti: 0.001 to 0.03%, Cr: 0.01 to 0.3%, Mo: 0.01 to 0.12%, Cu: 0.01 to 0.4% , Ni: 0.05 to 0.4%, Ca: 0.0005 to 0.004%, including the remaining Fe and other unavoidable impurities, Ceq according to the following relation 1 satisfies the range of 0.5 to 0.6, and the average particle size of prior austenite is 500 ⁇ m or less, preparing a slab having a thickness of 650 mm or more; First heating the slab in a temperature range of 1100 ⁇ 1300 °C; providing a primary intermediate material having a thickness of 450 to
- the central porosity of the secondary intermediate material may be 0.1mm 3 /g or less.
- the maximum surface crack depth of the hot rolled material may be 2 ⁇ m or less (including 0).
- an ultra-thick steel material for a steam drum having excellent surface quality and lamellar tearing resistance and a method for manufacturing the same can be provided.
- the present invention relates to an ultra-thick steel material for a steam drum having excellent surface quality and lamellar tearing resistance and a method for manufacturing the same, and preferred embodiments of the present invention will be described below. Embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The present embodiments are provided in order to further detailed the present invention to those of ordinary skill in the art to which the present invention pertains.
- the ultra-thick steel material for a steam drum is, by weight, C: 0.2 to 0.3%, Si: 0.05 to 0.5%, Mn: 1.0 to 2.0%, Al: 0.005 to 0.1%, P: 0.01 % or less, S: 0.015% or less, Nb: 0.001 to 0.02%, V: 0.001 to 0.03%, Ti: 0.001 to 0.03%, Cr: 0.01 to 0.3%, Mo: 0.01 to 0.12%, Cu: 0.01 to 0.4% , Ni: 0.05 to 0.4%, Ca: 0.0005 to 0.004%, remaining Fe and other unavoidable impurities, Ceq according to the following relation 1 satisfies the range of 0.5 to 0.6, and ferrite and pearlite having an average particle size of 20 ⁇ m or less It has a composite structure as a matrix, and the hard tissue fraction in the surface layer, which is a region from the surface to 10 mm in the thickness direction, is 5 area% or less, 3/8t to 5/8
- [C], [Mn], [Cr], [Mo], [V], [Ni] and [Cu] are respectively C, Mn, Cr, Mo, V, Ni and It means the content (wt%) of Cu, and 0 is substituted if these components are not intentionally added.
- alloy composition of the present invention will be described in more detail.
- % and ppm described in relation to the alloy composition are based on weight.
- carbon (C) is the most important element for securing basic strength, it needs to be contained in steel within an appropriate range, and 0.20% or more of carbon (C) may be added to obtain this additive effect. Preferably, 0.22% or more of carbon (C) may be added.
- the present invention can limit the carbon (C) content to 0.30%. More preferably, the upper limit of the carbon (C) content may be 0.26%.
- Silicon (Si) is a substitutional element that improves the strength of steel through solid solution strengthening and has a strong deoxidation effect, so it is an essential element in the manufacture of clean steel. Therefore, silicon (Si) may be added in an amount of 0.05% or more, more preferably 0.20% or more.
- Si silicon
- MA Martensite-Austenite
- the upper limit of the content is 0.50% can be limited to More preferably, the upper limit of the content of silicon (Si) may be 0.40%.
- Manganese (Mn) is a useful element for improving strength by solid solution strengthening and improving hardenability to generate a low-temperature transformation phase. Therefore, in order to secure a tensile strength of 550 MPa or more, it is preferable to add 1.0% or more of manganese (Mn). More preferably, the manganese (Mn) content may be 1.1% or more. On the other hand, manganese (Mn) forms MnS, a non-metallic inclusion elongated together with sulfur (S), which reduces toughness and acts as a factor for lowering elongation when tensile in the thickness direction. can be Therefore, it is preferable to manage the manganese (Mn) content to 2.0% or less, and more preferably, the manganese (Mn) content may be 1.5% or less.
- Aluminum (Al) is one of the strong deoxidizers in the steelmaking process together with silicon (Si), and in order to obtain this effect, it is preferable to be added in an amount of 0.005% or more. More preferably, the lower limit of the aluminum (Al) content may be 0.01%.
- the aluminum (Al) content is excessive, the fraction of Al 2 O 3 in the oxidative inclusions generated as a result of deoxidation is excessively increased and the size becomes coarse, and there is a problem that it becomes difficult to remove the inclusions during refining, It may be a factor that deteriorates the lamellar tearing resistance. Therefore, it is preferable to manage the aluminum (Al) content to 0.1% or less. More preferably, the aluminum (Al) content may be 0.07% or less.
- Phosphorus (P) and sulfur (S) are elements that induce embrittlement at grain boundaries or form coarse inclusions. Therefore, in order to improve the brittle crack propagation resistance, it is preferable to limit the phosphorus (P) to 0.010% or less, and to limit the sulfur (S) to 0.0015% or less.
- Niobium (Nb) is an element that improves the strength of the base material by precipitating it in the form of NbC or NbCN.
- niobium (Nb) dissolved in high-temperature reheating is very finely precipitated in the form of NbC during rolling to suppress recrystallization of austenite, and thus has an effect of refining the structure. Accordingly, niobium (Nb) is preferably added in an amount of 0.001% or more, and more preferably, the niobium (Nb) content may be 0.005% or more.
- the upper limit of the niobium (Nb) content It is preferable to limit it to 0.02%. More preferably, the niobium (Nb) content may be 0.017% or less.
- vanadium (V) Since vanadium (V) is almost completely re-dissolved during reheating, the reinforcing effect by precipitation or solid solution during subsequent rolling is insignificant, but it has an effect of improving strength by precipitating as very fine carbonitrides in the subsequent heat treatment process such as PWHT. In order to sufficiently obtain this effect, it is necessary to add 0.001% or more of vanadium (V). More preferably, the lower limit of the vanadium (V) content may be 0.01%. On the other hand, if the content is excessive, the strength and hardness of the base material and welded portion are excessively increased, which may act as factors such as surface cracks during steam drum processing, and the manufacturing cost is rapidly increased, which is not commercially advantageous. Accordingly, the vanadium (V) content may be limited to 0.03% or less. More preferably, the vanadium (V) content may be 0.02% or less.
- Titanium (Ti) is a component that significantly improves low-temperature toughness by precipitating as TiN during reheating to suppress the growth of crystal grains in the base material and in the heat-affected zone of welding. In order to obtain such an effect, it is preferable that 0.001% or more of titanium (Ti) is added. On the other hand, when titanium (Ti) is excessively added, the low-temperature toughness may be reduced due to clogging of the playing nozzle or crystallization of the center. In addition, since titanium (Ti) is combined with nitrogen (N) to form a coarse TiN precipitate in the center of the thickness, thereby reducing the elongation of the product, the lamellar tearing resistance of the final material may be deteriorated. Accordingly, the titanium (Ti) content may be 0.03% or less. A preferred titanium (Ti) content may be 0.025% or less, and a more preferred titanium (Ti) content may be 0.018% or less.
- Chromium (Cr) is a component that increases the hardenability and forms a low-temperature transformation structure, thereby increasing the yield yield and tensile strength. In addition, it is also a component effective in preventing a decrease in strength by slowing the decomposition rate of cementite during tempering after quenching or heat treatment after welding. For this effect, 0.01% or more of chromium (Cr) may be added.
- the present invention may limit the upper limit of the chromium (Cr) content to 0.30%.
- the upper limit of the preferred chromium (Cr) content may be 0.25%.
- Molybdenum (Mo) is an element that increases grain boundary strength and has a large solid solution strengthening effect in ferrite, and effectively contributes to increase the strength and ductility of the product.
- molybdenum (Mo) has an effect of preventing a decrease in toughness due to grain boundary segregation of an impurity element such as phosphorus (P). For this effect, 0.10% or more of molybdenum (Mo) may be added.
- Molybdenum (Mo) is an expensive element and if excessively added, manufacturing cost may greatly increase, so the upper limit of the molybdenum (Mo) content may be limited to 0.12%.
- Copper (Cu) is an element advantageous in the present invention because it can significantly improve the strength of the matrix phase by solid solution strengthening in ferrite, and has an effect of suppressing corrosion in a wet hydrogen sulfide atmosphere. For this effect, 0.01% or more of copper (Cu) may be included. More preferably, the copper (Cu) content may be 0.03% or more. However, when the content of copper (Cu) is excessive, the possibility of causing star cracks on the surface of the steel sheet increases, and copper (Cu) is an expensive element, and there may be a problem in that the manufacturing cost is greatly increased. Accordingly, the present invention may limit the upper limit of the copper (Cu) content to 0.40%. The upper limit of the preferable copper (Cu) content may be 0.35%.
- Nickel (Ni) is an element that effectively contributes to improving the strength by increasing the stacking defects at low temperatures to facilitate the cross slip of dislocations, improving the impact toughness, and improving the hardenability. For this effect, 0.05% or more of Nikek (Ni) may be added. A preferred nickel (Ni) content may be 0.10% or more. On the other hand, when nickel (Ni) is excessively added, the manufacturing cost may also increase due to high cost, so that the upper limit of the nickel (Ni) content may be limited to 0.40%. A preferable upper limit of the nickel (Ni) content may be 0.35%.
- the ultra-thick steel material for a steam drum of the present invention may include the remaining Fe and other unavoidable impurities in addition to the above-described components.
- unintended impurities from raw materials or the surrounding environment may inevitably be mixed in the normal manufacturing process, it cannot be entirely excluded. Since these impurities are known to those of ordinary skill in the art, all contents thereof are not specifically mentioned in the present specification.
- additional addition of effective ingredients other than the above-mentioned ingredients is not entirely excluded.
- Ceq according to Relation 1 below may satisfy the range of 0.5 to 0.6.
- [C], [Mn], [Cr], [Mo], [V], [Ni] and [Cu] are respectively C, Mn, Cr, Mo, V, Ni and It means the content (wt%) of Cu, and 0 is substituted if these components are not intentionally added.
- the ultra-thick steel material for a steam drum according to an aspect of the present invention has a thickness of 133 to 250 mm, it can effectively respond to the trend of enlargement of the steam drum.
- the surface layer portion of the ultra-thick steel material for a steam drum according to an aspect of the present invention may be formed of a ferrite and pearlite composite structure having an average particle size of 20 ⁇ m or less. Since the steel material for an ultra-thick steam drum according to an aspect of the present invention limits the introduction of hard tissue into the surface layer of the steel, it is possible to suppress the maximum surface crack depth of the final product to 0.1 mm or less. That is, the steel for ultra-thick steam drum according to one aspect of the present invention actively suppresses the formation of hard structures such as martensite and bainite in the surface layer of the steel, and even if these hard structures are unavoidably formed, the fraction can be actively suppressed to 5 area% or less (including 0%). Preferably, the hard tissue fraction of the surface layer portion of the steel may be 3% or less (including 0%).
- the surface layer portion of the steel may mean a region up to 10 mm in the thickness direction from the surface of the steel.
- the ultra-thick steel material for a steam drum may contain at least five fine VC precipitates having a diameter of 5 to 15 nm per 1 ⁇ m 2 when the cross-section of the steel material that has undergone post-welding heat treatment (PWHT) is observed.
- VC is formed in the form of carbides or carbonitrides in the temperature range of 600 to 700 ° C, causing precipitation strengthening. Therefore, the present invention can maintain an appropriate strength of 550 MPa or more even after heat treatment of the specimen at a high temperature.
- the ultra-thick steel material for a steam drum according to an aspect of the present invention may have a porosity of 0.1mm 3 /g or less at the center of the steel material. Therefore, the ultra-thick steel material for a steam drum according to an aspect of the present invention can effectively secure lamellar tearing resistance.
- the steel core means 3/8t to 5/8t (t: steel thickness, mm), and the central porosity can be confirmed by measuring the density and taking the reciprocal number.
- the ultra-thick steel material for a steam drum according to one aspect of the present invention may have a tensile strength of 550 to 690 MPa and a cross-sectional shrinkage ratio (ZRA) in the thickness direction of 35% or more.
- ZRA cross-sectional shrinkage ratio
- the maximum depth of surface cracks in the final product state may be 0.1 mm or less.
- the depth of the surface crack is determined by visual inspection of the existence of the surface crack, and if there is a crack, grinding is performed until the crack disappears at the corresponding point, and the depth from the surface layer to the place removed through grinding can be found by measuring
- Another ultra-thick steel material for steam drums in one aspect of the present invention is, by weight, C: 0.2 to 0.3%, Si: 0.05 to 0.5%, Mn: 1.0 to 2.0%, Al: 0.005 to 0.1%, P: 0.01 % or less, S: 0.015% or less, Nb: 0.001 to 0.02%, V: 0.001 to 0.03%, Ti: 0.001 to 0.03%, Cr: 0.01 to 0.3%, Mo: 0.01 to 0.12%, Cu: 0.01 to 0.4% , Ni: 0.05 to 0.4%, Ca: 0.0005 to 0.004%, including the remaining Fe and other unavoidable impurities, Ceq according to the following relation 1 satisfies the range of 0.5 to 0.6, and the average particle size of prior austenite is 500 ⁇ m or less, preparing a slab having a thickness of 650 mm or more; First heating the slab in a temperature range of 1100 ⁇ 1300 °C; providing a primary intermediate material having a thickness of 450 to
- the inventor of the present invention has conducted an in-depth study on a method for manufacturing an ultra-thick steel material having excellent surface quality while having suitable properties for a steam drum, especially in a slab manufactured to a thickness of 650 mm or more,
- the slab of the present invention is provided with an alloy composition corresponding to the steel material described above, the description of the alloy composition of the slab is replaced with a description of the alloy composition of the steel material described above.
- the alloy composition of the slab used in the present invention corresponds to the necessary conditions for securing a tensile strength of 550 to 690 MPa and a section shrinkage ratio (ZRA) of 35% or more.
- the casting speed of the large face casting machine for producing slabs with a thickness of 650 mm or more is 0.06 to 0.1 m/min, it is significantly slower than a general casting machine (casting speed: 0.4 to 1.5 m/min) for manufacturing slabs with a thickness of 250 to 400 mm. Casting is carried out at high speed. Therefore, when manufacturing a slab having a thickness of 650 mm or more, since the time maintained in the mold is relatively long, it is placed in an environment where austenite can be grown more coarsely.
- the manganese (Mn) segregation index at the austenite grain boundary increases, and the grain boundary strength decreases and hardenability increases at the same time. And the fraction of martensite is increased. Since the hard tissue has a low uniform elongation, intergranular cracking may easily occur when thermal deformation or external deformation or stress is applied. Therefore, when the grain size of the prior austenite (Prior Austenite) in the surface layer of the slab is large, the grain boundary cracks on the surface of the slab may occur more actively, and the depth of inflow of cracks may be further increased in the high deformation process such as forging and rolling thereafter. . Therefore, it is very important to control the grain size of prior austenite to an appropriate level or less in order to suppress surface cracks in the final product.
- Prior austenite Prior austenite
- the average prior austenite grain size of the slab can be derived from the following relation 2, the present invention can effectively suppress grain boundary cracks by limiting the average prior austenite grain size of the slab to 500 ⁇ m or less.
- the average prior austenite grain size of the slab may be 400 ⁇ m or less, and more preferably, the average prior austenite grain size of the slab may be 350 ⁇ m or less.
- [C], [Ni], [Cr] and [Mo] mean the contents (% by weight) of C, Ni, Cr and Mo contained in the steel slab, respectively, and R is 8.314 J/mol /K , T is the casting temperature (K), t is the casting time (s).
- the present invention can reduce the carbon equivalent (Ceq) of the steel slab according to the following relation 1 to 0.6 or less.
- a preferred carbon equivalent (Ceq) may be 0.5 to 0.6.
- the prepared slab can be heated in the temperature range of 1100 ⁇ 1300 °C.
- the thickness of the slab may be 650 mm or more, and a preferred thickness may be 700 mm or more.
- the slab primary heating of the present invention is preferably carried out in a temperature range of 1100 °C or more.
- the primary heating of the slab of the present invention is preferably carried out in the range of 1300 °C or less.
- the primary intermediate material can be provided by performing primary forging processing of the primary heated slab at a cumulative rolling reduction of 3 to 15% and a deformation rate of 1/s to 4/s.
- 1/s means that the deformation section per second is deformed by 100%.
- Primary forging is a step of forging the first heated slab to a thickness of 450 to 550 mm and processing it to the width of the final secondary intermediate material. Since low-speed forging with high deformation is essential in order to sufficiently compress the voids, the primary forging can be performed under the conditions of a cumulative rolling reduction of 3 to 15% and a deformation rate of 1/s to 4/s.
- the cumulative reduction in the primary forging may be 5% or more, and more preferably, the cumulative reduction in the primary forging may be 7% or more.
- the cumulative rolling reduction at or below the non-recrystallization temperature, which is not recovered or canceled by recrystallization exceeds 15%, the uniform elongation of the surface is extremely reduced due to work hardening of the overlapped dislocations, and in the forging process Surface cracks may occur.
- the cumulative reduction in the primary forging may be 13% or less, and more preferably, the cumulative reduction in the primary forging may be 11% or less.
- Secondary intermediate material with a thickness of 300 to 340 mm by second heating the primary intermediate material to a temperature range of 1000 to 1200 ° C, and secondary forging at a cumulative rolling reduction of 3 to 30% and a deformation rate of 1/s to 4/s can provide
- the maximum surface crack depth of the secondary intermediate material may be 5 ⁇ m or less.
- Secondary forging is a step of processing the primary intermediate material to the desired thickness and length of the final secondary intermediate material by forging by heating it to a temperature range of 1000 ⁇ 1200 °C.
- the secondary forging can be performed by applying a cumulative reduction amount of 3 to 30% and a deformation rate of 1/s to 4/s.
- the central porosity of the secondary intermediate material may be 0.1 mm 3 /g or less.
- the cumulative reduction in the secondary forging is not sufficient, it may not be possible to completely compress the micropores remaining after the primary forging.
- the physical properties may be deteriorated compared to the case of the circular void shape due to the notch effect. Therefore, it is necessary to sufficiently compress the voids with a cumulative reduction of 3% or more during secondary forging.
- the cumulative reduction amount is excessive, surface cracks may occur due to surface layer work hardening, so the upper limit of the cumulative reduction amount may be limited to 30%.
- the deformation rate of the second forging may be 1/s to 4/s as in the first forging. At a deformation rate of less than 1/s, the temperature of the finish forging may drop and surface cracks may occur. On the other hand, when a high strain rate of more than 4/s is applied in the non-recrystallization region, elongation may decrease and surface cracks may occur.
- the secondary intermediate material after the forging operation is completed can be heated for the third time in the temperature range of 1000 ⁇ 1200°C.
- the structure is homogenized by re-dissolving titanium (Ti) or niobium (Nb) complex carbonitrides or TiNb (C,N) coarse crystals formed during casting, and heating and maintaining the secondary intermediate material up to the recrystallization temperature or higher before hot rolling. , to ensure that the rolling end temperature is sufficiently high to minimize crushing of inclusions during the rolling process, tertiary heating can be performed in a temperature range of 1000°C or higher.
- the oxidation scale at high temperature may be a problem, and the manufacturing cost increase due to high temperature heating and maintenance may be a problem.
- the present invention provides an upper limit of the tertiary heating temperature can be limited to 1200 °C.
- hot rolled material having a thickness of 133 to 233 mm by hot rolling the tertiary heated secondary intermediate material in a temperature range of 900 to 1100 °C.
- the maximum surface crack depth of the hot rolled material may be 2 ⁇ m or less.
- the hot rolling temperature is preferably 900 ⁇ 1100 °C.
- Normalizing heat treatment in which the hot-rolled hot-rolled material is heated to a temperature range of 820 to 900° C. and maintained for 10 to 40 minutes, followed by air cooling to room temperature may be performed.
- the heating temperature is less than 820 ° C or the holding time is less than 10 minutes, re-dissolution of carbides generated during cooling after rolling or impurity elements segregated at grain boundaries does not occur smoothly, so the thickness direction elongation (ZRA) of the steel after heat treatment ) and low-temperature toughness may be greatly reduced.
- ZRA thickness direction elongation
- the heating temperature exceeds 900°C or the holding time exceeds 40 minutes, austenite coarsens and a group of precipitated phases such as Nb(C,N), V(C,N), etc. Dialogue may degrade my lamellar tearing quality.
- additional heat treatment (ASME section VIII-Division 1. Table UCS-56) can be performed to weld normalized products and remove residual stress.
- heat treatment after welding at 635° C. and 370 minutes may be performed.
- a cast steel having a thickness of 700 mm having the alloy components shown in Table 1 was prepared.
- Primary forging, secondary forging, hot rolling and normalizing heat treatment were performed according to the process conditions in Table 2.
- the primary heating temperature of 1200 °C, the secondary heating temperature of 1100 °C, and the tertiary heating temperature of 1050 °C were commonly applied, and the normalizing time of 30 minutes was commonly applied.
- each specimen was measured and described in Table 3.
- the microstructure of each specimen was observed using SEM, and it was confirmed that all specimens had ferrite and pearlite composite structures with an average particle size of 20 ⁇ m or less as matrix structures.
- the superficial hard tissue fraction was measured by using an automatic image analyzer after the MA was raised from the superficial tissue specimen through LePera etching, and the central porosity was determined by measuring the density of the center of the specimen.
- the tensile strength and thickness direction cross-sectional shrinkage (ZRA) of each specimen were measured using a tensile tester.
- VC precipitates were analyzed using TEM-Replica, and the diffraction pattern was first measured to confirm the crystal structure of VC. Since the (001) plane of the VC precipitate is parallel to the (001) plane of the ferrite, and the [110] direction of the VC precipitate forms a Baker-Nutting orientation relationship parallel to the [100] direction of the ferrite, the TEM image (TEM Image) can be easily found. For statistical processing, multiple images of 200nm 2 x 200nm 2 were used, and the number of VC precipitates per 1 ⁇ m 2 was counted.
- Comparative Examples 5 to 7 the manufacturing conditions proposed by the present invention are satisfied, but the alloy composition is not satisfied. As the conditions such as the microstructure type and fraction and the central porosity suggested by the present invention are not satisfied, the strength, ZRA, and surface quality are low. level can be seen. Since Comparative Example 8 does not satisfy the number of VC precipitates proposed by the present invention, it can be seen that the tensile strength is relatively low.
Abstract
Description
Claims (9)
- 중량%로, C: 0.2~0.3%, Si: 0.05~0.5%, Mn: 1.0~2.0%, Al: 0.005~0.1%, P: 0.01% 이하, S: 0.015% 이하, Nb: 0.001~0.02%, V: 0.001~0.03%, Ti: 0.001~0.03%, Cr: 0.01~0.3%, Mo: 0.01~0.12%, Cu: 0.01~0.4%, Ni: 0.05~0.4%, Ca: 0.0005~0.004%, 나머지 Fe 및 기타 불가피한 불순물을 포함하고,하기 관계식 1에 의한 Ceq가 0.5 내지 0.6의 범위를 만족하며,평균 입도가 20㎛ 이하인 페라이트 및 펄라이트 복합조직을 기지조직으로 가지고, 표면으로부터 두께방향으로 10mm까지의 영역인 표층부에서의 경질조직 분율이 5면적% 이하이며,3/8t 내지 5/8t(여기서, t는 강재 두께(mm)를 의미함)의 영역인 중심부의 공극율이 0.1mm3/g 이하이고,용접후 열처리(PWHT) 이후의 강재 단면에서 관찰되는 석출물 중 직경이 5~15nm인 미세 VC 석출물이 1㎛2 당 5개 이상인, 극후물 강재.[관계식 1]Ceq = [C] + [Mn]/6 + ([Cr] + [Mo] + [V])/5 + ([Ni] + [Cu])/15상기 관계식 1에서, [C], [Mn], [Cr], [Mo], [V], [Ni] 및 [Cu]는 각각 강재에 포함되는 C, Mn, Cr, Mo, V, Ni 및 Cu의 함량(중량%)을 의미하며, 이들 성분이 의도적을 첨가되지 않는 경우 0을 대입한다.
- 제1항에 있어서,상기 강재의 두께는 133~250mm인, 극후물 강재.
- 제1항에 있어서,상기 강재의 인장강도는 550~690MPa인, 극후물 강재.
- 제1항에 있어서,상기 강재의 두께방향 단면 수축률(ZRA)은 35% 이상인, 극후물 강재..
- 제1항에 있어서,상기 강재의 최대 표면 크랙 깊이는 0.1mm 이하(0 포함)인, 극후물 강재.
- 중량%로, C: 0.2~0.3%, Si: 0.05~0.5%, Mn: 1.0~2.0%, Al: 0.005~0.1%, P: 0.01% 이하, S: 0.015% 이하, Nb: 0.001~0.02%, V: 0.001~0.03%, Ti: 0.001~0.03%, Cr: 0.01~0.3%, Mo: 0.01~0.12%, Cu: 0.01~0.4%, Ni: 0.05~0.4%, Ca: 0.0005~0.004%, 나머지 Fe 및 기타 불가피한 불순물을 포함하고, 하기의 관계식 1에 의한 Ceq가 0.5 내지 0.6의 범위를 만족하며, 구오스테나이트의 평균 입도가 500㎛ 이하이고, 두께가 650mm 이상인 슬라브를 준비하는 단계;상기 슬라브를 1100~1300℃의 온도범위에서 1차 가열하는 단계;상기 1차 가열된 슬라브를 3~15%의 누적 압하량 및 1/s~4/s의 변형속도로 1차 단조 가공하여 450~550mm 두께의 1차 중간재를 제공하는 단계;상기 1차 중간재를 1000~1200℃의 온도범위로 2차 가열하는 단계;상기 2차 가열된 1차 중간재를 3~30%의 누적 압하량 및 1/s~4/s의 변형속도로 2차 단조 가공하여 300~340mm 두께의 2차 중간재를 제공하는 단계;상기 2차 중간재를 1000~1200℃의 온도범위로 3차 가열하는 단계;상기 3차 가열된 2차 중간재를 900~1100℃의 온도범위에서 열간압연하여 두께가 133~233mm인 열연재를 제공하는 단계; 및상기 열간압연이 완료된 열연재를 820~900℃의 온도범위로 가열하여 10~40분간 유지한 후 상온까지 공냉하는 노말라이징 열처리 단계를 포함하는, 극후물 강재의 제조방법.[관계식 1]Ceq = [C] + [Mn]/6 + ([Cr] + [Mo] + [V])/5 + ([Ni] + [Cu])/15상기 관계식 1에서, [C], [Mn], [Cr], [Mo], [V], [Ni] 및 [Cu]는 각각 강 슬라브에 포함되는 C, Mn, Cr, Mo, V, Ni 및 Cu의 함량(중량%)을 의미하며, 이들 성분이 의도적을 첨가되지 않는 경우 0을 대입한다.
- 제6항에 있어서,상기 2차 중간재의 중심부 공극률을 0.1mm3/g 이하인, 극후물 강재의 제조방법.
- 제6항에 있어서,상기 열연재의 최대 표면크랙 깊이는 2㎛ 이하(0 포함)인, 극후물 강재의 제조방법.
- 제6항에 있어서,상기 노말라이징 열처리된 강재를 용접하는 단계; 및상기 용접된 강재의 잔류응력을 제거하기 위해 추가적인 열처리(PWHT)를 실시하는 단계를 더 포함하는, 극후물 강재의 제조방법.
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US18/265,574 US20240026478A1 (en) | 2020-12-21 | 2021-11-24 | Extremely thick steel plate for steam drum having excellent surface quality and lamellar tear resistance, and manufacturing method for same |
CN202180085322.9A CN116583610A (zh) | 2020-12-21 | 2021-11-24 | 具有优异的表面品质和抗层状撕裂性的用于蒸汽锅筒的极厚钢板及其制造方法 |
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