A high-hardness nickel-plated steel strip and preparation method thereof

Abstract

The invention provides a high-hardness nickel-plated steel strip and a preparation method thereof. Fine grain strengthening is generated and hardness is improved by controlling the temperature and time of heat treatment of martensitic stainless steel; vacuum carburizing is performed in a pulse mode of low-pressure carburizing-vacuum diffusion; electrolytic decontamination and pickling are performed before nickel plating to improve the bonding strength between the pretreated martensitic stainless steel strip and the coating; pre-nickel plating is performed on the pickled martensitic stainless steel strip to form a pre-nickel plating layer, a nickel-phosphorus plating layer is obtained on the pre-nickel plating layer after a primary nickel plating, and a modified polytetrafluoroethylene coating is obtained after a secondary nickel plating; polymethylvinylsiloxane is introduced in the primary nickel plating, isobutylmonomercaptopropylsilsesquioxane and a titanium-doped nickel-based metal organic framework are introduced in the secondary nickel plating to modify polytetrafluoroethylene, and the hydrophobicity of the modified polytetrafluoroethylene coating is synergistically improved.

Description

Technical Field

[0001] The invention relates to the technical field of steel strips, in particular to a high-hardness nickel-plated steel strip and a preparation method thereof. Background Art

[0002] With the transformation and upgrading of the machinery and electronics industry, the quality and performance requirements of stainless steel required by the industry are constantly increasing. The stainless steel materials used mainly include martensitic stainless steel and martensitic stainless steel. Although martensitic stainless steel has high strength and hardness, the toughness and corrosion resistance of the material cannot meet the expected requirements.

[0003] Martensitic steel mainly increases its strength and hardness after heat treatment by adding carbon elements. However, the addition of carbon often easily forms carbon segregation during rolling and heat treatment, which reduces the corrosion resistance of martensitic stainless steel. Summary of the invention

[0004] The object of the present invention is to provide a high-hardness nickel-plated steel strip and a preparation method thereof, so as to solve the problems in the prior art.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for preparing a high-hardness nickel-plated steel strip comprises the following steps:

[0007] S1: The martensitic stainless steel is melted in a vacuum induction furnace, and a martensitic stainless steel strip is obtained after hot rolling and cold rolling;

[0008] S2: heat treating the martensitic stainless steel strip, and then vacuum carburizing it by pulse method of low-pressure carburizing-vacuum diffusion, cooling it to 850°C with the furnace, cooling it with nitrogen, and then tempering it to obtain a pretreated martensitic stainless steel strip;

[0009] S3: polishing the pretreated martensitic stainless steel strip, performing electrolytic decontamination and pickling, and transferring the pretreated martensitic stainless steel strip to a pre-plating solution for pre-nickel plating to obtain a pre-nickel-plated stainless steel strip;

[0010] S4: The pre-nickel-plated stainless steel strip is subjected to a primary nickel plating treatment, a secondary nickel plating treatment, and then irradiated with 350-400W ultraviolet light for 5-10 minutes to obtain a high-hardness nickel-plated steel strip.

[0011] Furthermore, the working conditions of the heat treatment are: heating to 905°C and keeping it for 1 hour and then air cooling, heating to 755°C and keeping it for 2 hours and then air cooling, heating to 505°C and keeping it for 1 hour and then air cooling.

[0012] Furthermore, the nitrogen pressure is 1 bar, and the working conditions of the tempering treatment are: 295-300℃ for 1h; the gas used for vacuum carburizing is acetylene, the time is 7.5-8.5h, and the vacuum carburizing temperature is 1065-1070℃; the pulse mode of low-pressure carburizing-vacuum diffusion is: acetylene is introduced at a pressure of 720-820Pa for 50-100s, and the heating chamber is evacuated to 20-50Pa for 100-200s to complete a pulse process.

[0013] Furthermore, the working conditions of electrolytic decontamination are as follows: immersing the pretreated martensitic stainless steel strip in an alkaline washing solution, with the pretreated martensitic stainless steel strip as the positive electrode and the nickel electrode plate as the negative electrode, performing electro-alkaline washing for 2-3 minutes at a current of 2A and a voltage of 5-7V, and rinsing after taking it out; the alkaline washing solution: deionized water as the solvent, wherein sodium hydroxide is 20-30g / L, sodium silicate is 10-15g / L, trisodium phosphate is 30-40g / L, and sodium carbonate is 20-30g / L; the working conditions of pickling are as follows: the stainless steel strip after electrolytic decontamination is immersed in a hydrochloric acid solution with a volume fraction of 35% and immersed for 35-45s.

[0014] Furthermore, the working conditions for pre-nickel plating are: placing the pretreated martensitic stainless steel strip in the pre-plating solution for 2-3 minutes, with the pre-treated martensitic stainless steel strip as the negative electrode, the nickel electrode plate as the positive electrode, the current is 2.5A, and the voltage is 5-7V; the pre-plating solution is: deionized water as the solvent, wherein nickel sulfate hexahydrate is 200-300g / L and sulfuric acid is 100-200mL / L.

[0015] Furthermore, the working conditions of the primary nickel plating are: placing the pre-nickel-plated stainless steel strip in a primary nickel plating solution at 80-90° C. for 1-2 hours, with the pre-nickel-plated stainless steel strip as the negative electrode, the nickel electrode plate as the positive electrode, the current of 2.5A, and the voltage of 5-7V; the primary nickel plating solution is: deionized water as the solvent, wherein 20-30g / L of nickel sulfate hexahydrate, 25-35g / L of sodium hypophosphite, 5-10g / L of anhydrous sodium acetate, 10-20g / L of polymethylvinylsiloxane, 0.8-1.4g / L of glycine, and 15-25mL / L of lactic acid, and the pH of the primary nickel plating solution is 4.3-5.2.

[0016] Furthermore, the working conditions of the secondary nickel plating are: placing the pre-nickel-plated stainless steel strip in a secondary nickel plating solution at 80-90° C. for 1-2 hours, with the pre-nickel-plated stainless steel strip as the negative electrode, the nickel electrode plate as the positive electrode, the current of 2.5A, and the voltage of 5-7V; the secondary nickel plating solution is: deionized water as the solvent, wherein 20-30g / L of nickel sulfate hexahydrate, 25-35g / L of sodium hypophosphite, 15-25g / L of sodium citrate, 10-15g / L of anhydrous sodium acetate, 6-14mL / L of modified polytetrafluoroethylene solution, 0.8-1.4g / L of glycine, and 15-25mL / L of lactic acid; FC-40.4-0.6g / L, and the pH of the secondary nickel plating solution is 4.5-5.

[0017] Further, the preparation of modified polytetrafluoroethylene liquid comprises the following steps:

[0018] 1) mixing nickel nitrate hexahydrate, isopropyl titanate, terephthalic acid and anhydrous ethanol and stirring for 30-50 minutes, transferring to a reaction kettle and treating at 145-150° C. for 5-6 hours, cooling, centrifuging and washing to obtain a titanium-doped nickel-based metal organic framework;

[0019] 2) Mix isobutyl monomercaptopropyl silsesquioxane, titanium-doped nickel-based metal organic framework, polytetrafluoroethylene and N,N-dimethylformamide, and stir at 40-50° C. for 1-2 hours to obtain a modified polytetrafluoroethylene liquid.

[0020] Furthermore, the mass ratio of isobutyl monomercaptopropyl silsesquioxane, titanium-doped nickel-based metal organic framework, and polytetrafluoroethylene is 1:1:20.

[0021] Further, the preparation of polymethylvinylsiloxane comprises the following steps:

[0022] (1) Tetramethylammonium hydroxide pentahydrate is vacuumed at 55-60°C to remove crystal water, and after dissolution, vacuuming is stopped, octamethylcyclotetrasiloxane is added, mixed and stirred, and kept at 90-95°C for 2 hours to obtain tetramethylammonium hydroxide alkaline gel;

[0023] (2) Mix octamethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane and tetramethylammonium hydroxide alkali glue, evacuate until dissolved, heat to 90-95°C, add tetramethyldivinyldisiloxane for 20-30 minutes, heat to 95-100°C and keep for 2 hours, heat to 140-145°C and keep for 1 hour, and distill under reduced pressure to obtain polymethylvinylsiloxane.

[0024] Beneficial effects of the present invention:

[0025] The invention provides a high-hardness nickel-plated steel strip and a preparation method thereof. The high-hardness nickel-plated steel strip comprises a pretreated martensitic stainless steel strip and the pretreated martensitic stainless steel strip is subjected to pre-nickel plating, primary nickel plating and secondary nickel plating. The prepared high-hardness nickel-plated steel strip has high hardness, high corrosion resistance and high hydrophobicity.

[0026] The strengthening and toughening mechanism of martensitic stainless steel is closely related to its heat treatment process. The present invention controls the temperature and time of the heat treatment of martensitic stainless steel so that during the cooling process from the solution temperature to room temperature, the austenite in the martensitic stainless steel undergoes martensitic transformation, generates high-density phase transformation dislocations, produces fine grain strengthening, and generates dispersed nano-scale intermetallic compounds through aging to enhance the hardness of the martensitic stainless steel.

[0027] Carburizing is performed on martensitic stainless steel to further improve its hardness. However, conventional carburizing of martensitic stainless steel is different from carburizing of low-alloy carbon steel. There is a passivation film on its surface, which is prone to the phenomenon of failure to carburize or uneven carburizing layer. In addition, the carburizing temperature of stainless steel is higher than that of low-carbon steel and low-alloy steel, while the maximum operating temperature of the traditional carburizing furnace is 950°C, which cannot meet the requirements. The present invention uses vacuum carburizing to carburize martensitic stainless steel, which has high production efficiency and low cost, and can perform blind hole or small hole carburizing. The present invention not only removes the passivation film of stainless steel, but also meets the requirements of higher temperature carburizing, and can also avoid defects such as internal oxidation generated during the carburizing process. The pulsed carburizing method of low-pressure carburizing-vacuum diffusion is used to carburize, so that the hardness of the martensitic stainless steel increases gradually in steps, thereby improving its thermal stability.

[0028] In order to extend the corrosion resistance and hydrophobicity of the stainless steel strip, thereby increasing the service life of the stainless steel strip, the present invention performs nickel plating on the pretreated martensitic stainless steel strip;

[0029] In order to improve the bonding strength between the pretreated martensitic stainless steel strip and the coating, and expose the structure of the pretreated martensitic stainless steel strip to facilitate the growth of the coating, electrolytic decontamination and pickling are carried out before nickel plating. The polarization effect in the electrolysis process reduces the surface tension between the dirt and the alkali solution, thereby reducing the adhesion between the dirt and the substrate surface, making it easier for the oil to be peeled off and emulsified. The gas generated by the electrolysis also has the effect of enhancing stirring, thereby strengthening the emulsification effect.

[0030] Moreover, after the surface oxide film of martensitic stainless steel is removed, a new oxide film will be rapidly generated, which will cause the problem of poor coating bonding strength; therefore, the martensitic stainless steel strip after pickling is pre-nickel plated to form a pre-nickel layer to prevent the formation of oxide film;

[0031] The present invention obtains a nickel-phosphorus coating on the pre-nickel coating by a single nickel plating, and obtains a modified polytetrafluoroethylene coating by a secondary nickel plating, thereby improving the corrosion resistance and hydrophobicity of the stainless steel strip; although adding polytetrafluoroethylene on the basis of nickel-phosphorus can reduce the free energy of the coating surface and reduce the surface adsorption. However, due to the large difference in elemental composition, nickel, phosphorus, and polytetrafluoroethylene cannot be directly mixed and deposited on the substrate surface, so that polytetrafluoroethylene particles, nickel, and phosphorus particles are precipitated in the plating solution. Therefore, the present invention first plates a nickel-phosphorus coating as a bottom layer on the pre-nickel coating, and then deposits a modified polytetrafluoroethylene coating as a top layer, thereby improving the stability of the plating solution and improving the performance of the coating;

[0032] In the present invention, isobutyl mercaptopropyl silsesquioxane and titanium-doped nickel-based metal organic framework are introduced into the secondary nickel plating to modify polytetrafluoroethylene, thereby synergistically improving the hydrophobicity of the modified polytetrafluoroethylene coating; polymethylvinylsiloxane is introduced into the primary nickel plating; and polymethylvinylsiloxane and isobutyl mercaptopropyl silsesquioxane undergo a mercapto-olefin click chemical reaction under ultraviolet irradiation, thereby enhancing the bonding force between the coatings. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] It should be noted that if the embodiments of the present invention involve directional indications such as up, down, left, right, front, back, etc., the directional indication is only used to explain a specific posture such as the relative position relationship between the components, the movement status, etc. If the specific posture changes, the directional indication will also change accordingly. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0035] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0036] Example 1

[0037] A method for preparing a high-hardness nickel-plated steel strip, characterized in that it comprises the following steps:

[0038] S1: The martensitic stainless steel is melted in a vacuum induction furnace, and a martensitic stainless steel strip is obtained after hot rolling and cold rolling;

[0039] S2: heat treating the martensitic stainless steel strip, and then vacuum carburizing it by pulse method of low-pressure carburizing-vacuum diffusion, cooling it to 850°C with the furnace, cooling it with nitrogen, and then tempering it to obtain a pretreated martensitic stainless steel strip;

[0040] The working conditions of heat treatment are: heating to 905℃ and keeping it for 1 hour, then air cooling; heating to 755℃ and keeping it for 2 hours, then air cooling; heating to 505℃ and keeping it for 1 hour, then air cooling;

[0041] The gas used for vacuum carburizing is acetylene, the vacuum carburizing time is 7.5h, and the vacuum carburizing temperature is 1065℃; the pulse mode of low-pressure carburizing-vacuum diffusion is: acetylene is introduced at a pressure of 720Pa for 100s, and the heating chamber is evacuated to 20Pa for 200s to complete a pulse process; the nitrogen pressure is 1bar, and the working conditions of tempering treatment are: 295℃ for 1h;

[0042] S3: polishing the pretreated martensitic stainless steel strip, performing electrolytic decontamination and pickling, and transferring the pretreated martensitic stainless steel strip to a pre-plating solution for pre-nickel plating to obtain a pre-nickel-plated stainless steel strip;

[0043] The working conditions of electrolytic decontamination are as follows: the pretreated martensitic stainless steel strip is immersed in an alkaline cleaning solution, with the pretreated martensitic stainless steel strip as the positive electrode and the nickel electrode plate as the negative electrode, and the electro-alkaline cleaning is performed for 2 minutes at a current of 2A and a voltage of 5V, and then rinsed after being taken out; the alkaline cleaning solution: deionized water is used as the solvent, wherein the sodium hydroxide is 20g / L, the sodium silicate is 10g / L, the trisodium phosphate is 30g / L, and the sodium carbonate is 20g / L;

[0044] The working conditions of pickling are: the stainless steel strip after electrolytic decontamination is immersed in a hydrochloric acid solution with a volume fraction of 35% for 35 seconds;

[0045] The working conditions of pre-nickel plating are: the pre-treated martensitic stainless steel strip is placed in the pre-plating solution for 2 minutes, the pre-treated martensitic stainless steel strip is used as the negative electrode, the nickel electrode plate is used as the positive electrode, the current is 2.5A, and the voltage is 5V; the pre-plating solution is: deionized water as the solvent, wherein the hexahydrate nickel sulfate is 200g / L and the sulfuric acid is 100mL / L;

[0046] S4: subjecting the pre-nickel-plated stainless steel strip to a primary nickel plating treatment, a secondary nickel plating treatment, and then irradiating the strip under 350W ultraviolet light for 10 minutes to obtain a high-hardness nickel-plated steel strip;

[0047] The working conditions of the primary nickel plating are as follows: the pre-nickel-plated stainless steel strip is placed in a primary nickel plating solution at 80°C for 2 hours, the pre-nickel-plated stainless steel strip is used as the negative electrode, the nickel electrode plate is used as the positive electrode, the current is 2.5A, and the voltage is 5V; the primary nickel plating solution is: deionized water as the solvent, wherein 20g / L of nickel sulfate hexahydrate, 25g / L of sodium hypophosphite, 5g / L of anhydrous sodium acetate, 10g / L of polymethylvinylsiloxane, 0.8g / L of glycine, and 15mL / L of lactic acid, and the pH of the primary nickel plating solution is 4.3;

[0048] The working conditions of secondary nickel plating are as follows: the pre-nickel-plated stainless steel strip is placed in a secondary nickel plating solution at 80°C for 2h, the pre-nickel-plated stainless steel strip is used as the negative electrode, the nickel electrode plate is used as the positive electrode, the current is 2.5A, and the voltage is 5V; the secondary nickel plating solution is: deionized water as the solvent, wherein 20g / L of nickel sulfate hexahydrate, 25g / L of sodium hypophosphite, 15g / L of sodium citrate, 10g / L of anhydrous sodium acetate, 6mL / L of modified polytetrafluoroethylene solution, 0.8g / L of glycine, 15mL / L of lactic acid; 0.4g / L of FC-4, the pH of the secondary nickel plating solution is 4.5;

[0049] The preparation of modified polytetrafluoroethylene liquid comprises the following steps:

[0050] 1) 0.58 g nickel nitrate hexahydrate, 0.48 g isopropyl titanate, 0.66 g terephthalic acid, and 25 mL anhydrous ethanol were mixed and stirred for 30 min, transferred to a reactor and treated at 145° C. for 6 h, cooled, centrifuged, and washed to obtain a titanium-doped nickel-based metal organic framework;

[0051] 2) 0.5 g of isobutyl monomercaptopropyl silsesquioxane, 0.5 g of titanium-doped nickel-based metal organic framework, 10 g of polytetrafluoroethylene, and 10 mL of N,N-dimethylformamide were mixed, and stirred at 40° C. for 2 h to obtain a modified polytetrafluoroethylene liquid.

[0052] Example 2

[0053] A method for preparing a high-hardness nickel-plated steel strip, characterized in that it comprises the following steps:

[0054] S1: The martensitic stainless steel is melted in a vacuum induction furnace, and a martensitic stainless steel strip is obtained after hot rolling and cold rolling;

[0055] S2: heat treating the martensitic stainless steel strip, and then vacuum carburizing it by pulse method of low-pressure carburizing-vacuum diffusion, cooling it to 850°C with the furnace, cooling it with nitrogen, and then tempering it to obtain a pretreated martensitic stainless steel strip;

[0056] The working conditions of heat treatment are: heating to 905℃ and keeping it for 1 hour, then air cooling; heating to 755℃ and keeping it for 2 hours, then air cooling; heating to 505℃ and keeping it for 1 hour, then air cooling;

[0057] The gas used for vacuum carburizing is acetylene, the vacuum carburizing time is 8 hours, and the vacuum carburizing temperature is 1068°C; the pulse mode of low-pressure carburizing-vacuum diffusion is: acetylene is introduced at a pressure of 800Pa for 80 seconds, and the heating chamber is evacuated to 30Pa for 160 seconds to complete a pulse process; the nitrogen pressure is 1 bar, and the working conditions of the tempering treatment are: 298°C for 1 hour;

[0058] S3: polishing the pretreated martensitic stainless steel strip, performing electrolytic decontamination and pickling, and transferring the pretreated martensitic stainless steel strip to a pre-plating solution for pre-nickel plating to obtain a pre-nickel-plated stainless steel strip;

[0059] The working conditions of electrolytic decontamination are as follows: the pretreated martensitic stainless steel strip is immersed in an alkaline cleaning solution, with the pretreated martensitic stainless steel strip as the positive electrode and the nickel electrode plate as the negative electrode, and the electro-alkaline cleaning is performed for 2.5 minutes at a current of 2A and a voltage of 6V, and then rinsed after being taken out; the alkaline cleaning solution: deionized water is used as the solvent, wherein the sodium hydroxide is 25g / L, the sodium silicate is 12g / L, the trisodium phosphate is 33g / L, and the sodium carbonate is 24g / L;

[0060] The working conditions of pickling are as follows: the stainless steel strip after electrolytic decontamination is immersed in a hydrochloric acid solution with a volume fraction of 35% for 40 seconds;

[0061] The working conditions of pre-nickel plating are: the pre-treated martensitic stainless steel strip is placed in the pre-plating solution for 2.5 minutes, the pre-treated martensitic stainless steel strip is used as the negative electrode, the nickel electrode plate is used as the positive electrode, the current is 2.5A, and the voltage is 6V; the pre-plating solution is: deionized water as the solvent, wherein the hexahydrate nickel sulfate is 250g / L and the sulfuric acid is 150mL / L;

[0062] S4: subjecting the pre-nickel-plated stainless steel strip to a primary nickel plating treatment, a secondary nickel plating treatment, and then irradiating the strip under 380W ultraviolet light for 8 minutes to obtain a high-hardness nickel-plated steel strip;

[0063] The working conditions of the primary nickel plating are as follows: the pre-nickel-plated stainless steel strip is placed in a primary nickel plating solution at 85°C for 1.5 hours, the pre-nickel-plated stainless steel strip is used as the negative electrode, the nickel electrode plate is used as the positive electrode, the current is 2.5A, and the voltage is 6V; the primary nickel plating solution is: deionized water as the solvent, wherein 25g / L of nickel sulfate hexahydrate, 30g / L of sodium hypophosphite, 8g / L of anhydrous sodium acetate, 15g / L of polymethylvinylsiloxane, 1g / L of glycine, and 20mL / L of lactic acid, and the pH of the primary nickel plating solution is 5;

[0064] The working conditions of secondary nickel plating are as follows: the pre-nickel-plated stainless steel strip is placed in a secondary nickel plating solution at 85°C for 1.5h, the pre-nickel-plated stainless steel strip is used as the negative electrode, the nickel electrode plate is used as the positive electrode, the current is 2.5A, and the voltage is 6V; the secondary nickel plating solution is: deionized water as the solvent, wherein 25g / L of nickel sulfate hexahydrate, 30g / L of sodium hypophosphite, 20g / L of sodium citrate, 12g / L of anhydrous sodium acetate, 10mL / L of modified polytetrafluoroethylene solution, 1g / L of glycine, and 18mL / L of lactic acid; 0.5g / L of FC-4, and the pH of the secondary nickel plating solution is 4.7;

[0065] The preparation of modified polytetrafluoroethylene liquid comprises the following steps:

[0066] 1) 0.58 g nickel nitrate hexahydrate, 0.48 g isopropyl titanate, 0.66 g terephthalic acid, and 25 mL anhydrous ethanol were mixed and stirred for 40 min, transferred to a reactor and treated at 148° C. for 5.5 h, cooled, centrifuged, and washed to obtain a titanium-doped nickel-based metal organic framework;

[0067] 2) 0.5 g of isobutyl monomercaptopropyl silsesquioxane, 0.5 g of titanium-doped nickel-based metal organic framework, 10 g of polytetrafluoroethylene, and 10 mL of N,N-dimethylformamide were mixed, and stirred at 45° C. for 1.5 h to obtain a modified polytetrafluoroethylene liquid.

[0068] Example 3

[0069] A method for preparing a high-hardness nickel-plated steel strip, characterized in that it comprises the following steps:

[0070] S1: The martensitic stainless steel is melted in a vacuum induction furnace, and a martensitic stainless steel strip is obtained after hot rolling and cold rolling;

[0071] S2: heat treating the martensitic stainless steel strip, and then vacuum carburizing it by pulse method of low-pressure carburizing-vacuum diffusion, cooling it to 850°C with the furnace, cooling it with nitrogen, and then tempering it to obtain a pretreated martensitic stainless steel strip;

[0072] The working conditions of heat treatment are: heating to 905℃ and keeping it for 1 hour, then air cooling; heating to 755℃ and keeping it for 2 hours, then air cooling; heating to 505℃ and keeping it for 1 hour, then air cooling;

[0073] The gas used for vacuum carburizing is acetylene, the vacuum carburizing time is 8.5h, and the vacuum carburizing temperature is 1070℃; the pulse mode of low-pressure carburizing-vacuum diffusion is: acetylene is introduced at a pressure of 820Pa for 50s, and the heating chamber is evacuated to 50Pa for 100s to complete a pulse process; the nitrogen pressure is 1bar, and the working conditions of tempering treatment are: 300℃ for 1h;

[0074] S3: polishing the pretreated martensitic stainless steel strip, performing electrolytic decontamination and pickling, and transferring the pretreated martensitic stainless steel strip to a pre-plating solution for pre-nickel plating to obtain a pre-nickel-plated stainless steel strip;

[0075] The working conditions of electrolytic decontamination are as follows: the pretreated martensitic stainless steel strip is immersed in an alkaline cleaning solution, with the pretreated martensitic stainless steel strip as the positive electrode and the nickel electrode plate as the negative electrode, and the electro-alkaline cleaning is performed for 2 minutes at a current of 2A and a voltage of 7V, and then rinsed after being taken out; the alkaline cleaning solution: deionized water is used as the solvent, wherein the sodium hydroxide is 30g / L, the sodium silicate is 15g / L, the trisodium phosphate is 40g / L, and the sodium carbonate is 30g / L;

[0076] The working conditions of pickling are as follows: the stainless steel strip after electrolytic decontamination is immersed in a hydrochloric acid solution with a volume fraction of 35% for 45 seconds;

[0077] The working conditions of pre-nickel plating are: the pre-treated martensitic stainless steel strip is placed in the pre-plating solution for 3 minutes, the pre-treated martensitic stainless steel strip is used as the negative electrode, the nickel electrode plate is used as the positive electrode, the current is 2.5A, and the voltage is 7V; the pre-plating solution is: deionized water as the solvent, wherein the hexahydrate nickel sulfate is 300g / L and the sulfuric acid is 200mL / L;

[0078] S4: subjecting the pre-nickel-plated stainless steel strip to a primary nickel plating treatment, a secondary nickel plating treatment, and then irradiating the strip under 400W ultraviolet light for 5 minutes to obtain a high-hardness nickel-plated steel strip;

[0079] The working conditions of the primary nickel plating are as follows: placing the pre-nickel-plated stainless steel strip in a primary nickel plating solution at 90° C. for 1 hour, with the pre-nickel-plated stainless steel strip as the negative electrode, the nickel electrode plate as the positive electrode, the current of 2.5 A, and the voltage of 7 V; the primary nickel plating solution is as follows: deionized water as the solvent, wherein 30 g / L of nickel sulfate hexahydrate, 35 g / L of sodium hypophosphite, 10 g / L of anhydrous sodium acetate, 20 g / L of polymethylvinylsiloxane, 1.4 g / L of glycine, and 25 mL / L of lactic acid are contained; and the pH of the primary nickel plating solution is 4.3-5.2;

[0080] The working conditions of secondary nickel plating are as follows: the pre-nickel-plated stainless steel strip is placed in a secondary nickel plating solution at 90°C for 1 hour, the pre-nickel-plated stainless steel strip is used as the negative electrode, the nickel electrode plate is used as the positive electrode, the current is 2.5A, and the voltage is 7V; the secondary nickel plating solution is: deionized water as the solvent, wherein 30g / L of nickel sulfate hexahydrate, 35g / L of sodium hypophosphite, 25g / L of sodium citrate, 15g / L of anhydrous sodium acetate, 14mL / L of modified polytetrafluoroethylene solution, 1.4g / L of glycine, and 25mL / L of lactic acid; 0.6g / L of FC-4, and the pH of the secondary nickel plating solution is 5;

[0081] The preparation of modified polytetrafluoroethylene liquid comprises the following steps:

[0082] 1) 0.58 g nickel nitrate hexahydrate, 0.48 g isopropyl titanate, 0.66 g terephthalic acid, and 25 mL anhydrous ethanol were mixed and stirred for 50 min, transferred to a reactor and treated at 150° C. for 5 h, cooled, centrifuged, and washed to obtain a titanium-doped nickel-based metal organic framework;

[0083] 2) 0.5 g of isobutyl monomercaptopropyl silsesquioxane, 0.5 g of titanium-doped nickel-based metal organic framework, 10 g of polytetrafluoroethylene, and 10 mL of N,N-dimethylformamide were mixed, and stirred at 50° C. for 1 h to obtain a modified polytetrafluoroethylene liquid.

[0084] Comparative Example 1

[0085] Example 3 was used as the control group, which was not subjected to heat treatment and had other processes as normal.

[0086] Comparative Example 2

[0087] Example 3 was used as a control group. The vacuum carburizing treatment was not performed by the pulse mode of low-pressure carburizing-vacuum diffusion. The vacuum carburizing treatment was performed directly, and the other processes were normal.

[0088] Comparative Example 3

[0089] Example 3 was used as a control group, without vacuum carburizing treatment, and other processes were normal.

[0090] Comparative Example 4

[0091] Example 3 was used as the control group, in which electrolytic decontamination and pickling were not performed, and other processes were normal.

[0092] Comparative Example 5

[0093] Example 3 was used as a control group, in which the sample was not transferred to the pre-plating solution for pre-nickel plating, and other processes were normal.

[0094] Comparative Example 6

[0095] Example 3 was used as a control group, in which nickel plating was not performed once, and other processes were normal.

[0096] Comparative Example 7

[0097] Example 3 was used as a control group. No polymethylvinylsiloxane was added during the first nickel plating process, and the other processes were normal.

[0098] Comparative Example 8

[0099] Example 3 was used as a control group, in which no secondary nickel plating was performed and other processes were normal.

[0100] Comparative Example 9

[0101] Taking Example 3 as the control group, the modified polytetrafluoroethylene liquid was replaced by polytetrafluoroethylene liquid, and the other processes were normal.

[0102] Comparative Example 10

[0103] Example 3 was used as a control group, in which isobutyl monomercaptopropyl silsesquioxane was not added, and other processes were normal.

[0104] Comparative Example 11

[0105] Example 3 was used as a control group, in which titanium-doped nickel-based metal organic framework was not added, and other processes were normal.

[0106] The preparation of the polymethylvinylsiloxane used in the above examples and comparative examples comprises the following steps:

[0107] 0.5 g of tetramethylammonium hydroxide pentahydrate was vacuumed at 60°C to remove crystal water, and after dissolution, vacuuming was stopped, and 1 g of octamethylcyclotetrasiloxane was added, mixed and stirred, and kept at 95°C for 2 hours to obtain tetramethylammonium hydroxide alkaline gel;

[0108] Mix 0.28g of octamethylcyclotetrasiloxane, 0.22g of tetramethyltetravinylcyclotetrasiloxane and 7.5mg of tetramethylammonium hydroxide alkali glue, evacuate until dissolved, heat to 95°C, add 0.46g of tetramethyldivinyldisiloxane for 30 minutes, heat to 100°C and keep for 2h, heat to 145°C and keep for 1h, and distill under reduced pressure to obtain polymethylvinylsiloxane.

[0109] The sources of raw materials used in the above examples and comparative examples are:

[0110] Shanghai Aladdin Biochemical Technology Co., Ltd.: isopropyl titanate (analytical grade), terephthalic acid (analytical grade); Sinopharm Chemical Reagent Co., Ltd.: nickel nitrate hexahydrate (analytical grade), N,N-dimethylformamide (analytical grade), anhydrous ethanol (analytical grade); Chengdu Cologne Chemical Co., Ltd.: sodium hydroxide, sodium silicate, trisodium phosphate, sodium carbonate, hydrochloric acid, nickel sulfate hexahydrate, sulfuric acid, sodium hypophosphite, anhydrous sodium acetate, sodium citrate; Shanghai McLean Biochemical Technology Co., Ltd.: glycine G800880, L-lactic acid L81 2422; J&K: tetramethylammonium hydroxide pentahydrate; Dow Corning: octamethylcyclotetrasiloxane, octamethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane; Hybrid: isobutyl monomercaptopropyl silsesquioxane; Beijing Huawei Ruike Chemical Co., Ltd.: fluorocarbon surfactant FC-4; In terms of mass percentage, martensitic stainless steel is 1Cr17Ni2 stainless steel: carbon 0.1%, silicon 0.45%, manganese 1.25%, phosphorus 0.001%, sulfur 0.01%, chromium 17.05%, nickel 7.5%, and the balance is iron.

[0111] Performance Testing:

[0112] The high-hardness nickel-plated steel strips prepared in Examples 1-3 and Comparative Examples 1-11 were tested for hardness, corrosion resistance, and hydrophobicity;

[0113] Hydrophobicity: measure contact angle; Corrosion resistance: refer to GB / T 1771-2007 for salt spray test, cut into 150X75mm, 1mm thick plates, put into salt spray box for test, the temperature in the salt spray box is 35℃, and the exposure time is 1500h; the results are shown in Table 1;

[0114] Hardness (HRC) Contact angle (°) Corrosion resistance Example 1 61 148 No discoloration or rust Example 2 60 145 No discoloration or rust Example 3 63 152 No discoloration or rust Comparative Example 1 40 142 No discoloration or rust Comparative Example 2 35 141 No discoloration or rust Comparative Example 3 30 142 No discoloration or rust Comparative Example 4 45 138 Discoloration and rust Comparative Example 5 41 135 Discoloration and rust Comparative Example 6 43 133 Discoloration and rust Comparative Example 7 42 128 Discoloration and rust Comparative Example 8 45 121 Discoloration and rust Comparative Example 9 46 118 Discoloration and rust Comparative Example 10 47 131 No discoloration or rust Comparative Example 11 44 132 No discoloration or rust

[0115] Table 1

[0116] The present invention provides a high-hardness nickel-plated steel strip and a preparation method thereof. According to Examples 1-3, it can be seen that the prepared high-hardness nickel-plated steel strip has high hardness, high corrosion resistance and high hydrophobicity.

[0117] Comparing Example 3 with Comparative Example 1, the strengthening and toughening mechanism of martensitic stainless steel is closely related to its heat treatment process. The present invention controls the temperature and time of the heat treatment of martensitic stainless steel so that during the cooling process from the solution temperature to the room temperature, the austenite in the martensitic stainless steel undergoes martensitic transformation, generates high-density phase transformation dislocations, produces fine grain strengthening, and generates dispersed nano-scale intermetallic compounds through aging to enhance the hardness of the martensitic stainless steel.

[0118] Comparing Example 3 with Comparative Examples 2 and 3, the present invention adopts vacuum carburizing to carburize martensitic stainless steel, which has high production efficiency, low cost, and can be used for blind hole or small hole carburizing; the present invention can remove the passivation film of stainless steel, meet the requirements of higher temperature carburizing, and avoid defects such as internal oxidation generated during the carburizing process; the pulse carburizing method of low-pressure carburizing-vacuum diffusion is adopted to make the hardness of martensitic stainless steel rise gradually in steps, thereby improving its thermal stability.

[0119] Comparing Example 3 with Comparative Example 4, electrolytic decontamination and pickling were performed before nickel plating to improve the bonding strength between the pretreated martensitic stainless steel strip and the coating and to expose the structure of the pretreated martensitic stainless steel strip to facilitate coating growth.

[0120] Example 3 is compared with Comparative Example 5. After the surface oxide film of martensitic stainless steel is removed, a new oxide film will be quickly generated, which will cause the problem of poor coating adhesion. Therefore, the martensitic stainless steel strip after pickling is pre-nickel plated to form a pre-nickel plating layer to prevent the formation of oxide film and affect the coating adhesion.

[0121] Comparing Example 3 with Comparative Example 6, the present invention improves the stability of the plating solution by first plating a nickel-phosphorus coating on the pre-nickel coating as a bottom layer and then depositing a modified polytetrafluoroethylene coating as a top layer, thereby improving the performance of the coating.

[0122] Comparing Example 3 with Comparative Example 7, the present invention obtains a nickel-phosphorus coating layer on the pre-nickel coating layer by a single nickel plating, and obtains a modified polytetrafluoroethylene coating layer by a secondary nickel plating, thereby improving the corrosion resistance and hydrophobicity of the stainless steel strip; although adding polytetrafluoroethylene on the basis of nickel-phosphorus can reduce the free energy of the coating surface and reduce the surface adsorption. However, due to the large difference in elemental composition, nickel, phosphorus, and polytetrafluoroethylene cannot be directly mixed and deposited on the substrate surface, so that polytetrafluoroethylene particles, nickel, and phosphorus particles are precipitated in the plating solution.

[0123] Example 3 is compared with Comparative Examples 8 and 9, and polymethylvinylsiloxane is introduced in the primary nickel plating; polymethylvinylsiloxane and isobutylmercaptopropylsilsesquioxane undergo a mercapto-olefin click chemical reaction under ultraviolet irradiation, thereby enhancing the bonding force between the coatings; Example 3 is compared with Comparative Examples 10 and 11, and the present invention introduces isobutylmercaptopropylsilsesquioxane and titanium-doped nickel-based metal organic framework in the secondary nickel plating to modify polytetrafluoroethylene, thereby synergistically improving the hydrophobicity of the modified polytetrafluoroethylene coating.

[0124] The above description is only an embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural changes made by using the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing a high-hardness nickel-plated steel strip, characterized in that: The following steps are involved: S1: The martensitic stainless steel is melted in a vacuum induction furnace, and a martensitic stainless steel strip is obtained after hot rolling and cold rolling; S2: heat treating the martensitic stainless steel strip, and then vacuum carburizing it by pulse method of low-pressure carburizing-vacuum diffusion, cooling it to 850°C with the furnace, cooling it with nitrogen, and then tempering it to obtain a pretreated martensitic stainless steel strip; S3: polishing the pretreated martensitic stainless steel strip, performing electrolytic decontamination and pickling, and transferring the pretreated martensitic stainless steel strip to a pre-plating solution for pre-nickel plating to obtain a pre-nickel-plated stainless steel strip; S4: The pre-nickel-plated stainless steel strip is subjected to a primary nickel plating treatment, a secondary nickel plating treatment, and then irradiated with 350-400W ultraviolet light for 5-10 minutes to obtain a high-hardness nickel-plated steel strip; The working conditions of heat treatment are: heating to 905℃ and keeping it for 1 hour, then air cooling; heating to 755℃ and keeping it for 2 hours, then air cooling; heating to 505℃ and keeping it for 1 hour, then air cooling; The gas used for vacuum carburizing is acetylene, the time is 7.5-8.5h, and the vacuum carburizing temperature is 1065-1070℃; the pulse mode of low-pressure carburizing-vacuum diffusion is: acetylene is introduced at a pressure of 720-820Pa for 50-100s, and the heating chamber is evacuated to 20-50Pa for 100-200s to complete a pulse process; The working conditions of electrolytic decontamination are as follows: immersing the pretreated martensitic stainless steel strip in an alkaline washing solution, taking the pretreated martensitic stainless steel strip as the positive electrode and the nickel electrode plate as the negative electrode, performing electro-alkaline washing for 2-3 minutes at a current of 2A and a voltage of 5-7V, and rinsing after taking it out; the alkaline washing solution is deionized water as a solvent, wherein the sodium hydroxide is 20-30g / L, the sodium silicate is 10-15g / L, the trisodium phosphate is 30-40g / L, and the sodium carbonate is 20-30g / L; the working conditions of pre-nickel plating are as follows: placing the pretreated martensitic stainless steel strip in the pre-plating solution for 2-3 minutes, taking the pre-treated martensitic stainless steel strip as the negative electrode and the nickel electrode plate as the positive electrode, the current is 2.5A, and the voltage is 5-7V; the pre-plating solution is deionized water as a solvent, wherein the nickel sulfate hexahydrate is 200-300g / L and the sulfuric acid is 100-200mL / L; The working conditions of the primary nickel plating are as follows: placing the pre-nickel-plated stainless steel strip in a primary nickel plating solution at 80-90° C. for 1-2 hours, with the pre-nickel-plated stainless steel strip as the negative electrode, the nickel electrode plate as the positive electrode, the current of 2.5A, and the voltage of 5-7V; the primary nickel plating solution is as follows: deionized water as the solvent, wherein 20-30 g / L of nickel sulfate hexahydrate, 25-35 g / L of sodium hypophosphite, 5-10 g / L of anhydrous sodium acetate, 10-20 g / L of polymethylvinylsiloxane, 0.8-1.4 g / L of glycine, and 15-25 mL / L of lactic acid are contained, and the pH value of the primary nickel plating solution is 4.3-5.2; The preparation of polymethylvinylsiloxane comprises the following steps: (1) Tetramethylammonium hydroxide pentahydrate is vacuumed at 55-60°C to remove crystal water, and after dissolution, vacuuming is stopped, octamethylcyclotetrasiloxane is added, mixed and stirred, and kept at 90-95°C for 2 hours to obtain tetramethylammonium hydroxide alkaline gel; (2) octamethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane and tetramethylammonium hydroxide alkali glue are mixed and stirred, vacuumized until dissolved, heated to 90-95°C, tetramethyldivinyldisiloxane is added for 20-30 minutes, heated to 95-100°C and maintained for 2 hours, heated to 140-145°C and maintained for 1 hour, and distilled under reduced pressure to obtain polymethylvinylsiloxane; The working conditions of the secondary nickel plating are as follows: placing the pre-nickel-plated stainless steel strip in a secondary nickel plating solution at 80-90° C. for 1-2 hours, with the pre-nickel-plated stainless steel strip as the negative electrode, the nickel electrode plate as the positive electrode, the current of 2.5A, and the voltage of 5-7V; the secondary nickel plating solution is as follows: deionized water as the solvent, wherein the hexahydrate nickel sulfate is 20-30g / L, the hypophosphite sodium is 25-35g / L, the sodium citrate is 15-25g / L, the anhydrous sodium acetate is 10-15g / L, the modified polytetrafluoroethylene solution is 6-14mL / L, the glycine is 0.8-1.4g / L, the lactic acid is 15-25mL / L; FC-4 is 0.4-0.6g / L, and the pH of the secondary nickel plating solution is 4.5-5; The preparation of modified polytetrafluoroethylene liquid comprises the following steps: 1) mixing nickel nitrate hexahydrate, isopropyl titanate, terephthalic acid and anhydrous ethanol and stirring for 30-50 minutes, transferring to a reaction kettle and treating at 145-150° C. for 5-6 hours, cooling, centrifuging and washing to obtain a titanium-doped nickel-based metal organic framework; 2) Mix isobutyl monomercaptopropyl silsesquioxane, titanium-doped nickel-based metal organic framework, polytetrafluoroethylene and N,N-dimethylformamide, and stir at 40-50° C. for 1-2 hours to obtain a modified polytetrafluoroethylene liquid.

2. The method for preparing a high-hardness nickel-plated steel strip according to claim 1, characterized in that: The nitrogen pressure is 1 bar, and the working conditions of the tempering treatment are: 295-300℃ for 1h.

3. The method for preparing a high-hardness nickel-plated steel strip according to claim 1, characterized in that: In the preparation of modified polytetrafluoroethylene liquid, the mass ratio of isobutyl monomercaptopropyl silsesquioxane, titanium-doped nickel-based metal organic framework, and polytetrafluoroethylene is 1:1:

20.

4. A high hardness nickel-plated steel strip, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 3.