EP3239329B1 - Structural ultra-thick steel having excellent resistance to brittle crack propagation, and production method therefor - Google Patents
Structural ultra-thick steel having excellent resistance to brittle crack propagation, and production method therefor Download PDFInfo
- Publication number
- EP3239329B1 EP3239329B1 EP15873530.8A EP15873530A EP3239329B1 EP 3239329 B1 EP3239329 B1 EP 3239329B1 EP 15873530 A EP15873530 A EP 15873530A EP 3239329 B1 EP3239329 B1 EP 3239329B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- slab
- bar
- central portion
- steel
- ferrite
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 229910000831 Steel Inorganic materials 0.000 title claims description 99
- 239000010959 steel Substances 0.000 title claims description 99
- 238000004519 manufacturing process Methods 0.000 title description 8
- 238000005096 rolling process Methods 0.000 claims description 55
- 229910001563 bainite Inorganic materials 0.000 claims description 35
- 229910000859 α-Fe Inorganic materials 0.000 claims description 32
- 238000001816 cooling Methods 0.000 claims description 29
- 229910001562 pearlite Inorganic materials 0.000 claims description 17
- 230000007704 transition Effects 0.000 claims description 11
- 239000002826 coolant Substances 0.000 claims description 9
- 239000012535 impurity Substances 0.000 claims description 9
- 230000009466 transformation Effects 0.000 claims description 9
- 230000009467 reduction Effects 0.000 claims description 8
- 238000000034 method Methods 0.000 claims description 7
- 229910001568 polygonal ferrite Inorganic materials 0.000 claims description 7
- 238000003303 reheating Methods 0.000 claims description 6
- 230000001186 cumulative effect Effects 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 238000001887 electron backscatter diffraction Methods 0.000 claims description 3
- 239000007788 liquid Substances 0.000 claims description 3
- 238000012360 testing method Methods 0.000 claims description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 23
- 230000000052 comparative effect Effects 0.000 description 16
- 239000010955 niobium Substances 0.000 description 16
- 239000010936 titanium Substances 0.000 description 15
- 239000011572 manganese Substances 0.000 description 13
- 229910001566 austenite Inorganic materials 0.000 description 10
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 5
- 229910052759 nickel Inorganic materials 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 229910052698 phosphorus Inorganic materials 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 3
- 229910052748 manganese Inorganic materials 0.000 description 3
- 229910000734 martensite Inorganic materials 0.000 description 3
- 229910052758 niobium Inorganic materials 0.000 description 3
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000011733 molybdenum Substances 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 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
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 239000005864 Sulphur Substances 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 210000001787 dendrite Anatomy 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000014509 gene expression Effects 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Images
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
- C21D8/02—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
- 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
- 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
-
- 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
- C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
-
- 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
- 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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing 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
- C21D2211/002—Bainite
-
- 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
-
- 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 disclosure relates to structural ultra-thick steel having excellent resistance to brittle crack propagation, and a production method therefor.
- structures When using high-strength steel to design structures, structures may be lightened in terms of the weight thereof, while obtaining an economic advantage through the thickness of a steel sheet, thus simultaneously achieving ease in machining and welding.
- coarsened structures may cause difficulties in securing impact toughness in the central portion.
- the technologies themselves may be expected to cause significant reductions in productivity when being employed in common mass production systems; thus, it may be difficult to commercialize such technologies.
- Ni nickel
- the resistance thereof to brittle crack propagation may be improved.
- a Ni element is relatively expensive, it may be difficult to apply the Ni element commercially in terms of manufacturing costs.
- WO 1999/032671 discloses a steel entirely or partially including iron, carbon, manganese, nickel, nitrogen, copper, chromium, molybdenum, silicon, niobium, vanadium, titanium, aluminum, boron additives, a ferrite-phase as a microstructure, a second phase composed mainly of lath martensite and lower bainite and a phase composed of residual austenite.
- WO 2014/132627 discloses a steel including carbon, silicon, manganese, phosphorus, sulphur, aluminum, niobium, titanium, copper, nickel, chromium, molybdenum and nitrogen, so as to satisfy certain relational expressions. It includes bainite and martensite microstructures as a main structure and polygonal ferrite of 10% or less.
- An aspect of the present disclosure may provide structural ultra-thick steel having excellent resistance to brittle crack propagation.
- Another aspect of the present disclosure may provide a method of producing structural ultra-thick steel having excellent resistance to brittle crack propagation by controlling alloy compositions and microstructures.
- structural ultra-thick steel having excellent resistance to brittle crack propagation consists of: 0.02-0.1 wt % of C, 0.8-2.5 wt % of Mn, 0.05-1.5 wt % of Ni, 0.005-0.1 wt % of Nb, 0.005-0.1 wt % of Ti, and the remainder of Fe and other inevitable impurities, the structural ultra-thick steel having microstructures consisting of one structure selected from the group consisting of a single-phase structure of ferrite, a single-phase structure of bainite, a complex-phase structure of ferrite and bainite, a complex-phase structure of ferrite and pearlite, and a complex-phase structure of ferrite, bainite, and pearlite, wherein the ferrite is acicular ferrite or polygonal ferrite, and the bainite is granular bainite, wherein when the microstructures have the complex-phase structure of ferrite, bainit
- a method of producing the structural ultra-thick steel having excellent resistance to brittle crack propagation comprises: reheating a slab or a bar consisting of 0.02-0.1 wt % of C, 0.8-2.5 wt % of Mn, 0.05-1.5 wt % of Ni, 0.005-0.1 wt % of Nb, 0.005-0.1 wt % of Ti, and the remainder of Fe and other inevitable impurities to 950-1,100°C and then rough rolling the reheated slab or bar at 900-1,100°C; obtaining a steel sheet by finish rolling the rough rolled slab or bar at an Ar3 transformation point or higher; and cooling the steel sheet to 700°C or lower, in which a temperature difference between a central portion of the slab or the bar in a thickness direction and an external surface of the slab or the bar before rough rolling is 100-300°C, wherein the temperature difference between the central portion of the slab or the bar in the thickness direction and the external surface of the slab
- structural ultra-thick steel having excellent resistance to brittle crack propagation, excellent yield strength and an excellent impact transition temperature in a central portion thereof, may be obtained.
- FIG. 1 is an image obtained by observing a central portion of Inventive Steel 1 in a plate thickness direction thereof with an optical microscope.
- the inventors of the present disclosure have conducted research to secure structural ultra-thick steel having excellent yield strength and an excellent impact transition temperature in a central portion thereof, compared to that in the related art, while solving conventional problems, to appropriately control alloy design and microstructures of the structural ultra-thick steel, thus recognizing that resistance of the structural ultra-thick steel to brittle crack propagation may be improved. Based on this, the inventors have completed the present invention.
- structural ultra-thick steel having excellent resistance to brittle crack propagation includes: 0.02-0.1 wt % of C, 0.8-2.5 wt % of Mn, 0.05-1.5 wt % of Ni, 0.005-0.1 wt % of Nb, 0.005-0.1 wt % of Ti, and the remainder of Fe and other inevitable impurities, the structural ultra-thick steel having microstructures including one structure selected from the group consisting of a single-phase structure of ferrite, a single-phase structure of bainite, a complex-phase structure of ferrite and bainite, a complex-phase structure of ferrite and pearlite, and a complex-phase structure of ferrite, bainite, and pearlite.
- Such structural ultra-thick steel has a thickness of 10-100 mm, more preferably 50-100 mm.
- C Since C is the most important element in securing basic strength, C is required to be contained in steel within an appropriate range. 0.02% or more of C is added in order to obtain such an addition effect.
- Mn is an element useful in improving strength by solid solution strengthening and to enhance hardenability so as to generate a low temperature transformation phase, 0.8% or more of Mn is added.
- Ni is an important element to facilitate cross slip of potentials at low temperatures to improve impact toughness and hardenability, increasing strength, 0.05% or more of Ni is added in order to improve impact toughness and resistance to brittle crack propagation.
- 0.05% or more of Ni is added in order to improve impact toughness and resistance to brittle crack propagation.
- hardenability may be excessively increased to generate a low temperature transformation phase, degrading toughness and increasing manufacturing costs, and an upper limit of the content of Ni is thus restricted to 1.5%.
- Nb may be precipitated in the form of NbC or NbCN to increase strength of a base material.
- Nb dissolved when reheated to a high temperature, may be precipitated very finely in the form of NbC at the time of rolling to suppress recrystallization of austenite, thus miniaturizing a structure.
- Nb 0.005% or more of Nb is added.
- an excessive amount of Nb may cause brittle cracking in an edge of the steel, and a lower limit of the content of Nb is thus restricted to 0.1%.
- Ti is precipitated as TiN when reheated and is an element that may significantly improve low temperature toughness by suppressing the growth of crystal grains of the base material and a weld heat affected zone. 0.005% or more of Ti is added in order to obtain such an addition effect.
- the remainder thereof is iron (Fe).
- Fe iron
- impurities of raw materials or steel manufacturing environments may be inevitably included in the steel, and such impurities may not be removed from the steel.
- the steel according to an embodiment has microstructures including one structure selected from the group consisting of a single-phase structure of ferrite, a single-phase structure of bainite, a complex-phase structure of ferrite and bainite, a complex-phase structure of ferrite and pearlite, and a complex-phase structure of ferrite, bainite, and pearlite.
- a ratio of pearlite is restricted to 30 vol% or less in the complex-phase structure of ferrite, bainite, and pearlite.
- the ferrite is acicular ferrite or polygonal ferrite and the bainite is granular bainite.
- the contents of Mn and Ni increase, fractions of acicular ferrite or polygonal ferrite and granular bainite may increase. Accordingly, strength may also increase.
- the steel has a grain size of 15 ⁇ m or less and a high-angle grain boundary of 15° or higher measured in the central portion in a plate thickness direction of the steel in an electron backscatter diffraction (EBSD) manner.
- EBSD electron backscatter diffraction
- the steel has a yield strength of 350 MPa or more, and an impact transition temperature of -60°C or lower in the central portion thereof.
- a method of producing structural ultra-thick steel having excellent resistance to brittle crack propagation includes: reheating a slab or a bar including 0.02-0.1 wt % of C, 0.8-2.5 wt % of Mn, 0.05-1.5 wt % of Ni, 0.005-0.1 wt % of Nb, 0.005-0.1 wt % of Ti, and the remainder of Fe and other inevitable impurities to 950-1,100°C and then rough rolling the reheated slab or bar at 900-1,100°C; obtaining a steel sheet by finish rolling the rough rolled slab or bar at an Ar3 transformation point or higher; and cooling the steel sheet to 700°C or lower, in which a temperature difference between a central portion of the slab or the bar in a thickness direction thereof and an external surface of the slab or the bar before rough rolling is 100-300°C.
- a slab reheating temperature is restricted to 950°C or higher, which is performed to dissolve a carbonitride of Ti and/or Nb formed during casting. Further, it may be more preferable to reheat the slab to 1,000°C or higher in order to sufficiently dissolve the carbonitride of Ti and/or Nb. However, when the slab is reheated to an excessively high temperature, there may be concerns that austenite is coarsened, and an upper limit of the slab reheating temperature is thus 1,100°C.
- Rough Rolling Temperature 900-1,100°C and Temperature Difference between Central Portion of Slab or Bar in Thickness Direction and External Surface of Slab or Bar before Rough Rolling: 100-300°C
- a rough rolling temperature is a temperature (Tnr) or higher at which recrystallization of austenite stops. Effects of destroying a cast structure, such as a dendrite or the like, formed during casting by rolling, and of reducing a size of austenite may also be obtained.
- the rough rolling temperature is restricted to 900-1,100°C in order to obtain such an effect.
- the temperature difference between the central portion of the slab or the bar in the thickness direction thereof and the external surface of the slab or the bar immediately before rolling at the time of rough rolling is 100-300°C.
- Such a temperature difference between the central portion and the external surface is obtained by cooling a heated slab or bar with a cooling device.
- the cooling device is not particularly limited and, for example, at least one of water, air, a liquid coolant, and a vapor coolant may be used as a cooling medium.
- the temperature difference between the central portion of the slab or the bar in the thickness direction thereof and the external surface of the slab or the bar may be given at the time of rough rolling to maintain a surface portion of the slab or the bar at a temperature lower than that of the central portion.
- the central portion having a temperature relatively higher than that of the surface portion may be further deformed, and a grain size of the central portion thus becomes finer.
- An average grain size of the central portion is maintained at 15 ⁇ m or less.
- the temperature difference between the central portion and the external surface is 100-300°C in order to effectively provide further deformation to the central portion..
- the temperature difference between the central portion of the slab or the bar in the thickness direction thereof and the external surface of the slab or the bar may refer to a difference between a surface temperature of the slab or the bar measured immediately before rough rolling and a temperature of the central portion calculated by considering cooling conditions and a thickness of the slab or the bar immediately before rough rolling.
- the measurements of the surface temperature and the thickness of the slab may be taken before initial rough rolling, and the measurements of the surface temperature and the thickness of the bar may be taken before initial rough rolling after two rough rolling processes.
- the temperature difference between the central portion of the slab or the bar in the thickness direction thereof and the external surface of the slab or the bar may refer to the fact that a temperature difference, obtained by measuring temperature differences in the respective passes during rough rolling and calculating a total average value, is 100-300°C.
- a total cumulative reduction ratio at the time of rough rolling is 40% or more in order to miniaturize the structure of the central portion at the time of rough rolling.
- a steel sheet is obtained by finish rolling the rough rolled bar at an Ar3 transformation point or higher.
- an austenite structure may be transformed.
- Cooling after Rolling Cooling to 700°C or Lower
- the steel sheet After finish rolling, the steel sheet is cooled to 700°C or lower.
- a cooling termination temperature exceeds 700°C, a microstructure may not be properly formed, and there may thus be a possibility that the yield strength is 350 MPa or less.
- the cooling of the steel sheet is performed at a central portion average cooling rate of 3-300 °C/s or more.
- the central portion average cooling rate of the steel sheet is less than 3 °C/s, the microstructure may not be properly formed, and there may thus be a possibility that the yield strength is 350 MPa or less.
- a steel slab having a composition illustrated in Table 1 below was reheated to 1,070°C, and rough rolled at a temperature of 1,050°C.
- An average temperature difference between an external surface and a central portion of the steel slab at the time of rough rolling of the steel slab is shown in Table 2 below, and a cumulative reduction ratio was 50%.
- the average temperature difference between the external surface and the central portion at the time of rough rolling as illustrated in Table 2 may represent a difference between a surface temperature of a slab or a bar measured immediately before rough rolling and a temperature of the central portion calculated by considering an amount of water injected to the slab or the bar and a thickness of the slab or the bar immediately before rough rolling, and the average temperature difference may be a result obtained by measuring temperature differences in respective passes during rough rolling and calculating a total average value.
- a steel sheet having a thickness illustrated in Table 2 below was obtained by finish rolling the steel slab at a finish rolling temperature of 780°C, and was cooled to a temperature of 700°C or lower at a cooling rate of 5 °C/s.
- the Kca value illustrated in Table 2 may be an estimate value obtained by performing an ESSO test.
- the average temperature difference between the central portion in the thickness direction and the external surface at the time of rough rolling presented in an embodiment is controlled to less than 100°C, that since a sufficient degree of deformation is not given to the central portion at the time of rough rolling, grain sizes of the central portion are 25.3 ⁇ m and 29.6 ⁇ m, respectively; thus, an impact transition temperature of the central portion is less than -60°C.
- the Kca value measured at -10°C does not exceed 6,000, required in a common steel for shipbuilding.
- Comparative Steels 3 and 5 have values greater than the upper limits of the contents of C and Mn proposed in an embodiment, that even though a grain size of austenite in the central portion is miniaturized through cooling at the time of rough rolling, grain sizes of final microstructures are 32 ⁇ m or more and 38 ⁇ m or more, respectively, due to the generation of upper bainite, and that since Comparative Steels 3 and 5 have the upper bainite, in which brittleness may easily occur, as a base structure; thus, an impact transition temperature of the central portion is -60°C or higher.
- a Kca value is 6,000 or less at -10°C.
- Comparative Steel 4 has a value greater than the upper limit of the content of Ni proposed in an embodiment, and that, in terms of high hardenability, microstructures of a base metal are granular bainite and upper bainite.
- a grain size of austenite in the central portion is miniaturized through cooling at the time of rough rolling, a grain size of the final microstructure is 26 ⁇ m, that the upper bainite, in which brittleness may easily occur, is a base structure; thus, an impact transition temperature of the central portion is -60°C or higher.
- a Kca value is 6,000 or less at -10°C.
- Inventive Steels 1 to 6 which satisfy the composition range in an embodiment and in which the grain size of austenite in the central portion is miniaturized through cooling at the time of rough rolling, it can be seen that Inventive Steels 1 to 6 satisfy a yield strength of 350 MPa or more, and a grain size of 15 ⁇ m or less in central portions thereof, and have, as microstructures, ferrite and pearlite structures, a single-phase structure of acicular ferrite, or a complex-phase structure of acicular ferrite or polygonal ferrite and granular bainite, and a complex-phase structure of acicular ferrite, pearlite, and granular bainite.
- an impact transition temperature of the central portion is -60°C or lower and that a Kca value satisfies 6,000 or more at -10°C.
- FIG. 1 depicting an image obtained by observing the central portion of Inventive Steel 1 in a thickness direction thereof with an optical microscope, in the case of Inventive Steel 1, it can be seen that a structure of the central portion is fine.
Landscapes
- 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)
Description
- The present disclosure relates to structural ultra-thick steel having excellent resistance to brittle crack propagation, and a production method therefor.
- In recent years, the development of ultra-thick steel having high-strength characteristics has been required in designing structures that have been used in fields such as domestic and overseas shipbuilding, maritime construction, architecture, and civil engineering.
- When using high-strength steel to design structures, structures may be lightened in terms of the weight thereof, while obtaining an economic advantage through the thickness of a steel sheet, thus simultaneously achieving ease in machining and welding.
- In general, in the case of high-strength steel, since a central portion thereof may not be sufficiently transformed, depending on a reduction in the total reduction ratio, during the manufacturing of ultra-thick steel, the structure of the central portion may be coarse. Hence, the hardenability of the high-strength steel may be increased, to thus generate a low temperature transformation phase, such as bainite or the like.
- In addition, coarsened structures may cause difficulties in securing impact toughness in the central portion.
- When resistance to brittle crack propagation representing the stability of structures is applied to primary structures, such as a ship and the like, the number of cases requiring guarantees is increasing. However, when a low temperature transformation phase is generated in the central portion, the resistance to brittle crack propagation may be significantly reduced. Thus, it may be very difficult to improve the resistance of an ultra-thick high-strength steel to brittle crack propagation.
- Meanwhile, in order to improve the resistance of high-strength steel, having a yield strength of 350 MPa or more, to brittle crack propagation, various technologies have been implemented, such as the adjustment of gain size through the application of surface cooling during finish rolling and through the application of bending stress during rolling, surface refinement through reverse rolling, and the like, in order to miniaturize the grain size of surface layers of high-strength steel.
- However, such technologies help to miniaturize the structure of surface layers, but cannot solve the problem of a reduction in impact toughness caused by structural coarsening of the central portion, so may not become fundamental measures to the resistance to brittle crack propagation.
- Furthermore, the technologies themselves may be expected to cause significant reductions in productivity when being employed in common mass production systems; thus, it may be difficult to commercialize such technologies.
- Moreover, when a large amount of an element, such as nickel (Ni) or the like, helping to improve toughness, is added to high-strength steel, the resistance thereof to brittle crack propagation may be improved. However, since a Ni element is relatively expensive, it may be difficult to apply the Ni element commercially in terms of manufacturing costs.
-
WO 1999/032671 discloses a steel entirely or partially including iron, carbon, manganese, nickel, nitrogen, copper, chromium, molybdenum, silicon, niobium, vanadium, titanium, aluminum, boron additives, a ferrite-phase as a microstructure, a second phase composed mainly of lath martensite and lower bainite and a phase composed of residual austenite. -
WO 2014/132627 discloses a steel including carbon, silicon, manganese, phosphorus, sulphur, aluminum, niobium, titanium, copper, nickel, chromium, molybdenum and nitrogen, so as to satisfy certain relational expressions. It includes bainite and martensite microstructures as a main structure and polygonal ferrite of 10% or less. -
- Patent Document 1: Korean Patent Publication No.
2009-0069818 - Patent Document 2: Korean Patent Publication No.
2002-0091844 - Patent Document 3:
WO 1999/032671 - Patent Document 4:
WO 2014/132627 - An aspect of the present disclosure may provide structural ultra-thick steel having excellent resistance to brittle crack propagation.
- Another aspect of the present disclosure may provide a method of producing structural ultra-thick steel having excellent resistance to brittle crack propagation by controlling alloy compositions and microstructures.
- According to an aspect of the present disclosure, structural ultra-thick steel having excellent resistance to brittle crack propagation consists of: 0.02-0.1 wt % of C, 0.8-2.5 wt % of Mn, 0.05-1.5 wt % of Ni, 0.005-0.1 wt % of Nb, 0.005-0.1 wt % of Ti, and the remainder of Fe and other inevitable impurities, the structural ultra-thick steel having microstructures consisting of one structure selected from the group consisting of a single-phase structure of ferrite, a single-phase structure of bainite, a complex-phase structure of ferrite and bainite, a complex-phase structure of ferrite and pearlite, and a complex-phase structure of ferrite, bainite, and pearlite, wherein the ferrite is acicular ferrite or polygonal ferrite, and the bainite is granular bainite, wherein when the microstructures have the complex-phase structure of ferrite, bainite, and pearlite a percentage of pearlite to the complex-phase structure is 30 vol% or less, wherein the steel has a grain size of 15 µm or less, the grain size having a high-angle grain boundary of 15° or higher measured in an EBSD manner in a central portion in a plate thickness direction, wherein the steel has a yield strength of 350 MPa or more, an impact transition temperature of -60°C or lower in of a central portion thereof, a thickness of 10-100 mm and 6,000 or more of Kca value obtained by performing an ESSO test.
- According to another aspect of the present disclosure, a method of producing the structural ultra-thick steel having excellent resistance to brittle crack propagation comprises: reheating a slab or a bar consisting of 0.02-0.1 wt % of C, 0.8-2.5 wt % of Mn, 0.05-1.5 wt % of Ni, 0.005-0.1 wt % of Nb, 0.005-0.1 wt % of Ti, and the remainder of Fe and other inevitable impurities to 950-1,100°C and then rough rolling the reheated slab or bar at 900-1,100°C; obtaining a steel sheet by finish rolling the rough rolled slab or bar at an Ar3 transformation point or higher; and cooling the steel sheet to 700°C or lower, in which a temperature difference between a central portion of the slab or the bar in a thickness direction and an external surface of the slab or the bar before rough rolling is 100-300°C, wherein the temperature difference between the central portion of the slab or the bar in the thickness direction and the external surface of the slab or the bar is obtained by cooling the slab or the bar with a cooling device, wherein a cooling medium of the cooling device is at least one of water, air, a liquid coolant, and a vapor coolant, wherein a total cumulative reduction ratio at the time of rough rolling is 40% or higher, wherein the cooling of the steel sheet is performed at a central portion average cooling rate of 3-300 °C/s.
- The foregoing technical solutions to the above-mentioned problems do not fully enumerate all of the features of the present disclosure.
- Various features of the present disclosure and the resulting advantages and effects will be understood in more detail with reference to the following detailed examples.
- According to an aspect of the present disclosure, structural ultra-thick steel having excellent resistance to brittle crack propagation, excellent yield strength and an excellent impact transition temperature in a central portion thereof, may be obtained.
-
FIG. 1 is an image obtained by observing a central portion of Inventive Steel 1 in a plate thickness direction thereof with an optical microscope. - The inventors of the present disclosure have conducted research to secure structural ultra-thick steel having excellent yield strength and an excellent impact transition temperature in a central portion thereof, compared to that in the related art, while solving conventional problems, to appropriately control alloy design and microstructures of the structural ultra-thick steel, thus recognizing that resistance of the structural ultra-thick steel to brittle crack propagation may be improved. Based on this, the inventors have completed the present invention.
- Hereinafter, structural ultra-thick steel having excellent resistance to brittle crack propagation according to an aspect of the present disclosure will be described in detail.
- According to an aspect of the present disclosure, structural ultra-thick steel having excellent resistance to brittle crack propagation includes: 0.02-0.1 wt % of C, 0.8-2.5 wt % of Mn, 0.05-1.5 wt % of Ni, 0.005-0.1 wt % of Nb, 0.005-0.1 wt % of Ti, and the remainder of Fe and other inevitable impurities, the structural ultra-thick steel having microstructures including one structure selected from the group consisting of a single-phase structure of ferrite, a single-phase structure of bainite, a complex-phase structure of ferrite and bainite, a complex-phase structure of ferrite and pearlite, and a complex-phase structure of ferrite, bainite, and pearlite.
- Such structural ultra-thick steel has a thickness of 10-100 mm, more preferably 50-100 mm.
- Hereinafter, steel compositions and composition ranges in an embodiment will be described.
- Carbon (C): 0.02-0.1% (hereinafter, a content of each composition refers to wt %).
- Since C is the most important element in securing basic strength, C is required to be contained in steel within an appropriate range. 0.02% or more of C is added in order to obtain such an addition effect.
- However, when the content of C exceeds 0.1%, low temperature toughness may be degraded due to generation of a large amount of martensite-austenite (M/A) constituents and high strength of ferrite itself, and the content of C is thus restricted to 0.02-0.1%.
- Since Mn is an element useful in improving strength by solid solution strengthening and to enhance hardenability so as to generate a low temperature transformation phase, 0.8% or more of Mn is added.
- However, when a content of Mn exceeds 2.5%, an excessive increase in hardenability may promote generation of upper bainite and martensite to degrade impact toughness and resistance to brittle crack propagation, and the content of Mn is thus restricted to 0.8-2.5%.
- Since Ni is an important element to facilitate cross slip of potentials at low temperatures to improve impact toughness and hardenability, increasing strength, 0.05% or more of Ni is added in order to improve impact toughness and resistance to brittle crack propagation. However, when 1.5% or more of Ni is added, hardenability may be excessively increased to generate a low temperature transformation phase, degrading toughness and increasing manufacturing costs, and an upper limit of the content of Ni is thus restricted to 1.5%.
- Nb may be precipitated in the form of NbC or NbCN to increase strength of a base material.
- Further, Nb, dissolved when reheated to a high temperature, may be precipitated very finely in the form of NbC at the time of rolling to suppress recrystallization of austenite, thus miniaturizing a structure.
- Thus, 0.005% or more of Nb is added. However, an excessive amount of Nb may cause brittle cracking in an edge of the steel, and a lower limit of the content of Nb is thus restricted to 0.1%.
- Ti is precipitated as TiN when reheated and is an element that may significantly improve low temperature toughness by suppressing the growth of crystal grains of the base material and a weld heat affected zone. 0.005% or more of Ti is added in order to obtain such an addition effect.
- However, when greater than 0.1% of Ti is added, low temperature toughness may be reduced due to clogging of a continuous casting nozzle or crystallization of the central portion, and a content of Ti is thus restricted to 0.005-0.1%.
- In an embodiment, the remainder thereof is iron (Fe). However, in a common manufacturing process, impurities of raw materials or steel manufacturing environments may be inevitably included in the steel, and such impurities may not be removed from the steel.
- These impurities are commonly known to a person skilled in the art, and are thus not specifically mentioned in this specification.
- The steel according to an embodiment has microstructures including one structure selected from the group consisting of a single-phase structure of ferrite, a single-phase structure of bainite, a complex-phase structure of ferrite and bainite, a complex-phase structure of ferrite and pearlite, and a complex-phase structure of ferrite, bainite, and pearlite.
- A ratio of pearlite is restricted to 30 vol% or less in the complex-phase structure of ferrite, bainite, and pearlite.
- The ferrite is acicular ferrite or polygonal ferrite and the bainite is granular bainite. As the contents of Mn and Ni increase, fractions of acicular ferrite or polygonal ferrite and granular bainite may increase. Accordingly, strength may also increase.
- The steel has a grain size of 15 µm or less and a high-angle grain boundary of 15° or higher measured in the central portion in a plate thickness direction of the steel in an electron backscatter diffraction (EBSD) manner.
- The steel has a yield strength of 350 MPa or more, and an impact transition temperature of -60°C or lower in the central portion thereof.
- According to another aspect of the present disclosure, a method of producing structural ultra-thick steel having excellent resistance to brittle crack propagation includes: reheating a slab or a bar including 0.02-0.1 wt % of C, 0.8-2.5 wt % of Mn, 0.05-1.5 wt % of Ni, 0.005-0.1 wt % of Nb, 0.005-0.1 wt % of Ti, and the remainder of Fe and other inevitable impurities to 950-1,100°C and then rough rolling the reheated slab or bar at 900-1,100°C; obtaining a steel sheet by finish rolling the rough rolled slab or bar at an Ar3 transformation point or higher; and cooling the steel sheet to 700°C or lower, in which a temperature difference between a central portion of the slab or the bar in a thickness direction thereof and an external surface of the slab or the bar before rough rolling is 100-300°C.
- A slab reheating temperature is restricted to 950°C or higher, which is performed to dissolve a carbonitride of Ti and/or Nb formed during casting. Further, it may be more preferable to reheat the slab to 1,000°C or higher in order to sufficiently dissolve the carbonitride of Ti and/or Nb. However, when the slab is reheated to an excessively high temperature, there may be concerns that austenite is coarsened, and an upper limit of the slab reheating temperature is thus 1,100°C.
- Rough Rolling Temperature: 900-1,100°C and Temperature Difference between Central Portion of Slab or Bar in Thickness Direction and External Surface of Slab or Bar before Rough Rolling: 100-300°C
- The reheated slab is rough rolled. A rough rolling temperature is a temperature (Tnr) or higher at which recrystallization of austenite stops. Effects of destroying a cast structure, such as a dendrite or the like, formed during casting by rolling, and of reducing a size of austenite may also be obtained. The rough rolling temperature is restricted to 900-1,100°C in order to obtain such an effect.
- In an embodiment, the temperature difference between the central portion of the slab or the bar in the thickness direction thereof and the external surface of the slab or the bar immediately before rolling at the time of rough rolling is 100-300°C.
- Such a temperature difference between the central portion and the external surface is obtained by cooling a heated slab or bar with a cooling device. The cooling device is not particularly limited and, for example, at least one of water, air, a liquid coolant, and a vapor coolant may be used as a cooling medium.
- As described above, the temperature difference between the central portion of the slab or the bar in the thickness direction thereof and the external surface of the slab or the bar may be given at the time of rough rolling to maintain a surface portion of the slab or the bar at a temperature lower than that of the central portion. When rolling is performed in a state in which such a temperature difference exists, the central portion having a temperature relatively higher than that of the surface portion may be further deformed, and a grain size of the central portion thus becomes finer. An average grain size of the central portion is maintained at 15 µm or less.
- This is a technology utilizing a phenomenon in which since the surface portion having a relatively low temperature has strength higher than that of the central portion having a relatively high temperature, the central portion having relatively low strength may be further deformed. The temperature difference between the central portion and the external surface is 100-300°C in order to effectively provide further deformation to the central portion..
- Here, the temperature difference between the central portion of the slab or the bar in the thickness direction thereof and the external surface of the slab or the bar may refer to a difference between a surface temperature of the slab or the bar measured immediately before rough rolling and a temperature of the central portion calculated by considering cooling conditions and a thickness of the slab or the bar immediately before rough rolling.
- The measurements of the surface temperature and the thickness of the slab may be taken before initial rough rolling, and the measurements of the surface temperature and the thickness of the bar may be taken before initial rough rolling after two rough rolling processes.
- When rough rolling is performed in two or more passes, the temperature difference between the central portion of the slab or the bar in the thickness direction thereof and the external surface of the slab or the bar may refer to the fact that a temperature difference, obtained by measuring temperature differences in the respective passes during rough rolling and calculating a total average value, is 100-300°C.
- A total cumulative reduction ratio at the time of rough rolling is 40% or more in order to miniaturize the structure of the central portion at the time of rough rolling.
- A steel sheet is obtained by finish rolling the rough rolled bar at an Ar3 transformation point or higher.
- At the time of finish rolling, an austenite structure may be transformed.
- After finish rolling, the steel sheet is cooled to 700°C or lower.
- When a cooling termination temperature exceeds 700°C, a microstructure may not be properly formed, and there may thus be a possibility that the yield strength is 350 MPa or less.
- The cooling of the steel sheet is performed at a central portion average cooling rate of 3-300 °C/s or more. When the central portion average cooling rate of the steel sheet is less than 3 °C/s, the microstructure may not be properly formed, and there may thus be a possibility that the yield strength is 350 MPa or less.
- Hereinafter, the present disclosure will be described in more detail through embodiments.
- It should be noted, however, that the following embodiments are intended to illustrate the present disclosure by way of illustration and not to limit the scope of the present disclosure.
- The scope of the present invention is determined by the matters described in the claims and those reasonably inferred therefrom.
- A steel slab having a composition illustrated in Table 1 below was reheated to 1,070°C, and rough rolled at a temperature of 1,050°C. An average temperature difference between an external surface and a central portion of the steel slab at the time of rough rolling of the steel slab is shown in Table 2 below, and a cumulative reduction ratio was 50%.
- The average temperature difference between the external surface and the central portion at the time of rough rolling as illustrated in Table 2 may represent a difference between a surface temperature of a slab or a bar measured immediately before rough rolling and a temperature of the central portion calculated by considering an amount of water injected to the slab or the bar and a thickness of the slab or the bar immediately before rough rolling, and the average temperature difference may be a result obtained by measuring temperature differences in respective passes during rough rolling and calculating a total average value.
- After rough rolling, a steel sheet having a thickness illustrated in Table 2 below was obtained by finish rolling the steel slab at a finish rolling temperature of 780°C, and was cooled to a temperature of 700°C or lower at a cooling rate of 5 °C/s.
- With respect to the steel sheet manufactured as described above, microstructures, yield strength, an average grain size of the central portion, an impact transition temperature of the central portion, and a Kca value (a brittle crack propagation resistance coefficient) were measured, and the results are illustrated in Table 2 below.
- The Kca value illustrated in Table 2 may be an estimate value obtained by performing an ESSO test.
[Table 1] CLASSIFICATION C (wt%) Mn (wt%) Ni (wt%) Ti (wt%) Nb (wt%) INVENTIVE STEEL 1 0.032 2.05 0.12 0.018 0.019 INVENTIVE STEEL 2 0.067 1.77 0.35 0.023 0.012 INVENTIVE STEEL 3 0.074 1.25 0.95 0.021 0.023 INVENTIVE STEEL 4 0.063 1.63 0.75 0.015 0.015 INVENTIVE STEEL 5 0.053 1.74 1.02 0.018 0.021 INVENTIVE STEEL 6 0.091 1.21 0.43 0.023 0.029 COMPARATIVE STEEL 1 0.082 0.92 0.65 0.012 0.018 COMPARATIVE STEEL 2 0.061 1.65 0.37 0.017 0.012 COMPARATIVE STEEL 3 0.12 1.59 0.23 0.021 0.011 COMPARATIVE STEEL 4 0.076 2.05 2.25 0.015 0.019 COMPARATIVE STEEL 5 0.071 2.65 0.45 0.017 0.022 [Table 2] CLASSIFICATION AVERAGE CENTRAL PORTION-SURFACE TEMPERATURE DIFFERENCE DURING ROUGH ROLLING (°C) PRODUCT THICKNESS (mm) * MICROSTRUCTURE, PHASE FRACTION (%) YIELD STRENGTH (MPa) AVERAGE GRAIN SIZE OF CENTRAL PORTION (µm) IMPACT TRANSITION TEMPERATURE OF CENTRAL PORTION (°C) Kca (N/mm1.5, @-10°C) INVENTIVE STEEL 1 256 85 AF+26%GB 506 11.3 -96 9314 INVENTIVE STEEL 2 165 95 AF 455 12.5 -86 8655 INVENTIVE STEEL 3 137 100 PF+23%P 395 13.1 -79 7956 INVENTIVE STEEL 4 259 90 AF+28%GB 486 9.7 -86 8165 INVENTIVE STEEL 5 215 95 AF+31%GB 512 10.1 -91 8964 INVENTIVE STEEL 6 189 100 PF+22%P 407 12.6 -77 7103 COMPARATIVE STEEL 1 23 90 PF+18%P 371 25.3 -53 5166 COMPARATIVE STEEL 2 35 85 AF+21%UB 495 29.6 -49 4931 COMPARATIVE STEEL 3 129 80 UB 578 32 -35 3655 COMPARATIVE STEEL 4 212 100 GB, 34%UB 566 26 -50 3984 COMPARATIVE STEEL 5 155 85 UB 613 38 -20 2850 * PF: Polygonal Ferrite, P: Pearlite AF: Acicular Ferrite, GB: Granular Bainite, and UB: Upper Bainite. Here, the product thicknesses show that they were evaluated for thick steels. - As illustrated in Table 2, in the case of Comparative Steels 1 and 2, it can be seen that the average temperature difference between the central portion in the thickness direction and the external surface at the time of rough rolling presented in an embodiment is controlled to less than 100°C, that since a sufficient degree of deformation is not given to the central portion at the time of rough rolling, grain sizes of the central portion are 25.3 µm and 29.6 µm, respectively; thus, an impact transition temperature of the central portion is less than -60°C. Further, it can also be seen that the Kca value measured at -10°C does not exceed 6,000, required in a common steel for shipbuilding.
- In the case of Comparative Steels 3 and 5, it can be seen that Comparative Steels 3 and 5 have values greater than the upper limits of the contents of C and Mn proposed in an embodiment, that even though a grain size of austenite in the central portion is miniaturized through cooling at the time of rough rolling, grain sizes of final microstructures are 32 µm or more and 38 µm or more, respectively, due to the generation of upper bainite, and that since Comparative Steels 3 and 5 have the upper bainite, in which brittleness may easily occur, as a base structure; thus, an impact transition temperature of the central portion is -60°C or higher.
- Accordingly, it can also be seen that a Kca value is 6,000 or less at -10°C.
- In the case of Comparative Steel 4, it can be seen that Comparative Steel 4 has a value greater than the upper limit of the content of Ni proposed in an embodiment, and that, in terms of high hardenability, microstructures of a base metal are granular bainite and upper bainite.
- Thus, it can be seen that, even though the grain size of austenite in the central portion is miniaturized through cooling at the time of rough rolling, a grain size of the final microstructure is 26 µm, that the upper bainite, in which brittleness may easily occur, is a base structure; thus, an impact transition temperature of the central portion is -60°C or higher.
- Further, it can also be seen that a Kca value is 6,000 or less at -10°C.
- In contrast, in the case of Inventive Steels 1 to 6, which satisfy the composition range in an embodiment and in which the grain size of austenite in the central portion is miniaturized through cooling at the time of rough rolling, it can be seen that Inventive Steels 1 to 6 satisfy a yield strength of 350 MPa or more, and a grain size of 15 µm or less in central portions thereof, and have, as microstructures, ferrite and pearlite structures, a single-phase structure of acicular ferrite, or a complex-phase structure of acicular ferrite or polygonal ferrite and granular bainite, and a complex-phase structure of acicular ferrite, pearlite, and granular bainite.
- Accordingly, it can be seen that an impact transition temperature of the central portion is -60°C or lower and that a Kca value satisfies 6,000 or more at -10°C.
- As illustrated in
FIG. 1 , depicting an image obtained by observing the central portion of Inventive Steel 1 in a thickness direction thereof with an optical microscope, in the case of Inventive Steel 1, it can be seen that a structure of the central portion is fine.
Claims (4)
- A structural ultra-thick steel having excellent resistance to brittle crack propagation, the structural ultra-thick steel consisting of:0.02-0.1 wt % of C, 0.8-2.5 wt % of Mn, 0.05-1.5 wt % of Ni, 0.005-0.1 wt % of Nb, 0.005-0.1 wt % of Ti, and the remainder of Fe and other inevitable impurities, the structural ultra-thick steel having microstructures consisting of one structure selected from the group consisting of a single-phase structure of ferrite, a single-phase structure of bainite, a complex-phase structure of ferrite and bainite, a complex-phase structure of ferrite and pearlite, and a complex-phase structure of ferrite, bainite, and pearlite, andwherein the ferrite is acicular ferrite or polygonal ferrite, and the bainite is granular bainite,wherein when the microstructures have the complex-phase structure of ferrite, bainite, and pearlite a percentage of pearlite to the complex-phase structure is 30 vol% or less,wherein the steel has a grain size of 15 µm or less, the grain size having a high-angle grain boundary of 15° or higher measured in an EBSD manner in a central portion in a plate thickness direction,wherein the steel has a yield strength of 350 MPa or more, an impact transition temperature of -60°C or lower in of a central portion thereof, a thickness of 10-100 mm and 6,000 or more of Kca value obtained by performing an ESSO test.
- A method of producing a structural ultra-thick steel of claim 1 having excellent resistance to brittle crack propagation, the method comprising:reheating a slab or a bar consisting of 0.02-0.1 wt % of C, 0.8-2.5 wt % of Mn, 0.05-1.5 wt % of Ni, 0.005-0.1 wt % of Nb, 0.005-0.1 wt % of Ti, and the remainder of Fe and other inevitable impurities to 950-1, 100°C and then rough rolling the reheated slab or bar at 900-1,100°C;obtaining a steel sheet by finish rolling the rough rolled slab or bar at an Ar3 transformation point or higher; andcooling the steel sheet to 700°C or lower,wherein a temperature difference between a central portion of the slab or the bar in a thickness direction thereof and an external surface of the slab or the bar before rolling at the time of rough rolling is 100-300°C,wherein the temperature difference between the central portion of the slab or the bar in the thickness direction and the external surface of the slab or the bar is obtained by cooling the slab or the bar with a cooling device,wherein a cooling medium of the cooling device is at least one of water, air, a liquid coolant, and a vapor coolant,wherein a total cumulative reduction ratio at the time of rough rolling is 40% or higher,wherein the cooling of the steel sheet is performed at a central portion average cooling rate of 3-300 °C/s.
- The method of claim 2, wherein the temperature difference between the central portion of the slab or the bar in the thickness direction and the external surface of the slab or the bar is a difference between a surface temperature of the slab or the bar measured immediately before rough rolling and a temperature of the central portion calculated by considering cooling conditions and a thickness of the slab or the bar immediately before rough rolling.
- The method of claim 2, wherein the rough rolling is performed in two passes or more, and the temperature difference between the central portion of the slab or the bar in the thickness direction and the external surface of the slab or the bar is a temperature difference obtained by measuring temperature differences in the respective passes during the rough rolling and calculating a total average value.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR1020140188465A KR101657827B1 (en) | 2014-12-24 | 2014-12-24 | Steel having excellent in resistibility of brittle crack arrestbility and manufacturing method thereof |
PCT/KR2015/013557 WO2016105003A1 (en) | 2014-12-24 | 2015-12-11 | Structural ultra-thick steel having excellent resistance to brittle crack propagation, and production method therefor |
Publications (4)
Publication Number | Publication Date |
---|---|
EP3239329A1 EP3239329A1 (en) | 2017-11-01 |
EP3239329A4 EP3239329A4 (en) | 2017-11-01 |
EP3239329B1 true EP3239329B1 (en) | 2019-10-09 |
EP3239329B8 EP3239329B8 (en) | 2019-11-20 |
Family
ID=56150967
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP15873530.8A Active EP3239329B8 (en) | 2014-12-24 | 2015-12-11 | Structural ultra-thick steel having excellent resistance to brittle crack propagation, and production method therefor |
Country Status (6)
Country | Link |
---|---|
US (1) | US20170342518A1 (en) |
EP (1) | EP3239329B8 (en) |
JP (1) | JP6475839B2 (en) |
KR (1) | KR101657827B1 (en) |
CN (1) | CN107109591A (en) |
WO (1) | WO2016105003A1 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR101940880B1 (en) * | 2016-12-22 | 2019-01-21 | 주식회사 포스코 | Sour resistance steel sheet having excellent low temperature toughness and post weld heat treatment property, and method of manufacturing the same |
KR102209547B1 (en) * | 2018-12-19 | 2021-01-28 | 주식회사 포스코 | Ultra thick structural steel having superior brittle crack initiation resistance and method of manufacturing the same |
CN115354219B (en) * | 2022-07-06 | 2023-09-15 | 江阴兴澄特种钢铁有限公司 | SA516Gr70 steel plate with excellent high-temperature strength at 200-400 ℃ and manufacturing method thereof |
Family Cites Families (26)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH064903B2 (en) * | 1985-04-09 | 1994-01-19 | 新日本製鐵株式会社 | Steel plate with excellent brittle crack propagation arresting property and its manufacturing method |
JPH04180521A (en) * | 1990-11-14 | 1992-06-26 | Kobe Steel Ltd | Production of high tensile thick steel plate having high yield strength and high toughness |
JP3474661B2 (en) * | 1995-01-24 | 2003-12-08 | 新日本製鐵株式会社 | Sour-resistant steel plate with excellent crack arrestability |
UA59411C2 (en) * | 1997-07-28 | 2003-09-15 | Ексонмобіл Апстрім Рісерч Компані | Super high-strength steels with perfect superlow temperature density |
TW459053B (en) * | 1997-12-19 | 2001-10-11 | Exxon Production Research Co | Ultra-high strength dual phase steels with excellent cryogenic temperature toughness |
US6254698B1 (en) * | 1997-12-19 | 2001-07-03 | Exxonmobile Upstream Research Company | Ultra-high strength ausaged steels with excellent cryogenic temperature toughness and method of making thereof |
JP3417878B2 (en) * | 1999-07-02 | 2003-06-16 | 株式会社神戸製鋼所 | High-strength hot-rolled steel sheet excellent in stretch flangeability and fatigue properties and its manufacturing method |
KR100380750B1 (en) | 2000-10-24 | 2003-05-09 | 주식회사 포스코 | Method for high strength steel plate having superior toughness in weld heat-affected zone |
US20060169368A1 (en) * | 2004-10-05 | 2006-08-03 | Tenaris Conncections A.G. (A Liechtenstein Corporation) | Low carbon alloy steel tube having ultra high strength and excellent toughness at low temperature and method of manufacturing the same |
JP4058097B2 (en) * | 2006-04-13 | 2008-03-05 | 新日本製鐵株式会社 | High strength steel plate with excellent arrestability |
JP5064150B2 (en) * | 2006-12-14 | 2012-10-31 | 新日本製鐵株式会社 | High strength steel plate with excellent brittle crack propagation stopping performance |
KR100851176B1 (en) * | 2006-12-27 | 2008-08-08 | 주식회사 포스코 | Hot-rolled steel sheet for line pipe having low anisotropy of low temperature toughness and yield strength and the method for manufacturing the same |
JP4309946B2 (en) * | 2007-03-05 | 2009-08-05 | 新日本製鐵株式会社 | Thick high-strength steel sheet excellent in brittle crack propagation stopping characteristics and method for producing the same |
KR100957961B1 (en) | 2007-12-26 | 2010-05-17 | 주식회사 포스코 | High strength steel plate having excellent welded zone toughness for linepipe and the method for manufacturing the same |
JP5337412B2 (en) * | 2008-06-19 | 2013-11-06 | 株式会社神戸製鋼所 | Thick steel plate excellent in brittle crack propagation stopping characteristics and method for producing the same |
KR101360737B1 (en) * | 2009-12-28 | 2014-02-07 | 주식회사 포스코 | High strength steel plate having excellent resistance to brittle crack initiation and method for manufacturing the same |
JP5425702B2 (en) * | 2010-02-05 | 2014-02-26 | 株式会社神戸製鋼所 | High-strength thick steel plate with excellent drop weight characteristics |
WO2012108543A1 (en) * | 2011-02-08 | 2012-08-16 | Jfeスチール株式会社 | Thick steel plate of at least 50mm in thickness with superior long brittle fracture propagation stopping properties, manufacturing method for same, and method for evaluating long brittle fracture propagation stopping performance and test apparatus for same |
JP5304925B2 (en) * | 2011-12-27 | 2013-10-02 | Jfeスチール株式会社 | Structural high-strength thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same |
BR112014015789B1 (en) * | 2011-12-27 | 2019-10-29 | Jfe Steel Corp | sheet steel and method for producing it |
TWI463018B (en) * | 2012-04-06 | 2014-12-01 | Nippon Steel & Sumitomo Metal Corp | High strength steel plate with excellent crack arrest property |
JP2013221190A (en) * | 2012-04-17 | 2013-10-28 | Nippon Steel & Sumitomo Metal Corp | High-strength thick steel plate excellent in brittle crack propagation arresting capability |
JP2013221189A (en) * | 2012-04-17 | 2013-10-28 | Nippon Steel & Sumitomo Metal Corp | High-strength thick steel plate excellent in brittle crack propagation arresting capability |
JP5811032B2 (en) * | 2012-05-23 | 2015-11-11 | 新日鐵住金株式会社 | Steel sheet for LPG tank |
EP2963138B1 (en) * | 2013-02-28 | 2019-04-10 | JFE Steel Corporation | Production method for thick steel plate |
JP6086086B2 (en) * | 2014-03-19 | 2017-03-01 | Jfeスチール株式会社 | Ultra-thick steel plate with excellent HIC resistance and manufacturing method thereof |
-
2014
- 2014-12-24 KR KR1020140188465A patent/KR101657827B1/en active IP Right Grant
-
2015
- 2015-12-11 WO PCT/KR2015/013557 patent/WO2016105003A1/en active Application Filing
- 2015-12-11 CN CN201580070961.2A patent/CN107109591A/en active Pending
- 2015-12-11 US US15/535,570 patent/US20170342518A1/en not_active Abandoned
- 2015-12-11 JP JP2017532807A patent/JP6475839B2/en active Active
- 2015-12-11 EP EP15873530.8A patent/EP3239329B8/en active Active
Non-Patent Citations (1)
Title |
---|
None * |
Also Published As
Publication number | Publication date |
---|---|
CN107109591A (en) | 2017-08-29 |
KR20160078668A (en) | 2016-07-05 |
JP6475839B2 (en) | 2019-02-27 |
EP3239329B8 (en) | 2019-11-20 |
KR101657827B1 (en) | 2016-09-20 |
WO2016105003A1 (en) | 2016-06-30 |
EP3239329A1 (en) | 2017-11-01 |
US20170342518A1 (en) | 2017-11-30 |
JP2018504524A (en) | 2018-02-15 |
EP3239329A4 (en) | 2017-11-01 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP3239332B1 (en) | High-strength steel having superior brittle crack arrestability, and production method therefor | |
EP3239330B1 (en) | High-strength steel having superior brittle crack arrestability, and production method therefor | |
EP3385401B1 (en) | High-strength steel having excellent brittle crack arrestability and welding part brittle crack initiation resistance, and production method therefor | |
EP3561111B1 (en) | Thick steel sheet having excellent cryogenic impact toughness and manufacturing method therefor | |
EP2520684B9 (en) | Austenite steel material having superior ductility | |
JP2016534230A (en) | High hardness hot rolled steel product and method for producing the same | |
EP3239331B1 (en) | High-strength steel having superior brittle crack arrestability, and production method therefor | |
EP3385402B1 (en) | High-strength steel having excellent brittle crack arrestability and welding part brittle crack initiation resistance, and production method therefor | |
EP3239329B1 (en) | Structural ultra-thick steel having excellent resistance to brittle crack propagation, and production method therefor | |
KR101657840B1 (en) | Steel having superior brittle crack arrestability and method for manufacturing the steel | |
EP3395988B1 (en) | High-strength structural steel sheet excellent in hot resistance and manufacturing method thereof | |
EP3231886B1 (en) | Complex-phase steel sheet with excellent formability and manufacturing method therefor | |
KR20150073024A (en) | Steel plate for pressure vessel having excellent strength and toughness after post welding heat treatment and method for manufacturing the same | |
EP4265782A1 (en) | High-yield-ratio ultra-high-strength steel sheet having excellent thermal stability, and manufacturing method therefor | |
JP2020164950A (en) | Clad steel plate and method of producing the same | |
KR102031453B1 (en) | Hot-rolled steel sheet and method for manufacturing the same | |
KR101696154B1 (en) | Steel having excellent in resistibility of brittle crack arrestbility and manufacturing method thereof | |
EP3889295A2 (en) | Ultra-thick steel excellent in brittle crack arrestability and manufacturing method therefor | |
EP4079897A1 (en) | High-strength steel having superior ductility, and manufacturing method therefor |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE INTERNATIONAL PUBLICATION HAS BEEN MADE |
|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: REQUEST FOR EXAMINATION WAS MADE |
|
17P | Request for examination filed |
Effective date: 20170620 |
|
A4 | Supplementary search report drawn up and despatched |
Effective date: 20170915 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR |
|
AX | Request for extension of the european patent |
Extension state: BA ME |
|
RAP1 | Party data changed (applicant data changed or rights of an application transferred) |
Owner name: POSCO |
|
DAV | Request for validation of the european patent (deleted) | ||
DAX | Request for extension of the european patent (deleted) | ||
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: EXAMINATION IS IN PROGRESS |
|
17Q | First examination report despatched |
Effective date: 20180727 |
|
GRAP | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOSNIGR1 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: GRANT OF PATENT IS INTENDED |
|
INTG | Intention to grant announced |
Effective date: 20190429 |
|
RIC1 | Information provided on ipc code assigned before grant |
Ipc: C22C 38/04 20060101AFI20190415BHEP Ipc: C22C 38/08 20060101ALI20190415BHEP Ipc: C22C 38/00 20060101ALI20190415BHEP Ipc: C21D 6/00 20060101ALI20190415BHEP Ipc: C22C 38/12 20060101ALI20190415BHEP Ipc: C21D 8/02 20060101ALI20190415BHEP Ipc: C22C 38/14 20060101ALI20190415BHEP |
|
RAP1 | Party data changed (applicant data changed or rights of an application transferred) |
Owner name: POSCO |
|
GRAS | Grant fee paid |
Free format text: ORIGINAL CODE: EPIDOSNIGR3 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE PATENT HAS BEEN GRANTED |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR |
|
REG | Reference to a national code |
Ref country code: GB Ref legal event code: FG4D |
|
REG | Reference to a national code |
Ref country code: CH Ref legal event code: EP |
|
GRAT | Correction requested after decision to grant or after decision to maintain patent in amended form |
Free format text: ORIGINAL CODE: EPIDOSNCDEC |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R096 Ref document number: 602015039706 Country of ref document: DE |
|
REG | Reference to a national code |
Ref country code: IE Ref legal event code: FG4D |
|
REG | Reference to a national code |
Ref country code: CH Ref legal event code: PK Free format text: BERICHTIGUNG B8 |
|
RAP2 | Party data changed (patent owner data changed or rights of a patent transferred) |
Owner name: POSCO |
|
REG | Reference to a national code |
Ref country code: AT Ref legal event code: REF Ref document number: 1188900 Country of ref document: AT Kind code of ref document: T Effective date: 20191115 |
|
REG | Reference to a national code |
Ref country code: NL Ref legal event code: MP Effective date: 20191009 |
|
REG | Reference to a national code |
Ref country code: LT Ref legal event code: MG4D |
|
REG | Reference to a national code |
Ref country code: AT Ref legal event code: MK05 Ref document number: 1188900 Country of ref document: AT Kind code of ref document: T Effective date: 20191009 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: AT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: NL Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: LV Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: SE Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: PT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20200210 Ref country code: LT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: NO Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20200109 Ref country code: PL Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: GR Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20200110 Ref country code: BG Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20200109 Ref country code: FI Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: HR Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: RS Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: IS Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20200224 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: AL Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R097 Ref document number: 602015039706 Country of ref document: DE |
|
PG2D | Information on lapse in contracting state deleted |
Ref country code: IS |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: CZ Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: RO Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: EE Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: DK Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: IS Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20200209 |
|
REG | Reference to a national code |
Ref country code: CH Ref legal event code: PL |
|
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
REG | Reference to a national code |
Ref country code: BE Ref legal event code: MM Effective date: 20191231 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: IT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: SK Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: SM Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: MC Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 |
|
26N | No opposition filed |
Effective date: 20200710 |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee |
Effective date: 20200109 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: ES Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: LU Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20191211 Ref country code: IE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20191211 Ref country code: GB Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20200109 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: BE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20191231 Ref country code: SI Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 Ref country code: LI Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20191231 Ref country code: CH Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20191231 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: CY Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: HU Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT; INVALID AB INITIO Effective date: 20151211 Ref country code: MT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: TR Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: MK Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20191009 |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R081 Ref document number: 602015039706 Country of ref document: DE Owner name: POSCO CO., LTD, POHANG-SI, KR Free format text: FORMER OWNER: POSCO, POHANG-SI, GYEONGSANGBUK-DO, KR Ref country code: DE Ref legal event code: R081 Ref document number: 602015039706 Country of ref document: DE Owner name: POSCO CO., LTD, POHANG- SI, KR Free format text: FORMER OWNER: POSCO, POHANG-SI, GYEONGSANGBUK-DO, KR Ref country code: DE Ref legal event code: R081 Ref document number: 602015039706 Country of ref document: DE Owner name: POSCO HOLDINGS INC., KR Free format text: FORMER OWNER: POSCO, POHANG-SI, GYEONGSANGBUK-DO, KR |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R081 Ref document number: 602015039706 Country of ref document: DE Owner name: POSCO CO., LTD, POHANG-SI, KR Free format text: FORMER OWNER: POSCO HOLDINGS INC., SEOUL, KR Ref country code: DE Ref legal event code: R081 Ref document number: 602015039706 Country of ref document: DE Owner name: POSCO CO., LTD, POHANG- SI, KR Free format text: FORMER OWNER: POSCO HOLDINGS INC., SEOUL, KR |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 20231121 Year of fee payment: 9 Ref country code: DE Payment date: 20231120 Year of fee payment: 9 |