WO2012091411A9 - 극저온 인성이 우수한 고강도 강판 및 그 제조방법 - Google Patents
극저온 인성이 우수한 고강도 강판 및 그 제조방법 Download PDFInfo
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- WO2012091411A9 WO2012091411A9 PCT/KR2011/010156 KR2011010156W WO2012091411A9 WO 2012091411 A9 WO2012091411 A9 WO 2012091411A9 KR 2011010156 W KR2011010156 W KR 2011010156W WO 2012091411 A9 WO2012091411 A9 WO 2012091411A9
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- Prior art keywords
- steel sheet
- less
- toughness
- strength steel
- high strength
- Prior art date
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 102
- 239000010959 steel Substances 0.000 title claims abstract description 102
- 238000004519 manufacturing process Methods 0.000 title claims description 12
- 238000000034 method Methods 0.000 title claims description 12
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 16
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 15
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 15
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 12
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 238000005096 rolling process Methods 0.000 claims description 48
- 230000009467 reduction Effects 0.000 claims description 15
- 229910001566 austenite Inorganic materials 0.000 claims description 14
- 238000010438 heat treatment Methods 0.000 claims description 14
- 238000010521 absorption reaction Methods 0.000 claims description 11
- 238000001953 recrystallisation Methods 0.000 claims description 10
- 229910000859 α-Fe Inorganic materials 0.000 claims description 9
- 229910052719 titanium Inorganic materials 0.000 claims description 8
- 229910052802 copper Inorganic materials 0.000 claims description 7
- 229910000734 martensite Inorganic materials 0.000 claims description 7
- 229910052698 phosphorus Inorganic materials 0.000 claims description 7
- 229910052799 carbon Inorganic materials 0.000 claims description 6
- 230000001186 cumulative effect Effects 0.000 claims description 6
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 5
- 229910052709 silver Inorganic materials 0.000 claims description 5
- 239000004332 silver Substances 0.000 claims description 5
- 230000007704 transition Effects 0.000 claims description 5
- 239000013078 crystal Substances 0.000 claims description 4
- 241000446313 Lamella Species 0.000 claims description 2
- 229910000746 Structural steel Inorganic materials 0.000 abstract description 3
- 239000011572 manganese Substances 0.000 description 27
- 239000010955 niobium Substances 0.000 description 27
- 230000000694 effects Effects 0.000 description 12
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 9
- 239000010936 titanium Substances 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 8
- 239000010949 copper Substances 0.000 description 7
- 230000015572 biosynthetic process Effects 0.000 description 5
- 239000007789 gas Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 229910052717 sulfur Inorganic materials 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 238000001816 cooling Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 239000010953 base metal Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- WWYNJERNGUHSAO-XUDSTZEESA-N (+)-Norgestrel Chemical compound O=C1CC[C@@H]2[C@H]3CC[C@](CC)([C@](CC4)(O)C#C)[C@@H]4[C@@H]3CCC2=C1 WWYNJERNGUHSAO-XUDSTZEESA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
- 239000005977 Ethylene Substances 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-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
- -1 acryl Chemical group 0.000 description 1
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 230000003466 anti-cipated effect Effects 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- GQPLMRYTRLFLPF-UHFFFAOYSA-N nitrous oxide Inorganic materials [O-][N+]#N GQPLMRYTRLFLPF-UHFFFAOYSA-N 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
Classifications
-
- 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
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- 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
-
- 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
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
-
- 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
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
-
- 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
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
-
- 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
Definitions
- the present invention relates to a high-strength steel sheet having excellent cryogenic toughness and a method for manufacturing the same, and more particularly, to a high strength steel sheet having excellent impact toughness even when applied to cryogenic environments such as structural steel such as ships and marine structures or steel for multi-purpose tanks. It relates to a steel sheet and a method of manufacturing the same.
- a technique for improving the hardness and strength of a steel sheet has been proposed by forming an low temperature transformation phase at any time by adding an element mainly improving hardenability for strength.
- the toughness of the steel sheet may be extremely poor due to the residual stress inside the steel sheet.
- the strength and toughness of steel sheet are two kinds of physical properties that are difficult to be compatible with each other conventionally.
- the marine structural steel and the hank steel have very high toughness at low temperature as well as strength.
- marine structural steels are gradually moving to cold regions such as the Arctic, which are rich in offshore oil and gas resources due to resource depletion in warmer regions. Therefore, it is difficult to withstand the harsh cryogenic environment as described above only with the existing high-strength steel sheet excellent in low temperature toughness.
- the thick steel plates for multi-purpose tanks can be Since it contains a liquefied gas, the steel sheet to transport and store it must be secured even at a temperature lower than the liquefaction temperature.
- the liquefaction temperatures of acetylene and ethylene are -82 ° C and 104 ° C, respectively, and therefore, a high strength steel sheet having excellent toughness at cryogenic temperatures is required even in such a use environment.
- a method of controlling the microstructure by adding Ni 6-12 wt% or by quenching tempering or the like is used, which is expensive in manufacturing cost and low in productivity. There was a limit.
- the steel sheet with excellent low temperature toughness can be secured at -60 ° C.
- the low temperature toughness can be ensured at about -60 ° C.
- One aspect of the present invention is to provide a high-strength steel sheet having excellent strength and excellent cryogenic toughness capable of securing toughness at a cryogenic temperature of less than -60 ° C to provide a steel material that can be used even at cryogenic temperatures and a method of manufacturing the same.
- One aspect of the present invention is by weight% C: 0.02-0.06%, Si: 0.1-0.35%, Mn: 1.0-1.6%, A1: 0.02% or less (excluding 0%), Ni: 0.7-2.0%, Cu: 0.4-0.9%, Ti: 0.003-0.015%, Nb: 0.003-0.02%, P: 0.01% or less, S: 0.005% or less, including residual Fe and inevitable impurities, [Mn] +5.4 [Si] Cryogenic toughness, which satisfies +26 [Al] +32.8 [Nb] ⁇ 4.3, where [Mn], [Si], [A1] and [Nb] represent the weight 3 ⁇ 4> unit content of Mn, Si, Al and Nb Provide this excellent high strength steel sheet.
- the microstructure of the steel sheet is an area fraction, more than 99% of the ash (accicular) It is preferred to include ferrite and up to 1% phase austenite / martensite (M & A).
- the effective grains having a grain boundary orientation of 15 ° or more are 70 area% or more in the microstructure, and the grains having a size of 10 / ⁇ or less in the effective grains are 70 or more 3 ⁇ 4 or more in the microstructure.
- the average size of the effective crystal grains is preferably 3-7 /.
- the steel sheet has a tensile strength of 490 MPa or more, Charpy impact absorption energy at -140 ° C is 300J or more, and the ductile-brittle transition temperature (DBT) is more preferably -140 ° C or less.
- another aspect of the present invention is% by weight, C: 0.02-0.06%, Si: 0.1-0.35%, Mn: 1.0-1.6%, A1: 0.02% or less (excluding 0%), Ni: 0.7 -2.0%, Cu: 0.4-0.9%, Ti: 0.003-0.015%, Nb: 0.003-0.02%, P: 0.01% or less, S: 0.005% or less, balance Fe and inevitable impurities, [Mn] + 5.4 [Si] +26 [Al] +32.8 [Nb] ⁇ 4.3, where [Mn] [Si], [A1] and [Nb] refer to the weight percent unit content of Mn, Si, A1 and Nb
- the first rolling step is preferably rolling the last two passes with a reduction ratio of 15 to 25% per pass, respectively.
- the cumulative reduction ratio is more preferably 50 to 60%.
- the cooling step is a point of t / 4 when the thickness of the steel sheet is t As a guide, it is preferable to cool to 320 to 380 ° C at an angular velocity of 8 to 15 ° C / s.
- 1 is a graph showing a change in Charpy impact absorption energy according to the temperature of the steel sheet according to the invention example.
- Figure 2 shows the microstructure of the steel sheet according to the invention example.
- One aspect of the present invention is by weight%, C: 0.02-0.06%, Si: 0.1-0.35%, Mn: 1.0-1.6%, Al: 0.02% or less (excluding 0%), Ni: 0.7-2.0%, Cu: 0.4-0.9%, Ti: 0.003-0.015%, Nb: 0.003-0.02%, P: 0.01% or less (excluding 0%), S: 0.005% or less, including residual Fe and unavoidable impurities, [Mn ] +5.4 [Si] +26 [Al] +32.8 [Nb] ⁇ 4.3, where [Mn], [Si], [Al] and [Nb] are MW, Si, Al and Nb by weight percent unit content It provides a high strength steel sheet excellent in cryogenic toughness. First, the component system and the composition range will be described. (Weight 3 ⁇ 4>)
- Si is an element added as a deoxidizer, and it is preferable to add 0.1% or more for deoxidation, but when the content exceeds 0.35%, toughness or weldability is lowered.
- the content of Si is preferably controlled to 0.1 to 0.35%.
- Mn is an element added to improve strength by solid solution strengthening and to refine grains and to improve base metal toughness, and in order to sufficiently obtain the effect, Mn is preferably added in an amount of 1.0% or more, but the addition amount may exceed 1.6%. In this case, since the toughness of the weld can be reduced by increasing the hardenability, the amount of Mn added is preferably controlled at 1.0-1.6%.
- A1 is an element capable of effectively deoxidation, it is preferable to limit the upper limit to 0.02% because it can promote MA formation in a small amount.
- Ni is an element that can improve the strength and toughness of the base material at the same time, it is preferable to add at least 0.7% in order to obtain the effect sufficiently, but it is an expensive element, if the amount is too large, the weldability may deteriorate, It is preferable to limit the upper limit to 2.0%.
- Cu is an element that can increase the strength by minimizing the toughness of the base material by solid solution strengthening and precipitation strengthening, and it is preferable to contain about 0.3% in order to achieve the effect of improving the strength. It is preferable to limit the upper limit to 0.93 ⁇ 4> since it may cause a defect of. Titanium (Ti): 0.003-0.015%
- Ti has an effect of forming nitrides with N to refine the grains of the HAZ portion to improve HAZ toughness. In order to secure such an effect sufficiently, it is preferable to add 0.003% or more. However, if the amount is too large, the low temperature toughness deteriorates, such as coarsening of the nitride, so that the amount is preferably controlled at 0.015% or less. therefore, It is preferable to control the addition amount of Ti to 0.003 to 0.015%. Niobium (Nb): 0.003-0.02%
- Nb is precipitated in the form of NbC and NbCN to greatly enhance the strength of the base metal and to suppress the transformation of ferrite and bainite to refine the grains.
- 0.003% or more must be added.
- the upper limit is preferably limited to 0.02%.
- the upper limit is preferably 0.0. Sulfur (S): 0.005% or less
- the component system should additionally satisfy [Mn] +5.4 [Si] +26 [Al] +32.8 [Nb] ⁇ 4.3, where [Mn], [Si], [A1] and [Nb] are Mn, Si, Al And a weight 3 ⁇ 4> unit content of Nb.
- Mn, Si, Al, and Nb are components that influence the formation of phase austenite / martensite (M & A).
- the microstructure of the steel sheet as an area fraction it is preferable to include more than 99% of an acylar (accicular) ferrite and less than 1% of the phase austenite / martensite (M & A).
- the microstructure in the steel sheet provided in the present invention has an acicle (accicular) ferrite as the main structure, and has a phase austenite / martensite (M & A) as the second phase structure.
- Ashicular ferrite has good strength, while on the other hand, austenite / martensitic (M & A) tissue Since it becomes a cause to inhibit toughness, it is more preferable to limit the said 2nd phase structure to 1% or less.
- the effective grain having a grain boundary orientation of 15 ° or more is 70 or more in area 3/4 of the microstructure, and the grain having a size of 10 or less in the effective grain is 70 or more in area of the microstructure.
- the decisive factor affecting the properties of the steel is effective grains having a grain boundary orientation of 15 ° or more, it is preferable that such effective grains contain 70 area% or more in the microstructure.
- the effective grains having an important effect on the properties of such steels have a size of ⁇ or less and a microstructure increase of more than 70% by area, which is closely related to the lamella toughness of the grain size of the acicular ferrite. The smaller is, the greater the stratified toughness.
- the microstructure of the effective grain size of 10 / or less is included in more than 70 areas 3 ⁇ 4
- the microstructure of the steel sheet according to the present invention is obtained that the average size of the effective grain is 3 ⁇ 7 ⁇ , if the effective grain size is controlled very fine in this way it is excellent in toughness at low temperature with the strength of the steel , Can be used as a steel sheet suitable for cryogenic use environment such as marine structures.
- the steel sheet of the present invention as described above can be obtained that the tensile strength is 490MPa or more, Charpy impact absorption energy at -14CTC is 300J or more, and the ductile-brittle transition temperature (DBTT) is -140 ° C or less.
- the strength of the steel sheet is 490MPa or more can exhibit a high strength that can be used in the environment to which the steel sheet of the present invention is applied, the Charpy impact absorption energy is 300J or more even at cryogenic temperature of -14C C has particularly excellent cryogenic toughness Can be.
- DBTT ductile-brittle transition temperature
- Another aspect of the present invention is% by weight, C: 0.02-0.06%, Si: 0.1-0.35%, Mn: 1.0-1.6%, A1: 0.02% or less (excluding 03 ⁇ 4>), Ni: 0.7 -2.0%, Cu: 0.4-0.9%, Ti: 0.003-0.015%, Nb: 0.003-0.02%, P: 0.01% or less, S: 0.005% or less, residual Fe and inevitable impurities, [Mn ] +5.4 [Si] +26 [Al] +32.8 [Nb] ⁇ 4.3, where [Mn] [Si], [A1] and [Nb] represent the weight percent unit content of Mn, Si, Al and Nb.
- the steel slab having the composition as described above is subjected to a heating step of heating at 1050 ⁇ 118 (C, the heating step of the slab is heated to ensure that the subsequent rolling process smoothly and to obtain the properties of the target steel sheet sufficiently
- the heating process should be carried out within the proper temperature range according to the purpose. The important thing in this heating process is not only need to heat uniformly enough that the precipitated elements inside the steel sheet can be sufficiently dissolved, To avoid excessive coarsening of grains, if the heating temperature of steel is less than 1050 ° C, Nb, Ti, etc. cannot be re-used in the steel, making it hard to achieve high strength of steel sheet and partial recrystallization occurs.
- the heating temperature of the slab is controlled to 1050 ⁇ 1180 ° C
- the slab is heated after the slab is heated, and in order for the steel sheet to have low temperature toughness, the austenitic grains must be present in a fine size, which is possible by controlling the rolling temperature and the rolling reduction rate.
- Rolling of the present invention The step is characterized in that it is carried out in two temperature ranges. In addition, since the recrystallization behavior in each temperature range is different from each other, the conditions are also set separately.
- a first rolling step of rolling four or more passes at austenite recrystallization temperature (Tnr) or more is performed. Rolling in the austenite recrystallization region produces an effect of making grains smaller through austenite recrystallization, and such grain refinement has an important effect on improving strength and toughness.
- the first rolling step is a multi-pass rolling four or more times at a temperature above the austenite recrystallization temperature (Tnr), it is more preferable that the last two passes of the rolling step with a rolling reduction of 15 ⁇ 253 ⁇ 4 per pass. That is, the present inventors recognize that in the multi-pass rolling in the first rolling, it is the last two passes that have a decisive influence on the grain size of the austenite.
- the total number of passes is also required at least four times in order to achieve grain refinement through intense reduction.
- the cumulative reduction ratio in the second rolling stage is 50% or more in total.
- the limit on the reduction ratio that can be applied in the first rolling stage becomes large, and thus the layer fraction One Since grain refinement cannot be achieved, it is more effective to limit the cumulative reduction ratio to 50-6.
- the steel sheet is angled to 320 to 380 ° C at an angle of angular velocity of 8 to 15 ° C / s based on the point t / 4.
- the angle condition is a factor that affects the microstructure. If the angle is less than 8 ° C / s, the amount of M & A is excessively increased, which may inhibit the strength and toughness, and when the angle speed exceeds 15 ° C / s. Due to the excessive amount of deflection, the deformation of the steel sheet may occur and shape control may be inferior. Therefore, it is preferable to control the deflection speed after rolling at 8 to 15 ° C / s.
- the angle temperature is preferably controlled to less than 380 ° C so that M & A structure is not generated. However, if the angle temperature is too low, the effect is not only saturated, but excessive cooling may cause the steel sheet to fall. In addition, since there may be a problem that the impact toughness is lowered due to excessive increase in strength, the lower limit is preferably limited to 320 ° C.
- the steel slab was subjected to first rolling (rough rolling) under the conditions shown in Table 2, followed by rolling (deformation rolling), followed by corner angles.
- the yield strength is more than 440MPa
- the tensile strength is more than 490MPa
- the Charpy impact absorption energy is more than 300J at -100 ° C, -120 ° C, -140 ° C all showed very excellent cryogenic toughness
- DBn value No embrittlement occurs at -140 ° C, the lowest measurement temperature It was found that the temperature is much lower than that.
- 1-4, 2-4, 3-4 used the invention steel, but the last
- FIG. 1 is a graph showing the change of Charpy impact absorption energy according to the temperature of the invention example using the invention steel and the manufacturing conditions also meet the scope of the present invention. All of the range of -140 ° C, the lowest measurable temperature at -40 ° C, showed high energy values of over 300J, indicating that the cryogenic toughness was very good.
- Figure 2 shows a microstructure photograph of the steel sheet according to the invention, black grains mean effective grains having a grain boundary orientation of 15 ° or more. This effective grain was found to be more than 70% by area, and it can be seen that the acylar (accicular) ferrite is a microstructure having a 99 area 3 ⁇ 4 or more.
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Abstract
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Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
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JP2013547333A JP5740486B2 (ja) | 2010-12-28 | 2011-12-27 | 極低温靭性に優れた高強度鋼板及びその製造方法 |
ES11853770.3T ES2585635T3 (es) | 2010-12-28 | 2011-12-27 | Lámina de acero de alta resistencia que tiene tenacidad superior a temperaturas criogénicas, y método para fabricar la misma |
US13/997,703 US9255305B2 (en) | 2010-12-28 | 2011-12-27 | High-strength steel sheet having superior toughness at cryogenic temperatures, and method for manufacturing same |
CN201180068651.9A CN103403204B (zh) | 2010-12-28 | 2011-12-27 | 在低温下具有优异韧性的高强度钢板及其制造方法 |
EP11853770.3A EP2660346B1 (en) | 2010-12-28 | 2011-12-27 | High-strength steel sheet having superior toughness at cryogenic temperatures, and method for manufacturing same |
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KR20100137340A KR20120075274A (ko) | 2010-12-28 | 2010-12-28 | 극저온 인성이 우수한 고강도 강판 및 그 제조방법 |
KR10-2010-0137340 | 2010-12-28 |
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WO2012091411A2 WO2012091411A2 (ko) | 2012-07-05 |
WO2012091411A9 true WO2012091411A9 (ko) | 2012-09-27 |
WO2012091411A3 WO2012091411A3 (ko) | 2012-11-15 |
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PCT/KR2011/010156 WO2012091411A2 (ko) | 2010-12-28 | 2011-12-27 | 극저온 인성이 우수한 고강도 강판 및 그 제조방법 |
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US (1) | US9255305B2 (ko) |
EP (1) | EP2660346B1 (ko) |
JP (1) | JP5740486B2 (ko) |
KR (1) | KR20120075274A (ko) |
CN (1) | CN103403204B (ko) |
ES (1) | ES2585635T3 (ko) |
WO (1) | WO2012091411A2 (ko) |
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CN107109592A (zh) * | 2014-12-24 | 2017-08-29 | Posco公司 | 耐脆性裂纹扩展性优异的高强度钢材及其制造方法 |
EP3239331B1 (en) * | 2014-12-24 | 2020-10-28 | Posco | High-strength steel having superior brittle crack arrestability, and production method therefor |
JP6475836B2 (ja) * | 2014-12-24 | 2019-02-27 | ポスコPosco | 脆性亀裂伝播抵抗性に優れた高強度鋼材及びその製造方法 |
KR101726082B1 (ko) * | 2015-12-04 | 2017-04-12 | 주식회사 포스코 | 취성균열전파 저항성 및 용접부 취성균열개시 저항성이 우수한 고강도 강재 및 그 제조방법 |
KR101736611B1 (ko) * | 2015-12-04 | 2017-05-17 | 주식회사 포스코 | 취성균열전파 저항성 및 용접부 취성균열개시 저항성이 우수한 고강도 강재 및 그 제조방법 |
KR101758520B1 (ko) * | 2015-12-23 | 2017-07-17 | 주식회사 포스코 | 열간 저항성이 우수한 고강도 구조용 강판 및 그 제조방법 |
CN106435392B (zh) * | 2016-09-23 | 2018-06-05 | 中国科学院合肥物质科学研究院 | 一种改进低活化马氏体钢力学性能的热机械处理方法 |
KR101819380B1 (ko) | 2016-10-25 | 2018-01-17 | 주식회사 포스코 | 저온인성이 우수한 고강도 고망간강 및 그 제조방법 |
KR101908819B1 (ko) | 2016-12-23 | 2018-10-16 | 주식회사 포스코 | 저온에서의 파괴 개시 및 전파 저항성이 우수한 고강도 강재 및 그 제조방법 |
EP3666911B1 (en) * | 2018-12-11 | 2021-08-18 | SSAB Technology AB | High-strength steel product and method of manufacturing the same |
KR102209547B1 (ko) * | 2018-12-19 | 2021-01-28 | 주식회사 포스코 | 취성균열개시 저항성이 우수한 구조용 극후물 강재 및 그 제조방법 |
KR102220739B1 (ko) * | 2018-12-19 | 2021-03-02 | 주식회사 포스코 | 두께 중심부 인성이 우수한 극후물 강판의 제조방법 |
JPWO2023181895A1 (ko) * | 2022-03-22 | 2023-09-28 | ||
CN114918262A (zh) * | 2022-04-22 | 2022-08-19 | 首钢集团有限公司 | 高韧性中厚板及其板型控制方法和控制装置 |
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-
2010
- 2010-12-28 KR KR20100137340A patent/KR20120075274A/ko not_active Ceased
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2011
- 2011-12-27 EP EP11853770.3A patent/EP2660346B1/en active Active
- 2011-12-27 CN CN201180068651.9A patent/CN103403204B/zh active Active
- 2011-12-27 WO PCT/KR2011/010156 patent/WO2012091411A2/ko active Application Filing
- 2011-12-27 US US13/997,703 patent/US9255305B2/en active Active
- 2011-12-27 JP JP2013547333A patent/JP5740486B2/ja active Active
- 2011-12-27 ES ES11853770.3T patent/ES2585635T3/es active Active
Also Published As
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WO2012091411A2 (ko) | 2012-07-05 |
CN103403204A (zh) | 2013-11-20 |
ES2585635T3 (es) | 2016-10-07 |
US20130292011A1 (en) | 2013-11-07 |
JP2014505170A (ja) | 2014-02-27 |
KR20120075274A (ko) | 2012-07-06 |
WO2012091411A3 (ko) | 2012-11-15 |
CN103403204B (zh) | 2016-04-06 |
JP5740486B2 (ja) | 2015-06-24 |
EP2660346B1 (en) | 2016-05-04 |
US9255305B2 (en) | 2016-02-09 |
EP2660346A4 (en) | 2014-07-09 |
EP2660346A2 (en) | 2013-11-06 |
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