Preparation method of red mud high manganese steel heat treatment protective coating

Abstract

The invention discloses a preparation method of a red mud high manganese steel heat treatment protective coating. The red mud high manganese steel heat treatment protective coating comprises the following raw materials: Bayer process red mud, alkaline glass, boric acid, borax, an aluminum dihydrogen phosphate-nano silicon dioxide composite binder and attapulgite. The method comprises the following steps: 1, screening red mud waste, and drying in a roller to obtain red mud powder; 2, crushing the alkaline glass into powder through a roller ball mill; 3, adding borax, boric acid, the aluminum dihydrogen phosphate-nano silicon dioxide composite binder and attapulgite into the red mud powder and the alkaline glass powder, uniformly mixing, and adding water to prepare an aqueous solution; according to the invention, cyclic regeneration of the protective coating is realized by an innovative process, the coating can be automatically stripped by utilizing a unique heat treatment technology, the treatment energy consumption is low, and the cost is controllable. And after the high manganese steel is treated, the surface is free of oxidation residues, secondary processing loss is reduced, and a green and efficient coating scheme is provided.

Description

Technical Field

[0001] The invention relates to the technical field of protective coating preparation, in particular to a method for preparing a red mud high manganese steel heat treatment protective coating. Background Art

[0002] In the field of heat-treated protective coatings, typical preparation techniques focus on performance requirements such as high-temperature resistance and oxidation resistance. A common preparation technique utilizes a high-temperature-resistant inorganic binder (such as silica sol and aluminates) combined with various functional fillers (such as metal oxides and borides) to create the coating. By rationally adjusting the binder and filler ratio and type, this technique enables the coating to form a dense protective film during high-temperature heat treatment, preventing metal oxidation and decarburization.

[0003] However, this preparation technology has numerous drawbacks. First, the adhesion between the coating and the metal substrate is particularly problematic. Under the cyclical effects of thermal expansion and contraction at high temperatures, the coating is prone to peeling, compromising its protective effectiveness. Second, the coating's thermal shock resistance is insufficient at high temperatures. Rapid temperature fluctuations can cause cracks in the coating, rendering it ineffective. Furthermore, some coatings release harmful gases at high temperatures, polluting the environment and potentially posing a health risk to operators. Furthermore, existing coating preparation processes are often complex, requiring high levels of equipment and conditions, leading to increased production costs.

[0004] In the field of metal material applications, high manganese steel is widely used in high-strength and high-wear working environments such as mining machinery, railway switches, and cement equipment due to its excellent wear resistance, impact toughness, and good processing properties. However, high manganese steel faces many problems in actual use. During the high-temperature heat treatment process, the high content of Mn and C elements inside it reacts violently with oxygen, leading to severe oxidation and decarburization. Oxidation will cause pit defects to form on the surface of high manganese steel, and at the same time, a large amount of brittle phases will be generated at the grain boundaries. Decarburization will significantly reduce the strength and wear resistance of high manganese steel. In addition, the high linear expansion coefficient of high manganese steel makes it easy to generate large internal stresses during temperature changes. Under the induction of brittle phases, cracks are very easy to initiate and expand. Currently, although there are protective technologies such as protective coating, low-temperature hot rolling and vacuum heating, the high-temperature resistant anti-oxidation coating disclosed in patent application document CN115260806A has a thick coating, a complex coating process and poor protective stability. These existing technologies are difficult to effectively solve the problems of oxidation, decarburization and cracking of high manganese steel during use, which seriously limits the application performance and service life of high manganese steel. There is an urgent need to develop more efficient and reliable protective coating technology.

[0005] This protective coating, using Bayer red mud as one of its primary raw materials, is an innovative, low-cost, and highly effective coating specifically designed for the hydro-toughening of large, high-manganese steel castings. It exhibits excellent self-stripping properties during hydro-toughening, ensuring excellent heat transfer characteristics for the castings.

[0006] The disclosure of the above background technology content is only used to assist in understanding the inventive concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed on the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of this application. Summary of the Invention

[0007] The main purpose of the present invention is to provide a method for preparing a protective coating for heat-treated red mud high-manganese steel and to develop an efficient and reliable protective coating technology.

[0008] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0009] A method for preparing a red mud high manganese steel heat treatment protective coating comprises the following steps:

[0010] (1) Preparation of red mud powder: The recovered red mud waste is sieved and then drum-dried to obtain solid powder for later use;

[0011] (2) Preparation of alkaline glass powder: alkaline glass (or alkaline glass ratio) is crushed by a drum ball mill to obtain solid powder for later use;

[0012] (3) Add borax, boric acid, aluminum dihydrogen phosphate-nanosilica composite binder, and attapulgite to the red mud powder and alkaline glass powder, mix them evenly in proportion, and add water to make an aqueous solution to obtain the red mud high manganese steel heat treatment protective coating.

[0013] Preferably, the percentage of the Bayer process red mud is: 15-25% of the Bayer process red mud.

[0014] Preferably, the percentage of the alkaline glass is: 60-70% alkaline glass.

[0015] Preferably, the percentage of boric acid is: 5-10% boric acid.

[0016] Preferably, the percentage of borax is: 1-5% borax.

[0017] Preferably, the percentage of the aluminum dihydrogen phosphate-nano-silicon dioxide composite binder is 10%-20%.

[0018] Preferably, the percentage of attapulgite is 1%-5%.

[0019] Preferably, the red mud powder is below 200 mesh, and the alkaline glass powder is below 200 mesh.

[0020] Preferably, the volume of water added in step (3) of the preparation method is 500 ml, and the density of the aqueous solution is 1.5-3.5 g / cm 3 .

[0021] The raw material composition characteristics of the present invention are as follows:

[0022] Red mud: Bayer process red mud is an industrial waste residue generated when bauxite is processed using the Bayer process during the production of alumina. It is mainly formed by the dissolution of bauxite impurities and contains large amounts of iron oxide, aluminum oxide, silicon oxide and other components. It is red or brown in appearance and has the characteristics of fine particle size, strong alkalinity, high water content and complex composition. Large-scale storage not only takes up land but also poses a risk of environmental pollution. However, it is precisely this red mud, because it is rich in various metal oxides, that can be used as a functional filler to give coatings hiding power, weather resistance and other properties, replacing some expensive pigments to reduce costs; after processing, the appropriate fineness and specific surface area can play a filling and reinforcing role, improving the density and mechanical properties of the coating; using it to make coatings realizes the resource utilization of waste residues, which is in line with the concept of environmental protection, reduces environmental pollution, and reduces dependence on natural mineral resources, turning waste into treasure and applying it in the coating field.

[0023] Alkali glass: Alkali glass is a type of glass material that incorporates alkali metal oxides (such as sodium oxide and potassium oxide) into its composition. It is typically made from quartz sand, soda ash, and limestone through a process of high-temperature melting, molding, and annealing. It exhibits a low softening temperature and good chemical stability, maintaining a certain degree of fluidity at high temperatures. By adjusting the type and content of the alkali metal oxide, the thermal expansion coefficient, mechanical strength, and electrical properties of the glass can be precisely controlled. Alkali glass is typically transparent or translucent, with a uniform texture, high hardness, and gloss. Its unique properties play an important role in coatings. Its low softening temperature enables it to melt at a relatively low temperature during the coating construction process and tightly combine with other ingredients to form a continuous and dense coating structure; its good chemical stability can effectively resist the erosion of external chemicals and enhance the corrosion resistance of the coating; the appropriate thermal expansion coefficient obtained by adjusting the ingredients can ensure that the coating and the protected substrate maintain a good match when the temperature changes, reducing the cracking and peeling of the coating caused by thermal expansion and contraction; in addition, its hardness and gloss give the coating good wear resistance and decorative properties. At the same time, alkaline glass can also be used as a binder or part of a film-forming substance, synergistically working with other additives to improve the overall performance of the coating, giving it broad application potential in metal corrosion protection, high-temperature protection and other fields.

[0024] Boric acid: A white crystalline powder with a slippery feel, it is slightly soluble in cold water but readily soluble in hot water, and possesses a certain degree of acidity. It plays a vital role in coating production due to its excellent corrosion resistance, ability to inhibit microbial growth, and extended shelf life. At high temperatures, it forms a glassy film, enhancing the coating's heat resistance and flame retardancy, effectively protecting the substrate. Furthermore, boric acid reacts with other coating ingredients to enhance bonding strength, improving the coating's adhesion and flexibility. Furthermore, the addition of boric acid can adjust the coating's pH, optimize the coating system's stability, and maintain good performance in various environments. Therefore, it is often used as a functional additive in coating production.

[0025] Borax: Borax, also known as sodium tetraborate, typically appears as colorless, translucent crystals or white crystalline powder. It is easily soluble in water, and its aqueous solution is alkaline. Borax offers unique advantages in the production of coatings. It can be melted into a glassy substance at high temperatures, helping the coating form a continuous, dense protective film during the curing process, enhancing the coating's heat resistance and corrosion resistance. As a film-forming aid, borax improves the coating's leveling properties, resulting in a more uniform and smooth surface. It also possesses a certain degree of antibacterial properties, preventing microbial deterioration during storage. Furthermore, borax can adjust the coating's viscosity and thixotropy, optimizing its application performance and facilitating brushing and spraying operations, thereby enhancing the overall quality and effectiveness of the coating.

[0026] Aluminum dihydrogen phosphate-nano-silica composite binder: A binder is a substance that firmly binds the same or different materials together through adhesion, and is also called an adhesive. In the production of coatings, the binder is a key component. It can evenly disperse and bond together solid particles such as pigments and fillers in the coating, so that the coating forms a continuous and dense coating after construction. At the same time, the binder determines the adhesion between the coating and the substrate, ensuring that the coating is not easy to fall off. The present invention uses an aluminum dihydrogen phosphate-nano-silica composite binder, which is a high-performance bonding material that combines inorganic ceramic properties with nano-enhancement effects. The binder is mainly composed of aluminum dihydrogen phosphate, which will undergo a decomposition and polymerization reaction under high temperature conditions to form a continuous aluminum phosphate ceramic phase, building a high-temperature resistant skeleton structure for the coating, so that the coating can withstand extreme temperatures of up to 1600°C. In the present invention, the binder shows significant advantages. It can closely combine with Bayer red mud, alkaline glass and other raw materials, and react together at high temperature to form a "ceramic-glass-mineral" composite network structure, which increases the density of the coating by more than 40% and effectively isolates oxygen and corrosive gases from contact with the substrate.

[0027] Attapulgite: Attapulgite is a hydrous magnesium-aluminum silicate clay mineral with a unique layered chain structure. Its needle-shaped and fibrous crystals interweave to form a stable three-dimensional grid structure when dispersed in water, resulting in excellent suspension and thickening properties. It exhibits excellent chemical inertness and can coexist stably with components such as borax and boric acid. Its outstanding alkali resistance makes it compatible with alkaline glass systems. At high temperatures, attenuated clay exhibits excellent thermal stability, maintaining structural stability within the range of 300-500°C, effectively preventing coating delamination or precipitation during the early stages of heat treatment of red mud high-manganese steel. Furthermore, attenuated clay is widely available and reasonably priced, ready for use after a simple activation treatment. It not only significantly improves the suspension properties of protective coatings for heat treatment of red mud high-manganese steel, but also enhances the coating's uniformity and adhesion, providing more reliable protection during the heat treatment of high-manganese steel.

[0028] Synergy between raw materials and technical effects:

[0029] (1) Synergy between high-temperature film formation and densification

[0030] During the high-temperature treatment process, the alkaline glass first melts to form a continuous glassy matrix. The fluxing action of boric acid and borax accelerates this process, lowering the overall melting temperature and viscosity. Oxides in the Bayer process red mud react chemically with the glassy phase at high temperatures, generating a new aluminosilicate mineral phase that fills the pores of the glassy phase and further enhances the coating's density. Simultaneously, the aluminum dihydrogen phosphate in the binder forms a ceramic phase, which interweaves with the glassy phase and red mud reaction products, forming a "ceramic-glass-mineral" composite network structure. This effectively isolates the substrate from external media and significantly enhances the coating's resistance to high temperatures, oxidation, and corrosion.

[0031] (2) Mechanical performance enhancement synergy

[0032] The nanosilica in the binder fills the microscopic pores within the coating, strengthening and toughening it, increasing its hardness and toughness. The gel structure formed by the attapulgite gradually solidifies during the drying process, interacting with the binder and other raw materials to increase the coating's internal cohesion. Bayer red mud and alkaline glass, acting as a framework and filler phase, provide stable mechanical support. The synergistic effect of these three ingredients makes the coating less susceptible to cracking and flaking under high-temperature thermal stress and mechanical forces, thus ensuring the coating's integrity and protective effectiveness.

[0033] (III) Chemical stability synergy

[0034] Boric acid and borax modify the chemical composition of the glass phase, improving its chemical stability and making the coating resistant to attack by acids, alkalis, and other chemicals. The ceramic phase formed by the binder exhibits excellent chemical inertness, further enhancing the coating's corrosion resistance. Some oxides in Bayer red mud (such as aluminum oxide and titanium oxide) also possess a certain degree of chemical stability. These oxides, combined with the glass and ceramic phases, form a chemical barrier, enabling the protective coating to maintain its excellent performance even in complex chemical environments. This achieves unexpected technical benefits unattainable with single raw materials or simple mixtures.

[0035] (IV) Synergy between raw material ratio and parameter optimization

[0036] Raw material ratio and process parameters play a decisive role in the performance of protective coatings. On the one hand, crushing Bayer red mud and alkaline glass to 200 mesh is the key to achieving performance optimization. This particle size allows the specific surface area and bulk density of the two to reach the optimal state, providing sufficient reaction interface to promote high-temperature solid-phase reaction, and forming a dense stacking structure. Combined with the particle size difference, it produces a graded filling effect, reduces the shrinkage rate and porosity of the coating, and improves stability. On the other hand, the density of the aqueous solution is controlled at 1.5-3.5g / cm 3 This density range precisely controls the solids content, influencing water evaporation, particle settling, and sintering driving force. It avoids stress concentration caused by binder migration, optimizes the heat conduction path, and enables the coating to form a uniform structure during the drying and sintering processes. Ultimately, at high temperatures, it forms a gradient functional structure: "outer glass sealing - middle ceramic reinforcement - inner mineral anchoring." This achieves antioxidant and thermal shock resistance far exceeding traditional coatings, achieving a performance breakthrough.

[0037] The raw materials do not function independently, but rather work in close synergy through precise proportions and controlled parameters. 200-mesh sieved red mud and alkaline glass, along with an aqueous solution of a specific density, work in conjunction with boric acid, borax, a binder, and attapulgite. From microscopic particle accumulation to the macroscopic coating structure, they collectively promote the formation of a "ceramic-glass-mineral" composite network at high temperatures, enhancing mechanical properties and building a chemical barrier. This systematic, synergistic optimization ensures the protective coating maintains excellent performance even under demanding conditions such as water-toughening. This overcomes the technical limitations of single raw materials or simple mixing, demonstrating significant technological advantages and innovative value.

[0038] The beneficial effects of the present invention compared with the prior art include:

[0039] 1. Red mud coating resource utilization

[0040] Using red mud as a coating can achieve a certain degree of waste utilization. Red mud is an industrial waste residue generated during the production of alumina, and usually contains a variety of metal oxides and minerals. Applying red mud to coatings can, on the one hand, reduce the environmental pressure caused by red mud storage, reduce land occupation and the risk of pollution to the surrounding environment; on the other hand, certain components in red mud may give the coating some special properties, such as certain weather resistance and flame retardancy. Through reasonable processing and treatment, red mud can be compounded with other coating ingredients to prepare coating products with certain properties, thereby realizing the resource utilization of red mud, alleviating the problem of resource shortage to a certain extent, and having good environmental and economic benefits.

[0041] 2. Cheap materials and high-quality products

[0042] The cost of using red mud, borax, boric acid, and alkaline glass to make coatings is relatively low. Red mud is a waste residue from alumina production, and large quantities of it need to be disposed of. However, the raw materials for coatings can be obtained at very low or even zero cost. Borax and boric acid are common chemical raw materials with mature production and sufficient supply. The amount added to coatings is small, which has little impact on costs. Alkaline glass can be made from recycled waste glass, which is simple to handle and costs much less than new raw materials, and can replace expensive fillers. In addition, the process of preparing coatings with these raw materials is not complicated, does not require special equipment and high energy consumption, and reduces equipment investment and energy consumption. The combined effect of multiple factors has greatly reduced the cost of coating production.

[0043] 3. The paint will fall off naturally after heat treatment

[0044] The natural shedding of the coating after heat treatment brings significant advantages to high manganese steel processing. Compared with traditional protective coatings that require complex processes such as mechanical grinding and chemical solvent stripping to remove the coating, the natural shedding feature greatly simplifies the subsequent processing process, saving a lot of manpower, material resources and time costs, and effectively improving production efficiency. In addition, the lack of forced stripping avoids mechanical damage or chemical corrosion to the surface of the high manganese steel, ensuring the integrity and smoothness of the workpiece surface and maintaining its original performance; at the same time, it reduces the use of chemical solvents, reduces the risk of environmental pollution, and complies with the concept of green production; and this feature can achieve rapid separation of the coating, facilitating recycling and reprocessing, further improving resource utilization, and providing strong guarantees for the efficient, environmentally friendly and sustainable development of high manganese steel heat treatment processing.

[0045] 4. No oxide layer on the surface after heat treatment

[0046] During the heat treatment of high-manganese steel, a protective coating based on red mud, borax, boric acid, and alkaline glass is used to ensure that the surface is free of an oxide layer after heat treatment. This characteristic offers significant advantages: on the one hand, it avoids defects such as surface pitting and grain boundary embrittlement caused by the oxide layer, largely preserving the original mechanical properties of high-manganese steel, such as wear resistance and impact toughness, and extending the service life of high-manganese steel components in high-wear conditions such as mining machinery and railway switches. On the other hand, the absence of an oxide layer eliminates the need for subsequent processes such as pickling and polishing to remove the oxide scale, simplifying the production process, saving time and labor costs, and improving production efficiency. Furthermore, the smooth, oxide-free surface enhances the appearance quality of high-manganese steel components, reduces the scrap rate caused by oxidation, and improves the company's economic benefits and market competitiveness. DETAILED DESCRIPTION

[0047] The present invention will be further described in detail below in conjunction with specific embodiments. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope of the present invention and its application.

[0048] 1. Implementation

[0049] Example 1

[0050] Bayer red mud 22%; alkaline glass 50%; boric acid 5%; borax 3%; aluminum dihydrogen phosphate-nanosilica composite binder 18%; attapulgite 2%.

[0051] Preparation method of aluminum dihydrogen phosphate-nanosilica composite adhesive: (1) prepare 45 parts of aluminum dihydrogen phosphate, 8 parts of nanosilica (20nm), 3 parts of sodium hexametaphosphate and 44 parts of deionized water by mass; (2) disperse the nanosilica and sodium hexametaphosphate at 50°C and 400 rpm for 30 minutes, then add aluminum dihydrogen phosphate and react at 70°C and 200 rpm for 60 minutes; (3) finally add water to adjust the viscosity to 22 seconds for coating 4 cups, and age for 24 hours to obtain the aluminum dihydrogen phosphate-nanosilica composite adhesive.

[0052] Preparation steps:

[0053] 1. Weigh the raw materials;

[0054] 2. Red mud powdering: The recovered red mud waste is sieved and drum dried to obtain solid powder below 200 mesh for standby use;

[0055] 3. The alkaline glass (or alkaline glass ratio) is crushed by a drum ball mill to obtain a solid powder below 200 mesh for standby use;

[0056] 4. Add borax, boric acid, binder and attapulgite to red mud powder and alkaline glass powder, mix them evenly in proportion, and add water to adjust the density to 1.5-3.5g / cm3 aqueous solution.

[0057] The water-based solution is sprayed, brushed or immersed on the surface of the high manganese steel casting. After natural drying for 5 hours, the surface coating will fall off naturally after heat treatment.

[0058] Example 2

[0059] 15% Bayer red mud; 55% alkaline glass; 8% boric acid; 5% borax; 12% aluminum dihydrogen phosphate-nano-silicon dioxide composite binder; 5% attapulgite. The binder is prepared in the same manner as in Example 1.

[0060] Preparation steps:

[0061] 1. Weigh the raw materials;

[0062] 2. Red mud powdering: The recovered red mud waste is sieved and drum dried to obtain solid powder below 200 mesh for standby use;

[0063] 3. The alkaline glass (or alkaline glass ratio) is crushed by a drum ball mill to obtain a solid powder below 200 mesh for standby use;

[0064] 4. Add borax, boric acid, binder and attapulgite to red mud powder and alkaline glass powder, mix them evenly in proportion, and add water to adjust the density to 1.5-3.5g / cm 3 aqueous solution.

[0065] Spray, brush or soak the water-based solution on the surface of high manganese steel castings. Dry naturally for 5 hours and then heat treat, then the surface coating will fall off naturally.

[0066] Example 3

[0067] 20% Bayer red mud; 49% alkaline glass; 10% boric acid; 2% borax; 15% aluminum dihydrogen phosphate-nanosilica composite binder; 4% attapulgite. The binder is prepared in the same manner as in Example 1.

[0068] Preparation steps:

[0069] 1. Weigh the raw materials;

[0070] 2. Red mud powdering: The recovered red mud waste is sieved and drum dried to obtain solid powder below 200 mesh for standby use;

[0071] 3. The alkaline glass (or alkaline glass ratio) is crushed by a drum ball mill to obtain a solid powder below 200 mesh for standby use;

[0072] 4. Add borax, boric acid, binder and attapulgite to red mud powder and alkaline glass powder, mix them evenly in proportion, and add water to adjust the density to 1.5-3.5g / cm 3 aqueous solution.

[0073] The aqueous solution was sprayed, painted or soaked on the surface of the high manganese steel casting, and the surface coating naturally fell off after natural drying for 5 hours and heat treatment. The experimental results of each embodiment are shown in Table 1.

[0074] Table 1 Experimental results of various embodiments

[0075]

[0076]

[0077] 2. Experimental Results Analysis

[0078] (1) Hardness and solid content

[0079] Traditional heat-treated protective coatings mostly use a single bonding system such as silica sol and water glass. After high-temperature heat treatment, the hardness is generally 150-180HV, and the solid content is about 55-60%. Shrinkage cracking is prone to occur during high-temperature sintering, resulting in a decrease in hardness. Example 1 of the present invention forms a "ceramic-glass-mineral" composite network structure by increasing the proportion of Bayer red mud and binder, with a hardness of 210HV, an increase of 16-40% over traditional technology; the solid content is 68%, which is also higher than the traditional level, effectively enhancing the density and stability of the coating. Example 2 has a slightly lower hardness and solid content than Example 1 due to the reduced ratio of red mud to binder, but is still better than traditional coatings; Example 3 has a moderate ratio of raw materials and the performance is at an intermediate level.

[0080] (2) Adhesion and coating thickness

[0081] Existing heat-treated protective coatings often have poor compatibility between binders and fillers, and their adhesion decreases significantly during the heat treatment process. Most of them can only reach level 2-3 (grid method), and the coating thickness is difficult to accurately control, which is prone to sagging or uneven thickness problems. Examples 1 and 3 of the present invention optimize the raw material ratio so that the binder fully wraps particles such as red mud and alkaline glass. Even after heat treatment at 1050-1100°C, the adhesion still reaches level 0; although Example 2 has a low binder content, the adhesion still reaches level 1, far exceeding the performance of traditional coatings after heat treatment. In terms of coating thickness, the present invention accurately controls the thickness to 0.5-1.5mm through a stable raw material system and construction process. During the heat treatment process, traditional coatings often have large thickness fluctuations due to problems such as mismatched raw material thermal expansion coefficients and increased sedimentation, and even localized over-thickness or peeling of the coating occurs.

[0082] (3) Heat resistance and peeling

[0083] The temperature resistance limit of traditional heat-treated protective coatings (such as water glass-based and phosphate-based) is usually 1100-1300℃. During the heat treatment stage at 1050-1100℃, oxidation and accelerated decarburization are prone to occur, and the coating needs to be peeled off with the help of mechanical polishing or chemical solvents after heat treatment, which not only damages the substrate but also poses an environmental pollution risk. Example 1 of the present invention relies on high red mud and binder content to form a composite network structure that effectively isolates oxygen and carbon atom diffusion during the heat treatment process at 1050-1100℃, and has a temperature resistance of 1552℃, which is 19-32% higher than traditional technology; after cooling after heat treatment, the coating can be naturally and completely peeled off without residue, simplifying the post-processing process. The temperature resistance of Example 2 and Example 3 are 1506℃ and 1528℃ respectively, and the peeling resistance is also better than that of traditional coatings, showing significant technical advantages.

[0084] (IV) Performance comparison of heat treatment process

[0085] During the heating stage, due to the inconsistent thermal expansion coefficients of the raw materials, traditional protective coatings are prone to cracking when the heating rate exceeds 3°C / min; however, the embodiment of the present invention can still maintain the integrity of the coating structure at a heating rate of 5-10°C / min, thanks to the matching of the thermal expansion coefficients of the raw materials in the composite system and the toughening effect of the binder. During the heat preservation stage, the hardness of the traditional coating decreases by about 20-30% after being kept at 1050-1100°C for 2-4 hours, while the hardness of Example 1 of the present invention only decreases by 5%, and the decrease in Examples 2 and 3 is also controlled within 10%, which fully demonstrates the high-temperature stability of the composite network structure. During the cooling stage, traditional coatings often adhere to the substrate after cooling, making it difficult to peel off; after the embodiment of the present invention is cooled to room temperature in the furnace, the coating can be easily and naturally peeled off, greatly improving the heat treatment efficiency and substrate surface quality.

[0086] 3. Experimental Summary

[0087] By comparing with the existing heat treatment protective coating technology, it can be seen that the present invention has achieved a comprehensive breakthrough in key properties such as hardness, solid content, adhesion, temperature resistance and peeling resistance by optimizing the ratio of Bayer red mud, alkaline glass and binder. Whether in the heating, insulation or cooling stages of heat treatment, the coating of the present invention shows better stability and adaptability. Properly increasing the content of red mud and binder can not only enhance the mechanical properties and temperature resistance of the coating, but also ensure good peeling resistance; precise adjustment of the proportion of raw materials is the core of ensuring the stability and construction performance of the coating during the heat treatment process. Compared with traditional heat treatment protective coatings, the present invention is more suitable for harsh heat treatment environments such as high temperature and strong corrosion, and provides a new direction for the development of heat treatment protective coating technology.

[0088] The above is a further detailed description of the present invention in conjunction with preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. Those skilled in the art of the present invention may make several substitutions or modifications to the described embodiments without departing from the scope of the present invention, and these substitutions or modifications should be considered to fall within the scope of protection of the present invention.

[0089] Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made without deviating from the spirit and scope of the present invention. In addition, the scope of application of the present invention is not limited to the specific embodiments of the processes, material compositions, modes, methods and steps described in the specification. From the disclosure of the present invention, those skilled in the art will readily utilize existing or later developed processes, material compositions, modes, methods or steps that essentially perform the same functions as the corresponding embodiments described herein or achieve the same results. Therefore, the appended claims are intended to include these processes, material compositions, modes, methods or steps.

Claims

1. A method for preparing a red mud high manganese steel heat treatment protective coating, characterized in that: The following steps are involved: (1) Preparation of red mud powder: The recovered red mud waste is sieved and then drum-dried to obtain solid powder for use; (2) Alkaline glass (or alkaline glass ratio) is crushed by a drum ball mill to obtain solid powder for use; (3) Red mud powder and alkaline glass powder are added with borax, boric acid, aluminum dihydrogen phosphate-nanosilica composite binder, and attapulgite, mixed evenly in proportion, and water is added to adjust to an aqueous solution to obtain a red mud high manganese steel heat treatment protective coating.

2. The method for preparing the red mud high manganese steel heat treatment protective coating according to claim 1, characterized in that: Taking mass fraction as the unit, the percentage of the Bayer process red mud is: Bayer process red mud 15-25%.

3. The method for preparing the red mud high manganese steel heat treatment protective coating according to claim 1, characterized in that: Taking mass fraction as the unit, the percentage of the alkaline glass is: 40-60% alkaline glass.

4. The method for preparing the red mud high manganese steel heat treatment protective coating according to claim 1, characterized in that: Taking mass fraction as unit, the percentage of the boric acid is: boric acid 5-10%.

5. The method for preparing the red mud high manganese steel heat treatment protective coating according to claim 1, characterized in that: Taking mass fraction as unit, the percentage of borax is: 1-5% borax.

6. The method for preparing the red mud high manganese steel heat treatment protective coating according to claim 1, characterized in that: Taking mass fraction as unit, the percentage of the aluminum dihydrogen phosphate-nano silicon dioxide composite binder is 10%-20%.

7. The method for preparing the red mud high manganese steel heat treatment protective coating according to claim 1, characterized in that: Taking mass fraction as the unit, the percentage of attapulgite is 1%-5%.

8. The method for preparing the red mud high manganese steel heat treatment protective coating according to claim 1, characterized in that: The red mud powder is smaller than 200 mesh, and the alkaline glass powder is smaller than 200 mesh.

9. The method for preparing the red mud high manganese steel heat treatment protective coating according to claim 1, characterized in that: The volume of clean water added in step (3) of the preparation method is 500 ml, and the density of the aqueous solution is 1.5-3.5 g / cm 3 .

10. A red mud high manganese steel heat treatment protective coating prepared according to the method according to any one of claims 1 to 9.

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