WO2023057062A1 - Alloyed steel - Google Patents
Alloyed steel Download PDFInfo
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- WO2023057062A1 WO2023057062A1 PCT/EP2021/077627 EP2021077627W WO2023057062A1 WO 2023057062 A1 WO2023057062 A1 WO 2023057062A1 EP 2021077627 W EP2021077627 W EP 2021077627W WO 2023057062 A1 WO2023057062 A1 WO 2023057062A1
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- Prior art keywords
- steel
- vanadium
- less
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- precipitates
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 326
- 239000010959 steel Substances 0.000 title claims abstract description 326
- 239000002244 precipitate Substances 0.000 claims abstract description 119
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 101
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims abstract description 99
- 230000016507 interphase Effects 0.000 claims abstract description 66
- 230000001427 coherent effect Effects 0.000 claims abstract description 60
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 33
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 33
- 238000010438 heat treatment Methods 0.000 claims abstract description 18
- 229910000859 α-Fe Inorganic materials 0.000 claims description 55
- 238000000034 method Methods 0.000 claims description 32
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 30
- 238000001816 cooling Methods 0.000 claims description 29
- 238000001556 precipitation Methods 0.000 claims description 29
- 229910052757 nitrogen Inorganic materials 0.000 claims description 28
- 229910001567 cementite Inorganic materials 0.000 claims description 25
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 claims description 24
- 230000005291 magnetic effect Effects 0.000 claims description 24
- 239000000203 mixture Substances 0.000 claims description 22
- 239000002245 particle Substances 0.000 claims description 21
- 239000010949 copper Substances 0.000 claims description 18
- 229910052804 chromium Inorganic materials 0.000 claims description 15
- 239000011651 chromium Substances 0.000 claims description 15
- 238000005098 hot rolling Methods 0.000 claims description 15
- 229910052750 molybdenum Inorganic materials 0.000 claims description 15
- 239000011572 manganese Substances 0.000 claims description 13
- 229910052710 silicon Inorganic materials 0.000 claims description 13
- 239000010703 silicon Substances 0.000 claims description 13
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 12
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 12
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 12
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 12
- 229910052802 copper Inorganic materials 0.000 claims description 12
- 229910052748 manganese Inorganic materials 0.000 claims description 12
- 239000011733 molybdenum Substances 0.000 claims description 12
- 229910001562 pearlite Inorganic materials 0.000 claims description 9
- 238000005096 rolling process Methods 0.000 claims description 8
- 238000001953 recrystallisation Methods 0.000 claims description 7
- ZLANVVMKMCTKMT-UHFFFAOYSA-N methanidylidynevanadium(1+) Chemical class [V+]#[C-] ZLANVVMKMCTKMT-UHFFFAOYSA-N 0.000 claims description 5
- 239000000126 substance Substances 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 24
- 229910052739 hydrogen Inorganic materials 0.000 description 21
- 239000001257 hydrogen Substances 0.000 description 21
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 20
- 229910045601 alloy Inorganic materials 0.000 description 19
- 239000000956 alloy Substances 0.000 description 19
- 229910001566 austenite Inorganic materials 0.000 description 17
- 230000015572 biosynthetic process Effects 0.000 description 16
- 230000001965 increasing effect Effects 0.000 description 16
- 230000009970 fire resistant effect Effects 0.000 description 15
- 229910052742 iron Inorganic materials 0.000 description 13
- 239000011159 matrix material Substances 0.000 description 13
- 239000002105 nanoparticle Substances 0.000 description 11
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 10
- 230000000694 effects Effects 0.000 description 10
- 230000009466 transformation Effects 0.000 description 10
- 230000008569 process Effects 0.000 description 8
- -1 carbides) Chemical compound 0.000 description 7
- 230000007246 mechanism Effects 0.000 description 7
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- 230000009286 beneficial effect Effects 0.000 description 6
- 239000011258 core-shell material Substances 0.000 description 6
- 230000006698 induction Effects 0.000 description 6
- INZDTEICWPZYJM-UHFFFAOYSA-N 1-(chloromethyl)-4-[4-(chloromethyl)phenyl]benzene Chemical compound C1=CC(CCl)=CC=C1C1=CC=C(CCl)C=C1 INZDTEICWPZYJM-UHFFFAOYSA-N 0.000 description 5
- 238000002441 X-ray diffraction Methods 0.000 description 5
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- 150000001247 metal acetylides Chemical class 0.000 description 5
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- 230000003068 static effect Effects 0.000 description 4
- 238000005275 alloying Methods 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
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- 238000001000 micrograph Methods 0.000 description 3
- 230000006911 nucleation Effects 0.000 description 3
- 238000010899 nucleation Methods 0.000 description 3
- 239000000523 sample Substances 0.000 description 3
- 229910000975 Carbon steel Inorganic materials 0.000 description 2
- 229910001208 Crucible steel Inorganic materials 0.000 description 2
- 206010037660 Pyrexia Diseases 0.000 description 2
- 238000000137 annealing Methods 0.000 description 2
- 230000000739 chaotic effect Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 239000010955 niobium Substances 0.000 description 2
- 238000005381 potential energy Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 238000010008 shearing Methods 0.000 description 2
- 238000007655 standard test method Methods 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- 238000005496 tempering Methods 0.000 description 2
- 238000009864 tensile test Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 238000003325 tomography Methods 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- 229910000922 High-strength low-alloy steel Inorganic materials 0.000 description 1
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 229910000756 V alloy Inorganic materials 0.000 description 1
- 230000004308 accommodation Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
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- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000005094 computer simulation Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000001595 contractor effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000010339 dilation Effects 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000002017 high-resolution X-ray diffraction Methods 0.000 description 1
- 238000000000 high-resolution scanning transmission electron microscopy Methods 0.000 description 1
- 238000002173 high-resolution transmission electron microscopy Methods 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 238000010884 ion-beam technique Methods 0.000 description 1
- 230000010511 looping mechanism Effects 0.000 description 1
- 230000005415 magnetization Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 238000000399 optical microscopy Methods 0.000 description 1
- 230000005298 paramagnetic effect Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
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- 239000007787 solid Substances 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 101150067597 treh gene Proteins 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/30—Stress-relieving
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/32—Soft annealing, e.g. spheroidising
-
- 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
- C21D6/002—Heat treatment of ferrous alloys containing Cr
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- 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
- C21D8/0273—Final recrystallisation annealing
-
- 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
- C21D8/0473—Final recrystallisation annealing
-
- 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
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
-
- 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
- C21D2211/001—Austenite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/004—Dispersions; Precipitations
-
- 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
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
Definitions
- the present disclosure relates to an alloyed steel and a method for producing the same. More particularly to a vanadium alloyed steel having an enhanced elastic modulus.
- a vanadium alloyed steel comprising, preferably consisting essentially of, more preferably consisting of carbon and vanadium; wherein the steel microstructure comprises coherent interphase precipitates comprising vanadium.
- a vanadium alloyed steel comprising, preferably consisting essentially of, more preferably consisting of carbon, vanadium and balance iron; wherein the steel microstructure comprises coherent interphase precipitates comprising vanadium.
- the vanadium alloyed steel comprises, preferably consists essentially of, more preferably consists of (in wt%):
- the vanadium alloyed steel comprises, preferably consists essentially of, more preferably consists of (in wt%):
- the vanadium alloyed steel comprises, preferably consists essentially of, more preferably consists of: vanadium and carbon; optionally one or more of nitrogen, molybdenum, copper, silicon, chromium, and/or manganese; and balance iron; wherein the steel microstructure comprises coherent interphase precipitates comprising vanadium.
- the vanadium alloyed steel comprises, preferably consists essentially of, more preferably consists of (in wt%):
- Vanadium in the range of from about 0.1 to about 1.5; optionally one or more of: about 0.015 or less Nitrogen, about 1.6 or less Molybdenum, about 1 or less Copper, about 1.2 or less Silicon, about 0.3 or less Chromium, and/or about 1.6 or less Manganese; and balance iron; wherein the steel microstructure comprises coherent interphase precipitates comprising vanadium.
- the average elastic modulus (i.e. Young's modulus) of the steel is enhanced. It is believed that the coherent vanadium precipitates generate large strain fields in the steel, resulting in latticeparameter changes which can modify the bulk elastic modulus of the steel.
- the enhancement of the elastic modulus is believed to be applicable at high- temperatures, due to the greater stability of coherent precipitates against tempering and coarsening, thereby enhancing the buckling resistance of the steel. In this way, improved fire-resistant performance is achieved, for example using lower alloying embodiments.
- higher modulus steels as disclosed herein may also be beneficial in providing enhanced structural benefits such as greater buckling resistance, for example using higher alloyed embodiments. This may enable construction of taller wind-turbines.
- higher modulus steels as disclosed herein may also be beneficial in providing enhanced deflection resistance, for example using higher alloyed embodiments. This may be beneficial in creating lighter, stiffer automotive structures.
- the lattice-parameter change effect is a direct consequence of the matrix dilatation and contraction caused upon elastic accommodation of the precipitates in the surrounding steel matrix.
- the precipitates comprising vanadium 2 have a different lattice parameter to that of the surrounding steel (e.g. ferrite) matrix 4.
- the surrounding steel e.g. ferrite
- there is a lattice-parameter misfit between the precipitates comprising vanadium and the surrounding steel which results in the generation of large strain fields (shown by the shaded region indicated with reference numeral 6 in Figure 1) when coherent precipitates comprising vanadium are formed. Consequently, the average lattice-parameter of the overall steel is altered, modifying the bulk elastic modulus of the steel. In contrast, where incoherent precipitates are formed, no such strain field is observed.
- Figure 2 demonstrates the uniqueness of vanadium in having relatively low misfits between the lattice parameter of precipitates comprising vanadium as compared to ferrite and austenite, for example.
- the data points relating to the misfit in ferrite are shown by the solid circles and triangles, and the data points relating to the misfit in austenite are shown by the outlined circles and triangles.
- Figure 2 illustrates the high limiting sizes for coherent precipitates comprising vanadium, in this case in ferrite, as compared to precipitates including other elements commonly used in steel. It is believed that this promotes the generation of coherent precipitate formation, since the greater coherency limit has the effect that it is easier to maintain coherency via established steel production methods.
- FIG 3 this illustrates a relationship between strengthening effects and the size of precipitates.
- the shear strength increases with increasing particle size up to a critical particle size. This is due to coherency strain hardening, as described above.
- the size of the particles exceeds the critical particle size, incoherent precipitates are formed and the modulus strengthening effect is no longer seen.
- precipitates comprising vanadium are very efficient in increasing the elastic modulus of steel by function of their high coherency limit and high shear modulus, as compared to other precipitates.
- the dislocation mechanism shifts from the well-established ashby-orowan looping mechanism (which is applicable for incoherent precipitates) to a particle shearing mechanism.
- the strengthening mechanisms attributed to dislocations shearing the ordered coherent particles results in the operation of order and modulus strengthening mechanisms.
- the resulting modulus strengthening increment can be described by the Knowles-Kelly equation (1).
- b « 0.248 nm is the Burgers vector of the dislocation
- r is the mean radius of the precipitates comprising vanadium, e.g. VC particles ( ⁇ 3.1 ⁇ 1.0nm)
- G « 81.6 GPa is the shear modulus of the ferrite matrix.
- the f (4/3)nnr 3 is the volume fraction of the VC nano-precipitates, where n is the number density of the precipitates ( ⁇ 1.18 ⁇ 0.03xl0' 4 nm' 3 ).
- Figure 5a shows a simulation of a ferritic steel as disclosed herein and illustrates the elastic strain fields associated with coherent interphase precipitates comprising vanadium, which are formed as nano-sized platelets in this embodiment.
- the platelets are arranged in rows with the spacing between rows indicated by the reference numeral 22. Only two rows of interphase precipitates are shown for the purposes of clarity.
- the steel is a fire-resistant steel.
- the enhancement of the elastic modulus as described above is applicable at high-temperatures, due to the greater stability of coherent precipitates against tempering and coarsening, thereby enhancing the buckling resistance of fire-resistant steels.
- the stability of buildings and other structures in a fire depends on the extent to which the steel structures soften when heated to the temperatures created by the fire.
- a steel is generally regarded as being fire-resistant if its short-term strength when heated to such temperatures is approximately 0.6-0.7 of its strength at room temperature.
- the average elastic modulus is 120GPa or higher at temperatures in the range from about 600°C about 700°C.
- the steel comprises vanadium in the range of from about 0.1 to about 0.3 (wt%).
- the steel is a ferritic steel (e.g. fire-resistant alloy HSLA (high strength low alloy)).
- the steel comprises vanadium in the range of from about 0.3 to about 1.5 (wt%).
- the steel is a ferritic steel (e.g. AHSS (advanced high strength steel)).
- the steel comprises vanadium in the range of from about 0.1 to about 1.5 (wt%).
- the steel is a ferritic steel (e.g. a hydrogen resistant steel).
- the steel comprises vanadium in the range of from about 0.1 to about 1 (wt%).
- the steel is a pearlitic steel.
- vanadium to form interphase precipitates is considered to be advantageous as compared to other alloying elements such at niobium and titanium, since vanadium exerts a relatively low influence on the transformation temperature (i.e. the temperature at which the steel transforms from austenite to ferrite). Lowering the transformation temperature has the disadvantageous effect of increasing the probability of random precipitation and not interphase precipitation. Accordingly, use of vanadium is beneficial in maintaining the transformation temperature in a desired range.
- Carbon contributes to the hardness, strength and hardenability of the steel. Carbon also acts as an austenite stabiliser.
- the steel comprises carbon in the range of from about 0.06 to about 0.2 (wt%).
- the steel is a ferritic steel (e.g. fire-resistant alloy HSLA (high strength low alloy)).
- the steel comprises carbon in the range of from about 0.06 to about 0.3 (wt%).
- the steel is a ferritic steel (e.g. AHSS (advanced high strength steel)).
- the steel comprises carbon in the range of from about 0.06 to about 0.3 (wt%).
- the steel is a ferritic steel (e.g. a hydrogen resistant steel).
- the steel comprises carbon in the range of from about 0.6 to about 1.1 (wt%).
- the steel is a pearlitic steel.
- the steel is a modulus-enhanced steel comprising an average elastic modulus (i.e. a measured bulk elastic modulus) of above about 210 Pa, for example about 220GPa or higher, for example in the range of from about 210GPa to about 300GPa, e.g. in the range of from about 220GPa to about 300GPa.
- an average elastic modulus i.e. a measured bulk elastic modulus
- the elastic modulus may be measured using dynamic resonance methods.
- a test-piece of steel with a uniform cross-section e.g. round, square or rectangle
- ASTM standard C1259 sets out the standard test method for Dynamic Young's Modulus, Shear Modulus, and Poisson's Ratio for Advanced Ceramics by Impulse Excitation of Vibration, for rectangular and round cross section bars.
- the steel is a modulus-enhanced AHSS steel.
- the steel is a fire- resistant steel (e.g. a HSLA steel) comprising an average elastic modulus of about 120 GPa or higher at temperatures in the range of from about 600°C to about 700°C.
- the coherent interphase precipitates have a particle size of about 9nm or less, optionally in the range of from about 5nm to about 9nm, optionally greater than about 5nm This can be measured with high-resolution transmission electron microscopy, X-ray diffraction, or any other suitable method.
- the coherent interphase precipitate particle size is taken to be the mean value of the largest particle dimension of a representative sample of particles.
- lamellae specimens are typically prepared using a focused ion beam (FIB) microscope. Analysis of thin lamellae is also typically carried out using a cold field emission guns in-situ with probe-corrected high- resolution scanning transmission electron microscope (HR STEM).
- HR STEM high- resolution scanning transmission electron microscope
- HAADF high angle annular dark-field
- the sizes, morphology and number density of coherent precipitates can be obtained given such HAADF and STEM micrographs, whereby the average number density is derived from averages taken from different grains.
- Concentration profiles can also be obtained via such HAADF data, which can verify the nature of our combined nano-particles.
- Atomic probe tomography can also be used to verify and offer improved 3D spatial resolution of the atomic concentration profiles (from HAADF micrographs) in the core-shell nanoparticles.
- the coherent interphase precipitates comprise vanadium carbides, optionally wherein the coherent interphase precipitates comprise precipitates having enhanced levels of vanadium with the chemical formula V x C y , where x>y (e.g. the coherent interphase precipitates comprise V4C3, VeCs, and/or V5C3).
- the precipitate-matrix interfacial energy increases thus a larger fraction of vacancies is necessary for the precipitate stability, causing a slight gradual decrease in the carbon-to-vanadium ratio, and thus, increases their stability.
- the steel is a hydrogen-resistant steel, for example using higher alloyed embodiments. Vanadium carbides within the steel are believed to act as hydrogen traps, which can irreversibly trap hydrogen.
- Figure 4b shows a 3D illustration of hydrogen atoms 8 occupying carbon vacancies in a V4C3 coherent interphase precipitate 2.
- Figure 4a illustrates the potential energy wells associated with a TiC precipitate 14, a NbC precipitate 12 and a V4C3 precipitate 10. As can be seen, the potential energy well associated with V4C3 precipitates 10 is deeper than that of the other precipitates, and hence acts as a more effective hydrogen trap.
- vanadium carbide precipitates containing enhanced vanadium contain carbon vacancies which are inherently more thermally stable under fire exposure conditions.
- the steel comprises a ferrite phase and the coherent interphase precipitates are formed in the ferrite phase, for example to form nodular ferrite or knotted ferrite.
- the coherent interphase precipitates are formed as an austenite phase transitions to a ferrite phase, in other words at conditions corresponding to a migrating phase boundary between austenite and ferrite.
- nodular ferrite NF
- Nodular Ferrite has only previously been identified in eutectic cast steels, caused due to lattice parameter misfit resulting from iron carbides (i.e. in cementite). It has been found that nodular ferrite can also be created due to the misfit generated by coherent alloy carbides. Nodular ferrite is characterised by chaotic grain orientations and chaotic grain boundary misorientations. The grains are not isomorphs and resemble a knotted appearance.
- Ferrite transformation with interphase precipitation is a kind of eutectoid transformation analogous to degenerate pearlite in high carbon steels, where alloy carbide is formed instead of ironcarbide, cementite. Therefore, it is believed that this nodular or knotted ferrite can be considered analogous to that of pearlite observed in high carbon steels.
- the steel composition comprises Mo, Cr and/ or Cu.
- core-shell nano-particles 16 may comprise a core 18 of VN.
- the core-shell nano-particles may comprise a shell 20 comprising Mo, Cr and/or Cu.
- Capillary-driven particle coarsening is impeded due to the interfacial segregation of Mo, Cr and/or Cu, which reduces the driving force for further particle coarsening due to a reduction in interface energy.
- the coarsening resistance is conducive to grain refinement and prior austenite grain size control during austenisation.
- Developing core-shell nanoparticles are inherently resistant to coarsening and exert a zener pinning mechanism on the austenite grain boundary to limit grain size.
- Copper is thought to have low misfits with the ferrite lattice, which enable it to contribute to elastic misfit strains by forming a high density of coherent interphase particles. It is thought that the low magnetic moment of Cu plays a positive role in increasing the number density of complex nano-particles. Without being bound by any particular theory, it is believed that the application of a magnetic field increases the Gibbs free energy of the system. The increase in Gibbs free energy promotes precipitation of alloying elements including Cu and, since Cu has a low magnetic moment, precipitation is not hindered by the magnetic field.
- the steel comprises copper in the range of from greater than 0 to about 0.5 (wt%).
- the steel is a ferritic steel (e.g. fire-resistant alloy HSLA (high strength low alloy)).
- the steel comprises copper in the range of from greater than 0 to about 1 (wt%).
- the steel is a ferritic steel (e.g. AHSS (advanced high strength steel)).
- the steel comprises copper in the range of from greater than 0 to about 1 (wt%).
- the steel is a ferritic steel (e.g. a hydrogen resistant steel).
- the steel comprises copper in the range of from greater than 0 to about 0.5 (wt%).
- the steel is a pearlitic steel.
- the presence of manganese is thought to contribute to refinement of ferrite gains, for example when higher coiling temperatures are used.
- the steel comprises manganese in the range of from about 0.4 to about 1.6 (wt%).
- the steel is a ferritic steel (e.g. fire-resistant alloy HSLA (high strength low alloy)).
- the steel comprises manganese in the range of from greater than 0 to about 0.8 (wt%).
- the steel is a ferritic steel (e.g. AHSS (advanced high strength steel)).
- the steel comprises manganese in the range of from greater than 0 to about 1.6 (wt%).
- the steel is a ferritic steel (e.g. a hydrogen resistant steel).
- the steel comprises manganese in the range of from about 0.6 to about 1.6 (wt%).
- the steel is a pearlitic steel.
- silicon is thought to increase the number density of coherent interphase precipitates, for example when higher coiling temperatures are used. Silicon retards the formation of pearlite and can allow for slower cooling rates, which promotes coherent interphase precipitate formation.
- the steel comprises silicon in the range of from greater than 0 to about 0.5 (wt%).
- the steel is a ferritic steel (e.g. fire-resistant alloy HSLA (high strength low alloy)).
- the steel comprises silicon in the range of from greater than 0 to about 0.5 (wt%).
- the steel is a ferritic steel (e.g. AHSS (advanced high strength steel)).
- the steel comprises silicon in the range of from greater than 0 to about 1.5 (wt%).
- the steel is a ferritic steel (e.g. a hydrogen resistant steel).
- the steel comprises silicon in the range of from greater than 0 to about 1.2 (wt%).
- the steel is a pearlitic steel.
- the steel comprises chromium in the range of from greater than 0 to about 0.3 (wt%).
- the steel is a ferritic steel (e.g. fire-resistant alloy HSLA (high strength low alloy)).
- the steel comprises chromium in the range of from greater than 0 to about 0.3 (wt%).
- the steel is a ferritic steel (e.g. AHSS (advanced high strength steel)).
- the steel comprises chromium in the range of from greater than 0 to about 0.3 (wt%).
- the steel is a ferritic steel (e.g. a hydrogen resistant steel).
- the steel comprises chromium in the range of from greater than 0 to about 0.1 (wt%).
- the steel is a pearlitic steel.
- molybdenum is thought to contribute to increasing the number density of the coherent interphase particles, by forming a complex with the precipitates which can improve diffusion kinetics of the precipitates.
- the coherent interphase precipitates comprise Mo, optionally wherein the coherent interphase precipitates comprise precipitates having the chemical formula (Mo,V) x Cy, where x>y, e.g. (Mo,V) 4 C3/(Mo,V)C
- the steel comprises molybdenum in the range of from greater than 0 to about 0.2 (wt%).
- the steel is a ferritic steel (e.g. fire-resistant alloy HSLA (high strength low alloy)).
- the steel comprises molybdenum in the range of from greater than 0 to about 0.5 (wt%).
- the steel is a ferritic steel (e.g. AHSS (advanced high strength steel)).
- the steel comprises molybdenum in the range of from greater than 0 to about 0.5 (wt%).
- the steel is a ferritic steel (e.g. a hydrogen resistant steel).
- the steel comprises molybdenum in the range of from greater than 0 to about 0.2 (wt%).
- the steel is a pearlitic steel.
- the ferrite phase comprises grains having a mean size of less than about 20pm.
- Grain size can be measured by any suitable method, for example using a scanning electron microscope and electron-backscattering diffraction. The intercept method may then be used to calculate the average grain size. In this method, a straight line is drawn on a micrograph and the number of grain boundaries crossing the line are counted. The average grain size is found by dividing the number of intersections by the actual line length.
- the steel microstructure comprises VN precipitates, optionally wherein the microstructure comprises intra-granular VN nucleated acicular ferrite (e.g. V(C,N)).
- VN nucleated acicular ferrite e.g. V(C,N)
- the VN precipitates form in austenite as intra-granular nucleants for acicular ferrite formation. It is believed that this is due to the lower solubility of VN in austenite, relative to Vanadium Carbides.
- the intragranular VN nucleated acicular ferrite structure improves the coherency of the interphase particles and refines the ferrite grains, resulting in the consequential benefits to the elastic modulus and toughness of the steel.
- the steel comprises nitrogen in the range of from greater than 0 to about 0.015 (wt%).
- the steel is a ferritic steel (e.g. fire-resistant alloy HSLA (high strength low alloy)).
- the steel comprises nitrogen in the range of from greater than 0 to about 0.015 (wt%).
- the steel is a ferritic steel (e.g. AHSS (advanced high strength steel)).
- the steel comprises nitrogen in the range of from greater than 0 to about 0.015 (wt%).
- the steel is a ferritic steel (e.g. a hydrogen resistant steel).
- the steel comprises nitrogen in the range of from greater than 0 to about 0.01 (wt%).
- the steel is a pearlitic steel.
- interphase vanadium carbonitrides may form as coherent interphase precipitates.
- the nitrogen will also further increase driving force for precipitation, which is beneficial for obtaining a high number density of interphase precipitates.
- the steel comprises a single phase ferritic steel e.g. HSLA, AHSS and/or hydrogen resistant steel.
- the steel comprises a pearlitic steel. Accordingly, the steel comprises a ferritic phase and a cementite phase. The modulus of the ferrite phase is enhanced via the presence of coherent interphase particles and the mechanisms described above.
- the pearlitic steel comprises a vanadium enhanced cementite phase
- the vanadium enhanced cementite phase comprises Vanadium dissolved in cementite e.g. to form FezVC and/or FeVzC
- the average lattice spacing in the ferrite phase is contracted as a result of misfit strains from both coherent interphase precipitates comprising vanadium, and cementite.
- vanadium can easily dissolve in cementite given an appropriate isothermal holding regime, which can further contribute to misfit-induced lattice strain due to the change in the cementite lattice parameter.
- cementite is notorious for its anisotropy and this applies also to the anisotropy of its elastic modulus components as a function of crystallographic orientation. The dissolution of vanadium into cementite reduces this anisotropy. It is believed that this will evolve as a function of isothermal holding duration as the composition of the cementite changes with ageing.
- the lattice strain associated with the elastic misfits of alloy carbides or V-enhanced cementite can be verified by the use of high-resolution scanning transmission electron microscopy (HR STEM) and X-ray diffraction (XRD), respectively.
- Atomic Probe Tomography could also be used as an additional method to quantify atomic concentrations within 3-dimensions.
- an exemplary embodiment is illustrated in which the steel comprises cementite colonies.
- the additional strain applied to the ferrite lattice is illustrated due to cementite is illustrated. This results in a reduction in the average lattice spacing of the ferrite matrix in regions proximal a cementite colony.
- Figure 5b also shows a schematic illustration of the microstructure of pearlite including V-enhanced cementite.
- the steel comprises a tensile strength in the range from about 690 MPa to about 2000 MPa, for example in the range from about 690 MPa to about 1800 MPa.
- the tensile strength may be measured by gripping the ends of a suitably prepared standard test piece in a tensile test machine and then applying a continuously increasing uni-axial load until such time as failure occurs.
- ASTM E8/E8M-13 "Standard Test Methods for Tension Testing of Metallic Materials” may be used.
- the structure of the steel alloy described herein can be determined by conventional microstructural characterisation techniques such as, for example, optical microscopy, TEM, SEM, AP-FIM, and X-ray diffraction, including combinations of two or more of these techniques.
- a method for preparing a vanadium alloyed steel as disclosed herein comprising: a. providing a starting steel; b. heating the starting steel to at least partially austenitise the steel; c. holding the temperature of the steel at 650°C ⁇ 200°C for about 25 mins or less; wherein the vanadium alloyed steel comprises coherent interphase precipitates comprising vanadium.
- the starting steel comprises, preferably consists essentially of, more preferably consists of: vanadium and carbon.
- the starting steel comprises, preferably consists essentially of, more preferably consists of: vanadium, carbon, and balance iron.
- the starting steel comprises, preferably consists essentially of, more preferably consists of (in wt%):
- Vanadium in the range of from about 0.1 to about 1.5.
- the starting steel comprises, preferably consists essentially of, more preferably consists of (in wt%):
- the starting steel comprises, preferably consists essentially of, more preferably consists of: vanadium and carbon; one or more of nitrogen, molybdenum, copper, silicon, chromium, and/or manganese; and balance iron.
- the starting steel comprises, preferably consists essentially of, more preferably consists of (in wt%):
- heating the starting steel to at least partially austenitise the steel involves raising the temperature to at least about 900°C, optionally to a temperature in the range of from about 920° to about 1300°C, for example to a temperature in the range of from about 1100°C to about 1300°C.
- the starting steel may be provided in the form of a billet, slab, bloom, or any other suitable form.
- said heating may be carried out by inductive heating and/or a roller hearth furnace.
- the temperature is held at 650°C ⁇ 200°C for about 20 mins or less.
- the temperature is held by placing the steel in an insulated thermal box.
- batch annealing is carried out, for example using an insulated thermal box to control the temperature applied to the steel.
- a bell furnace may be used to apply heat treatment to a full coil.
- the temperature is held by using an induction heating system, e.g. an induction furnace.
- an induction heating system e.g. an induction furnace.
- the temperature is held at 650°C ⁇ 200°C for about 15 minutes or less. In some embodiments, the temperature is held at 650°C ⁇ 200°C for in the range of from about 5 minutes to about 20 minutes, e.g. from about 10 to about 20 minutes.
- the steel is air cooled.
- the temperature is held at 650°C ⁇ 100°C.
- the steel is cooled at a cooling rate in the range of from about 2°C/s to about 80°C/s, prior to the temperature being held at 650°C ⁇ 200°C, optionally at a cooling rate in the range of from about 2°C/s to about 50°C/s.
- the cooling is carried out by air cooling, forced air cooling, lamellar cooling, and/or any other suitable cooling method.
- Mn is present in the steel composition, this may facilitate higher number density at faster cooling rates.
- the steel after heating the starting steel, the steel is hot rolled at temperatures above the recrystallisation stop temperature (RST), optionally by recrystallisation controlled rolling and/or V(C,N) precipitation controlled rolling.
- RST recrystallisation stop temperature
- hot rolling the steel is carried out prior to cooling the steel to 650°C ⁇ 200°C.
- hot rolling is carried out at a temperature(s) in the range of from about 820°C to about 1200°C.
- hot rolling comprises roughing, intermediate and/or finishing steps.
- V(C,N) precipitation controlled rolling may be used. This achieves low grain deformation levels.
- hot rolling the steel comprises hot rolling at substantially the V(C,N) precipitation temperature time nose.
- V(C,N) precipitation controlled rolling this may be carried out at substantially the V(C,N) precipitation temperature time nose.
- V(C,N) precipitation temperature time nose the system has optimal free energy for VN to precipitate. Accordingly, hot rolling at this temperature facilitates the formation of acicular ferrite.
- the V(C,N) precipitation temperature time nose depends on the particular composition of the steel, but is typically around 850°C.
- a magnetic field is applied to the steel composition.
- the magnetic field is a static magnetic field in the range of about 0.2T to about 16T.
- the magnetic field is a variable magnetic field e.g. applied by an induction heating system.
- the variable magnetic field is applied by an inductive heating system, which also controls the temperature of the steel (e.g. is used to hold the temperature at 650°C ⁇ 200°C).
- the application of a magnetic field facilitates increasing the number density of coherent precipitates and also optimises the composition of the constituent nano-sized precipitates.
- the proposed environmentally-friendly method to accelerate this isothermal hold duration is to utilize a magnetic field, which can act to decelerate the austenite to ferrite transformation kinetics (thus refining the spacing between precipitates and maximize number density of interphase precipitates). This can also increase the extent of higher V:C ratio carbides due to paramagnetic effects.
- Vanadium in solution prior to precipitation, acts to increase the Curie temperature, Tc, (but exerts a small effect on the magnetic moment and small interaction energy with the external magnetic field) so that the range of temperature between Tc and a given transformation temperature below the Curie point is increased and therefore, the magnetisation is larger at the transformation point.
- the external magnetization energy serves to significantly increase the Gibbs free energy of the system, increasing the free energy of the total nucleation of the nanoparticles, which subsequently increases the nucleation rate and significantly increases the quantitative number density of coherent interphase vanadium precipitates.
- the application of a magnetic field also acts to refine the interlamellar spacing of the pearlite (due to an increase in the nucleation rate of cementite). This can further contribute to lattice strain and modulus enhancement, as a result of strain applied to the ferrite lattice in regions proximal cementite colonies, as previously described.
- the steel is reheated to at least partially austenitise the steel.
- this reheating step comprises raising the temperature to in the range of from about 920°C to about 1150°C.
- the temperature is held at 650°C ⁇ 200°C for about 20 mins or less.
- the temperature is held at 650°C ⁇ 200°C for about 15 minutes or less.
- the temperature is held at 650°C ⁇ 200°C for in the range of from about 5 minutes to about 20 minutes, e.g. in the range of from about 10 minutes to about 20 minutes.
- the steel is air cooled.
- the temperature at is held at 650°C ⁇ 100°C.
- Isothermal holding in this manner enhances interphase precipitation (e.g. vanadium carbide and/or vanadium carbonitride precipitation), as previously described.
- interphase precipitation e.g. vanadium carbide and/or vanadium carbonitride precipitation
- the steel is cooled at a cooling rate in the range of from about 2°C/s to about 80°C/s, optionally to a temperature of 650°C ⁇ 200°C.
- the cooling rate is in the range of from about 2°C/s to 50°C/s.
- Controlled cooling enhances interphase precipitation (e.g. vanadium carbide and/or vanadium carbonitride precipitation) and inhibits the formation of undesirable phases, as previously described.
- Figure 1 illustrates a schematic showing the interaction of a coherent precipitate and an incoherent precipitate with a surrounding ferrite lattice matrix
- Figure 2 shows a comparison of lattice parameter misfits and limiting coherent precipitate sizes for precipitates including Ti, V, Zr or Nb;
- Figure 3 shows a relationship between strength and precipitate particle size
- Figures 4a and 4b are schematic illustrations of the capacity of coherent interphase precipitates to act as a hydrogen trap
- Figure 5a illustrates the impact of a strain field in a ferrite matrix on the average lattice parameter in a ferrite steel
- Figure 5b illustrates the impact of a strain field in a ferrite matrix on the average lattice parameter in a pearlite steel
- FIG. 6 illustrates three typical beam compositions (in accordance with Eurocode 3);
- Figure 7a shows a schematic illustration of a VN-nucleated acicular ferrite structure
- Figure 7b shows a schematic illustration of a core-shell nano-particle
- Figure 8 shows a process diagram representative of a process for manufacturing a steel in accordance with the present disclosure
- Figure 9 shows a flow chart describing additional steps that may be applied to the process of Figure 8.
- Figure 10 shows a process diagram representative of a process for manufacturing a modulus-enhanced hot-rolled high carbon wire steel in accordance with the present disclosure.
- Figure 11 shows a flow chart describing additional steps that may be applied to the process of Figure 10.
- Example 1 The vanadium alloyed steels and production processes disclosed herein will now be explained with reference to the following non-limiting examples.
- Example 1 The vanadium alloyed steels and production processes disclosed herein will now be explained with reference to the following non-limiting examples.
- Each composition also includes a balance amount of iron.
- Example 2 A typical composition for an enhanced-modulus AHSS steel is provided in Table 3. Such a composition also includes a balance amount of iron. In this case, the balance amount of iron is 97.6955 wt%.
- a conventional steel of grade S690MC (in accordance with EN 10051) was compared to a nano-structured enhanced modulus steel as disclosed herein.
- the conventional S690MC steel is taken as having a nominal elastic modulus of 210 GPa (in accordance with European Standard EN 1993-1-1: Eurocode 3: Design of steel structures, and European Standard EN 1993-1-12: General - High strength steels).
- the modulus enhanced steel is taken to have an average elastic modulus of 230 GPa, in other words, an increase of 20 GPa.
- Figure 6 illustrates three typical beam compositions (in accordance with Eurocode 3). The consequences with respect to reduced deflections with an enhanced elastic modulus are set out in Table 4. These results were obtained via a computer simulation.
- a slab (or alternatively a billet) of cast steel is heated to a reheating temperature in the range of from about 1100 to about 1300 °C (Treh). This is indicated by reference numeral 102 on Figure 8. This temperature is maintained until the steel slab is fully heated through its thickness (i.e. at Teq as shown in Figure 8).
- Teq °C
- the heated steel is then hot rolled at temperatures in the range of from about 820°C to about 1200°C, firstly in a roughing mill as indicated by reference numeral 106, followed by hot rolling in a finishing mill indicated by reference numeral 108.
- the temperature of the steel cools under standard air cooling, for example at about 0.7°C/s.
- Hot rolling in the finishing mill 108 can be carried out using conventional recrystallisation controlled rolling.
- V(C,N) precipitation controlled rolling can be carried out. This is carried out at the V(C,N) precipitation time temperature nose 110, at which there is optimal free energy for VN to precipitate.
- the V(C,N) precipitation time temperature nose varies depending to the particular steel composition, however is typically about 850°C.
- VN precipitates in austenite as intra-granular nucleants for acicular ferrite formation.
- the steel has a microstructure as illustrated schematically at reference numeral 112.
- the steel Prior to the recrystallization stop temperature (RST), and after hot rolling has been completed, the steel is rapidly cooled 114 at a cooling rate in the range of from about 2°C/s to about 80°C/s until a temperature of 650 ⁇ 100°C is reached. This may be by forced air cooling, lamellar cooling or any other suitable cooling means. Rapidly cooling the steel in this way prevents or impedes the formation of undesirable phases and/or promotes the formation of acicular ferrite, illustrated schematically at reference numeral 116.
- the steel When the temperature of 650 ⁇ 100°C is reached, the steel is formed into a coil. The temperature of the steel is then held 118 at 650 ⁇ 100°C for a time in the range of from about 10 minutes to about 20 minutes, after which the steel is air cooled. As described above, isothermal holding in this manner promotes the generation of interphase precipitates. In this way, a modulus enhanced nanostructured steel is produced.
- the method may further include the steps set out in Figure 9 to increase the number density of interphase precipitates.
- the coiled steel is cooled and then a blank is stamped or cut 120 from the decoiled strip. Optionally this step may be omitted.
- the steel may then be austenitised 122 a second time by heating to a temperature in the range of from about 920°C to about 1150°C, for example using a roller hearth furnace and/or inductive heating equipment.
- the reheated steel is then cooled 124 at a rate in the range of from about 2°C/s to about 50°C/s until a temperature of 650 ⁇ 40°C is reached. Cooling can be carried out using forced air cooling, lamellar cooling, or any other suitable method.
- a static magnetic field in the range of from about 0.2T to about 16T can then be applied 26 to the steel. Whilst the magnetic field is applied, the temperature is held at 650 ⁇ 40°C for about 15 minutes or less. For example, this may be carried out using an insulated thermal box.
- a variable magnetic field is applied 128 to the steel.
- this may be applied using an induction heating system. Whilst the variable magnetic field is applied, the temperature is held at 650 ⁇ 100°C for 15 minutes or less.
- a magnetic field is applied to the steel during the step of isothermal holding 118, either by using a static magnetic field or a variable magnetic field.
- the resulting modulus-enhanced nanostructured steel is then air cooled 130 and ready for cold stamping and/or forming as required.
- a full coil can be reheated (i.e. austenitised) 122, cooled 124 then held at 650 ⁇ 100°C for the required time.
- This can be carried out as a batch annealing process using an insulated thermal box, e.g. a bell furnace suitable for applying heat treatment to full coils. This method is applicable to both ferritic and pearlitic steels.
- Figure 10 shows a method of making a modulus-enhanced hot-rolled high carbon wire steel.
- a billet of cast steel is heated 202 to a reheating temperature, as described in relation to example 4.
- the heated steel is then hot rolled 206 at temperatures in the range of from about 840°C to about 1200°C using a roughing mill, intermediate mill, finishing mill and/or notwist V-block mill. Hot rolling is carried out above the recrystallization stop temperature, such that grain deformation is kept to a minimum.
- the steel is rapidly cooled 214 at a cooling rate of in the range of from about 2°C/s to about 80°C/s until a temperature of 650 ⁇ 100°C is reached.
- the temperature is then held 218 at 650 ⁇ 100°C, for example, using an in-line induction heating coil. With reference to Figure 11, the steel is then air cooled 230.
- the steel may then be cold drawn 132.
- the steel wire is induction heated and austenised, fan cooled to 600 ⁇ 50°C, then the temperature is held at 650 ⁇ 200°C for less than 5 minutes.
- a static magnetic field may also be applied at this stage in order to refine the interlamellar spacing of the pearlite, which can further contribute to lattice strain and modulus enhancement.
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2021
- 2021-10-06 KR KR1020247009958A patent/KR20240075821A/en unknown
- 2021-10-06 WO PCT/EP2021/077627 patent/WO2023057062A1/en active Application Filing
- 2021-10-06 CN CN202180101652.2A patent/CN117897507A/en active Pending
- 2021-10-06 CA CA3228109A patent/CA3228109A1/en active Pending
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