JP4579514B2 - Manufacturing method of grid substrate for lead acid battery - Google Patents

Description

  The present invention relates to a method for manufacturing a grid substrate for a lead storage battery, and more particularly to a method for manufacturing a grid substrate used for a lead storage battery such as an automotive lead storage battery or various backup batteries.

  Conventionally, a lattice substrate of a lead storage battery has been manufactured by gravity casting, but recently, a manufacturing method of expanding a lead alloy plate or a strip in a process of continuation of processes has been widespread. A continuous casting method and a continuous casting / rolling method are applied to the manufacturing method of the plate or strip subjected to the expanding process. The continuous casting method is a method in which a raw material is directly cast by injecting and contacting a molten metal into a roll mold to be solidified. In this method, the molten metal has a normal cast structure on the side in contact with the roll mold, but the structure has a double structure, such as a fine structure including poor precipitation on the side in contact with the opposite air. The lattice substrate manufactured by expanding has a problem that it is not sufficient in terms of corrosion resistance and fatigue strength. In addition, the thin plate has difficulty in flatness and plate thickness uniformity, and there are problems of the lattice shape on the expanded lattice substrate and the distortion of the entire substrate.

  The continuous casting / rolling method is a method of continuously rolling in-line a plate in which molten metal has been continuously cast into a grooved casting ring, and intermittently pulling out a hardened shell by solidifying the molten metal in a mold. There is a method in which an intermittently drawn cast plate is made and then rolled to make a material.

In the ring casting / rolling method and the intermittent drawing casting / rolling method, an ingot having a crystal grain size of 500 μm or more is usually cold worked by 90% or more, and the structure becomes lamellar and scaly. The lattice substrate manufactured by expanding this material has a problem that it undergoes general corrosion and causes a large elongation of the lattice substrate. In addition, since residual stress during rolling remains in the thin plate, there is a problem in that the lattice shape becomes defective or distortion occurs in the subsequent expanding process. Furthermore, in this method, since rolling processing is performed , the thin plate has an advantage that the plate thickness is uniform and has good flatness, while cold rolling causes residual stress to remain, and the balance of residual stress is lost due to expansion processing. There was a problem that the lattice shape and the distortion of the whole lattice were bad.

  As a method for improving the above method, a method of performing tube extrusion, tearing, opening, and flattening by a Hanson-Robertson extruder has been proposed (Patent Document 1).

International Patent Publication WO 02 / 069421A2

  In the method described in Patent Document 1, since the lead alloy is extruded at a temperature equal to or lower than the melting point and quenched with cooling water immediately after the extrusion, the heterogeneous crystal structure of the continuous casting method can be improved. However, segregation occurs in the vicinity of the grain boundary, resulting in insufficient corrosion resistance and causing gloss (elongation) of the positive electrode.

  Further, since there is some misalignment between the die and the nipple, there is a problem that the plate thickness accuracy is poor due to the thickness fluctuation in the pipe. In addition, a slit is made at one end of the pipe, and thereafter flat processing is performed with a rubber roll or the like, but there is a problem that a thin plate with poor flatness with burr at both ends is present. This is because the rolling reduction by the rubber roll is less than 5%, so that the burr at both ends and the flatness are only slightly improved. In addition, since some distortion due to extrusion, opening, and flattening remains, there is a problem that in the expanding process, the balance of residual stress is lost, resulting in poor lattice shape and overall distortion.

  The present invention improves the flatness by controlling the initial crystal size by extrusion directly under the melting point and controlling the final crystal size by promoting recrystallization during hot rolling, reducing the concentration gradient (segregation at grain boundaries) during solidification, and reducing residual strain. In addition, a high-quality lead alloy that has improved age-hardening properties and improved long-term storage and long-term stability of strength, in particular, a lattice made of a Pb—Ca—Sn—Ba-based lead alloy with excellent corrosion resistance and gloss resistance An object is to provide a method capable of manufacturing a substrate with high quality.

In order to achieve the above object, the present invention relates to claim 1, wherein 0.02 mass% or more and less than 0.06 calcium (Ca) and 0.4 mass% or more and 2.5 mass% or less tin ( Sn), Pb—Ca—Sn—Ba based lead alloy consisting of 0.002% by mass or more and 0.06% by mass or less of barium (Ba) and the balance of lead (Pb) from the melting point to 10 ° C. to 100 ° C. Continuous extrusion in a low temperature range, and then rolling this at a temperature range of 50 ° C. to 230 ° C. below the melting point with a total rolling reduction of 10 to 98%, and further forming this on a lattice substrate by expanding. Features.

  Furthermore, in claim 2, the extruded shape continuously extruded in a temperature range lower by 10 ° C to 100 ° C than the melting point is a pipe shape, and after being extruded, one end is opened and the open portion is expanded and rolled. It is characterized by that.

  Further, in claim 3, the extruded shape is a pipe shape or U shape with one end opened.

  As the alloy composition, the content of Ca is preferably 0.02% by mass to less than 0.06% by mass, and particularly preferably 0.03 to 0.045% by mass from the viewpoint of corrosion resistance and mechanical strength.

  Ba contributes to the improvement of mechanical strength, and its content is preferably 0.002% by mass to 0.014% by mass. Coexistence of Ca and Ba further improves the corrosion resistance, and the interface between the lattice substrate and the active material coated and filled therein becomes dense, and the electrical conductivity between the lattice substrate and the active material via the corroded layer. A new effect that the battery is stably maintained over a long period of time is developed, and the life of the storage battery is further improved.

  The content of Sn is preferably 0.4% by mass to 2.5% by mass from the viewpoints of hot metal flow and mechanical strength. Sn is further eluted at the lattice interface during the charge / discharge of the storage battery and is doped into the corrosion layer, causing a semiconducting effect in the corrosion layer, increasing the conductivity of the lattice substrate and improving the life of the storage battery. -2.5 mass% is preferable.

  Furthermore, these Pb—Ca—Sn—Ba based lead alloys may contain some Ag, Bi, and Tl, and other inevitable impurities. The amount of Ag is 0.005 to 0.07 mass%, the amount of Bi is 0.01 to 0.1 mass%, and the amount of Tl is about 0.001 to 0.05 mass%. .

  According to the present invention, the alloy at a predetermined temperature is continuously extruded, rolled at a predetermined temperature range and at a predetermined total rolling reduction, recrystallized, and the grain size is appropriately densified, so that intergranular corrosion does not occur. Corrosion resistance can be greatly improved, internal residual stress can be reduced, flatness when expanded, and a high quality lattice substrate can be manufactured. Furthermore, since age-hardening can be improved, storage management of the material can be made unnecessary or simple, and manufacturing management and manufacturing cost can be reduced.

  A Pb—Ca—Sn—Bi lead alloy was prepared in the composition shown in Table 1, and continuously extruded from an extruder at a temperature of 300 ° C. As shown in FIG. 1, the extruded shape at this time is a pipe shape having a slit 1 formed at one end and opened, and the thickness is 2.5 mm and the outer diameter is 32 mm. Thereafter, the open portion was spread and cooled after continuous rolling with a rolling mill to produce a thin strip having a strip thickness of 0.9 mm and a width of 100 mm. The rolling is performed in multiple stages at a start temperature of 270 ° C. and an end temperature of 220 ° C., and the total rolling reduction is 64% ((2.5−0.9) /2.5×100).

  In Comparative Example 1, the composition alloy shown in Table 1 was prepared by the same method as in the above Examples, and in Conventional Example 1, Alloy No. A composition alloy described in G was produced by casting and rolling at a total rolling reduction of 98%. Conventional Example 2 is the same composition alloy as Alloy No. Conventional Example 1 at the extrusion temperature of 0.9 mm. This pipe is extruded, quenched, cut with a fixed cutter, and flattened.

About each obtained thin strip, the corrosion test was done and the corrosion weight loss and elongation rate (gloss) were measured. The results are shown in Table 2. In the corrosion test, a thin strip was cut into a size of 15 × 70 mm, and the anode was continuously used for 30 days at a constant potential of 1350 mV (vs. Hg / Hg ₂ SO ₄ ) in 60 ° C. sulfuric acid having a specific gravity of 1.28. After oxidation, the product oxide was removed and mass loss was measured. Elongation rate (gross) was expressed as a percentage by cutting a thin strip into 1.5 mm × 100 mm, treating it in the same manner as the mass loss evaluation described above, measuring its elongation, and dividing by the length before the test. .

  Next, each thin strip obtained is expanded, cut to a predetermined size to obtain a lattice substrate, and this is coated with a paste-like positive electrode active material, which is then placed in an atmosphere at a temperature of 40 ° C. and a humidity of 95%. After aging for a period of time, drying was performed to obtain a positive electrode unformed sheet. Next, the negative electrode unformed plate manufactured under the same conditions as the positive electrode is combined with the positive electrode unformed plate through a polyethylene separator, and further dilute sulfuric acid having a specific gravity of 1.200 is added to form a battery case. A liquid lead-acid battery having a 5-hour rate capacity of 40 Ah was manufactured, and a life test (light load test) according to JIS D5301 was performed on this lead-acid battery in an accelerated test at a test temperature of 75 ° C. The results are shown in Table 2.

  As is clear from Table 2, compared with the results of the comparative examples, the alloys used in the examples showed higher corrosion resistance and low gloss than the conventional alloys, and compared with the results of the conventional examples 1 and 2. And it turns out that each characteristic improves further by the method of this invention.

  The total rolling reduction is preferably 10 to 98%, and if it is less than 10%, the crystal grain size increases, resulting in a decrease in corrosion resistance. If it exceeds 98%, the tensile strength decreases and the corrosion resistance also decreases slightly.

  Further, the extruded shape may be a pipe shape having no slit or a U shape having a wide slit, and the pipe shape or the U shape having the slit shown above is particularly preferable.

Sectional drawing which shows the extrusion shape of embodiment of this invention

Explanation of symbols

  1. Slit

Claims (3)

0.02 mass% or more and less than 0.06 calcium (Ca), 0.4 mass% or more and 2.5 mass% or less tin (Sn), 0.002 mass% or more and 0.06 mass% or more The following barium (Ba) and Pb—Ca—Sn—Ba based lead alloy consisting of lead (Pb) as the remainder are continuously extruded in a temperature range lower by 10 ° C. to 100 ° C. than the melting point, and then extruded from the melting point to 50 ° C. A method for producing a grid substrate for a lead-acid battery, comprising rolling at a temperature in a temperature range lower than 230 ° C. and a total rolling reduction of 10 to 98%, and further forming this on a grid substrate by expanding. The extrusion shape continuously extruded in a temperature range lower by 10 ° C to 100 ° C than the melting point is a pipe shape, and after extrusion, one end is opened and the open portion is expanded and rolled. The manufacturing method of the grid | lattice board | substrate for lead acid batteries of claim | item 1. The method for manufacturing a grid substrate for a lead storage battery according to claim 2, wherein the extruded shape is a pipe shape or U shape with one end open.

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