JP2595809B2 - Method of manufacturing base for lead-acid battery electrode plate - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a lead-acid battery, and more particularly to a substrate used for an electrode plate of a lead-acid battery for an automobile.

[Conventional technology]

Conventionally, an electrode plate of a lead-acid battery for an automobile is composed of a power generating material obtained by kneading lead oxide powder, which is called an active material, with dilute sulfuric acid to form a paste, and a base material that holds the powder and serves as a current collector. Consists of elements. There are roughly two types of substrate manufacturing methods. One is a casting method, and the other is an expanding method. (Hereinafter, a substrate manufactured by the casting method is referred to as a “cast substrate”, and a substrate manufactured by the expanding method is referred to as an “expand substrate”). However, a continuous casting machine using a drum-shaped mold has recently been developed, and hundreds to thousands of substrates have been cast in a continuous form. In the expanding method, a lead alloy sheet is fed into an expander, the sheet is cut by a cutter, and the sheet is stretched at the same time to form a mesh, and thousands of substrates are continuously produced as in the case of a continuously cast substrate.

On the other hand, lead alloys used for these substrates are roughly classified into two types. That is, a Pb-Sb-based alloy containing 2-3 wt% of Sb and a Pb-Ca-based alloy containing 0.05-0.1% of Ca. The former is applied to the casting method, but is not used for the expanding method.

By the way, in order to withstand the vibrations received during handling during manufacture of the electrode plates and during mounting on the automobile, and also the forces received from the volume change of the active material due to charge and discharge, the base must also have the appropriate strength. Needless to say. The above alloys secure this by age hardening. This is Sb or Ca
This is based on the fact that the solid solubility of alloy elements such as Pb in Pb is large at high temperatures and extremely small at around normal temperature. That is, after the alloy element is sufficiently dissolved in Pb at a high temperature, for example, just below the melting point, the alloy is rapidly cooled to room temperature or lower to create a supersaturated state of the alloy element. Thereafter, by keeping the alloy at a temperature slightly higher than room temperature for an appropriate time, the alloy element is precipitated in the dough as particles of the alloy element alone or intermetallic compound. This increases the strength of the alloy because the precipitated particles act to hinder the transfer of the transition. What is important here is that the precipitated particle diameter and the distance between the particles are appropriate, and fine particles must be precipitated in a uniformly dispersed form. If the holding temperature after the quenching is too high or the holding time is too long, the precipitated particles will aggregate, and both the particle size and the particle interval will increase, resulting in a decrease in strength. This phenomenon is called overaging.

[Problems to be solved by the invention]

Due to exhaust gas purification measures and high output of the engine by installing a turbo or supercharger, etc., the temperature inside the engine room of recent automobiles, especially passenger cars, has become extremely high, and the ambient temperature of the lead acid battery for automobiles placed here It is not unusual to reach 90-100 ° C.

Such a temperature is close to the limit in various aspects for the above-mentioned lead alloy, and for this reason, there have been some problems caused by phenomena that have been regarded as not so important or not recognized at all conventionally, The situation is such that it is difficult to take measures. One of the biggest problems among them is the lack of strength of the substrate at high temperatures, especially creep strength.

When used as an anode, a Pb-Ca-based alloy substrate elongates during use of the battery, causing short-circuiting by contact with the adjacent cathode plate and promoting the fall of the active material to extend the life of the battery. It is well known that there is the problem of shortening. This is due to intergranular corrosion caused by the precipitation of intermetallic compounds (such as Pb ₃ Ca), but the force caused by the volume expansion of the corrosion product is applied to the above-mentioned lead alloy that constitutes the base. Is intolerable.

As described above, the Pb-Ca alloy is an age hardened alloy,
Attention must be paid to overaging, but if a battery is used at a temperature of 90 to 100 ° C., overaging occurs, and a reduction in the strength of the substrate is inevitable. In addition, at such a temperature, the progress of intergranular corrosion becomes remarkable, and the generated force becomes large.
The occurrence of “elongation” becomes more and more remarkable.

In the case of a Pb-Sb alloy, the problem of strength reduction due to overaging is exactly the same as in the case of a Pb-Ca alloy. Further, the following also contributes to insufficient strength at high temperatures.
Recently, lead-acid batteries for automobiles use Pb-Sb alloys for the anode and
Hybrid batteries using Pb-Ca alloys are becoming mainstream. This battery is inferior to a battery using a Pb-Ca-based alloy base (hereinafter referred to as a "calcium battery") in both the positive and negative electrodes, so that the Sb content in the anode base alloy is reduced by 1% in order to enhance this. Or it tends to be lower. The strength obtained by age hardening depends on the Sb content and decreases as the content decreases.
Therefore, such a movement lowers the strength of the Pb-Sb-based alloy substrate from the beginning, and it goes without saying that the strength is insufficient at high temperatures. Further, as the Sb content is reduced, the Pb-Sb-based alloy also exhibits electrochemical properties similar to those of the Pb-Ca-based alloy. Therefore, the same inconvenience as in the case of the Pb-Ca-based alloy substrate occurs, for example, the "elongation", which has not been considered a problem so much because it is extremely vague, becomes remarkable.

[Means for solving the problem]

In order to solve the above-mentioned problems, the strength of the lead alloy at a high temperature such as 90 to 100 ° C., especially the creep strength, must be increased. For this purpose, it is necessary to create a state in which fine particles are uniformly dispersed in an appropriate amount even at such a high temperature even under such a high temperature, and to prevent the transfer of the transition. The present invention utilizes a difference in solid solubility of Pb in a conventional base alloy to precipitate alloying elements, thereby securing strength. An oxide or sulfide powder having a small particle size is added, and the powder is uniformly dispersed to secure the strength. That is, by adding a powder such as the oxide to the Pb-Ca-based alloy or Pb-Sb-based alloy, even if the precipitated particles based on Ca or Sb under high temperature aggregate and exhibit an overaged state, The dispersed particles of the added powder compensate for the decrease in strength.

[Action]

At the time of casting the substrate, a powder of an oxide or a sulfide having a low solid solubility in Pb is added to the molten metal, and the strength can be ensured by uniformly dispersing the powder.

〔Example〕

 An embodiment of the present invention will be described.

FIG. 1 shows a method of casting a substrate by a continuous casting machine (belt caster) using a drum-shaped mold. The belt 3 is brought into contact with a drum 2 having a sculpture 1 corresponding to the shape of the substrate on the surface, and both are rotated. A part where the drum 2 and the belt 3 start to contact is a gate 4, and a molten metal 5 made of a lead alloy as a base metal is supplied to the gate 4. The molten metal 5 filled with the engraving 1 solidifies while being sandwiched between both the drum 2 and the belt 3, and forms a continuous substrate 6.
Is taken out as The powder 7 is added to a basin 8 formed at the gate. When the powder 7 is added, the powder 7 is injected into the molten metal 5 using a pressurized inert gas using a powder feeder 9.

The powder 7 to be added is required to have properties such as having a melting point sufficiently higher than that of Pb, a high rigidity, a good dispersibility in the molten metal 5 and being dispersed as fine particles having a diameter of about 0.5 μm or less. We have repeatedly studied from such a viewpoint, and found that ZrO ₂ , SnO ₂ , PbS, ThO _2, etc. meet the purpose of powder 7
Was found. For example, when a Pb-0.08Ca-0.5Sn alloy is cast at 520 ° C. and ZrO ₂ powder of 8 to 13 μm is added at 1.2% by volume, the average particle diameter is 0.21 μm and the average particle interval is 0.56 μm. Was. Such a dispersion state is Pb−0.08
The creep strength of the Ca-0.5Sn alloy is clearly improved, and the stress required to generate 1% strain in one year at 80 ° C. is 0.19 kg / mm when powder 7 is not added. ² , whereas that of powder 7 was 0.35 kg / mm ²
Met.

Since the specific gravity of each of the powders 7 is smaller than that of Pb, if the solidification rate of the molten metal 5 after addition is low, that is, if the time until solidification is long, the powder 7 floats and is difficult to be uniformly dispersed. In this regard, in the case of continuous casting shown in FIG. 1, the solidification rate is high, so that the method for strengthening a lead alloy according to the present invention can be easily applied. In addition, the fluidity of the molten metal 5 is also an important factor for uniformly dispersing the powder 7, and for example, the addition of Sn greatly increases the fluidity of the lead alloy, and is effective for uniform dispersion.

As an example of the present invention, a substrate in which the above four kinds of powders 7 were added to a Pb-0.065Ca-0.55Sn alloy was manufactured by continuous casting. The continuous caster used a belt caster as shown in FIG. The casting temperature of the molten alloy 5 is 550 ° C.
Drum 2 was supplied with 55 ° C. hot water, and the temperature was controlled.

As shown in FIG. 1, the powder 7 was directly added to the molten metal 5 poured from a ladle between the drum 2 and the belt 3. This is to prevent the powder 7 of the oxide or sulfide from floating on the surface of the molten metal 5 due to its lightness and not being dispersed in the molten metal 5 together with the oxide (dross) as described above. For reference, an experiment was also conducted on the method of adding the lead alloy to the molten metal 5 in the melting pot, and it was confirmed whether the effect of strengthening was reduced. Note that an argon gas was used to inject the powder 7 from the powder feeder.

The size of the substrate cast in this way is 115 mm long,
It is 145mm wide and 1.6mm thick. Using this substrate, a 55K23 type battery was manufactured, and a cycle life test of a charge / discharge pattern equivalent to the life test according to the SAE standard was performed at 80 ° C. At the end of 3000 cycles, the battery was disassembled and the elongation of the anode substrate was measured. .

Table 1 shows the results of examining the effect of the amount of addition on the four types of powders 7 described above.

The addition of the powder 7 to the molten metal 5 according to the present invention makes the elongation of the anode substrate less than about 1/2 of that of the non-added (conventional method) by adding 1 to 1.5 vol%. Although not shown in Table 1 above, in the electrode plate using the substrate manufactured by the method according to the present invention, the fall of the active material was clearly smaller than in the electrode plate using the substrate without the addition of powder.

Table 2 shows the effect of the addition method (addition time) on ZrO ₂ powder 7.

As is clear from Table 2, when the powder 7 is added to the melting tank, the powder 7 is trapped in the floating dross due to a difference in specific gravity, so that the amount of the powder 7 effectively acting to increase the dispersion is reduced. Is not obtained.

[Effects of the Invention] The present invention can suppress a decrease in strength of a base when a battery is used at a high temperature, and can reduce the elongation of the base to half or less of that of a conventional product. As a result, troubles such as short circuits are greatly reduced, and the reliability of the battery can be greatly improved.

Although the present embodiment has been described with respect to the continuous casting of the substrate, it goes without saying that the present invention is also applicable to the production of a lead alloy sheet used for an expanded substrate.

[Brief description of the drawings]

FIG. 1 shows a method of manufacturing a substrate according to the present invention.
(A) is a side view, (b) is a front view. 2 is a drum, 3 is a belt, 5 is molten metal, 6 is a substrate, 7 is powder, and 8 is a basin.

Claims (4)

(57) [Claims] 1. A method for producing a lead-acid battery electrode plate base, wherein a fine powder of an oxide or sulfide is added to a Pb or Pb alloy melt when the melt is poured into a mold. 2. A Pb or Pb alloy sheet is manufactured by adding a fine powder of oxide or sulfide to the molten Pb or Pb alloy when the molten Pb or Pb alloy is poured into a mold. A method for producing a base for a lead-acid battery electrode plate, wherein the substrate is subjected to working or punching. 3. The method according to claim 1, wherein the casting method of the base is continuous casting. 4. The method according to claim 2, wherein the method of casting the sheet is continuous casting.