Carburizing and quenching process for wind power planet wheel

Abstract

The invention belongs to the technical field of heat treatment, and particularly relates to a wind power planet wheel carburizing and quenching process, which comprises the following steps: carrying out temperature equalization treatment twice before carburizing, carrying out strong carburizing once and diffusion treatment twice in a carburizing stage, quickly cooling to a high return temperature, carrying out temperature equalization, entering a slow cooling pit, cooling to a certain temperature, discharging from a furnace, and carrying out air cooling. Preheating in a tempering furnace before quenching, entering the furnace at high temperature and high carbon potential, entering a salt bath for quenching after austenitizing, controlling the water content of the salt bath, and improving the quenching intensity. According to the method, it can be guaranteed that the temperature of a workpiece rises at a slow speed before carburizing, the thermal stress influence caused by too large temperature difference is avoided, carbon deposition is reduced through two-time diffusion, and it is guaranteed that the surface metallographic structure meets the technical requirement; preheating is conducted before quenching, high-temperature and high-carbon-potential furnace feeding is conducted, it is guaranteed that a workpiece is rapidly heated in a nucleation temperature interval, and a good martensite structure is obtained; by controlling the water content of the salt bath, the quenching cooling speed can be increased, the formation of a bainite structure is reduced, and meanwhile, the requirement of the wind power planet wheel for the inner hole hardness is met.

Description

Technical Field

[0001] The invention belongs to the technical field of heat treatment, and in particular relates to a carburizing and quenching process for a wind power planetary gear. Background Art

[0002] At present, the heat treatment process route of carburizing and quenching in the gear industry is relatively mature, which can basically meet the requirements of the workpiece for surface metallographic structure, hardened layer depth, surface hardness, core structure and hardness. The common process route is to cool down and evenly heat after carburizing, air cool to room temperature after taking out of the furnace, air cool to room temperature after high return in the furnace, heat up to austenitizing temperature in the furnace, keep warm, and then quench and low return. However, in view of the current situation that wind power planetary gears have high requirements for controlling the martensite level, reducing deformation, and ensuring the hardness of the inner hole, a new process with simple route and practical effect is urgently needed to meet customer needs under the premise of controlling costs. Summary of the invention

[0003] The purpose of the present invention is to provide a new process with a simple route and practicability, which can effectively control the martensite level of the wind power planetary gear after carburizing and quenching, control the carbide, reduce the hardness, ensure the hardness of the inner hole, and meet the industry's growing requirements for gear organization and performance.

[0004] To achieve the above object, the technical solution adopted by the present invention is: a carburizing and quenching process for a wind turbine planetary gear, comprising the following steps:

[0005] S1. Perform two temperature treatments on the workpiece before carburizing;

[0006] S2, carburizing stage, the workpiece is subjected to one strong carburizing and two diffusion treatments;

[0007] S3, after rapid cooling, high return, enter the slow cooling pit to cool to a certain temperature and then take out of the furnace for air cooling;

[0008] S4, preheat the tempering furnace before quenching, enter the furnace with high temperature and high carbon potential, enter the salt tank for quenching after austenitization, control the water content of the salt tank, and increase the quenching intensity;

[0009] S5, air-cool after quenching, and then hang into the water tank for cleaning;

[0010] S6. After cleaning, test the surface hardness and temper.

[0011] Preferably, the two temperature equalization treatments in step S1 are two-stage step-by-step temperature rises, the first stage temperature is 630-660°C, the temperature equalization time is 2-3h; the second stage temperature is 790-810°C, the temperature equalization time is 2-3h, and the carbon potential is 0.8%-1.0%, and further preferably, the first stage temperature is 650°C, the temperature equalization time is 3h; the second stage temperature is 810°C, the temperature equalization time is 3h, and the carbon potential is 1.0%, wherein the carbon potential waiting is not limited in the temperature rise stage, nitrogen, methanol and propane are passed through the second temperature equalization section but no air is passed through, and the next section is directly entered after the temperature equalization is completed.

[0012] Preferably, in step S2, the strong infiltration temperature is 930-950°C, the time is 26-29h, and the carbon potential is 1.0%-1.2%; the first stage diffusion temperature is 930-950°C, the time is 6-9h, and the carbon potential is 0.85%-0.95%; the second stage diffusion temperature is 930-950°C, the time is 19-22h, and the carbon potential is 0.70%-0.85%. It is further preferred that the strong infiltration temperature is 940°C, the time is 28h, and the carbon potential is 1.15%; the first stage diffusion temperature is 940°C, the time is 7h, and the carbon potential is 0.95%; the second stage diffusion temperature is 940°C, the time is 21h, and the carbon potential is 0.80%.

[0013] Preferably, in step S3, the fast cooling time is no more than 8 hours, the high recovery temperature is 610°C, the time is 6 hours, at which time the main control temperature does not exceed 660°C, and the steel is cooled to 300°C in the slow cooling pit and air-cooled out of the furnace.

[0014] Preferably, the preheating temperature in step S4 is 400-670°C, and the holding time is 0.5-1.5h. More preferably, the wind turbine planetary gear is preheated in a tempering furnace before quenching, with nitrogen protection, a preheating temperature of 670°C, and a holding time of 1h.

[0015] Preferably, after the high temperature and high carbon potential enter the furnace in step S4, the austenitizing temperature of the first stage is 825-835°C, the holding time is 1-3h, and the carbon potential is 0.65-0.85%; the austenitizing temperature of the second stage is 823-830°C, the holding time is 1-3h, and the carbon potential is 0.65-0.85%. It is further preferred that the austenitizing temperature of the first stage is 825°C, the holding time is 1.5h, and the carbon potential is 0.68%; the austenitizing temperature of the second stage is 825°C, the holding time is 2h, and the carbon potential is 0.70%.

[0016] Preferably, in step S4, the salt tank temperature is 160-175° C., the water content is 0.8-1.0%, and the quenching time is 30-100 min. More preferably, the salt tank temperature is 165° C., the water content is 0.9%, and the quenching time is 50 min.

[0017] Preferably, before the quenching in step S5 is completed, the root temperature of the workpiece is measured, and if it is higher than the salt temperature, cooling is continued, and the salt is drained for 5 minutes after quenching, and then air-cooled to a surface temperature of 100-150°C, and then hoisted into a water tank for cleaning to a root temperature of 30-40°C.

[0018] Preferably, in step S6, the tempering temperature is 160-200° C., and the tempering time is 8-18 h, and more preferably, the tempering temperature is 162° C., and the tempering time is 13 h.

[0019] After adopting the above technical solution, the wind power planetary gear carburizing and quenching process provided by the present invention has the following beneficial effects:

[0020] 1) The two-stage step-wise heating before carburizing treatment of the present invention can ensure that the workpiece is heated at a slow speed before carburizing to avoid the influence of thermal stress caused by excessive temperature difference;

[0021] 2) In the carburizing stage of the present invention, one strong carburizing and two diffusion treatments are performed, and part of the strong carburizing time is divided into a diffusion transition section. If the carbon potential of the first diffusion section is difficult to be reduced to the desired level, carbon deposition can be avoided by reducing the carbon potential of the second diffusion section, thereby ensuring that the surface metallographic structure meets the technical requirements;

[0022] 3) The present invention performs preheating before quenching, and enters the furnace at high temperature and high carbon potential to ensure that the workpiece is quickly heated in the nucleation temperature range, the grains are quickly nucleated, finer initial grains are obtained, and better martensitic structure is obtained;

[0023] 4) The present invention can increase the quenching cooling speed and reduce the formation of bainite structure by controlling the water content of the salt tank, while meeting the requirements of the wind power planetary gear for the inner hole hardness. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the metallographic structure of a pre-inspection sample after carburizing according to the first embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of martensite and retained austenite structure in Example 1 of the present invention;

[0026] Figure 3 This is a schematic diagram of the metallographic structure of the pre-inspection sample after carburizing according to the second embodiment of the present invention;

[0027] Figure 4 This is a schematic diagram of the martensite and retained austenite structure of Example 2 of the present invention;

[0028] Figure 5 This is a schematic diagram of the metallographic structure of a pre-inspection sample after carburizing according to a comparative example 1 of the present invention;

[0029] Figure 6 This is a schematic diagram of martensite and retained austenite structures of Comparative Example 1 of the present invention;

[0030] Figure 7 A schematic diagram of the detection positions of the upper and lower inner holes of the wind turbine planetary gear in the present invention;

[0031] Figure 8 It is a schematic diagram of the detection position of the entire circle of the inner hole of the wind turbine planetary gear in the present invention. DETAILED DESCRIPTION

[0032] The present invention is further described clearly and completely below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Embodiment 1

[0034] The present embodiment provides a wind turbine planetary gear carburizing and quenching process, comprising the following steps:

[0035] S1, wind turbine planetary gear enters the furnace, two-stage step-by-step heating, the first stage average temperature is 650℃, the average temperature time is 3h; the second stage average temperature is 810℃, the average temperature time is 3h, and the carbon potential is 1.0%;

[0036] S2, carburizing treatment, including one strong carburizing and two diffusions, the strong carburizing temperature is 940℃, the time is 28h, and the carbon potential is 1.15%; the first diffusion temperature is 940℃, the time is 7h, and the carbon potential is 0.95%; the second diffusion temperature is 940℃, the time is 21h, and the carbon potential is 0.80%;

[0037] S3, high return after rapid cooling, high return temperature 610℃, time 6h; cool to 300℃ in slow cooling pit and then air cool out of furnace;

[0038] S4. Preheat the tempering furnace before quenching the wind turbine planetary gear, with nitrogen protection, preheating temperature of 670℃, and holding time of 1h; quenching treatment, after entering the furnace with high temperature and high carbon potential, the first stage austenitizing temperature is 825℃, the holding time is 1.5h, the carbon potential is 0.68%, the second stage austenitizing temperature is 825℃, the holding time is 2h, the carbon potential is 0.70%, and after the temperature is evenly balanced, enter the salt tank for quenching, the salt tank temperature is 165℃, the water content is 0.9%, and the quenching time is 50min;

[0039] S5. When quenching is almost over, measure the root temperature of the workpiece. If it is higher than the salt temperature, continue cooling. After quenching, drain the salt for 5 minutes, then air cool to 120℃ on the surface, and hang it in the water tank to clean until the root temperature reaches 30-40℃.

[0040] S6. After cleaning, the surface hardness is tested and tempered. The tempering temperature is 162°C and the tempering time is 13h.

[0041] Example 1: The metallographic structure of the pre-inspected sample after carburizing is as follows Figure 1 As shown, the martensite and retained austenite structures are Figure 2 shown.

[0042] Example 1 Detecting the upper and lower inner holes of the planetary gear Figure 7 Shows three points evenly distributed in the whole circle at ①②③④⑤⑥ Figure 8 The hardness of (A, B, C) is shown in Table 1 below.

[0043]

[0044] Table 1

[0045] Embodiment 2

[0046] The present embodiment provides a wind turbine planetary gear carburizing and quenching process, comprising the following steps:

[0047] S1, wind turbine planetary gear enters the furnace, two-stage step-by-step heating, the first stage average temperature is 630℃, the average temperature time is 2h; the second stage average temperature is 805℃, the average temperature time is 2h, and the carbon potential is 0.8%;

[0048] S2, carburizing treatment, including one strong carburizing and two diffusions, the strong carburizing temperature is 940℃, the time is 30h, and the carbon potential is 1.15%; the first diffusion temperature is 940℃, the time is 7h, and the carbon potential is 0.95%; the second diffusion temperature is 940℃, the time is 21h, and the carbon potential is 0.80%;

[0049] S3, high return after rapid cooling, high return temperature 610℃, time 6h; cool to 300℃ in slow cooling pit and then air cool out of furnace;

[0050] S4. Preheat the tempering furnace before quenching the wind turbine planetary gear, with nitrogen protection, preheating temperature 400℃, and holding time 1h; quenching treatment, after entering the furnace with high temperature and high carbon potential, the first stage austenitizing temperature is 828℃, the holding time is 2h, the carbon potential is 0.65%, the second stage austenitizing temperature is 825℃, the holding time is 2h, the carbon potential is 0.68%, and after the temperature is evenly balanced, enter the salt tank for quenching, the salt tank temperature is 165℃, the water content is 0.85%, and the quenching time is 50min;

[0051] S5. When quenching is almost over, measure the root temperature of the workpiece. If it is higher than the salt temperature, continue cooling. After quenching, drain the salt for 5 minutes, then air cool to 120℃ on the surface, and hang it in the water tank to clean until the root temperature reaches 30-40℃.

[0052] S6. After cleaning, test the surface hardness and temper. The tempering temperature is 162℃ and the tempering time is 12h.

[0053] Example 2: The metallographic structure of the pre-inspected sample after carburizing is as follows Figure 3 As shown, the martensite and retained austenite structures are Figure 4 shown.

[0054] Embodiment 2: Detecting the upper and lower inner holes of the planetary gear Figure 7 Shows three points evenly distributed in the whole circle at ①②③④⑤⑥ Figure 8 The hardness of (A, B, C) is shown in Table 2 below.

[0055]

[0056] Table 2

[0057] Comparative Example 1

[0058] The present embodiment provides a wind turbine planetary gear carburizing and quenching process, comprising the following steps:

[0059] S1, wind turbine planetary gear enters the furnace, two-stage step-by-step heating, the first stage average temperature is 650℃, the average temperature time is 2h; the second stage average temperature is 805℃, the average temperature time is 2h, and the carbon potential is 0.8%;

[0060] S2, carburizing treatment, including one strong carburizing and one diffusion, the strong carburizing temperature is 950℃, the time is 28h, the carbon potential is 1.15%; the diffusion temperature is 950℃, the time is 22h, and the carbon potential is 0.80%;

[0061] S3, high return after rapid cooling, high return temperature 610℃, time 6h; cool to 300℃ in slow cooling pit and then air cool out of furnace;

[0062] S4, quenching treatment, after entering the furnace at room temperature, the first stage austenitizing temperature is 830℃, the holding time is 2h, the carbon potential is 0.68%, the second stage austenitizing temperature is 825℃, the holding time is 3h, the carbon potential is 0.72%, after the temperature is evenly balanced, enter the salt tank for quenching, the salt tank temperature is 170℃, the water content is 0.85%, and the quenching time is 50min;

[0063] S5. When quenching is almost finished, measure the root temperature of the workpiece. If it is higher than the salt temperature, continue cooling. After quenching, drain the salt for 5 minutes, then air cool to 100℃ on the surface, and hang it in the water tank to clean until the root temperature reaches 30-40℃.

[0064] S6. After cleaning, test the surface hardness and conduct tempering. The tempering temperature is 170℃ and the tempering time is 14h.

[0065] Comparative Example 1: The metallographic structure of the pre-inspected sample after carburizing is as follows Figure 5 As shown, the martensite and retained austenite structures are Figure 6 shown.

[0066] Comparative Example 1 Detection of the upper and lower inner holes of the planetary gear Figure 7 Shows three points evenly distributed in the whole circle at ①②③④⑤⑥ Figure 8 The hardness of (A, B, C) is shown in Table 3 below.

[0067]

[0068] Table 3

[0069] In summary, the carburizing and quenching process of a wind power planetary gear of the present invention can ensure that the workpiece is heated at a slow speed before carburizing to avoid the influence of thermal stress caused by excessive temperature difference, and the carbon deposition is reduced by two diffusions, thereby ensuring that the surface metallographic structure meets the technical requirements; preheating is performed before quenching, and the workpiece is put into the furnace at high temperature and high carbon potential to ensure that the workpiece is heated quickly in the nucleation temperature range to obtain a better martensitic structure; by controlling the water content of the salt tank, the quenching cooling speed can be increased, the formation of bainitic structure can be reduced, and at the same time, the requirements of the wind power planetary gear for the inner hole hardness can be met.

[0070] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A carburizing and quenching process for a wind turbine planetary gear, characterized in that: The following steps are involved: S1. Perform two temperature treatments on the workpiece before carburizing; S2, carburizing stage, the workpiece is subjected to one strong carburizing and two diffusion treatments; S3, after rapid cooling, high return, enter the slow cooling pit to cool to a certain temperature and then take out of the furnace for air cooling; S4, preheat the tempering furnace before quenching, enter the furnace with high temperature and high carbon potential, enter the salt tank for quenching after austenitization, control the water content of the salt tank, and increase the quenching intensity; S5, air-cool after quenching, and then hang into the water tank for cleaning; S6. After cleaning, test the surface hardness and temper.

2. A wind turbine planetary gear carburizing and quenching process according to claim 1, characterized in that: The two temperature equalization treatments in step S1 are two-stage step-wise heating, the first stage temperature is 630-660°C, the temperature equalization time is 2-3h; the second stage temperature equalization is 790-810°C, the temperature equalization time is 2-3h, and the carbon potential is 0.8%-1.0%.

3. A wind turbine planetary gear carburizing and quenching process according to claim 1, characterized in that: In step S2, the strong penetration temperature is 930-950°C, the time is 26-29h, and the carbon potential is 1.0%-1.2%; The first stage diffusion temperature is 930-950°C, the time is 6-9h, and the carbon potential is 0.85%-0.95%; the second stage diffusion temperature is 930-950°C, the time is 19-22h, and the carbon potential is 0.70%-0.85%.

4. A wind turbine planetary gear carburizing and quenching process according to claim 1, characterized in that: In step S3, the rapid cooling time is no more than 8 hours, the high recovery temperature is 610° C., the time is 6 hours, and the steel is cooled in a slow cooling pit to 300° C. and then air-cooled out of the furnace.

5. The carburizing and quenching process for a wind turbine planetary gear according to claim 1, characterized in that: In step S4, the preheating temperature is 400-670° C. and the time is 0.5-1.5 h.

6. A wind turbine planetary gear carburizing and quenching process according to claim 1, characterized in that: After the high temperature and high carbon potential enter the furnace in step S4, the first stage austenitizing temperature is 825-835°C, the holding time is 1-3h, the carbon potential is 0.65-0.85%, and the second stage austenitizing temperature is 823-830°C, the holding time is 1-3h, and the carbon potential is 0.65-0.85%.

7. The carburizing and quenching process for a wind turbine planetary gear according to claim 1, characterized in that: In step S4, the salt tank temperature is 160-175° C., the water content is 0.8-1.0%, and the quenching time is 30-100 min.

8. The carburizing and quenching process for a wind turbine planetary gear according to claim 1, characterized in that: Before the quenching in step S5 is completed, the root temperature of the workpiece is measured. If it is higher than the salt temperature, cooling is continued. After quenching, the salt is drained for 5 minutes, and then air-cooled to a surface temperature of 100-150°C. The workpiece is then hoisted into a water tank for cleaning until the root temperature is 30-40°C.

9. The carburizing and quenching process for a wind turbine planetary gear according to claim 1, characterized in that: In step S6, the tempering temperature is 160-200° C., and the tempering time is 8-18 hours.

Images