JP4698205B2 - Steel plate for battery case, surface-treated steel plate for battery case, battery case and battery - Google Patents

Description

  The present invention relates to a steel plate for a battery case, a surface-treated steel plate for a battery case, a battery case using them, and a battery using them.

  In recent years, a battery used as a power source for a portable device is required to be downsized in response to downsizing of the device, but the battery capacity is inevitably reduced by downsizing. For this reason, various attempts have been made to ensure the battery capacity of a small battery as much as possible. In particular, for AA batteries and AAA batteries, a cylindrical battery case molded by drawing was used, but the side wall thickness was obtained by ironing the side wall of the drawn intermediate product cup. Is formed into a thin container to increase the battery case volume. When a battery case is formed by DTR processing (Drawing Thin and Redraw) or DI processing (Drawing and Ironing), the thickness of the battery case wall is reduced only by drawing. Although the strength of the battery case is reduced as compared with the case where the battery case is molded without any problem, the following method is used to ensure the strength of the container.

  For example, when manufacturing a battery can having a total height (total length of the trunk length) that is extremely large compared to the diameter and having a total height / outer diameter of 3.5 or more, the conventional method uses a cup-shaped intermediate product. For the purpose of suppressing the incidence of defective products such as cracks in the manufacturing process, a battery can material that is a nickel-plated steel sheet having a hardness of Hv 80 to 90 is used, and the hardness of the side wall of the battery case is reduced by the ironing process. A method for manufacturing a battery can characterized by ironing so as to be Hv200 or higher is disclosed (for example, see Patent Document 1). According to this method, it is possible to reduce the incidence of defective products during the deep drawing process for producing cup-shaped intermediate products as much as possible, and to sufficiently secure the pressure resistance and sealing strength of the battery can. I can do it. The method described in Patent Document 1 increases the can wall strength by work hardening by ironing and can increase the can wall strength, but cannot increase the strength of the can bottom.

Disclosed is a method for manufacturing steel sheets for DI (Drawing and Ironing) cans that are not battery cans, but are formed by drawing and ironing, as a means of increasing strength that does not depend on work hardening. (For example, refer to Patent Document 2). In a DI can used for a beverage can, after forming into a can body, the outer surface is painted or printed, and heated at a temperature of about 200 ° C. for several minutes to several tens of minutes for baking. The method of Patent Document 2 is to age-harden by this baking to increase the strength. That is, C0.01-0.10%, Mn 0.50% or less, sol.Al0.003-0.050%, N0.0040% or less (% is% by weight), the balance being Fe and inevitable impurities After hot-rolling, cold-rolling, continuous annealing, and temper-rolled steel sheet, tin-plated steel sheet was DI processed, and then heated under the above-mentioned baking conditions for coating and printing, so that C was dissolved in the steel. , N is precipitated to strengthen precipitation (strain age hardening). However, when the steel plate of this method is used, even if the above precipitation strengthening treatment is performed after DI processing, only a steel having a refining degree of T4 grade (61 ± 3 for HR30T) can be obtained.
JP-A-8-255598 Japanese Patent Publication No. 6-29465

  In the present invention, a battery case is molded using a high-strength material with a thin plate thickness, and the side wall of the battery case after molding by the drawing method, DTR processing method or DI processing method is thin. Another object of the present invention is to provide a battery case material, a battery case, and a battery with increased strength.

The steel sheet for battery case of the present invention that solves the above problems is, by weight, C: 0.04 to 0.60%, Si: 0.80 to 3.0%, Mn: 0.3 to 3.0. %, P: ≦ 0.06%, S: ≦ 0.06%, Al: ≦ 0.1%, N: 0.0010 to 0.0150%, the balance Fe and unavoidable impurities, The surface corresponding to the inner surface of the battery case has a nickel layer as the outermost layer, and the steel plate having the nickel layer has a tensile strength of 450 MPa or more and an elongation of 20% or more in the plate before processing, and a plate thickness of 20 The tensile strength after performing the processing of reducing the thickness by 550 MPa or more, and the tensile strength after processing of reducing the plate thickness by 50% is 700 MPa or more (Claim 1). By having such a chemical component, it is possible to obtain a high-strength steel sheet for battery cases having excellent mechanical properties such as tensile strength and malleability.
Moreover, the surface-treated steel sheet for battery case of the present invention that solves the above-mentioned problems is in weight%, C: 0.04 to 0.60%, Si: 0.80 to 3.0%, Mn: 0.3 to Steel plate made of 3.0%, P: ≦ 0.06%, S: ≦ 0.06%, Al: ≦ 0.1%, N: 0.0010 to 0.0150%, balance Fe and inevitable impurities in, the surface corresponding to at least the battery case inner surface, iron outermost layer - has a nickel alloy layer, wherein the iron - nickel steel plate with alloy layer, unprocessed tensile strength and 20% or more of elongation of at least 450MPa in plate The tensile strength after processing to reduce the plate thickness by 20% is 550 MPa or more, and the tensile strength after processing to reduce the plate thickness by 50% is 700 MPa or more. 2). Alternatively, in the steel plate having the chemical component, the steel plate having nickel and iron-nickel alloy in the outermost layer, and the steel plate having the nickel and iron-nickel alloy has a tensile strength of 450 MPa or more and an elongation of 20% or more in the plate before processing. The tensile strength after processing to reduce the plate thickness by 20% is 550 MPa or more, and the tensile strength after processing to reduce the plate thickness by 50% is 700 MPa or more. 3). By having these layers as the outermost layer, the corrosion resistance can be improved and the generation of oxides on the surface can be prevented.
And the battery case of this invention which solves the said subject is formed by employ | adopting the surface-treated steel sheet for battery cases in any one of Claims 1-3 , (Claim 4 ), The battery according to claim 5 employs the battery case according to claim 4 .

  The battery case steel sheet of the present invention formed in this way has the above chemical components, so that it has higher strength than the conventional battery steel sheet, and the battery case using the steel sheet has a thickness equivalent to that. It is possible to make the battery case thinner than in the past, and a thin and strong battery case can be obtained.

Embodiments of the present invention will be described below.
As a steel plate used as the base material of the surface-treated steel sheet for battery cases of the present invention, by weight, C: 0.04 to 0.60%, Si: 0.80 to 3.0%, Mn: 0.3 to Chemical component consisting of 3.0%, P: ≦ 0.06%, S ≦ 0.06%, Al: ≦ 0.1%, N: 0.0010 to 0.0150%, balance Fe and inevitable impurities A steel having is preferably used.

In the above chemical components, C is preferably 0.04% or more because C has a high tempering degree on the original plate. On the other hand, if the C component exceeds 0.60%, the amount of precipitated carbide increases and the workability of the original sheet decreases, and at the same time, the load of cold rolling increases, the shape deteriorates, and the plateability in the continuous annealing process is inhibited. Etc., causing a decrease in productivity. Therefore, in the present invention, the upper limit value of the C component is set to 0.60%.
Si has a large solid solution strengthening ability in steel and is an effective element for obtaining high strength. Therefore, 0.8% or more is necessary. Further, the higher the material strengthening surface, the better. However, the upper limit is set to 3.0% in order to increase the cold rolling load and deteriorate the shape.

  Mn is a component necessary for preventing red heat embrittlement during hot rolling due to the impurity S, and at the same time, in the same way as C, in order to give a high tempering degree to the original plate, the Mn component is 0.3% or more And However, as is the case with C here, too much load of cold rolling, crack generation during slab rolling, deterioration of shape, threadability hindrance in continuous annealing process, etc., cause productivity reduction, The upper limit is set to 3.0%.

  P is a crystal grain refining component and is added at a certain ratio because it increases the strength of the original plate, but it inhibits corrosion resistance. In the present invention, when P exceeds 0.06%, the corrosion resistance, particularly the hole resistance, is remarkably lowered, so the upper limit is made 0.06%.

  S is an impurity component that causes red hot brittleness during hot rolling, and it is desirable that it be as small as possible. However, it cannot completely prevent contamination from steel stones, and it is difficult to desulfurize during the process. Unavoidable. Since red heat brittleness due to a small amount of residual S can be reduced by Mn, the upper limit value of the S component is set to 0.06%.

  Al is added to the steel bath as a deoxidizer during steelmaking. However, when it becomes 0.10% or more, it is an oxidation inhibitor at the time of continuous casting and a mold powder used as an anti-seizure agent for the mold in continuous casting. Oxygen and excess Al react to inhibit the original powder effect. Therefore, the Al content is 0.10% or less.

  N, like C and Mn, gives a high degree of tempering to the original plate. Although it is a necessary component for strengthening the yield strength, if it is less than 0.001%, it causes difficulty in steelmaking, while addition over 0.0150% reduces the yield of ferronitride added during steelmaking. And is not stable, and at the same time, the anisotropy during press molding is significantly deteriorated. Further, since cracks are generated on the surface of the continuous cast piece, resulting in casting defects, the N component range is set to 0.001 to 0.0150% in the present invention.

  A slab having the chemical components as described above is subjected to hot rolling and primary cold rolling to obtain a steel plate that becomes a base material of the surface-treated steel sheet for battery cases. And the surface-treated steel sheet for battery cases is obtained by nickel-plating and annealing the obtained steel plate, and performing secondary cold rolling or temper rolling as needed. Each process is performed under the following conditions.

Hot rolling step The slab heating temperature in the hot rolling step is not specified in the present invention, but is preferably 1100 ° C or higher from the viewpoint of ensuring stable hot finishing rolling temperature. When the hot rolling finishing temperature is set to Ar3 point or lower, the hot steel strip crystal structure is mixed and coarsened, and the desired strength cannot be obtained. Therefore, the hot rolling finishing temperature is preferably set to Ar3 point or higher. .

  The coiling temperature is not specified in the present invention, but the coiling temperature is preferably 700 ° C. or lower in order to suppress the coarsening of crystal grains.

Primary cold rolling step The steel sheet hot-rolled in the above component system is subjected to primary cold rolling, and this cold rolling rate is an important strength factor of the present invention together with the components, and in order to obtain the desired strength. And 50-90%. If the rolling rate is 50% or less, the desired strength cannot be obtained, and if the rolling rate is 90% or more, the formability to the battery case is hindered.

Nickel plating process The material cold-rolled as described above is subjected to nickel plating. In the nickel plating, the steel sheet is subjected to a pretreatment after alkaline electrolytic degreasing, water washing, sulfuric acid immersion, and water washing by a conventional method, and then plating containing nickel as a main component is performed. Nickel plating may be performed after an annealing step described later. The plating thickness is preferably in the range of 0.5 to 4 μm. If it is less than 0.5 μm, the corrosion resistance is poor. Even if it exceeds 4 μm, there is no problem in terms of characteristics, but it is not preferable in terms of economy. As the plating mainly composed of nickel, matte nickel plating, semi-bright nickel plating, and bright nickel plating are performed. For these platings, a well-known plating bath such as a watt bath, a chloride bath, or a sulfamic acid bath can be applied.

Annealing Step The material plated with nickel as described above is annealed at 680 ° C. or higher by continuous annealing or at 500 ° C. or higher by batch annealing. On the surface corresponding to the inner surface of the battery case, it is desirable to anneal the outermost layer so that a nickel layer, an iron-nickel alloy layer, or a mixture of nickel and iron-nickel alloy is mixed. In particular, it is desirable that the outermost layer is a nickel layer and the lower layer is an iron-nickel alloy layer because the nickel layer becomes soft and can withstand severe processing sufficiently. The surface layer component can be achieved by controlling the annealing temperature and the annealing time. When the annealing temperature is increased, nickel-plated Ni and steel material Fe are interdiffused to form an iron-nickel alloy layer on the surface layer, and when the annealing temperature is low, only the nickel layer remains on the surface layer. At the intermediate temperature, nickel and iron-nickel alloy are mixed.
In the above, the annealing after the nickel plating has been described, but this annealing may be performed after the primary cold rolling and before the nickel plating. In this case, the annealing conditions may be the same as those performed after nickel plating.

  The present invention will be further specifically described with reference to the following examples.

Using hot-rolled steel having chemical components shown in Table 1, cold rolling, nickel plating, annealing, temper rolling and the like were performed. Table 1 shows the steel components of Examples and Comparative Examples and the conditions in each step.
Nickel plating was carried out by conventional methods such as alkaline electrolytic degreasing, water washing, sulfuric acid immersion, and water washing, followed by normal matte nickel plating, semi-bright nickel plating, or bright nickel plating.

1) Matte nickel plating Matte nickel plating was performed using the following nickel sulfate bath.
Bath composition nickel sulfate _{(NiSO 4 · 6H 2 O)} 300g / L
Nickel chloride _{(NiCl 2 · 6H 2 O)} 45g / L
Boric acid (H ₃ BO ₃ ) 30 g / L
Bath pH: 4 (adjusted with sulfuric acid)
Stirring: Air stirring Bath temperature: 60 ° C
As the anode, S pellets (trade name, manufactured by INCO, spherical shape) were loaded in a titanium basket and covered with a polypropylene bag.

2) Semi-bright nickel plating Semi-bright nickel plating was performed using the following nickel sulfate bath.
Bath composition nickel sulfate _{(NiSO 4 · 6H 2 O)} 300g / L
Nickel chloride _{(NiCl 2 · 6H 2 O)} 45g / L
Boric acid (H ₃ BO ₃ ) 30 g / L
Polyoxyethylene adduct of unsaturated alcohol 3.0g / L
Unsaturated carboxylic acid formaldehyde 3.0g / L
Bath pH: 4 (adjusted with sulfuric acid)
Stirring: Air stirring Bath temperature: 60 ° C
3) Bright nickel plating Bright nickel plating was performed by appropriately adding saccharin as a brightening agent to a nickel sulfate bath.
Bath composition nickel sulfate _{(NiSO 4 · 6H 2 O)} 300g / L
Nickel chloride _{(NiCl 2 · 6H 2 O)} 45g / L
Boric acid (H ₃ BO ₃ ) 30 g / L
Saccharin 3.0 g / L
Bath pH: 4 (adjusted with sulfuric acid)
Stirring: Air stirring Bath temperature: 60 ° C
The anode uses S pellets (trade name, manufactured by INCO, spherical) loaded in a titanium basket and covered with a polypropylene bag.

In Examples 1 to 6, matte nickel plating and semi-gloss plating were performed at 1.0 μm to 3.0 μm before annealing. In Examples 7 to 10, matte nickel plating and semi-gloss plating were performed at 1.0 μm to 3.0 μm before annealing, and after annealing and temper rolling, bright nickel plating was performed at 0.5 μm. In Comparative Examples 1 to 3, matte plating or semi-gloss plating was performed by 2.0 μm after annealing. In Comparative Examples 4 and 6 to 7, annealing was performed, and after the first rolling, matte plating was performed at 4 μm and semi-gloss at 2 to 3 μm. The nickel plating of Table 1 shows only the first nickel plating.
In Examples 1, 2, 8, 10 and Comparative Example 6, hot-rolled steel sheets were processed in the order of primary cold rolling, nickel plating, continuous annealing, and temper rolling. In Examples 3 and 9, box-type annealing was performed instead of continuous annealing in the above process. About Examples 4-10 and the comparative example 7, the hot-rolled steel plate was processed in order of primary cold rolling, nickel plating, continuous annealing, temper rolling, and nickel plating. In Examples 5 to 7 and Comparative Examples 1 to 5, hot-rolled steel sheets were processed in the order of primary cold rolling, annealing, temper rolling, and nickel plating.

Regarding the final plate thickness after the treatment, Examples 1, 4 to 6, 9 and Comparative Examples 1 to 3 were 0.3 mm, Examples 2 to 3 and 10, and Comparative Example 4 was 0.2 mm, Example 7 Was 0.25 mm, and Comparative Examples 5 to 7 were 0.4 mm.
When the component of the outermost surface layer was analyzed about the surface treatment steel plate obtained in this way, Examples 1, 4-10 and Comparative Examples 1-7 were nickel layers, and Example 2 3 was a nickel layer and an iron-nickel alloy layer.

The characteristics of the test materials are evaluated by the following test methods, and the evaluation results are shown in Table 2.

(Mechanical properties)
The mechanical properties in the case of an unprocessed original plate were evaluated by cutting the test material into a JIS No. 5 test piece size and tensile strength (displayed in TS, MPa) and elongation (displayed in T.EL,%). When TS is 450 MPa or more, T.S. An EL of 20% or more was considered good. Assuming that the DTR processing method and DI processing method are used, TS was evaluated by applying processing to reduce the plate thickness by 20% or 50%. After processing to reduce the plate thickness by 20%, TS was required to be 550 MPa or more, and after processing to reduce the plate thickness to 50%, TS was found to be 700 MPa or more.
In the comprehensive evaluation, in terms of mechanical strength, the original plate had a TS of 450 MPa or more. After processing with EL of 15% or more and plate thickness of 20%, TS is 550 MPa or more, and after processing of plate thickness is reduced by 50%, TS is 700 MPa or more and there is no rust on the bent part Was determined to be acceptable (indicated by ○ in Table 2). Otherwise, it was determined to be defective (indicated by x in Table 2). In addition, Comparative Examples 1-4 are T.W. Since EL was less than 20%, TS could not be measured because the plate thickness could not be reduced by 20%.

As shown in Table 2, the mechanical properties of steel plates used in the past (Comparative Examples 5 to 7) are TS processing of 336 to 376 MPa, so drawing processing or DI processing in which the side wall of the battery case is 20 to 50% thinner. Alternatively, the thickness of the original plate cannot be reduced for the use of a battery case formed by DTR processing. On the other hand, as shown in Table 2, the present invention can be applied to a thin original plate for battery case applications subjected to drawing processing, DI processing, and DTR processing. For example, in Table 2, the conventional plate thickness of 0.4 mm is 0.2 to 0.3 mm.
In Comparative Examples 1 and 5-7, the amount of C is out of the proper range, in Comparative Examples 2, 5-7, the amount of Si is out of the proper range, and in Comparative Examples 3, 5, and 6, the amount of Mn is Overall evaluation was bad because it was out of the proper range. In Comparative Example 4, since the annealing temperature was low, the overall evaluation was bad. In addition, this invention is not limited to the said embodiment and Example, It can change as needed.

  The steel sheet for battery case and the surface-treated steel sheet for battery case according to the present invention have higher strength than the conventional steel sheet for battery by having the above components, and the battery case using the steel sheet has the thickness of the conventional steel sheet. It becomes possible to make it thinner. Therefore, when the side wall thickness of the battery case is reduced, a larger amount of the active material serving as a power source for the battery stored in the battery case can be filled, so that a high-capacity battery can be obtained.

Claims (5)

By weight, C: 0.04 to 0.60%, Si: 0.80 to 3.0%, Mn: 0.3 to 3.0%, P: ≦ 0.06%, S: ≦ 0. 06%, Al: ≦ 0.1%, N: 0.0010 to 0.0150%, balance Fe and unavoidable impurities, a nickel layer as the outermost layer on at least the surface corresponding to the inner surface of the battery case The steel plate having the nickel layer has a tensile strength of 450 MPa or more and an elongation of 20% or more in the plate before processing, and a tensile strength after processing to reduce the plate thickness by 20% is 550 MPa or more. A surface-treated steel sheet for a battery case , wherein the tensile strength after processing to reduce the thickness by 50% is 700 MPa or more . By weight, C: 0.04 to 0.60%, Si: 0.80 to 3.0%, Mn: 0.3 to 3.0%, P: ≦ 0.06%, S: ≦ 0. 06%, Al: ≦ 0.1%, N: 0.0010 to 0.0150%, balance Fe and inevitable impurities, steel plate made of iron-nickel on the outermost layer at least on the surface corresponding to the inner surface of the battery case The steel plate having the alloy layer and the iron-nickel alloy layer has a tensile strength of 450 MPa or more and an elongation of 20% or more in the plate before processing, and is subjected to processing to reduce the plate thickness by 20%. A surface-treated steel sheet for a battery case , having a tensile strength of 550 MPa or more and a tensile strength of 700 MPa or more after processing to reduce the plate thickness by 50% . By weight, C: 0.04 to 0.60%, Si: 0.80 to 3.0%, Mn: 0.3 to 3.0%, P: ≦ 0.06%, S: ≦ 0. 06%, Al: ≦ 0.1%, N: 0.0010 to 0.0150%, balance Fe and unavoidable impurities, steel plate made of nickel and iron on the outermost layer at least on the surface corresponding to the inner surface of the battery case -A steel plate having a nickel alloy and having the nickel and iron-nickel alloy has a tensile strength of 450 MPa or more and an elongation of 20% or more in the plate before processing, and the thickness is reduced by 20%. A surface-treated steel sheet for a battery case , having a tensile strength of 550 MPa or more and a tensile strength of 700 MPa or more after processing to reduce the plate thickness by 50% . A battery case comprising the surface-treated steel sheet for a battery case according to any one of claims 1 to 3 . A battery comprising the battery case according to claim 4 .