Carbonitriding method for automobile rocker arm roller

Abstract

The invention discloses a carbonitriding method for an automobile rocker arm roller, and relates to the technical field of surface strengthening heat treatment of metal material parts, the carbonitriding method comprises the following steps: S1, pretreatment of a workpiece; step S2, coating a rare earth catalytic permeation agent; s3, dynamic carbonitriding is carried out; and S4, quenching and subzero treatment. The carbonitriding method for the automobile rocker arm roller is simple in process; the automobile rocker arm roller treated by the co-permeation method is high in hardness, long in fatigue life and good in wear resistance.

Description

Technical Field

[0001] This invention relates to the field of surface strengthening heat treatment technology for metal parts, and in particular to a carbonitriding method for automotive rocker arm rollers. Background Technology

[0002] As a key component of the engine valve train, the rocker arm roller in an automotive machine is subjected to high-frequency alternating loads and frictional wear over long periods, placing extremely high demands on its surface performance. Surface strengthening heat treatment is an effective method to improve the surface properties of automotive rocker arm rollers. However, traditional processes typically employ either carburizing or nitriding, which have significant drawbacks: while carburizing can achieve a deep hardened layer, the surface hardness is insufficient, and the high processing temperature can easily lead to part deformation; while nitriding can improve surface hardness, the depth of the nitrided layer is shallow and cannot meet the wear resistance requirements under heavy-load conditions.

[0003] Gas carbonitriding combines the advantages of carburizing and nitriding, forming a composite diffusion layer by simultaneously infiltrating carbon and nitrogen elements. This allows for a balance between diffusion layer depth and hardness over a wide temperature range. However, existing carbonitriding processes still suffer from technical drawbacks such as poor diffusion layer uniformity, high energy consumption, long cycle times, and the need for further improvement in surface properties. To address these issues, Chinese invention patent CN114737149A discloses a method for carbonitriding surface modification of GCr15 bearings, comprising the following processes: carbonitriding treatment of the bearing; slow cooling treatment under nitrogen protection in the pre-chamber after carbonitriding; and secondary heating and quenching of the bearing. The proposed carbonitriding surface modification method for GCr15 bearings, upon testing, shows that the bearing surface exhibits a fine acicular martensitic structure with a surface hardness reaching (62-64) HRC. Compared to traditional quenching and tempering processes, its surface wear resistance is improved by 3-4 times, and its service life is increased by more than 2 times, aligning with the development direction of bearing heat treatment technology that maximizes material limits, conserves material resources, and reduces pollution emissions. However, its fatigue life still needs to be further improved.

[0004] Therefore, there is still a need in the field for a more effective carbonitriding method for automotive rocker arm rollers to obtain automotive rocker arm rollers with high hardness, long fatigue life, and good wear resistance. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a simple carbonitriding method for automotive rocker arm rollers. The automotive rocker arm rollers treated by the above-mentioned carbonitriding method have high hardness, long fatigue life, and good wear resistance.

[0006] To achieve the above objectives, the present invention provides a carbonitriding method for automotive rocker arm rollers, comprising the following steps:

[0007] Step S1, Pretreatment of the workpiece: Place the automotive rocker arm roller workpiece in silicate electrolyte and treat it with pulse power for 2-4 minutes; then use a neutral cleaning agent to ultrasonically clean it at 58-62℃ for 7-10 minutes; finally, keep it at 710-730℃ for 1-2 hours, cool it with the furnace to 480-500℃, and then air cool it.

[0008] Step S2: Coating with rare earth carburizing agent: Apply rare earth carburizing agent evenly to the surface of the pretreated automotive rocker arm roller workpiece. The coating thickness is controlled at 0.1-0.3mm. After drying, load it into the pit-type carburizing furnace.

[0009] Step S3, Dynamic Carbonitriding: The furnace temperature is raised to 850-860℃, and ammonia and propane are supplied in a pulsed manner with a carbon potential of 1.3% for 50-60 minutes. Then the furnace temperature is lowered to 820-830℃, and the gas supply is kept constant with a carbon potential of 1.1% for 1-2 hours. Finally, the furnace temperature is maintained at 820-830℃, the carbon potential is reduced to 0.9%, the ammonia flow rate is reduced to 1.5L / min, and the temperature is maintained for 4-5 hours.

[0010] Step S4, Quenching and Cryogenic Treatment: After oil quenching, hold at -70℃ for 1-2 hours, then temper at 175-185℃ for 2.5-3.5 hours.

[0011] Preferably, the material of the automotive rocker arm roller workpiece in step S1 is GCr15 material.

[0012] Preferably, the silicate electrolyte in step S1 comprises: Na2SiO3 7-9 g / L and Na2B4O7 4-6 g / L.

[0013] Preferably, the voltage of the pulse power supply in step S1 is 445-455V and the frequency is 480-520Hz.

[0014] Preferably, the pH of the neutral cleaning agent in step S1 is 7.5-8.5.

[0015] Preferably, the rare earth penetration enhancer in step S2 comprises the following components by weight: 40-60 parts rare earth chloride, 15-30 parts ammonium chloride, 5-15 parts dicyandiamide, and 10-20 parts urea.

[0016] Preferably, the rare earth chloride is at least one of lanthanum chloride and cerium chloride.

[0017] Preferably, the pulsed supply of ammonia and propane in step S3 specifically involves: an ammonia flow rate of 3 L / min, flowing for 5 seconds and stopping for 3 seconds; and a propane flow rate of 1.2 L / min, flowing for 3 seconds and stopping for 5 seconds.

[0018] Preferably, in step S3, the flow rate of ammonia in the constant gas supply is 2 L / min, and the flow rate of propane is 0.8 L / min.

[0019] Preferably, the oil temperature for oil quenching in step S4 is 45-55℃; and the oil quenching is carried out at a cooling rate of 6-9℃ / s. Detailed Implementation

[0020] This invention provides a method for carbonitriding automotive rocker arm rollers, comprising the following steps:

[0021] Step S1, Pretreatment of the workpiece: Place the automotive rocker arm roller workpiece in silicate electrolyte and treat it with pulse power for 2-4 minutes; then use a neutral cleaning agent to ultrasonically clean it at 58-62℃ for 7-10 minutes; finally, keep it at 710-730℃ for 1-2 hours, cool it with the furnace to 480-500℃, and then air cool it.

[0022] Step S2: Coating with rare earth carburizing agent: Apply rare earth carburizing agent evenly to the surface of the pretreated automotive rocker arm roller workpiece. The coating thickness is controlled at 0.1-0.3mm. After drying, load it into the pit-type carburizing furnace.

[0023] Step S3, Dynamic Carbonitriding: The furnace temperature is raised to 850-860℃, and ammonia and propane are supplied in a pulsed manner with a carbon potential of 1.3% for 50-60 minutes. Then the furnace temperature is lowered to 820-830℃, and the gas supply is kept constant with a carbon potential of 1.1% for 1-2 hours. Finally, the furnace temperature is maintained at 820-830℃, the carbon potential is reduced to 0.9%, the ammonia flow rate is reduced to 1.5L / min, and the temperature is maintained for 4-5 hours.

[0024] Step S4, Quenching and Cryogenic Treatment: After oil quenching, hold at -70℃ for 1-2 hours, then temper at 175-185℃ for 2.5-3.5 hours.

[0025] Preferably, the material of the automotive rocker arm roller workpiece in step S1 is GCr15 material.

[0026] Preferably, the silicate electrolyte in step S1 comprises: Na2SiO3 7-9 g / L and Na2B4O7 4-6 g / L.

[0027] Preferably, the voltage of the pulse power supply in step S1 is 445-455V and the frequency is 480-520Hz.

[0028] Preferably, the pH of the neutral cleaning agent in step S1 is 7.5-8.5.

[0029] Preferably, the rare earth penetration enhancer in step S2 comprises the following components by weight: 40-60 parts rare earth chloride, 15-30 parts ammonium chloride, 5-15 parts dicyandiamide, and 10-20 parts urea.

[0030] Preferably, the rare earth chloride is at least one of lanthanum chloride and cerium chloride.

[0031] Preferably, the pulsed supply of ammonia and propane in step S3 specifically involves: an ammonia flow rate of 3 L / min, flowing for 5 seconds and stopping for 3 seconds; and a propane flow rate of 1.2 L / min, flowing for 3 seconds and stopping for 5 seconds.

[0032] Preferably, in step S3, the flow rate of ammonia in the constant gas supply is 2 L / min, and the flow rate of propane is 0.8 L / min.

[0033] Preferably, the oil temperature for oil quenching in step S4 is 45-55℃; and the oil quenching is carried out at a cooling rate of 6-9℃ / s.

[0034] Due to the application of the above technical solutions, this invention patent has the following advantages compared with the prior art: The carbonitriding method for automobile rocker arm rollers provided by this invention integrates a composite process of micro-arc oxidation pretreatment, a specific formulation of rare earth infiltration agent and pulsed gas regulation, to achieve synergistic optimization of infiltration layer performance and production economy, resulting in automobile rocker arm rollers treated by the above method having high hardness, long fatigue life and good wear resistance.

[0035] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art under the premise of equivalent changes and modifications should fall within the protection scope of the present invention.

[0036] Example 1

[0037] A method for carbonitriding automotive rocker arm rollers includes the following steps:

[0038] Step S1, Pre-treatment of the workpiece: Place the automotive rocker arm roller workpiece in silicate electrolyte and treat it with pulse power for 2 minutes; then use a neutral cleaning agent to ultrasonically clean it at 58°C for 7 minutes; finally, keep it at 710°C for 1 hour, cool it with the furnace to 480°C, and then air cool it.

[0039] Step S2: Coating with rare earth carburizing agent: Apply rare earth carburizing agent evenly to the surface of the pretreated automotive rocker arm roller workpiece, with the coating thickness controlled at 0.1mm. After drying, load it into the pit-type carburizing furnace.

[0040] Step S3, Dynamic carbonitriding: The furnace temperature is raised to 850℃, and ammonia and propane are supplied in a pulsed manner with a carbon potential of 1.3% for 50 min. Then the furnace temperature is lowered to 820℃, and the gas supply is kept constant with a carbon potential of 1.1% for 1 h. Finally, the furnace temperature is maintained at 820℃, the carbon potential is reduced to 0.9%, the ammonia flow rate is reduced to 1.5 L / min, and the temperature is maintained for 4 h.

[0041] Step S4, Quenching and Cryogenic Treatment: After oil quenching, hold at -70℃ for 1 hour, then temper at 175℃ for 2.5 hours.

[0042] The material of the automotive rocker arm roller workpiece in step S1 is GCr15 material; the silicate electrolyte in step S1 includes: Na2SiO3 7g / L and Na2B4O7 4g / L; the voltage of the pulse power supply in step S1 is 445V and the frequency is 480Hz; the pH of the neutral cleaning agent in step S1 is 7.5.

[0043] The rare earth penetration catalyst in step S2 comprises the following components by weight: 40 parts rare earth chloride, 15 parts ammonium chloride, 5 parts dicyandiamide, and 10 parts urea; the rare earth chloride is lanthanum chloride; the pulsed supply of ammonia and propane in step S3 specifically involves: an ammonia flow rate of 3 L / min, flowing for 5 seconds and stopping for 3 seconds; a propane flow rate of 1.2 L / min, flowing for 3 seconds and stopping for 5 seconds; the constant gas supply in step S3 involves an ammonia flow rate of 2 L / min and a propane flow rate of 0.8 L / min; the oil temperature for oil quenching in step S4 is 45°C; and the oil quenching is performed at a cooling rate of 6°C / s.

[0044] Example 2

[0045] A method for carbonitriding automotive rocker arm rollers includes the following steps:

[0046] Step S1, Pretreatment of the workpiece: Place the automotive rocker arm roller workpiece in silicate electrolyte and treat it with pulse power for 2.5 min; then use a neutral cleaning agent to ultrasonically clean it at 59℃ for 8 min; finally, keep it at 715℃ for 1.2 h, cool it with the furnace to 485℃ and then air cool it.

[0047] Step S2: Coating with rare earth carburizing agent: Apply rare earth carburizing agent evenly to the surface of the pretreated automotive rocker arm roller workpiece, with the coating thickness controlled at 0.15mm. After drying, load it into the pit-type carburizing furnace.

[0048] Step S3, Dynamic Carbonitriding: The furnace temperature is raised to 853℃, and ammonia and propane are supplied in a pulsed manner with a carbon potential of 1.3% for 52 min. Then the furnace temperature is lowered to 823℃, and the gas supply is kept constant with a carbon potential of 1.1% for 1.2 h. Finally, the furnace temperature is maintained at 823℃, the carbon potential is reduced to 0.9%, the ammonia flow rate is reduced to 1.5 L / min, and the temperature is maintained for 4.2 h.

[0049] Step S4, Quenching and Cryogenic Treatment: After oil quenching, hold at -70℃ for 1.2h, then temper at 178℃ for 2.7h.

[0050] The material of the automotive rocker arm roller workpiece in step S1 is GCr15 material; the silicate electrolyte in step S1 includes: Na2SiO3 7.5g / L, Na2B4O7 4.5g / L; the voltage of the pulse power supply in step S1 is 448V, and the frequency is 490Hz; the pH of the neutral cleaning agent in step S1 is 7.7.

[0051] The rare earth penetration catalyst in step S2 comprises the following components by weight: 45 parts rare earth chloride, 20 parts ammonium chloride, 8 parts dicyandiamide, and 13 parts urea; the rare earth chloride is cerium chloride; the pulsed supply of ammonia and propane in step S3 specifically involves: an ammonia flow rate of 3 L / min, running for 5 seconds and stopping for 3 seconds; a propane flow rate of 1.2 L / min, running for 3 seconds and stopping for 5 seconds; the constant gas supply in step S3 involves an ammonia flow rate of 2 L / min and a propane flow rate of 0.8 L / min; the oil temperature for oil quenching in step S4 is 48°C; and the oil quenching is performed at a cooling rate of 7°C / s.

[0052] Example 3

[0053] A method for carbonitriding automotive rocker arm rollers includes the following steps:

[0054] Step S1, Pretreatment of the workpiece: Place the automotive rocker arm roller workpiece in silicate electrolyte and treat it with pulse power for 3 minutes; then use a neutral cleaning agent to ultrasonically clean it at 60°C for 8.5 minutes; finally, keep it at 720°C for 1.5 hours, cool it in the furnace to 490°C, and then air cool it.

[0055] Step S2: Coating with rare earth carburizing agent: Apply rare earth carburizing agent evenly to the surface of the pretreated automotive rocker arm roller workpiece, with the coating thickness controlled at 0.2mm. After drying, load it into the pit-type carburizing furnace.

[0056] Step S3, Dynamic Carbonitriding: The furnace temperature is raised to 855℃, and ammonia and propane are supplied in a pulsed manner with a carbon potential of 1.3% for 55 min. Then the furnace temperature is lowered to 825℃, and the gas supply is kept constant with a carbon potential of 1.1% for 1.5 h. Finally, the furnace temperature is maintained at 825℃, the carbon potential is reduced to 0.9%, the ammonia flow rate is reduced to 1.5 L / min, and the temperature is maintained for 4.5 h.

[0057] Step S4, Quenching and Cryogenic Treatment: After oil quenching, hold at -70℃ for 1.5h, then temper at 180℃ for 3h.

[0058] The material of the automotive rocker arm roller workpiece in step S1 is GCr15 material; the silicate electrolyte in step S1 includes: Na2SiO3 8g / L, Na2B4O 75g / L; the voltage of the pulse power supply in step S1 is 450V, and the frequency is 500Hz; the pH of the neutral cleaning agent in step S1 is 8; the rare earth penetration catalyst in step S2 includes the following components by weight: rare earth chloride 50 parts, ammonium chloride 23 parts, dicyandiamide 10 parts of urea and 15 parts of rare earth chloride; the rare earth chloride is lanthanum chloride; the pulsed supply of ammonia and propane in step S3 is as follows: the ammonia flow rate is 3L / min, on for 5s and off for 3s; the propane flow rate is 1.2L / min, on for 3s and off for 5s; the constant gas supply in step S3 has an ammonia flow rate of 2L / min and a propane flow rate of 0.8L / min; the oil temperature for oil quenching in step S4 is 50℃; oil quenching is performed at a cooling rate of 7.5℃ / s.

[0059] Example 4

[0060] A method for carbonitriding automotive rocker arm rollers includes the following steps:

[0061] Step S1, Pretreatment of the workpiece: Place the automotive rocker arm roller workpiece in silicate electrolyte and treat it with pulse power for 3.5 min; then use a neutral cleaning agent to ultrasonically clean it at 61℃ for 9 min; finally, keep it at 725℃ for 1.8 h, cool it with the furnace to 495℃ and then air cool it.

[0062] Step S2: Coating with rare earth carburizing agent: Apply rare earth carburizing agent evenly to the surface of the pretreated automotive rocker arm roller workpiece, with the coating thickness controlled at 0.25mm. After drying, load it into the pit-type carburizing furnace.

[0063] Step S3, Dynamic carbonitriding: The furnace temperature is raised to 858℃, and ammonia and propane are supplied in a pulsed manner with a carbon potential of 1.3% for 58 min. Then the furnace temperature is lowered to 828℃, and the gas supply is kept constant with a carbon potential of 1.1% for 1.8 h. Finally, the furnace temperature is maintained at 828℃, the carbon potential is reduced to 0.9%, the ammonia flow rate is reduced to 1.5 L / min, and the temperature is maintained for 4.8 h.

[0064] Step S4, Quenching and Cryogenic Treatment: After oil quenching, hold at -70℃ for 1.8h, then temper at 183℃ for 3.3h.

[0065] The material of the automotive rocker arm roller workpiece mentioned in step S1 is GCr15 material; the silicate electrolyte mentioned in step S1 includes: Na2SiO3 8.5g / L, Na2B4O7 5.5g / L; the voltage of the pulse power supply mentioned in step S1 is 453V, and the frequency is 510Hz; the pH of the neutral cleaning agent mentioned in step S1 is 8.3; the rare earth penetration catalyst mentioned in step S2 includes the following components by weight: rare earth chloride 55 parts, ammonium chloride 28 parts, dicyandiamide 13 parts, ... 18 parts of urea; the rare earth chloride is a mixture of lanthanum chloride and cerium chloride in a mass ratio of 1:1; the pulse supply of ammonia and propane in step S3 is specifically as follows: the ammonia flow rate is 3L / min, on for 5s and off for 3s; the propane flow rate is 1.2L / min, on for 3s and off for 5s; the constant gas supply in step S3 has an ammonia flow rate of 2L / min and a propane flow rate of 0.8L / min; the oil temperature for oil quenching in step S4 is 53℃; and the oil quenching is carried out at a cooling rate of 8.5℃ / s.

[0066] Example 5

[0067] A method for carbonitriding automotive rocker arm rollers includes the following steps:

[0068] Step S1, Pre-treatment of the workpiece: Place the automotive rocker arm roller workpiece in silicate electrolyte and treat it with pulse power for 4 minutes; then use a neutral cleaning agent to ultrasonically clean it at 62°C for 10 minutes; finally, keep it at 730°C for 2 hours, cool it with the furnace to 500°C, and then air cool it.

[0069] Step S2: Coating with rare earth carburizing agent: Apply rare earth carburizing agent evenly to the surface of the pretreated automotive rocker arm roller workpiece, with the coating thickness controlled at 0.3mm. After drying, load it into the pit-type carburizing furnace.

[0070] Step S3, Dynamic carbonitriding: The furnace temperature is raised to 860℃, and ammonia and propane are supplied in a pulsed manner with a carbon potential of 1.3% for 60 min. Then the furnace temperature is lowered to 830℃, and the gas supply is kept constant with a carbon potential of 1.1% for 2 h. Finally, the furnace temperature is maintained at 830℃, the carbon potential is reduced to 0.9%, the ammonia flow rate is reduced to 1.5 L / min, and the temperature is maintained for 5 h.

[0071] Step S4, Quenching and Cryogenic Treatment: After oil quenching, hold at -70℃ for 2 hours, then temper at 185℃ for 3.5 hours.

[0072] The material of the automotive rocker arm roller workpiece in step S1 is GCr15 material; the silicate electrolyte in step S1 includes: Na2SiO3 9g / L, Na2B4O7 6g / L; the voltage of the pulse power supply in step S1 is 455V, and the frequency is 520Hz; the pH of the neutral cleaning agent in step S1 is 8.5; the rare earth penetration catalyst in step S2 includes the following components by weight: rare earth chloride 60 parts, ammonium chloride 30 parts, and bismuth suboxide... The ingredients are 15 parts cyanamide and 20 parts urea; the rare earth chloride is lanthanum chloride; the pulsed supply of ammonia and propane in step S3 is as follows: the ammonia flow rate is 3 L / min, running for 5 seconds and stopping for 3 seconds; the propane flow rate is 1.2 L / min, running for 3 seconds and stopping for 5 seconds; the constant gas supply in step S3 has an ammonia flow rate of 2 L / min and a propane flow rate of 0.8 L / min; the oil temperature for oil quenching in step S4 is 55℃; and the oil quenching is carried out at a cooling rate of 9℃ / s.

[0073] Comparative Example 1

[0074] This example provides a carbonitriding method for automotive rocker arm rollers, which is basically the same as that in Example 1, except that it uses traditional carbonitriding (880°C, constant gas supply, ammonia flow rate of 3L / min; propane flow rate of 1.2L / min).

[0075] Comparative Example 2

[0076] This example provides a carbonitriding method for automotive rocker arm rollers, which is basically the same as that in Example 1, except that the step of coating with a rare earth infiltration agent is omitted.

[0077] The performance of the automotive rocker arm rollers treated with the carbonitriding method in each example was tested. The test results are shown in Table 1. The test methods are as follows:

[0078] (1) Infiltration depth: Tested in accordance with GB / T 9450-2005;

[0079] (2) Surface hardness: tested using a Vickers hardness tester (load 0.3 kgf), in accordance with GB / T 230.1-2018;

[0080] (3) Wear resistance: The wear amount was tested using a reciprocating friction and wear tester (load 50N, frequency 2Hz), and the test was carried out in accordance with GB / T12444-2006;

[0081] (4) Fatigue life: L10 life was tested using a bearing fatigue testing machine (speed 6000r / min, radial load 1900N) and the test was carried out in accordance with GB-T 6391-2010.

[0082] Table 1 Performance Test Results of Automobile Rocker Arm Rollers

[0083] project Total depth of infiltration layer Surface hardness Wear Fatigue life L10 unit mm HV0.3 <![CDATA[mg / 10 3 Next h Example 1 0.55 920 0.08 1050 Example 2 0.57 925 0.06 1065 Example 3 0.61 933 0.05 1072 Example 4 0.62 940 0.04 1080 Example 5 0.65 946 0.02 1092 Comparative Example 1 0.32 770 0.25 780 Comparative Example 2 0.37 810 0.20 750

[0084] As can be seen from Table 1, the automotive rocker arm rollers treated by the carbonitriding method of the embodiments of the present invention have better surface properties. The composite process of using a specific rare earth infiltration agent and pulsed gas regulation has a beneficial effect on improving the above properties.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. At the same time, those skilled in the art should understand and implement the above description. Therefore, any equivalent changes or modifications made without departing from the concept disclosed in the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for carbonitriding automotive rocker arm rollers, characterized in that, Includes the following steps: Step S1, Pretreatment of the workpiece: Place the automotive rocker arm roller workpiece in silicate electrolyte and treat it with pulse power for 2-4 minutes; then use a neutral cleaning agent to ultrasonically clean it at 58-62℃ for 7-10 minutes; finally, keep it at 710-730℃ for 1-2 hours, cool it with the furnace to 480-500℃, and then air cool it. Step S2: Coating with rare earth carburizing agent: Apply rare earth carburizing agent evenly to the surface of the pretreated automotive rocker arm roller workpiece. The coating thickness is controlled at 0.1-0.3mm. After drying, load it into the pit-type carburizing furnace. Step S3, Dynamic Carbonitriding: The furnace temperature is raised to 850-860℃, and ammonia and propane are supplied in a pulsed manner with a carbon potential of 1.3% for 50-60 minutes. Then the furnace temperature is lowered to 820-830℃, and the gas supply is kept constant with a carbon potential of 1.1% for 1-2 hours. Finally, the furnace temperature is maintained at 820-830℃, the carbon potential is reduced to 0.9%, the ammonia flow rate is reduced to 1.5L / min, and the temperature is maintained for 4-5 hours. Step S4, Quenching and Cryogenic Treatment: After oil quenching, hold at -70℃ for 1-2 hours, then temper at 175-185℃ for 2.5-3.5 hours.

2. The carbonitriding method for automotive rocker arm rollers according to claim 1, characterized in that, The material of the automotive rocker arm roller workpiece mentioned in step S1 is GCr15 material.

3. The carbonitriding method for automotive rocker arm rollers according to claim 1, characterized in that, The silicate electrolyte in step S1 includes: Na2SiO3 7-9 g / L and Na2B4O7 4-6 g / L.

4. The carbonitriding method for automotive rocker arm rollers according to claim 1, characterized in that, The voltage of the pulse power supply mentioned in step S1 is 445-455V and the frequency is 480-520Hz.

5. The carbonitriding method for automotive rocker arm rollers according to claim 1, characterized in that, The pH of the neutral cleaning agent mentioned in step S1 is 7.5-8.

5.

6. The carbonitriding method for automotive rocker arm rollers according to claim 1, characterized in that, The rare earth penetration enhancer in step S2 comprises the following components by weight: 40-60 parts rare earth chloride, 15-30 parts ammonium chloride, 5-15 parts dicyandiamide, and 10-20 parts urea.

7. The carbonitriding method for automotive rocker arm rollers according to claim 6, characterized in that, The rare earth chloride is at least one of lanthanum chloride and cerium chloride.

8. The carbonitriding method for automotive rocker arm rollers according to claim 1, characterized in that, The pulsed supply of ammonia and propane in step S3 is as follows: the ammonia flow rate is 3L / min, with a 5s on and 3s off cycle; the propane flow rate is 1.2L / min, with a 3s on and 5s off cycle.

9. The carbonitriding method for automotive rocker arm rollers according to claim 1, characterized in that, In step S3, the constant gas supply has an ammonia flow rate of 2 L / min and a propane flow rate of 0.8 L / min.

10. The carbonitriding method for automotive rocker arm rollers according to claim 1, characterized in that, The oil temperature for oil quenching in step S4 is 45-55℃; the oil quenching is carried out at a cooling rate of 6-9℃ / s.