JPS59170251A - Manufacture of lead alloy material for lead storage battery - Google Patents

Abstract

PURPOSE:To obtain a lead alloy material for a lead storage battery inhibiting the intergranular corrosion and general corrosion of its plate grid by dissolving the surface of a Pb-Ca alloy material, sticking Sn, Ag, Mo, W or Cr to the dissolved surface, and subjecting the material to heat treatment and rolling. CONSTITUTION:The surface of a Pb-Ca alloy material is dissolved with a suitable etching soln., and one or more among Sn, Ag, Mo, W and Cr are stuck to the dissolved surface. The material is then subjected to heat treatment and rolling or other working. A corrosion resistant alloy is formed only at the surface part at high concn., and by the synergistic effect of the alloy and the preferential dissolution of metallic grain boundaries, an alloy material with improved corrosion resistance is obtd. When this alloy material is used as the material of the plate grid of a lead storage battery, the life of the battery can be prolonged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Prior Art and Problems] The present invention is directed to a method for producing lead alloy materials for lead-acid batteries. Although lead-antimony alloys have traditionally been used for the grids, poles, etc. of lead-acid batteries, lead-calcium alloys have recently been used for maintenance-free lead-acid batteries. Since the lead-calcium alloy has a higher hydrogen overvoltage than the lead-antimony alloy, it has the advantage of less electrolysis of water in the electrolyte during photovoltaic use and less self-discharge during storage. However, on the other hand, the castability is inferior to that of lead-antimony alloy, so after rolling the alloy material into a sheet shape, electrode plate grids are manufactured by expanding processing, punching processing, etc.

Lead alloys have age hardening properties, and when heat treated, the solute metal precipitates from a supersaturated solid solution, or the solute metal and lead,
Or it forms an intermetallic compound with other added metals. This precipitation of solute metals and the formation of intermetallic compounds mainly occur at metal grain boundaries, and this is the cause of corrosion of lead alloy materials. Alternatively, when intermetallic compounds are formed, that part becomes more susceptible to corrosion than other parts. When a crystalline alloy is rolled, grain boundaries are dispersed, and intergranular corrosion is alleviated. However, because the grain boundaries are dispersed, the entire calendar eclipse (general corrosion) becomes severe.

[Excellent Purpose] It is necessary for the electrode plate lattice of the lead S%' cell, especially the anode lattice, to eat away at the grain boundaries IA' and to suppress general corrosion. The reason for this is that intergranular corrosion causes elongation and cutting of the lattice, while general corrosion reduces the current collection effect and active material retention. In view of this point, it is an object of the present invention to provide a method for manufacturing a lead alloy material that suppresses both of these types of corrosion.

[Construction of Apology] The present invention involves dissolving only the surface opening 1'' of the surface of a lead-calcium alloy in a solution that dissolves them, and adding soot, silver, and molybdenum to the dissolved surface. This is a method for producing a lead alloy material for a lead-acid battery, which is characterized in that after adhering one or more of tungsten and chromium, the material is heat-treated and subjected to rolling or other processing.

When observing the metallographic structure of a cross section of a cast product of a lead-calcium alloy, as shown in Figure 1, the particle shape of the metal crystal at the center of the alloy part 13 is close to a circular shape with an equal ratio of length and width. Although it has a shape, it can be seen that the surface part that comes into contact with the mold during mining is long in the vertical direction, and this long direction is aligned toward the center. For this reason, it is thought that lead-calcium alloys have deeper intergranular corrosion at their surface, making them more likely to elongate or break.

Therefore, in order to improve the corrosion resistance of lead-calcium alloys, it is ideal to prevent the formation of grain boundaries, but since this is virtually impossible, it is necessary to reduce the grain boundaries. or is necessary. In view of this point, the present invention
Metals such as tin, especially molybdenum, tungsten, and chromium, which preferentially melt the metal grain boundaries on the surface of lead-calcium alloys cooled and solidified from the molten state, activate the surface, and spread corrosion resistance there. This is to attach metal to one or more of our buildings. Tin, silver, etc. are known as metals that are effective in improving the corrosion resistance of lead alloys, but due to cost and mechanical strength considerations, the amount of addition is limited to 1 tin for tin and 0.3 coefficient for silver/I'i. It is. Accordingly, in the present invention, a highly concentrated corrosion-resistant alloy is formed using these metals only on the surface area that is corroded first, and combined with the effect of preferentially dissolving the metal grain boundaries, the corrosion resistance is improved. In addition, molybdenum, tungsten, and chromium, which are effective in corrosion resistance but are not included in lead alloys, all have a smaller tendency to ionize than lead, and they adhere to the lead alloy surface 1m by the other reaction. In addition, when these metals are attached, the surface of the lead alloy is melted to activate the RJ part in Table 7, which improves the adhesion, and the dissolved metal grain boundaries preferentially adhere to these. coated with metal. Then, in order to improve the bonding properties between these deposited metals and the lead alloy, heat treatment is performed and further rolling is performed, and thus the lead-calcium alloy material with improved intergranular corrosion and general corrosion is made into scales. I can do it.

[Example ■] CaO as an example of lead-calcium alloy
,08% by weight (hereinafter all by weight) An alloy consisting of S, 0.5% and balance lead was heated to about 450°C and dissolved at f6 to about 150°C.
In a mold heated to
An iAQ product of No. 1 was prepared.

This casting was mixed with 20 parts of nitric acid, 10 parts of hydrogen peroxide,
The surface was dissolved by immersing it in an etching solution containing 100 parts of water for about 1 minute.

Silver is then deposited on the molten surface to provide corrosion resistance. Silver has a smaller tendency to ionize than lead, so when silver ions are added to the etching solution that has dissolved the surface of the lead alloy, silver precipitates and adheres to the surface of the dissolved lead alloy. The amount of silver deposited is controlled by the concentration of silver ions and the one-substitution reaction time. In this example, silver ions were added at a rate of 0.5 f to 100 cc of the etching solution. The substitution reaction time was 30 seconds, and after the surface was dissolved by the etching solution for 1 minute, silver ions were introduced into the etching solution. The sample thus obtained is designated as A.

Next, heat treatment is performed to improve the bond between the lead alloy and the metal attached to its surface, but it is not effective at temperatures below 50°C, and when the temperature exceeds 200°C, the strength of the lead alloy itself decreases. The temperature is between 200°C and 200°C. In Example 1, Sample A was heated at 125° C. for 20 hours. This is designated as sample B.

Next, rolling the sample B further strengthens the bond between the lead alloy and the deposited metal, and smooths out the unevenness caused by melting. It is preferable that the rolling thickness be reduced to 1/2 or less of the original thickness. In this example, two pieces of sample B each having a thickness of 4 mm were rolled. This is designated as sample C.

As a reference material, the surface of Pb-aα-E3n alloy was melted.
A sample without l'F L (conventional sample with no deposited metal) was used as a sample, and sample E was obtained by rolling this as it was to 1/2 of the original thickness. In addition, a sample F in which the surface of the Pb-Cα-8rL alloy was dissolved in the etching solution,
Sample G was obtained by rolling this to 1/2 of the original thickness.

Corrosion resistance was evaluated for the above samples A to G. The evaluation method was to use a pure lead plate as the counter electrode and sulfuric acid with a specific gravity of 1.28 as the electrolyte, and conduct anodic oxidation by flowing a constant current of 20 Q for 20 consecutive days at room temperature. After removing it by immersing it in a curry mannitol bath, it was weighed and the difference from the original weight was determined, which was taken as the oxidation weight loss. The elongation rate was also measured. The results are shown in Figure 2. From the same figure, the lead alloy material ABC produced by the method of the present invention is different from the conventional method.
, F, and G are clearly superior in terms of weight reduction and elongation.

[Example ■] This example is for confirming the effect of the electrode plate grid made of 1 μm of the lead alloy material of Example I of the present invention. (0
,08%) using Bn(0,5%)] 28
A plate grid of the usual shape of 56mm, 80mm long, 2.8mm thick, and 56mm thick was cast, and this was used as Sample A of Example I.
Processed by the same method as, Uchij! The lattice with a length of 28- is designated as H. Next, the 5.6 myn thick grid was rolled to about 1/2, 2.8 m, to have the same shape and size as A, and this was used as a workpiece. For reference, the 1\ lattice made of νJ construction and the lattice obtained by rolling this were designated as J and K, respectively.

These grids H1, J, and K were filled with live substances 5r by the packaging method and chemically formed to form a positive electrode plate, a negative electrode plate, a separator 9 (glass mat), and an o-electrolyte (kj with a specific gravity of 128). A storage pond with a capacity of about 3.3 AH was assembled using the same material as in tii) with a 10-hour rate discharge. These batteries can be charged at 0.10 for 336 hours and discharged at 0.3
The cycle was repeated until 1 cell was 0 and 1.75 cm, and the number of cycles until the capacity became 1/2 of the initial capacity was determined, and this was taken as the life span. The results are shown in Figure 3. From the figure, it can be seen that the storage battery using the grids H and J of the present invention is different from the conventional grid J.
, it is clear that the cycle life is improved compared to storage batteries using K. When the degree of corrosion of the positive electrode grid was investigated using another sample storage battery, it was confirmed that the oxidation loss was large in the order of ■(, ■, J, Saj, ta.

[Effects of the Invention] As shown in Examples I and Q.■, the lead alloy material produced by the method of the present invention is significantly inferior in corrosion resistance to the lead alloy material produced in the past. A storage battery that uses this as the electrode grid has an excellent effect of extending the lifespan compared to a conventional storage battery.

[Brief explanation of the drawing]

Part 1 (1): Schematic diagram showing the metal crystal structure of a cast product of lead-calcium alloy (2): Graph showing experimental data of Example (6)
: Graph showing the experimental data of Example ■
Masanobu Shibasaki, Par-1'-1 "7n u ÷ director lock °S^ wo (be 琥) Hagimi fu ii 4゜rami 蒐 ko + beak) enemy)

Claims (1)

[Claims] The surface of the lead-calcium alloy material is dissolved in a solution that dissolves only the surface part, and the dissolved surface part is
A lead alloy material for lead-acid batteries, characterized in that after one or more of tin, silver, molybdenum, tungsten and chromium is attached, the material is heat treated, rolled or otherwise processed. manufacturing method