Stainless steel weir gate outer frame and method of manufacturing the same

Abstract

The present application relates to the technical field of metal material plating, in particular to a stainless steel weir gate outer frame and a preparation method thereof, which comprises the following steps: step 1: a stainless steel outer frame is sequentially subjected to primary heat treatment, pickling, alkali washing and water washing to obtain a pretreated outer frame; step 2: the pretreated outer frame is subjected to low-temperature nitriding and air cooling to form a nitriding layer and obtain a nitriding outer frame; step 3: a nickel-chromium layer is deposited on the surface of the nitriding outer frame by magnetron sputtering, a nickel-phosphorus layer is chemically plated on the surface of the nickel-chromium layer, and the outer frame is subjected to water washing, nitrogen blowing and drying and secondary heat treatment and air cooling to obtain a stainless steel weir gate outer frame.

Description

Technical Field

[0001] The invention relates to the technical field of metal material plating, in particular to a stainless steel weir gate outer frame and a preparation method thereof. Background Art

[0002] Stainless steel weir gate frames are widely used in marine engineering, water conservancy facilities and other fields. They need to be in highly corrosive and high-strength environments such as seawater for a long time. Therefore, the corrosion resistance and strength of stainless steel can no longer meet people's demand for stainless steel weir gate frames.

[0003] Chromium depletion is a key factor that leads to a decrease in corrosion resistance. In the existing technology, in order to improve corrosion resistance, traditional metal plating, single chromium plating or nickel plating, is usually adopted. Although a protective layer can be formed on the surface of stainless steel, it cannot solve the problem of chromium depletion: In addition, due to the poor bonding between the protective layer and the stainless steel substrate, under actual corrosive conditions, the protective layer is prone to cracking and damage, failing to play a protective role, resulting in further loss of chromium in the substrate, exacerbating the chromium depletion problem and causing intergranular corrosion; and in the existing technology, multi-layer metal plating to improve the strength and other properties of stainless steel will have the problem of excessive stress, causing the coating to crack, forming surface defects, leading to accelerated corrosion and increased chromium depletion.

[0004] In summary, it is of great significance to solve the above problems and prepare a stainless steel weir gate outer frame. Summary of the Invention

[0005] The object of the present invention is to provide a stainless steel weir gate outer frame and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A method for preparing a stainless steel weir gate outer frame comprises the following steps:

[0008] Step 1: The stainless steel outer frame is subjected to heat treatment, pickling, alkali washing, and water washing in sequence to obtain a pre-treated outer frame;

[0009] Step 2: Pre-treating the outer frame to perform low-temperature nitriding and air cooling to form a nitriding layer to obtain a nitrided outer frame;

[0010] Step 3: magnetron sputtering is used to deposit a nickel-chromium layer on the surface of the nitrided outer frame, followed by chemical plating of a nickel-phosphorus layer, followed by water washing, nitrogen drying, secondary heat treatment, and air cooling to obtain a stainless steel weir gate outer frame.

[0011] In a further embodiment, the stainless steel is 316 stainless steel.

[0012] More optimally, the thickness of the nitriding layer is 5-10 μm; the thickness of the nickel-chromium layer is 0.5-1 μm; and the thickness of the nickel-phosphorus layer is 20-30 μm.

[0013] More optimally, in step 1, the temperature of the primary heat treatment is 1050~1100°C; the components of the pickling solution in the pickling include 10~15wt% sulfuric acid, 3~5wt% nitric acid, and the rest is deionized water; the components of the alkaline solution in the alkaline washing include 5~8wt% sodium hydroxide, 3~5wt% sodium phosphate, and the rest is deionized water.

[0014] More optimally, in step 2, the process parameters of the low-temperature nitriding are: a nitrogen to hydrogen ratio of 1:3; a working pressure of 150-250 Pa; and a temperature of 400-450°C.

[0015] More optimally, in step 3, the process parameters of the magnetron sputtering deposition are: the target material is NiCr20wt% nickel-chromium target material; the vacuum degree is 1×10 -4 Pa; the working gas is argon, the argon flow rate is 20~50sccm; the current parameter is 5~8A; the temperature is 120~180℃.

[0016] More optimally, in step 3, the process parameters of the chemical plating are: the components of the chemical plating solution include 20~30g / L nickel sulfate, 15~25g / L sodium hypophosphite, 10~20g / L sodium citrate, 12~15g / L sodium acetate, 2~3mg / L thiourea, and 0.5~0.8g / L modified nano-silica; the pH is 4.5~5.0; the temperature is 70~80°C; and the ultrasonic frequency is 35~45Hz.

[0017] More optimally, the process parameters of the secondary heat treatment are: the gas atmosphere is a nitrogen atmosphere; the temperature of the secondary heat treatment is 400-500° C., and the time is 30-60 min.

[0018] More optimally, the preparation method of the modified nano-silica is as follows: S1-1: adding nano-silica and N,N-diethyl-3-aminopropyltrimethoxysilane to a 75-85 wt% ethanol aqueous solution, stirring at 40-50° C. for 3-5 hours, centrifugally washing, and drying to obtain aminosilica;

[0019] S1-2: Under a nitrogen atmosphere, aminosilica, bromododecane, and triethylamine were added to anhydrous ethanol, reacted at 60-80° C. for 3-6 hours, washed, and dried to obtain modified nanosilica.

[0020] More optimally, the raw materials of the modified nano-silica include the following components: 4 to 5 parts of nano-silica, 2 to 3 parts of N,N-diethyl-3-aminopropyltrimethoxysilane, 1 to 3 parts of bromododecane, and 0.05 to 0.1 parts of triethylamine, by mass.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] To ensure that the stainless steel weir gate outer frame maintains high corrosion resistance and strength in seawater, this solution uses a combination of primary heat treatment, surface pretreatment, low-temperature nitriding, magnetron sputtering nickel-chromium coating, chemical nickel-phosphorus plating, and secondary heat treatment to reduce the occurrence of chromium depletion and improve corrosion resistance and strength.

[0023] In the plan, a single heat treatment is first used to optimize the internal structure of the stainless steel and eliminate residual stress; then the pretreatment methods of pickling and alkali washing are used to increase the surface roughness of the stainless steel, which is conducive to improving the adhesion of subsequent nitriding and other processes on its surface.

[0024] Subsequently, a low-temperature nitriding process is used to form nitrides that consume some metal atoms, inhibiting the preferential oxidation of chromium to chromium oxide on the surface, thereby reducing chromium depletion caused by chromium oxidation loss. Simultaneously, the introduction of nitrogen optimizes the chemical composition of the stainless steel, improving its strength and corrosion resistance. Compared to traditional high-temperature nitriding, low-temperature nitriding not only reduces chromium depletion, but more importantly, due to the low processing temperature and gentle diffusion of nitrogen atoms, the stress generated is relatively low, avoiding stress concentration and providing a more stable surface substrate for the subsequent magnetron sputtering process.

[0025] However, the corrosion resistance of a single nitride layer in a highly corrosive environment is still limited, and there are also issues with weak bonding with the remaining coating layers and nitrogen diffusion. Therefore, in this application, magnetron sputtering is further used to form a nickel-chromium layer, which acts as a barrier layer and transition layer; this improves the bonding between the coating layers, inhibits nitrogen diffusion, and optimizes the overall performance of stainless steel under highly corrosive conditions.

[0026] Among them, the formation of the nickel-chromium layer has the following advantages: first, it directly supplements the chromium element, increases the surface chromium content, and further reduces the occurrence of chromium depletion, thereby improving corrosion resistance; second, the nickel-chromium layer formed by magnetron sputtering is firmly bonded to the substrate, and as a transition layer, it can improve the interface bonding force between the nitriding layer and the nickel-phosphorus layer, further improving the overall performance; third, the nickel-chromium layer can prevent the migration of nitrogen in the nitriding layer and inhibit element diffusion; fourth, the nickel-chromium layer can prevent the subsequent nickel-phosphorus layer from being damaged in terms of substrate performance, thereby improving the ability to resist crack propagation; fifth, increasing the chromium content can also improve passivation and diffusion barrier, thereby improving the durability of stainless steel. It should be noted that the nickel-chromium layer should not be too thick. An overly thick nickel-chromium layer will cause excessive stress, induce interface cracks, and reduce toughness, thereby leading to a decrease in corrosion resistance and strength.

[0027] Subsequently, modified nano-silica is obtained by quaternization reaction and used as a nanomaterial additive for chemical nickel-phosphorus plating. On the one hand, the intermolecular force and electrostatic effect promote the uniform adsorption of nickel-phosphorus alloy on the surface of modified nano-silica, significantly improving the uniformity of the coating. On the other hand, the quaternary ammonium salt structure decomposes under subsequent secondary heat treatment to provide an active nitrogen source, promoting the interface bonding between the nitriding layer and the coating. The modified nano-silica works synergistically with the chemical nickel-phosphorus plating layer to refine the grains and further fill the pores of the coating, thereby increasing the density and thus the strength. At the same time, it is closely combined with the nickel-chromium layer to build a solid protective barrier and reduce the risk of chromium depletion. It should be noted that the nickel-phosphorus layer should not be too thick. Excessive thickness will lead to a significant increase in stress, which is difficult to eliminate during secondary heat treatment. At the same time, an excessively thick nickel-phosphorus layer will also lead to coarse crystals of nickel-phosphorus alloy during the deposition process, defects in the internal structure, and decreased corrosion resistance and strength.

[0028] In order to further reduce stress and increase stability, the plan finally adopts secondary heat treatment. While reducing stress, it further integrates each layer with the stainless steel matrix, optimizes the organizational structure, and strengthens the bonding between layers and between the treated layer and the matrix. DETAILED DESCRIPTION

[0029] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0030] It should be noted that the following parts are by mass, and all raw materials involved in the present invention are purchased from manufacturers without any special restrictions. Examples include: in the following examples, the specification of nano-silica is 30 nm; the CAS number of N,N-diethyl-3-aminopropyltrimethoxysilane is 41051-80-3; and the CAS number of bromododecane is 143-15-7.

[0031] Example 1: A method for preparing a stainless steel weir gate outer frame, comprising the following steps:

[0032] Step 1: Add 4.5 parts of nano-silica and 2.5 parts of N,N-diethyl-3-aminopropyltrimethoxysilane to 80wt% ethanol aqueous solution, stir at 45°C for 4 hours, centrifuge, wash, and dry to obtain aminosilica; under a nitrogen atmosphere, add aminosilica, 2 parts of bromododecane, and 0.07 parts of triethylamine to anhydrous ethanol, react at 70°C for 4.5 hours, wash, and dry to obtain modified nano-silica;

[0033] Step 2: The 316 stainless steel outer frame is subjected to a heat treatment at 1050°C for 20 minutes, acid washing at room temperature for 8 minutes, alkaline washing at room temperature for 6 minutes, water washing, and nitrogen drying to obtain a pretreated outer frame;

[0034] Step 3: With a nitrogen to hydrogen ratio of 1:3 and a working pressure of 200 Pa, the pretreated outer frame is subjected to low-temperature nitriding at 410°C and air-cooled to form a nitriding layer to obtain a nitrided outer frame;

[0035] Step 4: Select NiCr20wt% nickel-chromium target and set the vacuum degree to 1×10 -4 Pa, argon flow rate of 35sccm, current parameters of 6A, temperature of 150℃, a nickel-chromium layer was deposited on the surface of the nitrided outer frame by magnetron sputtering; then a nickel-phosphorus layer was chemically plated by adjusting the pH to 4.7, the temperature to 75℃, and the ultrasonic frequency to 40Hz, washed with water, dried with nitrogen, and subjected to secondary heat treatment at 450℃ for 40min in a nitrogen atmosphere, and air-cooled to obtain a stainless steel weir gate outer frame.

[0036] In this scheme, the thickness of the nitriding layer is 8μm; the thickness of the nickel-chromium layer is 0.7μm; the thickness of the nickel-phosphorus layer is 25μm; the components of the pickling solution include 12wt% sulfuric acid, 4wt% nitric acid, and the rest is deionized water; the components of the alkaline solution in the alkaline washing include 6.5wt% sodium hydroxide, 4wt% sodium phosphate, and the rest is deionized water; the components of the chemical plating solution include 25g / L nickel sulfate, 20g / L sodium hypophosphite, 15g / L sodium citrate, 13g / L sodium acetate, 2.5mg / L thiourea, and 0.6g / L modified nano-silica.

[0037] Example 2: A method for preparing a stainless steel weir gate outer frame, comprising the following steps:

[0038] Step 1: Add 4.5 parts of nano-silica and 2.5 parts of N,N-diethyl-3-aminopropyltrimethoxysilane to 80wt% ethanol aqueous solution, stir at 45°C for 4 hours, centrifuge, wash, and dry to obtain aminosilica; under a nitrogen atmosphere, add aminosilica, 2 parts of bromododecane, and 0.07 parts of triethylamine to anhydrous ethanol, react at 70°C for 4.5 hours, wash, and dry to obtain modified nano-silica;

[0039] Step 2: The 316 stainless steel outer frame is subjected to a heat treatment at 1050°C for 20 minutes, acid washing at room temperature for 8 minutes, alkaline washing at room temperature for 6 minutes, water washing, and nitrogen drying to obtain a pretreated outer frame;

[0040] Step 3: With a nitrogen to hydrogen ratio of 1:3 and a working pressure of 200 Pa, the pretreated outer frame is subjected to low-temperature nitriding at 410°C and air-cooled to form a nitriding layer to obtain a nitrided outer frame;

[0041] Step 4: Select NiCr20wt% nickel-chromium target and set the vacuum degree to 1×10 -4 Pa, argon flow rate of 20sccm, current parameters of 5A, temperature of 120℃, a nickel-chromium layer was deposited on the surface of the nitrided outer frame by magnetron sputtering; then a nickel-phosphorus layer was chemically plated by adjusting the pH to 4.5, the temperature to 70℃, and the ultrasonic frequency to 35Hz, washed with water, dried with nitrogen, and subjected to secondary heat treatment at 450℃ for 40min in a nitrogen atmosphere, and air-cooled to obtain a stainless steel weir gate outer frame.

[0042] In this scheme, the thickness of the nitriding layer is 5μm; the thickness of the nickel-chromium layer is 0.5μm; the thickness of the nickel-phosphorus layer is 20μm; the components of the pickling solution include 12wt% sulfuric acid, 4wt% nitric acid, and the rest is deionized water; the components of the alkaline solution in the alkaline washing include 6.5wt% sodium hydroxide, 4wt% sodium phosphate, and the rest is deionized water; the components of the chemical plating solution include 20g / L nickel sulfate, 15g / L sodium hypophosphite, 10g / L sodium citrate, 12g / L sodium acetate, 2mg / L thiourea, and 0.5g / L modified nano-silica.

[0043] Example 3: A method for preparing a stainless steel weir gate outer frame, comprising the following steps:

[0044] Step 1: Add 4.5 parts of nano-silica and 2.5 parts of N,N-diethyl-3-aminopropyltrimethoxysilane to 80wt% ethanol aqueous solution, stir at 45°C for 4 hours, centrifuge, wash, and dry to obtain aminosilica; under a nitrogen atmosphere, add aminosilica, 2 parts of bromododecane, and 0.07 parts of triethylamine to anhydrous ethanol, react at 70°C for 4.5 hours, wash, and dry to obtain modified nano-silica;

[0045] Step 2: The 316 stainless steel outer frame is subjected to a heat treatment at 1050°C for 20 minutes, acid washing at room temperature for 8 minutes, alkaline washing at room temperature for 6 minutes, water washing, and nitrogen drying to obtain a pretreated outer frame;

[0046] Step 3: With a nitrogen to hydrogen ratio of 1:3 and a working pressure of 200 Pa, the pretreated outer frame is subjected to low-temperature nitriding at 410°C and air-cooled to form a nitriding layer to obtain a nitrided outer frame;

[0047] Step 4: Select NiCr20wt% nickel-chromium target and set the vacuum degree to 1×10 -4 Pa, argon flow rate of 50sccm, current parameters of 8A, temperature of 180℃, a nickel-chromium layer was deposited on the surface of the nitrided outer frame by magnetron sputtering; then a nickel-phosphorus layer was chemically plated by adjusting the pH to 5.0, temperature to 80℃, and ultrasonic frequency to 45Hz, washed with water, dried with nitrogen, and subjected to secondary heat treatment at 450℃ for 40min in a nitrogen atmosphere, and air-cooled to obtain a stainless steel weir gate outer frame.

[0048] In this scheme, the thickness of the nitriding layer is 10 μm; the thickness of the nickel-chromium layer is 1 μm; the thickness of the nickel-phosphorus layer is 30 μm; the components of the pickling solution include 12 wt% sulfuric acid, 4 wt% nitric acid, and the rest is deionized water; the components of the alkaline solution in the alkaline washing include 6.5 wt% sodium hydroxide, 4 wt% sodium phosphate, and the rest is deionized water; the components of the chemical plating solution include 30 g / L nickel sulfate, 25 g / L sodium hypophosphite, 20 g / L sodium citrate, 15 g / L sodium acetate, 3 mg / L thiourea, and 0.8 g / L modified nano-silica.

[0049] Comparative Example 1: Based on Example 1, the magnetron sputtered nickel-chromium layer was changed to a magnetron sputtered nickel layer, and the other processes remained unchanged, specifically:

[0050] Step 1: Add 4.5 parts of nano-silica and 2.5 parts of N,N-diethyl-3-aminopropyltrimethoxysilane to 80wt% ethanol aqueous solution, stir at 45°C for 4 hours, centrifuge, wash, and dry to obtain aminosilica; under a nitrogen atmosphere, add aminosilica, 2 parts of bromododecane, and 0.07 parts of triethylamine to anhydrous ethanol, react at 70°C for 4.5 hours, wash, and dry to obtain modified nano-silica;

[0051] Step 2: The 316 stainless steel outer frame is subjected to a heat treatment at 1050°C for 20 minutes, acid washing at room temperature for 8 minutes, alkaline washing at room temperature for 6 minutes, water washing, and nitrogen drying to obtain a pretreated outer frame;

[0052] Step 3: With a nitrogen to hydrogen ratio of 1:3 and a working pressure of 200 Pa, the pretreated outer frame is subjected to low-temperature nitriding at 410°C and air-cooled to form a nitriding layer to obtain a nitrided outer frame;

[0053] Step 4: Select nickel target and set the vacuum degree to 1×10 -4 Pa, argon flow rate of 35sccm, current parameters of 6A, temperature of 150℃, a nickel layer was deposited on the surface of the nitrided outer frame by magnetron sputtering; then a nickel-phosphorus layer was chemically plated by adjusting the pH to 4.7, the temperature to 75℃, and the ultrasonic frequency to 40Hz, washed with water, dried with nitrogen, and subjected to secondary heat treatment at 450℃ for 40min in a nitrogen atmosphere, and air-cooled to obtain a stainless steel weir gate outer frame.

[0054] In this scheme, the thickness of the nitriding layer is 8μm; the thickness of the nickel layer is 0.7μm; the thickness of the nickel-phosphorus layer is 25μm; the components of the pickling solution include 12wt% sulfuric acid, 4wt% nitric acid, and the rest is deionized water; the components of the alkaline solution in the alkaline washing include 6.5wt% sodium hydroxide, 4wt% sodium phosphate, and the rest is deionized water; the components of the chemical plating solution include 25g / L nickel sulfate, 20g / L sodium hypophosphite, 15g / L sodium citrate, 13g / L sodium acetate, 2.5mg / L thiourea, and 0.6g / L modified nano-silica.

[0055] Comparative Example 2: Based on Example 1, the thickness of the nickel-chromium layer was increased to 2 μm, and the other processes remained unchanged.

[0056] Comparative Example 3: Based on Example 1, the thickness of the nickel-phosphorus layer was increased to 45 μm, and the other processes remained unchanged.

[0057] Comparative Example 4: Based on Example 1, no nickel-chromium layer is provided, and a single nickel-phosphorus layer is plated. The other processes remain unchanged, specifically:

[0058] Step 1: Add 4.5 parts of nano-silica and 2.5 parts of N,N-diethyl-3-aminopropyltrimethoxysilane to 80wt% ethanol aqueous solution, stir at 45°C for 4 hours, centrifuge, wash, and dry to obtain aminosilica; under a nitrogen atmosphere, add aminosilica, 2 parts of bromododecane, and 0.07 parts of triethylamine to anhydrous ethanol, react at 70°C for 4.5 hours, wash, and dry to obtain modified nano-silica;

[0059] Step 2: The 316 stainless steel outer frame is subjected to a heat treatment at 1050°C for 20 minutes, acid washing at room temperature for 8 minutes, alkaline washing at room temperature for 6 minutes, water washing, and nitrogen drying to obtain a pretreated outer frame;

[0060] Step 3: With a nitrogen to hydrogen ratio of 1:3 and a working pressure of 200 Pa, the pretreated outer frame is subjected to low-temperature nitriding at 410°C and air-cooled to form a nitriding layer to obtain a nitrided outer frame;

[0061] Step 4: Adjust the pH to 4.7, the temperature to 75°C, and the ultrasonic frequency to 40 Hz to chemically plate a nickel-phosphorus layer on the surface of the nitrided outer frame, wash with water, blow dry with nitrogen, and perform a secondary heat treatment at 450°C for 40 minutes in a nitrogen atmosphere, and air cool to obtain a stainless steel weir gate outer frame.

[0062] In this scheme, the thickness of the nitriding layer is 8 μm; the thickness of the nickel-phosphorus layer is 25 μm; the components of the pickling solution in the pickling process include 12 wt% sulfuric acid, 4 wt% nitric acid, and the rest is deionized water; the components of the alkaline solution in the alkaline washing process include 6.5 wt% sodium hydroxide, 4 wt% sodium phosphate, and the rest is deionized water; the components of the chemical plating solution include 25 g / L nickel sulfate, 20 g / L sodium hypophosphite, 15 g / L sodium citrate, 13 g / L sodium acetate, 2.5 mg / L thiourea, and 0.6 g / L modified nano-silica.

[0063] Comparative Example 5: Based on Example 1, no modified nano-silica was added to the chemical plating solution, and the rest of the process remained unchanged, specifically:

[0064] Step 1: The 316 stainless steel outer frame is subjected to a heat treatment at 1050°C for 20 minutes, acid washing at room temperature for 8 minutes, alkaline washing at room temperature for 6 minutes, water washing, and nitrogen drying to obtain a pretreated outer frame;

[0065] Step 2: With a nitrogen to hydrogen ratio of 1:3 and a working pressure of 200 Pa, the pretreated outer frame is subjected to low-temperature nitriding at 410°C, air-cooled, and a nitriding layer is formed to obtain a nitrided outer frame;

[0066] Step 3: Select NiCr20wt% nickel-chromium target and set the vacuum degree to 1×10 -4 Pa, argon flow rate of 35sccm, current parameters of 6A, temperature of 150℃, a nickel-chromium layer was deposited on the surface of the nitrided outer frame by magnetron sputtering; then a nickel-phosphorus layer was chemically plated by adjusting the pH to 4.7, the temperature to 75℃, and the ultrasonic frequency to 40Hz, washed with water, dried with nitrogen, and subjected to secondary heat treatment at 450℃ for 40min in a nitrogen atmosphere, and air-cooled to obtain a stainless steel weir gate outer frame.

[0067] In this scheme, the thickness of the nitriding layer is 8μm; the thickness of the nickel-chromium layer is 0.7μm; the thickness of the nickel-phosphorus layer is 25μm; the components of the pickling solution include 12wt% sulfuric acid, 4wt% nitric acid, and the rest is deionized water; the components of the alkaline solution in the alkaline washing include 6.5wt% sodium hydroxide, 4wt% sodium phosphate, and the rest is deionized water; the components of the chemical plating solution include 25g / L nickel sulfate, 20g / L sodium hypophosphite, 15g / L sodium citrate, 13g / L sodium acetate, and 2.5mg / L thiourea.

[0068] Comparative Example 6: Based on Example 1, the low-temperature nitriding process was adjusted to a conventional nitriding process, and the other processes remained unchanged, specifically:

[0069] Step 1: Add 4.5 parts of nano-silica and 2.5 parts of N,N-diethyl-3-aminopropyltrimethoxysilane to 80wt% ethanol aqueous solution, stir at 45°C for 4 hours, centrifuge, wash, and dry to obtain aminosilica; under a nitrogen atmosphere, add aminosilica, 2 parts of bromododecane, and 0.07 parts of triethylamine to anhydrous ethanol, react at 70°C for 4.5 hours, wash, and dry to obtain modified nano-silica;

[0070] Step 2: The 316 stainless steel outer frame is subjected to a heat treatment at 1050°C for 20 minutes, acid washing at room temperature for 8 minutes, alkaline washing at room temperature for 6 minutes, water washing, and nitrogen drying to obtain a pretreated outer frame;

[0071] Step 3: Set the nitrogen pressure to 1 MPa, perform conventional nitriding at 1050°C, and air-cool to form a nitriding layer to obtain a nitrided outer frame;

[0072] Step 4: Select NiCr20wt% nickel-chromium target and set the vacuum degree to 1×10 -4 Pa, argon flow rate of 35sccm, current parameters of 6A, temperature of 150℃, a nickel-chromium layer was deposited on the surface of the nitrided outer frame by magnetron sputtering; then a nickel-phosphorus layer was chemically plated by adjusting the pH to 4.7, the temperature to 75℃, and the ultrasonic frequency to 40Hz, washed with water, dried with nitrogen, and subjected to secondary heat treatment at 450℃ for 40min in a nitrogen atmosphere, and air-cooled to obtain a stainless steel weir gate outer frame.

[0073] In this scheme, the thickness of the nitriding layer is 8μm; the thickness of the nickel-chromium layer is 0.7μm; the thickness of the nickel-phosphorus layer is 25μm; the components of the pickling solution include 12wt% sulfuric acid, 4wt% nitric acid, and the rest is deionized water; the components of the alkaline solution in the alkaline washing include 6.5wt% sodium hydroxide, 4wt% sodium phosphate, and the rest is deionized water; the components of the chemical plating solution include 25g / L nickel sulfate, 20g / L sodium hypophosphite, 15g / L sodium citrate, 13g / L sodium acetate, 2.5mg / L thiourea, and 0.6g / L modified nano-silica.

[0074] Testing experiment: The performance of the stainless steel weir gate outer frame prepared in Examples 1 to 3 and Comparative Examples 1 to 6 was tested: (1) Wear resistance test: The stainless steel weir gate outer frame prepared in Examples 1 to 3 and Comparative Examples 1 to 6 was subjected to a wear resistance test. The wear tester was set to a speed of 100 r / min, a load of 195 N, and 1000 r, and then the wear resistance rate was calculated; wear rate = (product mass before test - product mass after test) / product mass before test; the test results are shown in Table 1; (2) Corrosion resistance test: Referring to the "GB / T 10125-2021" standard, 50 g / L sodium chloride solution was added to 0.2 g / L anhydrous copper chloride, the pH was adjusted to 3.2, and the salt spray deposition was set to 2 mL / 80 cm²·h. The product was subjected to a salt spray test at 50°C for 250 h; the time when the product was rusted was tested; the test results are shown in Table 1.

[0075] Table 1

[0076]

[0077] Result analysis: According to the data analysis of Table 1, it can be seen from the data of Examples 1 to 3 that the stainless steel weir gate outer frame prepared by the present invention through surface pretreatment, low-temperature nitriding, magnetron sputtering nickel-chromium layer, and chemical nickel-phosphorus plating has good corrosion resistance and strength. It can be seen from the data of Comparative Example 1 that chromium supplementation is completely missing, the problem of chromium depletion is not solved, the corrosion rate is fast, and the strength decreases significantly; it can be seen from the data of Comparative Example 2 that the nickel-chromium layer is too thick, the stress is too large, cracks appear at the interface, the brittleness increases, and the corrosion resistance and strength properties both decrease; it can be seen from the data of Comparative Example 3 that the nickel-phosphorus layer is too thick, the deposition stress is significantly enhanced, the porosity increases, defects appear inside, the secondary heat treatment cannot eliminate the stress, and the corrosion resistance and strength decrease; it can be seen from the data of Comparative Example 4 that there is a lack of nickel-chromium layer, a lack of chromium source supplementation and diffusion barrier in the nickel-chromium layer, the nitrogen element in the nitriding layer quickly migrates to the surface, the chromium depletion phenomenon increases, the bonding force decreases, it is easy to delaminate and peel off, and the corrosion resistance and strength properties both decrease significantly; it can be seen from the data of Comparative Example 5 that without the introduction of modified nano-silica, the density decreases, there is no nitrogen element supplement, and the corrosion resistance and strength decrease; it can be seen from the data of Comparative Example 6 that the traditional nitriding process is prone to chromium depletion, and the surface stress is large, the substrate stability decreases, and the strength and corrosion resistance decrease significantly.

[0078] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A method for preparing a stainless steel weir gate outer frame, characterized in that: The following steps are involved: Step 1: The stainless steel outer frame is subjected to heat treatment, pickling, alkali washing, and water washing in sequence to obtain a pre-treated outer frame; Step 2: Pre-treating the outer frame to perform low-temperature nitriding and air cooling to form a nitriding layer to obtain a nitrided outer frame; Step 3: magnetron sputtering is used to deposit a nickel-chromium layer on the surface of the nitrided outer frame, followed by chemical plating of a nickel-phosphorus layer, followed by water washing, nitrogen drying, secondary heat treatment, and air cooling to obtain a stainless steel weir gate outer frame; In step 2, the process parameters of the low-temperature nitriding are: a nitrogen to hydrogen ratio of 1:3; a working pressure of 150-250 Pa; and a temperature of 400-450° C. In step 3, the process parameters of the magnetron sputtering deposition are as follows: the target material is NiCr20wt% nickel-chromium target; the vacuum degree is 1×10 -4 Pa; the working gas is argon, the argon flow rate is 20~50sccm; the current parameter is 5~8A; the temperature is 120~180℃; The thickness of the nickel-chromium layer is 0.5-1 μm; the thickness of the nickel-phosphorus layer is 20-30 μm; In step 3, the process parameters of the chemical plating are as follows: the components of the chemical plating solution include 20-30 g / L nickel sulfate, 15-25 g / L sodium hypophosphite, 10-20 g / L sodium citrate, 12-15 g / L sodium acetate, 2-3 mg / L thiourea, and 0.5-0.8 g / L modified nano-silica; the pH is 4.5-5.0; the temperature is 70-80° C.; and the ultrasonic frequency is 35-45 Hz. The preparation method of the modified nano-silica is as follows: S1-1: adding nano-silica and N,N-diethyl-3-aminopropyltrimethoxysilane to a 75-85 wt% ethanol aqueous solution, stirring at 40-50° C. for 3-5 hours, centrifuging, washing, and drying to obtain aminosilica; S1-2: Under a nitrogen atmosphere, aminosilica, bromododecane, and triethylamine were added to anhydrous ethanol, reacted at 60-80° C. for 3-6 hours, washed, and dried to obtain modified nanosilica.

2. The method for preparing a stainless steel weir gate outer frame according to claim 1, characterized in that: The thickness of the nitriding layer is 5-10 μm.

3. The method for preparing a stainless steel weir gate outer frame according to claim 1, characterized in that: In step 1, the temperature of the primary heat treatment is 1050-1100° C.; the components of the pickling solution in the pickling process include 10-15wt% sulfuric acid, 3-5wt% nitric acid, and the remainder is deionized water; the components of the alkaline solution in the alkaline washing process include 5-8wt% sodium hydroxide, 3-5wt% sodium phosphate, and the remainder is deionized water.

4. The method for preparing a stainless steel weir gate outer frame according to claim 1, characterized in that: The process parameters of the secondary heat treatment are: the gas atmosphere is a nitrogen atmosphere; the temperature of the secondary heat treatment is 400-500° C., and the time is 30-60 minutes.

5. The method for preparing a stainless steel weir gate outer frame according to claim 1, characterized in that: The synthetic raw materials of the modified nano-silica include the following components: 4-5 parts of nano-silica, 2-3 parts of N,N-diethyl-3-aminopropyltrimethoxysilane, 1-3 parts of bromododecane, and 0.05-0.1 parts of triethylamine, calculated by mass.

6. A stainless steel weir gate outer frame prepared according to the method for preparing a stainless steel weir gate outer frame according to any one of claims 1 to 5.

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