304 stainless steel for underflow open weir gate and processing technology thereof

Abstract

The application relates to the technical field of stainless steel materials, and particularly discloses a 304 stainless steel for a flow-limiting open-type gate and a processing technology thereof. First, the surface of the 304 stainless steel is pretreated by using alumina particles to increase the roughness of the surface of the stainless steel; then, an aluminum-cobalt-chromium-iron-nickel high-entropy alloy layer is magnetron sputtered on the surface of the stainless steel; the aluminum is gradiently distributed in the alloy layer by increasing the power of the aluminum target, so that a gradient layer is formed; finally, the 304 stainless steel for the flow-limiting open-type gate with good hardness, erosion resistance and corrosion resistance is obtained through deep cooling treatment, pulse cycle treatment, sealing treatment by using a sealing agent and annealing treatment, the service life of the gate is prolonged, and the maintenance cost during replacement of the gate is reduced.

Description

Technical Field

[0001] This invention relates to the field of stainless steel materials technology, specifically to a 304 stainless steel for a flow-limiting, bottom-opening weir gate and its processing technology. Background Technology

[0002] A weir is a control component used to regulate the flow of liquid in pipelines, ditches, and other liquid transport systems. Based on its opening method, it can be classified into top-opening, bottom-opening, flap-type, and sliding weirs. A bottom-opening weir lowers when opened, creating a liquid channel above it. Because it requires no installation space above, and the water pressure helps to seal the weir tightly when closed, it has advantages such as requiring little space and providing good airtightness.

[0003] Common problems encountered during the use of weirs include: long-term erosion by the fluid or impurities carried in the fluid leading to wear, reduced sealing performance, and leakage; long-term chemical corrosion by the liquid causing rust on the weir or its connecting structures, resulting in the weir becoming stuck in the sealing position and unable to open normally; or the accumulation of silt and other impurities carried in the liquid clogging the sealing track, attracting algae, and affecting the normal use of the weir. Therefore, improving the strength, wear resistance, and corrosion resistance of weirs, and reducing wear and corrosion, plays a crucial role in extending their service life, reducing replacement frequency, and controlling costs. Summary of the Invention

[0004] The purpose of this invention is to provide a 304 stainless steel for a flow-limiting, open-type weir gate and its processing technology, which solves the problems of poor sealing and jamming of the weir gate caused by liquid erosion and chemical corrosion, resulting in wear or rust.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A processing technology for 304 stainless steel used in a flow-limiting, bottom-opening weir gate is as follows:

[0007] Step 1: Use sandblasting to treat the 304 stainless steel substrate with alumina particles to obtain pretreated stainless steel;

[0008] Step 2: After activating the pretreated stainless steel surface with argon plasma, a chromium transition layer, an alloy layer, an aluminum-doped alloy layer, and an aluminum layer are deposited sequentially on the surface to obtain high-entropy alloy surface stainless steel.

[0009] Step 3: Deep cryogenic treatment and pulsed current treatment are applied to the surface of high-entropy alloy stainless steel to obtain cryogenic pulse-strengthened stainless steel;

[0010] Step 4: After the cryogenic pulse-strengthened stainless steel is oxidized by oxygen plasma, the pores are sealed with sodium silicate mixed sol, and then annealed after heating and curing to obtain 304 stainless steel for the flow-limited open weir gate.

[0011] As a limitation of the present invention, in step 1, the particle size of alumina particles is 80-100μm, the sandblasting pressure is 0.6-0.8MPa, the sandblasting distance is 100-200mm, the sandblasting angle is 60-80°, and the sandblasting time is 5-10min.

[0012] By using sandblasting, alumina particles impact the surface of the stainless steel substrate at high speed, removing surface oxides, rust, and contaminants while forming a rough metal surface. This provides mechanical interlocking for the coating and improves the coating's adhesion.

[0013] As a limitation of the present invention, step 2 specifically includes:

[0014] Pretreated 304 stainless steel was placed in the reaction chamber of a magnetron sputtering device, and a vacuum was applied to a pressure of 5 × 10⁻⁶. -4 -7×10 -4 Pa, heat to 70-80℃, introduce argon gas, start the RF power supply, and perform plasma etching at a pressure of 0.8-1.0 Pa, a power of 100-120 W, and a bias voltage of (-150)-(-200) V for 10-15 min. After etching, start the chromium target pulse power supply, the cobalt-chromium-iron-nickel alloy target pulse power supply, and the aluminum target RF power supply in sequence to deposit a 50-70 nm thick chromium transition layer, an 800-900 nm thick alloy layer, a 400-500 nm thick aluminum-doped alloy layer, and a 200-250 nm thick aluminum layer on the etched stainless steel surface to obtain high-entropy alloy surface stainless steel.

[0015] After argon plasma etching activates the surface of the stainless steel substrate, a chromium transition layer is deposited, which acts as a diffusion barrier to prevent iron in the substrate from transferring and diffusing into the coating. Furthermore, the coefficient of thermal expansion of chromium is between that of the substrate and the coating, effectively relieving thermal stress.

[0016] On the chromium transition layer, a cobalt-chromium-iron-nickel high-entropy alloy and aluminum doping are deposited. The high-entropy alloy ensures the coating's hardness, corrosion resistance, and other properties. Through gradient aluminum doping, the bottom layer has a low aluminum content and is mainly composed of high-entropy alloy with low amorphous formation ability, resulting in an FCC solid solution (coarse-grained). The middle layer has a moderate aluminum content and moderate amorphous formation ability, and partially crystallizes after deposition to form B2 phase nanocrystals. The surface layer has a high aluminum content, which inhibits crystal nucleus growth and improves amorphous formation ability, resulting in an amorphous state during deposition. Through composition-structure gradient, the coefficient of thermal expansion gradually changes to the surface layer, reducing residual stress and achieving functional integration of a coarse-grained bottom layer (good bonding), a nanocrystalline middle layer (strong and tough structure), and an amorphous surface layer (wear and corrosion resistance).

[0017] As a limitation of the present invention, when depositing the chromium transition layer, the gas pressure is 0.3-0.5 Pa, the stainless steel temperature is 80-90℃, the pulse frequency is 50-60 kHz, the duty cycle is 50%-60%, the pulse power is 200-220 W, and the deposition time is 10-15 min; when depositing the alloy layer, the gas pressure is 0.4-0.6 Pa, the pulse power is 180-200 W, and the deposition time is 80-90 min; when depositing the aluminum-doped alloy layer, the gas pressure is 0.5-0.7 Pa, the pulse power is 150 W-170 W, the initial radio frequency power is 100-120 W, increasing at a rate of 5 W / min to a final value of 300-320 W, and the deposition time is 36-44 min; when depositing the aluminum layer, the gas pressure is 0.3-0.5 Pa, the radio frequency power is 300-320 W, and the deposition time is 10-15 min.

[0018] As a limitation of the present invention, step 3 specifically includes:

[0019] High-entropy alloy-surfaced stainless steel is rapidly cooled in liquid nitrogen for 8-10 minutes, then removed and allowed to warm to room temperature for 5-7 minutes before being placed back into liquid nitrogen. This cycle is repeated 5-7 times. Finally, the stainless steel is placed in a pulsed current system under nitrogen protection, with a current density of 800-1000 A / cm². 2 The pulse width is 1-2ms, the frequency is 8-10Hz, and the treatment time is 5-10min to obtain cryogenic pulse-strengthened stainless steel.

[0020] During cryogenic cycling, the decrease in material temperature triggers anisotropic shrinkage, and the local shear stress reaches the critical stress required for dislocation slip. Dislocation sources are activated and multiply. At low temperatures, atomic diffusion ability decreases, and recovery mechanisms such as dislocation climb and dislocation slip are hindered. The multiplied dislocations interact through slip, reaction, or pile-up to form a high-density structure at grain boundaries or secondary grain boundaries. After multiple cycles, the dislocation density continues to accumulate, forming a stable high-dislocation structure, which improves the hardness and strength of the coating.

[0021] Pulsed current promotes the absorption of vacancy clusters generated by cryogenic cooling by dislocations. Under the action of pulsed current, high-density dislocations form subgrain boundaries through dynamic recovery, dividing the original grains into nanoscale subgrains, further enhancing the coating performance. The synergistic effect of cryogenic cooling and pulsed current improves the hardness and strength of the coating, enhances crack propagation resistance, promotes the precipitation of the second phase during annealing, optimizes the residual stress distribution, and improves the material performance.

[0022] As a limitation of the present invention, the method for preparing the sodium silicate mixed sol in step 4 is as follows:

[0023] Sodium silicate was added to deionized water and stirred at 25-30℃ and 300-500 rpm for 20-30 min. Then, it was heated in a water bath at 40-50℃ for 1-1.5 h. Subsequently, cerium nitrate ethanol solution was slowly added while stirring at 500-700 rpm. After ultrasonic dispersion for 10-15 min, the mixture was degassed under vacuum to obtain a sodium silicate mixed sol.

[0024] Sodium silicate hydrolyzes into silanol during heating. The silanol further hydrolyzes and condenses to form a silica sol network, which serves as the framework for the sealing structure. Cerium nitrate hydrolyzes into cerium dioxide nanoparticles, which fill the pores of the silica network, inhibit the penetration of ions (such as chloride ions), and improve the corrosion resistance of the material surface. At the same time, it bonds with the silica network to form silicon-oxygen-cerium bonds, which enhances the hardness of the sealing material and the bonding performance with the coating, thereby improving the mechanical properties and corrosion resistance of the material.

[0025] As a limitation of the present invention, in the cerium nitrate ethanol solution, the mass fraction of cerium nitrate is 4%-6%, the concentration of sodium silicate in deionized water is 8-15 g / mL, and the volume ratio of cerium nitrate ethanol solution to deionized water is (20-30):(100-110).

[0026] As a limitation of the present invention, step 4 specifically includes:

[0027] Cryogenic pulse-strengthened stainless steel was placed on the base of an RF plasma oxidation system. A mixture of oxygen and argon in a volume ratio of 3-5:1 was introduced. The gas pressure was set to 0.5-0.8 Pa, the power supply to 300-320 W, and the oxidation time to 30-45 min. During the oxidation process, the temperature of the stainless steel substrate was maintained at 60-80℃. After oxidation, sodium silicate mixed sol was spin-coated onto the stainless steel surface to seal the pores. The spin-coating speed was 200-300 rpm, and the spin-coating time was 20-30 s. After spin-coating, the surface was heated to cure and then annealed to obtain 304 stainless steel for a flow-limited open weir gate.

[0028] Oxygen plasma oxidation technology is used to oxidize the outermost aluminum layer of a certain thickness into an alumina layer, which enhances the material's hardness, corrosion resistance, and rust resistance. After sealing the pores with sodium silicate mixed sol, annealing is performed. On the one hand, it promotes the conversion of trivalent cerium ions in the sealing agent to tetravalent ions, forming cerium dioxide nanoparticles to improve performance. On the other hand, it also promotes the diffusion of aluminum from the alloy layer to the surface, reacting with residual oxygen in the sealing layer to thicken the alumina layer. In addition, annealing can release residual stress from the previous processing and improve the bonding performance between the layers.

[0029] As a limitation of this invention, the curing and annealing process specifically includes:

[0030] Under nitrogen protection, the temperature is increased from room temperature to 80-100℃ at a heating rate of 5℃ / min and cured for 1-1.5h. After 1-1.5h, the temperature is increased to 150-170℃ and cured for 1-1.5h. Finally, the temperature is increased to 230-250℃ and cured for 0.5-1h. After curing, the temperature is increased to 450-470℃ for annealing for 0.5-1h. After annealing, the furnace is cooled to room temperature to obtain 304 stainless steel for the limited-flow open weir.

[0031] A flow-limiting, bottom-opening weir gate made of 304 stainless steel, processed using any of the above-mentioned processing techniques.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] This invention first employs sandblasting to pretreat the surface of a stainless steel substrate with alumina microparticles. This removes oxides, rust, and contaminants from the stainless steel substrate surface while increasing the surface roughness and enhancing the bonding performance between the substrate and the coating. Subsequently, an aluminum-cobalt-chromium-iron-nickel high-entropy alloy layer is deposited on the pretreated stainless steel substrate. In the alloy layer, the aluminum content exhibits a gradient change. The alloy layer near the substrate has a lower aluminum content and exhibits coarse grains. The middle alloy layer has a moderate aluminum content and exhibits strong and tough nanocrystals. The surface layer has a higher aluminum content and exhibits wear-resistant and corrosion-resistant amorphous structures.

[0034] This invention involves magnetron sputtering deposition of a high-entropy alloy coating, followed by cryogenic treatment and pulse strengthening treatment, which further increases the coating's strength, hardness, corrosion resistance, and erosion resistance. Subsequently, a sodium silicate mixed sol sealing treatment is used to improve the coating's density, hinder the penetration of corrosive ions into the coating, and further enhance the coating's corrosion resistance. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] 304 stainless steel (elemental content (wt%): Cr: 17.69%, Ni: 9.16%, Mn: 1.45%, Si: 0.82%, Co: 0.22%, C: 0.18%, Cu: 0.12%, Fe: balance), alumina particles (particle size: 100μm).

[0037] Example 1: A processing technology for 304 stainless steel used in a flow-limiting, bottom-opening weir gate, specifically as follows:

[0038] Step 1: Alumina particles are sprayed onto the surface of a 304 stainless steel substrate using sandblasting. The particle size of the alumina particles is 100μm. The sandblasting pressure is set to 0.6MPa, the sandblasting distance is 150mm, the sandblasting angle is 60°, and the sandblasting time is 5min. After sandblasting, the substrate is ultrasonically cleaned with acetone and ethanol for 5min each, and then dried at 60℃ for 2h to obtain pretreated 304 stainless steel.

[0039] Step 2: Place the pretreated 304 stainless steel into the reaction chamber of the magnetron sputtering equipment and evacuate it to a pressure of 5×10⁻⁶. -4 The pressure was increased to 70°C, argon gas was introduced, and the RF power supply was started. Plasma etching was performed at a pressure of 0.8 Pa, a power of 100 W, and a bias voltage of -200 V for 10 min. After etching, the pressure was adjusted to 0.3 Pa, the temperature was increased to 80°C, and the chromium target pulse power supply was started. The pulse frequency was set to 50 kHz, the duty cycle to 60%, and sputtering was performed at 200 W for 10 min to form a 50 nm thick chromium transition layer. Subsequently, the pulse power supply was switched to a cobalt-chromium-iron-nickel alloy target, maintaining a pulse frequency of 50 kHz, a duty cycle to 60%, and adjusting the pressure to 0.4 Pa. A high-entropy alloy layer with a thickness of 800 nm was formed by deposition at a rate of 180 W for 80 min. Then, the aluminum target RF power supply was turned on, maintaining a pulse frequency of 50 kHz, a duty cycle of 60%, an air pressure of 0.5 Pa, and a pulse power of 150 W. The RF power was set to 100 W and increased to 300 W at a rate of 5 W / min for a total deposition of 40 min, forming an aluminum-doped alloy layer with a thickness of 400 nm. Finally, the pulse power supply was turned off, the air pressure was adjusted to 0.3 Pa, the RF power was maintained at 300 W, and deposition was carried out for 13 min, forming an aluminum layer with a thickness of 200 nm, resulting in a high-entropy alloy surface stainless steel.

[0040] Step 3: After rapidly cooling the high-entropy alloy-surfaced stainless steel in liquid nitrogen for 10 minutes, remove it, allow it to warm to room temperature for 5 minutes, and then immerse it in liquid nitrogen again. Repeat this cycle 5 times. Finally, place it in a pulsed current system under nitrogen protection, setting the current density to 1000 A / cm². 2 With a pulse width of 1ms and a frequency of 10Hz, the process lasted for 5 minutes to obtain cryogenic pulse-strengthened stainless steel.

[0041] Step 4: Add 10g of sodium silicate to 100mL of deionized water, stir at 25℃ and 300rpm for 30min, then heat in a 40℃ water bath for 1h. Then, while stirring at 500rpm, slowly add 20mL of 4% cerium nitrate ethanol solution, sonicate for 10min, and then degas under vacuum to obtain sodium silicate mixed sol.

[0042] Step 5: Place the cryogenic pulse-strengthened stainless steel on the base of the RF plasma oxidation system, and introduce a mixture of oxygen and argon in a volume ratio of 3:1. Set the gas pressure to 0.5 Pa, the power supply to 300 W, and the oxidation time to 45 min. During the oxidation process, maintain the temperature of the stainless steel substrate at 80 °C. After oxidation, spin-coat the stainless steel surface with a sodium silicate mixed sol to seal the pores. The spin-coating speed is 200 rpm and the spin-coating time is 30 s. After spin-coating, under nitrogen protection, heat the stainless steel from room temperature to 80 °C at a heating rate of 5 °C / min for 1 h. After 1 h, continue heating to 150 °C for 1 h, and finally heat to 250 °C for 1 h. After curing, continue heating to 450 °C for annealing for 1 h. After annealing, cool the stainless steel to room temperature with the furnace to obtain 304 stainless steel for a flow-limited open weir.

[0043] Example 2: A processing technology for 304 stainless steel used in a flow-limiting, bottom-opening weir gate, specifically as follows:

[0044] Step 1: Alumina particles are sprayed onto the surface of a 304 stainless steel substrate using sandblasting. The particle size of the alumina particles is 100μm. The sandblasting pressure is set to 0.65MPa, the sandblasting distance is 150mm, the sandblasting angle is 60°, and the sandblasting time is 7min. After sandblasting, the substrate is ultrasonically cleaned with acetone and ethanol for 5min each, and then dried at 60℃ for 2h to obtain pretreated 304 stainless steel.

[0045] Step 2: Place the pretreated 304 stainless steel into the reaction chamber of the magnetron sputtering equipment and evacuate it to a pressure of 5×10⁻⁶. -4 The pressure was increased to 70°C, argon gas was introduced, and the RF power supply was started. Plasma etching was performed at a pressure of 0.9 Pa, a power of 110 W, and a bias voltage of -200 V for 10 min. After etching, the pressure was adjusted to 0.4 Pa, the temperature was increased to 80°C, and the chromium target pulse power supply was started. The pulse frequency was set to 50 kHz, the duty cycle to 60%, and sputtering was performed at 210 W for 10 min to form a 60 nm thick chromium transition layer. Subsequently, the pulse power supply was switched to a cobalt-chromium-iron-nickel alloy target, maintaining a pulse frequency of 50 kHz, a duty cycle to 60%, and adjusting the pressure to 0.5 Pa. A high-entropy alloy layer with a thickness of 850 nm was formed by deposition at a rate of 190 W for 85 min. Then, the aluminum target RF power supply was turned on, maintaining a pulse frequency of 50 kHz, a duty cycle of 60%, an air pressure of 0.6 Pa, and a pulse power of 160 W. The RF power was set to 110 W and increased to 310 W at a rate of 5 W / min for a total deposition of 40 min, forming an aluminum-doped alloy layer with a thickness of 450 nm. Finally, the pulse power supply was turned off, the air pressure was adjusted to 0.4 Pa, the RF power was maintained at 310 W, and deposition was carried out for 13 min, forming an aluminum layer with a thickness of 220 nm, resulting in a high-entropy alloy surface stainless steel.

[0046] Step 3: After rapidly cooling the high-entropy alloy-surfaced stainless steel in liquid nitrogen for 10 minutes, remove it, allow it to warm to room temperature for 5 minutes, and then immerse it in liquid nitrogen again. Repeat this cycle 6 times. Finally, place it in a pulsed current system under nitrogen protection, setting the current density to 1000 A / cm². 2 With a pulse width of 1ms and a frequency of 10Hz, the process lasted for 5 minutes to obtain cryogenic pulse-strengthened stainless steel.

[0047] Step 4: Add 12g of sodium silicate to 100mL of deionized water, stir at 300rpm for 30min at 25℃, heat in a water bath at 40℃ for 1h, then slowly add 25mL of 4% cerium nitrate ethanol solution while stirring at 500rpm, sonicate for 10min and then degas under vacuum to obtain sodium silicate mixed sol.

[0048] Step 5: Place the cryogenic pulse-strengthened stainless steel on the base of the RF plasma oxidation system, and introduce a mixture of oxygen and argon in a volume ratio of 3:1. Set the gas pressure to 0.5 Pa, the power supply to 300 W, and the oxidation time to 45 min. During the oxidation process, maintain the temperature of the stainless steel substrate at 80 °C. After oxidation, spin-coat the stainless steel surface with a sodium silicate mixed sol to seal the pores. The spin-coating speed is 200 rpm and the spin-coating time is 35 s. After spin-coating, under nitrogen protection, heat the stainless steel from room temperature to 80 °C at a heating rate of 5 °C / min for 1 h. After 1 h, continue heating to 150 °C for 1 h, and finally heat to 250 °C for 1 h. After curing, continue heating to 450 °C for annealing for 1 h. After annealing, cool the stainless steel to room temperature with the furnace to obtain 304 stainless steel for a flow-limited open weir.

[0049] Example 3: A processing technology for 304 stainless steel used in a flow-limiting, bottom-opening weir gate, specifically as follows:

[0050] Step 1: Alumina particles are sprayed onto the surface of a 304 stainless steel substrate using sandblasting. The particle size of the alumina particles is 100μm. The sandblasting pressure is set to 0.7MPa, the sandblasting distance is 140mm, the sandblasting angle is 60°, and the sandblasting time is 10min. After sandblasting, the substrate is ultrasonically cleaned with acetone and ethanol for 5min each, and then dried at 60℃ for 2h to obtain pretreated 304 stainless steel.

[0051] Step 2: Place the pretreated 304 stainless steel into the reaction chamber of the magnetron sputtering equipment and evacuate it to a pressure of 5×10⁻⁶. -4The pressure was increased to 70°C, argon gas was introduced, and the RF power supply was started. Plasma etching was performed at a pressure of 1.0 Pa, a power of 120 W, and a bias voltage of -200 V for 10 min. After etching, the pressure was adjusted to 0.5 Pa, the temperature was increased to 80°C, and the chromium target pulse power supply was started. The pulse frequency was set to 50 kHz, the duty cycle to 60%, and sputtering was performed at 220 W for 10 min to form a 70 nm thick chromium transition layer. Subsequently, the pulse power supply was switched to a cobalt-chromium-iron-nickel alloy target, maintaining a pulse frequency of 50 kHz, a duty cycle to 60%, and adjusting the pressure to 0.6 Pa. A 900nm thick alloy layer was formed by depositing at 200W for 90 minutes. Then, the aluminum target RF power supply was turned on, maintaining a pulse frequency of 50kHz, a duty cycle of 60%, an air pressure of 0.7Pa, and a pulse power of 170W. The RF power was set to 120W and increased to 320W at a rate of 5W / min for a total deposition time of 40 minutes, forming an aluminum-doped alloy layer with a thickness of 500nm. Finally, the pulse power supply was turned off, the air pressure was adjusted to 0.5Pa, the RF power was maintained at 320W, and deposition was carried out for 15 minutes to form an aluminum layer of 250nm, resulting in a high-entropy alloy surface stainless steel.

[0052] Step 3: After rapidly cooling the high-entropy alloy-surfaced stainless steel in liquid nitrogen for 10 minutes, remove it, allow it to warm to room temperature for 5 minutes, and then immerse it in liquid nitrogen again. Repeat this cycle 7 times. Finally, place it in a pulsed current system under nitrogen protection, setting the current density to 1000 A / cm². 2 With a pulse width of 1ms and a frequency of 10Hz, the process lasted for 5 minutes to obtain cryogenic pulse-strengthened stainless steel.

[0053] Step 4: Add 15g of sodium silicate to 100mL of deionized water, stir at 25℃ and 300rpm for 30min, then heat in a 40℃ water bath for 1h. Then, while stirring at 500rpm, slowly add 30mL of 4% cerium nitrate ethanol solution, sonicate for 10min, and then degas under vacuum to obtain sodium silicate mixed sol.

[0054] Step 5: Place the cryogenic pulse-strengthened stainless steel on the base of the RF plasma oxidation system, and introduce a mixture of oxygen and argon in a volume ratio of 3:1. Set the gas pressure to 0.5 Pa, the power supply to 300 W, and the oxidation time to 45 min. During the oxidation process, maintain the temperature of the stainless steel substrate at 80 °C. After oxidation, spin-coat the stainless steel surface with a sodium silicate mixed sol to seal the pores. The spin-coating speed is 200 rpm and the spin-coating time is 40 s. After spin-coating, under nitrogen protection, heat the stainless steel from room temperature to 80 °C at a heating rate of 5 °C / min for 1 h. After 1 h, continue heating to 150 °C for 1 h, and finally heat to 250 °C for 1 h. After curing, continue heating to 450 °C for annealing for 1 h. After annealing, cool the stainless steel to room temperature with the furnace to obtain 304 stainless steel for a flow-limited open weir.

[0055] Based on Example 1, the following comparative experiments were conducted, specifically Comparative Example 1, Comparative Example 2, and Comparative Example 3, as described below:

[0056] Comparative Example 1: This comparative example relates to a processing technology for 304 stainless steel used in a flow-limiting, bottom-opening weir gate. The difference from Example 1 is that deep cryogenic treatment was not performed. Specifically:

[0057] Step 1: Alumina particles are sprayed onto the surface of a 304 stainless steel substrate using sandblasting. The particle size of the alumina particles is 100μm. The sandblasting pressure is set to 0.6MPa, the sandblasting distance is 150mm, the sandblasting angle is 60°, and the sandblasting time is 5min. After sandblasting, the substrate is ultrasonically cleaned with acetone and ethanol for 5min each, and then dried at 60℃ for 2h to obtain pretreated 304 stainless steel.

[0058] Step 2: Place the pretreated 304 stainless steel into the reaction chamber of the magnetron sputtering equipment and evacuate it to a pressure of 5×10⁻⁶. -4 The pressure was increased to 70°C, argon gas was introduced, and the RF power supply was started. Plasma etching was performed at a pressure of 0.8 Pa, a power of 100 W, and a bias voltage of -200 V for 10 min. After etching, the pressure was adjusted to 0.3 Pa, the temperature was increased to 80°C, and the chromium target pulse power supply was started. The pulse frequency was set to 50 kHz, the duty cycle to 60%, and sputtering was performed at 200 W for 10 min to form a 50 nm thick chromium transition layer. Subsequently, the pulse power supply was switched to a cobalt-chromium-iron-nickel alloy target, maintaining a pulse frequency of 50 kHz, a duty cycle to 60%, and adjusting the pressure to 0.4 Pa. A high-entropy alloy layer with a thickness of 800 nm was formed by deposition at a rate of 180 W for 80 min. Then, the aluminum target RF power supply was turned on, maintaining a pulse frequency of 50 kHz, a duty cycle of 60%, an air pressure of 0.5 Pa, and a pulse power of 150 W. The RF power was set to 100 W and increased to 300 W at a rate of 5 W / min for a total deposition of 40 min, forming an aluminum-doped alloy layer with a thickness of 400 nm. Finally, the pulse power supply was turned off, the air pressure was adjusted to 0.3 Pa, the RF power was maintained at 300 W, and deposition was carried out for 13 min, forming an aluminum layer with a thickness of 200 nm, resulting in a high-entropy alloy surface stainless steel.

[0059] Step 3: Place the high-entropy alloy-surfaced stainless steel into the pulsed current system, and under nitrogen protection, set the current density to 1000 A / cm². 2 The pulse width is 1ms, the frequency is 10Hz, and the processing time is 5min to obtain pulse-strengthened stainless steel.

[0060] Step 4: Add 10g of sodium silicate to 100mL of deionized water, stir at 25℃ and 300rpm for 30min, then heat in a 40℃ water bath for 1h. Then, while stirring at 500rpm, slowly add 20mL of 4% cerium nitrate ethanol solution, sonicate for 10min, and then degas under vacuum to obtain sodium silicate mixed sol.

[0061] Step 5: Place the pulse-strengthened stainless steel on the base of the RF plasma oxidation system, and introduce a mixture of oxygen and argon in a volume ratio of 3:1. Set the gas pressure to 0.5 Pa, the power supply to 300 W, and the oxidation time to 45 min. During the oxidation process, maintain the temperature of the stainless steel substrate at 80 °C. After oxidation, spin-coat the stainless steel surface with a sodium silicate mixed sol to seal the pores. The spin-coating speed is 200 rpm and the spin-coating time is 30 s. After spin-coating, under nitrogen protection, heat the stainless steel from room temperature to 80 °C at a heating rate of 5 °C / min for 1 h. After 1 h, continue heating to 150 °C for 1 h, and finally heat to 250 °C for 1 h. After curing, continue heating to 450 °C for annealing for 1 h. After annealing, cool the stainless steel to room temperature with the furnace to obtain 304 stainless steel for a flow-limited open weir.

[0062] Comparative Example 2: This comparative example relates to a processing technology for 304 stainless steel used in a flow-limiting, downward-opening weir gate. The difference from Example 1 is that pulse strengthening treatment was not performed. Specifically:

[0063] Step 1: Alumina particles are sprayed onto the surface of a 304 stainless steel substrate using sandblasting. The particle size of the alumina particles is 100μm. The sandblasting pressure is set to 0.6MPa, the sandblasting distance is 150mm, the sandblasting angle is 60°, and the sandblasting time is 5min. After sandblasting, the substrate is ultrasonically cleaned with acetone and ethanol for 5min each, and then dried at 60℃ for 2h to obtain pretreated 304 stainless steel.

[0064] Step 2: Place the pretreated 304 stainless steel into the reaction chamber of the magnetron sputtering equipment and evacuate it to a pressure of 5×10⁻⁶. -4The pressure was increased to 70°C, argon gas was introduced, and the RF power supply was started. Plasma etching was performed at a pressure of 0.8 Pa, a power of 100 W, and a bias voltage of -200 V for 10 min. After etching, the pressure was adjusted to 0.3 Pa, the temperature was increased to 80°C, and the chromium target pulse power supply was started. The pulse frequency was set to 50 kHz, the duty cycle to 60%, and sputtering was performed at 200 W for 10 min to form a 50 nm thick chromium transition layer. Subsequently, the pulse power supply was switched to a cobalt-chromium-iron-nickel alloy target, maintaining a pulse frequency of 50 kHz, a duty cycle to 60%, and adjusting the pressure to 0.4 Pa. A high-entropy alloy layer with a thickness of 800 nm was formed by deposition at a rate of 180 W for 80 min. Then, the aluminum target RF power supply was turned on, maintaining a pulse frequency of 50 kHz, a duty cycle of 60%, an air pressure of 0.5 Pa, and a pulse power of 150 W. The RF power was set to 100 W and increased to 300 W at a rate of 5 W / min for a total deposition of 40 min, forming an aluminum-doped alloy layer with a thickness of 400 nm. Finally, the pulse power supply was turned off, the air pressure was adjusted to 0.3 Pa, the RF power was maintained at 300 W, and deposition was carried out for 13 min, forming an aluminum layer with a thickness of 200 nm, resulting in a high-entropy alloy surface stainless steel.

[0065] Step 3: Place the high-entropy alloy surface stainless steel into liquid nitrogen for rapid cooling for 10 minutes, then remove it, allow it to warm up at room temperature for 5 minutes, and then place it back into liquid nitrogen. Repeat this cycle 5 times to obtain cryogenic stainless steel.

[0066] Step 4: Add 10g of sodium silicate to 100mL of deionized water, stir at 25℃ and 300rpm for 30min, then heat in a 40℃ water bath for 1h. Then, while stirring at 500rpm, slowly add 20mL of 4% cerium nitrate ethanol solution, sonicate for 10min, and then degas under vacuum to obtain sodium silicate mixed sol.

[0067] Step 5: Place the cryogenic stainless steel on the base of the RF plasma oxidation system, and introduce a mixture of oxygen and argon in a volume ratio of 3:1. Set the gas pressure to 0.5 Pa, the power supply to 300 W, and the oxidation time to 45 min. During the oxidation process, maintain the temperature of the stainless steel substrate at 80 °C. After oxidation, spin-coat the stainless steel surface with a sodium silicate mixed sol to seal the pores. The spin-coating speed is 200 rpm and the spin-coating time is 30 s. After spin-coating, under nitrogen protection, heat the stainless steel from room temperature to 80 °C at a heating rate of 5 °C / min and cure for 1 h. After 1 h, continue heating to 150 °C and cure for 1 h. Finally, heat the stainless steel to 250 °C and cure for 1 h. After curing, continue heating to 450 °C for annealing for 1 h. After annealing, cool the stainless steel to room temperature with the furnace to obtain 304 stainless steel for a flow-limited open weir.

[0068] Comparative Example 3: This comparative example relates to a processing technology for 304 stainless steel used in a flow-limiting, open-type weir gate. The difference from Example 1 is that sodium silicate mixed sol was not used for sealing the pores. Specifically:

[0069] Step 1: Alumina particles are sprayed onto the surface of a 304 stainless steel substrate using sandblasting. The particle size of the alumina particles is 100μm. The sandblasting pressure is set to 0.6MPa, the sandblasting distance is 150mm, the sandblasting angle is 60°, and the sandblasting time is 5min. After sandblasting, the substrate is ultrasonically cleaned with acetone and ethanol for 5min each, and then dried at 60℃ for 2h to obtain pretreated 304 stainless steel.

[0070] Step 2: Place the pretreated 304 stainless steel into the reaction chamber of the magnetron sputtering equipment and evacuate it to a pressure of 5×10⁻⁶. -4 The pressure was increased to 70°C, argon gas was introduced, and the RF power supply was started. Plasma etching was performed at a pressure of 0.8 Pa, a power of 100 W, and a bias voltage of -200 V for 10 min. After etching, the pressure was adjusted to 0.3 Pa, the temperature was increased to 80°C, and the chromium target pulse power supply was started. The pulse frequency was set to 50 kHz, the duty cycle to 60%, and sputtering was performed at 200 W for 10 min to form a 50 nm thick chromium transition layer. Subsequently, the pulse power supply was switched to a cobalt-chromium-iron-nickel alloy target, maintaining a pulse frequency of 50 kHz, a duty cycle to 60%, and adjusting the pressure to 0.4 Pa. A high-entropy alloy layer with a thickness of 800 nm was formed by deposition at a rate of 180 W for 80 min. Then, the aluminum target RF power supply was turned on, maintaining a pulse frequency of 50 kHz, a duty cycle of 60%, an air pressure of 0.5 Pa, and a pulse power of 150 W. The RF power was set to 100 W and increased to 300 W at a rate of 5 W / min for a total deposition of 40 min, forming an aluminum-doped alloy layer with a thickness of 400 nm. Finally, the pulse power supply was turned off, the air pressure was adjusted to 0.3 Pa, the RF power was maintained at 300 W, and deposition was carried out for 13 min, forming an aluminum layer with a thickness of 200 nm, resulting in a high-entropy alloy surface stainless steel.

[0071] Step 3: After rapidly cooling the high-entropy alloy-surfaced stainless steel in liquid nitrogen for 10 minutes, remove it, allow it to warm to room temperature for 5 minutes, and then immerse it in liquid nitrogen again. Repeat this cycle 5 times. Finally, place it in a pulsed current system under nitrogen protection, setting the current density to 1000 A / cm². 2 With a pulse width of 1ms and a frequency of 10Hz, the process lasted for 5 minutes to obtain cryogenic pulse-strengthened stainless steel.

[0072] Step 4: Place the cryogenic pulse-strengthened stainless steel on the base of the RF plasma oxidation system, and introduce a mixture of oxygen and argon in a volume ratio of 3:1. Set the gas pressure to 0.5 Pa, the power supply to 300 W, and the oxidation time to 45 min. During the oxidation process, maintain the temperature of the stainless steel substrate at 80 °C. After oxidation, under nitrogen protection, anneal at a heating rate of 5 °C / min from room temperature to 450 °C for 1 h. After annealing, cool the furnace to room temperature to obtain 304 stainless steel for open weir gates under limited flow conditions.

[0073] Testing experiment:

[0074] Samples of 304 stainless steel were fabricated for flow-limiting, downward-opening weir gates according to the processing techniques in each embodiment and comparative example, and then tested.

[0075] Microhardness testing: The microhardness of the samples was tested using an HSV-1000 digital display microhardness tester. The test was conducted according to the "Vickers Hardness Test for Metallic Materials" (GB / T 4340-2024). The sample was fixed on the fixture of the microhardness tester. The position of the square pyramid indenter and the fixture was adjusted so that the center of the indenter lightly touched the test point of the sample. Then, the hardness tester was started to apply a load, so that the diamond indenter was pressed into the test point of the sample. The load was set to 0.981N and the time was 10s. After 10s, the indenter was raised and the diagonal length of the indentation was measured. The microhardness of the sample was calculated. Five points were tested on each sample, and the average value of the test results was taken.

[0076] Erosion resistance test: The erosion resistance of the samples was tested using an MF-20 erosion and wear tester (Jinan Yanrui). The sample size was 30mm×30mm×5mm. The erosion medium was water, and the erosion abrasive particles were quartz sand with a particle size of 100μm. The sand-to-water ratio was 3%. After weighing the sample, it was fixed on the fixture, ensuring that the water flow was in the direction directly facing the erosion surface. The water flow impact angle was 30°, the particle flow rate was 30g / min, the particle velocity was 50m / s, and the test time was 60min. After the test, the sample was dried and the residual particles on the surface were removed with a soft brush. The sample was weighed again, and the erosion and wear rate of the sample was calculated.

[0077] Corrosion resistance test: Weigh a 50mm×25mm×5mm sample and fix it with a PFTE hook, so that the sample is completely immersed in a 3.5% neutral sodium chloride solution. Maintain the test temperature at 25℃, and replace the neutral sodium chloride solution every 7 days for a total of 30 days. After 30 days, take out the sample and soak it in a 50℃ mixture of 10% nitric acid and 1% hydrofluoric acid for 10 minutes. After 10 minutes, rinse it with deionized water until neutral, dry it and weigh it again, and calculate the corrosion amount of the sample.

[0078] Coating adhesion performance test: The coating adhesion performance was tested using a universal tensile testing machine. E-7 epoxy resin adhesive was applied to the front of a 50mm×50mm×5mm sample. Then, a steel clamp was vertically pressed against the front of the sample. After the adhesive was fully cured at room temperature, the clamp was connected to the tensile clamp of the testing machine. The back of the sample was fixed to the testing machine with bolts. The testing machine was started and stretched at a uniform speed of 1mm / min until the coating peeled off. The stretching was stopped and the adhesion strength of the coating was calculated.

[0079]

[0080] Conclusion: The test data shows that the 304 stainless steel sample processed by the processing technology in the examples has good microhardness. Compared with the comparative example, the 304 stainless steel for the flow-limiting open weir proposed in this invention has high hardness, good erosion resistance, good corrosion resistance, and good coating adhesion. It can meet the working conditions of the flow-limiting open weir being subjected to long-term erosion and corrosion, has a long service life, and reduces the maintenance and replacement cost of the weir.

[0081] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A process for machining 304 stainless steel for a low-flow open flume gate, characterized by: Specifically, Step 1: the 304 stainless steel substrate is treated with aluminum oxide particles in the form of sand blasting to obtain a pretreated stainless steel; Step 2: Put the pretreated 304 stainless steel into the reaction chamber of a magnetron sputtering device, and vacuumize to a pressure of 5x10 -4 -7x10 -4 Pa, and warm up to 70-80℃, and then introduce argon, and start the RF power source, and perform plasma etching at a pressure of 0.8-1.0 Pa, a power of 100-120 W, and a bias voltage of (-150)-(-200) V, and the etching time is 10-15 min, and after etching, start the chromium target pulse power source, the cobalt-chromium-iron-nickel alloy target pulse power source, and the aluminum target RF power source in sequence, and deposit a 50-70 nm thick chromium transition layer, an 800-900 nm thick alloy layer, a 400-500 nm thick aluminum-doped alloy layer, and a 200-250 nm thick aluminum layer on the etched stainless steel surface, to obtain a high-entropy alloy surface stainless steel. Step 3: the high-entropy alloy surface stainless steel is put into liquid nitrogen and quenched for 8-10 min, taken out, warmed at room temperature for 5-7 min, and then put into liquid nitrogen again, cycled for 5-7 times, and then put into a pulse current system under nitrogen protection, with a current density of 800-1000 A / cm 2 , a pulse width of 1-2 ms, a frequency of 8-10 Hz, and a treatment time of 5-10 min, to obtain a cryogenic pulse strengthened stainless steel; Step 4: the cryogenic pulse strengthened stainless steel is placed on the base of the RF plasma oxidation system, and a mixture of oxygen and argon is introduced, the gas pressure is set to 0.5-0.8 Pa, the power is set to 300-320 W, the oxidation time is 30-45 min, and the stainless steel substrate temperature is maintained at 60-80℃ during the oxidation process, after the oxidation is completed, the stainless steel surface is coated with a sodium silicate mixed sol to seal the pores, the spin coating speed is 200-300 rpm, the spin coating time is 20-30 s, and after spin coating, the temperature is raised for curing and annealing to obtain a 304 stainless steel for a flow-restricted open weir gate.

2. The process for manufacturing of 304 stainless steel for flow restricting open flume gate as claimed in claim 1 wherein: In step 1, the particle size of the aluminum oxide particles is 80-100 μm, the sand blasting pressure is 0.6-0.8 MPa, the sand blasting distance is 100-200 mm, the sand blasting angle is 60-80°, and the sand blasting time is 5-10 min.

3. The process for manufacturing of 304 stainless steel for flashboard as claimed in claim 1, wherein: When depositing the chromium transition layer, the gas pressure is 0.3-0.5 Pa, the stainless steel temperature is 80-90℃, the pulse frequency is 50-60 KHz, the duty cycle is 50%-60%, the pulse power is 200-220 W, and the deposition time is 10-15 min; When depositing the alloy layer, the gas pressure is 0.4-0.6 Pa, the pulse power is 180-200 W, and the deposition time is 80-90 min; when depositing the aluminum-doped alloy layer, the gas pressure is 0.5-0.7 Pa, the pulse power is 150-170 W, the initial radio frequency power is 100-120 W, which is increased at a rate of 5 W / min, and the final radio frequency power is 300-320 W, and the deposition time is 36-44 min; when depositing the aluminum layer, the gas pressure is 0.3-0.5 Pa, the radio frequency power is 300-320 W, and the deposition time is 10-15 min.

4. The process for manufacturing of 304 stainless steel for low flow under sluice gate as claimed in claim 1 wherein the said process further comprises of the steps of: In step 4, the preparation method of the sodium silicate mixed sol is as follows: The sodium silicate is added to deionized water, stirred at 25-30℃ and 300-500 rpm for 20-30 min, heated in a water bath at 40-50℃ for 1-1.5 h, then slowly added with cerium nitrate ethanol solution under stirring at 500-700 rpm, ultrasonic dispersed for 10-15 min, and vacuum degassed to obtain the sodium silicate mixed sol.

5. The process for manufacturing of 304 stainless steel for flashboard as claimed in claim 4, wherein the said process further comprises of the following steps: In the cerium nitrate ethanol solution, the mass fraction of cerium nitrate is 4%-6%, the concentration of sodium silicate in deionized water is 8-15 g / mL, and the volume ratio of cerium nitrate ethanol solution to deionized water is (20-30):(100-110).

6. The process for manufacturing of 304 stainless steel for flashboard as claimed in claim 1, wherein: The curing and annealing process is as follows: Under nitrogen protection, the temperature is raised from room temperature to 80-100℃ at a rate of 5℃ / min for 1-1.5 h, then the temperature is continuously raised to 150-170℃ for 1-1.5 h, finally the temperature is raised to 230-250℃ for 0.5-1 h, after curing is completed, the temperature is continuously raised to 450-470℃ for annealing for 0.5-1 h, after annealing is completed, the furnace is cooled to room temperature, and the 304 stainless steel for a flow-restricted open weir gate is obtained.

7. A 304 stainless steel for a low-flow open flume gate, processed using the processing method of any one of claims 1-6.

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