阅读说明：本技术 一种电池壳用冷轧带钢及其制备方法 (cold-rolled strip steel for battery case and preparation method thereof ) 是由 孙超凡 方圆 王永强 潘宏伟 王雅晴 刘伟 李海旭 陈宏振 胡小明 李永新 于 2019-09-05 设计创作，主要内容包括：本发明涉及一种电池壳用冷轧带钢及其制备方法,属于新材料技术领域,本发明实施例提供的一种电池壳用冷轧带钢,按重量百分比计,所述钢化学成分为：0.03％≤C≤0.06％,Si≤0.03％,0.15％≤Mn≤0.25％,P≤0.012％,S≤0.010％,0.03％≤Cr≤0.05％,0.0004％≤B≤0.0008％,0.06％≤Alt≤0.09％,N≤0.003％,O≤0.0025％,余量为Fe和不可避免的杂质元素。(the invention relates to a cold-rolled strip steel for battery cases and a preparation method thereof, belonging to the technical field of new materials, and the cold-rolled strip steel for the battery cases provided by the embodiment of the invention comprises the following chemical components in percentage by weight: c is more than or equal to 0.03 percent and less than or equal to 0.06 percent, Si is more than or equal to 0.03 percent, Mn is more than or equal to 0.25 percent and less than or equal to 0.15 percent, P is less than or equal to 0.012 percent, S is less than or equal to 0.010 percent, Cr is more than or equal to 0.03 percent and less than or equal to 0.05 percent, B is more than or equal to 0.0004 percent and less than or equal to 0.0008 percent, Alt is more than or equal to 0.06 percent and less than or equal to 0.09 percent, N is less than or equal.)

1. The cold-rolled strip steel for the battery case is characterized by comprising the following chemical components in percentage by weight: c is more than or equal to 0.03 percent and less than or equal to 0.06 percent, Si is more than or equal to 0.03 percent, Mn is more than or equal to 0.25 percent and less than or equal to 0.15 percent, P is less than or equal to 0.012 percent, S is less than or equal to 0.010 percent, Cr is more than or equal to 0.03 percent and less than or equal to 0.05 percent, B is more than or equal to 0.0004 percent and less than or equal to 0.0008 percent, Alt is more than or equal to 0.06 percent and less than or equal to 0.09 percent, N is less than or equal.

2. The cold-rolled steel strip for battery cases as claimed in claim 1, wherein said metallographic structure is ferrite and free cementite.

3. The cold-rolled steel strip for battery cases as claimed in claim 1, wherein the ferrite content is not less than 95% by volume, and the balance is free cementite.

4. The cold-rolled steel strip for battery cases as set forth in claim 2 or 3, wherein the ferrite has a grain size of 10.0-11.0 grade and an average inclusion size of < 20 μm, and the method for manufacturing the same.

5. the cold-rolled steel strip for battery cases as claimed in claim 1, wherein the steel has a thickness of 0.30 to 0.50 mm.

6. A method for producing the cold-rolled steel strip for battery cases as defined in any one of claims 1 to 5, comprising the steps of smelting, continuous casting, slab heating, hot rolling, acid rolling, cover annealing, and flattening;

In the smelting, molten steel components are prepared according to the steel chemical components, and a KR-LD-RH-CC process is adopted;

The continuous casting drawing speed is 1.2-1.4 m/min;

In the process of heating the casting blank, the discharging temperature of the casting blank is 1180-1220 ℃;

In the hot rolling, the final rolling temperature is 850-890 ℃, and the hot rolling convexity is 20-60 mu m;

In the acid rolling, the total rolling reduction rate of the cold rolling is 82-89%;

In the cover annealing, the hot spot temperature is 650-660 ℃, and the cold spot temperature is 600-610 ℃;

The flat elongation is 0.9-1.1%.

7. the method for preparing the cold-rolled strip steel for the battery shell as claimed in claim 5, wherein in the smelting, the rare earth wire feeding treatment is carried out on the crystallizer, and the rare earth addition mass is 100-200g/t molten steel.

8. the method for preparing the cold-rolled steel strip for the battery case as claimed in claim 6, wherein the coiling is performed after the hot rolling is finished, and the coiling temperature is 560-600 ℃.

9. The preparation method of the cold-rolled strip steel for the battery case as claimed in claim 5, wherein the acid rolling is performed by adopting five-stand continuous rolling, 1-3# stands in the five stands adopt intermediate roll shifting, and the intermediate roll shifting UC-delta is 25 mm.

10. The method for preparing the cold-rolled steel strip for the battery case according to claim 5, wherein the soaking time in the hood annealing is 10-12 h.

Technical Field

The invention belongs to the technical field of new materials, and particularly relates to a cold-rolled strip steel for a battery case and a preparation method thereof.

Background

The steel for the battery steel shell is mainly used for producing high-end alkaline battery steel shells and rechargeable battery steel shells, is a precision cold-rolled strip steel with extremely high quality requirements, and the punching process generally comprises 7-10 times of stretching and thinning, so that strict requirements are provided for various technical indexes such as purity, anisotropy, performance uniformity, dimensional precision, surface quality and the like of the strip steel. Because of harsh processing conditions, the current steel for battery cases in China mainly depends on foreign import, so the development of the steel for battery cases, which has low cost and can reach various technical indexes, is urgently needed in the field.

Chinese patent CN1940109A adopts low-carbon components to produce the steel for the battery case with excellent plane isotropy, and the main chemical component ranges are as follows: c (percent) is more than or equal to 0.01 and less than or equal to 0.05, Si (percent) is more than or equal to 0.03, Mn (percent) is more than or equal to 0.1 and less than or equal to 0.5, P (percent) is more than or equal to 0.02, S (percent) is more than or equal to 0.015, Alt (percent) is more than or equal to 0.01 and less than or equal to 0.10, Ti (percent) is more than or equal to 0.005 and less than or equal to 0.020, N (percent) is more than or equal to 0.002 and less than or equal to 0.007, and the anisotropy index delta r is less than 0.3, thereby. The patent document does not make a clear explanation about the key index of the purity of the steel grade, namely the inclusion control level, and the defect of 'sand holes' caused by large-size inclusions exists in the actual punching process.

Chinese patent CN102286699A adopts ultra-low carbon components to produce steel for battery cases with the stamping speed more than or equal to 150 per minute, and the main chemical component ranges are as follows: c ((%) is more than or equal to 0.0001 and less than or equal to 0.0050, Mn ((%) is more than or equal to 0.10 and less than or equal to 0.20, Al ((%) is more than or equal to 0.01 and less than or equal to 0.05, N ((%) is more than or equal to 0.0001 and less than or equal to 0.0040, Nb ((%)) is more than or equal to 0.010 and less than or equal to 0.030, and controlling: p (%) < 0.020, S (%) < 0.015, Cu (%) < 0.05, Ni (%) < 0.05, Cr (%) < 0.08, Mo (%) < 0.05, Si (%) < 0.02. The nitrogen content is less than or equal to 30ppm, the size of the inclusion is less than or equal to 10 mu m, the yield ratio is less than or equal to 0.6, and the anisotropy index delta r is less than 0.3, so that the requirement of rapid processing and forming of a high-speed punch press can be met. The patent document adopts ultra-low carbon component design, so that the smelting cost is increased, and the cover type annealing adopts a high-temperature annealing process at 700 ℃, so that the bonding risk is increased, and the improvement of the surface quality of a finished product is not facilitated.

the patent (No. CN109136444A) adopts ultra-low carbon components to produce the steel for the battery case of the new energy automobile which is quickly and thinly stamped, and the steel mainly comprises the following chemical components in percentage by weight: c (percent) is more than or equal to 0.003 and less than or equal to 0.005, Mn (percent) is more than or equal to 0.10 and less than or equal to 0.20, Si (percent) is more than or equal to 0.03, Als (percent) is more than or equal to 0.05 and less than or equal to 0.09, Ti (percent) is more than or equal to 0.050 and less than or equal to 0.070, P (percent) is more than or equal to 0.015, S (percent) is more than or equal to 0.012, and N (percent) is more than or equal to 0.004, and the method. The patent document adopts ultra-low carbon component design, and adopts 700-740 ℃ low-temperature two-phase region annealing in the subsequent Continuous Annealing (CA) process to obtain an incomplete annealing structure, and the two-phase region annealing process involved in the patent is relatively unfavorable for realizing the precise control of the microstructure and the high performance uniformity of coil passing.

Disclosure of Invention

in view of the above problems, the present invention has been made to provide a cold rolled steel strip for battery cases and a method for manufacturing the same, which overcome the above problems or at least partially solve the above problems.

the embodiment of the invention provides a cold-rolled strip steel for a battery case, which comprises the following chemical components in percentage by weight: c is more than or equal to 0.03 percent and less than or equal to 0.06 percent, Si is more than or equal to 0.03 percent, Mn is more than or equal to 0.25 percent and less than or equal to 0.15 percent, P is less than or equal to 0.012 percent, S is less than or equal to 0.010 percent, Cr is more than or equal to 0.03 percent and less than or equal to 0.05 percent, B is more than or equal to 0.0004 percent and less than or equal to 0.0008 percent, Alt is more than or equal to 0.06 percent and less than or equal to 0.09 percent, N is less than or equal.

Further, the metallographic structure of the steel is ferrite and free cementite.

Further, the ferrite content is more than or equal to 95 percent, and the balance is free cementite according to volume percentage. .

Furthermore, the grain size of the ferrite is 10.0-11.0 grade, and the average size of the inclusions is less than 20 mu m.

further, the thickness of the steel is 0.30-0.50 mm.

Based on the same invention concept, the embodiment of the invention also provides a preparation method of the cold-rolled strip steel for the battery case, which comprises the working procedures of smelting, continuous casting, casting blank heating, hot rolling, acid rolling, cover annealing and flattening;

In the smelting, molten steel components are prepared according to the steel chemical components, and a KR-LD-RH-CC process is adopted;

the continuous casting drawing speed is 1.2-1.4 m/min;

In the process of heating the casting blank, the discharging temperature of the casting blank is 1180-1220 ℃;

In the hot rolling, the final rolling temperature is 850-890 ℃, and the hot rolling convexity is 20-60 mu m;

In the acid rolling, the total rolling reduction rate of the cold rolling is 82-89%;

In the cover annealing, the hot spot temperature is 650-660 ℃, and the cold spot temperature is 600-610 ℃;

The flat elongation is 0.9-1.1%.

Further, in the smelting, the rare earth wire feeding of the crystallizer is carried out, and the rare earth addition mass is 100-200g/t molten steel.

furthermore, coiling is carried out after the hot rolling is finished, and the coiling temperature is 560-600 ℃.

Further, the acid rolling adopts five machine frames for continuous rolling, 1-3# machine frames in the five machine frames adopt intermediate roll shifting, and the intermediate roll shifting UC-delta is 25 mm.

Furthermore, in the hood-type annealing, the soaking time is 10-12 h.

one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

According to the cold-rolled strip steel for the battery case and the preparation method thereof provided by the embodiment of the invention, the cold-rolled strip steel for the battery case with the yield strength of 200-230 MPa, the tensile strength of 330-360 MPa, the elongation A50 of 36.0% and the anisotropy delta r of less than 0.30 is obtained through steel chemical component control and preparation technology.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

FIG. 1 is a metallographic structure diagram of steel for a battery case in example 1 of the invention;

FIG. 2 is a diagram showing inclusions in steel for battery cases in example 1 of the present invention;

FIG. 3 is a metallographic structure diagram of steel for a battery case in example 2 of the invention;

FIG. 4 is a diagram showing inclusions in steel for battery cases in example 2 of the present invention;

FIG. 5 is a metallographic structure diagram of steel for a battery case in example 3 of the invention;

FIG. 6 is a drawing showing inclusions in steel for battery cases in example 3 of the present invention;

FIG. 7 is a metallographic structure diagram of steel for a battery case in example 4 of the invention;

FIG. 8 is a drawing showing inclusions in steel for battery cases in example 4 of the present invention;

FIG. 9 is a metallographic structure diagram of steel for a battery case in example 5 of the invention;

FIG. 10 is a diagram showing inclusions in steel for battery cases in example 5 of the present invention.

Detailed Description

The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.

Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

In order to solve the technical problems, the general idea of the embodiment of the application is as follows:

The application provides a cold-rolled strip steel for battery cases, which comprises the following chemical components in percentage by weight: c is more than or equal to 0.03 percent and less than or equal to 0.06 percent, Si is more than or equal to 0.03 percent, Mn is more than or equal to 0.25 percent and less than or equal to 0.15 percent, P is less than or equal to 0.012 percent, S is less than or equal to 0.010 percent, Cr is more than or equal to 0.03 percent and less than or equal to 0.05 percent, B is more than or equal to 0.0004 percent and less than or equal to 0.0008 percent, Alt is more than or equal to 0.06 percent and less than or equal to 0.09 percent, N is less than or equal.

in the present application, the metallographic structure of the steel is ferrite and free cementite.

In the application, the ferrite content is more than or equal to 95 percent, and the balance is free cementite according to volume percentage. .

In the application, the grain size of the ferrite is 10.0-11.0 grade, and the average size of the inclusions is less than 20 mu m.

in the present application, the thickness of the steel is 0.30-0.50 mm.

Based on the same invention concept, the embodiment of the invention also provides a preparation method of the cold-rolled strip steel for the battery case, which comprises the working procedures of smelting, continuous casting, casting blank heating, hot rolling, acid rolling, cover annealing and flattening;

in the smelting, molten steel components are prepared according to the steel chemical components, and a KR-LD-RH-CC process is adopted;

The continuous casting drawing speed is 1.2-1.4 m/min;

In the process of heating the casting blank, the discharging temperature of the casting blank is 1180-1220 ℃;

in the hot rolling, the final rolling temperature is 850-890 ℃, and the hot rolling convexity is 20-60 mu m;

in the acid rolling, the total rolling reduction rate of the cold rolling is 82-89%;

in the cover annealing, the hot spot temperature is 650-660 ℃, and the cold spot temperature is 600-610 ℃;

The flat elongation is 0.9-1.1%.

In the application, in the smelting, the rare earth wire feeding of the crystallizer is carried out, and the rare earth addition mass is 100-200g/t molten steel.

In the application, coiling is carried out after the hot rolling is finished, and the coiling temperature is 560-600 ℃.

In the application, the acid rolling adopts five-stand continuous rolling, 1-3# stand in five stands adopts middle roller to scurry the roller, middle roller scurry roller volume UC-delta sets for 25 mm.

In the present application, the soaking time in the hood-type annealing is 10 to 12 hours.

in the present application, acid rolling is a collective term for pickling and cold rolling processes.

In the embodiment of the invention, the steel has the following chemical component elements:

C: c is an important element for ensuring the required strength of the steel for the battery shell, the carbon content is too low, the strength of the strip steel is not enough, and the requirement on the compressive strength of the battery shell cannot be met. The carbon content is too high, a great amount of carbide precipitates in ferrite grain boundaries and crystal grains, and the interface of the carbide and the parent phase is often the initiation point of micro-cracks in the punching and drawing process, so that the punching performance is deteriorated. In order to ensure the stamping forming performance of the steel material for the battery shell and the basic strength requirement of the shell, the content of the C element is limited to 0.03-0.06.

Si: si has a certain strengthening effect, excessive Si may deteriorate the platability of Ni, and the Si content is limited to 0.03 or less in the present invention.

Mn: mn can play a role in solid solution strengthening so as to improve the strength of the steel, and can promote S in the steel to precipitate and separate out in a MnS form. Mn is not favorable for improving the corrosion resistance of the shell and the platability of the Ni plating layer, and the content of Mn element is controlled to be 0.15-0.25 on the premise of fully playing the solid solution strengthening and S fixing functions of Mn.

And (3) Alt: al is mainly used for fixing N in steel, and the aging performance of the battery case steel can be improved. Al and N in the steel are combined to form AIN, so that {111} texture can be obtained in the annealing process, and the stamping forming performance of the battery case steel is improved. The present invention limits the Al content to the range of 0.06-0.09.

Cr: the tiny cracks formed between the steel surface grains and between the carbide and the matrix in the battery case punching and drawing process tend to accelerate the corrosion of the surface of the case, and the addition of more than 0.03 percent of Cr in the steel can remarkably inhibit the corrosion resistance deterioration of the case caused by the surface damage in the punching process. The steel for battery cases is often subjected to Ni plating treatment before or after punching, and excessively high Cr in the steel tends to promote the formation of a dense Cr oxide film on the surface of the base material, resulting in deterioration of the platability of the Ni plating layer. In order to take the corrosion resistance of the shell and the platability of the Ni coating into consideration, the Cr content in the steel is limited to 0.03-0.05.

b: b can improve the binding force between ferrite grains and between carbide and a matrix and inhibit the expansion of microcracks in the drawing process. The addition of 0.0003% or more of B to steel improves the work embrittlement accompanying the ironing, and the strength of steel increases significantly when the B content exceeds 0.0015%, and the B/N ratio in steel increases when the B content is too high, and in particular, when the B/N content exceeds 1.0, the material anisotropy increases and the press-forming earing ratio increases. In order to improve the punching formability, the content of B in the steel is limited to 0.0004-0.0008.

N: the nitrogen dissolved in the gaps in the steel often causes the strength and the hardness of the steel to be improved, the plasticity is reduced, the punching forming is not favorable, the content of N in the battery case steel is required to be as low as possible, and the content of N is limited to be less than or equal to 0.003.

P: p has a serious segregation tendency, which often causes the strip structure in steel to be aggravated, the plasticity and the toughness of the steel to be reduced, the forming performance to be deteriorated, and the platability of Ni to be deteriorated due to the over-high content of P, and the content of P is limited to be less than or equal to 0.0012.

S: s is a harmful impurity element in steel, a sulfide inclusion in the steel often becomes a stress source during stamping cracking, the content of S in the battery case steel is strictly controlled, and the content of S is limited to be less than or equal to 0.012.

In the embodiment of the invention, the preparation method of the cold-rolled strip steel for the battery case mainly comprises the following steps:

Smelting: the smelting process adopts a production process of KR-LD-RH-CC, the rare earth wire feeding treatment of a crystallizer is carried out, the mark of rare earth RECe-48 is obtained, the addition amount of the rare earth is controlled at 200g/t, the continuous casting drawing speed is controlled at 1.2-1.4m/min, and the casting blank obtained by smelting is subjected to hot rolling after being subjected to the peeling treatment by a four-side machine.

Hot rolling: the hot rolling is finished in an austenite region, the tapping temperature of the plate blank is controlled to be 1180-1220 ℃, the finishing temperature is controlled to be 850-890 ℃, and the coiling temperature is controlled to be 560-600 ℃ by adopting a low-temperature coiling process. In order to ensure the dimensional accuracy of the subsequent cold-rolled finished product, the hot-rolling convexity is controlled to be 20-60 mu m.

Acid rolling (acid pickling and cold rolling): and (3) adopting an acid rolling combined unit, or pickling firstly and then carrying out cold continuous rolling or multiple reversible cold rolling. When the acid rolling is five-stand continuous rolling, the total reduction rate is controlled to be 82-89%, the acid rolling 1# -3# stand adopts intermediate roll shifting, and the intermediate roll shifting UC-delta is set to be 25 mm. .

Hood annealing (BA): after the steel coil is subjected to electrolytic degreasing, recrystallization annealing is carried out by adopting a full-hydrogen type hood-type annealing furnace, the temperature of a hot spot of the hood-type annealing is controlled to be 650-660 ℃, the temperature of a cold spot is controlled to be 600-610 ℃, and the soaking time is controlled to be 10-12 h. The cover annealing (BA) process promotes the full development of main texture components {111} < 110>, {111} < 112> and the like in the annealing process, reduces the anisotropy of materials, and reduces the occurrence of lug making defects in the stamping process.

Leveling by a double-machine frame: the flatness of the strip steel after recrystallization annealing can better improve the plate shape of the cold-rolled strip steel and improve the dimensional precision of the cold-rolled strip steel. The battery case steel is flattened by adopting the double-frame after annealing, and the total elongation of the flattening is controlled within 0.9-1.1% to meet the design requirement of product quality.

the cold rolled steel strip for battery cases of the present application will be described in detail with reference to specific examples.

The chemical composition (Wt%) of the steel in examples 1 to 5 described below is shown in Table 1.

TABLE 1