GB2047131A - Method of making turbine or compressor blade blanks and die set for performing this method - Google Patents

Abstract

A method of making turbine or compressor blade blanks includes providing a blank (18), applying a protecting and lubricating coating thereon, drying the coating and heating the blank (18). Following the above steps, the blank (18) is subjected to progressive deformation along its length conjointly with three-dimensional pressing in a single space of a closed die set (1, 10) in a single operation. Prior to shaping, the blank surface may be profiled to retain the lubricant. The blank is of titanium alloy. The blank is preferably deformed in a superplasticity mode. A die set for hot shaping of the blank comprises a male die (1) mounted on a top platen (7) of the die set for reciprocation relative to the blank (18) and for rotation in the plane of its reciprocation. In the initial position, the shaping surface of the male die (1) extends at an angle to the longitudinal axis of the blank (18). The female die (10) of the die set is mounted on a bottom platen (13). <IMAGE>

Description

SPECIFICATION Method of making turbine or compressor blade blanks and die set for performing this method The invention relates to working materials by application of pressure, and more particularly it relates to a method of manufacturing turbine or compressor blade blanks and to a die set for performing this method.

The present invention can be utilized to utmost effectiveness in the manufacture of aircraft engines, involving making blanks of large blades having antivibration platforms and of double-root blades.

The present invention can be also utilized in the manufacture of blades and vanes of steam and hydraulic turbines.

The growing production of aircraft engines and the requirement to prolong the service life of these engines have created another requirement - that of providing new and highly efficient techniques ensuring high reliabiliti of the engines at minimized cost.

Blades stand outfromthe restofthe numerous components of engines, being as they are among their most responsible parts operated at elevated temperatures and under great alternating loads.

Therefore, heat-resistant costly alloys are used for the manufacture of the blades which are to meet strict requirements as to their quality and stability of their performance. Thus, the blades are among the most numerous, complex and expensive component parts of an engine, their cost more often than not being as high as 35 to 40 per cent that of the engine as a whole. These facts explain the quest for providing new, more efficient blade manufacturing techniques.

In one aspect, the invention provides a method of making turbine or compressor blade blanks, including: (a) providing a blank of specified dimensions; (b) applying a protecting and lubricating coating onto said blank of specified dimensions; (c) drying said protecting and lubricating coating; (d) heating said blank; (e) drawing said blank along the longitudinal axis thereof conjointly with its three-dimensional pressing in a single space of a closed die set, in a single shaping operation.

It is thus possible to shape a blade using a process wherein both initial and final shaping is effected within the same shaping surface of a die set and it is thus possible to produce in a single stroke of a press an article of practically any type, size and form, with any ratio of the cross-sectional sizes longitudinally of the article.

This fact is important because the combination of the initial or preliminary pressing and final pressing within a single stroke of the die set renders it possible to eliminate intermediate heating of the blank and such operations as removing the lubricant, deburring and deflashing. Furthermore, the amount of shaping equipment used is substantially reduced (to one half or even one third), as is the amount of the tooling and auxiliary equipment (heating furnaces, theremostat-controlled chambers, etc.).

The utilization of the combination shaping pattern (drawing and upsetting or swaging) reduces the shaping effort required, as compared with the blade-manufacturing methods of the prior art, which provides for the controlled displacement of the material of the blank in the required direction over significantly greater distances than, for instance, with pure swaging.

It is expedient that the preliminary profiling of the blank should be performed conjointly with the final pressing in a superplasticity mode.

With this pressing mode, the plasticity of the material of the blank being shaped is increased, which makes it possible to produce a blade of any form in a single operation. Furthermore, the mechanical properties of the blade are substantially enhanced, such as its plasticity, fatigue resistance, impact strength, i.e. the very properties essential for the service life of the blade, which is increased by 20 to 25 per cent in comparison with the service life of blades produced by hot three-dimensional pressing.

In one embodiment of the invention, prior to the initial profiling and final pressing of the initial blank, the portions of its surface, which are to engage the shaping surfaces of the die set, are pre-profiled so that these portion should define with the shaping surfaces of the die set respective cavities retaining the lubricant in the deformation zone.

The provision of the profiled surfaces of the blank, engaging the shaping surfaces of the die set, improves the centering of the blank in the die set at the initial stage of the shaping.

While engaging the shaping surfaces of the die set, these surfaces of the blank lock up the lubricant in the deformation zone and guide its movement in the course of the deformation alongside of the motion ofthe blank metal.

Thus, the pressing operation may be conducted under liquid friction conditions, which improves the flow of blank metal throughout the process and precludes physical engagement of the surfaces of the blank and of the die set, thus reducing the specific pressing effort required, prolonging the life of the die set and improving the quality of the articles produced.

In a further aspect, the invention provides a die set for hot shaping of blade blanks, comprising: a top platen and a bottom platen; a male die mounted on said top platen for reciprocation relative to said blank and for rotation in the plane o the reciprocation thereof; the shaping surface of said male die in the initial position of pressing extending at an angle to the longitudinal axis of said blank; a female die mounted on said bottom platen and including a stationary bottom portion and a ring movable relative to said bottom portion by rods connected to a power-operated member of the press, the travel of said rods exceeding the travel of said male die.

The utilization of all the abovementioned advantages offered by the disclosed method is possible exclusively by employing a hot-shaping die set wherein the male die member is mounted for a complex motion which initially is pure translatory motion and afterwards is accompanied by rotation of the male die member. The actual path of this motion can be selected for shaping blades of any form and size in a single working stroke of the press.

To alter the path of the motion of the male die member, no essential reconstruction of the die set is required, since only the guideways or tracks defining the path of the male die member have to be replaced. The same guideways or tracks define the initial inclination angle of the male die member relative to the blank, which angle is likewise selected to correspond to the type, size and form of the article, as well as to the dimensions of the original blank.

The invention will now be more particularly described, by way of example, with reference to the accompanying drawings, wherein: Figure 1 is a longitudinal sectional view of a hot-shaping die set; Figure 2 is a sectional view taken on line ll-ll of Figure 1; Figures 3, 4and 5 illustrate the kinetics of the operation of the die set; Figure 6 illustrates a blank of a blade with antivibration platforms or lugs; Figure 7 illustrates the position of a cylindrical blank relative to the shaping surface of the die set at the beginning of the shaping process; Figure 8 illustrates the position of a profiled blank relative to the shaping surface of the die set at the beginning of the shaping process; Figures 9 and 10 show a modification of the actuatorofthe male die member.

Referring now to the drawings, the die set (Figure 1 ) comprises a male die member 1 fixed by means of a stud 2 and retaining members 3 and 4 to the crosspiece 5 of a rod 6 connected to the upper pusher or ejector of the press (not shown). The male die 1 is mounted on a support platen 7 with a groove 8, fixed, in its turn, to a carrier platen 9 mounted on the ram of the press. The upper portion of the male die 1 is parallel with its shaping surface.

The bottom portion of the female die member 10 and a ring 11 movable relative to this bottom portion with aid of rods 12 connected thereto and to the bottom ejector or pusher of the press are mounted on platens 13 and 14 secured to the work table of the press. The travel of the ring 11 exceeds that of the male die 1.

To ensure isothermal conditions in the deformation zone, the female die 10 and the ring 11 are mounted to be enclosed within respective heat in:;ulation casings 15 and 16 of a heater 17 (Figure 2).

The casings 15 and 16 are made of a ceramic material operable at temperatures of deformation of a titanium alloy.

In its initial position, the shaping surface of the male die 1 extends at an angle relative to the axis of a blank 18. The value of this angle is defined by the couple including the stud 2 and the groove 8, and this value is selected to correspond to the size, type and form of the blade to be manufactured, as well as to the material and dimensions of the original blank, within a range substially from 20 to 45 . This initial position is fixed by the retaining members 3 and 4 actuated by the upper pusher or ejector of the press (not shown).

For loading an original blank 18 and for removing a shaped article (Figure 2), the casing 16 has an opening 19 (Figure 1). Springs 20 each have one end attached to rods 21 (Figure 2) of the male die member 1 (Figure 2) and on opposite end attached to rods 22 (Figure 2) mounted on the carrier platen 9 (Figure 1). The springs 20 are provided to return the male die 1 to its initial position after the completion of the shaping process.

The method is performed as follows.

A cylindrical rod 32 mm in diameter, made of a titanium alloy is heated to 920j200C and passed between the rolls of a rolling mill to shape on the surface of the rod two profiled channels, of a 20-mm radius and 4-6 mm depth. The channels extend along the opposite sides of the rod, longitudinally thereof. The actual dimensions of the channels are selected to correspond to the dimensions of the blank, to the viscosity of the lubricant, to the size of the blade-to-be, etc. Within the framework of mass production, the suppliers - the metallurgical plants can supply already profiled rods requiring no additional working of their surface.

The profiled rod stock is cut into blanks of a specified length, of a volume equalling that of the pressed article, whereafter a blank is coated with a lubricating and protective coating, heated up in a furnace and placed via the opening 19 (Figure 1) as the blank 18 into the working space of a die set, so that the profiled portion shoul engage the bottom portion of the female portion of the female die 10 and the blank 18 should abut against the ring 11 (the area of shaping the root portion of the blade). The presence of the profiled portions on the blank 18 not only optimizes the conditions of shaping the article, owing to the lubricant being retained in the deformation zone, but also stabilizes the altitude of the blank 18 when it is initially engaged by the male die 1 (Figure 1).This feature is particularly important in the manufacture of large blades with the relatively great twisting angles of the airfoil portion, i.e. in cases when the attitude of a cylindrical blank in relation to the shaping surfaces of the die set tends to be inadequately stable (Figure 7).

The male die 1 fixed on the support platen 7 by the retaining elements 3 and 4 and the stud 2 is driven downward, with the angle of inclination of the shaping surface being permanent, to locally shape the original blank 18 by the leading portion of the shaping surface (Figure 3). This results in redistribution of the metal of the blank 18, with simultaneous shaping of the root portion of the blade and offsetting of the metal into the airfoil portion thereof.

Thus, there is effected the profiling of the blank, accompanied by the controlled redistribution of its metal and an increase in the blank length.

The inclination angle of the shaping surface of the male die 1 is selected to satisfy the conditions of the displacement and redistribution of the metal, to correspond to the relative positions of the root portion and platforms of the blade, to the ratio of their sizes, to the thickness of the airfoil portion of the blade. Upon the metal reaching the cavities corresponding to the antivibration platforms of the blade, the male die 1 is released by operating the pusher or ejector of the press to disengage the retaining elements 3 and 4 from the male die 1, which terminates the rigid connection of the male die 1 with the support platen 7 (Figure 4).From this moment on, the male die 1 is driven not only through translatory motion in a vertical plane, but also through rotation in this plane, the relationship between these two motions being determined by the conditions of the displacement of the metal of the blank 18 in the course of the deformation and being defined, primarily, by the couple consisting of the stud 2 and groove 8. In the course of its complex motion the male die eventually acquires the position where its shaping portion becomes parallel with that of the female die 10. This takes place when the top plane of the male die 1, parallel with its shaping surface, abuts against the support platen 7 (Figure 5).The process of the directed offsetting of the metal is now terminated, and the subsequent shaping (amounting to about 6 to 10 % of the total deformation of the blank) is carried out by upsetting the blank in the closed die set, with the metal filling the portions of the die set, which are the hardest to reach, such as the portions where the tip of the airfoil portion and the corners of the root portion are shaped.

With the pressing completed, the male die 1 and the ring 11 holding the pressed blank of the blade are driven upwardly, but with the travel of the ring 11 exceeding that of the male die 1, the article becomes pressed out from the ring 11, to drop upon the female die 10, wherefrom it is removed through the opening 19. This pattern of removing the article from the working space of the die set precludes warping of thin-wall articles, such as blades. Then the bottom pusher or ejector of the press is operated to return the ring 11 into its initial position, while the male die 1 is disengaged from the ring 11 by the action of the extension springs 20 extended by the rotation of the male die 1 in the course of the shaping, whereby the mals die resumes its initial position fixed once again byt ie retaining elements 3 and 4 (Figure 1).

Exa nple There was pressed an experimental lot of blades with activibration platforms, of a titanium alloy, with the volume of the platforms equalling that of the root portion, and with average overall dimensions 60 x 200 mm. Firstly, original profiled blanks 18,32 mm in diameter and 75 mm long, were coated with water glass-base lubrication coating, by a dipping technique. Then the blanks 18 were dried at 80 to 100 C and heated in a furnace to 950+5 C. The heated blank was then transferred into the die set likewise heated to 950+5 C. The die set was heated by an induction heater supplied from a solid-state frequency converter.The blank 18 was positioned for its profiled portion to engage the bottom of the female die 10, in abutment of the root portion against the ring 11, and shaped in the superplaticity mode at a rate not in excess of 2 mm/s, in a single stroke of the press.

The shaping was done with the male die 1, initially inclined at 28 relative to the longitudinal axis of the blank, engaging the blank 18 by the projecting portion of its shaping surface and being driven in a first phase through purely translatory motion, to effect directed redistribution of the metal of the blank 18 in the deformation zone.

While this was being done, the profiled portions of the blank 18 (Figure 8) defined with the shaped surfaces of the male die 1 and female die 10 respective channels or ducts therein the lubricant was retained by the engagement of the blank 18 with the male die 1 and female die 10. In the course of the deformation or shaping, the lubricant was moving predominantly axially of the original blank 18, i.e. in the same direction where the metal predominantly flowed, whereby there were provided practically ideal conditions of the engagement of the metal of the blank 18 and of the die set through a separating medium - the protective and lubricating coating.

Upon the metal of the blank having reached the area of the cavities for the antivibration platforms in the die set (Figures 3 and 4), the male die 1 pierced the blank 18 through 18 mm and started its rotation, so that the angle of inclination of the shaping surface of the male die 1 relative to the longitudinal axis of the blank 18 diminished.

Throughout the phase when the male die 1 was rotating, the process of directed deformation was continued, the termination of this process being the moment when the top of the male die 1 engaged the support platen 7, and the respective shaping surfaces of the male die 1 and of the female die 10 became parallel. From this moment on, the male die 1 no longer rotated and defined a closed working zone, with the motion of the male die 1 becoming once again purely translatory.

As the outcome of this displacement, of a value amounting to 6 % of the total deformation of the blank 18, there was effected the final filling-up of the shaping surfaces of the die set in the most hard-toreach areas. Then the blade (Figure 6) was removed from the shaping area of the die set and aircooled.

Figures 9 and 10 ofthe appended drawings illustrate a modification of the actuation or drive system of the male die 1, offering enhanced reliability and higher versatility of the die set at manufacturing of different articles, by quick readjustment and replacement of unified-design elements of the die set. This modification is operable in a press devoid of the top pusher or ejector means (not shown).

In this modification, the retaining of the male die 1 and its return the initial position are effected by a hydraulic power cylinder 23 connecting the male die 1 and the carrier plate 9 with aid of pins 3 and 5. To provide for rapid readjustment of the die set to shape a different article,as well as for having various selectable rates of the rotation of the male die 1 and its translatory motion in the vertical plane, the inclined grooves in the support platen 7 of the male die 1 are made in replaceable elements 24. Furthermore, this arrangement permits replacement of these elements 24 when they wear out in operation.

In this modification, the die set comprises the male die 1 mounted with aid of a male die holder 25 on a male die plate 26 which is supported by the support platen 7 with aid of the studs 2 engaged in the grooves 8 of the replaceable elements 24, the support platen 7 being mounted on the carrier platen 9.

The bottom portion of the female die 10 and the ring 11 movable relative thereto by the rods 12 of the bottom pusher or ejector of the press are mounted on the bottom support platens 13 and 14 secured to the work table of the press.

The male die 1 and the female die 10 are enciosed within the respective heat-insulation casings 15 and 16 of the heater 1,', with the opening 19 provided in the casing 16 for loading a blank 18 and removing a shaped article. The hydraulic power cylinder 23 is operatively connected between the male die 1 and the top carrier platen 9 with aid of pins 3 and 5.

Let us now discuss a concrete example of the performance of the disclosed method by the die set with the modified actuation system of the male die 1, with a large blade with the antivibration platform being shaped.

The original profiled blank 18 is coated with a lubricant, heated and placed through the opening 19 in the casing 16 onto the bottom portion of the female die 10, in abutmentagainstthe ring 11 in the area where the root portion of the blade is to be formed.

The male die 1 is rigidly fixed by the hydraulic power cylinder 23 operated in the initial shaping phase as a hydraulic lock, an is driven downward to effect local deformation of the blank 18 by the leading portion of the shaping surface. During this phase the metal of the blank 18 is redistributed, the root portion is filled, and the metal is being drawn longitudinally of the axis of the blade.

Then the hydraulic cylinder 23 is operated to release the rigid connection of the male die 1 with the platen 9, and the male die 1 begins its rotation in the vertical plane; if so desired, this rotation may be accompanied by translatory motion in the vertical plane. This is done by operating the hydraulic cylinder 23 accordingly, to either accelerate or decelerate the rotation of the male die 1. In the course of its complex motion, the male die 1 terminates its rotation relative to the female die 10 when the top plane of the platen 7 abuts against the platen 9. The drawing process is thus terminated, and the subseque it deformation for final filling-up of the shaping surfaces of the die set is effected by upsetting by the parallel shaping surfaces of the male die 1 and the bottom portion of the female die 10.

With the working stroke completed, the male die 1, the ring 11 and the shaped blank 18 are all driven upwardly, but with the travel of the ring 1 exceeding that of themale die 1, the shaped blank is pressed out from the ring 11,to drop upon the female die 10 and to be removed through the opening 19 from the die set. The ring 11 is returned to its initial position, and the male die 1 is disengaged from the ring 11 and returned into its initial position by the power cylinder 23 where it is locked by the same hydraulic cylinder 23 once again controlled in the hydraulic lock state.

With a new blank placed in the die set, the above-described cycle is repeated.

Claims (6)

1. A method of making turbine or compressor blade blanks, including: (a) providing a blank of specified dimensions; (b) applying a protecting and lubricating coating onto said blank of specified dimensions; (c) drying said protecting and lubricating coating; (d) heating said blank; (e) drawing said blank along the longitudinal axis thereof conjointly with its three-dimensional pressing in a single space of a closed die set, in a single shaping operation.

2. A method as claimed in Claim 1, wherein the drawing of said blank is conducted conjointly with the three-dimensional pressing thereof in a superplasticity mode.

3. A method as claimed in Claim 1, wherein, prior to the drawing and three-dimensional pressing of the original blank, the portions of the surface thereof, which are to engage the shaping surfaces of the die set, are profiled for these portions to define with the shaping surfaces of the die set respective cavities retaining the lubricant in the deformation zone.

4. A die set for hot shaping of blade blanks, comprising: a top platen and a bottom platen; a male die mounted on said top platen for reciprocation relative to said blank and for rotation in the plane of the reciprocation thereof; the shaping surface of said male die in the initial position of pressing extending at an angle to the longitudinal axis of said blank; a female die mounted on said bottom platen and including a stationary bottom portion and a ring movable relative to said bottom portion by rods connected to a power-operated member of the press, the travel of said rods exceeding the travel of said male die.

5. A method of making turbine or compressor blade blanks, substantially as herein before described with reference to the accompanying drawings.

6. A die set for hot shaping of blade blanks, substantially as hereinbefore described with reference to and as shown in Figures 1 - 8 or 9 and 10 of the accompanying drawings.