High-wear-resistance steel for heavy-duty gear and preparation method of high-wear-resistance steel

Abstract

The invention relates to high-wear-resistance heavy-duty gear steel and a preparation method thereof, and belongs to the technical field of metal materials. The preparation method comprises the following steps: S1, carrying out two-stage carburizing treatment on the steel for the heavy-duty gear at 925-935 DEG C; the two-stage carburizing treatment comprises a first strong carburizing period and a first diffusion period; s2, carrying out two-stage carbonitriding treatment on the steel for the heavy-duty gear, which is obtained in the step S1, at 845-870 DEG C; the two-stage carbonitriding treatment comprises a second strong nitriding period and a second diffusion period; s3, carrying out high-temperature tempering treatment on the steel for the heavy-duty gear obtained in S2; s4, quenching treatment is conducted on the steel, obtained in the S3, for the heavy-duty gear; and S5, subzero treatment and low-temperature tempering treatment are conducted on the heavy-duty gear steel obtained in the step S4, and the high-wear-resistance heavy-duty gear steel is obtained. The average friction coefficient of the high-wear-resistance steel for the heavy-duty gear ranges from 0.13 to 0.15, and the wear volume ranges from 0.23 mm < 3 > to 0.26 mm < 3 >; and compared with the steel for the heavy-duty gear prepared by the existing process, the wear resistance is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metal materials, and in particular relates to a high wear-resistant heavy-duty gear steel and a preparation method thereof. Background Art

[0002] With the rapid development of industrial technology, heavy-duty gears are key components in transmission systems, and their performance is directly related to the working efficiency, operating stability and service life of mechanical equipment. Under extreme working conditions, heavy-duty gears face severe friction and wear challenges, resulting in reduced transmission efficiency or even failure. Traditional heat treatment processes for heavy-duty gear steel can no longer meet the growing demand for wear resistance.

[0003] Traditional heavy-duty gear steel is mainly improved in wear resistance through a single carburizing or nitriding heat treatment process. The carburizing heat treatment process uses a high-temperature carbon-rich environment to allow active carbon atoms to penetrate into the surface of the steel, forming a high-carbon carburized layer structure, which gives the surface higher hardness and toughness. However, the carburizing process still faces problems such as insufficient wear resistance in the application of heavy-duty gear steel. The nitriding heat treatment process can form a nitrogen-rich hardened layer at a lower temperature, improving the surface hardness and wear resistance, but there are problems such as a thin and brittle carburized layer. Therefore, the development of a new heat treatment process method for heavy-duty gear steel has significantly improved the wear resistance of heavy-duty gear steel, which has become an important way to improve the overall performance of mechanical equipment, reduce maintenance costs, and extend service life. This is of great significance for promoting the development of my country's high-end equipment manufacturing industry. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a highly wear-resistant heavy-duty gear steel and a preparation method thereof, which combines carburizing treatment and carbonitriding treatment to form a high-carbon carburizing layer structure, and introduces carbon and nitrogen elements to form a more complex compound layer; in addition, it also combines high-temperature tempering, high-temperature oil quenching, deep cold treatment and low-temperature tempering and other processes to perform organizational regulation. Compared with the heavy-duty gear steel prepared by the existing process, the friction coefficient is reduced by more than 70% and the wear volume is reduced by more than 80%.

[0005] The first object of the present invention is to provide a method for preparing high wear-resistant heavy-duty gear steel, comprising the following steps:

[0006] S1. Carburizing the heavy-duty gear steel at 925° C.-935° C. in two stages; the two-stage carburizing treatment includes a first intensive carburizing period and a first diffusion period;

[0007] S2, subjecting the heavy-duty gear steel obtained in S1 to a two-stage carbonitriding treatment at 845° C.-870° C.; the two-stage carbonitriding treatment includes a second strong permeation period and a second diffusion period;

[0008] S3, subjecting the heavy-duty gear steel obtained in S2 to high-temperature tempering treatment;

[0009] S4, quenching the heavy-duty gear steel obtained in S3;

[0010] S5. Perform deep cryogenic treatment and low temperature tempering treatment on the heavy-duty gear steel obtained in S4 to obtain the highly wear-resistant heavy-duty gear steel.

[0011] In one embodiment of the present invention, in S1, the element composition and mass percentage of the heavy-duty gear steel are: C 0.18%-0.19%, Si 0.32%-0.37%, Mn 0.56%-0.60%, P 0-0.008%, S 0-0.006%, Cr 1.58%-1.63%, Ni 4.42%-4.49%, W 1.12%-1.18%, and the remainder is other inevitable impurities and iron.

[0012] In one embodiment of the present invention, in S1, the carbon potential of the first strong infiltration period is 1.5wt%-1.6wt%, and the time is 185h-222h; the carbon potential of the first diffusion period is 0.9wt%-1.0wt%, and the time is 35h-48h.

[0013] In one embodiment of the present invention, in S2, the carbon potential of the second strong infiltration period is 1.1wt%-1.2wt%, the time is 24h-28h, and the ammonia flow rate is 5L / min-7L / min; the carbon potential of the second diffusion period is 0.9wt%-1.0wt%, the time is 6h-8h, and the ammonia flow rate is 5L / min-7L / min.

[0014] In one embodiment of the present invention, in S3, the high temperature tempering treatment is performed at a temperature of 640°C-645°C, for a time of 3h-4h, and for 1-2 times.

[0015] In one embodiment of the present invention, in S3, the high temperature tempering treatment is performed under nitrogen protection.

[0016] In one embodiment of the present invention, in S4, the quenching treatment temperature is 820°C-825°C, the holding time is 60min-75min, the carbon potential is 0.8wt%-0.9wt%, and the method is oil quenching.

[0017] In one embodiment of the present invention, in S5, the temperature of the deep cryogenic treatment is -196°C to -150°C, and the time is 1h-2h, ensuring that the volume fraction of retained austenite in the hardened layer drops below 3.0% to improve the wear resistance of heavy-duty gear steel.

[0018] In one embodiment of the present invention, in S5, the low temperature tempering treatment is performed at a temperature of 180°C-200°C and for a time of 3h-4h.

[0019] The second object of the present invention is to provide a high wear-resistant heavy-duty gear steel prepared by the method described above.

[0020] The technical solution of the present invention has the following advantages over the prior art:

[0021] (1) The preparation method described in the present invention combines carburizing treatment and carbonitriding treatment, thereby increasing the carbon concentration in the surface layer to promote the formation of carbides, and introducing nitrogen atoms in the surface layer to obtain nitrogen-containing martensite, forming a more complex compound layer, and utilizing the precipitation strengthening of high-density, large-size carbides and the solid solution strengthening effect of carbon and nitrogen atoms to effectively improve the wear resistance of heavy-duty gear steel.

[0022] (2) The preparation method described in the present invention does not perform high-temperature tempering between carburizing and carbonitriding. The high-density dislocations after carburizing cooling can be used as diffusion channels for carbon and nitrogen atoms, which significantly promotes the penetration of carbon and nitrogen elements during the carbonitriding process. The microstructure is controlled by combining high-temperature tempering, high-temperature oil quenching, deep cryogenic treatment and low-temperature tempering after carbonitriding, and a microstructure of needle-shaped martensite + carbide + a small amount of nitride + a very small amount of residual austenite is obtained on the surface.

[0023] (3) The average friction coefficient of the high wear-resistant heavy-duty gear steel described in the present invention is 0.13-0.15, and the wear volume is 0.23mm 3 -0.26mm 3 Compared with heavy-duty gear steel produced by existing processes, the average friction coefficient is reduced by 71.2%-75.0%, the wear volume is reduced by 80.3%-82.6%, and the wear resistance is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0025] Figure 1 This is the wear surface morphology of the high wear-resistant heavy-duty gear steel prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with specific embodiments so that those skilled in the art can better understand the present invention and implement it. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. It should be understood that the specific embodiments are only used to explain the present invention, but the embodiments are not intended to limit the present invention.

[0027] In the present invention, unless otherwise explained, technical and scientific terms used in the present invention have the same meanings as commonly understood by those skilled in the art to which the present invention belongs.

[0028] In the present invention, unless otherwise stated, the term "and / or" used in the present invention includes any and all combinations of one or more of the associated listed items.

[0029] In the present invention, unless otherwise stated, the experimental methods used in the embodiments of the present invention are conventional methods unless otherwise stated, and the materials, reagents, etc. used are all commercially available unless otherwise stated.

[0030] In the present invention, unless otherwise specified, the element composition and mass percentage of the heavy-duty gear steel 18Cr2Ni4WA used in the embodiments of the present invention are C 0.185%, Si 0.35%, Mn 0.58%, P0.004%, S0.003%, Cr 1.60%, Ni 4.45%, W 1.15%, and the balance are other inevitable impurities and iron.

[0031] Example 1

[0032] The highly wear-resistant heavy-duty gear steel and the preparation method thereof of the present invention specifically comprise the following steps:

[0033] S1. Carburizing heavy-duty gear steel 18Cr2Ni4WA at 925°C in two stages: intensive carburizing and diffusion carburizing. The carbon potential in the intensive carburizing stage is 1.6wt%, the time is 222h, and the carbon potential in the diffusion stage is 1.0wt%, the time is 48h. After carburizing, the steel is air-cooled to room temperature.

[0034] S2. The heavy-duty gear steel 18Cr2Ni4WA was subjected to a two-stage carbonitriding treatment at 845°C, i.e., a strong infiltration period and a diffusion period. The carbon potential in the strong infiltration period was 1.2wt%, the time was 28h, and the ammonia flow rate was 7L / min. The carbon potential in the diffusion period was 1.0wt%, the time was 8h, and the ammonia flow rate was 7L / min. After the carbonitriding treatment, the steel was air-cooled to room temperature.

[0035] S3. Under nitrogen atmosphere, the heavy-duty gear steel 18Cr2Ni4WA was subjected to two high-temperature tempering treatments at a temperature of 640°C and a time of 4 hours;

[0036] S4. Heat the heavy-duty gear steel 18Cr2Ni4WA to 820°C and keep it at that temperature for 75 minutes. During the heat preservation process, the carbon potential is 0.9wt%, and then immediately oil quench it to room temperature;

[0037] S5. The heavy-duty gear steel 18Cr2Ni4WA is subjected to cryogenic treatment and low-temperature tempering treatment in sequence to obtain high wear-resistant heavy-duty gear steel. The cryogenic treatment temperature is -150°C for 2 hours, and the low-temperature tempering treatment temperature is 180°C for 4 hours.

[0038] Example 2

[0039] The highly wear-resistant heavy-duty gear steel and the preparation method thereof of the present invention specifically comprise the following steps:

[0040] S1. Carburizing heavy-duty gear steel 18Cr2Ni4WA at 935°C in two stages: intensive carburizing and diffusion carburizing. The carbon potential in the intensive carburizing stage is 1.5wt%, the time is 185h, and the carbon potential in the diffusion stage is 0.9wt%, the time is 35h. After carburizing, the steel is air-cooled to room temperature.

[0041] S2. The heavy-duty gear steel 18Cr2Ni4WA was subjected to a two-stage carbonitriding treatment at 870°C, i.e., a strong infiltration period and a diffusion period. The carbon potential in the strong infiltration period was 1.1wt%, the time was 24h, the ammonia flow rate was 5L / min, the carbon potential in the diffusion period was 0.9wt%, the time was 6h, the ammonia flow rate was 5L / min, and the carbonitriding treatment was followed by air cooling to room temperature.

[0042] S3. In nitrogen atmosphere, the heavy-duty gear steel 18Cr2Ni4WA was subjected to a high-temperature tempering treatment at 645°C for 3 hours.

[0043] S4, heating the heavy-duty gear steel 18Cr2Ni4WA to 825°C and holding the temperature for 60 min, during which the carbon potential is 0.8wt%, and then immediately oil quenching to room temperature;

[0044] S5. The heavy-duty gear steel 18Cr2Ni4WA is subjected to cryogenic treatment and low-temperature tempering treatment in sequence to obtain high wear-resistant heavy-duty gear steel. The cryogenic treatment temperature is -196°C for 1 hour, and the low-temperature tempering treatment temperature is 200°C for 3 hours.

[0045] Example 3

[0046] The highly wear-resistant heavy-duty gear steel and the preparation method thereof of the present invention specifically comprise the following steps:

[0047] S1. Carburizing heavy-duty gear steel 18Cr2Ni4WA at 930°C in two stages: intensive carburizing and diffusion carburizing. The carbon potential in the intensive carburizing stage is 1.6wt%, the time is 192h, and the carbon potential in the diffusion stage is 1.0wt%, the time is 44h. After carburizing, the steel is air-cooled to room temperature.

[0048] S2. The heavy-duty gear steel 18Cr2Ni4WA was subjected to a two-stage carbonitriding treatment at 860°C, i.e., a strong infiltration period and a diffusion period. The carbon potential in the strong infiltration period was 1.2wt%, the time was 24h, and the ammonia flow rate was 6L / min. The carbon potential in the diffusion period was 1.0wt%, the time was 7h, and the ammonia flow rate was 6L / min. After the carbonitriding treatment, the steel was air-cooled to room temperature.

[0049] S3. Under nitrogen atmosphere, the heavy-duty gear steel 18Cr2Ni4WA was subjected to two high-temperature tempering treatments at a temperature of 640°C and a time of 3.5 h.

[0050] S4, heating the heavy-duty gear steel 18Cr2Ni4WA to 825°C and holding the temperature for 65 minutes, during which the carbon potential is 0.9wt%, and then immediately oil quenching to room temperature;

[0051] S5. The heavy-duty gear steel 18Cr2Ni4WA is subjected to cryogenic treatment and low-temperature tempering treatment in sequence to obtain high wear-resistant heavy-duty gear steel. The cryogenic treatment temperature is -196°C for 1 hour, and the low-temperature tempering treatment temperature is 190°C for 3.5 hours.

[0052] Comparative Example 1

[0053] The method is basically the same as Example 1, except that the temperature of the two-stage carburizing treatment is adjusted to 915° C., and specifically includes the following steps:

[0054] S1. Carburizing heavy-duty gear steel 18Cr2Ni4WA at 915°C in two stages: intensive carburizing and diffusion carburizing. The carbon potential in the intensive carburizing stage is 1.6wt%, the time is 222h, and the carbon potential in the diffusion stage is 1.0wt%, the time is 48h. After carburizing, the steel is air-cooled to room temperature.

[0055] S2. The heavy-duty gear steel 18Cr2Ni4WA was subjected to a two-stage carbonitriding treatment at 845°C, i.e., a strong infiltration period and a diffusion period. The carbon potential in the strong infiltration period was 1.2wt%, the time was 28h, and the ammonia flow rate was 7L / min. The carbon potential in the diffusion period was 1.0wt%, the time was 8h, and the ammonia flow rate was 7L / min. After the carbonitriding treatment, the steel was air-cooled to room temperature.

[0056] S3. Under nitrogen atmosphere, the heavy-duty gear steel 18Cr2Ni4WA was subjected to two high-temperature tempering treatments at a temperature of 640°C and a time of 4 hours;

[0057] S4. Heat the heavy-duty gear steel 18Cr2Ni4WA to 820°C and keep it at that temperature for 75 minutes. During the heat preservation process, the carbon potential is 0.9wt%, and then immediately oil quench it to room temperature;

[0058] S5. The heavy-duty gear steel 18Cr2Ni4WA is subjected to cryogenic treatment and low-temperature tempering treatment in sequence to obtain high wear-resistant heavy-duty gear steel. The cryogenic treatment temperature is -150°C for 2 hours, and the low-temperature tempering treatment temperature is 180°C for 4 hours.

[0059] Comparative Example 2

[0060] The method is basically the same as Example 1, except that the temperature of the two-stage carbonitriding treatment is adjusted to 830° C., and specifically includes the following steps:

[0061] S1. Carburizing heavy-duty gear steel 18Cr2Ni4WA at 925°C in two stages: intensive carburizing and diffusion carburizing. The carbon potential in the intensive carburizing stage is 1.6wt%, the time is 222h, and the carbon potential in the diffusion stage is 1.0wt%, the time is 48h. After carburizing, the steel is air-cooled to room temperature.

[0062] S2. The heavy-duty gear steel 18Cr2Ni4WA was subjected to a two-stage carbonitriding treatment at 830°C, i.e., a strong infiltration period and a diffusion period. The carbon potential in the strong infiltration period was 1.2wt%, the time was 28h, and the ammonia flow rate was 7L / min. The carbon potential in the diffusion period was 1.0wt%, the time was 8h, and the ammonia flow rate was 7L / min. After the carbonitriding treatment, the steel was air-cooled to room temperature.

[0063] S3. Under nitrogen atmosphere, the heavy-duty gear steel 18Cr2Ni4WA was subjected to two high-temperature tempering treatments at a temperature of 640°C and a time of 4 hours;

[0064] S4. Heat the heavy-duty gear steel 18Cr2Ni4WA to 820°C and keep it at that temperature for 75 minutes. During the heat preservation process, the carbon potential is 0.9wt%, and then immediately oil quench it to room temperature;

[0065] S5. The heavy-duty gear steel 18Cr2Ni4WA is subjected to cryogenic treatment and low-temperature tempering treatment in sequence to obtain high wear-resistant heavy-duty gear steel. The cryogenic treatment temperature is -150°C for 2 hours, and the low-temperature tempering treatment temperature is 180°C for 4 hours.

[0066] Comparative Example 3

[0067] The method is basically the same as Example 1, except that the two-stage carbonitriding treatment is replaced by a two-stage nitriding treatment, which specifically includes the following steps:

[0068] S1. Carburizing heavy-duty gear steel 18Cr2Ni4WA at 925°C in two stages: intensive carburizing and diffusion carburizing. The carbon potential in the intensive carburizing stage is 1.6wt%, the time is 222h, and the carbon potential in the diffusion stage is 1.0wt%, the time is 48h. After carburizing, the steel is air-cooled to room temperature.

[0069] S2. The heavy-duty gear steel 18Cr2Ni4WA was subjected to two-stage nitriding treatment at 845°C, namely, the intensive nitriding period and the diffusion period. The intensive nitriding period lasted for 28 hours, the ammonia flow rate was 7L / min, the diffusion period lasted for 8 hours, the ammonia flow rate was 7L / min, and the nitriding treatment was followed by air cooling to room temperature.

[0070] S3. Under nitrogen atmosphere, the heavy-duty gear steel 18Cr2Ni4WA was subjected to two high-temperature tempering treatments at a temperature of 640°C and a time of 4 hours;

[0071] S4. Heat the heavy-duty gear steel 18Cr2Ni4WA to 820°C and keep it at that temperature for 75 minutes. During the heat preservation process, the carbon potential is 0.9wt%, and then immediately oil quench it to room temperature;

[0072] S5. The heavy-duty gear steel 18Cr2Ni4WA is subjected to cryogenic treatment and low-temperature tempering treatment in sequence to obtain high wear-resistant heavy-duty gear steel. The cryogenic treatment temperature is -150°C for 2 hours, and the low-temperature tempering treatment temperature is 180°C for 4 hours.

[0073] Comparative Example 4

[0074] The method is basically the same as Example 1, except that a high-temperature tempering treatment is performed between the two-stage carburizing treatment and the two-stage carbonitriding treatment, specifically comprising the following steps:

[0075] S1. Carburizing heavy-duty gear steel 18Cr2Ni4WA at 925°C in two stages: intensive carburizing and diffusion carburizing. The carbon potential in the intensive carburizing stage is 1.6wt%, the time is 222h, and the carbon potential in the diffusion stage is 1.0wt%, the time is 48h. After carburizing, the steel is air-cooled to room temperature.

[0076] S2. In nitrogen atmosphere, the heavy-duty gear steel 18Cr2Ni4WA was subjected to a high-temperature tempering treatment at 640°C for 4 hours.

[0077] S3. The heavy-duty gear steel 18Cr2Ni4WA was subjected to a two-stage carbonitriding treatment at 845°C, i.e., a strong infiltration period and a diffusion period. The carbon potential in the strong infiltration period was 1.2wt%, the time was 28h, and the ammonia flow rate was 7L / min. The carbon potential in the diffusion period was 1.0wt%, the time was 8h, and the ammonia flow rate was 7L / min. After the carbonitriding treatment, the steel was air-cooled to room temperature.

[0078] S4. Under nitrogen atmosphere, the heavy-duty gear steel 18Cr2Ni4WA was subjected to two high-temperature tempering treatments at a temperature of 640°C and a time of 4 hours;

[0079] S5. Heat the heavy-duty gear steel 18Cr2Ni4WA to 820°C and keep it at that temperature for 75 minutes. During the heat preservation process, the carbon potential is 0.9wt%, and then immediately oil quench it to room temperature;

[0080] S6. The heavy-duty gear steel 18Cr2Ni4WA is subjected to cryogenic treatment and low-temperature tempering treatment in sequence to obtain high wear-resistant heavy-duty gear steel. The cryogenic treatment temperature is -150°C for 2 hours, and the low-temperature tempering treatment temperature is 180°C for 4 hours.

[0081] Comparative Example 5

[0082] The method is basically the same as Example 1, except that the temperature of the cryogenic treatment is adjusted to -140°C. The method specifically comprises the following steps:

[0083] S1. Carburizing heavy-duty gear steel 18Cr2Ni4WA at 925°C in two stages: intensive carburizing and diffusion carburizing. The carbon potential in the intensive carburizing stage is 1.6wt%, the time is 222h, and the carbon potential in the diffusion stage is 1.0wt%, the time is 48h. After carburizing, the steel is air-cooled to room temperature.

[0084] S2. The heavy-duty gear steel 18Cr2Ni4WA was subjected to a two-stage carbonitriding treatment at 845°C, i.e., a strong infiltration period and a diffusion period. The carbon potential in the strong infiltration period was 1.2wt%, the time was 28h, and the ammonia flow rate was 7L / min. The carbon potential in the diffusion period was 1.0wt%, the time was 8h, and the ammonia flow rate was 7L / min. After the carbonitriding treatment, the steel was air-cooled to room temperature.

[0085] S3. Under nitrogen atmosphere, the heavy-duty gear steel 18Cr2Ni4WA was subjected to two high-temperature tempering treatments at a temperature of 640°C and a time of 4 hours;

[0086] S4. Heat the heavy-duty gear steel 18Cr2Ni4WA to 820°C and keep it at that temperature for 75 minutes. During the heat preservation process, the carbon potential is 0.9wt%, and then immediately oil quench it to room temperature;

[0087] S5. The heavy-duty gear steel 18Cr2Ni4WA is subjected to cryogenic treatment and low-temperature tempering treatment in sequence to obtain high wear-resistant heavy-duty gear steel. The cryogenic treatment temperature is -140°C for 2 hours, and the low-temperature tempering treatment temperature is 180°C for 4 hours.

[0088] Comparative Example 6

[0089] The method is basically the same as Example 1, except that no two-stage carbonitriding treatment is performed between the two-stage carburizing treatment and the high-temperature tempering treatment, and specifically comprises the following steps:

[0090] S1. Carburizing heavy-duty gear steel 18Cr2Ni4WA at 925°C in two stages: intensive carburizing and diffusion carburizing. The carbon potential in the intensive carburizing stage is 1.6wt%, the time is 222h, and the carbon potential in the diffusion stage is 1.0wt%, the time is 48h. After carburizing, the steel is air-cooled to room temperature.

[0091] S2. Under nitrogen atmosphere, the heavy-duty gear steel 18Cr2Ni4WA was subjected to two high-temperature tempering treatments at a temperature of 640°C and a time of 4 hours;

[0092] S3, heating the heavy-duty gear steel 18Cr2Ni4WA to 820°C and holding it for 75 minutes, during which the carbon potential is 0.9wt%, and then immediately oil quenching it to room temperature;

[0093] S4. The heavy-duty gear steel 18Cr2Ni4WA is subjected to deep cryogenic treatment and low-temperature tempering treatment in sequence to obtain high wear-resistant heavy-duty gear steel. The deep cryogenic treatment temperature is -150°C for 2 hours, and the low-temperature tempering treatment temperature is 180°C for 4 hours.

[0094] Test Example 1

[0095] The high wear-resistant heavy-duty gear steel of Example 1 was characterized, and the wear surface morphology after the wear resistance test was as follows: Figure 1 As shown. Figure 1 It can be seen that the surface of the test area is smooth and the wear marks are fine. There are no obvious typical wear features such as plowing, peeling or plastic deformation, showing a uniform and delicate microstructure.

[0096] Test Example 2

[0097] The wear resistance (average friction coefficient and wear volume) of the heavy-duty gear steel of Examples 1-3 and Comparative Examples 1-6 was tested with reference to the standard test "GB / T 12444-2006 Metallic Material Wear Test Method Test Ring-Test Block Sliding Wear Test" and the like.

[0098] Table 1 shows the final measured wear resistance of heavy-duty gear steel:

[0099] Table 1

[0100] Sample Average friction coefficient <![CDATA[Wear volume (mm 3 )]]> Example 1 0.15 0.26 Example 2 0.13 0.23 Example 3 0.14 0.24 Comparative Example 1 0.18 0.38 Comparative Example 2 0.18 0.34 Comparative Example 3 0.25 0.57 Comparative Example 4 0.22 0.48 Comparative Example 5 0.18 0.31 Comparative Example 6 0.52 1.32

[0101] It can be seen from Table 1 that the high wear-resistant heavy-duty gear steel obtained in the embodiment has good wear resistance, an average friction coefficient of 0.13-0.15, and a wear volume of 0.23 mm 3 -0.26mm 3 .

[0102] Comparing Example 1 with Comparative Example 1, it can be seen that the average friction coefficient and wear volume of the heavy-duty gear steel in Comparative Example 1 are higher than those in Example 1. This is because the temperature of the two-stage carburizing treatment in Comparative Example 1 is lower than that in Example 1, and the carbon atoms are not fully diffused, resulting in a low number density of large-sized carbides on the surface and a weak solid solution strengthening effect of carbon atoms, and the wear resistance is significantly reduced.

[0103] Comparison of Example 1 and Comparative Example 2 shows that the average friction coefficient and wear volume of the heavy-duty gear steel in Comparative Example 2 are higher than those in Example 1. This is because the temperature of the carbonitriding treatment in the two stages of Comparative Example 2 is lower than that in Example 1, and the carbon and nitrogen atoms are not fully diffused, resulting in a low number density of large-sized carbides in the surface layer and a weak solid solution strengthening effect of carbon and nitrogen atoms, and the wear resistance is significantly reduced.

[0104] Comparison of Example 1 and Comparative Example 3 shows that the average friction coefficient and wear volume of the heavy-duty gear steel in Comparative Example 3 are higher than those in Example 1. This is because the two-stage carbonitriding treatment is replaced by a two-stage nitriding treatment in Comparative Example 3, and the carbon atoms are not fully diffused, resulting in a low number density of large-sized carbides on the surface and a weak solid solution strengthening effect of carbon atoms, and the wear resistance is significantly reduced.

[0105] Comparison of Example 1 and Comparative Example 4 shows that the average friction coefficient and wear volume of the heavy-duty gear steel in Comparative Example 4 are higher than those in Example 1. This is because in Comparative Example 4, a high-temperature tempering treatment is performed between the carburizing treatment and the carbonitriding treatment, resulting in a decrease in the dislocation density after carburizing cooling, a slow diffusion of carbon and nitrogen elements during the carbonitriding process, a low number density of large-sized carbides on the surface, and a weak solid solution strengthening effect of carbon and nitrogen atoms, resulting in a significant decrease in wear resistance.

[0106] Comparison of Example 1 and Comparative Example 5 shows that the average friction coefficient and wear volume of the heavy-duty gear steel in Comparative Example 5 are higher than those in Example 1. This is because the temperature of the cryogenic treatment in Comparative Example 5 is higher than that in Example 1, the volume fraction of retained austenite in the hardened layer does not drop below 3.0%, and the wear resistance is significantly reduced.

[0107] Comparing Examples 1-3 and Comparative Example 6, it can be seen that the average friction coefficient of the heavy-duty gear steel prepared in the examples is reduced by 71.2%-75.0%, the wear volume is reduced by 80.3%-82.6%, and the wear resistance is greatly improved. This is because Examples 1-3 combine carburizing treatment with carbonitriding treatment, increase the surface carbon concentration to promote carbide formation, and introduce nitrogen atoms to obtain nitrogen-containing martensite in the surface layer, forming a more complex compound layer, which effectively improves the wear resistance of the heavy-duty gear steel.

[0108] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for preparing high wear-resistant heavy-duty gear steel, characterized in that: The following steps are involved: S1. Carburizing the heavy-duty gear steel at 925° C.-935° C. in two stages; the two-stage carburizing treatment includes a first intensive carburizing period and a first diffusion period; S2, subjecting the heavy-duty gear steel obtained in S1 to a two-stage carbonitriding treatment at 845° C.-870° C.; the two-stage carbonitriding treatment includes a second strong permeation period and a second diffusion period; S3, subjecting the heavy-duty gear steel obtained in S2 to high-temperature tempering treatment; S4, quenching the heavy-duty gear steel obtained in S3; S5. Perform deep cryogenic treatment and low temperature tempering treatment on the heavy-duty gear steel obtained in S4 to obtain the highly wear-resistant heavy-duty gear steel.

2. The method for preparing high wear-resistant heavy-duty gear steel according to claim 1, characterized in that: In S1, the element composition and mass percentage of the heavy-duty gear steel are: C 0.18%-0.19%, Si 0.32%-0.37%, Mn0.56%-0.60%, P 0-0.008%, S 0-0.006%, Cr 1.58%-1.63%, Ni 4.42%-4.49%, W1.12%-1.18%, and the remainder is other inevitable impurities and iron.

3. The method for preparing high wear-resistant heavy-duty gear steel according to claim 1, characterized in that: In S1, the carbon potential of the first strong infiltration period is 1.5wt%-1.6wt%, and the time is 185h-222h; the carbon potential of the first diffusion period is 0.9wt%-1.0wt%, and the time is 35h-48h.

4. The method for preparing high wear-resistant heavy-duty gear steel according to claim 1, characterized in that: In S2, the carbon potential of the second strong infiltration period is 1.1wt%-1.2wt%, the time is 24h-28h, and the ammonia flow rate is 5L / min-7L / min; the carbon potential of the second diffusion period is 0.9wt%-1.0wt%, the time is 6h-8h, and the ammonia flow rate is 5L / min-7L / min.

5. The method for preparing high wear-resistant heavy-duty gear steel according to claim 1, characterized in that: In S3, the high temperature tempering treatment is performed at a temperature of 640°C-645°C, for a time of 3h-4h, and for 1-2 times.

6. The method for preparing high wear-resistant heavy-duty gear steel according to claim 1, characterized in that: In S3, the high temperature tempering treatment is performed under nitrogen protection.

7. The method for preparing high wear-resistant heavy-duty gear steel according to claim 1, characterized in that: In S4, the quenching treatment temperature is 820°C-825°C, the holding time is 60min-75min, the carbon potential is 0.8wt%-0.9wt%, and the method is oil quenching.

8. The method for preparing high wear-resistant heavy-duty gear steel according to claim 1, characterized in that: In S5, the temperature of the deep cryogenic treatment is -196°C to -150°C, and the time is 1h-2h.

9. The method for preparing high wear-resistant heavy-duty gear steel according to claim 1, characterized in that: In S5, the low temperature tempering treatment is performed at a temperature of 180°C-200°C and for a time of 3h-4h.

10. A high wear-resistant heavy-duty gear steel prepared by the method according to any one of claims 1 to 9.

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