Corrosion-resistant reducing flange and method of making same

Abstract

The application discloses a kind of corrosion-resistant reducing flange and preparation method thereof, belong to reducing flange preparation technical field, manganese iron, silicon iron, iron ingot, copper ingot and graphite quality carbon additive are added into smelting furnace, smelt under argon protection, then add slag remover and stir evenly, after deslagging, rare earth alloy with silica coated magnesium oxide nano powder smelted is added, continue smelting, alloy liquid is cast into mould, and is cast into shape, it is immersed in electrolyte and is treated by anodic oxidation, surface is coated with polyamide imide primer, after solidification, polytetrafluoroethylene powder finish is sprayed using electrostatic spraying equipment, after electrostatic spraying, reducing flange semi-finished product is transferred to curing oven, and is cooled and taken out, to obtain a kind of corrosion-resistant reducing flange;The corrosion-resistant reducing flange has good high adhesion, high temperature resistance, long-acting anticorrosion performance.

Description

Technical Field

[0001] This invention belongs to the field of variable diameter flange manufacturing technology, specifically relating to a corrosion-resistant variable diameter flange and its manufacturing method. Background Technology

[0002] A flange, also called a flange plate or flange, is a part used to connect shafts, for connecting pipe ends; flanges are also used on equipment inlets and outlets to connect two pieces of equipment, such as speed reducer flanges. A flange connection or flange joint refers to a detachable connection consisting of a flange, gasket, and bolts connected together as a combined sealing structure.

[0003] Reducing flanges, also known as eccentric flanges, have an inner diameter that differs from that of standard flanges. In engineering, reducing flanges are used when standard flanges cannot be matched with pipe fittings or pipelines. Corrosion-resistant reducing flanges are typically made of materials with excellent corrosion resistance, which remain stable in various corrosive environments, extending their service life. Reducing flanges are widely used in various scenarios requiring connections of pipes with different diameters, particularly in petrochemical, food processing, and pharmaceutical industries. In these fields, due to the specific requirements of processes and equipment, standard flanges often cannot meet the needs, making reducing flanges an important connection solution.

[0004] Chinese invention patent application CN114607853A discloses a long-life flange based on cemented carbide and its manufacturing process. The outer walls of both the carbon steel plate and the ultrafine-grained alloy plate are coated with an acrylic coating. The ultrafine-grained alloy plate increases the flange's strength and hardness, expanding its application range. The acrylic coating isolates the flange from oxygen and water, preventing oxidation and rust. Furthermore, the acrylic coating improves the flange's corrosion resistance, oxidation resistance, and weather resistance, enhancing its performance and further extending its service life.

[0005] However, in practical applications, insufficient coating adhesion may be a problem. The coating on the outside of the reducing flange is prone to local peeling due to mechanical vibration, temperature changes, or installation stress. Once the coating peels off, the exposed metal substrate will form electrochemical corrosion with the surrounding coated area, accelerating the spread of rust. Moreover, this corrosion will deteriorate rapidly in humid or salt spray environments, leading to a decrease in protective performance. Summary of the Invention

[0006] This invention adds a rare earth alloy containing silica-coated magnesium oxide nanopowder during the casting process of the reducing flange billet. The rare earth elements lanthanum and cerium help improve the corrosion resistance of the billet. After the silica-coated magnesium oxide nanopowder is evenly dispersed, it can promote the uniform nucleation of micro-pits during anodizing, making the pore distribution of the anodized layer on the surface of the reducing flange semi-finished product more uniform, thereby improving the adhesion of the paint film and solving the problem of insufficient adhesion of the outer coating of the reducing flange.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A method for manufacturing a corrosion-resistant reducing flange includes the following steps:

[0009] Step 1: Add ferromanganese, ferrosilicon, iron ingots, copper ingots and graphitic carbon raiser to the melting furnace, and melt for 6-7 hours under argon protection and at 1450-1550℃. Then add slag remover and stir evenly. After removing slag, add rare earth alloy with silica-coated magnesium oxide nanopowder and continue melting for 1.5-2 hours. Pour the alloy liquid into a mold preheated to 500-800℃ and cast to obtain the variable diameter flange billet.

[0010] Step 2: The reducing flange billet is machined and shaped, cleaned with degreasing agent to remove oil, washed with water, and dried with nitrogen to obtain a semi-finished reducing flange; the semi-finished reducing flange is immersed in an electrolyte for anodizing treatment, then immersed in acetone and ultrasonically cleaned for 5-10 minutes, and dried with nitrogen to obtain a pre-treated semi-finished reducing flange.

[0011] Step 3: Coat the surface of the pre-treated reducing flange semi-finished product with polyamide-imide primer. After curing, use electrostatic spraying equipment to electrostatically spray polytetrafluoroethylene powder topcoat. Transfer the electrostatically sprayed reducing flange semi-finished product to a curing oven and cure at 380-420℃ for 30-50 minutes. Cool and remove to obtain a corrosion-resistant reducing flange.

[0012] Furthermore, rare earth alloys are prepared through the following steps:

[0013] Aluminum and magnesium ingots are transferred to a melting furnace and heated to 680-720℃ under argon protection. Then, lanthanum and cerium are added and the melting continues for 2-2.5 hours. Then, silica-coated magnesium oxide nanopowder is injected into the melt using an argon-carrying jet method and melted for 0.5-1 hour. The melt is then cast and naturally cooled to obtain a rare earth alloy.

[0014] Furthermore, the mass ratio of aluminum ingots, magnesium ingots, metallic lanthanum, metallic cerium, and silica-coated magnesium oxide nanopowder is 300-400:30-40:15-20:12-18:15-20.

[0015] Furthermore, the silica-coated magnesium oxide nanopowder is prepared through the following steps:

[0016] Polyethylene glycol hexadecyl ether and methylcyclohexane were added to a reaction vessel and magnetically stirred at 200-500 rpm for 15-30 min. Then, a 0.25 mol / L magnesium nitrate solution was added and stirring was continued for 2-3 h. Next, 25% ammonia water was added and stirring was continued for 0.5-1 h. Then, tetraethyl orthosilicate was added dropwise and stirring was continued for 4-5 h. Finally, sodium dodecyl sulfate and isopropanol were added to demulsify the mixture. The mixture was centrifuged at 6000-8000 rpm for 10-15 min. The precipitate was washed 2-3 times with isopropanol, vacuum dried to constant weight, ground and pulverized, and transferred to a tube furnace. The furnace was kept at 500-550℃ in an air atmosphere for 1-3 h and then naturally cooled to room temperature to obtain silica-coated magnesium oxide nanopowder.

[0017] Furthermore, the ratio of polyethylene glycol hexadecyl ether, methylcyclohexane, magnesium nitrate solution, ammonia, tetraethyl orthosilicate, sodium dodecyl sulfate, and isopropanol is 8-10 kg: 20-30 L: 0.4-0.8 L: 1.5-3 L: 2-4 kg: 0.5-1 kg: 10-15 L.

[0018] Furthermore, the voltage for anodizing is kept constant at 28-30V, the treatment temperature is 25℃, and the treatment time is 8-10min.

[0019] Furthermore, the electrolyte comprises 0.2 mol / L NH4F and 1.5 mol / L ethylene glycol, with water as the solvent.

[0020] Furthermore, the voltage for electrostatic spraying is 50-60kV, and the current is 1-1.5mA / cm. 2 The distance for electrostatic spraying is 20-25cm, and the pressure is 0.4-0.5MPa.

[0021] Furthermore, the reducing flange billet is composed of the following components by mass percentage: Mn 4.5-5%, Si 3.5-4.5%, Cu 1.5-3%, Al 3-4%, Mg 0.3-0.4%, La 0.15-0.2%, Ce 0.12-0.18%, C 1.8-2.5%, with the balance being iron.

[0022] The beneficial effects of this invention are:

[0023] 1. The corrosion-resistant reducing flange of this invention incorporates rare earth alloys during the casting process of the reducing flange billet. The rare earth elements lanthanum and cerium help refine the grains, resulting in uniform oxide film growth on the surface of the reducing flange semi-finished product during anodizing, thus improving the corrosion resistance of the billet. Simultaneously, the magnesium oxide in the rare earth alloy can form micro-cathodes, promoting uniform nucleation of micro-pits during anodizing. After anodizing, the pores on the surface of the pre-treated reducing flange semi-finished product are more uniform, with a smaller fluctuation range in pore diameter, which helps improve the adhesion of the paint film and reduces the probability of PTFE powder coating peeling off the surface of the corrosion-resistant reducing flange, thereby increasing the service life of the flange.

[0024] 2. The silica-coated magnesium oxide nanopowder of the present invention has a magnesium oxide nano core and a silica nano shell. The silica nano shell acts as a protective layer, preventing magnesium oxide from directly contacting and reacting with the active metals in the molten metal. This reduces agglomeration caused by chemical bonding between particles and helps to improve the dispersibility of the silica-coated magnesium oxide nanopowder in the melt. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments in the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1: A method for manufacturing a corrosion-resistant reducing flange, comprising the following steps:

[0027] S1: Add 8 kg of polyethylene glycol hexadecyl ether and 20 L of methylcyclohexane to a reactor. After stirring magnetically at 200 r / min for 15 min, add 0.4 L of 0.25 mol / L magnesium nitrate solution and continue stirring for 2 h. Then add 1.5 L of 25% ammonia water and continue stirring for 0.5 h. Next, add 2 kg of tetraethyl orthosilicate and stir for 4 h. Finally, add 0.5 kg of sodium dodecyl sulfate and 10 L of isopropanol for demulsification. Centrifuge at 6000 r / min for 10 min. Wash the precipitate twice with isopropanol, vacuum dry to constant weight, grind and pulverize, and transfer to a tube furnace. Keep at 500℃ in air atmosphere for 1 h, and naturally cool to room temperature to obtain silica-coated magnesium oxide nanopowder.

[0028] S2: Transfer 300g of aluminum ingot and 30g of magnesium ingot to a melting furnace, heat to 680℃ under argon protection until melted, then add 15g of metallic lanthanum and 12g of metallic cerium, continue melting for 2 hours, then inject 15g of silica-coated magnesium oxide nanopowder into the melt using argon-carrying jetting method, melt for 0.5 hours, cast into shape, and cool naturally to obtain a rare earth alloy.

[0029] S3: Add ferromanganese, ferrosilicon, iron ingots, copper ingots and graphitic carbon raiser to the melting furnace, melt for 6 hours under argon protection and at 1450℃, then add slag remover and stir evenly, after slag removal, add rare earth alloy, continue melting for 1.5 hours, pour the alloy liquid into a mold preheated to 500℃, cast into shape, and obtain the reducing flange billet.

[0030] The reducing flange billet is composed of the following components by mass percentage: Mn 4.5%, Si 3.5%, Cu 1.5%, Al 3%, Mg 0.3%, La 0.15%, Ce 0.12%, C 1.8%, with the balance being iron.

[0031] S4: The reducing flange billet is machined and shaped, cleaned with a degreasing agent to remove oil, washed with water, and dried with nitrogen to obtain a semi-finished reducing flange. The semi-finished reducing flange is then immersed in an electrolyte for anodizing treatment, followed by immersion in acetone and ultrasonic cleaning for 5 minutes, and dried with nitrogen to obtain a pre-treated semi-finished reducing flange. The anodizing treatment voltage is constant at 28V, the treatment temperature is 25℃, and the treatment time is 8 minutes. The electrolyte consists of 0.2 mol / L NH4F and 1.5 mol / L ethylene glycol, with water as the solvent.

[0032] S5: Apply polyamide-imide primer to the surface of the pre-treated reducing flange semi-finished product, and after curing, apply polytetrafluoroethylene powder topcoat using electrostatic spraying equipment. The voltage for electrostatic spraying is 50kV and the current is 1mA / cm. 2 The electrostatic spraying distance is 20cm and the pressure is 0.4MPa. The electrostatically sprayed reducing flange semi-finished product is transferred to a curing oven and cured at 380℃ for 30min. After cooling, it is taken out to obtain a corrosion-resistant reducing flange.

[0033] Example 2: A method for manufacturing a corrosion-resistant reducing flange, comprising the following steps:

[0034] S1: 9 kg of polyethylene glycol hexadecyl ether and 25 L of methylcyclohexane were added to a reactor and magnetically stirred at 350 r / min for 22 min. Then, 0.6 L of 0.25 mol / L magnesium nitrate solution was added and stirring was continued for 2.5 h. Next, 2.2 L of 25% ammonia water was added and stirring was continued for 0.8 h. Then, 3 kg of tetraethyl orthosilicate was added dropwise and stirring was continued for 4.5 h. Finally, 0.8 kg of sodium dodecyl sulfate and 12.5 L of isopropanol were added to demulsify the mixture. The mixture was centrifuged at 7000 r / min for 12.5 min. The precipitate was washed twice with isopropanol, vacuum dried to constant weight, ground and pulverized, and transferred to a tube furnace. The furnace was kept at 525 °C in air for 2 h and then naturally cooled to room temperature to obtain silica-coated magnesium oxide nanopowder.

[0035] S2: Transfer 350g of aluminum ingot and 35g of magnesium ingot to a melting furnace, heat to 700℃ under argon protection, then add 18g of metallic lanthanum and 16g of metallic cerium, continue melting for 2.2h, then inject 18g of silica-coated magnesium oxide nanopowder into the melt using argon-carrying jetting method, melt for 0.8h, cast into shape, and cool naturally to obtain a rare earth alloy.

[0036] S3: Add ferromanganese, ferrosilicon, iron ingots, copper ingots and graphitic carbon raiser to the melting furnace, melt for 6.5 hours under argon protection and at 1500℃, then add slag remover and stir evenly. After slag removal, add rare earth alloy and continue melting for 1.8 hours. Pour the alloy liquid into a mold preheated to 650℃ and cast to obtain the reducing flange billet.

[0037] The reducing flange billet is composed of the following components by mass percentage: Mn 4.8%, Si 4%, Cu 2.2%, Al 3.5%, Mg 0.35%, La 0.18%, Ce 0.16%, C 2.2%, with the balance being iron.

[0038] S4: The reducing flange billet is machined and shaped, cleaned with a degreasing agent to remove oil, washed with water, and dried under nitrogen to obtain a semi-finished reducing flange. The semi-finished reducing flange is then immersed in an electrolyte for anodizing treatment, followed by immersion in acetone and ultrasonic cleaning for 8 minutes, and dried under nitrogen to obtain a pre-treated semi-finished reducing flange. The anodizing treatment voltage is constant at 29V, the treatment temperature is 25℃, and the treatment time is 9 minutes. The electrolyte consists of 0.2 mol / L NH4F and 1.5 mol / L ethylene glycol, with water as the solvent.

[0039] S5: Apply polyamide-imide primer to the surface of the pre-treated reducing flange semi-finished product, and after curing, apply polytetrafluoroethylene powder topcoat using electrostatic spraying equipment. The electrostatic spraying voltage is 55kV and the current is 1.25mA / cm. 2The electrostatic spraying distance is 22.5cm and the pressure is 0.45MPa. The electrostatically sprayed reducing flange semi-finished product is transferred to a curing oven and cured at 400℃ for 40min. After cooling, it is taken out to obtain a corrosion-resistant reducing flange.

[0040] Example 3: A method for manufacturing a corrosion-resistant reducing flange, comprising the following steps:

[0041] S1: 10 kg of polyethylene glycol hexadecyl ether and 30 L of methylcyclohexane were added to a reactor and magnetically stirred at 500 r / min for 30 min. Then, 0.8 L of 0.25 mol / L magnesium nitrate solution was added and stirring was continued for 3 h. Then, 3 L of 25% ammonia water was added and stirring was continued for 1 h. Then, 4 kg of tetraethyl orthosilicate was added dropwise and stirring was continued for 5 h. Finally, 1 kg of sodium dodecyl sulfate and 15 L of isopropanol were added to demulsify the mixture. The mixture was centrifuged at 8000 r / min for 15 min. The precipitate was washed three times with isopropanol, vacuum dried to constant weight, ground and pulverized, and transferred to a tube furnace. The furnace was kept at 550 °C in air for 3 h and then naturally cooled to room temperature to obtain silica-coated magnesium oxide nanopowder.

[0042] S2: Transfer 400g of aluminum ingot and 40g of magnesium ingot to a melting furnace, heat to 720℃ under argon protection, then add 20g of metallic lanthanum and 18g of metallic cerium, continue melting for 2.5h, then inject 20g of silica-coated magnesium oxide nanopowder into the melt using argon-carrying jetting method, melt for 1h, cast into shape, and cool naturally to obtain rare earth alloy.

[0043] S3: Add ferromanganese, ferrosilicon, iron ingots, copper ingots and graphitic carbon raiser to the melting furnace, melt for 7 hours under argon protection and at 1550℃, then add slag remover and stir evenly, after slag removal, add rare earth alloy, continue melting for 2 hours, pour the alloy liquid into a mold preheated to 800℃, cast into shape, and obtain the reducing flange billet.

[0044] The reducing flange billet is composed of the following components by mass percentage: Mn 5%, Si 4.5%, Cu 3%, Al 4%, Mg 0.4%, La 0.2%, Ce 0.18%, C 2.5%, with the balance being iron.

[0045] S4: The reducing flange billet is machined and shaped, cleaned with a degreasing agent to remove oil, washed with water, and dried under nitrogen to obtain a semi-finished reducing flange. The semi-finished reducing flange is then immersed in an electrolyte for anodizing treatment, followed by immersion in acetone and ultrasonic cleaning for 10 minutes, and dried under nitrogen to obtain a pre-treated semi-finished reducing flange. The anodizing treatment voltage is constant at 30V, the treatment temperature is 25℃, and the treatment time is 10 minutes. The electrolyte consists of 0.2 mol / L NH4F and 1.5 mol / L ethylene glycol, with water as the solvent.

[0046] S5: Apply polyamide-imide primer to the surface of the pre-treated reducing flange semi-finished product, and after curing, apply polytetrafluoroethylene powder topcoat using electrostatic spraying equipment. The electrostatic spraying voltage is 60kV and the current is 1.5mA / cm. 2 The electrostatic spraying distance is 25cm and the pressure is 0.5MPa. The electrostatically sprayed reducing flange semi-finished product is transferred to a curing oven and cured at 420℃ for 50min. After cooling, it is taken out to obtain a corrosion-resistant reducing flange.

[0047] The slag remover described in this example is the commercially available Henan Xuchang Yuntie Mining Technology HS-3; the graphitic carbon raiser was purchased from Henan Nuoxin Ferroalloy Co., Ltd. 95 / 92; and the remaining raw materials are all commercially available products.

[0048] Comparative Example 1: The difference from Example 1 is that tetraethyl orthosilicate is not added in step S1 to prepare nano-magnesium oxide powder, and in step S2, the silica is replaced with nano-magnesium oxide powder to coat the magnesium oxide nanopowder. The remaining steps remain unchanged to prepare a corrosion-resistant reducing flange.

[0049] Comparative Example 2: The difference from Example 1 is that silica-coated magnesium oxide nanopowder is not added in step S2, while the other steps remain unchanged, and a corrosion-resistant reducing flange is prepared.

[0050] Comparative Example 3: The difference from Example 1 is that lanthanum and cerium are not added in step S2, and the rare earth alloy in step S3 is replaced by the prepared alloy. The remaining steps remain unchanged, and a corrosion-resistant reducing flange is prepared.

[0051] Different samples were prepared according to the methods described in Examples 1-3 and Comparative Examples 1-3, respectively. The specific preparation methods of the samples are as follows:

[0052] Referring to the methods in steps S1-S3 of the corresponding embodiments or comparative examples, an alloy plate of 120mm×50mm×3mm was prepared by casting and grinding the alloy liquid with the same composition as the variable diameter flange billet. Then, the alloy plate was anodized according to the method in step S4. Then, the anodized alloy plate was coated with polyimide primer and electrostatic sprayed polytetrafluoroethylene powder topcoat according to the method in step S5. The primer thickness was 50μm and the total paint film thickness was 140μm, resulting in different samples.

[0053] The paint film adhesion of different samples was tested at room temperature according to the cross-cut adhesion test in GB / T 9286-2021; the neutral salt spray test for 2000 h was carried out on different samples according to GB / T1771-2023, and the results are shown in Table 1.

[0054] Table 1: Performance Test Results of Each Sample

[0055]

[0056] As can be seen from Table 1, the paint films of the samples in Examples 1-3 of this invention have good adhesion and corrosion resistance.

[0057] The decreased adhesion of the paint film in Comparative Example 1 may be due to the lack of silica coating. During the smelting process, the nano-magnesium oxide reacts with the more reactive lanthanum and cerium in the rare earth alloy, resulting in poor dispersibility of magnesium oxide. This affects the uniformity of micro-pits on the surface of the alloy plate during the anodizing process, and the oxide film at the particle agglomeration points is prone to cracking, thereby reducing the adhesion of the paint film.

[0058] The adhesion between the substrate and the coating in Comparative Example 2 decreased significantly. This may be because the uniformity of the pores in the oxide film of the sample decreased after the addition of silica-coated magnesium oxide nanopowder, resulting in a decrease in the adhesion of the paint film.

[0059] The increased unidirectional corrosion at the scribed area of ​​the sample in Comparative Example 3 after the neutral salt spray test is due to the addition of rare earth elements lanthanum and cerium, which can refine the grains and improve the corrosion resistance of the alloy plate. The blistering of the paint film at the un-scribed area indicates that rare earth elements and silica-coated magnesium oxide nanopowder can synergistically improve the adhesion of the paint film.

[0060] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for manufacturing a corrosion-resistant reducing flange, characterized in that, Includes the following steps: Step 1: Add ferromanganese, ferrosilicon, iron ingots, copper ingots and graphitic carbon raiser to the melting furnace, and melt for 6-7 hours under argon protection and at 1450-1550℃. Then add slag remover and stir evenly. After removing slag, add rare earth alloy with silica-coated magnesium oxide nanopowder and continue melting for 1.5-2 hours. Pour the alloy liquid into a mold preheated to 500-800℃ and cast to obtain the variable diameter flange billet. Step 2: The reducing flange billet is machined and shaped, cleaned with degreasing agent to remove oil, washed with water, and dried with nitrogen to obtain a semi-finished reducing flange; the semi-finished reducing flange is immersed in an electrolyte for anodizing treatment, then immersed in acetone and ultrasonically cleaned for 5-10 minutes, and dried with nitrogen to obtain a pre-treated semi-finished reducing flange. Step 3: Coat the surface of the pre-treated reducing flange semi-finished product with polyamide-imide primer. After curing, use electrostatic spraying equipment to electrostatically spray polytetrafluoroethylene powder topcoat. Transfer the electrostatically sprayed reducing flange semi-finished product to a curing oven and cure at 380-420℃ for 30-50 minutes. Cool and remove to obtain a corrosion-resistant reducing flange.

2. The method for preparing a corrosion-resistant reducing flange according to claim 1, characterized in that, The rare earth alloy described in step one is prepared through the following steps: Aluminum and magnesium ingots are transferred to a melting furnace and heated to 680-720℃ under argon protection. Then, lanthanum and cerium are added and the melting continues for 2-2.5 hours. Then, silica-coated magnesium oxide nanopowder is injected into the melt using an argon-carrying jet method and melted for 0.5-1 hour. The melt is then cast and naturally cooled to obtain a rare earth alloy.

3. The method for preparing a corrosion-resistant reducing flange according to claim 2, characterized in that, The mass ratio of aluminum ingots, magnesium ingots, metallic lanthanum, metallic cerium, and silica-coated magnesium oxide nanopowder is 300-400:30-40:15-20:12-18:15-20.

4. The method for preparing a corrosion-resistant reducing flange according to claim 1, characterized in that, The silica-coated magnesium oxide nanopowder mentioned in step one is prepared through the following steps: Polyethylene glycol hexadecyl ether and methylcyclohexane were added to a reaction vessel and magnetically stirred at 200-500 rpm for 15-30 min. A 0.25 mol / L magnesium nitrate solution was added and stirring was continued for 2-3 h. Then, 25 wt% ammonia water was added and stirring was continued for 0.5-1 h. Tetraethyl orthosilicate was added dropwise and stirring was continued for 4-5 h. Finally, sodium dodecyl sulfate and isopropanol were added to demulsify the mixture. The mixture was centrifuged at 6000-8000 rpm for 10-15 min. The precipitate was washed 2-3 times with isopropanol, vacuum dried to constant weight, ground and pulverized, and transferred to a tube furnace. The furnace was kept at 500-550℃ in an air atmosphere for 1-3 h and then naturally cooled to room temperature to obtain silica-coated magnesium oxide nanopowder.

5. The method for preparing a corrosion-resistant reducing flange according to claim 4, characterized in that, The ratio of polyethylene glycol hexadecyl ether, methylcyclohexane, magnesium nitrate solution, ammonia, tetraethyl orthosilicate, sodium dodecyl sulfate, and isopropanol is 8-10 kg: 20-30 L: 0.4-0.8 L: 1.5-3 L: 2-4 kg: 0.5-1 kg: 10-15 L.

6. The method for manufacturing a corrosion-resistant reducing flange according to claim 1, characterized in that, In step two, the voltage for the anodizing treatment is constant at 28-30V, the treatment temperature is 25℃, and the treatment time is 8-10min.

7. The method for manufacturing a corrosion-resistant reducing flange according to claim 1, characterized in that, The electrolyte in step two includes NH4F at a concentration of 0.2 mol / L and ethylene glycol at a concentration of 1.5 mol / L, with water as the solvent.

8. The method for preparing a corrosion-resistant reducing flange according to claim 1, characterized in that, The electrostatic spraying voltage in step three is 50-60kV, and the current is 1-1.5mA / cm. 2 The distance for electrostatic spraying is 20-25cm, and the pressure is 0.4-0.5MPa.

9. A corrosion-resistant reducing flange, characterized in that, It is prepared by the method of any one of claims 1-8.

10. A corrosion-resistant reducing flange according to claim 9, characterized in that, The reducing flange billet is composed of the following components by mass percentage: Mn 4.5-5%, Si 3.5-4.5%, Cu 1.5-3%, Al 3-4%, Mg 0.3-0.4%, La 0.15-0.2%, Ce 0.12-0.18%, C 1.8-2.5%, with the balance being iron.

Images