Carburizing and quenching numerical simulation method for wind power speed increasing gear

Abstract

The invention discloses a carburizing and quenching numerical simulation method for a wind power speed increasing gear, which belongs to the field of gear processing and comprises the following steps: 1) calculating and determining a thermophysical performance parameter curve of each basic phase in a 20CrMnMo material by means of material performance calculation software; (2) a phase change kinetic model of 20CrMnMo is determined; 3) determining a heat transfer coefficient curve of the quenching oil medium based on the cooling speeds of the quenching oil for production measured at different temperatures; 4) selecting a C-shaped eccentric circular ring notch sample, and simulating a coupling result of a temperature field and a structure field in the 20CrMnMo wind power gear carburizing and quenching process gear; and 5) simulating the thickness of a carburized layer on the surface of the sample after the carburizing and quenching process is completed. According to the method, quantitative prediction of the effectiveness of the carburizing and quenching process of the wind power speed increasing gear is achieved, and the method has very high commercial application value.

Description

Technical Field

[0001] The invention relates to gear processing, and in particular to a numerical simulation method for carburizing and quenching of wind power speed increasing gears. Background Art

[0002] Wind power speed-increasing gearbox is one of the key components of wind power equipment. It is mainly used to speed up the blade rotation under the action of wind force and transmit it to the generator, thereby converting wind energy into electrical energy. With the development of wind power megawatt-level gearboxes, the specifications of gears are getting larger and larger, and higher requirements are also placed on the size and performance control of their production and processing processes. Since the gearbox is subjected to cyclically changing loads during the transmission process, fatigue damage often occurs during its service and causes failure. In order to ensure the service performance of gear parts, they are usually required to have good comprehensive mechanical properties.

[0003] In order to make gear parts obtain comprehensive mechanical properties of hardness on the outside and toughness on the inside, carburizing and quenching process is a relatively common heat treatment process method in the production process of heavy-duty gears. Carburizing heats the gear material to a certain temperature so that carbon atoms penetrate into the surface to form a carbide layer, thereby improving the surface hardness, wear resistance and fatigue strength of the gear. The comprehensive performance of the gear after carburizing and quenching mainly depends on the internal structure of the gear, the thickness of the carburized layer, etc. Therefore, how to predict the internal structure and thickness of the carburized layer of the gear after carburizing and quenching is of great significance to the evaluation of gear performance. Due to the mutual coupling of temperature, structure, stress and strain state during the heat treatment process, the change law is complex, and it is difficult to formulate the optimal carburizing and quenching process curve through the traditional trial-and-error process. Therefore, how to propose a numerical simulation method for carburizing and quenching of wind power speed increaser gears to provide a model basis for the formulation of gear process routes is an important problem that needs to be solved urgently. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a numerical simulation method for carburizing and quenching of wind power gear increasers, which is used to solve the technical problem of quantitatively predicting the effectiveness of the carburizing and quenching process of wind power gear increasers.

[0005] The technical solution of the present invention is: a numerical simulation method for carburizing and quenching of a wind power speed increasing gear, which is applied to the carburizing and quenching process of a 20CrMnMo wind power gear, comprising the following steps:

[0006] 1) Calculate and determine the thermophysical performance parameter curves of each basic phase in 20CrMnMo material with the help of material performance calculation software;

[0007] 2) Determine the phase transformation kinetic model of the carburizing and quenching process;

[0008] 3) Determine the heat transfer coefficient curve of the quenching oil medium based on the cooling rate measured at different temperatures of the quenching oil used in production;

[0009] 4) Select C-type eccentric ring notch specimen to simulate the temperature field and structure field coupling results inside the gear during the carburizing and quenching process of 20CrMnMo wind turbine gear;

[0010] 5) The thickness of the carburized layer on the surface of the sample after the simulated carburizing and quenching process is completed.

[0011] More specifically, the thermophysical property parameter curves of each basic phase in step 1) include: elastic modulus, Young's modulus, Poisson's ratio, specific heat capacity, thermal conductivity, and phase transformation plasticity coefficient of austenite, ferrite, martensite, pearlite, and bainite at different temperatures.

[0012] More specifically, the phase transformation kinetics model in step 2) includes: a diffusion-type phase transformation model, a martensitic phase transformation model, a carbon atom diffusion model and a carbon atom transfer model.

[0013] More specifically, the diffusion phase transition model is described by the classic JMAK equation:

[0014] f=1-exp(-Kt n ) Formula 1

[0015] Among them, the coefficient K and the Avrami index n are constants related to the carbon content and can be obtained by fitting calculation using material thermophysical property calculation software, such as JMatPro.

[0016] The martensitic phase transformation model is as follows:

[0017] f=1-exp[-0.0397(425-T)] Formula 2

[0018] The diffusion model of carbon atoms is as follows:

[0019]

[0020] Where T is temperature and C is carbon content.

[0021] The transfer model of carbon atoms is as follows:

[0022] β=0.000185-1.99033×10 -4 exp[-4.30399×(1.1-C s )] Formula 4

[0023] Where Cs is the surface carbon concentration.

[0024] More specifically, in the heat transfer coefficient curve of the quenching oil medium in step 3), the heat transfer coefficient of the quenching oil medium is the highest at 600°C, and the heat transfer coefficient is greater than 5000W / (cm 2 ·℃).

[0025] More specifically, the coupled simulation results of the temperature field and organizational field inside the gear of the 20CrMnMo wind turbine gear carburizing and quenching process in step 4) show that the cooling rate of the notch position of the C-notch specimen is relatively fast 0.5s after entering the oil; 3s after entering the oil, the lowest temperature at the notch position is lower than 400°C, and the temperature at the center position is close to 800°C, and the temperature difference between the notch position and the center position is large.

[0026] More specifically, the coupled simulation results of the temperature field and organizational field inside the 20CrMnMo wind turbine gear during the carburizing and quenching process in step 4) show that the cooling rate at the notch position of the specimen is faster, and the martensitic transformation first occurs at the notch position of the specimen; after quenching, high-carbon martensite is formed on the surface of the specimen; more bainite structure and a small amount of ferrite structure are formed in the thick end area of ​​the specimen.

[0027] More specifically, in step 5), the thickness of the carburized layer on the surface of the sample after the simulated carburizing and quenching process is completed is about 1.724 mm.

[0028] The beneficial technical effects of the present invention are:

[0029] The numerical simulation method of carburizing and quenching of wind power speed increaser gears adopted in the present invention intuitively reveals the evolution law of the macroscopic temperature field as well as the organization and concentration field of the carburizing heat treatment process, realizes the quantitative prediction of the effectiveness of the carburizing and quenching process of wind power speed increaser gears, and provides a model basis for the formulation of the subsequent gear carburizing and quenching process route, which has strong commercial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 :(a) is the size parameter of 20CrMnMo wind turbine gear Figure 1 ; (b) is the size parameters of 20CrMnMo wind turbine gear Figure 2 ;

[0031] Figure 2 It is a schematic diagram of the grid model structure of the C-notch specimen;

[0032] Figure 3 It is a curve diagram of the elastic modulus parameter of 20CrMnMo steel changing with temperature;

[0033] Figure 4 It is a curve diagram of the Poisson's ratio parameter of 20CrMnMo steel changing with temperature;

[0034] Figure 5 It is a curve diagram of the specific heat capacity parameter of 20CrMnMo steel changing with temperature;

[0035] Figure 6 It is a curve diagram of the thermal conductivity parameters of 20CrMnMo steel changing with temperature;

[0036] Figure 7 It is a curve diagram of the phase transformation plasticity parameters of 20CrMnMo steel changing with temperature;

[0037] Figure 8 is the heat transfer coefficient diagram of quenching oil;

[0038] Fig. 9 It is the temperature field distribution cloud diagram inside the C-notch specimen at different times obtained by simulating the quenching stage;

[0039] Fig.10 The final quenched microstructure distribution cloud diagram in the C-notch specimen obtained by simulation: (a) martensite; (b) bainite; (c) ferrite;

[0040] Fig.11 This is the hardness distribution curve from the surface to the core of the C-type notched ring specimen after carburizing. DETAILED DESCRIPTION

[0041] In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the specific implementation methods of the present invention are further described in detail below in conjunction with the drawings and examples. The following examples are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0042] See also Figure 1-11 The numerical simulation method of carburizing and quenching of wind power gear is applied to the carburizing and quenching process of 20CrMnMo wind power gear, including the following steps:

[0043] 1) Calculate and determine the thermophysical performance parameter curves of each basic phase in 20CrMnMo material with the help of material performance calculation software;

[0044] 2) Determine the phase transformation kinetic model of the carburizing and quenching process;

[0045] 3) Determine the heat transfer coefficient curve of the quenching oil medium based on the cooling rate measured at different temperatures of the quenching oil used in production;

[0046] 4) Select C-type eccentric ring notch specimen to simulate the temperature field and structure field coupling results inside the gear during the carburizing and quenching process of 20CrMnMo wind turbine gear;

[0047] 5) The thickness of the carburized layer on the gear surface after the simulated carburizing and quenching process is completed.

[0048] In this specific embodiment, the composition of 20CrMnMo is as shown in Table 1:

[0049] Table 1 Chemical composition of 20CrMnMo steel

[0050]

[0051] like Figure 1 As shown in (a) and (b), the present invention uses a C-notch carburizing and quenching deformation specimen to perform finite element simulation and experimental verification on the carburizing and quenching process of 20CrMnMo steel. The unit of size is mm. Figure 1 1, 2, 3, and 4 in (b) are the simulated points of the carburized layer thickness in step 5). 2D plane strain is used to simplify the model, and quadrilateral meshing is performed on the two-dimensional section, such as Figure 2 The number of meshes in the model is 20660. In order to improve the calculation accuracy, the mesh is refined near the surface of the model.

[0052] More specifically, the thermophysical property parameter curves of each basic phase in step 1) include: elastic modulus, Young's modulus, Poisson's ratio, specific heat capacity, thermal conductivity, and phase transformation plasticity coefficient of austenite, ferrite, martensite, pearlite, and bainite at different temperatures.

[0053] More specifically, the phase transformation kinetics model in step 2) includes: a diffusion-type phase transformation model, a martensitic phase transformation model, a carbon atom diffusion model and a carbon atom transfer model.

[0054] More specifically, the diffusion phase transition model is described by the classic JMAK equation:

[0055] f=1-exp(-Kt n ) Formula 1

[0056] Among them, the coefficient K and the Avrami index n are constants related to the carbon content and can be obtained by fitting calculation using material thermophysical property calculation software, such as JMatPro.

[0057] The martensitic phase transformation model is as follows:

[0058] f=1-exp[-0.0397(425-T)] Formula 2

[0059] The diffusion model of carbon atoms is as follows:

[0060]

[0061] Where T is temperature and C is carbon content.

[0062] The transfer model of carbon atoms is as follows:

[0063] β=0.000185-1.99033×10 -4 exp[-4.30399×(1.1-C s )] Formula 4

[0064] Where Cs is the surface carbon concentration.

[0065] More specifically, in the heat transfer coefficient curve of the quenching oil medium in step 3), the heat transfer coefficient of the quenching oil medium is the highest at 600°C, and the heat transfer coefficient is greater than 5000W / (cm 2 .℃).

[0066] More specifically, the coupled simulation results of the temperature field and the organizational field inside the gear of the 20CrMnMo wind turbine gear carburizing and quenching process in step 4) are as follows: Fig. 9 The cloud diagram of the temperature field change during the quenching process of the C-notch specimen shown in the figure selects the central section cloud diagrams at 0.5s, 1s, 2s, 3s, 4s and 5s after the start of quenching, so as to analyze the evolution of the temperature field of the workpiece during the quenching process. It can be seen intuitively from the cloud diagram that 0.5s after the C-notch is put into the oil, the cooling speed at the notch position is relatively fast due to its thin position; 3s after the oil is put into the oil, the lowest temperature at the notch position is lower than 400℃, but the temperature at the center of the specimen is still at a high temperature of nearly 800℃, and the temperature difference between the notch position and the center of the specimen is large.

[0067] like Fig.10 The microstructure distribution cloud diagram of the central section of the C-notch specimen after quenching is shown. Combined with the temperature field evolution results during the quenching process, it can be seen that the cooling rate at the notch position of the specimen is faster, and the martensite transformation first occurs at the notch position of the specimen. It can also be seen from the cloud diagram that after quenching, high-carbon martensite is formed on the surface of the workpiece. However, due to the difference in cooling rate between the center and surface of the thick end of the workpiece, more bainite and a small amount of ferrite are formed in the thick end area of ​​the workpiece.

[0068] More specifically, in step 5), the thickness of the carburized layer on the gear surface after the simulated carburizing and quenching process is completed is about 1.724 mm. Fig.11 As shown in the figure, based on the carbon concentration distribution cloud diagram of the C-type notched ring specimen after carburizing, the Figure 1 The simulated carburized layer thickness at the position point in (b) is about 1.724 mm. The simulation result corresponds well with the actual test result and can reflect the general law of carbon concentration distribution and evolution in the workpiece during the carburizing heat treatment process.

[0069] The numerical simulation method for carburizing and quenching of wind power speed increaser gears disclosed in the present invention intuitively reveals the evolution law of the macroscopic temperature field and the organizational field during the carburizing heat treatment process, realizes the quantitative prediction of the effectiveness of the carburizing and quenching process of wind power speed increaser gears, and provides a model basis for the formulation of the gear process route of this sample and other samples in the later stage, and has strong commercial application value.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. The numerical simulation method of carburizing and quenching of wind power gear is applied to the carburizing and quenching process of 20CrMnMo wind power gear, which is characterized by: The following steps are involved: 1) Calculate and determine the thermophysical performance parameter curves of each basic phase in 20CrMnMo material with the help of material performance calculation software; 2) Determine the phase transformation kinetic model of the carburizing and quenching process; 3) Determine the heat transfer coefficient curve of the quenching oil medium based on the cooling rate measured at different temperatures of the quenching oil used in production; 4) Select C-type eccentric ring notch specimen to simulate the temperature field and structure field coupling results inside the gear during the carburizing and quenching process of 20CrMnMo wind turbine gear; 5) The thickness of the carburized layer on the surface of the sample after the simulated carburizing and quenching process is completed.

2. The numerical simulation method for carburizing and quenching of wind power speed increasing gear according to claim 1 is characterized in that: The thermophysical property parameter curves of each basic phase in step 1) include: elastic modulus, Young's modulus, Poisson's ratio, specific heat capacity, thermal conductivity, and phase transformation plasticity coefficient of austenite, ferrite, martensite, pearlite, and bainite at different temperatures.

3. The numerical simulation method for carburizing and quenching of wind power speed increasing gear according to claim 1 is characterized in that: The phase transformation kinetics models in step 2) include: diffusion-type phase transformation model, martensitic phase transformation model, carbon atom diffusion model and carbon atom transfer model.

4. The numerical simulation method for carburizing and quenching of wind power speed increasing gear according to claim 3 is characterized in that: The diffusion phase change model is described by the classic JMAK equation: f=1-exp(-Kt n ) Formula 1 Among them, the coefficient K and the Avrami index n are constants related to the carbon content and can be obtained by fitting calculation using material thermophysical property calculation software, such as JMatPro. The martensitic phase transformation model is as follows: f=1-exp[-0.0397(425-T)]Formula 2 The diffusion model of carbon atoms is as follows: Where T is temperature and C is carbon content. The transfer model of carbon atoms is as follows: β=0.000185-1.99033×10 -4 exp[-4.30399×(1.1-C s )] Formula 4 Where Cs is the surface carbon concentration.

5. The numerical simulation method for carburizing and quenching of wind power speed increasing gear according to claim 1, characterized in that: In the heat transfer coefficient curve of the quenching oil medium in step 3), the heat transfer coefficient of the quenching oil medium is the highest at 600°C, and the heat transfer coefficient is greater than 5000W / (cm2·°C).

6. The numerical simulation method for carburizing and quenching of wind power speed increasing gear according to claim 1, characterized in that: The coupled simulation results of the temperature field and organizational field inside the gear of the 20CrMnMo wind turbine gear carburizing and quenching process in step 4) show that the cooling speed of the notch position of the C-notch specimen is relatively fast 0.5s after oil entry; 3s after oil entry, the lowest temperature at the notch position is lower than 400℃, and the temperature at the center position is close to 800℃, and the temperature difference between the notch position and the center position is large.

7. The numerical simulation method for carburizing and quenching of wind power speed increasing gear according to claim 6, characterized in that: The coupled simulation results of the temperature field and organizational field inside the 20CrMnMo wind turbine gear during the carburizing and quenching process in step 4) show that the cooling rate at the notch position of the specimen is faster, and the martensitic transformation first occurs at the notch position of the specimen; after quenching, high-carbon martensite is formed on the surface of the specimen; more bainite structure and a small amount of ferrite structure are formed in the thick end area of ​​the specimen.

8. The numerical simulation method for carburizing and quenching of wind power speed increasing gear according to claim 1, characterized in that: In step 5), the thickness of the carburized layer on the surface of the sample after the simulated carburizing and quenching process is completed is about 1.724 mm.

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