Vacuum carburizing method for swash plate of hydraulic pump

Abstract

The invention discloses a vacuum carburizing method for a swash plate of a hydraulic pump, and relates to the technical field of carburizing heat treatment. The method comprises the following steps: cleaning and drying the hydraulic pump swash plate to be treated; the cleaned and dried hydraulic pump swash plate is loaded into a carburizing furnace, vacuumized, heated to a first preset temperature and subjected to heat preservation, then heated to a target temperature and subjected to heat preservation, and the heated hydraulic pump swash plate is obtained; carburizing gas and diffusion gas are alternately and circularly introduced into the carburizing furnace in a pulse mode, and carburizing treatment is conducted on the heated hydraulic pump swash plate; and the carburized hydraulic pump swash plate is cooled to a second preset temperature along with the carburizing furnace, heat preservation is conducted, then quenching, cleaning and tempering are conducted, and the target hydraulic pump swash plate is obtained. According to the method, accurate and controllable surface recarburization can be achieved, the carburization efficiency is high, the process treatment time is short, and the method is clean and environmentally friendly, and the treated product has high hardness, a uniform hardened layer and an excellent metallographic structure and has high application value.

Description

Technical Field

[0001] This invention belongs to the field of carburizing heat treatment technology, specifically relating to a vacuum carburizing method for a hydraulic pump swashplate. Background Technology

[0002] The swashplate is one of the core components of a swashplate axial piston pump. During operation, it is subjected to high-frequency alternating contact stress and wear, thus requiring extremely high surface hardness, wear resistance, and fatigue strength. Simultaneously, the core must maintain sufficient strength and toughness to withstand complex loads. For this purpose, the swashplate is typically forged from low-carbon alloy steel (such as 20CrMnMo) and surface hardened through carburizing and quenching heat treatment.

[0003] With the continuous improvement of hydraulic pumps, higher requirements are placed on the precision and reliability of their core component, the swashplate. Currently, hydraulic pump swashplates face two major problems: First, traditional vacuum carburizing furnaces are used for valve stems and valve sleeves requiring a hardened layer of 0.3~0.6 mm. There is no relevant process technology for swashplates requiring a hardened layer depth of 1.1~1.4 mm, resulting in unqualified hardened layer and metallographic structure after heat treatment, failing to meet drawing requirements. Second, there is the challenge of controlling deformation during heat treatment. The swashplate is an irregular forging, and after vacuum pulse carburizing and quenching, there is a large amount of deformation, leading to excessive flatness, increased post-heat grinding, and low production efficiency.

[0004] Patent CN110846612A discloses a vacuum carburizing heat treatment process. The process involves evacuating the furnace, heating the parts inside, and then introducing carburizing gas into the furnace in a pulsed manner to initiate the diffusion stage. Nitrogen is then introduced into the furnace, and the process is repeated before evacuating the furnace again. However, this method has several drawbacks: 1) Directly heating the parts in the furnace can lead to uneven temperatures, resulting in a shallow hardened layer or insufficient surface carbon concentration after carburizing; 2) Periodically introducing carburizing gas during the strong carburizing stage can cause excessively high carbon concentrations on the part surface, and periodically introducing nitrogen during the diffusion stage, if the diffusion is uneven, can easily lead to carbide formation on the part surface. Furthermore, the long diffusion stage can result in low surface carbon concentrations and low surface hardness after quenching; 3) Quenching is performed directly after carburizing, leading to excessively high quenching temperatures and significant part deformation.

[0005] Therefore, it is necessary to provide a vacuum carburizing method to resolve the contradiction between setting carburizing temperature, carburizing concentration, and carburizing efficiency. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a vacuum carburizing method for a hydraulic pump swashplate. The carburizing process provided by this invention is simple; by introducing carburizing and diffusion gases in a pulsed manner, it ensures uniform carburizing, achieves precise and controllable surface carburization, shortens process time, and improves product processing efficiency and part lifespan.

[0007] This invention provides the following technical solution: A vacuum carburizing method for a hydraulic pump swashplate includes the following steps: Clean and dry the hydraulic pump swashplate to be processed; The cleaned and dried hydraulic pump swashplate is placed into a carburizing furnace and vacuumed. It is heated to the first preset temperature and held at that temperature. Then it is heated to the target temperature and held at that temperature to obtain the heated hydraulic pump swashplate. Carburizing gas and diffusion gas are alternately and circulated in a pulsed manner into the carburizing furnace to carburize the heated hydraulic pump swash plate. The carburized hydraulic pump swashplate is lowered to the second preset temperature in the carburizing furnace and held at that temperature. Then it is quenched, cleaned and tempered to obtain the target hydraulic pump swashplate.

[0008] Furthermore, the hydraulic pump swashplate to be treated is placed in a liquid at 55~65℃ and cleaned by immersion and spraying, and then dried at 85~90℃ for 30 minutes.

[0009] Furthermore, the cleaned and dried hydraulic pump swashplate is placed into a carburizing furnace, vacuumed to a vacuum degree ≤13 Pa, heated to the first preset temperature of 600~650℃, held for 60 min, and then heated to the target temperature of 920~940℃, held for 60 min, to obtain the heated hydraulic pump swashplate. The heating rate is ≤6℃ / min.

[0010] Furthermore, the flow rates of the carburizing gas and the diffusion gas are 25~35 L / min.

[0011] Furthermore, the carburizing gas is acetylene, and the diffusion gas is nitrogen.

[0012] Furthermore, the pulse cycle includes the introduction of a carburizing gas and a diffusion gas. As the pulse cycle increases, the time ratio of the carburizing gas to the diffusion gas in each pulse cycle decreases, with a decrease range of 1.68 to 0.04.

[0013] Furthermore, the pulse period is 18 cycles, and the total pulse time is 290~310 min.

[0014] Furthermore, during the carburizing process, the vacuum degree of the carburizing furnace is ≤700 Pa.

[0015] Furthermore, after the carburized hydraulic pump swashplate is lowered to the second preset temperature and held for a period of time, it is quenched in vacuum quenching oil at 58~62℃ for 25~35 min, stirred and cooled to room temperature, cleaned and then tempered to 150~170℃ and held for 230~250 min to obtain the target hydraulic pump swashplate.

[0016] Furthermore, the second preset temperature is 830~850℃, the holding time is 60 min, and the vacuum degree of the quenching treatment is ≤13 Pa.

[0017] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention adopts a stepped heating method to raise the hydraulic pump swashplate to the target temperature, ensuring uniform surface temperature of the parts and effectively reducing thermal stress of the hydraulic pump swashplate; heating and carburizing in a vacuum effectively prevents oxidation and decarburization, and is clean and environmentally friendly; during the carburizing stage, acetylene and nitrogen are alternately passed through in a pulse manner, and the heating chamber pressure is automatically adjusted by the regulating valve throughout the carburizing process, making the carburizing atmosphere more active and uniform, and ensuring sufficient active carbon atoms on the surface of the parts. The time ratio of carburizing gas to diffusion gas is gradually reduced, and the diffusion time is extended to ensure sufficient diffusion of carbon atoms while the carbon concentration on the surface is not too low, thereby improving diffusion efficiency and preventing carbide aggregation; after carburizing, the hydraulic pump swashplate is cooled down before quenching, reducing the quenching temperature and effectively reducing the heat treatment deformation of the hydraulic pump swashplate, thereby reducing the subsequent grinding amount and improving grinding efficiency. (2) By introducing low-pressure protective nitrogen into the furnace during the carburizing diffusion stage, pressure can be provided into the furnace to increase the diffusion rate of carbon atoms and improve efficiency. At the same time, it can prevent high carbon content near the surface of the parts. While maintaining the carburizing temperature and carburizing concentration in the furnace, the pressure in the furnace can be increased, the carburizing efficiency can be improved, the diffusion time can be shortened, and thus the production efficiency can be improved. Attached Figure Description

[0018] Figure 1 This is the vacuum carburizing process curve of the hydraulic pump swashplate in Embodiment 1 of the present invention; Figure 2 This is a 50x magnification image of the surface structure of the hydraulic pump swashplate in Embodiment 1 of the present invention; Figure 3 This is the hardness test result of the hydraulic pump swashplate in Embodiment 1 of the present invention; Figure 4 This refers to the carburized layer depth of the hydraulic pump swashplate in Embodiment 1 of the present invention, which is 100 times the magnification. Figure 5 This is a surface microstructure image of the hydraulic pump swashplate in Embodiment 1 of the present invention at 500x magnification; Figure 6This is a core tissue image of the hydraulic pump swashplate in Embodiment 1 of the present invention at 500x magnification; Figure 7 This is the vacuum carburizing process curve of the hydraulic pump swashplate in Comparative Example 1 of this invention; Figure 8 This is a surface microstructure image of the hydraulic pump swashplate in Comparative Example 1 of this invention at 50x magnification; Figure 9 The results are the hardness test results of the hydraulic pump swashplate in Comparative Example 1 of this invention. Figure 10 It is the carburized layer depth of the hydraulic pump swashplate in Comparative Example 1 of the present invention at a magnification of 100. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0020] In the description of this invention, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature.

[0021] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0022] like Figure 1 As shown, the present invention provides a vacuum carburizing process for a hydraulic pump swashplate, comprising the following steps:

[0023] S1. Load the hydraulic pump swashplate to be treated into the furnace and place it in the rear chamber of the water-based cleaning machine. Perform pre-cleaning in the cleaning liquid at 55~65℃, using immersion and spraying methods to clean it thoroughly. Then, dry it in the front chamber of the cleaning machine at 85~90℃ for 30 minutes to completely dry the cleaning liquid on the surface of the parts.

[0024] S2. Load the product into the front chamber of the vacuum carburizing furnace, start the rotary vane pump to evacuate the front chamber, and after evacuating to below 800 Pa, start the Roots pump. When the vacuum degree is ≤20 Pa and the vacuum in the front and rear chambers is basically the same, load the hydraulic pump to be processed into the rear chamber of the vacuum carburizing furnace and continue to evacuate the vacuum. When the vacuum degree is ≤13 Pa, raise the temperature to the first preset temperature and hold for 60 min, then heat to the target temperature and hold for 60 min.

[0025] S3. Carburizing gas and diffusion gas are alternately and cyclically introduced into the carburizing furnace in a pulsed manner. The flow rate of carburizing gas and diffusion gas is 25~35 L / min. Each pulse cycle includes one sequential introduction of carburizing gas and one sequential introduction of diffusion gas. As the number of pulse cycles increases, the time ratio of carburizing gas to diffusion gas in each pulse cycle gradually decreases, with a decrease range of 1.68~0.04. The pulse cycle is 18 cycles, and the total pulse time is 290~310 min.

[0026] S4. The carburized hydraulic pump swashplate is lowered to the second preset temperature in the carburizing furnace and held at that temperature. Then it is quenched in vacuum quenching oil at 60°C and cleaned. Finally, it is tempered at 150~170°C for 240 min to obtain the target hydraulic pump swashplate.

[0027] In some possible embodiments, the hydraulic pump swashplate to be processed is a shaped forging swashplate made of low-carbon alloy steel such as 20CrMnMo / 20CrMo.

[0028] In some possible embodiments, the furnace chamber is hot when the hydraulic pump swashplate to be processed enters the furnace, with an internal temperature of approximately 200°C. The first preset temperature is 600~650°C, the target temperature is 920~940°C, and the second preset temperature is 830~850°C.

[0029] In this embodiment, the furnace pressure is automatically adjusted by a Roots pump and regulating valve, and low-pressure protective nitrogen is introduced into the furnace. This not only provides pressure to the furnace to improve diffusion efficiency, but also prevents high carbon concentration near the surface of the parts. While maintaining the carburizing temperature and carburizing concentration in the furnace, the furnace pressure is increased to improve carburizing efficiency and shorten the diffusion time, thereby improving production efficiency. This effectively solves the problem of the contradiction between setting carburizing temperature, carburizing concentration and carburizing efficiency.

[0030] Example 1

[0031] like Figure 1 As shown, this embodiment provides a pulse vacuum carburizing method for a hydraulic pump swashplate, including the following steps:

[0032] Choose a relatively flat hydraulic pump swashplate, place the parts with the larger flat surface facing down, and load them into the furnace.

[0033] The assembled hydraulic pump swashplate is placed into the rear chamber of the water-based cleaning machine for pre-cleaning in a 60°C cleaning liquid. The cleaning process involves immersion and spraying to thoroughly remove any residues of cooling lubricating oil and certain metal cleaning agents from the cutting process. The parts are then dried in the front chamber at 85°C for 30 minutes to completely dry the cleaning liquid from the surface of the parts.

[0034] After cleaning and drying, the hydraulic pump swashplate is installed into the front chamber of the vacuum carburizing furnace. The front door is closed, and the rotary vane pump is started to evacuate the front chamber. After evacuating to below 800 Pa, the Roots pump is started and evacuated to below 20 Pa. When the vacuum in the front and rear chambers of the vacuum carburizing furnace is basically the same, the insulation door opens automatically. The material cart in the front chamber of the vacuum carburizing furnace automatically sends the product to the rear chamber of the vacuum carburizing furnace. The material cart returns to the front chamber of the vacuum carburizing furnace, and the insulation door is closed.

[0035] Continue to evacuate the heating chamber. When the vacuum degree is ≤13 Pa, the heating program will be automatically started. Step heating will be used to raise the temperature of the vacuum carburizing furnace to 600℃ and hold for 60 min. Then, the temperature will be raised to 930℃ and held for 60 min.

[0036] The heated hydraulic pump swashplate was alternately purged with acetylene and nitrogen in a pulsed manner. The gas flow rate was 30 L / min, and the acetylene-to-nitrogen ratio was gradually reduced from 1.68 to 0.04. After 18 pulse cycles, the total pulse time was 300 min. The acetylene and nitrogen purging time for each pulse cycle is shown in Table 1. Throughout the carburizing process, the Roots pump ran continuously, automatically adjusted by a proportional valve to ensure that the vacuum degree in the heating chamber was ≤700 Pa, ensuring sufficient acetylene supply in the early stage of carburizing and adequate activated carbon atoms on the surface of the parts.

[0037] After carburizing, the hydraulic pump swashplate is cooled in the vacuum carburizing furnace. Once the temperature drops to 850℃, it is held for 60 minutes. Then, it is removed from the front chamber and quenched in vacuum quenching oil at 60℃ for 30 minutes, stirred at 30 Hz until room temperature. The carburized and quenched hydraulic pump swashplate is then transferred to a cleaning machine to thoroughly clean the surface of the parts, removing the vacuum quenching oil. The cleaned swashplate is then transferred to a tempering furnace and tempered at 160℃ for 240 minutes to obtain the target hydraulic pump swashplate.

[0038] Table 1. Time details of carburizing gas and diffusion gas during different pulse cycles.

[0039] As shown in Table 1, with the increase of pulse period, nitrogen diffusion time increases, ensuring sufficient diffusion of carbon atoms while maintaining a high carbon concentration on the surface. This ensures that carbon atoms are uniformly dispersed on the surface of the hydraulic pump swashplate, preventing the formation of carbides on the surface of the hydraulic pump swashplate, resulting in more uniform processed products with moderate hardness.

[0040] Using the process described in this embodiment, 12 sets of hydraulic pump swashplates were subjected to low-pressure pulse vacuum carburizing treatment. The flatness results before and after heat treatment are shown in Table 2.

[0041] Table 2. Flatness of the hydraulic pump swashplate before and after vacuum carburizing heat treatment

[0042] As shown in Table 2, the flatness of the hydraulic pump swashplate is ≤0.05 mm after the low-pressure pulse vacuum carburizing treatment provided by the present invention, which meets the requirements.

[0043] like Figure 1 As shown, before carburizing the hydraulic pump swashplate, the vacuum level in the vacuum carburizing furnace is controlled to ≤13 Pa. After the carburizing stage, the vacuum level is still controlled to ≤13 Pa. During the carburizing stage, the vacuum level in the furnace is maintained at ≤700 Pa. The vacuum environment overcomes the shortcomings of traditional gas carburizing. Processing parts in a vacuum environment can effectively prevent oxidation and decarburization and is clean and environmentally friendly.

[0044] like Figure 2 The image shown is a 50x magnification image of the surface microstructure of the hydraulic pump swashplate. The hardened layer depth of the hydraulic pump swashplate after carburizing heat treatment in this embodiment was measured using the hardness method. With an HV1.0 load, starting from the surface, a point was measured at 0.1 mm intervals, up to a position of 1.5 mm. The vertical distance from the workpiece surface to the Vickers hardness limit of 550 HV (or equivalent Knoop hardness value) is the hardened layer depth (GB / T 9450-2025). The surface hardness was measured using a Rockwell hardness tester, with three test results of 60.8 HRC, 62.5 HRC, and 60.5 HRC. The core hardness was measured using a Rockwell hardness tester, with three test results of 33.5 HRC, 33.3 HRC, and 34.1 HRC. The hardness gradient curves are shown in Table 3. Figure 3 As shown, the hardness of the hydraulic pump swashplate treated by the carburizing heat treatment process in this embodiment meets the technical requirements.

[0045] Table 3 Hardened layer of hydraulic pump swashplate after carburizing heat treatment

[0046] like Figure 4 The image shown is an image of the carburized layer depth of the hydraulic pump swashplate at 100X magnification. The depths of the three tests were 1258.86 µm, 1279.61 µm and 1272.09 µm, respectively. This indicates that a relatively uniform hardened layer has been formed on the hydraulic pump swashplate, which meets the product's requirements for carburizing heat treatment.

[0047] like Figure 5As shown, according to the GB / T 25744 national standard chart, the surface has a very small amount of particulate carbides, which are rated as grade 1; the martensite is fine acicular martensite, and according to the national standard chart, the martensite grade is grade 3. Metallographic analysis shows that the content of retained austenite is 16%, and the retained austenite is rated as grade 3.

[0048] like Figure 6 As shown, the core microstructure consists of low-carbon martensite and a small amount of free ferrite. According to the GB / T 25744 national standard standard diagram, it is rated as level 3.

[0049] Comparative Example 1

[0050] like Figure 7 As shown in the comparative example, this method provides a pulse vacuum carburizing method for a hydraulic pump swashplate, comprising the following steps:

[0051] Choose a relatively flat hydraulic pump swashplate, place the parts with the larger flat surface facing down, and load them into the furnace.

[0052] The assembled hydraulic pump swashplate is placed into the rear chamber of the water-based cleaning machine for pre-cleaning in a 60°C cleaning liquid. The cleaning process involves immersion and spraying to thoroughly remove any residues of cooling lubricating oil and certain metal cleaning agents from the cutting process. The parts are then dried in the front chamber at 85°C for 30 minutes to completely dry the cleaning liquid from the surface of the parts.

[0053] Install the cleaned hydraulic pump swashplate into the front chamber of the vacuum carburizing furnace, close the front door, start the rotary vane pump to evacuate the front chamber, and after evacuating to below 800Pa, start the Roots pump to evacuate to below 20Pa and when the vacuum in the front and rear chambers of the vacuum carburizing furnace is basically the same, the insulation door will open automatically, the material cart in the front chamber of the vacuum carburizing furnace will automatically send the product to the rear chamber of the vacuum carburizing furnace, the material cart will return to the front chamber of the vacuum carburizing furnace, and the insulation door will be closed.

[0054] Continue evacuating the heating chamber until the vacuum level is ≤13Pa. The heating program will be automatically started, using a stepped heating method to raise the temperature of the vacuum carburizing furnace to 600℃ within 90 minutes and hold it for 60 minutes. Then, it will be heated to 930℃ within 60 minutes and held for 60 minutes.

[0055] The heated hydraulic pump swashplate was alternately purged with acetylene carburizing gas and nitrogen diffusion gas in a pulsed manner. The gas flow rate was 30 L / min, and the acetylene to nitrogen gas purging time ratio was gradually reduced from 1.68 to 0.07. After 15 pulse cycles, the total pulse time was 204 min. The purging time of carburizing gas and diffusion gas in each pulse cycle is shown in Table 4. Throughout the carburizing process, the Roots pump ran continuously, and the proportional valve was automatically adjusted to ensure that the vacuum in the heating chamber was ≤700 Pa, ensuring sufficient acetylene in the early stage of carburizing and sufficient activated carbon atoms on the surface of the parts.

[0056] After carburizing, the hydraulic pump swashplate is cooled in the vacuum carburizing furnace. Once the temperature drops to 850℃, it is held for 60 minutes. Then, it is removed from the front chamber and quenched in vacuum quenching oil at 60℃ for 30 minutes, with stirring at 30 Hz. The carburized and quenched hydraulic swashplate is then transferred to a cleaning machine to remove the quenching oil from its surface. The cleaned swashplate is then transferred to a tempering furnace and tempered at 160℃ for 240 minutes to obtain the target hydraulic pump swashplate.

[0057] Table 4. Time details of carburizing gas and diffusion gas during different pulse cycles.

[0058] like Figure 7 As shown, before carburizing the hydraulic pump swashplate, the vacuum level in the vacuum carburizing furnace is controlled to ≤13 Pa. After the carburizing stage, the vacuum level is still controlled to ≤13 Pa. During the carburizing stage, the vacuum level in the furnace is maintained at ≤700 Pa. The vacuum environment overcomes the shortcomings of traditional gas carburizing. Processing parts in a vacuum environment can effectively prevent oxidation and decarburization and is clean and environmentally friendly.

[0059] like Figure 8 The image shown is a 50x magnification image of the surface microstructure of the hydraulic pump swashplate. The hardened layer depth of the hydraulic pump swashplate after carburizing heat treatment in this comparative example was measured using the hardness method. With an HV1.0 load, starting from the surface, a point was measured at 0.1 mm intervals, up to a position of 0.9 mm. The vertical distance from the workpiece surface to the Vickers hardness limit of 550 HV (or equivalent Knoop hardness value) is the hardened layer depth (GB / T 9450-2025). The surface hardness was measured using a Rockwell hardness tester, with three test results of 59.5 HRC, 59.4 HRC, and 60.0 HRC. The core hardness was measured using a Rockwell hardness tester, with three test results of 32.4 HRC, 33.0 HRC, and 33.4 HRC. The hardness gradient curves are shown in Table 5. Figure 9 As shown, the hardness and metallographic structure of the hydraulic pump swashplate treated by the carburizing heat treatment process in this comparative example meet the technical requirements, but the hardened layer is relatively shallow.

[0060] Table 5 Hardened layer of hydraulic pump swashplate after carburizing heat treatment

[0061] like Figure 10 The image shown is an image of the carburized layer depth of the hydraulic pump swashplate at 100X magnification. The depths of the three tests were 923.02 µm, 940.36 µm and 948.93 µm, respectively. This indicates that a relatively uniform carburized layer was formed on the hydraulic pump swashplate, but the carburizing cycle was insufficient and the expected effect could not be achieved.

[0062] This invention achieves precise and controllable surface carburization by alternately introducing carburizing and diffusion gases in a pulsed manner, ensuring uniform carbon atom diffusion, improving efficiency and product physical properties. Combined with vacuum quenching oil quenching, it enables parts to obtain high hardness, a uniform hardened layer and excellent metallographic structure while controlling heat treatment deformation to the extreme. It is particularly suitable for high-precision irregular parts such as hydraulic pump swashplates.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A vacuum carburizing method for a hydraulic pump swashplate, characterized in that, Includes the following steps: Clean and dry the hydraulic pump swashplate to be processed; The cleaned and dried hydraulic pump swashplate is placed into a carburizing furnace and vacuumed. It is heated to the first preset temperature and held at that temperature. Then it is heated to the target temperature and held at that temperature to obtain the heated hydraulic pump swashplate. Carburizing gas and diffusion gas are alternately and circulated in a pulsed manner into the carburizing furnace to carburize the heated hydraulic pump swash plate. The carburized hydraulic pump swashplate is lowered to the second preset temperature in the carburizing furnace and held at that temperature. Then it is quenched, cleaned and tempered to obtain the target hydraulic pump swashplate.

2. The vacuum carburizing method for a hydraulic pump swashplate according to claim 1, characterized in that, The hydraulic pump swashplate to be treated was placed in a liquid at 55~65℃ and cleaned by immersion and spraying, and then dried at 85~90℃ for 30 minutes.

3. The vacuum carburizing method for a hydraulic pump swashplate according to claim 1, characterized in that, After cleaning and drying, the hydraulic pump swashplate is placed into a carburizing furnace. After evacuating to a vacuum degree of ≤13 Pa, it is heated to the first preset temperature of 600~650℃ and held for 60 min. Then it is heated to the target temperature of 920~940℃ and held for 60 min to obtain the heated hydraulic pump swashplate. And / or, the heating rate is ≤6℃ / min.

4. The vacuum carburizing method for a hydraulic pump swashplate according to claim 1, characterized in that, The flow rates of the carburizing gas and the diffusion gas are 25~35 L / min.

5. The vacuum carburizing method for a hydraulic pump swashplate according to claim 1, characterized in that, The carburizing gas is acetylene, and the diffusion gas is nitrogen.

6. The vacuum carburizing method for a hydraulic pump swashplate according to claim 1, characterized in that, The pulse cycle includes the introduction of a carburizing gas and a diffusion gas. As the pulse cycle increases, the time ratio of the carburizing gas to the diffusion gas in each pulse cycle decreases, with a decrease range of 1.68 to 0.

04.

7. The vacuum carburizing method for a hydraulic pump swashplate according to claim 6, characterized in that, The pulse period is 18 cycles, and the total pulse time is 290~310 min.

8. The vacuum carburizing method for a hydraulic pump swashplate according to claim 1, characterized in that, During the carburizing process, the vacuum degree of the carburizing furnace is ≤700 Pa.

9. The vacuum carburizing method for a hydraulic pump swashplate according to claim 1, characterized in that, After the carburized hydraulic pump swashplate is cooled to the second preset temperature and held for a period of time, it is quenched in vacuum quenching oil at 58~62℃ for 25~35 min, stirred and cooled to room temperature, cleaned and then tempered to 150~170℃ for 230~250 min to obtain the target hydraulic pump swashplate.

10. The vacuum carburizing method for a hydraulic pump swashplate according to claim 9, characterized in that, The second preset temperature is 830~850℃, the holding time is 60 min, and the vacuum degree of the quenching treatment is ≤13 Pa.

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