Black titanium coloring long-acting stability process based on flow and temperature control

Abstract

The invention discloses a black titanium system coloring long-acting stability process based on flow and temperature control. The black titanium system coloring long-acting stability process comprises the steps that 1, the surface of a titanium alloy is pretreated; step 2, preparing a black anodic oxide film; step 3, carrying out post-treatment; and 4, detecting the performance of the film layer, returning to the step 1 if the requirements are not met, and finishing production if the requirements are met. The flow of the electrolyte is controlled through the porous titanium basket, the temperature of the bath solution is stabilized through the staged temperature control strategy and the PID algorithm, the porosity and internal stress of the oxidation film are effectively reduced by combining the stepped boosting and pulse current technology, and the performance of the film layer is ensured through a real-time monitoring and self-adaptive adjusting system; the method has the advantages that the film uniformity, the process stability and the long-acting corrosion resistance are remarkably improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of titanium alloy surface treatment, in particular to a black titanium-based coloring long-term stability process based on flow and temperature control. BACKGROUND

[0002] Titanium alloy is widely used in aerospace, automobile, weapon and other fields due to its excellent mechanical properties, heat resistance and corrosion resistance. However, there are still some problems to be solved in the practical application of titanium alloy, such as poor wear resistance and low surface hardness, which limit its application in complex environments. In order to improve the comprehensive performance of titanium alloy, surface treatment technology has become an important research direction, among which anodic oxidation technology is widely used due to its low cost and simple process.

[0003] The traditional titanium alloy anodic oxidation process mainly adopts a direct current voltage loading mode, which has some inherent defects, such as poor film uniformity, insufficient long-term corrosion resistance, etc. Especially in the chromium-containing electrolyte, hexavalent chromium is easily dissolved out, which has a risk of carcinogenesis, and pitting corrosion easily occurs in a humid and hot environment. In addition, factors such as temperature fluctuation and uneven flow will cause large thickness deviation of the oxidation film, affecting the overall performance of the film. These problems seriously restrict the development and application of titanium alloy surface treatment technology.

[0004] In order to solve these problems, researchers have been exploring new surface treatment technologies. Micro-arc oxidation technology as a new type of surface treatment method has the advantages of high film hardness and good wear resistance, but still has some problems. In the existing titanium alloy anodic oxidation process, temperature fluctuation will cause large thickness deviation of the oxidation film, and uneven flow will easily cause local over-corrosion, which is difficult to ensure the uniformity and consistency of the film. These problems seriously affect the stability and reliability of the titanium alloy surface treatment process.

[0005] In view of the above problems, the existing technology needs to be improved. SUMMARY

[0006] The purpose of the present application is to provide a black titanium-based coloring long-term stability process based on flow and temperature control, which has the advantages of improving film uniformity, enhancing process stability and long-term corrosion resistance.

[0007] The application provides a black titanium-based coloring long-term stability process based on flow and temperature control, and the technical scheme is as follows:

[0008] Comprising:

[0009] Step 1, pretreating the surface of the titanium alloy;

[0010] Step 2, preparing a black anodic oxidation film;

[0011] Step 3, post-treatment is carried out;

[0012] Step 4, the performance of the film layer is detected, if it does not meet the requirements, it returns to Step 1, if it meets the requirements, the production is completed.

[0013] Further, the present application further proposes that Step 1 comprises:

[0014] Step 101, the titanium alloy plate is sequentially subjected to alkali washing, water washing, acid washing and water washing, to obtain a pretreated titanium alloy plate;

[0015] Step 102, the pretreated titanium alloy plate is placed in deionized water for water sealing treatment;

[0016] Step 103, the titanium alloy plate after water sealing treatment is placed in an anodic oxidation alkaline electrolyte for oxidation treatment.

[0017] Further, the present application further proposes that Step 2 comprises:

[0018] Step 201, a porous titanium basket is used to disperse electrolyte flow, so that the Reynolds number is controlled in the range of 2000-4000;

[0019] Step 202, a staged temperature control strategy is used, the initial control temperature is 5-10℃, and the later control temperature is 20-30℃;

[0020] Step 203, the tank liquid temperature fluctuation is controlled by a PID algorithm, within ±1℃;

[0021] Step 204, 0.02-0.2mol / L manganese sulfate is added, and the complexation of manganese ions and titanium ions is used to reduce the porosity of the oxidation film;

[0022] Step 205, a stepwise voltage boosting method is used, and the voltage is sequentially boosted to 30V and 60V, to reduce the stress in the film layer;

[0023] Step 206, a pulse current technology with a duty cycle of 30% and a frequency of 100Hz is used to improve the conductive performance of the film layer.

[0024] Further, the present application further proposes that Step 3 comprises:

[0025] Step 301, the titanium alloy plate after oxidation treatment is rinsed with deionized water and dried;

[0026] Step 302, the rinsed titanium alloy plate is placed in deionized water for water sealing treatment;

[0027] Step 303, the tank liquid temperature is adjusted by a plate heat exchanger, and is controlled below 35℃.

[0028] Further, the present application further proposes that Step 4 comprises:

[0029] Step 401, a high-resolution imaging system is built with a 5 million pixel CMOS camera and a 450 nm blue LED array;

[0030] Step 402, the thickness of the oxide film is detected by UV-VIS-NIR spectral reflectance;

[0031] Step 403, the surface roughness is measured based on the phase shift method;

[0032] Step 404, real-time monitoring of process parameters is realized by using infrared temperature measurement, laser displacement and gas flow sensors;

[0033] Step 405, the process parameters are adjusted by an adaptive PID algorithm;

[0034] Step 406, the process window is predicted based on a FEM simulation model;

[0035] Step 407, the film layer defects are identified by a deep learning classification system;

[0036] Step 408, the spraying angle and atomization pressure are automatically adjusted according to the identification results;

[0037] Step 409, control limits are established based on the six sigma principle.

[0038] Further, the present application also proposes that step 101 is specifically:

[0039] The titanium alloy plate is sequentially placed in a sodium bicarbonate solution with a mass concentration of 5% and ultrasonically cleaned at 65 ℃ for 2 min, then washed with deionized water for 3 times, and finally ultrasonically cleaned with a hydrochloric acid solution with a mass concentration of 5% at room temperature for 30 s, to obtain a pretreated titanium alloy plate;

[0040] Or, the titanium alloy plate is sequentially placed in a sodium bicarbonate solution with a mass concentration of 6% and ultrasonically cleaned at 68 ℃ for 1.5 min, then washed with deionized water for 2 times, and finally ultrasonically cleaned with a hydrochloric acid solution with a mass concentration of 6% at 40 ℃ for 45 s, to obtain a pretreated titanium alloy plate.

[0041] Further, the present application also proposes that in step 102, the water sealing treatment is set to be carried out at room temperature for 30 min, or at 50 ℃ for 45 min.

[0042] Further, the present application also proposes that step 103 is specifically:

[0043] The titanium alloy plate after water sealing treatment is placed into an anodic oxidation electrolyte with a mass concentration of 8 g / L sodium hydroxide, 12 g / L sodium nitrite, 24 g / L sodium bicarbonate, 64 g / L sodium borate, 32 g / L sodium silicate and 0.4 g / L sodium potassium tartrate, and oxidation treatment is carried out at room temperature;

[0044] Alternatively, the titanium alloy plate after water sealing treatment is placed into an anodic oxidation electrolyte with a mass concentration of 10 g / L sodium hydroxide, 15 g / L sodium nitrite, 30 g / L sodium bicarbonate, 80 g / L sodium borate, 40 g / L sodium silicate and 0.5 g / L sodium potassium tartrate, and oxidation treatment is carried out at 45 DEG C.

[0045] Further, the application further proposes that in step 204, the porosity of the oxidation film is 3% to 5%.

[0046] Further, the application further proposes that in step 205, each stage in the step-by-step boosting mode is maintained for 5 min.

[0047] Compared with the prior art, the application provides a black titanium-based coloring long-term stability process based on flow and temperature control, which has the following beneficial effects:

[0048] 1. By using an electrolyte containing manganese and adding manganese sulfate, the porosity of the oxidation film is effectively reduced from 8% to 3%, significantly improving the density and corrosion resistance of the film layer. 3 + / Mn 2 + oxidation-reduction buffer pH fluctuation, effectively solving the carcinogenic risk and hexavalent chromium dissolution problems existing in the traditional chromium-containing electrolyte, and greatly prolonging the service life of the film layer.

[0049] 2. The porous titanium basket is used to disperse the electrolyte flow, and the Reynolds number (Re) is accurately controlled in the range of 2000-4000, which realizes uniform film formation of the oxidation film, effectively solves the film thickness deviation problem caused by temperature fluctuation in the traditional process, and improves the consistency and stability of the film layer.

[0050] 3. The step-by-step boosting (0→30V→60V) and pulse current technology with a duty cycle of 30% and a frequency of 100 Hz are adopted, which effectively reduces the internal stress of the film layer, improves the hardness of the film layer to 800HV (conventional process only 500HV), significantly improves the wear resistance of the film layer, and prolongs the service life.

[0051] 4. By establishing a process parameter closed-loop control model, combining PID algorithm and FEM simulation model, accurate control and real-time monitoring of the oxidation process are realized, effectively solving the problem of inaccurate process parameter control in the traditional process, improving the production efficiency and stability of product quality.

[0052] 5.Using high-resolution imaging system and multi-spectral analysis technology, micron-level defect recognition and accurate measurement of oxide film thickness are realized, reliable data support for process parameter optimization and real-time compensation is provided, and product consistency and stability are effectively improved. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 A step flow chart of a black titanium-based coloring long-term stability process based on flow and temperature control;

[0054] Figure 2 A flow chart of step 1 of a black titanium-based coloring long-term stability process based on flow and temperature control;

[0055] Figure 3 A flow chart of step 2 of a black titanium-based coloring long-term stability process based on flow and temperature control;

[0056] Figure 4 A flow chart of step 3 of a black titanium-based coloring long-term stability process based on flow and temperature control;

[0057] Figure 5 A flow chart of step 4 of a black titanium-based coloring long-term stability process based on flow and temperature control. DETAILED DESCRIPTION

[0058] The technical solutions in the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. The components of the present application described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0059] It should be noted that: similar reference numbers and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. Meanwhile, in the description of the present application, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0060] In the implementation process of traditional titanium alloy anodic oxidation process, the uneven distribution of temperature field and the loss of control of electrolyte flow state lead to the instability of film forming dynamics. The coupling of thermal convection and forced convection in the electrolytic cell causes the local temperature gradient to exceed the critical value, resulting in the difference in the growth rate of the oxidation film, forming a thickness fluctuation zone. At the same time, the alternating appearance of laminar flow and turbulent flow makes the solute transport boundary layer thickness mutate, causing the abnormal polarization of manganese ion concentration, resulting in the formation of dendritic defects in the pore structure of the film layer. The non-steady state migration of hexavalent chromium ions in the chromium-containing electrolyte exacerbates the charge accumulation at the oxidation film / substrate interface, accelerating the breakdown process of the passivation film.

[0061] For example, in the surface treatment scene of the compressor blade of the aero-engine, when there are multiple parallel oxidation stations in the electrolytic cell, the uneven distribution of the circulating pump flow causes the difference in the Reynolds number of the inlet of each station to exceed the allowed range. When the flow rate of a certain station decreases to the laminar flow state, the mass transfer efficiency between the electrolyte and the electrode surface decreases, causing the compactness of the oxidation film in this area to be lower than the critical value. At the same time, the adjacent station produces vortex shedding effect due to the excessively high flow rate, causing micro-cracks in the formed oxidation film. The response lag of the bath temperature control system causes the temperature to rise periodically, causing the interface reaction activation energy to mutate, causing the abnormal transition of the crystal structure of the film layer from anatase to rutile.

[0062] If the above problems are not solved, the thickness deviation of the film layer will cause the assembly gap of the component to exceed the standard, directly affecting the aerodynamic performance. The area with excessive porosity will become the preferential site for stress corrosion cracking in a high temperature and high pressure environment, greatly shortening the service life of the key components. The continuous use of chromium-containing electrolyte will face increasingly strict environmental regulations, increasing the cost and compliance risk of waste liquid treatment. The out-of-control of process parameters will also cause performance fluctuations between batches, forcing the downstream application link to improve the detection level, significantly reducing the overall efficiency of the industry chain.

[0063] In the face of the above problems, the present application first considers how to eliminate the mass transfer unevenness caused by the loss of control of electrolyte flow state. The mass transfer efficiency is low when the electrolyte is in the laminar flow state in the traditional direct current oxidation process, and forced turbulent flow will cause the film layer to peel off. In this regard, the present application attempts to introduce a porous titanium basket as an electrolyte dispersion device to form a controlled turbulent flow state by adjusting the flow path, so that the Reynolds number is within the transition range, which can both strengthen the mass transfer and not produce destructive vortex. At the same time, for the phase transition anomaly caused by temperature gradient, the present application finds that the staged temperature control strategy can match the kinetic requirements of different growth stages of the oxidation film. The initial low temperature stage inhibits side reactions, and the appropriate temperature rise in the later stage promotes densification.

[0064] For the environmental hazards of chromium-containing electrolyte, the application explores a transition metal ion replacement scheme. Through experiments, it is found that manganese ions not only form stable complexes to reduce porosity, but also have redox characteristics to buffer pH fluctuations. To avoid the internal stress concentration caused by the traditional voltage boosting method, the application combines the stress-strain curve characteristics of the material to design a stepped voltage boosting mode, which improves the film layer bonding strength through staged stress release. In terms of process control, the application realizes that simple parameter setting cannot cope with dynamic changes, so a closed-loop system including real-time detection and parameter adjustment is constructed, and process optimization is achieved through multi-sensor data fusion.

[0065] For this, as Figures 1-5 shown, the application proposes a black titanium-based coloring long-term stability process based on flow and temperature control, including: step 1, pretreatment of titanium alloy surface; step 2, preparation of black anodic oxide film; step 3, post-treatment; step 4, detection of film layer performance, if not meet the requirements, return to step 1, if meet the requirements, complete production.

[0066] Among them, pretreatment refers to removing contaminants on the surface of titanium alloy and forming an active surface through chemical cleaning, which can be achieved by alternating alkali washing and acid washing, the alkali washing solution can be 5% sodium bicarbonate solution at 65℃ ultrasonic cleaning, the acid washing solution can be 5% hydrochloric acid solution at room temperature ultrasonic treatment, this process can remove oxide layer and oil stains and provide clean substrate for subsequent film formation.

[0067] Among them, black anodic oxide film preparation refers to generating a dense oxide film layer on the surface of titanium alloy through electrochemical reaction, which can be achieved by dispersing electrolyte flow with a porous titanium basket to make the Reynolds number in the interval of 2000-4000, combined with the staged temperature control strategy from 5℃ to 30℃ gradient heating, combined with the addition of 0.02-0.2mol / L manganese sulfate solution to reduce porosity, this process improves the uniformity of the film layer through fluid mechanics control and ion complexation.

[0068] Among them, post-treatment refers to stabilizing the microstructure of the oxide film by water sealing and temperature control, which can be achieved by deionized water flushing followed by water sealing treatment below 35℃, adjusting the tank liquid temperature through plate heat exchanger, this process can close the film layer pores and prevent structural distortion.

[0069] Among them, film layer performance detection refers to building a process parameter closed-loop control system, which can be achieved by using CMOS camera and 450nm blue LED array to build an imaging system to detect defects, combining UV-VIS-NIR spectral reflectance to measure film thickness, and adjusting process parameters in real time through adaptive PID algorithm, this mechanism forms a dynamic feedback to maintain process stability.

[0070] The core innovation of the present application is to realize process parameter closed-loop optimization through multi-stage collaborative control. A clean surface active layer is established in the pretreatment stage, fluid mechanics control and temperature gradient regulation are used to optimize film formation kinetics in the anodic oxidation stage, and a dynamic compensation mechanism is constructed by combining online detection and adaptive algorithm in the post-treatment stage, forming a complete technology chain from substrate treatment to process control to quality verification, solving the problems of high temperature sensitivity, poor film uniformity and chromium-containing electrolyte pollution in traditional processes.

[0071] The working process and principle of the present application are as follows: the process realizes film performance optimization through multi-stage collaborative control. First, the titanium alloy surface is pretreated to remove surface contaminants through alkaline washing and acid washing, creating a clean substrate for subsequent film formation. Then, black anodic oxide film is prepared by combining electrolyte flow control with temperature gradient regulation. Specifically, the Reynolds number is in the transition zone of turbulent flow by dispersing electrolyte flow through a porous titanium basket, promoting mass transfer uniformity. The temperature control strategy matches the kinetic requirements of different growth stages of the oxide film, and the PID algorithm is used to suppress temperature fluctuations. Adding manganese sulfate reduces the porosity of the film layer by complexing manganese and titanium ions. Step-up and pulse current are used to reduce internal stress and improve conductivity. Then, the film layer microstructure is stabilized by water sealing and temperature control. Finally, the film layer performance is detected, a detection feedback system is constructed, and multi-sensor fusion and adaptive algorithm are used to realize closed-loop control of process parameters, forming a dynamic optimization mechanism. These steps work together to ultimately achieve stable improvement of film performance.

[0072] As a preferred embodiment, the scheme of the present application is implemented as follows:

[0073] First, the titanium alloy surface is pretreated. The titanium alloy plate is sequentially subjected to alkaline washing, water washing, acid washing and water washing. Alkaline washing uses sodium bicarbonate solution under ultrasonic conditions. Deionized water is used for water washing. Acid washing uses hydrochloric acid solution, also under ultrasonic conditions. The pretreated titanium alloy plate is placed in deionized water for water sealing treatment.

[0074] Secondly, black anodic oxide film is prepared. The pretreated titanium alloy plate is placed in an anodic oxidation electrolyte containing sodium hydroxide, sodium nitrite, sodium bicarbonate, sodium borate, sodium silicate and sodium potassium tartrate. The electrolyte flow is dispersed by a porous titanium basket to control the Reynolds number in the range of 2000-4000. A staged temperature control strategy is used, with an initial control temperature of 5-10°C and a later control temperature of 20-30°C. The PID algorithm is used to control the tank temperature fluctuation within ±1°C. Manganese sulfate is added at a concentration of 0.02-0.2 mol / L. A step-up voltage is used, with the voltage being raised to 30V and 60V in turn. A pulse current technology with a duty cycle of 30% and a frequency of 100Hz is used.

[0075] Then, post-treatment is performed. The titanium alloy plate after oxidation treatment is rinsed with deionized water and dried. The rinsed titanium alloy plate is placed in deionized water for water sealing treatment. The tank liquid temperature is adjusted by a plate heat exchanger to be controlled below 35°C.

[0076] Finally, the film layer performance is detected. High-resolution imaging system and spectral reflectance are used to detect the thickness of the oxide film. Surface roughness is measured based on the phase shift method. Various sensors are used to monitor process parameters in real time. Process parameters are adjusted by adaptive PID algorithm. Process window is predicted based on FEM simulation model. Film layer defects are identified by deep learning classification system. The spraying angle and atomization pressure are automatically adjusted according to the identification results. Control limits are established based on six sigma principle. If the film layer performance does not meet the requirements, return to the pretreatment step, if it meets the requirements, complete the production.

[0077] Through the above scheme, the present application solves the problems of poor film uniformity, insufficient corrosion resistance, and poor long-term stability caused by temperature fluctuations and uneven flow in traditional titanium alloy anodic oxidation process. The uniform film of the oxidation film is realized by dispersing the electrolyte flow through the porous titanium basket, which improves the consistency and stability of the film layer. The use of manganese-containing electrolyte instead of traditional chromium-containing electrolyte reduces environmental risk. The step-up and pulse current technology reduces the internal stress of the film layer and improves the hardness and wear resistance of the film layer. The closed-loop control system realizes accurate control and real-time monitoring of the oxidation process, improves production efficiency and stability of product quality. High-resolution imaging system and multi-spectral analysis technology realize micron-level defect recognition and accurate measurement of the thickness of the oxidation film, providing reliable data support for process parameter optimization.

[0078] In some of the above schemes of the present application, the traditional pretreatment method has the problems of insufficient surface cleanliness and poor adhesion of the oxidation film caused by residual contaminants, which is specifically manifested in that it is difficult to completely remove the oxidation layer and oil stains on the surface of the titanium alloy, and secondary oxidation is easy to occur after water washing, resulting in uneven porosity and adhesion of the subsequent anodic oxidation film layer.

[0079] To this end, the present application further proposes a pretreatment step including alkali washing, water washing, acid washing and water washing, followed by water sealing treatment, and placing the treated plate in a specific component alkaline electrolyte for oxidation.

[0080] The alkali washing step is ultrasonic cleaning for 1.5-2 minutes at 65-68°C by using a sodium bicarbonate solution with a mass concentration of 5-6%, the high-temperature environment accelerates the saponification reaction to decompose the oil, and the ultrasonic cavitation effect assists in stripping the oxide layer. The water washing step is washing for 2-3 times by using deionized water, and the cross contamination of acid and alkali liquid is eliminated by multiple flushing. The acid washing step is ultrasonic treatment for 30-45 seconds at room temperature to 40°C by using a hydrochloric acid solution with a mass concentration of 5-6%, the neutralization reaction occurs between the hydrochloric acid and the residual alkaline substances on the titanium surface, and the passivation layer is dissolved at the same time. The water sealing treatment is soaking for 30-45 minutes in deionized water at room temperature or 50°C, the water molecules form a hydrogen-bonded adsorption layer on the metal surface to inhibit the contact of oxygen with the substrate. The alkaline electrolyte contains 8-10 g / L of sodium hydroxide, 12-15 g / L of sodium nitrite, 24-30 g / L of sodium bicarbonate, 64-80 g / L of sodium borate, 32-40 g / L of sodium silicate, and 0.4-0.5 g / L of sodium potassium tartrate, wherein the sodium borate and the sodium silicate form a buffer system, and the sodium potassium tartrate controls the reaction rate by chelating titanium ions.

[0081] Specifically, the sodium bicarbonate solution decomposes the oil and organic pollutants under the assistance of ultrasonic in the pretreatment process, the residual alkaline substances are neutralized and removed by hydrochloric acid, and the surface passivation layer is removed. The double water washing avoids the film layer defects caused by the residual acid and alkali liquid by controlling the flushing times and temperature. The water sealing treatment forms a hydration layer on the substrate surface by controlling the soaking time and temperature, and blocks the contact of oxygen to prevent secondary oxidation in the transfer process. When the treated plate enters the alkaline electrolyte, the sodium salt system forms an alkaline environment with a pH value of 10-12, which promotes the oxidation reaction of titanium to generate a TiO film layer. The sodium potassium tartrate forms a complex with titanium ions, reduces the concentration of free titanium ions in the reaction system, and inhibits the local overcorrosion phenomenon. By controlling the concentration ratio of electrolyte components, the growth rate and dissolution rate of the oxidation film reach a dynamic balance, and finally the oxidation film layer with uniform porosity and a bonding force of more than 20 MPa is formed.

[0082] As a preferred embodiment, the scheme of the present application is implemented as follows:

[0083] Firstly, the titanium alloy plate is placed in a sodium bicarbonate solution with a mass concentration of 5% and ultrasonic cleaning is performed for 2 minutes at 65°C. Then the plate is washed with deionized water for 3 times, each time for 30 seconds. Subsequently, the cleaned plate is placed in a hydrochloric acid solution with a mass concentration of 5% and ultrasonic cleaning is performed for 30 seconds at room temperature to obtain a pretreated titanium alloy plate.

[0084] Further, the pretreated titanium alloy plate is subjected to water sealing treatment in deionized water. The water sealing treatment is performed at room temperature for 30 minutes. After the water sealing treatment is completed, the titanium alloy plate is immediately transferred to the anodic oxidation alkaline electrolyte.

[0085] Specifically, the composition of the anodic oxidation alkaline electrolyte is: 8 g / L sodium hydroxide, 12 g / L sodium nitrite, 24 g / L sodium bicarbonate, 64 g / L sodium borate, 32 g / L sodium silicate and 0.4 g / L sodium potassium tartrate. The titanium alloy plate treated by water sealing is placed in the electrolyte for oxidation treatment at room temperature. The oxidation treatment time is 60 minutes, and the voltage is controlled at 30V.

[0086] Through the above technical solutions, the present application realizes efficient pretreatment of the surface of the titanium alloy. Thus, the oxide layer and oil stains on the surface of the titanium alloy are effectively removed, and the occurrence of secondary oxidation is prevented. Further, through the water sealing treatment, oxygen is isolated, and the surface active state is maintained. Finally, the oxidation treatment is carried out using a specific component alkaline electrolyte, the sodium salt system is used to form an alkaline environment to promote the oxidation reaction of titanium, and the complexation of sodium potassium tartrate can control the reaction rate to avoid local over-corrosion. This series of processing steps ensures that the subsequent formed oxide film has good bonding strength with the substrate, and at the same time ensures the uniformity of the film layer, effectively solving the problems of uneven porosity and adhesion of the oxide film caused by the traditional pretreatment method.

[0087] In some of the above schemes of the present application, in the traditional process, the Reynolds number exceeds the reasonable range due to uneven flow of the electrolyte, the temperature control precision is insufficient to cause high film layer porosity, the single voltage loading mode causes stress accumulation in the film layer, and the fixed current mode affects the conductivity, which together causes poor film layer density, insufficient mechanical properties and low process stability.

[0088] To this end, the present application further proposes a specific method for preparing a black anodic oxide film, which comprises dispersing electrolyte flow through a porous titanium basket, controlling bath temperature in stages, introducing a manganese sulfate additive, and using a stepwise voltage boosting and pulse current technology.

[0089] The inner diameter of the porous titanium basket is set to 0.5-2.0 mm, the hole density is controlled to 50-200 holes / cm2, and the flow rate of the circulating pump is adjusted to maintain the flow rate of the electrolyte at 0.5-1.2 m / s; in the staged temperature control strategy, the initial stage is controlled to 5-15 minutes, and the later stage is extended to 30-60 minutes; the preferred concentration of manganese sulfate is 0.05-0.15 mol / L, which forms a stable complex with titanium ions in the electrolyte; in the stepwise voltage boosting process, the voltage gradient is set to increase by 15-20 volts every 5 minutes; the on-off cycle of the pulse current is configured to alternate between 10 milliseconds on and 7 milliseconds off.

[0090] Specifically, in the electrolyte circulation system, the pore size and distribution density of the porous titanium basket are optimized through fluid mechanics simulation, so that the electrolyte forms a uniform distribution of micro-vortex when flowing through the titanium basket, and the Reynolds number is stabilized in the transition zone between laminar flow and turbulent flow. Temperature control in stages is realized through two independent temperature control circuits, low temperature conditions are used in the initial stage to promote uniform nucleation of the oxide film crystal nucleus, and the temperature is raised in the later stage to accelerate the grain growth rate. The addition of manganese sulfate makes the manganese ions form [Mn(OH)_2·Ti(OH)_4]^2+ complex with titanium hydroxyl ions in the electrolyte, and preferentially deposit to form a dense barrier layer at the pore of the oxide film. In the process of stepped voltage rise, the 30-volt stage forms a base oxide layer, and the 60-volt stage promotes the growth of the dense layer, and the voltage gradient is matched with the improvement of the dielectric strength of the oxide film. The on-off cycle design of the pulse current considers the double-layer charge-discharge time constant, and promotes ion diffusion redistribution during current interruption. The porosity of the oxide film formed is reduced to 3%-5%, the microhardness is increased to 750-850HV, the surface roughness is controlled to Ra 0.2-0.5 microns, and the color difference ΔE between batches is 1.5.

[0091] As a preferred embodiment, the scheme of the present application is implemented as follows:

[0092] In the preparation of black anodic oxide film, first, the electrolyte flow is dispersed by a porous titanium basket. The porous titanium basket is woven from titanium wires with a diameter of 0.5 mm, with a pore size of 2 mm and a surface area of 500 cm 2 . By adjusting the electrolyte flow rate, the Reynolds number is controlled at about 3000.

[0093] Secondly, a staged temperature control strategy is adopted. The temperature is controlled at 8℃ for 30 minutes in the initial stage, and then the temperature is raised to 25℃, and this temperature is maintained until the end of the oxidation process. The heating power is adjusted in real time through the PID algorithm, so that the tank liquid temperature fluctuation is controlled within ±0.5℃.

[0094] Further, 0.1 mol / L manganese sulfate is added to the electrolyte. The manganese sulfate solution is slowly added at a speed of 5 mL / min by a constant flow pump, while stirring to ensure uniform distribution.

[0095] In terms of voltage loading, a stepped voltage rise method is adopted. First, the voltage is raised to 30V and maintained for 15 minutes, and then raised to 60V and maintained until the end of the oxidation process. The voltage rise rate of each voltage rise stage is 1V / s.

[0096] Finally, pulse current technology is adopted. A square wave current with a duty cycle of 30% and a frequency of 100Hz is set, and the peak current density is 50mA / cm 2 . The pulse current is provided by a programmable DC power supply and switched by a MOSFET switch at high speed.

[0097] By the technical scheme, the electrolyte flow is accurately controlled, and local over-corrosion is effectively avoided. The application of the temperature control strategy in stages and the PID algorithm significantly improves the temperature control accuracy and reduces the membrane layer porosity. The addition of manganese sulfate further reduces the porosity of the oxide film and improves the membrane layer density. The step-up mode effectively reduces the stress accumulation in the membrane layer, and the pulse current technology improves the conductivity of the membrane layer. These measures work together to improve the density, mechanical properties and process stability of the black anodic oxide film, solving the problems existing in the traditional process.

[0098] In some of the above schemes of the application, the temperature control in the post-processing stage is not accurate, causing the membrane layer to deform or be insufficiently sealed, and the water sealing treatment effect is unstable, affecting the corrosion resistance of the membrane layer.

[0099] To this end, the application further proposes the following technical scheme: rinsing the titanium alloy plate after oxidation treatment with deionized water and air-drying; placing the rinsed titanium alloy plate in deionized water for water sealing treatment; adjusting the tank liquid temperature through a plate heat exchanger to be below 35°C.

[0100] Among them, the deionized water rinsing can adopt two or three cycles of cleaning, each rinsing time can be 30 seconds to 2 minutes, and the residual electrolyte concentration can be reduced to below 0.01 mol / L. The water sealing treatment can use static immersion or dynamic circulation, the immersion time can be adjusted in the range of 30 minutes to 2 hours, and the micropore filling rate can reach more than 95%. The plate heat exchanger can adopt a counter-flow heat exchange structure, the heat exchange area is set to 0.5-2 m 2 , the cooling medium flow is controlled at 1-3 m 3 / h, and the temperature sensor accuracy reaches ±0.5°C. The drying process can be naturally air-dried in a clean environment or nitrogen purging, and the surface water residue is controlled to be below 0.1 mg / cm 2 .

[0101] Specifically, the titanium alloy plate after oxidation treatment is first placed in flowing deionized water for multi-stage rinsing, and the residual electrolyte components are effectively removed, and the surface conductivity is reduced to below 5 μS / cm. Subsequently, the plate is transferred to the water sealing tank, and the deionized water penetrates into the oxide film pores by osmosis to form a hydration layer with a thickness of 2-5 nm, and the pore diameter is compressed to the range of 10-20 nm. The plate heat exchanger maintains the tank liquid temperature in the range of 28-32°C by adjusting the cooling water flow, and the heat exchange efficiency reaches more than 90%, and the temperature fluctuation is suppressed within ±1°C. In this process, the thermal stress in the membrane layer is controlled to be below 0.5 MPa, and the lattice distortion rate is reduced to below 0.2%. The surface roughness Ra value of the oxide film after this treatment can be stabilized in the range of 0.8-1.2 μm, and the neutral salt spray test corrosion resistance time is extended to more than 500 hours.

[0102] As a preferred embodiment, the scheme of the application is implemented as follows:

[0103] In step 301, the titanium alloy plate after oxidation treatment is first rinsed with deionized water. The rinsing process can use high-pressure spraying, the water pressure can be set to 0.5-1.0 MPa, and the rinsing time is 30-60 seconds. After rinsing, the titanium alloy plate is placed in a clean environment and naturally dried, and the drying time can be 10-15 minutes.

[0104] In step 302, the titanium alloy plate after rinsing and drying is immersed in deionized water for water sealing treatment. The temperature of water sealing treatment can be controlled at 20-25℃, and the treatment time is 30-45 minutes. During the water sealing process, a magnetic stirrer can be used for slow stirring at a speed of 50-100 rpm to promote the penetration of water molecules into the micropores of the oxidation film.

[0105] In step 303, a plate heat exchanger is used to accurately adjust the temperature of the tank liquid. Specifically, a stainless steel plate heat exchanger can be used, and the cooling medium can be an ethylene glycol aqueous solution. The tank liquid temperature is monitored in real time by a PID control system, and the flow of the cooling medium is adjusted according to the temperature change, so that the tank liquid temperature is strictly controlled below 35℃, and the temperature fluctuation range is controlled within ±0.5℃.

[0106] Through the above technical scheme, the application can effectively solve the problem of film deformation caused by inaccurate temperature control in the post-treatment stage, and improve the effect of water sealing treatment, thereby significantly improving the structural integrity and corrosion resistance of the oxidation film. Specifically, by accurately controlling the water sealing treatment temperature and time, the penetration of deionized water can be fully utilized to effectively fill the micropores of the oxidation film and improve the densification degree of the film. The use of a plate heat exchanger to accurately adjust the temperature of the tank liquid can avoid the accumulation of thermal stress and lattice distortion of the film caused by high temperature, and maintain the stability of the film structure. Therefore, the technical scheme of the application can significantly improve the long-term stability of the oxidation film, prolong the service life of the titanium alloy product, and improve its application reliability in complex environments.

[0107] In some of the above schemes of the application, the traditional detection means has the problems of insufficient resolution and single parameter, which cannot realize multi-dimensional quality evaluation, and lacks real-time feedback mechanism, leading to lag in process parameter adjustment, affecting production efficiency and product consistency.

[0108] To this end, the present application further proposes that step 4 includes: using a 5 million pixel CMOS camera and a 450 nm blue LED array to build a high-resolution imaging system; detecting the thickness of the oxide film by UV-VIS-NIR spectral reflectance; measuring the surface roughness based on the phase shift method; using infrared temperature measurement, laser displacement and gas flow sensors to monitor process parameters in real time; adjusting process parameters through adaptive PID algorithm; predicting process window based on FEM simulation model; identifying film layer defects through deep learning classification system; automatically adjusting the spraying angle and atomization pressure according to the identification result; establishing control limits based on the six sigma principle.

[0109] Among them, the high-resolution imaging system can use CMOS or CCD sensors of different pixel levels, such as 6 million pixel devices cooperating with 430 nm violet light sources, by adjusting the incident angle and light intensity distribution of the LED array, to form specific interference fringes. The spectral reflectance detection can select a detection device with a wavelength range of 300-2500 nm, such as establishing a linear regression model of thickness and reflectivity at a characteristic wavelength of 550 nm. The phase shift measurement device can be configured with a beam splitter prism group and a piezoelectric ceramic displacement platform to generate an interference phase difference through nanoscale displacement.

[0110] Specifically, during the film layer performance detection process, the high-resolution imaging system captures the surface topography image, generates interference patterns through the optical interference effect of blue light wavelength and oxide film thickness, such as generating specific ring-shaped fringes when the film thickness is 1.2 μm. The spectral reflectance detection device synchronously scans the sample surface, establishes a thickness distribution curve based on the difference in absorption characteristics of different wavebands, such as detecting nanoscale thickness changes in the ultraviolet waveband (300-400 nm). The phase shift measurement module generates a λ / 4 displacement amount by driving the reference mirror with a piezoelectric ceramic, calculates the phase change amount of scattered light, such as measuring a phase shift angle of 12° when the Ra value is 0.8 μm.

[0111] The multi-sensor system collects temperature, displacement and flow parameters in real time, such as monitoring the bath temperature gradient with an infrared thermal imager at a resolution of 0.1 °C. The collected data is input into the FEM simulation model for thermal-electric coupling analysis to predict the film layer growth rate under different voltage conditions. The deep learning system processes surface defect images through a convolutional neural network, such as a training set containing 2000 pore defect samples, achieving an identification accuracy of 98%. The identification result triggers the actuator to adjust the angle of the spraying robot arm, such as increasing the atomization pressure from 0.8 MPa to 1.2 MPa when edge cracks are detected. The amount of process parameter adjustment is calculated by the adaptive PID algorithm, such as outputting a heating power correction coefficient when the temperature deviation exceeds 0.5 °C. The fluctuation range of all parameters is defined by the six sigma statistical method, such as setting the flow control limit to ±5% of the standard deviation range.

[0112] As a preferred embodiment, the scheme of the present application is implemented as follows:

[0113] A high-resolution imaging system is built with a 5 million pixel CMOS camera and a 450 nm blue LED array. The CMOS camera has 5 million pixels, and the blue LED array has a wavelength of 450 nm. The thickness of the oxide film is detected by UV-VIS-NIR spectral reflectance. The surface roughness is measured based on the phase shift method. Real-time monitoring of process parameters is achieved using infrared temperature measurement, laser displacement, and gas flow sensors. Process parameters are adjusted using an adaptive PID algorithm. The process window is predicted based on a FEM simulation model. Defects in the film layer are identified by a deep learning classification system. The spray angle and atomization pressure are automatically adjusted based on the identification results. Control limits are established based on the six sigma principle.

[0114] Specifically, the high-resolution imaging system consists of a 5 million pixel CMOS camera and a blue LED array with a wavelength of 450 nm. The UV-VIS-NIR spectral reflectance detection system measures the thickness of the oxide film by analyzing the reflection intensity of light at different wavelengths. The phase shift method measures the surface roughness by analyzing the phase change of light waves scattered on the surface. The real-time monitoring system of process parameters includes infrared temperature measurement sensors, laser displacement sensors, and gas flow sensors. The adaptive PID algorithm dynamically adjusts the process parameters based on real-time monitoring data. The FEM simulation model predicts the film layer growth under different process parameters based on finite element analysis. The deep learning classification system identifies the type of film layer defects through a trained neural network model. The automatic adjustment system of spraying parameters adjusts the spray angle and atomization pressure based on the defect identification results. The six sigma control limit determines the reasonable fluctuation range of process parameters through statistical analysis.

[0115] Through the above technical solutions, the present application realizes comprehensive quality control of film layer performance. The high-resolution imaging system improves the detection accuracy of surface topography. The UV-VIS-NIR spectral reflectance detection realizes non-contact thickness measurement. The phase shift method avoids damage to the film layer caused by contact measurement. The multi-sensor fusion monitoring system realizes real-time acquisition of process parameters. The adaptive PID algorithm optimizes the parameter compensation process. The FEM simulation model provides theoretical guidance for process optimization. The deep learning classification system improves the accuracy of defect identification. The automatic adjustment system based on the identification results realizes closed-loop control of process parameters. The establishment of the six sigma control limit ensures the stability and repeatability of the production process. These technical means jointly construct a multi-modal detection system and an intelligent control mechanism, breaking through the limitations of traditional detection methods such as insufficient resolution and single parameter, realizing multi-dimensional quality evaluation and real-time feedback adjustment, and improving production efficiency and product consistency.

[0116] In some of the above schemes of the present application, a pretreatment step of alkaline washing, water washing, acid washing and water washing is proposed to obtain a pretreated titanium alloy plate with a clean surface. However, in actual operation, due to the lack of clear matching relationship between the concentration, temperature and treatment time of the alkaline washing solution, it is easy to cause residual oil stains or over-corrosion of the substrate. At the same time, the selection of acid washing conditions lacks pertinence, which may cause surface passivation or insufficient activity, thereby affecting the bonding strength and uniformity of the subsequent anodic oxidation film.

[0117] To this end, the present application further proposes that the titanium alloy plate is sequentially placed in a sodium bicarbonate solution with a mass concentration of 5 to 6 and ultrasonically cleaned at 65 to 68 degrees Celsius for 1.5 to 2 minutes, then washed with deionized water for 2 to 3 times, and finally ultrasonically cleaned with a hydrochloric acid solution with a mass concentration of 5 to 6 at room temperature to 40 degrees Celsius for 30 to 45 seconds to obtain a pretreated titanium alloy plate.

[0118] The mass concentration of the sodium bicarbonate solution is set to 5 to 6, the temperature is controlled at 65 to 68 degrees Celsius, and the ultrasonic time is adjusted to 1.5 to 2 minutes. The cavitation effect enhances the decontamination ability. This concentration and temperature combination can effectively decompose organic pollutants and avoid grain boundary corrosion. The washing times are dynamically adjusted to 2 to 3 times according to the alkaline washing parameters to ensure that the residual alkaline substances are completely removed. The mass concentration of the hydrochloric acid solution is matched synchronously to 5 to 6, the temperature gradient is set to room temperature to 40 degrees Celsius, and the ultrasonic time is correspondingly adjusted to 30 to 45 seconds to form a balance between activating the surface and inhibiting hydrogen embrittlement. The two parameter combination schemes correspond to titanium alloy plates with different thicknesses or surface states, for example, thin plates below 0.5 mm are suitable for 65 degrees Celsius alkaline washing and room temperature acid washing combination, and thick plates above 1.5 mm are suitable for 68 degrees Celsius alkaline washing and 40 degrees Celsius acid washing combination.

[0119] Specifically, when using a sodium bicarbonate solution with a concentration of 5 at 65 degrees Celsius for 2 minutes, the solution pH value is maintained in the interval of 9.2 to 9.5, the titanium alloy surface oxide layer dissolves at a rate of 0.5 microns per second, and the oil emulsification efficiency reaches 95.3. Three times of deionized water washing can reduce the residual alkali concentration to less than 10 ppm, avoiding neutralization reaction with the subsequent acid solution. A hydrochloric acid solution with a concentration of 5 is treated at room temperature for 30 seconds, the surface activation energy is increased to 0.45 eV, and the roughness Ra is controlled at 0.3 to 0.5 microns. When switching to a sodium bicarbonate solution with a concentration of 6 at 68 degrees Celsius for 1.5 minutes, the solution mass transfer coefficient increases by 12, and two water washes can reduce energy consumption by 20. Acid washing at 40 degrees Celsius reduces the reaction activation energy by 8, and a 45-second treatment time makes the surface hydroxyl density reach 3.5 x 10^15 per square centimeter, while the hydrogen permeation amount is controlled to be less than 510^-6 grams per square centimeter. The two schemes are adjusted by parameter linkage, so that the contact angle of the titanium alloy surface after pretreatment is stable in the interval of 5 to 10 degrees, providing a uniform active surface for subsequent anodic oxidation.

[0120] As a preferred embodiment, the scheme of the present application is implemented as follows:

[0121] The titanium alloy plate is first placed in a sodium bicarbonate solution with a mass concentration of 5% and ultrasonically cleaned at a temperature of 65℃. The duration of ultrasonic cleaning is 2 minutes. After cleaning, the titanium alloy plate is taken out and rinsed with deionized water three times. Subsequently, the rinsed titanium alloy plate is placed in a hydrochloric acid solution with a mass concentration of 5% and ultrasonically cleaned at room temperature. The duration of this step is 30 seconds. Through this series of treatments, the pretreated titanium alloy plate is obtained.

[0122] Another alternative embodiment is to place the titanium alloy plate in a sodium bicarbonate solution with a mass concentration of 6% and ultrasonically clean it at a temperature of 68℃. The duration of this step is 1.5 minutes. After cleaning, the titanium alloy plate is taken out and rinsed with deionized water twice. Subsequently, the rinsed titanium alloy plate is placed in a hydrochloric acid solution with a mass concentration of 6% and ultrasonically cleaned at a temperature of 40℃. The duration of this step is 45 seconds. Through this series of treatments, the pretreated titanium alloy plate is also obtained.

[0123] Through the above technical scheme, the present application realizes accurate pretreatment of the surface of the titanium alloy plate. In the alkali cleaning process, by controlling the concentration, temperature and treatment time of the sodium bicarbonate solution, the surface oil and oxide layer are effectively removed, while excessive corrosion of the substrate is avoided. In the acid cleaning process, by accurately controlling the concentration, temperature and treatment time of the hydrochloric acid solution, the surface of the titanium alloy is moderately activated, avoiding the problems of surface passivation or excessive activation. This accurate pretreatment method significantly improves the cleanliness and activity of the surface of the titanium alloy plate, laying a good foundation for the formation of the subsequent anodic oxidation film, and helps to improve the bonding strength and uniformity of the anodic oxidation film and the substrate. In addition, by providing two different parameter combinations, the present scheme enhances the adaptability to different batches or thicknesses of titanium alloy plates, improving the flexibility and scope of application of the process.

[0124] In some of the above schemes of the present application, the temperature condition and duration of the water sealing treatment of the pretreated titanium alloy plate are not explicitly limited, which may cause the formation of unstable passivation film layer on the surface of the plate, affecting the reaction activity of the subsequent anodic oxidation electrolyte and the substrate, thereby causing fluctuations in the porosity of the oxidation film and a decrease in the bonding force.

[0125] To this end, the present application further provides that the water sealing treatment is carried out at room temperature for 30 minutes, or at 50℃ for 45 minutes.

[0126] When the treatment is performed at room temperature for 30 minutes, the penetration of water molecules is limited within the diffusion rate range under natural temperature environment, ensuring that the growth rate of the passivation layer crystal nucleus matches the adsorption rate of the titanium alloy surface hydroxyl group. When the temperature is raised to 50℃ and the treatment time is extended to 45 minutes, the thermal activation effect increases the kinetic energy of water molecules, resulting in an increase in the nucleation density of passivation film grains to 1.8 times that of normal temperature treatment, while the grain size is controlled within the range of 200-300 nm. The combination of these two parameters forms a process chain with the pickling process in the pretreatment stage, for example, when the residual Cl- concentration after pickling is less than 5 ppm, room temperature treatment can effectively neutralize the surface acid residues; when the pickling temperature reaches 40℃, the 50℃ water sealing treatment can compensate for the loss of surface energy of the substrate, reducing the electrolyte wetting angle in the subsequent oxidation stage to less than 15°. The specific parameter selection needs to be matched with the surface roughness value after pickling, when the Ra value is in the range of 0.2-0.4 μm, the room temperature scheme is adopted, and when the Ra value is in the range of 0.5-0.8 μm, the high temperature scheme is adopted.

[0127] Specifically, during the water sealing treatment, when performing room temperature treatment for 30 minutes, the initial temperature of the deionized water is controlled in the range of 18-25℃, and the passivation film layer is deposited layer by layer through natural convection. Under this condition, the water temperature fluctuation per hour is limited within ±2℃, so that the passivation film thickness is stabilized within the range of 50-80 nm. After the treatment is completed, the surface hydroxyl group density of the plate is increased to 8-10 / nm 2 , providing active sites for the dissolution of titanium ions in the subsequent oxidation stage. When 50℃ treatment is used for 45 minutes, the water bath temperature is precisely controlled through a plate heat exchanger, with a temperature deviation of not more than ±0.5℃, at this time, a gradient structure is formed inside the passivation film, the film layer near the substrate side has a density of more than 95%, and the surface side maintains a porosity of 80%-85%. This structure design allows the electrolyte to quickly penetrate to the bottom of the film layer during anodic oxidation, while inhibiting the excessive accumulation of oxygen bubbles at the interface. Both treatment modes are time-matched with the ultrasonic cleaning process in the pretreatment stage, for example, when 30s ultrasonic is used in the pickling step, the water sealing time needs to be extended to more than 30 minutes to eliminate the surface microcracks caused by the ultrasonic cavitation effect.

[0128] As a preferred embodiment, the scheme of the present application is implemented as follows:

[0129] In the pretreatment process of the titanium alloy plate, the pretreated titanium alloy plate is placed in deionized water for water sealing treatment. The water sealing treatment can be performed at room temperature for 30 minutes. Alternatively, the water sealing treatment can also be performed at a temperature of 50℃ for 45 minutes.

[0130] Specifically, when the water sealing treatment is performed at room temperature, the pretreated titanium alloy plate can be immersed in a container filled with deionized water, and kept at room temperature for 30 minutes. Further, to ensure the uniformity of the water sealing treatment, a magnetic stirrer can be used to stir the deionized water at a low speed during the treatment.

[0131] As another implementation, when the water sealing treatment is performed at 50℃, the deionized water can be heated to 50℃ first, and then the pretreated titanium alloy plate is immersed in the deionized water. A constant temperature water bath device is used to maintain the water temperature at 50℃, and the treatment time is 45 minutes. After the treatment is completed, the titanium alloy plate is slowly taken out and rinsed with room temperature deionized water.

[0132] Through the above technical solutions, the present application can form a stable passivation film layer, effectively control the thickness and uniformity of the passivation film. Thus, the activity of the surface of the titanium alloy plate is enhanced, laying a good foundation for subsequent anodic oxidation treatment. Further, by precisely controlling the temperature and time of the water sealing treatment, the problem of passivation layer cracking or excessive thickness caused by excessive reaction is avoided, and the quality and consistency of the surface treatment of the titanium alloy plate are improved. Specifically, the water sealing treatment scheme at room temperature is suitable for conventional production environment, while the water sealing treatment scheme at 50℃ can be used in scenarios where the treatment efficiency needs to be improved, providing flexible choices for different production needs.

[0133] In some of the above schemes of the present application, when the titanium alloy plate treated by water sealing is placed in an anodic oxidation alkaline electrolyte for oxidation treatment to form an oxide film, since the composition and proportion of the electrolyte are not explicitly limited, problems such as insufficient stability of the electrolyte and inaccurate control of the oxidation reaction rate may occur in the actual process. Specifically, when the concentration of each component in the electrolyte is unbalanced, it is easy to cause lattice defects of the oxide film, and the synergistic effect of the temperature parameter and the electrolyte system is not fully optimized, affecting the compactness and surface uniformity of the film.

[0134] To this end, the present application further proposes that the titanium alloy plate treated by water sealing is placed in an anodic oxidation electrolyte with a mass concentration of 8g / L sodium hydroxide, 12g / L sodium nitrite, 24g / L sodium bicarbonate, 64g / L sodium borate, 32g / L sodium silicate and 0.4g / L potassium sodium tartrate, and is subjected to oxidation treatment at room temperature; or the titanium alloy plate treated by water sealing is placed in an anodic oxidation electrolyte with a mass concentration of 10g / L sodium hydroxide, 15g / L sodium nitrite, 30g / L sodium bicarbonate, 80g / L sodium borate, 40g / L sodium silicate and 0.5g / L potassium sodium tartrate, and is subjected to oxidation treatment at 45℃.

[0135] The sodium hydroxide in the anodic oxidation electrolyte is configured as 8 g / L or 10 g / L, which is used to establish an alkaline environment and adjust the solution conductivity; the sodium nitrite is configured as 12 g / L or 15 g / L, which is used to promote the oxidation release of titanium alloy surface metal ions; the combination of sodium bicarbonate and sodium borate is configured as 24 g / L+64 g / L or 30 g / L+80 g / L, which is used to stabilize the electrolyte pH value through the buffer system; the sodium silicate is configured as 32 g / L or 40 g / L, which is used to fill the oxide film pores by generating silicic acid colloid through hydrolysis; the sodium potassium tartrate is configured as 0.4 g / L or 0.5 g / L, which is used to complex metal ions to inhibit side reactions. The concentration gradient of the two embodiments is matched with the temperature condition of room temperature or 45°C respectively, wherein the lower concentration system under room temperature condition avoids local overheating by reducing the ion migration rate, and the higher concentration system under high temperature condition maintains the oxidation reaction kinetics balance through temperature compensation.

[0136] Specifically, under room temperature conditions, when the concentration of sodium hydroxide in the electrolyte is 8 g / L, the total molar ratio of sodium bicarbonate to sodium borate is controlled to be 1:2.6, at this time the pH buffer interval of the buffer system covers 8.5-9.2, which is matched with the alkaline environment required by the hydrolysis of sodium silicate, so that the particle size of the generated silicic acid colloid is stabilized in the range of 50-80 nm, effectively filling the oxide film micropores. At the same time, the concentration ratio of sodium nitrite to sodium potassium tartrate is 30:1, and the oxidation reaction rate is controlled in the range of 0.12-0.15 μm / min under this ratio, avoiding stress accumulation in the film layer due to too fast reaction. When the temperature is raised to 45°C, the concentration of sodium hydroxide is increased to 10 g / L to compensate for the decrease in solution conductivity caused by temperature, at this time the total molar ratio of sodium bicarbonate to sodium borate is adjusted to 1:2.7, which narrows the pH fluctuation range of the buffer system to ±0.3, and the concentration of sodium silicate is increased to 40 g / L, which increases the colloid filling efficiency to more than 92%. The concentration ratio of sodium nitrite to sodium potassium tartrate is maintained at 30:1, but the absolute concentration is increased to stabilize the oxidation reaction rate at 0.18-0.22 μm / min, which is matched with the increase in activation energy caused by the increase in temperature. By controlling the molar ratio of each component, a stable ion migration channel is formed at a specific temperature, which makes the oxide film crystals preferentially grow along the

[001] crystal direction, and the crystal size deviation is controlled within ±5 nm, finally making the oxide film thickness uniformity reach below ±3%, and the porosity is reduced to 2.8-3.5%.

[0137] As a preferred embodiment, the scheme of the present application is implemented as follows: the titanium alloy plate subjected to water sealing treatment is immersed in an anodic oxidation electrolyte system containing sodium hydroxide 8 g / L, sodium nitrite 12 g / L, sodium bicarbonate 24 g / L, sodium borate 64 g / L, sodium silicate 32 g / L and sodium potassium tartrate 0.4 g / L, and oxidation treatment is carried out at an ambient temperature of 25±2℃; or in another embodiment, the treatment object is placed in an electrolyte system containing sodium hydroxide 10 g / L, sodium nitrite 15 g / L, sodium bicarbonate 30 g / L, sodium borate 80 g / L, sodium silicate 40 g / L and sodium potassium tartrate 0.5 g / L, and anodic oxidation is carried out by maintaining the bath temperature at 45±1℃. The electrolyte composition is continuously circulated by a constant flow pump, and a jacket cooling system is configured for the tank to maintain temperature accuracy.

[0138] Through the above technical scheme, the present application constructs a composite electrolyte system with buffering effect, and by accurately limiting the mass concentration ratio of the six components, the components form a synergistic effect under specific temperature conditions. Among them, the combination of sodium bicarbonate and sodium borate effectively stabilizes the pH value of the electrolyte, the colloidal material produced by the hydrolysis of sodium silicate fills the micropores of the oxidation film, and sodium potassium tartrate inhibits the generation of byproduct. When implemented at room temperature, relatively low concentration components are used to slow down the reaction rate and avoid local overheating; under elevated temperature conditions, a higher concentration electrolyte system is matched to maintain the kinetic balance of the oxidation reaction through a temperature compensation mechanism. This technical scheme solves the problem of insufficient stability of the electrolyte caused by fluctuations in the concentration of components in traditional processes, realizes the directional growth of the crystal structure of the oxidation film, effectively eliminates the lattice defects of the film layer, and significantly improves the compactness and surface uniformity of the oxidation film.

[0139] In some of the above schemes of the present application, a technical means is proposed to reduce the porosity of the oxidation film by adding manganese sulfate to utilize the complexation of manganese ions and titanium ions, however, in the actual process implementation process, if only the concentration of manganese sulfate is added to adjust the porosity without specifying the specific porosity control range, it may lead to insufficient compactness or excessive densification of the film layer, and further cause problems such as increased film layer brittleness or stress concentration.

[0140] In this regard, the present application further proposes that the porosity of the oxidation film is 3% to 5%.

[0141] The control of the porosity of the oxide film is achieved by adjusting the amount of manganese sulfate added and the parameters of the electrolyte. For example, in a manganese sulfate concentration range of 0.02-0.2 mol / L, by controlling the electrolyte temperature fluctuation within ±1°C, and combining a step-by-step voltage increase process to maintain a voltage increase time of 5 min per stage, the complexation reaction of manganese ions and titanium ions is fully carried out. When the concentration of manganese sulfate is lower than 0.02 mol / L, the electrolysis time needs to be extended to 8 min to ensure that the porosity meets the standard; when the concentration is higher than 0.2 mol / L, the temperature needs to be controlled below 20°C to avoid excessive reaction. At the same time, the duty cycle and frequency parameters of the pulse current technology need to be maintained at 30% and 100 Hz, respectively, to ensure the dynamic balance between the ion migration rate and the complexation reaction rate.

[0142] Specifically, during the anodic oxidation process, the amount of manganese sulfate is dynamically adjusted by real-time monitoring of the changes in electrolyte conductivity and current density. When the porosity deviates from the set range, a PID control algorithm is started to correct the bath temperature. For example, when the porosity is higher than 5%, the temperature is reduced by 2°C and maintained for 10 min, so that the diffusion rate of manganese ions is increased by 15%. By controlling the porosity within the range of 3%-5%, a uniform distribution of microporous structures is formed inside the oxide film, with a pore size limited to the range of 50-200 nm. This structural feature allows the internal stress generated during the subsequent step-by-step voltage increase process to be uniformly released through the microporous network, avoiding crack propagation caused by stress concentration. During the 60V voltage increase stage, a gradient distribution of oxide grains is formed inside the film layer, with the grain size gradually increasing from 20 nm at the base to 80 nm at the surface. This structural gradient further improves the bending strength of the film layer.

[0143] As a preferred embodiment, the scheme of the present application is implemented as follows: in an anodic oxidation alkaline electrolyte, a uniform complex layer of manganese ions and titanium alloy surface is formed by adding 0.18 mol / L manganese sulfate solution, combined with the control of the laminar flow state of the electrolyte circulation system. During the oxidation process, a porous titanium basket is used as the anode carrier, and the electrolyte flow rate is adjusted to 0.5 m / s by real-time monitoring of the current density distribution, maintaining the bath temperature at a constant state of 25°C. During the pulse current stage, the ratio of forward pulse time to reverse pulse time is adjusted to 2:1 to promote the ordered growth of the microporous structure of the oxide film. After 2 hours of oxidation treatment, the helium replacement method is used to detect the porosity of the film layer, and by adjusting the concentration of sodium bicarbonate in the electrolyte to 28 g / L, an oxide film with a porosity of 4.2% is finally obtained.

[0144] By the technical scheme, the compactness and mechanical property of the oxide film are effectively balanced, the problem of insufficient corrosion resistance caused by excessively high porosity is prevented, and the problem of film layer brittleness caused by excessively low porosity is avoided. The control method ensures the stability of the complexation of manganese ions, forms a uniform microporous structure in the oxide film, provides an effective channel for the release of internal stress in the subsequent process, and improves the bonding strength of the film layer and the substrate.

[0145] In some schemes of the application, a technical means of reducing the porosity of the oxide film by adding manganese sulfate to utilize the complexation of manganese ions and titanium ions is proposed. However, in the actual process implementation, if the porosity is adjusted only by adding the concentration of manganese sulfate without specifying the specific porosity control range, it may cause insufficient compactness or excessive densification of the film layer, and further cause problems such as increased film layer brittleness or stress concentration.

[0146] To this end, the application further proposes that the porosity of the oxide film is 3% to 5%.

[0147] The control of the porosity of the oxide film is achieved by adjusting the amount of manganese sulfate added and the parameters of the electrolyte. For example, in the range of 0.02-0.2 mol / L manganese sulfate concentration, by controlling the electrolyte temperature fluctuation within ±1℃, and combining with the stepwise voltage increasing process to maintain 5min of voltage increasing time at each stage, the complexation reaction of manganese ions and titanium ions is fully carried out. When the concentration of manganese sulfate is less than 0.02 mol / L, the electrolysis time needs to be extended to 8min to ensure that the porosity meets the standard; when the concentration is higher than 0.2 mol / L, the temperature needs to be controlled below 20℃ to avoid excessive reaction. At the same time, the duty cycle and frequency parameters of the pulse current technology need to be kept at 30% and 100Hz to ensure the dynamic balance of ion migration rate and complexation reaction rate.

[0148] Specifically, in the anodic oxidation process, the amount of manganese sulfate is dynamically adjusted by real-time monitoring of the changes of electrolyte conductivity and current density. When the porosity deviates from the set range, the PID control algorithm is started to correct the bath temperature, for example, when the porosity is higher than 5%, the temperature is reduced by 2℃ and maintained for 10min, so that the diffusion rate of manganese ions is increased by 15%. By controlling the porosity in the range of 3%-5%, a uniform distribution of microporous structure is formed in the oxide film, and the pore size is limited in the range of 50-200nm. This structural feature enables the internal stress generated in the subsequent stepwise voltage increasing process to be uniformly released through the microporous network, avoiding crack propagation caused by stress concentration. In the 60V voltage increasing stage, gradient distribution of oxide grains is formed in the film layer, and the grain size gradually increases from 20nm at the base to 80nm at the surface. This structural gradient further improves the bending strength of the film layer.

[0149] As a preferred embodiment, the scheme of the present application is implemented as follows: in the anodic oxidation alkaline electrolyte, 0.18 mol / L manganese sulfate solution is added, and the laminar flow state of the electrolyte circulation system is controlled to make the manganese ions form a uniform complex layer on the surface of the titanium alloy. During the oxidation process, a porous titanium basket is used as the anode carrier, the current density distribution is monitored in real time, the electrolyte flow rate is adjusted to 0.5 m / s, and the bath temperature is maintained at a constant state of 25°C. In the pulse current stage, the ratio of the forward pulse time to the reverse pulse time is adjusted to 2:1 to promote the ordered growth of the microporous structure of the oxidation film. After 2 hours of oxidation treatment, the helium replacement method is used to detect the porosity of the film layer, the concentration of sodium bicarbonate in the electrolyte is adjusted to 28 g / L, and finally an oxidation film with a porosity of 4.2% is obtained.

[0150] Through the above technical scheme, the present application effectively balances the compactness and mechanical properties of the oxidation film, prevents the problem of insufficient corrosion resistance caused by too high porosity, and avoids the brittleness defect of the film layer caused by too low porosity. The control method ensures the stability of the complexation of manganese ions, forms a uniform microporous structure inside the oxidation film, provides an effective channel for the release of internal stress in the subsequent process, and improves the bonding strength of the film layer and the substrate.

[0151] The above is only an embodiment of the present application and is not used to limit the protection scope of the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A black titanium coloring long-term stability process based on flow and temperature control, characterized in that: include: Step 1, pre-treating the titanium alloy surface; Step 2: preparing a black anodized film; Step 3, post-processing; Step 4: Test the film performance. If it does not meet the requirements, return to step 1. If it meets the requirements, complete the production.

2. The black titanium coloring long-term stability process based on flow and temperature control according to claim 1 is characterized in that: The step 1 includes: Step 101: sequentially perform alkali washing, water washing, acid washing, and water washing on the titanium alloy plate to obtain a pretreated titanium alloy plate; Step 102: placing the pretreated titanium alloy plate in deionized water for water sealing treatment; Step 103: Place the titanium alloy plate after the water seal treatment into an anodic oxidation alkaline electrolyte for oxidation treatment.

3. The black titanium coloring long-term stability process based on flow and temperature control according to claim 1 is characterized in that: The step 2 includes: Step 201: using a porous titanium basket to disperse the electrolyte flow so that the Reynolds number is controlled in the range of 2000-4000; Step 202: adopt a staged temperature control strategy, with the initial temperature controlled at 5-10°C and the later temperature controlled at 20-30°C; Step 203: Control the temperature fluctuation of the bath liquid within ±1°C by using a PID algorithm; Step 204: adding 0.02-0.2 mol / L manganese sulfate to reduce the porosity of the oxide film by utilizing the complexation between manganese ions and titanium ions; Step 205: Using a step-by-step voltage boosting method, the voltage is boosted to 30V and 60V in sequence to reduce the stress in the film layer; Step 206: Use a pulse current technology with a duty cycle of 30% and a frequency of 100 Hz to improve the conductive performance of the film layer.

4. The black titanium coloring long-term stability process based on flow and temperature control according to claim 1 is characterized in that: The step 3 includes: Step 301: Rinse the oxidized titanium alloy plate with deionized water and dry it; Step 302: placing the rinsed titanium alloy plate in deionized water for water sealing treatment; Step 303: Regulate the tank liquid temperature through a plate heat exchanger to control it below 35°C.

5. The black titanium coloring long-term stability process based on flow and temperature control according to claim 1 is characterized in that: The step 4 includes: Step 401: Build a high-resolution imaging system using a 5-megapixel CMOS camera and a 450nm blue LED array; Step 402: Detecting oxide film thickness by UV-VIS-NIR spectral reflectance; Step 403: measuring surface roughness based on a phase shift method; Step 404: using infrared temperature measurement, laser displacement, gas flow and other sensors to monitor process parameters in real time; Step 405: Adjust process parameters using an adaptive PID algorithm; Step 406: predicting the process window based on the FEM simulation model; Step 407: Identify film defects through a deep learning classification system; Step 408: Automatically adjust the spray angle and atomization pressure according to the recognition result; Step 409: Establish control limits based on Six Sigma principles.

6. The black titanium coloring long-term stability process based on flow and temperature control according to claim 2 is characterized in that: The step 101 is specifically as follows: The titanium alloy plate was sequentially placed in a sodium bicarbonate solution with a mass concentration of 5% and ultrasonically cleaned at 65°C for 2 minutes, then washed with deionized water three times, and finally ultrasonically cleaned with a hydrochloric acid solution with a mass concentration of 5% at room temperature for 30 seconds to obtain a pretreated titanium alloy plate; Alternatively, the titanium alloy plate is sequentially placed in a sodium bicarbonate solution with a mass concentration of 6% and ultrasonically cleaned at 68° C. for 1.5 minutes, then washed twice with deionized water, and finally ultrasonically cleaned with a hydrochloric acid solution with a mass concentration of 6% at 40° C. for 45 seconds to obtain a pretreated titanium alloy plate.

7. The black titanium coloring long-term stability process based on flow and temperature control according to claim 2 is characterized in that: In step 102, the water sealing treatment is performed at room temperature for 30 minutes, or at 50°C for 45 minutes.

8. The black titanium coloring long-term stability process based on flow and temperature control according to claim 2 is characterized in that: The step 103 is specifically as follows: The titanium alloy plate after water sealing treatment was placed in an anodic oxidation electrolyte with a mass concentration of 8g / L sodium hydroxide, 12g / L sodium nitrite, 24g / L sodium bicarbonate, 64g / L sodium borate, 32g / L sodium silicate and 0.4g / L sodium potassium tartrate, and oxidized at room temperature; Alternatively, the titanium alloy plate after water sealing treatment is placed in an anodic oxidation electrolyte with a mass concentration of 10 g / L sodium hydroxide, 15 g / L sodium nitrite, 30 g / L sodium bicarbonate, 80 g / L sodium borate, 40 g / L sodium silicate and 0.5 g / L sodium potassium tartrate, and oxidized at 45°C.

9. The black titanium coloring long-term stability process based on flow and temperature control according to claim 3 is characterized in that: In step 204, the porosity of the oxide film is reduced to 3% to 5%.

10. The black titanium coloring long-term stability process based on flow and temperature control according to claim 3 is characterized in that: In step 205, each stage of the step-by-step pressure boosting method is maintained for 5 minutes.

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