A method for preparing corrosion-resistant titanium alloy foil for plate heat exchangers

Abstract

This invention relates to the field of plate heat exchanger material processing technology, specifically to a method for preparing corrosion-resistant titanium alloy foil for plate heat exchangers. The preparation method includes the following steps: S1, preparing titanium alloy ingots; S2, preparing billets to be rolled; S3, cooling and cold rolling; S4, post-treatment. This invention involves depositing boron oxide powder within micro-etched micropores, and then coating the surface of the titanium foil with a composite liquid of mesoporous ceramic powder loaded with ostinidine. This forms a protective layer with antibacterial and corrosion-resistant properties on the surface of the warm-pressed titanium alloy billet, thereby preventing direct contact between corrosive media and the titanium alloy foil, reducing the corrosion rate. Furthermore, in plate heat exchangers, coating the titanium alloy with this ostinidine-loaded mesoporous ceramic powder solution helps reduce the growth of microorganisms on the surface of the titanium alloy foil, improving the hygienic performance and operating efficiency of the heat exchanger.

Description

Technical Field

[0001] This invention relates to the field of plate heat exchanger material processing technology, specifically to a method for preparing corrosion-resistant titanium alloy foil for plate heat exchangers. Background Technology

[0002] Bipolar plates are a key component of proton exchange membrane fuel cells (PEMFCs), accounting for approximately 70% of the total weight and 40% of the cost of the fuel cell stack. The titanium alloy substrate for bipolar plates offers advantages such as excellent corrosion resistance, higher specific strength, and light weight. Plate heat exchangers may come into contact with various corrosive substances during operation, such as acids, alkalis, and salts, and the corrosion resistance of titanium alloy foil ensures long-term stable operation of the equipment in these environments. Titanium alloy foil possesses excellent mechanical properties such as high strength, high toughness, and high hardness, enabling it to maintain good stability and reliability under harsh environments such as high temperature and high pressure. The operating environment of plate heat exchangers can be quite harsh, and the mechanical properties of titanium alloy foil ensure that the equipment performs excellently in various complex environments.

[0003] Bipolar plates can be broadly classified into three categories: carbonaceous materials, metallic materials, and composite materials of metal and carbon. Among metallic materials, aluminum, nickel, titanium, and stainless steel are suitable for manufacturing bipolar plates. Metallic bipolar plates are easy to process, can be mass-produced, are low-cost, thin, and result in high volumetric power and energy density of the battery. The novel Ti-Ni-Nb near-α titanium alloy possesses excellent corrosion resistance, making it a good material for bipolar plate substrates. The thickness of titanium alloy foil used to manufacture bipolar plates is generally 0.05–0.15 mm, with a thickness deviation requirement of no more than ±5 μm. However, Ti-Ni-Nb foil typically requires processing on a 20-roll mill, a complex process with a long processing cycle and high cost. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for preparing corrosion-resistant titanium alloy foil for plate heat exchangers.

[0005] The technical solution of this invention is: a method for preparing corrosion-resistant titanium alloy foil for plate heat exchangers, comprising the following steps:

[0006] S1. Preparation of titanium alloy ingots

[0007] Weigh the raw materials and perform vacuum induction melting to obtain titanium alloy ingots;

[0008] S2. Preparation of the billet to be rolled

[0009] The ingot is heated to 480–520°C and held for 30–60 minutes before undergoing multiple hot pressing processes with a total processing rate of 60–80%, resulting in a hot-pressed billet. The surface of the hot-pressed billet is then micro-etched to create several micropores with a diameter of 0.01–0.03 mm. Boron oxide particles are then vapor-deposited inside the micropores, and a composite liquid of mesoporous ceramic powder loaded with oxytinidine is coated onto the surface of the hot-pressed billet to obtain a pre-formed oxide layer with a thickness of 0.03–0.05 mm. A protective atmosphere is then introduced, and laser cladding nickel plating is performed. After completion, a billet with a composite film layer on the surface is obtained for rolling.

[0010] During laser cladding: the processing power is 18-22W, the scanning speed is 500-700mm / s, the time is 15-18ns, and the loading of otinididine is 58-62%;

[0011] S3, Cooling Cold Rolling

[0012] The billet to be rolled is subjected to 3 to 8 passes of cooling cold rolling, with a temperature reduction of 30 to 50°C per pass and a deformation of 15 to 40% per pass. Vacuum annealing is performed between each pass to obtain the rolled billet. The vacuum annealing temperature is 650 to 700°C, the time is 20 to 30 minutes, and the vacuum degree is 10. -2 ~10 -1 Pa,

[0013] S4, Post-processing

[0014] After rolling, the material is straightened and then cleaned to obtain titanium alloy foil.

[0015] Explanation: The micropores on the titanium alloy surface provide physical anchoring points for the loaded boron oxide and subsequent mesoporous ceramic powder solution, allowing the solution to adhere more firmly to the titanium alloy surface and improving adhesion. The boron oxide particles possess good corrosion resistance. By micro-etching and redepositing boron oxide particles followed by coating with a composite solution of mesoporous ceramic powder loaded with oxytinidine, a protective layer with antibacterial and corrosion-resistant properties is formed on the surface of the titanium alloy foil. This protective layer effectively prevents direct contact between corrosive media and the titanium alloy foil, reducing the corrosion rate. Simultaneously, in the plate heat exchanger, oxytinidine can be released more effectively and adhere to the surface of the titanium alloy foil, forming an antibacterial barrier that further inhibits the growth and reproduction of corrosive bacteria, thereby enhancing the corrosion resistance of the titanium alloy foil and improving the hygienic performance and operating efficiency of the heat exchanger. Furthermore, the titanium alloy foil in the plate heat exchanger may be subjected to various forces such as fluid scouring and vibration, leading to wear. By coating with a nickel layer, the surface hardness and wear resistance of the titanium alloy foil can be significantly improved, extending its service life.

[0016] Further, the preparation method of the mesoporous ceramic powder composite liquid loaded with ostinidine is as follows: ostinidine is dissolved in acetone at a ratio of 25-40 g: 400-600 mL to obtain an ostinidine solution; then, the mesoporous ceramic powder and the ostinidine solution are mixed at a mass ratio of 1-5: 0.5-0.7, and then electromagnetically stirred at a temperature of 30-35°C for 23-25 ​​min; the electromagnetic power is 25-40 W, the magnetic strength is 100-200 T, and the rotation speed is 200-500 r / min, to obtain the mesoporous ceramic powder composite liquid loaded with ostinidine.

[0017] Note: Mesoporous ceramic powder has a large specific surface area and pore volume, thus providing abundant loading sites for ostinidine, which may enhance its antibacterial effect. Furthermore, the mesoporous ceramic powder itself has certain adsorption properties, which can adsorb and fix ostinidine molecules, preventing them from being rapidly released or lost during use. This helps maintain the concentration of ostinidine at the site of action, thereby prolonging its antibacterial action time. The antibacterial effect of ostinidine can also reduce the growth of microorganisms on the surface of titanium alloy foil, improving the hygienic performance and operating efficiency of the heat exchanger.

[0018] Furthermore, the coating method is a combined spin coating and dip coating process.

[0019] The method of combined spin coating and dip coating is as follows: During the first 1 / 4 to 1 / 3 of the coating thickness, the micro-etched warm-pressed blank is fixed on the tray of the spin coater. The spin coater is started and rotated at the first speed for 1 to 3 minutes. At the same time, 1 / 3 to 1 / 2 of the mesoporous ceramic powder composite liquid loaded with ostinidine is taken and dripped onto the top of the blank at a flow rate of 3 to 5 mL / s. After dripping, the spin coater is adjusted to rotate at the second speed for 2 to 5 minutes, and the first oxide layer is obtained by heating. The first speed is 30 to 50 r / min, the second speed is 1500 to 2000 r / min, the heating temperature is 85 to 90℃, and the heating time is 5 to 10 minutes.

[0020] Then, the blank loaded with the first oxide layer is vertically immersed in the remaining mesoporous ceramic powder composite liquid loaded with oxytetracycline, left to stand for 20-25 seconds, and then vertically lifted up. The dipping and coating process is repeated 3-5 times to obtain the pre-formed oxide layer.

[0021] Note: Spin coating in the early stage of coating allows the mesoporous ceramic powder composite liquid loaded with ostinidine to penetrate into the micropores of the titanium alloy foil, filling and partially sealing these micropores. This helps reduce the chance of corrosive media (such as water, oxygen, etc.) directly contacting the titanium alloy substrate, thereby improving its corrosion resistance. The coating formed by spin coating is often dense and uniform, forming a protective barrier on the surface of the titanium alloy foil to prevent the penetration of corrosive media. It can also bond with the titanium alloy substrate to enhance the adhesion of the coating, and has antibacterial effect in addition to preventing the penetration of corrosive media.

[0022] Furthermore, a smoothing treatment is performed after each dip coating. The smoothing treatment method is as follows: the surface of the blank is rinsed with high-pressure nitrogen for 5 to 8 minutes, and then rinsed with deionized water 2 to 4 times.

[0023] Note: High-pressure nitrogen rinsing during the smoothing process may help enhance the adhesion between the coating and the titanium alloy substrate, improve the coating's density, reduce peeling and cracking during subsequent use, thereby extending the coating's service life and improving its corrosion resistance. The smoothing process not only helps improve the appearance quality of the coating, but may also further improve the coating's smoothness and gloss by removing minor bumps and depressions on the coating surface. This smoother surface is more conducive to octinidine contacting bacteria and exerting its antibacterial effect.

[0024] Further, in step S2, the method of multi-stage hot pressing is as follows: continuously heating, and performing one pass of hot pressing treatment and holding for 25-30 minutes at temperatures 70-80°C below the β transformation temperature of the ingot, 35-45°C below the β transformation temperature, 10-15°C below the β transformation temperature, 25-40°C above the β transformation temperature, and 50-60°C above the β transformation temperature, respectively, and performing one pass of multi-directional forging at each corresponding temperature to obtain the hot-pressed billet;

[0025] The temperature and pressure treatment method is as follows: the pressing pressure is 450-550 MPa, the pressing time is 3-5 min, and the pressing method is bidirectional pressing or floating pressing.

[0026] Explanation: Multi-temperature warm pressing combined with multi-directional forging can make the internal structure of titanium alloys more uniform. Warm pressing and multi-directional forging in each temperature range help eliminate casting defects in ingots, such as shrinkage cavities and porosity, and make the distribution of alloying elements more uniform. Improved microstructure uniformity helps to improve the mechanical properties and corrosion resistance of titanium alloys. Warm pressing below the β transformation temperature helps to maintain the good plasticity and deformation capacity of titanium alloys. This makes titanium alloys easier to deform in subsequent processing, thereby improving processing efficiency. Heating titanium alloys to the above temperatures and holding them for a period of time can further improve the heat resistance and oxidation resistance of titanium alloys. The heat holding and aging treatment can refine and disperse the precipitates in titanium alloys, forming more stable intergranular phases, thereby improving the material's oxidation resistance and heat resistance. Processes such as bidirectional pressing and floating pressing can improve the density and uniformity of products, reduce internal defects and stress concentration, thereby improving the corrosion resistance of titanium alloy foils to a certain extent.

[0027] Furthermore, in step S1, during the vacuum induction melting process, the vacuum degree in the vacuum melting furnace is ≤4.5Pa, the arc stabilizing current is 1~3A, the melting voltage is 25~35V, the melting current is 3~5kA, and the melting time is 5~35min.

[0028] Note: Vacuum induction melting under the above conditions helps to ensure the smooth progress of the melting process, reduce temperature fluctuations in the molten pool and uneven electromagnetic stirring, and help to obtain a more uniform and fine grain structure, thereby improving the mechanical and processing properties of titanium alloys.

[0029] Further, in step S2, the micro-etching process is a laser micro-etching process, with a laser energy of 1000-1200mJ, a laser wavelength of 1050-1100nm, and a pulse time of 12-16ns;

[0030] Note: Under the above parameters, the micropores obtained by laser micro-etching are more stable and the etching is more efficient.

[0031] Further, in step S2, the vapor deposition parameters are: power of 5000-7000W, pressure of 180-200Pa, and electrode spacing of 400-550 mils;

[0032] Note: Under the above parameters, vapor deposition helps to form a uniform and dense coating, improving the wear resistance, corrosion resistance and high-temperature performance of titanium alloy foil.

[0033] Compared with existing technologies, the beneficial effects of this invention are:

[0034] (1) This invention uses micro-etching to deposit boron oxide powder in micropores, and then coats the surface of titanium foil with a composite liquid of mesoporous ceramic powder loaded with ostinidine, so that a protective layer with antibacterial and corrosion-resistant properties is formed on the surface of titanium alloy foil, thereby preventing the corrosive medium from directly contacting the titanium alloy foil and reducing the corrosion rate. At the same time, in plate heat exchangers, the use of this coating of mesoporous ceramic powder composite liquid loaded with ostinidine helps to reduce the growth of microorganisms on the surface of titanium alloy foil, improve the hygiene performance and operating efficiency of heat exchangers, and by coating with a nickel layer, the surface hardness and wear resistance of titanium alloy foil can be significantly improved, avoiding wear caused by fluid scouring, vibration and other effects in plate heat exchangers, and effectively extending its service life.

[0035] (2) This invention utilizes the adsorption and corrosion resistance properties of mesoporous ceramic powder to further adsorb and fix ostinidine molecules, preventing them from being rapidly released or lost during use. A layer of mesoporous ceramic powder composite liquid loaded with ostinidine is coated on the surface of the titanium alloy warm-pressed blank to enhance the antibacterial effect of the titanium alloy foil. This can achieve the purpose of maintaining the concentration of ostinidine at the site of action, reducing the growth of microorganisms on the surface of the titanium alloy foil, prolonging its antibacterial action time, and improving the hygienic performance and operating efficiency of the heat exchanger.

[0036] (3) The present invention enables a small amount of mesoporous ceramic powder composite liquid loaded with ostinidine to penetrate into the micropores of titanium alloy foil in the early stage of coating through spin coating and dip coating, filling and partially sealing these micropores, thereby reducing the chance of corrosive media directly contacting titanium alloy foil and thus improving its corrosion resistance. The subsequent dip coating can obtain a denser and more uniform coating. The composite coating obtained by the present invention not only further prevents the penetration of corrosive media, but also has a high antibacterial effect, which has the advantage of improving the performance of plate heat exchangers. Attached Figure Description

[0037] Figure 1 This is a comparison chart of the corrosion resistance of titanium alloy foils prepared in Examples 1 to 7 and Control Groups 1 to 2 of the present invention;

[0038] Figure 2 This is a comparison chart of the corrosion resistance of titanium alloy foils prepared in Examples 1, 8-15 and Control Groups 3-5 of the present invention;

[0039] Figure 3 This is a comparison chart of the corrosion resistance of titanium alloy foils prepared in Examples 1, 16 to 19 of the present invention and control group 6. Detailed Implementation

[0040] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0041] Example 1: A method for preparing corrosion-resistant titanium alloy foil for plate heat exchangers, comprising the following steps:

[0042] S1. Preparation of titanium alloy ingots

[0043] Weigh 50 kg of raw material and perform vacuum induction melting to obtain titanium alloy ingots. During vacuum induction melting, the vacuum degree in the vacuum melting furnace is 4.5 Pa, the arc stabilizing current is 2 A, the melting voltage is 30 V, the melting current is 4 kA, and the melting time is 10 min.

[0044] S2. Preparation of the billet to be rolled

[0045] The ingot is heated to 500℃ and held for 45 minutes before undergoing multiple hot pressing processes with a total processing rate of 70%, resulting in a hot-pressed billet. The surface of the hot-pressed billet is then micro-etched to create several micropores with a diameter of 0.02 mm. Boron oxide particles are then vapor-deposited inside the micropores, and a composite liquid of mesoporous ceramic powder loaded with oxytetracycline is coated onto the surface of the hot-pressed billet to obtain a pre-formed oxide layer with a thickness of 0.04 mm. A nitrogen protective atmosphere is then introduced, and laser cladding nickel plating is performed. After completion, a billet with a composite film layer on the surface is obtained for rolling.

[0046] The method of multi-stage warm pressing is as follows: the temperature is continuously increased, and one warm pressing is performed at each of the following temperatures: 75°C below the β transformation temperature of the ingot, 40°C below the β transformation temperature, 13°C below the β transformation temperature, 32°C above the β transformation temperature, and 55°C above the β transformation temperature, and the temperature is held for 27 minutes. At each corresponding temperature, one multi-directional forging is performed to obtain the warm pressed billet.

[0047] The temperature and pressure treatment method is as follows: the pressing pressure is 500MPa, the pressing time is 4min, and the pressing method is floating pressing.

[0048] The micro-etching process was laser micro-etching, with a laser energy of 1100mJ, a laser wavelength of 1075nm, and a pulse time of 14ns; the vapor deposition parameters were: power of 6000W, pressure of 190Pa, and electrode spacing of 480mil.

[0049] The preparation method of the mesoporous ceramic powder composite liquid loaded with ostinidine is as follows: Ostinidine is dissolved in acetone at a ratio of 30g:500mL to obtain an ostinidine solution; then, the mesoporous ceramic powder and the ostinidine solution are mixed at a mass ratio of 3:0.6, and then electromagnetically stirred at 33℃ for 24min; the electromagnetic power is 30W, the magnetic force is 150T, and the rotation speed is 350r / min to obtain the mesoporous ceramic powder composite liquid loaded with ostinidine; wherein, the mesoporous ceramic powder is commercially available mesoporous silica powder with a particle size of 2-50nm from Beijing Zhongke Keyou Technology Co., Ltd.

[0050] The coating method is a combined spin coating and dip coating process.

[0051] The method of combined spin coating and dip coating is as follows: During the first 7 / 24 of the coating thickness, the micro-etched warm-pressed blank is fixed on the tray of the spin coater. The spin coater is started and rotated at the first speed for 2 minutes. At the same time, 5 / 12 of the mesoporous ceramic powder composite liquid loaded with ostinidine is taken and dripped onto the top of the spin coater at a flow rate of 4 mL / s. After dripping, the spin coater is adjusted to rotate at the second speed for 3 minutes and heated to obtain the first oxide layer. The first speed is 40 r / min, the second speed is 1800 r / min, the heating temperature is 88℃, and the heating time is 8 minutes.

[0052] Then, the blank loaded with the first oxide layer is vertically immersed in the remaining mesoporous ceramic powder composite liquid loaded with oxytinidine. After standing for 22 seconds, it is vertically lifted up. The dip coating is repeated 4 times to obtain the pre-formed oxide layer. After each dip coating, a smoothing treatment is performed. The smoothing treatment method is to use high-pressure nitrogen to rinse the surface of the blank for 6 minutes, and then rinse it with deionized water 3 times.

[0053] During laser cladding: the processing power is 20W, the scanning speed is 600mm / s, the time is 17ns, and the loading of otinididine is 60%.

[0054] S3, Cooling Cold Rolling

[0055] The billet to be rolled was subjected to five passes of cooling cold rolling, with a temperature reduction of 40°C per pass and a deformation of 30% per pass. Vacuum annealing was performed between each pass to obtain the rolled billet. The vacuum annealing temperature was 680°C, the time was 25 minutes, and the vacuum degree was 10. -1.2 Pa;

[0056] S4, Post-processing

[0057] After rolling, the material is straightened and then cleaned to obtain titanium alloy foil.

[0058] Example 2: Unlike Example 1, in step S1, the vacuum degree in the vacuum melting furnace is 4.5 Pa, the arc stabilizing current is 1 A, the melting voltage is 25 V, the melting current is 3 kA, and the melting time is 5 min.

[0059] Example 3: Unlike Example 1, in step S1, the vacuum degree in the vacuum melting furnace is 4.5 Pa, the arc stabilizing current is 3 A, the melting voltage is 35 V, the melting current is 5 kA, and the melting time is 15 min.

[0060] Example 4: Unlike Example 1, in step S2, the ingot is heated to 480°C, held for 30 minutes, and then subjected to multiple heat-pressing processes, with a total processing rate of 60%, to obtain a heat-pressed billet.

[0061] Example 5: Unlike Example 1, in step S2, the ingot is heated to 520°C, held for 60 minutes, and then subjected to multiple hot pressing treatments, with a total processing rate of 80%, to obtain a hot-pressed billet.

[0062] Example 6: Unlike Example 1, in step S2, the multi-stage warm pressing process is as follows: the temperature is continuously increased, and one warm pressing process is performed at each of the following temperatures: 70°C below the β transformation temperature of the ingot, 35°C below the β transformation temperature, 10°C below the β transformation temperature, 25°C above the β transformation temperature, and 50°C above the β transformation temperature, and the temperature is held for 25 minutes. At each corresponding temperature, one multi-directional forging process is performed to obtain the warm-pressed billet. The warm pressing process is as follows: the pressing pressure is 450 MPa, the pressing time is 5 minutes, and the pressing method is bidirectional pressing.

[0063] Example 7: Unlike Example 1, in step S2, the multi-stage warm pressing process is as follows: the temperature is continuously increased, and one warm pressing process is performed at each of the following temperatures: 80°C below the β transformation temperature of the ingot, 45°C below the β transformation temperature, 15°C below the β transformation temperature, 40°C above the β transformation temperature, and 60°C above the β transformation temperature, and the temperature is held for 30 minutes. At each corresponding temperature, one multi-directional forging process is performed to obtain the warm-pressed billet. The warm pressing process is as follows: the pressing pressure is 550 MPa, the pressing time is 3 minutes, and the pressing method is floating pressing.

[0064] Example 8: Unlike Example 1, in step S2, the laser energy is 1000mJ, the laser wavelength is 1050nm, and the pulse time is 12ns.

[0065] Example 9: Unlike Example 1, in step S2, the laser energy is 1200mJ, the laser wavelength is 1100nm, and the pulse time is 16ns.

[0066] Example 10: Unlike Example 1, in step S2, the preparation method of the mesoporous ceramic powder composite liquid loaded with ostinidine is as follows: ostinidine is dissolved in acetone at a ratio of 25g:400mL to obtain an ostinidine solution; then, the mesoporous ceramic powder and the ostinidine solution are mixed at a mass ratio of 1:0.5, and then electromagnetically stirred at 30℃ for 23min; the electromagnetic power is 25W, the magnetic strength is 100T, and the rotation speed is 200r / min to obtain the mesoporous ceramic powder composite liquid loaded with ostinidine; in this example, the mesoporous ceramic powder is commercially available mesoporous yttrium oxide (Y2O3) powder with a particle size of 2-50nm.

[0067] Example 11: Unlike Example 1, in step S2, the preparation method of the mesoporous ceramic powder composite liquid loaded with ostinidine is as follows: ostinidine is dissolved in acetone at a ratio of 40g:600mL to obtain an ostinidine solution; then, the mesoporous ceramic powder and the ostinidine solution are mixed at a mass ratio of 5:0.7, and then electromagnetically stirred at 35℃ for 25min; the electromagnetic power is 40W, the magnetic strength is 200T, and the rotation speed is 500r / min to obtain the mesoporous ceramic powder composite liquid loaded with ostinidine; in this example, the mesoporous ceramic powder used is mesoporous ZrO2-SiO2 powder with a particle size of 2-50nm.

[0068] Example 12: Unlike Example 1, in step S2, the co-processing method is as follows: During the first quarter of the coating thickness, the micro-etched warm-pressed blank is fixed on the tray of a spin coater. The spin coater is started and rotated at the first speed for 1 minute. At the same time, 1 / 3 of the mesoporous ceramic powder composite liquid loaded with oxytinidine is taken and dripped onto the top of the spin coater at a flow rate of 3 mL / s. After dripping, the spin coater is adjusted to rotate at the second speed for 2-5 minutes, and heated to obtain the first oxide layer. The first speed is 30 r / min, the second speed is 1500 r / min, the heating temperature is 85℃, and the heating time is 5 minutes.

[0069] Then, the blank loaded with the first oxide layer is vertically immersed in the remaining mesoporous ceramic powder composite liquid loaded with oxytetracycline. After standing for 20-25 seconds, it is vertically lifted up. The dipping and coating is repeated 3-5 times to obtain the pre-formed oxide layer. After each dipping and coating, a smoothing treatment is performed. The smoothing treatment method is to use high-pressure nitrogen to rinse the surface of the blank for 5-8 minutes, and then rinse it with deionized water 2-4 times.

[0070] Example 13: Unlike Example 1, in step S2, the co-processing method is as follows: During the first 1 / 3 of the coating thickness, the micro-etched warm-pressed blank is fixed on the tray of a spin coater. The spin coater is started and rotated at the first speed for 3 minutes. At the same time, 1 / 2 of the mesoporous ceramic powder composite liquid loaded with oxytinidine is taken and dripped onto the top of the spin coater at a flow rate of 5 mL / s. After dripping, the spin coater is adjusted to rotate at the second speed for 5 minutes and heated to obtain the first oxide layer. The first speed is 50 r / min, the second speed is 2000 r / min, the heating temperature is 90℃, and the heating time is 10 minutes.

[0071] Then, the blank loaded with the first oxide layer is vertically immersed in the remaining mesoporous ceramic powder composite liquid loaded with oxytetracycline. After standing for 25 seconds, it is vertically lifted up. The dip coating is repeated 5 times to obtain the pre-formed oxide layer. After each dip coating, a smoothing treatment is performed. The smoothing treatment method is to use high-pressure nitrogen to rinse the surface of the blank for 8 minutes, and then rinse it with deionized water 4 times.

[0072] Example 14: Unlike Example 1, in the laser cladding process of step S2: the processing power is 18W, the scanning speed is 500mm / s, the time is 15ns, and the loading of otinididine is 58%.

[0073] Example 15: Unlike Example 1, in the laser cladding process of step S2: the processing power is 22W, the scanning speed is 700mm / s, the time is 18ns, and the loading of otinididine is 62%.

[0074] Example 16: Unlike Example 1, in step S3, the billet to be rolled is subjected to three passes of cooling cold rolling, with a temperature drop of 30°C per pass and a deformation of 15% per pass. Vacuum annealing is performed between each pass to obtain the rolled billet.

[0075] Example 17: Unlike Example 1, in step S3, the billet to be rolled is subjected to 8 passes of cooling cold rolling, with a temperature drop of 50°C per pass and a deformation of 40% per pass. Vacuum annealing is performed between each pass to obtain the rolled billet.

[0076] Example 18: Unlike Example 1, in step S3, the vacuum annealing temperature is 650°C, the time is 20 min, and the vacuum degree is 10. -2 Pa.

[0077] Example 19: Unlike Example 1, in step S3, the vacuum annealing temperature is 700°C, the time is 30 min, and the vacuum degree is 10. -1 Pa.

[0078] Experimental Example: The description of this experimental example is based on the scheme described in Example 1, and aims to illustrate the practical application effect of the present invention;

[0079] Corrosion resistance test: According to the national standard GB6458-86 for salt spray corrosion, this test uses 5wt% neutral NaCl corrosion solution. The pH value of the corrosion solution in the salt spray chamber is measured to be 6.9. The test temperature is set at about 35℃ and the test adopts continuous spray mode.

[0080] Salt spray corrosion test parameters: test cycle is 15 days, spray rate is 0.025 mL·cm. -2 ·h -1 The pressure is 0.08–0.15 MPa, and the relative humidity is 90–98%. The test specimens should be placed at a distance that allows the salt spray to freely settle onto all specimen surfaces. It is specified that after every 24 hours of salt spraying, the specimens should be placed at a distance of 80 cm. 2 The surface area should be able to collect 1-2 mL of salt solution every 1 hour, with the NaCl mass fraction within 4-6 wt%.

[0081] After 15 days of salt spray corrosion, the titanium alloy samples were cleaned with deionized water and weighed using an analytical balance with an accuracy of 0.1 mg. The results are as follows:

[0082] 1. Investigate the effects of process parameters for titanium alloy ingot preparation and warm pressing process parameters on the corrosion resistance of titanium alloy foil.

[0083] Control Group 1: Unlike Example 1, temperature and pressure treatment was not performed below the β transition temperature.

[0084] Control group 2: Unlike Example 1, no heat preservation was performed after each temperature and pressure treatment.

[0085] Conclusion: From Figure 1 A comparison of Examples 1 to 7 shows that excessively large or small process parameters during the preparation of titanium alloy ingots can affect the corrosion resistance of titanium alloy foil. Considering the overall corrosion resistance, the scheme in Example 1 is superior. However, a comparison of Examples 1 to 5 and Control Group 1 shows that the absence of warm pressing treatment below the β transformation temperature in Control Group 1 is not effective in maintaining the good plasticity and deformation capacity of the titanium alloy. This makes the titanium alloy more prone to deformation during subsequent rolling, thereby reducing its corrosion resistance. A comparison of Examples 1, Examples 6 to 7, and Control Group 2 shows that the corrosion resistance of the titanium alloy foil in Control Group 2 has significantly decreased. The main reason may be that the heat preservation and aging treatment can refine and disperse the precipitates in the titanium alloy, further improving the heat resistance and oxidation resistance of the titanium alloy and forming a more stable intergranular phase, thereby improving the oxidation resistance and heat resistance of the material.

[0086] 2. Investigate the effect of composite coating preparation methods on the corrosion resistance of titanium alloy foil.

[0087] Control group 3: Unlike Example 1, the mesoporous ceramic powder solution loaded with oxytocin was replaced with a commercially available ceramic dispersion.

[0088] Control group 4: Unlike Example 1, the surface of the blank after micro-etching was directly coated by dip coating.

[0089] Control group 5: Unlike Example 1, no smoothing treatment was performed after dip coating.

[0090] Conclusion: From Figure 2 A comparison of Examples 1 and 8-15 shows that excessively large or small process parameters for laser micro-etching, excessively large or small parameters for preparing the composite liquid of mesoporous ceramic powder loaded with oxytetracycline, excessively large or small parameters in the spin coating and dip coating processes, and excessively large or small laser cladding parameters all have a slight impact on the performance of titanium alloy foil. The titanium alloy foil prepared under the parameters of Example 1 has better corrosion resistance. However, a comparison of Examples 1, 10-11, and Control Group 3 shows that the corrosion resistance of the ceramic dispersion is significantly weakened. This indicates that oxytetracycline loaded in mesoporous ceramic powder can be more effectively released and adhered to the surface of titanium alloy foil, forming an antibacterial barrier, further preventing the growth and reproduction of corrosive bacteria, thereby enhancing the performance of titanium alloy foil. The corrosion resistance of titanium alloy foil was assessed through comparisons of Examples 1, 12-13, and Control Groups 4 and 5. Direct dipping coating of the micro-etched substrate and the absence of smoothing treatment after dipping both affected the corrosion resistance of the titanium alloy foil. This is primarily because spin coating in the early stages fills and partially seals micropores, reducing the direct contact of corrosive media such as water and oxygen with the titanium alloy substrate, thus improving its corrosion resistance. Smoothing treatment, using high-pressure nitrogen, removes loose particles and minor defects from the coating surface, resulting in a smoother and denser coating. The combined effect of spin coating, dipping coating, and subsequent smoothing treatment enhances the adhesion between the coating and the titanium alloy foil substrate. This dense coating further improves the overall density and stability of the titanium alloy foil, reduces the possibility of corrosive media penetration, and further improves corrosion resistance.

[0091] 3. Investigate the influence of cooling cold rolling process parameters on the corrosion resistance of titanium alloy foil.

[0092] Control group 6: Unlike Example 1, a vacuum annealing was performed after the complete cooling and cold rolling was completed.

[0093] Conclusion: From Figure 3A comparison of Examples 1, 16-19, and Control Group 6 shows that a single vacuum annealing process may not completely remove all surface defects and contaminants generated during cold rolling. This results in a weakened corrosion resistance of the titanium alloy foil obtained in Control Group 6. The combination of cooling cold rolling and vacuum annealing in this application helps to refine the grain structure of the titanium alloy foil and reduce cracks and pores. The finer the grains, the more grain boundaries formed by cracks and pores, and the more tortuous the path of corrosion medium diffusion, thereby improving the corrosion resistance of the material. Therefore, considering all factors, Example 1 is the optimal solution.

Claims

1. A method for preparing corrosion-resistant titanium alloy foil for plate heat exchangers, characterized in that, Includes the following steps: S1. Preparation of titanium alloy ingots Weigh the raw materials and perform vacuum induction melting to obtain titanium alloy ingots; S2. Preparation of the billet to be rolled The ingot is heated to 480–520°C and held for 30–60 minutes before undergoing multiple hot pressing processes with a total processing rate of 60–80%, resulting in a hot-pressed billet. The surface of the hot-pressed billet is then micro-etched to create several micropores with a diameter of 0.01–0.03 mm. Boron oxide particles are then vapor-deposited inside the micropores, and a composite liquid of mesoporous ceramic powder loaded with oxytinidine is coated onto the surface of the hot-pressed billet to obtain a pre-formed oxide layer with a thickness of 0.03–0.05 mm. A protective atmosphere is then introduced, and laser cladding nickel plating is performed. After completion, a billet with a composite film layer on the surface is obtained for rolling. During laser cladding: the processing power is 18-22W, the scanning speed is 500-700mm / s, the time is 15-18ns, and the loading of otinididine is 58-62%; S3, Cooling Cold Rolling The billet to be rolled is subjected to 3 to 8 passes of cooling cold rolling, with a temperature reduction of 30 to 50°C per pass and a deformation of 15 to 40% per pass. Vacuum annealing is performed between each pass to obtain the rolled billet. The vacuum annealing temperature is 650 to 700°C, the time is 20 to 30 minutes, and the vacuum degree is 10. -2 ~10 -1 Pa; S4, Post-processing After rolling, the material is straightened and then cleaned to obtain titanium alloy foil.

2. The method for preparing corrosion-resistant titanium alloy foil for plate heat exchangers as described in claim 1, characterized in that, The preparation method of the mesoporous ceramic powder composite liquid loaded with ostinidine is as follows: ostinidine is dissolved in acetone at a ratio of 25-40 g: 400-600 mL to obtain an ostinidine solution; then, the mesoporous ceramic powder and the ostinidine solution are mixed at a mass ratio of 1-5: 0.5-0.7, and then electromagnetically stirred at a temperature of 30-35℃ for 23-25 ​​min; the electromagnetic power is 25-40 W, the magnetic strength is 100-200 T, and the rotation speed is 200-500 r / min, to obtain the mesoporous ceramic powder composite liquid loaded with ostinidine.

3. The method for preparing corrosion-resistant titanium alloy foil for plate heat exchangers as described in claim 2, characterized in that, The coating method is a combined spin coating and dip coating process. The method of combined spin coating and dip coating is as follows: During the first 1 / 4 to 1 / 3 of the coating thickness, the micro-etched warm-pressed blank is fixed on the tray of the spin coater. The spin coater is started and rotated at the first speed for 1 to 3 minutes. At the same time, 1 / 3 to 1 / 2 of the mesoporous ceramic powder composite liquid loaded with ostinidine is taken and dripped onto the top of the blank at a flow rate of 3 to 5 mL / s. After dripping, the spin coater is adjusted to rotate at the second speed for 2 to 5 minutes, and the first oxide layer is obtained by heating. The first speed is 30 to 50 r / min, the second speed is 1500 to 2000 r / min, the heating temperature is 85 to 90℃, and the heating time is 5 to 10 minutes. Then, the blank loaded with the first oxide layer is vertically immersed in the remaining mesoporous ceramic powder composite liquid loaded with oxytetracycline, left to stand for 20-25 seconds, and then vertically lifted up. The dipping and coating process is repeated 3-5 times to obtain the pre-coated oxide layer.

4. The method for preparing corrosion-resistant titanium alloy foil for plate heat exchangers as described in claim 3, characterized in that, After each dip coating, a smoothing treatment is performed. The smoothing treatment method is as follows: use high-pressure nitrogen to rinse the surface of the blank for 5 to 8 minutes, and then rinse with deionized water 2 to 4 times.

5. The method for preparing corrosion-resistant titanium alloy foil for plate heat exchangers as described in claim 1, characterized in that, In step S2, the method of multi-stage hot pressing is as follows: the temperature is continuously increased, and one hot pressing treatment is performed at each of the following temperatures: 70-80°C below the β transformation temperature of the ingot, 35-45°C below the β transformation temperature, 10-15°C below the β transformation temperature, 25-40°C above the β transformation temperature, and 50-60°C above the β transformation temperature, and the temperature is held for 25-30 minutes. At each corresponding temperature, one multi-directional forging is performed to obtain the hot-pressed billet. The temperature and pressure treatment method is as follows: the pressing pressure is 450-550 MPa, the pressing time is 3-5 min, and the pressing method is bidirectional pressing or floating pressing.

6. The method for preparing corrosion-resistant titanium alloy foil for plate heat exchangers as described in claim 1, characterized in that, In step S1, during the vacuum induction melting process, the vacuum degree in the vacuum melting furnace is ≤4.5Pa, the arc stabilizing current is 1~3A, the melting voltage is 25~35V, the melting current is 3~5kA, and the melting time is 5~35min.

7. The method for preparing corrosion-resistant titanium alloy foil for plate heat exchangers as described in claim 1, characterized in that, In step S2, the micro-etching process is a laser micro-etching process with a laser energy of 1000-1200mJ, a laser wavelength of 1050-1100nm, and a pulse duration of 12-16ns.

8. The method for preparing corrosion-resistant titanium alloy foil for plate heat exchangers as described in claim 1, characterized in that, In step S2, the vapor deposition parameters are: power of 5000-7000W, pressure of 180-200Pa, and electrode spacing of 400-550 mils.

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