A processing method for the air intake holes at the bottom of the dovetail groove of a turbine disk

Abstract

The present invention relates to a processing method for the air intake holes at the bottom of the dovetail groove of a turbine disk, belonging to the technical field of aero-engine manufacturing, and specifically comprising the following steps: Step 1: Helical milling of a pilot hole; Step 2: Deep hole machining; Step 3: Reaming; Step 4: Using a ball-end milling cutter to perform two-axis interpolation milling of the flaring and transitional rounding in the symmetry plane of the dovetail groove. By adopting the method provided by the present invention, the processing of the air intake holes at the bottom of the turbine disk dovetail groove can be completed safely and quickly, and the actual application parameters obtained and the life control of each tool can stably and reliably achieve the stable and controlled processing of the air intake holes and the air intake hole inlet structure. The air intake holes and the rounding on the inlet side of the air intake holes processed by this method are detected to have a smooth transition on the hole wall surface and the flaring surface, and the processing process can meet the requirements of the processing quality of the turbine disk and risk avoidance, avoiding huge economic losses caused by part scrapping, and having great economic benefits.

Description

Technical Field

[0001] The present invention belongs to the technical field of aero-engine manufacturing, and particularly relates to a processing method for an air inlet hole at the bottom of a turbine disk tenon groove. Background Art

[0002] The air inlet hole at the bottom of the turbine disk tenon groove is a common structure on the high-pressure turbine disk, and it is an air passage for cooling the turbine blade. The air inlet hole at the bottom of the turbine disk tenon groove is located at the bottom of the tenon groove and is very close to the innermost working tooth of the tenon groove. The accuracy requirements for the process system are very strict, and it is extremely easy to touch the innermost working tooth. At the same time, the length-diameter ratio of the air inlet hole is relatively large, and the orifice of the air inlet hole is often designed with a flared structure in the direction of the symmetry plane of the tenon groove. Specifically, as Figure 1 shown, the air inlet hole on the turbine disk for providing cooling air to the working areas of the high-pressure turbine blade and the tenon groove of the disk rim obliquely passes through the upper web of the disk through the bottom of the tenon groove. The inlet is located in the air collecting ring structure cavity with a relatively closed front end face structure of the turbine disk, and intersects with the bottom fillet of the air collecting ring structure cavity to form a space curve interface. The design requires that this interface be smoothly transitioned with a fillet of R0.5 - R1.6 mm. On the outlet side of the air inlet hole at the bottom of the tenon groove, there is a flared opening with a circular bottom in the direction of the symmetry plane of the tenon groove, and the flared opening and the inner wall of the air inlet hole are smoothly transitioned with a fillet of R1.2 - 2.5. The length of the air inlet hole is nearly 52 mm, the aperture requirement is Φ6.7 mm, and the length-diameter ratio of the hole reaches more than 7. The drilling of the air inlet hole has reached the category of deep hole processing. The flared opening and the inner wall of the air inlet hole are smoothly connected and transitioned by a chamfer. Conventional processing methods usually use drilling, forming milling cutters to process the flared opening, and polishing and chamfering to complete the processing. However, the current method used has great processing difficulty, high labor intensity, and is prone to serious problems of damaging the tenon groove. The air inlet hole is a relatively sensitive part, and suspected crack indications have occurred many times during the engine overhaul. Therefore, the air inlet hole and the chamfering of the air inlet hole must be machined mechanically. Summary of the Invention

[0003] Aiming at the deficiencies of the existing technology, the present invention provides a processing method for an air inlet hole at the bottom of a turbine disk tenon groove. By providing processing steps, it ensures the safe and rapid processing of the air inlet hole and the flared opening at the bottom of the tenon groove, and makes the hole wall and the flared opening structure smoothly chamfered to meet the use requirements.

[0004] A processing method for an air inlet hole at the bottom of a turbine disk tenon groove specifically includes the following steps:

[0005] Step 1: Helical milling of the pilot hole;

[0006] Step 2: Deep hole processing;

[0007] Step 3: Reaming processing;

[0008] Step 4: Use a ball-end mill to perform two-axis interpolation milling for flaring and transitional rounding in the symmetry plane of the mortise groove.

[0009] In Step 1, for helical milling of the pilot hole, use an end mill and adopt a helical plunge milling method with a helix angle of 3°. Machine the flat-bottomed pilot hole with a linear speed of 25 - 30 m / min and a feed per tooth Fz = 0.05 - 0.1 mm. The diameter of the flat-bottomed pilot hole is 0.2 - 0.3 mm smaller than the air vent hole at the bottom of the turbine disk mortise groove and has a depth of 5 - 7 mm.

[0010] The minimum diameter of the end mill is 1 / 2 of the diameter of the air vent hole at the bottom of the turbine disk mortise groove to be machined.

[0011] The minimum diameter of the end mill is 0.6 times the diameter of the air vent hole at the bottom of the turbine disk mortise groove to be machined.

[0012] In Step 2, use an internal cooling drill bit. After entering the pilot hole along the axis of the air vent hole, machine at a linear speed of 8 - 10 m / min and a feed per revolution of 0.04 - 0.06 mm, supplemented by cooling with a pressure of more than 40 Bar, and drill through the air vent hole in one pass.

[0013] The diameter of the internal cooling drill bit is the same as the diameter of the flat-bottomed pilot hole.

[0014] In Step 3, use a three-edge expanding mill with the same diameter as the air vent hole at the bottom of the turbine disk mortise groove to be machined. Machine at a linear speed of 20 m / min and a feed per revolution of 0.06 mm, supplemented by cooling with a pressure of more than 40 Bar, and expand the air vent hole to the qualified diameter in one pass.

[0015] Step 4 specifically includes the following steps:

[0016] ① Use the coordinate transformation command in the numerical control system to offset the working coordinate system to the intersection position of the axis of the air vent hole and the bottom surface of the mortise groove. At the same time, make the XZ plane of the working coordinate system parallel to the symmetry plane of the mortise groove, and the Z axis form a 20° angle with the axis of the air vent hole. Use a ball-end mill with the same diameter as the flat-bottomed pilot hole, at a linear speed of 25 m / min, with a layer depth of cut not greater than 0.5 mm, and a feed per tooth Fz = 0.04 - 0.06 mm. Rough mill the circular round-bottom flaring of the air vent hole in layers along the flaring section line in the XZ plane, leaving a 0.2 mm allowance.

[0017] ② Use the coordinate transformation instruction in the numerical control system to offset the working coordinate system to the intersection position of the axis of the air intake hole and the bottom surface of the tenon groove. At the same time, make the XZ plane of the working coordinate system parallel to the symmetry plane of the tenon groove, and the Z axis parallel to the axis of the air intake hole. Use a ball-end milling cutter with the same aperture size as the flat-bottomed guide hole, with a linear velocity of 25 m / min, a cutting depth per layer not greater than 0.5 mm, and a feed per tooth Fz = 0.04 - 0.06 mm. Mill the fillet transition part between the flared opening and the inner wall of the air intake hole in layers along the fillet section line of the transition fillet in the XZ plane, leaving a margin of 0.2 mm.

[0018] ③ Use the coordinate transformation instruction in the numerical control system to offset the working coordinate system to the intersection position of the axis of the air intake hole and the bottom surface of the tenon groove. At the same time, make the XZ plane of the working coordinate system parallel to the symmetry plane of the tenon groove, and the Z axis parallel to the axis of the air intake hole. Precision mill the circular round-bottomed flared opening of the air intake hole and the fillet transition between the flared opening and the inner wall of the air intake hole along the flared opening and the fillet section line of the transition fillet in the XZ plane.

[0019] The beneficial effects of the present invention are as follows:

[0020] By using the method provided by the present invention, the machining of the air intake hole at the bottom of the tenon groove of the turbine disk can be completed safely and quickly. The obtained actual application parameters and the life control of each tool can stably and reliably achieve the stable and controlled machining of the air intake hole and the structure of the air intake hole inlet. The air intake hole and the chamfer on the inlet side of the air intake hole machined by this method are detected to have a smooth transition on the hole wall surface and the flared opening surface. The machining process can meet the machining quality requirements of the turbine disk and avoid risks, preventing huge economic losses caused by part scrapping, and having great economic benefits. Description of the Drawings

[0021] Figure 1 It is a structural diagram of the air intake hole at the bottom of the tenon groove of the turbine disk;

[0022] Figure 2 It is a schematic diagram of rough milling the flared opening of the air intake hole in step four of the present invention;

[0023] Figure 3 It is a schematic diagram of rough milling the transition part in step four of the present invention;

[0024] Figure 4 It is a schematic diagram of precision milling the flared opening and the fillet transition in step four of the present invention;

[0025] Among them,

[0026] 1 - ball-end milling cutter, 2 - air intake hole. Detailed Embodiments

[0027] To better explain the present invention for easy understanding, the technical solutions and effects of the present invention will be described in detail below with reference to the drawings and through specific embodiments.

[0028] Example 1

[0029] A processing method for the air intake hole at the bottom of the dovetail groove of a turbine disk specifically includes the following steps:

[0030] Step 1: Milling the pilot hole in a spiral

[0031] In this embodiment, a φ4 end mill is used, and a spiral ramp milling method with a spiral angle of 3° is adopted. With a linear velocity of 25 - 30 m / min and a feed per tooth Fz = 0.05 mm, a flat-bottom pilot hole with a diameter of φ6.4 and a depth of 5 mm is machined. On the one hand, a plane perpendicular to the axis of the air intake hole 2 is milled at the inclined bottom of the dovetail groove, facilitating drilling. On the other hand, the pilot hole can play a role in guiding the drill bit and improving the drilling accuracy.

[0032] Step 2: Deep hole machining

[0033] Using a φ6.4 internal cooling drill bit, after entering the pilot hole along the axis of the air intake hole 2, with a linear velocity of 8 m / min and a feed per revolution of 0.04 mm, and assisted by cooling with a pressure above 40 Bar, the air intake hole 2 is drilled through in one go.

[0034] Step 3: Reaming machining

[0035] Using a φ6.7 three-edge reaming cutter, with a linear velocity of 20 m / min and a feed per revolution of 0.06 mm, and assisted by cooling with a pressure above 40 Bar, the air intake hole 2 is reamed to the qualified aperture in one go.

[0036] Step 4: Using the ball-end mill 1 to perform two-axis interpolation milling for flaring and transitional rounding in the symmetric plane of the dovetail groove

[0037] ① Using the coordinate transformation instruction in the numerical control system, in this embodiment, the Cycle800 instruction is adopted. The working coordinate system is offset to the intersection position of the axis of the air intake hole 2 and the bottom surface of the dovetail groove. At the same time, the XZ plane of the working coordinate system is parallel to the symmetric plane of the dovetail groove, and the Z axis forms a 20° angle with the axis of the air intake hole 2. The purpose is to make the axis of the milling cutter form a certain Euler angle with the machined surface and avoid the zero point of the rotational speed of the tip of the milling cutter from contacting the machined surface. In this embodiment, a φ6.4 ball-end mill 1 is used, with a linear velocity of 25 m / min, a cutting depth per layer not greater than 0.5 mm, and a feed per tooth Fz = 0.04 mm. The circular bottom flaring of the air intake hole 2 is rough milled layer by layer along the flaring cross-section line in the XZ plane, leaving a 0.2 mm allowance. As Figure 2 shown.

[0038] ② Using the coordinate transformation instruction in the numerical control system, the working coordinate system is offset to the intersection position of the axis of the air intake hole 2 and the bottom surface of the dovetail groove. At the same time, the XZ plane of the working coordinate system is parallel to the symmetric plane of the dovetail groove, and the Z axis is parallel to the axis of the air intake hole 2. In this embodiment, use The ball-end milling cutter 1 mills the rounded transition part of the inner wall of the flared opening and the air intake hole 2 in layers along the cross-section line of the transition fillet in the XZ plane at a linear velocity of 25 m / min, with a cutting depth per layer not exceeding 0.5 mm and a feed per tooth Fz = 0.04 mm, leaving a margin of 0.2 mm. As Figure 3 shown.

[0039] ③ Use the coordinate transformation instruction in the numerical control system to offset the working coordinate system to the intersection position of the axis of the air intake hole 2 and the bottom surface of the mortise groove. At the same time, make the XZ plane of the working coordinate system parallel to the symmetry plane of the mortise groove, and the Z axis parallel to the axis of the air intake hole 2. Precision mill the circular round-bottom flared opening of the air intake hole 2 and the transition fillet between the flared opening and the inner wall of the air intake hole 2 along the cross-section lines of the flared opening and the transition fillet in the XZ plane. As Figure 4 shown.

Claims

1. A processing method for the air intake hole at the bottom of the dovetail groove of a turbine disk, characterized in that, Specifically, it includes the following steps: Step 1: Helical milling of the pilot hole; Use an end mill to mill the flat-bottomed pilot hole with a helical angle of 3° in a helical plunge milling mode at a linear speed of 25 - 30 m / min and a feed per tooth Fz = 0.05 - 0.1 mm; the diameter of the flat-bottomed pilot hole is 0.2 - 0.3 mm smaller than the air intake hole at the bottom of the turbine disk tenon groove and has a depth of 5 - 7 mm; Step 2: Deep hole machining; Use an internally cooled drill bit. After entering the pilot hole along the axis of the air intake hole, machine at a linear speed of 8 - 10 m / min and a feed per revolution of 0.04 - 0.06 mm, supplemented by cooling with a pressure of more than 40 Bar, and drill through the air intake hole in one pass; Step 3: Reaming machining; Use a three-edge reaming cutter with the same diameter as the air intake hole at the bottom of the turbine disk tenon groove to be machined. Machine at a linear speed of 20 m / min and a feed per revolution of 0.06 mm, supplemented by cooling with a pressure of more than 40 Bar, and ream the air intake hole to the qualified diameter in one pass; Step 4: Use a ball-end mill to perform two-axis interpolation milling of the flaring and transitional filleting within the symmetry plane of the tenon groove; Specifically, it includes the following steps: ① Use the coordinate transformation instruction in the numerical control system to offset the working coordinate system to the intersection position of the axis of the air intake hole and the bottom surface of the tenon groove, and at the same time make the XZ plane of the working coordinate system parallel to the symmetry plane of the tenon groove, and the Z axis form a 20° angle with the axis of the air intake hole; use a ball-end mill with the same diameter as the flat-bottomed pilot hole to perform rough milling of the circular round-bottom flaring of the air intake hole in layers along the flaring cross-section line in the XZ plane at a linear speed of 25 m / min, with a depth of cut per layer not greater than 0.5 mm and a feed per tooth Fz = 0.04 - 0.06 mm, leaving a 0.2 mm allowance; ② Use the coordinate transformation instruction in the numerical control system to offset the working coordinate system to the intersection position of the axis of the air intake hole and the bottom surface of the tenon groove, and at the same time make the XZ plane of the working coordinate system parallel to the symmetry plane of the tenon groove, and the Z axis parallel to the axis of the air intake hole; use a ball-end mill with the same diameter as the flat-bottomed pilot hole to perform milling of the fillet transition part between the flaring and the inner wall of the air intake hole in layers along the transitional fillet cross-section line in the XZ plane at a linear speed of 25 m / min, with a depth of cut per layer not greater than 0.5 mm and a feed per tooth Fz = 0.04 - 0.06 mm, leaving a 0.2 mm allowance; ③ Use the coordinate transformation instruction in the numerical control system to offset the working coordinate system to the intersection position of the axis of the air intake hole and the bottom surface of the tenon groove, and at the same time make the XZ plane of the working coordinate system parallel to the symmetry plane of the tenon groove, and the Z axis parallel to the axis of the air intake hole; perform finish milling of the circular round-bottom flaring of the air intake hole and the transitional fillet between the flaring and the inner wall of the air intake hole along the flaring and transitional fillet cross-section lines in the XZ plane.

2. The processing method of the air intake hole at the bottom of the dovetail groove of a turbine disk according to claim 1, characterized in that: The minimum diameter of the end mill is 1 / 2 of the diameter of the air intake hole at the bottom of the turbine disk tenon groove to be machined.

3. A machining method for the air intake holes at the bottom of the dovetail groove of a turbine disk according to claim 1, characterized in that: The minimum diameter of the end mill is 0.6 times the diameter of the air intake hole at the bottom of the turbine disk tenon groove to be machined.

4. A machining method for the air intake hole at the bottom of the dovetail groove of a turbine disk according to claim 1, characterized in that: The diameter of the internally cooled drill bit is the same as the diameter of the flat-bottomed pilot hole.

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