Manufacturing process of zero-coating inner container

Abstract

The manufacturing process comprises the following steps that a single-layer iron plate is selected, at least one process of etching, knurling, rolling, carving or stamping is conducted on the inner side surface of the single-layer iron plate, so that a texture surface with random patterns is formed, and the concave depth H of the texture surface is 0.2 mm-0. 5 mm; the processed single-layer iron plate is stretched and formed into the cooking utensil, and it is ensured that the grain surface is located on the inner surface of the formed cooking utensil; carrying out surface polishing and cleaning treatment on the inner surface of the cooking utensil subjected to stretching forming; and nitriding treatment is conducted on the inner surface of the polished and cleaned cooking utensil through nitriding equipment, so that the hardness and the anti-rust capacity of the inner surface of the cooking utensil are improved. The irregular contact area is formed between the rice and the surface of the cooking utensil, so that the contact area between the rice and the surface of the cooking utensil is reduced, the adsorption force between the rice and the surface of the cooking utensil is reduced, and rice grains are easier to fall off from the surface of the cooking utensil.

Description

Technical Field

[0001] The invention relates to the technical field of electrical appliances, and in particular to a manufacturing process of a zero-coating liner. Background Art

[0002] At present, most of the cooking utensils on the market use chemical coatings to achieve non-stick effects. However, chemical coatings may fall off and wear out during use, which not only affects the service life of cooking utensils, but also poses a potential threat to consumers' health. Therefore, the development of a zero-coating liner that does not require chemical coating has become an urgent need in the industry.

[0003] In order to achieve the non-stick effect of zero-coating liner, the existing technology mainly adopts two solutions:

[0004] The first is surface micron-level texture + vapor deposition method: This solution forms micron-level textures on the surface of the inner pot of the cooking utensil, and then uses vapor deposition method to form a hard protective film on the surface. Although this solution can achieve a good non-stick effect, it has the following disadvantages: micron-level textures are difficult to clean, and the vapor deposition method has expensive equipment, complex processes, and low yield, resulting in high costs.

[0005] The second method is direct polishing: This method involves directly polishing the inner surface of the cooking utensil. Although this method is inexpensive, the non-stick effect is poor because the substrate itself does not have non-stick properties. Summary of the invention

[0006] In order to overcome at least one of the defects of the prior art, the present invention provides a process for manufacturing a zero-coating inner pot, which can solve the problems of sticking of cooking utensils and high cost.

[0007] The technical solution adopted by the present invention to solve the problem is:

[0008] A manufacturing process for a zero-coating liner comprises the following steps: selecting a single-layer iron plate as a base material layer of a cooking utensil, and performing at least one of etching, embossing, rolling, carving or stamping on the inner surface of the single-layer iron plate to form a patterned road surface with a random pattern, wherein the depression depth H of the road surface is 0.2 mm to 0.5 mm; stretching the treated single-layer iron plate into a cooking utensil to ensure that the road surface is located on the inner surface of the cooking utensil after forming; performing surface polishing and cleaning on the inner surface of the stretched cooking utensil; and performing nitriding treatment on the inner surface of the cooking utensil after polishing and cleaning using a nitriding device to increase the inner surface hardness and rust resistance of the cooking utensil.

[0009] By adopting the above scheme, the randomly patterned surface makes the rice and the surface of the cooking utensil form an irregular contact area, thereby reducing the contact area between the rice and the surface of the cooking utensil, thereby reducing the adsorption force between the rice and the surface of the cooking utensil, making it easier for rice grains to fall off the surface of the cooking utensil. The surface is treated with nitriding, which not only improves the hardness of the inner pot surface, but also enhances its rust resistance. This makes the inner pot more resistant to wear and corrosion during use, prolongs the service life of the cooking utensil, and has the advantage of low processing cost.

[0010] Furthermore, the area of ​​the textured surface accounts for at least one half of the inner surface area of ​​the cooking utensil.

[0011] By adopting the above solution, the contact between food and the inner surface can be more effectively reduced, thereby improving the non-stick performance.

[0012] Furthermore, the area of ​​the textured road surface accounts for two-thirds of the inner surface area of ​​the cooking utensil.

[0013] By adopting the above solution, the maximum cooking amount of normal rice grains can be met and the non-stick effect can be maintained.

[0014] Furthermore, the area of ​​the textured road surface is consistent with the inner surface area of ​​the cooking utensil.

[0015] By adopting the above solution, it means that the inner surface of the cooking utensil is completely composed of this surface with a specific texture, and the full coverage of the texture helps to improve the heat transfer efficiency, so that the heat is more evenly distributed over the entire inner surface. This helps to ensure that the ingredients are heated evenly during the cooking process, thereby improving the consistency of cooking quality and taste.

[0016] Furthermore, in the textured road surface, the total area of ​​the depressions is not less than one half of the total area of ​​the textured road surface.

[0017] By adopting the above solution, the presence of the depressions reduces the direct contact area between the food and the inner surface of the cooking utensil, thereby reducing the adsorption force of the food. When the total area of ​​the depressions is not less than half of the total area of ​​the textured surface, the non-stick effect is significantly enhanced, making it less likely for the food to stick to the surface of the utensil during cooking. The tiny gaps formed by the depressions help improve the efficiency of heat transfer, so that the heat is more evenly distributed on the surface of the inner pot. This helps to ensure that the food is heated evenly during the cooking process, improving the consistency of cooking quality and taste.

[0018] Furthermore, after the inner surface of the cooking utensil is nitrided, a protective film is provided on the surface of the textured road surface.

[0019] By adopting the above scheme, the nitriding treatment itself can significantly increase the hardness of the inner surface of the cooking utensil, and setting a protective film on this basis can further improve the wear resistance of the surface. This protective film can resist scratches and wear in daily use, thereby extending the service life of the cooking utensil. The presence of the protective film helps to reduce the residue and adhesion of food on the inner surface, making the cleaning process easier. This reduces the time and difficulty of cleaning and improves the ease of use of the cooking utensil.

[0020] Furthermore, the protective film is a silicon dioxide film.

[0021] By adopting the above scheme, the silica film, as an inorganic thin film, is also very hard. Therefore, this combination can greatly enhance the wear resistance of cooking utensils, making them more resistant to scratches and wear in daily use.

[0022] Furthermore, the protective film has a thickness of 3 μm to 8 μm.

[0023] By adopting the above scheme, the silicon dioxide film in this thickness range can provide sufficient protection against scratches and wear in daily use, thereby extending the service life of the cooking utensils.

[0024] Furthermore, the single-layer iron plate is a cold-rolled iron plate or a galvanized iron plate.

[0025] By adopting the above scheme, the cold rolled iron plate is processed by the cold rolling process with high precision and flatness. This makes the inner surface of the cooking utensil smoother, which helps to reduce the adhesion of ingredients and improve the non-stick effect. It also has high strength and toughness, can withstand the high temperature and pressure changes during the cooking process, and ensure the stability and durability of the cooking utensil. The surface of the galvanized iron plate is covered with a layer of zinc, which can isolate air and moisture and prevent the iron plate from rusting. This is especially important for cooking utensils, because the humid environment and moisture in the ingredients can accelerate the corrosion process. It also has good welding properties, which makes it easy to connect and assemble with other parts during the manufacturing process.

[0026] Furthermore, the texture on the bottom of the cooking utensil is consistent with the texture at the transition position of the side wall.

[0027] By adopting the above solution, the entire cooking utensil is more visually unified and coordinated. This design helps to enhance the overall aesthetics of the product and make it more attractive to consumers. The design with consistent patterns also helps to reduce blind spots and difficulty during cleaning. When the patterns on the bottom and side walls are connected to each other, cleaning tools can more easily clean along the patterns, thereby ensuring the hygiene and cleanliness of the cooking utensil.

[0028] In summary, the manufacturing process of a zero-coating liner provided by the present invention has the following technical effects:

[0029] 1. By forming a random pattern on the inner surface of the inner pot, the direct contact area between food such as rice and the inner pot surface can be effectively reduced, thereby reducing the adsorption force, making it easier for food to fall off the inner pot surface after cooking, achieving a good non-stick effect;

[0030] 2. Using nitriding technology to treat the surface of the inner pot can significantly improve the hardness of the inner pot surface and enhance its ability to resist wear. At the same time, the nitriding layer can also effectively improve the rust resistance of the inner pot, preventing the inner pot from being damaged by corrosion during use, thereby extending the overall service life of the cooking utensil;

[0031] 3. Compared with traditional vapor deposition methods, the manufacturing process of the present invention is simpler and has lower costs. The textured road surface is formed by etching, embossing and other processes, and combined with nitriding treatment, without the need for expensive equipment and complicated process steps, which helps to reduce production costs;

[0032] 4. By rationally designing the depth and randomness of the patterns, the non-stick effect can be ensured while ensuring that the surface of the inner pot is easy to clean and hygienic. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the top structure of an embodiment of the present invention;

[0034] Figure 2 It is a schematic diagram of the side structure of an embodiment of the present invention;

[0035] Figure 3 It is a schematic diagram of the three-dimensional structure of an embodiment of the present invention;

[0036] Figure 4 for Figure 1 Enlarged view of area A in the middle;

[0037] Figure 5 for Figure 2 Enlarged view of area B in the middle;

[0038] Figure 6 is a flow chart of an embodiment of the present invention.

[0039] Among them, the meanings of the figure numbers are as follows: 1. cooking utensil; 11. substrate layer; 2. textured road surface; 21. pattern; 22. depression; 3. rice grains. DETAILED DESCRIPTION

[0040] For better understanding and implementation, the technical solutions in the embodiments of the present invention will be clearly and completely described and discussed below in conjunction with the accompanying drawings of the present invention. Obviously, what is described here is only a part of the examples of the present invention, not all the examples. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] In order to facilitate the understanding of the embodiments of the present invention, the following will be further explained by taking specific embodiments as examples in conjunction with the drawings, and each embodiment does not constitute a limitation on the embodiments of the present invention.

[0042] In the description of the present invention, it should be noted that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the present invention.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0044] Embodiment 1 of the present invention refers to Figure 1-Figure 5 As shown, a manufacturing process of a zero-coating liner is disclosed, comprising the following steps:

[0045] S1. Material selection: A single-layer iron plate is selected as the base material layer 11 of the cooking utensil 1, specifically a 1.5 mm cold-rolled iron plate, and the inner surface of the single-layer iron plate is laser etched to form a random pattern 21 on the road surface 2, wherein the random pattern 21 in the road surface 2 is surrounded by depressions 22, and the depressions 22 are interconnected. The depth H of the depressions 22 is 0.3 mm, and the area of ​​the road surface 2 accounts for two-thirds of the inner surface area of ​​the cooking utensil 1, ensuring that when steaming rice, the contact area between the rice and the surface of the cooking utensil 1 is effectively reduced;

[0046] S2 stretching: the treated single-layer iron plate is stretched into a cooking utensil 1, specifically an inner pot for steaming rice, and care should be taken to ensure that the grain road surface 2 is located on the inner surface of the cooking utensil 1 after molding;

[0047] S3. Surface polishing and cleaning: The inner surface of the stretched cooking utensil 1 is polished and cleaned;

[0048] S4. Nitriding treatment: The inner surface of the cooking utensil 1 after polishing and cleaning is subjected to nitriding treatment by using nitriding equipment to increase the hardness and rust resistance of the inner surface of the cooking utensil 1.

[0049] Through the above operation, the random textured surface 2 of the pattern 21 forms an irregular contact area between the rice and the surface of the cooking utensil 1, thereby reducing the contact area between the rice and the surface of the cooking utensil 1, thereby reducing the adsorption force between the rice and the surface of the cooking utensil 1, making it easier for the rice grains 3 to fall off the surface of the cooking utensil 1. The surface is treated with nitriding, which not only improves the hardness of the inner pot surface, but also enhances its rust resistance. This makes the inner pot more resistant to wear and corrosion during use, prolongs the service life of the cooking utensil 1, and has the advantage of low processing cost.

[0050] Embodiment 1 of the present invention refers to Figure 1-Figure 6 As shown, a manufacturing process of a zero-coating liner is disclosed, comprising the following steps:

[0051] S1. Material selection: A single-layer iron plate is selected as the base material layer 11 of the cooking utensil 1, specifically a 1.5 mm cold-rolled iron plate, and the inner surface of the single-layer iron plate is laser etched to form a random pattern 21 on the road surface 2, wherein the random pattern 21 in the road surface 2 is surrounded by depressions 22, and the depressions 22 are interconnected. The depth H of the depressions 22 is 0.3 mm, and the area of ​​the road surface 2 accounts for two-thirds of the inner surface area of ​​the cooking utensil 1, ensuring that when steaming rice, the contact area between the rice and the surface of the cooking utensil 1 is effectively reduced;

[0052] S2 stretching: the treated single-layer iron plate is stretched and formed into a cooking utensil 1, specifically a rice cooker liner for steaming rice, and care should be taken to ensure that the grain road surface 2 is located on the inner surface of the cooking utensil 1 after forming;

[0053] S3. Surface polishing and cleaning: Finely polish the inner surface of the liner to remove surface burrs and impurities, and then perform ultrasonic cleaning to ensure that the surface of the liner is clean and free of dirt;

[0054] S4. Nitriding treatment: Use ion nitriding equipment to nitride the inner surface of the liner to improve surface hardness and anti-rust ability.

[0055] Through the above operation, the random textured surface 2 of the pattern 21 forms an irregular contact area between the rice and the surface of the cooking utensil 1, thereby reducing the contact area between the rice and the surface of the cooking utensil 1, thereby reducing the adsorption force between the rice and the surface of the cooking utensil 1, making it easier for the rice grains 3 to fall off the surface of the cooking utensil 1. The surface is treated with nitriding, which not only improves the hardness of the inner pot surface, but also enhances its rust resistance. This makes the inner pot more resistant to wear and corrosion during use, prolongs the service life of the cooking utensil 1, and has the advantage of low processing cost.

[0056] Embodiment 2 of the present invention refers to Figure 1-Figure 6 As shown, a manufacturing process of a zero-coating liner is disclosed, comprising the following steps:

[0057] S1. Material selection: a single-layer iron plate is selected as the base material layer 11 of the cooking utensil 1, specifically a 1.2 mm galvanized iron plate, and the inner surface of the single-layer iron plate is mechanically embossed to form a pattern 21 with a random texture road surface 2, and the random pattern 21 in the texture road surface 2 is surrounded by depressions 22, and the depressions 22 are interconnected. The depth H of the depressions 22 is 0.4 mm, and the area of ​​the texture road surface 2 occupies the entire inner surface area of ​​the cooking utensil 1, ensuring a comprehensive non-stick effect when steaming rice, ensuring that the texture at the transition position between the bottom of the inner pot and the side wall is consistent, forming a coherent visual effect, and easy to clean;

[0058] S2 stretching: the treated single-layer iron plate is stretched and formed into a cooking utensil 1, specifically a rice cooker liner for steaming rice, and care should be taken to ensure that the grain road surface 2 is located on the inner surface of the cooking utensil 1 after forming;

[0059] S3. Surface polishing and cleaning: Electrolytic polishing is performed on the inner surface of the liner to improve the surface finish, and then high-pressure water gun cleaning is performed to remove surface oil and impurities;

[0060] S4. Nitriding treatment: Use gas nitriding equipment to nitride the inner surface of the liner to improve surface hardness and corrosion resistance.

[0061] Through the above operation, the random textured surface 2 of the pattern 21 forms an irregular contact area between the rice and the surface of the cooking utensil 1, thereby reducing the contact area between the rice and the surface of the cooking utensil 1, thereby reducing the adsorption force between the rice and the surface of the cooking utensil 1, making it easier for the rice grains 3 to fall off the surface of the cooking utensil 1. The surface is treated with nitriding, which not only improves the hardness of the inner pot surface, but also enhances its rust resistance. This makes the inner pot more resistant to wear and corrosion during use, prolongs the service life of the cooking utensil 1, and has the advantage of low processing cost.

[0062] Embodiment 3 of the present invention refers to Figure 1-Figure 6 As shown, a manufacturing process of a zero-coating liner is disclosed, comprising the following steps:

[0063] S1. Material selection: A single-layer iron plate is selected as the base material layer 11 of the cooking utensil 1, specifically a 2.0 mm cold-rolled iron plate, and the inner surface of the single-layer iron plate is rolled to form a random pattern 21 of a textured road surface 2, wherein the random pattern 21 in the textured road surface 2 is surrounded by depressions 22, the depressions 22 are interconnected, and the depth H of the depressions 22 is 0.25 mm. The area of ​​the textured road surface 2 occupies at least one-half of the inner surface area of ​​the cooking utensil 1, so as to meet the basic non-stick requirements;

[0064] S2 stretching: the treated single-layer iron plate is stretched and formed into a cooking utensil 1, specifically a rice cooker liner for steaming rice, and care should be taken to ensure that the grain road surface 2 is located on the inner surface of the cooking utensil 1 after forming;

[0065] S3. Surface polishing and cleaning: Manually polish the inner surface of the liner to remove surface defects, and then perform chemical cleaning to remove surface grease and oxides;

[0066] S4. Nitriding treatment: Use salt bath nitriding equipment to nitride the inner surface of the liner to improve surface hardness and corrosion resistance.

[0067] Through the above operation, the random textured surface 2 of the pattern 21 forms an irregular contact area between the rice and the surface of the cooking utensil 1, thereby reducing the contact area between the rice and the surface of the cooking utensil 1, thereby reducing the adsorption force between the rice and the surface of the cooking utensil 1, making it easier for the rice grains 3 to fall off the surface of the cooking utensil 1. The surface is treated with nitriding, which not only improves the hardness of the inner pot surface, but also enhances its rust resistance. This makes the inner pot more resistant to wear and corrosion during use, prolongs the service life of the cooking utensil 1, and has the advantage of low processing cost.

[0068] It should be noted that in Examples 1-3, the specific material selected is only a preferred implementation. In other embodiments, the specific material and thickness are not limited, and any material that can complete the above steps can be used. The method of designing a textured surface on the inner surface of a single-layer iron plate includes but is not limited to etching, embossing, rolling, engraving or stamping processes, and the processing technology can be multiple. The depth H of the depression 22 next to the pattern 21 of the processed textured surface 2 can be in the range of 0.2mm to 0.5mm. The cooking utensil 1 is not limited to the inner pot of an electric rice cooker, but can also be a wok, a cooking pot, etc. The method of polishing and cleaning the inner surface of the inner pot is not limited to the above three types, and this embodiment does not make specific limitations. Similarly, the method and equipment of nitriding treatment are not specifically limited in this embodiment, and it is sufficient to complete the nitriding treatment.

[0069] In order to further reduce the adsorption force between the food and the cooking utensil 1 during the cooking process, in some embodiments, in the textured road surface 2, the total area of ​​the depressions 22 is not less than half of the total area of ​​the textured road surface 2. The presence of the depressions 22 reduces the direct contact area between the food and the inner surface of the cooking utensil 1, thereby reducing the adsorption force of the food. When the total area of ​​the depressions 22 is not less than half of the total area of ​​the textured road surface 2, the non-stick effect is significantly enhanced, making it less likely for the food to stick to the surface of the utensil during the cooking process. Figure 5As shown, the rice grains 3 cannot enter the depression 22, and the contact area with the substrate is effectively reduced, thereby reducing the adsorption force on the food. The small gap formed by the depression 22 also helps to improve the heat transfer efficiency, so that the heat is more evenly distributed on the surface of the inner pot. This helps to ensure that the food is heated evenly during the cooking process, and improves the consistency of cooking quality and taste.

[0070] Preferably, the texture of the bottom of the cooking utensil 1 is consistent with the texture of the transition position of the side wall, so that the entire cooking utensil 1 is more unified and coordinated visually. This design helps to enhance the overall aesthetics of the product and make it more attractive to consumers. The design of consistent texture also helps to reduce dead angles and difficulty during cleaning. When the texture of the bottom and the side wall are connected to each other, the cleaning tool can be more easily cleaned along the texture, thereby ensuring the hygiene and cleanliness of the cooking utensil 1.

[0071] Embodiment 4 of the present invention adds steps on the basis of any one of Embodiments 1-3, specifically, after the inner surface of the cooking utensil 1 is nitrided, a protective film is provided on the surface of the textured road surface 2, which can further improve the wear resistance of the surface. This protective film can resist scratches and wear in daily use, thereby extending the service life of the cooking utensil 1. The presence of the protective film helps to reduce the residue and adhesion of food on the inner surface, making the cleaning process easier. This reduces the cleaning time and difficulty and improves the ease of use of the cooking utensil 1. Preferably, the protective film is a silicon dioxide film, which, as an inorganic thin film, has a very high hardness. Therefore, this combination can greatly enhance the wear resistance of the cooking utensil 1, making it more resistant to scratches and wear in daily use. It should be noted that in other embodiments, it is not limited to the use of silicon dioxide film, and any protective film that can achieve the above effect is acceptable.

[0072] Preferably, the thickness of the protective film is 3 μm to 8 μm. The silicon dioxide film in this thickness range can provide sufficient protection against scratches and wear in daily use, thereby extending the service life of the cooking utensil 1.

[0073] In summary, the manufacturing process of a zero-coating liner provided by the present invention has the following technical effects:

[0074] 1. By forming a random pattern 21 on the inner surface of the inner pot, the direct contact area between food such as rice and the inner pot surface can be effectively reduced, thereby reducing the adsorption force, making it easier for the food to fall off the inner pot surface after cooking, achieving a good non-stick effect;

[0075] 2. The nitriding process is used to treat the surface of the inner pot, which can significantly improve the hardness of the inner pot surface and enhance its ability to resist wear. At the same time, the nitriding layer can also effectively improve the rust resistance of the inner pot, preventing the inner pot from being damaged by corrosion during use, thereby extending the overall service life of the cooking utensil 1;

[0076] 3. Compared with the traditional vapor deposition method and other processes, the manufacturing process of the present invention is simpler and has lower cost. The textured road surface 2 is formed by etching, embossing and other processes, and combined with nitriding treatment, without the need for expensive equipment and complicated process steps, which helps to reduce production costs;

[0077] 4. By rationally designing the depth and randomness of the patterns, the non-stick effect can be ensured while ensuring that the surface of the inner pot is easy to clean and hygienic.

[0078] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above-mentioned implementation mode, but also include technical schemes composed of any combination of the above-mentioned technical features. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also regarded as the protection scope of the present invention.

Claims

1. A process for manufacturing a zero-coating liner, characterized in that: The steps include: A single-layer iron plate is selected as a base material layer (11) of a cooking utensil (1), and at least one of etching, embossing, rolling, carving or stamping is performed on the inner surface of the single-layer iron plate to form a random pattern (21) of a textured road surface (2), wherein the depth H of the depression (22) of the textured road surface (2) is 0.2 mm to 0.5 mm; stretching the treated single-layer iron plate into a cooking utensil (1), ensuring that the textured surface (2) is located on the inner surface of the cooking utensil (1) after forming; Performing surface polishing and cleaning treatment on the inner surface of the stretch-formed cooking utensil (1); A nitriding device is used to perform nitriding treatment on the inner surface of the cooking utensil (1) after polishing and cleaning, so as to increase the hardness and rust resistance of the inner surface of the cooking utensil (1).

2. The manufacturing process of a zero-coating liner according to claim 1, characterized in that: The area of ​​the textured surface (2) accounts for at least one half of the inner surface area of ​​the cooking utensil (1).

3. The manufacturing process of a zero-coating liner according to claim 1, characterized in that: The area of ​​the textured surface (2) accounts for two thirds of the inner surface area of ​​the cooking utensil (1).

4. The manufacturing process of a zero-coating liner according to claim 2, characterized in that: The area of ​​the textured surface (2) is consistent with the inner surface area of ​​the cooking utensil (1).

5. The manufacturing process of a zero-coating liner according to claim 1, characterized in that: In the textured road surface (2), the total area of ​​the depressions (22) is not less than half of the total area of ​​the textured road surface (2).

6. The manufacturing process of a zero-coating liner according to claim 1, characterized in that: After the inner surface of the cooking utensil (1) is subjected to nitriding treatment, a layer of protective film is provided on the surface of the textured road surface (2).

7. The manufacturing process of a zero-coating liner according to claim 6, characterized in that: The protective film is a silicon dioxide film.

8. The manufacturing process of a zero-coating liner according to claim 6, characterized in that: The thickness of the protective film is 3 μm to 8 μm.

9. The manufacturing process of a zero-coating liner according to claim 1, characterized in that: The single-layer iron plate is a cold-rolled iron plate or a galvanized iron plate.

10. The manufacturing process of a zero-coating liner according to claim 1, characterized in that: The texture on the bottom of the cooking utensil (1) is consistent with the texture at the transition position of the side wall.

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