Colorful hot-dip galvanizing alloy for medium-thickness steel plate and preparation and application methods of colorful hot-dip galvanizing alloy

Abstract

The invention discloses a colored hot-dip galvanizing alloy for a medium-thickness steel plate as well as a preparation method and an application method of the colored hot-dip galvanizing alloy. The thickness of the medium-thickness steel plate is 6-50mm; the zinc alloy comprises the following components in percentage by mass: 0.05 to 1.80 percent of Mn, 0.01 to 1.20 percent of Nb, 0.01 to 0.10 percent of Cu and the balance of Zn and impurity elements. According to the colorful hot-dip galvanizing alloy for the medium-thickness steel plate and the preparation method and the application method of the colorful hot-dip galvanizing alloy, the galvanizing alloy with more excellent performance is obtained mainly by optimizing the alloy components, the proportion and the preparation method, and the galvanizing quality is improved by controlling the alloy element content and the galvanizing temperature. According to the method, the thickness of oxidation films of plates with different thicknesses is ensured to have a slowly increasing platform (namely, the color change in the stage is relatively unobvious), rapid water cooling by using the platform is facilitated, so that a plated part with stable color is obtained, and the surface color stability of the plate is better, and the plate has better corrosion protection property, adaptability and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metal surface treatment, and particularly relates to a color hot-dip galvanized alloy for medium-thick steel plates and a preparation method and an application method thereof. BACKGROUND

[0002] Existing steel coloring technologies mainly include color coating and color passivation technology, but have various defects. For example, the color coating technology is complicated and has high material and equipment costs; hexavalent chromate passivation has been limited due to its toxicity, and the environment-friendly passivation process is not mature.

[0003] Color hot-dip galvanizing technology is a new method for obtaining a color plated layer. It is based on the traditional hot-dip galvanizing process, changes the alloy composition of the plating solution, adds a small amount of color elements in the zinc solution, and adjusts the immersion plating temperature and time and other process parameters to obtain a color plated layer. A variety of color elements can present more stable colors, but the existing color hot-dip galvanizing process has obvious oxygen potential differences between the main color elements Mn, Ti, Y and Ce, which leads to the need for more complex processes to control color uniformity.

[0004] For example, the patent with the publication number CN119287216A and the name “a color hot-dip galvanized alloy and a preparation method and a use method thereof” uses three or four of the elements Mn, Ti, Y and Ce, and controls the final color through a relatively complex process (temperature, thickness, cooling speed, cooling time, etc.), which significantly increases the production difficulty and seriously affects the production efficiency. SUMMARY

[0005] Therefore, the present application provides a color hot-dip galvanized alloy for medium-thick steel plates and a preparation and application method thereof to solve the problems of complex existing steel coloring process affecting production efficiency and poor surface color stability.

[0006] The technical scheme is as follows: A color hot-dip galvanized alloy for medium-thick steel plates, the key of which is that the thickness of the medium-thick steel plate is 6-50 mm. The zinc alloy includes, in terms of mass percentage, Mn: 0.05-1.80%, Nb: 0.01-1.20%, Cu: 0.01-0.10%, and the rest is Zn and impurity elements.

[0007] Using the above scheme, Mn is a commonly used alloying element in color zinc plating, while Nb has a similar oxidizing ability to Mn. Using them together can improve the color stability of the plated parts. At the same time, adding Cu can improve the fluidity of the alloy plating solution, which is beneficial for obtaining a uniformly composed alloy plating solution after melting. By controlling the content of alloying elements and the zinc plating temperature, a slow-growing plateau in the oxide film thickness of plates of different thicknesses is ensured (i.e., color changes are relatively insignificant during this stage). This plateau is advantageous for rapid water cooling, thereby obtaining plated parts with stable colors.

[0008] Preferably, the Mn content is 0.10~0.45%, the Nb content is 0.03~0.08%, and the Cu content is 0.03~0.07%. Using this scheme, Mn serves as the core coloring element. This range allows it to form a synergistic oxidation effect with Nb (their oxygen potentials are similar), avoiding both excessively low content leading to a pale color and excessively high content causing localized segregation. This ensures uniform oxide film thickness and ultimately presents a stable sandy stone color. Furthermore, this range of Nb content better matches the oxidation capacity of Mn, while avoiding excessively high content increasing costs and excessively low content failing to exert a synergistic coloring effect, thus minimizing color difference.

[0009] A method for preparing a color hot-dip galvanized alloy for medium-thick steel plates, the key of which includes the following steps: A1. Prepare pure Zn, Zn-Cu master alloy, Zn-Nb master alloy and Zn-Mn master alloy according to the alloy mass percentage ratio; A2, pure Zn is melted at 420~480℃, then Zn-Cu master alloy is added, Zn-Nb master alloy is added after complete melting, Zn-Mn master alloy is added after complete melting, the temperature of the alloy liquid is maintained at 425~465℃, and the alloy liquid is obtained after stirring evenly. A3, the zinc alloy is obtained by pouring and cooling the molten alloy.

[0010] When using the above scheme and adding elements in the above order, Cu is added first to optimize the fluidity of the zinc liquid, creating conditions for the uniform dispersion of Nb and Mn, avoiding local aggregation of elements, ensuring uniform element distribution, improving alloy uniformity and performance stability, and suitable temperature combined with stirring operation, which is conducive to further ensuring the full diffusion of elements in the zinc liquid, and the synergistic effect thus ensuring the color stability of the coating.

[0011] Preferably, the intermediate alloys are all smelted using vacuum melting, and the total mass of each Zn+X alloy is not less than 99.99%, where X is Mn, Nb, or Cu, and the purity of pure Zn before smelting is greater than or equal to 99.995%. Adopting this approach helps improve alloy purity, ensures accurate element ratios, and thus guarantees stable coating color and corrosion resistance.

[0012] A method for applying color hot-dip galvanized alloy for medium-thick steel plates, the key of which includes the following steps: B1, Pretreatment of the steel sheet to be plated; B2, The zinc alloy is placed in a zinc pot and melted to form a zinc alloy plating solution; B3. Maintain the zinc pot temperature within the range of 433~458℃, and immerse the steel sheet to be plated in the zinc pot for immersion plating. B4. After the immersion plating is completed, the plated steel sheet is removed and cooled.

[0013] By adopting the above scheme and combining the thermal conductivity characteristics of medium and thick plates, the temperature range is optimized to avoid excessive oxidation of Mn / Nb and increased color difference of the coating due to excessively high temperature, and to prevent poor fluidity of zinc liquid and insufficient coating adhesion due to excessively low temperature, thus ensuring that the oxide film thickness of plates of different thicknesses is in a stable plateau period.

[0014] As a preferred option: In step B3, the temperature of the zinc alloy plating solution is adjusted according to the thickness d of the steel sheet to be plated: when 6 < d ≤ 11 mm, the temperature is 446~458℃; when 11 < d ≤ 18 mm, the temperature is 441~446℃; when 18 < d ≤ 30 mm, the temperature is 437~441℃; when 30 < d ≤ 50 mm, the temperature is 433~437℃. By employing the above scheme and precisely matching "thickness and temperature," the oxide film growth of medium-thick plates of different thicknesses is simultaneously kept at a stable plateau, ultimately achieving a balance between coating color uniformity and corrosion resistance. The thicker the medium-thick plate, the greater its heat capacity and the slower its heating / cooling. Lowering the corresponding plating solution temperature can prevent excessive Mn / Nb oxidation due to residual heat in thick plates and insufficient oxidation due to insufficient temperature in medium-thick plates, ensuring consistent oxidation levels across different thicknesses. The precise correspondence between temperature and thickness ensures uniform oxide film thickness on all plate surfaces (without localized areas of excessive thickness or thinness), resulting in a uniform sandy-gray color for the final coating. At the appropriate temperature, the zinc bath fluidity and surface wetting effect are optimal, leading to a dense coating with strong adhesion. Combined with subsequent cooling processes, performance consistency can be further improved.

[0015] As a preferred method: In step B3, the immersion time is adjusted according to the thickness d of the steel sheet to be plated: when d ≤ 11 mm, the immersion time is 5.5~7 min; when 11 < d ≤ 18 mm, the immersion time is 6~7.5 min; when 18 < d ≤ 30 mm, the immersion time is 6.8~8.5 min; and when 30 < d ≤ 50 mm, the immersion time is 7~9 min. By adopting the above scheme and precisely matching the thickness with the immersion time, it is ensured that medium and thick plates of different thicknesses can achieve sufficient element diffusion and uniform oxidation, guaranteeing consistent coating color, strong adhesion, and stable corrosion resistance.

[0016] As a preferred option: In step B4, the fully coated steel sheet is first removed at a constant speed of 0.03 m / s to 0.05 m / s; Secondly, the air cooling time is 45~60 seconds. After the coating color stabilizes, it is then immersed in a water tank for cooling. Finally, after immersing evenly in the passivation bath, remove and air dry. Using this method, through the coordinated operation of multiple steps, the stability of the oxide film can be better secured, the density of the coating strengthened, and ultimately, color uniformity and corrosion resistance guaranteed.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. The colored hot-dip galvanizing alloy for medium and thick steel plates provided by this invention, as well as its preparation and application methods, mainly optimize the alloy composition, proportion, and preparation method to obtain a galvanizing alloy with superior performance. By controlling the content of alloying elements and the galvanizing temperature, it is ensured that the oxide film thickness of plates of different thicknesses has a slow growth plateau (i.e., the color change is relatively insignificant at this stage). This facilitates rapid water cooling using this plateau, thereby obtaining a color-stable plated part. Ultimately, the plate surface has better color stability, better corrosion protection, and better compatibility.

[0018] 2. The immersion plating process of the present invention has fewer variables to control and is similar to conventional zinc plating, making it simple and easy for industrial workers to operate and more conducive to implementation.

[0019] 3. The Mn and Nb elements used in this invention have low content and are reasonably priced, which can significantly save production costs and has remarkable economic benefits. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the time-temperature curve of the steel plate surface during the hot-dip galvanizing process; Figure 2 This is a partial schematic diagram of the cooling time-oxide film thickness curve of the steel plate surface after it has been removed from the zinc pot. Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] The terms “first”, “second”, etc. are used to distinguish similar objects, not to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein. The objects distinguished by “first”, “second”, etc. are usually of the same class and the number of objects is not limited. For example, the first object can be one or more.

[0023] Furthermore, the term "and / or" in the specification and claims is used to describe the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0024] In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0025] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0026] In one aspect, the present invention provides a color hot-dip galvanizing alloy for medium-thick steel plates, wherein the thickness of the medium-thick steel plates is defined as 6~50 mm, and the alloy includes Mn, Nb, Cu, Zn and impurity elements.

[0027] Based on the total weight, the zinc alloy comprises, by mass percentage: Mn: 0.05~1.80%, Nb: 0.01~1.20%, Cu: 0.01~0.10%, with the remainder being Zn and impurity elements.

[0028] Preferably, the Mn content is 0.10~0.45%, the Nb content is 0.03~0.08%, the Cu content is 0.03~0.07%, and the remainder is Zn and impurity elements.

[0029] A second aspect of the present invention provides a method for preparing the above-mentioned color hot-dip galvanized alloy for medium and heavy steel plates, wherein the preparation method mainly includes the following steps: Step A1: Prepare pure Zn, Zn-Cu master alloy, Zn-Nb master alloy and Zn-Mn master alloy according to the alloy mass percentage ratio.

[0030] Step A2: Melt pure Zn at 420~480℃, preferably 450℃. Then add Zn-Cu master alloy. After it is completely melted, add Zn-Nb master alloy. After it is completely melted, add Zn-Mn master alloy. Maintain the temperature of the alloy liquid at 425~465℃. Stir evenly to obtain the alloy liquid.

[0031] Step A3: The molten alloy is poured and cooled to obtain the zinc alloy.

[0032] Preferably, the intermediate alloys in step A1 are all melted by vacuum melting, and the total mass of each Zn+X is not less than 99.99%, where X is Mn, Nb, or Cu, and the purity of pure Zn before melting is greater than or equal to 99.995%.

[0033] A third aspect of the present invention provides a method for applying the above-mentioned color hot-dip galvanized alloy for medium and heavy steel plates, wherein the application method mainly includes the following steps: B1, Pretreatment of the steel sheet to be plated; B2, The zinc alloy is placed in a zinc pot and melted to form a zinc alloy plating solution; B3. Maintain the zinc pot temperature within the range of 433~458℃, and immerse the steel sheet to be plated in the zinc pot for immersion plating. B4. After the immersion plating is completed, the plated steel sheet is removed and cooled.

[0034] Preferably, in step B3, the temperature of the zinc alloy plating solution is adjusted according to the thickness d of the steel sheet to be plated: when 6 < d ≤ 11 mm, the temperature is 446~458℃; when 11 < d ≤ 18 mm, the temperature is 441~446℃; when 18 < d ≤ 30 mm, the temperature is 437~441℃; when 30 < d ≤ 50 mm, the temperature is 433~437℃.

[0035] Preferably, in step B3, the immersion plating time is adjusted according to the thickness d of the steel sheet to be plated: when d ≤ 11 mm, the immersion plating time is 5.5~7 min; when 11 < d ≤ 18 mm, the immersion plating time is 6~7.5 min; when 18 < d ≤ 30 mm, the immersion plating time is 6.8~8.5 min; and when 30 < d ≤ 50 mm, the immersion plating time is 7~9 min.

[0036] Preferably, in step B4, the plated steel sheet is first removed at a constant speed of 0.03 m / s to 0.05 m / s; Secondly, the air cooling time is 45~60 seconds. After the coating color stabilizes, it is then immersed in a water tank for cooling. Finally, soak the sample evenly in the passivation tank, then remove it and let it air dry.

[0037] The galvanizing temperature and cooling time are closely related to the thickness of the steel sheet to be galvanized. After the steel sheet is immersed in the zinc bath, the temperature is gradually increased to match the temperature of the zinc bath. After galvanizing is completed, it is removed and gradually cooled in the air. The time-temperature curve is shown below. Figure 1 As shown.

[0038] The thickness of the steel plate significantly affects its time-temperature curve: the thicker the steel plate, the longer the heating and holding time, i.e., the longer the galvanizing time. After being removed from the zinc bath, the steel plate surface cools rapidly, but the heat inside the steel plate gradually dissipates, maintaining the surface temperature within a certain range. This significantly increases the cooling time and also considerably prolongs the selective oxidation time. To maintain a consistent overall oxidation degree (oxide film thickness), it is necessary to lower the galvanizing temperature and extend the cooling time to the oxide film plateau stage before rapid cooling. This results in a uniform, sand-gravel-colored galvanized layer with a consistent oxide film thickness. Figure 2 As shown.

[0039] Example 1 In this embodiment, the selected steel plate to be plated was 8 mm thick. The corresponding alloy plating solution (i.e., the liquid formed by alloy melting in step B2) included Mn: 0.15%, Nb: 0.05%, Cu: 0.05%, with the remainder being Zn and impurity elements. According to the alloy ratio, pure Zn was first melted at 450℃, followed by the sequential addition of Zn-Cu and Zn-Nb intermediate alloys until completely melted. The temperature of the colored hot-dip galvanizing alloy solution was maintained at 451℃. The steel plate to be plated was immersed in the sand-colored hot-dip galvanizing alloy solution for 6 minutes, then removed at a speed of 0.05 m / s, cooled in air, immersed in a water tank, then placed in a passivation tank, and finally removed and dried. Finally, the color of the obtained coating was measured using the CIE Lab color model, and the corrosion performance of the obtained coating was tested using a salt spray test.

[0040] The results showed that the colored coating in this embodiment was a uniform sandy color, with the five-point average of the color saturation being: L=61, a=-1, b=4, and the average color difference ΔE* calculated from the reference value was <3.8; the salt spray test showed no red rust within 120 hours, and the area of ​​white rust was less than 4%.

[0041] Example 2 In this embodiment, the selected steel sheet thickness was 15 mm. The corresponding alloy plating bath consisted of Mn: 0.18%, Nb: 0.04%, Cu: 0.05%, with the remainder being Zn and impurity elements. According to the alloy ratio, pure Zn was first melted at 450℃, followed by the sequential addition of Zn-Cu and Zn-Nb intermediate alloys until complete melting. The temperature of the colored hot-dip galvanizing alloy bath was maintained at 444℃. The steel sheet was immersed in the sand-colored hot-dip galvanizing alloy bath for 6 minutes, then removed at a speed of 0.05 m / s, cooled in air, immersed in a water tank, then placed in a passivation tank, and finally removed and dried. The color of the obtained coating was measured using the CIE Lab color model, and the corrosion performance of the obtained coating was tested using a salt spray test.

[0042] The results showed that the colored coating in this embodiment was a uniform sandy color, with the five-point average of colorimetry being L=59, a=1, b=2, and the average color difference ΔE* calculated from the reference value was <3.5. The salt spray test showed no red rust within 120 hours, and the area of ​​white rust was less than 3%.

[0043] Comparative Example 1 The steel sheet selected for this comparative example has a thickness of 15 mm. The corresponding alloy plating bath includes Mn: 0.18%, Nb: 0.04%, Cu: 0.05%, with the remainder being Zn and impurity elements. According to the alloy ratio, pure Zn was first melted at 450℃, followed by the sequential addition of Zn-Cu and Zn-Nb intermediate alloys until complete melting. The temperature of the color hot-dip galvanizing alloy bath was maintained at 471℃. The steel sheet was immersed in the color hot-dip galvanizing alloy bath for 6 minutes, then removed at a speed of 0.05 m / s, cooled in air, immersed in a water tank, then placed in a passivation tank, and finally removed and dried. The color of the obtained coating was measured using the CIE Lab color model, and the corrosion performance of the obtained coating was tested using a salt spray test.

[0044] The results showed that the colored coating in this embodiment was an uneven blue-green color, with the five-point average of the color chromaticity being: L=31, a=-2, b=-30, and the average color difference ΔE* calculated from the reference value was <10; the salt spray test showed no red rust within 120 hours, and the area of ​​white rust was less than 7%.

[0045] Comparative Example 2 In this comparative example, the selected steel sheet thickness was 15 mm. The corresponding alloy plating bath consisted of Mn: 0.35%, Nb: 0.10%, Cu: 0.05%, with the remainder being Zn and impurity elements. According to the alloy ratio, pure Zn was first melted at 450℃, followed by the sequential addition of Zn-Cu and Zn-Nb intermediate alloys until complete melting. The temperature of the color hot-dip galvanizing alloy bath was maintained at 444℃. The steel sheet was immersed in the color hot-dip galvanizing alloy bath for 6 minutes, then removed at a speed of 0.05 m / s, cooled in air, immersed in a water tank, then placed in a passivation tank, and finally removed and dried. The color of the obtained coating was measured using the CIE Lab color model, and the corrosion performance of the obtained coating was tested using a salt spray test.

[0046] The results showed that the colored coating in this embodiment was an uneven yellow-green color, with the five-point average of the color chromaticity being: L=70, a=-10, b=5, and the average color difference ΔE* calculated from the reference value was <10; the salt spray test showed no red rust within 120 hours, and the area of ​​white rust was less than 5%.

[0047] Example 3 In this embodiment, the selected steel plate to be plated was 35 mm thick. The corresponding alloy plating solution included Mn: 0.20%, Nb: 0.03%, Cu: 0.05%, with the remainder being Zn and impurity elements. According to the alloy ratio, pure Zn was first melted at 450℃, followed by the sequential addition of Zn-Cu and Zn-Nb intermediate alloys until completely melted. The temperature of the colored hot-dip galvanizing alloy solution was maintained at 435℃. The steel plate to be plated was immersed in the sand-colored hot-dip galvanizing alloy solution for 6 minutes, then removed at a speed of 0.05 m / s, cooled in air, immersed in a water tank, then placed in a passivation tank, and finally removed and dried. Finally, the color of the obtained coating was measured using the CIE Lab color model, and the corrosion performance of the obtained coating was tested using a salt spray test.

[0048] The results showed that the colored coating in this embodiment was a uniform sandy color, with the five-point average of the color saturation being: L=58, a=-2, b=3, and the average color difference ΔE* calculated from the reference value was <4.0; the salt spray test showed no red rust within 120 hours, and the area of ​​white rust was less than 5%.

[0049] Comparative Example 3 In this comparative example, the selected steel sheet thickness was 35 mm. The corresponding alloy plating bath consisted of 0.20% Mn, 0.05% Cu, with the remainder being Zn and impurity elements. According to the alloy ratio, pure Zn was first melted at 450℃, followed by the sequential addition of Zn-Cu and Zn-Nb master alloys until complete melting. The temperature of the colored hot-dip galvanizing alloy bath was maintained at 435℃. The steel sheet was immersed in the sand-colored hot-dip galvanizing alloy bath for 6 minutes, then removed at a speed of 0.05 m / s, cooled in air, immersed in a water tank, then placed in a passivation tank, and finally removed and dried. The color of the obtained coating was measured using the CIE Lab color model, and the corrosion performance of the obtained coating was tested using a salt spray test.

[0050] The results showed that the colored coating in this embodiment was an uneven sandy color, with the five-point average of the color saturation being: L=54, a=-3, b=5, and the average color difference ΔE* calculated from the reference value was <12; the salt spray test showed no red rust within 120 hours, and the area of ​​white rust was less than 5%.

[0051] As described above, in Example 3, Nb (0.03%, within the preferred range of 0.03~0.08%) was added, resulting in a uniform sandy-gray color coating with a color difference ΔE* < 4.0, meeting the design target. In contrast, in Comparative Example 3, without Nb, the coating exhibited an uneven sandy-gray color with a color difference ΔE* < 12, significantly reducing color stability. Both examples showed no red rust in the 120-hour salt spray test, and the area of ​​white rust was < 5%, indicating that the addition of Nb does not affect the basic corrosion protection capability of the coating. Nb and Mn have similar oxygen potentials and can synergistically control the degree of oxidation. Without Nb, Mn oxidation alone is prone to local segregation, leading to uneven color, confirming the key role of Nb in optimizing the uniformity of the oxide film. Therefore, the addition of Nb to the zinc alloy in this application is crucial for ensuring the color uniformity of the coating on medium-thick plates without affecting the basic corrosion resistance performance.

[0052] Based on Example 2 and Comparative Example 1, it can be seen that a suitable immersion temperature can ensure that the coating is uniformly sandy and gravelly in color, with a color difference ΔE* < 3.5 and excellent color stability. If the immersion temperature deviates from the suitable range, the coating will be unevenly blue-green, with a color difference ΔE* < 10 and a serious color shift. The deviation of the immersion temperature has little effect on the corrosion resistance, but the final white rust area is smaller and the coating density is better under a suitable immersion temperature.

[0053] Combining Example 2 and Comparative Example 2, it can be seen that in Example 2, the element content is within the preferred range, the coating is uniformly sandy-gray in color, the color difference ΔE* < 3.5, and the color stability is excellent; in Comparative Example 2, the element content exceeds the preferred range, and even if the galvanizing temperature is suitable for the plate thickness (444℃), the coating is still unevenly yellowish-green, the color difference ΔE* < 10, and the color is severely segregated; the deviation in element content has little impact on corrosion resistance, but the area of ​​white rust is smaller and the coating density is better under the preferred content.

[0054] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention. Those skilled in the art, under the guidance of the present invention, can make various similar representations without departing from the spirit and claims of the present invention, and such modifications all fall within the protection scope of the present invention.

Claims

1. A color hot-dip galvanized alloy for medium-thick steel plates, characterized in that: The thickness of the medium-thick steel plate is 6~50 mm; The zinc alloy comprises, by mass percentage: Mn: 0.05~1.80%, Nb: 0.01~1.20%, Cu: 0.01~0.10%, with the remainder being Zn and impurity elements.

2. The color hot-dip galvanized alloy for medium and heavy steel plates according to claim 1, characterized in that: The Mn content is 0.10~0.45%, the Nb content is 0.03~0.08%, and the Cu content is 0.03~0.07%.

3. A method for preparing the zinc alloy as described in claim 1 or 2, characterized in that, Includes the following steps: A1. Prepare pure Zn, Zn-Cu master alloy, Zn-Nb master alloy and Zn-Mn master alloy according to the alloy mass percentage ratio; A2, pure Zn is melted at 420~480℃, then Zn-Cu master alloy is added, Zn-Nb master alloy is added after complete melting, Zn-Mn master alloy is added after complete melting, the temperature of the alloy liquid is maintained at 425~465℃, and the alloy liquid is obtained after stirring evenly. A3, the zinc alloy is obtained by pouring and cooling the molten alloy.

4. The preparation method according to claim 3, characterized in that: The intermediate alloys mentioned in step A1 are all smelted by vacuum melting, and the total mass of Zn+X is not less than 99.99%, where X is Mn, Nb or Cu, and the purity of pure Zn is greater than or equal to 99.995%.

5. A method for applying the zinc alloy as described in any one of claims 1 to 4, characterized in that, Includes the following steps: B1, Pretreatment of the steel sheet to be plated; B2, The zinc alloy is placed in a zinc pot and melted to form a zinc alloy plating solution; B3. Keep the zinc pot temperature within the range of 433℃~458℃, and immerse the steel sheet to be plated in the zinc pot for immersion plating. B4. After the immersion plating is completed, the plated steel sheet is removed and cooled.

6. The application method according to claim 5, characterized in that, In step B3, the temperature of the zinc alloy plating solution is adjusted according to the thickness d of the steel sheet to be plated: when 6 < d ≤ 11 mm, the temperature is 446~458℃; when 11 < d ≤ 18 mm, the temperature is 441~446℃; when 18 < d ≤ 30 mm, the temperature is 437~441℃; when 30 < d ≤ 50 mm, the temperature is 433~437℃.

7. The application method according to claim 5 or 6, characterized in that, In step B3, the immersion time is adjusted according to the thickness of the steel sheet to be plated: when d≤11 mm, the immersion time is 5.5~7 min; when 11<d≤18 mm, the immersion time is 6~7.5 min; when 18<d≤30 mm, the immersion time is 6.8~8.5 min; and when 30<d≤50 mm, the immersion time is 7~9 min.

8. The application method according to claim 5 or 6, characterized in that, In step B4, the galvanized steel sheet is first removed at a constant speed of 0.03 m / s to 0.05 m / s; Secondly, the air cooling time is 45~60 seconds. After the coating color stabilizes, it is then immersed in a water tank for cooling. Finally, soak the sample evenly in the passivation tank, then remove it and let it air dry.

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