Non-alloy steel forge piece surface heat treatment process method

Abstract

The invention discloses a surface heat treatment process method for a non-alloy steel forge piece. The surface heat treatment process method comprises the following steps that S1, the surface of the non-alloy steel forge piece is cleaned; s2, the cleaned non-alloy steel forge piece is preheated; s3, the non-alloy steel forge piece is heated; s4, keeping the temperature for a period of time at the heating temperature to ensure that the temperature of the whole workpiece is uniform; s5, when the surface of the non-alloy steel forge piece reaches the preset quenching temperature; s6, the quenched non-alloy steel forgings usually need to be subjected to tempering treatment; s7, performing chemical heat treatment on the non-alloy steel forge piece; and S8, the forged piece subjected to heat treatment is subjected to cleaning, straightening and destressing treatment. The hardness of the surface of the workpiece can be remarkably improved through surface heat treatment of the forge piece, so that the wear resistance is improved, favorable internal stress distribution can be introduced after surface heat treatment, the residual compressive stress can effectively resist generation and extension of fatigue cracks, and the service life of the workpiece is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of non-alloy steel forging processing, in particular to a non-alloy steel forging surface heat treatment process method. Background Art

[0002] Non-alloy steel forgings are a very important product in the field of metal processing, with a variety of characteristics and applications. Non-alloy steel forgings are metal parts made by forging processes, with excellent mechanical and physical properties. They are widely used in industries such as automobiles, aviation, ships, and machinery manufacturing. According to the temperature during processing, forgings can be divided into cold forging, warm forging, and hot forging. Hot forging is carried out at a temperature higher than the recrystallization temperature of the metal, while cold forging is carried out at room temperature. Forgings can be divided into different types according to the complexity of the geometric structure, such as forgings with vertical or horizontal main axis, and forgings with tortuous main axis. Forging processes include free forging, die forging, etc. Free forging uses universal tools to apply external force to the blank, while die forging is carried out in a forging die of a specific shape. The chemical composition and mechanical properties of non-alloy steel forgings depend on their specific material grade. For example, 15Cr2Ni2 steel has different mechanical properties such as tensile strength, yield strength, and elongation after carburizing, quenching, and tempering. The production of non-alloy steel forgings is a complex process involving multiple steps such as material selection, heating, forging, heat treatment and quality inspection. Through these processes, it can be ensured that the forgings meet the required performance and quality standards.

[0003] At present, when non-alloy steel forgings are produced and processed, the internal structure performance of the forged products after forming is poor, they do not have strong hardness and wear resistance, and their service life is short. Therefore, it is necessary to develop a surface heat treatment process method for non-alloy steel forgings to solve the above-mentioned technical problems. Summary of the invention

[0004] The purpose of the present invention is to provide a surface heat treatment process method for non-alloy steel forgings to solve the problems raised in the above background technology that during the current production and processing of non-alloy steel forgings, the internal structure performance of the forging products after forming is poor, they do not have strong hardness and wear resistance, and their service life is short.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a surface heat treatment process for non-alloy steel forgings, comprising the following method steps: S1, cleaning the surface of the non-alloy steel forgings, cleaning the oil, rust and oxide layer on the surface of the non-alloy steel forgings, and avoiding interference with subsequent heat treatment operations; S2, preheating the cleaned non-alloy steel forgings to reduce the internal stress caused by excessive temperature difference; S3, heating the non-alloy steel forgings, the heating temperature must be higher than the critical temperature of the material to form the required austenite structure, keep the heating uniform, and avoid local overheating; S4, keep warm for a period of time at the heating temperature to ensure that the temperature of the entire workpiece is uniform , the internal structure is fully transformed to obtain a uniform austenite structure; S5. When the surface of the non-alloy steel forging reaches the predetermined quenching temperature, it is rapidly cooled to form a martensite structure, thereby increasing the surface hardness; S6. After quenching, the non-alloy steel forgings usually need to be tempered to reduce quenching stress and improve the toughness and stability of the material; S7. The non-alloy steel forgings are subjected to chemical heat treatment to further improve the surface properties of the non-alloy steel forgings; S8. The forgings after heat treatment are cleaned, straightened, and stress relieved to eliminate defects generated during the heat treatment process, and the metallographic structure, dimensional tolerance and mechanical properties of the forgings after heat treatment are checked to see if they meet the requirements.

[0006] Preferably, the preheating temperature in step S2 can be determined according to the composition of the steel and the size of the forging, and the preheating temperature is controlled between 180°C and 250°C.

[0007] Preferably, the heating method in step S3 adopts conventional furnace heating, or surface rapid heating technology, including induction heating or flame heating, and the heating temperature is controlled at 40°C to 60°C above Ac3 (austenite transformation end temperature).

[0008] Preferably, the insulation time in step S4 is controlled to be 1-2 hours.

[0009] Preferably, the cooling medium for quenching in step S5 may be water, oil or other special quenching liquid.

[0010] Preferably, in step S6, the tempering temperature is controlled at a temperature lower than Ac1 (austenite transformation start temperature), and is kept warm and then cooled to room temperature.

[0011] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention can significantly improve the hardness of the workpiece surface by heat treating the forging surface, thereby improving the wear resistance. After the surface heat treatment, a favorable internal stress distribution can be introduced. This residual compressive stress can effectively resist the initiation and expansion of fatigue cracks, thereby improving the service life of the workpiece; (2) The above-mentioned surface heat treatment process can improve the yield strength and tensile strength of the surface, so that the workpiece can withstand a larger load. Through surface heat treatment, the performance of the workpiece surface can be improved without changing the core structure and performance of the workpiece. This not only saves costs but also meets the use requirements. The surface heat treatment process can reduce the dimensional change of the workpiece and improve the dimensional stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a flowchart of the process steps of the present invention. DETAILED DESCRIPTION

[0013] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0014] See also Figure 1 , an embodiment of the present invention: a non-alloy steel forging surface heat treatment process method, comprising the following method steps: S1, cleaning the surface of the non-alloy steel forging, cleaning the oil, rust and oxide layer on the surface of the non-alloy steel forging, avoiding interference with subsequent heat treatment operations; S2, preheating the cleaned non-alloy steel forging to reduce the internal stress caused by excessive temperature difference; S3, heating the non-alloy steel forging, the heating temperature should be higher than the critical temperature of the material to form the required austenite structure, keep the heating uniform, and avoid local overheating; S4, keep warm for a period of time at the heating temperature to ensure that the temperature of the entire workpiece is uniform, and the internal The organizational structure is fully transformed to obtain a uniform austenite structure; S5. When the surface of the non-alloy steel forging reaches the predetermined quenching temperature, it is rapidly cooled to form a martensite structure, thereby increasing the surface hardness; S6. After quenching, the non-alloy steel forging usually needs to be tempered to reduce the quenching stress and improve the toughness and stability of the material; S7. The non-alloy steel forging is subjected to chemical heat treatment to further improve the surface properties of the non-alloy steel forging; S8. The forgings after heat treatment are cleaned, straightened, and stress relieved to eliminate defects generated during the heat treatment process, and the metallographic structure, dimensional tolerance and mechanical properties of the forgings after heat treatment are checked to see if they meet the requirements.

[0015] Furthermore, the preheating temperature in step S2 can be determined according to the composition of the steel and the size of the forging, and the preheating temperature is controlled between 180°C and 250°C.

[0016] Furthermore, the heating method in step S3 adopts conventional furnace heating, or surface rapid heating technology, including induction heating or flame heating, and the heating temperature is controlled at 40°C to 60°C above Ac3 (austenite transformation end temperature).

[0017] Furthermore, the insulation time in step S4 is controlled to be 1-2 hours.

[0018] Furthermore, the cooling medium for quenching in step S5 may be water, oil or other special quenching liquid.

[0019] Furthermore, in step S6, the tempering temperature is controlled to be lower than Ac1 (austenite transformation start temperature), and the steel is kept at this temperature and then cooled to room temperature. Example

[0020] Preheat the cleaned non-alloy steel forgings to reduce the internal stress caused by the large temperature difference. Control the preheating temperature at 180°C, heat the non-alloy steel forgings, control the heating temperature at 40°C above Ac3, and keep it at the heating temperature for 1 hour.

[0021] Comparative Example 1 Preheat the cleaned non-alloy steel forgings to reduce the internal stress caused by excessive temperature difference. Control the preheating temperature at 200°C, heat the non-alloy steel forgings, control the heating temperature at 40°C above Ac3, and keep it at the heating temperature for 1 hour.

[0022] Comparative Example 2 Preheat the cleaned non-alloy steel forgings to reduce the internal stress caused by the large temperature difference. Control the preheating temperature at 220°C, heat the non-alloy steel forgings, control the heating temperature at 40°C above Ac3, and keep it at the heating temperature for 1 hour.

[0023] Comparative Example 3 Preheat the cleaned non-alloy steel forgings to reduce the internal stress caused by excessive temperature difference. Control the preheating temperature at 180°C, heat the non-alloy steel forgings, control the heating temperature at 50°C above Ac3, and keep it at the heating temperature for 1 hour.

[0024] Comparative Example 4 Preheat the cleaned non-alloy steel forgings to reduce the internal stress caused by the large temperature difference. Control the preheating temperature at 180°C, heat the non-alloy steel forgings, control the heating temperature at 60°C above Ac3, and keep it at the heating temperature for 1 hour.

[0025] By comparing Example 1 with Comparative Examples 1 and 2, it is found that when the preheating temperature is controlled between 180°C and 250°C, as the preheating temperature gradually increases, the structural hardness of the non-alloy steel forgings is measured to be increasingly greater.

[0026] By comparing Example 1 with Comparative Examples 3 and 4, it is found that when the heating temperature is controlled at 40°C to 60°C above Ac3 (austenite transformation end temperature), as the heating temperature gradually increases, the wear resistance of the non-alloy steel forgings is measured to be increasingly stronger.

[0027] It should be noted that, 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. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0028] The standard parts used in this application document can all be purchased from the market, and the specific connection methods of each part are connected by conventional means such as mature bolts, rivets, welding, etc. in the prior art. In addition, the machinery, parts and equipment all adopt conventional models in the prior art, and the circuit connection adopts the conventional connection method in the prior art, so no specific description is given here.

[0029] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A non-alloy steel forging surface heat treatment process, characterized in that: The method comprises the following steps: S1. Clean the surface of non-alloy steel forgings to remove oil, rust and oxide layer on the surface of non-alloy steel forgings to avoid interference with subsequent heat treatment operations; S2. Preheat the cleaned non-alloy steel forgings to reduce the internal stress caused by excessive temperature difference; S3. Heat the non-alloy steel forgings at a temperature higher than the critical temperature of the material to form the required austenite structure, maintain uniform heating, and avoid local overheating; S4. Keep the temperature at the heating temperature for a period of time to ensure that the temperature of the entire workpiece is uniform, the internal structure is fully transformed, and a uniform austenite structure is obtained; S5. When the surface of the non-alloy steel forging reaches the predetermined quenching temperature, it is rapidly cooled to form a martensitic structure, thereby increasing the surface hardness; S6. After quenching, non-alloy steel forgings usually need to be tempered to reduce quenching stress and improve the toughness and stability of the material; S7, performing chemical heat treatment on the non-alloy steel forging to further improve the surface properties of the non-alloy steel forging; S8. Clean, straighten and stress relieve the forgings after heat treatment to eliminate defects generated during the heat treatment process, and check whether the metallographic structure, dimensional tolerance and mechanical properties of the forgings after heat treatment meet the requirements.

2. The method for surface heat treatment of non-alloy steel forgings according to claim 1, characterized in that: The preheating temperature in step S2 can be determined according to the composition of the steel and the size of the forging, and the preheating temperature is controlled between 180°C and 250°C.

3. The method for surface heat treatment of non-alloy steel forgings according to claim 1, characterized in that: The heating method in step S3 adopts conventional furnace heating, or surface rapid heating technology, including induction heating or flame heating, and the heating temperature is controlled at 40°C to 60°C above Ac3 (austenite transformation end temperature).

4. The method for surface heat treatment of non-alloy steel forgings according to claim 1, characterized in that: The insulation time in step S4 is controlled to be 1-2 hours.

5. The method for surface heat treatment of non-alloy steel forgings according to claim 1, characterized in that: The cooling medium for quenching in step S5 may be water, oil or other special quenching liquid.

6. The method for surface heat treatment of non-alloy steel forgings according to claim 1, characterized in that: In the step S6, the tempering temperature is controlled to be lower than Ac1 (austenite transformation start temperature), and the temperature is kept and then cooled to room temperature.

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