Ultrathin corrosion-resistant lead belt and forming method

Abstract

The invention discloses an ultrathin corrosion-resistant lead belt and a forming method, and relates to the technical field of lead-acid power batteries, and the forming method comprises the following steps: step 1, continuously rolling a blank lead belt to obtain an ultrathin lead belt; secondly, the ultra-thin lead belt is subjected to heating drying tunnel treatment and vibration treatment, grains are refined, and the ultra-thin corrosion-resistant lead belt is obtained; according to the lead belt, the size in the MD direction is refined by treating coarse grains in the MD direction, so that the overall refining of the grains is realized, and the grain sizes in all directions of the lead belt are consistent, so that uniform corrosion in all directions during corrosion is ensured, the phenomenon that corrosion in one direction is faster than corrosion in other directions is avoided, and the corrosion resistance of the material is improved.

Description

Technical Field

[0001] The invention relates to the technical field of lead-acid power batteries, and in particular to an ultra-thin corrosion-resistant lead strip and a forming method thereof. Background Art

[0002] Lead-acid power batteries are widely used in the electric bicycle industry, accounting for more than 90%, occupying the electric bicycle power battery market with an absolute advantage.

[0003] In the production process of lead-acid power batteries, the grid forming generally relies on the traditional gravity casting process. This process is still widely used today because of its mature technology and wide application of molds. However, with the emergence of continuous production processes, continuous casting and rolling + punching, continuous casting and mesh and other processes have been rapidly promoted and used in lead-acid power batteries. Among them, the thickness of the traditional gravity casting grid is generally 1mm to 3.5mm. It is difficult to form if it is thinner, and the efficiency will be much lower. The thickness of the grid of continuous casting and rolling + punching can be as thin as 0.5mm, and the efficiency is very high, which is more than 10 times that of gravity casting.

[0004] Continuous casting and rolling + stamping has the advantage of efficiency, and it is also an effective means to reduce the cost of batteries. However, with the thinning of the grid thickness, the corrosion resistance of the positive grid of lead-acid batteries has become prominent. At present, the more common design of positive grid stamping is: the thickness of the positive grid is 0.8mm~1mm, and it is made into a lead strip by continuous casting and rolling, and then punched into a designed grid with a die. The lead strip of continuous casting and rolling generally adopts 7 continuous rolling, and the blank lead strip of about 13mm is rolled through 7 rollers with a thickness of 0.8mm~1mm. Continuous casting and rolling mainly causes the grain boundaries of the lead strip to slip and recrystallize by rolling, thereby achieving grain refinement to improve corrosion resistance. The service life of the grid using this lead strip is 1 to 2 years. However, the battery that needs to have a longer life cannot meet the requirements of 3 to 4 years using this ordinary continuous casting and rolling lead strip.

[0005] Lead strip continuous rolling production is a continuous rolling process, in which the lead strip is extended along its machine direction (MD) in the equipment (usually a rolling mill). Due to this continuous extension, the grains of the lead strip will also be elongated along the MD direction to form an elongated grain structure; in the length direction, the grains become "coarse" due to being elongated. This morphology will reduce the strength and creep resistance of the material, and the corrosion resistance will not meet the requirements of long-term use.

[0006] In view of this, it is particularly important to develop an ultra-thin corrosion-resistant lead strip and a forming method. Summary of the invention

[0007] The purpose of the present invention is to provide an ultra-thin corrosion-resistant lead strip and a forming method to solve the problem that the lead strip grains become "coarse" due to elongation, which reduces the strength and creep resistance of the material, and the corrosion resistance does not meet the requirements of long-term use.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] A method for forming an ultra-thin corrosion-resistant lead strip comprises the following steps:

[0010] Step 1, continuously rolling the blank lead strip to obtain an ultra-thin lead strip;

[0011] Step 2: subjecting the ultra-thin lead strip to a heating oven treatment and a vibration treatment to refine the grains and obtain an ultra-thin corrosion-resistant lead strip.

[0012] As a further solution of the present invention: the thickness of the blank lead strip is 10mm-13mm, and it is rolled into an ultra-thin lead strip through continuous 9 rolling, wherein the thickness of the ultra-thin lead strip is 0.3mm-0.8mm.

[0013] As a further solution of the present invention: the heating oven treatment and the vibration treatment are carried out simultaneously.

[0014] As a further solution of the present invention: the temperature of the heating oven treatment is 300° C. to 310° C., and the treatment time is 5 min to 15 min.

[0015] As a further solution of the present invention: the vibration treatment adopts a mechanical vibration table for vibration, the vibration frequency is 1000HZ~3000HZ, the amplitude is 1mm~2mm, and the treatment time is 1min~10min.

[0016] As a further solution of the present invention: an ultra-thin corrosion-resistant lead strip is formed using the above-mentioned forming method of an ultra-thin corrosion-resistant lead strip, and its thickness is 0.3mm to 0.8mm.

[0017] Beneficial effects of the present invention:

[0018] The present invention refines the size of the MD direction by processing the "coarse" grains in the MD direction, thereby achieving overall grain refinement, thereby increasing the number of grain boundaries in the fine-grained material, having higher strength and hardness, and making the grain size in all directions of the lead strip consistent, thereby ensuring uniform corrosion in all directions during corrosion, and preventing one direction from corroding faster than other directions, thereby improving the corrosion resistance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below in conjunction with the accompanying drawings.

[0020] Figure 1It is a schematic flow diagram of the molding method of the present invention;

[0021] Figure 2 is a schematic diagram of the crystal structure of the untreated lead strip of the present invention under an electron microscope;

[0022] Figure 3 It is a schematic diagram of the crystal structure of the lead strip treated by the present invention under an electron microscope. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Embodiment 1

[0025] like Figure 1 As shown, this embodiment provides a method for forming an ultra-thin corrosion-resistant lead strip, the method comprising the following steps:

[0026] Step 1, continuously rolling the blank lead strip to obtain an ultra-thin lead strip;

[0027] Step 2: subjecting the ultra-thin lead strip to a heating oven treatment and a vibration treatment to refine the grains and obtain an ultra-thin corrosion-resistant lead strip.

[0028] Specifically, in step one, the thickness of the blank lead strip is about 10 mm to 13 mm, and it is rolled into an ultra-thin lead strip through 9 consecutive rolling processes, wherein the thickness of the ultra-thin lead strip is 0.3 mm to 0.8 mm. Through continuous rolling, the grain boundaries of the lead strip are caused to slip and recrystallize, thereby achieving grain refinement to improve corrosion resistance.

[0029] More specifically, the temperature of the heating oven treatment in the above step 2 is 300°C to 310°C. Since the melting point of the lead alloy is 327°C, 300°C to 310°C is close to its melting point, and the crystals begin to recrystallize, which is similar to the metal heat treatment method, and the time is 5min to 15min.

[0030] Furthermore, the heating and drying tunnel treatment and the vibration treatment are carried out simultaneously, and the vibration treatment is carried out during the heating and drying tunnel treatment.

[0031] At the same time, high-frequency vibration treatment uses a mechanical vibration table for vibration treatment, with a vibration frequency of 1000HZ~3000HZ, an amplitude of 1mm~2mm, and a treatment time of 1min~10min, so that the grains of the ultra-thin lead strip in step one are further refined and its corrosion resistance is further improved.

[0032] Lead strip continuous rolling production is a continuous rolling process, in which the lead strip is stretched along its machine direction (MD) in the equipment (usually a rolling mill). Due to this continuous stretching effect, the grains of the lead strip are also elongated along the MD direction to form an elongated grain structure; in the length direction, the grains are elongated and become "coarse", and this morphology will reduce the strength and creep resistance of the material;

[0033] In this embodiment, the size of the grains in the MD direction is refined by processing the "coarse" grains in the MD direction, thereby achieving overall grain refinement. In contrast, fine grains have higher strength and hardness because there are more grain boundaries in fine grain materials.

[0034] Grain boundaries are interfaces between adjacent grains. As strengthening phases in the material, they can hinder the movement of dislocations (a defect in the crystal that manifests itself as a local disorder of the atomic arrangement), thereby increasing the material's ability to resist deformation because dislocations need to overcome higher energy barriers when passing through grain boundaries; this means that when the material is subjected to external forces, the grain boundaries in fine-grained materials will disperse and relieve stress concentration, thereby reducing the formation and expansion of cracks, thereby increasing the overall strength of the material.

[0035] The fine grains make the grain size of the lead strip consistent in all directions, thus ensuring uniform corrosion in all directions, and preventing one direction from corroding faster than other directions, thereby improving the corrosion resistance of the material. In addition, grain refinement can also purify the grain boundaries, making impurities more evenly distributed at the grain boundaries and reducing the risk of local corrosion.

[0036] At the same time, in fine-grained materials, due to the small grain size, the size of defects (such as voids, cracks, etc.) is also correspondingly small. These small-sized defects are not easy to cause overall damage to the material, because even if a defect begins to expand, it will quickly encounter another grain boundary and be blocked.

[0037] The grain sizes in the MD direction of multiple groups of lead strip samples were measured before and after refinement treatment (heating oven treatment and vibration treatment);

[0038] See Table 1 below for specific data:

[0039]

[0040]

[0041] It can be seen from the data in Table 1 above that before the lead strip is refined, the grain size in the MD direction is 100μm~200μm; after the lead strip is refined, the grain size in the MD direction is 5μm~35μm, and the grain size is basically consistent in the MD direction and the vertical direction, which uniforms the consistency of the grain size in different directions.

[0042] Furthermore, if Figure 2 and Figure 3 As shown, the transmission electron microscope was used to observe the above-mentioned thinning treatment before ( Figure 2 ) and after refinement ( Figure 3 ) grain structure, it can be seen that the grain structure after refinement treatment is finer and has more grain boundaries.

[0043] Furthermore, the refined lead strips and untreated lead strips were made into samples, and their corrosion resistance was compared by constant voltage corrosion.

[0044] Positive electrode (sample): lead sheet (5cm*1cm*0.8mm)

[0045] Negative electrode: lead sheet (36cm*25cm*0.5mm)

[0046] Reference electrode: Hg / Hg2SO4

[0047] Electrolyte: 1.35g / cm 3 H2SO4

[0048] Test voltage: The initial setting is 2.45V, which needs to be adjusted later according to the potential difference between the positive electrode and the reference electrode to ensure that the voltage difference between the positive electrode and the reference electrode remains consistent.

[0049] After 15 days, 30 days, 45 days and 80 days of corrosion, the metallographic microscope test results before and after constant pressure corrosion were compared to determine the corrosion resistance of the lead strip, as shown in Table 2:

[0050]

[0051] From the data in Table 2 above, we can see that:

[0052] The corrosion thickness of the lead strip after refinement treatment is significantly less than that of the untreated lead strip. For example, after 80 days, the corrosion thickness is doubled.

[0053] Width comparison reflects the creep resistance of the sample. The lead strip after refinement treatment did not change during the corrosion test cycle, while the untreated lead strip, for example, expanded by 1.24mm after 80 days. The width direction (the width direction here is the width direction of the sample (the positive electrode sample is 1cm), which actually corresponds to the length direction of the lead strip) is the MD direction. Under the same width conditions, the lead strip after refinement treatment has more grain refinement and grain boundaries in this direction, while the untreated lead strip has the opposite, so this phenomenon occurs.

[0054] Embodiment 2

[0055] This embodiment provides an ultra-thin corrosion-resistant lead strip, which is formed using the method of the above-mentioned embodiment 1.

[0056] The ultra-thin corrosion-resistant lead strip has a thickness of 0.3 mm to 0.8 mm and has excellent corrosion resistance.

[0057] In the description of the present invention, it should be understood that the terms "upper", "lower", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, and a specific direction structure and operation, and therefore, cannot be understood as a limitation on the present invention. In addition, "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0058] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", etc. should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0059] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for forming an ultra-thin corrosion-resistant lead strip, characterized in that: The following steps are involved: Step 1, continuously rolling the blank lead strip to obtain an ultra-thin lead strip; Step 2: subjecting the ultra-thin lead strip to a heating oven treatment and a vibration treatment to refine the grains and obtain an ultra-thin corrosion-resistant lead strip.

2. The method for forming an ultra-thin corrosion-resistant lead strip according to claim 1, characterized in that: The thickness of the blank lead strip is 10 mm to 13 mm, and it is rolled into an ultra-thin lead strip through continuous 9-rolling, wherein the thickness of the ultra-thin lead strip is 0.3 mm to 0.8 mm.

3. The method for forming an ultra-thin corrosion-resistant lead strip according to claim 1, characterized in that: The heating oven treatment and the vibration treatment are carried out simultaneously.

4. A method for forming an ultra-thin corrosion-resistant lead strip according to claim 1 or 3, characterized in that: The temperature of the heating oven treatment is 300° C. to 310° C., and the treatment time is 5 min to 15 min.

5. A method for forming an ultra-thin corrosion-resistant lead strip according to claim 1 or 3, characterized in that: The vibration treatment uses a mechanical vibration table for vibration, with a vibration frequency of 1000 Hz to 3000 Hz, an amplitude of 1 mm to 2 mm, and a treatment time of 1 min to 10 min.

6. An ultra-thin corrosion-resistant lead strip, characterized in that: The ultra-thin corrosion-resistant lead strip is formed using the forming method as described in any one of claims 1-5, and its thickness is 0.3mm to 0.8mm.

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