Corrosion resistant alloy steel valve body and method of manufacture

Abstract

The application discloses a kind of corrosion-resistant alloy steel van body and preparation method, belong to van body technical field, first by to van body blank is carried out normalizing, quenching, tempering treatment after obtaining van body semi-finished product, again to van body semi-finished product is sequentially using picosecond laser and nanometer laser and is etched, after anodic oxidation treatment form porous and uniform oxide layer, by laser cladding method uniform vanadium carbide, titanium carbide coating is formed on surface, the porous structure of oxide film can improve the adhesion of subsequent coating, form oxide film plus coating composite protection system, increase the corrosion resistance of corrosion-resistant alloy steel van body, prolong the service life of corrosion-resistant alloy steel van body in slurry pump.

Description

Technical Field

[0001] This invention belongs to the field of valve technology, specifically a corrosion-resistant alloy steel valve and its preparation method. Background Technology

[0002] As a core component of fluid control systems, valve bodies are exposed to high temperatures, high pressures, and corrosive media (such as acidic oil and gas, chlorinated seawater, and chemical solutions) for extended periods. The corrosion resistance, mechanical strength, and stability of the valve material directly determine its service life and safety. While traditional valve body materials (such as 304 / 316 austenitic stainless steel and duplex steel 2205) possess a certain degree of corrosion resistance, they still face problems such as pitting corrosion, stress corrosion cracking (SCC), and intergranular corrosion under extreme conditions. In deep-sea oil and gas extraction, high-concentration Cl- environments can easily cause the stainless steel passivation film to rupture, leading to a surge in localized corrosion rates. In the high-temperature sulfide media of the refining and chemical industry, ordinary alloy steels are prone to hydrogen sulfide stress corrosion failure, causing valve leakage or even system paralysis.

[0003] Chinese patent application CN117867413A discloses a valve body and its preparation process. The method includes casting the valve body, heating and forging the annealed valve body, normalizing the forging, quenching the normalized forging, tempering the quenched forging, and surface treating the tempered forging to obtain the valve body. This method improves the service life of the valve body by selecting raw materials and using process methods, thereby increasing the overall progress of on-site drilling and production operations and reducing maintenance costs.

[0004] However, when valves are used in mud pumps, the mud typically contains high concentrations of corrosive media (such as Cl). - H2S, CO2, and acidic dissolved substances can directly cause chemical or electrochemical corrosion on the metal surface. At the same time, hard particles (quartz sand, rock chips) in the mud impact the valve body surface with the high-speed fluid, causing corrosive damage. This keeps the fresh metal matrix continuously exposed to the corrosive medium, forming a "wear-corrosion synergistic effect," which further aggravates the corrosion of the valve body and ultimately leads to seal failure. Summary of the Invention

[0005] The purpose of this invention is to provide a corrosion-resistant alloy steel valve and its preparation method. By laser etching the surface of the valve semi-finished product to form uniformly distributed U-shaped grooves, and then anodizing it, a coating is finally formed by laser cladding to obtain a corrosion-resistant alloy steel valve. This solves the problem of easy corrosion of valves in mud pumps, and improves the corrosion resistance of the valve while also increasing the strength and adhesion of the coating.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for preparing a corrosion-resistant alloy steel valve, the method comprising: heat-treating a valve blank to obtain a valve semi-finished product, and then performing surface treatment, the specific steps of which are as follows:

[0008] Step 1: The valve semi-finished product is processed by a secondary laser etching process to etch uniformly distributed U-shaped grooves on the surface of the valve semi-finished product, thus obtaining a porous valve semi-finished product.

[0009] Step 2: The porous valve semi-finished product is subjected to anodizing treatment to form a uniform porous oxide film on the surface, thus obtaining the anodized porous valve semi-finished product.

[0010] Step 3: Ball mill and mix 12CrNi2 powder, graphite powder, vanadium powder and titanium powder to obtain a mixed powder. The mixed powder is then coated onto the surface of the anodized porous valve semi-finished product by laser cladding to obtain a corrosion-resistant alloy steel valve.

[0011] Furthermore, the preparation process of the valve preform in step one is as follows:

[0012] Pure iron bars, low-carbon ferrochrome, nickel sheets, and threaded steel bars are melted at 1500-1600℃ under argon protection. Then, low-carbon ferrosilicon, low-carbon ferromanganese, high-purity aluminum granules, ferrophosphorus powder, copper granules, and antimony granules are added. After melting, the mixture is stirred for 3-5 minutes, and alkaline slag-forming materials are added. The mixture is kept at this temperature for 2-3 hours, the slag is removed, and the temperature is lowered to 1440-1450℃ for casting. The mixture is then heated and forged at 900-1000℃, rolled, and air-cooled to room temperature to obtain a valve billet.

[0013] Furthermore, the secondary laser etching process in step one includes the following steps:

[0014] First, a picosecond laser is used for etching. The parameters for the picosecond laser etching are set as follows: power of 15W, scanning speed of 300-350mm / s, and number of scans of 100-120. Then, a nanosecond laser is used for etching. The parameters for the nanosecond laser etching are set as follows: power of 7.5W, scanning speed of 300-350mm / s, number of scans of 5-10, and defocusing distance of +50μm. Dust removal and air blowing are performed simultaneously during etching.

[0015] Furthermore, in step one, the depth of the trench is 80-120μm, the diameter is 50-80μm, and the gap between adjacent trenches is 200-300μm.

[0016] Furthermore, the preparation process of the anodized porous valve semi-finished product in step two is as follows:

[0017] Using graphite as the cathode and porous valve semi-finished product as the anode, anodizing treatment was carried out using sulfuric acid solution as the electrolyte. The reaction was carried out at 20-25℃ and 100-200r / min for 9-12min. The distance between graphite and porous valve semi-finished product was 6-8cm. The anodizing voltage was 50V. After washing, anodized porous valve semi-finished product was obtained.

[0018] Furthermore, in step three, the mass ratio of 12CrNi2 powder, graphite powder, vanadium powder, and titanium powder is 5-7:1-2:3-4.5:2-3.

[0019] Furthermore, the thickness of the laser cladding coating in step three is 700-800 μm.

[0020] Furthermore, heat treatment includes normalizing, quenching, and tempering.

[0021] A corrosion-resistant alloy steel valve blank, wherein the alloy steel valve blank comprises the following elements by weight percentage: C: 0.1-0.2%, Si: 0.25-0.35%, V: 0.05-0.1%, P: 0.08-0.12%, Mn: 0.5-1%, Al: 0.4-0.6%, Ti: 0.02-0.04%, Ni: 1.6-1.9%, Cr: 0.7-1%, Cu: 0.25-0.4%, Sb: 0.15-0.2%, with the balance being Fe and other impurities.

[0022] The beneficial effects of this invention are:

[0023] 1. The corrosion-resistant alloy steel valve in this invention is first obtained by normalizing, quenching, and tempering the valve blank to obtain a valve semi-finished product. Then, the valve semi-finished product is etched sequentially using a picosecond laser and a nano laser. After anodizing, a porous and uniform oxide layer is formed. A uniform vanadium carbide and titanium carbide coating is formed on the surface by laser cladding. The porous structure of the oxide film can improve the adhesion of subsequent coatings, forming a composite protective system of oxide film and coating, which increases the corrosion resistance of the corrosion-resistant alloy steel valve and extends the service life of the corrosion-resistant alloy steel valve in mud pumps.

[0024] 2. The porous valve product of this invention is made by first etching uniformly distributed pores on the surface of the valve semi-finished product using a picosecond laser, and then using a nano-laser to deepen the original pores through defocusing modification. This process remelts the disordered protrusions at the bottom of the microgrooves, thereby regularizing the bottom of the irregular microgrooves and obtaining grooves with good forming quality. The grooves have a U-shaped cross-section, a depth of 80-120μm, and a diameter of 50-80μm. They can form a physical interlock with the coating material to be clad subsequently, improving the adhesion of the coating. In addition, the arc-shaped bottom of the U-shaped groove can disperse the thermal stress during the cladding process, reducing the risk of coating cracking, and also reducing the thermal stress between the valve and the mud pump during use.

[0025] 3. The anodized porous valve semi-finished product in this invention is based on the porous valve semi-finished product, which undergoes anodizing treatment to uniformly coat its surface with a corrosion-resistant oxide film, thereby slowing down the corrosion rate of the alloy steel valve in the mud pump. In addition, the oxide film has a porous structure, which can increase the adhesion of the coating in the subsequent laser cladding process, thereby improving the strength of the coating and playing a synergistic role with the trench. Moreover, the porous structure has a certain degree of hydrophobicity, which can reduce the penetration of acidic substances in the mud into the valve, further improving the corrosion resistance of the valve. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of 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.

[0027] Example 1: This example provides a corrosion-resistant alloy steel valve, which is prepared through the following steps:

[0028] S1: Pure iron bars, low-carbon ferrochrome, nickel sheets, and HRB400 threaded steel bars are added to a pit furnace and held at 475℃ for 35 minutes. Then, they are transferred to a medium-frequency induction furnace and melted at 1550℃ under argon protection. After the melt is clear, low-carbon ferrosilicon and low-carbon ferromanganese are added and stirred for 4 minutes after melting. High-purity aluminum particles are then added for deoxidation and alloying. After removing the slag, ferrophosphorus powder, copper particles, and antimony particles are added and stirred for 4 minutes after melting. Alkaline slag-forming materials (calcium oxide, aluminum oxide, and calcium fluoride in a mass ratio of 9:3:1) are added and held at 2.5 hours. After removing the slag, the temperature is lowered to 1445℃ and cast. After casting, the material is air-cooled to room temperature and then taken out. It is then heated and forged at 950℃, rolled, and air-cooled to room temperature to obtain a valve billet.

[0029] The Sb2O3 oxide layer formed by Sb oxidation has low solubility in weak acids, which helps to improve the corrosion resistance of the valve blank. At the same time, Sb doping can reduce pitting corrosion on the surface of the valve blank, inhibit the chemical reaction between chloride ions and iron, thereby reducing the formation of iron-containing chlorides. It can also promote the formation of highly corrosion-inhibiting copper-containing compounds, further inhibiting anodic and cathodic reactions.

[0030] The gas compact contains the following elements by weight percentage: C: 0.15%, Si: 0.3%, V: 0.07%, P: 0.1%, Mn: 0.7%, Al: 0.5%, Ti: 0.03%, Ni: 1.7%, Cr: 0.8%, Cu: 0.3%, Sb: 0.17%, with the balance being Fe and other impurities.

[0031] S2: Quickly transfer the valve blank into a 550℃ heating furnace, raise the temperature to 775℃ within 2.5 hours, perform uniform annealing, and then directly raise the temperature to 1025℃ for normalizing. Place the normalized valve blank into a quenching tank, and after the surface temperature drops to 310℃, remove it and return it to 405℃. Place it back into the quenching tank, and when the surface temperature drops to 260℃, remove it and return it to 310℃. Place it back into the quenching tank, and when the surface temperature drops to 150℃, remove it and cool it to room temperature. Then place the valve blank into a tempering furnace, raise the temperature from 325℃ to 550℃, hold it for 30 minutes, and cool it to room temperature. After surface treatment, the valve semi-finished product is obtained.

[0032] S3: The surface of the valve semi-finished product is etched using a nano-picosecond composite laser processing equipment with a wavelength of 355nm. During the processing, a picosecond laser is first used for etching, with the following parameters: power of 15W, scanning speed of 325mm / s, and 110 scans. Then, a nanosecond laser is used for etching, with the following parameters: power of 7.5W, scanning speed of 325mm / s, 7 scans, and defocusing distance of +50μm. During the etching process, dust removal and air blowing are performed simultaneously to prevent the spatter generated by laser ablation from falling back into the ablation pit and causing irregular ablation morphology. This results in well-formed grooves with a U-shaped cross-section. The depth of the U-shaped grooves is 100μm, the diameter is 65μm, and the gap between adjacent U-shaped grooves is 250μm. The grooves are evenly distributed in a ring array around the center line of the valve semi-finished product, resulting in a porous valve semi-finished product.

[0033] S4: Using graphite as the cathode and porous valve semi-finished product as the anode, anodizing treatment is performed using a 15% sulfuric acid solution as the electrolyte. The reaction is carried out at 22℃ and 150r / min for 10min. The distance between graphite and porous valve semi-finished product is 7cm, and the reaction area ratio is maintained at 2:1. Current is applied, and the anodizing voltage is 50V. A uniform porous oxide film is formed on the surface of the porous valve semi-finished product. The porous valve semi-finished product is then washed with deionized water until neutral to obtain anodized porous valve semi-finished product.

[0034] S5: Mix 6g of 12CrNi2 powder (≥99.5% purity) with a particle size of 50-60μm, 1.5g of graphite powder with a particle size of 4-6μm, 3.7g of vanadium powder (≥99.5% purity) with a particle size of 2-8μm, and 2-3g of titanium powder (≥99.5% purity) with a particle size of 4-10μm, and add the mixture to a ball mill. Ball mill at 350r / min for 2.5h. Then, use sodium silicate water glass as a binder to uniformly coat the anodized porous valve semi-finished product. Then, form a continuous VC (vanadium carbide) and TiC (titanium carbide) coating on the anodized porous valve semi-finished product by laser cladding. The coating thickness is 750μm, and a corrosion-resistant alloy steel valve is obtained.

[0035] The parameters for laser cladding are: defocusing distance of 160mm, current of 175A, laser duration of 6.0ms, frequency of 5Hz, and laser input energy density of 82.5J / cm². 2 The scanning speed was 3 mm / s, the bonding rate was 9%, and argon gas was used for protection at a flow rate of 17 L / min during preparation. Nanoscale VC particles and nanoscale TiC particles were synthesized in situ under laser irradiation using vanadium powder, titanium powder, and graphite powder. These particles have high strength and corrosion resistance and can form a uniform coating on the surface of corrosion-resistant alloy steel valves.

[0036] Example 2: This example provides a corrosion-resistant alloy steel valve, prepared through the following steps:

[0037] S1: Pure iron bars, low-carbon ferrochrome, nickel sheets, and HRB400 threaded steel bars are added to a pit furnace and held at 450℃ for 30 minutes. Then, they are transferred to a medium-frequency induction furnace and melted at 1500℃ under argon protection. After melting, low-carbon ferrosilicon and low-carbon ferromanganese are added and stirred for 3 minutes. High-purity aluminum particles are then added for deoxidation and alloying. After removing the slag, ferrophosphorus powder, copper particles, and antimony particles are added and stirred for 3 minutes. Alkaline slag-forming materials (calcium oxide, aluminum oxide, and calcium fluoride in a mass ratio of 9:3:1) are added and held at 2 hours. After removing the slag, the temperature is lowered to 1440℃ and cast. After air cooling to room temperature, the casting is removed and heated to 900℃ for forging. After rolling, the casting is air cooled to room temperature to obtain a valve billet.

[0038] The gas compact contains the following elements by weight percentage: C: 0.1%, Si: 0.25%, V: 0.05%, P: 0.08%, Mn: 0.5%, Al: 0.4%, Ti: 0.02%, Ni: 1.6%, Cr: 0.7%, Cu: 0.25%, Sb: 0.15%, with the balance being Fe and other impurities.

[0039] S2: Quickly transfer the valve blank into a 500℃ heating furnace, raise the temperature to 750℃ within 2 hours, perform uniform annealing, and then directly raise the temperature to 1000℃ for normalizing. Place the normalized valve blank into a quenching tank, and after the surface temperature drops to 300℃, remove it and return it to 400℃. Place it back into the quenching tank, and when the surface temperature drops to 250℃, remove it and return it to 300℃. Place it back into the quenching tank, and when the surface temperature drops to 150℃, remove it and cool it to room temperature. Then place the valve blank into a tempering furnace, raise the temperature from 300℃ to 500℃, hold it for 30 minutes, and cool it to room temperature. After surface treatment, the valve semi-finished product is obtained.

[0040] S3: The surface of the valve semi-finished product is etched using a nano-picosecond composite laser processing equipment with a wavelength of 355nm. During the processing, a picosecond laser is first used for etching, with the following parameters: power of 15W, scanning speed of 300mm / s, and 100 scans. Then, a nanosecond laser is used for etching, with the following parameters: power of 7.5W, scanning speed of 300mm / s, 5 scans, and defocusing distance of +50μm. During the etching process, dust removal and air blowing are performed simultaneously to prevent the spatter generated by laser ablation from falling back into the ablation pit and causing irregular ablation morphology. This results in well-formed grooves with a U-shaped cross-section. The depth of the U-shaped grooves is 80μm, the diameter is 50μm, and the gap between adjacent U-shaped grooves is 200μm. The grooves are evenly distributed in a ring array around the center line of the valve semi-finished product, resulting in a porous valve semi-finished product.

[0041] S4: Using graphite as the cathode and porous valve semi-finished product as the anode, anodizing treatment is performed using a 15% sulfuric acid solution as the electrolyte. The reaction is carried out at 20℃ and 100r / min for 9min. The distance between graphite and porous valve semi-finished product is 6cm, and the reaction area ratio is maintained at 2:1. Current is applied, and the anodizing voltage is 50V. A uniform porous oxide film is formed on the surface of the porous valve semi-finished product. The porous valve semi-finished product is then washed with deionized water until neutral to obtain anodized porous valve semi-finished product.

[0042] S5: Mix 5g of 12CrNi2 powder (≥99.5% purity) with a particle size of 50-60μm, 1g of graphite powder with a particle size of 4-6μm, 3g of vanadium powder (≥99.5% purity) with a particle size of 2-8μm, and 2g of titanium powder (≥99.5% purity) with a particle size of 4-10μm, and add the mixture to a ball mill. Ball mill at 300r / min for 2h. Then, use sodium silicate water glass as a binder to uniformly coat the anodized porous valve semi-finished product. Then, form a continuous VC (vanadium carbide) and TiC (titanium carbide) coating on the anodized porous valve semi-finished product by laser cladding. The coating thickness is 700μm, and a corrosion-resistant alloy steel valve is obtained.

[0043] The parameters for laser cladding are: defocusing distance of 160mm, current of 170A, laser duration of 6.0ms, frequency of 5Hz, and laser input energy density of 80J / cm². 2 The scanning speed was 2 mm / s, the bonding rate was 8%, and argon gas was used for protection at a flow rate of 15 L / min during preparation. Nanoscale VC particles and nanoscale TiC particles were synthesized in situ under laser irradiation using vanadium powder, titanium powder, and graphite powder. These particles have high strength and corrosion resistance and can form a uniform coating on the surface of corrosion-resistant alloy steel valves.

[0044] Example 3: This example provides a corrosion-resistant alloy steel valve, prepared through the following steps:

[0045] S1: Pure iron bars, low-carbon ferrochrome, nickel sheets, and HRB400 threaded steel bars are added to a pit furnace and held at 500℃ for 40 minutes. Then, they are transferred to a medium-frequency induction furnace and melted at 1600℃ under argon protection. After the melt is clear, low-carbon ferrosilicon and low-carbon ferromanganese are added and stirred for 5 minutes after melting. High-purity aluminum particles are then added for deoxidation and alloying. After removing the slag, ferrophosphorus powder, copper particles, and antimony particles are added and stirred for 5 minutes after melting. Alkaline slag-forming materials (calcium oxide, aluminum oxide, and calcium fluoride in a mass ratio of 9:3:1) are added and held at 3 hours. After removing the slag, the temperature is lowered to 1450℃ and cast. After casting, the material is air-cooled to room temperature and then taken out. It is then heated and forged at 1000℃, rolled, and air-cooled to room temperature to obtain a valve billet.

[0046] The gas compact contains the following elements by weight percentage: C: 0.2%, Si: 0.35%, V: 0.1%, P: 0.12%, Mn: 1%, Al: 0.6%, Ti: 0.04%, Ni: 1.9%, Cr: 1%, Cu: 0.4%, Sb: 0.2%, with the balance being Fe and other impurities.

[0047] S2: Quickly transfer the valve blank into a 600℃ heating furnace, raise the temperature to 800℃ within 3 hours, perform uniform annealing, and then directly raise the temperature to 1050℃ for normalizing. Place the normalized valve blank into a quenching tank. After the surface temperature drops to 320℃, remove it and return it to 410℃. Place it back into the quenching tank. When the surface temperature drops to 270℃, remove it and return it to 320℃. Place it back into the quenching tank. When the surface temperature drops to 150℃, remove it and cool it to room temperature. Then place the valve blank into a tempering furnace, raise the temperature from 350℃ to 600℃, hold it for 30 minutes, and cool it to room temperature. After surface treatment, the valve semi-finished product is obtained.

[0048] S3: The surface of the valve semi-finished product is etched using a nano-picosecond composite laser processing equipment with a wavelength of 355nm. During the processing, a picosecond laser is first used for etching, with the following parameters: power of 15W, scanning speed of 350mm / s, and 120 scans. Then, a nanosecond laser is used for etching, with the following parameters: power of 7.5W, scanning speed of 350mm / s, 10 scans, and defocusing distance of +50μm. During the etching process, dust removal and air blowing are performed simultaneously to prevent the spatter generated by laser ablation from falling back into the ablation pit and causing irregular ablation morphology. This results in well-formed grooves with a U-shaped cross-section. The depth of the U-shaped grooves is 120μm, the diameter is 80μm, and the gap between adjacent U-shaped grooves is 300μm. The grooves are evenly distributed in a ring array around the center line of the valve semi-finished product, resulting in a porous valve semi-finished product.

[0049] S4: Using graphite as the cathode and porous valve semi-finished product as the anode, anodizing treatment is performed using a 15% sulfuric acid solution as the electrolyte. The reaction is carried out at 25℃ and 200r / min for 12min. The distance between graphite and porous valve semi-finished product is 8cm, and the reaction area ratio is maintained at 2:1. Current is applied, and the anodizing voltage is 50V. A uniform porous oxide film is formed on the surface of the porous valve semi-finished product. The porous valve semi-finished product is then washed with deionized water until neutral to obtain anodized porous valve semi-finished product.

[0050] S5: Mix 7g of 12CrNi2 powder (≥99.5% purity) with a particle size of 50-60μm, 2g of graphite powder with a particle size of 4-6μm, 4.5g of vanadium powder (≥99.5% purity) with a particle size of 2-8μm, and 3g of titanium powder (≥99.5% purity) with a particle size of 4-10μm, and add the mixture to a ball mill. Ball mill at 400r / min for 3h. Then, use sodium silicate water glass as a binder to uniformly coat the anodized porous valve semi-finished product. Then, form a continuous VC (vanadium carbide) and TiC (titanium carbide) coating on the anodized porous valve semi-finished product by laser cladding. The coating thickness is 800μm, and a corrosion-resistant alloy steel valve is obtained.

[0051] The parameters for laser cladding are: defocusing distance of 160mm, current of 180A, laser duration of 6.0ms, frequency of 5Hz, and laser input energy density of 85J / cm². 2 The scanning speed was 4 mm / s, the bonding rate was 10%, and argon gas was used for protection at a flow rate of 20 L / min during preparation. Nanoscale VC particles and nanoscale TiC particles were synthesized in situ under laser irradiation using vanadium powder, titanium powder, and graphite powder. These particles have high strength and corrosion resistance and can form a uniform coating on the surface of corrosion-resistant alloy steel valves.

[0052] The medium-frequency induction furnace in Examples 1-3 is model LSW-35KW, purchased from Zhengzhou Lanshuo Electronics Co., Ltd., while the others are commercially available products.

[0053] Comparative Example 1: Based on Example 1, in step S5, the porous valve semi-finished product prepared in step S3 is used to replace the anodized porous valve semi-finished product, while the other steps remain unchanged, to obtain a corrosion-resistant alloy steel valve.

[0054] Comparative Example 2: Based on Example 1, only a picosecond laser was used for etching in step S3, resulting in a trench depth of 10-20 μm and a diameter of 5-10 μm. The remaining steps remained unchanged, resulting in a corrosion-resistant alloy steel valve.

[0055] Comparative Example 3: Based on Example 1, the parameters for nanosecond laser etching in step S3 were set as follows: power of 7.5W, scanning speed of 325mm / s, number of scans of 50-100, and defocusing amount of +50μm. The resulting trench depth was 200-300μm and the diameter was 100-150μm. The remaining steps remained unchanged, and a corrosion-resistant alloy steel valve was obtained.

[0056] A blank control group ck was set up, and the corrosion-resistant alloy steel valve of ck is the valve semi-finished product obtained in step S2.

[0057] The corrosion-resistant alloy steel valves in Examples 1-3, Comparative Examples 1-3, and group ck were subjected to performance tests:

[0058] Corrosion resistance: The neutral salt spray test (NSS) was designed according to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test". The accelerated corrosion test was conducted using a ZK-60K fully automatic salt spray tester. Before the test, the surface was cleaned with deionized water and anhydrous ethanol. After cleaning, it was ultrasonically cleaned in acetone and then dried in an oven at 50℃ for 2 hours. After cooling, it was weighed using an electronic balance, retaining two significant figures after the decimal point. Three measurements were taken and the average value was used to reduce the error. A NaCl solution with a mass fraction of 5% and a pH value of 6.5-7.2 was used. The test cycle was 72 hours. The temperature of the salt spray chamber was set to 45±2℃ and the spray pressure was 0.1MPa. The NaCl solution was replenished every 24 hours. The salt spray chamber should not be opened during the experiment to minimize test interruptions. Under special circumstances, the total daily time the salt spray chamber was opened should not exceed 10 minutes. After the test is completed, the test sample is taken out. In order to reduce the shedding of corrosion products, the test sample is placed indoors to air dry for 0.5h-1h before cleaning. Then, it is gently cleaned with deionized water at a temperature not higher than 40℃ to remove the residual salt spray solution on the surface of the test sample. It is then dried at low temperature in a drying oven.

[0059] Strength performance: Tensile specimens were designed according to the national standard GB / T228.1-2010 "Metallic materials - Tensile testing - Part 1: Test method at room temperature". The mechanical properties of corrosion-resistant alloy steel valves were tested using a DDL200 universal testing machine with a 50kN sensor and a tensile rate set to 2mm / min. Each type of corrosion-resistant alloy steel valve was tested three times and the average value was taken to calculate the tensile strength and yield strength.

[0060] Impact toughness test: Standard V-notch Charpy impact specimens were prepared according to GB / T229-2007 "Metallic Materials - Charpy Pendulum Impact Test Method". To ensure the reliability of the experimental results, six specimens were used in each group. The impact testing equipment was a pendulum impact testing machine (model: PIT452D-4, China Kehua Testing Machine Manufacturing Co., Ltd.). The impact test parameters were: voltage 380V, impact energy 450J, power 37KW.

[0061] The results of the various performance tests are as follows:

[0062] Table 1. Summary of Sample Performance Tests

[0063]

[0064]

[0065] As shown in Table 1, the average corrosion rate in Examples 1-3 was lower than that in Comparative Example 1, while the average corrosion rate in Group CK was the highest. In Comparative Example 1, porous valve semi-finished products were used instead of anodized porous valve semi-finished products. Group CK did not undergo laser etching, anodizing, and laser cladding steps, indicating that anodizing and laser etching have a certain synergistic effect in improving the corrosion resistance of the alloy steel valve. The corrosion resistance effect of laser etching alone is limited. The groove depth on the corrosion resistance alloy steel valve in Comparative Example 2 was 10-20 μm and the diameter was 5-10 μm. The groove depth on the corrosion resistance alloy steel valve in Comparative Example 3 was 200-300 μm and the diameter was 100-150 μm. Their corrosion resistance effects were all lower than those in Examples 1-3, indicating that the corrosion resistance effect was best when the groove depth was 80-120 μm and the diameter was 50-80 μm.

[0066] The tensile strength and yield strength of Examples 1-3 and Comparative Examples 1-3 are higher than those of Group ck, indicating that the mechanical properties of the corrosion-resistant alloy steel valves after laser etching, anodizing and laser cladding are improved and the overall strength is better.

[0067] The impact energy in Examples 1-3 was higher than that in Comparative Example 1. In Comparative Example 1, a porous valve semi-finished product was used instead of anodized porous valve semi-finished product, indicating that the surface of the alloy steel valve after anodization can provide better adhesion for the coating. The impact energy in Comparative Examples 2-3 was lower than that in Examples 1-3, indicating that the coating adhesion was the highest when the trench depth was 80-120 μm and the diameter was 50-80 μm. The impact energy of group ck was the lowest, indicating that the corrosion-resistant alloy steel valve after laser etching, anodizing and laser cladding treatment has better impact resistance. The porous structure of the oxide film can improve the adhesion of the coating, which not only enables the coating to adhere firmly to the surface of the corrosion-resistant alloy steel valve, but also improves the corrosion resistance of the corrosion-resistant alloy steel valve together with the coating.

[0068] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0069] 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 alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a corrosion-resistant alloy steel valve, the method comprising: The valve blank is heat-treated to obtain a valve semi-finished product, and then surface-treated. The surface treatment process is characterized by the following specific steps: Step 1: The valve semi-finished product is processed by a secondary laser etching process to etch uniformly distributed U-shaped grooves on the surface of the valve semi-finished product, thus obtaining a porous valve semi-finished product. Step 2: The porous valve semi-finished product is subjected to anodizing treatment to form a uniform porous oxide film on the surface, thereby obtaining the anodized porous valve semi-finished product. Step 3: Ball mill and mix 12CrNi2 powder, graphite powder, vanadium powder and titanium powder to obtain a mixed powder. The mixed powder is then coated onto the surface of the anodized porous valve semi-finished product by laser cladding to obtain a corrosion-resistant alloy steel valve. The specific steps of the secondary laser etching process described in step one are as follows: First, a picosecond laser is used for etching, then a nanosecond laser is used for etching. Dust removal and air blowing are performed simultaneously during the etching process. The trenches described in step one have a depth of 80-120μm, a diameter of 50-80μm, and a gap of 200-300μm between adjacent trenches.

2. The method for preparing a corrosion-resistant alloy steel valve according to claim 1, characterized in that, The etching parameters for the picosecond laser are set as follows: power of 15W, scanning speed of 300-350mm / s, and number of scans of 100-120. The etching parameters for the nanosecond laser are set as follows: power of 7.5W, scanning speed of 300-350mm / s, number of scans of 5-10, and defocusing distance of +50μm.

3. The method for preparing a corrosion-resistant alloy steel valve according to claim 1, characterized in that, The specific steps of the anodizing treatment described in step two are as follows: Using graphite as the cathode and porous valve semi-finished product as the anode, anodizing treatment was carried out using sulfuric acid solution as the electrolyte. The reaction was carried out at 20-25℃ and 100-200r / min for 9-12min. The distance between graphite and porous valve semi-finished product was 6-8cm. The anodizing voltage was 50V. After washing, anodized porous valve semi-finished product was obtained.

4. The method for preparing a corrosion-resistant alloy steel valve according to claim 1, characterized in that, The mass ratio of 12CrNi2 powder, graphite powder, vanadium powder and titanium powder in step three is 5-7:1-2:3-4.5:2-3.

5. The method for preparing a corrosion-resistant alloy steel valve according to claim 1, characterized in that, The thickness of the laser cladding coating in step three is 700-800 μm.

6. The method for preparing a corrosion-resistant alloy steel valve according to claim 1, characterized in that, The preparation process of the valve preform is as follows: Pure iron bars, low-carbon ferrochrome, nickel sheets, and threaded steel bars are melted at 1500-1600℃ under argon protection. Then, low-carbon ferrosilicon, low-carbon ferromanganese, high-purity aluminum granules, ferrophosphorus powder, copper granules, and antimony granules are added. After melting, the mixture is stirred for 3-5 minutes, and alkaline slag-forming materials are added. The mixture is kept at this temperature for 2-3 hours, the slag is removed, and the temperature is lowered to 1440-1450℃ for casting. The mixture is then heated and forged at 900-1000℃, rolled, and air-cooled to room temperature to obtain a valve billet.

7. The method for preparing a corrosion-resistant alloy steel valve according to claim 6, characterized in that, The alloy steel valve blank comprises the following elements by weight percentage: C: 0.1-0.2%, Si: 0.25-0.35%, V: 0.05-0.1%, P: 0.08-0.12%, Mn: 0.5-1%, Al: 0.4-0.6%, Ti: 0.02-0.04%, Ni: 1.6-1.9%, Cr: 0.7-1%, Cu: 0.25-0.4%, Sb: 0.15-0.2%, with the balance being Fe and other impurities.

8. A corrosion-resistant alloy steel valve, characterized in that, It is prepared by the method for preparing a corrosion-resistant alloy steel valve according to any one of claims 1-7.

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