Preparation method of three-clamping piece

Abstract

The embodiment of the invention provides a three-clamping-piece preparation method which comprises the steps that a stainless steel band serves as a base material, and the three-clamping-piece is obtained through nickel electroplating, heat treatment, copper electroplating, heat treatment, flattening, slitting and cleaning. Wherein the three clamping pieces are of a three-layer structure, namely a nickel layer, a stainless steel layer and a copper layer in sequence; wherein the thicknesses of the nickel layer, the stainless steel layer, the nickel layer and the copper layer are respectively 1-10 microns, 80-210 microns and 10-30 microns, and the total thickness is 90-250 microns; the prepared three-clamping piece has excellent surface and interface stability, specifically, the bending resistance is good, cracks and defects are not generated on the surface after the three-clamping piece is bent by 90 degrees and 180 degrees, the consistency of the surface and the bent position can be kept after the three-clamping piece is stamped into a battery shell, and then bubbles cannot be generated due to the reaction with a test solution in a gas production experiment; in practical application, the stability of chemical reaction in the battery is guaranteed, and the electrochemical performance and safety of the battery are improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal surface treatment, and in particular to a method for preparing a three-clip sheet. Background Art

[0002] Compared with thicker nickel-plated materials, the shell made of three-clip material has reduced contact resistance, more beautiful appearance, and its strength can be changed by selecting specific thicknesses of different materials. Because the three-clip uses different materials inside and outside, it can also resist harmful electrochemical reactions inside the battery. In addition, the three-clip can produce a good crystal texture during the preparation process, so it has excellent deep drawing formability and can be further processed (stamped) into a thinner shape. The three-clip composite material is the preferred material for the anode current collector cover of button batteries because it has the characteristics of beauty, high strength, high corrosion resistance and low contact resistance. Common applications include batteries for portable electronic devices such as remote controls, toys, watches, calculators and hearing aids.

[0003] The three-piece sheet is composed of multiple layers of metal materials, so the bonding strength and mechanical / chemical stability of its interface are crucial to its application performance. At present, the three-piece sheet is usually made by calendering multiple layers of metal together, but its interface structure is unstable and easy to delaminate after stamping. It has poor corrosion resistance to the solution and reacts with the test solution in the gas production experiment to produce a large number of bubbles. Summary of the invention

[0004] In view of this, the present invention provides a method for preparing a three-piece sheet, which significantly optimizes the surface and interface stability of the three-piece sheet. The three-piece sheet prepared in this way has excellent bending resistance and corrosion resistance, and will not react with the test solution to produce bubbles in the gas production experiment.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] In a first aspect, an embodiment of the present invention provides a method for preparing a three-clip sheet, the method comprising: using a stainless steel strip as a substrate, electroplating nickel, heat treating, electroplating copper on one side, heat treating, flattening, slitting, and cleaning to obtain a three-clip sheet;

[0007] The three-layer structure of the three-layer sandwich panel is a nickel layer, a stainless steel layer, and a copper layer.

[0008] The thickness of the nickel layer, stainless steel layer and copper layer are 1-10, 80-210 and 10-30 μm respectively, and the total thickness is 90-250 μm;

[0009] In a second aspect, an embodiment of the present invention provides a method for preparing a three-clip sheet, the method further comprising:

[0010] (1) Soak the stainless steel strip in an alkaline degreasing solution for 3-8 minutes at a temperature of 40-70°C, then 2 The degreasing is carried out by electrolysis at a current density of , and then the degreasing stainless steel strip is washed with pure water at a temperature of 30-60°C; the formula of the degreasing solution is 20-60g / L sodium hydroxide, 20-60g / L sodium carbonate, 20-60g / L trisodium phosphate, and 1-3mL / L detergent;

[0011] (2) soaking the degreased stainless steel strip in an activation solution for 3-8 minutes at a temperature of 40-70° C., and then rinsing / cleaning the entire strip surface with pure water to obtain an activated stainless steel strip; the activation solution is formulated as 30-100 mL / L sulfuric acid, and the Baume degree of the solution is controlled to be 4-15;

[0012] (3) Electroplating the activated stainless steel strip with nickel, wherein the electroplating of the nickel layer includes pre-nickel plating, composite nickel plating and semi-bright nickel plating processes. First, pre-nickel plating is performed, wherein the plating solution comprises 175-275 g / L nickel chloride and 110-155 mL / L hydrochloric acid, and then pure water immersion / spray washing is performed after completion; then, electroplating of the composite nickel layer is performed, wherein the plating solution comprises 240-380 g / L nickel sulfate and 35-70 g / L boric acid; finally, electroplating of semi-bright nickel is performed, wherein the plating solution comprises 240-380 g / L nickel sulfate, 20-50 g / L nickel chloride, 40-50 g / L boric acid and 10-50 ml / L additives; after completion, the strip is washed with hot water at 40-60° C., and then the surface moisture is completely removed by blowing air, and the strip is dried in an oven at 100-180° C. for 24 h to obtain a nickel-plated stainless steel strip;

[0013] (4) heat treating the nickel-plated stainless steel strip in (3) in a heating hood, heating to a certain temperature, keeping the temperature, and then cooling, and removing from the furnace after cooling to 80° C., thereby obtaining a heat-treated nickel-plated stainless steel strip;

[0014] (5) Degreasing the nickel-plated stainless steel strip after the heat treatment in (4), firstly, chemical degreasing, immersing the double-sided nickel-plated stainless steel strip in a degreasing solution for 3-5 minutes, the treatment temperature is 40-70°C, the degreasing solution contains 30-60g / L sodium hydroxide, 30-60g / L sodium carbonate, and 30-60g / L trisodium phosphate, after completion, brushing the surface with hot water; then electrolytic degreasing, the current density is 1-5A / dm 2 , the temperature is 40-70℃, and then washed alternately with pure water and hot water;

[0015] (6) Electrolytic activation with a current density of 0-3A / dm 2, the temperature is 40-70℃, the solution composition is 30-100mL / L sulfuric acid, the solution Baume degree is 4-15, and then washed alternately with pure water and hot water;

[0016] (7) Pre-nickel plating with a current density of 1-5A / dm 2 , the temperature is 25-55℃, the solution composition is nickel chloride 180-270g / L, hydrochloric acid 90-160mL / L, the solution Baume degree is 15-23, and then wash with pure water and hot water alternately;

[0017] (8) immersing the strip in (7) in a 30-100 mL / L sulfuric acid solution for activation, wherein the solution has a Baume degree of 4-15 and a temperature of 20-55° C., and then washing with pure water in a circulating manner;

[0018] (9) electroplating copper on one side of the strip treated in (8), wherein the copper plating solution comprises 180-280 g / L copper sulfate and 30-60 ml / L sulfuric acid, wherein the Baume degree of the solution is controlled to be 18-25, and the chloride ion concentration is controlled to be 60-110 mg / L, and then washing alternately with pure water and hot water;

[0019] (10) performing surface protection on the single-sided copper-plated strip in (9), specifically, immersing the strip in an aqueous solution with a concentration of 2-10 g / L of benzotriazole for 1 min at a solution temperature of 25-55° C., and then washing the surface with hot water at 40-60° C.;

[0020] (11) using air blowing to completely dry the moisture on the surface of the strip, and drying it in an oven at 120-140° C. for 24 h to obtain a single-sided copper-plated nickel-plated stainless steel strip;

[0021] (12) heat treating the nickel-plated stainless steel strip with copper plating on one side in (11), the process is the same as step (4);

[0022] (13) Use leveling equipment to level the material;

[0023] (14) cutting the material after the flattening treatment in (13) into required widths, and then cleaning the belt surface;

[0024] (15) The strip is cleaned with 30-100 mL / L sulfuric acid solution, then cleaned with pure water, and then immersed in an aqueous solution with a concentration of 2-10 g / L of benzotriazole for 1 min at a solution temperature of 25-55°C, and finally surface washed with hot water at 40-60°C;

[0025] (16) The moisture on both sides of the strip is completely dried by air blowing, and the strip is placed in an oven and dried at 110-190° C. for 24 hours to obtain the three-ply sheet.

[0026] Wherein, the current density of the pre-nickel plating is 1-5A / dm 2 The solution Baume degree is 14-18, the temperature is 25-60°C, and the current density of the composite nickel layer electroplating is 1-5A / dm 2 , solution Baume degree 18-24, pH 1.0-2.5, temperature 35-75°C; the current density of the semi-bright nickel is 2-10A / dm 2 , solution Baume degree 20-25, pH 4.0-4.5, temperature 40-70℃;

[0027] The single-sided copper electroplating is performed twice, and the current density is 5-8A / dm 2 and 5-30A / dm 2 , the Baume degree of the solution is 18-25;

[0028] The heating rate of the heat treatment is 3°C / min, the treatment temperature is 630-660°C, and the temperature is kept until the center plate temperature reaches 620-650°C;

[0029] The surface roughness of the leveling roller used in the leveling process is 0.1-0.5 μm, and the leveling pressure is 28-35 T;

[0030] The embodiment of the present invention provides a method for preparing a three-piece clamp, the method comprising: taking a stainless steel strip as a substrate, and obtaining a three-piece clamp by nickel electroplating, heat treatment, single-sided copper electroplating, heat treatment, flattening, slitting, and cleaning; wherein the three-piece clamp is a three-layer structure, which is a nickel layer, a stainless steel layer, and a copper layer in sequence; wherein the thicknesses of the nickel layer, the stainless steel layer, and the copper layer are 1-10, 80-210, and 10-30 μm, respectively, and the total thickness is 90-250 μm; the three-piece clamp prepared in this way has excellent surface and interface stability, which is specifically manifested in good bending resistance. Not only does the surface not produce cracks and defects after being bent at 90° and 180°, but the consistency of the surface and the bend can be maintained after being stamped into a battery shell, and thus it will not react with the test solution to produce bubbles in the gas production experiment; in practical applications, it is beneficial to ensure the stability of the internal chemical reaction of the battery and improve the electrochemical performance and safety of the battery.

[0031] Compared with the prior art, the preparation method of the three-clip sheet provided by the present invention has the following beneficial effects:

[0032] Different from the conventional calendering preparation method, the present invention in-situ composites copper and nickel metal layers on both sides of the stainless steel by electroplating, and forms an alloy diffusion layer at the composite interface by heat treatment, and finally further improves the composite strength of the interface by flattening. After the synergistic effect of the above three processes, the prepared three-piece has good surface and interface stability, not only exhibits excellent bending resistance, but also does not produce cracks and defects on the surface after bending at 90° and 180°, and can maintain the consistency of the surface and the bend after being stamped into a battery shell, and thus will not react with the test solution to produce bubbles in the gas production experiment; in addition, compared with the conventional calendering preparation method, the three-piece prepared by electrodeposition in the present invention has high preparation efficiency, low energy consumption, and better surface and interface performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart of the preparation of the three-clip sheet in an embodiment of the present invention;

[0034] Figure 2 It is a schematic diagram of the structure of three clamps in an embodiment of the present invention;

[0035] Figure 3 The microscope images of the three-clip sheet in the embodiment of the present invention after being bent at 90° and 180°;

[0036] Figure 4 The microscope images of the three-piece plate in Comparative Example 1 of the present invention after being bent at 90° and 180°;

[0037] Figure 5 This is a microscope image of the three-clip sheet after flattening in an embodiment of the present invention;

[0038] Figure 6 This is a microscope image of the uneven three-clip sheet in Comparative Example 3 of the present invention;

[0039] Figure 7 This is a microscope image of the three-clip sheet in the gas production experiment in the embodiment of the present invention;

[0040] Figure 8 This is a microscope image of the three-clip sheet in comparative example 3 of the present invention during the gas production experiment. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0043] Before further describing the present invention in detail, the nouns and terms involved in the embodiments of the present invention are explained. The nouns and terms involved in the embodiments of the present invention are subject to the following explanations.

[0044] Example

[0045] This embodiment uses a stainless steel strip as an electroplating substrate, and takes the preparation of a three-piece sheet having a nickel layer, a stainless steel layer, and a copper layer as an example. The thicknesses of the nickel layer, the stainless steel layer, and the copper layer are 1-10, 80-210, and 10-30 μm, respectively, and the total thickness is 90-250 μm. The specific preparation steps are as follows:

[0046] (1) Soak the stainless steel strip in an alkaline degreasing solution for 3-8 minutes at a temperature of 40-70°C, then 2 The degreasing is carried out by electrolysis at a current density of , and then the degreasing stainless steel strip is washed with pure water at a temperature of 30-60°C; the formula of the degreasing solution is 20-60g / L sodium hydroxide, 20-60g / L sodium carbonate, 20-60g / L trisodium phosphate, and 1-3mL / L detergent;

[0047] (2) soaking the degreased stainless steel strip in an activation solution for 3-8 minutes at a temperature of 40-70° C., and then rinsing / cleaning the entire strip surface with pure water to obtain an activated stainless steel strip; the activation solution is formulated as 30-100 mL / L sulfuric acid, and the Baume degree of the solution is controlled to be 4-15;

[0048] (3) The activated stainless steel strip is electroplated with nickel. The electroplating of the nickel layer includes pre-nickel plating, composite nickel plating and semi-bright nickel plating. First, the nickel plating is carried out at 1-5A / dm 2 The current density is 1-5A / dm for pre-nickel plating. The plating solution composition is nickel chloride 175-275g / L, hydrochloric acid 110-155mL / L, solution Baume degree 14-18, temperature 25-60℃, and pure water immersion / spray washing is performed after completion; then, the plating solution is pre-nickel plated at 1-5A / dm 2 The composite nickel layer is electroplated at a current density of 240-380 g / L nickel sulfate, 35-70 g / L boric acid, 18-24 degrees Baume, 3-30 ml / L additives, 1.0-2.5 pH, and 35-75 °C temperature; finally, at 2-10 A / dm 2The current density is 200-300°C for electroplating semi-bright nickel, the plating solution composition is 240-380g / L nickel sulfate, 20-50g / L nickel chloride, 40-50g / L boric acid, 10-50ml / L additives, the solution Baume degree is 20-25, the pH is 4.0-4.5, the temperature is 40-70°C, after completion, it is washed with hot water at 40-60°C, and then the surface moisture is completely removed by blowing, and it is dried in an oven at 100-180°C for 24h to obtain a nickel-plated stainless steel strip;

[0049] (4) heat treating the nickel-plated stainless steel strip in (3), raising the treatment temperature to 630-660° C. at a heating rate of 3° C. / min in a heating hood, and keeping the temperature until the center plate temperature reaches 620-650° C.; then starting to cool, and taking the strip out of the furnace after cooling to 80° C., to obtain a heat-treated nickel-plated stainless steel strip;

[0050] (5) Degreasing the nickel-plated stainless steel strip after the heat treatment in (4), firstly, chemical degreasing, immersing the double-sided nickel-plated stainless steel strip in a degreasing solution for 3-5 minutes, the treatment temperature is 40-70°C, the degreasing solution contains 30-60g / L sodium hydroxide, 30-60g / L sodium carbonate, and 30-60g / L trisodium phosphate, after completion, brushing the surface with hot water; then electrolytic degreasing, the current density is 1-5A / dm 2 , the temperature is 40-70℃, and then washed alternately with pure water and hot water;

[0051] (6) Electrolytic activation with a current density of 0-3A / dm 2 , the temperature is 40-70℃, the solution composition is 30-100mL / L sulfuric acid, the solution Baume degree is 4-15, and then washed alternately with pure water and hot water;

[0052] (7) Pre-nickel plating with a current density of 1-5A / dm 2 , the temperature is 25-55℃, the solution composition is nickel chloride 180-270g / L, hydrochloric acid 90-160mL / L, the solution Baume degree is 15-23, and then wash with pure water and hot water alternately;

[0053] (8) immersing the strip in (7) in a 30-100 mL / L sulfuric acid solution for activation, wherein the solution has a Baume degree of 4-15 and a temperature of 20-55° C., and then washing with pure water in a circulating manner;

[0054] (9) The strip treated in (8) is subjected to single-sided copper electroplating at 5-8A / dm 2 and 5-30A / dm 2The copper plating solution is composed of 180-280 g / L copper sulfate and 30-60 ml / L sulfuric acid, wherein the Baume degree of the solution is controlled to be 18-25, and the chloride ion concentration is 60-110 mg / L, and then pure water and hot water are alternately washed;

[0055] (10) performing surface protection on the single-sided copper-plated strip in (9), specifically, immersing the strip in an aqueous solution with a concentration of 2-10 g / L of benzotriazole for 1 min at a solution temperature of 25-55° C., and then washing the surface with hot water at 40-60° C.;

[0056] (11) using air blowing to completely dry the moisture on the surface of the strip, and drying it in an oven at 120-140° C. for 24 h to obtain a single-sided copper-plated nickel-plated stainless steel strip;

[0057] (12) heat treating the nickel-plated stainless steel strip with copper plating on one side in (11), the process is the same as step (4);

[0058] (13) The surface roughness of the leveling roller of the leveling equipment is 0.1-0.5 μm, and the material is leveled with a leveling pressure of 28-35 T;

[0059] (14) cutting the material after the flattening treatment in (13) into required widths, and then cleaning the belt surface;

[0060] (15) The strip is cleaned with 30-100 mL / L sulfuric acid solution, then cleaned with pure water, and then immersed in an aqueous solution with a concentration of 2-10 g / L of benzotriazole for 1 min at a solution temperature of 25-55°C, and finally surface washed with hot water at 40-60°C;

[0061] (16) The moisture on both sides of the strip is completely dried by air blowing, and the strip is placed in an oven and dried at 110-190° C. for 24 hours to obtain the three-ply sheet.

[0062] Comparative Example 1

[0063] Compared with the embodiment, this comparative example only deletes the heat treatment process of step (4) and step (12), and the other steps and solutions are consistent with the embodiment.

[0064] Comparative Example 2

[0065] Compared with the embodiment, the nickel electroplating in step (3) is changed to only include a pre-nickel plating process, that is, at 2A / dm 2The stainless steel strip activated in (2) is directly electroplated with nickel at a current density of 180-260 g / L nickel chloride and 120-150 mL / L hydrochloric acid, with a solution Baume degree of 14-18, a temperature of 25-40° C., and a nickel plating layer thickness of 5-9 μm. After completion, pure water immersion / spray washing is performed; in addition, the pre-nickel plating process of step (7) is deleted, and in the copper electroplating process of step (9), only 5-8 A / dm 2 The copper plating solution is composed of 200-260 g / L copper sulfate and 30-50 ml / L sulfuric acid, wherein the Baume degree of the solution is controlled to be 18-25, and the chloride ion concentration is 60-90 mg / L, and then pure water and hot water are alternately washed, and the other steps and solutions are consistent with the embodiment.

[0066] Comparative Example 3

[0067] Compared with the embodiment, in this comparative example, a nickel strip and a copper strip of the same thickness are directly compounded to both sides of a stainless steel strip by a rolling method, and the thickness of the nickel strip and the copper strip are consistent with that of the embodiment.

[0068] Comparative Example 4

[0069] Compared with the embodiment, this comparative example only deletes the leveling process in step (13), and the other steps and solutions are consistent with the embodiment.

[0070] Comparative Example 5

[0071] Compared with the embodiment, this comparative example only deletes the copper surface protection process in step (10) and step (14), and the other steps and solutions are consistent with the embodiment.

[0072] Please refer to Table 1 and Table 2, which are the comparison summaries of all embodiments and comparative examples in the present invention, from which it can be seen that:

[0073] 1) By comparing Example 1 with Comparative Examples 1, 2 and 3, it can be seen that the design of the metal layer structure and the heat treatment in the embodiment effectively improve the bending resistance of the prepared three-clip sheet. After bending at 90° and 180°, no cracks or defects are generated at the bending part (see attached Figure 3 ), and the iron content on the surface of the three-piece is also relatively stable, indicating that the iron leakage rate of the material surface after bending is low and the metal layer structure is stable; while the three-piece prepared without heat treatment in Comparative Example 1 has poor bending resistance. After 90° bending, a small amount of cracks are observed at the bending, and after 180° bending, a large number of cracks and defects are observed at the bending (see Appendix Figure 4), and the surface iron content showed a large fluctuation, indicating that the microcracks in the nickel and copper metal layers on the surface of the material after bending were larger in size, exposing the underlying stainless steel substrate. Therefore, the comparison results of the embodiment and the comparative example 1 show that the heat treatment effectively improves the interface bonding strength between the stainless steel, nickel and copper layers, and improves the structural stability of the three-piece under bending; in addition, in the comparative example 2, the nickel layer and the copper layer are directly electroplated on the stainless steel in one step, and after the three-piece obtained in this way is bent at 90°, a small amount of cracks are observed at the bending position, and after being bent at 180°, more cracks are observed at the bending position. Defects, and the fluctuation of surface iron content is also higher than that of the embodiment, which shows that the multi-level design of the nickel layer and the copper layer on both sides of the stainless steel in the embodiment is also one of the important factors to ensure the stability of the three-piece structure; in comparative example 3, the copper layer and the nickel layer are directly compounded to the two sides of the stainless steel strip by the calendering method to obtain a three-piece, and its interface stability is poorer than that of the embodiment. After bending at 90°, more cracks are observed at the bending point, and after bending at 180°, more cracks and defects are observed at the bending point. The iron content on the final surface is also higher, which shows that the surface / interface stability of the three-piece prepared by the electroplating method is better.

[0074] 2) By comparing Example 1 with Comparative Example 4 and Comparative Example 5, and combining the attached Figure 5-8 It can be seen that the flattening and surface protection in the embodiment effectively improve the corrosion resistance of the three-clip sheet in the gas production experiment, and no bubbles generated by the reaction with the test solution were observed in the gas production experiment (see attached). Figure 7 ), the metal layer has a clear, dense and defect-free surface texture after flattening (see attached Figure 5 ), further improving the effect of surface protection. The synergistic effect of the two is an important reason for the excellent corrosion resistance of the three-clip plate; while many cracks and pores were observed on the surface of the material that was not flattened in Comparative Example 4 (see Appendix Figure 6 ), bubbles were observed in the gas production experiment, indicating that the material reacted with the test solution, that is, the corrosion resistance was slightly lower than that of the embodiment, because the unsmoothed material surface affected the surface protection treatment effect; in Example 5, the material without smoothing and surface protection treatment had significantly reduced corrosion resistance, and a large number of bubbles were observed in the gas production experiment, indicating that it reacted violently with the test solution and had poor corrosion resistance.

[0075] Table 1

[0076]

[0077]

[0078] Table 2

[0079]

[0080] In summary, the example of the present invention provides a method for preparing a three-piece sandwich, and the prepared three-piece sandwich has excellent surface and interface stability, which is specifically manifested in good bending resistance and corrosion resistance. Not only does the surface not produce cracks and defects after being bent at 90° and 180°, but the surface and the bends can be kept consistent after being stamped into a battery shell, and thus will not react with the test solution to produce bubbles in the gas production experiment. In practical applications, it is beneficial to ensure the stability of the chemical reaction inside the battery and improve the electrochemical performance and safety of the battery.

[0081] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0082] In this document, the terms "comprises," "comprising," or any other variations thereof, are intended to cover a non-exclusive inclusion of elements other than those listed and may also include additional elements not expressly listed.

[0083] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a three-clip sheet, characterized in that: The method comprises: A three-piece sheet is obtained by taking a stainless steel strip as a substrate through nickel electroplating, heat treatment, single-side copper electroplating, heat treatment, flattening, slitting and cleaning; wherein the three-piece sheet is a three-layer structure, which is a nickel layer, a stainless steel layer and a copper layer in sequence; wherein the thicknesses of the nickel layer, the stainless steel layer and the copper layer are 1-10 μm, 80-210 μm and 10-30 μm respectively.

2. The method for preparing a three-clip sheet according to claim 1, characterized in that: The preparation method further comprises: (1) Soak the stainless steel strip in an alkaline degreasing solution for 3-8 minutes at a temperature of 40-70°C, then 2 The degreasing is carried out by electrolysis at a current density of , and then the degreasing stainless steel strip is washed with pure water at a temperature of 30-60°C; the formula of the degreasing solution is 20-60g / L sodium hydroxide, 20-60g / L sodium carbonate, 20-60g / L trisodium phosphate, and 1-3mL / L detergent; (2) soaking the degreased stainless steel strip in an activation solution for 3-8 minutes at a temperature of 40-70° C., and then rinsing / cleaning the entire strip surface with pure water to obtain an activated stainless steel strip; the activation solution is formulated as 30-100 mL / L sulfuric acid, and the Baume degree of the solution is controlled to be 4-15; (3) Electroplating the activated stainless steel strip with nickel, wherein the electroplating of the nickel layer includes pre-nickel plating, composite nickel plating and semi-bright nickel plating processes. First, pre-nickel plating is performed, wherein the plating solution comprises 175-275 g / L nickel chloride and 110-155 mL / L hydrochloric acid, and then pure water immersion / spray washing is performed after completion; then, electroplating of the composite nickel layer is performed, wherein the plating solution comprises 240-380 g / L nickel sulfate and 35-70 g / L boric acid; finally, electroplating of semi-bright nickel is performed, wherein the plating solution comprises 240-380 g / L nickel sulfate, 20-50 g / L nickel chloride, 40-50 g / L boric acid and 10-50 ml / L additives; after completion, the strip is washed with hot water at 40-60° C., and then the surface moisture is completely removed by blowing air, and then the strip is dried in an oven at 100-180° C. for 24 h to obtain a nickel-plated stainless steel strip; (4) heat treating the nickel-plated stainless steel strip in (3) in a heating hood, heating to a certain temperature, keeping the temperature, and then cooling, and removing from the furnace after cooling to 80° C., thereby obtaining a heat-treated nickel-plated stainless steel strip; (5) Degreasing the nickel-plated stainless steel strip after the heat treatment in (4), firstly, chemical degreasing, immersing the double-sided nickel-plated stainless steel strip in a degreasing solution for 3-5 minutes, the treatment temperature is 40-70°C, the degreasing solution contains 30-60g / L sodium hydroxide, 30-60g / L sodium carbonate, and 30-60g / L trisodium phosphate, after completion, brushing the surface with hot water; then electrolytic degreasing, the current density is 1-5A / dm 2 , the temperature is 40-70℃, and then washed alternately with pure water and hot water; (6) Electrolytic activation with a current density of 0-3A / dm 2 , the temperature is 40-70℃, the solution composition is 30-100mL / L sulfuric acid, the solution Baume degree is 4-15, and then washed alternately with pure water and hot water; (7) Pre-nickel plating with a current density of 1-5A / dm 2 , the temperature is 25-55℃, the solution composition is nickel chloride 180-270g / L, hydrochloric acid 90-160mL / L, the solution Baume degree is 15-23, and then wash with pure water and hot water alternately; (8) immersing the strip in (7) in a 30-100 mL / L sulfuric acid solution for activation, wherein the solution has a Baume degree of 4-15 and a temperature of 20-55° C., and then washing with pure water in a circulating manner; (9) electroplating copper on one side of the strip treated in (8), wherein the copper plating solution comprises 180-280 g / L copper sulfate and 30-60 ml / L sulfuric acid, wherein the Baume degree of the solution is controlled to be 18-25, and the chloride ion concentration is controlled to be 60-110 mg / L, and then washing alternately with pure water and hot water; (10) performing surface protection on the single-sided copper-plated strip in (9), specifically, immersing the strip in an aqueous solution with a concentration of 2-10 g / L of benzotriazole for 1 min at a solution temperature of 25-55° C., and then washing the surface with hot water at 40-60° C.; (11) using air blowing to completely dry the moisture on the surface of the strip, and placing it in an oven to dry at 120-140° C. for 24 hours to obtain a single-sided copper-plated nickel-plated stainless steel strip; (12) heat treating the nickel-plated stainless steel strip with copper plating on one side in (11), the process is the same as step (4); (13) Use leveling equipment to level the material; (14) cutting the material after the flattening treatment in (13) into required widths, and then cleaning the belt surface; (15) The strip is cleaned with 30-100 mL / L sulfuric acid solution, then cleaned with pure water, and then immersed in an aqueous solution with a concentration of 2-10 g / L of benzotriazole for 1 min at a solution temperature of 25-55°C, and finally surface washed with hot water at 40-60°C; (16) The moisture on both sides of the strip is completely dried by air blowing, and the strip is placed in an oven and dried at 110-190° C. for 24 hours to obtain the three-ply sheet.

3. The method for preparing a three-clip sheet according to claim 2, characterized in that: The current density of the pre-nickel plating is 1-5A / dm 2 The solution Baume degree is 14-18, the temperature is 25-60°C, and the current density of the composite nickel layer electroplating is 1-5A / dm 2 , solution Baume degree 18-24, pH 1.0-2.5, temperature 35-75°C; the current density of the semi-bright nickel is 2-10A / dm 2 , the solution Baume degree is 20-25, the pH is 4.0-4.5, and the temperature is 40-70℃.

4. The method for preparing a three-clip sheet according to claim 2, characterized in that: The single-sided copper electroplating is performed twice, and the current density is 5-8A / dm 2 and 5-30A / dm 2 , the Baume degree of the solution is 18-25.

5. The method for preparing a three-clip sheet according to claim 2, characterized in that: The heating rate of the heat treatment is 3°C / min, the treatment temperature is 630-660°C, and the heat is maintained until the center plate temperature reaches 620-650°C.

6. The method for preparing a three-clip sheet according to claim 2, characterized in that: The surface roughness of the leveling roller used in the leveling process is 0.1-0.5 μm, and the leveling pressure is 28-35T.

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