Forging tool for the manufacturing of a shaped rolled ring, notably for the manufacture of a turbomachine disc

Abstract

Mandrels for rolling a ring include recesses for receiving the ring, which have rounded parts at the connection between the various faces, so as to avoid the formation of sharp angles on the rolled ring and the accidental formation of cracks.

Claims

1. A method for manufacturing a turbomachine disc, comprising: providing a ring including an alloy based on either nickel or nickel and chromium; heating the ring up to a forgeability temperature window; placing the heated ring in a tool; and performing a rolling step of the heated ring which reduces a cross section of the ring, the rolling step being performed by the tool, which comprises two mandrels turning about axes parallel to each other, wherein each of the mandrels comprises a circular, the ring passing between the recesses, each of the recesses comprising a bottom face and lateral faces, wherein the bottom face of each recess of the mandrels is connected to the lateral faces by curved portions having radii of curvature of between 10 mm and 20 mm, wherein the ring presents an essentially polygonal cross section and comprises corners which are situated on the curved portions during the placing, wherein the corners of the ring are curved during the rolling step, wherein the ring presents a diameter between 300 mm and 1500 mm after the rolling step, wherein sharp angles at the corners of the ring are crushed by said curved portions and consequently cracks are prevented from forming, and wherein the rolling step is carried out without any reheating.

2. The method for manufacturing a turbomachine disc according to claim 1, wherein the radii of curvature of the curved portions are between 12 and 15 mm.

3. The method for manufacturing a turbomachine disc according to claim 1, wherein the bottom face is cylindrical or conical, defined by a rectilinear generatrix, and the lateral faces are conical, defined by rectilinear generatrices.

4. The method for manufacturing a turbomachine disc according to claim 1, wherein the curved portions, which have a concavity opening up towards an outside of the recesses, connect the lateral faces by a profile with no angle.

5. The method for manufacturing a turbomachine disc according to claim 1, wherein the disc includes a Rene 65 super alloy.

6. The method for manufacturing a turbine disc according to claim 1, wherein the disc includes an AD730 super alloy.

7. The method for manufacturing a turbomachine disc according to claim 1, wherein the axes of the two mandrels are vertical, the tool further comprises two supports between which a horizontal rebate is delimited, and a part of the ring which is most opposite to a space between the mandrels extends in the horizontal rebate.

8. The method for manufacturing a turbomachine disc according to claim 1, wherein the rolling step is performed without carrying out any corrective grinding of the ring after the rolling step.

9. A method for manufacturing a turbomachine disc, comprising: providing a ring including an alloy based on either nickel or nickel and chromium; heating the ring up to a forgeability temperature window; placing the heated ring in a tool; and performing a rolling step of the heated ring which reduces a cross section of the ring, the rolling step being performed by the tool, which comprises two mandrels turning about axes parallel to each other, wherein each of the mandrels comprises a circular recess, the ring passing between the recesses, each of the recesses comprising a bottom face and lateral faces, wherein the bottom face of each recess of the mandrels is connected to the lateral faces by curved portions having radii of curvature of between 10 mm and 20 mm, wherein the ring presents an essentially polygonal cross section and comprises corners which are situated on the curved portions during the placing, wherein the corners of the ring are curved during the rolling step, wherein the ring presents a diameter between 300 mm and 1500 mm after the rolling step, and wherein sharp angles at the corners of the ring are crushed by said curved portions and consequently cracks are prevented from forming.

10. The method for manufacturing a turbomachine disc according to claim 9, wherein the curved portions have radii of curvature of between 12 mm and 15 mm.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The invention will now be described more completely, in its various aspects and purely illustratively, in relation to the following figures:

(2) FIG. 1 is a general view of the tool used;

(3) FIG. 2 is an enlargement of its essential parts; and

(4) FIG. 3 is view of the product obtained.

DETAILED DESCRIPTION OF THE INVENTION

(5) The invention forms part of a method for manufacturing a turbomachine disc, in particular with a large diameter, and constitutes a first step of this method, the following ones of which, which are not changed, will not be described. It relates to the rolling of a ring 7, which is a blank of the disc, to reduce its cross section, while increasing its diameter. It has recourse to a tool that comprises, as shown by FIG. 1, a driving mandrel 1 and a loose mandrel 2, situated side by side, and turning about parallel axes O1 and O2, vertical in the figure. The driving mandrel 1 contains a shaft 3, which belongs to the drive motor, not shown, and which rotates it, whereas the loose mandrel 2 contains a shaft 4, mounted freely in bearings. The mandrels 1 and 2 each comprise a recess 5 or 6 circular about the respective axis O1 or O2, the recesses 5 and 6 being situated at the same height and therefore having portions coming face to face. The ring 7 to be rolled is held there between the recesses 5 and 6. It moreover extends around the loose mandrel 2, and its part most opposite to the space between the sleeves and 2, where the rolling occurs, extends at a distance from said loose mandrel 2, the diameter of which is smaller, and in a horizontal rebate 8, delimited between two supports 9 and 10.

(6) FIG. 2 shows that the recesses 5 and 6 each comprise a bottom face 11, two lateral faces 12 and 13 being connected to an external face 14 of the respective mandrel 1 or 2. The bottom faces 11 are cylindrical, and the lateral faces 12 and 13 conical, all these faces being defined by rectilinear generatrices. In a variant, the faces of the recesses 5 and 6 could be defined by other shapes, provided that sharp angles are avoided for reasons that will now be detailed: in accordance with the invention, the bottom faces 11 are joined to the lateral faces 12 and 13 by respective connections 15 and 16, which are portions of surfaces the cross sections of which are curved, with a concavity opening towards the outside of the recesses 5 and 6, and have a radius of curvature that can be chosen, in the envisaged application, advantageously between 10 and 20 mm, and even more advantageously from 12 to 15 mm, for diameters of blanks typically between 300 and 1500 mm, at the end of rolling. The connections and 16 provide a transition without an angle, and therefore with a continuous variation in slope, between the faces that they connect.

(7) The ring 7 has an approximately polygonal and rectangular cross section, the internal and external faces of which are tangent to the faces of the bottom 11, and the lateral faces of which extend in front of the lateral faces 12 and 13 of the recesses. The connections of the lateral faces to the internal and external faces should form sharp angles, at the corners of the cross section of the ring 7, but the rolling produced by the mandrels 1 and 2, which compresses the cross section of the ring 7, also crushes its corners and forces them to be modelled to the form of the portions 15 and 16, which gives the appearance in FIG. 3, where the faces of the ring 7 are delimited by the rounded connections 17. This arrangement avoids forming, during rolling, right angles that cool very quickly, leading locally to deforming the material outside its forgeability window and consequently creating cracks. This arrangement therefore prevents cracks from forming and therefore ensures good quality of forging, even at the lower limit of the forgeability temperature range.