Shot peening arc height consistency adjustment method for gear parts and test piece fixing tool

Abstract

The application discloses a shot peening arc height consistency adjusting method of gear parts and a test piece fixing tool thereof. The test piece fixing tool comprises a tool main body, the tool main body is divided into a first part and a second part along a length direction, a front end surface of the first part is used as a first base, two side surfaces of the second part are used as a second base and a third base, the first base, the second base and the third base are respectively used for fixing an Almen test piece, a center hole penetrating up and down is arranged in a middle part of the tool main body, the center hole is used for mounting cooperation with a mounting interface of a shot peening equipment base, and a plurality of bolt holes are respectively arranged on the first base, the second base and the third base. The shot peening arc height consistency adjusting method and the test piece fixing tool thereof ensure the consistency of shot peening strength of a gear tooth surface and a gear dedendum, and correspondingly ensure the consistency of residual stress of the gear tooth surface and the gear dedendum.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of mechanical strengthening of metal surface, and relates to a shot blasting arc height consistency adjustment method for gear parts and a test piece fixing tool thereof. BACKGROUND

[0002] In the gear processing industry, gear parts are generally steel parts, and a carburizing and quenching process is used to form a high-strength and wear-resistant surface layer on the gear surface, so that the gear surface has better wear resistance and fatigue life, and can withstand greater load and torque. In the subsequent process, the shot blasting process can be used to remove burrs, scales and other uneven substances on the gear surface, improve the surface roughness, increase the surface hardness, and enhance the wear resistance and fatigue life of the gear. At the same time, the shot blasting process can produce residual compressive stress, which forms a region with a pressure exceeding the yield limit of the material on the metal surface, and the region changes from tensile stress to compressive stress. This residual compressive stress is beneficial to improving the wear resistance and crack propagation resistance of the part surface, and can avoid more plastic deformation or damage caused by external load or temperature change, and can also delay the occurrence of surface cracks, corrosion and other problems.

[0003] The conventional shot blasting process has a higher requirement for the residual compressive stress of the part tooth root, but a lower requirement for the tooth surface. The existing special gear structure parts require that the shot blasting strength of the tooth surface and the tooth root be consistent and meet the shot blasting strength requirements of the drawing. According to the current shot blasting process control means, it is difficult to ensure the consistency of the shot blasting strength of the tooth surface and the tooth root during process debugging, and the tooth surface and the tooth root are often affected. Therefore, it is necessary to research new shot blasting tools and processes. SUMMARY

[0004] The present application aims to provide a shot blasting arc height consistency adjustment method for gear parts and a test piece fixing tool thereof, to solve the problem that the existing shot blasting process is difficult to ensure the consistency of the shot blasting strength of the tooth surface and the tooth root during process debugging of the gear.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] On the one hand, the present application provides an Almen test piece fixing tool, which comprises a tool main body, the tool main body is divided into a first part and a second part along the length direction; the front end surface of the first part serves as a first base, and the two side surfaces of the second part serve as a second base and a third base; the first base, the second base and the third base are respectively used for fixing the Almen test piece; a center hole penetrating up and down is arranged in the middle of the tool main body, and the center hole is used for mounting and cooperating with the mounting interface of the shot blasting equipment base; a plurality of bolt holes are respectively arranged on the first base, the second base and the third base;

[0007] The tooth root circle and the center of the division circle of the gear part are both coincident with the center of the cross section of the center hole; in the same height horizontal section, the line connecting the midpoint of the first base and the center of the center hole is perpendicular to the first base, and the midpoint of the first base is located on the tooth root circle; the second base and the third base are symmetrically arranged, and the included angle between the second base and the third base ranges from 0° to 60°; in the same height horizontal section, the included angle between the line connecting the midpoint of the second base and the center of the center hole and the corresponding base ranges from 14.5° to 30°, and the midpoint of the second base and the third base are both located on the division circle.

[0008] Further, at least four bolt holes are arranged on the first base, the second base and the third base respectively.

[0009] In another aspect, the application provides a shot height consistency adjustment method of a gear part, which is based on the Almen test piece fixing tool of the application, and specifically includes the following steps:

[0010] Step 1, the gear is installed on the shot blasting device base, and the two shot guns are adjusted to point to the center of the gear, and the distance between the two shot guns and the center of the gear is equal, and the relative distance x between the shot gun and the center of the gear for the first shot is determined; the three Almen test pieces are fixed on the Almen test piece tool;

[0011] Step 2, the gear is removed, and the Almen test piece tool with the Almen test pieces installed is replaced, and the shot blasting operation is performed, and after the operation, the arc height values of the three Almen test pieces are detected and recorded; the arc height values of the three Almen test pieces represent the arc height values of the tooth root part, the left tooth surface part and the right tooth surface part of the gear part respectively;

[0012] Step 3, the shot parameters in step 2 are kept unchanged, the Almen test piece tool is removed and replaced with the gear, and the relative distance between the shot gun and the center of the gear is adjusted step by step, and the distance adjustment amount a of each time is determined according to the modulus m of the gear tooth; for the relative distance between the shot gun and the center of the gear after each adjustment, step 2 is performed to obtain the arc height values of the three Almen test pieces when the relative distance between the shot gun and the center of the gear is x+a, x+2a, …, x+na, x-a, x-2a, …, x-na respectively;

[0013] Step 4, the arc height value data of the Almen test pieces corresponding to the left tooth surface part, the right tooth surface part and the tooth root part obtained in step 3 are plotted to obtain three arc height value curves, and the two curves of the arc height value curves of the Almen test pieces of the left tooth surface part and the right tooth surface part are combined into one curve, which intersects with the arc height value curve of the Almen test piece of the tooth root part at one point, and the relative distance between the shot gun and the center of the gear corresponding to the arc height value at the intersection point is taken as the final determined relative distance between the shot gun and the center of the gear.

[0014] Further, in step 1, the relative distance x between the shot gun and the center of the gear in the initial shot is in the range of 0.5d≤x≤1.5d, d being the diameter of the gear.

[0015] Further, in step 1, the single distance adjustment amount a≤m*20mm.

[0016] Compared with the prior art, the present application has the following technical effects:

[0017] 1. The present application designs a general-purpose structure tool for gear structure parts, which combines the key dimensions and angles of the tool with the gear size, and can effectively simulate the shot blasting environment of the gear tooth surface and gear root.

[0018] 2. On the basis of the tool of the present application, the present application provides a shot blasting arc height consistency adjustment method for gear parts applied in shot blasting process, which ensures the consistency of the shot blasting strength of the gear tooth surface and gear root through the use of the tool and the adjustment of the distance between the shot gun and the center of the gear, and accordingly ensures the consistency of the residual stress of the tooth surface and gear root. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a front view of the Almen test piece fixing tool of the present application.

[0020] Figure 2 It is a left view of the Almen test piece fixing tool of the present application.

[0021] Figure 3 It is a schematic view of the Almen test piece after being fixed by the Almen test piece fixing tool of the present application.

[0022] Figure 4 It is a top view of the Almen test piece fixing tool of the present application.

[0023] Figure 5 It is a top view of the Almen test piece fixing tool with the first base and the second base at an angle of 60°.

[0024] Figure 6 It is a test flow of the shot blasting method after the method of the present application.

[0025] Figure 7 It is a curve of the relative distance between the shot gun and the center of the gear and the arc height values of the three test pieces in the shot blasting test of a certain gear.

[0026] Figure 8 It is the detection results of the residual stress of the tooth surface and gear root of a certain gear.

[0027] The present application is further explained and described in conjunction with the accompanying drawings and specific embodiments. DETAILED DESCRIPTION

[0028] In the shot blasting process, the size of impact energy in the shot blasting process is generally detected by using an Almen test piece. The surface layer of the Almen test piece is plastically rheological under the impact of the shot, causing the Almen test piece to bend spherically towards the shot blasting surface. The size of the impact energy is represented by measuring the bending degree. In order to better simulate the shot blasting environment of the gear tooth surface and the gear tooth root, the Almen test piece fixing tool is provided.

[0029] As shown in Figures 1 to 5 , the Almen test piece fixing tool provided by the application comprises a tool body 1, which is divided into a first part 11 and a second part 12 along the length direction; the front end surface of the first part 11 serves as a first base, and the two side surfaces of the second part 12 serve as a second base and a third base; the first base, the second base and the third base are respectively used for fixing the Almen test piece; a center hole 2 penetrating up and down is arranged in the middle of the tool body 1, and the center hole 2 is used for mounting and cooperating with the mounting interface of the shot blasting equipment base; at least four bolt holes are respectively arranged on the first base, the second base and the third base, the four bolt holes are distributed in two rows and two columns, the bolt holes are provided with screws, and are used for detachably mounting the Almen test piece.

[0030] The centers of the gear tooth root circle and the pitch circle of the gear part are coincided with the center of the cross section of the center hole 2 (the gear tooth root circle and the pitch circle are two dashed circles in Figure 4 、 5 , and the diameter of the gear tooth root circle is smaller than that of the pitch circle). In the same height horizontal section, the line connecting the midpoint of the first base and the center of the center hole 2 is perpendicular to the first base, and the midpoint of the first base is located on the gear tooth root circle.

[0031] The second base and the third base are symmetrically arranged, and the included angle between the second base and the third base ranges from 0° to 60°; the design idea of the angle is as follows: A, according to the different types of gear parts, the angle range can adapt to multiple types of gear parts. As shown in Figure 4 , the included angles of the two bases are both 0°, and as shown in Figure 5 , the included angle of the two bases is 60°. B, when the threaded holes of the second base and the third base do not conflict, the second base and the third base can be in parallel state, when the threaded holes at two positions may conflict, the second base and the third base can be avoided by setting a certain included angle, the angle is not suitable to be greater than 60°, in order to ensure the quality distribution uniformity of the tool, if the included angle is too large, the included angle between the Almen test piece and the adjacent area tool surface is too small during shot blasting, and the shot blasting effect is easily affected by the rebounding steel shots of the tool surface.

[0032] In the same height horizontal section, the included angle between the line connecting the midpoint of the second base and the third base and the center of the center hole 2 and the corresponding base ranges from 14.5° to 30° (the angle is consistent with the pressure angle of the gear), and the midpoints of the second base and the third base are located on the pitch circle.

[0033] Because the base size (the base refers to the fixing plane of the test piece on the tool) of the Almen test piece fixing tool has a consistent provision in the national standards, the length, width size and the specification and position of the threaded hole of the fixing plane are set, and the above technical scheme of the present application sets three fixing planes of the Almen test piece as the base, and the Almen test pieces are installed on the three fixing planes to realize the shot blasting environment of the tooth root, the left tooth surface and the right tooth surface of the simulated gear part.

[0034] In the shot blasting process, the hardness of the steel shot is about 58-63 HRC, and in order to ensure the service life of the tool, the surface hardness of the tool 1 is required to be greater than or equal to 60 HRC, and the material and heat treatment process can be selected as low-carbon steel carburizing and quenching or high-carbon tool steel quenching. After heat treatment, the base of the Almen test piece is subjected to heat finishing to ensure the roughness and flatness requirements of the base.

[0035] Based on the Almen test piece tool of the present application, the present application provides a gear part shot blasting arc height consistency adjustment method, which is used before the shot blasting process debugging stage, and specifically includes the following steps:

[0036] Step 1, the gear is installed on the shot blasting device base, and the two shot guns are adjusted to point to the gear center, and the distance between the two shot guns and the gear center is equal, the relative distance x between the shot gun and the gear center is determined for the first time, when the gear diameter is d, the initial selection range of x is generally 0.5d≤x≤1.5d; three Almen test pieces are fixed on the Almen test piece tool;

[0037] Step 2, the gear is removed and replaced with the Almen test piece tool installed with the Almen test piece, and the shot blasting operation is performed, and after the operation, the arc height values of the three Almen test pieces are detected and recorded; the arc height values of the three Almen test pieces respectively represent the arc height values of the tooth root part, the left tooth surface part and the right tooth surface part of the gear part;

[0038] Step 3, keeping the shot blasting parameters in step 2 unchanged, the Almen test piece tool is removed and replaced with the gear, and the relative distance between the shot gun and the gear center is adjusted step by step, and the single distance adjustment amount a is determined according to the modulus m of the part tooth (the smaller the modulus m, the smaller the single distance increase amount a), a≤m*20mm; for the relative distance between the shot gun and the gear center after each adjustment, step 2 is performed to obtain the arc height values of the three Almen test pieces when the relative distance between the shot gun and the gear center is x+a, x+2a, …, x+na, x-a, x-2a, …, x-na respectively;

[0039] Step 4, all the data obtained in step 3 for each part are plotted, and three arc height value curves are obtained (see Figure 5), the test can see that the curve shape of the arc height value of the left tooth surface part and the right tooth surface part of the Almen test piece is basically consistent, and it can be considered as coinciding. The two curves are combined into one curve, and the curve intersects with the arc height value curve of the tooth root part at one point (the arc height values of the three curves at the intersection point are basically equal). The relative distance between the intersection point arc height value corresponding spray gun and the gear center is taken as the final determined relative distance between the spray gun and the gear center. The arc height consistency adjustment method ends.

[0040] The method of the present application is suitable for single-station equipment equipped with double spray guns. The principle of the above method operation is that when the relative distance between the spray gun and the gear center changes, the angle between the spray gun and the gear tooth root and tooth surface also changes when the angle of the spray gun itself does not change. When the angle between the spray gun and the tooth root and tooth surface remains consistent, the corresponding Almen test piece arc height value data is also consistent.

[0041] The conventional shot blasting process focuses on the residual stress of the gear tooth root, and the direction of the spray gun is generally directed to the center of the gear. At this time, the angle between the spray gun and the tooth surface division circle position is about 20-30°. A large number of documents prove that when the shot blasting angle gradually decreases from 90° to 0°, the shot blasting strength gradually decreases. Therefore, in this case, the shot blasting strength of the tooth surface is less than that of the tooth root, which leads to poor consistency of the shot blasting strength of the tooth surface and the tooth root. Based on the above, the present application develops a shot blasting process according to the tooth size of the gear part to design the Almen test piece fixing tooling, and then adjusts the arc height value consistency. The relative distance between the spray gun and the gear center is adjusted to perform shot blasting test, and the test data of each time is counted and summarized. According to the data plot, the relative distance between the spray gun and the gear center that makes the arc height value of the tooth surface and the tooth root consistent is determined. Then the distance is kept unchanged, and the subsequent shot blasting process adjustment is performed to determine the process parameters. After the process parameters are determined, the parts are subjected to shot blasting treatment. The subsequent process adjustment is adjusted according to the part requirements and actual production experience, such as coverage test, shot blasting strength test, etc., which are all conventional operations in the field. As shown in the figure. Finally, the residual stress of the tooth surface and the tooth root is detected to verify the effectiveness of the process. Figure 6

[0042] Figure 7 For the relative distance between the spray gun and the gear center and the arc height value data of each part of a certain gear shot blasting test, it can be seen that when the relative distance x between the spray gun and the gear center is about 190 mm, the arc height value of the tooth surface part and the tooth root part is basically consistent. Figure 8 For the residual stress detection data of the tooth surface and the tooth root of the gear, it can be seen that the residual stress data of the tooth surface and the tooth root is basically consistent, which proves that the method of the present application is effective.​

Claims

1. An Almen specimen fixing fixture, characterized in that, The fixture includes a main body (1), which is divided into a first part (11) and a second part (12) along its length. The front end of the first part (11) serves as a first base, and the two sides of the second part (12) serve as a second base and a third base, respectively. The first base, the second base, and the third base are used to fix the Almen test piece. A central hole (2) is provided in the middle of the fixture body (1), which is used to install and cooperate with the mounting interface of the shot peening equipment base. Multiple bolt holes are provided on the first base, the second base, and the third base, respectively. The centers of the root circle and pitch circle of the gear parts coincide with the center of the cross-section of the central hole (2); in the horizontal cross-section at the same height, the line connecting the midpoint of the first base and the center of the central hole (2) is perpendicular to the first base, and the midpoint of the first base is located on the root circle; the second base and the third base are symmetrically arranged, and the included angle between them is [0°, 60°]; in the horizontal cross-section at the same height, the included angle between the line connecting the midpoint of the second base and the third base and the center of the central hole (2) and the corresponding base is 14.5°~30°, and the midpoints of the second base and the third base are both located on the pitch circle.

2. The Almen specimen fixing fixture as described in claim 1, characterized in that, At least four bolt holes are provided on the first base, the second base and the third base respectively.

3. A method for adjusting the consistency of shot peening arc height in gear parts, characterized in that, The Almen specimen fixing fixture according to claim 1 or 2 specifically includes the following steps: Step 1: Install the gear into the base of the shot peening device, adjust both spray guns to point to the center of the gear, and ensure that the distance between the two spray guns and the center of the gear is equal. Determine the relative distance x between the spray gun and the center of the gear for the first shot peening. Fix the three Almen specimens on the Almen specimen fixture. Step 2: Remove the gear, replace it with an Almen test piece fixture with an Almen test piece installed, and perform shot peening. After the operation, measure and record the arc height values ​​of the three Almen test pieces. The arc height values ​​of the three Almen test pieces represent the arc height values ​​of the tooth root, left tooth surface, and right tooth surface of the gear part, respectively. Step 3: Keeping the shot peening parameters unchanged in Step 2, remove the Almen test piece fixture and replace it with a gear. Adjust the relative distance between the spray gun and the center of the gear one by one. The adjustment amount 'a' for each adjustment is determined according to the module m of the part's teeth. For each adjustment of the relative distance between the spray gun and the center of the gear, execute Step 2 to obtain the arc height values ​​of the three Almen test pieces when the relative distances between the spray gun and the center of the gear are x+a, x+2a, ..., x+na, xa, x-2a, ..., x-na. Step 4: Plot all the data corresponding to each part obtained in Step 3 to obtain three arc height value curves. Combine the arc height value curves of the left tooth surface and the right tooth surface of the Almen test piece into one curve. This curve intersects with the arc height value curve of the Almen test piece at the tooth root at one point. The relative distance between the spray gun and the center of the gear corresponding to the arc height value at the intersection point is taken as the final determined relative distance between the spray gun and the center of the gear.

4. The method for adjusting the shot peening arc height consistency of gear parts as described in claim 3, characterized in that, In step 1, the relative distance x between the shot peening gun and the center of the gear during the initial shot peening is in the range of 0.5d ≤ x ≤ 1.5d, where d is the diameter of the gear.

5. The method for adjusting the consistency of shot peening arc height of gear parts as described in claim 3, characterized in that, In step 1, the distance adjustment amount per step is a ≤ m * 20 mm.

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