High grade surface flash nickel plated cold rolled sheet and method of production thereof

Abstract

The present application relates to a kind of high-grade surface flash nickel-plated cold-rolled plate and its production method, when flash nickel-plated, control the following process: 1) the upper surface and the lower surface of the strip steel are simultaneously sprayed with plating solution, and nickel is electroplated;2) the liquid supply flow is adjusted according to the set nickel plating layer thickness;3) the process temperature of plating solution is 50-60 ℃ when flash nickel-plated, heating heat exchanger is used to heat the plating solution when the flash nickel-plated unit starts, and the plating solution is cooled by cooling heat exchanger when the flash nickel-plated unit works normally;4) the plating solution is recycled, and a pre-coated backwash filter device is used to filter the plating solution.The present application is based on the formation mechanism of flash nickel-plated layer, and the main technical means is to improve the uniformity of plating solution distribution and the cleanliness of filtered plating solution, to realize the stable control of the surface quality of high surface grade flash nickel-plated cold-rolled plate, to improve the production efficiency of high surface grade flash nickel-plated cold-rolled plate, to improve the product competitiveness, and to meet the growing market demand, which has great significance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cold-rolled sheet production, and particularly relates to a high-grade surface flash nickel-plated cold-rolled sheet and a production method thereof. BACKGROUND

[0002] Flash nickel plating, also known as nano nickel plating, is a new electroplating technology developed in the past decade. Flash plating refers to a short-time and high-current electroplating process, which can quickly form a layer of plating on the surface of the plated part. In general, the current during flash plating is more than twice the normal electroplating current, and the time is 1-3 minutes.

[0003] In order to improve the quality of zinc plating, a flash nickel plating process is often added between the pretreatment and normal electroplating sections of a zinc electroplating unit to prepare an intermediate layer, which can significantly reduce the influence of defects on the surface of incoming materials on the electroplating quality, greatly improve the uniformity of the surface plating after electroplating of the strip steel, and obtain a fine and bright zinc layer.

[0004] During the production, transportation, storage and use of cold-rolled sheets, rusting is prone to occur on the surface if the cold-rolled sheets are in a humid environment. Therefore, protective treatments such as applying anti-rust oil and anti-rust packaging are required before the cold-rolled sheets are shipped, so as to ensure that the cold-rolled sheets have good surface quality and corrosion resistance. Although applying anti-rust oil and anti-rust packaging can effectively prevent the rusting of cold-rolled sheets, the cold-rolled sheets still need to be subjected to oil removal treatment before subsequent processing, which increases the process and the cost of treating oil-containing wastewater for users. In addition, anti-rust oil and oil removal waste liquid also pollute the environment, which does not meet the green requirements of the production process and reduces the competitiveness of the products. High-strength steel is widely used due to its excellent mechanical properties. The implementation of nickel plating on the surface of high-strength steel can effectively improve the corrosion resistance of the high-strength steel, and also can improve the wear resistance and hardness of the high-strength steel. Experiments have shown that flash nickel plating can change the electrochemical properties of the surface of cold-rolled sheets. When the flash plating time reaches 15 seconds, the self-corrosion potential of the cold-rolled sheets is obviously positively shifted, the self-corrosion current density is reduced by one order of magnitude compared with that before flash nickel plating, the polarization resistance is twice that before flash nickel plating, and the impedance value is also obviously increased. It can be seen that flash nickel plating reduces the surface activity and corrosion tendency of cold-rolled sheets and improves the corrosion resistance of the surface of cold-rolled sheets. After a certain amount of nickel is flash plated, the surface activity of the cold-rolled sheets is significantly reduced, and the rust prevention ability is significantly improved. Flash nickel plating can improve the corrosion resistance of the surface of cold-rolled sheets, and is a new and simple rust prevention method for cold-rolled sheets during storage, transportation and use.

[0005] The research on the surface quality stability control technology in the process of flash nickel plating of high-grade surface flash nickel-plated cold-rolled steel sheets is based on the formation mechanism of the flash nickel plating layer. The process and equipment of flash nickel plating are improved, so as to realize the stable control of the quality of high-grade surface flash nickel-plated cold-rolled sheets, improve the production efficiency of flash nickel-plated steel sheets, improve the competitiveness of products, and meet the growing market demand.

[0006] Chinese patent application CN202310022848.3 discloses a "cooling water collection and recycling system and method for cold-rolled flash-plated nickel mechanical seals". The system includes a cooling water collection tank, a static supply tank, a pump, an evaporator, and a switching valve. It mainly focuses on improving the cooling water collection and recycling system and process control for cold-rolled flash-plated nickel mechanical seals, but does not address the control of the surface quality of high-level flash-plated nickel cold-rolled sheets.

[0007] Chinese patent application CN201410255569.2 discloses a "method for nickel plating on steel plates", which includes the following steps: (1) ultrasonically dewaxing the steel plate; (2) immersing the steel plate in an alkaline cleaning solution with pH 10-12 for 5-8 minutes and performing electrolytic treatment with a cathode current density of 3-5 A / dm³. 2 , perform surface cleaning to remove surface oil stains, and rinse with clean water after electrolysis; (3) immerse the steel plate in an acidic solvent for cleaning to remove the oxide film on its surface, and after pickling, put the steel plate into clean water for cleaning; (4) perform activation treatment on the treated steel plate, and rinse with clean water after treatment; (5) put the steel plate into the electroplating solution for electroplating. The electroplating solution used includes the following components: nickel sulfate with a concentration of 150g / L-280g / L, nickel aminosulfonate with a concentration of 360g / L-420g / L, nickel chloride with a concentration of 15g / L-25g / L, and boric acid with a concentration of 20g / L. The solution temperature is 45-75℃, and the current density is 6-12A / dm. 2 With 38-50A / dm 2 Alternate between the two, with 10-15 alternations, where the time ratio between low current density and high current density is 1:2-2:3, and the electroplating time is 15-20 min; (6) pass the plated steel plate through a 4%-6% sodium hydroxide solution; (7) rinse the steel plate with clean water; (8) send the steel plate into a vacuum oven for drying, with the oven temperature controlled at 280-300℃. It involves the process and control of ordinary nickel plating of a single steel plate, which is completely different from the continuous cold-rolled strip surface flash nickel plating process using short time, high current, extremely thin plating thickness and continuous annealing unit, and does not involve the stable control of the surface quality of high surface level flash nickel plated cold-rolled plates. Summary of the Invention

[0008] This invention provides a high-grade flash-plated nickel cold-rolled sheet and its production method. Based on the formation mechanism of flash-plated nickel coating, the main technical means are to improve the uniformity of plating solution distribution and the cleanliness of the plating solution after filtration. This achieves stable control of the surface quality of high-grade flash-plated nickel cold-rolled sheet, which is of great significance for improving the production efficiency of high-grade flash-plated nickel cold-rolled sheet, enhancing product competitiveness, and meeting the growing market demand.

[0009] To achieve the above objectives, the present invention employs the following technical solution:

[0010] A high-grade surface flash-plated nickel cold-rolled sheet, the chemical composition of the cold-rolled sheet by weight percentage is: C: 0.001%~0.80%, Si: 0.01%~0.60%, Mn: 0.20%~1.60%, Cr: 0.01%~0.06%, Mo: 0.01%~0.05%, Ni≤0.10%, Cu≤0.10%, Nb≤0.500%, Ti≤0.300%, V≤0.008%, B≤0.005%, Al: 0.015%~0.0045%, N≤0.004%, P≤0.080%, S≤0.012%, with the remainder being Fe and unavoidable impurities; both the upper and lower surfaces of the cold-rolled sheet are covered with a flash-plated nickel layer.

[0011] A method for producing high-grade surface flash-plated nickel cold-rolled sheet, wherein the following process is controlled during flash plating:

[0012] 1) Nickel is electroplated by simultaneously spraying plating solution onto the upper and lower surfaces of the strip;

[0013] 2) The liquid supply flow rate for flash nickel plating is 5-40 m³ / h. 3 / h, using a variable frequency pump for liquid supply, with flow meters and manual valves installed on both branch liquid supply pipelines, the liquid supply flow rate is adjusted according to the set nickel plating layer thickness;

[0014] 3) The process temperature of the plating solution during flash nickel plating is 50-60℃. When the flash nickel plating unit is started, a heating heat exchanger is used to heat the plating solution. When the flash nickel plating unit is working normally, a cooling heat exchanger is used to cool the plating solution.

[0015] 4) The plating solution is recycled, and a pre-coated backwashing filter is used to filter the plating solution.

[0016] Nickel plating is performed using a horizontal flash nickel plating tank. The upper part of the horizontal flash nickel plating tank has an upper liquid inlet, and the lower part has a lower liquid inlet. Nickel is electroplated by simultaneously spraying plating solution onto the upper and lower surfaces of the strip. Buffer chambers are set on the outside of the upper and lower liquid inlets respectively. The plating solution enters the two corresponding buffer chambers from the supply pipe through the upper branch supply pipe and the lower branch supply pipe, and then enters the electroplating area through the corresponding buffer slope.

[0017] The buffer chamber is provided with a damping plate in the middle, and two branch liquid supply pipes are provided at intervals in both the upper and lower parts. The damping plate is inclined and the angle between the damping plate and the horizontal plane is 30° to 60°. Multiple damping holes are evenly opened on the damping plate.

[0018] The damping plate is divided into n regions on both sides from the corresponding upper and lower branch liquid supply pipes. The region opposite to the upper and lower branch liquid supply pipes is region 1, the regions on both sides of region 1 are region 2, the regions on both sides of region 2 are region 3, and so on. The diameter of the damping holes in regions 1 to n increases sequentially.

[0019] The angle α between the damping plate and the horizontal plane is related to the nickel flash plating solution supply L; L≤6m 3 When the speed is 6 / h, α = 50°~60°; 6<L≤10m 3 When the speed is / h, α = 45°~49°; 10<L≤14m 3 When the speed is / h, α = 40°~44°; L>14m 3 When the speed is / h, α = 30°~39°.

[0020] The pre-coated backwashing filtration device includes a plating solution circulation tank, a transfer pump, a diatomaceous earth mixing tank, a filter transfer pump, and a pre-coated diatomaceous earth plate-type sealed filter. First, the plating solution in the plating solution circulation tank is transferred to the diatomaceous earth mixing tank by the transfer pump to mix with diatomaceous earth. The mixture is then transferred to the pre-coated diatomaceous earth plate-type sealed filter by the filter transfer pump for preliminary filtration. The plating solution after preliminary filtration is returned to the plating solution circulation tank. Then, the plating solution is transferred from the plating solution circulation tank to the pre-coated diatomaceous earth plate-type sealed filter for precision filtration. After one filtration cycle, the pre-coated diatomaceous earth plate-type sealed filter is backwashed with compressed air and demineralized water. After the backwashing is completed, the next filtration cycle begins.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] Based on the formation mechanism of flash nickel plating, this study focuses on improving the uniformity of plating solution distribution and the cleanliness of the plating solution after filtration as the main technical means to achieve stable control of the surface quality of high-surface-level flash nickel-plated cold-rolled sheets. This is of great significance for improving the production efficiency of high-surface-level flash nickel-plated cold-rolled sheets, enhancing product competitiveness, and meeting the growing market demand. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the flash nickel plating process described in this invention.

[0024] Figure 2 This is a schematic diagram of the arrangement of the damping plate described in this invention.

[0025] Figure 3 This is a schematic diagram of the partitioning of the damping orifice described in this invention.

[0026] In the diagram: 1. Strip steel; 2. Anode plate; 3. Electroplating area; 41. Upper branch liquid supply pipe; 42. Lower branch liquid supply pipe; 5. Buffer chamber; 6. Buffer slope; 7. Horizontal flash nickel plating tank; 8. Damping plate; 9. Damping hole. Detailed Implementation

[0027] The present invention discloses a high-grade surface flash-plated nickel cold-rolled sheet. The chemical composition of the cold-rolled sheet, by weight percentage, is: C: 0.001%–0.80%, Si: 0.01%–0.60%, Mn: 0.20%–1.60%, Cr: 0.01%–0.06%, Mo: 0.01%–0.05%, Ni≤0.10%, Cu≤0.10%, Nb≤0.500%, Ti≤0.300%, V≤0.008%, B≤0.005%, Al: 0.015%–0.0045%, N≤0.004%, P≤0.080%, S≤0.012%, with the remainder being Fe and unavoidable impurities. Both the upper and lower surfaces of the cold-rolled sheet are covered with a flash-plated nickel layer.

[0028] The present invention discloses a method for producing high-grade surface flash-plated nickel cold-rolled steel sheet, wherein the flash-plating process is controlled as follows:

[0029] 1. Use a horizontal flash nickel plating bath 7 (e.g.) Figure 2 As shown), strip 1 is the negative electrode and anode plate 2 is the positive electrode, establishing an electroplating system; the horizontal flash nickel plating tank 7 has an upper liquid inlet at the top and a lower liquid inlet at the bottom, and nickel is electroplated by simultaneously spraying plating solution onto the upper and lower surfaces of strip 1; as shown Figure 1 As shown, buffer chambers 5 are respectively provided on the outer side of the upper liquid inlet and the lower liquid inlet. The plating solution enters the corresponding two buffer chambers 5 from the liquid supply pipe through the upper branch liquid supply pipe 41 and the lower branch liquid supply pipe 42, and then enters the electroplating area 3 through the corresponding buffer slope 6.

[0030] 2. The liquid supply flow rate for flash nickel plating is 5-40 m³ / h. 3 / h, using a variable frequency pump for liquid supply, with flow meters and manual valves installed on both branch liquid supply pipelines, the liquid supply flow rate is adjusted according to the set nickel plating layer thickness;

[0031] 3. The process temperature of the plating solution during flash nickel plating is 50-60℃. When starting the flash nickel plating unit, a heating heat exchanger is needed to heat the room-temperature plating solution to the process temperature. However, the electroplating process itself is exothermic, so the temperature of the plating solution will gradually increase after flash nickel plating begins. At this time, a cooling heat exchanger is needed to cool the plating solution and maintain its temperature within the process temperature range. In this invention, both heating and cooling of the plating solution are bypassed. A plate heat exchanger is preferred for cooling, and a tubular heat exchanger is preferred for heating.

[0032] In addition, since the plating solution (such as NiSO4) crystallizes to form nickel sulfate hexahydrate at 31.5-53.3℃ and to form nickel sulfate heptahydrate at temperatures below 31.5℃, the heat exchanger tubes are prone to blockage due to crystallization when the heating heat exchanger is shut down. When selecting a tubular heat exchanger, the end-bent tube type cannot be used, but the end-straight tube type needs to be used to facilitate direct disassembly and cleaning of the end when the machine is shut down.

[0033] The buffer chamber and buffer ramp are designed to prevent the plating solution from directly impacting the strip surface due to excessively concentrated flow. As a preferred solution, a damping plate 8 can be added to the buffer chamber 5. Figure 2 As shown, this is to further disperse the flow rate of the plating solution and make the flow field of the plating solution uniform. The damping plate 8 is located in the middle of the buffer chamber 5, and two branch liquid supply pipes 41 and two branch liquid supply pipes 42 are arranged at intervals. The damping plate 8 is inclined and multiple damping holes 9 are evenly opened on the damping plate 8.

[0034] To make the plating solution flow field more uniform, the damping plate 8 can be further divided into three regions (e.g., from the corresponding upper branch liquid supply pipe 41 and lower branch liquid supply pipe 42) on both sides. Figure 3 As shown in the figure, the area opposite to the upper branch liquid supply pipe 41 and the lower branch liquid supply pipe 42 is zone 1, the areas on both sides of zone 1 are zone 2, and the areas on both sides of zone 2 are zone 3; the diameter of the damping orifice 9 in zones 1 to 3 increases sequentially. The optimal distribution of the damping orifice 9 can be obtained through simulation, as shown in Table 1:

[0035] Table 1 Damping Orifice Parameters

[0036]

[0037] Through qualitative and quantitative comparisons and simulations, the optimal tilt angle α of the damping plate is between 30° and 60°. The angle α between the damping plate and the horizontal plane is related to the nickel flash plating supply volume L; as shown in Table 2:

[0038] Table 2 Damping Plate Angle Parameters

[0039]

[0040] By setting the optimal aperture, aperture spacing, and damping plate tilt angle, the CV value (flow coefficient) of the plating solution at the inlet section of the electroplating zone can be reduced by about 15% compared to before the improvement, which greatly improves the uniformity of the plating solution flow rate entering the electroplating zone, and thus improves the uniformity of the coating.

[0041] 4. The plating solution is recycled, and a pre-coated backwashing filter is used to filter the plating solution.

[0042] During flash nickel plating, sludge carried in by the strip steel can contaminate the plating solution, thus affecting the surface quality of the strip steel after flash nickel plating. Generally, a bypass filtration method is required to filter the plating solution. However, since the sludge particles in the plating solution are very small, conventional barrel-type filter screens are easily clogged. This invention uses a pre-coated backwashing filter device to filter the plating solution.

[0043] The pre-coated backwashing filtration device includes a plating solution circulation tank, a transfer pump, a diatomaceous earth mixing tank, a filter transfer pump, and a pre-coated diatomaceous earth plate-type sealed filter. First, the plating solution in the plating solution circulation tank is transferred to the diatomaceous earth mixing tank by the transfer pump to mix with diatomaceous earth. The mixture is then transferred to the pre-coated diatomaceous earth plate-type sealed filter for preliminary filtration by the filter transfer pump. The plating solution after preliminary filtration is returned to the plating solution circulation tank. Then, the plating solution is transferred from the plating solution circulation tank to the pre-coated diatomaceous earth plate-type sealed filter for precision filtration. After one filtration cycle, the pre-coated diatomaceous earth plate-type sealed filter is backwashed with compressed air and demineralized water. After the backwash is completed, the next filtration cycle begins.

[0044] To more intuitively illustrate the present invention, the embodiments of the present invention will be further described in conjunction with the examples. The following examples are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technical solutions that can be obviously obtained by those skilled in the art within the scope of the technology disclosed in the present invention, including simple variations or equivalent substitutions, are all within the scope of protection of the present invention.

[0045] Example:

[0046] The chemical composition of the strip steel in each embodiment is shown in Table 3, and the process parameters and the downgrade rate after flash nickel plating in each embodiment are shown in Table 4.

[0047] Table 3 Chemical composition of strip steel (wt%)

[0048]

[0049] Table 4 Process parameters and downgrade rate after flash nickel plating

[0050]

[0051] Before implementation, the downgrade rate of high-grade flash nickel-plated cold-rolled sheets due to nickel plating quality issues was approximately 9%. After implementation, the downgrade rate decreased to below 2%. This demonstrates that the implementation of this invention's technical solution has achieved a stable improvement in the surface quality and coating uniformity of high-grade flash nickel-plated cold-rolled products.

[0052] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for producing high-grade surface flash-plated nickel cold-rolled sheet, characterized in that, The chemical composition of the cold-rolled sheet, by weight percentage, is: C: 0.001%–0.80%, Si: 0.01%–0.60%, Mn: 0.20%–1.60%, Cr: 0.01%–0.06%, Mo: 0.01%–0.05%, Ni≤0.10%, Cu≤0.10%, Nb≤0.500%, Ti≤0.300%, V≤0.008%, B≤0.005%, Al: 0.015%–0.0045%, N≤0.004%, P≤0.080%, S≤0.012%, with the remainder being Fe and unavoidable impurities; both the upper and lower surfaces of the cold-rolled sheet are coated with a flash nickel layer. The production method of the high-grade surface flash-plated nickel cold-rolled sheet controls the following process during flash plating: 1) A horizontal flash nickel plating tank is used for nickel plating. The upper part of the horizontal flash nickel plating tank is equipped with an upper liquid inlet, and the lower part is equipped with a lower liquid inlet. The nickel is electroplated by spraying the plating solution onto the upper and lower surfaces of the strip simultaneously. Buffer chambers are set on the outside of the upper and lower liquid inlets respectively. The plating solution enters the corresponding two buffer chambers from the supply pipe through the upper branch supply pipe and the lower branch supply pipe, and then enters the electroplating area through the corresponding buffer slope. A damping plate is set in the middle of the buffer chamber. Two upper branch supply pipes and two lower branch supply pipes are set at intervals. The damping plate is inclined and the angle between the damping plate and the horizontal plane is 30° to 60°. Multiple damping holes are evenly opened on the damping plate. 2) The liquid supply flow rate for flash nickel plating is 5-40 m³ / h. 3 / h, using a variable frequency pump for liquid supply, with flow meters and manual valves installed on both branch liquid supply pipelines, the liquid supply flow rate is adjusted according to the set nickel plating layer thickness; 3) The process temperature of the plating solution during flash nickel plating is 50-60℃. When the flash nickel plating unit is started, a heating heat exchanger is used to heat the plating solution. When the flash nickel plating unit is working normally, a cooling heat exchanger is used to cool the plating solution. 4) The plating solution is recycled, and a pre-coated backwashing filter is used to filter the plating solution.

2. The method for producing a high-grade surface flash-plated nickel cold-rolled sheet according to claim 1, characterized in that, The damping plate is divided into n regions on both sides from the corresponding upper and lower branch liquid supply pipes. The region opposite to the upper and lower branch liquid supply pipes is region 1, the regions on both sides of region 1 are region 2, the regions on both sides of region 2 are region 3, and so on. The diameter of the damping holes in regions 1 to n increases sequentially.

3. The method for producing a high-grade surface flash-plated nickel cold-rolled sheet according to claim 1, characterized in that, The angle α between the damping plate and the horizontal plane is related to the nickel flash plating solution supply L; L≤6m 3 When the speed is 6 / h, α = 50°~60°; 6<L≤10m 3 When the speed is / h, α = 45°~49°; 10<L≤14m 3 When the speed is / h, α = 40°~44°; L>14m 3 When the speed is / h, α = 30°~39°.

4. The method for producing a high-grade surface flash-plated nickel cold-rolled sheet according to claim 1, characterized in that, The pre-coated backwashing filtration device includes a plating solution circulation tank, a transfer pump, a diatomaceous earth mixing tank, a filter transfer pump, and a pre-coated diatomaceous earth plate-type sealed filter. First, the plating solution in the plating solution circulation tank is transferred to the diatomaceous earth mixing tank by the transfer pump to mix with diatomaceous earth. The mixture is then transferred to the pre-coated diatomaceous earth plate-type sealed filter by the filter transfer pump for preliminary filtration. The plating solution after preliminary filtration is returned to the plating solution circulation tank. Then, the plating solution is transferred from the plating solution circulation tank to the pre-coated diatomaceous earth plate-type sealed filter for precision filtration. After one filtration cycle, the pre-coated diatomaceous earth plate-type sealed filter is backwashed with compressed air and demineralized water. After the backwashing is completed, the next filtration cycle begins.

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