High-hardness material large-specification turbine disc mortise machining process method

Abstract

The invention relates to a high-hardness material large-specification turbine disc mortise machining process method. The method comprises the steps that firstly, a cutting test is conducted before machining; (2) formal parts are machined; (3) a remelting layer with the thickness of 0.003 mm left after electric spark cutting 1 and trimming 3 is removed through a magnetic grinding technology; and 4, the surface fatigue performance is improved through the shot peening strengthening effect. According to the technical scheme, through design fatigue performance test verification, the performance meets the practical requirement, all technological processes and parameters are solidified, regular inspection is conducted, and the machining quality stability is guaranteed. The precision wire cut electrical discharge machining technology is adopted, and the product performance is guaranteed in combination with the low-cost surface defect post-treatment and strengthening technology.

Description

Technical Field

[0001] The invention relates to the technical field of powder metallurgy materials for aviation engines, and in particular to a method for processing the tenon groove of a large-size turbine disc made of high-hardness materials. Background Art

[0002] The turbine disc is an important component in aircraft engines. Figure 1 The mortise and tenon grooves are generally straight grooves, forming a certain angle with the plate surface. Figure 2 , conventional processing uses broaching technology. With the continuous development of aero-engine technology, the material of the turbine disc has been upgraded from traditional high-temperature alloy materials to powder metallurgy high-temperature alloy materials. At the same time, the geometry of the mortise and tenon parts has become more and more complex, and the thickness has gradually increased. This has created many technical problems in the field of parts processing. Electric spark wire cutting technology is a highly mature process at home and abroad. It is suitable for processing high-hardness materials, has high cutting accuracy, and has fewer thermal effects and defects. It has been widely used in the processing of precision parts in the aerospace and aviation fields. However, surface defects after wire cutting still affect the batch performance of parts. It is necessary to use low-cost post-processing technology to achieve surface performance after wire cutting to meet product requirements. At the same time, it is necessary to study methods for evaluating surface quality and monitor the stability of processing quality. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a method for processing the tenon groove of a large-sized turbine disc made of high-hardness material; the specific technical solution is as follows:

[0004] A method for machining the tenon groove of a large-sized turbine disc made of high-hardness material, the specific process steps are as follows:

[0005] Step 1: Cutting test before processing

[0006] Before formal parts processing, the surface test of the same height test block is carried out by EDM precision slow wire cutting to meet the target requirements of the mortise and tenon size and surface;

[0007] The requirements are to ensure that the height of the upper thread nozzle is consistent with the height of the part and the actual processing state, the contour of the cutting groove is consistent with the actual mortise, and the angle between the wire cutting wire and the part surface is consistent with the actual angle; the target cutting roughness Ra is set to ≯0.3μm, and the cut 1 trim 3 method is adopted to gradually reduce the processing energy and control the surface quality of each cutting step; the processing energy parameters are iterated through metallographic detection and feedback to control the surface quality of each cutting step; the contour size is measured through three-coordinate or magnified projection detection methods to ensure dimensional accuracy, and the corresponding contour line position needs to be trimmed in case of deviation;

[0008] Step 2: Formal parts processing

[0009] Choose equipment with precision swing shaft and turntable for part cutting; before processing, check the turntable positioning accuracy, swing shaft swing angle position and electrode wire verticality; use low-priced EDM fast wire cutting machine for stress release cutting; use precision multi-axis slow wire cutting machine to perform surface cutting of the final size of the mortise and tenon according to the cut 1 repair 3 method, and the cutting sequence is clockwise or counterclockwise. After completing the fine processing of one mortise and tenon, proceed to the next mortise and tenon processing. This method ensures that the surface state of the processing is consistent with the test state before processing;

[0010] Step 3: Remove the 0.003mm thick remelted layer remaining after EDM cutting 1 and trimming 3 by magnetic grinding process;

[0011] Step 4: Improve surface fatigue performance through shot peening, verify through design fatigue performance test, ensure performance meets practical requirements, solidify each process flow and parameters, and conduct regular inspections to ensure processing quality stability.

[0012] The preferred embodiment of the method for processing the tenon groove of a large-sized turbine disc of a high-hardness material is that in step three, the grinding process step is:

[0013] (1) Magnetic grinding remelting layer process test

[0014] The magnetic grinding parameter test was carried out using a sector-shaped test block. The length and diameter of the magnetic needle were designed according to the minimum R groove of the mortise and tenon. A steel rod with a diameter of 0.1 mm to 0.3 mm was selected as a general magnetic material. The magnetic running direction was designed according to the angle between the mortise and the end face of the part.

[0015] (2) Fixture design and process parameter optimization

[0016] In order to ensure uniform grinding and minimize equipment design, the controllable central shaft drives the turbine disc to rotate, and the turbine disc is used in a vertical manner for grinding the lower tenon groove. 3-5 tenons are ground into the processing groove at one time. During the processing, the turbine disc rotates around the center to change the position of the tenon groove. At the same time, the magnetic pole located below the processing groove is changed through the controllable electromagnetic commutator 4 to achieve the effect of disturbing the abrasive to grind back and forth; thereby achieving a continuous and uniform grinding effect;

[0017] The preferred embodiment of the method for processing the tenon groove of a large-sized turbine disc of a high-hardness material is that in step 4, the shot peening strengthening step is:

[0018] (1) Spear gun shot peening is used instead of conventional shot peening, with the focus on shot peening strengthening at the joint of the mortise and tenon to ensure that the compressive stress intensity at each location is uniform and controllable;

[0019] (2) Design of the mortise and tenon structure test

[0020] Simulate the working conditions of parts and design a set of disc-tenon structure test pieces to meet the design requirements.

[0021] The preferred embodiment of the method for machining the tenon groove of a large-sized turbine disc made of high-hardness material is that in step (2), the actual abrasive and grinding material and the specifications need to be screened according to the grinding material and the minimum R angle polarity of the tenon groove.

[0022] The preferred embodiment of the method for machining the tenon groove of a large-sized turbine disc made of high-hardness material is that, in step (2), 2 to 4 turbine discs are designed according to the weight of the parts for parallel rotation and grinding.

[0023] Beneficial Effects

[0024] Compared with the prior art, the present invention has the following beneficial technical effects:

[0025] The present invention first adopts the electric spark wire cutting process for mortise and tenon cutting. In order to further reduce the manufacturing cost, a low-priced electric spark fast wire machine tool is used for stress release cutting. Then, a higher-priced multi-axis precision electric spark slow wire cutting process is used to achieve the turbine disk mortise and tenon cutting contour accuracy ≯0.02mm, surface roughness Ra ≯0.3μm, and finally metallographic detection is used to verify that the remelted layer thickness is ≤0.003mm.

[0026] The technical solution of the present invention reduces the problems of high cost and large stress deformation in broaching of large-sized turbine disks made of powder materials, realizes a low-cost mortise and tenon processing solution, reduces processing costs for products and shortens development cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a partial schematic diagram of the turbine disc;

[0028] Figure 2 It is a schematic diagram of the tenon-and-groove structure of a turbine disc;

[0029] Figure 3 It is the mortise and tenon structure and the mortise and tenon line cutting route map;

[0030] Figure 4 This is a demonstration diagram of the turbine disc tenon and groove grinding process;

[0031] Figure 5 Schematic diagram of the key shot peening locations.

[0032] In the figure: 1-controllable central shaft, 2-mortise and tenon, 3-magnetic pole, 4-controllable electromagnetic commutator 5-abrasive, 6-turbine disc, 11-rotating thin rod spray gun, 12-mortise and tenon working area, 13-mortise and tenon weak area, 21-slit stress relief cutting path, 22-rectangular stress relief cutting path, 23-rough cutting for blanking, 24-fine cutting once, 25-fine cutting twice, 26-fine cutting three times, 27-cutting groove contour. DETAILED DESCRIPTION

[0033] The following is combined with Figure 1-5 The present invention is described in detail, but the protection scope of the present invention is not limited by the accompanying drawings.

[0034] A low-cost processing method for large-scale turbine disc tenon grooves made of high-hardness materials, which first uses a multi-axis precision EDM wire cutting process to achieve a turbine disc tenon groove cutting contour accuracy of ≯0.02mm, a surface roughness Ra≯0.3μm, and a remelting layer thickness of ≤0.003mm verified by metallographic testing. The steps are as follows:

[0035] Step 1: Cutting test before processing

[0036] Before the formal part processing, the same height test block is carried out for EDM wire cutting test cutting. The key point is to ensure that the height of the upper wire nozzle is consistent with the part height and the actual processing state, the cutting groove profile 27 is consistent with the actual mortise and tenon groove, and the angle between the wire cutting wire and the part surface is consistent with the actual angle. The target setting cutting roughness Ra≯0.3μm, using the cut 1 trim 3 method, see attached Figure 3 ; Cut 1 path is the rough cutting 23 contour line for blanking. After cutting, the mortise and tenon are basically formed, providing uniform margin for fine trimming, generally ≯0.02mm; Repair 1 path is the fine trimming 1 time cutting 24 contour line. After cutting, the contour accuracy is further improved by ≯0.01mm, and the residual surface heat effect of Cut 1 is removed. The general cutting removal amount is 0.06mm; Repair 2 path is the fine trimming 2 times cutting 25 contour line. After cutting, the corner R accuracy is further improved. The overall contour accuracy is ≯0.01. Compared with Repair 1 path, the processing energy is reduced and the roughness is The standard reaches Ra0.6μm~Ra0.7μm. Metallographic inspection is required to ensure that the thickness of the remelted layer is ≤0.006mm, otherwise the parameters need to be optimized. The cutting allowance is generally 0.02mm. The repair 3 path is to fine-tune 3 cutting 26 contour lines. Compared with the repair 2 path, the processing energy is further reduced, and the removal amount is generally 0.007mm, ensuring that the affected layer of the repair 2 path is removed. The roughness target reaches Ra0.3μm, and the residual remelted layer thickness is controlled at ≤0.003mm. If the metallographic inspection fails, the parameters need to be optimized.

[0037] Step 2: Formal parts processing

[0038] Select equipment with a precision swing shaft and turntable to cut parts. The parts are installed on the turntable. After each mortise is cut, it is rotated to the next mortise position through the turntable positioning angle to ensure that the cutting position trajectory is minimized and the contour processing stability is controlled. The wire cutting electrode wire is vertically operated by swinging the B-axis to ensure that there is no interference in the processing of flushing and wire transportation, and it is also convenient to realize the automatic blanking of cutting residues. Before processing, it is necessary to verify the positioning accuracy of the turntable, the swing angle position of the swing shaft, and the verticality of the electrode wire. The diameter of the large-scale engine turbine disk is generally greater than Ф500mm. The internal stress of the part material and the residual stress of the previous mechanical cutting process will cause deformation of the parts during the mortise and tenon grooving process. The deformation includes changes in the outer diameter of the mortise of the disk body and the runout of the end face of the mortise. The changes will affect the cutting size accuracy. Therefore, before proceeding to step one, it is necessary to perform stress release cutting in the middle area of ​​the mortise. The stress release cutting uses a low-priced EDM fast wire-feeding machine. The cutting route is shown in the figure. Figure 3 The middle slit stress relief cutting path 21 and the rectangular stress relief cutting path 22. Generally, the slit stress relief cutting path 21 can basically release the stress of the disk body. The rectangular stress relief cutting path 22 is adopted when cutting thicker mortises or when the material stress changes greatly. Compared with the slit stress relief cutting path 21, the cutting time is longer, but it is not easy to break the wire and the stress release effect is better.

[0039] Step 3: After the EDM fast wire process completes one round of stress release cutting, the part is transferred to a precision multi-axis wire-cutting machine with a swing head and a turntable for mortise and tenon cutting 1, trimming 3, and the cutting sequence is clockwise or counterclockwise. After completing the fine processing of one mortise and tenon, it will proceed to the next mortise and tenon processing. This method can ensure that the processed surface state is consistent with the test state before processing.

[0040] The 0.003mm thick remelted layer remaining after EDM cutting 1 and trimming 3 is removed by magnetic grinding process. After testing, the removal effect of magnetic grinding is relatively uniform, but the removal amount is only 0.005mm, so the surface quality of wire cutting must be strictly controlled according to the wire cutting process plan.

[0041] Step 4: Improve surface fatigue performance through shot peening, verify through design fatigue performance test, ensure performance meets practical requirements, solidify each process flow and parameters, and conduct regular inspections to ensure processing quality stability.

[0042] The grinding process steps are:

[0043] Step 1: Magnetic grinding remelting layer process test

[0044] The magnetic grinding parameter test is carried out using a sector-shaped test block. The length and diameter of the magnetic needle are designed according to the minimum R groove of the mortise and tenon. Generally, a steel bar with a diameter of 0.1mm to 0.3mm is selected from a general magnetic material. The magnetic running direction is designed according to the angle between the mortise and the end face of the part.

[0045] Step 2: Fixture design and process parameter optimization

[0046] In order to ensure uniform grinding and minimize equipment design, the controllable central shaft 1 drives the turbine disc to rotate, and the turbine disc is used in a vertical manner for grinding the lower mortise and tenon grooves. 3-5 mortise grooves 2 in the processing groove are ground at one time. During the processing, the turbine disc 6 rotates around the center to change the position of the mortise and tenon groove 2. At the same time, the magnetic pole 3 located below the processing groove is changed through the controllable electromagnetic commutator 4 to achieve the effect of disturbing the abrasive 5 to grind back and forth; thereby achieving a continuous and uniform grinding effect;

[0047] The test shows that the magnetic grinding process takes a long time, so 2-4 turbine discs can be designed for parallel rotation grinding according to the weight of the parts. The actual abrasives and grinding materials and specifications need to be screened according to the grinding materials and the minimum R angle polarity of the mortise and tenon.

[0048] The shot peening steps are as follows:

[0049] Step 1: Use a rotating thin rod spray gun 11 to perform trajectory shot peening instead of conventional shot peening, see Figure 5 , the focus is on shot peening strengthening at the mortise and tenon joint position. The shot peening trajectory and position can be determined according to the size of the mortise and tenon, and the shot peening direction is consistent with the mortise and tenon direction. The purpose of this process is to ensure that the compressive stress intensity of each point of the overall mortise and tenon is uniform and controllable. At the same time, the surface of the EDM wire cutting is cleaned twice, and the mortise and tenon R position and the mortise and tenon working joint surface are strengthened and cleaned. Before this step, the process parameters should be explored, the surface metallographic inspection and shot peening stress inspection should be carried out on the test piece, and the metallographic inspection of the surface remelting layer residue and the surface depletion phenomenon should be carried out to meet the index requirements, and the surface and surface stress should be checked to meet the index requirements.

[0050] Step 2: Design a test for the tenon-and-mortise structure. Simulate the working conditions of the parts and design a set of high-cycle fatigue test pieces for the tenon-and-mortise structure to meet the required indicators. If the test is not ideal, the shot peening parameters and performance optimization should be focused on the tenon-and-mortise working area 12 and the tenon-and-mortise weak area 13.

Claims

1. A method for processing the tenon groove of a large-sized turbine disc of high-hardness material, characterized in that: The specific process steps are as follows: Step 1: Cutting test before processing Before formal parts processing, the surface test of the same height test block is carried out by EDM precision slow wire cutting to meet the target requirements of the mortise and tenon size and surface; The requirements are to ensure that the height of the upper thread nozzle is consistent with the height of the part and the actual processing state, the contour of the cutting groove is consistent with the actual mortise, and the angle between the wire cutting wire and the part surface is consistent with the actual angle; the target cutting roughness Ra is set to ≯0.3μm, and the cut 1 trim 3 method is adopted to gradually reduce the processing energy and control the surface quality of each cutting step; the processing energy parameters are iterated through metallographic detection and feedback to control the surface quality of each cutting step; the contour size is measured through three-coordinate or magnified projection detection methods to ensure dimensional accuracy, and the corresponding contour line position needs to be trimmed in case of deviation; Step 2: Formal parts processing Choose equipment with precision swing shaft and turntable for part cutting; before processing, check the turntable positioning accuracy, swing shaft swing angle position and electrode wire verticality; use low-priced EDM fast wire cutting machine for stress release cutting; use precision multi-axis slow wire cutting machine to perform surface cutting of the final size of the mortise and tenon according to the cut 1 repair 3 method, and the cutting sequence is clockwise or counterclockwise. After completing the fine processing of one mortise and tenon, proceed to the next mortise and tenon processing. This method ensures that the surface state of the processing is consistent with the test state before processing; Step 3: Remove the 0.003mm thick remelted layer remaining after EDM cutting 1 and trimming 3 by magnetic grinding process; Step 4: Improve surface fatigue performance through shot peening, verify through design fatigue performance test, ensure performance meets practical requirements, solidify each process flow and parameters, and conduct regular inspections to ensure processing quality stability.

2. The method for machining the tenon groove of a large-sized turbine disk made of high-hardness material according to claim 1 is characterized in that: In step three, the grinding process steps are: (1) Magnetic grinding remelting layer process test A sector-shaped test block was used to conduct a magnetic grinding parameter test. The length and diameter of the magnetic needle were designed according to the minimum R groove of the mortise and tenon. A steel rod with a diameter of 0.1 mm to 0.3 mm was selected as a general magnetic material. The magnetic running direction was designed according to the angle between the mortise and the end face of the part. (2) Fixture design and process parameter optimization In order to ensure uniform grinding and minimize equipment design, the controllable central shaft drives the turbine disk to rotate, and the turbine disk is used in a vertical manner for the lower tenon grinding. 3-5 tenons are ground in the processing groove at a time. During the processing, the turbine disk body rotates around the center to change the position of the tenon. At the same time, the magnetic pole located below the processing groove is changed through a controllable electromagnetic commutator to achieve the effect of disturbing the abrasive for reciprocating grinding; thereby achieving continuous and uniform grinding effect.

3. The method for machining the tenon groove of a large-sized turbine disk made of high-hardness material according to claim 1 is characterized in that: In step 4, the shot peening steps are: (1) Spear gun shot peening is used instead of conventional shot peening, with the focus on shot peening strengthening at the mortise and tenon joints to ensure that the compressive stress intensity at each position is uniform and controllable; (2) Design of the mortise and tenon structure test Simulate the working conditions of parts and design a set of disc-tenon structure test pieces to meet the design requirements.

4. The method for machining the tenon groove of a large-sized turbine disk made of high-hardness material according to claim 2 is characterized in that: In step (2), the actual abrasive and grinding material and specifications need to be screened based on the grinding material and the minimum R angle polarity of the mortise and tenon.

5. The method for machining the tenon groove of a large-sized turbine disk made of high-hardness material according to claim 2 is characterized in that: In step (2), 2 to 4 turbine discs are designed according to the weight of the parts for parallel rotation and grinding.

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