CN111304661A - Al-Si-Mg coating and preparation method thereof - Google Patents

Abstract

The invention discloses an aluminum-silicon-magnesium coating and a preparation method thereof. The silicon content of the aluminum-silicon-magnesium coating is 5-15wt.%, the magnesium content is 3-10wt.%, and 1.0-2.0wt.% of titanium, 0.2 ‑1.0 wt.% chromium and 0.01‑0.1 wt.% rare earth. The preparation method is as follows: firstly, adding Ti in the Al-Si plating solution to refine the crystal grains of the plating layer, adding Cr to improve the oxidation resistance of the plating layer, and adding RE to improve the fluidity of the plating solution to obtain an aluminum-silicon coating plate; and then using a vacuum evaporation coating machine A layer of magnesium thin film is vapor-deposited on the aluminum-silicon coated plate; and then vacuum diffusion annealing is performed on the aluminum-silicon coated plate on which the magnesium thin-film has been deposited to obtain a new aluminum-silicon-magnesium coated plate. Compared with the aluminum-silicon-magnesium coated board prepared by the method of the invention, the aluminum-silicon-magnesium coated board has better comprehensive performance, excellent surface quality and corrosion resistance, and the preparation method is green and environmentally friendly, and is more friendly to the environment .

Description

Al-Si-Mg coating and preparation method thereof

technical field

The invention relates to a coating and a preparation method thereof, in particular to an aluminum-silicon coating and a preparation method thereof, which are applied to the technical fields of metal corrosion and protection and metal surface treatment.

Background technique

Al-Si coating is a commonly used high temperature resistant coating, which has excellent high temperature oxidation resistance and can effectively prevent the surface oxidation and decarburization of steel sheets under high temperature conditions. The addition of Ti in the Al-Si bath can refine the grains of the coating, the addition of Cr can improve the oxidation resistance of the coating, and the addition of rare earth (RE) can improve the fluidity of the bath. Because Al-Si coating has the characteristics of no oxide peeling off when heating, no sandblasting after stamping, and high forming accuracy, it has been widely used in the production of hot stamping steel, especially in the field of automobile manufacturing, which has broad application prospects.

At room temperature, the direct oxidation of dry air has very little loss of metal coating, but in humid environment or water environment, electrochemical corrosion behavior will significantly accelerate the consumption of metal coating and significantly increase the corrosion rate of the coating. Adding an appropriate amount of Mg to the Al-Si coating, a sufficient amount of Mg ₂ Si phase appears in the coating, the corrosion resistance of the coating can be significantly improved, and the addition of Mg can enhance the compactness of the corrosion products of the coating, making the coating corrosion resistance better.

Due to the very active chemical properties of magnesium, the magnesium content in the plating solution cannot be higher than 3wt.%, otherwise the surface of the plating solution in the plating pot will be severely oxidized, which will affect the adhesion between the coating and the substrate. Therefore, the effective content of magnesium in the coating It is difficult to control, and it is extremely technically difficult to prepare Al-Si-Mg coatings by hot dip plating. At present, the existing Al-Si coating only has high temperature oxidation resistance and no electrochemical corrosion resistance, which is far from meeting the higher performance requirements of modern industry for Al-Si coating. Adding an appropriate amount of Mg can make the Al-Si coating not only have high temperature oxidation resistance, but also have electrochemical corrosion resistance. If the traditional hot dip plating method is used to prepare the Al-Si-Mg coating, the bonding force of the coating is weak and the corrosion resistance is low. Therefore, the current process for preparing the Al-Si-Mg coating has great social needs, especially High magnesium content (Mg>3wt.%) Al-Si-Mg coating.

How to add Mg is a key issue in the preparation of Al-Si-Mg coatings, and physical vapor deposition (PVD) technology is a feasible method. Vacuum evaporation is the earliest and most mature method in PVD. Al-Si-Mg coatings with excellent electrochemical corrosion resistance can be obtained by vacuum evaporation. Vacuum evaporation is to heat and evaporate or sublime the plating material under vacuum conditions, so that a large number of atoms and molecules are vaporized and leave the surface of the liquid plating material or solid plating material, and then the gaseous atoms and molecules pass through very little in the vacuum. The collision migrates to the substrate, and finally the atoms and molecules of the plating material are deposited on the surface of the substrate, and condense, nucleate, grow, and form a film to form a thin film. Vacuum evaporation has the advantages of simple equipment, easy operation, high film purity, good quality, controllable thickness, fast deposition rate and high efficiency, and has a wide range of applications in automotive, construction, electrical and computer industries. The cost of depositing Al-Si-Mg coating is high, the control of multi-component co-evaporation is difficult, and the efficiency is low, which limits its application in conventional metal parts coating.

SUMMARY OF THE INVENTION

In order to solve the problems of the prior art, the purpose of the present invention is to overcome the deficiencies of the prior art, and to provide an aluminum-silicon-magnesium coating and a preparation method thereof. The invention adopts the combined method of "hot dip plating-vacuum evaporation-diffusion annealing" to prepare Al-Si-Mg coating with high magnesium content of Mg≥3wt.%, which not only improves the surface quality and performance of the coating, but also improves the overall Compared with the existing hot dip plating process, the preparation process is more green and environmentally friendly.

In order to achieve the above-mentioned purpose of invention and creation, the present invention adopts the following technical solutions:

An aluminum-silicon-magnesium coating, the content of silicon in the coating is 5-15wt.%, the content of magnesium is 3-10wt.%, the content of titanium is 1.0-2.0wt.%, the content of chromium is 0.2-1.0wt.%, the content of rare earth RE is 0.01-0.1 wt.%.

As a preferred technical solution of the present invention, an Al-Si-Mg intermediate transition layer composed of a Mg-Si alloy phase and a Mg-Al alloy phase is formed in the coating layer. Preferably, the aluminum-silicon-magnesium coating has a matrix Fe surface to form a composite coating with an Al-Si/Al-Si-Mg/Mg-MgO structure.

A preparation method of aluminum-silicon-magnesium coating of the present invention, comprising the following steps:

a. Hot dip plating process:

Add Ti, Cr and rare earth to the aluminum-silicon plating solution, set the hot-dip plating temperature and time, and perform hot-dip aluminum-silicon plating on the steel plate to be plated to form a basic coating;

b. Vacuum evaporation process:

The aluminum-silicon-coated steel sheet prepared in the step a is taken out, cooled, and then put into a vacuum evaporation coating machine, and the evaporation temperature is controlled by adjusting the discharge current of the vacuum coating machine. Evaporation is performed, and after the evaporation is completed, the steel plate is taken out to obtain an aluminum-silicon-coated plate with an evaporated magnesium film;

c. Diffusion annealing treatment:

Vacuum diffusion annealing is performed on the aluminum-silicon-coated steel plate prepared in the step b by vapor-depositing the magnesium film, and then cooled to finally obtain an aluminum-silicon-magnesium coated plate.

As a preferred technical solution of the present invention, during the hot dip coating process, the hot dip coating temperature is controlled to be 670-690° C., and the treatment time is 30-60 s. Adding 1.0-2.0wt.% of titanium to the aluminum-silicon plating solution is mainly used to refine the grains of the coating; adding 0.2-1.0wt.% of chromium is mainly used to improve the oxidation resistance of the coating; adding 0.01-0.1wt .% rare earth RE, mainly used to improve the fluidity of the bath.

As a preferred technical solution of the present invention, the hot dip plating process is controlled to obtain an aluminum-silicon coating with a thickness of 10-30 μm.

As a preferred technical solution of the present invention, during the vacuum evaporation process, the evaporation voltage is controlled to be 1.0-1.6V, the evaporation current is 100-120A, and the evaporation time is 5-10min. The use of vacuum evaporation of magnesium can effectively avoid the leakage phenomenon in the process of hot-dip magnesium plating of steel plate, and improve the surface quality of the aluminum-silicon-magnesium coated plate. The magnesium content in the prepared aluminum-silicon-magnesium coating is as high as 3-10wt. Comprehensive application performance, especially excellent high temperature oxidation resistance and electrochemical corrosion resistance.

As a preferred technical solution of the present invention, the vacuum evaporation process is controlled to obtain a magnesium film with a thickness of 1-2 μm. The present invention does not need to prepare a thick magnesium film or deposit an alloy thin film, but only needs to prepare a magnesium thin film with a thickness of 1-2 μm, the manufacturing cost is relatively low, the control is easy, and the efficiency is high.

As a preferred technical solution of the present invention, when the diffusion annealing treatment is performed, the annealing temperature is controlled to be 440-460° C., and the holding time is 2-5 minutes. The vacuum diffusion annealing treatment method not only effectively prevents the excessive oxidation of the surface of the magnesium film, but also improves the bonding force between the coating and the substrate, and also makes the aluminum-silicon coating of the vapor-deposited magnesium film to form an aluminum-silicon-magnesium alloy layer. Aluminum-silicon-magnesium coated board with excellent corrosion resistance.

As a preferred technical solution of the present invention, before the hot dip plating process, the steel plate to be treated is first cut into a set size, firstly subjected to alkali washing to remove oil, acid to remove rust, and then to ultrasonic cleaning with ethanol or acetone. Dry and wait for use; then put the pretreated steel plate into the flux for flux plating, and after the flux plating is completed, dry the steel plate for later use.

Then add 1.0-2.0wt.% Ti, 0.2-1.0wt.% Cr and 0.01-0.1wt.% rare earth to the aluminum-silicon plating solution, set the hot dip plating temperature to 670-690°C, and set the time to 30- After 60s, the steel plate was hot-dipped with aluminum-silicon; after the steel plate was taken out of the plating solution, it was immediately water-cooled to obtain an aluminum-silicon coated plate; then the aluminum-silicon coated plate was put into a vacuum evaporation coating machine, and the vacuum coating was adjusted by adjusting The discharge current of the machine controls the evaporation temperature, and the magnesium is evaporated in a vacuum environment. The evaporation voltage is 1.0-1.6V, and the evaporation current is 100-120A. After 5-10min of evaporation, the aluminum-silicon coating plate is taken out to obtain the evaporation. The aluminum-silicon-coated board of magnesium film is ready for use; the aluminum-silicon-coated board of vapor-deposited magnesium film is then subjected to vacuum diffusion annealing at 440-460° C., and the holding time is 2-5min to finally obtain the aluminum-silicon-magnesium coated board.

Compared with the prior art, the present invention has the following obvious outstanding substantive features and significant advantages:

1. The preparation method of the aluminum-silicon-magnesium coating of the present invention has the following characteristics and advantages compared to the traditional hot dip plating method for preparing the aluminum-silicon coating:

1) The amount of scum in the hot dip plating process is greatly reduced, and the amount of slag and the number of times of slag fishing are also greatly reduced;

2) The magnesium content in the aluminum-silicon-magnesium alloy coating is as high as 3-10wt.%, and the corrosion resistance is greatly improved;

3) The bonding force between the coating and the substrate is stronger, the grains on the surface of the coating are uniform, and there are no defects such as leakage plating and cracks, which effectively improves the surface quality of the coating;

4) The whole preparation process is green and environmentally friendly, more friendly to the environment, and has reference significance for the clean production of coated boards;

2. The present invention refines the crystal grains of the coating by adding Ti in the Al-Si hot dip plating solution, adding Cr to improve the oxidation resistance of the coating, and adding rare earth (RE) to improve the fluidity of the coating solution; the vacuum evaporation effectively avoids the steel plate plating. The phenomenon of leakage plating in the magnesium process improves the surface quality of the aluminum-silicon-magnesium coated plate, and the prepared aluminum-silicon-magnesium coating has excellent comprehensive application performance, especially excellent corrosion resistance; Mg-Si is formed in the coating through diffusion annealing. The alloy phase and the Mg-Al alloy phase not only improve the corrosion resistance of the aluminum-silicon-magnesium coated plate, but also the coated plate has good application properties such as welding, painting and forming;

3. The microstructure of the coating layer of the steel sheet prepared by the present invention has been greatly improved, the grains have been greatly refined, and the corrosion resistance of the coating layer has been greatly improved; the present invention can effectively suppress the Fe-Al interlayer Compared with the existing commercial hot-dip aluminum-silicon coated board, the aluminum-silicon-magnesium coated board prepared by this method has a better coating than the existing commercial hot dip aluminum-silicon-magnesium coated board. The bonding force of the substrate is strong, the crystal grains on the surface of the coating layer are uniform, and there are no defects such as leakage plating and cracks, which effectively improves the quality of the product; the magnesium content in the aluminum-silicon-magnesium alloy coating layer of the present invention can reach 3-10wt.%, and the corrosion resistance is comparable to The commercial aluminum-silicon alloy coating is greatly improved; the aluminum-silicon-magnesium coated board prepared by the method of this aspect greatly reduces the amount of slag and the number of times of slag in the hot-dip plating process, and can effectively solve the problem of slag in the vacuum evaporation process; The combined method of "hot-dip plating-vacuum evaporation-diffusion annealing" of the aluminum-silicon-magnesium coated board prepared by the invention is more environmentally friendly, and has important reference significance for the clean production of the coated board;

4. The method of the present invention is simple and easy to implement, has low cost, and is suitable for popularization and use.

Description of drawings

Fig. 1 is a surface topography diagram of a sample of Al-Si-Mg coating prepared by the method of Example 1 of the present invention after "hot dipping-vacuum evaporation" and before "diffusion annealing".

Fig. 2 is the surface topography of the aluminum-silicon-magnesium coating sample prepared by the method in the first embodiment of the present invention

FIG. 3 is a cross-sectional morphological diagram of an Al-Si-Mg coating sample prepared by the method of Example 1 of the present invention after "hot dip plating-vacuum evaporation" and before "diffusion annealing".

FIG. 4 is a cross-sectional morphological diagram of a sample of Al-Si-Mg coating prepared by the method in Embodiment 1 of the present invention.

FIG. 5 is the cross-sectional line scanning analysis result of the aluminum-silicon-magnesium coating sample prepared by the method of Example 1 of the present invention after “hot dipping-vacuum evaporation” and before “diffusion annealing”.

FIG. 6 is a cross-sectional line scan analysis result of an Al-Si-Mg coating sample prepared by the method in Embodiment 1 of the present invention.

FIG. 7 is the XRD pattern of the surface of the aluminum-silicon-magnesium coating sample prepared by the method in Example 1 of the present invention after “hot dipping-vacuum evaporation” and before “diffusion annealing”.

FIG. 8 is the XRD pattern of the surface of the aluminum-silicon-magnesium coating sample prepared by the method in Example 1 of the present invention.

9 is a comparison diagram of polarization curves of Al-Si coating samples before and after vacuum evaporation of Mg by the method according to the first embodiment of the present invention.

Detailed ways

The above scheme will be further described below in conjunction with specific embodiments, and preferred embodiments of the present invention are described in detail as follows:

Example 1:

In this embodiment, an aluminum-silicon-magnesium coating, the content of silicon in the coating is 5-15wt.%, the content of magnesium is 3-10wt.%, the content of titanium is 1.0-2.0wt.%, and the content of chromium is 0.2-1.0wt% .%, the rare earth RE content is 0.01-0.1 wt.%.

In the present embodiment, a preparation method of Al-Si-Mg coating comprises the following steps:

1) Grinding: The surface of the high-strength steel plate is polished with 600-mesh, 800-mesh, 1000-mesh, 1200-mesh, 1500-mesh, and 2000-mesh sandpaper to remove the oxide layer on the surface;

2) Alkaline washing: prepare an aqueous solution of NaOH with a mass percentage concentration of 5% and an aqueous solution of Na ₂ CO ₃ with a mass percentage concentration of 5%, put the solution into a constant temperature water bath with a temperature of 80° C. Soak in the solution to remove the oil stains on its surface, the alkali washing time is 15min, then take out the steel plate and rinse it with warm deionized water;

3) Pickling: put the steel plate washed with deionized water into an HCl solution with a mass percentage concentration of 50% and an aqueous solution with a concentration of 3g/L urotropine (hexamethylenetetramine, corrosion inhibitor) to remove rust, put the solution in a constant temperature water bath with a temperature of 40°C, pickling time is 15min, after taking it out, wash it with deionized water and anhydrous ethanol in turn, and dry it for later use;

4) Helping plating: put the steel plate into a plating aid of K ₂ ZrF ₆ with a concentration of 4% by mass, and the plating aid solution is placed in a constant temperature water bath with a temperature of 80° C. The plating time is 3min , after the plating is completed, the steel plate is blown dry for use;

5) Equipment preparation: firstly check whether the crucible used in the experiment has cracks or other defects to prevent danger during the experiment; They are all coated with paint and dried in an oven for later use, which can effectively avoid the increase of iron in the alloy melt and the carry-out of the alloy liquid; the composition of the paint used in the experiment is: 5% zinc oxide, 1.5% water glass, 93.5% water;

6) Alloy smelting: first put the weighed Al-10Si alloy into the corundum crucible, and add a covering agent of 1-5% of the total mass of the Al-10Si alloy to prevent oxidation. The composition of the covering agent is 50% by mass. A mixed covering agent of NaCl and 50% KCl; the temperature is raised to 750°C in a pit furnace, and after the alloy in the crucible is completely melted, 1.0-2.0wt.% titanium, 0.2-1.0wt.% chromium and 0.01 wt. -0.1wt.% rare earth RE, and keep it for 1h; after the added master alloy is completely melted, the temperature is lowered to 720℃, and high-purity argon gas is introduced for refining and degassing. The refining time is 1min, and then the scum on the surface is removed;

7) Hot dip plating: Pour 5L/min of N ₂ for atmosphere protection, set the temperature of the hot dip coating furnace to 680°C, wait for the alloy to be completely melted and the furnace temperature to stabilize, then perform hot dip plating, and the dip coating time is 60s ;

8) Water cooling: After the steel plate is taken out of the plating solution, water cooling is carried out immediately, and the water cooling temperature is about 25°C to obtain a high-strength steel plate with aluminum-silicon coating, and the thickness of the aluminum-silicon coating is 10-30 μm;

9) Vacuum: open the cooling water system of the vacuum coating machine; place the magnesium particles in the crucible, fix the high-strength steel plate with aluminum-silicon coating on the substrate plate, 15-20cm away from the crucible mouth, close the vacuum chamber, open the vacuum system and Vacuum measurement system, start vacuuming; among them, the vacuum system consists of a mechanical pump and a molecular pump to form a pump group, first use the mechanical pump to reduce the vacuum degree from 10 ⁵ Pa to 1Pa, and then use the molecular pump to reduce the vacuum degree from 1Pa to 10 ^{- 3} Pa, the vacuum degree of the molecular pump can reach 10 ^-5 Pa; the vacuum measurement system consists of a resistance vacuum gauge and an ionization vacuum gauge, the low vacuum degree measurement part is a resistance vacuum gauge, and the high vacuum degree measurement part is an ionization vacuum gauge;

10) Evaporation deposition: when the vacuum degree is better than 10 ^-3 Pa, turn on the substrate disk rotating device, the substrate disk heating device and the crucible heating device in turn, and start evaporation, the evaporation time is 10min, and the evaporation voltage is 1.5- 1.6V, the evaporation current is 115-120A, try to maintain a constant power during the evaporation process;

11) Take the substrate: after the evaporation is over, turn off the crucible heating device, the substrate disk heating device and the substrate disk rotating device in turn, after the vacuum chamber is lowered to a certain temperature, turn off the vacuum system and the vacuum measurement system in turn, and wait to cool down to After the room temperature, the vacuum chamber was opened, the substrate was taken out, and a high-strength steel plate with aluminum-silicon coating on which a magnesium film was evaporated was prepared, and the thickness of the magnesium film was 1-2 μm. Turn off the cooling water system of the vacuum coating machine;

12) Diffusion annealing: vacuum diffusion annealing is performed on the aluminum-silicon-coated high-strength steel sheet with the vapor-deposited magnesium film at 450°C, the holding time is 2-5min, and then water cooling is performed, and the water-cooling temperature is about 25°C to obtain the aluminum-silicon-magnesium-coated high-strength steel sheet. , wherein the Si content is 5-15 wt.%, and the Mg content is 3-10 wt.%.

FIG. 1 and FIG. 2 are the surface topography diagrams of the samples obtained by the method of this embodiment before and after diffusion annealing. Before diffusion annealing, Mg grains were observed on the surface of the sample, and a large amount of metallic Mg was deposited on the surface. After diffusion annealing, the boundaries between Mg grains gradually disappeared. FIG. 3 and FIG. 4 are the sectional topography diagrams of the sample before and after diffusion annealing, and FIG. 5 and FIG. 6 are the cross-sectional line scanning analysis results of the sample before and after diffusion annealing. Before diffusion annealing, a layer of Mg deposition layer can be observed on the cross section of the sample, which is composed of Mg and a small amount of MgO, and the boundary line between the Mg layer and the Al-Si layer is obvious. Vacuum annealing can improve the adhesion between Mg coating and Al-Si coating surface. After diffusion annealing, the Mg layer and the Al-Si layer in the sample were transformed into a layer of Al-Si/Al-Si-Mg/Mg-MgO structure composed of Al-Mg, Mg-Si, Al-Si and other compounds. Composite coating.

7 and 8 are the surface XRD patterns of the samples obtained by the method of this embodiment before and after diffusion annealing. Before diffusion annealing, the surface layer of the sample is mainly composed of Mg and Al. After diffusion annealing, the boundary line between the Mg layer and the Al _- Si layer gradually disappeared, Mg _diffused into the Al _- Si layer, and Al _diffused into the _Mg layer. Al becomes the main phase of the sample surface, and the final sample surface is mainly composed of Mg ₂ Si, Al ₃ Mg ₂ and Al ₁₂ Mg ₁₇ . The existence of Al-Mg and Mg-Si compound layers helps to improve the corrosion resistance of the coating, so that the aluminum-silicon-magnesium coated plate not only has good high-temperature oxidation resistance, but also has excellent electrochemical corrosion resistance.

Figure 9 shows the polarization curves of the Al-Si coating samples before and after vacuum evaporation of Mg, and Table 1 shows the self-corrosion current density and self-corrosion potential of the samples. Among them, samples 1 and 2 are Al-Si coating; sample 3 is Al-Si-Mg coating; sample 4 is Al-Si-Mg coating, annealed at 450 ℃ for 5 min. The self-corrosion current density reflects the degree of corrosion of the material. The lower the self-corrosion current density, the slower the corrosion rate of the material. The self-corrosion potential reflects the difficulty of corrosion of the material. The higher the self-corrosion potential, the less likely the material is to corrode. Compared with Al-Si coating, Al-Si-Mg coating has lower self-corrosion current density and self-corrosion potential. The decrease of self-corrosion current density shows that the corrosion rate of the coating decreases significantly, and the negative shift of self-corrosion potential will make the coating better play the role of sacrificial anode and better protect the iron matrix. After that, the corrosion resistance of the Al-Si plated sheet is improved, and after vacuum annealing, the corrosion resistance of the Al-Si plated sheet is further improved. The corrosion resistance of the Al-Si-Mg coated plate prepared by the method of the invention is better than that of the hot-dip Al-Si coated plate, so adding an appropriate amount of Mg can make the Al-Si coating not only have good resistance to high temperature oxidation performance, and has excellent electrochemical corrosion resistance.

Table 1 Self-corrosion current density and self-corrosion potential of Al-Si coating samples before and after vacuum evaporation of Mg

Embodiment 2:

This embodiment is basically the same as the first embodiment, and the special features are:

In this embodiment, for a preparation method of an Al-Si-Mg coating, during the hot dip coating process, the hot dip coating temperature is controlled to be 690° C. and the treatment time is 30 s; when the vacuum evaporation process is performed, the evaporation voltage is controlled to be 1.0 V, the evaporation current is 100A, and the evaporation time is 5min; when the diffusion annealing treatment is performed, the annealing temperature is controlled to be 460°C, the holding time is 2min, and then cooled to finally obtain an aluminum-silicon-magnesium coated plate. In this example, the parameter conditions different from those in Example 1 are used, and the aluminum-silicon-magnesium coating is also prepared. The method of this embodiment firstly hot dips Al-Si coating, adds 1.0-2.0wt.% Ti to the Al-Si bath to refine the grains of the coating, adds 0.2-1.0wt.% Cr to improve the oxidation resistance of the coating, and adds 0.01 wt. -0.1wt.%RE improves the fluidity of the plating solution to obtain an aluminum-silicon coated board; then vacuum evaporation of magnesium film is performed, and a vacuum evaporation coating machine is used to vaporize a layer of magnesium film on the aluminum-silicon coated board; then the coated board is diffusion annealed treatment, and vacuum diffusion annealing is performed on the aluminum-silicon-coated plate on which the magnesium film is evaporated, and finally a new type of aluminum-silicon-magnesium coated plate is obtained. Compared with the aluminum-silicon coated board prepared by the hot dip plating method, the aluminum-silicon-magnesium coated board prepared by the method of this embodiment has better comprehensive performance, especially excellent surface quality and corrosion resistance. Compared with the existing hot dip plating method, the preparation method is green and environmentally friendly, and is more friendly to the environment, and is of great significance to the clean production of the coated plate.

Embodiment three:

This embodiment is basically the same as the previous embodiment, and the special features are:

In this embodiment, for a preparation method of an Al-Si-Mg coating, during the hot dip coating process, the hot dip coating temperature is controlled to be 670° C. and the treatment time is 30 s; when the vacuum evaporation process is performed, the evaporation voltage is controlled to be 1.0 V, the evaporation current is 100A, and the evaporation time is 5min; when the diffusion annealing treatment is performed, the annealing temperature is controlled to be 440°C, the holding time is 2min, and then cooled to finally obtain an aluminum-silicon-magnesium coated plate. In this example, the parameter conditions different from those in Example 1 are used, and the aluminum-silicon-magnesium coating is also prepared. The method of this embodiment firstly hot dips Al-Si coating, adds 1.0-2.0wt.% Ti to the Al-Si bath to refine the grains of the coating, adds 0.2-1.0wt.% Cr to improve the oxidation resistance of the coating, and adds 0.01 wt. -0.1wt.%RE improves the fluidity of the plating solution to obtain an aluminum-silicon coated board; then vacuum evaporation of magnesium film is performed, and a vacuum evaporation coating machine is used to vaporize a layer of magnesium film on the aluminum-silicon coated board; then the coated board is diffusion annealed treatment, and vacuum diffusion annealing is performed on the aluminum-silicon-coated plate on which the magnesium film is evaporated, and finally a new type of aluminum-silicon-magnesium coated plate is obtained. Compared with the aluminum-silicon coated board prepared by the hot dip plating method, the aluminum-silicon-magnesium coated board prepared by the method of this embodiment has better comprehensive performance, especially excellent surface quality and corrosion resistance. Compared with the existing hot dip plating method, the preparation method is green and environmentally friendly, and is more friendly to the environment, and is of great significance to the clean production of the coated plate.

To sum up, the amount of scum in the hot-dip plating process of the present invention is greatly reduced, and the amount of slag and the number of times of slag are also greatly reduced; the magnesium content in the aluminum-silicon-magnesium alloy coating is as high as 3-10wt.%, and the corrosion resistance is greatly improved. Improve; the bonding force between the coating and the substrate is stronger, the grains on the surface of the coating are uniform, and there are no defects such as leakage plating and cracks, which effectively improves the surface quality of the coating; the whole preparation process is green and environmentally friendly, more environmentally friendly, and has the advantages of clean production of the coated board. D.

The embodiments of the present invention have been described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned embodiments, and various changes can also be made according to the purpose of the invention and creation of the present invention. Changes, modifications, substitutions, combinations or simplifications should be equivalent replacement methods, as long as they meet the purpose of the present invention, as long as they do not deviate from the technical principles and inventive concepts of the aluminum-silicon-magnesium coating and its preparation method of the present invention, all belong to protection scope of the present invention.

Claims (9)

1. an aluminum-silicon-magnesium coating, characterized in that: the silicon content in the coating is 5-15wt.%, the magnesium content is 3-10wt.%, the titanium content is 1.0-2.0wt.%, and the chromium content is 0.2-1.0wt% .%, the rare earth RE content is 0.01-0.1 wt.%. 2 . The Al-Si-Mg coating according to claim 1 , wherein an Al-Si-Mg intermediate transition layer composed of Mg-Si alloy phase and Mg-Al alloy phase is formed in the coating layer. 3 . 3 . The Al-Si-Mg coating according to claim 2 , wherein a composite coating layer having an Al-Si/Al-Si-Mg/Mg-MgO structure is formed on the surface of the base Fe. 4 . 4. a preparation method of claim 1 aluminum-silicon-magnesium coating, is characterized in that: comprise the following steps: a. Hot dip plating process: Add Ti, Cr and rare earth to the aluminum-silicon plating solution, set the hot-dip plating temperature and time, and perform hot-dip aluminum-silicon plating on the steel plate to be plated to form a basic coating; b. Vacuum evaporation process: The aluminum-silicon-coated steel sheet prepared in the step a is taken out, cooled, and then put into a vacuum evaporation coating machine, and the evaporation temperature is controlled by adjusting the discharge current of the vacuum coating machine. Evaporation is performed, and after the evaporation is completed, the steel plate is taken out to obtain an aluminum-silicon-coated plate with an evaporated magnesium film; c. Diffusion annealing treatment: Vacuum diffusion annealing is performed on the aluminum-silicon-coated steel plate prepared in the step b by vapor-depositing the magnesium film, and then cooled to finally obtain an aluminum-silicon-magnesium coated plate. 5. The preparation method of the aluminum-silicon-magnesium coating according to claim 4, characterized in that: in the step a, during the hot-dip plating process, the control hot-dip plating temperature is 670-690° C., and the treatment time is 30- 60s. 6 . The preparation method of the Al-Si-Mg coating according to claim 4 , wherein in the step a, the hot-dip plating process is controlled to obtain the Al-Si coating with a thickness of 10-30 μm. 7 . 7. The preparation method of the Al-Si-Mg coating according to claim 4, characterized in that: in the step b, during the vacuum evaporation process, the control evaporation voltage is 1.0-1.6V, and the evaporation current is 100-1. 120A, the evaporation time is 5-10min. 8 . The preparation method of the aluminum-silicon-magnesium coating according to claim 4 , wherein in the step b, the vacuum evaporation process is controlled to obtain a magnesium film with a thickness of 1-2 μm. 9 . 9 . The preparation method of the aluminum-silicon-magnesium coating according to claim 4 , wherein in the step c, when the diffusion annealing treatment is performed, the annealing temperature is controlled to be 440-460° C., and the holding time is 2-5 min. 10 .

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