A High-Efficiency Hot-Dip Galvanizing Method and System Based on Zinc Liquid Purification Process

Abstract

The application provides a high-efficiency hot galvanizing method based on a zinc liquid purification process, and the technical scheme is as follows: incoming material inspection, degreasing, pickling, rinsing, plating assisting, drying, hot galvanizing, zinc draining and cooling. The hot galvanizing process is dynamically matched with the gradual temperature control and the electromagnetic stirring intensity, and the multi-gradient temperature control coupling deslagging technology is adopted. Based on a temperature-iron content response curve, the process parameters and the temperature dynamic adjustment are accurately controlled, the zinc liquid purification and the deslagging process are synergistically optimized, and the zinc slag generation is reduced, the plating layer uniformity is improved, and the energy consumption is reduced.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, and more specifically, to a highly efficient hot-dip galvanizing method and system based on zinc bath purification process. Background Technology

[0002] Galvanizing technology, as an important means of metal corrosion protection, has wide applications in industrial production. Traditional hot-dip galvanizing processes suffer from problems such as large amounts of zinc dross generation, high energy consumption, and unstable coating quality. Zinc dross is mainly generated by the reaction of elements such as aluminum and iron in the zinc bath, which not only affects the surface quality of the coating but also wastes zinc resources. Existing technologies mainly treat zinc dross through post-processing separation, but this method cannot control zinc dross generation at its source and increases equipment investment and operating costs.

[0003] In terms of process control, conventional hot-dip galvanizing processes lack precise control over key parameters such as temperature, pickling, and fluxing, making it difficult to guarantee coating uniformity and adhesion. Particularly in zinc immersion temperature control, static constant temperature mode cannot meet the needs of workpieces of different specifications, easily causing localized overheating or insufficient temperature. Furthermore, uneven distribution of alloying elements in the zinc bath also affects coating performance.

[0004] In terms of equipment, traditional galvanizing systems lack intelligent control methods, resulting in poor coordination between processes and low waste heat utilization. Although some improved technologies have introduced devices such as electromagnetic stirring, they have failed to achieve dynamic matching between the temperature field and stirring intensity, leading to limited zinc dross suppression. Existing systems also lack comprehensive monitoring of process parameters, making it difficult to adjust deviations in the production process in a timely manner. Therefore, existing technologies urgently need improvement to address these issues. Summary of the Invention

[0005] The purpose of this application is to provide a highly efficient hot-dip galvanizing method and system based on zinc liquid purification process, which has the advantages of reducing zinc dross generation, improving coating uniformity and reducing energy consumption.

[0006] This application provides a highly efficient hot-dip galvanizing method based on zinc bath purification technology. The specific steps are: incoming material inspection → pickling → rinsing → fluxing → drying → hot-dip galvanizing → zinc leaching → cooling. A degreasing process is included between the incoming material inspection and pickling. The hot-dip galvanizing process employs progressive temperature control and dynamic matching of electromagnetic stirring intensity to reduce zinc dross formation. Specifically, in Stage 1 – Preheating Period: Before the steel pipe enters the zinc bath, the zinc bath temperature is set to 440-445℃, and the steel pipe is preheated to… ≥100℃; Stage 2 - Zinc Immersion Period: After the steel pipe is immersed, the temperature of the zinc bath rises to 450-455℃ at a rate of 1-2℃ / min, and is dynamically adjusted with the immersion time. The adjustment formula is: T=445+0.1×t, where t is the immersion time in seconds; Stage 3 - Zinc Removal Period: When the steel pipe is removed from the zinc bath, the temperature drops to 448-452℃ to reduce zinc bath oxidation; Stage 4 - Steady-State Period: When no steel pipe is immersed, the temperature returns to 445℃ to save energy and inhibit the Fe-Zn reaction.

[0007] Furthermore, this application also proposes that, in the efficient hot-dip galvanizing method of zinc bath purification process, incoming material inspection should meet the following requirements: surface oil contamination ≤50mg / m², oxide scale thickness ≤30μm; pickling time is 150 seconds, Fe residue after pickling ≤0.5g / m²; Cl- residue after rinsing ≤50mg / m²; flux pH value during fluxing process = 4.5-5, Fe in flux... 2+ Concentration ≤1g / L; the zinc bath temperature during hot-dip galvanizing is 445-455℃, the immersion time is 20-40 seconds, and the alloy content during hot-dip galvanizing is 0.04% aluminum, 0.03% nickel, and 0.002% copper.

[0008] Furthermore, this application also proposes that a waste heat recovery device be provided before the hot-dip galvanizing process to preheat the steel pipe to be galvanized using the waste heat of the zinc pot; and that the uniform distribution of alloy in the zinc liquid is achieved by placing a movable alloy cage during the hot-dip galvanizing process.

[0009] Furthermore, this application also proposes that the degreasing process adopts a combination of spraying and immersion, the degreasing process uses a NaOH solution at 70-80℃ with a concentration of 80-100g / L, and adds 5-10g / L of surfactant, the degreasing time is 5-8 minutes, and the pH value of the degreasing process is 12-13.

[0010] Furthermore, this application also proposes that the zinc liquid flow rate during the hot-dip galvanizing process is 0.1-0.3 m / s, and mechanical slag is removed every 2 hours. The slag removal equipment adopts an arc-shaped slag removal funnel with an opening curvature radius R=10cm, and the funnel body is uniformly provided with several zinc-draining holes with a diameter of 1.5cm. The slag removal funnel is made of silicon carbide coated steel.

[0011] Furthermore, this application also proposes that the time interval between the drying process and the hot-dip galvanizing process is <30 seconds; and the temperature difference between the fluxing process and the hot-dip galvanizing process is <50°C.

[0012] Furthermore, this application also proposes a system for implementing the above method, comprising: a pretreatment unit, a fluxing unit, a hot-dip galvanizing unit, and a post-treatment unit. A waste heat recovery unit is provided between the pretreatment unit and the hot-dip galvanizing unit for preheating the steel pipe to be galvanized using waste heat from the zinc pot. It also includes a control unit. The pretreatment unit includes an incoming material inspection device, a degreasing tank, a pickling tank, a rinsing tank, a fluxing tank, and a drying workshop. The hot-dip galvanizing unit includes a zinc pot. The post-treatment unit includes a zinc plating device and a cooling workshop. The incoming material inspection device is equipped with a barcode scanner and image acquisition components. The degreasing tank contains... The system is equipped with pH sensors and alkali concentration detectors. Both the pickling and fluxing tanks are equipped with pH sensors and Fe²⁺ detectors. The rinsing tank is equipped with a conductivity meter. The drying workshop uses an infrared drying oven and is equipped with temperature and humidity sensors. Temperature sensor arrays are installed at the bottom, middle, and edges of the zinc pot. The zinc pot also contains an electromagnetic stirrer, an online XRF analyzer, and a gas-fired heating module with electromagnetic auxiliary heating. The control unit includes a PLC controller, which communicates with the XRF analyzer, temperature sensors, and pH sensors to dynamically adjust process parameters.

[0013] Furthermore, this application also proposes that the zinc pot is connected to a ceramic filtration system with a filtration pore size ≤50μm; and that the rinsing process adopts a countercurrent rinsing system.

[0014] Furthermore, this application also proposes that the control unit further includes a cloud monitoring module and an audible and visual alarm module, enabling remote data viewing and abnormal alarms through the Industrial Internet of Things.

[0015] Furthermore, this application also proposes that the PLC controller has a built-in PID algorithm to automatically match the temperature curve according to the steel pipe diameter and wall thickness.

[0016] The advantages of this invention are:

[0017] (1) Adopting multi-gradient temperature control coupled slag removal technology: Based on the temperature-iron content response curve, the parameters of each process and the dynamic temperature adjustment are precisely controlled to achieve synergistic optimization of zinc liquid purification and slag removal process;

[0018] (2) The solubility of iron and the density of the coating are controlled by the aluminum-nickel-copper ternary alloy system. Through the synergistic effect of aluminum powder and nickel alloy, impurities such as iron and copper in zinc liquid are effectively adsorbed, and the viscosity of zinc liquid is significantly reduced by 20%.

[0019] (3) Arc-shaped slag removal funnel and efficient zinc slag cleaning technology: In response to the problem of low cleaning efficiency of traditional square slag removal tools, an innovative arc-shaped funnel is designed. Several zinc-draining holes (1.5cm in diameter) are evenly opened on the body of the funnel, and the opening curvature radius (R=10cm) is optimized through fluid simulation to reduce the resistance of zinc liquid backflow.

[0020] (4) Introduce an automated control unit to dynamically preprocess the parameter matching of each process and establish a closed-loop parameter linkage model for the entire production process from incoming material inspection to hot-dip galvanizing, thereby obtaining the best process conditions and improving galvanizing efficiency and quality.

[0021] (5) The technical solution of this application also incorporates a built-in PID algorithm to automatically match the temperature curve according to the diameter and wall thickness of the steel pipe. At the same time, it can combine CFD simulation to construct a zinc liquid flow field model, optimize the steel pipe immersion trajectory and angle to further improve the zinc liquid adhesion and reduce the surface defect rate. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of existing hot-dip galvanizing methods;

[0023] Figure 2 This is a process flow diagram of the hot-dip galvanizing method of Embodiment 3 of the present invention;

[0024] Figure 3 This is a schematic diagram of the arc-shaped slag-collecting funnel created in this invention;

[0025] Figure 4 This is a schematic diagram of the movable alloy cage created by the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be noted that the various installation methods and technical terms mentioned in this invention are all well-known technical terms in the relevant technical field, and therefore will not be explained further. Furthermore, the same reference numerals are used for the same components, but this does not affect, nor should it constitute, an accurate understanding of the technical solution by those skilled in the art.

[0028] In existing technologies, hot-dip galvanizing processes commonly face the problem of zinc dross formation leading to a decline in coating quality. Traditional methods maintain production by subsequently separating or removing zinc dross, but this approach cannot prevent zinc dross formation at its source and instead increases equipment wear and energy consumption. Zinc dross is mainly composed of intermetallic compounds of iron, aluminum, and zinc, and its formation is closely related to material pretreatment, flux composition, and hot-dip galvanizing parameters. Existing process parameters are poorly controlled, and there is insufficient coordination between different steps, resulting in the continuous entry of iron ions into the zinc bath, exacerbating zinc dross formation.

[0029] Based on the above research, this application proposes a high-efficiency hot-dip galvanizing method based on zinc bath purification technology. The process flow is as follows: incoming material inspection, degreasing, pickling, rinsing, fluxing, drying, hot-dip galvanizing, zinc leaching, and cooling. The hot-dip galvanizing process adopts progressive temperature control and dynamic matching of electromagnetic stirring intensity to reduce zinc dross formation. Specifically, the implementation method is as follows: Stage 1 - Preheating period: Before the steel pipe enters the zinc pot, the zinc bath temperature is set to 440-445℃, and the steel pipe is preheated to ≥100℃. Stage 2 - Zinc Immersion Period: After the steel pipe is immersed, the temperature of the zinc bath rises to 450-455℃ at a rate of 1-2℃ / min, and is dynamically adjusted with the immersion time. The adjustment formula is: T=445+0.1×t, where t is the immersion time in seconds; Stage 3 - Zinc Removal Period: When the steel pipe is removed from the zinc bath, the temperature drops to 448-452℃ to reduce zinc oxidation; Stage 4 - Steady-State Period: When no steel pipe is immersed, the temperature returns to 445℃ to save energy and inhibit the Fe-Zn reaction.

[0030] It should be noted that when the steel pipe wall thickness is greater than 5 mm, the heating rate in stage 2 should be increased to 2-3℃ / min to avoid uneven coating due to high heat capacity.

[0031] The progressive temperature control is specifically implemented by dividing the hot-dip galvanizing process into multiple temperature control stages. This can be achieved by linking a temperature sensor with a PLC controller, and by dynamically matching the temperature changes with the intensity of electromagnetic stirring to adjust the flow state of the zinc liquid, thereby suppressing the formation of intermetallic compounds.

[0032] Specifically, in the preheating stage, the steel pipe is preheated to above 100℃ before entering the zinc pot, avoiding localized sudden cooling of the zinc liquid caused by the low-temperature workpiece and reducing the rapid dissolution of Fe. In the zinc immersion stage, a linear temperature increase mechanism is activated, using the formula T=445+0.1t to achieve a positive correlation between temperature and immersion time, allowing the zinc liquid temperature to gradually increase as the reaction progresses, controlling the Fe-Zn reaction rate within a reasonable range. During the heating stage, the electromagnetic stirring device increases its operating frequency to promote uniform heat conduction in the zinc liquid and prevent the formation of localized overheating areas. In the zinc leaching stage, the zinc liquid temperature is controlled within the 448-452℃ range. At this point, the zinc liquid viscosity remains moderate, which is beneficial for the natural reflux of the surface zinc liquid and reduces the oxidation rate exposed to air. In the steady-state stage, the zinc liquid temperature is lowered to 445℃, suppressing the continuous reaction between Fe and zinc by reducing the base temperature, while also reducing energy consumption. The temperature parameters and electromagnetic stirring intensity at each stage are dynamically matched through a closed-loop control system, disrupting the formation conditions of the Fe-Al-Zn ternary compound.

[0033] Compared with existing technologies, this solution effectively suppresses intermetallic reactions caused by temperature abrupt changes by establishing a dynamic temperature-time correlation model and combining it with staged electromagnetic stirring intensity adjustment, thus solving the technical problem of the accumulation of zinc slag generation over production time.

[0034] Through the above technical solution, this application achieves coordinated control of the temperature field and flow field of the zinc bath, suppressing zinc dross formation from both thermodynamic and kinetic perspectives. Preheating treatment reduces the temperature difference impact between the workpiece and the zinc bath, the linear heating mechanism during zinc immersion balances the reaction rate and coating quality, and dynamic electromagnetic stirring effectively disperses the reaction products. This solution, while ensuring coating uniformity, significantly reduces the dross layer thickness at the bottom of the zinc pot, decreases the frequency of subsequent dross removal operations, and extends the service life of the zinc bath.

[0035] As a preferred embodiment, this application also proposes a high-efficiency hot-dip galvanizing method, which requires adjustments to the process parameters of each step to achieve high-efficiency hot-dip galvanizing through synergistic cooperation. Specific parameters are as follows: incoming material inspection meets the following requirements: surface oil contamination ≤ 50 mg / m², oxide scale thickness ≤ 30 μm; pickling time controlled between 120 and 300 seconds, Fe residue after pickling ≤ 0.5 g / m²; Cl after rinsing... - Residual amount ≤50mg / m²; the pH value of the flux is maintained in the weakly acidic range (4.5-5) during the fluxing process, and the Fe content in the flux is... 2+ Concentration ≤1g / L; The temperature of the zinc bath during hot-dip galvanizing is controlled at 445-455℃, and the immersion time is dynamically adjusted according to the temperature change. The alloy composition is added at 0.04%~0.25% aluminum, 0.025%~0.03% nickel, and 0.002%~0.0025% copper.

[0036] Compared to existing technologies, traditional processes typically optimize pickling or hot-dip plating parameters individually, lacking synergistic effects across the entire process. For example, conventional fluxes use a neutral environment, which can easily lead to continuous iron ion precipitation; the large temperature fluctuation range in hot-dip plating accelerates the iron-zinc reaction. This solution establishes a multi-stage, interconnected zinc slag suppression system by setting pretreatment cleanliness standards, pickling leaching thresholds, flux component stability control, and a synergistic mechanism for hot-dip plating alloys. This addresses the problem of limited effectiveness of single-process improvements.

[0037] To achieve the aforementioned preheating function, this application further proposes setting up a waste heat recovery device before the hot-dip galvanizing process. This device utilizes the waste heat from the zinc pot to preheat the steel pipe to be galvanized. Simultaneously, during the hot-dip galvanizing process, a movable alloy cage is used to achieve uniform alloy distribution in the molten zinc. Specifically, this is achieved by alternately placing zinc and aluminum blocks in the zinc pot within the movable alloy cage. This promotes the formation of a dynamic diffusion field of alloying elements in the molten zinc, breaking the concentration gradient. For the specific structure of the stainless steel cage, please refer to [reference needed]. Figure 4 The alloy cage includes a cage body 3 (the cage body is a hollow frame structure), a top cover 31, and a connecting arm 4. The connecting arm 4 has a connecting hole and is connected to the robotic arm through the connecting hole. In actual operation, the robotic arm is driven by a motor to realize the lifting and lowering of the entire alloy cage in the zinc pot, and to precisely control the placement position of the alloy.

[0038] The waste heat recovery device transfers heat lost from the zinc pot to a preheating device for the steel pipes to be treated via heat exchange equipment. This device recovers radiant heat from the zinc molten metal surface and conductive heat from the zinc pot walls, reducing external energy input and lowering the temperature difference when the steel pipes enter the zinc pot. Compared to existing technologies, traditional processes directly discharge waste heat from the zinc pot, resulting in energy waste, and the fixed-position feeding of alloying elements leads to uneven element distribution. This solution, through dual optimization of waste heat recovery and dynamic alloy distribution, achieves thermal energy recycling without requiring additional energy-consuming equipment. Furthermore, it breaks the static aggregation of alloying elements through mechanical displacement, solving the problem of zinc dross formation caused by temperature fluctuations and concentration gradients.

[0039] Through the above technical solutions, this application effectively reduces the energy consumption of zinc liquid temperature control, reduces the sudden change in Fe-Zn reaction rate caused by local overcooling or overheating, and suppresses the segregation of elements such as aluminum and iron in zinc liquid. It controls the formation of intermetallic compounds from two dimensions: thermodynamic conditions and compositional uniformity, thereby reducing the formation of zinc dross at the source.

[0040] As a further preferred embodiment, this application further proposes that the degreasing process adopts a combination of spraying and immersion. The degreasing process uses a NaOH solution at 70-80℃ with a concentration of 80-100g / L, and adds 5-10g / L of surfactant. The degreasing time is 5-8 minutes, and the pH value of the degreasing process is 12-13.

[0041] The combined spraying and immersion method refers to a composite cleaning mode that uses high-pressure spraying to remove surface deposits and immersion tanks for deep cleaning. This is achieved through a multi-angle rotating nozzle linked to the immersion tank. This combination can simultaneously treat contaminants on both flat and complex surfaces. The surfactant addition amount of 5–10 g / L refers to the mass concentration of nonionic surfactants in the degreasing solution. This concentration can be achieved through an online concentration monitor linked to an automatic dosing pump. This concentration range effectively reduces the surface tension of the solution and enhances the emulsification of grease.

[0042] Through the above technical solution, this application effectively solves the problem of subsequent process contamination caused by oil residue in the degreasing process, significantly reduces the Fe residue in the pickling process, and reduces the generation of impurities in the zinc bath. This solution, through a composite cleaning mechanism and precise parameter control, ensures the degreasing effect while avoiding resource waste caused by over-treatment, providing a reliable surface pretreatment guarantee for the hot-dip galvanizing process.

[0043] As a further preferred embodiment, this application further proposes controlling the zinc liquid flow rate within the range of 0.1 to 0.3 m / s during the hot-dip galvanizing process, and performing mechanical slag removal operation at a frequency of once every 2 hours. The slag removal equipment is a further improved structure based on a zinc pot slag removal device developed by the inventor. For the specific shape, please refer to a zinc pot slag removal device disclosed in application number 201910658498.3, which includes a station control mechanism 1 and a grabbing hopper mechanism. It should be emphasized that the slag removal funnel 2 in the grabbing hopper mechanism used in this application is an arc-shaped slag removal funnel 21 with an opening curvature radius of 10 cm. This funnel is made of silicon carbide coated steel material, and the arc-shaped slag removal funnel 21 has several zinc draining holes 22 with a diameter of 1.5 cm evenly opened on the body, which facilitates the drainage of zinc liquid while removing slag, resulting in high slag removal efficiency. For the specific structure, please refer to [link to relevant documentation]. Figure 3 .

[0044] The zinc liquid flow rate can be controlled by adjusting the power of the electromagnetic stirrer or the output parameters of the zinc pump. This flow rate range can balance the fluidity of the zinc liquid and the settling efficiency of the zinc dross. In summary, this solution, by limiting the flow rate range and improving the structure of the dross removal tool, combined with the selection of corrosion-resistant materials, achieves synergistic optimization of zinc dross removal efficiency and plating solution purity, reduces secondary diffusion of zinc dross caused by tool disturbance, and extends the service life of the dross removal tool, thereby ensuring the surface finish of the coating and reducing production and maintenance costs.

[0045] As a more preferred embodiment, this application further proposes a technical solution where the time interval between the drying process and the hot-dip galvanizing process is less than 30 seconds, and the temperature difference between the fluxing process and the hot-dip galvanizing process (the difference between the surface temperature of the workpiece after fluxing treatment and the temperature of the zinc liquid) is less than 50°C.

[0046] Specifically, the workpiece enters the zinc immersion plating process immediately after drying. The residual flux on the surface does not undergo oxidative decomposition, maintaining its activating effect on the substrate. By completing the transfer within 30 seconds, the workpiece surface microstructure remains wet, which is beneficial for the formation of a uniform coating through zinc immersion. Simultaneously, the temperature difference between the fluxing and immersion plating processes is controlled within 50°C to prevent the flux from forming crystalline particles due to sudden temperature drops, which would hinder the metallurgical bonding between the zinc and the substrate. This synergistic control strategy maintains the stability of the active components of the flux, reduces abnormal interfacial reactions caused by temperature fluctuations, and thus inhibits the excessive formation of Fe-Al-Zn intermetallic compounds.

[0047] As a more preferred embodiment, this application further proposes a system for implementing a hot-dip galvanizing method, including a pretreatment unit, a fluxing unit, a hot-dip galvanizing unit, and a post-treatment unit. A waste heat recovery unit is provided between the pretreatment unit and the hot-dip galvanizing unit, and a control unit is also included. The pretreatment unit includes an incoming material inspection device, a degreasing tank, a pickling tank, a rinsing tank, a fluxing tank, and a drying workshop. The hot-dip galvanizing unit includes a zinc pot, and the post-treatment unit includes a zinc plating device and a cooling workshop. The incoming material inspection device is equipped with a barcode scanner and image acquisition components. The degreasing tank is equipped with a pH sensor and an alkali concentration detector. Both the pickling tank and the fluxing tank are equipped with pH sensors and Fe²⁺ detectors. The rinsing tank is equipped with a conductivity meter. The drying workshop uses an infrared drying furnace and is equipped with temperature and humidity sensors. The zinc pot is equipped with bottom, middle, and edge temperature sensor arrays, an electromagnetic stirrer, an online XRF analyzer, and gas heating and electromagnetic auxiliary heating modules. The control unit includes a PLC controller, which is communicatively connected to the XRF analyzer, temperature sensors, and pH sensors.

[0048] Specifically, in the pretreatment unit, a pH sensor in the degreasing tank continuously monitors the acidity and alkalinity of the alkaline solution, while an alkali concentration detector ensures that the effective components of the degreasing agent are maintained within a set range, controlling the amount of residual oil at the source. In the pickling tank, an Fe²⁺ detector provides real-time feedback on iron ion concentration to prevent excessive pickling and subsequent over-corrosion of the substrate. The waste heat recovery unit transfers the heat energy emitted from the zinc pot to the preheating zone of the steel pipe to be plated via heat conduction pipelines, reducing the temperature gradient before the steel pipe enters the zinc pot. A temperature sensor array inside the zinc pot collects real-time temperature data from different areas, and an electromagnetic stirrer automatically adjusts the stirring intensity based on temperature distribution differences to eliminate localized overheating areas. An XRF online analyzer scans the zinc liquid composition at set intervals, and gas heating and electromagnetic auxiliary heating modules work together to compensate for temperature fluctuations. The PLC controller receives data uploaded from each detection unit and dynamically adjusts the heating power, stirring frequency, and process sequence through a preset algorithm, automatically matching the immersion temperature curve with the steel pipe specifications. This multi-parameter collaborative monitoring mechanism ensures that the amount of residual impurities in the pretreatment process meets standards, preventing contaminants from entering the zinc liquid at the process source. The automated control module replaces manual parameter adjustment, significantly improving process stability and product consistency.

[0049] As a more preferred embodiment, this application further proposes a zinc pot connected to a ceramic filter system with a filter pore size not exceeding 50 micrometers, and a countercurrent rinsing system for the rinsing process.

[0050] This application further proposes integrating a cloud monitoring module and an audible and visual alarm module into the control unit to achieve remote data viewing and anomaly alarms through the Industrial Internet of Things (IIoT). The cloud monitoring module can be implemented using a data platform system deployed on a server cluster, used to receive and store sensor data from the production site, while providing a visual interface for remote terminals. This module achieves bidirectional communication between the device layer and the cloud through an industrial protocol conversion gateway. The audible and visual alarm module refers to a hardware device with multimodal warning functions, specifically implemented using an alarm controller integrating a buzzer and LED warning lights. When abnormal parameters are detected, this module triggers a tiered warning by activating a combination of audible and visual signals of different frequencies. The IIoT can be implemented using a hybrid networking approach combining OPC UA and MQTT protocols to ensure real-time data transmission between the zinc liquid temperature sensor, pH sensor, and cloud monitoring module.

[0051] This application further proposes configuring a PLC controller with a built-in PID algorithm in the hot-dip galvanizing control system. This controller automatically matches the corresponding temperature control curve according to the pipe diameter and wall thickness parameters.

[0052] Specifically, when steel pipes of different specifications enter the zinc bath, the PLC controller reads the geometric parameters of the steel pipes, calls the preset pipe diameter-wall thickness heat conduction model, and calculates the temperature compensation required for the steel pipe to absorb heat. The PID algorithm adjusts the output power of the electromagnetic heating module in real time based on the deviation between the feedback value from the zinc bath temperature sensor and the target value, maintaining a dynamic balance in the zinc bath temperature during the immersion process. For example, for steel pipes with larger wall thicknesses, the system automatically extends the holding time and increases the initial heating power to prevent a sudden drop in localized temperature of the zinc bath due to excessively rapid heat absorption by the steel pipe. Thus, through the synergistic effect of the algorithm and the parameter model, temperature fluctuations caused by differences in steel pipe specifications are suppressed, reducing zinc dross formation at the source.

[0053] Through the above technical solution, this application solves the problem of zinc liquid temperature control deviation caused by the difference in steel pipe specifications, effectively suppresses the abnormal Fe-Zn reaction rate caused by zinc liquid temperature fluctuation, thereby reducing the amount of zinc dross generated and improving coating uniformity and surface quality.

[0054] Example 1: Galvanized Φ50mm×3mm steel pipe

[0055] (1) Pre-treatment: Incoming material conveyor line → Scan code to identify steel pipe specifications (pipe diameter / wall thickness) to ensure that the incoming material inspection meets the requirements of surface oil stains ≤50mg / m² and oxide scale thickness ≤30μm (if the incoming material exceeds the standard, it will be marked and further pre-treatment such as pre-degreasing process until the above conditions are met).

[0056] (2) Degreasing: 75℃ NaOH solution (concentration of 90g / L) + 8g / L surfactant, spray for 6 minutes, and keep the pH value between 12 and 13;

[0057] (3) Pickling: The pickling time is 150 seconds, the HCl concentration is 18%, and the Fe residue is 0.4 g / m²;

[0058] (4) Rinsing: After countercurrent rinsing, Cl - =45mg / m², and the wastewater is recycled;

[0059] (5) Hot-dip galvanizing: Flux: pH=4.8, Fe²⁺=0.8g / L, preheat to 110℃; Zinc immersion: initial temperature 442℃, increase to 450℃ according to T=445+0.1×t, immerse in zinc for 30 seconds (electromagnetic stirring speed is 0.15m / s); Alloy control: Al 0.04%, Ni 0.03%, copper 0.002%, the above alloys are evenly distributed in the zinc pot through an alloy cage.

[0060] (6) Post-treatment: after zinc plating, water cooling (50℃) is applied, and the coating thickness is 82±2μm.

[0061] Results: The coating is free of drips, with a thickness of 82±2μm. The amount of zinc dross generated is 0.8kg / ton of steel pipe, which is 68% less than that of the traditional process (Comparative Example 1). The defect rate is 0.5%.

[0062] Example 2: Galvanizing of Φ200mm×8mm thick-walled pipe

[0063] The different conditions from those in Example 1 were as follows: the heating rate in Stage 2 was increased to 2.5℃ / min, with a maximum temperature of 455℃; the electromagnetic stirring speed was 0.25m / s to suppress the Fe-Zn reaction; and the alloy composition was controlled as follows: Al 0.035%, Ni 0.03%, and Copper 0.002%; a slag removal funnel (1.5cm aperture) was used during the galvanizing process, and slag was removed every 2 hours.

[0064] Results: The coating is free of drips, with a thickness of 120±3μm. The amount of zinc dross generated is 1.0kg / ton of steel pipe, which is 42% less than that of traditional processes. The defect rate is 0.7%.

[0065] Example 3: Galvanized Φ50mm×3mm steel pipe

[0066] The different conditions set compared to Example 1 are as follows: an automated production line is adopted, and the PLC calls the CFD pre-stored flow field model based on the barcode data (pipe diameter / wall thickness) to optimize the immersion angle to (15° tilt); XRF provides real-time feedback on Al content, and the automatic feeding accuracy is ±0.002%.

[0067] Results: The coating is free of drips, with a thickness of 85±1μm, zinc dross generation is 1.0kg / ton of steel pipe, and the product qualification rate is 99.7%.

[0068] Comparative Example 1: Galvanized Φ50mm×3mm steel pipe (constant temperature galvanizing)

[0069] The operation was the same as in Example 1, but with different conditions: the hot-dip galvanizing process was carried out at a constant temperature of 450°C. The operation showed that the Fe-Zn reaction was intense, the amount of zinc dross reached 2.5 kg / ton, and the coating showed "teardrop" defects.

[0070] Comparative Example 2: Φ50mm×3mm galvanized steel pipe (without alloy cage)

[0071] The operation was the same as in Example 1, but with different conditions: the direct addition of Al blocks resulted in local concentration exceeding the standard (0.06%), causing cracks to appear in the coating.

[0072] Comparative Example 3: Galvanized steel pipe with diameter 50mm x 3mm (traditional slag removal)

[0073] The operation is the same as in Example 1, but with different conditions: unlike Example 1, the zinc pot temperature is directly raised to 450℃ and maintained at 445-455℃. Ordinary slag removal equipment leaves a lot of residual zinc liquid (about 15%) and has a slag leakage rate as high as 30%, requiring frequent shutdowns for cleaning.

[0074] Salt spray tests were conducted on the steel pipes prepared in the above embodiments and comparative examples, and the results are shown in Table 1:

[0075] Table 1 Corrosion Area Detection

[0076]

[0077] The steel pipes prepared in the above examples and comparative examples were immersed in copper sulfate solution five times to observe the uniformity of the zinc coating. The results are shown in Table 2. The steel pipes prepared in the above examples and comparative examples were placed between two flat plates and squeezed. When the distance between the two plates was 3 / 4 of the outer diameter of the steel pipe, the phenomenon of zinc coating peeling off the steel pipe was observed. The results are shown in Table 2.

[0078] Table 2 Inspection of the uniformity and adhesion of the zinc coating

[0079]

[0080] The above results show that the steel pipes produced by the technical solution of this application have the following properties: (1) corrosion resistance: neutral salt spray test ≥96h; (2) surface defect rate: zinc nodules ≤3 / pipe, scratches ≤0.05mm; at the same time, the galvanizing quality is significantly improved after the above method is optimized (the rate of missing galvanizing is <3%) and the amount of zinc dross generated is effectively controlled, which greatly saves costs and improves production efficiency.

[0081] In summary, the above technical solutions significantly reduce the amount of zinc dross generated during hot-dip galvanizing, effectively improving the surface finish and adhesion of the coating. Besides the synergistic effect of the hot-dip alloy ratio and temperature / time parameters suppressing excessive intermetallic compound formation, the systematic matching of parameters throughout the process further reduces the impurity content of the zinc bath, decreases the frequency of subsequent dross removal and equipment wear, and improves the stability of the coating quality.

[0082] For those skilled in the art, this invention is not limited to the details of the exemplary embodiments described above, and can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Any minor modifications, equivalent substitutions, and improvements made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-efficiency hot galvanizing method based on a zinc liquid purification process, the specific steps being incoming material inspection→ pickling→ rinsing→ plating aid→ drying→ hot dip galvanizing→ zinc draining→ cooling, characterized in that, The degreasing process is arranged between the incoming material inspection and the pickling, and the hot-dip galvanizing process adopts progressive temperature control and dynamic matching of electromagnetic stirring intensity to reduce the generation of zinc slag, and the specific implementation manner is as follows: stage 1-preheating period: before the steel pipe enters the zinc pot, the temperature of the zinc liquid is set to 440-445 DEG C, and the steel pipe is preheated to >= 100 DEG C; Stage 2-zinc immersion period: after the steel pipe is immersed, the temperature of the zinc liquid is increased to 450-455 DEG C at a rate of 1-2 DEG C / min, and is dynamically adjusted with the zinc immersion time, and the adjustment formula is: T = 445 + 0.1 x t, wherein t is the zinc immersion time in seconds; Stage 3-zinc draining period: when the steel pipe is taken out of the zinc liquid, the temperature is reduced to 448-452 DEG C to reduce the oxidation of the zinc liquid; Stage 4-steady period: when no steel pipe is immersed, the temperature is adjusted back to 445 DEG C to save energy and inhibit the Fe-Zn reaction; the flow rate of the zinc liquid in the hot-dip galvanizing process is 0.1-0.3 m / s, and the slag is mechanically removed once every 2 hours, the slag removal device adopts a circular arc-shaped slag removal funnel with an opening curvature radius R = 10 cm, and a plurality of zinc draining holes with a hole diameter of 1.5 cm are uniformly arranged on the funnel body.

2. The high-efficiency galvannealing method according to claim 1, characterized by, The incoming material inspection meets the requirements of surface oil stain ≤50 mg / m2 and scale thickness ≤30 μm; the pickling time is 120-300 seconds, Fe residual amount after pickling ≤0.5 g / m2; Cl - residual amount after rinsing ≤50 mg / m2; the pH value of the plating aid in the auxiliary plating process is 4.5-5, Fe 2+ concentration in the plating aid ≤1 g / L; the zinc liquid temperature in the hot-dip galvanizing process is 445-455 ℃, the zinc dipping time is 20-40 seconds, and the alloy content in the hot-dip galvanizing process is 0.04%-0.25% of aluminum, 0.025%-0.03% of nickel, and 0.002%-0.0025% of copper.

3. The high-efficiency galvannealing method according to claim 1 or 2, characterized by, The hot-dip galvanizing process is provided with a waste heat recovery device before the hot-dip galvanizing process for preheating the steel pipe to be plated by using the waste heat of the zinc pot; and the uniform distribution of the alloy in the zinc liquid is realized by placing a movable alloy cage in the zinc liquid.

4. The high-efficiency galvannealing method according to claim 1 or 2, characterized by, The degreasing process adopts a combination of spraying and immersion, the degreasing process uses a NaOH solution with a concentration of 80-100 g / L at 70-80 DEG C, and 5-10 g / L of a surfactant is added, the degreasing time is 5-8 minutes, and the pH value of the degreasing process is 12-13.

5. The high-efficiency galvannealing method according to claim 1 or 2, characterized by, The time interval between the drying process and the hot-dip galvanizing process is < 30 seconds; and the temperature difference between the plating aid process and the hot-dip galvanizing process is < 50 DEG C.

6. A system implementing the method of any of claims 1 or 2, comprising: The pretreatment unit, the plating aid unit, the hot-dip galvanizing unit and the post-treatment unit are provided with a waste heat recovery unit between the pretreatment unit and the hot-dip galvanizing unit, which is used for preheating the steel pipe to be plated by zinc pot waste heat; further comprising a control unit; wherein the pretreatment unit comprises a incoming material inspection device, a degreasing tank, an acid pickling tank, a rinsing tank, a plating aid tank and a drying workshop, the hot-dip galvanizing unit comprises a zinc pot, and the post-treatment unit comprises a zinc draining device and a cooling workshop; the incoming material inspection device is provided with a code scanning and image acquisition assembly, the degreasing tank is provided with a pH sensor and a lye concentration detector, the acid pickling tank and the plating aid tank are both provided with a pH sensor and a Fe 2+ detector, the rinsing tank is provided with a conductivity detector, the drying workshop adopts an infrared drying furnace, which is provided with a temperature and humidity sensor, the zinc pot is provided with an array of temperature sensors at the bottom, the middle and the edge respectively, and the zinc pot is further provided with an electromagnetic stirrer, an XRF online analyzer, a gas heating module and an electromagnetic auxiliary heating module; the control unit comprises a PLC controller, which is in communication connection with the XRF analyzer, the temperature sensor and the pH sensor, and is used for dynamically adjusting process parameters.

7. The system of claim 6, wherein, The zinc pot is also connected with a ceramic filtration system with a filtration pore size of <= 50 mu m; and the rinsing process adopts a countercurrent rinsing system.

8. The system of claim 6, wherein, The control unit further comprises a cloud monitoring module and an audible and visual alarm module, and remote data viewing and abnormal alarm are realized through industrial internet of things.

9. The system of claim 6, wherein, The PLC controller is built-in with a PID algorithm, and the temperature curve is automatically matched according to the pipe diameter and wall thickness of the steel pipe.

Images