A method for controlling defects in machining thin-walled edges of deformed TiAl alloy blades

Abstract

A method for controlling machining defects on the thin-walled edges of deformed TiAl alloy blades belongs to the field of aeroengine machining technology. The method includes the following steps: first, designing a process table based on the blade structure, using this process table as a unified machining benchmark and clamping location; dividing the thin-walled blade areas prone to chipping and falling into vulnerable areas; during milling, controlling these vulnerable areas, employing a variable parameter programming strategy, and programming the blade using numerical control programming software; outputting the program's cutting force values; applying maximum cutting force limits to program segments, and outputting the optimized program; clamping the deformed TiAl alloy blade's ends in a machining fixture via the process table, installing the fixture on a machining machine; and inputting the optimized program output into the machining machine to machine the blade. This method effectively addresses difficult machining issues such as surface chipping and falling during milling of TiAl alloy workpieces.

Description

Technical Field

[0001] The present invention relates to the technical field of aero-engine machining, and in particular to a method for controlling machining defects of thin-wall edges of deformed TiAl alloy blades. Background Art

[0002] Lightweight and high strength have always been the dominant direction of aviation material research. The technical approach to improving thrust-to-weight ratio, a hallmark of aircraft engines, is to increase the temperature before the turbine and reduce structural weight, which inevitably requires new materials with higher operating temperatures and lower specific gravity. TiAl alloys, also known as TiAl intermetallic compounds, have excellent properties such as low density, high strength, high modulus, high creep resistance, and combustion resistance. Compared with high-temperature alloys, their weight reduction effect can reach 40-50%. TiAl alloys have currently become an ideal weight-reducing material to replace high-temperature alloys in the 650-800°C range. They are suitable for the manufacture of components such as low-pressure turbine blades, high-pressure compressor blades, and stator rings, achieving a significant weight reduction effect.

[0003] At present, the main methods for forming titanium aluminum blade blanks in China are precision casting, additive manufacturing, isothermal precision forging, etc. Since titanium aluminum alloy is a typical hard and brittle material that is difficult to process, thin-walled parts such as the blade intake and exhaust edges and edge plates are very prone to defects such as cracking and falling off during the machining process. This technology mainly focuses on the milling processing of isothermal precision forged titanium aluminum blades. The various surfaces of isothermal precision forged titanium aluminum blades have machining allowances, and full-surface machining is required to obtain the final part shape and size. During the milling process of titanium aluminum blades, due to the hard and brittle problem of the material, the milling process often produces cracking and falling off, and the qualified rate is low, which cannot meet the application requirements of parts.

[0004] This technology is aimed at Figure 1 The deformation TiAl alloy blade processing shown in the figure includes blade body profile, edge plate, blade crown, tenon and other features. The edge plate thickness of the deformed TiAl alloy blade is about 1mm, the exhaust edge thickness is about 0.9mm, and the intake and exhaust edge thickness is about 0.45mm. The deformed TiAl alloy blade has multiple thin-walled structures. Due to the hardness and brittleness of the material and the excessive cutting force and milling vibration during the milling process, the following problems often occur: Figure 2 The cracking and falling of pieces shown in the figure are the main technical difficulties in processing deformed TiAl alloy blades. Realizing defect-free milling of deformed TiAl alloy blades is the key to this technology. Summary of the Invention

[0005] In order to solve the problem that defects such as cracking and falling off are easily generated during the milling process of deformed TiAl alloy blades, the present invention provides a method for controlling processing defects of thin-wall edges of deformed TiAl alloy blades, thereby achieving high-performance and high-quality manufacturing of deformed TiAl alloy blades and improving the surface integrity and working reliability of the workpiece.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] A method for controlling machining defects of thin-walled edges of deformed TiAl alloy blades, comprising the following steps:

[0008] Step 1: Reference design: Based on the deformed TiAl alloy blade structure, two process tables are designed at both ends of the blade. These process tables serve as the unified reference for machining and as the clamping and holding locations.

[0009] Step 2: Area division: The thin-walled parts of the deformed TiAl alloy blades that are prone to cracking and falling off are divided into areas. The area 3mm to 5mm from the intake and exhaust edges is divided into the vulnerable area. At the same time, the edge of the edge plate is divided into the vulnerable area.

[0010] Step 3: Variable parameter low stress milling programming: During milling, control the easily damaged areas, adopt variable parameter programming strategy in the thin wall of edge plate and intake and exhaust edge, and use NC programming software to compile NC milling program for deformed TiAl alloy blade;

[0011] Step 4: Cutting force program simulation: Output the cutting force value of the deformed TiAl alloy blade CNC milling program and analyze the distribution of the cutting force;

[0012] Step 5: Program optimization: According to the cutting force distribution, the NC program of the vulnerable area is segmented. According to the cutting force state of different processing areas, the coordinate critical points of the vulnerable area are extracted. The cutting force is maximized for the program segments within the coordinate critical point area of ​​the deformed TiAl alloy blade NC milling program. The NC milling program of the deformed TiAl alloy blade is optimized and output through simulation software.

[0013] Step 6: Parts clamping: Clamp both ends of the deformed TiAl alloy blade in the processing fixture through the process table, and install the fixture on the processing machine tool;

[0014] Step seven: trial cutting: input the program output after the optimized CNC milling program of the deformed TiAl alloy blade into the processing machine tool, and process the deformed TiAl alloy blade. If the deformed TiAl alloy blade still has local cracks and pieces falling off during the trial cutting, further reduce the cutting force and re-optimize the CNC milling program of the deformed TiAl alloy blade until the deformed TiAl alloy blade size is processed without defects.

[0015] Step 8 Surface inspection: Use 10x magnifying glass for visual inspection and fluorescent inspection to check for cracks and chipping defects in the easily damaged areas of the deformed TiAl alloy blade. If there are no defects, the parameters can be solidified.

[0016] Furthermore, the fixture described in step six part clamping includes a large-end positioning seat, a small-end positioning seat, fastening bolt one, fastening bolt two, pressure plate one and pressure plate two. The large-end positioning seat and the small-end positioning seat are symmetrically arranged. The upper end of the large-end positioning seat is fixed to pressure plate one by bolts, and the upper end of the small-end positioning seat is fixed to pressure plate two by bolts. The end of the large-end positioning seat is screwed into fastening bolt one to fix the process table, and the end of the small-end positioning seat is screwed into fastening bolt two to fix the process table.

[0017] Furthermore, the program compilation described in step three of variable parameter low stress milling programming adopts a spiral machining programming method.

[0018] Furthermore, in step seven, the test cutting is performed Carbide milling cutter, milling cutter coating is PVDAITiN coating, milling cutter consumption is controlled at 0.5~1.

[0019] Beneficial effects of the present invention:

[0020] The present invention can complete high-quality processing of the entire surface of a deformed TiAl alloy blade, effectively solving difficult processing problems such as surface cracking and chipping during the milling process of a TiAl alloy workpiece. The geometric accuracy after processing is stable, and the processing qualification rate is increased by more than 50%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the structure of the deformed TiAl alloy blade provided by the present invention;

[0022] Figure 2 This is a schematic diagram of the cracking and falling defects of the deformed TiAl alloy blade provided by the present invention;

[0023] Figure 3 This is a schematic diagram of the area where the deformed TiAl alloy blade provided by the present invention is prone to cracking and falling off;

[0024] Figure 4 This is a schematic structural diagram of the clamping state of the fixture provided by the present invention;

[0025] Figure 5 This is a schematic diagram of a program with variable parameters after optimization provided by the present invention;

[0026] Figure 6 It is a schematic diagram of the AA cross-sectional structure of the clamp provided by the present invention.

[0027] The reference numerals in the drawings of the specification include:

[0028] 1-large end positioning seat, 2-small end positioning seat, 3-fastening bolt one, 4-fastening bolt two, 5-pressing plate one, 6-pressing plate two, 7-inlet edge, 8-exhaust edge, 9-edge plate, 10-mortise, 11-process table. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0030] A method for controlling machining defects of thin-walled edges of deformed TiAl alloy blades, comprising the following steps:

[0031] Step 1: Reference design: Based on the deformed TiAl alloy blade structure, a process table 11 with a length of 10-15 mm, a width of 25-30 mm, and a thickness of 15-20 mm is milled at both ends.

[0032] Step 2: Area division: The deformed TiAl alloy blade includes the inlet edge 7, the exhaust edge 8, the edge plate 9 and the tenon 10. The area 3mm to 5mm from the edge of the inlet and exhaust 7 is divided into the easily damaged area. At the same time, the edge of the edge plate 9 is also divided into the easily damaged area. The easily damaged area is as follows: Figure 3 shown.

[0033] Step three: variable parameter low stress milling programming: During milling, focus on controlling the milling cutting force and processing parameters of the above-mentioned vulnerable areas, use CNC programming software to compile the CNC milling program of the deformed TiAl alloy blade, use the spiral processing programming method, set the initial processing parameters, the rough processing speed is 2000r / min~3000r / min, the feed speed is 400mm / min~500mm / min, the finishing speed is 3500r / min~4000r / min, and the feed speed is 200mm / min~300mm / min.

[0034] Step 4: Cutting force program simulation: Output the cutting force value of the deformed TiAl alloy blade CNC milling program, analyze the cutting force value of the cutting force simulation result, and the cutting force output result value is between 60N and 100N.

[0035] Step 5: Program optimization: The cutting force will fluctuate with the change of blade shape, especially at the edge position. According to the distribution of cutting force, the NC program of the easily damaged area is segmented. According to the cutting force state of different processing areas, the coordinate critical points of the easily damaged area are extracted. The maximum cutting force of the program segment in the coordinate critical point area of ​​the deformed TiAl alloy blade NC milling program is optimized, and the cutting force of the easily damaged area is set below 40N. The program is optimized through simulation software and output after optimization. The program parameters are as follows: Figure 5 shown.

[0036] Step 6: Clamp the two ends of the deformed TiAl alloy blade into the processing fixture through the process table 11. Figure 4 Install the fixture on the processing machine as shown in Figure 6 The fixture shown includes a large end positioning seat 1, a small end positioning seat 2, a fastening bolt 3, a fastening bolt 4, a pressure plate 5 and a pressure plate 6. The large end positioning seat 1 and the small end positioning seat 2 are symmetrically arranged. The upper end of the large end positioning seat 1 is fixed to the pressure plate 5 by bolts, and the upper end of the small end positioning seat 2 is fixed to the pressure plate 6 by bolts. The end of the large end positioning seat 1 is screwed into the fastening bolt 3 to fix the process table 11, and the end of the small end positioning seat 2 is screwed into the fastening bolt 4 to fix the process table 11. During installation, the process tables 11 at the left and right ends of the deformed TiAl alloy blade are used as the clamping and positioning reference. The clamping at both ends replaces the traditional clamping method of clamping one end of the blade and tightening the top end of the other end. By pressing at both ends, the rigidity of the blade processing process can be increased and the vibration can be reduced. The clamping method of the fixture is as follows Figure 4 As shown. Install the process table 11 at the end of the deformed TiAl alloy blade tenon 10 on the large end positioning seat 1 of the fixture, with the end faces close together. Install the process table 11 at the other end of the blade on the small end positioning seat 2. First, slightly tighten the fastening bolts 1 3 and fastening bolts 2 4, then alternately tighten the pressure plate 1 5 and pressure plate 2 6, check each installation surface with a 0.03mm feeler gauge, and the feeler gauge should not pass. Finally, tighten the fastening bolts 1 3 and fastening bolts 2 4. In this embodiment, the milling cutter is used for processing. For carbide milling cutters, the milling cutter coating is PVD AITiN coating, and the milling cutter consumption is controlled at 0.5~1 to avoid the increase in cutting force caused by milling cutter wear.

[0037] Step seven: trial cutting: input the program output after the optimized CNC milling program of the deformed TiAl alloy blade into the processing machine tool, and process the deformed TiAl alloy blade. The air inlet edge 7, the exhaust edge 8 and the edge plate 9 of the deformed TiAl alloy blade do not produce cracks or falling pieces. If the deformed TiAl alloy blade still has local cracks and falling pieces during the trial cutting, further reduce the cutting force and re-optimize the CNC milling program of the deformed TiAl alloy blade until the deformed TiAl alloy blade size is processed without defects.

[0038] Step 8 Surface inspection: Use 10x magnifying glass for visual inspection and fluorescent inspection to check for cracks and chipping defects in the easily damaged areas of the deformed TiAl alloy blade. If there are no defects, the parameters can be solidified.

Claims

1. A method for controlling machining defects of thin-walled edges of deformed TiAl alloy blades, characterized in that: The following steps are involved: Step 1: Reference design: Based on the deformed TiAl alloy blade structure, two process tables are designed at both ends of the blade. These process tables serve as the unified reference for machining and as the clamping and holding locations. Step 2: Area division: The thin-walled parts of the deformed TiAl alloy blades that are prone to cracking and falling off are divided into areas. The area 3 mm to 5 mm from the intake and exhaust edges is divided into the vulnerable area. The edge of the edge plate is also divided into the vulnerable area. Step 3: Variable parameter low stress milling programming: During milling, control the easily damaged areas, adopt variable parameter programming strategy in the thin wall of edge plate and intake and exhaust edge, and use CNC programming software to compile CNC milling program for deformed TiAl alloy blade; Step 4: Cutting force program simulation: Output the cutting force value of the deformed TiAl alloy blade CNC milling program and analyze the distribution of the cutting force; Step 5: Program optimization: According to the cutting force distribution, the NC program of the vulnerable area is segmented. According to the cutting force state of different processing areas, the coordinate critical points of the vulnerable area are extracted. The cutting force is maximized for the program segments within the coordinate critical point area of ​​the deformed TiAl alloy blade NC milling program. The NC milling program of the deformed TiAl alloy blade is optimized and output through simulation software. Step 6: Parts clamping: Clamp both ends of the deformed TiAl alloy blade in the processing fixture through the process table, and install the fixture on the processing machine tool; Step 7: Processing trial cutting: Input the program output after the CNC milling program optimization processing of the deformed TiAl alloy blade into the processing machine tool, and process the deformed TiAl alloy blade. If the deformed TiAl alloy blade still has local cracking and falling pieces during the trial cutting, further reduce the cutting force and re-optimize the CNC milling program of the deformed TiAl alloy blade until the deformed TiAl alloy blade is processed without defects in size; Step 8 Surface inspection: Use 10x magnifying glass for visual inspection and fluorescent inspection to check for cracks and chipping defects in the easily damaged areas of the deformed TiAl alloy blade. If there are no defects, the parameters can be solidified.

2. The method for controlling defects in thin-wall edge processing of a deformed TiAl alloy blade according to claim 1, characterized in that: The fixture described in step six part clamping includes a large-end locating seat, a small-end locating seat, fastening bolt one, fastening bolt two, pressure plate one and pressure plate two. The large-end locating seat and the small-end locating seat are symmetrically arranged. The upper end of the large-end locating seat is fixed to pressure plate one by bolts, and the upper end of the small-end locating seat is fixed to pressure plate two by bolts. The end of the large-end locating seat is screwed into fastening bolt one to fix the process table, and the end of the small-end locating seat is screwed into fastening bolt two to fix the process table.

3. The method for controlling defects in thin-wall edge processing of a deformed TiAl alloy blade according to claim 1, characterized in that: In step three, the program compilation of variable parameter low stress milling adopts the programming method of spiral machining.

4. The method for controlling machining defects of thin-walled edges of deformed TiAl alloy blades according to claim 1, characterized in that: Step 7: Use φ4~φ10 carbide milling cutter for trial cutting, and use PVD AITiN coating for milling cutter coating.

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