2cr3wmo v material and its heat treatment process

Abstract

The application relates to the technical field of material heat treatment, and more specifically to a 2Cr3WMoV material and a heat treatment process thereof. The heat treatment of the application comprises preheating, temperature rising and strong penetration, first diffusion, second diffusion, temperature adjusting quenching and tempering, the 2Cr3WMoV material is carburized and nitrided at 860-870 DEG C by taking propane and methanol as carbon sources and ammonia as a nitrogen source, then the first diffusion is carried out at 860-870 DEG C, and the second diffusion is carried out at 850-860 DEG C. The carbon and nitrogen atoms promote each other through the carburizing and nitriding, the thickness of the carbonitride layer is increased, the carbon atoms promote the gradual densification of the carbonitride layer, and through quenching and tempering, the hardness of the 2Cr3WMoV material after the heat treatment is improved, and the thickness of the hardened layer is increased compared with the carburizing process in the prior art, and the 2Cr3WMoV material is more in line with the requirements specified in HB5492-2011.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material heat treatment, and more particularly to a 2Cr3WMoV material and a heat treatment process thereof. BACKGROUND

[0002] The 2Cr3WMoV material is a low-alloy heat-resistant steel, which is mainly used for manufacturing fuel pumps, gears and other parts in the field of aerospace. The surface hardness of the 2Cr3WMoV material directly subjected to quenching and tempering heat treatment can only reach 35-45HRC, which cannot meet the requirements of high hardness and long service life of the 2Cr3WMoV gear, and thus the surface of the 2Cr3WMoV gear needs to be modified.

[0003] At present, the surface strengthening treatment is mainly carried out by using the carburizing process. However, due to the high carburizing temperature, slow carburizing speed and difficulty in controlling the furnace atmosphere, the 2Cr3WMoV gear is prone to deformation, coarse grains, insufficient overall depth of the carburized layer and insufficient hardness, and thus it is difficult to meet the requirements specified in HB5492-2011. SUMMARY

[0004] In order to solve the problem that the existing 2Cr3WMoV material is difficult to meet the requirements of HB5492-2011 by using the carburizing process for surface strengthening treatment, the present application provides a 2Cr3WMoV material and a heat treatment process thereof. The 2Cr3WMoV material treated by the heat treatment process has higher hardness, deeper carburized layer depth and higher grain size grade, and thus it is more in line with the requirements specified in HB5492-2011.

[0005] In a first aspect, the present application provides a heat treatment process for a 2Cr3WMoV material, which adopts the following technical scheme: a heat treatment process for a 2Cr3WMoV material, comprising the following steps:

[0006] Preheating: preheating and holding the 2Cr3WMoV material under inert gas;

[0007] High-temperature carburizing: when the temperature is increased to 745-755℃ from the preheating temperature, propane and methanol are introduced, the temperature is continuously increased to 860-870℃, ammonia gas is introduced, and the 2Cr3WMoV material is kept at 860-870℃ for 210-270min;

[0008] First diffusion: after the high-temperature carburizing, the carbon potential is reduced, and the 2Cr3WMoV material is subjected to first diffusion for 120-180min;

[0009] Second diffusion: after the first diffusion, the carbon potential and the ammonia gas flow are reduced, the temperature is adjusted to 850-860℃, and the 2Cr3WMoV material is subjected to second diffusion for 120-180min.

[0010] tempering: after the quenching, the 2Cr3WMoV material is tempered, and after the tempering, the 2Cr3WMoV material is cooled to obtain the 2Cr3WMoV material.

[0011] tempering: after the quenching, the 2Cr3WMoV material is tempered, and after the tempering, the 2Cr3WMoV material is cooled to obtain the 2Cr3WMoV material.

[0012] By adopting the above technical scheme, first, in order to reduce the deformation and cracking of the product caused by rapid high temperature, the 2Cr3WMoV material is preheated and kept warm, then propane and methanol are used as carbon sources during the heating period, a large number of active carbon atoms are generated, and the active carbon atoms begin to penetrate into the inner layer of the 2Cr3WMoV material; after reaching the strong penetration temperature, ammonia gas is used as a nitrogen source, a large number of active nitrogen atoms are generated, and the active nitrogen atoms begin to penetrate into the inner layer of the 2Cr3WMoV material, the active carbon atoms have formed a large number of fine carbon compounds in the 2Cr3WMoV material, which act as nucleation media, promoting the formation of nitrides and the penetration of nitrogen; with the penetration of nitrogen atoms, the phase transition temperature of the penetration layer is reduced, and the diffusion coefficient of carbon atoms is increased, and during the carbonitriding process, the active carbon atoms and the active nitrogen atoms promote each other; in addition, at the strong penetration temperature, the carbon and nitrogen atoms have a large solubility in the alloy, which is beneficial to the absorption and diffusion of carbon and nitrogen atoms, and after the carbonitriding of the 2Cr3WMoV material, a carbonitride layer is formed;

[0013] After the temperature is raised and the strong penetration is performed, the carbonitride layer of the 2Cr3WMoV material is initially formed, the carbon atoms will promote the carbonitride layer to form a large number of crystal nuclei from the inside, the crystal nuclei are continuously refined, and the carbonitride layer is gradually densified, and the dense carbonitride layer will hinder the penetration of new active carbon atoms and nitrogen atoms, so that the growth of the carbonitride layer of the 2Cr3WMoV material gradually slows down;

[0014] During the first diffusion, the carbon potential is reduced, and the densification efficiency of the carbonitride layer is reduced, so that the carbonitride layer of the 2Cr3WMoV material continues to grow; during the second diffusion, the carbonitride layer of the 2Cr3WMoV material is highly densified, the growth of the new carbonitride layer of the 2Cr3WMoV material is more slow, and too many nitrogen atoms in the outside of the carbonitride layer will generate nitrogen gas, so that a large number of pores and loose areas appear in the outside of the carbonitride layer; the pores and loose areas in the outside of the carbonitride layer will reduce the hardness of the 2Cr3WMoV material, therefore, the carbon potential is further reduced, and the temperature and the flow of ammonia gas are reduced, which can further generate new carbonitride layers, and at the same time, reduce the pores and loose areas of the carbonitride layer;

[0015] The quenching makes the dense carbonitride layer form a high-hardness martensite surface layer; after quenching, the 2Cr3WMoV material has a large quenching stress, and thus needs appropriate tempering treatment to promote the residual dense carbonitride layer to transform into a high-hardness martensite surface layer;

[0016] Compared with the 2Cr3WMoV material prepared by the carburizing process, the 2Cr3WMoV material prepared by the heat treatment has higher hardness and deeper hardening layer depth, and is more in line with the requirements specified in HB5492-2011.

[0017] Preferably, in the step of the temperature rising and strong carburizing, the carbon potential is 0.95-1.05%, and the ammonia flow rate is 6-8 NL / min.

[0018] By adopting the above technical solution, when the carbon potential is too low, the active carbon atoms and the active nitrogen atoms are difficult to promote each other to penetrate into the 2Cr3WMoV material, which reduces the thickness of the hardening layer and causes more holes and loose areas in the carbonitride layer, thereby reducing the hardness of the 2Cr3WMoV material; when the carbon potential is too high, too many carbon atoms accelerate the densification rate of the carbonitride layer, thereby reducing the thickness of the hardening layer; when the ammonia flow rate is too low, the active carbon atoms and the active nitrogen atoms are difficult to promote each other to penetrate into the 2Cr3WMoV material, which reduces the thickness of the hardening layer; when the ammonia flow rate is too high, there are more holes and loose areas in the carbonitride layer, thereby reducing the hardness of the 2Cr3WMoV material; therefore, the applicant finally determines that the carbon potential and the ammonia flow rate should be as above after a large number of researches and experimental verifications.

[0019] Preferably, in the step of the first diffusion, the carbon potential is 0.85-0.95%.

[0020] By adopting the above technical solution, when the carbon potential is too low, the active carbon atoms and the active nitrogen atoms are difficult to promote each other to penetrate into the 2Cr3WMoV material, which reduces the thickness of the hardening layer and causes more holes and loose areas in the carbonitride layer, thereby reducing the hardness of the 2Cr3WMoV material; when the carbon potential is too high, too many carbon atoms accelerate the densification rate of the carbonitride layer, thereby reducing the thickness of the hardening layer; when the ammonia flow rate is too low, the active carbon atoms and the active nitrogen atoms are difficult to promote each other to penetrate into the 2Cr3WMoV material, which reduces the thickness of the hardening layer; when the ammonia flow rate is too high, there are more holes and loose areas in the carbonitride layer, thereby reducing the hardness of the 2Cr3WMoV material; therefore, the applicant finally determines that the carbon potential and the ammonia flow rate should be as above after a large number of researches and experimental verifications.

[0021] Preferably, in the step of the second diffusion, the carbon potential is 0.75-0.85%, and the ammonia flow rate is 4-6 NL / min.

[0022] By adopting the technical scheme, when the carbon potential is too low, active carbon atoms and active nitrogen atoms are difficult to promote each other to penetrate into the 2Cr3WMoV material, the thickness of the hardened layer is reduced, and the carbonitride layer has more holes and loose areas, which reduces the hardness of the 2Cr3WMoV material; when the carbon potential is too high, too many carbon atoms will accelerate the densification rate of the carbonitride layer, reducing the thickness of the hardened layer; when the ammonia flow is too low, active carbon atoms and active nitrogen atoms are difficult to promote each other to penetrate into the 2Cr3WMoV material, reducing the thickness of the hardened layer; when the ammonia flow is too high, the carbonitride layer has more holes and loose areas, which reduces the hardness of the 2Cr3WMoV material; therefore, after a large amount of research and experimental verification, the applicant finally determines that the carbon potential and the ammonia flow should be as described above.

[0023] Preferably, in the step of temperature-adjusted quenching, the quenching temperature is 105-115℃, and the quenching time is 8-12min.

[0024] By adopting the technical scheme, if the quenching temperature is too low, the carbonitride layer is difficult to fully convert into a high-hardness martensite surface layer; if the quenching temperature is too high, the carbonitride layer has already fully converted into a high-hardness martensite surface layer, and it is unnecessary to continue to increase the quenching temperature in order to reduce production costs; therefore, after a large amount of research and experimental verification, the applicant finally determines that the quenching temperature and time should be as described above.

[0025] Preferably, in the step of temperature-adjusted quenching, the quenching temperature is 105-115℃, and the quenching time is 8-12min.

[0026] By adopting the technical scheme, when the flow rates of propane and methanol are too low, the active carbon atoms generated by propane and methanol as a carbon source are less, reducing the thickness of the hardened layer; when the flow rates of propane and methanol are too high, a large amount of carbon atoms will promote the densification of the carbonitride layer, reducing the thickness of the hardened layer; therefore, after a large amount of research and experimental verification, the applicant finally determines that the flow rates of propane and methanol should be as described above.

[0027] Preferably, in the step of cleaning and tempering, the tempering temperature is 165-175℃, and the tempering time is 230-250min.

[0028] By adopting the technical scheme, if the tempering temperature is too low, the quenching stress in the 2Cr3WMoV material is difficult to eliminate, and the residual dense carbonitride layer is difficult to transform into a high-hardness martensite surface layer, reducing the hardness of the 2Cr3WMoV material; if the tempering temperature is too high, the quenching stress in the 2Cr3WMoV material is fully eliminated, and the residual dense carbonitride layer has been fully transformed into a high-hardness martensite surface layer, so as to reduce the production cost, it is unnecessary to continue to increase the tempering temperature; therefore, the applicant finally determines, through a large number of researches and experimental verifications, that the tempering temperature and the tempering time in the application are preferably as above.

[0029] Preferably, the heat treatment process of the 2Cr3WMoV material further comprises a pretreatment, and the pretreatment is to perform three-stage heating on the 2Cr3WMoV material.

[0030] By adopting the technical scheme, the three-stage heating causes the 2Cr3WMoV material to generate defects such as dislocations, so that the carbon and nitrogen atoms are more easily migrated in the defects of the 2Cr3WMoV material than in the complete crystal, and the diffusion efficiency of the carbon and nitrogen atoms is improved; in addition, the carbonitride preferentially forms nuclei at the grain boundaries and defects such as dislocations, which helps the 2Cr3WMoV material to form a thicker hardened layer.

[0031] Preferably, the three-stage heating comprises the following steps:

[0032] First-stage heating: heating temperature 695-705℃, holding time 25-45min;

[0033] Second-stage heating: heating temperature 795-805℃, holding time 30-50min;

[0034] Third-stage heating: heating temperature 950-1010℃, holding time 70-110min;

[0035] Cooling: after the third-stage heating is completed, the 2Cr3WMoV material is cooled to obtain a pretreated 2Cr3WMoV material.

[0036] By adopting the technical scheme, if the above three-stage heating temperature is too low, the 2Cr3WMoV material generates fewer defects such as dislocations, which is difficult to improve the diffusion efficiency of the carbon and nitrogen atoms and to improve the thickness of the hardened layer; if the above three-stage heating temperature is too high, the 2Cr3WMoV material has poor heat conduction efficiency, is easy to generate large internal stress, has large defects, and reduces the grain size of the 2Cr3WMoV material, thereby reducing the hardness of the 2Cr3WMoV material; therefore, the applicant finally determines, through a large number of researches and experimental verifications, that the three-stage heating temperature and the holding time in the application are preferably as above.

[0037] In a second aspect, the present application provides a 2Cr3WMoV material, which adopts the technical scheme as follows:

[0038] The 2Cr3WMoV material treated by any one of the heat treatment processes.

[0039] The 2Cr3WMoV material has the same advantages as the heat treatment processes described above relative to the prior art, and will not be described here again.

[0040] In summary, the present application has the following beneficial effects:

[0041] 1. Since the present application uses propane and methanol as carbon sources, ammonia as a nitrogen source, and adopts a carbonitriding treatment method, carbon and nitrogen atoms promote each other, increasing the thickness of the carbonitride layer; carbon atoms promote the gradual densification of the carbonitride layer, and through quenching and tempering, the hardness of the 2Cr3WMoV material after heat treatment is improved compared to the carburizing process of the prior art, and the thickness of the hardened layer is also improved, which is more in line with the requirements specified in HB5492-2011;

[0042] 2. The present application performs a three-stage heating pretreatment before the carbonitriding process, which produces dislocations and other defects in the 2Cr3WMoV material, improves the diffusion efficiency of carbon and nitrogen atoms, and helps the 2Cr3WMoV material to form a thicker hardened layer. DETAILED DESCRIPTION

[0043] The raw materials in the present application include the following parts:

[0044] Propane, ammonia and methanol are commercially available products with a purity of ≥99.99%.

[0045] The present application will be further described in detail in conjunction with the examples and comparative examples.

[0046] Example 1

[0047] I. Pretreatment

[0048] (1) Put the 2Cr3WMoV gear into a high-temperature box-type resistance furnace and start three-stage heating;

[0049] (2) The three-stage heating includes: the first stage is set to 700℃, and the holding time is 35 min; the second stage is set to 800℃, and the holding time is 40 min; the third stage is set to 980℃, and the holding time is 90 min;

[0050] (3) After the holding is completed, air cooling treatment is performed to obtain the pretreated 2Cr3WMoV gear.

[0051] II. Carbonitriding

[0052] (1) Preheating: the pretreated 2Cr3WMoV gear is sent into the front chamber of the pre-vacuum multi-purpose furnace, vacuum is extracted to make the pressure of the pre-vacuum multi-purpose furnace ≤300 Pa, nitrogen is filled, when the pressure of the front chamber and the rear chamber is the same, the pretreated 2Cr3WMoV gear is sent into the rear chamber, and the temperature is raised to 700℃, and the holding time is 30 min;

[0053] (2) Temperature rising: the temperature is raised from 700℃ to 870℃, when the temperature reaches 750℃ (745-755℃ are suitable), the propane and methanol flow meters are opened, and propane and methanol are introduced, the propane flow is 5 NL / min, and the methanol flow is 40 mL / min; when the temperature reaches 870℃, the carbon potential reaches 1.00%, the ammonia gas flow meter is opened, and ammonia gas is introduced, and the ammonia gas flow is 7 NL / min;

[0054] (3) Strong infiltration: the 2Cr3WMoV gear is subjected to carbon and nitrogen strong infiltration at a strong infiltration temperature of 870℃, a strong infiltration time of 270 min, a strong infiltration carbon potential of 1.00%, and a strong infiltration ammonia gas flow of 7 NL / min;

[0055] (4) First diffusion: the 2Cr3WMoV gear is subjected to first diffusion at a diffusion temperature of 870℃, a diffusion time of 180 min, a carbon potential of 0.90%, and a diffusion ammonia gas flow of 7 NL / min;

[0056] (5) Second diffusion: the 2Cr3WMoV gear is subjected to second diffusion at a diffusion temperature of 860℃, a diffusion time of 180 min, a carbon potential of 0.80%, and a diffusion ammonia gas flow of 5 NL / min;

[0057] (6) Temperature adjustment quenching: after the second diffusion is completed, the temperature of the pre-vacuum multi-purpose furnace is reduced to 850℃ and held for 35 min, then the 2Cr3WMoV gear is cooled in 115℃ oil for 12 min, and then oil draining is performed;

[0058] (7) Cleaning: the 2Cr3WMoV gear is sent into a cleaning machine at a water temperature of 70℃ for cleaning, and after the cleaning is completed, drying is performed at 150℃;

[0059] (8) Tempering: after the 2Cr3WMoV gear is dried, it is sent into a tempering furnace, tempered at 175℃ for 250 min, and then air cooled after the tempering is completed.

[0060] Example 2-5

[0061] Example 2-5 is based on the preparation method of Example 1, and the pretreatment three-stage heating temperature and holding time are adjusted, and the specific adjustment is shown in Table 1.

[0062] Example 6

[0063] Example 6 Based on the heat treatment method of Example 1, no pretreatment was performed, and the rest of the treatment was unchanged.

[0064] Comparative Example 1-2

[0065] Comparative Example 1-2 Based on the preparation method of Example 1, the pretreatment three-stage heating temperature and holding time were adjusted, and the specific adjustments are shown in Table 1.

[0066] Comparative Example 3

[0067] Comparative Example 3 Based on Example 1, the ammonia gas was not passed through and the pretreatment was not performed, and the rest was unchanged.

[0068] Table 1 Three-stage heating temperature and time data table of Example 1-5 and Comparative Example 1-2

[0069]

[0070] Performance detection test

[0071] I. Surface hardness detection

[0072] The 2Cr3WMoV gears provided by Examples 1-6 and Comparative Examples 1-3 of the present application were polished, and then detected using a Rockwell hardness tester, with a test load of 150 kg. The detection results are shown in Table 2.

[0073] II. Hardened layer depth detection

[0074] The 2Cr3WMoV gears provided by Examples 1-6 and Comparative Examples 1-3 of the present application were cut and then inlaid and polished. A Vickers hardness tester was used with a load of 1 kg and a holding time of 10 S. From the surface of the 2Cr3WMoV gear tooth position, a point was detected every 0.1 mm in the direction perpendicular to the surface until the hardness value of the detection point was lower than 550 HV, and then the detection was stopped. The hardened layer depth was calculated, and the calculation results are shown in Table 2.

[0075] III. Core hardness detection

[0076] The 2Cr3WMoV gears provided by Examples 1-5 and Comparative Examples 1-3 of the present application were cut and then inlaid and polished. In the area without a penetration layer, a Rockwell hardness tester was used for detection with a test load of 150 kg. The detection results are shown in Table 2.

[0077] IV. Grain size grade

[0078] The 2Cr3WMoV gears provided by Examples 1-6 and Comparative Examples 1-3 of the present application were detected according to GB / T6394-2002. The detection results are shown in Table 2.

[0079] Table 2 Performance detection data table of Examples 1-6 and Comparative Examples 1-3

[0080]

[0081] As shown in Table 2, with the increase of the temperature and time of each stage in the three-stage heating, the surface hardness, hardened layer thickness, core hardness and grain size of the 2Cr3WMoV gear show a trend of first increasing and then decreasing, which may be due to the fact that, within a certain range, with the increase of the temperature and time of each stage in the three-stage heating, the dislocation defects of the 2Cr3WMoV gear increase, which can continuously improve the diffusion efficiency of carbon and nitrogen atoms, thereby continuously increasing the thickness of the hardened layer, and continuously increasing the surface hardness and core hardness of the 2Cr3WMoV gear.

[0082] When the temperature and time of each stage in the three-stage heating exceed a certain range, with the increase of the temperature and time of each stage in the three-stage heating, the 2Cr3WMoV gear is prone to generate greater internal stress, which affects the continuous penetration of carbon and nitrogen atoms, reduces the grain size and hardened layer thickness of the 2Cr3WMoV gear, and thus reduces the surface hardness and core hardness of the 2Cr3WMoV gear.

[0083] Examples 7-9

[0084] Examples 7-9 are based on the preparation method of Example 1, and the temperature and time of each stage for forming the carbonitride compound layer are adjusted, and the specific adjustments are shown in Table 3.

[0085] Comparative Examples 4-5

[0086] Comparative Examples 4-5 are based on the preparation method of Example 1, and the temperature and time of each stage for forming the carbonitride compound layer are adjusted, and the specific adjustments are shown in Table 3.

[0087] The 2Cr3WMoV gears after heat treatment of Examples 7-9 and Comparative Examples 4-5 are subjected to the above performance detection, and the test results are shown in Table 4.

[0088] Table 3 Data table of the temperature and time of each stage for forming the carbonitride compound layer of Example 1, Examples 7-9 and Comparative Examples 4-5

[0089]

[0090] Table 4 Performance detection data table of Example 1, Examples 7-9 and Comparative Examples 4-5

[0091]

[0092] As shown in Table 4, compared with Example 1, the surface hardness, hardening layer thickness, core hardness and grain size of Examples 7-9 are slightly lower than those of Example 1, the surface hardness, hardening layer thickness, core hardness and grain size of Comparative Example 4 are greatly lower than those of Example 1, and the surface hardness, hardening layer thickness, core hardness and grain size of Comparative Example 5 are equal to those of Example 1. Therefore, the heat treatment conditions of Example 1 do not need to be changed for the purpose of reducing production cost.

[0093] Examples 10-12

[0094] Examples 10-12 are prepared based on the preparation method of Example 1, and the propane flow rate and the methanol flow rate are adjusted, and the specific adjustment is shown in Table 5.

[0095] Comparative Examples 6-7

[0096] Comparative Examples 6-7 are prepared based on the preparation method of Example 1, and the propane flow rate and the methanol flow rate are adjusted, and the specific adjustment is shown in Table 5.

[0097] The 2Cr3WMoV gears of Examples 10-12 and Comparative Examples 6-7 after heat treatment are subjected to the performance test as described above, and the test results are shown in Table 6.

[0098] Table 5 Propane flow rate and methanol flow rate of Example 1, Examples 10-12 and Comparative Examples 6-7

[0099]

[0100] Table 6 Performance test data of Example 1, Examples 10-12 and Comparative Examples 6-7

[0101]

[0102] As shown in Table 6, with the continuous increase of the flow rates of propane and methanol, the surface hardness, hardening layer thickness, core hardness and grain size grade of the 2Cr3WMoV gears show a trend of first increasing and then decreasing. It is possible that, within a certain range, with the continuous increase of the flow rates of propane and methanol, the active carbon atoms generated by propane and methanol continuously penetrate into the 2Cr3WMoV gears, the thickness of the hardening layer continuously increases, and the grains continuously refine, so that the surface hardness and core hardness of the 2Cr3WMoV gears continuously increase. When the flow rates of propane and methanol exceed a certain range, with the continuous increase of the flow rates of propane and methanol, the densification rate of the carbonitride layer continuously increases, and new active carbon atoms and nitrogen atoms are difficult to penetrate, so that the thickness of the hardening layer continuously decreases, thereby reducing the surface hardness and core hardness of the 2Cr3WMoV gears.

[0103] Examples 13-15

[0104] Examples 13-15 are based on the preparation method of Example 1, and the carbon potential and ammonia flow rate during the temperature rising penetration are adjusted, and the specific adjustment is shown in Table 7.

[0105] Comparative Examples 8-9

[0106] Comparative Examples 8-9 are based on the preparation method of Example 1, and the carbon potential and ammonia flow rate during the temperature rising penetration are adjusted, and the specific adjustment is shown in Table 7.

[0107] The 2Cr3WMoV gears after heat treatment of Examples 13-15 and Comparative Examples 8-9 are subjected to performance detection as above, and the test results are shown in Table 8.

[0108] Table 7 Carbon potential and ammonia flow rate data table during temperature rising penetration of Example 1, Examples 13-15 and Comparative Examples 8-9

[0109]

[0110] Table 8 Performance detection data table of Example 1, Examples 13-15 and Comparative Examples 8-9

[0111]

[0112] As shown in Table 8, by comparing Example 1, Examples 13-15 and Comparative Examples 8-9, with the continuous increase of carbon potential and ammonia flow rate, the surface hardness, hardened layer depth, core hardness and grain size of the 2Cr3WMoV gear show a trend of first increasing and then decreasing. Within a certain range, with the continuous increase of carbon potential, the carbon and nitrogen atoms promote each other, and the carbonitride layer continuously increases, thereby increasing the thickness of the hardened layer and the grain size, thereby increasing the surface hardness and core hardness of the 2Cr3WMoV gear; when exceeding a certain range, with the continuous increase of carbon potential, the carbonitride layer is continuously densified, which hinders the penetration of new carbon and nitrogen atoms into the 2Cr3WMoV gear to form a carbonitride layer, thereby reducing the thickness of the hardened layer and the surface hardness and core hardness of the 2Cr3WMoV gear.

[0113] Within a certain range, with the continuous increase of the flow rate of ammonia, the thickness of the carbonitride layer continuously increases, the carbonitride continuously densifies, and the hardness and core hardness of the 2Cr3WMoV gear continuously increase; when exceeding a certain range, with the continuous increase of the flow rate of ammonia, the holes and loose areas of the carbonitride layer gradually increase, and the generated hardened layer also has a large number of holes and loose areas, thereby reducing the surface hardness and core hardness of the 2Cr3WMoV gear.

[0114] Examples 16-18

[0115] Examples 16-18 were based on the preparation method of Example 1, and the carbon potential and ammonia flow during the first diffusion were adjusted, and the specific adjustments are shown in Table 9.

[0116] Comparative Examples 10-11

[0117] Comparative Examples 10-11 were based on the preparation method of Example 1, and the carbon potential and ammonia flow during the first diffusion were adjusted, and the specific adjustments are shown in Table 9.

[0118] The 2Cr3WMoV gears after heat treatment of Examples 16-18 and Comparative Examples 10-11 were subjected to performance testing as above, and the test results are shown in Table 10.

[0119] Table 9 Carbon potential and ammonia flow data table during the first diffusion of Example 1, Examples 16-18 and Comparative Examples 10-11

[0120]

[0121] Table 10 Performance testing data table of Example 1, Examples 16-18 and Comparative Examples 10-11

[0122]

[0123]

[0124] As shown in Table 10, by comparing Example 1, Examples 16-18 and Comparative Examples 10-11, with the continuous increase of carbon potential and ammonia flow, the surface hardness, hardened layer depth, core hardness and grain size of the 2Cr3WMoV gear showed a trend of first increasing and then decreasing. Within a certain range, with the continuous increase of carbon potential, the carbon and nitrogen atoms promoted each other, the carbonitride layer continuously increased, thereby increasing the thickness of the hardened layer, and the grain continuously increased and refined, thereby increasing the surface hardness and core hardness of the 2Cr3WMoV gear; beyond a certain range, with the continuous increase of carbon potential, the carbonitride layer densified continuously, hindering the penetration of new carbon and nitrogen atoms into the 2Cr3WMoV gear to form a carbonitride layer, thereby reducing the thickness of the hardened layer, and thus reducing the surface hardness and core hardness of the 2Cr3WMoV gear.

[0125] Within a certain range, with the continuous increase of the flow of ammonia, the thickness of the carbonitride layer continuously increased, the carbonitride continuously densified, and the hardness and core hardness of the 2Cr3WMoV gear continuously increased; beyond a certain range, with the continuous increase of the flow of ammonia, the holes and loose areas of the carbonitride layer gradually increased, and the generated hardened layer also had a large number of holes and loose areas, thereby reducing the surface hardness and core hardness of the 2Cr3WMoV gear.

[0126] Examples 19-21

[0127] Examples 19-21 were based on the preparation method of Example 1, and the carbon potential and ammonia flow during the secondary diffusion were adjusted, and the specific adjustment was shown in Table 11.

[0128] Comparative Examples 12-13

[0129] Comparative Examples 12-13 were based on the preparation method of Example 1, and the carbon potential and ammonia flow during the secondary diffusion were adjusted, and the specific adjustment was shown in Table 11.

[0130] The 2Cr3WMoV gears after heat treatment of Examples 19-21 and Comparative Examples 12-13 were subjected to performance detection as above, and the test results were shown in Table 12.

[0131] Table 11 Carbon potential and ammonia flow data table during secondary diffusion of Example 1, Examples 19-21 and Comparative Examples 12-13

[0132]

[0133]

[0134] Table 12 Performance detection data table of Example 1, Examples 19-21 and Comparative Examples 12-13

[0135]

[0136] As shown in Table 12, by comparing Example 1, Examples 19-21 and Comparative Examples 12-13, with the continuous increase of carbon potential and ammonia flow, the surface hardness, hardened layer depth, core hardness and grain size of 2Cr3WMoV gear showed a trend of first increasing and then decreasing. Within a certain range, with the continuous increase of carbon potential, carbon and nitrogen atoms promoted each other, and the carbonitride layer continuously increased, thereby increasing the thickness of the hardened layer and the grain continuously refined, thereby increasing the surface hardness and core hardness of 2Cr3WMoV gear; beyond a certain range, with the continuous increase of carbon potential, the densification of carbonitride layer continuously accelerated, which hindered the penetration of new carbon and nitrogen atoms into 2Cr3WMoV gear to generate carbonitride layer, thereby reducing the thickness of the hardened layer, and thus reducing the surface hardness and core hardness of 2Cr3WMoV gear.

[0137] Within a certain range, as the flow of ammonia increases, the thickness of the carbonitride layer increases, the carbonitride densifies, and the hardness and core hardness of the 2Cr3WMoV gear increase; beyond a certain range, as the flow of ammonia increases, the number of pores and loose areas in the carbonitride layer gradually increases, and the hardened layer also has a large number of pores and loose areas, thereby reducing the surface hardness and core hardness of the 2Cr3WMoV gear.

[0138] Examples 22-24

[0139] Examples 22-24 are based on the preparation method of Example 1, and the quenching temperature and time are adjusted, as shown in Table 13.

[0140] Comparative Examples 14-15

[0141] Comparative Examples 14-15 are based on the preparation method of Example 1, and the quenching temperature and time are adjusted, as shown in Table 13.

[0142] The 2Cr3WMoV gears after heat treatment of Examples 22-24 and Comparative Examples 14-15 are subjected to performance testing as above, and the test results are shown in Table 14.

[0143] Table 13 Quenching temperature and time data table of Example 1, Examples 22-24 and Comparative Examples 14-15

[0144]

[0145] Table 14 Performance testing data table of Example 1, Examples 22-24 and Comparative Examples 14-15

[0146]

[0147] As shown in Table 14, by comparing Example 1, Examples 22-24 and Comparative Examples 14-15, as the quenching temperature and quenching time increase, the surface hardness, hardened layer depth, core hardness and grain size of the 2Cr3WMoV gear all show a trend of first increasing and then stabilizing. As the quenching temperature and quenching time increase, the dense carbonitride layer gradually fully transforms into a high-hardness martensite surface layer, and the dense hardened layer of the 2Cr3WMoV gear increases in depth until it stabilizes, thereby increasing the surface hardness and core hardness of the 2Cr3WMoV gear until it stabilizes.

[0148] Examples 25-27

[0149] Examples 25-27 are based on the preparation method of Example 1, and the carbon potential and ammonia flow during the second diffusion are adjusted, as shown in Table 15.

[0150] Comparative Examples 16-17

[0151] Comparative Examples 16-17 were prepared based on the preparation method of Example 1, and the carbon potential and ammonia flow during the secondary diffusion were adjusted, and the specific adjustments are shown in Table 15.

[0152] The 2Cr3WMoV gears after heat treatment of Examples 25-27 and Comparative Examples 16-17 were subjected to performance testing as above, and the test results are shown in Table 16.

[0153] Table 15 Table of tempering temperature and time data of Example 1, Examples 25-27 and Comparative Examples 16-17

[0154]

[0155] Table 16 Performance testing results of Example 1, Examples 25-27 and Comparative Examples 16-17

[0156]

[0157] As can be seen from Table 16, Examples 1, Examples 25-27 and Comparative Examples 16-17, as the tempering temperature and tempering time continuously increase, the surface hardness, hardened layer depth, core hardness and grain size of the 2Cr3WMoV gear all show a trend of first increasing and then tending to be stable. It is possible that as the tempering temperature and tempering time continuously increase, the residual dense carbonitride layer gradually fully transforms into a high-hardness martensite surface layer, and the dense hardened layer of the 2Cr3WMoV gear continuously increases in depth until it tends to be stable, thereby causing the surface hardness and core hardness of the 2Cr3WMoV gear to continuously increase until it tends to be stable.

[0158] The specific embodiments are merely illustrative of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, and as long as the modifications are within the scope of the claims of the present application, they are protected by the Patent Law.

Claims

1. A heat treatment process for 2Cr3WMoV material, characterized in that, Includes the following steps: Preheating: The 2Cr3WMoV material was preheated and kept at a constant temperature under an inert gas atmosphere; Temperature-intensified infiltration: When the temperature is raised from the preheating temperature to 745-755℃, propane and methanol are introduced, and the temperature is further raised to 860-870℃ and ammonia is introduced. The 2Cr3WMoV material is held at 860-870℃ for 210-270 minutes. First diffusion: After strong infiltration, the carbon potential is reduced, and the 2Cr3WMoV material undergoes the first diffusion, with a diffusion time of 120-180 min; Secondary diffusion: After the primary diffusion is completed, the carbon potential and ammonia flow rate are reduced, and the temperature is adjusted to 850-860℃. The 2Cr3WMoV material undergoes a second diffusion, with a diffusion time of 120-180 min. Temperature-controlled quenching: After the secondary diffusion is completed, the temperature is adjusted to 840-850℃ and held for 25-35 minutes. Then the 2Cr3WMoV material is quenched. Tempering: After quenching, the 2Cr3WMoV material is tempered, and after tempering, it is cooled to obtain the 2Cr3WMoV material. In the step of heating and strong percolation, the carbon potential is 0.95-1.05%, and the ammonia flow rate is 6-8 NL / min; In one diffusion step, the carbon potential is 0.85-0.95%; In the secondary diffusion step, the carbon potential is 0.75-0.85%, and the ammonia flow rate is 4-6 NL / min; In the step of heating and strong permeation, the flow rate of propane is 4-6 mL / min, and the flow rate of methanol is 30-50 mL / min; It also includes a pretreatment, which involves heating the 2Cr3WMoV material in three stages. The three-stage heating includes the following steps: First stage heating: heating temperature 695-705℃, holding time 25-45min; Second stage heating: heating temperature 795-805℃, holding time 30-50min; Third stage heating: heating temperature 950-1010℃, holding time 70-110min; Cooling: After the third stage of heating is completed, the 2Cr3WMoV material is cooled to obtain pretreated 2Cr3WMoV material.

2. The heat treatment process for the 2Cr3WMoV material according to claim 1, characterized in that: In the temperature-controlled quenching step, the quenching temperature is 105-115℃ and the quenching time is 8-12min.

3. The heat treatment process for the 2Cr3WMoV material according to claim 1, characterized in that: In the cleaning and tempering step, the tempering temperature is 165-175℃ and the tempering time is 230-250min.

4. 2Cr3WMoV material treated by any one of the heat treatment processes according to claims 1-3.

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