JP2011046976A - Lead alloy for lead storage battery and lead storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide Sb-containing lead alloy for a lead storage battery, the alloy undergoing no deterioration in mechanical strength, corrosion resistance and castability even when an As content is reduced in consideration of the environment. <P>SOLUTION: In Pb-Sb-As alloy in which the content of As in an Sb-containing lead alloy for a lead storage battery is controlled to ≤0.09%, and the content of Sb is controlled to 1.7 to 3.5%, the mechanical strength, corrosion resistance and castability of the lead alloy can be remarkably improved by controlling the content of Ag to 0.0015 to 0.015%, controlling the content of Sn to 0.0015 to 0.015%, and controlling the mass ratio of Sb/As to ≤70. Further, by incorporating 0.0015 to 0.015% Cu therein, the various properties of the above lead alloy can be improved more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a lead alloy for a lead storage battery and a lead storage battery.

  Conventionally, lead alloys used for grids of lead-acid batteries and lead alloys for lead parts such as terminal bushings, connectors, straps or pole poles must have hardness and corrosion resistance according to the characteristics of the parts used. As such a lead alloy, Pb—Sb to which 1.5% by mass to 6.0% by mass of antimony (Sb) and 0.2% by mass to 0.5% by mass of arsenic (As) are added. -As alloys are generally used.

  Various technologies have been developed so far for Pb—Sb—As alloys used in lead-acid batteries, but many of these are other than Sb and As for improving the corrosion resistance of Pb—Sb—As alloys. The present invention relates to the study of other alloy components and their contents, and the reduction of the Sb content for the purpose of suppressing the reduction of water in the electrolyte.

  For example, in Patent Document 1, the Sb content is 1.6 mass% to 3.5 mass%, the As content is less than 0.2 mass%, the Sn content is 0.06 mass% to 1 mass%, Cu There has been proposed a lead alloy for a storage battery having a content of 0.002% by mass to 0.01% by mass, an Se content of 0.006% by mass to 0.1% by mass, and the balance being lead. In the lead alloy of Patent Document 1, even if the Sb content is reduced, the crystal grains of the lead alloy become fine and good corrosion resistance can be obtained, and the amount of oxide film generated on the molten metal surface is suppressed. It has been shown that material loss can be reduced.

  In the lead alloy disclosed in Patent Document 1, As content is limited to less than 0.2% by mass, As and its inorganic compounds are highly toxic to the human body and other organisms, and environmental health It is an unpreferable substance, and it is preferable to further limit the As content in order to reduce the environmental load. In particular, when a storage battery is manufactured using such a lead alloy containing As or when lead is recovered from such a storage battery, there is an unavoidable process of melting the lead alloy. May sublimate or may diffuse into the air as a fume containing As.

  Therefore, for the purpose of reducing the environmental load due to As in the lead alloy, the As content in the Pb—Sb alloy for the lead storage battery is further reduced, or a lead alloy not containing As has been studied. I came. However, merely reducing the As content in the Pb—Sb—As alloy does not provide the hardness required for the lead alloy for lead-acid batteries.

  In view of such a situation, in Patent Document 2, the As content is 0.095 mass% or less, Sb is contained, Sn is 0.001 mass% to 0.02 mass%, and Ag is 0.001 mass%. A lead alloy composed of ~ 0.02 mass% and the balance being lead has been proposed. According to such a composition, it is shown that even if the As content in the Pb—Sb-based lead alloy used in the lead storage battery is reduced, the hardness of the lead alloy is not lowered.

  Moreover, in patent document 3, As content is 0.1 mass% or less, Sb content is 0.7 mass%-3.0 mass%, Sn content is 0.001 mass%-0.02 mass%, Pb-Sb lead alloys for lead-acid batteries that have a Zn content of 0.001 mass% to 0.02 mass% and the balance consisting of lead have been proposed. According to such a composition, even when the As content is limited to 0.1% by mass or less, by specifying the contents of Sb, Sn and Zn in the lead alloy to the above values, the lead storage battery It has been shown that the required hardness can be obtained as a lead alloy.

JP-A-4-2055 JP 2008-266739 A JP 2009-68094 A

  According to Patent Document 2 and Patent Document 3 as described above, it has been shown that the decrease in the hardness of the alloy can be suppressed while reducing the As content in the Pb—Sb-based alloy. Compared with the Pb—Sb—As alloy containing 0.2% by mass to 0.5% by mass of As, the mechanical strength was inferior. Moreover, the corrosion resistance of the lead alloy is not yet sufficient, and it cannot be said that the castability is excellent.

  In the lead alloy for Pb-Sb lead storage battery containing Sb, the present invention reduces the environmental load by reducing As which has a strong toxicity to the living body, and has excellent mechanical strength and corrosion resistance. It is an object to provide a lead storage battery having excellent durability by using an alloy and this lead alloy.

  It is another object of the present invention to provide a lead alloy that is excellent in castability and advantageous in productivity at the time of producing a lead storage battery.

  In order to solve the above-described problems, the invention according to claim 1 of the present invention is a lead alloy for a lead storage battery having an Sb content of 1.7 mass% to 3.5 mass%, wherein the lead alloy As content of 0.09 mass% or less, the lead alloy contains 0.0015 mass% to 0.15 mass% Ag and 0.0015 mass% to 0.015 mass% Sn, and The lead is characterized in that the mass ratio (MSb / MAs) of the mass (MSb) of Sb contained in the lead alloy to the mass (MAs) of As contained in the lead alloy is 70.0 or less. The lead alloy for storage batteries is shown.

  The invention according to claim 2 of the present invention shows a lead alloy for a lead storage battery, characterized in that the lead alloy of claim 1 further contains 0.0015 mass% to 0.015 mass% of Cu. Is.

  Moreover, the invention which concerns on Claim 3 of this invention shows the lead acid battery provided with the lead alloy for lead acid batteries of Claims 1-2. In addition, as the use part of lead storage battery of lead alloy, it applies to the positive pole, the negative pole grid, the strap that collects and welds the same polarity electrode plate ear, the inter-cell connection parts, the terminal, and the pole column that connects the terminal and the cell. can do.

  Furthermore, the invention according to claim 4 of the present invention shows a lead storage battery characterized in that the lead alloy for a lead storage battery according to claims 1 to 2 is used for a strap formed by burning welding. Members used for lead-acid batteries, that is, members such as positive and negative grids, inter-cell connection components, terminals, and poles are manufactured by casting molten lead or rolling the cast product.

  On the other hand, the strap, particularly the strap formed by the burning method, heats the added lead with a high-temperature flame, so As in the lead alloy is more easily diffused than the above-described members. Therefore, in consideration of the environmental load at the time of manufacture, it is preferable to form the strap formed by the burning method.

  Furthermore, the invention which concerns on Claim 5 of this invention shows the lead acid battery which used the lead alloy of Claims 1-2 for any one of the pole pole and terminal components which are welded by burner welding mutually. According to this configuration, the generation of an oxide film containing As that occurs at the time of terminal welding and remains on the terminal surface after welding is suppressed, and the exposure amount of As outside the battery is suppressed, which is preferable in terms of the environment.

  According to the configuration of the present invention described above, although the content of As, which has been conventionally added to improve the mechanical strength with respect to the Pb—Sb alloy used in the lead storage battery, is reduced. Therefore, it is possible to ensure sufficient mechanical strength, corrosion resistance, and castability by actual use of the lead storage battery. Therefore, by reducing the content of As, the environmental load can be reduced, and mechanical strength and corrosion resistance superior to the conventional Pb-Sb alloy containing about 0.2% to 0.5% by weight of As. And the remarkable effect that the lead alloy of lead storage battery with castability can be applied is acquired.

  Moreover, the lead acid battery excellent in durability can be obtained by using the lead alloy for lead acid batteries by this invention.

(First embodiment)
The lead alloy for lead acid battery by the 1st Embodiment of this invention is a lead alloy containing 1.7 mass%-3.5 mass% Sb. The As content contained in the lead alloy for the lead storage battery of the present invention (hereinafter referred to as the lead alloy of the present invention) is 0.09% or less. The lead alloy of the present invention contains 0.0015 mass% to 0.015 mass% of Ag and 0.0015 mass% to 0.015 mass% of Sn. The mass ratio (MSb / MAs) of the mass (MSb) of Sb contained in the lead alloy of the present invention to the mass (MAs) of As contained in is defined in a range of 70.0. In the present invention, the present invention stipulates that the range of Sb content is 1.7 to 3.5% by mass and the range of As content is 0.09% by mass or less. The lower limit of the mass ratio (MSb / MAs) is uniquely 18.8.

  The inventor of the present invention, in the process of examining in detail the mechanism of mechanical strength improvement by adding As to the Pb-Sb alloy, the mass of Sb relative to the mass of As (MAs) contained in the Pb-Sb alloy ( It was found that the mass ratio of MSb) (MSb / MAs) strongly affects the mechanical strength of the lead alloy. In this invention, the said mass ratio (MSb / MAs) shall be 70.0 or less, and the intensity | strength of the Pb-Sb system lead alloy for lead acid batteries is raised.

  On the other hand, as a mechanism for increasing the strength of the Pb—Sb-based lead alloy, the inventors of the present invention have considered as follows in the above-described examination.

  That is, in the process where the melted Pb—Sb alloy is cooled and solidified, Pb crystals in which Pb and a small amount of Sb are dissolved are grown, and Sb is crystallized between the Pb crystals. When the solidification of the Pb-Sb alloy is completed, Sb is precipitated at the crystal grain boundary between the Pb crystal and the Pb crystal. As the Sb content in the lead alloy is reduced, the Sb crystals that are grain boundary precipitates are naturally reduced, so that the Pb crystal growth is not hindered by the Sb crystals that are grain boundary precipitates and is solidified. The subsequent Pb crystal grains are coarsened and the grain boundary thickness is reduced.

  Since Sb, which is a grain boundary precipitate, increases the bonding strength between Pb crystal grains and increases the strength of the lead alloy, it is important to grow Sb, which is a grain boundary precipitate, with a certain thickness. From this viewpoint, the Sb content in the Pb—Sb-based lead alloy is 1.7% by mass or more. Moreover, in the area | region where Sb content exceeds 3.5 mass%, since the liquid reduction performance of a lead storage battery falls by Sb eluted by the intergranular corrosion of lead alloy, and the amount of liquid reduction increases, Pb-Sb type | system | group Sb content in an alloy shall be 3.5 mass% or less.

  Then, when attention was paid to the correlation between the mass ratio (MSb / MAs) and the strength of the lead alloy, the Pb-Sb lead alloy having an Sb content of 1.7% to 3.5% by mass contained As. When the amount is 0.09% by mass or less, when the mass ratio (MSb / MAs) exceeds 70.0, As which becomes the nucleus of Sb crystals precipitated at the crystal grain boundary is insufficient, and Sb at the grain boundary is insufficient. The crystal size becomes coarse, the bonding strength between the Pb crystal grains decreases, and as a result, the strength of the lead alloy decreases.

  From the above, in the lead alloy for Pb-Sb lead storage battery containing 1.7 mass% to 3.5 mass% of Sb, the As content is set to 0.09 for the purpose of reducing the environmental load due to As. When the content is less than or equal to mass%, in order to ensure the mechanical strength of the lead alloy, the mass ratio (MSb / MAs) needs to be within the range of 70.0 or less.

  In addition, the inventors of the present invention have a Pb—Sb-based lead alloy that is equivalent to or better than that obtained by As present at a content of about 0.2% by mass to 0.5% by mass. In order to ensure corrosion resistance, a lead alloy containing 1.7% to 3.5% by mass of Sb and having an As content of 0.09% by mass or less should contain Ag in an amount of 0.0015% by mass or more. Has been found to be extremely effective. When the Ag content is less than 0.0015%, the corrosion resistance of the lead alloy is lowered. Therefore, in the present invention, the Ag content is set to 0.0015% by mass or more.

  In addition, in the Pb-Sb-based alloy having an As content of 0.09% by mass or less, in a region where the Ag content exceeds 0.015% by mass, no further improvement in corrosion resistance is observed, and excessive addition of Ag is corrosion resistance. In addition, since Ag itself is extremely expensive compared to lead, the price of the lead alloy becomes high, which is not practical. Therefore, in the present invention, the Ag content should be 0.015% or less.

  Furthermore, in the conventional Pb—Sb-based alloy containing As with a content of about 0.2% by mass to 0.5% by mass, As has an effect of improving the flowability of the molten alloy, When the As content is 0.09% by mass or less as in the present invention, the molten metal flowability of the molten alloy is lowered, and as a result, the castability is lowered. Deterioration of castability causes defects such as shrinkage cavities and cracks in lead parts such as grids, terminals, and connectors, resulting in poor casting and reduced yield in the casting process. Further, due to such casting defects, the mechanical strength and corrosion resistance of the parts are significantly reduced.

  In the lead alloy for the lead storage battery of the present invention, the Sn content is set to 0.0015 mass% to 0.015 mass%, thereby improving the castability of the lead alloy and caused by casting defects such as shrinkage cavities and cracks. Decrease in mechanical strength and corrosion resistance can be suppressed. As a result of improving the castability, the yield when casting a grid or a lead part from a lead alloy is improved, and at the same time, the mechanical strength and corrosion resistance of the lead part can be suppressed. In addition, since Sn containing more than 0.015 mass% cannot expect the effect of the further castability improvement, content of Sn should be 0.015 mass% or less. Further, if the Sn content is less than 0.0015% by mass, the effect of improving the castability cannot be obtained sufficiently, so the Sn content is set to 0.0015% by mass or more.

(Second Embodiment)
The lead alloy for a lead storage battery according to the second embodiment of the present invention further contains 0.0015 mass% to 0.015 mass% of Cu in the lead alloy for the lead storage battery according to the first embodiment. By containing such an amount of Cu, the growth of coarse Pb crystals is suppressed, and the mechanical strength and corrosion resistance of the lead alloy can be further improved.

  When the Cu content is less than 0.0015% by mass, there is substantially no difference from the lead alloy according to the first embodiment of the present invention. Further, if the Cu content exceeds 0.015 mass%, the liquid reduction amount and self-discharge amount of the lead storage battery increase, so the Cu content should be 0.015 mass% or less.

  The lead alloy for the lead storage battery according to the first and second embodiments of the present invention has a conventional As content in the Pb-Sb alloy used for the lattice, strap, connector, pole pole, and terminal component used for the lead storage battery. Since it is reduced compared to lead alloys, As is scattered in the atmosphere in the lead component manufacturing process and the lead recovery process from the lead-acid battery, the As exposure to the living body and the As emission to the environment are suppressed. It is suppressed and preferable from the viewpoint of environmental hygiene.

  Further, by reducing the As content, the reduction in strength, corrosion resistance and castability of the lead alloy, which has been conventionally generated, is suppressed by the present invention, and the reduction in As content, the strength and corrosion resistance of the lead alloy, and There is a remarkable effect that it is possible to provide a lead alloy for a lead storage battery having both excellent castability.

(Third embodiment)
By applying the lead alloy according to the first embodiment and the lead alloy according to the second embodiment to at least one of positive and negative grids, straps, connectors, pole posts, and terminal components, the lead of the present invention A storage battery can be obtained.

  Moreover, as a site | part using the lead alloy of this invention, it is preferable to apply to a strap, a connection body, a pole pole, and a terminal component in which a Pb-Sb system alloy is generally used, and especially the strap formed by the burning method. And most preferably applied to the pole and terminal parts joined together by welding.

  The strap formed by the burning method and the pole column and the terminal component joined to each other by welding heat the molten lead with a flame at the time of each formation, so the temperature of the molten lead is the temperature of the molten lead in the casting (450 ° C ~ This is because the As is easily diffused into the environment because the temperature is higher than (550 ° C.) (about 600 ° C. to 1200 ° C.).

  In particular, in the burning method, in order to strengthen the welding between the strap and the electrode plate ear, or between the strap and the connection body or the pole column, the molten lead is moved by moving the torch that releases the welding flame or by the discharge pressure of the welding flame. Since the temperature of the molten lead is likely to rise and the oxide film is likely to be generated due to the oscillation, As in the lead alloy is sublimated or welded fume (formed on the surface of the molten metal). As is contained in the smoke-like oxide in which the oxide is blown off as a powder), As is diffused into the atmosphere.

  Therefore, the lead acid battery according to the preferred embodiment of the present invention is a lead acid battery in which the lead alloy according to the first or second embodiment is applied to a strap formed by the burning method, and the lead according to the first or second embodiment. A lead-acid battery used for a pole column and a terminal component joined by welding the alloys together is also preferable.

  Moreover, it is preferable also for the lead storage battery which uses the lead alloy of this invention for any one of a pole pole or the terminal components connected to this, and welds both by burner welding. In such a lead storage battery, the amount of As scattered during burner welding can be reduced. Moreover, generation | occurrence | production of the oxide film containing As which covers the terminal after completion | finish of welding is suppressed, and exposure of As on the terminal surface is suppressed, and it is preferable.

  Moreover, you may apply the lead alloy by the 1st or 2nd embodiment of this invention to the connection body and / or pole column which connect electrode board groups. In both the burning method and the caston method, the connection body is formed by casting. When the lead alloy of the present invention is applied to a connection body, a lead storage battery having few casting defects and excellent in strength and corrosion resistance can be obtained. Moreover, melting of the connecting body and the pole pole, that is, suppressing the release of As into the atmosphere when melting the lead alloy in the parts casting process at the time of lead acid battery manufacturing and the process of regenerating and recovering lead from the lead acid battery it can.

  Moreover, the lead alloy according to the first embodiment or the second embodiment of the present invention can be applied to the positive grid and / or the negative grid. Since the lead alloy of the present invention is excellent in strength, by using both the positive electrode and the negative electrode, deformation of the electrode plate can be suppressed, an electrode plate excellent in mechanical strength can be obtained, and the reliability of the lead storage battery can be improved. Can do.

  In particular, when used in a positive electrode grid, a highly reliable lead storage battery can be obtained due to the excellent corrosion resistance of the lead alloy of the present invention.

  On the other hand, when the lead alloy of the present invention, which is a Pb—Sb alloy, is used for the positive electrode lattice and / or the negative electrode lattice, the life of the lead storage battery is reduced by the action of Sb contained in the lead alloy although it has a long life. Since the liquid increases, rehydration work is required.

  Therefore, in the present invention, the lead alloy of the present invention is not used for the positive electrode lattice and / the negative electrode lattice, and the Sb-free Pb—Ca alloy or Pb—Sn alloy is used. The lead alloy of the present invention may be used for at least one of the above. However, in such a case, the Pb—Ca alloy or the Pb—Sn alloy used as the lattice alloy, like the lead alloy of the present invention, does not impair the environmental load reduction effect due to the reduction of the As content of the present invention. The content of is 0% by mass or, if included, should be limited to 0.09% by mass or less.

  Since the As content of the lead alloy used in the lead storage battery of the present invention is reduced, the release of As into the environment in the production or recovery process is suppressed, which is preferable in terms of environmental hygiene. Moreover, although the As content is significantly reduced as compared with the conventional lead alloy for lead-acid batteries, the conventional As is 0.2 mass% or more in terms of strength, corrosion resistance and castability of the lead alloy. The lead alloy containing 0.5% by mass has no inferiority, and has a remarkable effect that a highly reliable lead storage battery can be manufactured with a high yield.

Example 1
Hereinafter, the effects of the present invention will be described with reference to examples.

  In this example, as shown in Table 1, lead alloys for lead storage batteries containing Sb, As, Ag, Sn, and Cu with various contents were prepared for the Pb—Sb alloy. The content of Sb, As, Sn and Cu contained in these lead alloys and the ratio (MSb / MAs) of the mass (MSb) of Sb contained in the lead alloy to the mass of As (MAs) contained in the lead alloy Table 1 shows.

  In the Vickers hardness measurement specified in JIS Z2244 “Vickers Hardness-Test Method”, the mechanical strength of each lead alloy shown in Table 1 was set to 10 gf (0.098 N) at the time of measurement. It was evaluated by a thickness test.

  Moreover, the corrosion resistance of each lead alloy of Table 1 was performed by the following method. That is, each lead alloy was melted, and a plate-shaped test piece having a width of 80 mm, a height of 80 mm, and a thickness of 1.0 mm was produced by casting. Separately from the plate-shaped test piece, a pure lead plate (Pb content 99.999 mass%) having a width of 80 mm, a height of 80 mm, and a thickness of 1.0 mm was prepared.

  The plate-like test piece was packed into a bag with a separator made of microporous polyethylene having a thickness of 1 mm. A pure lead plate was placed on both sides of the separator and stored in an acrylic container to form a model cell.

Dilute sulfuric acid with a density of 1.30 g / cm ³ (25 ° C. converted value) was poured into an acrylic container. The liquid level of the dilute sulfuric acid was 30 mm above the upper end of the plate-shaped test piece. Then, continuous energization was performed using the plate-like test piece as the anode and the pure lead plate as the cathode. The current density during energization was set to 0.5 mA / cm ² based on the area of the plate-shaped test piece. The energization period was 60 consecutive days. During energization, the model cell was placed in a thermostat controlled at 75 ° C. When the dilute sulfuric acid liquid level of the model cell was lowered, ion exchange water was appropriately replenished so that the dilute sulfuric acid liquid surface did not fall below the position of 5 mm above the upper end of the pure lead plate.

  After the continuous energization for 60 days, the plate-like test piece was washed with water. Thereafter, the working electrode was washed with water and then immersed in an alkaline aqueous solution of mannitol to remove the corrosive matter generated on the surface of the plate-shaped test piece, and then washed with water and dried.

  Next, the mass (W1) of the plate-like test piece from which the corrosive substance was removed was weighed. The difference (W0-W1) between the plate-like test piece mass (W0) weighed in advance before energization and the mass (W1) of the plate-like test piece after energization is determined as the corrosion amount. The percentage of the test piece mass (W0) was calculated as corrosion weight loss, and the corrosion resistance was evaluated based on the amount of the corrosion weight loss. The smaller the corrosion weight loss of the lead alloy, the better the corrosion resistance. Evaluation results of Vickers hardness and corrosion weight loss using this plate-like test piece will be described later.

  Further, a lead storage battery grid was cast using each lead alloy shown in Table 1. The castability of each lead alloy was evaluated based on the rate of occurrence of casting defects such as broken bones in the casting grid and defective nests. In addition, the defect of bone breakage was confirmed by visual observation that the molten lead alloy did not sufficiently flow into the digging portion of the frame bone and the middle bone of the lattice casting mold, and the frame bone and the middle bone became discontinuous in the middle. .

  Further, when each lattice after visual confirmation was bent into a V-shape, one that was cut at the bent portion or one that had a crack that could be visually confirmed at the bent portion was regarded as a poor nest. In addition, regarding the count of casting defects, when bone breakage defects and shrinkage defects occur simultaneously on one lattice, when bone breakage defects only occur, when shrinkage defect only occurs and In the case where neither a bone defect nor a hollow defect occurred (non-defective product), the occurrence rate of the lattice excluding the non-defective product was calculated as a defective casting rate.

  Table 2 shows the measurement results of Vickers hardness, corrosion weight loss and casting defect rate of each lead alloy shown in Table 1.

  The lead alloy 1 contains 1.7% by mass of Sb and 0.2% by mass of As, respectively, and the lead alloy 2 contains 3.5% by mass of Sb and 0.2% by mass of As. It is a comparative example, and is a Pb—Sb—As alloy generally used as a lead alloy for a lead storage battery.

  The lead alloys 3 to 38 change the Sb content in the range of 1.7 mass% to 3.5 mass% and the As content in the range of 0.025 mass% to 0.09 mass%. Lead alloy.

  Comparing the Vickers hardness of each lead alloy shown in Table 1, the ratio (MSb / MAs) of Sb mass (MSb) and As mass (MAs) contained in the lead alloy is 70 or less. It can be seen that even when As is 0.095% by mass or less, the strength equivalent to that of lead alloys 1 and 2 having a conventional As content of 0.2% by mass can be obtained. That is, it is possible to obtain both the effect of mitigating the environmental load and the effect of suppressing the decrease in mechanical strength of the lead alloy by reducing the As content in the Pb—Sb alloy.

  On the other hand, the ratios (MSb / MAs) in the lead alloys 21, 22, 24, 28, 37 and 38 are 85, 85, 83.3, 80, 78 and 78, respectively, according to the results shown in Table 2. For example, the Vickers hardness of each of these lead alloys is smaller than that of the lead alloys 1 and 2 of the comparative example, indicating that the mechanical strength has decreased.

  As a factor for reducing the strength of such a lead alloy, when the ratio (MSb / MAs) ratio exceeds 70, when the lead alloy is rapidly cooled from a molten state, there is very little As for Sb. It is presumed that the crystal grain size of Sb, which is a grain boundary precipitate that precipitates, becomes coarse and the strength of the grain boundary precipitate itself decreases, or the bond strength between the grain boundary precipitate and the lead crystal decreases.

  Therefore, in order to suppress a decrease in the strength of the lead alloy by reducing the amount of As in the Pb—Sb alloy, at least the above ratio (MSb / MAs) should be 70 or less.

  Moreover, it is the lead alloy which does not contain Ag and Sn, or contains either one or the ratio (MSb / MAs) ratio exceeds 70, that is, lead alloys 3 to 5, lead alloys 8 to 9, lead alloy 12 -14, lead alloys 17-18, lead alloys 21-22, lead alloy 24, lead alloys 28-30, lead alloys 33-34 and lead alloys 37-38 contain both Ag and Sn, or the ratio (MSb / MAs), compared to lead alloys with 70 or less, the corrosion weight loss increased and the casting defect rate increased.

  From the above results, among lead alloys with reduced As content, the mechanical strength of lead alloys decreases, corrosion resistance decreases (increased corrosion weight loss), and castability decreases (increased casting defect rate). Was recognized. Therefore, it is presumed that As added to the Pb—Sb alloy has the effects of improving the mechanical strength of the lead alloy, improving the corrosion resistance of the lead alloy, and improving the castability.

  On the other hand, the ratio (MSb / MAs) is 70 or less, the As content in the lead alloy is 0.09% by mass or less, and the lead alloys 6, 10, 15 and Ag containing Ag and Sn in the lead alloy. Nos. 19, 22 to 28, 31, 35 and 38 have Vickers hardness at a level sufficient as a lead alloy used for a lead storage battery, and corrosion weight loss and casting defect rate are suppressed to a low level. From this, in this invention, it is thought that the corrosion resistance and castability fall by As content reduction can be suppressed by making Ag and Sn coexist in a lead alloy.

  From the above, for the purpose of reducing the environmental load, As added to the Pb—Sb lead alloy for lead-acid batteries is reduced to 0.09% or less, which is a level at which the influence on the environmental load hardly poses a problem. In this case, in order to obtain a practical mechanical strength, corrosion resistance and castability as a lead alloy for a lead storage battery, the ratio (MSb / MAs) is set to 70 or less, and 0.0015% by mass to 0.015% by mass. % Ag and 0.0015% by mass to 0.015% by mass Sn can be obtained by coexisting only one of Ag and Sn. Cannot be obtained.

  Therefore, in order to obtain the effect of the present invention, it is necessary to set the ratio (MSb / MAs) to 70 or less and to allow Sn and Ag to coexist in the lead alloy.

  And in this invention, Ag content in a lead alloy shall be the range of 0.0015 mass%-0.015 mass%. When the Ag content is less than 0.0015%, the mechanical strength and the corrosion resistance are lowered. On the other hand, even if the Ag content exceeds 0.015 mass, there is no further effect on the improvement of mechanical strength and corrosion resistance, and further, the cost increase due to the Ag increase can be an obstacle, so the upper limit of the Ag content Should be 0.015% by weight.

  Further, the Sn content is also set to 0.0015 mass% to 0.015 mass% for the same reason as Ag. When Sn content is less than 0.0015%, the effect of improving mechanical strength and corrosion resistance cannot be obtained. On the other hand, if the Sn content exceeds 0.015% by mass, there is no further effect on the mechanical strength and corrosion resistance, but rather the liquid reduction amount and the self-discharge amount of the lead storage battery are increased.

  Furthermore, in the lead alloy of the present invention, the lead alloys 7, 11, 16, 20, 32, and 36 containing 0.0015 mass% to 0.015 mass% of Cu are the lead alloys 6 and 6 of the present invention that do not contain Cu. Compared with 10, 15, 19, 31, and 35, Vickers hardness is improved, and corrosion weight loss and casting failure rate are further suppressed. Therefore, in this embodiment, the lead alloy is most preferable as a lead alloy. I understand that.

  In addition, Cu content should be in the range of 0.0015 mass%-0.015 mass%. If the content is less than 0.0015%, the effect of improving the mechanical strength and corrosion resistance due to the Cu content cannot be obtained. Since addition of Cu exceeding 0.015 mass% increases self-discharge and liquid reduction of the lead storage battery, the upper limit of the Cu content should be 0.015 mass%.

  According to the present invention, in the lead alloy containing Sb for lead-acid batteries, the As content can be reduced to 0.09% by mass or less, so a lead alloy with reduced environmental load is obtained, and this lead alloy is used. As a result, the emission of As into the environment during the production of the lead storage battery and the lead recovery process from the lead storage battery is suppressed. In addition, a lead alloy having mechanical strength equal to or higher than that of a conventional lead alloy containing a large amount of As of about 0.2% by mass and excellent in corrosion resistance and castability can be obtained.

  Furthermore, the lead storage battery excellent in durability can be obtained by using the lead alloy of this invention for a grating | lattice, a strap, a connection body, a pole pole, and a terminal.

(Example 2)
As Example 2, the lead alloy 1 (comparative example) of Example 1 and the lead alloy 6 (example of the present invention) were added as lead, and a strap was formed by the burning method and the caston method. In any strap, an oxide film containing As is formed on the surface of the molten metal exposed to air. The thickness of the oxide film containing As is the thickness of the oxide film formed on the surface of the strap by the burning method of lead alloy 1. Is 1, the thickness of the oxide film containing As produced on the surface of the strap 2 of the lead alloy 1 by the Caston method was 0.2.

  On the other hand, the thickness of the oxide film formed on the surface of the strap by the burning method of the lead alloy 6 (example of the present invention) is 0.2, and the thickness of the oxide film generated on the strap surface by the Caston method is 0.15. In the strap using the lead alloy 6 of the present invention, the formation of an oxide film on the surface was suppressed, and the reduction effect was particularly remarkable in the strap by the burning method. Moreover, the As content contained in the oxide film produced from the lead alloy 1 and the lead alloy 2 correlates with the content of As in the lead alloy, and the strap formed by the burning method particularly of the lead alloy of the present invention. By applying to an alloy, it can be understood that the production of oxides containing As produced during strap welding is suppressed, which is preferable from the viewpoint of environmental hygiene, that is, the exposure of As to workers is suppressed.

(Example 3)
Lead alloy 1 and lead alloy 6 shown in Table 1 in Example 1 were cast to prepare two types of terminal bushings for terminal bushings (for tapered terminals specified by JIS D5301 (lead storage battery for starting)).

  Next, a pole column suitable for the terminal bushing described above was prepared by casting using lead alloy 1 and lead alloy 6.

  With the combination of the terminal bushing and the pole column shown in Table 3, the tip of the pole column is inserted into the through hole formed in the terminal bushing, and the pole column protrudes at a height of 3.0 mm from the top surface of the terminal bushing. These were welded to form a terminal. As a method of forming the terminal, with the lead bushing die placed on the side surface of the terminal bushing, a burner flame is emitted to the top surface of the terminal bushing, and the heat of this flame causes the top surface of the terminal bushing to contact the pole. The melting point of the lead alloy on the top of the terminal bushing and the tip of the pole column protruding from it, with the burner welding that melts and solidifies the tip of the pillar, and the lead outflow prevention mold placed on the side of the terminal bushing A terminal using a welding method (hereinafter referred to as heating body welding) in which the terminal bushing and the pole column are melted by welding a cylindrical heating body whose bottom surface is kept in a circular plane and maintained at the above temperature. Formed.

  EPMA analysis of the thickness of the oxide film on the terminal top surface and As in the oxide film when the terminal was formed by the combination shown in Table 3 with the lead alloy and terminal welding method described above was performed. These results are shown in Table 4. The thickness of the oxide film is the maximum value in the same terminal, the lead alloy 1 is used for both the terminal bushing and the pole column, and the maximum thickness of the oxide film at the terminal welded by burner welding is 1. Shown as a relative value. As for As in the oxide film, the detection peak value of As in EPMA was compared. The detection peak value is a relative value when the detection peak of As detected by the oxide film of the terminal using the lead alloy 1 for both the terminal bushing and the pole column and welding both by burner welding is 1. It showed in.

  From the results shown in Table 4, by using the lead alloy of the present invention for one or both of the terminal bushing and the pole pole, the thickness of the oxide film containing As on the terminal top surface is reduced, and the oxide film It can be seen that the amount of As also decreased. Moreover, these reduction amounts are especially larger in the burner welding than in the heating body welding, and it can be seen that the effects of the present invention are obtained more remarkably.

  From Example 3, by configuring the lead storage battery using the lead alloy for the lead storage battery of the present invention for the terminal and / or the pole, the exposure amount of As in the portion exposed to the outside of the lead storage battery can be reduced, A lead-acid battery with reduced environmental load can be provided. In addition, the strength of the terminal of the lead storage battery thus obtained is at least equal to that of a terminal composed of the conventional lead alloy 1.

  In addition, the lead alloy for the lead storage battery of the present invention has the same strength or castability as that of the conventional lead alloy, and has superior corrosion resistance compared to the conventional lead alloy. It can be used for an inter-cell connection body or a lattice body.

  When a Pb—Sb-based alloy is used for the positive electrode lattice, a long-life lead-acid battery can be obtained due to the positive electrode active material modification effect by Sb and the effect of improving the bonding force between the active material and the positive electrode lattice. However, since Sb in the positive electrode lattice moves to the negative electrode, the self-discharge characteristic and the liquid reducing characteristic of the lead storage battery may be deteriorated. Therefore, the lead alloy of the present invention may be used for the positive electrode grid in accordance with required self-discharge characteristics and liquid reduction characteristics.

  The lead alloy of the present invention can also be used for the negative electrode lattice of the lead storage battery. However, as in the case where the lead alloy of the present invention described above is used for the positive electrode grid, the presence of Sb in the lead alloy may reduce the self-discharge characteristics and the liquid reduction characteristics of the lead storage battery. Therefore, the lead alloy of the present invention may be used for the negative electrode grid according to the required self-discharge characteristics and liquid reduction characteristics.

  According to the configuration of the present invention, the As content in the lead alloy can be reduced without reducing the mechanical strength, corrosion resistance, and castability required for the lead storage battery, and the environmental load due to As can be reduced. Moreover, the lead alloy of the present invention can be applied to parts such as terminals, pole columns, straps, connectors, and grids. Moreover, such a lead storage battery can be applied to various uses such as a lead storage battery for start-up and a lead storage battery for cycle service.

Claims (5)

A lead alloy for a lead-acid battery having an Sb content of 1.7 mass% to 3.5 mass%,
As content of the lead alloy is 0.09 mass% or less,
The lead alloy contains 0.0015 mass% to 0.15 mass% Ag and 0.0015 mass% to 0.015 mass% Sn,
In addition, the mass ratio (MSb / MAs) of the mass (MSb) of Sb contained in the lead alloy to the mass (MAs) of As contained in the lead alloy is 70.0 or less. Lead alloy for lead-acid batteries. The lead alloy for a lead-acid battery according to claim 1, comprising 0.0015 mass% to 0.015 mass% Cu. The lead acid battery provided with the lead alloy for lead acid batteries of Claims 1-2. The lead acid battery which used the lead alloy for lead acid batteries of Claims 1-2 for the strap formed by burning welding. The lead acid battery which used the lead alloy for lead acid batteries of Claims 1-2 for any one or both of the pole pole and terminal which are welded mutually by burner welding.