JPH04198441A - Zinc alloy for manganese dry cell - Google Patents

Abstract

PURPOSE:To obtain a zinc alloy for a manganese dry cell having high mechani cal strength and excellent corrosion resistance by incorporating specified compositional amounts of Pb, Mg and Bi into an alloy. CONSTITUTION:This is a zinc alloy for a manganese dry cell contg., by weight, 0.1 to 0.5% Pb and 0.001 to 0.002% Mg or 0.001 to 0.005% Bi. The alloy does not contain harmful Cd, having high mechanical strength and excellent corrosion resistance and is suitable as the negative polarity can of a manganese dry cell.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a zinc alloy for manganese dry batteries, and more specifically, a zinc alloy for manganese dry batteries that has mechanical strength and corrosion resistance suitable for cans of manganese dry batteries. Regarding.

[Prior Art] Zinc alloys have long been used as metal containers (hereinafter referred to as negative electrode cans) that also serve as negative electrodes for manganese dry batteries.

Conventional zinc alloys used as negative electrode cans for manganese dry batteries are made with zero .1-0.8% by weight lead and 0.02-00
Contains 6% by weight of cadmium.

Although the amount of cadmium contained in this zinc alloy is small,
Cadmium is harmful to the human body, and as its distribution and consumption increases, it has become urgent to prevent environmental pollution caused by cadmium, which is mixed into industrial and household waste and disposed of. As a countermeasure, it is strongly desired to use a zinc alloy that does not contain cadmium in the negative electrode can of manganese dry batteries.

However, when evaluated as negative electrode can materials for manganese dry batteries, alloys prepared by simply removing cadmium from conventionally used zinc alloys have considerably lower mechanical strength than cadmium-containing zinc alloys, and Scratches and deformations (bent, dented, etc.) occur during the process, causing internal short circuits.

[Problems to be Solved by the Invention] The present invention solves the mechanical strength defects of such conventional cadmium-free alloys, does not contain cadmium,
Furthermore, the present invention aims to provide a zinc alloy for manganese dry batteries that has higher mechanical strength and better corrosion resistance than cadmium-containing alloys.

[Means for Solving the Problem] As a result of repeated research to achieve the above object, the present inventors found that a zinc alloy containing specific amounts of lead and magnesium or bismuth was found to be suitable for the purpose. The present invention was made based on the finding that the two methods are compatible.

That is, the zinc alloy for manganese dry batteries of the present invention contains 01 to 0.5% by weight of zinc and lead, and 0.001 to 0.002% by weight of magnesium or 0.001 to 0005% by weight of bismuth. It is characterized by

Note that zinc inevitably contains impurities such as copper, iron, cadmium, and lead in ppm units during its refining process, but the present invention is not concerned with the presence of these impurities.

In the present invention, lead contained as a component of the zinc alloy is
It provides the alloy with extensibility, impact extrudability and corrosion resistance. The content of lead in the present invention is 0.1 to 0.5% by weight, preferably 0.3 to 0.5% by weight. If this amount is less than 0.1% by weight, the zinc alloy becomes brittle, making it particularly difficult to perform rolling or impact processing. Furthermore, satisfactory corrosion resistance cannot be obtained with respect to the electrolyte of manganese dry batteries. If it exceeds 0.5% by weight, it becomes too flexible and the mechanical strength, especially the hardness, decreases.

Magnesium contained as a component in the present invention is
It provides mechanical strength to the alloy.

If the magnesium content is less than 0.001% by weight, it will not be able to provide sufficient mechanical strength, and if it exceeds 0.002% by weight, it will be susceptible to corrosion by the electrolyte, and its long-term storage stability will be significantly reduced. .

Furthermore, like magnesium, bismuth contained as a component in the present invention provides mechanical strength to the alloy. If the content of bismuth is less than 0.001% by weight, sufficient mechanical strength cannot be provided, and if it exceeds 0.005% by weight, it becomes susceptible to corrosion by the electrolyte.

In addition, in the present invention, what is required as mechanical strength is:
Mainly mechanical strength that can withstand various can manufacturing processes,
There is no problem in evaluating it by representing it with hardness (Vickers).

[Effects of the Invention] The present invention provides a zinc alloy for manganese dry batteries that does not contain cadmium that pollutes the environment and has higher mechanical strength and superior corrosion resistance than conventional cadmium-containing zinc alloys. And ゛ was completed. The zinc alloy of the present invention is useful as a negative electrode can for manganese dry batteries.

[Examples] Hereinafter, the present invention will be explained in detail by Examples and Comparative Examples. The invention is not limited by the examples.

Using heat-refined zinc ingot with a purity of 99.99% by weight or more, blending lead and magnesium or bismuth,
Alloy samples (Examples 1 to 8) according to the composition of the present invention as shown in Table 1 were prepared.

For comparison, a conventional product containing lead and cadmium was prepared (Comparative Example 1), and various samples (Comparative Examples 2 to 18) outside the composition range of the present invention shown in Table 2 were similarly prepared.

These were evaluated by the following tests. Note that n is the number of test samples for each structure of each example and comparative example.

(1) Hardness (n=30) An R20 manganese dry battery negative electrode can having a thickness of 0.42 to 0147 mm was prepared, and the hardness of its side surface was measured using a micro Vickers hardness meter (MV).

(2) Corrosion loss (n=20) A negative electrode can similar to (1) was created. After weighing this,
It was immersed in an electrolytic solution for manganese dry batteries consisting of an aqueous solution containing 26% by weight of zinc chloride and 1.5% by weight of ammonium chloride, sealed, and left at 45° C. for 15 days. Then, it was taken out from the electrolytic solution, washed with water, dried and weighed, and the weight loss rate was calculated to determine the corrosion weight loss.

(3) Appearance defect rate during the process (n = 1,000) A negative electrode can similar to that in (1) was made by impact extrusion using a mixture of flaky graphite and boric acid as a lubricant from pellets of the test metal. We conducted mass trial production and obtained R20 manganese dry batteries. Then, the metal exterior of the battery was removed and the negative electrode can was inspected to determine the percentage of defects in appearance such as scratches, bends, and dents.

These evaluation results are shown in Tables 1 and 2 together with the component compositions.

Table 1 Table 2 As is clear from Tables 1 and 2, the hardness and appearance defect rate are better as the magnesium or bismuth content increases;
Shows performance equivalent to or better than conventional products. On the other hand, the corrosion loss decreases as the content of magnesium or bismuth increases, and this tendency is particularly noticeable when the content of lead is low.

Considering hardness, appearance defect rate, and corrosion resistance, zinc alloy for manganese dry batteries contains 0.1 to 0.5% by weight of lead and 0.001 to 0.002% by weight of magnesium or o. , ooi to 0.005% by weight was found to be suitable.

Claims (1)

[Claims] (1) Contains 0.1 to 0.5% by weight of lead: and 0.001 to 0.002% by weight of magnesium or 0% of bismuth.
．． A zinc alloy for manganese dry batteries, characterized in that the zinc alloy contains 001 to 0.005% by weight.