Efficient hot galvanizing method and system based on zinc liquid purification process

Abstract

According to the technical scheme, the efficient hot-dip galvanizing method based on the zinc liquid purification technology comprises the following steps of incoming material inspection, degreasing, acid pickling, rinsing, plating assisting, drying, hot-dip galvanizing, zinc draining and cooling, and the hot-dip galvanizing process is dynamically matched with electromagnetic stirring strength through gradual temperature control; based on a temperature-iron content response curve, parameters of all procedures are accurately controlled, temperature dynamic adjustment is achieved, collaborative optimization of the zinc liquid purification and slag salvaging process is achieved, and the method has the advantages that zinc slag is reduced, the coating uniformity is improved, and energy consumption is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of metal surface treatment, and in particular to an efficient hot-dip galvanizing method and system based on a zinc liquid purification process. Background Art

[0002] Galvanizing technology, an important means of metal corrosion protection, is widely used in industrial production. Traditional hot-dip galvanizing processes suffer from issues such as high zinc slag production, high energy consumption, and unstable coating quality. Zinc slag, primarily generated by the reaction of elements such as aluminum and iron in the zinc bath, not only affects the surface quality of the coating but also wastes zinc resources. Existing technologies primarily treat zinc slag through post-processing separation, but this method fails to control slag 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 ensure coating uniformity and adhesion. In particular, static constant-temperature control during galvanizing cannot adapt to the needs of varying workpiece sizes, easily leading to localized overheating or insufficient temperatures. Furthermore, uneven distribution of alloying elements in the zinc bath can also affect coating performance.

[0004] Regarding equipment, traditional galvanizing systems lack intelligent control, resulting in poor coordination between processes and low waste heat utilization. While some improved technologies have incorporated devices like electromagnetic stirring, these fail to dynamically match the temperature field with stirring intensity, resulting in limited zinc slag suppression. Existing systems also lack comprehensive monitoring of process parameters, making it difficult to promptly adjust for deviations during production. Addressing these issues, existing technologies urgently need improvement. Summary of the Invention

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

[0006] The present application provides an efficient hot-dip galvanizing method based on zinc liquid purification process, the specific steps of which are incoming material inspection → pickling → rinsing → plating → drying → hot-dip galvanizing → zinc dipping → cooling, wherein a degreasing process is set between the incoming material inspection and pickling, and the hot-dip galvanizing process adopts progressive temperature control and dynamic matching of electromagnetic stirring intensity to reduce zinc slag generation, and the specific implementation method is as follows: Stage 1 - preheating period: before the steel pipe enters the zinc pot, the zinc liquid temperature is set to 440-445 ° C, and the steel pipe is preheated to ≥100℃; Stage 2 - zinc immersion period: after the steel pipe is immersed, the zinc liquid temperature rises to 450-455℃ at a rate of 1-2℃ / min, and is dynamically adjusted with the zinc immersion time. The adjustment formula is: T=445+0.1×t, where t is the zinc immersion time in seconds; Stage 3 - zinc drop period: when the steel pipe is taken out of the zinc liquid, the temperature drops to 448-452℃ to reduce zinc liquid oxidation; Stage 4 - steady state period: when no steel pipe is immersed, the temperature is adjusted back to 445℃ to save energy and inhibit Fe-Zn reaction.

[0007] Furthermore, the present application also proposes that in the efficient hot-dip galvanizing method of the zinc liquid purification process, the incoming material inspection meets the requirements of surface oil stain ≤50mg / m², oxide scale thickness ≤30μm; pickling time is 150 seconds, and the Fe residual amount after pickling is ≤0.5g / m²; Cl- residual amount after rinsing is ≤50mg / m²; the pH value of the plating agent during the plating process is 4.5-5, and the Fe2+ concentration in the plating agent is ≤1g / L; the zinc liquid temperature during the hot-dip galvanizing process is 445-455℃, the zinc immersion time is 20-40 seconds, and the alloy content of the hot-dip galvanizing process is 0.04% aluminum, 0.03% nickel, and 0.002% copper.

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

[0009] Furthermore, the present application also proposes that the degreasing process adopts a combination of spraying and immersion, the degreasing process uses a 70-80°C NaOH solution 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, the present application also proposes that the zinc liquid flow rate 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 equipment adopts an arc-shaped slag removal funnel with an opening curvature radius of R=10 cm, and a number of zinc removal holes with an aperture of 1.5 cm are evenly opened on the shaking body of the funnel. The slag removal funnel is made of silicon carbide coated steel.

[0011] Furthermore, the present application also proposes that the time interval between the drying process and the hot-dip galvanizing process is less than 30 seconds; and the temperature difference between the assist plating process and the hot-dip galvanizing process is less than 50°C.

[0012] Furthermore, the present application also proposes a system for implementing the above method, comprising: a pretreatment unit, a plating assist unit, a hot-dip galvanizing unit and a post-treatment unit, wherein a waste heat recovery unit is provided between the pretreatment unit and the hot-dip galvanizing unit for preheating the steel pipe to be plated using the waste heat of the zinc pot; and further comprising a control unit; wherein the pretreatment unit comprises an incoming material inspection device, a degreasing tank, a pickling tank, a rinsing tank, a plating assist tank and a drying workshop, the hot-dip galvanizing unit comprises a zinc pot, and the post-treatment unit comprises a zinc leaching device and a cooling workshop; a code scanning and image acquisition component is installed on the incoming material inspection device, and a A pH sensor and an alkali solution concentration detector are installed. pH sensors and Fe²⁺ detectors are installed in the pickling tank and the flux plating tank. A conductivity meter is installed in the rinsing tank. An infrared drying furnace is used in the drying workshop. Temperature and humidity sensors are installed in the workshop. Temperature sensor arrays are set at the bottom, middle and edge of the zinc pot. The zinc pot is also equipped with an electromagnetic stirrer, an XRF online analyzer, and a gas heating + electromagnetic auxiliary heating module. The control unit includes a PLC controller, which is connected to the XRF analyzer, temperature sensor, and pH sensor for dynamic adjustment of process parameters.

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

[0014] Furthermore, the present application also proposes that the control unit also includes a cloud monitoring module and an audio-visual alarm module to realize remote data viewing and abnormal alarm through the industrial Internet of Things.

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

[0016] The advantages of the present invention are:

[0017] 1) Adopting multi-gradient temperature control coupled slag removal technology: Based on the temperature-iron content response curve, the process parameters and temperature dynamic adjustment are precisely controlled to achieve the coordinated optimization of zinc liquid purification and slag removal process; 2) The solubility of iron and the density of the coating are regulated 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 the zinc liquid are effectively adsorbed, which significantly reduces the viscosity of the zinc liquid by 20%; 3) Arc-shaped slag removal funnel and zinc slag efficient cleaning technology: To address the low cleaning efficiency of traditional square slag removal tools, an innovative arc-shaped funnel is designed. Several zinc removal holes (aperture 1.5 cm) are evenly opened on the shaking body of the funnel, and the opening curvature radius (R=10 cm) is optimized through fluid simulation to reduce the reflux resistance of the zinc liquid.

[0018] 4) Introducing an automated control unit to dynamically pre-process parameter matching for 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 optimal process conditions and improving galvanizing efficiency and quality;

[0019] 5) The technical solution of this application also integrates 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 be combined with CFD simulation to build a zinc liquid flow field model, optimize the steel pipe immersion trajectory and angle, further increase the zinc liquid adhesion, and reduce the surface defect rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a process flow chart of the hot-dip galvanizing method of the prior art;

[0021] Figure 2 1 is a process flow chart of the hot-dip galvanizing method according to Example 3 of the present invention;

[0022] Figure 3 This is a structural diagram of the arc-shaped slag hopper created by the present invention;

[0023] Figure 4 It is a structural schematic diagram of the movable alloy cage created by the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] It should be noted that the various installation methods and technical terms mentioned in the present invention are technical terms that have long been clearly known in the relevant technical field and therefore will not be further explained. In addition, the same reference numerals are used for the same components, but this does not affect nor constitute an accurate understanding of the technical solution by those skilled in the art.

[0026] In existing technologies, hot-dip galvanizing processes generally face the problem of zinc slag formation, which leads to a decrease in coating quality. Traditional methods maintain production through subsequent separation or removal of zinc slag, but this method cannot suppress zinc slag formation at the source and instead increases equipment losses and energy consumption. Zinc slag is mainly composed of intermetallic compounds of iron, aluminum, and zinc. Its formation is closely related to material pretreatment, flux composition, and hot-dip galvanizing parameters. Existing process parameter control is extensive, and there is insufficient synergy between the various process steps, resulting in the continuous influx of iron ions into the zinc solution, exacerbating zinc slag formation.

[0027] Based on the above research, this application proposes an efficient hot-dip galvanizing method based on zinc liquid purification process. Its process flow is incoming material inspection, degreasing, pickling, rinsing, fluxing, drying, hot-dip galvanizing, zinc dipping, and cooling. The hot-dip galvanizing process adopts progressive temperature control and dynamic matching of electromagnetic stirring intensity to reduce zinc slag generation. The specific implementation method is as follows: Stage 1 - Preheating period: Before the steel pipe enters the zinc pot, the zinc liquid 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 zinc liquid temperature rises to 450-455℃ at a rate of 1-2℃ / min, and is dynamically adjusted with the zinc immersion time. The adjustment formula is: T=445+0.1×t, where t is the zinc immersion time in seconds; Stage 3 - zinc drop period: When the steel pipe is taken out of the zinc liquid, the temperature drops to 448-452℃ to reduce the oxidation of the zinc liquid; Stage 4 - steady state period: when there is no steel pipe immersed, the temperature is adjusted back to 445℃ to save energy and inhibit the Fe-Zn reaction.

[0028] It should be noted that when the wall thickness of the steel pipe is greater than 5mm, the heating rate in stage 2 is increased to 2-3℃ / min to avoid uneven coating due to large heat capacity.

[0029] Among them, the specific implementation method of progressive temperature control is to divide the hot-dip galvanizing process into multiple temperature control stages, which can be achieved through the linkage of temperature sensors and PLC controllers, and dynamically match the temperature changes through the electromagnetic stirring intensity to adjust the flow state of the zinc liquid, which is used to inhibit the formation of intermetallic compounds.

[0030] Specifically, during the preheating phase, the steel pipe is preheated to above 100°C before entering the zinc bath. This prevents localized quenching of the zinc bath caused by low-temperature workpieces and reduces the rapid dissolution of Fe. During the zinc immersion phase, a linear temperature ramp mechanism is activated. Using the formula T = 445 + 0.1t, a positive correlation is established between temperature and immersion time, allowing the zinc bath temperature to gradually increase as the reaction progresses, thereby controlling the Fe-Zn reaction rate within a reasonable range. During the heating phase, the electromagnetic stirring device increases its operating frequency to promote uniform heat transfer and prevent the formation of localized overheating areas. During the zinc immersion phase, the zinc bath temperature is controlled within a range of 448-452°C, maintaining a moderate viscosity that facilitates surface reflow and reduces oxidation rates when exposed to air. During the steady-state phase, the zinc bath temperature is adjusted back to 445°C. This lowers the base temperature to suppress the continued reaction between Fe and the bath, while also reducing energy consumption. A closed-loop control system dynamically matches the temperature parameters and electromagnetic stirring intensity at each stage, disrupting the formation conditions for Fe-Al-Zn ternary compounds.

[0031] Compared with the existing technology, this solution effectively suppresses the intermetallic reaction caused by temperature mutation by establishing a dynamic correlation model of temperature and time and combining it with staged electromagnetic stirring intensity adjustment, thus solving the technical problem of zinc slag generation accumulating with production time.

[0032] Through the above-mentioned technical solution, this application achieves coordinated control of the zinc bath's temperature and flow fields, suppressing zinc slag formation from both thermodynamic and kinetic perspectives. Preheating reduces the temperature differential shock between the workpiece and the zinc bath. The linear temperature rise mechanism during the zinc immersion phase balances the reaction rate and coating quality. Dynamic electromagnetic stirring effectively disperses the reaction products. While ensuring coating uniformity, this solution significantly reduces the thickness of the slag layer at the bottom of the zinc pot, reduces the frequency of subsequent slag removal operations, and extends the service life of the zinc bath.

[0033] As a preferred embodiment, the present application also proposes an efficient hot-dip galvanizing method, which needs to meet the process parameter adjustment of each process and achieve efficient hot-dip galvanizing through coordinated cooperation. The specific parameters are as follows: incoming material inspection meets the surface oil pollution ≤50mg / m², oxide scale thickness ≤30μm; pickling time is controlled within 120~300s, Fe residual amount after pickling ≤0.5g / m²; Cl after rinsing - Residue ≤ 50mg / m²; during the plating process, the pH value of the plating agent is maintained in the weak acid range (4.5-5), and the Fe 2+ Concentration ≤1g / L; during the hot-dip galvanizing process, the temperature of the zinc solution is controlled at 445-455℃, the zinc dipping time is dynamically adjusted to match the temperature change, and the alloy composition is added according to 0.25%~0.04% aluminum, 0.025%~0.03% nickel, and 0.02%~0.0025% copper.

[0034] Compared with existing technologies, traditional processes typically optimize pickling or hot-dip plating parameters separately, lacking synergistic coordination across the entire process. For example, conventional plating fluxes utilize a neutral environment, which can lead to continuous precipitation of iron ions; hot-dip plating also experiences wide temperature fluctuations, accelerating the iron-zinc reaction. This solution establishes a multi-step zinc slag suppression system by establishing pretreatment cleanliness standards, pickling dissolution thresholds, plating flux composition stability control, and a synergistic mechanism for hot-dip alloying. This approach addresses the limited effectiveness of single process improvements.

[0035] At the same time, in order to achieve the above-mentioned preheating function, the present application further proposes to set up a waste heat recovery device before the hot-dip galvanizing process, which is used to preheat the steel pipe to be plated by using the waste heat of the zinc pot. At the same time, during the hot-dip galvanizing process, the alloy is evenly distributed in the zinc liquid by placing a movable alloy cage. Specifically, the movable alloy cage is used to alternately place zinc blocks and aluminum blocks in the zinc pot, so as to promote the formation of a dynamic diffusion field of alloy elements in the zinc liquid and break the concentration gradient. The specific structure of the stainless steel cage can be seen in Figure 4 The alloy cage includes a cage body 3 (the cage body is a hollow frame structure), an upper cover 31 and a connecting arm 4. The connecting arm 4 is provided with 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 the position of the alloy is accurately controlled.

[0036] The waste heat recovery device transfers heat lost from the zinc pot to a device that preheats the steel pipes to be treated via heat exchange equipment. This device reduces external energy input by recovering radiant heat from the zinc liquid surface and heat conducted from the zinc pot walls, while also minimizing the temperature difference when the steel pipes enter the zinc pot. Compared to existing technologies, the traditional process wastes energy by directly discharging waste heat from the zinc pot, and the fixed-position dosing of alloys leads to uneven element distribution. This solution, through the dual optimization of waste heat recovery and dynamic alloy distribution, achieves thermal energy recycling without the need for additional energy-consuming equipment. It also breaks up the static aggregation of alloying elements through mechanical displacement, solving the problem of zinc slag formation caused by temperature fluctuations and concentration gradients.

[0037] Through the above technical solution, the present application effectively reduces the energy consumption of zinc liquid temperature control, reduces the sudden change of Fe-Zn reaction rate caused by local overcooling or overheating, and at the same time inhibits the segregation of elements such as aluminum and iron in zinc liquid, and controls the formation of intermetallic compounds from the two dimensions of thermodynamic conditions and composition uniformity, thereby reducing zinc slag formation at the source.

[0038] As a further preferred embodiment, the present application further proposes that the degreasing process adopts a combination of spraying and immersion, the degreasing process uses a 70-80°C NaOH solution 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.

[0039] The combined spray and immersion method involves a high-pressure spray to remove surface deposits and a deep immersion tank for cleaning. This is achieved by using a multi-angle rotating nozzle linked to an immersion tank. This combination can simultaneously treat contaminants on both flat and complex surfaces. The surfactant addition level of 5-10 g / L refers to the mass concentration of the non-ionic surfactant in the degreasing solution. This can be achieved by linking an online concentration monitor with an automatic dosing pump. This concentration range effectively reduces the surface tension of the solution and enhances the emulsification of oils and fats.

[0040] Through the above technical solution, this application effectively solves the problem of subsequent process contamination caused by residual oil in the degreasing process, significantly reduces the amount of Fe residue in the pickling process, and reduces the generation of impurities in the zinc solution. Through a composite cleaning mechanism and precise parameter control, this solution ensures effective degreasing while avoiding the waste of resources caused by excessive treatment, providing reliable surface pretreatment for the hot-dip galvanizing process.

[0041] As a further preferred embodiment, the present application further proposes to control the flow rate of the zinc liquid in the range of 0.1 to 0.3 m / s during the hot-dip galvanizing process, and implement mechanical slag removal operation at a frequency of once every 2 hours. The slag removal equipment is a structure further improved on the basis of a zinc pot slag removal device developed by the inventor. For its specific shape, please refer to a zinc pot slag cleaning device disclosed in application number 201910658498.3, which includes a work station control mechanism 1 and a grab hopper mechanism. It should be emphasized that the slag removal funnel 2 in the grab hopper mechanism used in the present application is an arc-shaped slag removal funnel 21 with an opening curvature radius of 10 cm. The funnel is made of silicon carbide coated steel material, and a number of zinc leaching holes 22 with an aperture of 1.5 cm are evenly opened on the shaking body of the arc-shaped slag removal funnel 21, which facilitates the leaching of zinc liquid while removing slag, and has high slag removal efficiency. For its specific structure, please refer to Figure 3 .

[0042] The zinc bath flow rate can be controlled by adjusting the electromagnetic stirrer power or zinc pump output parameters. This flow rate range balances zinc bath fluidity with zinc slag settling efficiency. In summary, this solution, by combining a limited flow rate range with improvements to the slag removal tool structure and the selection of corrosion-resistant materials, achieves a synergistic optimization of zinc slag removal efficiency and bath purity. This reduces secondary diffusion of zinc slag caused by tool disturbances, while extending the life of the slag removal tool, thereby ensuring a smooth coating surface and reducing production and maintenance costs.

[0043] As a more preferred embodiment, the present application further proposes a technical solution in which the time interval between the drying process and the hot-dip galvanizing process is less than 30 seconds, and the temperature difference between the electroplating process and the hot-dip galvanizing process (the difference between the surface temperature of the workpiece after the electroplating process and the temperature of the zinc liquid) is less than 50°C.

[0044] Specifically, once the workpiece is dried, it immediately enters the zinc bath immersion process. The residual flux on the surface does not undergo oxidative decomposition, maintaining its activation effect on the substrate. By limiting the transfer to 30 seconds, the workpiece surface microstructure is kept wet, which is conducive to the infiltration of the zinc bath to form a uniform coating. At the same time, the temperature difference between the flux-plating process and the immersion-plating process is controlled within 50°C to prevent the flux from forming crystalline particles due to a sudden drop in temperature, which would hinder the metallurgical bonding of the zinc bath to the substrate. This synergistic control strategy maintains the stability of the active ingredients of the flux, reduces abnormal interfacial reactions caused by temperature fluctuations, and thus inhibits the excessive formation of Fe-Al-Zn intermetallic compounds.

[0045] As a more preferred embodiment, the present application further proposes a system for implementing a hot-dip galvanizing method, comprising a pretreatment unit, a fluxing unit, a hot-dip galvanizing unit, and a post-treatment unit. A waste heat recovery unit is located between the pretreatment unit and the hot-dip galvanizing unit, as well as 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 chamber. The hot-dip galvanizing unit includes a zinc pot. The post-treatment unit includes a zinc droplet unit and a cooling chamber. The incoming material inspection device is equipped with a code scanning and image acquisition component. The degreasing tank is equipped with a pH sensor and an alkali solution concentration detector. The pickling tank and fluxing tank are both equipped with a pH sensor and a Fe²⁺ detector. The rinsing tank is equipped with a conductivity meter. The drying chamber 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 connected to the XRF analyzer, temperature sensor, and pH sensor.

[0046] Specifically, a pH sensor in the degreasing tank of the pretreatment unit continuously monitors the pH of the alkaline solution. An alkaline solution concentration meter ensures that the effective ingredients of the degreasing agent remain within the set range, effectively controlling residual oil and contamination at the source. A Fe²⁺ meter in the pickling tank provides real-time feedback on iron ion concentration to prevent excessive corrosion of the substrate caused by excessive pickling. A waste heat recovery unit transfers heat from the zinc pot to the preheating area of the steel pipe to be plated via a heat transfer pipe, reducing the temperature gradient before the steel pipe enters the zinc pot. An array of temperature sensors within the zinc pot collects real-time temperature data from different areas, and an electromagnetic stirrer automatically adjusts stirring intensity based on temperature distribution differences to eliminate localized overheating. An online XRF analyzer scans the zinc bath composition at set intervals, while gas-fired heating and electromagnetic auxiliary heating modules work together to compensate for temperature fluctuations. A PLC controller receives data uploaded by each detection unit and, using a pre-set algorithm, dynamically adjusts heating power, stirring frequency, and process timing to automatically match the zinc immersion temperature profile to the steel pipe specifications. A multi-parameter coordinated monitoring mechanism ensures that residual impurities in the pretreatment process meet standards, preventing contamination from entering the zinc bath at the source. The automated control module replaces manual parameter adjustment, significantly improving process stability and product consistency.

[0047] As a more preferred embodiment, the present application further proposes a zinc pot connected to a ceramic filtration system with a filtration pore size not exceeding 50 microns, and a countercurrent rinsing system is used in the rinsing process.

[0048] The present application further proposes to integrate a cloud monitoring module and an audible and visual alarm module into the control unit, and realize remote data viewing and abnormal alarm through the industrial Internet of Things. The cloud monitoring module can be implemented specifically by a data middle-end system deployed on a server cluster, which is used to receive and store sensor data from the production site, and provide a visual interface for remote terminal access. The module realizes two-way communication between the device layer and the cloud through an industrial protocol conversion gateway. Among them, the audible and visual alarm module refers to a hardware device with a multimodal warning function, which can be implemented specifically by an alarm controller that integrates a buzzer and an LED warning light. When a parameter abnormality is detected, the module triggers a graded warning by triggering a combination of audible and visual signals of different frequencies. The industrial Internet of Things can be implemented by a hybrid networking method of the OPC UA protocol and the MQTT protocol to ensure real-time data transmission between the zinc liquid temperature sensor, the pH sensor and the cloud monitoring module.

[0049] The present application further proposes configuring a PLC controller with a built-in PID algorithm in the hot-dip galvanizing control system, which automatically matches the corresponding temperature control curve according to the steel pipe diameter and wall thickness parameters.

[0050] Specifically, when steel pipes of varying specifications enter the zinc pot, the PLC controller reads the pipe's geometric parameters, invokes a preset diameter-wall thickness heat conduction model, and calculates the temperature compensation required for the pipe's heat absorption. The PID algorithm adjusts the output power of the electromagnetic heating module in real time based on the deviation between the zinc bath temperature sensor's feedback value and the target value, maintaining a dynamic equilibrium in the zinc bath temperature during the galvanizing process. For example, for thicker-walled steel pipes, the system automatically extends the holding time and increases the initial heating power to prevent a sudden drop in the zinc bath temperature due to rapid heat absorption. Thus, through the synergistic effect of the algorithm and parameter model, temperature fluctuations caused by differences in steel pipe specifications are suppressed, reducing zinc slag generation at the source.

[0051] Through the above technical solution, this application solves the problem of zinc liquid temperature control deviation caused by differences in steel pipe specifications, effectively suppresses the abnormal Fe-Zn reaction rate caused by zinc liquid temperature fluctuations, thereby reducing the amount of zinc slag generated and improving the uniformity and surface quality of the coating.

[0052] Example 1: Galvanizing of Φ50mm×3mm steel pipe

[0053] (1) Pretreatment: Incoming material conveyor line → Scan the code to identify the steel pipe specifications (pipe diameter / wall thickness), and ensure that the incoming material inspection meets the surface oil pollution ≤50mg / m² and the oxide scale thickness ≤30μm (if the incoming material exceeds the standard, it will be marked and further pretreated, such as pre-degreasing process, until the above conditions are met);

[0054] (2) Degreasing: 75℃ NaOH solution (concentration 90g / L) + 8g / L surfactant, spray for 6 minutes, maintain the pH value between 12-13;

[0055] (3) Pickling: Pickling time is 150 seconds, HCl concentration is 18%, and Fe residual is 0.4 g / m²;

[0056] (4) Rinse: After countercurrent rinsing, Cl - =45mg / m², and recycle the wastewater;

[0057] (5) Hot-dip galvanizing: plating aid: pH = 4.8, Fe²⁺ = 0.8 g / L, preheating to 110 °C; zinc immersion: initial temperature 442 °C, heating to 450 °C according to T = 445 + 0.1 × t, zinc immersion for 30 seconds (electromagnetic stirring speed 0.15 m / s); alloy control: Al 0.04%, Ni 0.03%, Cu 0.002%, the above alloys are evenly distributed in the zinc pot through the alloy cage.

[0058] (6) Post-treatment: Zinc casting followed by water cooling (50°C), coating thickness 82±2μm.

[0059] Effect: The coating has no sag, the coating thickness is 82±2μm, the zinc slag generation is 0.8kg / ton steel pipe, and the zinc slag generation is 68% less than that of the traditional process (Comparative Document 1), and the defect rate is 0.5%.

[0060] Example 2: Galvanizing of Φ200mm×8mm Thick-Walled Pipe

[0061] Different conditions were set from those in Example 1: the heating rate in stage 2 was increased to 2.5°C / min, with a maximum temperature of 455°C; the electromagnetic stirring speed was 0.25 m / s to suppress the Fe-Zn reaction; the alloy content was controlled as follows: Al 0.035%, Ni 0.03%, and Cu 0.002%; a slag hopper (1.5 cm aperture) was used during the galvanizing process, and the slag was removed every 2 hours.

[0062] Effect: The coating has no sag, thickness is 120±3μm, zinc slag generation is 1.0kg / ton steel pipe, which is 42% less than that of traditional process, and defect rate is 0.7%.

[0063] Example 3: Galvanizing of Φ50mm×3mm steel pipe

[0064] Different conditions from those in Example 1: an automated production line was used, and the CFD pre-stored flow field model was called by PLC based on the scanned data (tube diameter / wall thickness), with the optimized immersion angle being (15° tilt); XRF provided real-time feedback on the Al content, and the automatic feeding accuracy was ±0.002%.

[0065] Effect: The coating has no sag, the thickness is 85±1μm, the zinc slag generation amount is 1.0kg / ton steel pipe, and the product qualification rate is 99.7%, which is 2.6 times higher than that of comparative example 3.

[0066] Comparative Example 1: Φ50mm×3mm steel pipe galvanizing (constant temperature galvanizing)

[0067] The operation was the same as that in Example 1, but the conditions were different from those in Example 1: the hot-dip galvanizing process was performed at a constant temperature of 450° C. The operation process showed that the Fe-Zn reaction was violent, the amount of zinc slag reached 2.5 kg / ton, and the coating had a "teardrop" defect.

[0068] Comparative Example 2: Φ50mm×3mm galvanized steel pipe (without alloy cage)

[0069] The same operation as in Example 1 was performed, but the conditions were different from those in Example 1: direct addition of Al blocks resulted in a local concentration exceeding the standard (0.06%), and cracks appeared in the coating.

[0070] Comparative Example 3: Galvanizing of Φ50mm×3mm Steel Pipe (Traditional Slag Removal)

[0071] The same operation as in Example 1 was performed, with the following differences in the conditions: The difference from Example 1 was that the zinc pot temperature was directly raised to 450°C and maintained at 445-455°C. Conventional slag removal equipment produces a high level of residual zinc liquid (approximately 15%) and a slag leakage rate as high as 30%, requiring frequent shutdowns for cleaning.

[0072] The steel pipes prepared in the above examples and comparative examples were subjected to salt spray tests. The results are shown in Table 1:

[0073] Table 1 Corrosion area detection

[0074]

[0075] The steel pipes prepared in the above embodiments and comparative examples were immersed in a copper sulfate solution for 5 consecutive times to observe the uniformity of the zinc coating. The results are shown in Table 2. The above embodiments and comparative examples were squeezed between two flat plates with the distance between the two plates being 3 / 4 of the outer diameter of the steel pipe. The peeling phenomenon of the zinc coating on the steel pipes was observed. The results are shown in Table 2.

[0076] Table 2 Uniformity and adhesion test of galvanized layer

[0077]

[0078] The above results show that: the steel pipe produced by the technical solution of the present application (1) has corrosion resistance: neutral salt spray test ≥96h; (2) surface defect rate: zinc nodules ≤3 / tube, scratches ≤0.05mm; at the same time, after the optimization of the above method, the galvanizing quality is significantly improved (leakage rate <3%) and the amount of zinc slag generated is effectively controlled, which greatly saves costs and improves production efficiency.

[0079] In summary, the above technical solution significantly reduces the amount of zinc slag generated during the hot-dip galvanizing process, effectively improving the surface finish and adhesion of the coating. In addition to the synergistic effect of the hot-dip alloy ratio and temperature-time parameters, which inhibits the excessive formation of intermetallic compounds, the systematic matching of all process parameters further reduces the impurity content of the zinc solution, reduces the subsequent slag removal frequency and equipment loss, and improves the stability of the coating quality.

[0080] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention may be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the foregoing description. It is intended that all variations that fall within the meaning and range of equivalents of the claims be embraced within the present invention. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any minor modifications, equivalent replacements, and improvements made to the above embodiments based on the technical essence of the present invention shall be included in the scope of protection of the technical solution of the present invention.

Claims

1. An efficient hot-dip galvanizing method based on zinc liquid purification process, the specific steps are: incoming material inspection → pickling → rinsing → flux plating → drying → hot-dip galvanizing → zinc dipping → cooling, characterized in that: A degreasing process is set between the incoming material inspection and pickling. The hot-dip galvanizing process adopts progressive temperature control and dynamic matching of electromagnetic stirring intensity to reduce the generation of zinc slag. The specific implementation method is as follows: Stage 1 - Preheating period: Before the steel pipe enters the zinc pot, the zinc liquid temperature is set to 440-445℃, and the steel pipe is preheated to ≥100℃; Stage 2 - Galvanizing period: After the steel pipe is immersed, the temperature of the zinc solution is raised to 450-455℃ at a rate of 1-2℃ / min and is dynamically adjusted with the galvanizing time. The adjustment formula is: T=445+0.1×t, where t is the galvanizing time in seconds; Stage 3 - Zinc Drainage: When the steel pipe is removed from the zinc solution, the temperature drops to 448-452°C to reduce zinc oxidation. Stage 4 - Steady State: When no steel pipe is immersed, the temperature is adjusted back to 445°C to save energy and suppress the Fe-Zn reaction.

2. The high-efficiency hot-dip galvanizing method according to claim 1, characterized in that: The incoming material inspection meets the requirements of surface oil pollution ≤ 50mg / m², oxide scale thickness ≤ 30μm; the pickling time is 120-300s, and the Fe residue after pickling is ≤ 0.5g / m²; after rinsing, Cl - Residue ≤ 50mg / m²; pH value of flux during flux plating = 4.5-5, Fe in flux 2+ The concentration is ≤1g / L; the zinc liquid temperature of the hot-dip galvanizing process is 445-455°C, the zinc dipping time is 20-40 seconds, and the alloy content of the hot-dip galvanizing process is 0.25% to 0.04% aluminum, 0.025% to 0.03% nickel, and 0.02% to 0.0025% copper.

3. The high-efficiency hot-dip galvanizing method according to claim 1 or 2, characterized in that: A waste heat recovery device is provided before the hot dip galvanizing process, which is used to preheat the steel pipe to be plated using the waste heat of the zinc pot; and during the hot dip galvanizing process, the alloy in the zinc liquid is evenly distributed by placing a movable alloy cage.

4. The high-efficiency hot-dip galvanizing method according to claim 1 or 2, characterized in that: The degreasing process adopts a combination of spraying and dipping. The degreasing process uses a 70-80°C NaOH solution with a concentration of 80-100g / L and 5-10g / L of surfactant. The degreasing time is 5-8 minutes and the pH value of the degreasing process is 12-13.

5. The high-efficiency hot-dip galvanizing method according to claim 1 or 2, characterized in that: The zinc liquid flow rate during 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 equipment adopts an arc-shaped slag removal funnel with an opening curvature radius R=10 cm, and a number of zinc removal holes with an aperture of 1.5 cm are evenly opened on the shaking body of the funnel.

6. The high-efficiency hot-dip galvanizing method according to claim 1 or 2, characterized in that: The time interval between the drying process and the hot-dip galvanizing process is less than 30 seconds; the temperature difference between the assist plating process and the hot-dip galvanizing process is less than 50°C.

7. A system for implementing the method according to any one of claims 1 or 2, comprising: A pretreatment unit, a plating-boosting unit, a hot-dip galvanizing unit and a post-treatment unit, wherein a waste heat recovery unit is provided between the pretreatment unit and the hot-dip galvanizing unit for preheating the steel pipe to be plated using the waste heat of the zinc pot; and a control unit is also provided; wherein the pretreatment unit includes an incoming material inspection device, a degreasing tank, a pickling tank, a rinsing tank, a plating-boosting tank and a drying workshop, the hot-dip galvanizing unit includes a zinc pot, and the post-treatment unit includes a zinc leaching device and a cooling workshop; the incoming material inspection device is equipped with a code scanning and image acquisition component, the degreasing tank is equipped with a pH sensor and an alkali solution concentration detector, the pickling tank and the plating-boosting tank are both equipped with a pH sensor and a Fe 2+ The detector is installed in the rinsing tank. A conductivity meter is installed in the drying workshop. The drying workshop adopts an infrared drying furnace. Temperature and humidity sensors are installed in the workshop. Temperature sensor arrays are set at the bottom, middle and edge of the zinc pot respectively. The zinc pot is also equipped with an electromagnetic stirrer, an XRF online analyzer, and a gas heating + electromagnetic auxiliary heating module; the control unit includes a PLC controller, which is communicated with the XRF analyzer, temperature sensor, and pH sensor for dynamically adjusting process parameters.

8. The system according to claim 7, characterized in that The zinc pot is also connected to a ceramic filtration system with a filtration pore size of ≤50 μm; the rinsing process adopts a countercurrent rinsing system.

9. The system according to claim 7, wherein: The control unit also includes a cloud monitoring module and an audible and visual alarm module, which enable remote data viewing and abnormal alarms through the industrial Internet of Things.

10. The system according to claim 7, wherein: The PLC controller has a built-in PID algorithm that automatically matches the temperature curve according to the diameter and wall thickness of the steel pipe. It can also combine CFD simulation to build a zinc liquid flow field model to optimize the steel pipe immersion trajectory and angle.

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