Zinc alloy for hot dipping and application thereof

Abstract

The invention belongs to the technical field of batch hot galvanizing technologies, and particularly relates to a zinc alloy for hot galvanizing and application of the zinc alloy. The zinc alloy for hot dipping comprises 10 wt%-20 wt% of Al, 0.6 wt%-1.0 wt% of Bi, 0.06 wt%-0.15 wt% of RE, 0.1 wt%-0.5 wt% of Ni and the balance Zn, and further comprises inevitable impurities. Wherein RE is a mixture of lanthanum and cerium, and the mass ratio of lanthanum to cerium is (30-40): (60-70). The zinc alloy provided by the invention is suitable for hot galvanizing of steel materials such as angle steel, channel steel, profiles and sundries, and by adding the alloy into a zinc bath, the flowability of the zinc bath can be improved, the surface tension of the zinc bath is reduced, a Fe-Zn alloy layer and a pure zinc layer are thinned, and a plating layer has no chromatic aberration, no Sandelin effect, no redundant zinc tumor, no burr and the like; and zinc ash and bottom slag are reduced, the coating quality of a product is improved, and the production cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of batch hot-dip galvanizing technology, and specifically relates to a zinc alloy for hot-dip galvanizing and its application. The alloy is mainly used for blown hot-dip galvanizing of steel materials such as angle steel and channel steel, and a small amount is used for rack hot-dip galvanizing of structural steel parts such as profiles and miscellaneous parts. Background Art

[0002] With the steady growth of the domestic hot-dip galvanizing market, the market remains highly active. In particular, the types and varieties of hot-dip galvanizing alloys are diversifying due to the diverse steel materials, complex and diverse steel parts, diverse customer galvanizing processes, and varying alloy coating requirements during batch galvanizing. Batch hot-dip galvanizing involves immersing steel structures and other materials in a zinc bath in batches to produce hot-dip galvanized parts. It is widely used in industries such as power, telecommunications, railway and highway infrastructure, road lighting poles, marine components, building steel structures, substation ancillary facilities, light industry, heating, and refrigeration. In recent years, the successful application of batch hot-dip galvanizing in bridges, building steel structures and rebar, telecommunication microwave towers, mining machinery, and shipbuilding has further broadened the application prospects of batch hot-dip galvanizing technology. The batch hot-dip galvanizing process typically consists of pre-treatment, hot-dip galvanizing, and post-treatment. The commonly used batch galvanizing process, both domestically and internationally, is as follows: black metal → pickling and rust removal → water rinsing → tackification solvent application → drying → hot-dip galvanizing → water cooling → passivation → drying → coating inspection. With the development and application of hot-dip galvanizing, traditional Zn-Al(-RE) and Zn-Ni alloys have certain limitations in terms of poor fluidity in the zinc bath, poor surface quality, and large amounts of zinc slag and zinc ash. Summary of the Invention

[0003] The purpose of the present invention is to solve the technical problems in the prior art that the existing zinc alloy is not suitable for galvanizing special types of steel (mainly materials such as Q195, Q215, Q235B, Q345B, Q355B, etc.), such as poor zinc liquid fluidity, poor coating surface quality, and excessive zinc ash and zinc slag during the hot-dip galvanizing process of blown plating of angle steel, channel steel, and rack plating of profiles and miscellaneous parts.

[0004] The inventors explored adding Bi to alloys used in specific batch galvanizing applications and gradually discovered that a specific Bi content in a specific zinc alloy is highly beneficial for hot-dip galvanizing. Adding an appropriate amount of Bi to batch galvanized zinc-aluminum alloys can reduce surface tension, zinc loading, and zinc slag and ash. Targeting the specific characteristics of hot-dip galvanizing for angle steel and channel steel, as well as rack hot-dip galvanizing for structural components such as towers, profiles, and miscellaneous components, the inventors developed and produced a diverse range of Bi-containing alloys to better meet the needs of batch galvanizing for these products.

[0005] To this end, a first aspect of the present invention provides a hot-dip zinc alloy, based on the total mass of the hot-dip zinc alloy, the hot-dip zinc alloy comprises:

[0006] 10wt%-20wt% Al, 0.6wt%-1.0wt% Bi, 0.06wt%-0.15wt% RE, 0.1wt%-0.5wt% Ni, the balance being Zn, and also including unavoidable impurities;

[0007] Wherein, RE is a mixture of lanthanum (La) and cerium (Ce), and the mass ratio of lanthanum to cerium is 30-40:60-70.

[0008] According to the present invention, the rare earth metal RE is a mixed rare earth, and the mass ratio of lanthanum to cerium can be controlled to be approximately 35:65.

[0009] According to the present invention, the unavoidable impurities include at least one of Pb, Cu, Sn, Cd and Fe. Typically, Pb≤0.005wt%, Cu≤0.002wt%, Sn≤0.002wt%, Cd≤0.002wt%, and Fe≤0.02wt%.

[0010] As a preferred solution, the raw material zinc ingot for producing the alloy is 0# zinc.

[0011] A second aspect of the present invention provides use of the above-mentioned hot-dip zinc alloy in hot-dip galvanizing.

[0012] As a preferred solution, the hot-dip galvanized material includes at least one of steel materials.

[0013] As a further preferred solution, the steel material includes at least one of angle steel, channel steel, profiles and miscellaneous parts.

[0014] The application method comprises: adding the hot-dip zinc alloy into a zinc bath.

[0015] As a preferred solution, after adding the hot-dip zinc alloy, when the zinc bath contains: Al

[0016] When the content of Bi is 0.02wt% to 0.05wt%, Bi is 0.005wt% to 0.02wt%, RE is 0.0002wt% to 0.001wt%, and Ni is 0.005wt% to 0.2wt%, the fluidity and wettability of the zinc solution are significantly improved, resulting in lower surface tension. The appropriate addition of Bi influences the crystallization process of the pure zinc layer, making it easier to flow in the liquid state, reducing the formation of zinc nodules. This allows the zinc solution to flow smoothly out of threaded holes and gaps in steel structures. When plating pig iron, steel pipes, channel steel, angle steel, profiles, and other miscellaneous parts, zinc nodules, zinc ash, and zinc slag are reduced on the surface of the plated parts, effectively reducing the size and number of zinc nodules, holes, and burrs on the plated parts. The bismuth-containing zinc slag sinks to the bottom of the zinc pot, making it easier to salvage the zinc slag. It can be used to replace traditional lead and reduce lead pollution.

[0017] According to the present invention, in several specific embodiments, the resulting coating has a thickness of 20 to 80 μm. Because metallic bismuth forms a eutectic structure when alloyed with aluminum, zinc, nickel, RE, and other metals, trace amounts of bismuth have a eutectic point at the high-zinc end that is lower than the zinc melting point. During the galvanizing process, this can lower the zinc melting point and surface tension, increasing the fluidity of the zinc solution and reducing the thickness of the zinc coating. During the condensation process, a eutectic reaction occurs, extending the solidification time of the zinc solution, which also contributes to the reduction in zinc coating thickness.

[0018] According to the present invention, the hot-dip galvanizing method is blown hot-dip galvanizing or rack hot-dip galvanizing. For example, steel materials such as angle steel and channel steel are subjected to blown hot-dip galvanizing, while structural steel materials such as profiles and miscellaneous parts are subjected to rack hot-dip galvanizing.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] The zinc alloy provided by the present invention is suitable for hot-dip galvanizing of steel materials such as angle steel, channel steel, profiles and miscellaneous parts by appropriately selecting the types and contents of the various components in the zinc alloy by the inventors, specifically maintaining appropriate contents of elements such as Al, Ni, Bi and RE in the zinc bath. By adding the alloy to the zinc bath, the fluidity of the zinc bath can be improved, the surface tension of the zinc bath can be reduced, the Fe-Zn alloy layer and the pure zinc layer can be thinned, the coating has no color difference, no Sanderin effect, no unnecessary zinc nodules, burrs, etc., the generation of zinc ash and bottom slag is reduced, the quality of the product coating is improved, and the production cost is reduced.

[0021] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. DETAILED DESCRIPTION

[0022] In the following description, a number of specific details are provided to provide a more thorough understanding of the technical solutions provided by the present invention. However, it is obvious to those skilled in the art that the technical solutions provided by the present invention can be implemented without one or more of these details.

[0023] Preliminary experiments

[0024] The salt spray corrosion test was conducted on pure zinc and multi-element alloys with different bismuth contents, zinc-aluminum rare earth alloys and zinc-nickel alloy hot-dip steel sheets. The neutral salt spray corrosion test of GB6458-86NSS was adopted. The test conditions were: salt spray deposition rate (80cm 2)1~2mL, the corrosion system is about 50g / L NaCl solution, pH 6.5~7.2; temperature 35±2℃; the test cycle is intermittent spraying 8h and stopping 16h, the total time is 96h (a total of 4 cycles), the corrosion rates of different alloys are (g / m 2 h): Pure zinc 10.03, zinc-bismuth multi-element alloy 1.23, zinc-nickel alloy 2.944, zinc-aluminum rare earth alloy 3.01. Comparison of laboratory test results shows that variations in alloy composition significantly influence corrosion resistance. Combining these alloying elements in a specific ratio significantly enhances the corrosion resistance of the coating, with the zinc-bismuth multi-element alloy exhibiting the best corrosion resistance.

[0025] In the examples and comparative examples of the present invention, the zinc ingot used to produce the alloy raw material should be Zn99.995, which should comply with the national standard "GB / T470-2008 Zinc Ingots." The aluminum ingot should be 99.85Al, which should comply with the national standard "GB / T 1196-2023 Aluminum Ingots for Remelting." Nickel should be Ni99.99, which should comply with the national standard "GB / T 6516-2010 Electrolytic Nickel." Rare earths should be mixed rare earths with a total rare earth content (RE) ≥ 99% and a non-rare earth impurity limit, which should comply with the national standard "GB / T 40795.2-2021 Lanthanum, Cerium, and Rare Earth."

[0026] In the embodiments and comparative examples of the present invention, the preparation method of zinc alloy for hot-dip coating includes: using an industrial frequency coreless furnace, adding zinc ingots, aluminum ingots, nickel ingots, and rare earth (RE) as solid materials at the same time in proportion, performing slag treatment after complete melting, adding metal bismuth after slag removal, and placing the furnace for casting after complete melting.

[0027] In the embodiments and comparative examples of the present invention, the impurity elements are Pb, Cu, Sn, Cd, and Fe, and satisfy Pb≤0.005wt%, Cu≤0.002wt%, Sn≤0.002wt%, Cd≤0.002wt%, and Fe≤0.02wt%.

[0028] In the embodiment of the present invention, the zinc bath is controlled to contain: Al 0.02wt% to 0.05wt%, Bi

[0029] 0.005wt%~0.02wt%, RE 0.0002wt%~0.001wt%, Ni 0.005wt%~0.2wt%.

[0030] Example 1

[0031] A hot-dip zinc alloy S1 contains, based on the total mass of the zinc alloy, 10wt% Al, 0.6wt% Bi, 0.06wt% RE, 0.1wt% Ni, and the balance Zn. Impurity elements include Pb, Cu, Sn, Cd, and Fe. The rare earth metal RE is a mixed rare earth, in which the ratio of lanthanum (La) to cerium (Ce) is approximately 35%:65%.

[0032] Hot-dip galvanizing of the hot-dip zinc alloy S1 of this embodiment on angled steel (Q235B) for 10-15 seconds produces a uniform coating thickness of 60-80 μm. The coating exhibits no color difference at high and low temperatures, maintains a good surface finish, and exhibits a uniform outer color with no missing spots, sags, or wrinkles. Mechanical adhesion tests using a press, vise, or bend tester revealed no zinc layer shedding. Zinc slag and ash generation were reduced by approximately 20% compared to using a Zn-Al(-RE) alloy.

[0033] Example 2

[0034] A zinc alloy S2 for hot-dip coating, based on the total mass of the zinc alloy, contains 12wt% Al, 0.7wt% Bi, 0.08wt% RE, 0.2wt% Ni, and the balance is Zn. Impurity elements include Pb, Cu, Sn, Cd, and Fe. The rare earth metal RE is a mixed rare earth, wherein the ratio of lanthanum (La) to cerium (Ce) is ≈35%:65%.

[0035] Hot-dip galvanizing of Q195 channel steel using the hot-dip zinc alloy S2 of this embodiment for 10-15 seconds produces a uniform coating thickness ranging from 50 to 70 μm. The coating exhibits no color difference at high and low temperatures, a good surface finish, and a uniform outer surface color. There are no missing spots, sags, or other surface defects, such as wrinkles. Mechanical adhesion tests using a press, vise, or bend tester revealed no zinc layer shedding. Zinc slag and ash generation were reduced by approximately 20% compared to using a Zn-Al(-RE) alloy.

[0036] Example 3

[0037] A zinc alloy S3 for hot-dip coating, based on the total mass of the zinc alloy, contains 15wt% Al, 0.8wt% Bi, 0.10wt% RE, 0.3wt% Ni, and the balance is Zn. Impurity elements include Pb, Cu, Sn, Cd, and Fe. The rare earth metal RE is a mixed rare earth, wherein the ratio of lanthanum (La) to cerium (Ce) is ≈35%:65%.

[0038] Using the hot-dip zinc alloy S3 of this embodiment for hot-dip galvanizing of profiles or miscellaneous parts (Q215 material) for 40-60 seconds, the resulting coating has a uniform thickness of 80-100 μm. The coating exhibits no color difference at high and low temperatures, a good surface finish, and a uniform outer color. There are no missing spots, sags, or other surface defects, such as wrinkles. Mechanical adhesion tests using a press, vise, or bend tester revealed no zinc layer shedding. Zinc slag and ash generation is approximately 10% lower than when using a Zn-Al(-RE) alloy.

[0039] Example 4

[0040] A zinc alloy S4 for hot-dip coating, based on the total mass of the zinc alloy, contains 18wt% Al, 0.9wt% Bi, 0.12wt% RE, 0.4wt% Ni, and the balance is Zn. Impurity elements include Pb, Cu, Sn, Cd, and Fe. The rare earth metal RE is a mixed rare earth, wherein the ratio of lanthanum (La) to cerium (Ce) is approximately 35%:65%.

[0041] Hot-dip galvanizing of the zinc alloy S4 angle steel (Q345B) of this embodiment was performed by rack galvanizing for 10 to 15 seconds, resulting in a uniform coating thickness of 50 to 70 μm. The coating exhibited no color difference at high and low temperatures, a good surface finish, and a uniform outer surface color. There were no surface defects such as missing spots, sags, or wrinkles. Mechanical adhesion tests using a press, vise, or bend tester revealed no zinc layer shedding. Zinc slag and ash generation was reduced by approximately 15% compared to using a Zn-Al(-RE) alloy.

[0042] Example 5

[0043] A hot-dip zinc alloy S5 contains, based on the total mass of the zinc alloy, 20wt% Al, 1.0wt% Bi, 0.15wt% RE, 0.5wt% Ni, and the balance Zn. Impurity elements include Pb, Cu, Sn, Cd, and Fe. The rare earth metal RE is a mixed rare earth, in which the ratio of lanthanum (La) to cerium (Ce) is approximately 35%:65%.

[0044] Hot-dip zinc alloy S5 of this embodiment was used to hot-dip galvanize Q235B angle steel (Q235B) for 8-12 seconds. The resulting coating had a uniform thickness of 20-40 μm. The coating showed no color difference at high and low temperatures, and the surface finish was excellent. The outer surface color was uniform, with no missing spots, sags, or wrinkles. Mechanical adhesion tests using a press, vise, or bend tester revealed no zinc layer detachment. Zinc slag and zinc ash generation was reduced by approximately 20% compared to using a Zn-Al(-RE) alloy.

[0045] Comparative Example 1

[0046] The difference from Example 1 is that the Bi content is 0.5wt%. That is, when the zinc alloy contains 10wt% Al, 0.5wt% Bi, 0.06wt% RE, and 0.1wt% Ni, the Bi content in the zinc bath is less than 0.005wt%. At this time, the hot-dip zinc alloy S1 of this comparative example is used to hot-dip galvanize the angle steel (Q235B material) for 10 to 15 seconds. The resulting coating thickness is uniform, with a coating thickness distribution of 80 to 100μm. The coating has no color difference under high and low temperature conditions, good surface finish, uniform outer surface color, no missing plating points, and no surface defects such as sagging and wrinkling. Mechanical adhesion does not cause the zinc layer to fall off when bending tests are performed using equipment such as a press, a vise, or a bending tester. The amount of zinc slag and zinc ash produced remains basically the same as when using the Zn-Al(-RE) alloy, and the coating thickness is significantly increased.

[0047] It can be seen that although the Bi content is only reduced from 0.6 wt % to 0.5 wt %, the thickness of the coating is seriously affected.

[0048] Comparative Example 2

[0049] The difference from Example 5 is that the Bi content is 1.1wt%. The hot-dip zinc alloy S5 of this comparative example was used to hot-dip galvanize Q235B angle steel (Q235B) for 8 to 12 seconds. The resulting coating thickness was uneven, with a coating thickness distribution of 15 to 35μm. There was no color difference at high and low temperatures, but wrinkles appeared on the coating surface, the outer surface was dark in color, and surface defects such as missing plating spots and peeling occurred. Mechanical adhesion was tested by bending using equipment such as a press, a vise, or a bending tester, resulting in significant detachment of the zinc layer. The amount of zinc slag and zinc ash generated was reduced by approximately 20% compared to when using a Zn-Al(-RE) alloy.

[0050] It can be seen that although the Bi content is only increased from 1wt% to 1.1wt%, wrinkles have appeared, the outer surface color is dark, and surface defects such as missing plating points and peeling have appeared.

[0051] The above embodiments are only preferred implementations of the present invention. It should be pointed out that for those skilled in the art, several improvements made without departing from the principles of the present invention should also be regarded as within the scope of protection of the present invention.

Claims

1. A zinc alloy for hot-dip galvanizing, characterized in that: Based on the total mass of the hot-dip zinc alloy, the hot-dip zinc alloy includes: 10wt%-20wt% Al, 0.6wt%-1.0wt% Bi, 0.06wt%-0.15wt% RE, 0.1wt%-0.5wt% Ni, the balance being Zn, and also including unavoidable impurities; Wherein, RE is a mixture of lanthanum and cerium, and the mass ratio of lanthanum to cerium is 30-40:60-70.

2. The hot-dip zinc alloy according to claim 1, wherein: The unavoidable impurities include at least one of Pb, Cu, Sn, Cd and Fe.

3. The hot-dip zinc alloy according to claim 2, wherein: Pb≤0.005wt%, Cu≤0.002wt%, Sn≤0.002wt%, Cd≤0.002wt%, Fe≤0.02wt%.

4. Use of the hot-dip zinc alloy according to any one of claims 1 to 3 in hot-dip galvanizing.

5. The use according to claim 4, characterized in that The hot-dip galvanized material includes at least one of steel materials.

6. The use according to claim 5, characterized in that The steel material includes at least one of angle steel, channel steel, profile steel and miscellaneous parts.

7. The use according to claim 4, characterized in that The application method includes: The hot-dip zinc alloy is added to a zinc bath.

8. The use according to claim 7, characterized in that After adding the hot dip zinc alloy, the zinc bath contains: Al 0.02 wt% to 0.05 wt%, Bi 0.005 wt% to 0.02 wt%, RE 0.0002wt%~0.001wt%, Ni0.005wt%~0.2wt%.

9. The use according to claim 4, characterized in that The thickness of the obtained coating is 20 to 80 μm.

10. The use according to claim 4, characterized in that The hot-dip galvanizing method is blown hot-dip galvanizing or rack hot-dip galvanizing.