Hardness quality control method for internal spline of wind power sun gear before spline arrangement

Abstract

The invention belongs to the technical field of heat treatment, and particularly relates to a method for controlling the hardness quality of an internal spline of a wind power sun gear before spline arrangement, the method comprises a heat treatment process and a cold machining process, the heat treatment process comprises carburizing, quenching and tempering which are carried out in sequence, and the cold machining process comprises a semi-finish turning process arranged after carburizing and before quenching. The semi-finish turning process is used for reducing the unilateral allowance of a flower key arrangement part of an inner hole of the wind power sun gear and forming an upper boss structure and a lower boss structure so as to reduce the change of medium flow to the hardness trend. On the premise that the hardness quality index of the internal spline of the wind power sun gear is met, mass excess is avoided; meanwhile, by means of the control method, the overall production and machining efficiency can be more efficiently improved, the machining difficulty of the cold machining flower key arrangement procedure is relieved, and the productivity is improved; the tool loss in the cold machining spline arrangement procedure is reduced, and the tool loss cost is reduced; the method is suitable for design and popularization of a wind power sun gear internal spline heat treatment process and a related cold machining process.

Description

Technical Field

[0001] This invention belongs to the field of heat treatment technology, specifically relating to a method for controlling the hardness quality of the internal spline of a wind turbine sun gear before spline insertion. Background Technology

[0002] The gearbox, a core mechanical component of a wind turbine generator, primarily functions to transmit the power generated by the wind turbine under wind power to the generator, thereby increasing its rotational speed. Since the wind turbine's rotational speed is typically low, it's difficult to meet the generator's required speed. Therefore, the gearbox utilizes the speed-increasing effect of its internal gear pairs, hence the name "speed increaser." In the overall layout of the turbine, two common designs exist: one integrates the drive shaft (main shaft) directly connected to the wind turbine hub with the gearbox as a single unit; the other arranges the main shaft and gearbox independently, connected via a shrink-fit sleeve or coupling. Furthermore, to enhance the turbine's braking performance, braking devices are typically installed at the gearbox's input or output ends, working in conjunction with tip braking (for constant-pitch turbines) or variable-pitch braking to provide combined braking for the turbine's transmission system. Given that wind turbine generators are mostly installed in areas with strong winds, such as high mountains, wilderness, beaches, and islands, they must withstand not only the impact of irregular, changing winds and strong gusts, but also extreme temperature differences. Furthermore, these areas often have poor transportation access, placing more stringent requirements on gearboxes in terms of design and service life compared to ordinary machinery. For example, component materials, in addition to meeting conventional mechanical performance requirements, must also possess resistance to brittleness in low-temperature environments. Currently, the primary and secondary torque transmission of wind turbine main gearboxes mainly relies on spline structures. The sun gear is an indispensable part of its gear transmission. The external splines of the primary sun gear undergo carburizing and quenching heat treatment to form a hardened tooth surface, while the internal splines, mostly designed within the low-speed shaft or secondary planetary carrier, cannot undergo other heat treatments, resulting in a lower tooth surface hardness. This meshing mode of hard and soft tooth surfaces easily leads to severe wear on the soft tooth surface. Therefore, a process method to control the hardness quality index of the soft tooth surface, i.e., the internal spline, is urgently needed. Summary of the Invention

[0003] The purpose of this invention is to address the defects and shortcomings in the existing technology and to provide a method for controlling the hardness quality of the internal spline of a wind turbine sun wheel before spline insertion.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is: a method for controlling the hardness quality of the spline in the inner hole of a wind turbine sun wheel before spline insertion, comprising a heat treatment process and a cold working process, wherein the heat treatment process includes carburizing, quenching and tempering performed sequentially, and the cold working process includes a semi-finish turning process set after carburizing and before quenching. The semi-finish turning process is used to reduce the single-sided allowance of the spline part of the inner hole of the wind turbine sun wheel and form two boss structures, so as to reduce the change of hardness trend due to medium flow.

[0005] Preferably, the carburizing process adopts a three-stage stepped carburizing process: heating to 980°C and holding at a carbon potential of 1.2% / 1.1% / 0.80% respectively; rapid cooling to 620°C for temperature homogenization and balancing of the workpiece microstructure; and then heating to 720°C for spheroidization and holding in the two-phase region followed by gas quenching to achieve micro-austenization of the workpiece.

[0006] Preferably, the temperature is first raised to 800°C and held for a period of time before the temperature is raised to 980°C, with a carbon potential of 0.6%.

[0007] Preferably, the carbon potential is 0.75% in both the rapid cooling to 620°C stage and the reheating to 720°C stage.

[0008] Preferably, the quenching process involves raising the temperature to 950℃ before entering the furnace to minimize the initial austenite grains to level 10 or higher, while simultaneously reducing surface oxidation of the workpiece. A high carbon potential of 0.85-0.90% is used for heat preservation to achieve carbon retention and replenishment effects on the workpiece, reducing surface decarburization. Salt bath quenching at 170℃ is employed to achieve a high-density, dispersed spherical carbide layer of 1-2μm within a 0.3mm range on the workpiece surface. Carbide grain boundary accumulation and volume expansion increase the compressive stress on the workpiece surface.

[0009] Preferably, the high carbon potential holding temperature of 0.85-0.90% is 860℃, and a uniform temperature of 830℃ and 0.75% carbon potential is used between the high carbon potential holding temperature and the salt bath quenching.

[0010] Preferably, the tempering is performed at a low temperature of 160-180℃, and the workpiece is shot blasted immediately after being removed from the tempering furnace to maintain the workpiece temperature and provide a temperature basis for subsequent shot peening.

[0011] Preferably, the sun gear is made of 18CrNiMo7-6, with a tooth surface hardness of 58-62HRC, a core hardness of 35-45HRC, and an internal spline hardness of ≥300HB.

[0012] Preferably, the sun gear is loaded into the furnace using either a sequential or non-sequential loading method.

[0013] After adopting the above technical solution, the present invention provides a method for controlling the hardness quality of the internal spline of a wind turbine sun rotor before spline insertion, which has the following beneficial effects:

[0014] 1) The hardness and quality of the inner spline of the sun gear prepared by the present invention can meet the wind power application index, namely, the hardness of the tooth surface is 58-62HRC, the hardness of the core is 35-45HRC, and the hardness of the inner spline is ≥300HB.

[0015] 2) This invention can avoid over-quality while meeting quality standards, making the hardness of the internal spline to be processed uniform, reducing the processing difficulty of cold working spline, speeding up the spline process efficiency, increasing production capacity, and reducing tool wear costs due to the uniform hardness of the processed parts, thus improving the overall production efficiency.

[0016] 3) This invention uses a pit-type carburizing and quenching furnace. When loading the sun gear into the furnace, it can be either loaded by passing the inner hole through the tooling hanger rod, i.e., through-loading; or it can be loaded around the inner hole without passing the hanger rod, i.e., non-through-loading. Different quenching loading methods can provide selection space for different quality requirements and the selection of cold working tools in production. According to the actual situation, under the premise of ensuring quality, the hardness of the surface to be processed can be controlled more efficiently and reasonably, and the hardness can be made uniform. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the heat treatment process of the present invention;

[0018] Figure 2 This is a schematic diagram of the semi-finished double boss structure in this invention. Detailed Implementation

[0019] The present invention will now be described more clearly and completely with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0020] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0021] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0022] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0023] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0024] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0025] like Figure 1-2As shown, the present invention provides a method for controlling the hardness quality of the internal spline of a wind turbine sun rotor before spline insertion, comprising a heat treatment process and a cold working process, wherein the heat treatment process includes:

[0026] Carburizing: A three-stage stepped carburizing process is adopted. The temperature is raised to 980℃ and held at that temperature, with carbon potentials of 1.2% / 1.1% / 0.80% respectively. Under the high-temperature carburizing and high carbon potential conditions, the degree of oxidation of the workpiece is reduced, thereby improving the carburizing efficiency. Then, it is rapidly cooled to 620℃ for homogenization to achieve microstructure equilibrium. Finally, it is heated to 720℃ for spheroidization and holding in the two-phase region, followed by gas quenching to achieve micro-austenization of the workpiece, providing microstructure preparation for the grain refinement process in the subsequent quenching heat treatment stage.

[0027] Quenching: To improve the nucleation rate and refine the grains of the workpiece microstructure during the austenitization stage, the temperature is raised to 950℃ before quenching in the furnace to minimize the initial austenite grain size, which can basically reach level 10 or above, and reduce the oxidation degree of the workpiece surface. Then, a high carbon potential in the range of 0.85-0.90% is used for holding at that temperature for an appropriate time to achieve carbon retention and carbon replenishment, thereby reducing decarburization on the workpiece surface and avoiding affecting the final workpiece performance. Finally, a 170℃ salt bath quenching is performed to achieve a high-density dispersed spherical carbide of 1-2μm within a 0.3mm range on the surface of the workpiece. The carbide grain boundaries accumulate and the volume expands to increase the compressive stress on the workpiece surface.

[0028] Tempering: Low-temperature tempering is adopted in the range of 160-180℃. After tempering, shot blasting is performed immediately to maintain the temperature of the workpiece, provide a temperature basis for subsequent shot peening, and improve the surface plasticity of the workpiece.

[0029] The cold working process includes a semi-finish turning process set after carburizing and before quenching. The semi-finish turning process is used to reduce the single-sided allowance of the spline part of the inner hole of the wind turbine sun wheel and form two boss structures, so as to reduce the change of hardness trend due to the flow of the medium.

[0030] During the carburizing process, the temperature is first raised to 800°C and held before reaching 980°C, with a carbon potential of 0.6%. The carbon potential is 0.75% during the rapid cooling to 620°C stage and the subsequent heating to 720°C stage.

[0031] During the quenching process, the holding temperature for the 0.85-0.90% high carbon potential is 860℃, and a temperature equalization process of 830℃ and 0.75% carbon potential is also used between the high carbon potential holding temperature and the salt bath quenching.

[0032] Furthermore, the sun gear of this invention is made of 18CrNiMo7-6, and after adopting the above control method, the surface hardness is 58-62HRC, the core hardness is 35-45HRC, and the internal spline part is ≥300HB.

[0033] Furthermore, the present invention uses a pit-type carburizing and quenching furnace. For wind turbine solar wheel products, the furnace loading method can be one of the following two methods: the first is that the inner hole of the wind turbine solar wheel passes through the tooling hanger rod for mounting, i.e., through-mounting; the second is that the inner hole of the wind turbine solar wheel does not pass through the hanger rod but is mounted around it, i.e., non-through-mounting.

[0034] Both mounting methods can meet the required hardness quality indicators, namely, tooth surface hardness 58-62HRC, core hardness 35-45HRC, and internal spline hardness ≥300HB. Therefore, the following data collection and comparison were carried out on the hardness uniformity and hardness requirements of the internal spline.

[0035] When the first quenching loading method - cascading loading - is used, the hardness test results after hot working and the hardness test results after precision machining are shown in Table 1 and Table 2 below.

[0036]

[0037]

[0038] Table 1. Results of hardness test after heating (Leibluck).

[0039]

[0040] Table 2. Hardness test results after precision machining (Leibbur scale)

[0041] When the second quenching loading method - non-channel loading - is adopted, the hardness test results after hot working and the hardness test results after precision machining are shown in Tables 3 and 4 below.

[0042]

[0043]

[0044] Table 3. Results of hardness test after heating (Leibbur scale)

[0045]

[0046] Table 4. Hardness test results after precision machining (Leibhold)

[0047] As can be seen from the above data, the hardness of the inner hole after quenching is between 300-320 HB regardless of the furnace loading method. The average hardness of the non-parallel loading workpiece is slightly higher than that of the parallel loading workpiece, but the average hardness of both meets the product requirement of ≥300 HB. The double boss structure reduces the hardness of the sun gear spline part after quenching as much as possible while ensuring hardness, so as to facilitate the subsequent spline insertion. In addition, this structure makes the quenching medium flow more uniform, and the hardness of the spline to be processed is relatively uniform, which facilitates subsequent processing.

[0048] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for controlling the quality of the hardness of a spline inserted into a spline hole of a wind power sun gear, characterized by, The method comprises a heat treatment process and a cold working process, wherein the heat treatment process comprises carburizing, quenching and tempering in sequence, and the cold working process comprises a semi-finishing process arranged after carburizing and before quenching, which is used for reducing the single-side allowance of the inner hole key insertion part of the wind power sun gear and forming upper and lower boss structures to reduce the change of the hardness trend caused by medium flow.

2. The method for controlling the front hardness quality of the spline inserted into the sun gear of a wind power solar according to claim 1, characterized in that: The carburizing adopts a three-stage step carburizing process, and the temperature is raised to 980 DEG C for heat preservation, and the carbon potential is 1.2% / 1.1% / 0.80% respectively; the temperature is quickly cooled to 620 DEG C for temperature equalization, and the workpiece organization is balanced; then the temperature is raised to 720 DEG C for two-phase zone spheroidizing heat preservation, and then air quenching is carried out to realize micro-austenite of the workpiece.

3. The method for controlling the front hardness quality of the spline inserted into the sun gear of a wind power solar according to claim 2, characterized in that: Before the temperature is raised to 980 DEG C, the temperature is first raised to 800 DEG C for heat preservation, and the carbon potential is 0.6%.

4. The method for controlling the front hardness quality of the spline inserted into the sun gear of a wind power solar according to claim 2, characterized in that: The carbon potential is 0.75% in the stage of quickly cooling to 620 DEG C and the stage of raising the temperature to 720 DEG C.

5. A method of controlling the quality of the front hardness of an inserted spline in a wind power sun gear according to claim 1, characterized in that: The temperature is raised to 950 DEG C before entering the furnace to realize the minimization of the initial austenite grain, reach 10 levels and above, and reduce the workpiece surface oxidation; high carbon potential of 0.85-0.90% is used for heat preservation to realize the carbon preservation and carbon supplement effect of the workpiece, and reduce the workpiece surface decarburization; 170 DEG C salt bath quenching is used to realize high-density dispersed spherical carbide of 1-2 mu m in the workpiece surface layer of 0.3 mm, carbide grain boundary accumulation, volume expansion, and increase of the workpiece surface layer compressive stress.

6. A method of controlling the quality of the front hardness of an inserted spline in a wind power sun gear according to claim 5, characterized in that: The high carbon potential heat preservation temperature of 0.85-0.90% is 860 DEG C, and 830 DEG C, 0.75% carbon potential is used for temperature equalization between high carbon potential heat preservation and salt bath quenching.

7. A method of controlling the quality of the front hardness of an inserted spline in a wind power sun gear according to claim 1, characterized in that: The tempering adopts low-temperature tempering of 160-180 DEG C, and the workpiece temperature is immediately shot blasted after the tempering is discharged from the furnace, and the temperature basis is provided for the subsequent shot blasting.

8. A method of controlling the quality of the front hardness of an inserted spline in a sun gear of a wind turbine according to claim 1, characterized in that: The material of the sun gear is 18CrNiMo7-6, the tooth surface hardness is 58-62 HRC, the core hardness is 35-45 HRC, and the inner key part is greater than or equal to 300 HB.

9. A method of controlling the quality of the front hardness of an inserted spline in a sun gear of a wind turbine according to claim 1, characterized in that: The furnace charging mode of the sun gear adopts the shuffling charging or non-shuffling charging.

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