A method of forming and machining a high fatigue life blade

Abstract

The application discloses a forming and machining method of a high fatigue life blade, and belongs to the field of blade forming and machining. The method is optimized according to the high fatigue life requirement of the blade, and comprises steps of material selection, forging, precision machining and the like. When a blade blank is prepared, first, titanium alloy bar stock is forged at high temperature to below 50% of the initial height in the axial direction, then the titanium alloy ingot is forged along the radial direction, and further, the TC6 titanium alloy with high homogeneity and weak texture is prepared, which is helpful to improve the durability and fatigue life of the blade. In the blade machining process, when the reverse surface machining is completed and the front surface machining is switched, the machining datum needs to be found again. Since the clamped part of the blade root cannot be used as the machining datum, the method sets a middle table as the machining datum. The positioning and measuring difficulty in the front surface machining is reduced, and the deformation in the machining process caused by the too long clamped machining cantilever of the bottom is also reduced, so that the dimensional accuracy is ensured.

Description

Technical Field

[0001] This invention belongs to the field of blade forming and processing, and more specifically, relates to a method for forming and processing blades with high fatigue life. Background Technology

[0002] Blades are core components of aero-engines, with their surfaces mostly composed of complex free-form surfaces, making them very difficult to manufacture. The processing technology of the material is crucial to the microstructure and significantly affects the fatigue performance of the blade material. Traditional blade manufacturing processes include casting, forging, and machining. These methods meet the manufacturing requirements of blades to a certain extent, but may have limitations under high fatigue life requirements. Advanced manufacturing processes, such as composite material manufacturing processes and precision forming processes, are widely used in blade manufacturing. These processes can provide higher strength, stiffness, and fatigue life, but may also have problems such as high cost and complexity. Summary of the Invention

[0003] In view of the above-mentioned defects or improvement needs of the prior art, the present invention provides a forming and processing method for high fatigue life blades, which can improve the fatigue life of blades while ensuring the processing accuracy of blades.

[0004] To achieve the above objectives, according to a first aspect of the present invention, a method for forming and processing a high fatigue life blade is provided, comprising:

[0005] S1, the titanium alloy bar is axially forged at high temperature to less than 50% of its initial length, then rotated radially and forged multiple times, and then annealed and wire-cut in sequence to obtain the blank;

[0006] S2, use a flat cutter to rough mill the blade root on the reverse side of the blank, and then rough mill the part of the blade on the side of the blade root. Use the unmilled blank as a dividing platform, and fine mill the plane of the dividing platform near the blade root side to make it smooth and parallel to the bottom of the blade root.

[0007] S3. Using the plane as a reference, the workpiece obtained in S2 is rough machined on the front side in sequence using a flat cutter. Then, the centering platform is milled off layer by layer. Finally, the flat cutter, bullnose cutter and ball cutter are used for fine milling in sequence to obtain the target blade.

[0008] According to a second aspect of the present invention, a high fatigue life blade is provided, which is processed by the method described in the first aspect.

[0009] According to a third aspect of the invention, an application of a high fatigue life blade as described in the second invention is provided, which is used as a blade for an aero-engine.

[0010] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0011] 1. The method provided by this invention is optimized for the high fatigue life requirements of blades, including steps such as material selection, forging, and precision machining. For example, when preparing the blade blank, the titanium alloy bar is first forged at high temperature to less than 50% of its length in the axial direction, which can produce a highly homogeneous and weakly textured TC6 titanium alloy, which helps to improve the durability and fatigue life of the blade. Furthermore, in the blade processing flow, when switching from back-side machining to front-side machining, it is usually necessary to find a new machining reference. Since the clamped part of the blade root cannot be used as a machining reference, this method sets a centering platform as the machining reference. This reduces the difficulty of positioning and measurement during front-side machining, and also reduces the excessive deformation during machining caused by the excessively long bottom clamping machining cantilever, thereby ensuring dimensional accuracy.

[0012] 2. The method provided by this invention takes into account the special shape of the blade root, which is difficult to fix. If a CNC center vise is used for clamping, it is difficult to ensure the stability of the processing and thus affect the processing accuracy. Based on this, the method uses a specially made jig for clamping and fixing. The shape of the clamping part (i.e., the groove) formed between the base of the jig and the adjacent sides of the two pads matches the shape of the blade root, which can ensure the stability and accuracy of the blade during the processing. In addition, the manufacture and use of the jig helps to improve the repeatability and efficiency of the process.

[0013] 3. The method provided by the present invention, through the combined use of forging and machining steps, can better control the size and shape of the blades, and improve machining accuracy and consistency; at the same time, the use of aging treatment to eliminate internal residual stress helps to improve the stability and durability of the blades.

[0014] 4. The method provided by the present invention uses tools of different diameters and shapes to perform multiple machining operations in the fine milling step of front-side machining in order to achieve the required surface accuracy and smoothness, which helps to improve the aerodynamic performance and efficiency of the blades.

[0015] 5. The method provided by this invention involves a detailed breakdown and arrangement of the manufacturing and processing of blades to ensure that each step can proceed smoothly and meet the requirements of high fatigue life blades. The optimization and coordination of the overall process helps to improve production efficiency and quality control. Attached Figure Description

[0016] Figure 1 A schematic diagram of the forming and processing method for high fatigue life blades provided in an embodiment of the present invention;

[0017] Figure 2This is a schematic diagram of the intermediate platform for the reverse side processing stage provided in an embodiment of the present invention;

[0018] Figure 3 This is a schematic diagram of the fixture structure provided in an embodiment of the present invention;

[0019] Figure 4 This is a schematic diagram of the front processing stage sub-platform provided in an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0021] This invention provides a method for forming and processing high fatigue life blades, such as... Figure 1 As shown, it includes:

[0022] S1. The titanium alloy bar is axially forged at high temperature to less than 50% of its length, then forged in other directions, and then subjected to annealing heat treatment and wire cutting to obtain a blank.

[0023] Specifically, step S1 includes: blade blank forming stages S1.1-S1.4 and blanking stage S1.5.

[0024] S1.1: Place the original titanium alloy bar into a holding furnace and heat it to 930-950℃ for more than 30 minutes, while preheating the forging die of the forging press.

[0025] S1.2: Forging is performed. First, the titanium alloy bar is forged axially to less than 50% of its length, then repeatedly forged radially while rotating. During forging, the temperature of the billet is carefully observed. If the temperature is insufficient, it needs to be reheated in the furnace for 30 minutes. This continues until the target size block is achieved. Defects generated during forging can be removed by grinding, but the grinding depth must not exceed 1 / 2 of the actual allowance to ensure surface integrity.

[0026] S1.3: After natural cooling, remeasure the blank and check whether the dimensional tolerances meet the requirements; if not, repeat steps S1.1 and S1.2 until the requirements are met.

[0027] S1.4: Perform annealing heat treatment, wherein the annealing temperature range is 800-900℃, preferably 850℃, and the holding time range is 1-2h; allow natural cooling, and note that when heating to 850℃, the heating rate should be greater than 10℃ / min. After the temperature reaches 850℃, place the blank that meets the requirements of S1.3 into the container.

[0028] S1.5: Blanking: Since there may be a tolerance between the blank size obtained in S1.4 and the target size, it is necessary to remove it using a wire EDM machine. Therefore, a wire EDM machine is used to remove most of the blank's excess material, and quality inspection is performed to check whether the dimensions are qualified.

[0029] S2, use a flat cutter to rough mill the blade root on the reverse side of the blank, and then rough mill the part of the blade on the side of the blade root. Use the unmilled blank as a centering platform, and fine mill the plane of the centering platform near the blade root side to make it smooth and parallel to the bottom of the blade root.

[0030] Preferably, the roughness Ra of the plane is less than 0.5 μm.

[0031] Specifically, S2 is the reverse machining stage. In this stage, the blanked part is clamped in a vise and placed in a five-axis machining center for milling, including rough milling and finish milling.

[0032] S2.1: Rough Milling: Using a vise, rough mill the blade root using a flat milling cutter on the reverse side. First, rough mill the blade root portion, then mill the arc surface between the blade root and the top surface of the splitter, i.e., rough mill the blade root side portion. Figure 2 As shown.

[0033] S2.2: Finish Milling: Maintaining the rough milling clamping state, mill the workpiece obtained in S2.1 to perform finish machining, reserving and milling out a centering platform for positioning and measurement during subsequent front-side machining, and accurately finding the zero point of the workpiece. For example... Figure 2 As shown, the plane M of the dividing platform near the leaf root is smooth and parallel to the bottom of the leaf root.

[0034] S3. Using the plane as a reference, the workpiece obtained in S2 is rough machined on the front side in sequence using a flat cutter. Then, the centering platform is milled off layer by layer. Finally, the flat cutter, bullnose cutter and ball cutter are used for fine milling in sequence to obtain the target blade.

[0035] Specifically, S3 is the front-side processing stage.

[0036] It is understandable that in this case, "reverse processing" refers to the vertical placement of the leaf with the root facing upwards during processing, while "front processing" refers to the vertical placement of the leaf with the root facing downwards during processing.

[0037] Preferably, in step S3, before milling the dividing platform layer by layer, the process further includes: aging treatment of the workpiece after rough machining of the front side.

[0038] Preferably, in step S3, a jig is used to clamp the blade root of the workpiece, and a bench vise is used to clamp the jig;

[0039] Among them, such as Figure 3 As shown, the fixture includes a base, screw holes, and two pads; the two pads are embedded in two forming grooves of the base and positioned by the screw holes; the groove formed between the adjacent sides of the base and the two pads is used to clamp the blade root, and the shape of the groove is adapted to / fits the blade root.

[0040] Specifically, the fixture is used for clamping and fixing during front-side machining and milling of the center platform. The fixture consists of two parts: a base and a pad. The angle of the pad's clamping surface needs to be adjusted according to the blade root portion being machined. The machining process of the fixture includes:

[0041] (1) Blanking: Use aluminum machining fixtures and use bench vises to hold the parts in a five-axis machining center for milling.

[0042] (2) Base milling: D10 flat cutter is used to machine the outer shape of the fixture base, and D6 flat cutter is used to finish machine two forming grooves. The forming grooves are located on the upper surface of the fixture and are used to place the pad block; Pad block milling: D10 flat cutter is used to machine the outer shape of the pad block, and D6 flat cutter is used to finish machine the clamping surface and the bottom surface.

[0043] (3) Tapping threaded holes: Tapping two M8 internal threaded holes on the base and the pad respectively;

[0044] (4) Inspection: Inspect the dimensions of the fixture.

[0045] In the S3 front-side machining stage, the aforementioned fixture is used to clamp the blades after the reverse side machining. A vise is then used to fix the fixture on a five-axis machining center for milling, including:

[0046] S3.1: Rough milling: Use a flat milling cutter to rough machine the front side;

[0047] S3.2: Aging treatment: After rough milling, the blade is removed and placed in an aging furnace for 24 hours of free-state aging treatment to eliminate the influence of internal residual stress;

[0048] S3.3: Milling the Centering Platform: After the aging treatment, use the process fixture made in S4 to clamp the blades. Use a vise to fix the fixture on the five-axis machining center, perform tool setting again, and then begin milling the centering platform. Figure 4 As shown ( Figure 4 (Part of the centering platform has been milled), and the previously reserved centering platform is milled flat layer by layer to finally obtain the rough-machined blade.

[0049] S3.4: Finish milling: Use a flat cutter, bullnose cutter and ball cutter in sequence for finish milling to finally obtain the target blade.

[0050] Understandably, for blades of different thicknesses, since the blade shapes are similar, the order of cutting tools is the same for different thickness requirements. However, the size of each type of tool needs to be selected according to the thickness requirements of the blade. For example, if a blade with a thickness of less than 2mm needs to be machined, steps S2 and S3 can both use a D10 flat cutter. In S2.1, a 1mm allowance should be left overall; in S3.1, a 0.6mm allowance should be left on one side; in S3.4, a D10 flat cutter is used to machine the calibration position; a D6R1 bullnose cutter is used to machine the profile (product surface), leaving a 0.1mm allowance; an R1.5 ball end mill is used to machine the profile (the allowance left by D6R1), leaving a 0.1mm allowance; an R1.5 ball end mill is used for finishing the profile, leaving a 0.03mm allowance; an R1 ball end mill is used for the final finishing of the profile, leaving no allowance; machining is complete.

[0051] This invention provides a high fatigue life blade, which is processed using the method described in any of the above embodiments.

[0052] This invention provides an application of a high fatigue life blade as described in the above embodiments, which is used as a blade for an aero-engine.

[0053] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for forming and processing a high fatigue life blade, characterized in that, include: S1, the titanium alloy bar is axially forged at high temperature to less than 50% of its initial height, then forged while rotating radially, and then subjected to annealing heat treatment and wire cutting in sequence to obtain a blank; S2, use a flat cutter to rough mill the blade root on the reverse side of the blank, and then rough mill the part of the blade on the side of the blade root. Use the unmilled blank as a dividing platform, and fine mill the plane of the dividing platform near the blade root side to make it smooth and parallel to the bottom of the blade root. S3. Using the plane as a reference, the workpiece obtained in S2 is rough machined on the front side in sequence using a flat cutter. Then, the centering platform is milled off layer by layer. Finally, the flat cutter, bullnose cutter and ball cutter are used for fine milling in sequence to obtain the target blade.

2. The method as described in claim 1, characterized in that, In step S1, the annealing temperature range of the annealing heat treatment is 800~900℃, and the holding time ranges from 1 to 2 hours.

3. The method as described in claim 1 or 2, characterized in that, In step S3, the blade root of the workpiece is clamped using a jig, and the jig is clamped using a bench vise; The fixture includes a base, screw holes, and two pads; the two pads are embedded in two forming grooves of the base and positioned by the screw holes; the groove formed between the adjacent sides of the base and the two pads is used to clamp the root of the blade, and the shape of the groove is adapted to / fits the root of the blade.

4. The method as described in claim 1, characterized in that, In step S3, before milling away the dividing platform layer by layer, the process further includes: aging treatment of the workpiece after rough machining of the front side.

5. The method as described in claim 1, characterized in that, Steps S2 and S3 are both performed in a five-axis machining center.

6. A blade with high fatigue life, characterized in that, It is obtained by processing using the method described in any one of claims 1-5.

7. An application of the high fatigue life blade as described in claim 6, characterized in that, It is used as blades for aircraft engines.

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