JPH07296813A - Anode zinc can of battery - Google Patents

Abstract

PURPOSE:To provide good corrosion resistance and mechanical strength without the addition of lead, cadmium and mercury which are environmentally hazardous by employing predetermined amounts of bismuth and calcium and no appreciable amounts of topic materials such as mercury. CONSTITUTION:The addition to zinc of environmentally hazardous materials such as mercury, cadmium and lead is not carried out, but instead highly safe metals such as bismuth, calcium, nickel, aluminum and silicon are added in a predetermined combination and ratio; that is, a zinc base alloy that contains 0.004-0.75wt.% bismuth, 0.001-0.25wt.% calcium, and no appreciable amounts of toxic materials such as mercury, cadmium, and lead, is employed. This can restrain degradation of rollability and enhance corrosion resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative electrode zinc can for a battery, which is made of a zinc-based alloy to which a trace amount of metal is added and is formed into a cylindrical shape with a bottom. The present invention relates to a technology for realizing a high-performance negative electrode zinc can.

[0002]

[Prior art]

[Manufacturing Method of Negative Electrode Zinc Can] As is well known, the negative electrode zinc can used in the manganese battery is manufactured by the following series of steps. ... An appropriate trace amount of metal, which will be described later, is added to zinc ingot and dissolved. ... The molten zinc-based alloy is continuously cast to obtain a continuous strip. ... The continuously cast strip is continuously hot-rolled to obtain a plate having a predetermined thickness. ... Punch pellets, such as circles or hexagons, of specified dimensions from a rolled plate. ... The pellets are set in a mold and impacted by a punch to form a bottomed cylindrical shape (impact backward extrusion method). … Cut the opening of a zinc can that has been molded into a bottomed cylinder to make the height of the cylinder uniform. For example, in the case of a negative electrode zinc can of a single-type manganese battery, the thickness of the plate-shaped body is about 5.2 mm in the rolling process, a circular pellet with a diameter of 30 mm is punched in the punching process, and the outer diameter is 31.4 mm in the forming process It is molded into a bottomed cylinder with a thickness of 0.5 mm, and the height of the cylinder is 53.5 mm in the height cutting process.

[Characteristics Required for Negative Electrode Zinc Can and Its Material] In the continuous hot rolling process and the forming process by impact backward extrusion method, the material must have sufficient rolling workability or plastic workability (spreadability). However, cracks, cracks, burrs, etc. occur in the material and interfere with the subsequent processing.
It is a fundamental and essential requirement to be able to form a cylindrical can with a good yield without causing defects such as cracking (this is called workability).

The completed negative electrode zinc can then proceeds to the battery assembly line, the positive electrode, the separator, the electrolytic solution, etc. are stored in this can, and the positive electrode terminal plate and the sealing gasket are fitted into the opening of the can to seal the can. To do. If the mechanical strength of the zinc can as a can is too low, the can will be deformed during and after the battery assembly, causing various problems. Therefore, the zinc can after being formed needs a certain level of mechanical strength. The strength after the canning is in a relationship contradictory to the plastic workability (spreadability).

In the completed battery, the negative electrode zinc can is constantly in contact with the internal electrolytic solution, but the zinc can must have sufficient corrosion resistance to the electrolytic solution to prevent self-discharge during storage of the battery. I have to.

As described above, the negative electrode zinc can of a battery is required to have such properties as plastic workability, mechanical strength after forming, and corrosion resistance to an electrolytic solution. These characteristics include not only the composition of the zinc-based alloy, but also the melting temperature of the melting process in the manufacturing process, the temperature of the casting process mold, the rolling process temperature and rolling rate, the pellet punching process temperature, and the forming container process temperature. Factors such as temperature and processing rate (these are called process factors) are also involved.

[Additional metal of zinc-based alloy] The above-mentioned workability,
In order to improve various properties such as mechanical strength and corrosion resistance,
In the old manganese battery, about 0.15% by weight of lead and 0.
A negative electrode zinc can was made of a zinc-based alloy to which about 05% by weight of cadmium was added, and the surface of the zinc can was amalgamated. However, as is well known, under the technical idea of removing harmful substances from the constituent materials of batteries as much as possible, first, the anhydrous silver was achieved, and then the non-use of cadmium was achieved. In other words, technical improvements have been made to eliminate the added metal, which has been used for a long time and has a great effect of improving the characteristics, and does not deteriorate the performance of the battery (for example, JP-A-61-273861, Japanese Patent Publication No. No. 30712,
JP-A-4-198441).

However, even in recent manganese batteries, it is the actual situation that the negative electrode zinc can still contains about 0.4% by weight of lead, and the next technical problem is to abolish the addition of lead. Has become.

[0009]

[Problems to be Solved by the Invention]

[Prototype Evaluation of Zinc Can Made of Pure Zinc] A pure zinc can was experimentally manufactured and compared with a conventional negative electrode zinc can containing 0.4% by weight of lead and showing good characteristics.

A zinc can is manufactured by the above-described manufacturing process without using any other metal at all, by using a base metal having a zinc purity of 99.9986% by weight as a raw material. At that time, process factors (melting temperature of melting process, mold temperature of casting process, temperature and rolling rate of rolling process, temperature of pellet punching process, temperature and processing rate of forming container process) are appropriately changed to make a prototype. repeat. Prototypes with different process factors were made to the extent that they satisfy the basic requirement (plastic workability) that defect-free cans can be formed with good yield. Corrosion resistance to was examined under the following conditions and compared with the conventional product (comparison test was conducted on negative electrode zinc cans for single-type manganese batteries).

(A) 20 from the outer center of the molded can
5 mm square sample pieces were cut out, the Vickers hardness of each sample piece was measured at 5 points, and the average value of 10 samples was obtained. This was used as the evaluation of mechanical strength.

(B) As for the evaluation of corrosion resistance, the similarly cut out 10 mm square sample pieces were immersed in the electrolytic solution for a certain period of time, and the corrosion weight loss was measured to obtain the average value of 10 samples. The electrolytic solution contains ZnCl ₂ (26.4% by weight) and NH ₄ Cl (2.2% by weight) and has a pH of 4.7.
Is an aqueous solution of. The period of standing is 20 days, and the ambient temperature is 45 ° C.

As a result, the hardness of the conventional product containing lead was HV45, whereas the hardness of the prototype of pure zinc was HV37 at the maximum. The corrosion weight loss of the conventional product was 0.93 mg / cm ² , whereas the corrosion weight loss of the prototype of pure zinc was 9.5 mg / cm ² at the minimum.
It cannot be said that the hardness is extremely inferior, but the corrosion weight loss is significantly inferior. The addition of lead has a great effect.

[Prototype Evaluation Using Zinc-Based Alloy With Bismuth Addition] A negative electrode zinc can for a single-type manganese battery similar to the previous example was manufactured by the above-mentioned process using a zinc-based alloy containing a trace amount of bismuth added to pure zinc. Vickers hardness and corrosion weight loss were measured by the methods (a) and (b). as a result,
In the prototype with 0.0010% by weight of bismuth,
Hardness HV38.1, corrosion weight loss is 8.91mg / cm ²
Which is an improvement over that of pure zinc. But,
Some cracks were formed on both sides of the plate-shaped body manufactured in the hot rolling process (there was no problem in the subsequent forming process).

Therefore, the addition amount of bismuth is set to 0.0040.
I tried to make a prototype by increasing the weight to 0.0% and further increasing it to 0.0100% by weight. In this case, the rolling workability of the material (zinc-based alloy containing bismuth) was remarkably deteriorated, normal rolling could not be performed in the hot rolling step, and the material was broken into pieces.

[Object of the Invention] An object of the present invention is to provide a negative electrode zinc can having good corrosion resistance and mechanical strength without adding lead, cadmium and mercury which are harmful to the environment.

[0017]

A negative electrode zinc can of the first invention contains 0.004 to 0.75% by weight of bismuth, 0.001 to 0.25% by weight of calcium, and mercury. It consists of a zinc-based alloy that does not significantly contain harmful substances such as cadmium and lead.

The negative electrode zinc can of the second invention contains 0.004 to 1.00% by weight of bismuth, 0.001 to 0.25% by weight of calcium, and 0.001 to 0 of nickel. It is composed of a zinc base alloy containing 25% by weight and containing no significant harmful substances such as mercury, cadmium and lead.

The negative electrode zinc can of the third invention contains 0.004 to 1.00% by weight of bismuth, 0.001 to 0.25% by weight of calcium, and 0.0005 of aluminum or silicon. .About.0.20% by weight and does not contain harmful substances such as mercury, cadmium and lead significantly.

[0020]

As can be seen from the results of many comparative tests described below, the addition of bismuth to pure zinc improves corrosion resistance, but tends to reduce rolling workability. However, by adding calcium in addition to bismuth in the above proportion, it is possible to prevent the rolling workability from deteriorating. Also,
By adding nickel, aluminum, or silicon in addition to bismuth and calcium in the above-mentioned proportion, even if the amount of bismuth added is further increased (corrosion resistance is further improved), deterioration of rolling workability is suppressed. As a result, the target value of hardness of 40 HV or more, corrosion loss of 7.0
It is possible to achieve mg / cm ² or less.

[0021]

EXAMPLE A pure zinc metal having a zinc purity of 99.9986% by weight was used as a raw material (inevitable impurities were not taken into consideration), and a trace amount of metal was added to this pure zinc at the following ratio, and the above-mentioned manufacturing process was performed. Will manufacture a negative electrode zinc can for a single manganese battery. Then, for each prototype, the Vickers hardness (HV) and the corrosion weight loss (mg / cm ² ) were measured according to the methods (a) and (b) detailed above. At the same time, the workability in the hot rolling step was evaluated as follows.

In the hot rolling process, as shown in FIG.
The plate-shaped body 1 having a width of 10 cm and a thickness of about 5 mm is obtained. However, if the rolling workability of the material is poor, cracks 2 are generated in portions of the plate-shaped body 1 on both sides. It can be said that the longer the cracks 2 are and the more the cracks 2 are, the worse the workability of the material is. If the workability of the material is extremely poor, as in the case of the trial product containing a large amount of bismuth, the plate-shaped body 1 cannot be formed, and the material breaks into pieces.

In the following tables of a large number of test examples, the rolling workability is evaluated and entered in five stages as follows. "○": Very good with no cracks. “◯ / Δ” ... The length of the crack 2 is within 1% of the width of the plate-shaped body 1 and is good. “Δ”: The length of the crack 2 is within 3% of the width of the plate-shaped body 1, which is almost good. “Δ / ×”: The length of the crack 2 exceeds 3% of the width of the plate-shaped body 1 and is defective. “×”… The material was shattered and could not be rolled.

[0024]

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[Table 6]

[Table 7]

[Table 8]

[0025]

As described in detail above, according to the present invention, the addition of harmful substances such as mercury, cadmium and lead to zinc is abolished, and safety such as bismuth, calcium, nickel, aluminum and silicon is replaced. By adding metals having high properties in the above combination and ratio, a negative electrode zinc can having characteristics equal to or better than those of conventional lead-added negative electrode zinc cans can be realized.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing how cracking occurs in a hot rolling process.

[Explanation of symbols]

 1 Plate 2 Crack

Claims (3)

[Claims] 1. Bismuth 0.004 to 0.75% by weight
In addition to containing 0.001 to 0.25 calcium
A negative electrode zinc can for a battery, which is made of a zinc-based alloy containing 50% by weight and containing no significant harmful substances such as mercury, cadmium and lead. 2. 0.004 to 1.00% by weight of bismuth
In addition to containing 0.001 to 0.25 calcium
% By weight, and 0.001-0.25 nickel
A negative electrode zinc can for a battery, which is made of a zinc-based alloy containing 50% by weight and containing no significant harmful substances such as mercury, cadmium and lead. 3. Bismuth in an amount of 0.004 to 1.00% by weight
In addition to containing 0.001 to 0.25 calcium
% Of aluminum, and 0.0005 to 0.20% by weight of aluminum or silicon, and a zinc-based alloy containing no harmful substances such as mercury, cadmium and lead significantly. Negative electrode zinc can.