Corrosion-resistant alloy material for crossover flange and forging process of flange

Abstract

The invention discloses a corrosion-resistant alloy material for a crossover flange and a forging process of the crossover flange, and belongs to the technical field of alloy materials.The corrosion-resistant alloy material is forged into a semi-finished flange, then titanium dioxide whiskers grow on the surface of the semi-finished flange in situ through micro-arc oxidation treatment, and the corrosion-resistant alloy material is obtained. Basic zinc carbonate is deposited on the surface of the oxidation treatment flange through a zinc sulfate solution and an ammonium bicarbonate solution, the zinc oxide composite flange with the surface combined with zinc oxide is obtained after calcination treatment, titanium dioxide whiskers and zinc oxide cooperate to form a compact composite oxidation film, permeation of corrosive media in seawater is effectively blocked, and the corrosion resistance of the seawater is improved. Zinc oxide has broad-spectrum antibacterial property and can inhibit attachment of sulfate reducing bacteria and other microorganisms in the ocean and reduce local corrosion, titanium dioxide can absorb full-wave-band ultraviolet light and decompose attached organic matter through photocatalytic reaction, surface self-cleaning is achieved through the synergistic effect of zinc oxide and titanium dioxide, and therefore it is guaranteed that the flange works stably for a long time.

Description

Technical Field

[0001] The present invention belongs to the technical field of alloy materials, and particularly relates to a corrosion-resistant alloy material for a conversion flange and a forging process of the flange. Background Art

[0002] With the rapid development of modern industry, especially in fields such as ocean engineering, petrochemical industry, and nuclear industry, the performance requirements for high-pressure pipeline connectors are getting higher and higher. Traditional forged flanges mostly use ordinary carbon steel or low-alloy steel. Although they meet the basic connection requirements to a certain extent, in some special applications, such as seawater corrosion in ocean engineering and acid-base corrosion in petrochemical industry, the corrosion resistance of traditional materials cannot meet the requirements for long-term use. Traditional forging processes usually adopt simple preheating, forging, quenching treatment, and surface treatment, such as galvanizing, painting, etc. Although they can improve the corrosion resistance to a certain extent, the protective layer is easy to fall off and has poor durability.

[0003] Chinese Patent Publication No. CN102921852B discloses a preparation method of a titanium alloy flange forging. This solution provides a method for preparing a flange from titanium alloy. Titanium alloy is a new type of medium-strength corrosion-resistant titanium alloy, which has strength, high plasticity, good processing and formability, excellent corrosion resistance, and is widely used in ships, chemical industry, and ocean industry, etc.

[0004] Chinese Patent Publication No. CN112126869B discloses a highly corrosion-resistant alloy flange and its preparation method, including an aluminum alloy material and a corrosion-resistant coating. The NiF2-TiF4-Ni coating is used to enhance the corrosion resistance of the aluminum alloy. However, the titanium alloy in this solution is applied in ocean engineering and is easily corroded by the high salt content of seawater. Although spraying a corrosion-resistant coating on the alloy surface can improve the corrosion resistance to a certain extent, it is vulnerable to the parasitism of marine organisms in ocean pipelines, resulting in the easy detachment of the protective layer, thus unable to ensure the effective and stable operation of the flange in the ocean. Summary of the Invention

[0005] The object of the present invention is to provide a corrosion-resistant alloy material for a conversion flange and a forging process of the flange. The corrosion-resistant alloy material is forged into a semi-finished flange, and then through micro-arc oxidation treatment, titanium dioxide whiskers are in-situ grown on the surface of the semi-finished flange. Zinc hydroxycarbonate is deposited on the surface of the oxidized flange by using zinc sulfate solution and ammonium bicarbonate solution. After calcination treatment, a zinc oxide composite flange with zinc oxide bonded to the surface is obtained. Then, the surface of the zinc oxide composite flange is sealed with phenolic resin to obtain a surface-sealed flange, and after calcination, a conversion flange is obtained. The titanium dioxide whiskers and zinc oxide synergistically form a dense composite oxide film, effectively blocking the penetration of corrosive media in seawater. Moreover, zinc oxide has broad-spectrum antibacterial properties, which can inhibit the attachment of sulfates, microorganisms and marine organisms in the ocean, reduce local corrosion. Titanium dioxide can absorb ultraviolet light in the full wavelength band and decompose the attached organic matter through photocatalytic reaction. The flange prepared by this forging process is different from the traditional process of spraying a corrosion-resistant coating on the surface, and realizes surface self-cleaning through the synergistic action of the two, avoiding the attachment of marine organisms, thereby ensuring the long-term stable operation of the flange.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] A corrosion-resistant alloy material for a conversion flange, by mass percentage, comprises the following components:

[0008] Fe 0.2 - 0.3%, Ru 0.1 - 0.15%, Cr 0.05 - 0.10%, Ni 0.2 - 0.30%, Mo 0.05 - 0.10%, Pt 0.3 - 0.5% and Al 0.3 - 0.6%, and the balance is titanium and inevitable impurities.

[0009] A forging process of a flange, the steps of the forging process are as follows:

[0010] Step 1: Forge the corrosion-resistant alloy material into a semi-finished flange, and then through micro-arc oxidation treatment, titanium dioxide whiskers are in-situ grown on the surface of the semi-finished flange to obtain an oxidized flange.

[0011] Step 2: Deposit zinc hydroxycarbonate on the surface of the oxidized flange by using zinc sulfate solution and ammonium bicarbonate solution, and after calcination treatment, a zinc oxide composite flange with zinc oxide bonded to the surface is obtained.

[0012] Step 3: Seal the surface of the zinc oxide composite flange with phenolic resin to obtain a surface-sealed flange, and after calcination, a conversion flange is obtained, completing the forging process of the flange.

[0013] Further, the specific forging steps of the semi-finished flange are as follows:

[0014] Place the corrosion-resistant alloy material in a smelting furnace, perform forging terminal forming at 920 - 940 °C, trim the edge of the corrosion-resistant alloy material after terminal forming, and keep it at 1150 - 1200 °C for 1 - 2 h, then cool it naturally to room temperature to obtain a flange blank; perform structural hardening treatment on the flange blank, keep it at 700 - 750 °C for 8 - 9 h, cool it to 600 - 650 °C and keep it for 10 - 11 h, and then cool it naturally to obtain a semi-finished flange.

[0015] Further, the specific steps of micro-arc oxidation treatment are as follows:

[0016] Place the semi-finished flange in a stainless steel electrolytic cell of a micro-arc oxidation system, use the semi-finished flange as the anode, use a stainless steel plate as the negative electrode of the power supply, immerse it in the electrolytic cell containing the electrolyte, and perform micro-arc oxidation for 40 - 50 min at a temperature of 20 - 25 °C, a frequency of 100 - 120 Hz, and a current density of 3 - 4 A / dm 2 to complete the micro-arc oxidation treatment.

[0017] Further, the electrolyte is prepared through the following steps:

[0018] Add 3-aminopropyltriethoxysilane, potassium hydroxide, sodium silicate, sodium hexametaphosphate, triethanolamine, sodium tetraborate, sodium fluoride, yttrium nitrate, ethylenediaminetetraacetic acid, and deionized water into a reaction kettle, stir at 15 - 20 °C and 200 - 220 r / min for 40 - 45 min, and perform ultrasonic dispersion for 20 - 30 min to obtain the electrolyte.

[0019] Further, the dosage ratio of 3-aminopropyltriethoxysilane, potassium hydroxide, sodium silicate, sodium hexametaphosphate, triethanolamine, sodium tetraborate, sodium fluoride, yttrium nitrate, ethylenediaminetetraacetic acid, and deionized water is 500 - 600 mL : 100 - 200 g : 800 - 900 g : 300 - 400 g : 500 - 600 mL : 80 - 90 mL : 50 - 100 mL : 20 - 25 mL : 18 - 20 mL : 8 - 9 L.

[0020] Further, the specific preparation steps of the zinc oxide composite flange are as follows:

[0021] Immerse the oxidized flange in a 10 - 15 wt% zinc sulfate solution, soak it at 40 - 50 °C for 30 - 40 min, then add a 10 - 15 wt% ammonium bicarbonate solution, continue to soak for 2 - 3 h, take it out and wash it 2 - 3 times with deionized water and absolute ethanol respectively, dry it with nitrogen, transfer the product to a muffle furnace, and calcine it at 500 - 550 °C for 2 - 3 h in a nitrogen atmosphere to obtain the zinc oxide composite flange.

[0022] Further, the volume ratio of the zinc sulfate solution to the ammonium bicarbonate solution is 4 - 5 L : 5 - 7.5 L.

[0023] Furthermore, the specific preparation steps of the conversion flange are as follows:

[0024] Immerse the zinc oxide composite flange in the sealing solution, soak it at 80 - 100 °C for 4 - 5 h, cool it naturally to room temperature, take it out and wash it 2 - 3 times with ionized water and anhydrous ethanol respectively, and dry it with nitrogen to obtain the surface-sealed flange; place the surface-sealed flange in a muffle furnace, under a nitrogen atmosphere, keep it at 900 - 950 °C for 1 - 2 h, then heat it to 1500 - 1600 °C and keep it for 1 - 2 h, and cool it naturally to room temperature to obtain the conversion flange.

[0025] Furthermore, the sealing solution is prepared through the following steps:

[0026] Add resorcinol, 35 - 40 wt% formaldehyde solution, 1 - 2 wt% hydrochloric acid solution, ethanol and deionized water into a reaction kettle, stir and react at 80 - 100 °C and 450 - 500 r / min for 1 - 2 h to obtain the sealing solution.

[0027] Furthermore, the dosage ratio of resorcinol, formaldehyde solution, hydrochloric acid solution, ethanol and deionized water is 1 - 2 kg : 1 - 2 L : 50 - 60 mL : 2 - 3 L : 3 - 4 L.

[0028] Advantages of the present invention:

[0029] 1. The conversion flange prepared by the present invention, when applied in marine pipelines, has good corrosion resistance, wear resistance and self-cleaning properties, can avoid the attachment of marine organisms, and at the same time has excellent compressive strength and can resist the strong water pressure in the ocean.

[0030] 2. For the surface-sealed flange of the present invention, using phenolic resin as the sealing agent, the surface of titanium dioxide whiskers has an interlaced network, which provides more anchoring points for phenolic resin and enhances the mechanical interlocking effect. The surface of the sealed flange is rough and has a low porosity, which can avoid the penetration of corrosive substances in the ocean. At high temperatures, phenolic resin serves as a carbon source and titanium dioxide whiskers provide a titanium source to form titanium carbide at the sealing position, so that part of the titanium dioxide whiskers can be retained. Titanium carbide can significantly improve the hardness and wear resistance of the flange surface and can effectively resist the corrosion of strong acids and strong alkalis, thus making the flange suitable for harsh environments such as chemical engineering and ocean engineering.

[0031] 3. The corrosion-resistant alloy material of the present invention promotes the growth of zinc oxide on the surface by oxidizing the titanium dioxide whisker structure on the flange surface as the active site for zinc oxide nucleation. The surface of the titanium dioxide whiskers is rich in hydroxyl groups, which can adsorb zinc ions to form a uniform zinc oxide coating layer. The two work together to form a dense composite oxide film, effectively blocking the penetration of corrosive media in seawater. Moreover, zinc oxide has broad-spectrum antibacterial properties, which can inhibit the attachment of sulfates, microorganisms, and marine organisms in the ocean, reducing local corrosion. Titanium dioxide can absorb ultraviolet light in the full wavelength range and decompose the attached organic matter through photocatalytic reactions to achieve surface self-cleaning, ensuring that the flange can work stably in marine pipelines for a long time. Detailed implementation manners

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0033] Example 1: A forging process of a conversion flange includes the following steps:

[0034] S1: Place the corrosion-resistant alloy material in a melting furnace, forge it at 920 °C, and perform terminal forming. Cut the edge of the corrosion-resistant alloy material after terminal forming, keep it warm at 1150 °C for 1 h, and naturally cool it to room temperature to obtain a flange blank. Perform structure hardening treatment on the flange blank, keep it warm at 700 °C for 8 h, cool it down to 600 °C and keep it warm for 10 h, and naturally cool it to room temperature to obtain a semi-finished flange.

[0035] The corrosion-resistant alloy material is composed of the following components by mass percentage: Fe 0.2%, Ru 0.1%, Cr 0.05%, Ni 0.2%, Mo 0.05%, Pt 0.3%, and Al 0.3%, and the balance is titanium and inevitable impurities.

[0036] S2: Add 500 mL of 3-aminopropyltriethoxysilane, 100 g of potassium hydroxide, 800 g of sodium silicate, 300 g of sodium hexametaphosphate, 500 mL of triethanolamine, 80 mL of sodium tetraborate, 50 mL of sodium fluoride, 20 mL of yttrium nitrate, 18 mL of ethylenediaminetetraacetic acid, and 8 L of deionized water into a reaction kettle, stir it at 15 °C and 200 r / min for 40 min, and perform ultrasonic dispersion for 20 min to obtain an electrolyte.

[0037] S3: Place the semi-finished flange in the stainless-steel electrolytic cell of the micro-arc oxidation system. Use the semi-finished flange as the anode and a 100 mm × 100 mm 304 stainless-steel plate as the negative electrode of the power supply. Immerse them in the electrolytic cell containing the electrolyte. Perform micro-arc oxidation for 40 min at 20 °C, a frequency of 100 Hz, and a current density of 3 A / dm 2 to obtain an oxidized flange with titanium dioxide whiskers on its surface.

[0038] In micro-arc oxidation, through the high-temperature and high-pressure action of instantaneous breakdown discharge, an oxide film layer mainly composed of the matrix metal oxide and supplemented with the electrolyte components is formed on the flange surface. Titanium dioxide whiskers grow in-situ on the flange surface through high-voltage discharge. The grown titanium dioxide whiskers have a very strong bonding force with the matrix and are not easily peeled off.

[0039] In the electrolyte components, sodium fluoride etches the titanium surface to form a local high-electric-field region, inducing the directional growth of whiskers. Yttrium nitrate doping inhibits grain coarsening. Through micro-arc oxidation treatment, a micro-arc oxidation film layer can be formed, which can endow the material with better mechanical properties. However, during the micro-arc oxidation process, the plasma discharge causes the internal molten oxides and gases to escape outward, resulting in the formed micro-arc oxidation film layer having a porous and rough microstructure, which is easily invaded by seawater in ocean engineering, causing corrosion of the flange matrix and even cracking or peeling of the film layer.

[0040] S4: Immerse the oxidized flange in 4 L of a zinc sulfate solution with a mass fraction of 10%. Soak it at 40 °C for 30 min, then add 5 L of an ammonium bicarbonate solution with a mass fraction of 10%, continue to soak for 2 h, take it out and wash it 2 times with ionized water and absolute ethanol respectively, dry it with nitrogen, transfer the product to a muffle furnace, and calcine it at 500 °C for 2 h in a nitrogen atmosphere to obtain a zinc oxide composite flange.

[0041] The hydroxyl groups on the surface of titanium dioxide whiskers are the active sites for the nucleation of zinc oxide, thus promoting the growth of zinc oxide on the surface of the oxidized flange. The surface of titanium dioxide whiskers is rich in hydroxyl groups, which can adsorb zinc ions to form a uniform zinc oxide coating layer. The two work together to form a dense composite oxide film, effectively blocking the penetration of corrosive media in seawater. Zinc oxide has broad-spectrum antibacterial properties and can inhibit the attachment of microorganisms such as marine sulfate-reducing bacteria, reducing local corrosion. Titanium dioxide can absorb ultraviolet light in the entire wavelength range and decompose the attached organic matter through photocatalytic reaction to achieve surface self-cleaning.

[0042] S5: Add 1 kg of resorcinol, 1 L of a formaldehyde solution with a mass fraction of 35%, 50 mL of a hydrochloric acid solution with a mass fraction of 1%, 2 L of ethanol, and 3 L of deionized water to the reaction kettle. Stir and react at 80 °C and 450 r / min for 1 h to obtain a sealing solution;

[0043] Immerse the zinc oxide composite flange in the sealing solution, soak it at 80 °C for 4 h, cool it naturally to room temperature, take it out and wash it twice with ionized water and anhydrous ethanol respectively, and dry it with nitrogen to obtain a surface-sealed flange; place the surface-sealed flange in a muffle furnace, under a nitrogen atmosphere, keep it at 900 °C for 1 h, then heat it to 1500 °C and keep it for 1 h, and cool it naturally to room temperature to obtain a converted flange, completing the forging process of the converted flange.

[0044] Using phenolic resin as a sealing agent, the surface of titanium dioxide whiskers has an interlaced network structure, providing more anchoring points for phenolic resin and enhancing the mechanical interlocking effect. The surface of the sealed flange is rough and has a low porosity, which can avoid the penetration of corrosive substances in the ocean. At high temperatures, phenolic resin serves as a carbon source and titanium dioxide whiskers provide a titanium source to form titanium carbide at the sealing point. Titanium carbide can significantly improve the hardness and wear resistance of the flange surface and can effectively resist the corrosion of strong acids and alkalis, making the flange suitable for harsh environments such as chemical engineering and ocean engineering.

[0045] Example 2: A forging process for a converted flange, including the following preparation steps:

[0046] S1: Place the corrosion-resistant alloy material in a melting furnace, perform forging terminal forming at 930 °C, trim the corrosion-resistant alloy material after terminal forming, and keep it at 1180 °C for 1.2 h, then cool it naturally to room temperature to obtain a flange blank; perform structural hardening treatment on the flange blank, keep it at 730 °C for 8.5 h, cool it down to 630 °C and keep it for 10.5 h, and cool it naturally to room temperature to obtain a semi-finished flange.

[0047] The corrosion-resistant alloy material is composed of the following components by mass percentage: Fe 0.25%, Ru 0.13%, Cr 0.08%, Ni 0.25%, Mo 0.08%, Pt 0.4% and Al 0.5%, and the balance is titanium and unavoidable impurities.

[0048] S2: Add 750 mL of 3-aminopropyltriethoxysilane, 150 g of potassium hydroxide, 850 g of sodium silicate, 350 g of sodium hexametaphosphate, 550 mL of triethanolamine, 85 mL of sodium tetraborate, 75 mL of sodium fluoride, 22.5 mL of yttrium nitrate, 19 mL of ethylenediaminetetraacetic acid and 8.5 L of deionized water into a reaction kettle, stir it at 18 °C and 210 r / min for 42.5 min, and perform ultrasonic dispersion for 25 min to obtain an electrolyte solution.

[0049] S3: Place the semi-finished flange in a stainless steel electrolytic cell of a micro-arc oxidation system, use the semi-finished flange as the anode, a 100 mm × 100 mm 304 stainless steel plate as the power supply cathode, immerse it in the electrolytic cell containing the electrolyte solution, at 22.5 °C, a frequency of 110 Hz and a current density of 3.5 A / dm2 Micro-arc oxidation was carried out for 45 min under the following conditions to obtain an oxidized flange with titanium dioxide whiskers on the surface.

[0050] S4: Immerse the oxidized flange in a 4.5 L zinc sulfate solution with a mass fraction of 13%, soak it at 45 °C for 35 min, then add 6 L of ammonium bicarbonate solution with a mass fraction of 13%, continue to soak for 2.5 h, take it out and wash it twice with ionized water and anhydrous ethanol respectively, dry it with nitrogen, transfer the product to a muffle furnace, heat it to 530 °C in a nitrogen atmosphere and calcine it for 2.3 h to obtain a zinc oxide composite flange.

[0051] S5: Add 1.5 kg of resorcinol, 1.5 L of formaldehyde solution with a mass fraction of 37.5%, 55 mL of hydrochloric acid solution with a mass fraction of 1.5%, 2.5 L of ethanol and 3.5 L of deionized water to a reaction kettle, stir and react at 90 °C and 475 r / min for 1.5 h to obtain a sealing solution;

[0052] Immerse the zinc oxide composite flange in the sealing solution, soak it at 90 °C for 4.5 h, naturally cool it to room temperature, take it out and wash it twice with ionized water and anhydrous ethanol respectively, dry it with nitrogen to obtain a surface-sealed flange; place the surface-sealed flange in a muffle furnace, keep it at 925 °C for 1.5 h in a nitrogen atmosphere, heat it to 1550 °C and keep it for 1.5 h, and naturally cool it to room temperature to obtain a converted flange, completing the forging process of the converted flange.

[0053] Example 3: A forging process for a converted flange, including the following preparation steps:

[0054] S1: Place the corrosion-resistant alloy material in a melting furnace, carry out forging terminal forming at 940 °C, trim the edge of the corrosion-resistant alloy material after terminal forming, and keep it at 1200 °C for 2 h, then naturally cool it to room temperature to obtain a flange blank; carry out structure hardening treatment on the flange blank, keep it at 750 °C for 9 h, cool it down to 650 °C and keep it for 11 h, and naturally cool it to room temperature to obtain a semi-finished flange.

[0055] The corrosion-resistant alloy material is composed of the following components by mass percentage: Fe 0.3%, Ru 0.15%, Cr 0.10%, Ni 0.30%, Mo 0.10%, Pt 0.5% and Al 0.6%, and the balance is titanium and inevitable impurities.

[0056] S2: Add 600 mL of 3-aminopropyltriethoxysilane, 200 g of potassium hydroxide, 900 g of sodium silicate, 400 g of sodium hexametaphosphate, 600 mL of triethanolamine, 90 mL of sodium tetraborate, 100 mL of sodium fluoride, 25 mL of yttrium nitrate, 20 mL of ethylenediaminetetraacetic acid, and 9 L of deionized water into a reaction kettle, stir for 45 min at 20 °C and 220 r / min, and perform ultrasonic dispersion for 30 min to obtain an electrolyte solution.

[0057] S3: Place the semi-finished flange in the stainless-steel electrolytic cell of the micro-arc oxidation system. Use the semi-finished flange as the anode and a 100 mm × 100 mm 304 stainless-steel plate as the negative electrode of the power supply. Immerse it in the electrolytic cell containing the electrolyte solution, and perform micro-arc oxidation for 50 min at 25 °C, a frequency of 120 Hz, and a current density of 4 A / dm 2 to obtain an oxidized flange with titanium dioxide whiskers on its surface.

[0058] S4: Immerse the oxidized flange in a 5 L zinc sulfate solution with a mass fraction of 15%, soak it at 50 °C for 40 min, then add 7.5 L of ammonium bicarbonate solution with a mass fraction of 15%, continue to soak for 3 h, take it out, wash it 3 times with deionized water and anhydrous ethanol respectively, dry it with nitrogen, transfer the product to a muffle furnace, and calcine it at 550 °C for 3 h in a nitrogen atmosphere to obtain a zinc oxide composite flange.

[0059] S5: Add 2 kg of resorcinol, 2 L of formaldehyde solution with a mass fraction of 40%, 60 mL of hydrochloric acid solution with a mass fraction of 2%, 3 L of ethanol, and 8 L of deionized water into a reaction kettle, stir and react for 2 h at 100 °C and 500 r / min to obtain a sealing solution; immerse the zinc oxide composite flange in the sealing solution, soak it at 100 °C for 5 h, naturally cool to room temperature, take it out, wash it 3 times with deionized water and anhydrous ethanol respectively, dry it with nitrogen to obtain a surface-sealed flange; place the surface-sealed flange in a muffle furnace, keep it at 950 °C for 2 h in a nitrogen atmosphere, heat it to 1600 °C and keep it for 2 h, and then naturally cool to room temperature to obtain a converted flange, thus completing the forging process of the converted flange.

[0060] Comparative Example 1: Based on Example 3, without immersing the zinc oxide composite flange in the sealing solution in step S4, and keeping the other steps unchanged, a converted flange is prepared.

[0061] Comparative Example 2: Based on Example 3, without placing the surface-sealed flange in the muffle furnace in step S4, and directly using it as the converted flange.

[0062] Comparative Example 3: Based on Example 3, without immersing the oxidized flange in the zinc sulfate solution and ammonium bicarbonate solution in step S4, and keeping the other steps unchanged, a converted flange is prepared.

[0063] Comparative Example 4: On the basis of Example 3, in step S4, the oxidized flange is not immersed in the zinc sulfate solution and ammonium bicarbonate solution for treatment. According to the method of step S4, the oxidized flange is immersed in the sealing solution for treatment to obtain a surface-sealed flange, which is carbonized in a muffle furnace to obtain a conversion flange containing a titanium carbide structure. The conversion flange containing a titanium carbide structure is immersed in the zinc sulfate solution and ammonium bicarbonate solution for treatment to obtain a conversion flange.

[0064] Performance tests were carried out on the conversion flanges obtained in Examples 1 - 3 and Comparative Examples 1 - 3, and the results are shown in Table 1:

[0065] 1. Compressive strength test: Referring to GB / T228.1 - 2021, a universal testing tensile machine was used to test the yield strength and tensile strength of the conversion flange.

[0066] 2. Hardness test: A micro-Vickers hardness tester was used to test the surface hardness of the conversion flange. The test load was 0.025 N, and the holding time was 15 s.

[0067] 3. Wear resistance test: A friction and wear testing machine was used to test the wear resistance of the conversion flange. A corundum ball with a friction diameter of 4.16 mm was used, the normal load was 5 N, the frequency was 2 Hz, the reciprocating distance was 5 mm, the total thawing formed 30 cm, the test temperature was 25 °C, and the relative humidity was 65%.

[0068] 4. Anti-fouling performance test: In June 2024, each conversion flange was immersed in the water body of Lianyungang Sea area, and the growth of attached organisms on the contact surface between the conversion flange and the marine water body was observed after the 1st month and the 6th month.

[0069] Table 1 Performance test table of conversion flange

[0070]

[0071] As can be seen from Table 1, the tensile strength, yield strength and hardness of the conversion flanges obtained in Examples 1 - 3 are significantly better than those of the comparative examples, and the corrosion rate and wear volume are significantly lower than those of the comparative examples. This shows that the conversion flange prepared by the present invention, when applied to marine pipelines, has good corrosion resistance, wear resistance and self-cleaning properties, can avoid the attachment of marine organisms, and at the same time has excellent compressive strength and can withstand the strong water pressure in the ocean.

[0072] In Comparative Example 1, the oxidized flange is not immersed in the sealing solution. Through the high temperature and high pressure action of the instantaneous breakdown discharge of micro-arc oxidation, titanium dioxide whiskers are in-situ grown on the surface of the flange. The binding force with the matrix is extremely strong and it is not easy to peel off. Using phenolic resin as the sealing agent, the surface of the titanium dioxide whiskers has an interlaced network structure, providing more anchoring points for the phenolic resin and enhancing the mechanical interlocking effect. The surface of the flange after sealing is rough and has a low porosity, which can avoid the penetration of corrosive substances in the ocean. However, after losing the sealing of the phenolic resin, it is extremely easy to cause the penetration of corrosive substances in the ocean, and it will also affect the formation of titanium carbide subsequently. Therefore, it shows the worst performance in the performance test.

[0073] In Comparative Example 2, the surface-sealed flange is not placed in a muffle furnace for treatment. Using phenolic resin as the sealing agent, at high temperature, the phenolic resin serves as a carbon source and the titanium dioxide whiskers provide a titanium source to form titanium carbide at the sealing site, so that some of the titanium dioxide whiskers are retained. Titanium carbide can significantly improve the hardness and wear resistance of the flange surface and can effectively resist the corrosion of strong acids and alkalis. When replaced with a surface-sealed flange, only a soft carbon layer is formed in the titanium dioxide whiskers, and the overall performance of the flange cannot be improved well.

[0074] In Comparative Example 3, the titanium carbide composite flange is directly used as a conversion flange with a corrosion-resistant alloy material. The hydroxyl groups on the surface of the titanium dioxide whiskers are active sites for the nucleation of zinc oxide, which promotes the growth of zinc oxide on the surface of the titanium carbide composite flange. The two work together to form a dense composite oxide film, effectively blocking the penetration of corrosive media in seawater. Zinc oxide has broad-spectrum antibacterial properties and can inhibit the attachment of microorganisms such as marine sulfate-reducing bacteria, reducing local corrosion. Without zinc oxide, only relying on the photocatalytic effect of titanium dioxide to decompose the attached organic matter to achieve surface self-cleaning, but it cannot effectively avoid the attachment of marine organisms.

[0075] In Comparative Example 4, when the calcination temperature is higher than 700 °C, the crystal form of titanium dioxide is all converted into the rutile type. The degree of surface hydroxylation of the rutile phase is significantly lower than that of the anatase phase. Therefore, it cannot rely on the hydroxyl groups on the surface of the titanium dioxide whiskers as active sites, and zinc oxide cannot grow on the surface, resulting in poor test results in the anti-fouling performance test. It should be noted that in this article, terms such as "including", "comprising" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0076] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention.

Claims

1. A corrosion-resistant alloy material for a conversion flange, characterized in that, By mass percentage, it includes the following components: Fe 0.2 - 0.3%, Ru 0.1 - 0.15%, Cr 0.05 - 0.10%, Ni 0.2 - 0.30%, Mo 0.05 - 0.10%, Pt 0.3 - 0.5% and Al 0.3 - 0.6%, and the balance is titanium and inevitable impurities.

2. A forging process for a flange, characterized in that, The steps of the forging process are as follows: Step 1: Forge the corrosion-resistant alloy material in Claim 1 into a semi-finished flange, and then through micro-arc oxidation treatment, grow titanium dioxide whiskers in-situ on the surface of the semi-finished flange to obtain an oxidized flange; Step 2: Deposit basic zinc carbonate on the surface of the oxidized flange using zinc sulfate solution and ammonium bicarbonate solution, and after calcination treatment, obtain a zinc oxide composite flange with zinc oxide bonded on the surface; Step 3: Seal the pores of the zinc oxide composite flange through phenolic resin to obtain a surface-sealed flange, and after calcination, obtain a converted flange to complete the forging process of the flange.

3. The forging process of a flange according to claim 2, characterized in that, The specific forging steps of the semi-finished flange are as follows: Place the corrosion-resistant alloy material in a melting furnace, perform forging terminal forming at 920 - 940 °C, trim the corrosion-resistant alloy material after terminal forming, and keep it warm at 1150 - 1200 °C for 1 - 2 h, then naturally cool to room temperature to obtain a flange blank; perform structure hardening treatment on the flange blank, keep it warm at 700 - 750 °C for 8 - 9 h, cool down to 600 - 650 °C and keep it warm for 10 - 11 h, and then naturally cool to obtain a semi-finished flange.

4. The forging process of a flange according to claim 2, characterized in that, The specific steps of the micro-arc oxidation treatment in Step 1 are as follows: Place the semi-finished flange in the stainless steel electrolytic cell of the micro-arc oxidation system. Use the semi-finished flange as the anode and the stainless steel plate as the negative electrode of the power supply. Immerse them in the electrolytic cell containing the electrolyte. Conduct micro-arc oxidation for 40 - 50 minutes at a temperature of 20 - 25 °C, a frequency of 100 - 120 Hz, and a current density of 3 - 4 A / dm 2 . Complete the micro-arc oxidation treatment.

5. The forging process of a flange according to claim 4, characterized in that, The electrolyte is prepared through the following steps: Add 3-aminopropyltriethoxysilane, potassium hydroxide, sodium silicate, sodium hexametaphosphate, triethanolamine, sodium tetraborate, sodium fluoride, yttrium nitrate, ethylenediaminetetraacetic acid and deionized water into a reaction kettle, stir at 15 - 20 °C and 200 - 220 r / min for 40 - 45 min, and perform ultrasonic dispersion for 20 - 30 min to obtain the electrolyte.

6. The forging process of a flange according to claim 5, characterized in that, The dosage ratio of 3-aminopropyltriethoxysilane, potassium hydroxide, sodium silicate, sodium hexametaphosphate, triethanolamine, sodium tetraborate, sodium fluoride, yttrium nitrate, ethylenediaminetetraacetic acid and deionized water is 500 - 600 mL: 100 - 200 g: 800 - 900 g: 300 - 400 g: 500 - 600 mL: 80 - 90 mL: 50 - 100 mL: 20 - 25 mL: 18 - 20 mL: 8 - 9 L.

7. The forging process of a flange according to claim 2, characterized in that, The specific preparation steps of the zinc oxide composite flange in Step 2 are as follows: Immerse the oxidized flange in a 10 - 15 wt% zinc sulfate solution, soak it at 40 - 50 °C for 30 - 40 min, then add a 10 - 15 wt% ammonium bicarbonate solution, continue to soak for 2 - 3 h, take it out and wash it 2 - 3 times with ionized water and anhydrous ethanol respectively, dry it with nitrogen, transfer the product to a muffle furnace, and heat it to 500 - 550 °C in a nitrogen atmosphere and calcine it for 2 - 3 h to obtain the zinc oxide composite flange.

8. The forging process of a flange according to claim 7, characterized in that, The volume ratio of the zinc sulfate solution and the ammonium bicarbonate solution is 4 - 5 L: 5 - 7.5 L.

9. The forging process of a flange according to claim 2, characterized in that, The specific preparation steps of the converted flange in Step 3 are as follows: Immerse the zinc oxide composite flange in the sealing solution, soak it at 80 - 100 °C for 4 - 5 h, naturally cool it to room temperature, take it out and wash it 2 - 3 times with ionized water and anhydrous ethanol respectively, and dry it with nitrogen to obtain a surface-sealed flange; place the surface-sealed flange in a muffle furnace, under a nitrogen atmosphere, keep it at 900 - 950 °C for 1 - 2 h, then heat it to 1500 - 1600 °C and keep it for 1 - 2 h, and naturally cool it to room temperature to obtain a converted flange.

10. A forging process of a flange according to claim 9, characterized in that, The sealing solution is prepared through the following steps: Add resorcinol, 35 - 40 wt% formaldehyde solution, 1 - 2 wt% hydrochloric acid solution, ethanol and deionized water into a reaction kettle, stir and react at 80 - 100 °C and 450 - 500 r / min for 1 - 2 h to obtain the sealing solution; The dosage ratio of resorcinol, formaldehyde solution, hydrochloric acid solution, ethanol and deionized water is 1 - 2 kg : 1 - 2 L : 50 - 60 mL : 2 - 3 L : 3 - 4 L.

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