A method for spraying and blackening the outer wall of a gun barrel

Abstract

The present application belongs to the technical field of surface chemical treatment of metal materials, and particularly relates to a method for spraying and blackening the outer wall of a gun barrel. The method comprises the following steps: while rotating the barrel at a constant speed, the barrel is divided into multiple sections in the axial direction, each section is sprayed in sequence, and an accelerated airflow is immediately sprayed to instantaneously promote drying, so as to improve the viscosity of the liquid film and prevent the liquid film from flowing. In addition, the rotation speed is dynamically adjusted according to the position of the spray head on the upper half or lower half of the circumference of the barrel, and the centrifugal force generated by the higher rotation speed of the lower half is used to offset the gravity. Through the cooperation of zoning, promoting drying and dynamic speed adjustment, a black conversion film with uniform thickness and firm adhesion is finally formed on the outer wall of the barrel, and the corrosion resistance and concealment performance are effectively improved. Through the synergistic effect of axial zoning, instant drying and dynamic speed adjustment, the uniformity of the blackening liquid film is effectively ensured.

Description

Technical Field

[0001] This invention belongs to the field of surface chemical treatment technology for metallic materials, specifically relating to a method for blackening the outer wall of an artillery barrel by spraying. Background Technology

[0002] Artillery, as large steel equipment used in harsh environments such as the field and coast for extended periods, is highly susceptible to rust due to electrochemical reactions with oxygen and moisture in the air. Furthermore, the pure metal surface strongly reflects light, easily creating flashes in sunlight or battlefield conditions, thus revealing the equipment's location. Therefore, it is necessary to treat the surface of artillery to prevent corrosion and reduce its brightness, achieving a camouflage effect.

[0003] The material of artillery barrels is usually steel. Reference 1 discloses a blackening process for steel surface treatment. Through blackening treatment, a dense black oxide film is generated on the steel surface. This film can effectively isolate the base metal from direct contact with the corrosive medium, significantly improve its corrosion resistance, and the black color also plays a camouflage role.

[0004] Patent document 2 discloses a steel pipe spraying system that achieves uniform spraying by actively driving the steel pipe to rotate around its own axis during the transportation process.

[0005] However, artillery barrels are usually long and have a large caliber. Due to gravity, the blackening liquid is very likely to accumulate and flow in the lower semicircle or local area of ​​the barrel, resulting in uneven liquid film thickness. This leads to uneven thickness of the blackening film that is ultimately formed on the barrel, which affects its performance.

[0006] Reference 1: Research on Problems and Countermeasures of Room Temperature Blackening Process for Steel, Wei Shuai, Li Xiangsong; DOI:10.13726 / j.cnki.11-2706 / tq.2015.10.057.04; Publication date: October 2015.

[0007] Patent Document 2: Chinese invention patent with publication number CN115921190B and first publication date of 2023-04-07. Summary of the Invention

[0008] The purpose of this invention is to provide a method for blackening the outer wall of an artillery barrel by spraying. When the nozzle is working above the barrel, slow rotation allows for a uniform spreading time of the initial liquid film. When the barrel rotates to the lower area, the liquid adhering to the barrel wall is most likely to drip or thicken due to gravity. At this time, increasing the rotation speed can counteract the liquid falling and accumulating caused by gravity.

[0009] The technical solution adopted by the present invention to solve the above problems is: a method for blackening the outer wall of an artillery barrel by spraying, comprising the following blackening treatment steps: S1: Rotate the barrel and divide its outer surface into multiple continuous sections along the barrel axis; S2: Control the nozzle to travel along the tube axis. When the nozzle travels to a section, spray blackening liquid onto the section to form an initial liquid film on its surface. S3: After spraying, the initial liquid film is subjected to instantaneous drying treatment to increase the viscosity of the initial liquid film; S4: After all sections of the barrel have been sprayed and dried, spray and instantaneously dry all sections of the outer surface of the barrel at least once. S5: Maintain the tube rotation for the set time to complete the blackening chemical reaction; In the spraying process of S2, based on the circumferential position of the nozzle relative to the body tube and / or the axial position of the body tube, when the nozzle sprays a section of the outer surface of the body tube, when the nozzle is in the upper semicircular area of ​​the section, the body tube is controlled to rotate at a first speed; when the nozzle is in the lower semicircular area of ​​the section, the body tube is controlled to rotate at a second speed; wherein the second speed is greater than the first speed.

[0010] A further preferred technical solution is that the first rotational speed is 4~5 r / min and the second rotational speed is 6~8 r / min.

[0011] A further preferred technical solution is that, in step S3, the instantaneous drying process specifically involves spraying an accelerated airflow at a preset temperature onto the surface of the current section after spraying, in order to accelerate the evaporation of the solvent in the initial liquid film, thereby increasing the viscosity of the initial liquid film.

[0012] A further preferred technical solution is that the temperature of the accelerating airflow is 20℃~50℃.

[0013] A further preferred technical solution is that the accelerated airflow is provided by a flat slit-type air knife, the length direction of the air knife is parallel to the axis of the tube, and the distance between the air outlet of the air knife and the outer surface of the tube is 150mm~180mm.

[0014] A further preferred technical solution is that, in step S1, the specific way of dividing the tube into multiple continuous sections is that, outside the tube, multiple openable and closable axial partition plates are provided along its axial direction. When a section is being processed, the nozzle and the device for instantaneous drying are located in the space corresponding to that section, and the axial partition plates at both ends of the space are in a closed state to form a relatively independent processing chamber.

[0015] A further preferred technical solution is that, in step S2, the blackening solution includes copper sulfate, selenite, hydroquinone, and nitric acid.

[0016] A further preferred technical solution is that the content of each component in the blackening solution is as follows: copper sulfate 1~3g / L, hydroquinone 2~4g / L, selenite 3~5g / L, nitric acid 30~40g / L, and the balance is water.

[0017] A further preferred technical solution is that the blackening liquid also includes hydroxypropyl methylcellulose. Hydroxypropyl methylcellulose is used as a thickener.

[0018] A further preferred technical solution is that the hydroxypropyl methylcellulose content is 1~2g / L.

[0019] A further preferred technical solution is that the content of each component in the blackening solution is as follows: copper sulfate 1~3g / L, hydroquinone 2~4g / L, selenite 3~5g / L, nitric acid 30~40g / L, hydroxypropyl methylcellulose 1~2g / L, and the balance is water.

[0020] A further preferred technical solution includes the following step before the aforementioned blackening process: S0: The tube to be processed is clamped on the rotating bracket and driven to rotate, and the outer surface of the tube to be processed is pre-treated to obtain the tube. A further preferred technical solution includes the following steps after the aforementioned blackening process: S6: Maintain the rotation of the blackened tube and perform post-processing on the outer surface of the blackened tube to obtain the processed tube.

[0021] In summary, the present invention has the following advantages: 1. This invention employs three core measures—axial segmentation, instantaneous drying, and dynamic speed adjustment—to counteract the effects of gravity from three dimensions: spatial isolation, physical drying, and mechanical compensation. This effectively solves the problem of liquid film flow and accumulation caused by gravity during the blackening process of ultra-long, large-diameter artillery barrels, thereby obtaining a black conversion film with uniform thickness and excellent performance.

[0022] 2. This invention divides the tube into multiple independent chambers along the axial direction for processing, and immediately applies gentle airflow to the liquid film after spraying each section to promote drying, rapidly increasing its viscosity, thus fundamentally preventing the blackening liquid from flowing and cross-contaminating in the axial and circumferential directions.

[0023] 3. This invention dynamically adjusts the tube rotation speed based on the nozzle position. A higher rotation speed is used in the lower semi-circle, utilizing increased centrifugal force to counteract gravity, further ensuring uniform distribution of the liquid film in areas prone to accumulation. Experimental data shows that by combining dynamic adjustment and a thickener, the vertical deviation of the film thickness can be controlled within 0.3 micrometers to even 0.1 micrometers, exhibiting excellent uniformity.

[0024] 4. This invention forms a uniform black film layer on the artillery barrel, avoiding differences in reflectivity caused by uneven thickness, eliminating local flashes, and achieving an overall low visibility concealment effect, thus meeting the requirements of military equipment.

[0025] 5. The spray dynamic treatment method of the present invention is particularly suitable for large workpieces that cannot be immersed, and solves the limitations of traditional immersion or spraying processes for large workpieces.

[0026] 6. The present invention adds hydroxypropyl methylcellulose as a thickener, which increases the adhesion of the blackening solution and produces a synergistic effect with dynamic speed adjustment, further improving the process window and film formation stability. Attached Figure Description

[0027] The invention will be further described below with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the artillery barrel.

[0028] Figure 2 A schematic diagram of a rotating bracket installed on the artillery barrel.

[0029] Figure 3 A schematic diagram of a rotating bracket and nozzle mounted on a cannon barrel.

[0030] Figure 4 A schematic diagram of a rotating bracket, nozzle, and partition plate installed on a cannon barrel, with the partition plate in the open position.

[0031] Figure 5 for Figure 4 A schematic diagram showing the middle partition plate switching to the closed state, dividing the barrel into three continuous sections.

[0032] Figure 6 A schematic diagram of a structure for installing air blades on the barrel.

[0033] Figure 7 This is a schematic diagram showing the distribution of sampling points on the tube.

[0034] In the attached diagram, the components represented by each number are as follows: gun barrel 1, front end head 1.1, rear end head 1.2, active drive end 2.1, driven support end 2.2, nozzle 3, partition plate 4, upper test point 5.1, middle test point 5.2, lower test point 5.3, and air knife 6. Detailed Implementation

[0035] The present invention will be specifically illustrated below with reference to embodiments: This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

[0036] Example: Specific form of artillery barrel.

[0037] In this embodiment, the specific form of the gun barrel is as shown in the attached figure. Figure 1 As shown, the gun barrel 1 is a hollow cylinder with a large length-to-diameter ratio, and its outer surface is a continuous, regular cylindrical surface. The gun barrel 1 has at least a front end 1.1 and a rear end 1.2 to facilitate the "clamping on the rotating bracket and driving its rotation" and the "movement of the nozzle along the axial direction". In the following embodiment, the barrel of the PLZ89 122mm self-propelled howitzer is used as the gun barrel 1 for blackening treatment. Its specific specifications are: inner diameter 122mm, wall thickness 60mm, length 3660mm, and the surface of the barrel has no giant protrusions or complex grooves, and is a flat hollow tubular component. The above specifications meet the so-called "ultra-long, large-diameter" geometric characteristics. Conventional soaking or spraying processes will cause the blackening liquid to accumulate and flow in the lower half-circumference due to gravity, resulting in the technical problem of "uneven film thickness".

[0038] The material for the artillery barrel conforms to the "PCrMo" grade as specified in Section 3.1.1 of the People's Republic of China Ferrous Metallurgical Industry Standard YB475-93 "Steel for Artillery Barrel Parts," with the following specific composition by mass percentage: C: 0.32~0.42%; Mn: 0.25~0.5%; Si: 0.17~0.37%; Cr: 0.9~1.3%; Ni: ≤0.5%; Mo: 0.2~0.3%; with the balance being Fe. In a preferred embodiment, the total mass percentage of the material is: C: 0.4%; Mn: 0.35%; Si: 0.3%; Cr: 1.2%; Ni: 0.4%; Mo: 0.25%; with the balance being Fe.

[0039] Example: Specific form of the rotating bracket.

[0040] In step S0, the tube to be treated is clamped onto a rotating bracket and driven to rotate. This rotating bracket, a type of support with a drive motor, is used in existing technology. Both ends of the tube are fixed to the bracket, with at least one end fixedly connected to the rotor of the drive motor. The other end can be connected to another drive motor or a rotatable device, such as a bracket with bearings. Driven by the drive motor, the tube rotates at an adjustable speed to facilitate subsequent spraying steps. The core purpose of rotating the tube using the rotating bracket is to ensure the uniformity of the subsequent blackening process. Because the tube is long and has a large diameter, if it were not rotated, the nozzle would need to be rotated, which would be more cumbersome. This method of rotating the tube ensures that the entire circumference of the tube is aligned with the nozzle, receiving uniform spraying.

[0041] In this embodiment, the rotating bracket must at least have the function of safely and stably supporting the ultra-long and ultra-heavy artillery barrel and driving it to rotate at a uniform speed and smoothly around its own axis. Its essential feature is that it drives the barrel to rotate and only acts on the two ends of the barrel to avoid contact with and block the outer surface of the middle part of the barrel, so as not to affect the spraying and drying process.

[0042] In a preferred embodiment, refer to the appendix Figure 2 This demonstrates a basic form of rotating bracket, where the rotating bracket 2 includes an active drive end 2.1 and a driven support end 2.2. The active drive end 2.1 is typically connected to a rotor that provides rotational force, such as an existing high-torque, adjustable-speed drive motor. Specifically, the active drive end 2.1 is a robust rotating chuck, such as a three-jaw chuck, a four-jaw chuck, or a dedicated flange clamp for the tube, capable of precisely mating and locking with the front end 1.1. The rotor directly drives the tube to rotate via the active drive end 2.1. The driven support end 2.2 is generally similar in structure to the active drive end 2.1, except that it is connected to a rotatable device and can cooperate with the active drive end 2.1 to support the tube.

[0043] The "drive motor" is a servo motor system designed to achieve precise, high-speed and position control of the motor body. The servo motor system has a servo driver for stepless, precise setting and adjustment of the motor's speed, maintaining a constant speed even under varying loads. The servo motor system can also receive pause commands to immediately and precisely stop at any angular position and remain locked. After pausing, rotation can be seamlessly resumed from that position.

[0044] The “rotatable device” refers to a mechanical component installed at the driven support end to support the other end of the tube and allow it to rotate freely. It is usually a rotary bearing unit, which contains a heavy-duty ball bearing or roller bearing. The outer ring of the bearing is fixed to the seat at the driven support end, while the inner ring is connected to a rotatable shaft or sleeve for connecting to the driven support end 2.2.

[0045] Example: Specific steps of pretreatment.

[0046] Step S0 requires pretreatment of the outer surface of the barrel to be processed, resulting in the barrel. In this embodiment, the pretreatment should include at least the following steps: Degreasing is essential for thoroughly removing oil and grease from the surface of the tube to be treated. This is crucial for the quality of the blackening process; incomplete degreasing can lead to defects such as poor adhesion of the blackening film, peeling, and mottling. The degreasing agent used is typically an alkaline water-based degreaser with surfactants. The contact method with the tube is not limited; it is usually done by spraying or immersion, as long as it achieves uniform contact with the tube.

[0047] The first water rinse aims to remove residual alkaline degreasing agent and emulsified oil from the workpiece surface, preventing these residues from contaminating the subsequent pickling tank and blackening solution, thus affecting the treatment effect. The rinsing solution used is usually purified water or tap water with impurities meeting the standards for subsequent blackening treatment. The contact method between the rinsing solution and the workpiece is not limited, typically involving immersion or spraying, as long as it achieves uniform contact with the workpiece.

[0048] Rust removal aims to thoroughly remove oxide rust from the surface of a workpiece. Similar to degreasing, incomplete rust removal can lead to poor adhesion and mottled appearance of the blackening film. Furthermore, pickling can activate the steel surface, increasing its surface activity and making it more susceptible to reaction with the blackening solution. The rust removal solution typically used is a strong acid such as concentrated hydrochloric acid.

[0049] The purpose of the second rinse is to thoroughly remove any residual strong acid (such as hydrochloric acid) from the workpiece surface. If the acid is carried into the blackening solution, it will alter the pH value of the solution, severely affecting the control of the blackening process and the final film quality. The second rinse is usually performed in the same manner as the first rinse.

[0050] In a preferred embodiment, the pretreatment step specifically involves a first water wash with purified water, followed by rust removal with concentrated hydrochloric acid, and finally a second water wash with purified water.

[0051] Example: Specific steps of post-processing.

[0052] In step S6, while maintaining the rotation of the blackened tube, post-processing is performed on the outer surface of the blackened tube to obtain the processed tube. In this embodiment, the post-processing should include at least the following steps: The purpose of the third rinse is to wash away any acidic blackening solution remaining on the workpiece surface after the blackening treatment, preventing the acidic liquid from causing a sharp decrease in the workpiece's corrosion resistance. The third rinse is usually performed in the same way as the first rinse.

[0053] The purpose of the sealing treatment is that the alkaline nature of the soap solution can neutralize any trace amounts of acidic substances that may remain after washing with water. Furthermore, the resulting blackened film may contain pores, and the soap solution treatment fills these pores, thus blocking the channels for corrosive media penetration and significantly improving the film's density and rust prevention capabilities. The sealing solution used in the sealing process is typically a soap solution of a certain concentration.

[0054] Oil immersion aims to form a hydrophobic oil film on the surface of the sealed coating, further isolating moisture and oxygen to achieve the final rust-preventive effect. For room temperature blackening processes, dehydrating rust-preventive oil must be used for sealing to achieve the desired rust-preventive effect. This is because "dehydrating oil" can replace the moisture on the surface of the workpiece and in the pores of the coating, preventing the workpiece from rusting during storage due to residual moisture. The method of oil immersion involves removing the treated tube from the soap solution and drying it, then directly immersing it in dehydrating rust-preventive oil. This significantly improves the blackness, gloss, and corrosion resistance of the treated tube.

[0055] In a preferred embodiment, the post-treatment step specifically involves a third water rinsing with purified water, followed by a sealing treatment with soap solution, and finally an oil immersion treatment with dehydrating rust-preventive oil.

[0056] Example: Specific steps of the blackening process.

[0057] In this embodiment, the blackening process includes the following steps: S1: Rotate the barrel and divide its outer surface into multiple continuous sections along the barrel axis; S2: Control the nozzle to travel along the tube axis. When the nozzle travels to a section, spray blackening liquid onto the section to form an initial liquid film on its surface. S3: After spraying, the initial liquid film is subjected to instantaneous drying treatment to increase the viscosity of the initial liquid film; S4: After all sections of the barrel have been sprayed and dried, spray and instantaneously dry all sections of the outer surface of the barrel at least once. S5: Maintain the tube rotation for the set time to complete the blackening chemical reaction.

[0058] In this embodiment, the instantaneous drying process encompasses all technical means that can achieve the result of "rapidly increasing the viscosity of the liquid film to prevent flow," such as airflow, infrared radiation, microwaves, and low-pressure environments. In a preferred embodiment, the instantaneous drying process specifically involves spraying an accelerating airflow at a preset temperature onto the surface of the current section after spraying, to accelerate the evaporation of the solvent in the initial liquid film, thereby increasing the viscosity of the initial liquid film. If the preset temperature of the accelerating airflow is too low, the solvent will evaporate slowly, resulting in insufficient drying effect, and the liquid film may still flow; if the temperature is too high, such as exceeding the boiling point of water or the solvent, it may cause violent boiling and film rupture on the liquid film surface, thus destroying uniformity. In a preferred embodiment, the temperature of the accelerating airflow is 20°C to 50°C.

[0059] In a preferred embodiment, reference Figure 6 The accelerated airflow is provided by a flat slit-type air knife 6, the length of which is parallel to the axial direction of the tube 1, and the distance between the air knife 6's outlet and the outer surface of the tube 1 is 150mm~180mm. In this embodiment, the "flat slit-type air knife" is an industrial drying or cleaning device. Its core structure is a device with an internal air channel and an outlet in the shape of a long, flat slit. When compressed air passes through this slit, it forms a uniform, continuous, high-speed, flat airflow curtain. When it moves along the surface of the tube or is fixed to blow on a section, it can generate an airflow band of uniform width covering the entire circumference of that section. This ensures that the liquid film on the entire circumferential surface of the tube is dried uniformly and synchronously, thereby rapidly increasing the overall viscosity and fundamentally preventing the liquid film from accumulating and flowing in the lower half-circumference due to gravity. Compared to ordinary circular nozzles, flat slit air knives generate an airflow curtain with a larger contact area, more concentrated energy, and higher wind speed, enabling them to sweep the liquid film surface more quickly and effectively, accelerating solvent (usually water) evaporation and thus achieving instantaneous drying. By precisely controlling the airflow temperature, pressure, and slit width, the drying rate can be finely adjusted, avoiding excessively high temperatures that could cause the liquid film to boil and break, or excessively low temperatures that could lead to insufficient drying. In a preferred embodiment, the flat slit air knife is specifically a MISUMI AFTSA15 model.

[0060] In step S2 of this embodiment, the specific way to divide it into multiple continuous sections is as follows: on the outside of the tube, multiple axial partition plates that can be opened and closed are provided along its axial direction. When a section is processed, the nozzle and the device for instantaneous drying are located in the space corresponding to the section, and the axial partition plates at both ends of the space are in a closed state to form a relatively independent processing chamber.

[0061] The "axial partition plate" used in this embodiment has a basic structure of a series of rigid plates, such as metal plates or composite material plates. Its shape matches the curvature of the outer cylindrical surface of the tube, typically being an arc shape, and has sufficient width to effectively isolate the tube from the surrounding equipment. These partition plates are arranged parallel to each other along the axial direction of the tube, either at equal intervals or according to the length of the process section. Each partition plate is located on the periphery of the tube, maintaining a small, fixed gap with the outer surface of the tube to prevent contact friction while effectively blocking airflow and droplets. Structurally, each partition plate is not fixedly connected to the tube but is mounted on an independent support frame or drive mechanism, allowing it to have both open and closed states.

[0062] The "openable and closable" implementation method used in this embodiment is specifically achieved through an automated drive mechanism, including hinge rotation type, lifting and translation type, and rotating split type. In the open state, the partition plate is completely moved out of the space around the body tube, ensuring that it does not interfere with the rotation of the body tube, the axial movement of the nozzle, or the loading and unloading of the workpiece. In the closed state, the partition plate moves to a predetermined position close to the outside of the body tube, and together with the nozzle / air knife device above, it forms a relatively independent "processing chamber".

[0063] In a preferred embodiment, such as Figure 4 As shown, two partition plates 4 are provided on both sides of the nozzle 3. The position of the partition plates 4 does not affect the normal movement of the nozzle 3. The device for moving the nozzle 3 and the partition plates 4 is not shown in the figure, indicating that the specific form of the device for moving the nozzle 3 and the partition plates 4 is not limited in this embodiment. As long as the device for moving the nozzle 3 is not affected by the partition plates 4, and the device for moving the partition plates 4 is not affected by the nozzle 3, it is acceptable. Figure 5 The diagram shows the partition plate 4 in a closed state. It is evident that the two partition plates 4 effectively enclose the central nozzle 3, forming a relatively independent treatment chamber. It is important to note that only one partition plate is needed at each end of the tube to achieve the same separation of the nozzle 3, and this is also considered an independent chamber. This is because the purpose of the partition plates 4 is to ensure that spraying one section does not affect adjacent sections.

[0064] In this embodiment, during the spraying process in step S2, the rotational speed of the tube is dynamically adjusted according to the circumferential position of the nozzle relative to the tube and / or the axial position of the tube. Specifically, dynamically adjusting the rotational speed of the tube means that during the spraying process, the tube rotational speed is dynamically changed based on the circumferential position of the nozzle and / or the axial position of the tube. That is, the rotational speed is no longer a fixed value, but a variable that is adjusted in real time according to the position of the nozzle and / or the position of the tube.

[0065] In this embodiment, the dynamic adjustment of the tube rotation speed is specifically as follows: when the nozzle sprays a section of the outer surface of the tube, when the nozzle is in the upper semicircular area of ​​that section, the tube is controlled to rotate at a first rotation speed; when the nozzle is in the lower semicircular area of ​​that section, the tube is controlled to rotate at a second rotation speed. Specifically, the upper semicircular area refers to the upward-facing semicircular area of ​​the tube after treatment; correspondingly, the lower semicircular area refers to the downward-facing semicircular area of ​​the tube after treatment. When spraying the upper semicircle of the tube, the blackening liquid is less affected by gravity and mainly relies on adhesion, resulting in a relatively stable liquid film. Therefore, a lower first rotation speed is used to ensure sufficient coverage and wetting time. When spraying the lower semicircle, in addition to adhesion, the liquid film is also affected by gravity, causing it to accumulate and flow downwards. Therefore, a higher second rotation speed is used to utilize the increased centrifugal force to partially counteract gravity, promoting a more uniform distribution of the liquid film and reducing flow. In a preferred embodiment, speed switching is achieved through direct position detection. Specifically, sensors are installed on the tube rotation axis and on the nozzle swing mechanism or the tube rotation axis to directly measure the relative angle between the nozzle and the highest / lowest point of the tube. When the angle value is between 0° and 180°, it is determined that the nozzle is in the upper half of the tube's rotation, and the controller outputs a first speed command; when it is between 180° and 360°, it is determined that the nozzle is in the lower half of the tube's rotation, and a second speed command is output. In a preferred embodiment, the first speed is 4~6 r / min, and the second speed is 6~10 r / min.

[0066] Example: Specific components of blackening liquid.

[0067] In this embodiment, the blackening process requires the use of a blackening solution. The blackening solution is used in step S2 to control the nozzle to travel axially along the tube. When the nozzle reaches a section, the blackening solution is sprayed onto that section to form an initial liquid film on its surface. The blackening solution can be divided into selenium-containing and selenium-free types. The selenium-containing blackening solution includes at least the following components: Copper sulfate (CuSO4), as the main salt, provides Cu. 2+ (Copper ions). Copper ions are the key component in the formation of the black black film. Whether through iron displacement reaction or reaction with selenite, they will eventually combine with selenium ions to form a black copper selenide (CuSe) film.

[0068] Selenite (H2SeO3) provides Se. 4+ Selenium ions are another key component of the blackening reaction. They react with copper ions to form black copper selenide (CuSe), which is the main component of the final black surface film. Compared to the Fe3O4 film produced by the selenium-free process, CuSe produces a deeper black color, better meeting the requirements for artillery exterior decoration.

[0069] Hydroquinone, Fe produced by steel surface activation 2+Will with Se 2- The reaction produces a white precipitate, consuming the active ingredient. Adding hydroquinone can reduce the Fe... 2+ Oxidized to Fe 3+ This reduces the formation of harmful precipitates, thus stabilizing the blackening solution and extending its service life.

[0070] Strong acids, such as nitric acid (HNO3), require the pH of the blackening solution to be strictly controlled within the strongly acidic range of 1-3. The addition of nitric acid is crucial for maintaining this acidity. If the acidity is too high (pH too low), the reaction is too fast, resulting in a loose membrane; if the acidity is too low (pH too high), the reaction is slow, resulting in a thin membrane and an unstable solution. Nitric acid plays a role in regulating and stabilizing the process conditions.

[0071] In this embodiment, the specific content of each component is as follows: copper sulfate 1~3g / L, hydroquinone 2~4g / L, selenite 3~5g / L, nitric acid 30~40g / L, and the balance is water.

[0072] In this embodiment, the blackening solution also includes additives, which typically play auxiliary roles such as surface activity, complexation, stabilization, or improvement of film properties. For example, they can improve the wettability of the blackening solution on the workpiece surface or complex certain interfering ions to keep the solution clean. In a preferred embodiment, the additive is a thickener. Thickeners can increase the overall viscosity of the blackening solution. High-viscosity liquids are less likely to flow and accumulate, which helps to maintain a more uniform liquid film thickness on inclined surfaces. In a preferred embodiment, the thickener is hydroxypropyl methylcellulose. Hydroxypropyl methylcellulose is a nonionic cellulose ether with good chemical stability. It can maintain good thickening performance in acidic solutions and is relatively inert to metal ions, making it less prone to complexation reactions.

[0073] Experimental example: Film thickness and uniformity test.

[0074] In this embodiment, a CM-8821 iron-based coating thickness gauge was used for testing. This gauge operates on the principle of magnetic induction. The instrument probe generates a low-frequency magnetic field, the intensity of which varies depending on the thickness of the non-magnetic blackened CuSe film between the probe and the ferromagnetic steel substrate. Through calibration, the instrument can directly convert this change in magnetic flux into a coating thickness value.

[0075] Before testing, substrate calibration is required. A steel sample of the same material and surface roughness as the workpiece to be tested, and which has not undergone blackening treatment, must be used as the substrate. The instrument probe is brought into close and perpendicular contact with the clean substrate surface to perform zero-point calibration or substrate calibration. Instrument calibration is then performed using the standard film thickness calibration sheet provided with the instrument, typically a non-magnetic foil of known thickness, such as a plastic sheet, for multi-point calibration. The calibration sheet is laid flat on the zero-point calibrated substrate, and the measurement reading should match the nominal value of the calibration sheet. Preferably, calibration is performed before measurement and after a period of time during measurement. Finally, the workpiece is prepared, ensuring that the surface of the workpiece to be tested is clean, dry, and free of oil, dust, and other contaminants.

[0076] During testing, the first step is to select test points, referring to... Figure 7 Test points 5.1 (top), 5.2 (middle), and 5.3 (bottom) were taken from the top of tube 1 and tested. The tube was tested at least 24 hours after the blackening treatment. During testing, the thickness gauge probe was held steadily and vertically against the surface of the tube being tested. The probe should be in complete contact with the surface, avoiding tilting. After the instrument reading stabilized, the thickness value was recorded. Each measurement point could be measured 2-3 times consecutively, and the average value was taken as the final measurement value for that point. The thickness values ​​of different areas were analyzed. If there were significant differences in thickness between the top test point 5.1, the middle test point 5.2, and the bottom test point 5.3, it indicated that there was a thickness unevenness problem.

[0077] The uniformity of the film layer in the tube after different treatments was measured using different processes and blackening solutions with different compositions, as detailed below: The specific form of the artillery barrel, the specific form of the rotating bracket, the specific steps of the pre-processing, and the specific steps of the post-processing are all performed using the above-mentioned preferred embodiments.

[0078] First blackening solution: copper sulfate 2g / L, selenite 4g / L, hydroquinone 3g / L, nitric acid 35g / L, balance water.

[0079] The following examples and comparative examples all use the above-described preferred embodiments and the first blackening liquor.

[0080] Example 1: In this embodiment, a method for blackening the outer wall of an artillery barrel by spraying includes the following steps: S0: The tube to be processed is clamped on the rotating bracket and driven to rotate at a speed of 4r / min. The outer surface of the tube to be processed is pre-treated to obtain the tube. S1: Maintain the barrel rotation speed at 4r / min, and divide its outer surface into three continuous sections along the barrel axis, each section being 1220mm in length; S2: Control the nozzle to travel along the tube axis. When the nozzle travels to a section, spray blackening liquid onto the section to form an initial liquid film on its surface. S3: After spraying is completed, the initial liquid film is subjected to instantaneous drying treatment, and the nozzle is moved to the next section; S4: After all sections of the barrel have been sprayed and dried, spray and instantaneously dry all sections of the outer surface of the barrel at least once. S5: Maintain the tube at 4r / min for 5min to complete the blackening chemical reaction; S6: Maintain the blackened tube at 4r / min and perform post-processing on the outer surface of the blackened tube to obtain the processed tube.

[0081] In step S3, the instantaneous drying process specifically involves spraying an accelerated airflow at a preset temperature onto the surface of the current section after spraying to accelerate the evaporation of the solvent in the initial liquid film, thereby increasing the viscosity of the initial liquid film.

[0082] The temperature of the accelerating airflow is 20°C.

[0083] Accelerated airflow is provided by a flat slit-type air knife, the length of which is parallel to the axis of the tube, and the distance between the air knife outlet and the outer surface of the tube is 150mm.

[0084] In step S2, two axially closable partition plates 4 are provided on the outside of the tube along its axial direction. When a section is being processed, the nozzle and the device for instantaneous drying are located in the space corresponding to that section, and the axial partition plates at both ends of the space are in a closed state to form a relatively independent processing chamber.

[0085] Example 2 This embodiment is basically the same as embodiment 1, except that: The temperature of the accelerating airflow is 50°C.

[0086] The distance between the air outlet of the air knife and the outer surface of the tube is 180mm.

[0087] Example 3: This embodiment is basically the same as embodiment 1, except that: The temperature of the accelerating airflow is 20°C.

[0088] The distance between the air outlet of the air knife and the outer surface of the tube is 180mm.

[0089] Example 4: This embodiment is basically the same as embodiment 1, except that: The temperature of the accelerating airflow is 50°C.

[0090] The distance between the air outlet of the air knife and the outer surface of the tube is 150mm.

[0091] Example 5: This embodiment is basically the same as embodiment 1, except that: The temperature of the accelerating airflow is 40°C.

[0092] The distance between the air outlet of the air knife and the outer surface of the tube is 165mm.

[0093] Example 6: This embodiment is basically the same as embodiment 5, except that: Maintain the tube at a rotation speed of 6 r / min throughout the entire process.

[0094] Example 7: This embodiment is basically the same as embodiment 5, except that: During the spraying process in step S2, the rotational speed of the tube is dynamically adjusted according to the circumferential position of the nozzle relative to the tube and / or the axial position of the tube.

[0095] The dynamic adjustment of the tube rotation speed is as follows: when the nozzle is spraying a section of the outer surface of the tube, when the nozzle is in the upper half-circumference area of ​​the section, the tube is controlled to rotate at a first rotation speed; when the nozzle is in the lower half-circumference area of ​​the section, the tube is controlled to rotate at a second rotation speed higher than the first rotation speed.

[0096] The first rotational speed is 4 r / min, and the second rotational speed is 6 r / min.

[0097] Example 8: This embodiment is basically the same as embodiment 7, except that: The first rotational speed is 5 r / min, and the second rotational speed is 8 r / min.

[0098] Example 9: This embodiment is basically the same as embodiment 5, except that: Replace the first blackening solution with the second blackening solution, which consists of: 2 g / L copper sulfate, 4 g / L selenite, 3 g / L hydroquinone, 35 g / L nitric acid, 1.0 g / L hydroxypropyl methylcellulose, and the remainder is water.

[0099] Example 10: This embodiment is basically the same as embodiment 9, except that: Maintain the tube at a rotation speed of 6 r / min throughout the entire process.

[0100] Example 11: This embodiment is basically the same as embodiment 9, except that: During the spraying process in step S2, the rotational speed of the tube is dynamically adjusted according to the circumferential position of the nozzle relative to the tube and / or the axial position of the tube.

[0101] The dynamic adjustment of the tube rotation speed is as follows: when the nozzle is spraying a section of the outer surface of the tube, when the nozzle is in the upper half-circumference area of ​​the section, the tube is controlled to rotate at a first rotation speed; when the nozzle is in the lower half-circumference area of ​​the section, the tube is controlled to rotate at a second rotation speed higher than the first rotation speed.

[0102] The first rotational speed is 4 r / min, and the second rotational speed is 6 r / min.

[0103] Comparative Example 1: This comparative example is basically the same as Example 5, except that: Axial partition plate 4 was not set for section division.

[0104] Comparative Example 2: This comparative example is basically the same as Example 7, except that: Axial partition plate 4 was not set for section division.

[0105] The film thickness and uniformity of the processed tubes obtained in Examples 1-11 and Comparative Examples 1-2 were tested, and the results are shown in Table 1: ; Table 1: Test results of film thickness and uniformity in Examples 1-11 and Comparative Examples 1-2.

[0106] Analysis of the data in Table 1 shows that: Examples 1-5 all employed a core architecture of segmented drying, instantaneous drying with air knives, and axial partitions, but with different air knife parameters (temperature and distance). Example 5 (airflow 40℃, distance 165mm) showed significantly better uniformity (top-bottom difference of -0.6μm) than Examples 1-4. This indicates that within the temperature range of 20-50℃, an accelerating airflow of 40℃ and a suitable distance (165mm) can better balance drying speed and uniformity, effectively increasing liquid film viscosity to prevent flow while avoiding insufficient effect due to excessively low temperature or excessively high temperature / air velocity, which could lead to liquid film breakage or uneven drying.

[0107] Example 6 increased the rotational speed from 4 r / min to 6 r / min throughout the entire process, based on Example 5. The uniformity of the result was basically the same as that of Example 5, indicating that a relatively uniform liquid film distribution can be obtained within a certain rotational speed range.

[0108] Examples 7 and 8, based on Example 5, added a dynamic adjustment of "slow speed in the upper half of the circumference (4 or 5 r / min) and fast speed in the lower half of the circumference (6 or 8 r / min)". This is one of the most significant technical improvements in terms of effect. Compared with Example 5, which uses a constant speed, the uniformity of Examples 7 (upper and lower difference -0.3 μm) and Examples 8 (upper and lower difference -0.3 μm) is significantly improved. Compared with Example 6, which also uses a constant speed but a higher rotation speed, Examples 7 and 8, which use dynamic adjustment, still have a significant advantage in uniformity. This verifies that dynamic adjustment can more intelligently counteract the effects of gravity: providing sufficient immersion time in the upper half and increasing centrifugal force by increasing the rotation speed in the lower half to prevent accumulation.

[0109] Examples 9, 10, and 11 added hydroxypropyl methylcellulose to the blackening solution. Examples 9 and 10 (thickener + basic parameters) showed slightly improved uniformity compared to Example 5 (the difference between the top and bottom changed from -0.6 μm to -0.5 μm), indicating that the thickener itself increases the film adhesion and reduces flow. Example 11 (thickener + dynamic adjustment) achieved the best uniformity among all examples (top-middle difference 0 μm, top-bottom difference -0.1 μm, middle-bottom difference -0.1 μm). This indicates a synergistic effect between the thickener and dynamic speed adjustment. The thickener improves the film's anti-flow ability through physicochemical properties, while dynamic adjustment provides precise intervention from a mechanical perspective; the combination of the two achieves ultimate film uniformity.

[0110] Comparative Examples 1 and 2 did not use axial partitions. Even though Comparative Example 1 used the optimized parameters of Example 5 and Comparative Example 2 used the dynamic adjustment technology of Example 7, their uniformity was far inferior to either example. The absolute values ​​of the "upper and lower differences" (-1.2μm, -1.0μm) were several times, even more than ten times, the optimal data in the examples. This strongly demonstrates the crucial importance of the "processing chamber" formed by the axial partition. It effectively prevents airflow and blackening liquid from interfering with adjacent sections, ensuring that each section can complete spraying and drying in an independent and controlled environment. This is the fundamental prerequisite for achieving axial uniformity throughout the long tube. Without this design, the effectiveness of other local optimization measures would be greatly reduced.

[0111] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the invention. Furthermore, the terms "vertical," "horizontal," "front," and "rear," etc., mentioned in the embodiments of the present invention, indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationships commonly used when the product is in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

Claims

1. A method for blackening the outer wall of an artillery barrel by spraying, characterized in that, Includes the following steps: S1: Rotate the barrel and divide its outer surface into multiple continuous sections along the barrel axis; S2: Control the nozzle to travel along the axial direction of the tube. When the nozzle travels to a section, spray blackening liquid onto the current section to form an initial liquid film on its surface. S3: After spraying, the initial liquid film is subjected to instantaneous drying treatment to increase the viscosity of the initial liquid film; S4: After all sections of the barrel have been sprayed and dried, at least one round of spraying and instantaneous drying is performed on all sections of the outer surface of the barrel. S5: Maintain the rotation of the tube for a set time to complete the blackening chemical reaction; In step S2, during the spraying process, based on the circumferential position of the nozzle relative to the body tube and / or the axial position of the body tube, when the nozzle is spraying a section of the outer surface of the body tube, the body tube is controlled to rotate at a first rotational speed when the nozzle is in the upper semicircular region of that section; and when the nozzle is in the lower semicircular region of that section, the body tube is controlled to rotate at a second rotational speed; wherein the second rotational speed is greater than the first rotational speed; the first rotational speed is 4~5 r / min, and the second rotational speed is 6~8 r / min; in step S3, the instantaneous drying treatment specifically involves spraying an accelerated drying agent of a preset temperature onto the surface of the current section after spraying. Airflow is used to accelerate the evaporation of the solvent in the initial liquid film, thereby increasing the viscosity of the initial liquid film; in step S1, the specific way of dividing the space into multiple continuous sections is that multiple openable and closable axial partition plates are provided along the axial direction outside the tube. When a section is being processed, the nozzle and the device for performing the instantaneous drying treatment are located in the space corresponding to that section, and the axial partition plates at both ends of the space are in a closed state to form a relatively independent processing chamber; in step S2, the blackening solution includes copper sulfate, selenite, hydroquinone, and nitric acid; the blackening solution also includes hydroxypropyl methylcellulose.

2. The method for blackening the outer wall of an artillery barrel by spraying according to claim 1, characterized in that, The temperature of the accelerating airflow is 20℃~50℃.

3. The method for blackening the outer wall of an artillery barrel by spraying according to claim 1, characterized in that, The accelerating airflow is provided by a flat slit-type air knife, the length direction of which is parallel to the axial direction of the tube, and the distance between the air outlet of the air knife and the outer surface of the tube is 150mm~180mm.

4. The method for blackening the outer wall of an artillery barrel by spraying according to claim 1, characterized in that, The blackening solution contains the following components: copper sulfate 1-3 g / L, hydroquinone 2-4 g / L, selenite 3-5 g / L, nitric acid 30-40 g / L, hydroxypropyl methylcellulose 1-2 g / L, and the remainder is water.

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