JP2000182624A - Manufacture of lead-acid battery grating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the corrosion rate at a grating and to provide a lead-acid battery with excellent life properties by injecting a molten metal of a lead-tin- calcium alloy including calcium of a specific ratio into a mold, and by cooling at a specific rate to solidify the molten metal. SOLUTION: In this manufacturing method, it is preferable that a molten metal of a lead-tin-calcium alloy including calcium of 0.01 to 0.06 wt.% is injected into a mold and is cooled at a cooling rate of 27 deg/sec. or under for solidification. Grating-like engraving is applied to a pair of a molding material consisted of Meehanite cast iron buried with a cooling pipe, a lubricant is sprayed and a metal mold of a grating provided with a thermal barrier of 100 μm is attained. The temperature of the metal mold is maintained at 150 deg.C and the lead-tin-calcium alloy is injected and cooled. When calcium is 0.01 wt.%, the cooling rate is 23 deg/sec. and the grain boundary corrosion rate is 0.15 (mm/mm2); and when the cooling rate is 33 deg/sec., the grain boundary corrosion rate is 0.40 (mm/mm2). When calcium is 0.06 wt.%, the cooling rate is 23 deg/sec. and the grain boundary corrosion rate is 0.06 (mm/mm2); and when the cooling rate is 33 deg/sec. and the grain boundary corrosion rate is 0.28 (mm/mm2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a grid for a lead storage battery.

[0002]

2. Description of the Related Art In a sealed lead-acid battery, it is necessary to eliminate the need for water refilling. Therefore, self-discharge due to the generation of hydrogen gas on the negative electrode plate must be reduced as much as possible. For this reason, lead-calcium alloys are widely used for lattices. Also,
Recently, lead-tin-calcium alloys with added tin have been used to increase the corrosion resistance of this alloy.

There is a casting method as a method of manufacturing a grid for a lead-acid battery. In this method, usually, a molten metal of the alloy is poured into a mold, and water is poured into a water cooling tube engraved in the mold. Is cooled to solidify the molten metal and take out the solidified lattice from the mold.

[0004] When a lattice body is manufactured using the above alloy by this method, a lattice body having a different crystal size depending on the content of calcium is obtained, which has affected the life performance of a lead-acid battery using the lattice body. . That is, when an alloy having a large calcium content was used, the crystals were refined during casting, and the amount of corrosion increased (see FIG. 3). On the other hand, when the amount of calcium is small, the crystal becomes large at the time of casting, and the penetration rate of the corroded portion into the lattice during use of the battery (hereinafter, referred to as corrosion penetration) increases (see FIG. 2). Breakage became easy to occur. Therefore, calcium is generally 0.06 to
Lead-tin-calcium alloys containing about 0.1% by weight have been frequently used.

[0005]

However, using the above alloy, the conventional manufacturing conditions (the cooling rate of the molten alloy is about 33
g / sec), when a battery using a grid prepared as a positive electrode plate in a high-temperature atmosphere is used in a high-temperature atmosphere, intergranular corrosion of the alloy linearly penetrates into the inside, and the grid expands and breaks. Or the active material falls off from the lattice, leading to an early life. In order to solve such a problem, it has been desired that the lattice body has a longer life.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a lead-acid battery having excellent life performance by suppressing the degree of corrosion penetration of the grid.

[0007]

In order to achieve the above object, the present invention provides a method for injecting a molten metal of a lead-tin-calcium alloy containing 0.01 to 0.06% by weight of calcium into a mold, and applying 27 deg. The molten metal is solidified at a cooling rate of / sec or less.

[0008]

The present inventors have found that by lowering the cooling rate of the molten metal in the mold, it is possible to reduce the degree of corrosion penetration with a small calcium content. Therefore, when a lattice body manufactured by the method of the present invention is used for a lead storage battery by using an alloy having a smaller calcium content than before, the degree of corrosion penetration of the lattice body is reduced, and the life performance of the lead storage battery is excellent.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail.

[0010] A pair of mold members made of cast iron having a width of 400 mm, a height of 240 mm and a thickness of 40 mm, in which a cooling pipe is embedded, are formed of 140 mm wide, 225 mm high, 3.9 mm thick rib, and 3.9 mm thick rib cross-sectional area. A lattice body having a 3 mm ² , 2.0 mm thickness of the rib bone, and a 1.8 mm ² cross-sectional area of the rib bone, engraved with a grid material, sprayed with a sliding material mainly containing cork, and provided with a heat insulating layer of about 100 μm. Was prepared.

The temperature of the mold was raised to 150 ° C., and at this temperature, a molten metal of lead-0.06% by weight calcium-1.5% by weight tin alloy was poured, and various conditions were obtained under the conditions shown in Table 1. Solidified at the cooling temperature.

The cooling rate is a value obtained by dividing the difference between the molten metal temperature and the solidification temperature in the shortest time from the time when the molten metal is poured into the mold to the time when the molten metal is solidified without collapse.

[0013]

[Table 1]

The lattice prepared under the above conditions was treated with a specific gravity of 1.28.
d. A current is continuously supplied for 6 days under the conditions of a temperature of 60 ° C. and a current density of 0.02 A / cm ² , and the lattice section is observed with a metallographic microscope, and the length of grain boundary corrosion progressing inside the lattice is accumulated. Then, the intergranular corrosion penetration (mm / mm ² ) was determined. The result is shown in FIG. The number of data (n) at each cooling rate is 3.

FIG. 1 shows that the cooling rate is 27 deg / sec,
It can be seen that the intergranular corrosion penetration is preferably low at 25 deg / sec or less. Further, the content of calcium in the alloy was variously changed, and water cooling at 25 ° C. (1) in Table 1 was performed.
A lattice body was produced under the following conditions, and the degree of corrosion penetration and the amount of corrosion were examined in the same manner as described above. The results are shown in FIGS. In addition, the corrosion amount was represented by a corrosion amount relative value (%), where the corrosion amount of a lattice produced using a lead-0.1 wt% calcium-1.5 wt% tin alloy at a cooling rate of 33 deg / sec was 100. .

From these results, it was found that 0.01 to 0.06% by weight
It was found that when an alloy containing calcium was used and the cooling rate was slower than before, a lattice body with a lower corrosion penetration and a slightly smaller amount of corrosion than before was obtained.

Accordingly, from the results shown in FIGS.
Using a calcium-tin alloy of 6% by weight or less, 27deg
If the grid is manufactured at a cooling rate of not more than / sec, the grid can be formed with a low degree of intergranular corrosion penetration, and the lead storage battery using this grid has a long life.

When the amount of calcium is less than 0.01% by weight, the mechanical strength of the lattice body is weakened and the lattice is easily deformed, which is not practical. In addition, the present invention is not applied to pressure casting of a low-temperature molten metal such as pressure casting only in heavy casting.

[0019]

As described above, according to the present invention, it is possible to obtain a grid body having a lower degree of corrosion penetration than the conventional one and having almost the same amount of corrosion, thereby extending the life of the lead storage battery. Can be.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a cooling rate of a mold and a degree of corrosion penetration of a lattice body.

FIG. 2 is a graph showing the relationship between the calcium content and the degree of corrosion penetration of the lattice.

FIG. 3 is a graph showing a relationship between a calcium content and a corrosion amount (relative value) of a lattice body.

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Claims (1)

[Claims] 1. A molten metal of a lead-tin-calcium alloy containing 0.01 to 0.06% by weight of calcium is poured into a mold, and the molten metal is solidified at a cooling rate of 27 deg / sec or less. Of producing a grid body for a lead-acid battery.