Carburizing method of steel plate

Abstract

The invention provides a carburizing method of a steel plate, and belongs to the field of metal processing. Comprising the following steps: coating at least partial surface of a steel plate with a carburizing medium; the carburizing medium is a self-adhesive damping high polymer material; and rapidly heating the steel sheet containing the carburizing medium under an inert gas atmosphere to infiltrate carbon into at least part of the surface. During rapid heating, the self-adhesive damping high polymer material can be pyrolyzed and carbonized, part of carbon elements can be released from the high polymer material, and the carbon elements can permeate into the surface layer of the steel plate due to the high activity at high temperature and the catalytic action of the surface of the steel plate. In addition, as the high polymer material is tightly adhered to the surface of the steel plate, a channel for carbon elements to diffuse into the steel plate is provided. And under the condition of rapid heating, the diffusion rate of the carbon element can be increased, so that the carburizing process is promoted. Therefore, the carburizing speed of the steel plate is increased.

Description

Technical Field

[0001] The present application relates to the technical field of metal processing, and in particular to a carburizing method for a steel plate. Background Art

[0002] The carburizing process in China can be traced back to ancient times more than 2,000 years ago, and was initially carried out using solid carburizing media. As time went by, technology continued to advance, and the 20th century witnessed the rise and widespread application of liquid and gas carburizing technologies. The emergence of these technologies has greatly improved the efficiency and quality of carburizing, making the carburizing process occupy an important position in industrial production. In recent years, carburizing technology has made new breakthroughs, including the emergence of new processes such as vacuum carburizing, ion carburizing, and high-concentration carburizing. These new processes not only further improve the accuracy and effect of carburizing, but also broaden the application field of carburizing technology. Unlike the traditional carburizing process, which is carried out in the complete austenite zone, the high-concentration carburizing process is carried out in an uneven austenite state between Ac1 and Accm. This allows the carbon concentration on the surface of the carburized layer to reach 2% to 4%, which is much higher than the 0.85% to 1.05% of the traditional process. The fine particles of carbide in the high-concentration carburized layer are evenly and dispersedly distributed, which significantly improves the wear resistance, corrosion resistance, contact and bending fatigue strength of the workpiece, while maintaining high impact toughness and low brittleness. In addition, the high-concentration carburizing process also has a lower carburizing temperature and a wider process window, so that general steel can be directly quenched after carburizing, which improves production efficiency and product quality. The high-concentration carburizing process has a wide range of applicability, no special requirements for equipment, and has high economic benefits and practical value. It can not only replace expensive high-alloy steel with low-cost carbon steel or alloy steel, but also maintain the toughness of the core material, so that the workpiece can withstand impact loads, which is in line with the direction of energy saving, consumption reduction and sustainable development.

[0003] The core design concept of the carburizing process is "local strengthening", that is, to achieve high surface hardness, high wear resistance, fatigue strength and corrosion resistance by infiltrating elements such as carbon in the places on the surface of the steel that are subject to the most various loads. This local strengthening method avoids the expensive and complicated alloying treatment of the entire material, thereby greatly reducing production costs and energy consumption. However, in the existing carburizing process, the carburized parts need to be placed in a gaseous active medium with a carburizing atmosphere, and in the higher heating temperature range, the diffusion rate of carbon atoms is relatively slow, and it takes a long time to reach the required carburized layer depth, resulting in a long carburizing process, which is time-consuming and energy-consuming. Therefore, it is urgent to develop a method that can speed up the carburizing process. Summary of the invention

[0004] The present application provides a carburizing method for a steel plate to solve the following technical problem: how to increase the carburizing speed of the steel plate.

[0005] The present application provides a method for carburizing a steel plate, the method comprising:

[0006] Applying a carburizing medium to at least a portion of the surface of the steel plate; the carburizing medium is a self-adhesive damping polymer material; and

[0007] The steel plate containing the carburizing medium is rapidly heated under an inert gas atmosphere to allow carbon to penetrate into at least a portion of the surface.

[0008] Optionally, the temperature of the rapid heating is the local melting temperature of the steel plate, and the time of the rapid heating is less than 1 s.

[0009] Optionally, the rapid heating method includes: welding short-circuit heating.

[0010] Optionally, the current of the welding short-circuit heating is 20KA~25KA.

[0011] Optionally, the welding short-circuit heating device includes: an electric welder and an auxiliary clamping tool.

[0012] Optionally, the self-adhesive damping polymer material includes one or more of butyl rubber, nitrile rubber, polyurethane, polyacrylate and epoxy resin.

[0013] Optionally, the coating thickness of the carburizing medium is ≤40 μm.

[0014] Optionally, after applying the carburizing medium to at least a portion of the surface of the steel plate, the method further comprises:

[0015] The steel plate is covered on the other side of the carburizing medium.

[0016] Optionally, in said allowing carbon to penetrate into at least a portion of said surface, said method further comprises:

[0017] The carburized steel sheet is cooled to room temperature in the inert gas atmosphere.

[0018] Optionally, the steel plate after carburizing satisfies at least one of the following properties: carburizing concentration is 0.2% to 0.7%, and carburizing depth is ≤80 μm.

[0019] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0020] The present application provides a carburizing method for a steel plate, comprising: applying a carburizing medium to at least a portion of the surface of the steel plate; the carburizing medium is a self-adhesive damping polymer material; and rapidly heating the steel plate containing the carburizing medium under an inert gas atmosphere so that carbon penetrates into at least a portion of the surface. First, the self-adhesive damping polymer material can adhere tightly to the surface of the steel plate to form a uniform coating. Secondly, during rapid heating, the self-adhesive damping polymer material undergoes pyrolysis and carbonization, and some carbon elements are released from the polymer material, and due to the high activity at high temperature and the catalytic effect of the steel plate surface, these carbon elements penetrate into the surface layer of the steel plate. In addition, since the polymer material adheres tightly to the surface of the steel plate, it provides a channel for the carbon element to diffuse into the interior of the steel plate. Under the condition of rapid heating, the diffusion rate of the carbon element will increase, thereby promoting the progress of the carburizing process. Thereby, the carburizing speed of the steel plate is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0023] Figure 1 A schematic diagram of a process for carburizing a steel plate provided in an embodiment of the present application;

[0024] Figure 2 A metallographic structure diagram of a cross section of a steel plate after infiltration provided in Example 1 of the present application;

[0025] Figure 3 A metallographic structure diagram of a cross section of a steel plate after infiltration provided in Example 2 of the present application;

[0026] Figure 4 This is a metallographic structure diagram of the cross section of the steel plate after infiltration provided in Example 3 of the present application. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0028] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0029] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "the following at least one item (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc or abc, where a, b, c can be single or plural, respectively.

[0030] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0031] Figure 1 A schematic flow chart of a carburizing method for a steel plate provided in an embodiment of the present application.

[0032] See also Figure 1 The present application provides a method for carburizing a steel plate, the method comprising:

[0033] S1, applying a carburizing medium to at least a portion of the surface of the steel plate; the carburizing medium is a self-adhesive damping polymer material; and

[0034] It should be noted that the self-adhesive damping polymer material has the following properties: Self-adhesiveness: This material can be directly adhered to the metal surface without the need for additional adhesives or complex processing technology, and the construction is convenient and quick. Damping performance: It has good damping performance, can effectively absorb and dissipate vibration energy, and reduce mechanical vibration and noise. Weather resistance: It has good weather resistance and can maintain stable performance under various environmental conditions. Corrosion resistance: Some materials also have corrosion resistance and can be used in humid and corrosive environments.

[0035] In some embodiments, the self-adhesive damping polymer material includes one or more of butyl rubber, nitrile rubber, polyurethane, polyacrylate and epoxy resin.

[0036] It should be noted that polyacrylate is a homopolymer or copolymer with acrylic acid ester as a monomer. The models of polyacrylate in the embodiments of the present application include but are not limited to the following: polyacrylate 563T (CAS No. 57828-93-0), water-soluble polyacrylate polymer (Carbospers K-702 of Lubrizol Germany Lubrizol), epoxy polyacrylate, fluorinated polyacrylate (Hydropalat WE 3500 and Hydropalat WE 3370 produced by BASF), Evonik TEGOMER HC 5002 (polyacrylate with hydroxyl functional group), Smart HMPE 9663 polyacrylate, etc.

[0037] In some embodiments, the coating thickness of the carburizing medium is ≤ 40 μm.

[0038] The coating thickness of the polymer material can be adjusted according to the concentration and depth requirements of carburizing. A thicker coating thickness can provide more carbon sources, thereby increasing the depth of carburizing; while a thinner coating thickness can achieve a shallower carburizing layer or a more uniform carburizing effect. At the same time, the polymer material can be evenly applied to the surface of the steel plate by brushing, spraying, roller coating or automated coating machine. Before coating, it is necessary to ensure that the surface of the steel plate is clean, free of oil and rust. Exemplarily, the coating thickness of the carburizing medium can be 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, etc.

[0039] In some embodiments, after applying the carburizing medium to at least a portion of the surface of the steel plate, the method further includes: covering the steel plate on another side of the carburizing medium.

[0040] It should be noted that the steel plate can be the same piece or two different pieces.

[0041] In the embodiment of the present application, the steel plate is covered on the other side of the carburizing medium to form a closed space, so that the carburizing medium can fully contact and react with the steel surface during heating. The closed space helps to reduce the heat loss during carburizing, improves the activity and concentration of the carburizing medium, and thus accelerates the diffusion and infiltration process of carbon atoms. Therefore, it is very advantageous to form a closed space for carburizing process. It can not only improve the carburizing efficiency and effect, but also reduce the consumption and environmental pollution of the carburizing medium. At the same time, when the carburizing medium is exposed to an inert medium, heating can cause a part of the carbon to diffuse into the inert gas, but because the polymer material is closely adhered to the surface of the steel plate, there is still a part of the carbon element to diffuse into the steel plate, so the structure of the two steel plates sandwiching the carburizing medium is not formed, and the purpose of the present application can still be achieved.

[0042] S2. In an inert gas atmosphere, rapidly heating the steel plate containing the carburizing medium to allow carbon to penetrate into at least a portion of the surface.

[0043] Specifically, the inert gas atmosphere is formed by adding a sealed protective cover to the local carburizing area, and a protective inert atmosphere is injected into the protective cover to prevent the carburizing area from being oxidized.

[0044] In the embodiment of the present application, under the protection of inert atmosphere, carburizing medium (such as activated carbon atom gas) can be carried out carburizing reaction in the local area predetermined on the steel surface by controlling conditions such as temperature and pressure. Due to the presence of inert atmosphere, carburizing process can be more stable and controllable, while reducing the risk of oxidation of the steel surface. In addition, the combination of sealing protective cover and inert atmosphere also helps to improve carburizing efficiency. In a closed space, carburizing medium can act more intensively on the steel surface, reducing the waste caused by gas diffusion. Meanwhile, the stability and uniformity of inert atmosphere also help to maintain the consistency of carburizing process, thereby improving the quality and performance of carburized layer.

[0045] In some embodiments, the inert gas includes helium or argon.

[0046] In some embodiments, the rapid heating temperature is the local melting temperature of the steel plate, and the rapid heating time is less than 1 s.

[0047] In some embodiments, the rapid heating method includes: welding short-circuit heating.

[0048] In some embodiments, the current of the welding short-circuit heating is 20KA-25KA.

[0049] In some embodiments, the welding short-circuit heating device includes: an electric welder and an auxiliary clamping tool.

[0050] The present application can use a welding device similar to an electric welder and apply its short-circuit heating method to locally heat the metal, which is an efficient and controllable metal processing method. This method mainly uses the high temperature energy generated when the arc is short-circuited to quickly melt the metal surface locally, thereby achieving the purpose of surface carburization modification.

[0051] In some embodiments, in the step of allowing carbon to penetrate into at least a portion of the surface, the method further comprises: cooling the carburized steel plate to room temperature under the inert gas atmosphere.

[0052] In some embodiments, the steel plate after carburization satisfies at least one of the following properties: carburization concentration is 0.2% to 0.7%, and carburization depth is ≤80 μm.

[0053] It should be noted that carburizing concentration refers to the mass percentage of carbon in the surface layer of steel parts. Carburizing depth refers to the depth of carbon penetration into the surface of steel parts.

[0054] It can be seen that carburizing is a process of infiltrating carbon into the metal surface to increase its hardness and wear resistance. In the traditional carburizing process, carbon-containing gas (such as carbon monoxide) is usually used to react with the metal surface at high temperature to infiltrate carbon atoms into the metal lattice. However, the present application creatively uses a new type of carburizing medium-a self-adhesive damping polymer material that can adhere to the metal surface. This polymer material can adhere tightly to the surface of the steel plate to form a uniform coating. When the steel plate is heated rapidly, the polymer material in this coating will undergo a series of complex physical and chemical changes. Among them, the most critical is the pyrolysis and carbonization process of the polymer material. As the temperature rises, the polymer material begins to pyrolyze, that is, its molecular chain begins to break, producing small molecular gases and solid residues. In this process, some carbon elements will be released from the polymer material, and due to the high activity at high temperature and the catalytic effect of the steel plate surface, these carbon elements will penetrate into the surface layer of the steel plate. In addition, since the polymer material is tightly adhered to the surface of the steel plate, it provides a channel for the carbon element to diffuse into the interior of the steel plate. Under rapid heating conditions, the diffusion rate of carbon increases, thereby promoting the carburizing process.

[0055] In summary, when the self-adhesive damping polymer material that can be adhered to the metal surface is applied to the steel plate and quickly heated, the principle of carburization is mainly based on the pyrolysis and carbonization process of the polymer material, and the diffusion of carbon elements to the surface of the steel plate at high temperature. This new carburizing process has the advantages of simple operation and uniform carburizing, and is expected to be widely used in the field of metal processing in the future.

[0056] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0057] Example 1

[0058] This embodiment provides a method for carburizing a steel plate, comprising the following steps:

[0059] The polyacrylate is applied and adhered to the surface of the steel plate in the area to be carburized, and the polyacrylate on the surface of the area not to be carburized is removed; wherein the coating thickness of the polyacrylate is 20 μm;

[0060] Cover the other side of the polyacrylate with another steel plate to form a structure in which two steel plates sandwich the polyacrylate;

[0061] Use a clamping tool to place the carburized area of ​​the steel plate horizontally upward, center the carburized area and align it with the heating position of the heating equipment, add a sealed protective cover to the carburized area, and pass argon gas into the protective cover for protection. Use welding short-circuit heating to generate high temperature through the short-circuit heat of the arc to melt the carburized area locally, so that carbon can penetrate into the interior of the steel plate. The welding short-circuit heating time is 0.5s, and the welding short-circuit heating current is 20KA;

[0062] The carburized steel sheet was cooled to room temperature in an argon atmosphere. The carburized concentration of the steel sheet after infiltration was 0.5% and the carburized depth was 40 μm.

[0063] Example 2

[0064] This embodiment provides a method for carburizing a steel plate, comprising the following steps:

[0065] The polyacrylate is applied and adhered to the surface of the steel plate in the area to be carburized, and the polyacrylate on the surface of the area not to be carburized is removed; wherein the coating thickness of the polyacrylate is 10 μm;

[0066] Cover the other side of the polyacrylate with another steel plate to form a structure in which two steel plates sandwich the polyacrylate;

[0067] Use a clamping tool to place the carburized area of ​​the steel plate horizontally upward, center the carburized area and align it with the heating position of the heating equipment, add a sealed protective cover to the carburized area, and pass argon gas into the protective cover for protection. Use welding short-circuit heating to generate high temperature through the short-circuit heat of the arc to melt the carburized area locally, so that carbon can penetrate into the interior of the steel plate. The welding short-circuit heating time is 0.43s, and the welding short-circuit heating current is 20KA;

[0068] The carburized steel sheet was cooled to room temperature in an argon atmosphere. The carburized concentration of the steel sheet after infiltration was 0.3% and the carburized depth was 20 μm.

[0069] Example 3

[0070] This embodiment provides a method for carburizing a steel plate, comprising the following steps:

[0071] The polyacrylate is applied and adhered to the surface of the steel plate in the area to be carburized, and the polyacrylate on the surface of the area not to be carburized is removed; wherein the coating thickness of the polyacrylate is 20 μm;

[0072] Cover the other side of the polyacrylate with another steel plate to form a structure in which two steel plates sandwich the polyacrylate;

[0073] Use a clamping tool to place the carburized area of ​​the steel plate horizontally upward, center the carburized area and align it with the heating position of the heating equipment, add a sealed protective cover to the carburized area, and pass argon gas into the protective cover for protection. Use welding short-circuit heating to generate high temperature through the short-circuit heat of the arc to melt the carburized area locally, so that carbon can penetrate into the interior of the steel plate. The welding short-circuit heating time is 0.44s, and the welding short-circuit heating current is 20KA;

[0074] The carburized steel sheet was cooled to room temperature in an argon atmosphere. The carburized concentration of the steel sheet after infiltration was 0.4% and the carburized depth was 10 μm.

[0075] Example 4

[0076] This embodiment provides a method for carburizing a steel plate, comprising the following steps:

[0077] The polyacrylate is applied and adhered to the surface of the steel plate in the area to be carburized, and the polyacrylate on the surface of the area not to be carburized is removed; wherein the coating thickness of the polyacrylate is 20 μm;

[0078] Use a clamping tool to place the carburized area of ​​the steel plate horizontally upward, center the carburized area and align it with the heating position of the heating equipment, add a sealed protective cover to the carburized area, and pass argon gas into the protective cover for protection. Use welding short-circuit heating to generate high temperature through the short-circuit heat of the arc to melt the carburized area locally, so that carbon can penetrate into the interior of the steel plate. The welding short-circuit heating time is 0.44s, and the welding short-circuit heating current is 20KA;

[0079] The carburized steel sheet was cooled to room temperature in an argon atmosphere. The carburized concentration of the steel sheet after infiltration was 0.2% and the carburized depth was 5 μm.

[0080] Figure 2 to Figure 4 Detailed explanation:

[0081] Figure 2 A metallographic structure diagram of a cross section of a steel plate after infiltration provided in Example 1 of the present application; Figure 3 A metallographic structure diagram of a cross section of a steel plate after infiltration provided in Example 2 of the present application; Figure 4 This is a metallographic structure diagram of the cross section of the steel plate after infiltration provided in Example 3 of the present application. Figure 2 to Figure 4 In the figure, the middle dotted line is the contact surface of the two steel plates, and the contact surface is carburized. The darker area in the middle is the high carbon structure after carburization, and the white area is the matrix (ferrite) of the low carbon steel plate. Figure 2 It can be seen that the carburizing depth of a steel plate is about 40μm. Figure 3 It can be seen that the carburizing depth of a steel plate is about 20μm. Figure 4 It can be seen that the carburizing depth of a steel plate is about 10 μm.

[0082] In addition, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0083] (1) In the embodiment of the present invention, an innovative carburizing method is used to avoid the need for a heating and holding furnace that must be used in the traditional method, which not only greatly saves the space occupied by the equipment, but also significantly reduces energy consumption.

[0084] (2) In the embodiments of the present invention, the conventional carburizing process often requires heating and carburizing the entire workpiece, which easily causes the workpiece to deform due to thermal stress. However, the present invention can achieve local carburizing, that is, only the specific area where the performance needs to be improved is carburized, thereby avoiding the problem of overall heating and deformation of the workpiece. This is particularly important for workpieces that need to maintain high precision and high shape stability.

[0085] (3) In the embodiments of the present invention, the conventional gas carburizing and ion carburizing methods require a long heating and heat preservation process, which takes at least several hours or even longer. However, the present invention achieves rapid carburizing by optimizing the carburizing medium and carburizing process, and the entire process can be completed within a few minutes or even seconds. This not only greatly improves production efficiency, but also shortens the production cycle.

[0086] (4) In the embodiments of the present invention, the carburizing medium used has a unique formula, which not only uses a small amount but also has a relatively low cost. This is because these carburizing media are mostly common adhesive materials, which are easy to obtain and affordable. In addition, due to the small amount used, waste emissions and environmental pollution problems in the production process can be further reduced.

[0087] (5) In the embodiments of the present invention, in the conventional carburizing process, due to the diffusivity of the carburizing medium and the complexity of the workpiece, carburization easily occurs in places where carburization is not required. This not only wastes the carburizing medium, but also may cause the workpiece performance to not meet the requirements. However, the present invention ensures that carburization reaction only occurs in places where carburization is required, through precise local carburizing technology and precise control of the carburizing medium, thereby greatly improving the accuracy and reliability of carburization.

[0088] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for carburizing a steel plate, characterized in that: The method comprises: Applying a carburizing medium to at least a portion of the surface of the steel plate; the carburizing medium is a self-adhesive damping polymer material; and The steel plate containing the carburizing medium is rapidly heated under an inert gas atmosphere to allow carbon to penetrate into at least a portion of the surface.

2. The method according to claim 1, characterized in that: The temperature of the rapid heating is the local melting temperature of the steel plate, and the time of the rapid heating is less than 1 s.

3. The method according to claim 2, characterized in that The rapid heating method includes: welding short-circuit heating.

4. The method according to claim 3, characterized in that The current of the welding short-circuit heating is 20KA-25KA.

5. The method according to claim 4, characterized in that The welding short-circuit heating device comprises: an electric welder and an auxiliary clamping tool.

6. The method according to claim 1, characterized in that The self-adhesive damping polymer material includes one or more of butyl rubber, nitrile rubber, polyurethane, polyacrylate and epoxy resin.

7. The method according to claim 1, characterized in that The coating thickness of the carburizing medium is ≤40 μm.

8. The method according to claim 1, characterized in that After applying the carburizing medium to at least a portion of the surface of the steel plate, the method further comprises: The steel plate is covered on the other side of the carburizing medium.

9. The method according to claim 1, characterized in that: In said infiltrating carbon into at least a portion of said surface, said method further comprises: The carburized steel sheet is cooled to room temperature in the inert gas atmosphere.

10. The method according to claim 1, characterized in that The carburized steel plate meets at least one of the following properties: carburizing concentration is 0.2% to 0.7%, and carburizing depth is ≤80 μm.

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