High-hardness material large-size turbine disc mortise processing method

Abstract

The present application relates to a kind of high-hardness material large-size turbine disc mortise processing process method, step one: cutting test before processing;Step two: formal part processing step three: through magnetic abrasive process, remove the 0.003mm thickness remelt layer after electric spark cutting 1 repair 3;Step four: through shot peening strengthening effect, improve surface fatigue performance, the technical scheme of the present application is verified by designing fatigue performance test, performance reaches practical demand, solidifies each process flow and parameter, and is regularly checked, guarantee processing quality stability.The present application adopts precision wire electrical discharge machining technology, combines low-cost surface defect post-processing and strengthening technology to ensure product performance.

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-scale turbine disc made of high-hardness material. Background Art

[0002] The turbine disc is an important component in the aircraft engine. Figure 1 The mortise and tenon are generally straight grooves, forming a certain angle with the disk surface. Figure 2 , conventional processing adopts broaching process. With the continuous development of aviation engine technology, the material of turbine disc has been upgraded from traditional high-temperature alloy material to powder metallurgy high-temperature alloy material. At the same time, the geometry of the tongue and groove part has become more and more complex, and the thickness has gradually increased. This has created many technical difficulties in the field of parts processing. Electric spark wire cutting technology is a relatively mature process at home and abroad. It is suitable for processing high-hardness materials, with high cutting accuracy, less thermal impact 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 have an impact on the batch performance of parts. It is necessary to use low-cost post-processing technology to achieve the surface performance after wire cutting to meet product requirements. At the same time, it is necessary to study the method of surface quality evaluation and monitor the stability of the processing process quality. Summary of the Invention

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

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

[0005] Step 1: Cutting test before processing

[0006] Before formal part processing, a surface test of an equal height test block is carried out using precision slow wire EDM to ensure that the mortise and tenon size and surface target requirements are met;

[0007] The requirements are to ensure that the height of the upper wire nozzle from the part is consistent with the actual processing state, the contour of the cutting groove 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 cutting roughness is set to Ra ≤ 0.3μm, and a 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 testing and feedback to control the surface quality of each cutting step; the contour dimensions are measured through three-dimensional coordinate or magnified projection detection methods to ensure dimensional accuracy, and the corresponding contour line position needs to be trimmed if there is a deviation problem;

[0008] Step 2: Formal parts processing

[0009] The device with precision swing shaft and rotary table is selected for part cutting; before processing, the rotary table positioning accuracy, swing shaft swing angle position and electrode wire perpendicularity need to be checked; the low-price electric spark quick wire-cutting machine tool is used for stress relief cutting; the precise multi-axis slow wire-cutting machine tool is used for surface cutting of tenon groove final size according to cutting 1 and repairing 3, the cutting sequence is cut clockwise or counterclockwise in turn, and after the complete precision machining of one tenon groove is completed, the next tenon groove is processed, which ensures that the surface state after processing is consistent with the test state before processing;

[0010] Step three: removing the residual 0.003mm thick remelted layer after electric spark cutting 1 and repairing 3 through magnetic grinding process;

[0011] Step four: improving the surface fatigue performance through shot peening strengthening effect, and verifying the performance through the design of fatigue performance test, the performance meets the practical demand, the process and parameters are solidified, and periodic inspection is carried out to ensure the stability of the processing quality.

[0012] The preferred scheme of the high-hardness material large-specification turbine disc tenon groove machining process method is that, in step three, the grinding process step is:

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

[0014] Fan-shaped test blocks are used for magnetic grinding parameter test, the length and diameter of the magnetic needle are designed according to the smallest R groove of the tenon groove, and a general magnetic material steel bar with a diameter of Ф0.1mm- Ф0.3mm is selected; the magnetic force running direction is designed according to the angle between the tenon groove and the part end face;

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

[0016] In order to ensure uniform grinding and minimize equipment design, the controllable central rotating shaft drives the turbine disc to rotate, and the turbine disc vertical type is used for lower tenon groove grinding, 3-5 tenon grooves in the processing groove are grinded at one time, and the turbine disc body rotates around the center during processing, the tenon groove position is replaced, and the magnetic pole below the processing groove changes through the controllable electromagnetic commutator 4 to achieve the effect of disturbing the abrasive back and forth grinding; so as to achieve the effect of continuous and uniform grinding;

[0017] The preferred scheme of the high-hardness material large-specification turbine disc tenon groove machining process method is that, in step four, the shot peening strengthening step is:

[0018] (1) The lance shot peening method is used instead of the conventional shot peening form, and the shot peening strengthening effect is focused on the tenon groove joint position to ensure that the stress intensity of each bit is uniform and controllable;

[0019] (2) Design of disc tenon structure test

[0020] A set of disc tenon structure test pieces are designed to simulate the working condition of the parts, and the design requirements are met.

[0021] The preferred scheme of the high-hardness material large-specification turbine disc mortise machining process method is that in step (2), the actual abrasive and grinding material and specification need to be selected according to the polarity of the minimum R angle of the grinding material and the mortise.

[0022] The preferred scheme of the high-hardness material large-specification turbine disc mortise machining process method is that in step (2), 2-4 turbine discs are designed for parallel rotary grinding according to the weight of the parts.

[0023] Beneficial effects

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

[0025] The application firstly adopts the wire electrical discharge machining process to cut the mortise, adopts the low-price wire electrical discharge quick machine tool to cut for stress release, then adopts the high-price multi-axis precise wire electrical discharge slow wire cutting process to realize the turbine disc mortise cutting profile precision ≤0.02mm, the surface roughness Ra≤0.3μm, and finally verifies the remelted layer thickness ≤0.003mm through metallographic detection.

[0026] The technical scheme of the application reduces the problems of high cost and large stress deformation of the powder material large-specification turbine disc broaching, realizes the low-cost mortise machining scheme, and reduces the processing cost and shortens the development cycle of the product. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a local schematic view of a turbine disc;

[0028] Figure 2 It is a schematic view of a turbine disc mortise structure;

[0029] Figure 3 It is a mortise structure and mortise wire cutting route view;

[0030] Figure 4 It is a turbine disc mortise grinding process demonstration view;

[0031] Figure 5 It is a schematic view of a key shot peening strengthening position.

[0032] In the figure: 1-controllable center shaft, 2-mortise, 3-magnetic pole, 4-controllable electromagnetic commutator, 5-abrasive, 6-turbine disc, 11-rotary thin rod spray gun, 12-mortise working area, 13-mortise weak area, 21-slotted stress relief cutting path, 22-rectangular stress relief cutting path, 23-rough cutting, 24-1st fine cutting, 25-2nd fine cutting, 26-3rd fine cutting, 27-cutting groove profile. 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 machining process for large-scale turbine disc mortises made of high-hardness materials uses a multi-axis precision wire EDM process to achieve a profile accuracy of ≤0.02mm and a surface roughness Ra ≤0.3μm. Metallographic testing verifies that the remelted layer thickness is ≤0.003mm. 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 points are to ensure that the height of the upper wire nozzle is consistent with the height of the part 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 allowance 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 heat effect of the residual surface 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 main purpose is to further improve the corner R accuracy. 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, and 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 refine the cutting of 26 contour lines 3 times. 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] Choose equipment with a precision swing shaft and turntable for part cutting. The parts are mounted 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 moved by swinging the B-axis to ensure that there is no interference in the processing of flushing and wire feeding, and it is 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 mechanical cutting in the previous process will cause deformation of the parts during the mortise and tenon grooving process. The deformation includes the change of the outer diameter of the mortise of the disk body and the change of the runout of the end face of the mortise. The change will affect the cutting size accuracy. Therefore, before proceeding to step one, stress release cutting is required in the middle area of ​​the mortise. The stress release cutting adopts a low-priced EDM fast wire cutting 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 relief 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-cut machine with a swing head and a turntable for mortise and tenon cutting 1, trimming 3, and cutting. The cutting order is clockwise or counterclockwise. After completing the fine processing of one mortise and tenon, it is transferred 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 was removed by magnetic grinding process. After testing, the removal effect of magnetic grinding was relatively uniform, but the removal amount was only 0.005mm, so the surface quality of wire cutting should 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 that the performance meets practical requirements, solidify each process flow and parameters, and conduct regular inspections to ensure the stability of processing quality.

[0042] The grinding process steps are:

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

[0044] A sector-shaped test block is used for magnetic grinding parameter testing. The length and diameter of the magnetic needle are designed based on the minimum R-slot of the mortise and tenon. Steel rods with a diameter of 0.1mm to 0.3mm are generally used as general-purpose magnetic materials. The direction of magnetic force operation is designed based on the angle between the mortise and the end face of the part.

[0045] Step two: fixture design and process parameter optimization

[0046] To ensure uniform grinding and minimize equipment design, the controllable central rotating shaft 1 drives the turbine disc to rotate, and the turbine disc vertical type is used for lower mortise grinding. 3-5 mortises 2 are processed in the mortise grinding process. The turbine disc 6 rotates around the center, and the magnetic pole 3 below the processing groove changes through the controllable electromagnetic commutator 4 to achieve the effect of disturbing the abrasive 5 back and forth grinding. To achieve continuous and uniform grinding effect;

[0047] After testing, the magnetic force grinding process takes a long time, so 2-4 turbine discs can be designed for parallel rotation grinding according to the weight of the part. The actual abrasive and grinding material and specification need to be selected according to the grinding material and the minimum R angle polarity of the mortise.

[0048] The shot peening step is as follows:

[0049] Step one: replace the conventional shot peening form with a rotating thin rod spray gun 11 for trajectory shot peening, see Figure 5 , the key is to perform shot peening strengthening at the mortise joint position. The shot peening trajectory and position can be determined according to the size of the mortise, and the shot peening direction is consistent with the direction of the mortise. The purpose of this process is to ensure that the stress intensity of each point of the overall mortise is uniform and controllable, and to clean the wire cut surface twice. The R position of the mortise and the working joint surface of the mortise are highlighted and cleaned. Before this step, test pieces should be used to explore process parameters, surface metallographic detection, and shot peening stress detection. The surface remelt layer residue and surface layer depletion phenomenon are checked to meet the index requirements, and the surface and surface layer stress meet the index requirements.

[0050] Step two: design disc mortise structure test. A set of disc mortise structure high cycle fatigue test pieces are designed to simulate the working condition of the part and meet the required index. When the test is not ideal, the mortise working area 12 and the mortise weak area 13 should be highlighted for shot peening parameter optimization and performance optimization.

Claims

1. A method for machining the tenon groove of a large-scale turbine disc made of high-hardness material, characterized by: The specific process steps are as follows: Step 1: Cutting test before processing Before formal part processing, a surface test of an equal height test block is carried out using precision slow wire EDM to ensure that the mortise and tenon size and surface target requirements are met; The requirements are to ensure that the height of the upper wire nozzle from the part is consistent with the actual processing state, the contour of the cutting groove is consistent with the actual groove, and the angle between the wire cutting wire and the part surface is consistent with the actual angle; the target cutting roughness is set to Ra ≤ 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 testing and feedback to control the surface quality of each cutting step; the contour dimensions are measured through three-dimensional coordinate or magnified projection detection to ensure dimensional accuracy, and the corresponding contour line position needs to be trimmed if there is a deviation problem; Step 2: Formal parts processing Select equipment with a precision swing shaft and turntable for part cutting. Before processing, verify the turntable positioning accuracy, swing shaft swing angle position, and electrode wire verticality. Use a high-speed EDM machine for stress relief cutting. Use a precision multi-axis slow-speed EDM machine to perform surface cutting of the final mortise and tenon dimensions using a cut-one-trim-three method. Cut in a clockwise or counterclockwise order, and proceed to the next mortise and tenon after finishing one mortise. This method ensures that the processed surface condition is consistent with the pre-processing test condition. Step 3: Use magnetic grinding process to remove the 0.003mm thick remelted layer remaining after EDM cutting 1 and repair 3; Step 4: Improve surface fatigue performance through shot peening, verify through design fatigue performance test, ensure that the performance meets practical requirements, solidify each process flow and parameters, and conduct regular inspections to ensure the stability of processing quality.

2. The method for machining the mortise and tenon groove of a large-scale turbine disk made of high-hardness material according to claim 1, 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 based on the minimum R groove of the mortise and tenon. A steel rod with a diameter of 0.1mm to 0.3mm was selected as a general magnetic material. The direction of magnetic operation was designed based on the angle between the mortise and the end face of the part. (2) Fixture design and process parameter optimization 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 the lower mortise and tenon grinding. 3-5 mortises in the processing groove are ground at a time. During the processing, the turbine disc rotates around the center to change the mortise and tenon position. 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 back-and-forth grinding; thereby achieving continuous and uniform grinding effect.

3. The method for machining the tongue and groove of a large-scale turbine disk made of high-hardness material according to claim 1, characterized in that: In step 4, the shot peening steps are: (1) Using spear gun shot peening instead of conventional shot peening, shot peening is performed at the joint of the mortise and tenon 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-scale turbine disk made of high-hardness material according to claim 2, characterized in that: In step (2), the actual abrasive and grinding materials and specifications need to be screened based on the grinding materials and the minimum R angle polarity of the mortise and tenon.

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

Images