US20150110667A1 - High-strength and high-ductility steel sheet and method of manufacturing the same - Google Patents
High-strength and high-ductility steel sheet and method of manufacturing the same Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 112
- 239000010959 steel Substances 0.000 title claims abstract description 112
- 238000004519 manufacturing process Methods 0.000 title claims description 16
- 239000000203 mixture Substances 0.000 claims abstract description 18
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 16
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 10
- 239000012535 impurity Substances 0.000 claims abstract description 6
- 239000011651 chromium Substances 0.000 claims description 44
- 238000001816 cooling Methods 0.000 claims description 35
- 229910000937 TWIP steel Inorganic materials 0.000 claims description 16
- 238000005098 hot rolling Methods 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 11
- 238000000137 annealing Methods 0.000 claims description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 8
- 238000005097 cold rolling Methods 0.000 claims description 6
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 5
- 229910052782 aluminium Inorganic materials 0.000 claims description 5
- -1 chromium carbides Chemical class 0.000 claims description 5
- 239000010960 cold rolled steel Substances 0.000 claims description 4
- 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 claims description 4
- 230000009467 reduction Effects 0.000 claims description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 3
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 229910001566 austenite Inorganic materials 0.000 abstract description 59
- 239000004033 plastic Substances 0.000 abstract description 18
- 229910052748 manganese Inorganic materials 0.000 abstract description 7
- 238000005482 strain hardening Methods 0.000 abstract description 5
- 239000011572 manganese Substances 0.000 description 32
- 229910000734 martensite Inorganic materials 0.000 description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 22
- 229910000859 α-Fe Inorganic materials 0.000 description 11
- 230000009466 transformation Effects 0.000 description 10
- 239000011159 matrix material Substances 0.000 description 9
- 229910000794 TRIP steel Inorganic materials 0.000 description 8
- 230000000087 stabilizing effect Effects 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- 238000001556 precipitation Methods 0.000 description 7
- 230000015572 biosynthetic process Effects 0.000 description 5
- 150000001247 metal acetylides Chemical class 0.000 description 4
- 238000004626 scanning electron microscopy Methods 0.000 description 4
- 239000010935 stainless steel Substances 0.000 description 4
- 229910001220 stainless steel Inorganic materials 0.000 description 4
- 230000007423 decrease Effects 0.000 description 3
- 230000009977 dual effect Effects 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 229910002551 Fe-Mn Inorganic materials 0.000 description 2
- 229910017112 Fe—C Inorganic materials 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 239000006096 absorbing agent Substances 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
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- 239000000446 fuel Substances 0.000 description 2
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- 238000003754 machining Methods 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 230000036961 partial effect Effects 0.000 description 2
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- 230000002829 reductive effect Effects 0.000 description 2
- 230000035939 shock Effects 0.000 description 2
- 239000003351 stiffener Substances 0.000 description 2
- 229910002058 ternary alloy Inorganic materials 0.000 description 2
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 229910000797 Ultra-high-strength steel Inorganic materials 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- RBVYPNHAAJQXIW-UHFFFAOYSA-N azanylidynemanganese Chemical compound [N].[Mn] RBVYPNHAAJQXIW-UHFFFAOYSA-N 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
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- 229910052710 silicon Inorganic materials 0.000 description 1
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Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
-
- 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
- C21D6/005—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
- C21D8/0221—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
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- 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
- 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
Definitions
- the present invention relates to a high-strength and high-ductility steel sheet, and more particularly, to an automotive steel sheet for which high workability is required, a high manganese (Mn) steel sheet applicable as a shock absorber such as a vehicle bumper stiffener, and a method of manufacturing the same.
- Mn manganese
- high-strength automotive steel examples include dual phase (DP) steel, transformation induced plasticity (TRIP) steel and twin induced plasticity (TWIP) steel.
- DP steel is produced by lowering the cooling end temperature below the martensite start temperature (Ms) in the process of quenching hot-rolled steel to room temperature so that part of austenite transforms to martensite. Consequently, the dual phases of martensite transformed from austenite and ferrite exist at room temperature.
- Ms martensite start temperature
- Such DP steel can have a variety of mechanical properties due to an adjustment in the proportions of martensite and ferrite.
- TRIP steel has improved workability, and is produced by partially forming retained austenite in a structure, followed by the martensitic transformation of austenite during the machining of components.
- TRIP steel has the advantage of high strength caused by significant hardening through the martensitic transformation, its elongation is too short, which is problematic.
- the hardening mechanism of either DP steel or TRIP steel is typically based on martensite, the hard phase. Martensite exhibits a significant increase in hardening during plastic deformation, thereby enabling the manufacture of high-strength hot-rolled steel. However, the extremely low ductility of martensite makes it difficult to achieve an elongation of 30% or more, which is problematic.
- TWIP steel contains a large amount of Mn and has a single austenite phase, which is stable at room temperature and allows mechanical twins to form in the austenite structure during the machining of component, thereby increasing the level of work hardening. That is, TWIP steel has an austenite structure instead of a ferrite structure as a matrix and has improved elongation through additional work hardening by continuously generating mechanical twins in austenite grains to obstruct movement of the dislocations during plastic deformation. Further, TWIP steel may have large elongation and high tensile strength due to the mechanical twins causing a high level of work hardening. In particular, TWIP steel has elongation 50% larger than that of conventional DP steel or TRIP steel and is thus preferably applied to steel sheets for automobiles.
- TWIP steel has a high Mn content ranging from about 18% to about 30% in order to guarantee austenite stability and adjust stacking fault energy, and requires the addition of large amounts of aluminum or silicon together with manganese, causing a significant increase in material and manufacturing costs.
- TWIP steel having a low Mn content in order to avoid an additional increase in manufacturing costs caused by volatilization of Mn or temperature decrease during a steel manufacturing process or continuous casting process.
- mechanical properties since currently developed TWIP steel has a low yield strength of about 300 MPa and a tensile strength of 1 GPa or less, there is a need for steel sheets which have a higher strength without deteriorating elongation.
- Various aspects of the present invention provide a steel sheet able to overcome the problems of dual phase (DP) steel, transformation induced plasticity (TRIP) steel and twin induced plasticity (TWIP) steel of the related art.
- DP dual phase
- TRIP transformation induced plasticity
- TWIP twin induced plasticity
- a high-strength and high-ductility steel sheet having a composition including, by weight, 0.8 to 1.4% C, 5.0 to 10.0% Mn, 2.0 to 8.0% Cr and the balance Fe, and unavoidable impurities.
- the steel sheet may be formed of twinning-induced plasticity steel.
- the steel sheet may exclude chromium carbides.
- the steel sheet may be a hot-rolled steel sheet heat-treated at a temperature of 1100° C. or higher.
- the hot-rolled steel may be manufactured by heating the steel sheet at a temperature of 1100° C. or higher, hot-rolling the heated steel sheet at a temperature of 900° C. or higher, and subsequently cooling the hot-rolled steel sheet by air cooling or forced cooling.
- the steel sheet may be a cold-rolled annealed steel manufactured by cold-rolling the hot-rolled steel.
- the cold-rolled annealed steel may be manufactured by cold-rolling the cooled steel sheet with a thickness reduction ratio of 30% or greater at room temperature, annealing the cold-rolled steel sheet at a temperature of 800° C. or higher, and subsequently cooling the annealed steel sheet by air cooling or forced cooling.
- a value obtained by multiplying the tensile strength and the total elongation of the steel sheet may be 30,000 MPa % or greater.
- the amount of the Cr may range from 4.0 to 7.0% by weight.
- the composition may further include, by weight, 0.1 to 2.0% Al.
- a method of manufacturing a high-strength and high-ductility steel sheet includes the following operations of: preparing a steel sheet having a composition comprising, by weight, 0.8 to 1.4% carbon, 5.0 to 10.0% manganese, 2.0 to 8.0% chromium and the balance iron, and unavoidable impurities; heating the steel sheet at a temperature of 1100° C. or higher; hot-rolling the heated steel sheet at a temperature of 900° C. or higher; and cooling the hot-rolled steel sheet by air cooling or forced cooling.
- the method may further include the operations of: cold-rolling the cooled steel sheet with a thickness reduction ratio of 30% or greater at room temperature; annealing the cold-rolled steel sheet at a temperature of 800° C. or higher; and cooling the annealed steel sheet by air cooling or forced cooling.
- Twin induced plasticity (TWIP) steel must have an austenite phase at room temperature after being hot rolled, since mechanical twins are formed in an austenite matrix at room temperature during plastic deformation.
- Mn is an austenite stabilizing alloying element that allows austenite, i.e. a high-temperature phase in the Fe—C binary phase diagram, to form at room temperature.
- austenite i.e. a high-temperature phase in the Fe—C binary phase diagram
- the austenite phase becomes remarkably unstable.
- a ferrite or martensite phase is formed in the austenite structure during cooling, whereby no mechanical twins can be formed during plastic deformation. Accordingly, the Mn content is required to be 5.0% by weight or greater.
- the Mn content is limited to the range from 5.0 to 9.0% by weight.
- Fe—Mn binary alloys have ⁇ martensite or ⁇ ′ martensite partially formed instead of a single austenite phase at room temperature.
- C can be desirably added as an inexpensive and highly effective austenite stabilizing element.
- it is difficult to obtain a single austenite phase during cooling after hot rolling since austenite stability is still insufficient.
- phase transformation occurs from austenite to martensite during plastic deformation to form TRIP steel, due to insufficient austenite stability. Consequently, TWIP steel intended in the present invention cannot be obtained.
- the C content is limited to the range from 1.0 to 1.4% by weight.
- Cr has been mainly used in stainless steel since it improves corrosion resistance. Cr not only functions as a ferrite stabilizing element, but also stabilizes austenite by lowering martensite transformation temperature when added to austenite steel. When Cr is added to the Fe—Mn—C ternary system, Cr can control martensite transformation to promote the formation of mechanical twins in the austenite matrix. In contrast, at a Cr content less than 2.0% by weight, austenite stability is insufficient, and strain induced martensite is formed instead of mechanical twins during plastic deformation, thereby producing TRIP steel.
- Cr decreases stacking fault energy in stainless steel like Mn.
- Fe—Mn—C ternary alloys Cr increases stacking fault energy. If the Cr content exceeds 8.0% by weight, the stacking fault energy of austenite becomes excessively high. Hardening is caused by simple perfect dislocation movement instead of mechanical twins during plastic deformation, making it difficult to achieve either high strength or high ductility.
- Cr is a ferrite stabilizing element, the Cr content exceeding 8.0% by weight may cause partial formation of ferrite during hot rolling. Furthermore, the use of a large amount Cr significantly increases manufacturing costs. Therefore, it is preferable that the Cr content is limited to the range from 2.0 to 8.0% by weight.
- composition of the steel sheet according to the present invention may selectively include Al. Hydrogen permeation into the steel sheet according to the invention may cause problems involving hydrogen embrittlement. These problems can be effectively overcome by the addition of Al.
- Al content is not specifically limited, Al is typically added at an amount of 2.0% or less by weight.
- the steel sheet according to the present invention has the austenite structure formed at room temperature while containing a small amount of Mn.
- the stacking fault energy is effectively controlled. Therefore, mechanical twins are formed during the plastic deformation of steel, leading to high levels of work hardening, tensile strength and workability. That is, in the steel sheet according to the present invention, the product of the tensile strength and the total elongation (TS ⁇ El) has a very large value of 30,000MPa % or greater.
- the product of the tensile strength and the total elongation is substantially the same and manufacturing costs are significantly reduced comparing to those of related-art TWIP steel having a Mn content of about 20% by weight.
- the high manganese nitrogen-containing steel sheet can be implemented as a variety of steel sheets, such as a hot-rolled steel sheet and a cold-rolled annealed steel sheet.
- FIG. 1 is a scanning electron microscopy (SEM) picture of an annealed steel sheet according to a comparative example of the present invention
- FIG. 2 is an SEM picture of an annealed steel sheet according to an example of the present invention.
- FIG. 3 is an SEM picture illustrating mechanical twins formed in a steel sheet according to an example of the present invention.
- a steel sheet according to an exemplary embodiment of the invention has a composition including, by weight, 0.8 to 1.4% C, 5.0 to 10.0% Mn, 2.0 to 8.0% Cr and the balance Fe, and unavoidable impurities.
- the present invention has been devised in order to overcome the problems of twin induced plasticity (TWIP) steel of the related art.
- TWIP twin induced plasticity
- the steel sheet according to this embodiment suitably adjusted amounts of C, Cr and the like are added, whereas the Mn content is lowered to be, by weight, 10% or less. This can consequently obtain a single austenite phase at room temperature while minimizing the Mn content.
- the composition of the steel sheet according to the present invention includes these alloy elements, thereby achieving a large elongation and high yield strength and tensile strength than related-art TWIP steel while reducing the contents of expensive alloy elements, such as Mn and Al, below those of the related-art TWIP steel.
- the steel sheet according to an exemplary embodiment of the invention includes, by weight, 5.0 to 10.0% Mn.
- Mn is employed as an austenite stabilizing element.
- austenite stability is significantly reduced, allowing ferrite or martensite to form in the austenite region during cooling after hot rolling.
- the stacking fault energy of the austenite phase excessively increases, thereby making it difficult to form mechanical twins.
- the stacking fault energy excessively increases, such that plastic deformation may occur in the austenite phase.
- one object of the invention is to minimize the content of expensive Mn, it is preferable to maintain the Mn content within 10% by weight according to this embodiment in order to reduce manufacturing costs as low as possible.
- composition of the steel sheet according to this embodiment includes, by weight, 0.8 to 1.4% C.
- Fe—Mn binary alloys have ⁇ or ⁇ ′ martensite partially formed therein instead of a single austenite phase at room temperature. Therefore, according to this embodiment, C is added as an inexpensive and effective austenite stabilizing element in order to obtain a single austenite phase structure at room temperature.
- the composition of the steel sheet according to this embodiment includes, by weight, 2.0 to 8.0% Cr.
- Cr has been mainly used in stainless steel since it improves corrosion resistance. Cr not only functions as a ferrite stabilizing element, but also stabilizes austenite by lowering martensite transformation temperature when added to austenite steel. When Cr is added to the Fe—Mn—C ternary system, Cr can control martensite transformation to promote the formation of mechanical twins in the austenite matrix. In contrast, at a Cr content less than 2.0% by weight, austenite stability is insufficient, and strain induced martensite is formed instead of mechanical twins during plastic deformation, thereby producing TRIP steel.
- Cr decreases stacking fault energy in stainless steel like Mn.
- Fe—Mn—C ternary alloys Cr increases stacking fault energy. If the Cr content exceeds 8.0% by weight, the stacking fault energy of austenite becomes excessively high. Hardening is caused by simple perfect dislocation movement instead of mechanical twins during plastic deformation, making it difficult to achieve either high strength or high ductility.
- Cr is a ferrite stabilizing element, the Cr content exceeding 8.0% by weight may cause partial formation of ferrite during hot rolling. Furthermore, the use of a large amount Cr significantly increases manufacturing costs. Therefore, it is preferable that the Cr content is limited to the range from 2.0 to 8.0% by weight.
- 3 mm thick steel sheets were formed by heating at a temperature of 1100° C. or higher, followed by hot rolling at a temperature of 900° C. or higher.
- the steel sheets were subsequently subjected to oil cooling or water cooling, thereby manufacturing steel samples (Inventive Examples 1 to 3 and Comparative Examples 1 to 7).
- part of the hot-rolled steel samples were subjected to annealing heat treatment at 800 to 1200° C. for 5 to 10 minutes, followed by oil cooling or water cooling.
- Comparative Examples 4, 5 and 6 have a greater amount of precipitations within the austenite matrix than the examples annealed at 1000° C., since Comparative Examples 4, 5 and 6 were annealed at 800° C. where the precipitation of chromium carbides is most active. Since the stability within the austenite matrix is significantly lowered, stress induced martensite is formed during plastic deformation. It is appreciated that the maximum tensile stress is very high but the elongation is very short.
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Abstract
A high-strength and high-ductility steel sheet having a composition including, by weight, 1.0 to 1.4% C, 5.0 to 9.0% Mn, 2.0 to 8.0% Cr and the balance Fe, and unavoidable impurities. The steel sheet has an austenite structure formed at room temperature, and stacking fault energy is effectively controlled by the addition of Cr and N2. Mechanical twins are formed during the plastic deformation of the steel, thereby leading to high levels of work hardening, tensile strength and workability.
Description
- The present application claims priority from Korean Patent Application Number 10-2013-00125214 filed on Oct. 21, 2013, the entire contents of which are incorporated herein for all purposes by this reference.
- 1. Field of the Invention
- The present invention relates to a high-strength and high-ductility steel sheet, and more particularly, to an automotive steel sheet for which high workability is required, a high manganese (Mn) steel sheet applicable as a shock absorber such as a vehicle bumper stiffener, and a method of manufacturing the same.
- 2. Description of Related Art
- Steel sheets applicable for vehicle bodies typically require high workability. In order to satisfy this requirement, ultra-low carbon steel has been mainly used for automotive steel sheets in the related art regardless of its low tensile strength ranging from 200 to 300 MPa, since it has high workability. Recently, a variety of methods for improving vehicle fuel efficiency have been proposed in response to environmental issues such as air pollution. In particular, as a lighter weight of a vehicle is considered important to improve fuel efficiency, automotive steel sheets are required to have not only high workability but also high strength.
- In addition, the necessity of commercializing high-strength steel is significantly increasing since some vehicle parts, such as bumper stiffeners or shock absorbers within the vehicle doors, are directly related to the safety of the occupants. For example, the use of ultra-high-strength steel having a high tensile strength of typically 780 MPa or higher and a large elongation is required.
- Examples of such high-strength automotive steel include dual phase (DP) steel, transformation induced plasticity (TRIP) steel and twin induced plasticity (TWIP) steel.
- First, DP steel is produced by lowering the cooling end temperature below the martensite start temperature (Ms) in the process of quenching hot-rolled steel to room temperature so that part of austenite transforms to martensite. Consequently, the dual phases of martensite transformed from austenite and ferrite exist at room temperature. Such DP steel can have a variety of mechanical properties due to an adjustment in the proportions of martensite and ferrite.
- TRIP steel has improved workability, and is produced by partially forming retained austenite in a structure, followed by the martensitic transformation of austenite during the machining of components. Although TRIP steel has the advantage of high strength caused by significant hardening through the martensitic transformation, its elongation is too short, which is problematic.
- The hardening mechanism of either DP steel or TRIP steel is typically based on martensite, the hard phase. Martensite exhibits a significant increase in hardening during plastic deformation, thereby enabling the manufacture of high-strength hot-rolled steel. However, the extremely low ductility of martensite makes it difficult to achieve an elongation of 30% or more, which is problematic.
- On the other hand, TWIP steel contains a large amount of Mn and has a single austenite phase, which is stable at room temperature and allows mechanical twins to form in the austenite structure during the machining of component, thereby increasing the level of work hardening. That is, TWIP steel has an austenite structure instead of a ferrite structure as a matrix and has improved elongation through additional work hardening by continuously generating mechanical twins in austenite grains to obstruct movement of the dislocations during plastic deformation. Further, TWIP steel may have large elongation and high tensile strength due to the mechanical twins causing a high level of work hardening. In particular, TWIP steel has elongation 50% larger than that of conventional DP steel or TRIP steel and is thus preferably applied to steel sheets for automobiles.
- However, current TWIP steel has a high Mn content ranging from about 18% to about 30% in order to guarantee austenite stability and adjust stacking fault energy, and requires the addition of large amounts of aluminum or silicon together with manganese, causing a significant increase in material and manufacturing costs. Moreover, there is a need for the development of TWIP steel having a low Mn content in order to avoid an additional increase in manufacturing costs caused by volatilization of Mn or temperature decrease during a steel manufacturing process or continuous casting process. Furthermore, in terms of mechanical properties, since currently developed TWIP steel has a low yield strength of about 300 MPa and a tensile strength of 1 GPa or less, there is a need for steel sheets which have a higher strength without deteriorating elongation.
- The information disclosed in the Background of the Invention section is provided only for better understanding of the background of the invention and should not be taken as an acknowledgment or any form of suggestion that this information forms a prior art that would already be known to a person skilled in the art.
- Various aspects of the present invention provide a steel sheet able to overcome the problems of dual phase (DP) steel, transformation induced plasticity (TRIP) steel and twin induced plasticity (TWIP) steel of the related art.
- Also provided is a steel sheet able to achieve both high strength and high ductility while reducing the content of Mn.
- In an aspect of the present invention, provided is a high-strength and high-ductility steel sheet having a composition including, by weight, 0.8 to 1.4% C, 5.0 to 10.0% Mn, 2.0 to 8.0% Cr and the balance Fe, and unavoidable impurities.
- The steel sheet may be formed of twinning-induced plasticity steel.
- The steel sheet may exclude chromium carbides.
- The steel sheet may be a hot-rolled steel sheet heat-treated at a temperature of 1100° C. or higher.
- The hot-rolled steel may be manufactured by heating the steel sheet at a temperature of 1100° C. or higher, hot-rolling the heated steel sheet at a temperature of 900° C. or higher, and subsequently cooling the hot-rolled steel sheet by air cooling or forced cooling.
- The steel sheet may be a cold-rolled annealed steel manufactured by cold-rolling the hot-rolled steel.
- The cold-rolled annealed steel may be manufactured by cold-rolling the cooled steel sheet with a thickness reduction ratio of 30% or greater at room temperature, annealing the cold-rolled steel sheet at a temperature of 800° C. or higher, and subsequently cooling the annealed steel sheet by air cooling or forced cooling.
- In the steel sheet, a value obtained by multiplying the tensile strength and the total elongation of the steel sheet may be 30,000 MPa % or greater.
- The amount of the Cr may range from 4.0 to 7.0% by weight.
- The composition may further include, by weight, 0.1 to 2.0% Al.
- In an aspect of the present invention, provided is a method of manufacturing a high-strength and high-ductility steel sheet. The method includes the following operations of: preparing a steel sheet having a composition comprising, by weight, 0.8 to 1.4% carbon, 5.0 to 10.0% manganese, 2.0 to 8.0% chromium and the balance iron, and unavoidable impurities; heating the steel sheet at a temperature of 1100° C. or higher; hot-rolling the heated steel sheet at a temperature of 900° C. or higher; and cooling the hot-rolled steel sheet by air cooling or forced cooling.
- The method may further include the operations of: cold-rolling the cooled steel sheet with a thickness reduction ratio of 30% or greater at room temperature; annealing the cold-rolled steel sheet at a temperature of 800° C. or higher; and cooling the annealed steel sheet by air cooling or forced cooling.
- The reasons why the composition of the steel sheet according to the invention is limited as above will be described as follows.
- Mn: 5.0 to 10.0 wt %
- Twin induced plasticity (TWIP) steel must have an austenite phase at room temperature after being hot rolled, since mechanical twins are formed in an austenite matrix at room temperature during plastic deformation. Mn is an austenite stabilizing alloying element that allows austenite, i.e. a high-temperature phase in the Fe—C binary phase diagram, to form at room temperature. At a Mn content less than 5% by weight, the austenite phase becomes remarkably unstable. After hot rolling, a ferrite or martensite phase is formed in the austenite structure during cooling, whereby no mechanical twins can be formed during plastic deformation. Accordingly, the Mn content is required to be 5.0% by weight or greater.
- At a Mn content exceeding 10.0% by weight, it is possible to produce a single austenite phase and form mechanical twins at room temperature. However, there are no significant differences from related-art TWIP steel. Thus, some problems, such as expensive manufacturing costs, degraded weldability and inserts, may still occur. Therefore, according to the invention, the Mn content is limited to the range from 5.0 to 9.0% by weight.
- C: 0.8 to 1.4 wt %
- At a Mn content less than 5.0% by weight, Fe—Mn binary alloys have ε martensite or α′ martensite partially formed instead of a single austenite phase at room temperature. In order to form a single austenite phase structure at room by overcoming this problem, C can be desirably added as an inexpensive and highly effective austenite stabilizing element. At a C content less than 0.8% by weight, it is difficult to obtain a single austenite phase during cooling after hot rolling since austenite stability is still insufficient. Even if the single austenite phase is obtained at room temperature, phase transformation occurs from austenite to martensite during plastic deformation to form TRIP steel, due to insufficient austenite stability. Consequently, TWIP steel intended in the present invention cannot be obtained. On the other hand, at a C content exceeding 1.4% by weight, stable austenite can be obtained at room temperature, but cementite precipitation occurs, thereby decreasing elongation and reducing weldability. Even if the cooling rate is controlled after annealing heat treatment, it is still difficult to control the precipitation of carbides. Since C increases stacking fault energy, a large C content makes it difficult to form mechanical twins during deformation. Accordingly, it is preferable that the C content is limited to the range from 1.0 to 1.4% by weight.
- Cr: 2.0 to 8.0 wt %
- Cr has been mainly used in stainless steel since it improves corrosion resistance. Cr not only functions as a ferrite stabilizing element, but also stabilizes austenite by lowering martensite transformation temperature when added to austenite steel. When Cr is added to the Fe—Mn—C ternary system, Cr can control martensite transformation to promote the formation of mechanical twins in the austenite matrix. In contrast, at a Cr content less than 2.0% by weight, austenite stability is insufficient, and strain induced martensite is formed instead of mechanical twins during plastic deformation, thereby producing TRIP steel.
- Although it is known that Cr decreases stacking fault energy in stainless steel like Mn. In contrast, in Fe—Mn—C ternary alloys, Cr increases stacking fault energy. If the Cr content exceeds 8.0% by weight, the stacking fault energy of austenite becomes excessively high. Hardening is caused by simple perfect dislocation movement instead of mechanical twins during plastic deformation, making it difficult to achieve either high strength or high ductility. In addition, since Cr is a ferrite stabilizing element, the Cr content exceeding 8.0% by weight may cause partial formation of ferrite during hot rolling. Furthermore, the use of a large amount Cr significantly increases manufacturing costs. Therefore, it is preferable that the Cr content is limited to the range from 2.0 to 8.0% by weight.
- The composition of the steel sheet according to the present invention may selectively include Al. Hydrogen permeation into the steel sheet according to the invention may cause problems involving hydrogen embrittlement. These problems can be effectively overcome by the addition of Al. Although the Al content is not specifically limited, Al is typically added at an amount of 2.0% or less by weight.
- As set forth above, the steel sheet according to the present invention has the austenite structure formed at room temperature while containing a small amount of Mn. In addition, the stacking fault energy is effectively controlled. Therefore, mechanical twins are formed during the plastic deformation of steel, leading to high levels of work hardening, tensile strength and workability. That is, in the steel sheet according to the present invention, the product of the tensile strength and the total elongation (TS×El) has a very large value of 30,000MPa % or greater. The product of the tensile strength and the total elongation is substantially the same and manufacturing costs are significantly reduced comparing to those of related-art TWIP steel having a Mn content of about 20% by weight.
- In addition, the high manganese nitrogen-containing steel sheet can be implemented as a variety of steel sheets, such as a hot-rolled steel sheet and a cold-rolled annealed steel sheet.
- The methods and apparatuses of the present invention have other features and advantages that will be apparent from, or are set forth in greater detail in the accompanying drawings, which are incorporated herein, and in the following Detailed Description of the Invention, which together serve to explain certain principles of the present invention.
-
FIG. 1 is a scanning electron microscopy (SEM) picture of an annealed steel sheet according to a comparative example of the present invention; -
FIG. 2 is an SEM picture of an annealed steel sheet according to an example of the present invention; and -
FIG. 3 is an SEM picture illustrating mechanical twins formed in a steel sheet according to an example of the present invention. - Reference will now be made in detail to exemplary embodiments of a steel sheet and a method of manufacturing the same according to the present invention.
- First, a steel sheet according to an exemplary embodiment of the invention has a composition including, by weight, 0.8 to 1.4% C, 5.0 to 10.0% Mn, 2.0 to 8.0% Cr and the balance Fe, and unavoidable impurities.
- The present invention has been devised in order to overcome the problems of twin induced plasticity (TWIP) steel of the related art. In the steel sheet according to this embodiment, suitably adjusted amounts of C, Cr and the like are added, whereas the Mn content is lowered to be, by weight, 10% or less. This can consequently obtain a single austenite phase at room temperature while minimizing the Mn content. Accordingly, the composition of the steel sheet according to the present invention includes these alloy elements, thereby achieving a large elongation and high yield strength and tensile strength than related-art TWIP steel while reducing the contents of expensive alloy elements, such as Mn and Al, below those of the related-art TWIP steel.
- Specifically, the steel sheet according to an exemplary embodiment of the invention includes, by weight, 5.0 to 10.0% Mn. Since TWIP steel has mechanical twins formed in an austenite matrix at room temperature during plastic deformation, it is important to expand an austenite region from high temperature to room temperature on the Fe—C phase diagram. In addition, stacking fault energy must be about 50 mmJ/m2 or less in order to form mechanical twins during plastic deformation. According to the present invention, Mn is employed as an austenite stabilizing element.
- At a Mn content less than 5% by weight, austenite stability is significantly reduced, allowing ferrite or martensite to form in the austenite region during cooling after hot rolling. In addition, at the Mn content less than 5% by weight, the stacking fault energy of the austenite phase excessively increases, thereby making it difficult to form mechanical twins.
- On the other hand, if the Mn content is too great, the stacking fault energy excessively increases, such that plastic deformation may occur in the austenite phase. In addition, since one object of the invention is to minimize the content of expensive Mn, it is preferable to maintain the Mn content within 10% by weight according to this embodiment in order to reduce manufacturing costs as low as possible.
- In addition, the composition of the steel sheet according to this embodiment includes, by weight, 0.8 to 1.4% C. Here, Fe—Mn binary alloys have ε or α′ martensite partially formed therein instead of a single austenite phase at room temperature. Therefore, according to this embodiment, C is added as an inexpensive and effective austenite stabilizing element in order to obtain a single austenite phase structure at room temperature.
- At a C content less than 0.8% by weight, it is difficult to obtain a single austenite phase during cooling after hot rolling since austenite stability is still insufficient. Even if the single austenite phase is obtained at room temperature, phase transformation occurs from austenite to martensite during plastic deformation to form TRIP steel, due to insufficient austenite stability. Consequently, TWIP steel intended in the present invention cannot be obtained.
- On the other hand, at a C content exceeding 1.4% by weight, stable austenite can be obtained at room temperature, but carbide precipitation occurs, thereby decreasing elongation and reducing weldability. Even if the cooling rate is controlled after annealing heat treatment, it is still difficult to control the precipitation of carbides. Since C is an element that increases stacking fault energy, a large C content makes it difficult to form mechanical twins during deformation, which is problematic. Accordingly, it is preferable that the C content is limited to the range from 1.0 to 1.4% by weight.
- Furthermore, the composition of the steel sheet according to this embodiment includes, by weight, 2.0 to 8.0% Cr. Cr has been mainly used in stainless steel since it improves corrosion resistance. Cr not only functions as a ferrite stabilizing element, but also stabilizes austenite by lowering martensite transformation temperature when added to austenite steel. When Cr is added to the Fe—Mn—C ternary system, Cr can control martensite transformation to promote the formation of mechanical twins in the austenite matrix. In contrast, at a Cr content less than 2.0% by weight, austenite stability is insufficient, and strain induced martensite is formed instead of mechanical twins during plastic deformation, thereby producing TRIP steel.
- Although it is known that Cr decreases stacking fault energy in stainless steel like Mn. In contrast, in Fe—Mn—C ternary alloys, Cr increases stacking fault energy. If the Cr content exceeds 8.0% by weight, the stacking fault energy of austenite becomes excessively high. Hardening is caused by simple perfect dislocation movement instead of mechanical twins during plastic deformation, making it difficult to achieve either high strength or high ductility. In addition, since Cr is a ferrite stabilizing element, the Cr content exceeding 8.0% by weight may cause partial formation of ferrite during hot rolling. Furthermore, the use of a large amount Cr significantly increases manufacturing costs. Therefore, it is preferable that the Cr content is limited to the range from 2.0 to 8.0% by weight.
- 3 mm thick steel sheets, the chemical compositions of which are presented in Table 1 below, were formed by heating at a temperature of 1100° C. or higher, followed by hot rolling at a temperature of 900° C. or higher. The steel sheets were subsequently subjected to oil cooling or water cooling, thereby manufacturing steel samples (Inventive Examples 1 to 3 and Comparative Examples 1 to 7). In addition, part of the hot-rolled steel samples were subjected to annealing heat treatment at 800 to 1200° C. for 5 to 10 minutes, followed by oil cooling or water cooling.
-
TABLE 1 Composition (wt %) Sample No. C Mn Cr Remarks Inventive Ex. 1 1.22 7.34 3.03 Water cooled after annealed at 1200° C. Inventive Ex. 2 1.18 7.23 4.89 Water cooled after annealed at 1200° C. Inventive Ex. 3 1.23 7.42 6.92 Water cooled after annealed at 1200° C. Comp. Ex. 1 1.22 7.34 3.03 Water cooled after annealed at 1000° C. Comp. Ex. 2 1.18 7.24 4.89 Water cooled after annealed at 1000° C. Comp. Ex. 3 1.23 7.42 6.92 Water cooled after annealed at 1000° C. Comp. Ex. 4 1.22 7.34 3.03 Water cooled after annealed at 800° C. Comp. Ex. 5 1.18 7.24 4.89 Water cooled after annealed at 800° C. Comp. Ex. 6 1.23 7.42 6.92 Water cooled after annealed at 800° C. Comp. Ex. 7 1.19 8.08 <1 wt % Water cooled after annealed at 1000° C. -
TABLE 2 YS1 TS2 El3 TS × El Sample No. (MPa) (MPa) (%) (MPa %) Remarks Inventive 410 829 38.6 31999 Water cooled after Ex. 1 annealed at 1200° C. Inventive 484 953 39.7 37834 Water cooled after Ex. 2 annealed at 1200° C. Inventive 515 1014 38.0 38532 Water cooled after Ex. 3 annealed at 1200° C. Comp. Ex. 1 512 1074 22.2 23843 Water cooled after annealed at 1000° C. Comp. Ex. 2 595 1211 22.0 26642 Water cooled after annealed at 1000° C. Comp. Ex. 3 614 1162 15.6 18127 Water cooled after annealed at 1000° C. Comp. Ex. 4 893 1054 2.1 2213 Water cooled after annealed at 800° C. Comp. Ex. 5 984 1625 6.3 10237 Water cooled after annealed at 800° C. Comp. Ex. 6 1021 1557 5.5 8563 Water cooled after annealed at 800° C. Comp. Ex. 7 371 830 23.1 19173 Water cooled after annealed at 1000° C. Note) YS1: Yield Strength, TS2: Tensile Strength, El3: Total Elongation - The strength and elongation were measured from the samples manufactured by the above-described process, and the results are presented in Table 2. As presented in Table 2, tensile properties were significantly different according to the annealing temperatures even at the same composition. This relates to chromium carbides formed by the addition of Cr. As illustrated in
FIG. 1 , the microstructure of comparative steel 2 has a large amount of carbides formed within the grains and matrix. In contrast, no chromium carbides were observed in the annealed microstructure of inventive steel 2 having the same composition. Therefore, when a low annealing temperature or a slow cooling rate causes carbide precipitation within the austenite matrix, C and Cr in austenite have a small solubility, thereby degrading the stability of austenite. Since carbides are already precipitated to coarse sizes, tensile properties are subjected to an adverse effect even in the same type of steel. As a result, as presented in Table 2, the strength X elongation of each of Inventive Examples is 30,000 MPa % or greater, whereas the strength X elongation of each of Comparative Examples 1, 2 and 3 is smaller than 30,000 MPa %. - Comparative Examples 4, 5 and 6 have a greater amount of precipitations within the austenite matrix than the examples annealed at 1000° C., since Comparative Examples 4, 5 and 6 were annealed at 800° C. where the precipitation of chromium carbides is most active. Since the stability within the austenite matrix is significantly lowered, stress induced martensite is formed during plastic deformation. It is appreciated that the maximum tensile stress is very high but the elongation is very short.
- Even in the case where Mn or C is within the range of the inventive examples, if Cr is added at an amount smaller than the reference content, no superior tensile properties are obtained, as apparent from Comparative Example 7. The microstructure of Inventive Example 3 during plastic deformation was observed using a scanning electron microscope (SEM) in order to examine the formation of mechanical twins during plastic deformation. As illustrated in
FIG. 3 , well-developed mechanical twins are appreciated. - As set forth above, the exemplary embodiments of the high-strength and high-ductility steel sheet and the method of manufacturing the same according to the present invention have been described in detail. However, a person skilled in the art can make various alternatives and modifications of the exemplary embodiments. It should be therefore understood that the scope of the present invention shall be defined by the Claims appended hereto and their equivalents.
Claims (14)
1. A high-strength and high-ductility steel sheet having a composition comprising, by weight, 0.8 to 1.4% carbon, 5.0 to 10.0% manganese, 2.0 to 8.0% chromium and the balance iron, and unavoidable impurities.
2. The steel sheet according to claim 1 , comprising twinning-induced plasticity steel.
3. The steel sheet according to claim 1 , excluding chromium carbides.
4. The steel sheet according to claim 1 , comprising a hot-rolled steel sheet heat-treated at a temperature of 1100° C. or higher.
5. The steel sheet according to claim 4 , wherein the hot-rolled steel is manufactured by heating the steel sheet at a temperature of 1100° C. or higher, hot-rolling the heated steel sheet at a temperature of 900° C. or higher, and subsequently cooling the hot-rolled steel sheet by air cooling or forced cooling.
6. The steel sheet according to claim 4 , comprising a cold-rolled annealed steel manufactured by cold-rolling the hot-rolled steel.
7. The steel sheet according to claim 6 , wherein the cold-rolled annealed steel is manufactured by cold-rolling the cooled steel sheet with a thickness reduction ratio of 30% or greater at room temperature, annealing the cold-rolled steel sheet at a temperature of 800° C. or higher, and subsequently cooling the annealed steel sheet by air cooling or forced cooling.
8. The steel sheet according to claim 1 , wherein a value obtained by multiplying a tensile strength with a total elongation is 30,000 MPa % or greater.
9. The steel sheet according to claim 1 , wherein an amount of the chromium ranges from 4.0 to 7.0% by weight.
10. The steel sheet according to claim 1 , wherein the composition further comprises, by weight, 0.1 to 2.0% aluminum.
11. A method of manufacturing a high-strength and high-ductility steel sheet, the method comprising:
preparing a steel sheet having a composition comprising, by weight, 0.8 to 1.4% carbon, 5.0 to 10.0% manganese, 2.0 to 8.0% chromium and the balance iron, and unavoidable impurities;
heating the steel sheet at a temperature of 1100° C. or higher;
hot-rolling the heated steel sheet at a temperature of 900° C. or higher; and
cooling the hot-rolled steel sheet by air cooling or forced cooling.
12. The method according to claim 11 , further comprising:
cold-rolling the cooled steel sheet with a thickness reduction ratio of 30% or greater at room temperature;
annealing the cold-rolled steel sheet at a temperature of 800° C. or higher; and
cooling the annealed steel sheet by air cooling or forced cooling.
13. The method according to claim 11 , wherein an amount of the chromium ranges, by weight, 4.0 to 7.0%.
14. The method according to claim 11 , wherein the composition further comprises, by weight, 0.1 to 2.0% aluminum.
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CN110592490A (en) * | 2019-09-17 | 2019-12-20 | 北京科技大学 | High-strength-ductility plasticity-free unstable hot-rolled medium manganese steel and preparation method thereof |
CN111074051A (en) * | 2019-12-11 | 2020-04-28 | 舞阳钢铁有限责任公司 | Production method of steel wear-resisting plate BTW for coal mine |
CN112280941A (en) * | 2020-09-28 | 2021-01-29 | 燕山大学 | Preparation method of ultrahigh-strength ductile bainite steel based on stacking fault energy regulation |
CN114507803A (en) * | 2022-01-14 | 2022-05-17 | 西安建筑科技大学 | Quenching distribution steel with gradient distribution of stacking fault energy, preparation method and application |
CN115287542A (en) * | 2022-08-19 | 2022-11-04 | 四川大学 | High-strength low-magnetic steel with uniform nano twin crystal distribution and preparation method thereof |
CN115418577A (en) * | 2022-08-30 | 2022-12-02 | 鞍钢集团北京研究院有限公司 | Seawater corrosion resistant high-strength high-toughness damping alloy and preparation method thereof |
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KR100742833B1 (en) * | 2005-12-24 | 2007-07-25 | 주식회사 포스코 | High Mn Steel Sheet for High Corrosion Resistance and Method of Manufacturing Galvanizing the Steel Sheet |
KR20160039304A (en) * | 2008-01-30 | 2016-04-08 | 타타 스틸 이즈무이덴 베.뷔. | Method of producing a hot-rolled twip-steel and a twip-steel product produced thereby |
KR101193718B1 (en) * | 2010-03-25 | 2012-10-22 | 현대제철 주식회사 | Nitrogen-added high manganese steel having high strength and large ductility and method for manufacturing the same |
KR20120026249A (en) * | 2010-09-09 | 2012-03-19 | 연세대학교 산학협력단 | Steel having high strength and large ductility and method for manufacturing the same |
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US2965478A (en) * | 1958-10-10 | 1960-12-20 | Allis Chalmers Mfg Co | Austenitic steel alloy |
US6358338B1 (en) * | 1999-07-07 | 2002-03-19 | Usinor | Process for manufacturing strip made of an iron-carbon-manganese alloy, and strip thus produced |
US8999085B2 (en) * | 2005-12-26 | 2015-04-07 | Posco | High manganese steel strips with excellent coatability and superior surface property, coated steel strips using steel strips and method for manufacturing the steel strips |
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CN110592490A (en) * | 2019-09-17 | 2019-12-20 | 北京科技大学 | High-strength-ductility plasticity-free unstable hot-rolled medium manganese steel and preparation method thereof |
CN111074051A (en) * | 2019-12-11 | 2020-04-28 | 舞阳钢铁有限责任公司 | Production method of steel wear-resisting plate BTW for coal mine |
CN112280941A (en) * | 2020-09-28 | 2021-01-29 | 燕山大学 | Preparation method of ultrahigh-strength ductile bainite steel based on stacking fault energy regulation |
CN114507803A (en) * | 2022-01-14 | 2022-05-17 | 西安建筑科技大学 | Quenching distribution steel with gradient distribution of stacking fault energy, preparation method and application |
CN115287542A (en) * | 2022-08-19 | 2022-11-04 | 四川大学 | High-strength low-magnetic steel with uniform nano twin crystal distribution and preparation method thereof |
CN115418577A (en) * | 2022-08-30 | 2022-12-02 | 鞍钢集团北京研究院有限公司 | Seawater corrosion resistant high-strength high-toughness damping alloy and preparation method thereof |
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