FORGING APPARATUS AND METHOD

Abstract

The present disclosure provides a method of upset forging comprising inserting a stock material into a die, the stock material having a free axial portion with upper and lower surfaces. Next, a punch is used to apply an axial (e.g. horizontal) compression force against the free axial portion of the stock material whilst constraining the upper and lower surfaces of the free axial portion. The constraining position restricts movement of the free axial portion in a direction substantially perpendicular (e.g. vertical) to the axial compression force thus preventing buckling of the free axial portion.

Claims

1. A method of upset forging comprising inserting stock material into a die, such that the stock material has a holding portion and a free axial portion with upper and lower surfaces, the holding portion held in a holding section of the die preventing movement of the stock material in the holding section both in a parallel and perpendicular direction relative to the axial compression force, and using a punch to apply an axial compression force against the free axial portion whilst constraining the upper and lower surfaces of the free axial portion during forging of the free axial portion so as to restrict movement of the free axial portion in a direction substantially perpendicular to the axial compression force.

2. A method according to claim 1, wherein an axial length of the free axial portion is greater than 3 times (optionally 4 or 4.5 times) a thickness of the free axial portion.

3. A method according to claim 1 for forming a fan blade for a gas turbine engine, the method comprising applying an axial compression force to compress the free axial portion of the stock material to form a root section having an increased cross-sectional area.

4. A method according to claim 1 comprising inserting the stock material into the die such that the free axial portion is positioned within a constraining section of the die and preventing movement of the free axial portion of the stock material in a perpendicular direction relative to the axial compression force during forging of the free axial portion whilst allowing axial compression of the free axial portion.

5. A method according to claim 1 comprising inserting the stock material between a first plate and a second plate of a split die where the first and second plates are spaced by a first distance in the holding section, the first spacing equaling the thickness of the portion of the stock material.

6. A method according to claim 5 comprising inserting the free axial portion of the stock material in the constraining section where the first plate and second plate are spaced by a third spacing, the third spacing being up to 5% greater than the first spacing.

7. A method according to claim 1 comprising preventing vertical movement of the free axial portion of stock material by vertically constraining the upper and lower surfaces of the free axial portion during forging of the free axial portion upon application of a horizontal compression force.

8. A die for upset forging by axial compression of a stock material having a holding portion and a free axial portion with upper and lower surfaces, said die having a holding section at a first axial end for securing the holding portion and a constraining section at a second axial end, the holding section and constraining section being axially spaced by a cavity, the constraining section for constraining the upper and lower surfaces of the free axial portion so as to restrict movement of the free axial portion in a direction substantially perpendicular to the axial compression.

9. A die according to claim 8 wherein the holding section is adapted to prevent movement of the stock material both in a parallel and perpendicular direction relative to the axial compression.

10. A die according to claim 8 comprising a first plate and a second plate spaced by a first distance in the holding section, a second spacing in the cavity and a third spacing in the constraining section, wherein the first and second plates in the constraining section define an opening at the second axial end for receiving a punch and the constraining section extends from the cavity to the opening.

11. A die according to claim 10 wherein the second spacing is greater than the first and third spacing.

12. A die according to claim 10 wherein the third spacing is up to 5% greater than the first spacing.

13. A die according to claim 12 wherein the first and third spacings are approximately equal.

14. A die according to claim 10 wherein the die has a diverging section distal the opening in which the first and second plates diverge from the first spacing of the holding section to the increased second spacing of the cavity.

15. A die according to claim 14 further comprising a converging section proximal the opening in which the first and second plates converge to form the constraining section.

16. A die according to claim 10 wherein the first plate is substantially planar and the diverging section is formed by the second plate diverging from the first plate, the second plate creating an inner end wall defining the cavity distal the opening.

17. A die according to claim 16 wherein the converging section of the die is formed by the second plate converging towards the first plate, the second plate creating a second inner end wall defining the cavity proximal the opening.

18. A die according to claim 8 wherein the die is horizontally arranged and the holding section is adapted to prevent horizontal and vertical movement of the portion of stock material and the constraining section is adapted to prevent vertical movement of the free axial end.

19. A forging apparatus comprising a die according to claim 8, and a punch for applying an axial force against the free axial portion of the stock material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Embodiments will now be described by way of example with reference to the accompanying drawings in which:

[0050] FIG. 1 shows a prior art upset forging apparatus;

[0051] FIG. 2 shows a prior art upset forging apparatus for forming a root portion of a blade for a gas turbine engine;

[0052] FIG. 3 shows a first embodiment of an upset forging apparatus according to the third aspect for forming a root portion of a blade for a gas turbine engine; and

[0053] FIG. 4 shows a sectional side view of a gas turbine engine.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0054] FIG. 1 shows a die 12 for forming a root section of a fan blade by upset forging of a portion (sheet or bar) of titanium 11 having a thickness of around 20.8 mm.

[0055] The die 12 comprises a lower plate 16 and an upper plate 17. They extend along the axis of the die from a first axial end defining an opening 20 for receiving a punch 14 to a holding section 21 at a second axial end of the die 12. In the holding section 21, the upper and lower plates 16, 17 are spaced by a first spacing equal to the thickness of the portion of titanium 11 such that the portion of titanium is held/secured in the holding section 21. Both horizontal and vertical movement of the portion of titanium are prevented by the holding section 21.

[0056] The die 12 has a diverging section 22 distal the opening 20 in which the upper and lower plates 16, 17 diverge from the first spacing to an increased spacing to form a cavity 13 between the plates 16, 17. The lower plate 16 diverges away from the substantially planar upper plate 17 and forms an inclined first inner end wall 18.

[0057] The substantially planar upper plate defines a shallow recess 23 which provides a slightly enlarged section of the cavity 13.

[0058] The portion of titanium 11 extends from the holding section 20 at the diverging section 22 and into the cavity 13.

[0059] The die 12 further comprises a converging section 24 proximal the opening 20 in which the upper and lower plates 16, 17 converge to form a constraining section 25 extending from the cavity 13 to the opening 20. The lower plate 16 converges back towards the substantially planar upper plate 17 and forms an inclined second inner end wall 26. The first and second inner end walls 18, 19 are substantially mirror images of one another i.e. the lower plate 16 is substantially symmetrical about the axial centre of the cavity 13.

[0060] The constraining section 25 has a spacing between the upper and lower plates 16, 17 that is less than the spacing between the upper and lower plates in the cavity 13. The spacing between the upper and lower plates 16, 17 in the constraining section substantially matches the first spacing i.e. the spacing between the plates 16, 17 in the holding section and thus the thickness of the portion of titanium 11.

[0061] The portion of titanium extends through the cavity 13 and into the constraining section 25 where it is vertically restrained by the upper and lower plates 16, 17. The total length of the portion of titanium 11 extending from the diverging section equals 95 mm.

[0062] A punch 14 is inserted into the opening 20 between the upper and lower plates 16, 17 at the first axial end of the die 12. The die 14 has a contact surface 19 which has a vertical portion 19A and an inclined portion 19B. The height of the punch 14 matches the spacing between the upper and lower plates 16, 17 in the constraining section 25.

[0063] The die 14 is forced towards the second axial end of the die 12 and the contact surface 19 compresses the portion of titanium 11 into the cavity 13. Even though the forging ratio of length:thickness of 4.57:1 exceed the industry standard of 3:1, buckling of the portion of titanium 11 is prevented by the vertical constraint (perpendicular to the axis of the die) provided by the constraining section 25. Only horizontal movement of the portion of titanium 11 (along the axis of the die) is allowed within the constraining section.

[0064] The cavity 13 (including the recess 23), first and second inner end walls 18, 26 and the contact surface 19 define the impression of the profile of the root section of the fan blade and the compressed titanium 11 is forced into this enlarged cross-sectional profile to form the root section. The portion of titanium 11 remaining uncompressed in the holding section 22 can be machined to form the aerofoil section of the fan blade.

[0065] With reference to FIG. 4, a gas turbine engine is generally indicated at 30, having a principal and rotational axis 31. The engine 30 comprises, in axial flow series, an air intake 32, a propulsive fan 33, an intermediate pressure compressor 34, a high-pressure compressor 35, combustion equipment 36, a high-pressure turbine 37, an intermediate pressure turbine 38, a low-pressure turbine 39 and an exhaust nozzle 40. A nacelle 41 generally surrounds the engine 30 and defines both the intake 32 and the exhaust nozzle 40.

[0066] The gas turbine engine 30 works in the conventional manner so that air entering the intake 32 is accelerated by the fan 33 to produce two air flows: a first air flow into the intermediate pressure compressor 34 and a second air flow which passes through a bypass duct 42 to provide propulsive thrust. The intermediate pressure compressor 34 compresses the air flow directed into it before delivering that air to the high pressure compressor 35 where further compression takes place.

[0067] The compressed air exhausted from the high-pressure compressor 35 is directed into the combustion equipment 36 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines 37, 38, 39 before being exhausted through the nozzle 40 to provide additional propulsive thrust. The high 37, intermediate 38 and low 39 pressure turbines drive respectively the high pressure compressor 35, intermediate pressure compressor 34 and fan 33, each by suitable interconnecting shaft.

[0068] The blades of the fan 33, compressors 34, 35, or turbines 37, 38, 39 may be manufactured using an upset forging apparatus as shown in FIG. 3. It is particularly contemplated that the blades of the fan will be manufactured using the apparatus shown in FIG. 3.

[0069] Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. By way of example such engines may have an alternative number of interconnecting shafts (e.g. two) and/or an alternative number of compressors and/or turbines. Further the engine may comprise a gearbox provided in the drive train from a turbine to a compressor and/or fan.

[0070] It will be understood that the disclosure is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.