Method for detecting depth of carburizing layer of tooth root fillet of involute gear

Abstract

The invention belongs to the technical field of carburizing heat treatment surfaces, relates to an involute gear tooth root fillet carburizing layer depth detection method, and aims at judging whether the tooth root fillet carburizing layer depth given by a design part can meet process requirements or not on the premise of not carrying out a process experiment. According to the technical scheme, the method comprises the steps that 1, the modulus and the tooth number of the involute gear are searched through a drawing, and the reference circle diameter and the tooth root circle diameter are calculated respectively; 2, according to the effective carburized layer average value xep and the HRC60 carburized layer depth minimum value x60p of the tooth middle and middle part degree circle process given by design, the tooth root effective carburized layer average value xer and the HRC60 carburized layer depth average value x60r are calculated; and 3, comparing the calculated x < er > with a designed and given average value x < e > of the effective carburized layer of the tooth root, and comparing the calculated x < 60r > of the tooth root HRC60 with a designed and given average value x < 60 > of the effective carburized layer of the tooth root HRC60 to obtain a detection conclusion. The method is suitable for gear detection.

Description

Technical Field

[0001] The invention belongs to the technical field of carburizing heat treatment surface and relates to a method for detecting the depth of a carburizing layer at a root fillet of an involute gear. Background Art

[0002] When conventional gears are carburized, the depth of the carburized layer of the gear usually refers to the thickness of the carburized layer in the normal direction at the position of the middle graduation circle of the tooth height of the tooth profile. In the fields of aerospace and the like, affected by the service conditions, the root of some meshing gears needs to bear force. Therefore, when some high-precision gears are subjected to carburization chemical surface modification, in addition to stipulating the effective depth of the carburized layer at the middle graduation circle of the tooth height and its HRC60 carburized layer depth ratio, the design part will also simultaneously limit the effective depth of the carburized layer at the tooth root fillet and the HRC60 depth ratio to ensure the reliability of the gear service.

[0003] Although the document CN115266792A adopts electron probe to test carbon element, which can solve the problem of applicability of conventional carbon content determination of curved surface samples, it still needs to carburize the sample before using electron probe for quantitative detection, and it is unable to directly give the effective carburized layer depth and HRC60 carburized layer depth ratio.

[0004] "A method for manufacturing carburized hardened gears" CN110948190A improves the service reliability of gears from the perspective of controlling the machining allowance before and after carburization, but cannot infer the relevant metallurgical characteristics of the carburized layer at the root fillet. "A method for controlling film-like residual austenite suitable for heavy-duty carburized gears" CN114908242A controls the morphological characteristics of the residual austenite film in the carburized layer to improve the load-bearing capacity and wear resistance of the carburized layer. The entire text does not mention the evaluation information and methods of the metallurgical characteristics of the carburized layer at the root fillet.

[0005] In "A high-performance gear heat treatment method to achieve fine and uniform structure" CN110951962A, the martensitic structure and average grain size in different areas of the gear are made finer and more uniform by refining and optimizing the process parameters, and the carbide distribution in the carburized layer is more dispersed, which significantly enhances the fatigue strength, impact toughness and wear resistance of the gear. However, this process method does not consider the influence of the curvature difference of the gear tooth surface on the metallurgical characteristics of the root carburized layer area. Heat treatment practitioners cannot understand the metallurgical characteristics of the effective depth of the root fillet carburized layer and the HRC60 depth ratio through the metallurgical characteristics of the carburized layer of the intermediate circle of the tooth height.

[0006] "Carburizing and quenching method for low-speed heavy-loaded gears" CN106756753A and "Heat treatment method for shallow carburizing of steel" CN111424230B mainly describe the carburizing and quenching method and parameters of gears, and do not involve the metallurgical characteristics of the carburized layer at the root fillet. "A controlled carburizing process method for aviation carburized parts" CN111364000A and "A conventional carburized gear steel carburizing layer control method" CN117089801A achieve the process purpose of controlling the effective carburizing layer depth and HRC60 depth by controlling the furnace cooling time and carbon potential after strong carburization. However, the relevant patents only consider the carburizing layer depth of the tooth profile surface and the tooth height, and do not consider the negative curvature at the root fillet due to the curvature factor, which leads to a significant decrease in the carburizing layer depth and HRC60 ratio.

[0007] The paper "The Effect of Carburizing Method on the Carburized Layer of 18CrNi4A Steel Gears" analyzes the difference in carburized layer depth and HRC60 effective carburized layer depth caused by curvature at the middle graduation circle of gear teeth and the root fillet position, but does not establish a numerical relationship between the effective carburized layer depth and HRC60 carburized layer depth between the middle graduation circle of tooth height and the root fillet. Process personnel can only determine whether the measured metallurgical properties related to the root fillet can simultaneously meet the process requirements when the metallurgical properties of the carburized layer at the middle graduation circle of tooth height meet the requirements after carburizing the parts.

[0008] During the carburizing surface modification of the gear tooth surface, due to the influence of curvature, the effective carburizing layer depth and HRC60 layer depth at the root fillet position are lower than the relevant values ​​at the middle graduation circle position of the tooth height. As a result, the carburizing process cannot meet the relevant numerical index requirements given in the design, resulting in poor coordination between design and manufacturing.

[0009] High-precision gears have high manufacturing costs and long production cycles. Currently, there is a lack of effective evaluation methods to determine whether the metallurgical properties of the carburized layer depth at the given tooth root fillet position can meet the process requirements directly through the involute gear tooth profile parameters and the carburized layer depth of the tooth height intermediate circle (the effective carburized layer depth ranges from 0.70 to 1.50 mm) without part testing. Summary of the invention

[0010] The technical problem to be solved by the present invention is to provide a method for detecting the carburized layer depth of the tooth root fillet of an involute gear, so as to determine whether the carburized layer depth of the tooth root fillet given by the design part can meet the process requirements without undergoing process experiments.

[0011] The technical solution of the present invention is:

[0012] A method for detecting the depth of a carburized layer of an involute gear tooth root fillet, comprising:

[0013] Step 1: Find the module and number of teeth of the involute gear through the drawing, and calculate the pitch circle diameter and root circle diameter respectively.

[0014] Step 2: According to the given tooth height partial graduation circle process, the average value x of the effective carburized layer ep And the minimum depth of HRC60 penetration layer x 60p , calculate the average value x of the effective carburized layer at the tooth root er And the average value of HRC60 penetration depth x 60r ;

[0015] Step 3: The calculated x er Compared with the average value x of the effective carburized layer at the tooth root given in the design e By comparison, the calculated tooth root HRC60 x 60r Compared with the designed effective carburized layer average value x of the tooth root HRC60 60 When the calculated x is compared er and x 60r All values ​​are greater than the design given x e and x 60 When the values ​​are calculated, the test conclusion is that the given carburizing layer depth of the tooth root fillet and the HRC60 layer depth can be achieved through the carburizing process.

[0016] Specifically, step 1 includes:

[0017] Pitch circle diameter d1 = m × z, where m is the module and z is the number of teeth; tooth root circle diameter h f ; The grinding allowance setting value is δ;

[0018] The equivalent carburizing area diameter at the pitch circle is d=d1+δ=m×z+δ.

[0019] Step 2 includes:

[0020] Calculate the average value x of the effective carburized layer at the tooth root er And the average value of HRC60 penetration depth x 60r :

[0021]

[0022] Furthermore, step 3 also includes:

[0023] When the calculated x er Less than the design given x e The value of x is calculated. 60r The value is less than the design given x 60 When the values ​​are calculated, the test conclusion is that the given carburizing layer depth of the tooth root fillet and the HRC60 layer depth cannot be achieved through the carburizing process.

[0024] When the given carburizing layer depth and HRC60 layer depth of the tooth root fillet cannot be achieved through the carburizing process, it is necessary to coordinate the design part to change the effective carburizing layer depth and HRC60 layer depth of the tooth root fillet, x e and x 60 The corresponding value is changed to x er and x 60r .

[0025] Step 3 further includes:

[0026] When the calculated x er and x 60r In the numerical value, x er Less than x e , or x 60r Less than x 60 When e or x 60 The value in the calculation is changed to the corresponding value.

[0027] Specifically, the initial setting value of the grinding allowance is δ≤0.3 mm.

[0028] Root diameter h f =1.25m.

[0029] The beneficial effect of the present application is that, without conducting part testing, by designing given gear tooth profile parameters and information related to the carburizing layer depth at the tooth height half circle and the grinding allowance after carburizing in the middle of the tooth height, it is possible to directly detect whether the carburizing layer depth design of the root fillet of an involute gear with an effective carburizing layer depth range of 0.70 to 1.50 mm at the position of the tooth height half circle meets the requirements, and a corresponding adjustment strategy is given. DETAILED DESCRIPTION

[0030] The present application is further described in detail below with reference to embodiments.

[0031] The present invention provides a method for detecting the carburized layer depth of the tooth root fillet of an involute gear, especially when the effective carburized layer depth at the middle graduation circle position of the tooth profile surface tooth height is 0.70-1.50 mm, under the premise of not undergoing a process experiment, it is determined whether the carburized layer depth of the tooth root fillet given by the design part can meet the process requirements.

[0032] First, find the involute gear module and number of teeth through the drawing, and calculate the pitch circle diameter and root circle diameter respectively.

[0033] Pitch circle diameter d1 = m × z;

[0034] Root diameter h f =1.25m;

[0035] Considering the grinding allowance corresponding to the carburized layer depth of 0.70-1.50 mm, the grinding allowance setting value is δ, δ≤0.3 mm. The equivalent carburized area diameter at the pitch circle is d=d1+δ=m×z+δ.

[0036] Secondly, set the average value x of the effective carburized layer of the tooth height partial graduation circle process given by the design ep And the minimum depth of HRC60 penetration layer x 60p .

[0037] Calculate the average value x of the effective carburized layer at the tooth root er And the average value of HRC60 penetration depth x 60r :

[0038]

[0039] Calculate the obtained x er and x 60r , respectively, and the average value x of the effective carburized layer at the tooth root given in the design e and the mean value x 60 For comparison:

[0040] 1) When the calculated x er and x 60r All values ​​are greater than the design given x e and x 60 When the value is , it indicates that the given designed carburizing layer depth of tooth root fillet and HRC60 layer depth can be achieved through the carburizing process.

[0041] 2) When the calculated x er and x 60r All values ​​are less than the design given x e and x 60 When the value is x, it indicates that the given carburizing layer depth and HRC60 layer depth of the tooth root fillet cannot be achieved through the carburizing process, and the design needs to coordinate the change of the effective carburizing layer depth and HRC60 layer depth of the tooth root fillet. e and x 60 The corresponding value is changed to x er and x 60r .

[0042] 3) When the calculated x er and x 60r Among the values, there is one that is smaller than the designed x e and x 60 When a value is smaller than a certain value, change the smaller value to the calculated value.

[0043] Example

[0044] A certain involute sun planetary gear has a module of 2.822mm, 47 teeth, a pressure angle of 20°, and is made of 9310 steel. The grinding allowance of the tooth surface after carburizing is 0.20mm. The design requires that the carburizing layer depth at the middle graduation circle of the tooth surface and tooth height be 0.90~1.10mm, and the HRC60 carburizing layer depth be ≥0.45mm. The carburizing layer depth at the root fillet position is 0.85~1.05mm, and the HRC carburizing layer depth is ≥0.36mm.

[0045] First, the involute gear module and number of teeth are used to calculate the pitch circle diameter and root circle diameter respectively.

[0046] Pitch circle diameter d1 = m × z = 2.822 × 47 = 132.634 mm;

[0047] The modulus at the middle graduation circle of the tooth height is δ = 0.20 mm;

[0048] Root diameter h f =1.25m=1.25×2.822=3.5275mm;

[0049] The diameter of the carburized area d = d1 + δ = m × z + δ = 132.634 + 0.20 = 132.834 mm.

[0050] Then calculate the average value x of the effective carburized layer at the tooth root er And the average value of HRC60 penetration depth x 60r ——

[0051]

[0052] x er =(0.90+1.10)÷2×e -6×3.5275÷(3.5275+132.834+0.20) =0.8562mm<(0.85+1.05)

[0053] ÷2=0.95mm

[0054]

[0055] x 60r =0.45×e -8×3.5275÷(3.5275+132.834+0.20) =0.3659mm>0.36mm

[0056] The calculation results show that the depth of the HRC60 infiltration layer of the tooth root fillet that can be achieved by the process is 0.365877mm, which is higher than the 0.36mm given in the design, and there is no process risk. The effective infiltration layer depth of the tooth root fillet that can be achieved by the process is 0.8562mm, which is lower than the 0.95mm given in the design, and there is a process risk.

[0057] Therefore, it is necessary to carry out design and manufacturing collaboration to reduce the effective carburized layer depth of the tooth root fillet after carburizing to below 0.85mm.

[0058] Through the above simple calculation method, the rationality of the effective carburized layer depth and HRC60 layer depth at the root fillet position can be directly determined according to the effective carburized layer depth and HRC60 layer depth at the middle graduation circle position of the tooth height given in the design, which provides a design feasibility determination method for the metallurgical characteristics of the carburized layer at the root fillet of involute gears.

Claims

1. A method for detecting the depth of carburized layer at the root fillet of an involute gear, characterized in that: include: Step 1: Find the module and number of teeth of the involute gear through the drawing, and calculate the pitch circle diameter and root circle diameter respectively. Step 2: According to the given tooth height partial graduation circle process, the average value x of the effective carburized layer ep And the minimum depth of HRC60 penetration layer x 60p , calculate the average value x of the effective carburized layer at the tooth root er And the average value of HRC60 penetration depth x 60r ; Step 3: The calculated x er Compared with the average value x of the effective carburized layer at the tooth root given in the design e By comparison, the calculated tooth root HRC60 x 60r Compared with the designed effective carburized layer average value x of the tooth root HRC60 60 When the calculated x is compared er and x 60r All values ​​are greater than the design given x e and x 60 When the values ​​are calculated, the test conclusion is that the given carburizing layer depth of the tooth root fillet and the HRC60 layer depth can be achieved through the carburizing process.

2. A method for detecting the depth of carburized layer at the root fillet of an involute gear according to claim 1, characterized in that: Step 1 includes: Pitch circle diameter d1 = m × z, where m is the module and z is the number of teeth; tooth root circle diameter h f ; The grinding allowance setting value is δ; The equivalent carburizing area diameter at the pitch circle is d=d1+δ=m×z+δ.

3. A method for detecting the depth of carburized layer at the root fillet of an involute gear as claimed in claim 2, characterized in that: Step 2 includes: Calculate the average value x of the effective carburized layer at the tooth root er And the average value of HRC60 penetration depth x 60r :

4. A method for detecting the depth of carburized layer at the root fillet of an involute gear as claimed in claim 3, characterized in that: Step 3 also includes: When the calculated x er Less than the design given x e The value of x is calculated. 60r The value is less than the design given x 60 When the values ​​are calculated, the test conclusion is that the given carburizing layer depth of the tooth root fillet and the HRC60 layer depth cannot be achieved through the carburizing process.

5. A method for detecting the depth of carburized layer at the root fillet of an involute gear as claimed in claim 4, characterized in that: When the given carburizing layer depth and HRC60 layer depth of the tooth root fillet cannot be achieved through the carburizing process, it is necessary to coordinate the design part to change the effective carburizing layer depth and HRC60 layer depth of the tooth root fillet, x e and x 60 The corresponding value is changed to x er and x 60r .

6. A method for detecting the depth of carburized layer at the root fillet of an involute gear as claimed in claim 4, characterized in that: Step 3 also includes: When the calculated x er and x 60r In the numerical value, x er Less than x e , or x 60r Less than x 60 When e or x 60 The value in the calculation is changed to the corresponding value.

7. A method for detecting the depth of carburized layer at the root fillet of an involute gear according to claim 1, characterized in that: The initial setting value of grinding allowance is δ≤0.3mm.

8. A method for detecting the depth of carburized layer at the root fillet of an involute gear according to claim 1, characterized in that: Root diameter h f =1.25m.

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