Black zinc-aluminum-magnesium coated steel plate with excellent coating performance and manufacturing method of black zinc-aluminum-magnesium coated steel plate

Abstract

The invention relates to a black zinc-aluminum-magnesium coated steel plate with excellent coating performance and a manufacturing method of the black zinc-aluminum-magnesium coated steel plate. The black zinc-aluminum-magnesium coated steel plate consists of a steel substrate, a zinc-aluminum-magnesium coating, a blackening layer and a black paint film in sequence from inside to outside, the content of Mg in the zinc-aluminum-magnesium coating is 1.0%-4%, and the content of Al is 1%-13%; the thickness of the zinc-aluminum-magnesium coating is 5-30 [mu] m; the thickness of the blackening layer is 5-30 [mu] m; the thickness of the black paint film is 5-30 microns; and the brightness value L of the blackening layer is less than 30. The atomized strong oxidant solution is used for blackening the surface of the zinc-aluminum-magnesium plating layer, the black zinc-aluminum-magnesium plating layer steel plate which is free of painting after stamping and good in corrosion resistance and heat dissipation performance is obtained, the blackened plating layer surface is clean and is of a compact structure with tiny holes, the degreasing procedure and the surface conditioning procedure can be omitted in the black paint film coating process, and the production cost is reduced. The process cost is saved, and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of coated steel plate production, and in particular to a black zinc-aluminum-magnesium coated steel plate with excellent coating performance and a manufacturing method thereof. Background Art

[0002] For steel used in industries such as construction, home appliances, and automobiles, good surface appearance, excellent corrosion resistance, and simple operating procedures are the main factors in material selection. Zinc-aluminum-magnesium coatings have good corrosion resistance and can form a corrosion product film with good adhesion and certain fluidity in a corrosive environment, thereby preventing further erosion by harmful substances. However, the Mg element in the zinc-aluminum-magnesium coating is more active and easily oxidized and blackened. Under the action of strong chemical oxidants, the blackening of the coating surface can be deepened. This process is called blackening. The Mg content in the coating and the oxidizing environment are the main factors affecting the degree of blackening.

[0003] The Chinese patent application with application publication number CN 116987997 A discloses "a surface blackened high aluminum hot dip coated steel plate and its manufacturing method". The coated steel plate is composed of Al2O3-ZnO-SiO2 surface mixed oxide layer, Al-Fe intermetallic compound layer and steel substrate, wherein the surface mixed oxide layer thickness is 1.0-5μm; the Fe-Al intermetallic compound layer thickness is 15-20μm. It obtains a surface blackened coated steel plate with good corrosion resistance by secondary heating treatment of the hot dip high aluminum coated steel plate, which can be used directly without painting.

[0004] The Chinese patent application with application publication number CN 104024475 A discloses a "conversion coating composition comprising: 0.01wt% to 0.2wt% phosphorus (P); 0.01wt% to 0.2wt% magnesium (Mg); 0.005wt% to 0.15wt% zirconium (Zr); 0.005wt% to 0.15wt% titanium (Ti); 0.005wt% to 0.15wt% vanadium (V); 0.05wt% to 1wt% phenolic resin; the balance water and other Inevitable impurities. The surface-treated steel sheet comprises a base steel sheet; a zinc or zinc alloy coating formed on the base steel sheet; a blackened layer formed on the zinc or zinc alloy coating; and an organic and inorganic composite conversion coating formed on the blackened layer, wherein the organic and inorganic composite conversion coating may satisfy the following weight ratio: P:Mg:Zr:Ti:V=1:0.045-2:0.035-1.5:0.035-1.3:0.035-1.5 (based on the weight of P).

[0005] In the industrial production process of strip steel, the zinc-aluminum-magnesium coated steel plate is subjected to blackening treatment by an atomized blackening system, and then coated with a black paint film after drying. After the prepared black zinc-aluminum-magnesium steel plate is deformed by stamping, the inner layer exposed by the cracking of the surface black paint film has a similar black appearance to the black zinc-aluminum-magnesium coating, which reduces the step of repainting in the subsequent process, saves the process cost of re-coating, and improves production efficiency. Summary of the invention

[0006] The present invention provides a black zinc-aluminum-magnesium coated steel plate with excellent coating performance and a manufacturing method thereof. The surface of the zinc-aluminum-magnesium coating is blackened by using an atomized strong oxidant solution to obtain a black zinc-aluminum-magnesium coated steel plate which is free of paint after stamping and has good corrosion resistance and heat dissipation. The surface of the blackened coating is clean and has a dense structure with fine pores. The degreasing process and the surface adjustment process can be omitted in the process of coating the black paint film, thereby saving process costs and improving production efficiency.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A black zinc-aluminum-magnesium coated steel plate with excellent coating performance, which is composed of a steel substrate, a zinc-aluminum-magnesium coating, a blackened layer and a black paint film from the inside to the outside; the zinc-aluminum-magnesium coating has a Mg content of 1.0% to 4% and an Al content of 1% to 13% by mass; the thickness of the zinc-aluminum-magnesium coating is 5 to 30 μm; the thickness of the blackened layer is 5 to 30 μm; the thickness of the blackened film is 5 to 30 μm; and the lightness value L of the blackened layer is less than 30.

[0009] A method for manufacturing a black zinc-aluminum-magnesium coated steel plate with excellent coating performance includes a blackening treatment and a black paint film coating process; wherein the blackening treatment process is implemented by an atomizing blackening system, the atomizing blackening system includes an atomizing device arranged on a steel plate running path, the atomizing device is composed of a plurality of atomizing nozzles arranged above and below the steel plate; an atomized strong oxidant solution is sprayed onto the surface of the steel plate through the atomizing nozzle; the excess blackening liquid on the surface of the steel plate after the blackening treatment is squeezed out and then dried, and then a black paint film is coated and dried to obtain a black zinc-aluminum-magnesium coated steel plate.

[0010] Furthermore, the atomization concentration of the strong oxidant solution during the blackening treatment is 85% to 100%, the atomization time is 10 to 25 seconds, and the atomization temperature is 10 to 35°C; the drying temperature after the blackening treatment is 10 to 200°C, and the drying time is 10 to 35 seconds; the drying temperature after the black paint film is coated is 210 to 250°C, and the drying time is 50 to 200 seconds; the coating thickness of the black paint film is 10 to 35 μm.

[0011] Furthermore, the strong oxidant solution is composed of a hydrogen peroxide solution and a corrosion inhibitor, wherein the mass concentration of the hydrogen peroxide is 15% to 50%, the mass concentration of the corrosion inhibitor is 0.3 to 5%, and the balance is water.

[0012] Furthermore, the corrosion inhibitor is one or more of hexamethylenetetramine, ethanolamine, ethylenediamine, and thiourea.

[0013] Furthermore, the steel plate is preheated before the blackening treatment, and the preheating temperature is 40-200°C.

[0014] Furthermore, the atomizing blackening system is composed of a closed box, a sealing roller 1, an atomizing device, and a sealing roller 2; one end of the closed box is the steel plate inlet end, and the other end is the steel plate outlet end; a sealing roller 1 is provided at the steel plate inlet end, and a sealing roller 2 is provided at the steel plate outlet end; a plurality of groups of atomizing nozzles are respectively provided at the top and bottom of the closed box along the moving direction of the steel plate.

[0015] Furthermore, an extrusion roller and a drying device are sequentially arranged on the steel plate running path downstream of the atomization blackening system, and a water receiving trough is arranged below the extrusion roller.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1) The zinc-aluminum-magnesium coated steel plate is blackened by using an atomized strong oxidant solution. The surface of the blackened coating is clean and has a dense structure with fine pores. The degreasing process and the surface adjustment process can be omitted in the black paint film coating process, which saves process costs and improves production efficiency;

[0018] 2) The atomized blackening system is used for blackening treatment, so that the blackening effect of zinc-aluminum-magnesium coated steel plate is better and more uniform;

[0019] 3) A black zinc-aluminum-magnesium coated steel plate which does not require painting after stamping is prepared. The surface of the steel plate is black, and the base color exposed after stamping is also black, which saves the subsequent painting process;

[0020] 4) After blackening treatment, a stable oxide layer is formed on the coating, and the coating performance is more stable and the corrosion resistance is better;

[0021] 5) The black appearance of the black zinc-aluminum-magnesium coated steel plate is decorative and has good heat dissipation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic structural diagram of the black zinc-aluminum-magnesium coated steel plate of the present invention.

[0023] Figure 2 It is a schematic diagram of the composition of the atomization blackening system of the present invention.

[0024] In the figure: 1. Steel substrate 2. Zinc-aluminum-magnesium coating 3. Black layer 4. Black paint film 5. Sealing roller 1 6. Atomizing device 7. Atomizing nozzle 8. Sealing roller 2 9. Squeeze roller 10. Water tank 11. Drying device DETAILED DESCRIPTION

[0025] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings:

[0026] like Figure 1 As shown, the black zinc-aluminum-magnesium coated steel plate with excellent coating performance described in the present invention consists of a four-layer structure including a steel substrate 1, a zinc-aluminum-magnesium coating 2, a blackening layer 3, and a black paint film 4. The mass percentage content of Mg in the zinc-aluminum-magnesium coating 2 is 1.0% to 4%, the mass percentage content of Al is 1% to 13%, the thickness of the zinc-aluminum-magnesium coating 2 is 5 to 30 μm, the thickness of the blackening layer 3 is 5 to 30 μm, and the thickness of the black paint film 4 is 5 to 30 μm.

[0027] The invention discloses a method for manufacturing a black zinc-aluminum-magnesium coated steel plate with excellent coating performance, which comprises spraying an atomized strong oxidant solution onto the surface of the zinc-aluminum-magnesium coated steel plate, wherein the main component of the strong oxidant solution is a hydrogen peroxide solution of different concentrations, and a small amount of corrosion inhibitor is added at the same time, and the corrosion inhibitor has the effect of reducing the reflectivity and brightness of the steel plate.

[0028] When manufacturing the black zinc-aluminum-magnesium coated steel sheet with excellent coating performance described in the present invention, the zinc-aluminum-magnesium coated steel sheet is first preheated at a temperature of 40 to 200° C. The preheating method may be box-type furnace baking, induction heating, etc. The preheated zinc-aluminum-magnesium coated steel sheet is subjected to the following steps: Figure 2 The atomized blackening system shown first enters the closed box through the sealing roller 1 5. In the closed box, the strong oxidant solution is sprayed from the atomizing nozzles 7 at the top and bottom to blacken the surface of the zinc-aluminum-magnesium coated steel plate. The zinc-aluminum-magnesium coated steel plate after blackening is moved out of the closed box through the sealing roller 2 8, and then the excess blackening liquid on the surface is squeezed out by the squeezing roller 9 (the squeezed blackening liquid falls into the water receiving tank 10 below), and then enters the drying device 11 for drying. After drying, the surface of the zinc-aluminum-magnesium coated steel plate is dry, clean and has a dense structure with fine pores. Using the atomized blackening system, the blackening effect on the surface of the zinc-aluminum-magnesium coated steel plate can be made more uniform. The atomization concentration is controlled by controlling the amount of liquid sprayed by the atomizing nozzle 7 during the blackening process.

[0029] Preferably, in the strong oxidant solution, the mass concentration of hydrogen peroxide is 15% to 50%, the mass concentration of the corrosion inhibitor is 0.3% to 5%, and the balance is water. The corrosion inhibitor can be one or more of hexamethylenetetramine, ethanolamine, ethylenediamine, and thiourea.

[0030] Preferably, the atomization concentration during the blackening treatment is 85% to 100%, the atomization time is 10 to 25 seconds, and the atomization temperature is 10 to 35° C. The drying temperature after the blackening treatment is 10 to 200° C., and the drying time is 10 to 35 seconds.

[0031] Since the surface of the zinc-aluminum-magnesium coated steel plate after blackening treatment is dry, clean and has a dense structure with tiny pores, it provides a basis for coating the black paint film. Before the next step of black paint film coating, the degreasing and surface conditioning treatment steps can be omitted and the passivation treatment can be carried out directly.

[0032] Preferably, the drying temperature after coating the black paint film is 210-250° C., and the drying time is 50-200 s; the thickness of the black paint film is 10-35 μm.

[0033] The lightness value L is used to characterize lightness and darkness. The smaller the value is, the better the black decoration effect is. In the present invention, the lightness value L of the blackened layer is less than 30.

[0034] The higher the Mg content in the zinc-aluminum-magnesium coating, the darker the color after blackening. The higher the atomization concentration of the strong oxidant solution, the longer the atomization time, and the higher the atomization temperature, the higher the blackening degree of the zinc-aluminum-magnesium coating. However, when the atomization concentration of the strong oxidant solution is too high, the atomization time is too long, the atomization temperature is too high, and the black paint film is too thick, the corrosion resistance of the zinc-aluminum-magnesium coating and the adhesion of the surface paint film will be affected.

[0035] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] [Example]

[0037] In this embodiment, a zinc-aluminum-magnesium coating is firstly hot-dip coated on a steel substrate, and then a strong oxidant solution with hydrogen peroxide as the main component is used to blacken the zinc-aluminum-magnesium coated steel plate in an atomized blackening system to blacken the surface of the zinc-aluminum-magnesium coating.

[0038] like Figure 1 As shown, in this embodiment, the atomized blackening system is composed of a closed box, a sealing roller 1 5, an atomizing device 6, and a sealing roller 2 8; one end of the closed box is the steel plate inlet end, and the other end is the steel plate outlet end; a sealing roller 1 5 is provided at the steel plate inlet end, and a sealing roller 2 8 is provided at the steel plate outlet end; a plurality of atomizing nozzles 7 are provided at the top and bottom of the closed box respectively along the moving direction of the steel plate. Along the conveying direction of the steel plate, the downstream of the atomized blackening system is provided with an extrusion roller 9 and a drying device 11 in sequence. The production line of black zinc-aluminum-magnesium coated steel plate also includes a black paint film coating device and a corresponding drying device.

[0039] This embodiment includes 8 specific embodiments. The plating solution composition and coating thickness of the zinc-aluminum-magnesium coated steel sheet in each embodiment are shown in Table 1.

[0040] In this embodiment, the surface of the zinc-aluminum-magnesium coating is blackened by using hydrogen peroxide strong oxidant solutions of different concentrations, and hexamethylenetetramine is used as a corrosion inhibitor. The blackening process parameters of each embodiment are shown in Table 2.

[0041] After atomization and blackening, the zinc-aluminum-magnesium coated steel plate enters the drying system. The drying process parameters and the brightness value after blackening are shown in Table 3.

[0042] A layer of black paint film is coated on the surface of the blackened zinc-aluminum-magnesium coated steel plate. The coating process parameters of the black paint film are shown in Table 4.

[0043] According to items 7 and 8 of GB / T13448-2019 “Test methods for color coated steel sheets and steel strips”, the bendability and reverse impact adhesion of black zinc-aluminum-magnesium coated steel sheets were tested. The test results are shown in Table 5.

[0044] According to item 26.5.1 of GB / T13448-2019 "Test methods for color coated steel sheets and strips", a periodic aging test was carried out (12 hours as a cycle, 8 hours of aster light, blackboard temperature of 60℃±3℃, 4 hours of condensation, blackboard temperature of 50℃±3℃, light source type of UVA-340, irradiation intensity of 0.89W / (m 2 ·nm), wavelength is 340nm. ), after 100 cycles, the gloss loss rate and color difference of the black zinc-aluminum-magnesium coated steel sheets of Examples 1-8 before and after aging, as well as the chalking grade after aging were evaluated in accordance with GB / T1766-2008 "Rating Method for Aging of Paint and Varnish Coatings", and the test results are shown in Table 6.

[0045] Table 1 Plating solution composition and coating thickness of zinc-aluminum-magnesium coated steel sheets

[0046]

[0047] Table 2 Blackening process parameters

[0048]

[0049] Table 3 Drying process parameters after blackening and brightness value after blackening

[0050]

[0051] Table 4 Coating process parameters of black paint film

[0052]

[0053] Table 5 Properties of black zinc-aluminum-magnesium coated steel sheets

[0054]

[0055] Table 6 Black zinc-aluminum-magnesium coated steel plate coating aging test results

[0056]

[0057] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A black zinc-aluminum-magnesium coated steel plate with excellent coating performance, characterized in that: The black zinc-aluminum-magnesium coated steel plate is composed of a steel substrate, a zinc-aluminum-magnesium coating, a blackened layer and a black paint film from the inside to the outside. The Mg content of the zinc-aluminum-magnesium coating is 1.0% to 4%, and the Al content is 1% to 13% by mass; the thickness of the zinc-aluminum-magnesium coating is 5 to 30 μm; the thickness of the blackened layer is 5 to 30 μm; the thickness of the blackened layer is 5 to 30 μm; the brightness value L of the blackened layer is less than 30.

2. A method for manufacturing a black zinc-aluminum-magnesium coated steel sheet with excellent coating performance as claimed in claim 1, characterized in that: The invention comprises a blackening treatment and a black paint film coating process; wherein, the blackening treatment process is implemented by an atomizing blackening system, the atomizing blackening system comprises an atomizing device arranged on the running path of the steel plate, the atomizing device is composed of a plurality of atomizing nozzles arranged above and below the steel plate; an atomized strong oxidant solution is sprayed onto the surface of the steel plate through the atomizing nozzle; after the blackening treatment, the excess blackening liquid on the surface of the steel plate is squeezed out and then dried, and then a black paint film is coated and dried to obtain a black zinc-aluminum-magnesium coated steel plate.

3. The method for manufacturing a black zinc-aluminum-magnesium coated steel sheet with excellent coating performance according to claim 2, characterized in that: During the blackening treatment, the atomization concentration of the strong oxidant solution is 85% to 100%, the atomization time is 10 to 25 seconds, and the atomization temperature is 10 to 35° C.; the drying temperature after the blackening treatment is 10 to 200° C., and the drying time is 10 to 35 seconds; The drying temperature of the black paint film after coating is 210-250° C., and the drying time is 50-200s; the coating thickness of the black paint film is 10-35 μm.

4. The method for manufacturing a black zinc-aluminum-magnesium coated steel sheet with excellent coating performance according to claim 2, characterized in that: The strong oxidant solution is composed of a hydrogen peroxide solution and a corrosion inhibitor, wherein the mass concentration of the hydrogen peroxide is 15% to 50%, the mass concentration of the corrosion inhibitor is 0.3% to 5%, and the balance is water.

5. The method for manufacturing a black zinc-aluminum-magnesium coated steel sheet with excellent coating performance according to claim 4, characterized in that: The corrosion inhibitor is one or more of hexamethylenetetramine, ethanolamine, ethylenediamine and thiourea.

6. The method for manufacturing a black zinc-aluminum-magnesium coated steel sheet with excellent coating performance according to claim 2, characterized in that: The steel plate is preheated before blackening treatment, and the preheating temperature is 40-200°C.

7. The method for manufacturing a black zinc-aluminum-magnesium coated steel sheet with excellent coating performance according to claim 2, characterized in that: The atomizing blackening system consists of a closed box, a sealing roller 1, an atomizing device, and a sealing roller 2; one end of the closed box is the steel plate inlet end, and the other end is the steel plate outlet end; a sealing roller 1 is provided at the steel plate inlet end, and a sealing roller 2 is provided at the steel plate outlet end; a plurality of groups of atomizing nozzles are provided at the top and bottom of the closed box along the moving direction of the steel plate.

8. The method for manufacturing a black zinc-aluminum-magnesium coated steel sheet with excellent coating performance according to claim 2 or 7, characterized in that: An extrusion roller and a drying device are sequentially arranged on the steel plate running path downstream of the atomization blackening system, and a water receiving trough is arranged below the extrusion roller.

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