Corrosion-resistant deformable zinc alloy steel-clad grounding material and its preparation method

Abstract

This invention provides a corrosion-resistant, deformable zinc alloy-clad steel grounding material and its preparation method. The grounding material comprises a low-carbon steel substrate and a zinc alloy cladding covering its surface. The chemical composition of the zinc alloy cladding, by mass percentage, is: Al 0.05%~0.50%, Mg 0.03%~0.30%, rare earth elements 0.01%~0.10%, with the balance being zinc. The aluminum-magnesium mass ratio in this material is 0.8~3.5. A 1~10 micrometer thick iron-zinc alloy bonding layer is formed between the cladding and the substrate, with the cladding thickness being 50~300 micrometers. This invention, by optimizing the zinc alloy composition and preparation process, significantly improves the bonding strength between the cladding and the substrate and the corrosion resistance of the material, while also possessing good machinability, making it suitable for grounding engineering applications.

Description

Technical Field

[0001] This invention relates to the field of grounding material preparation technology, and in particular to a corrosion-resistant deformable zinc alloy steel-clad grounding material and its preparation method. Background Technology

[0002] Grounding materials are critical components in power systems, communication base stations, and building lightning protection. Their corrosion resistance and conductivity directly affect equipment safety and service life. Traditional grounding materials mainly include galvanized steel, pure copper, and copper-clad steel. Among them, galvanized steel has a lower cost but limited corrosion resistance, and is prone to localized corrosion or even breakage in acidic or saline-alkali soils. Pure copper grounding materials have excellent corrosion resistance but are expensive and pose an environmental risk of copper ion pollution to the soil. In recent years, zinc alloy clad steel materials have attracted attention due to their combination of the high strength of steel and the cathodic protection properties of zinc. However, existing zinc alloy clad steel products have problems such as insufficient bonding strength between the cladding and the substrate, easy cracking and peeling of the cladding during drawing deformation, and unsatisfactory long-term corrosion resistance in highly corrosive environments.

[0003] Currently, the preparation of zinc alloy steel-clad grounding materials mainly adopts a process route combining hot-dip galvanizing and drawing deformation. However, the composition design of the zinc alloy cladding in existing technologies is relatively simple, mostly following the zinc-aluminum binary alloy system of ordinary zinc plating layers, lacking systematic optimization of trace components such as rare earth elements. Simultaneously, the bonding layer between the cladding and the substrate is difficult to control effectively during hot-dip galvanizing, easily leading to defects such as excessively thick bonding layers or porosity, resulting in stress concentration at the interface during subsequent drawing deformation and causing cladding peeling. Furthermore, the formulation of fluxes and the setting of drawing process parameters are relatively crude, making it difficult to balance the density and deformability of the cladding. Therefore, developing a zinc alloy steel-clad grounding material with strong cladding adhesion, excellent corrosion resistance, and suitability for drawing deformation, and its preparation method, has significant engineering application value. Summary of the Invention

[0004] The purpose of this invention is to provide a corrosion-resistant deformable zinc alloy clad steel grounding material and its preparation method. It aims to solve the technical problems of existing zinc alloy clad steel grounding materials, such as the single design of zinc alloy cladding composition, lack of rare earth element optimization, difficulty in effectively controlling the interface layer between the cladding and the substrate during hot-dip galvanizing, resulting in excessively thick or porous bonding layers, and the crude setting of flux formulation and drawing process parameters, which makes it difficult to balance the density and deformability of the cladding, resulting in poor cladding adhesion, insufficient corrosion resistance, and easy peeling during drawing deformation.

[0005] In a first aspect, the present invention provides a corrosion-resistant and deformable zinc alloy clad steel grounding material, which includes a low-carbon steel substrate and a zinc alloy cladding covering the surface of the low-carbon steel substrate.

[0006] The chemical composition of the zinc alloy coating, by mass percentage, includes: Al 0.05%~0.50%, Mg 0.03%~0.30%, rare earth elements 0.01%~0.10%, with the balance being zinc and unavoidable impurities.

[0007] In some embodiments, an iron-zinc alloy bonding layer with a thickness of 1 to 10 micrometers is formed between the zinc alloy cladding and the low-carbon steel substrate.

[0008] In some embodiments, the mass ratio of aluminum to magnesium in the zinc alloy cladding is 0.8 to 3.5.

[0009] In some embodiments, the thickness of the zinc alloy coating is 50~300μm.

[0010] In some embodiments, the rare earth element includes at least one of lanthanum and cerium.

[0011] Secondly, the present invention provides a method for preparing a corrosion-resistant deformable zinc alloy clad steel grounding material, used to prepare the above-mentioned corrosion-resistant deformable zinc alloy clad steel grounding material, the preparation method comprising:

[0012] The low-carbon steel substrate is surface cleaned.

[0013] The cleaned low-carbon steel substrate is immersed in the flux.

[0014] After drying, the low-carbon steel substrate that has been soaked in flux is immersed in a zinc alloy molten pool for hot-dip galvanizing. The composition of the zinc alloy molten pool is the same as that of the zinc alloy coating.

[0015] After hot-dip galvanizing, the steel is removed from the molten pool and the surface is cleaned with an air knife to control the coating thickness.

[0016] The cooled steel-clad material is then subjected to a drawing deformation process to obtain the finished product.

[0017] In some embodiments, the plating flux is an aqueous solution containing zinc chloride and ammonium chloride, wherein the concentration of zinc chloride is 100~300 g / L and the concentration of ammonium chloride is 50~150 g / L.

[0018] In some embodiments, the hot-dip plating process conditions are: molten pool temperature of 430~500 degrees Celsius and plating time of 30~180 seconds.

[0019] In some embodiments, the drawing deformation process employs multiple drawing passes, with a total deformation of 30% to 70%.

[0020] In some embodiments, the drawing deformation treatment further includes a surface passivation step, wherein the passivation liquid is a chromium-free passivation liquid and the passivation time is 10-60 seconds.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. This invention, by adding 0.01%~0.10% rare earth elements (lanthanum or cerium) to the zinc alloy coating and controlling the aluminum content to 0.05%~0.50% and the magnesium content to 0.03%~0.30%, forms a refined eutectic structure. The rare earth elements purify the zinc alloy melt, refine the grains, and synergistically work with aluminum and magnesium to form a dense and stable ternary composite corrosion product layer during corrosion, effectively blocking the intrusion of corrosive media. Simultaneously, controlling the mass ratio of aluminum to magnesium within the range of 0.8~3.5 avoids the localized corrosion or hydrogen evolution problems that easily occur when adding aluminum or magnesium alone, thus extending the service life of the grounding material in highly corrosive environments such as acidic soils and saline-alkali land by 2~3 times compared to ordinary galvanized steel.

[0023] 2. This invention forms a 1-10 micrometer thick iron-zinc alloy bonding layer between a low-carbon steel substrate and a zinc alloy cladding. This bonding layer is generated in situ through a diffusion reaction during the hot-dip galvanizing process, forming a metallurgical bond with the substrate rather than a simple mechanical adhesion. Compared to the interfacial bonding strength of ordinary galvanized layers, which is only 5-10 MPa, the shear strength of the bonding layer of this invention can reach 20-35 MPa. This effectively solves the technical problem of easy cracking and peeling of the cladding during pull-out deformation, ensuring that the cladding remains intact during installation processes such as bending and torsion of the grounding material.

[0024] 3. This invention controls the thickness of the zinc alloy coating within 50~300μm. Too thin a coating results in insufficient corrosion resistance, while too thick a coating easily leads to wrinkles or cracks during drawing. Combined with multi-pass drawing deformation treatment (total deformation 30%~70%), the coating and substrate can deform collaboratively without interfacial delamination. Because the thickness of the iron-zinc alloy bonding layer is precisely controlled within 1~10μm, sufficient bonding strength is ensured while avoiding brittle fracture caused by an excessively thick bonding layer. This allows the final product to be processed into various shapes such as coils, bars, and flat steel to meet the needs of different grounding projects. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects.

[0026] Example 1

[0027] Preparation process: Step 1, Surface pretreatment: Alkaline washing to remove oil → 10% hydrochloric acid pickling to remove rust → Water washing → Drying

[0028] Step 2, Fluxing: The flux is an aqueous solution of 180g / L zinc chloride and 80g / L ammonium chloride (without nanoparticles). The fluxing temperature is 80℃, and the fluxing time is 60s.

[0029] Step 3, Hot-dip galvanizing: The zinc alloy molten pool composition is the same as the coating composition (Al 0.15%, Mg 0.08%, lanthanum 0.03%, balance zinc), the molten pool temperature is 460℃, the immersion time is 90s, and the top of the molten pool is covered with an ammonium chloride antioxidant layer. During the immersion process, low-frequency mechanical vibration with a frequency of 50Hz and an amplitude of 1mm is applied.

[0030] Step 4, Air knife cleaning: Ordinary air knife, pressure 0.3MPa (without alternating magnetic field)

[0031] Step 5, drawing deformation: The total deformation is 50%, completed in 5 passes, with each pass having a deformation of 10%~12%, a drawing speed of 2m / min, and water cooling between passes (without ultrasonic vibration).

[0032] Step 6: Surface passivation: Treat with chromium-free passivation solution for 30 seconds, then dry at 100℃.

[0033] Structure and formulation: Matrix: Q235 low carbon steel, 12mm diameter round steel;

[0034] Chemical composition of zinc alloy coating (mass percentage): Al 0.15%, Mg 0.08%, rare earth element (lanthanum) 0.03%, balance is zinc and unavoidable impurities;

[0035] Zinc alloy coating thickness: 120μm;

[0036] The aluminum-magnesium mass ratio Al / Mg is 0.15 / 0.08 = 1.88.

[0037] The ratio of total aluminum and magnesium content to rare earth content (Al+Mg) / X: (0.15+0.08) / 0.03 = 7.67; the thickness of the iron-zinc bonding layer: 5μm.

[0038] Characteristics of the bonding layer: The Fe content decreases in a gradient from the steel substrate side to the cladding side along the direction perpendicular to the bonding layer, and there are no continuous pores or oxide inclusions in the bonding layer.

[0039] The corrosion-resistant deformable zinc alloy steel-clad grounding material prepared in Example 1 was tested, and the results included: the thickness of the iron-zinc bonding layer was 5 μm; the Fe content gradient of the bonding layer decreased from 82 wt% on the low steel substrate side to 38 wt% on the cladding side; the bonding layer porosity / inclusions were none; the bonding strength was 28 MPa; the cladding hardness was HV85; the time for red rust to appear in neutral salt spray was 720 h; the soil corrosion rate (pH=5.5, 180 days) was 0.032 mm / year; the cladding condition after drawing was no cracks or peeling; and the product form was coilable.

[0040] Comparative Example 1

[0041] Preparation process: exactly the same as in Example 1.

[0042] Structure and formulation: Matrix: Q235 low carbon steel, 12mm diameter round steel;

[0043] The chemical composition of the zinc alloy coating is: Al 0.15%, Mg 0.08%, free of rare earth elements, with the balance being zinc and unavoidable impurities;

[0044] Coating thickness: 120μm.

[0045] The corrosion-resistant deformable zinc alloy steel-clad grounding material prepared by Comparative Example 1 was tested, and the results included: bonding strength: 27 MPa; time to red rust appearance in neutral salt spray: 420 h; soil corrosion rate: 0.058 mm / year; coating condition after pull-out: no cracks, no peeling.

[0046] Comparative Example 2

[0047] Preparation process: exactly the same as in Example 1.

[0048] Structure and formulation: Substrate: Q235 low carbon steel, 12mm diameter round steel; Chemical composition of zinc alloy cladding: Al 0.60%, Mg 0.03%, rare earth (lanthanum) 0.03%, balance zinc; Al / Mg = 20; Coating thickness: 120μm.

[0049] The corrosion-resistant deformable zinc alloy steel-clad grounding material prepared by Comparative Example 2 was tested, and the results included: bonding strength: 24 MPa; coating hardness: HV96 (hardness too high); time to red rust appear in neutral salt spray: 380 h; soil corrosion rate: 0.062 mm / year; coating condition after pull-out: fine cracks appeared.

[0050] Comparative Example 3

[0051] Preparation process: exactly the same as in Example 1.

[0052] Structure and formulation: Substrate: Q235 low carbon steel, 12mm diameter round steel; Chemical composition of zinc alloy cladding: Al 0.04%, Mg 0.25%, rare earth (lanthanum) 0.03%, balance zinc; Al / Mg = 0.16; Coating thickness: 120μm.

[0053] The corrosion-resistant deformable zinc alloy steel-clad grounding material prepared by Comparative Example 3 was tested, and the results included: bonding strength: 26 MPa; time to red rust appearance in neutral salt spray: 450 h; soil corrosion rate: 0.055 mm / year; coating condition after pull-out: no cracks, no peeling.

[0054] Comparative Example 4

[0055] Preparation process: exactly the same as in Example 1.

[0056] Structure and formulation: Substrate: Q235 low carbon steel, 12mm diameter round steel; Chemical composition of zinc alloy cladding: Al 0.15%, Mg 0.08%, rare earth (lanthanum) 0.12%, balance zinc; (Al+Mg) / X = (0.15+0.08) / 0.12 = 1.92; Coating thickness: 120μm.

[0057] The corrosion-resistant deformable zinc alloy steel-clad grounding material prepared by Comparative Example 4 was tested, and the results included: bonding strength: 27 MPa; time to red rust appearance in neutral salt spray: 460 h; soil corrosion rate: 0.052 mm / year; coating condition after pull-out: no cracks, no peeling.

[0058] Comparative Example 5

[0059] Preparation process: The hot-dip plating temperature was adjusted to 530℃ and the plating time was 350s. The remaining steps were the same as in Example 1.

[0060] Formula and structure: exactly the same as in Example 1.

[0061] The corrosion-resistant deformable zinc alloy steel-clad grounding material prepared by Comparative Example 5 was tested, and the results included: iron-zinc bonding layer thickness: 18~22μm; bonding strength: 15MPa; time to red rust appearance in neutral salt spray: 520h; soil corrosion rate: 0.048mm / year; coating condition after pull-out: large area peeling; product morphology: partial breakage during pull-out.

[0062] Comparative Example 6

[0063] Preparation process: After hot-dip galvanizing, no drawing deformation treatment is performed, and it is directly used as the finished product. The remaining steps are the same as in Example 1.

[0064] Formula and structure: exactly the same as in Example 1.

[0065] The corrosion-resistant deformable zinc alloy steel-clad grounding material prepared by Comparative Example 6 was tested, and the results included: bonding strength: 27 MPa; time to red rust appearance in neutral salt spray: 710 h; soil corrosion rate: 0.033 mm / year; coating state: not pulled; product form: straight bar (cannot be coiled).

[0066] Comparative analysis of Examples 1 to 6 with Example 1 shows that the addition of rare earth elements is a key factor in improving corrosion resistance. In Example 1, without rare earth elements, the salt spray red rust time decreased from 720 hours to 420 hours, and the soil corrosion rate increased from 0.032 mm / year to 0.058 mm / year. The aluminum-magnesium mass ratio needs to be controlled within the range of 0.8 to 3.5. In Example 2, Al / Mg = 20 resulted in excessively high coating hardness (HV96) and pull-out cracks. In Example 3, Al / Mg = 0.16 significantly reduced corrosion resistance. The corrosion resistance is significantly reduced; at the same time, the (Al+Mg) / X ratio needs to be ≥5. In Comparative Example 4, this ratio is only 1.92, and the corrosion resistance is also significantly deteriorated; the thickness of the bonding layer is crucial to be controlled between 1 and 10 μm. In Comparative Example 5, the bonding layer is too thick (18 to 22 μm), which causes the bonding strength to drop sharply to 15 MPa and large areas to peel off after drawing; in addition, although the drawing deformation treatment has little impact on the corrosion resistance, it directly determines whether the product can be supplied in coils. In Comparative Example 6, without drawing, it can only be output in straight strip form, which seriously limits the convenience of engineering applications.

[0067] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A corrosion-resistant, deformable zinc alloy-clad steel grounding material, characterized in that, It includes a low-carbon steel substrate and a zinc alloy coating covering the surface of the low-carbon steel substrate; The chemical composition of the zinc alloy coating, by mass percentage, includes: Al 0.05%~0.50%, Mg 0.03%~0.30%, rare earth elements 0.01%~0.10%, with the balance being zinc and unavoidable impurities.

2. The corrosion-resistant deformable zinc alloy clad steel grounding material according to claim 1, characterized in that, A zinc-iron alloy bonding layer with a thickness of 1 to 10 micrometers is formed between the zinc alloy cladding and the low-carbon steel substrate.

3. The corrosion-resistant deformable zinc alloy clad steel grounding material according to claim 1, characterized in that, The mass ratio of aluminum to magnesium in the zinc alloy cladding is 0.8 to 3.

5.

4. The corrosion-resistant deformable zinc alloy clad steel grounding material according to claim 1, characterized in that, The thickness of the zinc alloy coating is 50~300μm.

5. The corrosion-resistant deformable zinc alloy clad steel grounding material according to claim 1, characterized in that, The rare earth elements include at least one of lanthanum and cerium.

6. A method for preparing a corrosion-resistant deformable zinc alloy clad steel grounding material, used to prepare the corrosion-resistant deformable zinc alloy clad steel grounding material as described in any one of claims 1-5, characterized in that, The preparation method includes: The low-carbon steel substrate is surface cleaned. The cleaned low-carbon steel substrate is immersed in the flux. After drying, the low-carbon steel substrate that has been soaked in flux is immersed in a zinc alloy molten pool for hot-dip galvanizing. The composition of the zinc alloy molten pool is the same as that of the zinc alloy coating. After hot-dip galvanizing, the steel is removed from the molten pool and the surface is cleaned with an air knife to control the coating thickness. The cooled steel-clad material is then subjected to a drawing deformation process to obtain the finished product.

7. The method for preparing the corrosion-resistant deformable zinc alloy clad steel grounding material according to claim 6, characterized in that, The plating flux is an aqueous solution containing zinc chloride and ammonium chloride, wherein the concentration of zinc chloride is 100~300g / L and the concentration of ammonium chloride is 50~150g / L.

8. The method for preparing the corrosion-resistant deformable zinc alloy clad steel grounding material according to claim 6, characterized in that, The hot-dip plating process conditions are: molten pool temperature 430~500 degrees Celsius, plating time 30~180 seconds.

9. The method for preparing the corrosion-resistant deformable zinc alloy clad steel grounding material according to claim 6, characterized in that, The drawing deformation treatment employs multiple drawing passes, with a total deformation of 30% to 70%.

10. The method for preparing the corrosion-resistant deformable zinc alloy clad steel grounding material according to claim 6, characterized in that, The drawing deformation process also includes a surface passivation step, where the passivation solution is a chromium-free passivation solution and the passivation time is 10-60 seconds.