42CrMo carburizing and quenching and medium-frequency induction quenching process

Abstract

The invention discloses a 42CrMo carburizing and quenching and medium-frequency induction quenching process. The process comprises the following steps: S1, carrying out carburizing and quenching treatment on a 42CrMo shaft; s2, performing high-temperature tempering treatment on the shaft; s3, the shaft is subjected to medium-frequency induction quenching treatment; and S4, carrying out low-temperature tempering treatment on the shaft. According to the carburizing and quenching treatment, the carbon content of the surface of the shaft is increased by accurately controlling heating, strong carburizing, diffusion, cooling, temperature equalizing and quenching parameters; nitrogen protection is adopted for high-temperature tempering treatment, surface carbide is refined, and a core structure is converted into tempered sorbite; the surface structure is further refined through medium-frequency induction quenching, and the surface hardness is enhanced; and the size stability is guaranteed through low-temperature tempering. The method can effectively refine the infiltrated layer structure on the shaft surface, improve the surface hardness and wear resistance, and optimize the hardness gradient, the core structure is a fine tempered sorbite structure, the bending resistance is higher, and the comprehensive performance is higher than that of a shaft product obtained through a low-carbon alloy steel carburizing and quenching process and a medium-carbon alloy steel quenching and tempering process and an induction quenching process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal material heat treatment, and particularly relates to a 42CrMo carburizing quenching and medium-frequency induction quenching process. BACKGROUND

[0002] As the core component of mechanical transmission system, the performance of shaft parts directly affects the running stability and service life of equipment. At present, the mainstream heat treatment process of shaft parts mainly has two kinds: one is low-carbon alloy steel carburizing quenching process, which can improve the surface hardness and wear resistance of the part, but the core hardness is difficult to control with the increase of alloy content, and the high core hardness easily leads to the decrease of the bending limit of the shaft, and the low-carbon martensite organization makes the overall toughness of the shaft insufficient; the other is medium-carbon alloy steel quenching and tempering + induction quenching process, and the core of the tempering sorbite organization has better comprehensive performance, but the surface carbon content is limited, which leads to insufficient surface wear resistance and strength, and the service life is limited.

[0003] Under the complex working conditions of high impact and high wear resistance, the above two processes cannot meet the dual requirements of high strength and high wear resistance on the surface and high toughness in the core at the same time. Therefore, it is urgent to develop a new type of heat treatment process to solve the defects of the prior art and realize the optimal matching of the internal and external performance of the shaft parts. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art, and to provide a 42CrMo carburizing quenching and medium-frequency induction quenching process. Through the composite heat treatment method, the high hardness and high wear resistance of the part surface are ensured, the core high toughness is ensured, and the internal and external organizations are refined, the comprehensive performance of the part is improved, and the use requirements under complex working conditions are met.

[0005] The present application is realized by the following technical scheme: a 42CrMo carburizing quenching and medium-frequency induction quenching process, comprising the following steps: S1, carburizing quenching treatment is performed on the 42CrMo shaft; S2, high-temperature tempering treatment is performed on the shaft; S3, medium-frequency induction quenching treatment is performed on the shaft; S4, low-temperature tempering treatment is performed on the shaft.

[0006] Further, the carburizing quenching treatment of step S1 specifically comprises the following steps: S11, the shaft is controlled to be heated to 920 DEG C, and strong carburizing treatment is performed, the carbon potential is controlled to be 1.2, and the treatment time is 4h; S12, isothermal diffusion treatment is performed on the shaft at 920 DEG C, the carbon potential is controlled to be 0.8, and the treatment time is 2h; S13, the shaft is cooled to 840 DEG C, and the carbon potential is controlled to be 0.8 during the cooling stage; S14: homogenizing the shaft after cooling, homogenizing the shaft for 30 min, and controlling the carbon potential to 0.8; S15: quenching the shaft.

[0007] In step S15, quenching is performed using quenching oil, the quenching oil temperature is 60 DEG C, and the cooling time is 30 min.

[0008] In step S2, the tempering temperature is 600-630 DEG C, the tempering time is 2-4 h, and fast cooling to 100 DEG C is performed to discharge the furnace.

[0009] In step S2, the cooling mode of high-temperature tempering is furnace fast cooling.

[0010] In step S2, nitrogen protection is adopted during the tempering heating, holding and cooling processes to prevent surface oxidation.

[0011] In step S3, the medium-frequency induction quenching adopts a scanning heating quenching mode, and the shaft outer surface and spline parts are treated.

[0012] In step S3, the medium-frequency induction quenching parameters are as follows: power 40 KW, frequency 6 KHz, and scanning speed F150.

[0013] In step S4, the process parameters of low-temperature tempering are as follows: tempering temperature 180 DEG C, and holding time 2 h.

[0014] In step S4, the cooling mode after low-temperature tempering is air cooling to room temperature.

[0015] The present application has the following advantages: the 42CrMo carburizing and quenching and medium-frequency induction quenching process of the present application sequentially comprises four core steps of carburizing and quenching treatment, high-temperature tempering treatment, medium-frequency induction quenching treatment and low-temperature tempering treatment, the carburizing and quenching treatment improves the carbon content on the shaft surface by precisely controlling the heating, strong penetration, diffusion, cooling, homogenizing and quenching parameters; the high-temperature tempering treatment adopts nitrogen protection, refines the surface carbide and converts the core structure to tempered sorbite; the medium-frequency induction quenching further refines the surface structure and strengthens the surface hardness; and the low-temperature tempering guarantees the dimensional stability. The present application realizes good matching of high hardness, high wear resistance on the 42CrMo shaft surface and high toughness in the core, the hardening layer depth is more than 2 mm, the comprehensive performance is better than that of the existing low-carbon alloy steel carburizing and quenching and medium-carbon alloy steel quenching and tempering + induction quenching process, is suitable for complex working conditions with high impact and high wear resistance, and has a wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings, which are part of the specification, serve to further illustrate the application and, to the extent that they are to be taken as illustrative of the application, together with the description, serve to explain the application, but are not to be construed as limiting the application in any way. It is apparent that the accompanying drawings, which are described below, are only some embodiments, and other drawings can be obtained from these drawings by those of ordinary skill in the art without creative effort.

[0017] In the drawings: Figure 1 is a process flow chart of carburizing and quenching + medium frequency induction quenching provided by an embodiment of the application; Figure 2 is a process flow chart of carburizing and quenching of low-carbon alloy steel provided by a comparative example 1 of the application; Figure 3 is a process flow chart of quenching and tempering + induction quenching of medium-carbon alloy steel in a comparative example 2 of the application.

[0018] It should be noted that these drawings and written descriptions are not intended to limit the scope of the concept of the application in any way, but to illustrate the concept of the application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the embodiments of the application more clear, the technical scheme in the embodiments will be described clearly and completely below in conjunction with the drawings in the embodiments of the application. The following embodiments are used to illustrate the application, but are not used to limit the scope of the application.

[0020] In the description of the application, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application.

[0021] In the description of the application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0022] As shown in Figure 1 A 42CrMo carburizing and medium frequency induction quenching process, comprising the following steps: S1, the 42CrMo shaft is subjected to carburizing quenching treatment; The step lays a foundation for subsequent strengthening treatment by precisely controlling the carbon potential and temperature and increasing the carbon content of the shaft surface, and the carburizing quenching treatment specifically comprises the following steps: S11: The 42CrMo shaft is placed in a heat treatment furnace, and the temperature is controlled to 920 DEG C to perform strong carburizing treatment, the carbon potential is controlled to 1.2, and the treatment time is 4 h, so that carbon atoms are rapidly penetrated into the surface of the shaft; S12: The temperature is kept unchanged at 920 DEG C, the carbon potential is adjusted to 0.8, and isothermal diffusion treatment is performed for 2 h, so that the carbon atoms penetrated into the surface are uniformly distributed, and the layer structure is optimized; S13: The temperature in the furnace is reduced to 840 DEG C, and the carbon potential is maintained at 0.8 during the cooling process to avoid surface decarburization; S14: The shaft after cooling is subjected to temperature equalization treatment, the shaft is subjected to temperature equalization for 30 min, the carbon potential is controlled to 0.8, the temperature of the shaft is ensured to be uniform, and the consistency of the quenching effect is ensured; S15: The shaft is subjected to quenching treatment, quenching oil is used for quenching, the quenching oil temperature is 60 DEG C, and the cooling time is 30 min, and the carburizing quenching is completed.

[0023] S2, the shaft is subjected to high-temperature tempering treatment; The shaft subjected to carburizing quenching is placed in a tempering furnace, the temperature is raised to 600-630 DEG C, and is kept for 2-4 h, and then is quickly cooled to 100 DEG C and is discharged. The entire tempering process (temperature rising, temperature keeping, temperature falling) is protected by nitrogen gas to prevent the shaft surface from being oxidized and decarburized. This step can refine the surface carbide, and at the same time, the medium-carbon martensite in the core is converted into tempered sorbite, the core hardness control and structure refinement are realized, and the core toughness is improved.

[0024] S3, the shaft is subjected to medium-frequency induction quenching treatment; The outer circle and spline part of the shaft are scanned and heated for quenching by using a medium-frequency induction heating device, the medium-frequency induction quenching parameters are respectively 40 KW of power, 6 KHz of frequency, and F150 of scanning speed; by rapid austenitizing and rapid liquid quenching, the surface high-carbon concentration structure is further refined, a 1.5-2.5 mm induction hardened layer is obtained, the double effects of surface hardening strengthening and structure refinement are realized.

[0025] S4, the shaft is subjected to low-temperature tempering treatment; The shaft after medium-frequency induction quenching is placed in a low-temperature tempering furnace, the temperature is raised to 180 DEG C, and is kept for 2 h, and then is air-cooled to room temperature. This step can eliminate quenching stress, stabilize the size of the part, and at the same time, retain the surface high hardness and wear resistance.

[0026] The application provides a 42CrMo carburizing quenching+medium-frequency induction quenching process, which increases the surface carbon content by performing carburizing quenching treatment on the 42CrMo shaft, controls the carburizing layer at about 0.8-1.0 mm, performs high-temperature tempering treatment on the shaft after quenching, can refine the surface carbide, and can also temper the central carbon martensite into tempered sorbite, realizes the central hardness control and organization refinement; the induction quenching treatment is performed on the shaft outer circle and spline, the fast austenitizing is performed, and then the fast liquid quenching is performed, the induction quenching hardened layer is 1.5-2.5 mm, the surface high-carbon concentration organization is further refined, and the surface hardening strengthening and surface organization refinement double effects are realized.

[0027] The application will be further described in detail below in combination with specific examples. Examples

[0028] 1) Prepare the shaft part, and the requirements are as follows Material: 42CrMo; Surface hardness: 156-217 HB; Grain size level: greater than or equal to 6 levels; Banded structure level: less than or equal to 2 levels; Diameter: 38 mm.

[0029] Carburizing quenching treatment is performed: Stage one: heat to 920 DEG C, strong carburizing for 4 h, carbon potential 1.2; Stage two: isothermal diffusion treatment is performed on the shaft, 920 DEG C, carbon potential 0.8, time 2 h; Stage three: cooling treatment is performed on the shaft, and the cooling temperature is 840 DEG C, and the carbon potential in the cooling stage is controlled to be 0.8; Stage four: the shaft is uniformly heated for 30 min, and the carbon potential is 0.8; Stage five: quenching treatment is performed on the shaft, and the quenching oil temperature is 60 DEG C, and the cooling time is 30 min.

[0030] High-temperature tempering treatment is performed: Tempering temperature is 600 DEG C, tempering time is 3 hours, the furnace cooling mode is adopted for cooling, nitrogen is passed through the heating, holding and cooling stages to prevent surface oxidation, and the shaft is cooled to 100 DEG C and taken out of the furnace and air-cooled to room temperature; Surface medium-frequency induction quenching treatment is performed: Quenching heating power is 40 KW, frequency is 6 KHz, and scanning speed F is 150; 5) Low-temperature tempering treatment is performed: temperature is 180 DEG C, holding time is 2 h, and air-cooling is performed to room temperature.

[0031] After the end of the shaft metallographic physical sample detection, the data are shown in Table 1, the shaft parts using the carburizing and quenching + medium frequency induction quenching process provided by the application meet the national standard and drawing requirements, although the 23CrNi3Mo used in Comparative Example 1 is replaced by 42CrMo and an induction quenching process is added, but the overall cost per kilogram is reduced by more than 40%, at the same time, the core organization refinement degree is better than that of Comparative Example 1, the surface is dispersed due to the two times of refinement of carbides and organizations, and the strengthening degree and wear resistance are better than those of Comparative Examples 1 and 2, and the overall service life is the longest among the three processes.

[0032] Table 1 metallographic detection data of the shaft of Example 1

[0033] 1) Prepare the shaft blank, with the following requirements Material: 23CrNi3Mo; Surface hardness: 156-217 HB; Grain size level: ≥ 6 levels; Banded structure level: ≤ 2 levels; Diameter: 38 mm; Single piece weight: 4.9 kg; 2) Use the 400℃±5℃, 90min pre-oxidation treatment on the multi-purpose furnace production line, and after the pre-oxidation is completed, the shaft is brought into the multi-purpose furnace production line heating furnace at temperature; 3) The shaft is heated in the multi-purpose furnace production line heating furnace according to the process shown in Figure 2 for carburizing treatment: 31) 1 hour of temperature rise, temperature rises to 780℃±5℃, no carbon potential control, 30min of temperature holding; 32) 1 hour of temperature rise, temperature rises to 920℃±5℃, no carbon potential control, 30min of temperature holding; 33) 920℃±5℃ temperature holding, carbon potential control 1.1%±0.05%, 4 hours of strong carburizing; 34) 920℃±5℃ temperature holding, carbon potential control 0.8%±0.05%, 3 hours of diffusion; 35) 2 hours of temperature drop, temperature drops to 820℃±5℃, quenching holding, 0.5h of temperature holding, carbon potential control 0.8%±0.05% during temperature drop and temperature holding; 4) The shaft is transferred from the heating chamber to the air cooling chamber for quenching (oil temperature: 100℃), quenching transfer time is 40s, stirring speed is 1000rpm, and cooling time is 30min; 5) After leaving the furnace, after cleaning, use the multi-purpose furnace production line retempering furnace to perform two times of tempering at 200℃±5℃, 4 hours of low temperature tempering, and air cooling to room temperature after leaving the furnace.

[0034] After finishing, the shaft is detected by metallographic physical cutting sample, and the data is shown in Table 2, the surface strength and wear resistance of the material carburizing and quenching are better, but the core is low-carbon plate martensite, the toughness of the core is insufficient, the overall bending strength is not high enough due to the influence of the core structure, and the service life is limited.

[0035] Table 2 metallographic detection data of the shaft of the comparative example one

[0036] 1) Prepare the shaft parts, and the requirements are as follows Material: 42CrMo; Surface hardness: 156-217HB; Grain size level: ≥6 levels; Banded structure level: ≤2 levels; Diameter: 38mm; 2) Quenching and tempering treatment is carried out on the shaft parts As shown in Figure 3 840℃ for 70min, rapid oil quenching and cooling, oil temperature 60℃, 30min, cleaning and tempering after discharging, tempering temperature 600℃, holding for 2.5h, air cooling to room temperature.

[0037] 3) After semi-finishing, the shaft parts are subjected to induction quenching treatment, the quenching heating power is 40KW, the frequency is 6KHz, and the scanning speed F is 150; 4) Low-temperature tempering treatment is carried out, the temperature is 180℃, the holding time is 2h, and air cooling to room temperature After finishing, the shaft is detected by metallographic physical cutting sample, and the data is shown in Table 3, the surface carbon content of this process is limited, so that the surface hardness of the workpiece after induction quenching is the highest 58HRC, the core is uniform tempering sorbite, and the toughness is better, but the surface wear resistance and impact resistance are poor, and the overall service life is still insufficient.

[0038] Table 3 metallographic detection data of the shaft of the comparative example two

[0039] The surface hardness (62HRC) of the embodiment one is higher than that (60HRC) of the comparative example one and (58HRC) of the comparative example two, the effective hardening layer depth (2.2mm) is better than that (1.0mm) of the comparative example one, and is equivalent to that of the comparative example two; the core structure level (1 level) and hardness (300HB) all meet the requirements, and the core toughness is better than that of the comparative example one, and the surface wear resistance is better than that of the comparative example two. Meanwhile, the cost per kilogram of the embodiment one is reduced by more than 40% than that of the comparative example one, and the service life is the longest among the three processes.

[0040] The 42CrMo carburizing and quenching and medium-frequency induction quenching process of the application has the following beneficial effects: Excellent comprehensive performance: through the composite process of carburizing quenching + medium-frequency induction quenching, the optimized matching of high carbon concentration (carbide granular dispersion distribution) on the surface and fine tempered sorbite structure in the core is realized, the surface hardness can reach 62HRC, the total depth of the hardened layer exceeds 2mm, and the hardness within 1mm on the surface is above 60HRC, the core hardness is controlled at 270-310HB, and high wear resistance, high strength and high toughness are combined, meeting the requirements of high impact and high wear resistance under complex working conditions; Good organization refinement effect: high-temperature tempering refines surface carbide and core organization, and medium-frequency induction quenching further refines surface organization, so that the internal and external organizations are uniform and fine, and the bending resistance and service life of the part are improved; Obvious cost advantage: compared with the traditional low-carbon alloy steel (such as 23CrNi3Mo) carburizing quenching process, the present application adopts 42CrMo material, although an induction quenching process is added, the cost per kilogram is reduced by more than 40%, and the core organization refinement degree and surface strengthening effect are better; High process stability: the parameters of each step are accurately controllable, nitrogen protection avoids surface oxidation and decarburization, quenching and tempering process guarantees the dimensional stability of the part, and the product qualified rate is high.

[0041] In the specification provided herein, a large number of specific details are described. However, it can be understood that the embodiments of the present application can be practiced without these specific details. In some examples, well-known methods, structures and techniques are not shown in detail in order not to obscure the understanding of the present specification.

[0042] In addition, those skilled in the art can understand that although some embodiments described herein include certain features included in other embodiments rather than other features, combinations of features of different embodiments also mean to be within the protection scope of the present application and form different embodiments. For example, in the above embodiments, those skilled in the art can use in a combined manner according to the known technical solutions and the technical problems to be solved by the present application.

[0043] The above is only the preferred embodiment of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiment, it is not intended to limit the present application, and any skilled person in the art can make some changes or modifications as equivalent embodiments with the above-mentioned technical content without departing from the technical solution range of the present application. Any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present application are still within the scope of the present application.

Claims

1. A 42CrMo carburizing and quenching process with intermediate frequency induction quenching, characterized by: It comprises the following steps: S1, carrying out carburizing quenching treatment on the 42CrMo shaft; S2, carrying out high-temperature tempering treatment on the shaft; S3, carrying out medium-frequency induction quenching treatment on the shaft; S4, carrying out low-temperature tempering treatment on the shaft.

2. The carburizing and quenching process of 42CrMo steel according to claim 1, characterized in that: The carburizing quenching treatment of the step S1 specifically comprises the following steps: S11: control the temperature of the shaft to 920 DEG C, carry out strong carburizing treatment, control the carbon potential to 1.2, and the treatment time is 4h; S12: carry out isothermal diffusion treatment on the shaft at 920 DEG C, control the carbon potential to 0.8, and the treatment time is 2h; S13: carry out cooling treatment on the shaft, cool to 840 DEG C, and control the carbon potential to 0.8 during the cooling stage; S14: carry out isothermal treatment on the cooled shaft, isothermally treat the shaft for 30 min, and control the carbon potential to 0.8; S15: carry out quenching treatment on the shaft.

3. A carburizing and quenching process for 42CrMo as claimed in claim 2, wherein: In the step S15, quenching oil is used for quenching, the quenching oil temperature is 60 DEG C, and the cooling time is 30 min.

4. The carburizing and quenching process of 42CrMo steel according to claim 1, characterized in that: In the step S2, the tempering temperature is 600-630 DEG C, the tempering time is 2-4h, and fast cooling to 100 DEG C is carried out to discharge the furnace.

5. A carburizing and quenching process for 42CrMo as claimed in claim 4 wherein: In the step S2, the cooling mode of high-temperature tempering is furnace fast cooling.

6. The carburizing and quenching process of 42CrMo steel according to claim 1, characterized in that: In the step S2, nitrogen protection is used in the processes of tempering temperature rising, holding and cooling to prevent surface oxidation.

7. The carburizing and quenching process of 42CrMo steel according to claim 1, characterized in that: In the step S3, the medium-frequency induction quenching adopts scanning heating quenching mode, and the outer surface and spline parts of the shaft are treated.

8. The carburizing and quenching process of 42CrMo steel according to claim 1, characterized in that: In the step S3, the medium-frequency induction quenching parameters are as follows: power 40KW, frequency 6KHz, and scanning speed F150.

9. The carburizing and quenching process of 42CrMo steel according to claim 1, characterized in that: In the step S4, the process parameters of low-temperature tempering are as follows: tempering temperature 180 DEG C, and holding time 2h.

10. The carburizing and quenching process of 42CrMo steel according to claim 1, characterized in that: In the step S4, the cooling mode after low-temperature tempering is air cooling to room temperature.

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