A composite coating for hot-dip galvanized sinking roller, a preparation method and application thereof, and a hot-dip galvanized sinking roller

Abstract

The present invention belongs to the technical field of hot-dip galvanized steel strip processing, and discloses a composite coating for hot-dip galvanized sinking rollers, and a preparation method and application thereof. The preparation method of the composite coating comprises the following steps: S1, spraying tantalum on the surface of a metal substrate by cold spraying to form a transition layer; S2, spraying a mixed metal powder and tungsten carbide powder by cold spraying on the side of the transition layer away from the metal substrate to form a functional layer, thereby preparing the composite coating; wherein the mixed metal powder comprises tantalum, niobium and titanium. The composite coating provided by the present invention has nano-embedded packaging, low porosity, uniform and dense structure, excellent wear resistance and corrosion resistance, and can be well applied to hot-dip galvanizing equipment as a good corrosion-resistant coating.

Description

Technical Field

[0001] The invention belongs to the technical field of hot-dip galvanized steel strip processing, and in particular relates to a composite coating for a hot-dip galvanized sinking roller, a preparation method and application thereof, and a hot-dip galvanized sinking roller. Background Art

[0002] Hot-dip galvanizing is one of the most effective means to delay the corrosion of steel materials. Specifically, the cleaned and activated steel products are immersed in molten zinc liquid. Through the reaction and diffusion between iron and zinc, a zinc alloy coating with good adhesion is plated on the surface of the steel products. In hot-dip galvanizing, a sinking roller is used to keep the steel sheet in a straight state to achieve a better plating effect.

[0003] When in use, the sinking roller will be completely immersed in molten zinc-aluminum liquid at 450-650°C. Due to the corrosion and penetration of the zinc-aluminum liquid, the surface of the sinking roller will produce pitting and corrosion pits and become rough, thus affecting the normal work of the sinking roller.

[0004] At present, the sinking roller is treated by surface treatment methods such as thermal spraying, thermal spraying and supersonic flame spraying to form an anti-corrosion layer on the surface of the sinking roller or change the morphology, chemical composition, organizational structure and stress of the sinking roller, so that the sinking roller has better corrosion resistance.

[0005] However, the corrosion-resistant layer obtained by surface treatment of the sinking roller in the prior art has the problems of high brittleness, poor bonding with the metal substrate of the sinking roller, defects caused by unevenness and short life, and cannot effectively solve the problems of poor corrosion resistance and short life of the sinking roller. Summary of the invention

[0006] In order to improve the corrosion resistance and service life of a hot-dip galvanized sinking roller, the present invention provides a composite coating for a hot-dip galvanized sinking roller, a preparation method and application thereof, and a hot-dip galvanized sinking roller.

[0007] One of the objects of the present invention is to provide a method for preparing a composite coating, comprising the following steps:

[0008] S1. Spraying tantalum onto the surface of a metal substrate by cold spraying to form a transition layer;

[0009] S2, spraying the mixed metal powder and tungsten carbide powder on the side of the transition layer away from the metal substrate by cold spraying to form a functional layer, so as to obtain the composite coating;

[0010] Wherein, the mixed metal powder includes tantalum, niobium and titanium.

[0011] In the present invention, a cold spraying (supersonic cold spraying) method is adopted to prepare a composite coating, and tantalum is sprayed onto the surface of a metal substrate by a supersonic gas-solid two-phase gas flow to form a transition layer, which is specifically a dense tantalum metal layer. Compared with the surface treatment method in the prior art, the method adopted by the present invention can avoid the oxidation of tantalum metal, so that a tantalum metal layer is formed on the surface of the metal substrate, and the prepared transition layer has better bonding strength with the metal substrate, and also has good bonding ability with the composite coating, so that the composite coating structure is more stable. In actual use, the composite coating has more excellent corrosion resistance and a long service life.

[0012] Moreover, in the preparation method of the composite coating, the particle size and oxygen content of the tantalum metal powder used have a great influence on the porosity, bonding ability with the metal substrate and mechanical properties of the transition layer finally prepared. Therefore, the inventors, through creative labor and a large number of experiments, finally determined the specific process conditions for cold spraying the transition layer in S1.

[0013] In some specific embodiments, the particle size of the tantalum is 10 to 45 μm, and the oxygen content is 0 to 500 ppm. Further, the particle size of the tantalum can be 10 μm, 11 μm, 15 μm, 18 μm, 20 μm, 24 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or any value therebetween; the oxygen content of the tantalum can be 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm or any value therebetween.

[0014] In some specific embodiments, in S1, the powder feeding amount of cold spraying is 80-150 g / min, and the working temperature of the inert gas is 800-1000° C. Further, in S1, the powder feeding amount of cold spraying can be 80 g / min, 90 g / min, 100 g / min, 110 g / min, 120 g / min, 135 g / min, 140 g / min, 150 g / min or any value therebetween; the working temperature of the inert gas is adjusted accordingly with the powder feeding amount of cold spraying, and can be 800° C., 810° C., 850° C., 900° C., 950° C., 990° C., 1000° C. or any value therebetween.

[0015] In the technical solution provided by the present invention, tantalum, niobium, titanium and tungsten carbide are sprayed at a supersonic speed onto the side of the transition layer away from the metal substrate through a cold spraying treatment method to form a functional layer. The tantalum, niobium and titanium in the functional layer exist in the form of metal, and cooperate with tungsten carbide to achieve the effects of anti-molten zinc corrosion and wear resistance. At the same time, the functional layer has low porosity and is relatively dense, which can reduce the occurrence of corrosion of the functional layer due to holes and cracks caused by microscopic defects on the surface of the functional layer, thereby improving the service life of the composite coating.

[0016] In some specific implementations, the input mass ratio of the mixed metal powder to the tungsten carbide powder is 1:(0.5-5).

[0017] In some specific embodiments, the particle size of the tungsten carbide is 60-400 nm, and the oxygen content is 0-300 ppm.

[0018] In some specific embodiments, in the mixed metal powder, the mass ratio of tantalum, niobium and titanium is 1:(0.5-5):(0.5-5).

[0019] In some specific embodiments, the mixed metal powder has a particle size of 10 to 30 μm and an oxygen content of 0 to 500 ppm.

[0020] When the mass ratio of the mixed metal powder and the tungsten carbide powder in the functional layer is 1:(0.5~5), and the mass ratio of tantalum, niobium and titanium is 1:(0.5~5):(0.5~5), the components can achieve the most ideal combination, the functional layer and the transition layer have good bonding ability, and at the same time have good wear resistance and corrosion resistance.

[0021] In some specific implementations, in S2, the powder feeding amount of cold spraying is 60-120 g / min, and the working temperature of the inert gas is 700-900°C.

[0022] Compared with supersonic flame spraying, by adopting the above technical solution, the oxidation and volatilization of carbon elements in tungsten carbide during the preparation process can be reduced, and the oxidation of tantalum, niobium and titanium metals can be reduced, so that the above substances can exist in the functional layer in the form of metal and tungsten carbide, so as to better play the role of corrosion resistance and wear resistance.

[0023] The second object of the present invention is to provide a composite coating, which is prepared by the above-mentioned composite coating preparation method.

[0024] In some specific implementations, the thickness of the transition layer is 0.05-0.10 mm; the thickness of the functional layer is 0.1-0.3 mm.

[0025] When the thickness of the transition layer in the composite coating is 0.05-0.10 mm, the thickness of the transition layer is moderate, and it has a good connection with the metal substrate and the functional layer, making the composite coating structure more stable. The transition layer is a dense tantalum metal layer and also has excellent resistance to zinc corrosion. When the thickness of the functional layer is 0.1-0.3 mm, the thickness of the functional layer is moderate, and it has good mechanical properties and corrosion resistance.

[0026] The third purpose of the present invention is to provide a hot-dip galvanized sinking roller, on the surface of which the above-mentioned composite coating is provided, so that it has excellent performance in terms of wear resistance and corrosion resistance, and its life in a molten zinc-aluminum solution at 650°C is 40 days. Compared with the existing method of coating a layer of corrosion-resistant coating on the surface of the sinking roller, it can withstand more severe working environments and has a longer service life.

[0027] A fourth object of the present invention is to provide an application of a composite coating in hot-dip galvanizing, which can not only be applied to the surface of a sinking roller to improve its mechanical properties and corrosion resistance, but can also be used as a surface protective layer for devices in contact with molten zinc in a strip hot-dip galvanizing unit.

[0028] Beneficial effects:

[0029] (1) The present invention adopts cold spraying as a surface treatment technology, creatively selects tantalum, niobium, titanium and tungsten carbide as the main anti-corrosion components, and controls the mass ratio of the above metals or compounds within a specific range, so that the components in the composite coating can achieve the best synergistic effect and achieve good anti-corrosion effect;

[0030] (2) The composite coating provided in the present invention includes a transition layer and a functional layer. Through the setting of the transition layer, the composite coating can have good bonding ability with the metal substrate, so that the composite coating can be well adhered to the sinking roller in actual use, which can greatly improve the wear resistance of the composite coating; at the same time, the functional layer has a sponge-like nano-embedded encapsulation structure with low porosity, uniform and dense structure, and high corrosion resistance and wear resistance. DETAILED DESCRIPTION

[0031] Embodiments of the present invention are described in detail below, and the examples of the embodiments are intended to be used to explain the present invention, but should not be construed as limiting the present invention. In the embodiments, if specific techniques or conditions are not specified, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not specified for reagents or instruments used, they are all conventional products that can be obtained commercially.

[0032] Example 1.

[0033] This embodiment provides a composite coating, which includes a transition layer and a functional layer and has excellent wear resistance and corrosion resistance. The preparation of the composite coating specifically includes the following steps:

[0034] S1. Surface cleaning: First, use gas to blow away the dust on the surface of the sinking roller, then use dilute sulfuric acid to clean the zinc or aluminum coating remaining on the surface, then use an organic solvent to wipe off the surface grease, and finally dry it;

[0035] S2. Surface treatment: The surface of the washed sinking roller is roughened by sandblasting to a roughness of 4.5 or above;

[0036] S3. Preparation of transition layer: heated compressed inert gas is accelerated by a Raoult nozzle as a working carrier gas, and the high-speed carrier gas accelerates tantalum powder to be ejected from the spray gun at a powder feeding rate of 80 g / min and an inert gas working temperature of 800°C, and collides with the sinking roller substrate at low temperature, high speed and in a completely solid state, and plastic deformation of the tantalum powder and the surface of the sinking roller substrate occurs simultaneously, forming a transition layer on the surface of the sinking roller;

[0037] S4. Preparation of functional layer: A Raoult nozzle is used to accelerate the heated compressed inert gas as the working carrier gas. The high-speed carrier gas accelerates the mixed metal powder and tungsten carbide powder to be sprayed out from the spray gun at a powder feeding amount of 60g / min and an inert gas working temperature of 700°C. The mixed powder collides with the sinking roller substrate at a low temperature, high speed and in a completely solid state. Plastic deformation occurs simultaneously on the surface of the mixed powder and the sinking roller substrate, and the adiabatic shear effect accumulates to form a functional layer on the side of the transition layer away from the sinking roller.

[0038] In this embodiment, the tantalum powder used in the transition layer has a particle size of 45μm and an oxygen content of 400ppm, and the thickness of the prepared transition layer is 0.08mm; the mixed metal powder used in the functional layer includes 1 part of tantalum powder, 0.5 part of niobium powder and 0.5 part of sponge titanium powder, the particle size of the mixed metal powder is 20μm, and the oxygen content is 400ppm, and the particle size of the tungsten carbide nanopowder used is 400nm, and the oxygen content is 300ppm, and the thickness of the prepared functional layer is 0.15mm.

[0039] Example 2.

[0040] Example 2 A composite coating was prepared according to the method provided in Example 1, with the differences shown in Table 1, and the remaining conditions were consistent with those of Example 1.

[0041] Table 1.

[0042]

[0043]

[0044] Example 3.

[0045] In this embodiment, the composite coating is prepared by the method provided in Embodiment 1, except that the mass ratio of tantalum, niobium and titanium in the functional layer is 1:6:6, and other conditions are the same.

[0046] Comparative Example 1.

[0047] In this comparative example, the composite coating was prepared by the method provided in Example 1, except that tantalum was not added to the transition layer, but was replaced by tungsten carbide of equal mass, and other conditions were the same.

[0048] Comparative Example 2.

[0049] In this comparative example, the composite coating was prepared by the method provided in Example 1, except that niobium was not added to the transition layer, but was replaced by tungsten carbide of equal mass, and other conditions were the same.

[0050] Comparative Example 3.

[0051] In this comparative example, the composite coating was prepared by the method provided in Example 1, except that titanium was not added to the transition layer, but was replaced by tungsten carbide of equal mass, and other conditions were the same.

[0052] Experimental example.

[0053] The following properties of the composite coatings provided in Examples 1 to 3 and Comparative Examples 1 to 3 were tested:

[0054] (1) Hardness test: Micro Vickers hardness HV0.3 is used for evaluation;

[0055] (2) Corrosion resistance: The sample to be tested was immersed in a zinc-aluminum melt (mass ratio of zinc to aluminum was 55:45) at 650°C and observed for 20 days, and then the change in coating thickness was detected.

[0056] The specific test results are shown in Table 2:

[0057] Table 2. Properties of composite coatings

[0058]

[0059] It can be seen from Table 2 that, compared with Comparative Examples 1 to 3, the composite coatings provided by Examples 1 to 3 of the present invention have higher mechanical strength and good resistance to corrosion by molten zinc-aluminum liquid, and when used as the corrosion-resistant coating of the sinking roller, they exhibit excellent performance and a longer service life; wherein, from the comparison of the test results of Examples 1 and 2 with those of Example 3, it can be seen that when the mass ratio of tantalum, niobium and titanium in the functional layer is 1:(0.5-5):(0.5-5), the components in the functional layer and between the functional layer and the transition layer can play an ideal role together, so that the prepared composite coating has certain mechanical strength and resistance to corrosion by molten zinc-aluminum liquid.

[0060] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for preparing a composite coating, characterized in that: The following steps are involved: S1. Spraying tantalum onto the surface of a metal substrate by cold spraying to form a transition layer; S2, spraying the mixed metal powder and tungsten carbide powder on the side of the transition layer away from the metal substrate by cold spraying to form a functional layer, so as to obtain the composite coating; Wherein, the mixed metal powder includes tantalum, niobium and titanium, the particle size of the tungsten carbide is 60~400nm, the oxygen content is 0~300ppm, the particle size of the mixed metal powder is 10~30µm, the oxygen content is 0~500ppm, and the titanium is sponge titanium; the tantalum, niobium and titanium in the functional layer exist in metal form; the particle size of the tantalum is 10~45µm, the oxygen content is 0~500ppm, the input mass ratio of the mixed metal powder and tungsten carbide powder is 1:(0.5~5), and the mass ratio of tantalum, niobium and titanium in the mixed metal powder is 1:(0.5~5):(0.5~5).

2. The method for preparing the composite coating according to claim 1, characterized in that: In S1, the powder feeding amount of cold spraying is 80-150 g / min, and the working temperature of the inert gas is 800-1000° C.

3. The method for preparing the composite coating according to claim 1, characterized in that: In S2, the powder feeding amount of cold spraying is 60-120 g / min, and the working temperature of the inert gas is 700-900°C.

4. A composite coating prepared by the method for preparing a composite coating according to any one of claims 1 to 3.

5. The composite coating according to claim 4, characterized in that: The thickness of the transition layer is 0.05-0.10 mm; the thickness of the functional layer is 0.1-0.3 mm.

6. A hot dip galvanized sinking roller, characterized in that: The surface is provided with the composite coating according to claim 4 or 5.

7. Use of the composite coating according to claim 4 or 5 in hot-dip galvanizing.

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