JP2784746B2 - Battery case - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to deep drawability, DI
The present invention relates to a battery case using a surface-treated steel sheet having excellent formability, and more particularly, to a battery case suitable for battery use such as an alkaline manganese battery and a nickel cadmium battery.

[0002]

2. Description of the Related Art Conventionally, containers for enclosing a strong alkaline solution such as an alkaline manganese battery and a nickel cadmium battery have been manufactured by pressing a cold-rolled steel strip into a battery case and then performing barrel plating. Alternatively, a method of pressing a nickel-plated steel strip into a battery case has been adopted. However, the barrel plating method has problems that productivity is low, inefficiency is high, and variation in plating thickness is large. Therefore, a nickel-plated steel strip for plating on a cold-rolled steel strip has been widely used in place of the barrel plating method. By the way, the reason why nickel-plated steel strips are often used for battery applications such as alkaline manganese batteries and nickel cadmium battery containers is as follows. That is, since these batteries mainly use strong alkaline potassium hydroxide or the like as an electrolyte, nickel plating is excellent in terms of corrosion resistance to an alkaline electrolyte, and a stable contact when connecting the batteries to external terminals. This is because nickel has resistance and spot welding is performed when each component is assembled into a battery. The nickel-plated steel strip is also excellent in spot weldability. Nickel plating is also necessary from the following viewpoints. That is, when an alkaline manganese battery is described as an example, when an iron plate is used for the battery case, iron is eluted in the alkaline electrolyte of the battery, and this is precipitated on the surface of the zinc particles of the anode to induce self-discharge of zinc. It is the cause. Therefore, the nickel-plated steel strip has been suitably used as a battery case material using an alkaline solution as an electrolyte.

[0003]

SUMMARY OF THE INVENTION In battery manufacturing,
As a method of increasing the battery capacity, the thickness of the material has been further reduced, and a DI (drawing and ironing) processing method has been used (see Japanese Patent Application Laid-Open No. 60-180058). The DI processing method is considered to be a molding method that is thicker than the side surface of the battery case and is advantageous in terms of pressure resistance. Furthermore, the conventional alkaline manganese battery is a three-piece sealed case consisting of a battery case, a positive electrode terminal, and a negative electrode terminal. However, from the viewpoint of cost reduction, a convex integral type with the positive electrode terminal and the battery case is integrated. It is changing to a two-piece battery case and negative electrode terminal. However, in the production of the above-mentioned battery case integrated with the convex portion using the DI processing method, the material characteristics required for the nickel-plated steel strip are extremely severe. In other words, in the DI processing method, the thickness of the side surface of the can is about 1/2 of the thickness of the bottom surface, and furthermore, two-step step forming for finishing into a convex integral battery case is added. In addition, the corners are frequently broken during the deep drawing of the integral projection, which hinders productivity. For this reason, in combination with the application of a non-aging ultra-low carbon steel which is soft and has excellent deep drawing properties, a method of heat-treating a cold-rolled steel sheet after nickel plating has been proposed from the viewpoint of improving the material surface and corrosion resistance. However, these measures cannot sufficiently cope with severe processing conditions, and further improvement in workability is required. In recent years, as batteries have been used in a wide variety of applications, those which conventionally functioned satisfactorily with the contact resistance of nickel plating have become problematic. In other words, the contact load at both battery electrodes has become wide ranging from a very light load to a high load. For this reason, a battery case that is more stable and has a lower electric contact resistance has been required. If the electric contact resistance is high, the contact voltage between the positive or negative electrode terminal and the contact surface on the other side increases, and the influence of the contact voltage shortens the battery life. in this way,
With the demand for lightweight and high capacity batteries, the required performance of nickel-plated steel strip, which is a material material, has become more stringent. In other words, as described above, the demand for thinner battery cases and strict processing methods have been widely applied, and the problem that conventional battery cases formed from nickel-plated steel sheets cannot follow the progress of can manufacturing technology. There was a point. Therefore, the present invention provides a battery case molded using a suitable material that does not impair the corrosion resistance of the battery case against the enclosed alkaline liquid and that improves the battery case moldability. And the outer surface of the case has improved electrical contact performance.

[0004]

In order to solve the above-mentioned problems, the present invention provides a battery case in which the inner surface of a can is plated with nickel or nickel and then tin, and the outer surface of the can is plated with tin. That is, the battery case of the present invention has the following features. [1] The inner surface of the case is plated with nickel at a plating amount of 5 to 40 g / m ² , and the outer surface of the case is plated with tin at a plating amount of 2.8 to 17 g / m ² . [2] The inner surface of the case is plated with nickel at a plating amount of 5 to 40 g / m ² , and the outer surface of the case is plated with tin at a plating amount of 2.8 to 17 g / m ² ,
Further, a part of the nickel plating layer forms an iron-nickel alloy layer. [3] Nickel plating with a plating amount of 5 to 40 g / m ² is applied to the inner surface of the case, and nickel plating with a plating amount of 1 to 10 g / m ² and a plating amount of 2.8 to 17 g / m ² of tin plating is applied. [4] Nickel plating with a plating amount of 5 to 40 g / m ² is applied to the inner surface of the case, and nickel plating with a plating amount of 1 to 10 g / m ² and a plating amount of 2.8 to 17 g / m ² of tin plating is applied, and part of the nickel plating layers on both surfaces forms an iron-nickel alloy layer. [5] The case of the inner surface, the plating quantity 5 to 40 g / m ² of nickel plating has been applied on the outer surface of the case, the plating weight of the nickel plating and the plating of 40 g / m ² exceed 10 g / m ² The tin plating is applied in an amount of 1.7 to 17 g / m ² . [6] The case of the inner surface, the plating quantity 5 to 40 g / m ² of nickel plating has been applied on the outer surface of the case, the plating weight of the nickel plating and the plating of 40 g / m ² exceed 10 g / m ² An amount of 1.7 to 17 g / m ² of tin plating is applied, and a part of the nickel plating layers on both surfaces forms an iron-nickel alloy layer. [7] Deep drawing or D
I obtained by molding.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The battery case of the present invention will be described separately for the inner surface of the case and the outer surface of the case. (Inner surface of case) In the present invention, nickel plating is applied to the inner surface side of the case. The amount of plating is determined as follows (see FIG. 1). FIG. 1 shows the result of measuring the iron elution amount after a potassium hydroxide solution was placed in a cylindrical draw can (the inner surface of the case was plated with nickel) and allowed to stand for 12 days. Several types of plated steel sheets with different plating amounts were prepared, and a cylindrical can with an outer diameter of 13 mm and a height of 49 mm was prepared by drawing, and a potassium hydroxide solution (concentration: 8 mol) was placed therein, and the temperature was 65 ° C. After 12 days, the amount of iron eluted into the solution was measured. The amount of iron eluted was measured by inductively coupled plasma emission spectroscopy suitable for the measurement of trace amounts. FIG.
From this, it can be seen that when the nickel plating amount is less than 5 g / mm ² , the iron elution amount sharply increases and deteriorates the durability of the battery case. On the other hand, even if it exceeds 32 g / m ² , the effect of the nickel plating amount does not appear remarkably, and it is uneconomical. Therefore, the nickel plating amount is preferably in the range of 5 g to 32 g / mm ² . It is preferable that the nickel-plated surface also has a dull finish. The reason for this is that the self-discharge rate becomes lower because the adhesion to the battery active material (manganese dioxide corresponds to an alkaline manganese battery) is high and the contact resistance is low.

(External Case) The reason why the tin plating is formed on the external surface of the case is that the tin plating has a stable electric contact resistance and excellent processing performance (see FIG. 2). The reason why tin plating is stable in electrical contact resistance is considered to be that the electrical contact resistance is stabilized by the soft surface layer of the plating. When the surface hardness of the cold-rolled steel sheet was tin-plated and nickel-plated and compared, the tin-plated (plating amount 17 g / m ² ) weighed 4 g under an HV 5 g load.
5, nickel plating (adhesion amount: 17 g / m
² ) is as-plated 305, from the tin-plated surface
It was found that the surface layer of nickel plating was hard. Further, the hardness was maintained at 210 even when heat treatment was performed at a heating temperature of 550 ° C. and a soaking time of 6 hours after nickel plating, and softening heat treatment was performed after nickel plating. Nickel plating also has better electrical contact resistance than other metals such as iron, but still has higher electrical contact resistance than tin plating.
The reason is that the nickel plating surface layer is oxidized to form NiO having a high electric resistance, and the nickel plating layer is harder than the tin plating layer as described above, that is, the deformation area is high, so that the contact area is tin plating. Probably because it is smaller. FIG. 2 shows the result of measuring the actual electric contact resistance.

FIG. 2 shows that the lower the measured load, the higher the electrical contact resistance, and the lower the measured load, the lower the electrical contact resistance. This is considered to be due to the fact that the higher the load, the greater the contact area and the destruction of the oxide film on the surface.
However, regardless of the magnitude of the contact load, it can be seen that the electrical contact resistance becomes stable when the tin plating adhesion amount is 0.5 g / m ² or more. Therefore, the lower limit of the tin plating adhesion amount from the viewpoint of stabilizing the electric contact resistance is set to 0.5 g / m ² . Here, the measuring method of the electric contact resistance was performed as follows. The contact is made of a brass bar and the tip is 1R by the AC 4-terminal method.
Using gold plated on the processed surface, the applied current was 10 mmA, and the contact load was 200 g and 100 g.
It was measured under a constant load of 0 g.

Next, another reason for tin plating on the outer surface side of the case is that it has excellent processing performance even in severe forming processing such as DI processing and convex processing. Tin is soft and rich in ductility, and recrystallizes even at room temperature, so that it does not harden as iron or nickel does. Furthermore, since it is a low melting point metal (melting point: 232 ° C), severe deep drawing and DI
If the temperature rises at the contact surface with the press die during processing,
Since the tin plating layer exhibits a more lubricating effect, the processing performance of the workpiece is significantly improved. In particular, when considering the punch side and the die side that affect the processing performance, the die side more affects the processing performance. This means that the present invention is a single-sided tin plating,
In addition, since the mold is formed outside the battery parts such as the battery case, the side surfaces of the die and the tin-plated surface are in contact with each other, which is convenient.
The lower limit of the amount of tin plating from the viewpoint of workability is determined from the degree of occurrence of cracks in the case. That is, if the amount of tin plating is small, a drawing process cannot be performed on a plate having a large blank diameter, and cracks occur during case molding. FIG. 3 shows the results of investigating workability by changing the amount of tin plating. From the results of FIG. 3, when the amount of tin plating was 1.7 g / m ² or more, good molding was possible, but when the amount was less than 1.7 g / m ² , cracks occurred in the case. The case was formed and processed as follows. Punch diameter 57.0mm, die diameter 5
The cup was drawn with a blank diameter of 120 mm at 7.64 mm, punch and die radius of 2 mm, and blank holder of 500 kg. On the other hand, even if the tin plating amount exceeds 17 g / m ² , no technical improvement is seen, and the upper limit is 17 g from an economic viewpoint.
/ M ² . Therefore, in consideration of the electric contact resistance, drawability, and economy, the tin plating amount is 1.7 to 17 g / m.
² is the appropriate range. In addition, tin plating includes a reflow treatment (tin melting treatment) after plating and a no reflow method as it is, but either method may be used in the present invention. However, more preferably, a method of performing temper rolling after the no reflow treatment is more preferable. The reason is,
This is because the retention of the lubricating oil on the plating surface during the press working is superior to that in the case of the reflow treatment in which the surface of the tin plating layer is smoother.

(Inventions of Claims 3 to 6) From the viewpoint of further improving the corrosion resistance of the outer surface of the case, it is more preferable that nickel plating is applied as a base plating treatment before tin plating. coating weight of plating and when it is 1 to 10 g / m ^2, which may exceed 10 g / m ² and 40 g / m ² or less. The reason is that if the plating amount of nickel plating is 1 to 10 g / m ² , sufficient corrosion resistance cannot be secured, and it is necessary to supplement with tin plating. On the other hand, the plating amount of nickel plating is 10 g /
If it exceeds m ² , corrosion resistance can be ensured by nickel plating, so that the amount of tin plating can be reduced. Therefore, when the nickel plating of 1 to 10 g / m ² is applied, the tin plating amount is 2.8 to
17 g / m ² of tin plating needs to be applied. Further, when the coating weight is subjected to a nickel plating 40 g / m ² exceed 10 g / m ^2, the tin plating amount 1.
It may be 7 to 17 g / m ² . Based on this ground, a salt spray test was conducted to investigate the corrosion resistance (shown in FIG. 4). Areas A (claims 3 and 4) and area B (claims 5) in FIG.
In (6) and (6), sufficient corrosion resistance was obtained, but in region C, the corrosion resistance was poor, and in region D, the workability was not sufficient.

Next, a method for producing a surface-treated steel sheet for producing the battery case of the present invention will be described in detail. (Steel plate) As a plating base plate, low carbon aluminum killed steel is usually used. Further, a cold-rolled steel strip produced from a non-aging ultra-low carbon steel (carbon content: 0.003% or less) to which niobium and titanium are added is also used. Normally, after cold rolling, electrolytic cleaning,
The steel strip that has been annealed and temper-rolled is used as the base plate for plating, but the steel sheet after cold rolling may be used as the base plate for nickel plating as it is. In this case, after the nickel plating is performed after the cold rolling, the step of successively recrystallization annealing the steel base and the step of thermally diffusing the nickel plating layer are simultaneously performed.

(Nickel Plating) The plating base plate is subjected to pretreatment of alkaline electrolytic degreasing, water washing, sulfuric acid or hydrochloric acid pickling (electrolysis or immersion), and water washing, and then nickel plating. In the present invention, the nickel plating bath may be any of known plating baths such as a Watt bath, a sulfamic acid bath, and a chloride bath. Further, the types of nickel plating include matte plating, semi-glossy plating and bright plating.
Matte or semi-glossy plating other than bright plating to which a sulfur-containing organic substance is added is suitably applied in the present invention. This is because, in the case of bright plating, the plating layer is hard, so that more surface cracks occur during processing and the corrosion resistance is impaired, and when heat treatment is performed after nickel plating, the plating layer becomes brittle because of the sulfur content, which impairs the corrosion resistance.

(Heat treatment) Although the effects of the present invention can be obtained by using nickel plating as it is, as a method of further improving corrosion resistance, a method of performing heat treatment after nickel plating is also suitably used. That is, by performing a heat treatment after nickel plating, the nickel plating layer is softened, and the amount of cracks generated in the plating layer during processing is reduced. As the heat treatment conditions, the heating temperature is 450 to 850 in a non-oxidizing atmosphere gas.
The treatment is performed at a temperature of 30 ° C. and a heating time of 30 seconds to 15 hours. As a method of heat-treating the steel strip, there are a box-type annealing method and a continuous annealing method. In the present invention, either method may be used, and in the box-type annealing method, (450 to 650) ° C. × (5 to 15)
), And in the continuous annealing method, heat treatment conditions of high temperature and short time, that is, (600 to 850) ° C x (30 seconds to 5 minutes) are preferable.

(Tin plating) After nickel plating, subsequently, tin plating is applied to a surface corresponding to the outside of the case. The prescribed range of the tin plating differs depending on whether or not the nickel plating applied before the tin plating is applied to the base. The bath composition includes an acidic bath and an alkali bath which are usually used. In the present invention, a stannous sulfate bath or a phenolsulfonic acid bath is used. In addition, the method of tin plating used for materials for cans and the like is generally manufactured in the steps of degreasing, pickling, tin plating, reflow (tin melting treatment), and chemical treatment. A similar method is applied. However, in the case of more severe processing conditions such as DI processing, no reflow (without tin melting treatment) having good wax lubrication retention is more desirable.

(Temperature Rolling) As a method of making the surface more glossy without impairing the processing performance, a method of performing temper rolling after tin plating is also used. According to this method, light rolling is performed with a bright work roll at a rolling reduction of 2 to 3% or less without tin melting treatment after tin plating. According to this method, a dull whitish tin plating layer without tin melting or a nickel plating layer having a dull metallic luster has a beautiful glossy surface appearance. Further, by rolling using a finish-polished work roll, a clean silver-white surface appearance having a metallic luster can be obtained. When the steel strip is warped due to different types of front and back plating and different friction coefficients on the surface in the temper rolling, the warpage can be corrected by passing the steel strip through a leveler device after the temper rolling.

[0016]

The present invention will be described in more detail with reference to the following examples. A cold-rolled and annealed low-carbon aluminum-killed steel sheet having a sheet thickness of 0.25 mm was used as a plating base sheet. The steel chemical composition is as follows (% by weight): C: 0.04%, Mn: 0.21%, Si: 0.01
%, P: 0.013%, S: 0.010%, Al: 0.
064%, N: 0.0038% The above steel sheet was subjected to alkaline electrolytic degreasing (caustic soda: 30 g /
1, anodizing: 5A / dm ² × 10 seconds, cathodic processing: 5A
/ Dm ² × 10 seconds, bath temperature: 70 ° C.), washing with sulfuric acid (sulfuric acid:
50 g / l, bath temperature: 30 ° C., immersion for 20 seconds)
Nickel plating was performed under the following conditions. Bath composition: Nickel sulfate 320 g / l Nickel chloride 40 g / l Boric acid 30 g / l Sodium lauryl sulfate 0.5 g / l Bath temperature: 55 ± 2 ° C pH: 4.1-4.6 Stirring: Air stirring Current Density: 10 A / dm ² Anode: Nickel pellets (Titanium basket filled with nickel pellets) Under the above conditions, matte nickel plating is performed on one side and both sides, and the thickness is changed by changing the electrolysis time under the above conditions. The thickness was changed. When heat treatment is performed after nickel plating, heat treatment is performed at a soaking temperature of 550 ° C. and a soaking time of 6 hours using a protective gas having a hydrogen content of 6.5%, a balance of nitrogen gas, and a dew point of −40 ° C. . Following the nickel plating, tin plating was performed using the following stannous sulfate plating bath. Bath composition: stannous sulfate 30 g / l (S ++) Phenolsulfonic acid 60 g / l ethoxylated α-naphthol 5 g / l Bath temperature: 50 ± 2 ° C. Current density: 20 A / dm ² Anode: tin plate plating The steel strip was heated to 270 ° C. by resistance heating to change the amount of adhesion by changing the electrolysis time, and was tin-melted to impart gloss. Further, in order to suppress yellowing due to the growth of the oxide film of the tin plating layer, a chemical treatment applied to a usual tinplate manufacturing was performed. Treatment bath: sodium dichromate 30 g / l Bath temperature: 45 ° C. Cathodic electrolysis: 5 A / dm ² × 5 seconds A sample was prepared under the conditions described above. Using each sample, the salt spray test, the elution amount of the alkaline solution iron, and the electrical contact resistance were measured. The salt spray test shows a result of a spraying time of 2 hours based on JIS Z-2371. The corrosion resistance was evaluated using a right-angled bending test piece (○: good, ×: inferior). From the results in Table 1, Examples 1 to 13 which are within the scope of the present invention showed extremely good results in any of the salt spray test, the elution amount of the alkaline liquid iron, the electric contact resistance, and the workability. On the other hand, Comparative Examples 14 to 19 were out of the range of the present invention, and no good results were obtained.

[0017]

[Table 1]

[0018]

The battery case of the present invention is manufactured by a deep drawing method,
It can be easily manufactured by the I molding method, and is suitable for use in a container for enclosing an alkaline liquid, for example, a battery case such as an alkaline manganese battery or a nickel cadmium battery. That is, the battery case is easily formed as a battery case without impairing the corrosion resistance of the battery case against the sealed alkaline solution. Further, the inner surface of the case retains alkali corrosion resistance, and the outer surface of the case can improve electric contact performance.

[Brief description of the drawings]

FIG. 1 shows a measurement result of an iron elution amount when a nickel plating amount is changed.

FIG. 2 shows measurement results of electrical contact resistance when the amount of tin plating is changed.

FIG. 3 shows the degree of occurrence of cracks during case molding when the amount of tin plating is changed.

FIG. 4 is a diagram illustrating the relationship between the plating amount on the inner surface of the case.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-177991 (JP, A) JP-A-4-154993 (JP, A) JP-A-60-5894 (JP, A) JP-A-4-1992 154995 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C25D 5/00-5/52 H01M 2/02

Claims (7)

(57) [Claims] 1. The inner surface of the case has a plating amount of 5 to 40 g.
/ M ² nickel-plated, and the outer surface of the case is tin-plated with a plating amount of 2.8 to 17 g / m ² . 2. The inner surface of the case has a plating amount of 5 to 40 g.
/ M and ² of the nickel plating is applied, the outer surface of the case have been subjected to tin plating of the plating amount 2.8～17G / m ^2, and a portion of the nickel plating layer is an iron - nickel alloy layer Forming a battery case. 3. The inner surface of the case has a plating amount of 5 to 40 g.
/ M of which the nickel-plated ^2, the outer surface of the case, the battery case tin plating coating weight 1 to 10 g / m ² of the nickel plating and the plating amount 2.8～17G / m ² is applied . 4. The inner surface of the case has a plating amount of 5 to 40 g.
/ M of which the nickel-plated ^2, the outer surface of the case, with tin plating in the plating amount 1 to 10 g / m ² of the nickel plating and the plating amount 2.8～17G / m ² is not subjected, and A battery case in which a part of the nickel plating layers on both surfaces forms an iron-nickel alloy layer. 5. The inner surface of the case has a plating amount of 5 to 40 g.
/ M of which the nickel-plated ^2, the outer surface of the case, the plating weight of the tin plating facilities of 10 g / m ^2, greater 40 g / m ² of the nickel plating and the plating amount 1.7～17G / m ² Battery case. 6. The inner surface of the case has a plating amount of 5 to 40 g.
/ M of which the nickel-plated ^2, the outer surface of the case, the plating weight of the tin plating facilities of 10 g / m ^2, greater 40 g / m ² of the nickel plating and the plating amount 1.7～17G / m ² A battery case, wherein a part of the nickel plating layers on both surfaces forms an iron-nickel alloy layer. 7. The battery case according to claim 1, wherein the battery case is obtained by deep drawing or DI forming a steel sheet whose surface has been previously treated.