CN113774274B - Low-cost well-formed battery case steel and production method thereof - Google Patents
Low-cost well-formed battery case steel and production method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 122
- 239000010959 steel Substances 0.000 title claims abstract description 122
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 27
- 239000000126 substance Substances 0.000 claims abstract description 9
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- 229910052748 manganese Inorganic materials 0.000 claims abstract description 7
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 5
- 238000004080 punching Methods 0.000 claims abstract description 5
- 229910052802 copper Inorganic materials 0.000 claims abstract description 4
- 238000005096 rolling process Methods 0.000 claims description 42
- 238000000137 annealing Methods 0.000 claims description 30
- 238000005097 cold rolling Methods 0.000 claims description 25
- 238000010438 heat treatment Methods 0.000 claims description 18
- 238000005098 hot rolling Methods 0.000 claims description 17
- 238000002791 soaking Methods 0.000 claims description 14
- 238000010583 slow cooling Methods 0.000 claims description 13
- 239000002253 acid Substances 0.000 claims description 11
- 230000009467 reduction Effects 0.000 claims description 11
- 229910000859 α-Fe Inorganic materials 0.000 claims description 10
- 238000005266 casting Methods 0.000 claims description 9
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- 239000010960 cold rolled steel Substances 0.000 claims description 7
- 238000001816 cooling Methods 0.000 claims description 7
- 239000001257 hydrogen Substances 0.000 claims description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims description 7
- 238000005406 washing Methods 0.000 claims description 7
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- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 3
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- 239000000243 solution Substances 0.000 description 3
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
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- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
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- 239000011248 coating agent Substances 0.000 description 1
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- 229910052840 fayalite Inorganic materials 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
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Images
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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing 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
- 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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- 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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/10—Primary casings; Jackets or wrappings
- H01M50/116—Primary casings; Jackets or wrappings characterised by the material
- H01M50/117—Inorganic material
- H01M50/119—Metals
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Sealing Battery Cases Or Jackets (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
The application relates to the field of iron and steel smelting, in particular to low-cost well-formed battery case steel and a production method thereof, wherein the battery case steel comprises the following chemical components in percentage by mass: c: 0.008% -0.02%, Mn: 0.1% -0.3%, Si: less than or equal to 0.01 percent, Als: 0.050-0.10%, P: less than or equal to 0.015%, S: less than or equal to 0.0020 percent, N: less than or equal to 0.004%, Cu: less than or equal to 0.01, Ti: less than or equal to 0.01-0.04%, less than or equal to 0.002% of T [ O ], and the balance of Fe and inevitable impurities, wherein T [ O ] is an oxidation system inclusion; t [ O ] in steel making is the content of the oxide inclusions, so that the deoxidation time can be reduced, the inclusions in steel can be reduced, and the steel plate formed by subsequent punching has more excellent processing and forming performances; the toughness of the steel is improved, the anisotropy of the steel is reduced, and the steel has good yield strength elongation and good forming performance by matching the process.
Description
Technical Field
The application relates to the field of steel smelting, in particular to low-cost well-formed battery case steel and a production method thereof.
Background
The battery case steel is a thin cold-rolled steel strip, is mainly used for manufacturing battery cases, plays a role in sealing battery media, and has high requirements on the structure performance, inclusion, surface quality and the like of materials.
At present, the battery case substrate products are mainly divided into two types: one is high strength IFInterstitial Free steel with low C content and no ageing formed by fixing the C atom in the steel with Nb and Ti elements, and IF type battery case steel has excellent deep drawing performance. The other type is aluminum killed steel which adopts a low-carbon steel component system and is deoxidized by adding Al element, and the technical requirements of battery products are met by controlling the performance of the steel plate. The IF steel needs vacuum degassing and additional addition of alloy elements, so that the production cost is obviously increased, inclusions in the steel are also obviously increased along with the increase of the deoxidation time, the adverse effect is also caused on subsequent stamping forming, and the forming performance of the aluminum killed low-carbon steel is poorer than that of the IF steel and has certain anisotropy.
How to solve the technical difficulties by new components and a new process and produce the low-carbon steel for the aluminum-killed battery shell with good formability and low cost becomes the key point of research.
Patent publication No. CN02139076.2 discloses an extremely thin steel strip for battery cases and a production method thereof, belonging to the field of low alloy steel manufacturing. The method comprises the steps of adopting Mn for solid solution strengthening, compositely adding trace Nb and Ti, controlling the content of surplus Ti to be less than 0.01%, adopting molten iron desulphurization, converter blowing, RH vacuum treatment and continuous casting, wherein the hot rolling soaking temperature is 1200 +/-50 ℃, the finishing rolling temperature FT meets the conditions that Ar3 is not less than or equal to FT and is not greater than Ar3+30 ℃, the coiling temperature is 650-720 ℃, a hot rolled plate is subjected to acid washing, a single-stand rolling mill is adopted for cold rolling, and the steel strip is subjected to continuous annealing, longitudinal shearing, oil coating and packaging to produce the ultra-thin precise steel strip with high strength, high elongation, low earing and low yield ratio. The production method is simple, can be implemented in various large steel mills, and has a price greatly reduced compared with that of an import plate. The strip steel can be widely used for producing electronic basic elements such as dry battery shells, communication cables, television color tubes, carbon film resistors and the like.
Patent application No. CN201110232765.4 discloses steel for a battery case and a preparation method thereof, wherein the steel is formed by rapid stamping. The components and weight percentage are as follows: c: 0.0001 to 0.0050%, Mn: 0.10-0.20%, Al: 0.010-0.050%, N: 0.0001-0.0040%, Nb: 0.010-0.030%, and controlling: less than or equal to 0.020% of P, less than or equal to 0.015% of S, less than or equal to 0.05% of Cu, less than or equal to 0.05% of Ni, less than or equal to 0.08% of Cr, less than or equal to 0.05% of Mo, and less than or equal to 0.020% of Si; the method comprises the following steps: smelting according to a pure steel process and continuously casting to form a blank; heating a continuous casting billet; rough rolling; finish rolling in a single-phase austenite region; coiling; acid washing; cold rolling; degreasing; annealing in an all-hydrogen bell-type furnace; and flattening for later use. The finished product of the invention has stable mechanical property, hardness value of 90-100, tensile strength of more than or equal to 300MPa, elongation of more than or equal to 36 percent, yield ratio of less than or equal to 0.6, difficult fracture of punched battery shell, good shape fixity of the cylinder body and high corrosion resistance of the finished product.
Patent application No. CN200510030154.6 discloses steel for a battery steel shell and a manufacturing method thereof. Mainly solves the defects of larger plane anisotropy, poorer secondary processing embrittlement resistance, higher production cost and the like of the traditional steel for battery cases. The steel for the battery case with excellent plane isotropy comprises the following chemical elements in percentage by weight: c: not more than 0.01 to 0.05%, Si: less than or equal to 0.03%, Mn: 0.10 to 0.50%, P: less than or equal to 0.02 percent, S: less than or equal to 0.015 percent, Al: 0.01-0.10%, N: 0.002-0.007%, Ti: 0.005-0.02% and the balance of iron and inevitable impurities. The manufacturing method comprises the following steps: the method comprises the following steps of molten iron pretreatment, converter smelting, furnace post-refining, hot rolling, acid washing, cold rolling, cover annealing, leveling and finishing to form a finished coil, and is characterized in that: heating temperature: not more than 1270 ℃, and finishing temperature: 860-930 ℃, and coiling temperature: at most 640 ℃; the cold rolling deformation is controlled to be 75-90%, and the annealing temperature of a bell-type furnace is as follows: 650-800 ℃; the rest is carried out according to the conventional process. The product is used for stamping after nickel electroplating or directly stamping into a battery case.
Disclosure of Invention
The application provides low-cost good-forming battery case steel and a production method thereof, and aims to solve the technical problem of how to prepare battery case steel with excellent forming performance.
In a first aspect, the present application provides a low-cost well-formed battery case steel, wherein the chemical composition of the battery case steel comprises, by mass: c: 0.008% -0.02%, Mn: 0.1% -0.3%, Si: less than or equal to 0.01 percent, Als: 0.050-0.10%, P: less than or equal to 0.015 percent, S: less than or equal to 0.0020 percent, N: less than or equal to 0.004%, Cu: less than or equal to 0.01, Ti: less than or equal to 0.01-0.04%, less than or equal to 0.002% of T [ O ], and the balance of Fe and inevitable impurities, wherein T [ O ] is an oxidation-system inclusion.
Optionally, the metallographic structure of the battery case steel comprises, by volume fraction: 97-98% ferrite and 2-3% pearlite.
Optionally, the thickness of the battery case steel is 0.2-0.5 mm.
Optionally, the mechanical properties of the battery case steel include: the yield strength is 160-190 MPa, the tensile strength is 300-350 MPa, and the elongation is more than or equal to 30%.
In a second aspect, the present application provides a method for producing a battery case steel according to the first aspect, the method comprising:
obtaining a casting blank containing the chemical components;
carrying out hot rolling on the casting blank to obtain a hot rolled steel coil;
sequentially carrying out acid washing and cold rolling on the hot-rolled steel coil to obtain a cold-rolled steel coil;
continuously annealing and flattening the cold-rolled steel coil to obtain battery case steel;
the continuous annealing comprises the following steps in sequence: preheating, soaking, slow cooling, quick cooling and overaging;
the temperature of the overaging is 300-400 ℃.
Optionally, the soaking temperature is 730-780 ℃, the soaking time is 50-200 s, the termination temperature of slow cooling is 670-710 ℃, the slow cooling rate is less than or equal to 15 ℃/s, and the fast cooling rate is greater than or equal to 50 ℃/s.
Optionally, the dew point temperature of the continuous annealing is-20 to-50 ℃;
the continuous annealing comprises: and carrying out continuous annealing under the condition of a protective atmosphere, wherein the protective atmosphere is 1-10% of hydrogen by volume percentage, 1-20 ppm of oxygen by mass concentration, and the balance of nitrogen.
Optionally, the hot rolling sequentially comprises slab heating, rough rolling, finish rolling and coiling; the heating temperature of the plate blank is 1120-1180 ℃, the starting temperature of finish rolling is 820-850 ℃, the finishing temperature of finish rolling is 740-770 ℃, and the coiling temperature is 680-700 ℃.
Optionally, the total rolling reduction rate of the cold rolling is 80-90%.
Optionally, in the cold rolling, the reduction rate of the primary cold rolling is 40-60%.
Compared with the prior art, the technical scheme provided by the embodiment of the application has the following advantages:
the chemical composition of the battery case steel provided by the embodiment of the application, C: 0.008% -0.02%, the aluminum killed steel deoxidized by adding AI elements in a low-carbon steel component system is adopted, the lower S content is controlled in the component system, the sulfide content in the steel is reduced, and the toughness of the product is improved; ti is added to play a role in precipitation strengthening, and the grains of the strip steel are refined, so that the anisotropy of the grains is reduced, and the anisotropy of the strip steel is reduced; the content of harmful elements such as N, H in the steel is reduced, the content of nitride and harmful gas in the steel is reduced, and the toughness of the product can be improved; t [ O ] is the content of the oxide inclusions in the steel making, so that the deoxidation time can be reduced, the inclusions in the steel can be reduced, and the steel formed by subsequent punching has more excellent processing and forming performances; the toughness of the steel is improved, the anisotropy of the steel is reduced, and the steel plate has good yield strength elongation and good forming performance by matching the process.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
Fig. 1 is a schematic flow chart of a method for producing a battery case steel according to an embodiment of the present application;
FIG. 2 shows the optical microstructure morphology (OM) of the battery case steels of the examples and comparative examples.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The application provides a low-cost good shaping battery case steel, the chemical composition of battery case steel includes by mass fraction: c: 0.008% -0.02%, Mn: 0.1% -0.3%, Si: less than or equal to 0.01 percent, Als: 0.050-0.10%, P: less than or equal to 0.015 percent, S: less than or equal to 0.0020 percent, N: less than or equal to 0.004%, Cu: less than or equal to 0.01, Ti: less than or equal to 0.01-0.04%, less than or equal to 0.002% of T [ O ], and the balance of Fe and inevitable impurities, wherein T [ O ] is an oxidation-system inclusion.
The low-cost well-formed battery case steel is low-yield aluminum killed battery case steel, the yield strength is 160-190 MPa, the tensile strength is 300-350 MPa, the elongation A is more than or equal to 30%, and the punching speed can reach 100 per minute.
The action and mechanism of the main elements and processes in this application:
c: carbon is used for solid solution strengthening to improve the strength of steel, but the obvious increase of the strength of the steel plate can reduce the plasticity and the formability of the steel plate, and the lower carbon content is beneficial to reducing the precipitation of cementite at crystal boundary, so the content of C in the steel is selected to be 0.008% -0.02%.
Mn: mn plays a solid solution strengthening role in steel. The Mn content is increased to reduce the product toughness, and is particularly unfavorable for elongation, hole expansion and cold bending performance, so that the Mn content is 0.1-0.3%.
Si: si is a solid solution strengthening element, which can obviously improve the strength of the steel, but 2FeO & SiO are easily formed on the surface of the steel plate in the hot rolling process with excessively high Si content 2 The (fayalite) oxide skin is not easy to remove by hot rolling descaling, and the content of Si is not too high, so that the content of Si is less than or equal to 0.01 percent in the invention.
And (3) Als: al is a deoxidizer, reduces the oxygen content in steel and reduces inclusions in the steel, thereby improving the toughness of the steel, but the Al content is too high, coarse AlN particles are easily formed, and the toughness of the steel is reduced, so the Al content is 0.03-0.10%.
P: p is an impurity element in steel, is easy to segregate in grain boundaries and influences the toughness of products, so the lower the content of P is, the better the content of P is, and the content of P is controlled to be below 0.015 percent according to an actual control level.
S: s is an impurity element in steel, is easy to generate segregation in a crystal boundary, forms low-melting-point sulfide with Fe and Mn in the steel, reduces cold bending, hole expansion and extensibility of the steel, and is fully removed during steel making and controlled to be 0.002%.
N: n is an impurity element in steel, and reduces the toughness of steel, so the content of N is controlled to be less than 0.004%.
Cu: the Cu can obviously improve the corrosion resistance and corrosion resistance of steel, and the increase of the Cu content can increase the strength, particularly the yield ratio of the steel, so the Cu content is less than or equal to 0.1.
Ti: ti can play a role in precipitation strengthening, and the grains of the strip steel are refined, so that the anisotropy of the grains is reduced, and the anisotropy of the strip steel is reduced, but the strength of the material is increased and the production cost is increased due to the excessively high Ti content, so that the Ti content is less than or equal to 0.01-0.04%.
T [ O ]: the content of TiO in the steel is less than 0.002% and is easy to form oxide inclusion.
As an alternative embodiment, the metallographic structure of the steel for battery cases comprises, in volume fraction: 97-98% ferrite and 2-3% pearlite.
As an optional embodiment, the thickness of the battery case steel is 0.2-0.5 mm.
As an alternative embodiment, the mechanical properties of the battery case steel include: the yield strength is 160-190 MPa, the tensile strength is 300-350 MPa, and the elongation A is more than or equal to 30%.
In a second aspect, the present application provides a method for producing a low-cost, well-formed battery case steel, as shown in fig. 1, the method comprising:
s1, obtaining a casting blank containing the chemical components;
in the embodiment of the application, before the casting blank is obtained, LF refining is adopted, so that the S content in steel can be effectively reduced, the sulfide content in the steel is reduced, and the toughness of the product is improved; the RH vacuum is adopted to reduce the content of harmful elements such as N, H in the steel, reduce the content of nitride and harmful gas in the steel and improve the toughness of the product.
S2, carrying out hot rolling on the casting blank to obtain a hot rolled steel coil;
s3, carrying out acid washing and cold rolling on the hot-rolled steel coil in sequence to obtain a cold-rolled steel coil;
s4, continuously annealing and flattening the cold-rolled steel coil to obtain battery case steel;
in the embodiment of the application, the flat elongation can be 0.3-1.0%.
The invention adopts the wet leveling process, the surface quality of the steel plate obtained by adopting the wet leveling process is better than that obtained by adopting the dry leveling process, the rolling force of the leveler is smaller, the energy consumption is reduced, and the elimination of the yield platform of the steel plate is facilitated. Meanwhile, the yield strength can be further reduced by adopting the flat elongation of 0.3-1.0, and finally the battery case steel with good surface and low yield is obtained.
The continuous annealing comprises the following steps in sequence: preheating, soaking, slow cooling, fast cooling and overaging;
the temperature of the overaging is 300-400 ℃.
The overaging refers to the temperature and time when the aging temperature exceeds the normal aging temperature, namely the temperature and time when the peak hardness is reached, at the moment, a precipitation phase in the material begins to grow, the distance is increased, the macroscopic expression is that the strength of the material is reduced, and the ductility and toughness are improved.
As an optional implementation mode, the soaking temperature is 730-780 ℃, the soaking time is 50-200 s, the termination temperature of slow cooling is 670-710 ℃, the slow cooling rate is less than or equal to 15 ℃/s, and the fast cooling rate is greater than or equal to 50 ℃/s.
In the embodiment of the application, the soaking temperature is 730-780 ℃ to easily obtain a uniform ferrite grain structure, the slow cooling termination temperature is 670-710 ℃, the higher soaking and slow cooling temperature can enable the strip steel to stay for a longer time at the ferrite recrystallization temperature, the grains can fully grow, and the anisotropy is eliminated.
As an alternative embodiment, the dew point temperature of the continuous annealing is-20 to-50 ℃; the continuous annealing includes: and carrying out continuous annealing under the condition of a protective atmosphere, wherein the protective atmosphere comprises 1-10% of hydrogen by volume percentage, 1-20 ppm of oxygen by mass concentration, and the balance of nitrogen.
In the embodiment of the application, the dew point in the annealing furnace is controlled to be-20 to-50 ℃, the content of hydrogen in the furnace is controlled to be 1 to 10 percent, and the residual oxygen is controlled to be 1 to 20 ppm. The control of the dew point, the residual oxygen and the hydrogen content in the annealing furnace is beneficial to obtaining better surface quality, thereby achieving the best strength, elongation, hole expanding rate and cold bending performance.
As an alternative embodiment, the hot rolling comprises slab heating, rough rolling, finish rolling and coiling in sequence; the heating temperature of the plate blank is 1120-1180 ℃, the starting temperature of finish rolling is 820-850 ℃, the finishing temperature of finish rolling is 740-770 ℃, and the coiling temperature is 680-700 ℃.
In the embodiment of the application, before entering a finishing mill, the gamma-alpha phase change is completed, ferrite rolling is adopted for hot rolling, and the initial rolling and final rolling temperature is lower than Ar 3 The rolling force required by the ferrite phase region rolling is lower than that required by the austenite rolling. The hot rolling coiling temperature is 670-700 ℃, and coarse grains are easily formed when the hot rolling coiling temperature is too high.
In the embodiment of the application, the energy consumption of hot rolling is low, and the cost is low. Compared with the traditional austenite rolling strength, the hot rolling product has lower rolling strength, is easier to roll, is suitable for a production line with low rolling equipment capacity, reduces the load of a cold rolling mill and prolongs the service life of a roller. The heating temperature of the steel rolled in the ferrite zone is lower than that of the steel rolled in the conventional rolling process, so that the heating energy consumption can be greatly reduced, the yield of the heating furnace can be increased, the low heating temperature can also reduce the temperature rise of the roller, the fatigue cracking and the fracture of the roller caused by thermal stress are reduced, the abrasion of the roller is reduced, the generation of secondary oxide scales can be reduced by low-temperature rolling, the surface quality of a hot-rolled product is improved, and the running speed of a pickling line can also be increased.
As an optional embodiment, the total rolling reduction rate of the cold rolling is 80-90%.
In the embodiment of the application, the high cold rolling reduction rate is adopted, the structure in the steel can be fully refined, and the high reduction rate is beneficial to forming a deep drawing [111] texture, so that the total cold rolling reduction rate is 80-90 percent
In an optional embodiment, in the cold rolling, a reduction rate of the primary cold rolling is 40 to 60%.
In the embodiment of the application, the structure in the steel can be fully refined, and the surface is rolled in a post-stand or better, so that the one-time cold rolling reduction rate is 40-60%.
The present application will be described in detail below with specific examples and comparative examples.
The following table shows the main control process parameters of the examples and comparative examples of the present application: (1) adopting desulfurized molten iron, smelting the product according to preset components, and casting the product into a plate blank; (2) heating the plate blank, and then carrying out hot continuous rolling, wherein the hot rolling heating temperature is 1150 ℃, and the heat preservation time is 130-160 min; carrying out dephosphorization; carrying out rough rolling on the plate blank subjected to heat preservation, wherein the rough rolling temperature is 1030-1060 ℃; and (3) performing finish rolling, wherein the start temperature of the finish rolling is 820-850 ℃, the finish rolling finishing temperature is 740-770 ℃, and the coiling is 680-700 ℃. (3) And (3) rolling the hot rolled plate after the hot rolled plate is acid-washed by an acid-washing continuous rolling mill, wherein the cold rolling reduction rate is 80-90%, and a lap welding machine is adopted for welding the mill.
(4) Annealing heat treatment is carried out in a continuous annealing machine set, and the process comprises continuous annealing, wet flattening, coiling and packaging. The soaking temperature is 730-780 ℃, the soaking time is 50-200 s, the slow cooling termination temperature is 670-710 ℃, the slow cooling rate is less than or equal to 15 ℃/s, the fast cooling rate is more than or equal to 50 ℃/s, and the overaging temperature is 300-400 ℃. Hydrogen content H in furnace 2 And (3) leveling by a wet leveling process at 1-10%, wherein the leveling elongation is 0.3-1.0%.
TABLE 1 list of chemical components (wt%) of inventive examples and comparative examples
Table 2 main process parameter list of each example of the present invention and comparative example.
Table 3 list of main process parameters of each example of the present invention and comparative example.
TABLE 4 Table of the results of mechanical Properties measurements of the examples of the present invention and the comparative examples
From tables 1 to 4, the mechanical properties of the battery case steels of examples 1 to 5 include: the yield strength is 160-190 MPa, the tensile strength is 300-350 MPa, and the elongation A is more than or equal to 40%; while the comparative example had a mechanical yield strength of 221MPa and a tensile strength of 343MPa, and a planar anisotropy coefficient (. DELTA.r value) of o.39, the closer to 0 the absolute value, the smaller the anisotropy. The metallographic structure of example 1 is shown in the left picture of FIG. 1; the plastic strain ratios of the examples of the application are all below 0.16, meanwhile, the performance of the steel plates with different finished product thicknesses is kept stable, and the plane anisotropy coefficient (delta r value) of the comparative example is 0.39, so that the steel plates have certain anisotropy and are not beneficial to punching forming. The metallographic structure of comparative example 1 is shown in the right part of FIG. 1. The above examples are merely preferred examples and are not intended to limit the embodiments of the present invention.
The conventional hot rolled finished plate of the battery case steel is thin and has the thickness of less than 3mm, the temperature of FT7 rolled by a final stand easily enters a two-phase region (austenite + ferrite) in the rolling process, and the two-phase structure in the application is ferrite and pearlite.
The conventional battery case steel, particularly the head and the edge of strip steel, causes the phenomenon of mixed crystals after two-phase region rolling, the mixed crystals are inherited to the cold rolling stage, snowflake point defects are generated during the process of manufacturing the battery case by stamping, the appearance quality of the battery case is influenced, and the isotropy of materials is not favorable. The common method in production adopts the method of increasing the finishing rolling temperature FT7 or increasing the edge temperature by adopting the edge heating mode, increases the production cost of edge heating and shielding, is not easy to control, if the finishing rolling temperature is too high, the quality of iron scale on the surface of a steel plate can be influenced, further the acid pickling surface of dephosphorization and post-process cold rolling is influenced, excessive iron oxide layers need to be removed by increasing the acid liquor concentration of an acid pickling tank or increasing the acid pickling time, and meanwhile, although the method can effectively deal with the occurrence of thick iron scale, the acid pickling cost is increased and the final surface quality is influenced undoubtedly. The battery shell steel has a plurality of adverse factors for the requirement of equipment and further increasing the energy consumption and the production cost in the traditional hot rolling production mode; the battery case steel has better surface quality and more excellent processing performance.
The conventional annealing manufacturing method for the battery shell steel after cold rolling adopts a hood-type annealing furnace for annealing heat treatment, and although the hood-type annealing furnace can effectively ensure that the crystal grains after cold rolling deformation can obtain completely recovered and recrystallized grains, the production efficiency of the hood-type annealing furnace is lower and is not as efficient as the production rhythm of a continuous annealing furnace. Therefore, the battery case steel has the advantages of less heat requirement and lower cost.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in the process, method, article, or apparatus that comprises the element.
The foregoing are merely exemplary embodiments of the present invention, which enable those skilled in the art to understand or practice the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (3)
1. The battery case steel is characterized by comprising the following chemical components in percentage by mass: c: 0.008% -0.02%, Mn: 0.1% -0.3%, Si: less than or equal to 0.01 percent, Als: 0.050-0.10%, P: less than or equal to 0.015 percent, S: less than or equal to 0.0020 percent, N: less than or equal to 0.004%, Cu: less than or equal to 0.1 percent, Ti: 0.01-0.04 wt%, less than or equal to 0.002 wt% of T O, and the balance Fe and inevitable impurities, wherein T O is an oxidation-system inclusion;
the metallographic structure of the battery case steel comprises the following components in percentage by volume: 97-98% ferrite and 2-3% pearlite;
the thickness of the battery case steel is 0.2-0.5 mm;
the mechanical properties of the battery case steel comprise: the yield strength is 160-190 MPa, the tensile strength is 300-350 MPa, the elongation is more than or equal to 30%, and the punching speed is more than or equal to 100 per min; the production method of the battery case steel comprises the following steps:
obtaining a casting blank containing the chemical components;
carrying out hot rolling on the casting blank to obtain a hot rolled steel coil;
sequentially carrying out acid washing and cold rolling on the hot-rolled steel coil to obtain a cold-rolled steel coil;
continuously annealing and wet-flattening the cold-rolled steel coil to obtain battery case steel;
the continuous annealing comprises the following steps in sequence: preheating, soaking, slow cooling, fast cooling and overaging;
the overaging temperature is 300-400 ℃;
the soaking temperature is 730-780 ℃, the soaking time is 50-200 s, the termination temperature of slow cooling is 670-710 ℃, the slow cooling rate is less than or equal to 15 ℃/s, and the fast cooling rate is greater than or equal to 50 ℃/s;
the dew point temperature of the continuous annealing is-20 to-50 ℃;
the continuous annealing comprises: carrying out continuous annealing under the condition of a protective atmosphere, wherein the protective atmosphere is 1-10% of hydrogen by volume percentage, 1-20 ppm of oxygen by mass concentration, and the balance of nitrogen;
the hot rolling sequentially comprises plate blank heating, rough rolling, finish rolling and coiling; the heating temperature of the plate blank is 1120-1180 ℃, the starting temperature of finish rolling is 820-850 ℃, the finishing temperature of finish rolling is 740-770 ℃, and the coiling temperature is 680-700 ℃.
2. The low-cost and well-formed battery case steel according to claim 1, wherein the total reduction rate of the cold rolling is 80 to 90%.
3. The low-cost, satisfactorily-formed battery case steel as set forth in claim 2, wherein a reduction ratio in the cold rolling is 40 to 60% in one cold rolling.
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