A galvanized steel material having high toughness and a method for manufacturing the same

Abstract

This invention discloses a high-toughness galvanized steel and its preparation method, belonging to the field of alloy steel technology. The main component is modified water-based acrylic powder as a passivating agent. This modified water-based acrylic powder contains nano-titanium dioxide modified with γ-(methacryloyloxy)propyltrimethoxysilane, which allows it to polymerize and fix within the modified water-based acrylic powder, preventing titanium dioxide from agglomerating. This results in a high-toughness galvanized steel with good strength and toughness, as well as long-lasting corrosion resistance. A layer of calcium carbonate is pre-deposited on the steel surface before zinc plating, serving as nucleation sites for easy adhesion of the subsequent zinc layer and generating ammonium ions. These ammonium ions thoroughly remove the oxide layer and activate the steel surface. Before the steel enters the high-temperature zinc bath, the ammonium ions form a thin protective film on its surface, preventing the steel from being re-oxidized in the air.

Description

Technical Field

[0001] This invention belongs to the field of alloy steel technology, specifically a galvanized steel with high toughness and its preparation method. Background Technology

[0002] In the infrastructure sector, on the one hand, the complexity of construction projects and their environments is constantly increasing; on the other hand, higher demands are being placed on construction efficiency. Completing complex infrastructure projects in a short period inevitably places higher demands on construction machinery. Taking cranes as an example, to have the ability to lift large, heavy objects to great heights, their structural components must be large-scale, lightweight, and precise. As the functions of construction machinery continue to improve, the requirements for the steel used in structural components are becoming increasingly stringent. They must not only possess good strength, toughness, weldability, and fatigue resistance, but also high hardenability, uniform mechanical properties, and stability of mechanical properties under complex service environments. Increasing the carbon and other alloying element content is an effective way to improve the strength of steel; however, increasing the carbon equivalent will adversely affect the toughness, weldability, and fatigue resistance of the steel. How to improve the weldability and fatigue resistance of steel while maintaining both strength and toughness has become a critical issue that urgently needs to be addressed.

[0003] Hot-dip galvanized steel refers to steel that has been cleaned and activated, then immersed in molten zinc. Through the reaction and diffusion between iron and zinc, an iron-zinc alloy layer is formed on the surface of the steel, resulting in steel material with certain corrosion resistance. The hot-dip galvanizing process plays a decisive role in the corrosion resistance of the steel.

[0004] The invention patent with authorization announcement number CN116732507B discloses a passivation solution for galvanized steel and its preparation method. The main raw materials of the passivation solution are composed of the following components by mass fraction: 3-20% water-based acrylic resin, 0.5-15% isopropyltris(dioctylpyrophosphoryloxy)titanate, 0.01-5% ammonium titanate, 1-5% vanadium oxooxoate, 0.01-2% nano-silica, 0.01-2% polyethylene wax, 0-10% ethanol, 0-5% regulator A, 0-5% additive B, and the balance being deionized water. It can form a film layer on the surface of the galvanized layer with high adhesion and high density, and also has certain corrosion resistance, fingerprint resistance and lubrication properties. However, the water-based acrylic emulsion used in this solution is prone to aging, and the film layer formed on the surface of the galvanized layer is also prone to aging, leading to failure of corrosion resistance. Summary of the Invention

[0005] To address the problems mentioned in the background section, the technical solution of this invention is as follows: A method for preparing galvanized steel with high toughness includes the following steps: Step 1: After pickling and alkali treatment, the steel is pretreated. Activated bacterial solution is evenly sprayed onto the surface of the pretreated steel, and then it is immersed in a flux containing calcium chloride and urea to obtain fluxed steel.

[0006] Step 2: After treating the nano-titanium dioxide with γ-(methacryloyloxy)propyltrimethoxysilane, modified nano-titanium dioxide is obtained.

[0007] Step 3: The double bonds on the surface of modified nano-titanium dioxide are polymerized with acrylic acid under the initiation of ammonium persulfate to obtain modified waterborne acrylic powder. A passivating agent is prepared using the modified waterborne acrylic powder, polyethylene wax emulsion, vanadium oxoacetate, ethanol, sodium fluorozirconate and zinc sulfate as raw materials.

[0008] Step 4: Place the Zn block and Al block in an electric arc vacuum melting furnace to form an alloy plating bath. Immerse the fluxed steel in the alloy plating bath to obtain hot-dip galvanized steel. Immerse the hot-dip galvanized steel in a passivating agent to obtain galvanized steel with high toughness.

[0009] Furthermore, the specific steps for preparing the activated bacterial solution are as follows: The culture medium was prepared using the ATCC 1376 NH4-YE formula recommended by the American Culture Collection Center. The culture medium was then sterilized at 120-122℃ for 20-30 minutes, followed by UV sterilization on a clean bench with ventilation. Once the culture medium cooled to room temperature, it was transferred to a container, and *Bacillus pasteurellii* was added using a sterile pipette to obtain the bacterial suspension. The volume ratio of *Bacillus pasteurellii* to the culture medium was 1:100. The bacterial suspension was then placed in a constant-temperature shaking incubator at 28-30℃, with a shaking frequency of 200-300 rpm, for 48-49 hours to obtain the activated bacterial suspension.

[0010] Furthermore, the specific preparation steps of the flux are as follows: Zinc chloride, calcium chloride, glucose, dipotassium hydrogen phosphate, ammonium chloride, urea, magnesium sulfate, nickel chloride, sodium sulfate, and deionized water are mixed to obtain a plating flux.

[0011] Furthermore, the ratio of zinc chloride, calcium chloride, glucose, dipotassium hydrogen phosphate, ammonium chloride, urea, magnesium sulfate, nickel chloride, sodium sulfate, and deionized water is 35-40g: 20-30g: 18-20g: 8-10g: 15-20g: 4-7g: 0.8-1g: 0.8-1g: 0.4-0.6g: 950-980g.

[0012] Furthermore, the specific preparation steps for pretreated steel are as follows: The steel is immersed in an alkaline washing solution consisting of 100-110 g / L NaOH and 1-2 g / L sodium alkyl sulfonate at 55-60°C for 4-5 minutes. Then, it is immersed in an acid pickling solution consisting of 15-20% hydrochloric acid and 2-2.2 g / L hexamethylenetetramine at 20-25°C for 25-30 minutes. After filtration, the filter cake is washed 2-4 times with deionized water to obtain the pretreated steel.

[0013] Furthermore, the specific preparation steps for fluxed steel are as follows: The activated bacterial solution is uniformly sprayed onto the surface of the pretreated steel by spraying at a rate of 8-12 g / m². The surface moisture content is 20-35%. After spraying, the surface is left to stand for 30-40 minutes, then immersed in a fluxing agent and left to stand at 20-25°C for 24-26 hours. Next, it is immersed in a 70-72% ethanol solution for 2-4 minutes and then vacuum dried at 60-70°C for 1-2 hours to obtain the fluxed steel.

[0014] Furthermore, the steel is composed of the following components by mass percentage: C: 0.05-0.08%, Mn: 1.45-1.55%, Si: 0.05-0.20%, P: 0.010-0.012%, S: 0.006-0.008%, Nb: 0.052-0.065%, Cr: 0.30-0.40%, Al: 0.03-0.06%, Ti: 0.040-0.060%, N: 0.003-0.005%, with the balance being Fe and unavoidable impurities.

[0015] Furthermore, the specific preparation steps for modified nano-titanium dioxide are as follows: Nano-titanium dioxide, anhydrous ethanol, and deionized water were added to a reaction vessel and stirred for 10-12 min at 50-60℃ and 500-600 r / min. Then, γ-(methacryloyloxy)propyltrimethoxysilane was added, and the pH was adjusted to 3-4 with hydrochloric acid solution. The reaction was continued with stirring for 6-7 h. After filtration, the precipitate was washed 2-3 times with deionized water and anhydrous ethanol and dried under vacuum at 60-70℃ for 1-2 h to obtain modified nano-titanium dioxide.

[0016] Furthermore, the ratio of nano-titanium dioxide, anhydrous ethanol, deionized water, and γ-(methacryloyloxy)propyltrimethoxysilane is 20-30g: 250-300mL: 100-150mL: 6-7g.

[0017] Furthermore, the specific preparation steps for the modified waterborne acrylic powder are as follows: Modified nano-titanium dioxide, an acrylic acid solution with a neutralization degree of 50-60%, and deionized water were added to a reaction vessel. Nitrogen gas was introduced for protection, and the reaction was stirred at 70-80℃ and 500-600 r / min for 1-2 hours. After cooling to 50-60℃, ammonium persulfate as an initiator and hydroxymethylacrylamide as a crosslinking agent were added to the reaction vessel, and stirring was continued for 2-4 hours. The mixture was filtered, and the filter cake was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried at 60-70℃ for 1-2 hours to obtain modified waterborne acrylic acid powder.

[0018] Furthermore, the ratio of modified nano-titanium dioxide, acrylic acid solution, deionized water, ammonium persulfate and hydroxymethylacrylamide is 12-14g: 250-280mL: 2-3L: 2-4g: 1-2g.

[0019] Furthermore, for the acrylic acid solution with a neutralization degree of 50-60%, a sodium hydroxide solution with a mass fraction of 5-10% is used as a neutralizing agent. During the neutralization process, the target pH value of the system is controlled to be 6.0-7.5, and the conductivity is maintained at 1000-2000 μS / cm.

[0020] Furthermore, the specific preparation steps of the passivating agent are as follows: Modified waterborne acrylic powder, 40-50% polyethylene wax emulsion, vanadium oxooxoate, 10-12% ethanol, sodium fluorozirconate, and zinc sulfate are stirred and mixed at 20-25℃ and 500-600 r / min for 30-40 min to obtain a passivating agent with a solid content of 8-12%, a free fluorine degree of 0.2-0.4%, and an emulsion viscosity of 20-30 mPa·s.

[0021] Furthermore, the ratio of modified waterborne acrylic powder, polyethylene wax emulsion, vanadium oxoacetate, ethanol, sodium fluorozirconate, and zinc sulfate is 10-12g: 8-10mL: 1-2g: 50-60mL: 2-3g: 1-1.2g.

[0022] Furthermore, the specific preparation steps for hot-dip galvanized steel are as follows: Zn and Al blocks are placed in an electric arc vacuum melting furnace at a mass ratio of 1:0.1 and melted at 650-660℃ to obtain an alloy melt. After cooling to 480-500℃, 0.6-0.8% In by mass is added, and the mixture is kept at this temperature for 2-3 hours while being stirred evenly to obtain an alloy plating bath. The temperature is maintained at 480℃. After peeling off the oxide layer on the surface of the alloy plating bath, the fluxed steel is immersed in the alloy plating bath for 60-70 seconds. After removing the fluxed steel from the alloy plating bath, it is quickly placed in deionized water to cool its temperature to 20-30℃ to obtain hot-dip galvanized steel.

[0023] A galvanized steel with high toughness is prepared based on the above-described preparation method.

[0024] The beneficial effects of this invention are: 1. The galvanized steel with high toughness prepared by this invention uses modified waterborne acrylic powder as the main component of the passivating agent. The modified waterborne acrylic powder contains nano-titanium dioxide modified by γ-(methacryloyloxy)propyltrimethoxysilane, which enables it to polymerize and be fixed in the modified waterborne acrylic powder, making it less prone to agglomeration, thus giving it good strength and toughness, as well as long-term corrosion resistance.

[0025] 2. After pickling to remove impurities, the activated bacterial solution is sprayed onto the steel surface using a spraying method. The steel is then immersed in a flux. The activated bacterial solution contains Bacillus pasteurellii, which uses microbial-induced calcium carbonate precipitation technology to pre-deposit a layer of calcium carbonate on the steel surface before zinc plating. The presence of calcium carbonate serves as a nucleation site, facilitating the adhesion of the subsequent zinc layer. Furthermore, the microbial-induced calcium carbonate precipitation technology generates ammonium ions, which react with the naturally formed ferrous oxide film on the steel surface, thoroughly removing the oxide layer and activating the steel surface, making it more reactive with the zinc bath. This lays the foundation for the subsequent zinc layer adhesion. Before the steel enters the high-temperature zinc bath, the ammonium ions form a thin protective film on its surface, preventing the steel from being re-oxidized in the air and ensuring the stability of the zinc plating process.

[0026] 3. The passivation solution of the present invention contains modified waterborne acrylic powder, which contains nano-titanium dioxide modified by γ-(methacryloyloxy)propyltrimethoxysilane. The presence of nano-titanium dioxide partly acts as a reinforcing phase to improve the strength of the steel, and partly acts as an anti-aging agent to prevent the aging of waterborne acrylic. After the waterborne acrylic emulsion dries, it will form a continuous film on the steel surface, which can effectively isolate air, moisture, salt and other corrosive substances from contacting the steel surface, fundamentally slowing down or preventing the steel from rusting. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1: A method for preparing galvanized steel with high toughness, comprising the following steps: S1: The culture medium was prepared using the formula ATCC 1376 NH4-YE recommended by the American Culture Collection Center. The culture medium was then sterilized at 122℃ for 30 min, and then placed on a clean bench for UV sterilization and ventilation. When the temperature of the culture medium dropped to room temperature, the culture medium was taken into a container, and Bacillus pasteurellii was added to the culture medium using a sterile pipette to obtain the bacterial solution. The volume ratio of Bacillus pasteurellii to culture medium was 1:100. The bacterial solution was placed in a constant temperature shaking incubator for incubation at a temperature of 30℃ and a shaking frequency of 300 r / min for 49 h to obtain the activated bacterial solution.

[0029] S2: Mix 40g zinc chloride, 30g calcium chloride, 20g glucose, 10g dipotassium hydrogen phosphate, 20g ammonium chloride, 7g urea, 1g magnesium sulfate, 1g nickel chloride, 0.6g sodium sulfate and 980g deionized water to obtain a plating flux.

[0030] S3: Immerse the steel in an alkaline washing solution composed of 110 g / L NaOH and 2 g / L sodium alkyl sulfonate at 60°C for 5 min, then immerse it in an acid washing solution composed of 20% hydrochloric acid and 2.2 g / L hexamethylenetetramine at 25°C for 30 min. Filter the solution and wash the filter cake four times with deionized water to obtain pretreated steel. Spray an activated bacterial solution evenly onto the surface of the pretreated steel using a spraying method, with a spraying amount of 8-12 g / m² and a surface moisture content of 20-35%. After spraying, let it stand for 30-40 min, then immerse it in a fluxing agent and let it stand at 25°C for 26 h. Finally, immerse it in a 72% ethanol solution for 4 min and vacuum dry it at 70°C for 2 h to obtain fluxed steel.

[0031] The steel is composed of the following components by mass percentage: C: 0.08%, Mn: 1.55%, Si: 0.20%, P: 0.012%, S: 0.008%, Nb: 0.065%, Cr: 0.40%, Al: 0.06%, Ti: 0.060%, N: 0.005%, with the remainder being Fe and unavoidable impurities.

[0032] S4: Add 30g of nano-titanium dioxide, 300mL of anhydrous ethanol and 150mL of deionized water to a reaction vessel, stir for 12min at 60℃ and 600r / min, then add 7g of γ-(methacryloyloxy)propyltrimethoxysilane, adjust the pH to 4 with hydrochloric acid solution, continue stirring for 7h, filter, wash the precipitate three times with deionized water and anhydrous ethanol, and vacuum dry at 70℃ for 2h to obtain modified nano-titanium dioxide.

[0033] S5: 14g of modified nano-titanium dioxide, 280mL of acrylic acid solution with a neutralization degree of 60% and 3L of deionized water were added to a reaction vessel, and nitrogen gas was introduced for protection. The mixture was stirred at 80℃ and 600r / min for 2h. After cooling to 60℃, 4g of ammonium persulfate as an initiator and 2g of hydroxymethylacrylamide as a crosslinking agent were added to the reaction vessel. The mixture was stirred for another 4h and filtered. The filter cake was washed 4 times with deionized water and anhydrous ethanol, respectively, and dried under vacuum at 70℃ for 2h to obtain modified waterborne acrylic acid powder. 12g of modified waterborne acrylic acid powder, 10mL of 50% polyethylene wax emulsion, 2g of vanadium oxoacetate, 60mL of 12% ethanol, 3g of sodium fluorozirconate and 1.2g of zinc sulfate were stirred and mixed at 25℃ and 600r / min for 40min to obtain a passivating agent with a solid content of 12%, a free fluorine degree of 0.4% and an emulsion viscosity of 30mPa·s.

[0034] S6: Place Zn blocks and Al blocks in an electric arc vacuum melting furnace at a mass ratio of 1:0.1 and melt them at 660℃ to obtain an alloy melt. After cooling to 500℃, add 0.8% In by mass, keep warm for 3 hours and stir evenly to obtain an alloy plating bath. Maintain the temperature at 480℃, peel off the oxide layer on the surface of the alloy plating bath, and immerse the fluxed steel in the alloy plating bath for 70 seconds. After removing the fluxed steel from the alloy plating bath, quickly place it in deionized water to cool its temperature to 30℃ to obtain hot-dip galvanized steel.

[0035] S7: Place the passivating agent in the passivation tank, add 10-15% hydrochloric acid solution to adjust the pH value to 3-4, then immerse the hot-dip galvanized steel in the passivating agent to form a uniform wet film on the surface of the hot-dip galvanized steel with a thickness of 15μm. Let it stand for 4 minutes, then vacuum dry at 60℃ for 3 hours to obtain galvanized steel with a dry film thickness of 1.5μm and high toughness.

[0036] Example 2: This example provides a method for preparing galvanized steel with high toughness. The difference from Example 1 is that the ratio of zinc chloride, calcium chloride, glucose, dipotassium hydrogen phosphate, ammonium chloride, urea, magnesium sulfate, nickel chloride, sodium sulfate and deionized water in step S2 is 38g:25g:19g:9g:18g:5g:0.9g:0.9g:0.5g:960g.

[0037] Example 3: This example provides a method for preparing galvanized steel with high toughness. The difference from Example 1 is that in step S4, the ratio of nano titanium dioxide, anhydrous ethanol, deionized water and γ-(methacryloyloxy)propyltrimethoxysilane is 25g:280mL:130mL:6.5g.

[0038] Example 4: This example provides a method for preparing galvanized steel with high toughness. The difference from Example 1 is that the ratio of modified nano-titanium dioxide, acrylic acid solution, deionized water, ammonium persulfate and hydroxymethylacrylamide in step S5 is 13g:260mL:2.3L:3g:1.2g.

[0039] Example 5: This example provides a method for preparing galvanized steel with high toughness. The difference from Example 1 is that the ratio of modified waterborne acrylic powder, polyethylene wax emulsion, vanadium oxoacetate, ethanol, sodium fluorozirconate and zinc sulfate in step S5 is 11g:9mL:1.2g:55mL:2.3g:1.1g.

[0040] Comparative Example 1: Based on Example 1, the activated bacterial solution in step S3 was omitted.

[0041] Comparative Example 2: Based on Example 1, the passivating agent in step S7 was replaced with a commercially available water-based acrylic emulsion.

[0042] Comparative Example 3: Based on Example 1, the modified nano titanium dioxide in step S5 was replaced with nano titanium dioxide.

[0043] The high-strength, corrosion-resistant, lightweight steels prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to performance tests. The tensile properties, impact properties, and corrosion resistance of the steels were measured. Tensile properties were determined according to the national standard GB / T228-2002 "Metallic Materials - Tensile Testing at Room Temperature" and impact properties were determined according to GB / T229-2007 "Metallic Materials - Charpy Impact Test". The corrosion rate was calculated using the weight loss method formula: V = (W1 - W2) / (S * t), where t is the time (96 h). The corrosion medium was a 5% NaCl solution at 50°C, and the solution volume to the exposed sample area ratio was 20 mL / cm². 2 The test was conducted using a magnetic stirrer at a speed of 900 r / min.

[0044] The results are shown in Table 1: Table 1. Steel Performance Test Data Tensile properties 529 523 525 522 521 443 453 501 Impact performance 832 825 828 823 824 553 576 780 <![CDATA[Corrosion rate (g / m 2 ·h)]]> 0.002 0.003 0.003 0.004 0.004 0.053 0.070 0.025 As can be seen from Table 1, the high-strength, corrosion-resistant, and lightweight steel prepared in Examples 1-3 has significantly better tensile and impact properties than the comparative example, and significantly lower corrosion properties than the comparative example. This indicates that the high-strength, corrosion-resistant, and lightweight steel prepared in this invention has good mechanical strength and corrosion resistance.

[0045] In Comparative Example 1, the activated bacterial solution was discarded. Without the activated bacterial solution, a calcium carbonate layer could not be deposited on the steel surface, resulting in the lack of zinc nucleation sites. Furthermore, the residual ferrous oxide film after pickling could not be completely removed by ammonium ions, leading to a significant reduction in the bonding force between the zinc layer and the steel substrate during subsequent hot-dip galvanizing. The zinc layer was prone to delamination and peeling, and could not cooperate with the steel substrate to bear the load, ultimately resulting in a decrease in tensile and impact properties, and the loss of ultra-high strength and high toughness characteristics. The residual oxide layer and the loose zinc layer adhesion allowed corrosive media to easily penetrate the gaps in the zinc layer and react directly with the steel substrate, while the physical barrier effect of the calcium carbonate layer was absent.

[0046] Comparative Example 2 replaced the passivating agent with a commercially available water-based acrylic emulsion. The commercially available water-based acrylic emulsion does not contain γ-(methacryloyloxy)propyltrimethoxysilane-modified titanium dioxide. The passivation film is prone to cracking due to ultraviolet aging, and the film layer is loose with pinholes. The passivation film is brittle and easily cracks when the steel is subjected to tensile or impact stress. It cannot help disperse stress, resulting in a decrease in tensile properties, a decrease in impact properties, and a deterioration in mechanical property stability. The commercially available emulsion has not been modified with nano-titanium dioxide, and has poor interfacial compatibility with the hot-dip galvanized layer. After drying, the film layer is prone to peeling, which further accelerates the intrusion of corrosive media and aggravates performance degradation.

[0047] In Comparative Example 3, the modified nano-titanium dioxide was replaced with nano-titanium dioxide. The unmodified nano-titanium dioxide had many hydroxyl groups on its surface and strong hydrophilicity, resulting in poor compatibility with hydrophobic acrylic emulsions. It was easy for it to agglomerate in the emulsion, forming interparticle gaps. After drying, the passivation film had a large number of micropores, through which corrosive media could penetrate. The agglomerated nano-titanium dioxide could not be uniformly dispersed in the acrylic emulsion and easily became stress concentration points.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing galvanized steel with high toughness, characterized in that, Includes the following steps: Step 1: After pickling and alkali treatment, steel is pretreated to obtain pretreated steel. Activated bacterial solution is evenly sprayed onto the surface of the pretreated steel using a spraying method, and then it is immersed in a flux containing calcium chloride and urea to obtain fluxed steel. Step 2: After treating the nano-titanium dioxide with γ-(methacryloyloxy)propyltrimethoxysilane, modified nano-titanium dioxide is obtained; Step 3: The double bonds on the surface of modified nano-titanium dioxide are polymerized with acrylic acid under the initiation of ammonium persulfate to obtain modified waterborne acrylic powder. A passivating agent is prepared using the modified waterborne acrylic powder, polyethylene wax emulsion, vanadium oxoacetate, ethanol, sodium fluorozirconate and zinc sulfate as raw materials. Step 4: Place the Zn block and Al block in an electric arc vacuum melting furnace to form an alloy plating bath, immerse the fluxed steel in the alloy plating bath to obtain hot-dip galvanized steel, and immerse the hot-dip galvanized steel in a passivating agent to obtain galvanized steel with high toughness. The specific steps for preparing the activated bacterial solution are as follows: Culture medium was prepared using the ATCC 1376 NH4-YE formula recommended by the American Culture Collection Center. The culture medium was then sterilized at 120-122℃ for 20-30 minutes, and then placed on a clean bench for UV sterilization with ventilation. When the culture medium temperature dropped to room temperature, the culture medium was taken into a container, and Bacillus pasteurellii was added to the culture medium using a sterile pipette to obtain bacterial suspension. The volume ratio of Bacillus pasteurellii to culture medium was 1:

100. The bacterial suspension was placed in a constant temperature shaking incubator for incubation at a temperature of 28-30℃, a shaking frequency of 200-300 r / min, and an incubation time of 48-49 hours to obtain activated bacterial suspension. The specific preparation steps of the plating flux are as follows: Zinc chloride, calcium chloride, glucose, dipotassium hydrogen phosphate, ammonium chloride, urea, magnesium sulfate, nickel chloride, sodium sulfate, and deionized water are stirred and mixed to obtain a plating flux. The ratio of zinc chloride, calcium chloride, glucose, dipotassium hydrogen phosphate, ammonium chloride, urea, magnesium sulfate, nickel chloride, sodium sulfate, and deionized water is 35-40g: 20-30g: 18-20g: 8-10g: 15-20g: 4-7g: 0.8-1g: 0.8-1g: 0.4-0.6g: 950-980g; The specific preparation steps for the hot-dip galvanized steel are as follows: Zn and Al blocks are placed in an electric arc vacuum melting furnace at a mass ratio of 1:0.1 and melted at 650-660℃ to obtain an alloy melt. After cooling to 480-500℃, 0.6-0.8% In by mass is added, and the mixture is kept at this temperature for 2-3 hours while being stirred evenly to obtain an alloy plating bath. The temperature is maintained at 480℃. After peeling off the oxide layer on the surface of the alloy plating bath, the fluxed steel is immersed in the alloy plating bath for 60-70 seconds. After removing the fluxed steel from the alloy plating bath, it is quickly placed in deionized water to cool its temperature to 20-30℃ to obtain hot-dip galvanized steel.

2. The method for preparing a high-toughness galvanized steel according to claim 1, characterized in that, The specific preparation steps for the fluxed steel are as follows: The steel is immersed in an alkaline washing solution composed of 100-110 g / L NaOH and 1-2 g / L sodium alkyl sulfonate at 55-60°C for 4-5 minutes. Then, it is immersed in an acid pickling solution composed of 15-20% hydrochloric acid and 2-2.2 g / L hexamethylenetetramine at 20-25°C for 25-30 minutes. After filtration, the steel is washed 2-4 times with deionized water to obtain pretreated steel. An activated bacterial solution is then uniformly sprayed onto the surface of the pretreated steel using a spraying method, with a spraying amount of 8-12 g / m². 2 The surface moisture content is 20-35%. After spraying, let it stand for 30-40 minutes, then immerse it in the flux and stand at 20-25℃ for 24-26 hours. Then soak it in a 70-72% ethanol solution for 2-4 minutes and vacuum dry it at 60-70℃ for 1-2 hours to obtain the fluxed steel.

3. The method for preparing a high-toughness galvanized steel according to claim 2, characterized in that, The steel is composed of the following components by mass percentage: C: 0.05-0.08%, Mn: 1.45-1.55%, Si: 0.05-0.20%, P: 0.010-0.012%, S: 0.006-0.008%, Nb: 0.052-0.065%, Cr: 0.30-0.40%, Al: 0.03-0.06%, Ti: 0.040-0.060%, N: 0.003-0.005%, with the balance being Fe and unavoidable impurities.

4. The method for preparing a high-toughness galvanized steel according to claim 1, characterized in that, The specific preparation steps for the modified nano-titanium dioxide are as follows: Nano-titanium dioxide, anhydrous ethanol, and deionized water were added to a reaction vessel and stirred for 10-12 min at 50-60℃ and 500-600 r / min. Then, γ-(methacryloyloxy)propyltrimethoxysilane was added, and the pH was adjusted to 3-4 with hydrochloric acid solution. The reaction was continued to be stirred for 6-7 h. After filtration, the precipitate was washed 2-3 times with deionized water and anhydrous ethanol and dried under vacuum at 60-70℃ for 1-2 h to obtain modified nano-titanium dioxide. The ratio of nano-titanium dioxide, anhydrous ethanol, deionized water and γ-(methacryloyloxy)propyltrimethoxysilane is 20-30g: 250-300mL: 100-150mL: 6-7g.

5. The method for preparing a high-toughness galvanized steel according to claim 1, characterized in that, The specific preparation steps of the modified water-based acrylic powder are as follows: Modified nano-titanium dioxide, an acrylic acid solution with a neutralization degree of 50-60%, and deionized water were added to a reaction vessel. Nitrogen gas was introduced for protection, and the reaction was stirred at 70-80℃ and 500-600 r / min for 1-2 hours. The mixture was then cooled to 50-60℃, and ammonium persulfate as an initiator and hydroxymethylacrylamide as a crosslinking agent were added to the reaction vessel. The mixture was stirred for another 2-4 hours, filtered, and washed 2-4 times with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried at 60-70℃ for 1-2 hours to obtain modified waterborne acrylic acid powder. The acrylic acid solution with a neutralization degree of 50-60% uses a sodium hydroxide solution with a mass fraction of 5-10% as a neutralizing agent. During the neutralization process, the target pH value of the system is controlled to be 6.0-7.5, and the conductivity is maintained at 1000-2000 μS / cm. The ratio of modified nano-titanium dioxide, acrylic acid solution, deionized water, ammonium persulfate and hydroxymethylacrylamide is 12-14g: 250-280mL: 2-3L: 2-4g: 1-2g.

6. The method for preparing a high-toughness galvanized steel according to claim 1, characterized in that, The specific preparation steps of the passivating agent are as follows: Modified waterborne acrylic powder, polyethylene wax emulsion (40-50% by mass), vanadium oxoacetate, ethanol (10-12% by mass), sodium fluorozirconate, and zinc sulfate are stirred and mixed at 20-25℃ and 500-600 r / min for 30-40 min to obtain a passivating agent with a solid content of 8-12%, a free fluorine degree of 0.2-0.4%, and an emulsion viscosity of 20-30 mPa·s. The ratio of the modified waterborne acrylic powder, polyethylene wax emulsion, vanadium oxoacetate, ethanol, sodium fluorozirconate, and zinc sulfate is 10-12g: 8-10mL: 1-2g: 50-60mL: 2-3g: 1-1.2g.

7. A galvanized steel with high toughness, characterized in that, It was prepared according to the preparation method described in claim 1.