A Galfan hot-dip galvanizing process using induction heating and gas reduction.

Abstract

This invention belongs to the field of hot-dip galvanizing technology, specifically relating to an induction heating gas reduction hot-dip galvanizing process for Galfan. The process includes the following steps: First, grinding the steel substrate sample to remove surface oil, rust, and burrs, followed by alkaline washing, water washing, and shot blasting. Second, subjecting the steel substrate sample obtained in the first step to fluxing treatment. The flux contains chloride and is applied in a constant temperature water bath at 90-95℃ for 30-50 seconds, ensuring the flux fully coats the steel substrate surface. Third, preheating and drying the steel plate. Fourth, reducing the surface of the steel substrate sample in a high-frequency induction heating device by passing a reducing gas through the Galfan Zn-5Al-Re plating solution. The reducing atmosphere consists of 75% nitrogen and 25% hydrogen, with a reduction temperature of 550-650℃ and a reduction time of 5-15 seconds. Fifth, cooling. This invention not only enables batch hot-dip galvanizing of Galfan but also significantly improves the performance of the anti-corrosion coating, extending its service life or maintenance cycle.

Description

Technical Field

[0001] This invention belongs to the field of hot-dip galvanizing technology, specifically relating to an induction heating gas reduction hot-dip galvanizing process. Background Technology

[0002] Compared with electro-galvanizing, hot-dip galvanizing can produce a protective layer with strong adhesion, thick coating, and good corrosion resistance. Galfan alloy is a coating alloy developed by the Belgian Metallurgical Research Center in the 1970s with the support of the International Lead and Zinc Organization. Its corrosion resistance in atmospheric environments is 2 to 3 times that of pure zinc coating.

[0003] Currently, hot-dip galvanizing uses a solvent method, which cannot achieve mass production of hot-dip galvanized steel components. This is the fundamental reason why there are no hot-dip galvanized steel components on the market. This technological bottleneck severely restricts the upgrading and replacement of hot-dip galvanized steel components, becoming a core technical challenge. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an induction heating gas reduction hot-dip galfan process that can achieve mass hot-dip galfan.

[0005] The technical solution adopted by this invention to solve the technical problem is:

[0006] A process for hot-dip galvanizing using induction heating and gas reduction, comprising the following steps:

[0007] The first step is to grind the steel substrate sample to remove surface oil, rust, and burrs. The steel substrate sample is then subjected to alkaline washing, water washing, and shot blasting for rust removal.

[0008] The second step is to perform fluxing treatment on the steel substrate sample obtained in the first step. The flux contains chloride. Under constant temperature water bath conditions of 90-95℃, the fluxing time is 30-50s to fully coat the surface of the steel substrate with the flux.

[0009] The third step is to preheat the steel plate by drying it at 200-230℃ for 3-10 minutes.

[0010] The fourth step involves reducing the surface of the steel substrate sample in a high-frequency induction heating device by passing a reducing gas through the Galfan Zn-5Al-Re plating solution. The reducing atmosphere consists of 75% nitrogen and 25% hydrogen, with a reduction temperature of 550–650°C and a reduction time of 5–15 seconds.

[0011] Step 5: After removing the specimen from the plating solution, cool it with water.

[0012] Furthermore, the alkaline washing reagent is a 5wt% to 20wt% NaOH aqueous solution, and the alkaline washing time is 3 to 10 min.

[0013] Furthermore, the composition of the plating flux is: 5wt% to 25wt% zinc chloride, 5wt% to 10wt% lithium chloride, 10wt% to 25wt% ammonium chloride, and the balance is water.

[0014] Furthermore, the purity of the hydrogen gas is 99.995%, and the purity of the nitrogen gas is 99.995%.

[0015] Furthermore, the high-frequency induction heating equipment used is the SPG-06A type high-frequency induction heating equipment.

[0016] The advantages and positive effects of this invention are:

[0017] This invention utilizes an induction heating gas reduction method for hot-dip galfan coating, which not only enables batch hot-dip galfan coating but also significantly improves the performance of the anti-corrosion coating and extends its service life or maintenance cycle. Attached Figure Description

[0018] Figure 1 A line graph plotted for the average corrosion rate data;

[0019] Figure 2 SEM images of Galfan coated steel sheets: (a) uncorroded, (b) corroded for 24 hours, (c) corroded for 48 hours, (d) corroded for 72 hours, (e) corroded for 96 hours, and (f) corroded for 120 hours. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0021] The induction heating gas reduction hot-dip galvanizing process of this invention includes the following steps:

[0022] The first step involves grinding the steel substrate sample using a grinding wheel to remove surface oil, rust, and burrs. The sample then undergoes alkaline washing, water washing, and shot blasting for rust removal. The alkaline washing reagent is a 15wt% NaOH aqueous solution, and the washing time is carefully controlled. During water washing, the sample surface is rinsed with deionized water.

[0023] The second step is to perform fluxing treatment on the steel substrate sample obtained in the first step. The fluxing agent is chloride-containing. Under constant temperature water bath conditions of 90-95℃, the fluxing time is 30-50s, so that the surface of the steel substrate is fully coated with the fluxing agent.

[0024] The third step is to preheat the steel plate by drying it at 220℃ for 5 minutes.

[0025] Step 4, gas reduction

[0026] The substrate surface was reduced in a high-frequency induction heating device, specifically the SPG-06A type. A reducing gas was passed through the Galfan (Zn-5Al-Re) plating solution. The reducing atmosphere consisted of 75% nitrogen and 25% hydrogen, with hydrogen purity of 99.995% and nitrogen purity of 99.995%. The reduction temperature was 600℃, and the reduction time was 10 seconds.

[0027] Step 5: Cooling

[0028] After the specimen is removed from the plating solution, it is cooled rapidly to effectively prevent the zinc solution carried out by the sample from oxidizing. Water cooling is used for cooling.

[0029] Comparative Example 1

[0030] The comparative examples are pure Zn-coated steel sheet and Galfan (Zn-5Al-Re) alloy-coated steel sheet hot-dip galvanized by induction heating gas reduction method.

[0031] Coating corrosion rate: Pure Zn-coated steel sheets and Galfan (Zn-5Al-Re) alloy-coated steel sheets were placed in a salt spray chamber for a 5% NaCl neutral salt spray corrosion test. Every 24 hours, three samples of each coating were taken out. The NaCl salt and loose corrosion products on the sample surface were removed with deionized water and 10% NH4Cl solution. Corrosion weight loss was calculated, and the corrosion rate was calculated according to the corrosion rate formula. Finally, the average corrosion rate data of the three samples was calculated. Specific test results are shown in [link to test results]. Figure 1 .

[0032] Comparative experiments show that the corrosion rate of pure Zn coating is greater than that of Galfan alloy coating obtained by induction heating gas reduction hot-dip galvanizing.

[0033] Figure 2 The surface morphology of Galfan-coated steel sheets after immersion in the solution for 24h, 48h, 72h, 96h, and 120h is shown. After immersion for 24h, only a few corrosion pits are observed on the Galfan coating surface. Compared to the corrosion pits on the pure Zn coating surface, the Galfan coating has smaller pits, which is attributed to the presence of dendritic Zn-rich phases preventing the expansion of the corrosion pits. Only a small number of clustered corrosion products appear on the coating surface, and these products are all attached to the binary eutectic sites. After immersion for 48h and 72h, the corrosion products on the Zn-5Al-Re coating surface significantly increase, and the resulting corrosion products are finer and denser than those generated by the pure Zn coating. Figure 2c and d in the diagram. After immersion for 96 hours, the corrosion products completely covered the surface of the Zn-5Al-Re coating. The corrosion products were also in cluster and lamellar form, with lamellar corrosion products being more abundant. However, after immersion for 120 hours, the surface morphology of the Galfan coating was not significantly different from that after immersion for 96 hours.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A Galfan hot-dip galvanizing process using induction heating and gas reduction, characterized in that, The process includes the following steps: The first step is to grind the steel substrate sample to remove surface oil, rust, and burrs. The steel substrate sample is then subjected to alkaline washing, water washing, and shot blasting for rust removal. The second step is to perform fluxing treatment on the steel substrate sample obtained in the first step. Under constant temperature water bath conditions of 90-95℃, the fluxing time is 30-50s, so that the surface of the steel substrate is fully coated with flux. The third step is to preheat the steel substrate by drying it at 200-230℃ for 3-10 minutes. The fourth step involves reducing the surface of the steel substrate sample in a high-frequency induction heating device by passing a reducing gas through the Galfan Zn-5Al-Re plating solution. The reducing atmosphere consists of 75% nitrogen and 25% hydrogen, with a reduction temperature of 550–650°C and a reduction time of 5–15 seconds. Step 5: After removing the sample from the plating solution, cool it using water cooling. The composition of the flux is: 5wt% to 25wt% zinc chloride, 5wt% to 10wt% lithium chloride, 10wt% to 25wt% ammonium chloride, and the balance is water; Mass production of Galfan was achieved by using induction heating gas reduction hot-dip galfan.

2. The process method according to claim 1, characterized in that, The alkaline washing reagent is a 5wt% to 20wt% NaOH aqueous solution, and the alkaline washing time is 3 to 10 minutes.

3. The process method according to claim 2, characterized in that, The hydrogen gas has a purity of 99.995%, and the nitrogen gas has a purity of 99.995%.

4. The process method according to claim 3, characterized in that, The high-frequency induction heating equipment used is the SPG-06A type.

Images