Perforated tin-plated steel strip

Abstract

This application relates to the field of surface modification technology for metallic materials, specifically disclosing a perforated tin-plated steel strip. It includes a steel substrate layer, a nickel-activated underlayer fixedly connected to the upper surface of the steel substrate layer, an amorphous nickel-phosphorus functional layer fixedly connected to the upper surface of the nickel-activated underlayer, a microcrystalline tin-plated layer fixedly connected to the upper surface of the amorphous nickel-phosphorus functional layer, an inorganic conversion film fixedly connected to the upper surface of the microcrystalline tin-plated layer, and an organosilane sealing layer containing corrosion inhibitor microcapsules fixedly connected to the upper surface of the inorganic conversion film. The corrosion-resistant, high-precision perforated tin-plated steel strip of this application can be used in stamped parts requiring high surface quality and dimensional accuracy, such as electronic components, communication shielding covers, and precision instruments. It has advantages such as stable coating adhesion, high resistance to stamping peeling, long corrosion resistance, and good coating integrity at the perforation edges.

Description

Technical Field

[0001] This application relates to the field of surface modification technology for metallic materials, and more specifically, to perforated tin-plated steel strip. Background Technology

[0002] In industries such as new energy, energy storage, and consumer electronics, key components such as battery current collectors and precision connectors place extremely high demands on the conductivity, weldability, corrosion resistance, and cost control of materials. Traditionally, tin-plated copper strip has been the preferred material in this field, but the persistently high price of copper resources has severely hampered the cost optimization process in related industries. Therefore, developing low-cost and reliable alternative materials has become an important technological direction in the industry.

[0003] The low-cost solution of replacing tin-plated copper strip with tin-plated steel strip still faces a series of technical bottlenecks when expanding into high-end applications: First, due to significant physical and electrochemical differences between the steel substrate and the tin layer, traditional tin plating processes struggle to form a metallurgical transition, resulting in weak interfacial bonding and easy peeling or flaking of the plating during stamping and bending; second, high-density punching easily generates burrs, deteriorating edge morphology and plating uniformity, leading to assembly and safety hazards; third, plating pores or damage can trigger accelerated galvanic corrosion of the steel substrate, and existing passivation treatments offer limited protection and lack self-healing capabilities; finally, existing technologies often address single problems in isolation, lacking integrated synergy between punching precision, interfacial structure, plating function, and surface protection, making it difficult to balance performance and cost, thus hindering its systematic application.

[0004] Therefore, there is a need in this field for an innovative multi-layer composite structure to solve the bonding problem of the steel-tin interface and the electrochemical corrosion tendency of the steel substrate, while integrating high-precision punching technology with advanced surface treatment technology, so as to obtain tin-plated steel strip products with comprehensive performance comparable to or even surpassing traditional tin-plated copper strip while ensuring low cost advantages. Summary of the Invention

[0005] To address the problem of plating peeling or flaking caused by replacing tin-plated copper strip with tin-plated steel strip, this application provides perforated tin-plated steel strip.

[0006] This application provides perforated tin-plated steel strip, using the following technical solution: A perforated tin-plated steel strip includes a steel substrate layer, a nickel-activated underlayer fixedly connected to the upper surface of the steel substrate layer, an amorphous nickel-phosphorus functional layer fixedly connected to the upper surface of the nickel-activated underlayer, a microcrystalline tin-plated layer fixedly connected to the upper surface of the amorphous nickel-phosphorus functional layer, an inorganic conversion film fixedly connected to the upper surface of the microcrystalline tin-plated layer, and an organosilane sealing layer containing corrosion inhibitor microcapsules fixedly connected to the upper surface of the inorganic conversion film.

[0007] By adopting the above technical solution, a multi-layer integrated structural design from the steel substrate to the surface is used to systematically construct a protection system with progressively evolving functions. The composite gradient transition layer, composed of a nickel-activated bottom layer and an amorphous nickel-phosphorus functional layer, first solves the physical and electrochemical mismatch between steel and tin, providing a high-strength anchoring foundation and a smooth deposition substrate for the upper layer. The microcrystalline tin-plated layer, as the main functional layer, provides excellent conductivity, weldability, and corrosion resistance. The outer inorganic conversion film and the organosilane sealing layer combine to form a dual protection that combines static shielding and dynamic repair. Therefore, a tin-plated steel strip product with improved interface bonding strength, uniformity of plating at the punched edge, and long-term corrosion resistance is obtained.

[0008] Preferably, the nickel-activated bottom layer and the amorphous nickel-phosphorus functional layer together constitute a composite gradient transition layer, and the overall thickness of the composite gradient transition layer is 0.2 μm-0.6 μm; the inorganic conversion film and the organosilane sealing layer containing corrosion inhibitor microcapsules together constitute a composite self-healing passivation layer, and the overall thickness of the composite self-healing passivation layer is 0.1 μm-0.4 μm.

[0009] By adopting the above technical solution, a balance is achieved between performance and cost by limiting the total thickness of the key functional layers. For the composite gradient transition layer, the set overall thickness range ensures that it effectively acts as a bridge between the steel substrate and the tin plating layer, achieving a gradient transition of mechanical properties from flexible to rigid to disperse stress, while avoiding the increase in internal stress and cost caused by excessively thick plating layers. For the composite self-healing passivation layer, the set thickness range is sufficient to form a continuous and dense film, providing effective static physical and chemical shielding for the underlying metal layer, while ensuring that the contained corrosion inhibitor microcapsules can be triggered and release repair substances when the plating layer is damaged. Therefore, a plating system with a compact structure, good protective performance, and good economic efficiency is obtained.

[0010] Preferably, the nickel activation underlayer is a pure nickel pre-plating layer with a thickness of 0.1μm-0.3μm.

[0011] By adopting the above scheme, a pure nickel layer is directly deposited on the steel substrate using a high-adhesion electroplating process. This thin layer serves as the initial bonding layer of the entire plating system, forming a strong metallurgical interface with the iron substrate. The pure nickel layer within this thickness range is sufficient to cover and eliminate the microscopic inhomogeneities on the steel substrate surface, providing a substrate surface with high bonding strength and uniform catalytic activity, creating conditions for the uniform deposition of subsequent electroless nickel-phosphorus functional layers. If the layer is too thin, the coverage will be incomplete and the interface cannot be effectively improved; if it is too thick, the process cost and time will increase, and the marginal benefit to the improvement of bonding strength will be limited. Therefore, an activated underlayer with strong adhesion to the steel substrate and capable of providing a deposition interface for subsequent processes is obtained.

[0012] Preferably, the amorphous nickel-phosphorus functional layer is a chemically plated nickel-phosphorus alloy layer with a thickness of 0.1 μm to 0.3 μm, and the mass percentage content of phosphorus in the nickel-phosphorus alloy layer is 7% to 11%.

[0013] By adopting the above technical solution, a nickel-phosphorus alloy layer with controlled composition and structure is deposited on a nickel-activated substrate using a chemical plating process. This process is independent of electric field distribution, has uniform plating capability, and can obtain a uniform thickness coating on large areas and complex contours. By controlling the phosphorus content within a set mass percentage range, it is ensured that the deposited alloy exhibits a long-range disordered amorphous structure. This amorphous structure is free of crystal defects such as grain boundaries and dislocations, resulting in a smooth surface and low roughness, providing an ideal nucleation and growth substrate for subsequent tin plating. At the same time, the layer itself has high hardness, high density, and chemical inertness, forming a physical barrier that prevents corrosive media from penetrating into the steel substrate. The set thickness is sufficient to enable it to function as a smoothing transition layer and a corrosion barrier. Therefore, an intermediate layer that combines interface smoothing, corrosion resistance, and provides a substrate for subsequent plating layers is obtained.

[0014] Preferably, the inorganic conversion membrane is a chemical conversion membrane with a thickness of 0.05μm-0.15μm and based on trivalent chromium compounds or titanium or zirconium salts.

[0015] By employing the above technical solution, a chemical conversion process is used to cause the surface metal of the microcrystalline tin plating layer to react chemically with a specific conversion solution, thereby generating an extremely thin inorganic conversion film in situ on the tin layer surface. This film is based on trivalent chromium compounds or chromium-free titanium, zirconium salts, etc., and its formation process is accompanied by slight dissolution of the metal and deposition of passivation products, thus achieving a strong bond with the substrate. The set thickness range allows the film to effectively cover the tin layer surface, inhibiting the natural oxidation and discoloration of tin in the air, and providing basic electrochemical corrosion protection. This thin layer, as the bottom layer of the composite passivation layer, not only has its own protective function, but its porous microstructure also provides anchoring points for the penetration and chemical bonding of the upper organosilane sealing layer. Therefore, an inorganic pretreatment film with good bonding with the substrate, providing basic protection, and facilitating the adhesion of the upper organic film is obtained.

[0016] Preferably, the organosilane sealing layer containing corrosion inhibitor microcapsules is an organosilane network structure with a thickness of 0.05μm-0.25μm formed by cross-linking and curing, and the corrosion inhibitor microcapsules are uniformly dispersed and encapsulated in the organosilane network structure.

[0017] By adopting the above technical solution, a three-dimensional network structure organic-inorganic hybrid film is formed by cross-linking and curing organosilanes on the surface of an inorganic conversion film after hydrolysis and condensation. This film is hydrophobic and dense, physically blocking the penetration of water vapor and corrosive media. More importantly, microcapsules encapsulating corrosion inhibitors are uniformly dispersed in the silane network. When the passivation layer is micro-scratched by external mechanical action, the shell of the microcapsules in the damaged area ruptures, releasing the internal corrosion inhibitor. These slowly released corrosion inhibitor molecules can migrate to the newly exposed metal surface and inhibit the electrochemical corrosion reaction in that area through chemical adsorption or the formation of a complex protective film. The set film thickness ensures effective sealing and support of a number of microcapsules while avoiding brittleness or affecting the conductive contact of the product due to excessive thickness. Therefore, a protective outer layer with both static shielding and dynamic active repair functions is obtained.

[0018] Preferably, the thickness of the microcrystalline tin plating layer is 2μm-4μm, and the average grain size of the tin plating layer is less than 500nm.

[0019] By employing the above technical solution, the microstructure of the tin plating layer is controlled through a specific electroplating process, refining its grain size to the submicron level. The fine equiaxed grain structure results in a higher grain boundary density than traditional coarse-grained plating layers. This high-density grain boundary facilitates the formation of a more complete and denser natural oxide film in the early stages of corrosion, thereby enhancing the corrosion resistance of the plating layer itself. Simultaneously, the fine grain structure also means reduced porosity and a denser structure within the plating layer, which can delay the penetration of corrosive media. The set thickness range ensures sufficient tin layer to guarantee good solderability, conductivity, and basic protection while balancing material costs and avoiding the internal stress and impact on the geometry of punched hole edges caused by excessively thick plating layers. Therefore, a dense, uniform, corrosion-resistant, and functional tin plating layer is obtained.

[0020] Preferably, the steel substrate layer is an SPCC low-carbon cold-rolled steel strip with a thickness of 0.035mm-0.1mm, and the steel substrate layer has a punched structure pre-formed by a precision stamping process, and the residual height of the burrs at the edge of the punch is not greater than 0.020mm.

[0021] By adopting the above technical solution, SPCC low-carbon cold-rolled steel strip is selected as the base material and first subjected to high-precision punching, defining its basic form as a component such as a current collector from the source of product manufacturing; the set thickness range balances the material's mechanical strength, formability, and the application's need for thinness; by optimizing the stamping die clearance, punch material, and lubrication process, the residual height of burrs generated after punching is controlled; low burrs ensure the dimensional accuracy of product assembly, eliminate the safety hazard of short circuit caused by puncturing the separator during subsequent battery winding, and also lay the geometric foundation for obtaining uniform coating deposition, avoiding abnormal coating accumulation at burr points due to the tip effect; therefore, a metal base material with low cost, high-precision geometry, and safety characteristics is obtained.

[0022] Preferably, an interfacial intersoluble region with a thickness of nanometer scale is formed between the nickel-activated bottom layer and the amorphous nickel-phosphorus functional layer, and between the amorphous nickel-phosphorus functional layer and the microcrystalline tin-plated layer, through atomic interdiffusion.

[0023] By adopting the above technical solution, the atomic interdiffusion at the interface of adjacent coating layers is promoted by controlling the deposition conditions and subsequent treatments of each layer during the continuous deposition process. This diffusion forms a nanoscale intersoluble region with continuous transition in composition and structure between the nickel-activated bottom layer and the amorphous nickel-phosphorus functional layer, and between the amorphous nickel-phosphorus functional layer and the microcrystalline tin plating layer. The existence of this intersoluble region enables a gradual bonding at the atomic scale between material layers with originally large differences in physical properties, eliminating sharp physical interfaces. This metallurgically bonded interface can reduce interfacial energy, effectively transfer and disperse the stress generated by each layer under stress or heat, enhance the overall bonding strength and structural integrity of the multilayer coating system, and overcome the risk of coating peeling and flaking. Therefore, a composite coating system with strong interfacial bonding and continuous transition in mechanical properties is obtained.

[0024] Preferably, the microcrystalline tin plating layer is prepared using a pulsed current electroplating process, with the following parameters: forward current density 10-20 A / dm², reverse current density 30-50 A / dm², forward pulse width 5-15 ms, and reverse pulse width 0.5-2 ms.

[0025] By employing the above technical solution, a pulse electroplating mode alternating between forward and reverse currents is used. During the forward pulse, tin ions are reduced and deposited on the cathode surface. During the brief reverse pulse, the current direction is reversed, resulting in slight anodic dissolution, which dissolves overgrown, poorly bonded grains at the tips or protrusions. The set forward current density and pulse width ensure the deposition rate and coating thickness. The higher reverse current density and shorter pulse width effectively remove abnormal deposits at burrs or protrusions. This periodic deposition-dissolution process forces grains to nucleate repeatedly, thereby refining the grains to the submicron level. At the same time, this process can improve the uniformity of current distribution on the surface of complex-shaped workpieces, ensuring that a uniform thickness and dense structure coating can be obtained even in low current density areas such as planes, edges, and even the inner walls of punched holes. Therefore, a microcrystalline tin plating layer with fine grains, uniform thickness, and high coverage is obtained.

[0026] In summary, this application has the following beneficial effects: 1. The composite gradient transition layer designed in this invention helps to solve the interface bonding problem. The nickel-activated bottom layer forms a stable metallurgical anchor point on the steel substrate; the amorphous nickel-phosphorus functional layer on it provides a rigid support platform; and the outer microcrystalline tin-plated layer has toughness. This mechanical property gradient transition from flexibility to rigidity and then to toughness can disperse and absorb the interface stress generated during subsequent processing or use, avoid stress concentration on a single interface, and thus reduce the risk of coating peeling.

[0027] 2. The corrosion-resistant system of this invention is based on the synergistic effect of multiple protections. The amorphous nickel-phosphorus functional layer has a dense structure and no grain boundaries, forming a physical barrier layer that slows down the penetration of corrosive media into the steel substrate. The microcrystalline tin plating layer obtained by pulse electroplating has fine grains and a high grain boundary density, which helps to form a denser passivation film. Its own porosity is low, which improves the protective ability of the tin layer. The composite self-healing passivation layer provides static shielding through the composite structure of inorganic and organic materials. The corrosion inhibitor microcapsules contained in it can release corrosion inhibitors when the plating layer is damaged, inhibiting the corrosion development in the damaged area. Thus, the corrosion resistance of the product can be improved.

[0028] 3. This invention integrates and optimizes precision punching and coating preparation. By controlling the punching process parameters, the burr height is controlled, and the subsequent composite coating process can maintain this precision. The chemical plating process of the amorphous nickel-phosphorus functional layer has uniform plating capability, which can replicate the outline after punching with equal thickness. The pulsed reverse electroplating tin process reduces the unevenness of the coating at the edge of the hole. This ensures that the punched hole has a smooth, regular edge with uniform coating, providing a guarantee for the current density distribution and electrochemical stability when used as a current collector.

[0029] 4. This invention uses low-carbon steel strip as the base material and improves product performance through structural design and process integration. The chemical plating, pulse electroplating and other processes used are mature and continuous production technologies, which improve the corrosion resistance and mechanical reliability of the product while controlling process costs. Attached Figure Description

[0030] Figure 1 This is a three-dimensional structural diagram of the perforated tin-plated steel strip proposed in this application.

[0031] Among them, 100 is the steel substrate layer; 200 is the composite gradient transition layer; 210 is the nickel activation bottom layer; 220 is the amorphous nickel-phosphorus functional layer; 300 is the microcrystalline tin plating layer; 400 is the composite self-healing passivation layer; 410 is the inorganic conversion film; and 420 is the organosilane sealing layer containing corrosion inhibitor microcapsules. Detailed Implementation

[0032] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0033] Technical concept: The low-cost solution of replacing tin-plated copper strip with tin-plated steel strip still faces a series of technical bottlenecks when expanding into high-end applications: First, due to significant physical and electrochemical differences between the steel substrate and the tin layer, traditional tin plating processes struggle to form a metallurgical transition, resulting in weak interfacial bonding and easy peeling or flaking of the plating during stamping and bending; second, high-density punching easily generates burrs, deteriorating edge morphology and plating uniformity, leading to assembly and safety hazards; third, plating pores or damage can trigger accelerated galvanic corrosion of the steel substrate, and existing passivation treatments offer limited protection and lack self-healing capabilities; finally, existing technologies often address single problems in isolation, lacking integrated synergy between punching precision, interfacial structure, plating function, and surface protection, making it difficult to balance performance and cost, thus hindering its systematic application.

[0034] This application discloses a perforated tin-plated steel strip. It includes a steel substrate layer, a nickel-activated underlayer fixedly connected to the upper surface of the steel substrate layer, an amorphous nickel-phosphorus functional layer fixedly connected to the upper surface of the nickel-activated underlayer, a microcrystalline tin-plated layer fixedly connected to the upper surface of the amorphous nickel-phosphorus functional layer, an inorganic conversion film fixedly connected to the upper surface of the microcrystalline tin-plated layer, and an organosilane sealing layer containing corrosion inhibitor microcapsules fixedly connected to the upper surface of the inorganic conversion film.

[0035] The composite gradient transition layer designed in this application helps to solve the interface bonding problem. The nickel-activated bottom layer forms a stable metallurgical anchor point on the steel substrate; the amorphous nickel-phosphorus functional layer on top provides a rigid support platform; and the outer microcrystalline tin-plated layer has toughness. This gradient transition of mechanical properties from flexibility to rigidity and then to toughness can disperse and absorb the interface stress generated during subsequent processing or use, avoid stress concentration on a single interface, and thus reduce the risk of coating peeling.

[0036] Example 1: This example provides a perforated tin-plated steel strip, the detailed manufacturing process of which includes the following steps: Step 1: Substrate Pretreatment and Precision Stamping SPCC cold-rolled low-carbon steel strip coil conforming to JIS G3141 standard is selected as the steel substrate layer (100), with a thickness of 0.08mm. The steel strip coil is fed into a continuous high-speed stamping machine. The stamping die material is M42 high-cobalt high-speed tool steel. The stamping process parameters are set as follows: the die clearance on one side accounts for 6.25% of the substrate thickness, specifically 0.005mm, and the alloy punch diameter is 1.0mm. During the stamping process, low-viscosity volatile stamping oil containing extreme pressure additives is used for sufficient lubrication, and the stamping speed is controlled at 1500 times / minute. Through the synergistic effect of the above process parameters, a punch array with a hole diameter of 1.0mm and a hole spacing of 1.3mm is prepared on the steel strip. After stamping, an online optical inspection system is used to monitor the hole edge quality to ensure that the maximum burr height does not exceed 0.020mm and the skirt height does not exceed 0.015mm.

[0037] Step 2: Pre-treatment Cleaning The stamped steel strip is sequentially passed through an online continuous treatment tank and undergoes the following treatments: 1) Alkaline electrolytic degreasing to remove stamping oil and surface contaminants; 2) Multi-stage countercurrent hot water rinsing; 3) Acid pickling activation, short-term treatment in a 5% hydrochloric acid solution to remove any slight oxide layer that may be present on the surface; 4) Multi-stage countercurrent pure water rinsing until the steel strip surface reaches the cleanliness and activation state required for subsequent electroplating processes.

[0038] Step 3: Construction of the composite gradient transition layer 200. This is the core process step of the present invention, and it is completed on a continuous electroplating production line: Nickel activation underlayer 210: A clean steel strip is introduced into an impact nickel plating bath; the electroplating solution uses a high chloride Watt nickel formulation; rapid impact electroplating is performed for 2-5 seconds at a high cathode current density of 60-80 A / dm²; this process deposits a pure nickel layer with a thickness of 0.1 μm, extremely fine grains, and strong adhesion to the substrate on the entire surface of the steel substrate layer 100; this nickel activation underlayer 210 not only provides a high-adhesion base, but also provides a uniform catalytically active surface for subsequent chemical plating layers.

[0039] Amorphous nickel-phosphorus functional layer 220 deposition: After being washed with water, the steel strip enters the electroless nickel-phosphorus plating bath. The plating solution is a medium-phosphorus electroless nickel plating formula with sodium hypophosphite as the reducing agent. By controlling the composition of the plating solution and the operating parameters, the phosphorus mass percentage in the deposited layer is kept stable within the range of 8.5wt%±1.5wt%. The working temperature of the plating solution is maintained at 88±2°C, and the pH value is continuously monitored and adjusted to be controlled at 4.6-5.0. The residence time of the steel strip in the plating solution is determined by controlling its running speed. Finally, an amorphous nickel-phosphorus functional layer 220 with a thickness of 0.2μm is deposited on the nickel activation underlayer 210. Due to the self-catalytic characteristics of the electroless plating process, the thickness distribution of this layer is highly consistent on the plane and edge of the steel strip. X-ray diffraction analysis of the layer structure shows that the spectrum exhibits the typical broadened diffuse scattering peaks characteristic of amorphous materials, confirming that it is an amorphous structure.

[0040] Step 4: Preparation of the Microcrystalline Tin Plating Layer 300. After thorough washing, the steel strip is placed in a tin plating bath with a methanesulfonic acid system. Electroplating is performed using a bidirectional pulse power supply to prepare the microcrystalline tin plating layer 300. The plating solution contains specific organic additives such as grain refiners, brighteners, and leveling agents. The pulse electroplating parameters are set as follows: forward peak current density 15 A / dm², reverse peak current density 40 A / dm², forward conduction time 10 ms, and reverse conduction time 1 ms. By controlling the traveling speed of the steel strip, the average thickness of the final pure tin layer is ensured to be 3.0 μm. The surface morphology of the plating layer is observed using a scanning electron microscope, revealing that the grains are fine, dense, and equiaxed, with a statistically average grain size of approximately 300 nm. The thickness of the steel strip at different locations is measured using an X-ray fluorescence thickness gauge, and the thickness deviation at each point is less than 8%, verifying the excellent uniform plating capability of the pulse reverse electroplating process in complex morphology areas.

[0041] Step 5: Formation of the composite self-healing passivation layer 400 Formation of inorganic conversion film 410: After tin plating, the steel strip is cleaned and then immersed in a trivalent chromium passivation bath for 20 seconds at room temperature; the tin layer surface reacts chemically with the passivation solution to form a dense and stable inorganic conversion film 410 with a thickness of about 0.1 μm in situ; this film can effectively inhibit the natural oxidation and discoloration of tin and provide basic corrosion protection.

[0042] Formation of organosilane sealing layer 420: Subsequently, the steel strip is coated with an organosilane working solution containing corrosion inhibitor microcapsules through a continuous process of dip coating-air knife blowing-drying; the working solution uses γ-(2,3-epoxypropoxy)propyltrimethoxysilane as the main film-forming agent, and microcapsules with an average particle size of 1 μm are uniformly dispersed in it by mechanical stirring; the microcapsules are prepared by complex coagulation method with benzotriazole as the core material and gelatin-gum arabic as the wall material; the coated steel strip is heated and cured in a 120°C oven for 5 minutes, during which the silane hydrolyzes and crosslinks to form a 0.2 μm thick, hydrophobic three-dimensional network film, namely the organosilane sealing layer 420 containing corrosion inhibitor microcapsules; this layer is stably bonded to the inorganic conversion film 410 below through chemical bonds.

[0043] Example 2: This example provides a perforated tin-plated steel strip, including a steel substrate layer 100. A nickel activation underlayer 210 is fixedly connected to the upper surface of the steel substrate layer 100. An amorphous nickel-phosphorus functional layer 220 is fixedly connected to the upper surface of the nickel activation underlayer 210. A microcrystalline structure tin plating layer 300 is fixedly connected to the upper surface of the amorphous nickel-phosphorus functional layer 220. An inorganic conversion film 410 is fixedly connected to the upper surface of the microcrystalline structure tin plating layer 300. An organosilane sealing layer 420 containing corrosion inhibitor microcapsules is fixedly connected to the upper surface of the inorganic conversion film 410.

[0044] The nickel-activated bottom layer 210 and the amorphous nickel-phosphorus functional layer 220 together constitute the composite gradient transition layer 200, which has an overall thickness of 0.2 μm. The inorganic conversion film 410 and the organosilane sealing layer 420 containing corrosion inhibitor microcapsules together constitute the composite self-healing passivation layer 400, which has an overall thickness of 0.1 μm.

[0045] Among them, the nickel-activated bottom layer 210 is a pure nickel pre-plating layer with a thickness of 0.1μm.

[0046] Among them, the amorphous nickel-phosphorus functional layer 220 is a chemically plated nickel-phosphorus alloy layer with a thickness of 0.1 μm, and the mass percentage content of phosphorus element in the nickel-phosphorus alloy layer is 7%.

[0047] Among them, the inorganic conversion film 410 is a chemical conversion film with a thickness of 0.05 μm and based on trivalent chromium compounds.

[0048] Among them, the organosilane sealing layer 420 containing corrosion inhibitor microcapsules is an organosilane network structure with a thickness of 0.05 μm formed by cross-linking and curing, and the corrosion inhibitor microcapsules are uniformly dispersed and encapsulated in the network structure.

[0049] The thickness of the microcrystalline tin plating layer 300 is 2μm, and the average grain size of the tin plating layer is less than 500nm.

[0050] The steel substrate layer 100 is a 0.035mm thick SPCC low-carbon cold-rolled steel strip with a pre-formed punched structure through a precision stamping process, and the residual height of the punched hole edge burrs is no more than 0.020mm.

[0051] Among them, between the nickel-activated bottom layer 210 and the amorphous nickel-phosphorus functional layer 220, and between the amorphous nickel-phosphorus functional layer 220 and the microcrystalline tin-plated layer 300, an interfacial intersolubility region with a thickness of nanometer level is formed through atomic interdiffusion.

[0052] The microcrystalline tin plating layer 300 is prepared using a pulsed current electroplating process. The parameters of this process are set as follows: forward current density 10A / dm², reverse current density 30A / dm², forward pulse width 5ms, and reverse pulse width 0.5ms.

[0053] Example 3: This example provides a perforated tin-plated steel strip, including a steel substrate layer 100. A nickel-activated underlayer 210 is fixedly connected to the upper surface of the steel substrate layer 100. An amorphous nickel-phosphorus functional layer 220 is fixedly connected to the upper surface of the nickel-activated underlayer 210. A microcrystalline tin-plated layer 300 is fixedly connected to the upper surface of the amorphous nickel-phosphorus functional layer 220. An inorganic conversion film 410 is fixedly connected to the upper surface of the microcrystalline tin-plated layer 300. An organosilane sealing layer 420 containing corrosion inhibitor microcapsules is fixedly connected to the upper surface of the inorganic conversion film 410.

[0054] The nickel-activated bottom layer 210 and the amorphous nickel-phosphorus functional layer 220 together constitute the composite gradient transition layer 200, which has an overall thickness of 0.6 μm. The inorganic conversion film 410 and the organosilane sealing layer 420 containing corrosion inhibitor microcapsules together constitute the composite self-healing passivation layer 400, which has an overall thickness of 0.4 μm.

[0055] Among them, the nickel-activated bottom layer 210 is a pure nickel pre-plating layer with a thickness of 0.3μm.

[0056] Among them, the amorphous nickel-phosphorus functional layer 220 is a chemically plated nickel-phosphorus alloy layer with a thickness of 0.3 μm, and the mass percentage content of phosphorus element in the nickel-phosphorus alloy layer is 11%.

[0057] Among them, the inorganic conversion membrane 410 is a chemical conversion membrane with a thickness of 0.15 μm and based on zirconium salt.

[0058] Among them, the organosilane sealing layer 420 containing corrosion inhibitor microcapsules is an organosilane network structure with a thickness of 0.25 μm formed by cross-linking and curing, and the corrosion inhibitor microcapsules are uniformly dispersed and encapsulated in the network structure.

[0059] The thickness of the microcrystalline tin plating layer 300 is 4 μm, and the average grain size of the tin plating layer is less than 500 nm.

[0060] The steel substrate layer 100 is a 0.1mm thick SPCC low-carbon cold-rolled steel strip with a pre-formed punched structure through a precision stamping process, and the residual height of the punched hole edge burrs is no more than 0.020mm.

[0061] Among them, between the nickel-activated bottom layer 210 and the amorphous nickel-phosphorus functional layer 220, and between the amorphous nickel-phosphorus functional layer 220 and the microcrystalline tin-plated layer 300, an interfacial intersolubility region with a thickness of nanometer level is formed through atomic interdiffusion.

[0062] The microcrystalline tin plating layer 300 is prepared using a pulsed current electroplating process. The parameters of this process are set as follows: forward current density 20A / dm², reverse current density 50A / dm², forward pulse width 15ms, and reverse pulse width 2ms.

[0063] Example 4: This example provides a perforated tin-plated steel strip, including a steel substrate layer 100. A nickel-activated underlayer 210 is fixedly connected to the upper surface of the steel substrate layer 100. An amorphous nickel-phosphorus functional layer 220 is fixedly connected to the upper surface of the nickel-activated underlayer 210. A microcrystalline tin-plated layer 300 is fixedly connected to the upper surface of the amorphous nickel-phosphorus functional layer 220. An inorganic conversion film 410 is fixedly connected to the upper surface of the microcrystalline tin-plated layer 300. An organosilane sealing layer 420 containing corrosion inhibitor microcapsules is fixedly connected to the upper surface of the inorganic conversion film 410.

[0064] The nickel-activated bottom layer 210 and the amorphous nickel-phosphorus functional layer 220 together constitute the composite gradient transition layer 200, which has an overall thickness of 0.4 μm. The inorganic conversion film 410 and the organosilane sealing layer 420 containing corrosion inhibitor microcapsules together constitute the composite self-healing passivation layer 400, which has an overall thickness of 0.25 μm.

[0065] Among them, the nickel-activated bottom layer 210 is a pure nickel pre-plating layer with a thickness of 0.2μm.

[0066] Among them, the amorphous nickel-phosphorus functional layer 220 is a chemically plated nickel-phosphorus alloy layer with a thickness of 0.2 μm, and the mass percentage content of phosphorus element in the nickel-phosphorus alloy layer is 9%.

[0067] Among them, the inorganic conversion film 410 is a chemical conversion film with a thickness of 0.1 μm and based on titanium salt.

[0068] Among them, the organosilane sealing layer 420 containing corrosion inhibitor microcapsules is an organosilane network structure with a thickness of 0.15 μm formed by cross-linking and curing, and the corrosion inhibitor microcapsules are uniformly dispersed and encapsulated in the network structure.

[0069] The thickness of the microcrystalline tin plating layer 300 is 3μm, and the average grain size of the tin plating layer is less than 500nm.

[0070] The steel substrate layer 100 is a 0.067mm thick SPCC low-carbon cold-rolled steel strip with a pre-formed punched structure through a precision stamping process, and the residual height of the punched hole edge burrs is no more than 0.020mm.

[0071] Among them, between the nickel-activated bottom layer 210 and the amorphous nickel-phosphorus functional layer 220, and between the amorphous nickel-phosphorus functional layer 220 and the microcrystalline tin-plated layer 300, an interfacial intersolubility region with a thickness of nanometer level is formed through atomic interdiffusion.

[0072] The microcrystalline tin plating layer 300 is prepared using a pulsed current electroplating process. The parameters of this process are set as follows: forward current density 15A / dm², reverse current density 40A / dm², forward pulse width 10ms, and reverse pulse width 1.25ms.

[0073] Performance testing Comparative Example 1: This comparative example refers to the content of Example 1, except that in step one, the single-sided clearance of the stamping die is adjusted to be 9.4% of the thickness of the substrate, specifically 0.0075 mm. This value is 50% larger than 6.25% in Example 1. The rest of the content is the same as in Example 1.

[0074] Comparative Example 2: This comparative example refers to Example 1, except that step three, "construction of the composite gradient transition layer 200", is omitted. That is, the nickel activation underlayer 210 and the amorphous nickel-phosphorus functional layer 220 are not deposited on the steel substrate layer 100. After the pretreatment in step two, the tin plating in step four is performed directly. The rest of the content is the same as in Example 1.

[0075] Comparative Example 3: This comparative example refers to the content of Example 1, except that in step four, “Preparation of microcrystalline tin plating layer 300”, the bidirectional pulse electroplating process is replaced with the traditional DC electroplating process; the DC current density is set to 15A / dm² to obtain a plating thickness similar to that of Example 1; the rest of the content is the same as that of Example 1.

[0076] Comparative Example 4: This comparative example refers to Example 1, except that in step five, "formation of composite self-healing passivation layer 400", only the "formation of inorganic conversion film 410" is performed, omitting the entire process of "formation of organosilane sealing layer 420"; that is, the passivation layer is only a single trivalent chromium inorganic conversion film. The rest is the same as in Example 1.

[0077] Performance testing Sample preparation: The corrosion-resistant high-precision punched tin-plated steel strip with a composite gradient interface structure prepared according to Example 1 was selected as the test sample. At the same time, corresponding products manufactured according to the processes of Comparative Examples 1 to 4 were prepared for subsequent performance comparison tests.

[0078] Salt spray resistance test: The sample is placed in a neutral salt spray test chamber with a concentration of 5% sodium chloride and a continuous spray test is carried out according to the standard specified in the national standard GB T10125; after 96 hours, the sample is taken out and its surface condition is observed.

[0079] Coating adhesion test: The cross-cut test method specified in the national standard GB / T9286 is used for evaluation; a grid array is drawn on the sample coating surface using a special tool, and then standard pressure-sensitive tape is tightly adhered to the grid area and quickly peeled off; the sample is taken out and its surface condition is observed.

[0080] Bending and welding performance test: Simulate the real battery assembly process, repeatedly bend the sample at a 90-degree angle and perform laser welding; after completing these simulated processes, carefully inspect the hole edge area and the heat-affected zone generated by welding.

[0081] Table 1: Performance Comparison Table Example Conclusion: As can be seen from Example 1 and Comparative Example 1, and Table 1, the optimization of the single-sided clearance of the stamping die is one of the factors affecting the overall performance of the product. By controlling the clearance to a low ratio, burrs and skirt defects during the punching process can be reduced, thereby providing a smoother and more stable substrate surface for subsequent coatings. This fine stamping condition helps to enhance the bonding strength between the coating and the substrate, and improves the uniformity of coating coverage in complex morphology areas such as hole edges, ultimately improving the product's corrosion resistance, coating adhesion, and structural integrity, demonstrating the synergistic effect between precision forming process and subsequent surface treatment.

[0082] As can be seen from Example 1 and Comparative Example 2, and Table 1, the construction of the composite gradient transition layer has an impact on product performance. The synergistic effect of the nickel-activated underlayer and the amorphous nickel-phosphorus functional layer not only provides the tin plating layer with high adhesion and a uniform catalytic surface, but also effectively blocks the penetration of corrosive media through its amorphous structure and alleviates the difference in physical properties between the substrate and the plating layer. This gradient interface structure improves the adhesion stability, environmental corrosion resistance, and resistance to bending and welding damage of the plating layer.

[0083] As can be seen from Example 1 and Comparative Example 3, and Table 1, the use of bidirectional pulse electroplating to prepare a microcrystalline tin plating layer is a technical means to improve product performance. Compared with DC electroplating, pulse electroplating promotes grain refinement and densification through periodic current changes, resulting in a more uniform crystallization and a denser structure in the plating layer, especially showing excellent coverage in areas such as the edges of punched holes. This microcrystalline structure enhances the mechanical strength and corrosion resistance of the plating layer and improves its resistance to cracking and peeling in subsequent processing.

[0084] As can be seen from Example 1 and Comparative Example 4, and Table 1, the formation of the composite self-healing passivation layer is a key step in ensuring the long-term protection of the product. The combination of the inorganic conversion film and the organosilane sealing layer not only forms a stable three-dimensional network barrier through chemical bonding, but also the introduction of corrosion inhibitor microcapsules endows the film with active repair capabilities. This composite structure improves the product's barrier effect against corrosive media, its resistance to damp heat oxidation, and its resistance to mechanical damage, highlighting the advantages of organic-inorganic synergistic passivation technology in achieving long-lasting protection and functional integration.

[0085] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A perforated tin-plated steel strip, characterized in that, The system includes a steel substrate layer (100), on the upper surface of which a nickel-activated underlayer (210) is fixedly connected, on the upper surface of which an amorphous nickel-phosphorus functional layer (220) is fixedly connected, on the upper surface of which a microcrystalline tin plating layer (300) is fixedly connected, on the upper surface of which an inorganic conversion film (410) is fixedly connected, and on the upper surface of which an organosilane sealing layer (420) containing corrosion inhibitor microcapsules is fixedly connected.

2. The perforated tin-plated steel strip according to claim 1, characterized in that, The nickel-activated bottom layer (210) and the amorphous nickel-phosphorus functional layer (220) together constitute a composite gradient transition layer (200), the overall thickness of which is 0.2 μm-0.6 μm; the inorganic conversion film (410) and the organosilane sealing layer (420) containing corrosion inhibitor microcapsules together constitute a composite self-healing passivation layer (400), the overall thickness of which is 0.1 μm-0.4 μm.

3. The perforated tin-plated steel strip according to claim 1, characterized in that, The nickel-activated underlayer (210) is a pure nickel pre-plating layer with a thickness of 0.1μm-0.3μm.

4. The perforated tin-plated steel strip according to claim 1, characterized in that, The amorphous nickel-phosphorus functional layer (220) is a chemically plated nickel-phosphorus alloy layer with a thickness of 0.1 μm to 0.3 μm, and the mass percentage content of phosphorus in the nickel-phosphorus alloy layer is 7% to 11%.

5. The perforated tin-plated steel strip according to claim 1, characterized in that, The inorganic conversion membrane (410) is a chemical conversion membrane with a thickness of 0.05μm-0.15μm and based on trivalent chromium compounds or titanium and zirconium salts.

6. The perforated tin-plated steel strip according to claim 1, characterized in that, The organosilane sealing layer (420) containing corrosion inhibitor microcapsules is an organosilane network structure with a thickness of 0.05μm-0.25μm, formed by cross-linking and curing, and the corrosion inhibitor microcapsules are uniformly dispersed and encapsulated in the organosilane network structure.

7. The perforated tin-plated steel strip according to claim 1, characterized in that, The thickness of the microcrystalline tin plating layer (300) is 2μm-4μm, and the average grain size of the tin plating layer is less than 500nm.

8. The perforated tin-plated steel strip according to claim 1, characterized in that, The steel substrate layer (100) is a SPCC low carbon cold-rolled steel strip with a thickness of 0.035mm-0.1mm. The steel substrate layer (100) has a punched structure pre-formed by a precision stamping process, and the residual height of the burrs at the edge of the punch is not greater than 0.020mm.

9. The perforated tin-plated steel strip according to claim 1, characterized in that, Between the nickel-activated bottom layer (210) and the amorphous nickel-phosphorus functional layer (220), and between the amorphous nickel-phosphorus functional layer (220) and the microcrystalline tin-plated layer (300), an interfacial intersolubility region with a thickness of nanometers is formed through atomic interdiffusion.

10. The perforated tin-plated steel strip according to claim 1, characterized in that, The microcrystalline tin plating layer (300) is prepared by a pulsed current electroplating process. The parameters of the process are set as follows: forward current density 10-20A / dm², reverse current density 30-50A / dm², forward pulse width 5-15ms, and reverse pulse width 0.5-2ms.

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