A coated steel sheet suitable for hot working, its preparation method and application

Abstract

This invention provides a hot-working coated steel sheet, its preparation method, and its application, relating to the field of coated steel sheets. The hot-working coated steel sheet comprises a steel substrate and an aluminum-containing composite coating. The aluminum-containing composite coating is applied to at least one surface of the steel substrate. The aluminum-containing composite coating consists of a cured silicon-based ceramic precursor and aluminum powder. After hot working the coated steel sheet at 740~1100℃, a ceramic coating composed of Al-rich and Si-rich ceramic phases is obtained, with Si internal oxides and Fe carbides forming at the coating / substrate interface. The thickness of the ceramic coating is 2~60 μm. This invention, through coating design, achieves a reasonable coating structure and morphology, and through the design of the preparation method for the coated steel sheet, enables the coated steel sheet to possess excellent oxidation resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coated steel plates, in particular to a coated steel plate for hot working and a preparation method and application thereof. BACKGROUND

[0002] Low-alloy steel has excellent mechanical properties and is widely used in industrial production. Due to the low content of alloying elements, low-alloy steel has extremely high economic efficiency, but at the same time, the oxidation resistance and corrosion resistance are poor. Especially in the hot working process such as hot forming which requires high temperature environment, the surface oxidation of low-carbon steel will seriously affect the product quality and production efficiency. Coating / plating a protective layer on the surface of low-alloy steel is one of the most economical and effective protection methods.

[0003] Aluminum-silicon coating, zinc-based coating, and zinc-aluminum-magnesium coating are typical metal coatings, which are produced by hot-dip plating process. For example, the patents with patent application numbers CN202210827700, CN202010918859, and CN202010636873 all use hot-dip plating method to produce metal-coated plates. Hot-dip plating production method has the characteristics of fast production speed and high production efficiency. However, due to the need for continuous heating during production to ensure that the plated metal is in a liquid state (metal liquid is usually at 420-720℃), the production process is also accompanied by high energy consumption. Electroplating is also one of the commonly used process methods for metal coating production, but the size of the electroplated part is usually limited, so it is not suitable for the production of coated plates. At the same time, the electroplating process usually has huge energy consumption.

[0004] Organic coating is a new type of metal surface protective coating. For example, the organic coated steel plate disclosed in patent application number CN201910977367 provides protection to the substrate at room temperature. The production method of this coated plate is to coat organic paint on the surface of the steel plate at room temperature, and after the paint is cured, a coated steel plate with an organic coating is obtained. Since only the paint needs to be coated on the surface of the substrate, and the preparation process only needs to be heated to 100-280℃ for curing, this production process has the characteristics of convenience and low energy consumption. Since the organic paint will decompose and shrink at high temperatures, this coating cannot have high-temperature protection ability like metal plating. Some researchers improve the high-temperature performance of organic coatings by improving the coating formula and coating structure. For example, a wear-resistant and high-temperature-resistant organic coated steel plate is developed in patent application number CN201711172240. Through the design of the composite structure of the coating, the service temperature of the organic coating is increased to 300℃, but compared with the service temperature of metal plating (about 900℃), there is still a certain gap. Moreover, the composite structure of the coating increases the difficulty of preparing the coated steel plate. Therefore, the quality of the organic coating needs to be improved by improving the composition formula and the coating structure, and the service temperature needs to be improved.

[0005] In view of the above, there is a need to develop a new coating / plating layer which has performance not inferior to that of conventional aluminum alloy plating layer, is thin, does not rely on hot-dip plating process and can be used for hot working. SUMMARY

[0006] To achieve the above object, the present application provides a coating steel plate for hot working, a preparation method and application thereof.

[0007] To achieve the above object, the technical solution of the present application is as follows:

[0008] The present application provides a coating steel plate for hot working, which is composed of a steel plate substrate and an aluminum-containing composite coating, and the aluminum-containing composite coating is coated on at least one surface of the steel plate substrate; the aluminum-containing composite coating is composed of a solidified silicon-based ceramic precursor and aluminum powder; after the coating steel plate is hot worked at 740-1100℃, the coating steel plate obtains a ceramic coating composed of Al-rich ceramic phase and Si ceramic phase, and an internal oxide of Si and a C compound of Fe are formed at the coating / substrate interface; the thickness of the ceramic coating is 2-60μm.

[0009] Preferably, when the steel plate substrate is cooled from 740-1100℃ to room temperature at a speed of 10-50℃ / s, the content of martensite structure in the substrate is 50-100%. Most of the commonly used steels, such as low manganese steel, medium manganese steel, high manganese steel, hot forming steel, CP steel, QP steel, DP steel, etc., meet the above requirements, and the above steel plate has excellent mechanical properties after hot working.

[0010] The present application also provides a preparation method of the coating steel plate for hot working, which comprises the following steps:

[0011] S1. Pretreatment: preparing a hot-rolled or cold-rolled steel plate as a steel plate substrate and removing the surface oil stains thereof;

[0012] S2. Preparing a coating slurry: uniformly mixing raw materials of the coating in a certain proportion without lumps to obtain a coating slurry;

[0013] S3. Coating: uniformly coating the coating slurry obtained in S2 on the surface of the pretreated steel plate substrate obtained in S1, and the coating thickness is 6-180μm, and the coating is completed; the coating method can be roller coating, dip coating or spraying;

[0014] S4. Solidification: solidifying the coating obtained in S3 in a dry environment at 180-300℃ to convert the coating slurry into a solid coating, and the solidification time is 0.3-90min according to different temperatures and slurry ratios, and the coating steel plate for hot working is obtained after solidification.

[0015] Further, when using different methods for coating, the following steps are respectively:

[0016] a) Roller coating: coating the coating slurry on the surface of the metal substrate with a rotating roller as the carrier, and removing the excess coating slurry on at least one surface of the substrate by air knife blowing or the like before the coating slurry on the at least one surface is deposited and layered, so as to control the thickness of the coating slurry on the at least one surface;

[0017] b) Dip coating: immersing the metal substrate into a pool of coating slurry for dip coating, and removing the excess coating slurry on at least one surface of the substrate by air knife blowing or centrifugation or the like after the substrate leaves the pool of coating slurry and before the coating slurry on the at least one surface is deposited and layered, so as to control the thickness of the coating slurry on the at least one surface;

[0018] c) Spray coating: spraying the coating slurry on the surface of the substrate after atomization, and adjusting the process parameters such as the amount of spraying by the nozzle and the moving speed of the workpiece during spraying, so as to control the thickness of the coating slurry on at least one surface of the substrate before the coating slurry on the at least one surface is deposited and layered.

[0019] Further, in the step S2, the raw material of the coating, i.e. the coating slurry, can be divided into two parts: the main material and the auxiliary material. The main material is the key component of the coating slurry, which is composed of a silicon-based ceramic precursor and a filler. The mass ratio of the ceramic precursor to the filler is 1:1 to 10:1. The auxiliary material is the auxiliary component of the coating slurry, which is composed of an auxiliary solvent and an auxiliary curing agent, and can be selectively added or not added. Taking the mass fraction of the coating slurry as 100%, the main material accounts for 40-100% of the coating slurry, the auxiliary solvent in the auxiliary material accounts for 0-60% of the coating slurry, and the auxiliary curing agent in the auxiliary material accounts for 0-20% of the coating slurry. The sum of the mass percentages of the above components is 100%. Preferably, in the coating slurry, the main material accounts for 40-95% of the coating slurry, the auxiliary solvent in the auxiliary material accounts for 5-60% of the coating slurry, and the auxiliary curing agent in the auxiliary material accounts for 0-20% of the coating slurry. The sum of the mass percentages of the above components is 100%.

[0020] In the raw material composition of the coating, the silicon-based ceramic precursor refers to an organic polymer material containing silicon in the main chain and / or side chain, which can be partially or completely converted into an inorganic ceramic phase after high-temperature pyrolysis, and is selected from at least one of polysilazane, polysiloxane, polycarbosilane and polysilane, or an organic polymer modified by functional groups based on the above organic polymers;

[0021] Preferably, the mass fraction of polysilazane in the silicon-based ceramic precursor is ≥80%. In order to obtain excellent protective effect of the coating, the content of polysilazane in the silicon-based ceramic precursor needs to meet the above conditions. Polysiloxane, polycarbosilane, polysilane, etc. can fill the gaps caused by sintering of polysilazane in the coating and improve the performance of the coating. Therefore, it is preferred to increase the content of polysilazane in the silicon-based ceramic precursor, and a small amount of other types of silicon-based ceramic precursor is added.

[0022] In the raw material composition of the coating, the filler is composed of aluminum powder. The aluminum powder is a powder of pure aluminum or aluminum alloy, and the aluminum alloy is preferably an alloy type with a mass fraction of aluminum ≥90%. The micro shape of the filler is one or both of lamellar and particulate, and the size range of the lamellar filler is preferably ≤70 μm in equivalent diameter, and the particle size range of the particulate filler is preferably ≤10 μm in equivalent diameter; further preferably, the micro shape of the aluminum powder is lamellar.

[0023] The raw materials of the coating are mixed to prepare a coating slurry, and the state of the filler when added can be powder or a filler slurry prepared by mixing the filler with an auxiliary solvent. After the filler is mixed with the auxiliary solvent to form a slurry, the filler is wrapped by the auxiliary solvent; the auxiliary solvent can form a protective film on the surface of the filler, effectively preventing the denaturation of the filler powder, and greatly improving the bonding between the filler powders and the wettability with different solutions; preferably, when the filler is added to the coating slurry, the state of the filler is a slurry. Further, the amount of auxiliary solvent used in the slurry should be included in the total amount of auxiliary solvent in the raw materials.

[0024] In the raw material composition of the coating, the composition of the auxiliary solvent is selected from one or more of hydrocarbons (such as isomeric alkanes, xylene, petroleum spirits), ethers (such as aromatic ethers, dimethyl ether), alcohols (such as ethanol, methanol), esters (such as butyl acetate, ethyl acetate, methyl acetate), and silane coupling agents. When mixing the coating slurry, the auxiliary solvent can adjust the solution viscosity and improve the coating wettability, so that the coating slurry can more easily adhere to various substrate surfaces, thereby adapting to complex working conditions.

[0025] In the raw material composition of the coating, the auxiliary curing agent is selected from one or more of diazabicyclo, aluminum trisacetylacetone, and phosphazene; in the raw material of the coating, the auxiliary curing agent mainly plays the role of adjusting the curing time of the coating slurry, improving the interface bonding between the metal and the coating, and improving the adhesion of the coating on the substrate. When the mass content of the auxiliary curing agent is greater than 20%, increasing the content of the auxiliary curing agent has no improvement effect on shortening the curing time of the coating slurry. Therefore, according to the time of the curing process and the adhesion requirement, the mass content of the auxiliary curing agent in the slurry is in the range of 0-20%.

[0026] Further, the curing time should be determined in combination with the coating slurry ratio, curing temperature and coating thickness: when no auxiliary curing agent is added, the curing time of the coating is 30-90 min when the coating is cured at a temperature of 180-300 DEG C; when an auxiliary curing agent is added, the curing time of the coating is 0.3-40 min when the coating is cured at a temperature of 180-300 DEG C.

[0027] Further, the coating is obtained after the coating is cured. The coating is composed of a preceramic phase formed by a silicon-based ceramic precursor and a filler phase containing aluminum, the preceramic phase is connected into a three-dimensional network structure in the coating, and the filler phase is distributed in the gap of the preceramic phase, and the coating has a three-dimensional network-gap structure; wherein the volume fraction of the preceramic phase is ≤80%, and the volume fraction of the filler phase is ≥20%. The thickness of the coating after curing is 3-100 μm.

[0028] The application also provides the use of the coating steel plate which can be used for hot working, and the coating steel plate has an intersection with the temperature range of 740-1100 DEG C in the thermal history of the hot working of the coating steel plate, and is maintained at least for 10 s in the temperature range of 740-1100 DEG C.

[0029] Further, the coating steel plate still has good surface quality after being maintained at least for 10 s in the temperature range of 740-1100 DEG C; the coating and the steel plate substrate of the coating steel plate diffuse with each other, and the oxides of Fe and Si and the carbide of Fe are formed at the coating / substrate interface, and the coating is converted into a ceramic coating composed of an Al-rich ceramic phase and a Si ceramic phase; the thickness of the ceramic coating is 2-60 μm.

[0030] Compared with the prior art, the application has the following advantages:

[0031] 1. The coating slurry of the application has simple components, is convenient to adjust and control, is easy to configure, and is suitable for different production rhythms;

[0032] 2. The coating process of the coating slurry of the application is simple, and the preparation method is various, and the coating can be coated by roll coating, dip coating, spraying and the like, which is beneficial to adapt to different working conditions;

[0033] 3. The coating steel plate of the application has excellent oxidation resistance;

[0034] 4. In the production process of the coating steel plate of the application, the production energy consumption cost is lower than that of the same type of product. BRIEF DESCRIPTION OF DRAWINGS

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the structure of the coated steel plate of the present invention;

[0037] Figure 2 This is a flowchart of a method for preparing a coated steel sheet that can be used for hot working, as described in this invention.

[0038] Figure 3 This is a cross-sectional morphology diagram of the coating after heat treatment of the coated plate in Example 1;

[0039] Figure 4 The images show a comparison of the surface macromorphology of the coated plate in Example 1 and the bare plate in Comparative Example 7 after heat treatment. Detailed Implementation

[0040] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0041] All embodiments and comparative examples used 22MnB5 cold-rolled steel sheet as the substrate.

[0042] Example 1

[0043] In this embodiment, the present invention relates to a coated steel plate that can be used for hot working and a method for preparing the same, which includes the following steps: S1 pretreatment, S2 preparation of coating slurry, S3 coating, and S4 curing. Each step will be described in detail below.

[0044] S1. Preprocessing

[0045] The substrate surface is subjected to shot blasting, pickling, alkali washing, drying and other processes to completely remove oxides, grease and other substances that are not conducive to coating, thereby obtaining a clean substrate surface.

[0046] S2. Preparation of coating slurry:

[0047] The coating slurry in this embodiment was prepared in a dry, room-temperature environment.

[0048] In the coating slurry, the mass ratio of each component is as follows: main material 80%, auxiliary solvent 20%, auxiliary curing agent 0%, and the sum of the mass fractions of the above components is 100%. In the main material, the mass ratio of silicon-based ceramic precursor to filler is 4:1.

[0049] In the silicon-based ceramic precursor, the mass fraction of polysilazane is 100%.

[0050] In order to improve the wettability of the filler in the coating slurry, the filler is mixed with an appropriate amount of auxiliary solvent to form a slurry, and then the filler slurry is mixed with other components of the coating slurry.

[0051] The auxiliary solvents and their contents used in the coating slurry are: 10% dimethyl methanol, 80% light aromatic hydrocarbons, and 10% silane coupling agent, with the sum of the mass fractions of the above components being 100%.

[0052] Weigh the above ingredients according to the stated mass percentages and add them to the container. Mix the ingredients using mechanical stirring for 3 minutes. At this point, the mixed solution is a solid-liquid suspension, with all components uniformly dispersed in the solution and no clumping, agglomeration, sedimentation, or other signs of uneven mixing.

[0053] S3. Coating application:

[0054] The coating slurry was applied using a roller coating process, with a coating thickness of approximately 34 μm.

[0055] S4. Coating Curing:

[0056] The sample was placed in a dry environment at 250°C for 45 minutes. At the end of the time, the coating had completely cured.

[0057] Thus, a coated steel plate with an aluminum-containing composite protective coating, as described in this invention, has been prepared. Figure 1 This is a schematic diagram of the structure of the coated steel plate of the present invention. As can be seen from the figure, after hot working, a ceramic coating composed of Al-rich ceramic phase and Si ceramic phase is obtained on the surface of the steel plate substrate, and Si internal oxide and Fe carbide are formed at the coating / substrate interface. Figure 2 This is a flowchart illustrating a method for preparing a coated steel sheet suitable for hot working, as described in this invention.

[0058] Example 2

[0059] In this embodiment, the present invention relates to a coated steel plate that can be used for hot working and a method for preparing the same, which includes the following steps: S1 pretreatment, S2 preparation of coating slurry, S3 coating, and S4 curing. Each step will be described in detail below.

[0060] S1. Preprocessing

[0061] The substrate surface is subjected to shot blasting, pickling, alkali washing, drying and other processes to completely remove oxides, grease and other substances that are not conducive to coating, thereby obtaining a clean substrate surface.

[0062] S2. Preparation of coating slurry:

[0063] The coating slurry in this embodiment was prepared in a dry, room-temperature environment.

[0064] In the coating slurry, the mass ratio of each component is as follows: main material 95%, auxiliary solvent 5%, auxiliary curing agent 0%, and the sum of the mass fractions of the above components is 100%. Among them, the mass ratio of silicon-based ceramic precursor to filler is 8:1.

[0065] In the silicon-based ceramic precursor, the mass fraction of polysilazane is ≥90%, and the remainder is polysiloxane, with the sum of the mass fractions of the above components being 100%.

[0066] In order to improve the wettability of the filler in the coating slurry, the filler is mixed with an appropriate amount of auxiliary solvent to form a slurry, and then the filler slurry is mixed with other components of the coating slurry.

[0067] The auxiliary solvents and their contents used in the coating slurry are: 30% light aromatic hydrocarbons, 60% petroleum spirits, 5% ethanol, and 5% silane coupling agent, and the sum of the mass fractions of the above components is 100%.

[0068] Weigh the above ingredients according to the stated mass percentages and add them to the container. Mix the ingredients using mechanical stirring for 3 minutes. At this point, the mixed solution is a solid-liquid suspension, with all components uniformly dispersed in the solution and no clumping, agglomeration, sedimentation, or other signs of uneven mixing.

[0069] S3. Coating application:

[0070] The coating slurry is applied using a spraying process, with a coating thickness of approximately 12 μm.

[0071] S4. Coating Curing:

[0072] The sample was placed in a dry environment at 200℃ for 50 minutes. At the end of the time, the coating had completely cured.

[0073] Thus, a coated steel plate with an aluminum-containing composite protective coating, as described in this invention, has been prepared.

[0074] Example 3

[0075] In this embodiment, the present invention relates to a coated steel plate that can be used for hot working and a method for preparing the same, which includes the following steps: S1 pretreatment, S2 preparation of coating slurry, S3 coating, and S4 curing. Each step will be described in detail below.

[0076] S1. Preprocessing

[0077] The substrate surface is subjected to shot blasting, pickling, alkali washing, drying and other processes to completely remove oxides, grease and other substances that are not conducive to coating, thereby obtaining a clean substrate surface.

[0078] S2. Preparation of coating slurry:

[0079] The coating slurry in this embodiment was prepared in a dry, room-temperature environment.

[0080] In the coating slurry, the mass ratio of each component is as follows: main material 40%, auxiliary solvent 60%, auxiliary curing agent 0%, and the sum of the mass fractions of the above components is 100%. Among them, the mass ratio of silicon-based ceramic precursor to filler is 7:1.

[0081] In the silicon-based ceramic precursor, the mass fraction of polysilazane is ≥85%, and the remainder is polysiloxane, with the sum of the mass fractions of the above components being 100%.

[0082] In order to improve the wettability of the filler in the coating slurry, the filler is mixed with an appropriate amount of auxiliary solvent to form a slurry, and then the filler slurry is mixed with other components of the coating slurry.

[0083] The auxiliary solvents used in the coating slurry and their contents are: 75% butyl acetate, 10% ethanol, and 15% silane coupling agent, and the sum of the mass fractions of the above components is 100%.

[0084] Weigh the above ingredients according to the stated mass percentages and add them to the container. Mix the ingredients using mechanical stirring for 3 minutes. At this point, the mixed solution is a solid-liquid suspension, with all components uniformly dispersed in the solution and no clumping, agglomeration, sedimentation, or other signs of uneven mixing.

[0085] S3. Coating application:

[0086] The coating slurry was applied using a dip-coating process, with a coating thickness of approximately 78 μm.

[0087] S4. Coating Curing:

[0088] The sample was placed in a dry environment at 180°C for 90 minutes. At the end of the time, the coating had completely cured.

[0089] Thus, a coated steel plate with an aluminum-containing composite protective coating, as described in this invention, has been prepared.

[0090] Example 4

[0091] In this embodiment, the present invention relates to a coated steel plate that can be used for hot working and a method for preparing the same, which includes the following steps: S1 pretreatment, S2 preparation of coating slurry, S3 coating, and S4 curing. Each step will be described in detail below.

[0092] S1. Preprocessing

[0093] The substrate surface is subjected to shot blasting, pickling, alkali washing, drying and other processes to completely remove oxides, grease and other substances that are not conducive to coating, thereby obtaining a clean substrate surface.

[0094] S2. Preparation of coating slurry:

[0095] The coating slurry in this embodiment was prepared in a dry, room-temperature environment.

[0096] In the coating slurry, the mass ratio of each component is as follows: main material 80%, auxiliary solvent 20%, auxiliary curing agent 0%, and the sum of the mass fractions of the above components is 100%. Among them, the mass ratio of silicon-based ceramic precursor to filler is 1:1.

[0097] In the silicon-based ceramic precursor, the mass fraction of polysilazane is 100%.

[0098] In order to improve the wettability of the filler in the coating slurry, the filler is mixed with an appropriate amount of auxiliary solvent to form a slurry, and then the filler slurry is mixed with other components of the coating slurry.

[0099] The auxiliary solvents used in the coating slurry and their contents are: 80% petroleum ether, 5% ethanol, and 15% dimethyl methanol, with the sum of the mass fractions of the above components being 100%.

[0100] Weigh the above ingredients according to the stated mass percentages and add them to the container. Mix the ingredients using mechanical stirring for 3 minutes. At this point, the mixed solution is a solid-liquid suspension, with all components uniformly dispersed in the solution and no clumping, agglomeration, sedimentation, or other signs of uneven mixing.

[0101] S3. Coating application:

[0102] The coating slurry is applied using a roller coating process, with a coating thickness of approximately 60 μm.

[0103] S4. Coating Curing:

[0104] The sample was placed in a dry environment at 280℃ for 35 minutes. At the end of the time, the coating had completely cured.

[0105] Thus, a coated steel plate with an aluminum-containing composite protective coating, as described in this invention, has been prepared.

[0106] Example 5

[0107] In this embodiment, the present invention relates to a coated steel plate that can be used for hot working and a method for preparing the same, which includes the following steps: S1 pretreatment, S2 preparation of coating slurry, S3 coating, and S4 curing. Each step will be described in detail below.

[0108] S1. Preprocessing

[0109] The substrate surface is subjected to shot blasting, pickling, alkali washing, drying and other processes to completely remove oxides, grease and other substances that are not conducive to coating, thereby obtaining a clean substrate surface.

[0110] S2. Preparation of coating slurry:

[0111] The coating slurry in this embodiment was prepared in a dry, room-temperature environment.

[0112] In the coating slurry, the mass ratio of each component is as follows: main material 70%, auxiliary solvent 20%, auxiliary curing agent 10%, and the sum of the mass fractions of the above components is 100%. Among them, the mass ratio of silicon-based ceramic precursor to filler is 6:1.

[0113] In the silicon-based ceramic precursor, the mass fraction of polysilazane is ≥95%, and the remainder is polysiloxane, with the sum of the mass fractions of the above components being 100%.

[0114] In order to improve the wettability of the filler in the coating slurry, the filler is mixed with an appropriate amount of auxiliary solvent to form a slurry, and then the filler slurry is mixed with other components of the coating slurry.

[0115] The auxiliary solvents used in the coating slurry and their contents are: 20% dimethyl methanol, 75% light aromatic hydrocarbons, and 5% silane coupling agent, with the sum of the mass fractions of the above components being 100%.

[0116] The auxiliary curing agent used in the coating slurry includes: diazabicyclohexane.

[0117] Weigh the above ingredients according to the stated mass percentages and add them to the container. Mix the ingredients using mechanical stirring for 3 minutes. At this point, the mixed solution is a solid-liquid suspension, with all components uniformly dispersed in the solution and no clumping, agglomeration, sedimentation, or other signs of uneven mixing.

[0118] S3. Coating application:

[0119] The coating slurry is applied using a roller coating process, with a coating thickness of approximately 30 μm.

[0120] S4. Coating Curing:

[0121] The sample was placed in a dry environment at 200°C for 10 minutes. At the end of the time, the coating had completely cured.

[0122] Thus, a coated steel plate with an aluminum-containing composite protective coating, as described in this invention, has been prepared.

[0123] Example 6

[0124] In this embodiment, the present invention relates to a coated steel plate that can be used for hot working and a method for preparing the same, which includes the following steps: S1 pretreatment, S2 preparation of coating slurry, S3 coating, and S4 curing. Each step will be described in detail below.

[0125] S1. Preprocessing

[0126] The substrate surface is subjected to shot blasting, pickling, alkali washing, drying and other processes to completely remove oxides, grease and other substances that are not conducive to coating, thereby obtaining a clean substrate surface.

[0127] S2. Preparation of coating slurry:

[0128] The coating slurry in this embodiment was prepared in a dry, room-temperature environment.

[0129] In the coating slurry, the mass ratio of each component is as follows: main material 65%, auxiliary solvent 15%, auxiliary curing agent 20%, and the sum of the mass fractions of the above components is 100%. Among them, the mass ratio of silicon-based ceramic precursor to filler is 10:1.

[0130] In the silicon-based ceramic precursor, the mass fraction of polysilazane is 100%.

[0131] In order to improve the wettability of the filler in the coating slurry, the filler is mixed with an appropriate amount of auxiliary solvent to form a slurry, and then the filler slurry is mixed with other components of the coating slurry.

[0132] The auxiliary solvents used in the coating slurry and their contents are: 95% petroleum ether and 5% silane coupling agent, and the sum of the mass fractions of the above components is 100%.

[0133] The auxiliary curing agent used in the coating slurry includes: aluminum triacetylacetonate.

[0134] Weigh the above ingredients according to the stated mass percentages and add them to the container. Mix the ingredients using mechanical stirring for 3 minutes. At this point, the mixed solution is a solid-liquid suspension, with all components uniformly dispersed in the solution and no clumping, agglomeration, sedimentation, or other signs of uneven mixing.

[0135] S3. Coating application:

[0136] The coating slurry is applied using a spraying process, with a coating thickness of approximately 8 μm.

[0137] S4. Coating Curing:

[0138] The sample was placed in a dry environment at 280℃ for 0.5 minutes. At the end of the time, the coating had completely cured.

[0139] Thus, a coated steel plate with an aluminum-containing composite protective coating, as described in this invention, has been prepared.

[0140] Example 7

[0141] In this embodiment, the present invention relates to a coated steel plate that can be used for hot working and a method for preparing the same, which includes the following steps: S1 pretreatment, S2 preparation of coating slurry, S3 coating, and S4 curing. Each step will be described in detail below.

[0142] S1. Preprocessing

[0143] The substrate surface is subjected to shot blasting, pickling, alkali washing, drying and other processes to completely remove oxides, grease and other substances that are not conducive to coating, thereby obtaining a clean substrate surface.

[0144] S2. Preparation of coating slurry:

[0145] The coating slurry in this embodiment was prepared in a dry, room-temperature environment.

[0146] In the coating slurry, the mass ratio of each component is as follows: main material 60%, auxiliary solvent 40%, auxiliary curing agent 0%, and the sum of the mass fractions of the above components is 100%. Among them, the mass ratio of silicon-based ceramic precursor to filler is 2:1.

[0147] In the silicon-based ceramic precursor, the mass fraction of polysilazane is ≥80%, and the remainder uses polysilane and polysiloxane, with the sum of the mass fractions of the above components being 100%.

[0148] In order to improve the wettability of the filler in the coating slurry, the filler is mixed with an appropriate amount of auxiliary solvent to form a slurry, and then the filler slurry is mixed with other components of the coating slurry.

[0149] The auxiliary solvents used in the coating slurry and their contents are: 25% dimethyl methanol, 65% light aromatic hydrocarbons, and 10% silane coupling agent, and the sum of the mass fractions of the above components is 100%.

[0150] Weigh the above ingredients according to the stated mass percentages and add them to the container. Mix the ingredients using mechanical stirring for 3 minutes. At this point, the mixed solution is a solid-liquid suspension, with all components uniformly dispersed in the solution and no clumping, agglomeration, sedimentation, or other signs of uneven mixing.

[0151] S3. Coating application:

[0152] The coating slurry is applied using a roller coating process, with a coating thickness of approximately 50 μm.

[0153] S4. Coating Curing:

[0154] The sample was placed in a dry environment at 230°C for 45 minutes. At the end of the time, the coating had completely cured.

[0155] Thus, a coated steel plate with an aluminum-containing composite protective coating, as described in this invention, has been prepared.

[0156] To more fully demonstrate the aluminum-containing composite protective coating for metal surfaces and its preparation method according to the present invention, comparative examples 1 to 7 are provided.

[0157] Comparative Example 1

[0158] In this comparative example, the present invention relates to a coated steel plate that can be used for hot working and a method for preparing the same, comprising the following steps: S1 pretreatment, S2 preparation of coating slurry, S3 coating, and S4 curing.

[0159] S1. Preprocessing

[0160] The substrate surface is subjected to shot blasting, pickling, alkali washing, drying and other processes to completely remove oxides, grease and other substances that are not conducive to coating, thereby obtaining a clean substrate surface.

[0161] S2. Prepare the coating slurry:

[0162] The coating slurry in this embodiment was prepared in a dry, room-temperature environment.

[0163] In the coating slurry, the mass ratio of each component is as follows: main material 100%, auxiliary solvent 0%, auxiliary curing agent 0%, and the sum of the mass fractions of the above components is 100%. Among them, the mass ratio of silicon-based ceramic precursor to filler is 100:1.

[0164] In the silicon-based ceramic precursor, the mass fraction of polysilazane is 100%.

[0165] Before adding filler, in order to improve the wettability of filler in coating slurry, an appropriate amount of auxiliary solvent is used to mix filler to form a slurry, and then the filler slurry is mixed with other components of coating slurry.

[0166] The auxiliary solvents used in the coating slurry are: 90% butyl acetate and 10% silane coupling agent, with the sum of the mass fractions of these components being 100%. Weigh the above components according to the stated mass percentages and add them to the container. Mix the components using mechanical stirring for 3 minutes. At this point, the mixed solution is a solid-liquid suspension, with all components uniformly dispersed in the solution without any lumps, agglomerates, sediments, or other signs of uneven mixing.

[0167] S3. Coating:

[0168] Using a roller coating process, the coating slurry is evenly applied to a clean substrate surface, with a coating thickness of approximately 60 μm.

[0169] S4. Curing:

[0170] The sample was placed in a dry environment at 250°C for 45 minutes. At the end of the time, the coating had completely cured.

[0171] Comparative Example 2

[0172] In this comparative example, the present invention relates to a coated steel plate that can be used for hot working and a method for preparing the same, comprising the following steps: S1 pretreatment, S2 preparation of coating slurry, S3 coating, and S4 curing.

[0173] S1. Preprocessing

[0174] The substrate surface is subjected to shot blasting, pickling, alkali washing, drying and other processes to completely remove oxides, grease and other substances that are not conducive to coating, thereby obtaining a clean substrate surface.

[0175] S2. Prepare the coating slurry:

[0176] The coating slurry in this embodiment was prepared in a dry, room-temperature environment.

[0177] In the coating slurry, the mass ratio of each component is as follows: main material 95%, auxiliary solvent 5%, auxiliary curing agent 0%, and the sum of the mass fractions of the above components is 100%. Among them, the mass ratio of silicon-based ceramic precursor to filler is 13:1.

[0178] In the silicon-based ceramic precursor, the mass fraction of polysilazane is 100%.

[0179] Before adding filler, in order to improve the wettability of filler in coating slurry, an appropriate amount of auxiliary solvent is used to mix filler to form a slurry, and then the filler slurry is mixed with other components of coating slurry.

[0180] The auxiliary solvents and their contents used in the coating slurry are: 90% butyl acetate and 10% silane coupling agent, and the sum of the mass fractions of the above components is 100%.

[0181] Weigh the above ingredients according to the stated mass percentages and add them to the container. Mix the ingredients using mechanical stirring for 3 minutes. At this point, the mixed solution is a solid-liquid suspension, with all components uniformly dispersed in the solution and no clumping, agglomeration, sedimentation, or other signs of uneven mixing.

[0182] S3. Coating:

[0183] Using a roller coating process, the coating slurry is evenly applied to a clean substrate surface, with a coating thickness of approximately 60 μm.

[0184] S4. Curing:

[0185] The sample was placed in a dry environment at 250°C for 45 minutes. At the end of the time, the coating had completely cured.

[0186] Comparative Example 3

[0187] In this comparative example, the present invention relates to a coated steel plate that can be used for hot working and a method for preparing the same, comprising the following steps: S1 pretreatment, S2 preparation of coating slurry, S3 coating, and S4 curing.

[0188] S1. Preprocessing

[0189] The substrate surface is subjected to shot blasting, pickling, alkali washing, drying and other processes to completely remove oxides, grease and other substances that are not conducive to coating, thereby obtaining a clean substrate surface.

[0190] S2. Prepare the coating slurry:

[0191] The coating slurry in this embodiment was prepared in a dry, room-temperature environment.

[0192] In the coating slurry, the mass ratio of each component is as follows: main material 75%, auxiliary solvent 5%, auxiliary curing agent 20%, and the sum of the mass fractions of the above components is 100%. Among them, the mass ratio of silicon-based ceramic precursor to filler is 1:2.

[0193] In the silicon-based ceramic precursor, the mass fraction of polysilazane is ≥90%, and the remainder uses polysilane and polycarbosilane, with the sum of the mass fractions of the above components being 100%.

[0194] Before adding filler, in order to improve the wettability of filler in coating slurry, an appropriate amount of auxiliary solvent is used to mix filler to form a slurry, and then the filler slurry is mixed with other components of coating slurry.

[0195] The auxiliary solvents and their contents used in the coating slurry are: 90% butyl acetate and 10% silane coupling agent, and the sum of the mass fractions of the above components is 100%.

[0196] The auxiliary curing agent used in the coating slurry includes: phosphazene.

[0197] Weigh the above ingredients according to the stated mass percentages and add them to the container. Mix the ingredients using mechanical stirring for 3 minutes. At this point, the mixed solution is a solid-liquid suspension, with all components uniformly dispersed in the solution and no clumping, agglomeration, sedimentation, or other signs of uneven mixing.

[0198] S3. Coating:

[0199] Using a roller coating process, the coating slurry is evenly applied to a clean substrate surface, with a coating thickness of approximately 60 μm.

[0200] S4. Curing:

[0201] The sample was placed in a dry environment at 250°C for 45 minutes. At the end of the time, the coating had completely cured.

[0202] Comparative Example 4

[0203] In this comparative example, the present invention relates to a coated steel plate that can be used for hot working and a method for preparing the same, comprising the following steps: S1 pretreatment, S2 preparation of coating slurry, S3 coating, and S4 curing.

[0204] S1. Preprocessing

[0205] The substrate surface is subjected to shot blasting, pickling, alkali washing, drying and other processes to completely remove oxides, grease and other substances that are not conducive to coating, thereby obtaining a clean substrate surface.

[0206] S2. Prepare the coating slurry:

[0207] The coating slurry in this embodiment was prepared in a dry, room-temperature environment.

[0208] In the coating slurry, the mass ratio of each component is as follows: main material 35%, auxiliary solvent 65%, auxiliary curing agent 0%, and the sum of the mass fractions of the above components is 100%. Among them, the mass ratio of silicon-based ceramic precursor to filler is 6:1.

[0209] In the silicon-based ceramic precursor, the mass fraction of polysilazane is ≥80%, and the remainder is polysiloxane, with the sum of the mass fractions of the above components being 100%.

[0210] Before adding filler, in order to improve the wettability of filler in coating slurry, an appropriate amount of auxiliary solvent is used to mix filler to form a slurry, and then the filler slurry is mixed with other components of coating slurry.

[0211] The auxiliary solvents and their contents used in the coating slurry are: 90% butyl acetate and 10% silane coupling agent, and the sum of the mass fractions of the above components is 100%.

[0212] Weigh the above ingredients according to the stated mass percentages and add them to the container. Mix the ingredients using mechanical stirring for 3 minutes. At this point, the mixed solution is a solid-liquid suspension, with all components uniformly dispersed in the solution and no clumping, agglomeration, sedimentation, or other signs of uneven mixing.

[0213] S3. Coating:

[0214] Using a roller coating process, the coating slurry is evenly applied to a clean substrate surface, with a coating thickness of approximately 60 μm.

[0215] S4. Curing:

[0216] The sample was placed in a dry environment at 250°C for 45 minutes. At the end of the time, the coating had completely cured.

[0217] Comparative Example 5

[0218] In this comparative example, the present invention relates to a coated steel plate that can be used for hot working and a method for preparing the same, comprising the following steps: S1 pretreatment, S2 preparation of coating slurry, S3 coating, and S4 curing.

[0219] S1. Preprocessing

[0220] The substrate surface is subjected to shot blasting, pickling, alkali washing, drying and other processes to completely remove oxides, grease and other substances that are not conducive to coating, thereby obtaining a clean substrate surface.

[0221] S2. Prepare the coating slurry:

[0222] The coating slurry in this embodiment was prepared in a dry, room-temperature environment.

[0223] In the coating slurry, the mass ratio of each component is as follows: main material 80%, auxiliary solvent 20%, auxiliary curing agent 0%, and the sum of the mass fractions of the above components is 100%. Among them, the mass ratio of silicon-based ceramic precursor to filler is 7:1.

[0224] In the silicon-based ceramic precursor, the mass fraction of polysilazane is ≤65%, and the remainder is polysiloxane, with the sum of the mass fractions of the above components being 100%.

[0225] Before adding filler, in order to improve the wettability of filler in coating slurry, an appropriate amount of auxiliary solvent is used to mix filler to form a slurry, and then the filler slurry is mixed with other components of coating slurry.

[0226] The auxiliary solvents and their contents used in the coating slurry are: 90% butyl acetate and 10% silane coupling agent, and the sum of the mass fractions of the above components is 100%.

[0227] Weigh the above ingredients according to the stated mass percentages and add them to the container. Mix the ingredients using mechanical stirring for 3 minutes. At this point, the mixed solution is a solid-liquid suspension, with all components uniformly dispersed in the solution and no clumping, agglomeration, sedimentation, or other signs of uneven mixing.

[0228] S3. Coating:

[0229] Using a roller coating process, the coating slurry is evenly applied to a clean substrate surface, with a coating thickness of approximately 60 μm.

[0230] S4. Curing:

[0231] The sample was placed in a dry environment at 250°C for 45 minutes. At the end of the time, the coating had completely cured.

[0232] Comparative Example 6

[0233] In this comparative example, the present invention relates to a coated steel plate that can be used for hot working and a method for preparing the same, comprising the following steps: S1 pretreatment, S2 preparation of coating slurry, S3 coating, and S4 curing.

[0234] S1. Preprocessing

[0235] The substrate surface is subjected to shot blasting, pickling, alkali washing, drying and other processes to completely remove oxides, grease and other substances that are not conducive to coating, thereby obtaining a clean substrate surface.

[0236] S2. Prepare the coating slurry:

[0237] The coating slurry in this embodiment was prepared in a dry, room-temperature environment.

[0238] In the coating slurry, the mass ratio of each component is as follows: main material 65%, auxiliary solvent 10%, auxiliary curing agent 25%, and the sum of the mass fractions of the above components is 100%. Among them, the mass ratio of silicon-based ceramic precursor to filler is 3:1.

[0239] In the silicon-based ceramic precursor, the mass fraction of polysilazane is 100%.

[0240] Before adding filler, in order to improve the wettability of filler in coating slurry, an appropriate amount of auxiliary solvent is used to mix filler to form a slurry, and then the filler slurry is mixed with other components of coating slurry.

[0241] The auxiliary solvents and their contents used in the coating slurry are: 90% butyl acetate and 10% silane coupling agent, and the sum of the mass fractions of the above components is 100%.

[0242] The auxiliary curing agent used in the coating slurry includes: diazabicyclohexane.

[0243] Weigh the above ingredients according to the stated mass percentages and add them to the container. Mix the ingredients using mechanical stirring for 3 minutes. At this point, the mixed solution is a solid-liquid suspension, with all components uniformly dispersed in the solution and no clumping, agglomeration, sedimentation, or other signs of uneven mixing.

[0244] S3. Coating:

[0245] Using a roller coating process, the coating slurry is evenly applied to a clean substrate surface, with a coating thickness of approximately 60 μm.

[0246] S4. Curing:

[0247] The sample was placed in a dry environment at 250°C for 45 minutes. At the end of the time, the coating had completely cured.

[0248] Comparative Example 7 is an uncoated steel plate substrate. Its surface is subjected to shot blasting, pickling, alkali washing, drying and other processes to completely remove oxides, grease and other substances on the substrate surface that are not conducive to coating, and obtain a clean substrate surface.

[0249] Table 1 lists the types and proportions of raw materials used in Examples 1-7 and Comparative Examples 1-7, as well as relevant parameters for coating preparation, to facilitate comparison of the differences in parameters between different examples and comparative examples.

[0250] Table 1

[0251]

[0252] The appearance and adhesion of Examples 1-7 and Comparative Examples 1-7 were evaluated. The appearance of the coatings of Examples 1-7 and some comparative examples were observed, the thickness was measured, the phase ratio was statistically analyzed, and the hardness was measured.

[0253] Metallographic observation was performed on the coating samples, and the microstructure of the coating cross section was observed using a scanning electron microscope. The thickness of the coating cross section was measured using Image-Pro Plus 6.0 software, and the proportion of filler phase in the coating cross section was statistically analyzed.

[0254] The hardness of the coating samples was rated using the pencil scratch test as specified in standard GB-T6739-2022. A Mitsubishi (UNI) 1887 pencil with a hardness range of 8B to 10H was used for the rating. When the surface hardness of the sample exceeded the 10H pencil scratch hardness, it was indicated by ">10H".

[0255] The coating appearance is evaluated by visual inspection. In a clean environment with sufficient light, the surface quality of the coating is observed with the naked eye, especially whether the coating is flat, whether the thickness is uniform, whether the coating is damaged or cracked, and whether there are defects such as pits or peeling.

[0256] For examples and comparative examples where no obvious defects were observed in appearance, the coating adhesion was evaluated. The grid method in standard GB / T9286-2021 was used as the evaluation method, and the coating peeling was visually inspected. The adhesion was rated from 0 to 5, with 0 being the best and 5 being the worst.

[0257] Table 2 lists the relevant data on appearance evaluation, adhesion evaluation, thickness, phase ratio and hardness for Examples 1-10 and Comparative Examples 1-8.

[0258] Table 2

[0259]

[0260] To further illustrate the method of using the novel coated steel sheet suitable for hot working according to the present invention, samples with good coating appearance in the examples and comparative examples were hot-worked at 950°C in an atmospheric atmosphere for 30 minutes according to the method described in the present invention. After hot working, the samples were cooled to room temperature at a rate of 25°C / s, and the volume fraction of martensite in the matrix was approximately 85%.

[0261] Metallographic observation was performed on the coating samples, and the microstructure of the coating cross section was observed using a scanning electron microscope. The coating cross section thickness was statistically analyzed using Image-Pro Plus 6.0 software.

[0262] The Fe oxide content on the sample surface was tested using X-ray diffraction (XRD) to evaluate the antioxidant properties of the coating after heat treatment. The degree of oxidation of the coating was evaluated based on the Fe oxide content obtained from XRD analysis. Specifically, a Fe oxide content ≥ 50% indicated poor antioxidant properties; 50% > Fe oxide content ≥ 20% indicated relatively poor antioxidant properties; 20% > Fe oxide content ≥ 5% indicated average antioxidant properties; and 5% > Fe oxide content indicated good antioxidant properties.

[0263] Table 3 lists the coating thickness, coating microstructure, Fe oxide content, and antioxidant performance rating of the samples with good coating appearance after hot processing.

[0264] Table 3

[0265]

[0266] Among them, the cross-sectional morphology of the coating after hot processing in Example 1 is as follows: Figure 3 As shown in the figure, the coating becomes a ceramic coating, composed of Al-rich ceramic phases and Si ceramic phases. Internal oxides of Si and carbides of Fe are formed at the coating / substrate interface. The coating thickness is 8 μm. The surface macroscopic morphology of the coated steel plate in Example 1 and the bare plate in Comparative Example 7 are shown in the figure. Figure 4 As shown in the figure, the coated plate exhibits good surface quality and is free of oxidation after hot working, while the bare steel plate shows severe oxidation and poor surface quality. This demonstrates that the coated plate described in this invention possesses excellent oxidation resistance during hot working.

[0267] The above examples and comparative examples illustrate the necessity of preparing coatings according to the preparation method of the present invention. Examples 1-7 prepared coatings according to the preparation method of a novel coated steel sheet suitable for hot working according to the present invention, and the coatings all exhibited excellent oxidation resistance during hot working. In Comparative Examples 3, 4, and 6, the coating quality on the coated sheets was poor due to improper coating slurry ratio. In Comparative Examples 1, 2, and 5, although the improper coating slurry ratio did not cause poor coating quality, it led to improper coating deformation during hot working, resulting in a severe decrease in the oxidation resistance of the coated sheets.

[0268] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A coated steel sheet suitable for hot working, comprising a steel sheet substrate and an aluminum-containing composite coating, wherein the aluminum-containing composite coating is coated on at least one surface of the steel sheet substrate, characterized in that, The aluminum-containing composite coating is composed of a cured silicon-based ceramic precursor and aluminum powder. When the coated steel plate is hot-processed at 740~1100℃, the coated steel plate obtains a ceramic coating composed of Al-rich ceramic phase and Si ceramic phase, and Si internal oxide and Fe carbide are formed at the coating / substrate interface. The thickness of the ceramic coating is 2~60μm. The method for preparing the coated steel sheet suitable for hot working includes the following steps: S1. Pretreatment: Prepare hot-rolled or cold-rolled steel sheets as the base material and remove oil stains from their surfaces; S2. Preparation of coating slurry: After mixing the raw materials for coating in a certain proportion until they are uniform and free of lumps, a coating slurry is obtained; S3. Coating: The coating slurry obtained in S2 is uniformly coated onto the pretreated steel plate substrate obtained in S1, with a coating thickness of 6~180μm. The coating is then complete. S4. Curing: The coating obtained in S3 is cured in a dry environment at 180~300℃ to transform the coating slurry into a solid coating. The curing time is 0.3~90min. After curing, the coated steel plate that can be used for hot working is obtained. In step S2, the coating slurry is divided into two parts: main material and auxiliary material. The main material consists of silicon-based ceramic precursor and filler, wherein the mass ratio of ceramic precursor to filler is 1:1 to 10:

1. The filler is composed of aluminum powder, which is pure aluminum or aluminum alloy powder, and the aluminum alloy is an alloy type with an aluminum mass fraction ≥90%; the microstructure of the filler is one or both of lamellar and granular, the size range of the lamellar filler is equivalent diameter ≤70μm, and the particle size range of the granular filler is equivalent diameter ≤10μm. The coating is composed of a pre-ceramic phase formed from a silicon-based ceramic precursor and an aluminum-containing filler phase. The pre-ceramic phase is linked in the coating to form a three-dimensional network structure, and the filler phase is distributed in the gaps between the pre-ceramic phase. The coating has a three-dimensional network-gap structure. The volume fraction of the pre-ceramic phase is ≤80%, the volume fraction of the filler phase is ≥20%, and the thickness of the cured coating is 3~100μm.

2. The coated steel sheet suitable for hot working according to claim 1, characterized in that, When the steel plate matrix is ​​cooled from 740 to 1100°C to room temperature at a rate of 10 to 50°C / s, the martensite content in the matrix is ​​50 to 100%.

3. The coated steel sheet suitable for hot working according to claim 2, characterized in that, The material of the steel plate substrate is selected from at least one of low manganese steel, medium manganese steel, high manganese steel, hot-formed steel, CP steel, QP steel, and DP steel.

4. The coated steel sheet suitable for hot working according to claim 1, characterized in that, In step S2, the coating method is roller coating, dip coating, or spray coating.

5. The coated steel sheet suitable for hot working according to claim 1, characterized in that, In step S2, the auxiliary materials consist of auxiliary solvents and auxiliary curing agents, and the auxiliary materials may be added selectively or not. Based on the mass percentage of the coating slurry being 100%, the main material accounts for 40-100% of the coating slurry, the auxiliary solvent in the auxiliary materials accounts for 0-60% of the coating slurry, the auxiliary curing agent in the auxiliary materials accounts for 0-20% of the coating slurry, and the sum of the mass percentages of the above components is 100%.

6. The coated steel sheet suitable for hot working according to claim 5, characterized in that, In step S2, the silicon-based ceramic precursor is selected from at least one of polysilazane, polysiloxane, polycarbosilane, and polysilane. The auxiliary solvent is selected from one or more of hydrocarbons, ethers, alcohols, esters, and silane coupling agents; the auxiliary curing agent is selected from one or more of diazabicyclohexane, aluminum triacetylacetonate, and phosphazene.

7. The coated steel sheet suitable for hot working according to claim 6, characterized in that, In step S2, the mass fraction of polysilazane in the silicon-based ceramic precursor is ≥80%.

8. The application of the coated steel sheet that can be used for hot working as described in any one of claims 1 to 3, characterized in that, During the use of the coated steel plate, the thermal history of the hot working of the coated steel plate overlaps with the temperature range of 740~1100℃, and it is maintained in the temperature range of 740~1100℃ for at least 10 seconds.

9. The application of the coated steel sheet for hot working as described in claim 8, characterized in that, After the coated steel plate is held at a temperature range of 740~1100℃ for at least 10s, the coating of the coated steel plate diffuses with the steel plate substrate, forming Fe and Si oxides and Fe C compounds at the coating / substrate interface. The coating is transformed into a ceramic coating composed of Al-rich ceramic phase and Si ceramic phase; the thickness of the ceramic coating is 2~60μm.

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