Red mud heat treatment protective coating and application thereof in heat treatment of high manganese steel

Abstract

The invention discloses a red mud heat treatment protective coating and application thereof in high manganese steel heat treatment, the red mud heat treatment protective coating is composed of Bayer process red mud, alkaline glass, boric acid, borax, silica sol, bentonite and calcium carbonate, and the red mud heat treatment protective coating is used for heat treatment after being coated on the surface of a high manganese steel casting and dried. The raw materials in the coating are synergistic, and a high-temperature-resistant framework is combined with a rapid densified glass phase, so that diffusion of oxygen and carbon is effectively blocked, and oxidation and decarbonization of high-manganese steel during heat treatment at 1000-1150 DEG C are prevented; silica sol enhances adhesion, and calcium carbonate improves hardness. The coating naturally falls off after heat treatment, post-treatment is simplified, industrial solid waste is utilized as raw materials, cost is low, environment friendliness is good, and the heat treatment quality and efficiency of the high-manganese steel are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of heat treatment protection for metal materials, and more particularly to a heat treatment protective coating for high-manganese steel castings based on industrial solid waste and its application method. The coating, prepared using Bayer red mud and waste alkaline glass as primary raw materials through a rational mix and specific process, effectively prevents oxidation and decarburization during the heat treatment of high-manganese steel castings. The coating is also easily removable after heat treatment, significantly improving the quality of high-manganese steel castings, reducing production costs, and promoting the resource utilization of industrial solid waste. Background Art

[0002] As a key engineering material, high-manganese steel is widely used in mining, railways, construction, and other fields due to its exceptional work-hardening properties under impact loads, excellent wear resistance, and toughness. For example, in key components such as crusher parts in mining machinery and railway switches, high-manganese steel, thanks to its unique properties, effectively extends the service life of equipment and ensures efficient and stable production operations.

[0003] However, the heat treatment step is crucial in the production and processing of high-manganese steel, yet it faces numerous challenges. During high-temperature heat treatment, the manganese element in high-manganese steel, due to its higher metallic activity than elements such as iron, has a melting point of only 1244°C and is easily oxidized during the heating process, leading to serious oxidation and burning problems. At the same time, the serious microsegregation of elements such as carbon and manganese at the grain boundaries will significantly reduce the melting point of the alloy at the grain boundaries, making thermal cracks prone to occur during high-temperature homogenization annealing. Furthermore, the thermal conductivity of high-manganese steel is much lower than that of general alloy steels, and excessively fast or uneven heating rates can cause crack defects. Especially for large high-manganese steel ingots, the microsegregation of composition is more prominent. To achieve compositional homogenization, the holding time at high temperature often exceeds 20 hours, and can even reach 50 hours. The oxidation and burning rate of the ingots is as high as 2%-8%, which not only causes serious economic losses but also affects product quality.

[0004] To solve the problem of metal oxidation during heating, currently commonly used methods include inert gas protection, vacuum heating, salt bath heating, rapid heating, and heat treatment protective coating. However, the inert gas protection, vacuum heating, salt bath heating, and rapid heating methods have extremely high requirements for equipment and operating techniques, and conventional equipment of general enterprises is difficult to meet the requirements. In contrast, the coating preparation cost is low, the process is simple, and it is not limited by the volume and shape of the equipment and workpiece. In addition, the holes, cracks and other defects in the coating can self-heal when the temperature rises, forming a closed film layer with suitable high-temperature viscosity. Therefore, it is more suitable for the heating process before large-scale production of forging and steel rolling.

[0005] However, the currently disclosed anti-oxidation coating technology for steel billets is mostly based on glass-based protective coatings based on SiO2, which have a low softening temperature and can only meet the requirements for use under relatively low temperature and short heating conditions. For the complex working conditions of long-term and high-temperature heat treatment of high-manganese steel, existing coatings are difficult to meet the requirements. For example, in some disclosed technologies, patent application document CN112940544A discloses a high-alloy steel billet anti-oxidation coating that is resistant to high temperature and long-term heating. This coating is mainly used for nickel-based alloy steel ingots. It is designed for the good corrosion resistance of nickel in nickel-based alloys, and has relatively low corrosion resistance requirements for the coating. In addition, the coating construction process is complicated and requires room temperature polishing before coating, which cannot meet the production requirements of high-manganese steel high-temperature hot charging. For example, although patent CN115260806B is committed to solving the anti-oxidation problem of medium and high manganese steel, its coating formula and process are significantly different from the present invention, and it cannot achieve the technical solution of the present invention that uses a specific raw material ratio and is prepared through a specific process to exert a unique protective effect during the heat treatment of high manganese steel. However, patent application document CN118359948A uses raw materials such as αAl2O3 micropowder and fused magnesia fine powder to prepare the coating, which is different from the present invention in terms of raw material selection and preparation process. It is difficult to achieve the synergistic protective performance of high manganese steel during heat treatment, such as forming a high-temperature resistant skeleton, improving the ability to form a glass phase, enhancing the initial adhesion, and improving the hardness and wear resistance of the coating.

[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 propose a protective coating and application method suitable for long-term, high-temperature heat treatment of high-manganese steel, so as to solve the technical problems existing in the above-mentioned prior art, such as difficulty in adapting to the complex working conditions of high-manganese steel, complex coating construction, single protective performance, and inability to achieve multi-faceted coordinated protection. To this end, the present invention proposes a protective coating prepared by a specific proportion and stirring process using Bayer red mud, alkaline glass, boric acid, borax, silica sol, bentonite and calcium carbonate as raw materials. During the heat treatment of high-manganese steel, the coating can form a high-temperature resistant skeleton and a rapidly densified glassy protective film, enhance the adhesion and hardness of the coating, and can fall off naturally after heat treatment, simplifying the post-processing process and significantly improving the heat treatment quality and production efficiency of high-manganese steel.

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

[0009] A red mud heat-treated protective coating comprises the following raw materials, calculated by mass percentage: 30-40% Bayer red mud, 20-30% alkaline glass, 5-10% boric acid, 5-10% borax, 10-15% silica sol, 2-5% bentonite, and 5-10% calcium carbonate.

[0010] Preferably, the Bayer process red mud has a particle size that passes through a 200-mesh sieve, the alkaline glass is recycled crushed waste glass with a particle size of 2-5 μm, and the average particle size of the calcium carbonate is 1-5 μm. Preferably, the bentonite is sodium-based bentonite and has been treated with sodium to have a montmorillonite content of no less than 80%.

[0011] Preferably, the red mud heat-treated protective coating is prepared by adding Bayer process red mud, alkaline glass, boric acid, borax, calcium carbonate, and bentonite in proportion to a stirring container, and dry mixing them at 100-200 rpm for 10-15 minutes; then adding silica sol, increasing the stirring speed to 200-300 rpm, and continuing stirring for 15-20 minutes to form a uniform paste-like mixture.

[0012] Preferably, during the stirring process, 500 ml of water or ethanol may be added to adjust the viscosity of the paste mixture so that the viscosity of the paste mixture after 4 cups of application is between 20-40 seconds.

[0013] Preferably, the application method of the red mud heat treatment protective coating comprises: uniformly applying the coating to the surface of the high manganese steel casting by spraying, brushing or immersion, naturally drying at room temperature for 2-6 hours to form a pre-coating layer, performing water toughening treatment on the dried high manganese steel casting, and naturally falling off the coating after cooling.

[0014] Preferably, the air pressure of the spray gun is adjusted to 0.3-0.5 MPa during spraying; the coating is ensured to be smooth and free of bubbles during brushing; the casting is completely immersed during immersion, and is allowed to stand and drain excess paint after being taken out.

[0015] Preferably, when the dried high manganese steel casting is subjected to water toughening treatment, the temperature is raised to 1000-1150° C. at 50-100° C. / h (determined according to the manganese content of the high manganese steel) and kept warm for 4-8 hours (adjusted according to the size and cross-sectional thickness of the casting).

[0016] Preferably, the coating thickness is controlled at 0.5-2 mm.

[0017] The following is an introduction to the raw materials in red mud heat treatment protective coatings:

[0018] 1. Bayer red mud: This solid waste is generated during the alumina production process. Its main components include various metal oxides, such as iron oxide, aluminum oxide, and silicon oxide. It has high heat resistance and can form a high-temperature resistant skeleton with alkaline glass in coatings, providing stable structural support for the coating, enabling it to withstand the high temperatures encountered during the heat treatment of high-manganese steel.

[0019] 2. Alkali glass: With its high melting point and excellent chemical stability, it interacts with Bayer red mud to form a strong, high-temperature-resistant framework. At high temperatures, alkaline glass interacts with other components to enhance the overall strength and stability of the coating, while also helping to improve the coating's adhesion to the high-manganese steel substrate.

[0020] 3. Boric acid: A white crystalline powder, it promotes the formation of a glass phase in coatings. At high temperatures, boric acid can lower the glass phase's formation temperature, accelerating its formation and allowing the coating to densify rapidly during heat treatment. This improves the coating's protective properties, effectively blocking the diffusion of oxygen and carbon atoms and preventing oxidation and decarburization of high-manganese steel.

[0021] 4. Borax: Also known as sodium tetraborate, it is an important boron-containing mineral and boron compound. Similar to boric acid, borax promotes the formation of a glassy phase at high temperatures, improving its quality and performance. It optimizes the structure of the glassy phase, making it more uniform and dense, further enhancing the protective effect of the coating while also improving its high-temperature stability and chemical resistance.

[0022] 5. Silica sol: A dispersion of nano-sized silica particles in water, it exhibits excellent adhesion and high-temperature resistance. In coatings, silica sol chemically reacts with the surface of the high-manganese steel substrate, forming a strong chemical bond. This strengthens the initial adhesion between the coating and the substrate, ensuring that the coating does not easily fall off during heat treatment. Furthermore, at high temperatures, silica sol undergoes a polycondensation reaction, forming a three-dimensional network structure that interweaves with the high-temperature-resistant skeleton, enhancing the overall strength and toughness of the coating.

[0023] 6. Bentonite: This clay mineral, primarily composed of montmorillonite, exhibits excellent water absorption, swelling, dispersibility, and suspension properties. In coatings, bentonite absorbs large amounts of water, forming a high-viscosity colloid that evenly disperses other solid particles within the system, preventing particle sedimentation and agglomeration, and ensuring the uniformity and stability of the coating. Furthermore, it works with silica sol to adjust the coating's rheological properties, imparting excellent thixotropy, facilitating application and preventing sagging.

[0024] 7. Calcium carbonate: A common inorganic compound with high hardness and chemical stability. In coatings, calcium carbonate acts as a reinforcing filler and can be evenly dispersed throughout the coating, increasing its hardness and wear resistance, improving its ability to withstand mechanical wear and thermal stress, and reducing the occurrence of surface cracks, thereby enhancing the coating's protective performance and service life during the heat treatment of high-manganese steel.

[0025] Synergistic effect of red mud heat treatment protective coating raw materials:

[0026] In the high manganese steel heat treatment protective coating of the present invention, raw materials such as Bayer red mud, alkaline glass, boric acid, borax, silica sol, bentonite and calcium carbonate do not play a role independently, but work together through multiple mechanisms to achieve excellent protective performance and process characteristics.

[0027] (1) High-temperature resistant frame and glass work together to build a protective barrier

[0028] Bayer red mud is rich in various metal oxides, and alkaline glass has a high melting point. These two elements work together to form a high-temperature resistant framework, providing stable high-temperature structural support for the coating. High-manganese steel can withstand the 1000-1150°C heat treatment temperature without collapsing or decomposing. Boric acid and borax play a key role at high temperatures. Due to their relatively low melting points, they melt first at high temperatures, promoting the rapid formation of a glassy phase. This glassy phase fills the pores of the high-temperature resistant framework, tightly bonding to it and forming a continuous, dense, and uniform glassy protective film on the surface of the high-manganese steel. This protective film acts like a sturdy armor, effectively isolating the diffusion of oxygen and carbon atoms, preventing oxidation and decarburization of the high-manganese steel. It also exhibits excellent self-healing properties at high temperatures. When tiny holes or cracks appear in the coating, the molten glass phase quickly flows to fill the defects, maintaining the protective effect.

[0029] (2) Adhesion and reinforcement synergistically improve coating stability

[0030] As a binder, silica sol acts as a "bridge" in the coating. On the one hand, it chemically reacts with active groups on the surface of the high-manganese steel substrate, forming a strong chemical bond. This strengthens the initial adhesion between the coating and the substrate, ensuring that the coating does not easily peel off due to the stress generated by thermal expansion and contraction during the heating and cooling process of the heat treatment. On the other hand, silica sol undergoes a polycondensation reaction at high temperatures, forming a three-dimensional network structure. This interweaves with the high-temperature-resistant skeleton formed by Bayer red mud and alkaline glass, further enhancing the overall strength of the coating. Calcium carbonate, as a reinforcing filler, leverages its high hardness to be evenly dispersed in the coating, acting like gravel in concrete. This enhances the coating's hardness and wear resistance, effectively protecting it from mechanical wear and thermal stress during the heat treatment process, and reducing the occurrence of cracks on the coating surface. Working in synergy with silica sol, it ensures the coating's stability and integrity under harsh heat treatment conditions.

[0031] (3) Synergistic optimization of coating processability by dispersion and rheology

[0032] Bentonite, as a suspending agent, exhibits excellent water absorption, swelling, and dispersibility. During the coating preparation process, it absorbs large amounts of water, forming a high-viscosity colloid that evenly disperses solid particles such as Bayer red mud, alkaline glass, boric acid, borax, and calcium carbonate throughout the system. This prevents these particles from settling and agglomerating during storage and application, ensuring excellent coating uniformity and stability. Bentonite also works in conjunction with silica sol to adjust the coating's rheological properties. The silica sol imparts viscosity to the coating, while the bentonite increases its thixotropy. This ensures excellent fluidity during application, facilitating spray, brush, or immersion application. It also rapidly thickens after application, preventing sagging and ensuring uniform coating thickness. This synergistic optimization of dispersion and rheological properties makes the coating suitable for high-manganese steel castings of various shapes and sizes, and the coating process is simple and efficient.

[0033] Bayer red mud and alkaline glass form a high-temperature-resistant framework, boric acid and borax enhance glass-forming properties, silica sol strengthens the initial adhesion of the coating to the high-manganese steel substrate, and calcium carbonate improves the coating's hardness and wear resistance. Through the synergistic effect of these ingredients, the protective coating of this invention achieves comprehensive improvements in raw material and coating properties, protective effectiveness, and process performance during the heat treatment of high-manganese steel, providing an efficient and reliable protective solution for high-manganese steel heat treatment.

[0034] The beneficial effects of the present invention compared with the prior art include:

[0035] (1) Adapting to the characteristics of high manganese steel and overcoming the problem of high temperature oxidation and decarburization

[0036] During heat treatment of high-manganese steel, problems such as manganese easily oxidizing, component segregation easily causing thermal cracks, and poor thermal conductivity easily causing cracks are prominent. The present invention specifically designs the raw material formula. The high-temperature resistant skeleton formed by Bayer red mud and alkaline glass can withstand the high-temperature environment of 1000-1150°C during the water toughening treatment of high-manganese steel, effectively resisting high-temperature oxidation corrosion. Boric acid and borax enhance the glass phase formation ability, allowing the coating to quickly densify at high temperatures, building a continuous and stable protective barrier on the surface of the high-manganese steel, blocking the diffusion channels of oxygen and carbon atoms, and accurately solving the problems of oxidation, burning, and decarburization of high-manganese steel. This ensures the chemical composition of the high-manganese steel is stable after heat treatment, maintaining its excellent work hardening properties and wear resistance.

[0037] (2) Enhance coating performance and improve heat treatment quality of high manganese steel

[0038] Existing coatings are difficult to meet the protection requirements of high-manganese steel during long-term high-temperature heat treatment. The present invention uses silica sol to enhance the initial adhesion between the coating and the high-manganese steel substrate, ensuring that the coating is always tightly fitted during the heat treatment process, avoiding coating peeling due to thermal expansion and contraction, and making the protective effect continuous and stable. Calcium carbonate improves the hardness and wear resistance of the coating, effectively resists mechanical wear and thermal stress shock during the heat treatment process, reduces the occurrence of surface cracks, ensures the surface finish and integrity of the high-manganese steel, and significantly improves the mechanical properties of the high-manganese steel after heat treatment, and greatly reduces the scrap rate. After the protective coating falls off naturally, there is no mechanical damage or chemical corrosion marks on the surface of the high-manganese steel casting, the surface finish remains in its original state, and no mechanical polishing or chemical solvent stripping treatment is required.

[0039] (3) Simplify the process flow and improve the heat treatment efficiency of high manganese steel

[0040] In order to solve the problems of long heat treatment time and high oxidation burning rate of large high manganese steel ingots, the coating coating process of the present invention is simple and can be applied by spraying, brushing or immersion and other methods, and is suitable for high manganese steel castings of different shapes and sizes. The coating thickness is controlled at 0.5-2 mm, and a pre-coating layer can be formed by natural drying at room temperature for 2-6 hours, without the need for complicated pretreatment and curing processes. More importantly, after the heat treatment is completed, the coating falls off naturally without the need for mechanical grinding or chemical solvent peeling. Compared with traditional processes, the post-processing process is greatly simplified, the post-processing time is shortened by more than 60%, and the production efficiency of high manganese steel heat treatment is significantly improved, and the overall production cost is reduced.

[0041] (4) Innovative raw material application to achieve green and low-carbon heat treatment

[0042] Traditional high manganese steel heat treatment protection methods, such as inert gas protection and vacuum heating, consume extremely high energy, and chemical solvent stripping of the coating will cause environmental pollution. The raw materials of the present invention are industrial waste slag and recycled materials, which are low-cost and widely available; the preparation process is simple and has low energy consumption. During the heat treatment process, the efficient coating protection reduces the number of repeated heating caused by oxidation and burning, and reduces energy consumption. At the same time, the natural shedding characteristics of the coating avoid the use of chemical solvents, reduce wastewater and exhaust gas emissions, achieve green heat treatment of high manganese steel, meet the requirements of sustainable development, and bring significant environmental and economic benefits to high manganese steel production enterprises. DETAILED DESCRIPTION

[0043] 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.

[0044] 1. Design of the embodiment

[0045] Example 1

[0046] Raw material ratio: Bayer red mud 30%, alkaline glass 30%, boric acid 5%, borax 10%, silica sol 10%, bentonite 5%, calcium carbonate 10%

[0047] Preparation process: Bayer red mud (passing a 200-mesh sieve), alkaline glass waste recycling material with a particle size of 3μm, boric acid, borax, calcium carbonate with an average particle size of 3μm, and sodium-treated sodium bentonite with a montmorillonite content of not less than 80% are added in proportion to a mixing vessel and dry-mixed at 100 rpm for 10 minutes. Silica sol is then added, and the stirring speed is increased to 200 rpm. Stirring is continued for 15 minutes to form a uniform paste. The paste viscosity is adjusted to 20 seconds by adding 500ml of water. The coating is evenly applied to the surface of the high-manganese steel casting using a brushing process. The coating thickness is controlled at 0.5mm. The pre-coating layer is naturally dried at room temperature for 2 hours to form a pre-coating layer. The pre-coating layer is then water-toughened at 1080°C, heated at 80°C / h, and held at that temperature for 6 hours.

[0048] Example 2

[0049] Raw material ratio: Bayer red mud 40%, alkaline glass 20%, boric acid 10%, borax 5%, silica sol 15%, bentonite 2%, calcium carbonate 8%

[0050] Preparation process: Same as Example 1, except for the raw material ratio. The paste mixture was adjusted to a viscosity of 20 seconds by adding 500 ml of water. The coating was evenly applied to the surface of the high-manganese steel casting using a brushing process, with a coating thickness of 0.5 mm. The coating was naturally dried at room temperature for 2 hours to form a pre-coating layer. The coating was then water-toughened at 1080°C, heated at 80°C / h, and held at that temperature for 6 hours.

[0051] Example 3

[0052] Raw material ratio: Bayer red mud 35%, alkaline glass 25%, boric acid 9%, borax 7%, silica sol 12%, bentonite 3%, calcium carbonate 9%

[0053] Preparation process: Same as Example 1, except for the raw material ratio. The paste mixture was adjusted to a viscosity of 20 seconds by adding 500 ml of water. The coating was evenly applied to the surface of the high-manganese steel casting using a brushing process, with a coating thickness of 0.5 mm. The coating was naturally dried at room temperature for 2 hours to form a pre-coating layer. The coating was then water-toughened at 1080°C, heated at 80°C / h, and held at that temperature for 6 hours.

[0054] Example 4

[0055] Raw material ratio: Bayer red mud 38%, alkaline glass 22%, boric acid 8%, borax 8%, silica sol 13%, bentonite 4%, calcium carbonate 7%

[0056] Preparation process: Same as Example 1, except for the raw material ratio. The paste mixture was adjusted to a viscosity of 20 seconds by adding 500 ml of water. The coating was evenly applied to the surface of the high-manganese steel casting using a brushing process, with a coating thickness of 0.5 mm. The coating was naturally dried at room temperature for 2 hours to form a pre-coating layer. The coating was then water-toughened at 1080°C, heated at 80°C / h, and held at that temperature for 6 hours.

[0057] The experimental results of each embodiment are shown in Table 1.

[0058] Table 1 Experimental results of various embodiments

[0059]

[0060] 2. Analysis and Summary

[0061] (1) Relationship between raw material ratio and performance

[0062] Oxidation Weight Gain: Example 3 achieved the lowest oxidation weight gain due to its raw material ratio, which resulted in a more continuous and dense glassy protective film formed at high temperatures. Alkaline glass, boric acid, and borax fully reacted at high temperatures, generating a low-melting-point glass phase that filled the coating pores. Bayer red mud provided a stable framework, while silica sol enhanced adhesion, reduced oxygen permeability, and effectively isolated oxygen, minimizing oxidation weight gain. In Example 1, the alkaline glass content was high, but the boric acid and borax ratios were low, resulting in incomplete glass phase formation. This resulted in a less dense coating and a relatively high oxidation weight gain.

[0063] Decarburization Layer Thickness: Example 3 exhibits the thinnest decarburization layer, thanks to a well-balanced raw material ratio. Bentonite improves the adhesion of the coating to the casting surface, reducing gaps. Carbon dioxide produced by the decomposition of calcium carbonate inhibits carbon oxidation to a certain extent. Furthermore, the dense coating formed with this ratio effectively blocks contact between carbon and the external environment, thereby reducing the degree of decarburization. Example 4, due to its lower calcium carbonate content, exhibits a weaker inhibitory effect on carbon oxidation, resulting in a thicker decarburization layer.

[0064] Coating Adhesion: Example 3 achieved the highest grade of 0 on the cross-hatch method, demonstrating excellent adhesion. The synergistic effect of silica sol and sodium bentonite enhanced the coating's adhesion to the high-manganese steel surface. The alkaline glass reacted with the metal surface to form a chemical bond, further enhancing the bonding strength. Due to adjustments in the proportions of some raw materials, the adhesion and chemical reactions of the other examples were slightly inferior, resulting in a grade 1 adhesion.

[0065] High-manganese steel surface hardness: The high-manganese steel in Example 3 had the highest surface hardness. This is because the coating with this ratio achieved more optimal element diffusion during the heat treatment process. The coating's components exchanged appropriately with the high-manganese steel surface, optimizing the surface structure and increasing the hardness.

[0066] In Example 1, due to relatively severe oxidation and decarburization, the surface structure is damaged and the hardness is low.

[0067] (2) Overall Conclusion

[0068] While maintaining the same preparation process, the raw material ratio significantly affects the performance of the protective coating. The raw material ratio of Example 3 performs best in terms of oxidation weight gain, decarburization layer thickness, coating adhesion, and high-manganese steel surface hardness, verifying the feasibility and scientificity of the raw material ratio range in the claims. Subsequent research can focus on this ratio to further refine the raw material ratio and explore the impact of factors such as different raw material purity and particle size on performance. At the same time, the coating process and heat treatment parameters can be optimized based on actual production needs to achieve more efficient and high-quality high-manganese steel casting protection.

[0069] 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.

[0070] 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 red mud heat treatment protective coating, characterized in that: Calculated by mass percentage, the raw materials include: 30-40% of Bayer red mud, 20-30% of alkaline glass, 5-10% of boric acid, 5-10% of borax, 10-15% of silica sol, 2-5% of bentonite, and 5-10% of calcium carbonate.

2. The red mud heat treatment protective coating according to claim 1, characterized in that: The particle size of the Bayer red mud is such that it can pass through a 200-mesh sieve. The alkaline glass is a recycled material obtained by crushing waste glass with a particle size of 2-5 μm. The average particle size of the calcium carbonate is 1-5 μm.

3. The red mud heat treatment protective coating according to claim 1, characterized in that: The bentonite is sodium-based bentonite and has been treated with sodium, with a montmorillonite content of not less than 80%.

4. The red mud heat treatment protective coating according to claim 1, characterized in that: The preparation method is as follows: Bayer process red mud, alkaline glass, boric acid, borax, calcium carbonate and bentonite are added to a stirring container in proportion, and dry mixed at 100-200 rpm for 10-15 minutes; then silica sol is added, the stirring speed is increased to 200-300 rpm, and stirring is continued for 15-20 minutes to form a uniform paste mixture.

5. The red mud heat treatment protective coating according to claim 4, characterized in that: During the stirring process, 500 ml of water or ethanol was added to adjust the viscosity of the paste mixture so that the viscosity of the paste mixture after 4 cups of application was between 20 and 40 seconds.

6. A method for applying the red mud heat treatment protective coating according to claim 1, characterized in that: include: The coating is evenly applied to the surface of the high manganese steel casting by spraying, brushing or dipping, and is naturally dried at room temperature for 2-6 hours to form a pre-coating layer. The dried high manganese steel casting is subjected to water toughening treatment, and the coating falls off naturally after cooling.

7. The method for applying the red mud heat treatment protective coating according to claim 6, characterized in that: During the spraying process, the air pressure of the spray gun is adjusted to 0.3-0.5 MPa; during the brushing process, the coating is ensured to be smooth and free of bubbles; during the immersion process, the casting is completely immersed, and after being taken out, it is allowed to stand and drain off excess paint.

8. The method for applying the red mud heat treatment protective coating according to claim 6, characterized in that: When the dried high manganese steel casting is subjected to water toughening treatment, the temperature is raised to 1000-1150° C. at a rate of 50-100° C. / h and kept at this temperature for 4-8 hours.

9. The method for applying the red mud heat treatment protective coating according to claim 6, characterized in that: The coating thickness is controlled at 0.5-2 mm.

10. A high manganese steel heat treatment process, characterized in that: The high manganese steel casting is treated by the application method described in any one of claims 6 to 9, thereby preventing the high manganese steel casting from oxidation and decarburization during the heat treatment process and simplifying the coating removal process after the heat treatment.

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