Self-repairing galvanized aluminum-magnesium steel plate coating alloy design method and hot dipping process

Abstract

The invention discloses a self-repairing galvanized aluminum-magnesium steel plate coating alloy design method and a hot dipping process, and relates to the technical field of alloy design, the method comprises the following steps: calculating crystallization pressure safety redundancy according to the maximum chlorine salt concentration and thermodynamic temperature of a working state area; calculating the comprehensive interface energy of the double-layer plating layer structure of the to-be-plated steel strip based on the crystallization pressure safety redundancy; quantifying a crack tip passivation factor of an interface crack tip area in the metallurgical bonding interface, and calculating corrected interface energy of the metallurgical bonding interface based on the crack tip passivation factor and the comprehensive interface energy; and salt elimination micro-grooves are formed in the surface of the to-be-plated steel strip, qualification judgment is conducted on the to-be-plated steel strip based on the corrected interface energy, and the micro-groove steel strip is obtained. The salt crystal splitting resistance of the plating layer is improved, and the corrosion resistance service life of the plating layer is prolonged.

Description

Technical Field

[0001] This invention relates to the field of alloy design technology, and in particular to a self-healing alloy design method and hot-dip galvanizing process for galvanized aluminum-magnesium steel sheet. Background Technology

[0002] In complex service environments such as marine engineering facilities, bridge supports, automobile chassis, and power transmission towers, galvanized aluminum-magnesium steel sheets, as important structural and protective materials, are highly susceptible to corrosion damage when exposed to chloride-containing environments for extended periods. Particularly in confined spaces such as steel component joints, chloride solutions continuously accumulate under wet-dry cycles, forming needle-like salt crystals when supersaturated. During crystallization, the salt crystals expand in volume, exerting significant crystallization pressure on the interface between the coating and the steel substrate. This pressure often exceeds the interfacial adhesion strength, inducing interfacial delamination and coating splitting, rapidly leading to exposed red rust and corrosion propagation. With increasing service life, failure to effectively suppress the crystallization-induced cracking effect of salt crystals will result in a decline in the overall mechanical properties of the steel sheet, a shortened service life, and even jeopardize the structural safety and reliability.

[0003] However, existing design methods for galvanized aluminum-magnesium steel sheets generally fail to systematically quantify salt crystallization pressure and lack effective design mechanisms to prevent interfacial delamination caused by crystallization pressure. In typical service environments such as lap joints, salt crystallization pressure can reach tens of megapascals, significantly higher than the bonding strength of conventional coatings, easily triggering interfacial splitting failure. Without quantitative assessment of the effects of crystallization pressure and effective assurance of the metallurgical bonding interface's resistance to splitting, the coating will frequently fail under complex operating conditions, leading to a loss of protective effect, increased structural maintenance costs, and potential safety risks. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing galvanized aluminum-magnesium steel sheet design methods, which generally fail to systematically quantify salt crystallization pressure and lack effective design mechanisms to prevent interface peeling caused by crystallization pressure. Therefore, this invention proposes a self-healing galvanized aluminum-magnesium steel sheet coating alloy design method and hot-dip galvanizing process.

[0005] To address the problems existing in the prior art, the present invention adopts the following technical solution:

[0006] A design method for a self-healing galvanized aluminum-magnesium steel sheet coating alloy includes:

[0007] S1. Calculate the safety margin of crystallization pressure based on the maximum chloride concentration and thermodynamic temperature in the working state area;

[0008] S2. Calculate the comprehensive interfacial energy of the double-layer coating structure of the steel strip to be coated based on the safety margin of crystallization pressure;

[0009] S3. Quantify the crack tip passivation factor in the crack tip region of the metallurgical bonding interface, and calculate the corrected interface energy of the metallurgical bonding interface based on the crack tip passivation factor and the comprehensive interface energy.

[0010] S4. Salt drainage micro-grooves are formed on the surface of the steel strip to be plated. Based on the modified interface, the steel strip to be plated can be qualified, and micro-grooved steel strip is obtained.

[0011] S5. Perform silanization treatment on the microgrooved steel strip to form a dry silane film on the surface of the microgrooved steel strip, and mark the microgrooved steel strip as silanized steel strip.

[0012] S6. Based on silanized steel strip, lap joint test specimens are made, and the lap joint test specimens are judged to be qualified in order to obtain qualified test specimens.

[0013] Preferably, the safety margin for crystallization pressure is calculated based on the maximum chloride concentration and thermodynamic temperature in the operating region, including:

[0014] Locate the working area of ​​the lap joint between two steel components;

[0015] The chloride concentration in the working area is continuously monitored to record the chloride concentration change curve;

[0016] Peak values ​​were extracted from the change curves to obtain the maximum chloride concentration.

[0017] The temperature of the steel plate in the working area is monitored synchronously. When the chloride concentration in the working area reaches the maximum chloride concentration, the real-time steel plate temperature corresponding to the maximum chloride concentration is recorded.

[0018] Convert the real-time steel plate temperature to the thermodynamic temperature at which the salt solution crystallizes.

[0019] Positioning the metallurgical bonding interface between the zinc-aluminum-magnesium coating and the steel substrate;

[0020] Based on the thermodynamic temperature of the steel plate, the crystallization pressure exerted by salt crystals at the lap joint on the metallurgical interface at the gap triple line is calculated. The formula for calculating the crystallization pressure is as follows:

[0021]

[0022] In the formula, P crys It is the crystallization pressure, R is the universal gas constant, T is the thermodynamic temperature, and V is the temperature. m C is the molar volume of the salt crystal. max It is the maximum chloride concentration, C sat It is the saturated solubility of the target salt corresponding to the salt crystal. It is the natural logarithm of the concentration ratio;

[0023] Multiply the crystallization pressure by the preset safety margin to obtain the crystallization pressure safety margin.

[0024] Preferably, the comprehensive interfacial energy of the double-layer coating structure of the steel strip to be coated is calculated based on the safety margin of crystallization pressure, including:

[0025] The first thickness parameter of the soft prepreg layer in the double-layer coating structure and the second thickness parameter of the tough body layer in the double-layer coating structure are set according to the safety margin of crystallization pressure.

[0026] A pre-impregnated alloy bath with zinc as the base and aluminum accounting for 15% by mass was prepared, and the temperature of the alloy bath was adjusted to 460℃, and a main alloy bath was prepared.

[0027] The immersion time and pulling speed of the steel strip to be plated are controlled based on the first thickness parameter and the second thickness parameter.

[0028] The pretreated steel strip to be plated is sequentially immersed in a pre-impregnation alloy bath and a main alloy bath. Under the constraints of immersion time and pulling speed, a double-layer coating structure consisting of a soft pre-impregnation layer and a tough main layer is formed on the surface of the steel strip to be plated.

[0029] The comprehensive interface energy of the double-layer coating structure is calculated based on the first and second thickness parameters. The formula for calculating the comprehensive interface energy is as follows:

[0030]

[0031] In the formula, Γ total It is the comprehensive interfacial energy of the double-layer coating structure, Γ soft It is the interfacial energy of the soft prepreg layer, t soft It is the first thickness parameter, Γ tough It is the interfacial energy of the tough main body layer, t tough It is the second thickness parameter.

[0032] Preferably, the crack tip passivation factor of the interfacial crack tip region in the metallurgical bonding interface is quantified, and the corrected interfacial energy of the metallurgical bonding interface is calculated based on the crack tip passivation factor and the comprehensive interfacial energy, including:

[0033] In-Al master alloy wire and Sn-Zn master alloy wire are fed into the main alloy bath, and In and Sn are incorporated into the tough main body layer.

[0034] The toughened substrate layer is subjected to rapid cooling treatment to precipitate β(In / Sn)-Zn particles at the metallurgical bonding interface;

[0035] The crack tip passivation characteristics of the interfacial crack tip region containing β(In / Sn)-Zn particles were tested and analyzed to obtain the crack tip passivation factor. The crack tip passivation characteristics test and analysis included: salt crystal crystallization pressure cracking test and passivation effect quantitative analysis.

[0036] The crack tip passivation factor is multiplied by the comprehensive interface energy to calculate the corrected interface energy of the metallurgical bonding interface.

[0037] Preferably, a salt-removing microgroove is formed on the surface of the steel strip to be plated, and the steel strip to be plated is qualified based on the modified interface, resulting in a microgrooved steel strip, comprising:

[0038] The steel strip to be plated is conveyed to the knurling equipment, and the linear speed of the knurling rollers in the knurling equipment is synchronized with the running speed of the steel strip to be plated.

[0039] Set the knurling pressure of the knurling roller;

[0040] The surface of the steel strip to be plated is knurled by knurling pressure to form salt drainage micro-grooves.

[0041] Once the depth of the salt drainage micro-ditch reaches the preset geometric depth, measure the actual width and actual depth of the salt drainage micro-ditch.

[0042] The actual capillary siphon height of the salt drainage micro-channel is calculated based on the actual micro-channel width and actual micro-channel depth.

[0043] If the actual capillary siphon height is greater than or equal to the target capillary siphon height of the salt drainage micro-ditch, and the corrected interface energy is greater than or equal to the interface requirement value of the metallurgical bonding interface, then the steel strip to be plated will be marked as a micro-ditch steel strip; otherwise, the steel strip to be plated will be marked as a substandard steel strip.

[0044] Preferably, the microgrooved steel strip is subjected to silanization treatment to form a dry silane film on the surface of the microgrooved steel strip, comprising:

[0045] Cleaning and coating treatment of microgrooved steel strip;

[0046] Spray hydroxyl-terminated silane sol onto the surface of the microgrooved steel strip until the measured wet film thickness of the silane wet film reaches the preset thickness value, then stop spraying.

[0047] The microgrooved steel strip is dried to form a dry silane film on its surface.

[0048] Reverse pressure verification was performed on the dry silane membrane.

[0049] Preferably, lap joint specimens are prepared based on silanized steel strips, and the lap joint specimens are judged to be qualified to obtain qualified specimens, including:

[0050] The silanized steel strip was lapped and assembled to obtain lapped specimens;

[0051] The lap joint specimens were subjected to performance tests, including salt spray tests and peel tests.

[0052] After the performance test is completed, if the lapped specimen does not show interface delamination or exposed red rust, it is determined to be a qualified specimen; otherwise, it is determined to be an unqualified specimen and the test is returned to S1.

[0053] To address the aforementioned issues, this invention also provides a self-healing hot-dip galvanized aluminum-magnesium steel sheet coating alloy hot-dip galvanizing process, including the aforementioned self-healing galvanized aluminum-magnesium steel sheet coating alloy design method.

[0054] Compared with the prior art, the beneficial effects of the present invention are:

[0055] 1. This invention calculates the crystallization pressure and sets a safety margin for the crystallization pressure by utilizing the maximum chloride salt concentration and corresponding thermodynamic temperature in the working state region. This is used as the boundary condition for coating design. It can accurately predict the intensity of the effect that salt crystals may exert on the metallurgical bonding interface in the service environment during the design stage. This avoids the problem of insufficient interface crack resistance caused by the lack of quantitative assessment in traditional methods, and significantly improves the targeting and reliability of the coating.

[0056] 2. This invention constructs a double-layer coating structure and utilizes the thickness parameter allocation of the soft prepreg layer and the tough substrate layer to balance the interfacial bonding energy and overall mechanical properties. The soft prepreg layer enhances the wettability and transition buffering capacity of the coating with the steel substrate, while the tough substrate layer improves crack resistance and load-bearing capacity. The thickness of both is precisely constrained by the safety margin of crystallization pressure, ensuring that the coating remains stable when subjected to salt crystallization pressure, thereby improving the coating's resistance to salt crystal splitting and corrosion resistance life.

[0057] 3. In the coating formation process, this invention introduces alloying control of In-Al master alloy wire and Sn-Zn master alloy wire, which causes β(In / Sn)-Zn particles to precipitate at the metallurgical interface. The β(In / Sn)-Zn particles can play a role in crack tip passivation in the crack tip region. The overall interface energy is corrected by quantitative analysis of the passivation factor, thereby improving the interface's resistance to salt crystallization pressure. Through this microstructure control and interface energy correction mechanism, the coating system is endowed with self-healing characteristics while effectively preventing the propagation of interface crack tips, thus solving the problems of interface peeling and red rust exposure. Attached Figure Description

[0058] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0059] Figure 1 This is a flowchart illustrating a self-healing galvanized aluminum-magnesium steel plate coating alloy design method according to an embodiment of the present invention. Detailed Implementation

[0060] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0061] Example: This example provides a design method for a self-healing galvanized aluminum-magnesium steel plate coating alloy. See [link to example]. Figure 1 Specifically, including:

[0062] S1. Calculate the safety margin of crystallization pressure based on the maximum chloride concentration and thermodynamic temperature in the working state area;

[0063] In embodiments of the present invention, the safety margin of crystallization pressure is calculated based on the maximum chloride concentration and thermodynamic temperature of the operating region, including:

[0064] Locate the working area of ​​the lap joint between two steel components;

[0065] Specifically, an lap joint refers to the narrow gap between the overlapping parts formed when two steel components are connected by lapping at their ends or edges. This area becomes a sensitive spot for corrosion and crystallization pressure concentration due to the long-term retention of salt water film.

[0066] The chloride concentration in the working area is continuously monitored to record the chloride concentration change curve;

[0067] Peak values ​​were extracted from the change curves to obtain the maximum chloride concentration.

[0068] The temperature of the steel plate in the working area is monitored synchronously. When the chloride concentration in the working area reaches the maximum chloride concentration, the real-time steel plate temperature corresponding to the maximum chloride concentration is recorded.

[0069] Specifically, machine vision recognition technology is used to locate the spatial range of the lap joint between two steel components, defining this spatial range as the working area. Distributed chloride concentration sensors are deployed in the working area to continuously collect chloride concentration data according to a set sampling period, generating a curve of chloride concentration changing over time. A peak extraction algorithm is used to analyze the curve, extracting the maximum value to determine the maximum chloride concentration. Simultaneously, a temperature sensor is installed on the surface of the steel plate in the working area to monitor the steel plate temperature in real time. When the chloride concentration detected by the chloride concentration sensor reaches the maximum chloride concentration, the temperature sensor is triggered to record the real-time steel plate temperature at that moment.

[0070] Convert the real-time steel plate temperature to the thermodynamic temperature at which the salt solution crystallizes.

[0071] Specifically, the real-time steel plate temperature is converted to Celsius using a unified unit, and the measurement point number and timestamp are recorded. Then, based on the thermal conditions of strong coupling between the narrow liquid film at the lap joint and the steel strip surface, an engineering assumption is established that the film temperature and the steel plate temperature are equivalent. During the factory calibration stage, the temperature hysteresis constant and the film temperature correction value are obtained through comparative experiments. If the difference between the two is less than one Kelvin, it is recorded as zero correction. Then, the real-time steel plate temperature is added to the film temperature correction value to obtain the equivalent Celsius temperature when the salt solution crystallizes. Subsequently, a unit conversion is performed, and 273.15 is added to the equivalent Celsius temperature to obtain the thermodynamic temperature T in Kelvin.

[0072] Positioning the metallurgical bonding interface between the zinc-aluminum-magnesium coating and the steel substrate;

[0073] Specifically, the metallurgical bonding interface refers to the alloy layer formed during the hot-dip galvanizing process by the diffusion and reaction of molten zinc, aluminum, and magnesium alloy elements with the surface of the steel substrate. This alloy layer achieves a metallurgical bond between the coating and the steel substrate in terms of microstructure, providing the steel plate with strong adhesion and excellent corrosion resistance.

[0074] Based on the thermodynamic temperature of the steel plate, the crystallization pressure exerted by salt crystals at the lap joint on the metallurgical interface at the gap triple line is calculated. The formula for calculating the crystallization pressure is as follows:

[0075]

[0076] In the formula, P crys It is the crystallization pressure, R is the universal gas constant, T is the thermodynamic temperature, and V is the temperature. m C is the molar volume of the salt crystal. max It is the maximum chloride concentration, C sat It is the saturated solubility of the target salt corresponding to the salt crystal. It is the natural logarithm of the concentration ratio;

[0077] Specifically, the calculation of crystallization pressure is based on the principles of solution thermodynamics and phase equilibrium. When the actual concentration of a salt solution is higher than its saturation solubility at a given temperature, the system is in a supersaturated state. The logarithm of the supersaturation is proportional to the chemical potential difference at the molecular level. This chemical potential difference is converted into a driving force acting on the crystal growth interface and manifests as crystallization pressure. According to thermodynamic formulas, the chemical potential difference is proportional to the universal gas constant R and the thermodynamic temperature T, and also proportional to the natural logarithm of the concentration ratio of the solution. Combining this with the molar volume of the salt crystal, the chemical potential difference can be converted into macroscopic pressure, yielding the expression for crystallization pressure. P obtained from this crysThis refers to the actual crystallization pressure applied to the metallurgical interface during the crystallization of salt crystals in the three-phase region of the lap joint.

[0078] Multiply the crystallization pressure by the preset safety margin to obtain the crystallization pressure safety margin.

[0079] Specifically, multiplying the crystallization pressure by a preset safety margin factor is based on the margin principle commonly used in structural safety design. That is, based on the theoretically calculated value of the known crystallization pressure, a correction factor greater than one is introduced to offset the uncertainties caused by environmental fluctuations, measurement errors, and local defects in materials. This ensures that even if there are instantaneous peak fluctuations in chloride concentration or measurement deviations in steel plate temperature during actual service, the calculated crystallization pressure safety margin is still higher than the maximum crystallization pressure that may actually occur. This provides a reliable guarantee for the resistance of the metallurgical interface to salt crystal splitting, ensuring that the design has higher reliability and safety.

[0080] Specifically, the preset safety margin is determined based on the material's service environment and failure statistics. The process involves collecting experimental data on steel plate interface splitting under different chloride concentrations and temperatures, statistically determining the actual distribution range of crystallization pressure, setting a failure probability threshold using probabilistic safety assessment methods, and determining the safety margin value based on the partial factor principle in reliability engineering. This safety margin is typically between one and three, and by multiplying it by the crystallization pressure, a crystallization pressure safety margin is formed. This ensures that the result covers most extreme situations that may occur under most service conditions, thereby ensuring that the coating design has sufficient anti-splitting safety and applicability.

[0081] In detail, during the service life of lap joints in galvanized aluminum-magnesium steel sheets, the accumulation of chloride and sulfate ions in the triple phase lines at narrow joint openings easily leads to the formation of long, needle-like salt crystals. This crystallization growth process is accompanied by volume expansion and generates crystallization pressures as high as 10 to 40 MPa. This pressure is far higher than the adhesion strength of conventional coatings, easily causing delamination and failure of the metallurgical interface between the coating and the steel substrate, accompanied by rapid red rust expansion. To avoid these failure modes, a quantitative assessment of the interface's load-bearing capacity is necessary during the design phase. Therefore, the maximum crystallization pressure during salt crystallization must be calculated based on the maximum chloride concentration and corresponding thermodynamic temperature in the actual working area. A safety margin factor is then introduced to obtain a safety margin for the crystallization pressure, ensuring that the interface still possesses sufficient load-bearing capacity under extreme environmental conditions. This allows for early prevention of salt crystal splitting failure and improves the long-term corrosion resistance reliability of the coating structure.

[0082] S2. Calculate the comprehensive interfacial energy of the double-layer coating structure of the steel strip to be coated based on the safety margin of crystallization pressure;

[0083] In embodiments of the present invention, the comprehensive interfacial energy of the double-layer coating structure of the steel strip to be coated is calculated based on the safety margin of crystallization pressure, including:

[0084] The first thickness parameter of the soft prepreg layer in the double-layer coating structure and the second thickness parameter of the tough body layer in the double-layer coating structure are set according to the safety margin of crystallization pressure.

[0085] Specifically, the soft prepreg layer refers to a transitional alloy layer formed on the surface of the steel substrate by a prepreg alloy bath containing a certain proportion of aluminum before the steel strip enters the main molten bath. This layer has good wettability and ductility, which can act as a buffer and improve the bonding effect of the subsequent main layer. The first thickness parameter of the soft prepreg layer refers to the target thickness value of this layer in the coating structure, and its size directly affects the interfacial adhesion and the distribution of the overall interfacial energy. The tough main layer refers to a high-strength and tough alloy layer formed on the soft prepreg layer by a main alloy bath. This layer provides the main crack resistance and corrosion resistance. The second thickness parameter of the tough main layer refers to the target thickness value of this layer in the coating structure, and its size determines the mechanical support and long-term service performance of the overall coating.

[0086] Specifically, the safety margin of crystallization pressure is used as the design input, and the target lower limit of the interface requirement value is determined accordingly. This target lower limit is then used as the constraint target for the thickness distribution of the double-layer coating structure. Subsequently, the interfacial energy constants and manufacturable thickness ranges corresponding to the soft prepreg layer and the tough substrate layer are selected from the process database to give the upper and lower limits of the total thickness. The total thickness is then proportionally distributed between the two layers using empirical initial values ​​to obtain the first and second initial thickness values. Next, based on the comprehensive interfacial energy calculation formula for the double-layer coating structure, the interfacial energy of the soft prepreg layer and the interfacial energy of the tough substrate layer are weighted by thickness and summed, then divided by the total thickness to obtain the predicted value of the comprehensive interfacial energy. This predicted value is then compared with the boundary... The interfacial requirements are compared; if the predicted value is insufficient, the second thickness is increased first to improve structural toughness, while the first thickness is finely adjusted to maintain the adhesion and buffering capacity with the substrate, provided that the total thickness and linear speed are not exceeded, until the comprehensive interfacial energy is not lower than the target lower limit; if the predicted value is too high and exceeds the material and production capacity optimization criteria, the thickness of the two layers is reduced by the same amount without reducing the safety of the interfacial requirements, and the comprehensive interfacial energy is recalculated to achieve a balance between thickness and performance; finally, the thickness of the soft prepreg layer that meets the interfacial requirements and is within the manufacturable window is determined as the first thickness parameter, and the thickness of the tough main body layer that meets the interfacial requirements and takes into account both strength and toughness is determined as the second thickness parameter.

[0087] A pre-impregnated alloy bath with zinc as the base and aluminum accounting for 15% by mass was prepared, and the temperature of the alloy bath was adjusted to 460℃, and a main alloy bath was prepared.

[0088] Specifically, firstly, high-purity zinc ingots are added to the melting furnace as the base metal and heated to a fully molten state. Then, aluminum ingots are weighed according to their mass percentage and slowly added to the molten zinc. At the same time, the stirring device is activated to ensure uniform diffusion of aluminum in the zinc matrix until the composition of the melt reaches a pre-dip alloy composition with aluminum accounting for 15% of the mass. During this process, the solution composition is monitored in real time through online sampling and spectral analysis, and the amount of aluminum added is finely adjusted according to the test results to ensure the accuracy of the alloy ratio. After the alloy composition stabilizes, the furnace temperature is gradually adjusted to 460 degrees Celsius and maintained at a constant temperature to give the melt suitable fluidity and wettability. After the pre-dip alloy bath is prepared, a separate main alloy bath is prepared. Specifically, zinc-aluminum-magnesium alloy raw materials are added to another melting tank and heated to the set value. At the same time, an appropriate amount of rare earth elements or regulators are added to the main alloy bath according to the process requirements, and thorough stirring and composition testing are carried out until the main bath reaches the preset chemical composition and temperature conditions, providing a stable alloy environment for the subsequent hot-dip galvanizing steps.

[0089] The immersion time and pulling speed of the steel strip to be plated are controlled based on the first thickness parameter and the second thickness parameter.

[0090] Specifically, the process control system inputs the first thickness parameter of the soft prepreg layer and the second thickness parameter of the tough substrate layer, determined by the previous steps. These two parameters are then matched with the thickness-process time-speed mapping relationship established in the process database to obtain the corresponding target immersion time range and target pull-out speed range. Subsequently, before the steel strip enters the prepreg alloy bath, the linear velocity of the steel strip is detected by sensors, and the closed-loop control unit compares the detected velocity with the target pull-out speed range. When the deviation exceeds the allowable range, the speed of the traction motor is automatically adjusted to achieve real-time correction of the pull-out speed. Simultaneously, the process begins after the steel strip is fully immersed in the bath. The timing program controls the dwell time of the steel strip in the molten bath based on the lower and upper limits of the immersion time corresponding to the first and second thickness parameters. It also confirms whether the steel strip is at the set immersion depth through a depth detection device. If it is insufficient, the dwell time is extended until the design requirements are met. During the process of pulling the steel strip out of the molten bath, the pulling speed is continuously monitored and compared with the target value. When the speed fluctuation causes the thickness prediction to deviate, the pulling speed is adjusted in real time so that the actual coating thickness gradually approaches the set value. After the pulling is completed, the measured immersion time and pulling speed are immediately compared with the thickness parameter correspondence table to confirm that they meet the requirements of the first and second thickness parameters.

[0091] The pretreated steel strip to be plated is sequentially immersed in a pre-impregnation alloy bath and a main alloy bath. Under the constraints of immersion time and pulling speed, a double-layer coating structure consisting of a soft pre-impregnation layer and a tough main layer is formed on the surface of the steel strip to be plated.

[0092] Specifically, the steel strip to be plated, after surface cleaning and flux treatment, is first fed into a pre-impregnation alloy bath under the drive of a constant-speed conveyor system. This ensures that the steel strip is uniformly immersed in the molten metal across its entire width. It remains in this state for the immersion time set by the control system, allowing the aluminum elements in the molten metal to form a continuous and uniform soft pre-impregnation layer on the steel substrate surface. After the initial immersion, the steel strip is pulled out of the bath at a preset speed to avoid uneven molten metal flow. Immediately afterwards, the steel strip is introduced into the main alloy bath, maintaining an immersion time that matches the first and second thickness parameters, so that… In the main molten bath, zinc, aluminum, and magnesium alloy elements form a dense, tough substrate layer on top of the soft prepreg layer. During this process, online temperature monitoring and liquid level detection ensure the stability of the molten bath temperature and liquid level, guaranteeing the integrity and bonding strength of the coating interface. After the immersion coating reaches the set time, the steel strip is pulled out at a uniform speed corresponding to the thickness parameters. An air knife or scraping device is used to control the residual thickness of the surface molten liquid, ensuring that the thickness of the soft prepreg layer and the tough substrate layer meets the design requirements. Finally, a double-layer coating structure consisting of the soft prepreg layer and the tough substrate layer is obtained on the surface of the steel strip.

[0093] The comprehensive interface energy of the double-layer coating structure is calculated based on the first and second thickness parameters. The formula for calculating the comprehensive interface energy is as follows:

[0094]

[0095] In the formula, Γ total It is the comprehensive interfacial energy of the double-layer coating structure, Γ soft It is the interfacial energy of the soft prepreg layer, t soft It is the first thickness parameter, Γ tough It is the interfacial energy of the tough main body layer, t tough It is the second thickness parameter.

[0096] Specifically, the comprehensive interface energy calculation follows the principle of interface energy superposition and thickness weighting. Physically, the bonding strength between the coating and the substrate depends not only on the interface energy of a single layer but also on the thickness proportion of that layer within the overall coating structure. The soft prepreg layer provides wetting and transition between the coating and the substrate, while the tough substrate layer provides overall mechanical support and crack resistance. Therefore, in the comprehensive evaluation, the interface energies of both layers need to be multiplied by their corresponding thickness parameters to reflect the actual contribution of each layer to the overall bonding energy. The two are then added together and divided by the total thickness to normalize the thickness proportion. This weighted average calculation method is equivalent to the weighting principle of layered composite system performance in materials mechanics. It can accurately characterize the interface bonding level of the two-layer coating under different thickness distributions, thus obtaining a comprehensive interface energy reflecting the overall structural characteristics, providing a theoretical basis for subsequent determination of coating stability and crack resistance.

[0097] Specifically, the pre-impregnation alloy bath is a molten alloy liquid with zinc as the base and containing a certain proportion of aluminum, used to first generate a soft pre-impregnation layer on the surface of the steel substrate; the main alloy bath is a molten alloy liquid containing zinc, aluminum, magnesium and other regulating elements, used to form a tough main layer on top of the pre-impregnation layer; the comprehensive interfacial energy of the double-layer coating structure refers to the weighted average value of the contributions of the soft pre-impregnation layer and the tough main layer to the interfacial bonding under different thickness distributions, used to characterize the bonding energy level between the overall double-layer coating and the steel substrate.

[0098] S3. Quantify the crack tip passivation factor in the crack tip region of the metallurgical bonding interface, and calculate the corrected interface energy of the metallurgical bonding interface based on the crack tip passivation factor and the comprehensive interface energy.

[0099] In embodiments of the present invention, the crack tip passivation factor of the crack tip region in the metallurgical bonding interface is quantified, and the corrected interface energy of the metallurgical bonding interface is calculated based on the crack tip passivation factor and the comprehensive interface energy, including:

[0100] In-Al master alloy wire and Sn-Zn master alloy wire are fed into the main alloy bath according to a preset fixed ratio, and In and Sn are integrated into the tough main body layer.

[0101] The toughened substrate layer is subjected to rapid cooling treatment to precipitate β(In / Sn)-Zn particles at the metallurgical bonding interface;

[0102] Specifically, firstly, according to the fixed ratio preset in the process design, the weighed In-Al master alloy wire and Sn-Zn master alloy wire are simultaneously and continuously fed into the main alloy molten bath maintained at a constant temperature using an automatic wire feeding device. During the wire feeding process, the uniformity of the liquid phase is maintained by a molten bath stirring mechanism, allowing indium and tin elements to fully melt and uniformly disperse in the main alloy molten liquid. Subsequently, as the steel strip passes through the main alloy molten bath to form a toughened main body layer, these alloying elements are deposited into the coating structure along with the melt and dissolved within the toughened main body layer. To further achieve elemental microstructure control, the steel strip immediately enters a rapid cooling unit after leaving the main alloy molten bath. Through the synergistic effect of high-pressure cooling gas and sprayed cooling liquid, the coating temperature is rapidly reduced, causing the toughened main body layer to generate a supersaturated solid solution under rapid cooling conditions. This induces the precipitation of β(In / Sn)-Zn particles with passivating effects at the metallurgical bonding interface. These particles can exert energy dissipation and passivation effects in the interface crack tip region, thereby significantly improving the bonding stability between the coating and the substrate.

[0103] The crack tip passivation characteristics of the interfacial crack tip region containing β(In / Sn)-Zn particles were tested and analyzed to obtain the crack tip passivation factor. The crack tip passivation characteristics test and analysis included: salt crystal crystallization pressure cracking test and passivation effect quantitative analysis.

[0104] Specifically, firstly, an interface sample containing β(In / Sn)-Zn particles and a control sample without these particles were prepared. Micro-incisions were pre-fabricated at the metallurgical interface of both samples to define the crack initiation location, and the crack tip region was calibrated under a microscope as an observation window. Subsequently, a salt crystallization pressure-induced cracking testing device was constructed. Liquid was supplied to the equivalent slit of the lap joint at a predetermined chloride concentration and in a wet-dry cycle within a constant-temperature chamber. A supersaturated state was maintained through controlled evaporation and replenishment, generating calculable crystallization pressure at the crack opening. Concentration and temperature were recorded simultaneously for pressure amplitude calculation. During the cracking loading process, digital image correlation and high-magnification microscopic imaging were used to measure the crack tip opening displacement, crack propagation threshold, and propagation rate in real time. Acoustic emission signals were used as needed to identify crack initiation. At the cracking moment, the critical value based on the energy release rate or J integral is calculated and recorded as the critical interface energy threshold for salt crystal cracking. After completing the test of the particle-containing sample, the test is repeated on the control sample under the same conditions to obtain the critical interface energy threshold of the control. Then, the passivation effect is quantitatively analyzed. The crack tip morphology and particle distribution are observed by scanning electron microscopy and focused ion beam sample preparation. The crack tip round radius and particle spacing are statistically analyzed. Combined with the relationship between stress intensity factor and energy release rate, the critical data of the particle-containing and control groups are normalized. The crack tip passivation factor is defined as the ratio of the critical interface energy threshold under particle-containing conditions to the control threshold, or equivalently the square of the ratio of the critical stress intensity factors of the two. The repeatability and uncertainty of this factor are evaluated.

[0105] The crack tip passivation factor is multiplied by the comprehensive interface energy to calculate the corrected interface energy of the metallurgical bonding interface.

[0106] In detail, in the lap joint environment of Zn-Al-Mg self-healing coatings, due to the continuous enrichment of chloride ions, salt crystals will crystallize in the narrow seam opening in the form of long needles, generating crystallization pressures as high as 10 to 40 MPa. When this pressure acts on the crack tip region of the metallurgical interface, it can easily trigger interface delamination and failure. In order to accurately evaluate the crack resistance of the coating interface, the comprehensive interfacial energy obtained by weighting the thickness of the soft prepreg layer and the tough substrate layer alone is insufficient to reflect the true load-bearing state of the crack tip. Therefore, it is necessary to further introduce a crack tip passivation factor. The crack tip passivation factor is derived from the quantification of the buffering effect and crack tip rounding effect generated by β(In / Sn)-Zn particles at the crack tip. Its value can reflect the actual ability of the crack tip to resist salt crystal crystallization pressure splitting at the microscale. Multiplying the crack tip passivation factor with the comprehensive interface energy, the obtained modified interface energy not only includes the binding energy contributed by the macroscopic thickness structure, but also comprehensively reflects the additional toughness of the microscopic crack tip region due to the particle passivation effect. Therefore, this modified interface energy can more realistically characterize the resistance level of the metallurgical interface to salt crystal splitting failure.

[0107] Specifically, In-Al master alloy wire is an alloy wire made with zinc as the main matrix and indium and aluminum added. It is used to introduce indium and aluminum into the coating in the main molten bath to improve interfacial properties. Sn-Zn master alloy wire is an alloy wire made with zinc as the main matrix and tin added. It is used to introduce tin into the coating in the main molten bath to enhance the corrosion resistance and interfacial stability of the toughened matrix layer. β(In / Sn)-Zn particles refer to zinc-based precipitates rich in indium and tin that precipitate at the metallurgical interface after rapid cooling of the toughened matrix layer. These particles can crack at the interface. The passivation effect at the crack tip reduces stress concentration and enhances the crack tip's resistance to cracking. Salt crystal crystallization pressure-induced cracking test refers to an experimental method that, under controlled chloride concentration and temperature conditions, induces salt crystal growth in the crack tip or fissure region, utilizes the pressure generated by its crystallization expansion to act on the interface crack tip, and records the critical value of crack propagation. Quantitative analysis of passivation effect refers to the determination of the roundness and energy dissipation effect of β(In / Sn)-Zn particles on the crack tip region through methods such as microscopic morphology observation and mechanical threshold comparison, and converts this effect into a crack tip passivation factor for use in correcting the calculation of interface energy.

[0108] S4. Salt drainage micro-grooves are formed on the surface of the steel strip to be plated. Based on the modified interface, the steel strip to be plated can be qualified, and micro-grooved steel strip is obtained.

[0109] In an embodiment of the present invention, salt drainage microgrooves are formed on the surface of the steel strip to be plated. Based on the modified interface, the steel strip to be plated is qualified, resulting in a microgrooved steel strip, comprising:

[0110] The steel strip to be plated is conveyed to the knurling equipment, and the linear speed of the knurling rollers in the knurling equipment is synchronized with the running speed of the steel strip to be plated.

[0111] Set the knurling pressure of the knurling roller;

[0112] The surface of the steel strip to be plated is knurled by knurling pressure to form salt drainage micro-grooves.

[0113] Specifically, salt drainage micro-grooves refer to small groove structures with specific geometric morphologies formed on the surface of coated steel strips through mechanical pressing or knurling processes. The function of these grooves is to utilize capillary action to actively adsorb and siphon out chloride salt solutions that have penetrated the surface of the steel strip, thereby preventing the salt solution from stagnating in the interface area and causing interface splitting failure due to crystal expansion.

[0114] Specifically, the steel strip to be coated is first stably fed into the inlet of the knurling equipment via a conveyor. During the conveying process, tension control and a sway correction system maintain the steel strip in a constant running state. Simultaneously, a synchronous control system compares and adjusts the linear speed of the knurling rollers with the running speed of the steel strip to be coated, keeping the speed difference within an allowable range to avoid surface scratches or slippage caused by speed mismatch. Based on the comparison between the corrected interfacial energy and the required interfacial value, the geometric target parameters required for the salt drainage microgrooves are determined, including the width, depth, and angle of groove intersection. Combining the groove depth and knurling pressure correspondence specified by the equipment manufacturer, the required knurling pressure setting value is derived. During the setting process, the rate of increase and maximum value of the knurling pressure are limited to ensure that the microgroove depth does not exceed the coating thickness and thus does not damage the steel substrate. Under the constraints of synchronous linear speed and set knurling pressure, the surface of the steel strip to be coated is knurled, gradually forming salt drainage microgrooves with a flow guiding function.

[0115] Once the depth of the salt drainage micro-ditch reaches the preset geometric depth, measure the actual width and actual depth of the salt drainage micro-ditch.

[0116] Specifically, after the salt drainage micro-groove is pressed and stabilized by the knurling equipment, the depth of the salt drainage micro-groove is first monitored in real time by an online displacement sensor and a contour measuring instrument. When the depth of the micro-groove reaches the preset geometric depth threshold, the precision optical measurement system is activated to scan the cross-section of the salt drainage micro-groove. The three-dimensional contour data of the groove cross-section is obtained by a non-contact optical interferometer, and the actual width and actual depth of the salt drainage micro-groove are extracted by the data processing module.

[0117] It should be noted that the preset geometric depth is determined comprehensively based on the capillary action requirements of the salt drainage micro-groove in actual use environment, as well as the thickness and mechanical properties of the coated steel strip. Specifically, this involves establishing a theoretical relationship between the capillary height and the geometric dimensions of the micro-groove, and calculating the minimum groove depth that can meet the target capillary height by combining physical parameters such as the surface tension, density, and contact angle of the salt solution. At the same time, the surface processing capability of the steel strip, the pressing limit of the knurling process, and the stability and non-collapse requirements of the micro-groove during long-term service are also considered. Thus, a geometric depth value that can ensure the full utilization of capillary action without damaging the overall strength and surface integrity of the steel strip is determined as the preset standard.

[0118] The actual capillary siphon height of the salt drainage microchannel is calculated based on the actual microchannel width and actual microchannel depth. The formula for calculating the actual capillary siphon height is as follows:

[0119]

[0120] In the formula, h is the actual capillary siphon height, γ is the liquid surface tension, θ is the contact angle between the salt solution and the coating surface of the steel strip to be coated, ρ is the liquid density, g is the gravitational acceleration, and r is the equivalent capillary radius.

[0121] Specifically, before calculating the capillary siphon height of the desalination microchannel, the actual microchannel width and actual microchannel depth are substituted into the approximate formula of hydraulic radius. The product of the actual microchannel width and actual microchannel depth is used as the cross-sectional area of ​​the microchannel, and the sum of the actual microchannel width and twice the actual microchannel depth is used as the wetting perimeter of the microchannel. Then, the cross-sectional area of ​​the microchannel is divided by the wetting perimeter to obtain the equivalent capillary radius. The equivalent capillary radius can reflect the liquid absorption capacity of the irregular microchannel in the capillary siphon process, which is equivalent to that of an ideal capillary.

[0122] Specifically, the capillary siphon height of the salt drainage microchannel is determined by the balance between the capillary action of the liquid on the solid surface and the liquid's own gravity. When the salt solution enters the microchannel on the surface of the steel strip to be coated, the cohesive force between liquid molecules and the adhesion force between the liquid and the solid surface work together to generate surface tension at the liquid interface and form a curved liquid surface. The degree of curvature of the liquid surface is determined by the contact angle between the salt solution and the coating surface. The upward capillary pressure generated by this curved liquid surface pushes the liquid upward along the microchannel, while the gravity of the liquid column itself acts downward. When the capillary pressure and the gravity of the liquid column are balanced, the liquid rise height reaches a stable value, which is the capillary siphon height. In the formula, the cosine of the liquid surface tension and the contact angle is used as the driving force numerator, and the liquid density, gravitational acceleration, and equivalent capillary radius are used as the resistance denominator, thus establishing a functional relationship between the liquid capillary rise height and the interfacial wetting properties and the geometry of the microchannel.

[0123] If the actual capillary siphon height is greater than or equal to the target capillary siphon height of the salt drainage micro-ditch, and the corrected interface energy is greater than or equal to the interface requirement value of the metallurgical bonding interface, then the steel strip to be plated will be marked as a micro-ditch steel strip; otherwise, the steel strip to be plated will be marked as a substandard steel strip.

[0124] Specifically, this judgment logic is to ensure that the salt drainage micro-grooves not only achieve sufficient capillary action in terms of geometric structure, but also meet the requirements for long-term service in terms of mechanical properties and interface stability. When the actual capillary height is greater than or equal to the target capillary height, it indicates that the micro-grooves have the ability to effectively absorb and drain salt, which can prevent chloride salts from accumulating in the interface area. When the modified interface strength is greater than or equal to the interface requirement value of the metallurgical bonding interface, it indicates that the bonding strength between the coating and the substrate is sufficient to resist the destructive effect of salt crystallization pressure. Only when both conditions are met is the steel strip to be coated marked as a micro-grooved steel strip, thereby ensuring that it has reliable protective performance. Otherwise, it is marked as an unqualified steel strip to avoid potential failure risks.

[0125] S5. Perform silanization treatment on the microgrooved steel strip to form a dry silane film on the surface of the microgrooved steel strip, and mark the microgrooved steel strip as silanized steel strip.

[0126] In an embodiment of the present invention, the microgrooved steel strip is subjected to silanization treatment to form a dry silane film on the surface of the microgrooved steel strip, comprising:

[0127] Cleaning and coating treatment of microgrooved steel strip;

[0128] Spray hydroxyl-terminated silane sol onto the surface of the microgrooved steel strip until the measured wet film thickness of the silane wet film reaches the preset thickness value, then stop spraying.

[0129] The microgrooved steel strip is dried to form a dry silane film on its surface.

[0130] Reverse pressure verification was performed on the dry silane membrane.

[0131] Specifically, the microgrooved steel strip is first fed into the surface pretreatment station, where the coating surface is cleaned with deionized water spray and a weak alkaline degreasing agent. It is then rinsed with pure water and dried with an air knife and hot air until the surface is clean, oil-free, and watermark-free. Next, at the spraying station, hydroxyl-terminated silane sol is used for circulating spraying and coverage. The spray volume is controlled by a combination of mass flow rate and linear velocity, and the thickness of the silane wet film is continuously read using an online wet film thickness gauge. Spraying is stopped immediately when the measured wet film thickness reaches the preset value, while simultaneously checking the uniformity of coverage in the microgrooved area and ensuring no openings or blockages. Finally, the microgrooved steel strip is fed into the hot air curing channel. Solvent evaporation and silane polycondensation reactions are completed at a set temperature and time, forming a continuous and dense dry silane film on the surface of the microgrooved steel strip. The thickness and smoothness of the dry film are verified using infrared or laser thickness measurement devices, and the process parameters and test results are recorded simultaneously. Finally, the dry silane film is subjected to water absorption and expansion tests and mechanical characterization under controlled humidity conditions. The back pressure generated is calculated and determined to be not lower than the preset safety threshold. If the requirement is met, the silanization treatment is confirmed to be qualified. If not, the sol ratio or curing conditions are adjusted and the above spraying and curing process is repeated until the back pressure reaches the requirement and the data is archived.

[0132] S6. Based on silanized steel strip, lap joint test specimens are made, and the lap joint test specimens are judged to be qualified in order to obtain qualified test specimens.

[0133] In an embodiment of the present invention, lap joint specimens are prepared based on silanized steel strips, and the lap joint specimens are judged to be qualified to obtain qualified specimens, including:

[0134] The silanized steel strip was lapped and assembled to obtain lapped specimens;

[0135] The lap joint specimens were subjected to performance tests, including salt spray tests and peel tests.

[0136] After the performance test is completed, if the lapped specimen does not show interface delamination or exposed red rust, it is determined to be a qualified specimen; otherwise, it is determined to be an unqualified specimen and the test is returned to S1.

[0137] Specifically, the silanized steel strip is first cut, chamfered, deburred, and cleaned and dried according to the tooling dimensions. Then, it is assembled on a special fixture according to the preset overlap width and fastening method. The overlap gap and fastener preload are checked, and the specimen number, sampling surface, microgroove direction, and silane film batch information are marked to form a traceable overlap specimen. Subsequently, the overlap specimen is placed in the salt spray test station and continuously exposed according to the preset spray medium, temperature, and time regime or exposure cycle. Appearance changes, micro-channel permeability, and film condition are recorded at specified intervals. After exposure, the specimen is cleaned, dried, and... Like archiving; then place the same specimen in a peel tester and conduct a peel test under preset peel angle, load increase rate and test speed conditions, simultaneously collect peel force and displacement curves and record interface failure morphology; after all performance tests are completed, check for interface delamination, exposed red rust or other failure signs according to the judgment rules. If no abnormalities are found, the overlapping specimen is judged as a qualified specimen and the corresponding process parameters are solidified for mass production control; if any failure occurs, the overlapping specimen is judged as a non-qualified specimen, the failure data is summarized and backtracking is initiated, returning to S1 to recheck the crystallization pressure safety margin and subsequent related parameters.

[0138] A self-healing hot-dip galvanized aluminum-magnesium steel sheet coating alloy hot-dip galvanizing process includes the above-mentioned design method for a self-healing galvanized aluminum-magnesium steel sheet coating alloy.

[0139] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A design method of a plated alloy of a self-repairing galvannealed steel sheet, characterized by, The method comprises the following steps: S1. Calculate the crystallization pressure safety margin according to the maximum chloride salt concentration and the thermodynamic temperature of the working state area; S2. Calculate the comprehensive interface energy of the double-layer coating structure of the plated steel strip based on the crystallization pressure safety margin; S3. Quantify the crack tip blunting factor of the interface crack tip area in the metallurgical bonding interface, and calculate the modified interface energy of the metallurgical bonding interface based on the crack tip blunting factor and the comprehensive interface energy; S4. Form salt-removing micro-grooves on the surface of the plated steel strip, and perform qualified judgment on the plated steel strip based on the modified interface energy to obtain a micro-grooved steel strip; S5. Perform silanization treatment on the micro-grooved steel strip to form a dry silane film on the surface of the micro-grooved steel strip, and mark the micro-grooved steel strip as a silanized steel strip; S6. Based on the silanized steel strip, a lap joint specimen is prepared, and the lap joint specimen is subjected to qualified judgment to obtain a qualified specimen.

2. The self-repairing galvanizing aluminum magnesium steel sheet coating alloy design method according to claim 1, characterized by, According to the maximum chloride salt concentration and the thermodynamic temperature of the working state area, the crystallization pressure safety margin is calculated, including: Locate the working state area of the lap joint between the two steel members; Continuously monitor the chloride salt concentration of the working state area to record the change curve of the chloride salt concentration; Peak extraction is performed on the change curve to obtain the maximum chloride salt concentration; Synchronously monitor the steel plate temperature of the working state area, and record the real-time steel plate temperature corresponding to the maximum chloride salt concentration when the chloride salt concentration of the working state area reaches the maximum chloride salt concentration; Convert the real-time steel plate temperature into the thermodynamic temperature of the salt solution crystallization; Locate the metallurgical bonding interface between the zinc-aluminum-magnesium coating and the steel substrate; Based on the steel plate thermodynamic temperature and the steel plate thermodynamic temperature, the crystallization pressure of the salt crystal at the crack tip of the lap joint is calculated, and the crystallization pressure safety margin is calculated by multiplying the crystallization pressure by a predetermined safety margin. In the formula, P crys It is the crystallization pressure, R is the universal gas constant, T is the thermodynamic temperature, and V is the temperature. m C is the molar volume of the salt crystal. max It is the maximum chloride concentration, C sat It is the saturated solubility of the target salt corresponding to the salt crystal. It is the natural logarithm of the concentration ratio; Based on the crystallization pressure safety margin, the comprehensive interface energy of the double-layer coating structure of the plated steel strip is calculated, including:

3. The self-repairing galvanizing aluminum magnesium steel sheet coating alloy design method according to claim 1, characterized by, According to the crystallization pressure safety margin, set the first thickness parameter of the soft pre-impregnation layer in the double-layer coating structure, and the second thickness parameter of the tough main layer in the double-layer coating structure; Configure a pre-impregnation alloy bath with zinc as the base and an aluminum mass ratio of 15%, adjust the temperature of the alloy bath to 460°C, and configure a main alloy bath; Control the immersion time and pulling speed of the plated steel strip based on the first thickness parameter and the second thickness parameter; The pre-processed plated steel strip is sequentially immersed in the pre-impregnation alloy bath and the main alloy bath, and under the constraint of the immersion time and the pulling speed, a double-layer coating structure composed of a soft pre-impregnation layer and a tough main layer is formed on the surface of the plated steel strip; Based on the first thickness parameter and the second thickness parameter, the comprehensive interface energy of the double-layer coating structure is calculated, and the calculation formula of the comprehensive interface energy is as follows: Quantify the crack tip blunting factor of the interface crack tip area in the metallurgical bonding interface, and calculate the modified interface energy of the metallurgical bonding interface based on the crack tip blunting factor and the comprehensive interface energy, including: where Γ total is the overall interfacial energy of the bi-layer coating structure, Γ soft is the interfacial energy of the soft pre-preg layer, t soft is the first thickness parameter, Γ tough is the interfacial energy of the tough matrix layer, t tough is the second thickness parameter.

4. The self-repairing galvanizing aluminum magnesium steel sheet coating alloy design method according to claim 3, characterized by, Send In-Al master alloy wire and Sn-Zn master alloy wire into the main alloy bath, and let In and Sn melt into the tough main layer; ​ The ductile matrix layer is subjected to cold speed cooling treatment to precipitate β(In / Sn)-Zn particles at the metallurgical bonding interface; The interface crack tip region containing the β(In / Sn)-Zn particles is subjected to crack tip passivation characteristic test analysis to obtain a crack tip passivation factor, wherein the crack tip passivation characteristic test analysis comprises salt crystal crystallization pressure cracking test and passivation effect quantitative analysis; The crack tip passivation factor is multiplied by the comprehensive interface energy to calculate the modified interface energy of the metallurgical bonding interface.

5. The self-repairing galvanizing aluminum magnesium steel sheet coating alloy design method according to claim 1, characterized by, Salt discharge microgrooves are formed on the surface of the steel strip to be plated, and the steel strip to be plated is subjected to qualified judgment based on the modified interface energy to obtain a microgrooved steel strip, comprising: The steel strip to be plated is conveyed to a knurling device, and the linear speed of the knurling roller and the running speed of the steel strip to be plated are synchronized; The knurling pressure of the knurling roller is set; The surface of the steel strip to be plated is subjected to knurling pressure treatment by the knurling pressure to form salt discharge microgrooves; When the microgroove depth of the salt discharge microgroove reaches the preset geometric depth, the actual microgroove width and the actual microgroove depth of the salt discharge microgroove are measured; The actual capillary siphon height of the salt discharge microgroove is calculated based on the actual microgroove width and the actual microgroove depth; If the actual capillary siphon height is greater than or equal to the target capillary siphon height of the salt discharge microgroove, and the modified interface energy is greater than or equal to the interface requirement value of the metallurgical bonding interface, the steel strip to be plated is marked as a microgrooved steel strip, otherwise, the steel strip to be plated is marked as an unqualified steel strip.

6. The self-repairing galvanizing aluminum magnesium steel sheet coating alloy design method according to claim 1, characterized by, The microgrooved steel strip is subjected to silanization treatment to form a dry silane film on the surface of the microgrooved steel strip, comprising: The microgrooved steel strip is subjected to clean plating layer treatment; The surface of the microgrooved steel strip is sprayed with a hydroxyl-terminated silane sol until the measured wet film thickness of the silane wet film reaches a preset thickness value, and then the spraying is stopped; The microgrooved steel strip is subjected to drying treatment to form a dry silane film on the surface of the microgrooved steel strip; The dry silane film is subjected to reverse pressure verification.

7. The self-repairing galvanizing aluminum magnesium steel sheet coating alloy design method according to claim 1, characterized by, Based on the silanized steel strip, a lap joint specimen is prepared, and the lap joint specimen is subjected to qualified judgment to obtain a qualified specimen, comprising: The silanized steel strip is subjected to lap joint assembly treatment to obtain a lap joint specimen; The performance of the lap joint specimen is tested, wherein the performance test includes salt spray test and peeling test; After the performance test is completed, if the interface delamination and red rust exposure do not occur in the lap joint specimen, the lap joint specimen is determined to be a qualified specimen, otherwise, the lap joint specimen is determined to be an unqualified specimen, and the process returns to S1.

8. A hot-dip galvanizing process for a self-repairing type zinc-aluminum-magnesium plated steel sheet plated alloy, characterized by, A self-repairing galvanized aluminum magnesium steel plate coating alloy design method is provided. A self-repairing galvanized aluminum magnesium steel plate coating alloy design method is provided.

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