WO2023186795A1

WO2023186795A1 - Method and unit for manufacturing an elongate intermediate part by hot forging

Info

Publication number: WO2023186795A1
Application number: PCT/EP2023/057821
Authority: WO
Inventors: Philippe Sagot; Laurent Foucher; Paul Jacob CHEERAN; Benjamin FLAGEOLET
Original assignee: Aubert & Duval
Priority date: 2022-03-28
Filing date: 2023-03-27
Publication date: 2023-10-05
Also published as: FR3133773B1; FR3133773A1

Abstract

The invention relates to a method for manufacturing, by forging, an intermediate part (1) which is made of a metal alloy and is elongate along a longitudinal axis (Z), the method comprising the following steps: - manufacturing, by hot forging, an elongate blank comprising at least one section, the cross-section of which varies little; - shaping the blank to obtain a semi-finished product that is elongate along a longitudinal axis and comprises a central part and a first and a second part of increased cross-section, extending on either side of the central part in the direction of the longitudinal axis, the shaping of the blank comprising producing the first part of increased cross-section of the semi-finished product by hot forging and producing the second part of increased cross-section of the semi-finished product by hot forging, selected from upsetting, spinning, die forging or backward extrusion techniques; and - hot-drawing the semi-finished product to obtain the intermediate part (1).

Description

Method and installation for manufacturing an elongated intermediate part by hot forging

The present invention relates to a method and an installation for manufacturing by hot forging an intermediate part elongated along an axis Z, of total length L, in metal alloy, the intermediate part comprising a central part comprising at least one section section to low variation and two parts of increased section located on either side of the central part.

Usually, parts such as aircraft engine shafts are produced by implementing the following successive operations: manufacturing an elongated blank of section with low variation by hot spinning or drawing in free forging, then production by forging at hot, for example via hot upsetting, of a part of increased section, called head, located for example at one of the ends of the blank, and finally machining to reduce the transverse dimensions of the central part while maintaining a part of increased section at one end of the central part opposite the head in the longitudinal direction of the part.

This process is, however, not entirely satisfactory. In fact, the elongated blank of section with low variation has transverse dimensions whose value, over the entire length of the blank, is fixed by the transverse dimensions of the largest section of the part (head excluded), and therefore in particular by the transverse dimensions of the part of increased section of the part opposite the head in the longitudinal direction, machining then being necessary to reduce the transverse dimensions of the central part, and obtain the desired final shape of the central part. This results, taking into account the significant length of the central part for the applications mentioned above, in a relatively high loss of material, and consequently in significant cost costs, in particular in the case where the part is made in a so-called noble alloy, that is to say including relatively large quantities of expensive alloy elements, such as maraging steels, superalloys or titanium alloys.

An aim of the invention is to provide a method and an installation allowing the manufacture of elongated intermediate parts made of metal alloy such as described above at a reduced cost price.

For this purpose, the invention relates to a method of manufacturing by forging an intermediate piece of metal alloy elongated along a longitudinal axis, the intermediate piece comprising a central part comprising at least one section of cross section to low variation, the area of the cross sections of the or each section of cross section with low variation varying by at most 20% along said section, the intermediate part further comprising a first part of increased section and a second part of section increased located on either side of the central part along the longitudinal axis, the process comprising the following steps:

- manufacture by hot forging of a blank elongated along a longitudinal axis comprising at least one section of cross section with low variation;

- shaping of the blank to obtain a semi-product elongated along a longitudinal axis comprising a central part and a first part of increased section and a second part of increased section, extending on either side of the part central in the direction of the longitudinal axis, the shaping of the blank comprising the production of the first part of increased section of the semi-product by hot forging and the production of the second part of increased section of the semi-product by hot forging chosen from upsetting, spinning, stamping or reverse spinning; And

- hot stretching of the semi-finished product to obtain the intermediate piece.

The method according to the invention may comprise one or more of the following characteristics, taken in isolation or in any technically possible combination:

- the metal alloy is chosen from a superalloy, a titanium-based alloy and a steel, more particularly a steel chosen from the following list: a structural hardening steel and an alloyed martensitic steel.

- the length of the intermediate piece is greater than or equal to 800 mm and the ratio between the length of the intermediate piece and the maximum transverse dimension of the central part of the intermediate piece is greater than or equal to 2.5.

- the area of the cross sections of the or of each section of cross section with low variation varies by at most 10% along said section, preferably the area of the cross sections of the or of each section of cross section with low variation is constant along said section.

- the cumulative length of the section(s) of cross section with low variation, taken along the longitudinal axis, is greater than or equal to 40% of the length of the intermediate part, preferably greater than or equal to 60% of the length of the part intermediate, and even more preferably greater than or equal to 70% of the length of the intermediate piece.

- the center of the first part of increased section and/or the center of the second part of increased section, taken in the longitudinal direction of the intermediate piece, is located at a distance from the corresponding end of the lower intermediate piece or equal to 25% of the length of the intermediate piece, preferably less than or equal to 15% of the length of the intermediate piece.

- the first part of increased section of the semi-product is produced by upsetting, spinning, stamping or reverse spinning.

- the second part of increased section of the semi-product is produced by upsetting and, preferably, the first part of increased section is produced by upsetting or by stamping.

- the second part of increased section of the semi-product is produced by stamping and, preferably, the first part of increased section is produced by upsetting or by stamping.

- the production of the first part of increased section of the semi-product and the production of the second part of increased section of the semi-product are carried out successively.

- the production of the first part of increased section of the semi-product and the production of the second part of increased section of the semi-product are carried out simultaneously, in particular in the same tool.

- the semi-finished product is not reheated between the production of the second part of increased section of the semi-finished product and hot stretching.

- the production of the second part of increased section and the hot stretching are carried out in the same tool.

The invention also relates to a method of manufacturing an elongated part of a metal alloy comprising:

- the manufacture of an intermediate part by implementing the process described above;

- finishing the intermediate part to obtain the part, the finishing including in particular machining.

According to a particular characteristic of the process, the part is chosen from: an axle, a motor shaft, a landing gear part, an extension tube for a pump intended for the extraction of oil or gas, an underwater valve , in particular for large boat engines, such as a liner or a supertanker and a missile launcher tube.

The invention also relates to an installation for manufacturing by forging an intermediate piece of metal alloy elongated along a longitudinal axis, the manufacturing installation being intended to be used for implementing the method, comprising:

- a housing defining a longitudinal axis intended to receive a blank elongated along a longitudinal axis comprising at least one section of cross section with low variation or a semi-worked part elongated along a longitudinal axis comprising a rod comprising at least one section of cross section with low variation, and a first part of increased section;

- a device for shaping the blank or the semi-finished part received in the housing so as to form a semi-product elongated along a longitudinal axis comprising a central part and a first part of increased section and a second part of increased section, located on either side of the central part in the direction of the longitudinal axis, the shaping device comprising a production device, by hot forging by stamping, by upsetting, by spinning or by reverse spinning, of at least the second part of increased section of the semi-finished product; And

- a hot stretching device configured to hot straighten the semi-product so as to form the intermediate part.

The installation according to the invention may include one or more of the following characteristics, taken individually or in any technically possible combination:

- the hot stretching device is configured to hot straighten the half-product received in the housing.

- the hot stretching device comprises a stretching punch, movable in translation relative to the housing in a direction perpendicular to the longitudinal axis of the housing from a rest position to an end of stretching position, moving the stretching punch from its rest position to its end of stretching position causing the hot straightening of the semi-finished product received in the housing to obtain the intermediate part.

- the installation further comprises a matrix delimiting the housing, the matrix comprising a fixed part and a mobile part, said mobile part of the matrix being movable in translation relative to said fixed part in the direction of the longitudinal axis of the housing between a close position, the movable part being in contact with the fixed part and a spaced position, the movable part being distant from the fixed part by an elongation distance, this movement causing an elongation of the housing by a length equal to the elongation distance, the hot stretching device further comprising, for each stretching punch, a housing for receiving the stretching punch, configured to receive an end section of the stretching punch when it it moves from its rest position to its end of stretching position, the insertion of the stretching punch in the corresponding receiving housing causing the translational movement of the part mobile of the die relative to the fixed part of the die from its close position to its spaced position so as to straighten the semi-product received in the housing.

- the installation further comprises a support on which the or each actuating member and the or each stretching punch are fixed, the support being movable in translation relative to the housing in a direction parallel to the direction of movement of the or of each actuating member and of each stretching punch so as to successively occupy the following positions:

- a rest position, in which the or each actuating member and the or each stretching punch occupies its rest position,

- an end of shaping position, in which the or each actuating member occupies its end of shaping position, and

- an end of stretching position, in which the or each stretching punch occupies its end of stretching position.

- the installation is used as forging press tools.

- the installation as described above constitutes forging press tools.

The invention also relates to the use of the installation as described above as forging press tools.

The invention will be better understood on reading the description which follows, given solely by way of example, and made with reference to the appended drawings, in which:

Figure 1 is a schematic representation of an intermediate part obtained by the method according to the invention according to a first embodiment;

Figure 2 is a schematic sectional representation along the plane F-F' of the intermediate part of Figure 1 according to one embodiment;

Figure 3 is a schematic representation similar to that of Figure 2 of an intermediate part according to a variant;

Figure 4 is a schematic representation of an intermediate part obtained by the method according to the invention according to a variant;

Figure 5 is a schematic representation of a blank used in the context of the method according to the invention;

Figure 6 is a schematic representation of a semi-product obtained within the framework of the process according to the invention;

Figure 7 is a schematic representation of a semi-finished part obtained as part of the process according to the invention;

Figure 8 is a schematic representation of an intermediate part according to a variant; Figure 9 is a schematic perspective representation of an installation for manufacturing by forging an intermediate part according to a first embodiment;

Figure 10 is a schematic representation in section along a vertical plane of part of the installation of Figure 9;

Figure 11 is a schematic top view of part of the installation of Figure 9;

Figure 12 is a schematic perspective representation of a manufacturing installation by forging an intermediate part according to a second embodiment;

Figure 13 is a schematic representation in section along a vertical plane of the installation of Figure 12; And

Figure 14 is a schematic top view of part of the installation in Figure 12.

Figure 15 is a schematic representation of shaping a part of increased section by spinning from a hollow blank at the end.

Figure 16 is a schematic representation of shaping a part of increased section by pushing back using a needle from a hollow blank at the end.

Figure 17 is a schematic representation of shaping a part of increased section by stamping from a solid blank.

Figure 18 is a schematic representation of shaping a part of increased section by reverse spinning from a solid blank.

Figure 19 is a schematic representation of a shaping of a part of section increased by upsetting from a solid blank.

Figure 20 is a schematic representation of a shaping of a part of increased section by upsetting from a hollow blank comprising a lost mandrel.

The invention relates to a method of manufacturing by forging an elongated intermediate part 1 made of metal alloy.

An example of intermediate part 1 obtained by the manufacturing process according to a first embodiment of the invention is represented schematically in Figure 1.

The intermediate part 1 is elongated along a longitudinal axis Z and has a total length L. The intermediate part 1 comprises a central part 3 comprising at least one section of cross section with low variation and a first part of section increased section 5 and a second part of increased section 5' located on either side of the central part 3 in the direction of the longitudinal axis Z.

The central part 3 and the or each low variation section section are elongated along the longitudinal axis Z.

Throughout the description, cross section means the section perpendicular to the longitudinal axis Z.

Throughout the description, by section of cross section with low variation is meant in particular a section whose areas of cross sections vary by at most 20% along said section, that is to say along of the longitudinal axis Z. This variation is estimated by the ratio between on the one hand the difference between the area of the largest cross section and the area of the smallest cross section, and on the other hand the average of the areas of the cross sections of the at least one section of cross section with low variation. More particularly, this variation is at most 10%. Even more particularly, the cross sections of said section are identical along said section. In other words, the variation defined above is zero. In this case, we will subsequently speak of a section of constant cross section.

The central part 3 has a cumulative length L _o of the section(s) of low variation cross section, taken along the longitudinal axis Z, greater than or equal to 40% of the length L of the intermediate part 1. By way of example, the cumulative length Lo of the section(s) of low variation cross section of the central part 3 is greater than or equal to 60% of the length L of the intermediate part 1, and in particular greater than or equal to 70% of the length L of the intermediate piece 1.

Preferably, the first part of increased section 5 and the second part of increased section 5' are each adjacent to a section of cross section with low variation of the central part 3 in the direction of the longitudinal axis Z, i.e. that is to say without interposition of other parts of the part.

According to one embodiment, the central part 3 consists of a section of cross section with low variation, and more particularly, the central part 3 consists of a section of constant cross section.

According to a variant not shown, the central part 3 comprises, in the direction of the longitudinal axis Z, several sections of cross section with low variation and at least one intermediate part arranged between the sections of cross section with low variation.

According to another variant not shown, the central part 3 comprises several sections of constant cross section and at least one intermediate part arranged between the sections of constant cross section. In the example shown in Figure 1, the central part 3 consists of a section of constant cross section and the first and second parts of increased section 5, 5' are adjacent to the central part 3 in the direction of the longitudinal axis Z.

The first and second parts of increased section 5, 5' are preferably each located near a respective end 4, 4' of the intermediate piece 1. In particular, the center of each part of increased section 5, 5', taken in the direction of elongation Z of the intermediate piece 1, is located at a respective distance Li, L ₂ from the corresponding lower end 4, 4' or equal to 25% of the length L of the intermediate piece 1. More particularly, the center of each part of increased section 5, 5' is located at a respective distance Li, L ₂ from the corresponding lower end 4, 4' or equal to 15% of the length L of the intermediate piece 1.

Each of the parts of increased section 5, 5' comprises a cross section of respective minimum area A _min , corresponding to its smallest cross section. For each of the parts of increased section 5, 5', the area A _min of this cross section is greater than the area A of the largest cross section of at least one of the sections of cross section with low variation of the central part 3, and in particular of the or each section of cross section with low variation of the central part 3.

In particular, the cross section of minimum area A _min of each of the parts of increased section 5, 5' has a maximum dimension Di, D ₂ greater than the maximum dimension D of the largest cross section of at least one of the sections of section with low variation of the central part 3, and in particular of or each section of cross section with low variation of the central part 3.

The term maximum dimension of a cross section is understood in particular to be the external diameter of this cross section in the case of a circular cross section or the diagonal of this cross section in the case of a polygonal cross section, and for example square or hexagonal. .

According to one embodiment, the first and second parts of increased section 5, 5' have identical shapes. According to a variant, illustrated in the figures, the first and second parts of increased section 5, 5' have different shapes, and for example different lengths and/or transverse dimensions.

For example, the first part of increased section 5 and/or the second part of increased section 5' has a shape chosen from:

- a shape of constant cross section, in particular an annular or cylindrical shape;

- an axisymmetric shape of variable cross section along the longitudinal axis Z, in particular a trumpet, cone, or other shape; - a non-axisymmetric shape, in particular a yoke shape, a cardan shape, or any other suitable complex shape.

In the case of a part of increased section 5, 5' having a constant cross-section shape, that is to say the area of the cross-sections along said part of increased section is constant, the cross-section of minimum area A _min corresponds to any cross section of the part of increased section 5, 5' considered.

In the case where the first part of increased section 5 and/or the second part of increased section 5' has an annular or cylindrical shape, this part of increased section 5, 5' is, according to one embodiment, located at the distance from the ends 4, 4' of the intermediate piece 1, or, according to a variant, located at one end 4, 4' of the intermediate piece 1, so as to form a flange.

In the case of a part of increased section 5, 5' having a shape of variable cross section along the longitudinal axis Z, the cross section of minimum area A _min corresponds to a particular cross section of the part of increased section 5 , 5' considered, in which the area of the increased section part 5, 5' is the smallest.

The first part of increased section 5 and the second part of increased section 5' advantageously have different shapes, chosen from any combination of the shapes mentioned above.

The intermediate part 1 illustrated in Figure 1 is a solid part.

According to a first variant, illustrated in Figure 4, the intermediate part 1 is a hollow part, in particular tubular.

According to a second variant, the central part 3 of the intermediate piece 1 is solid and at least the second part of increased section 5' is hollow and forms one of the ends of the intermediate piece 1. For example, the first part of increased section 5 and the second part of increased section 5' are hollow and each form one end of the intermediate part 1.

According to a third variant, the intermediate part 1 is a composite part comprising a core formed by a lost mandrel as described in patent application WO 2019/141798 A1 made in a first metal alloy and an envelope made in a second metal alloy.

According to one embodiment of the invention, the intermediate part 1 is a part of revolution relative to the Z axis.

For example, the central part 3 of the intermediate part 1 is of revolution with respect to the axis Z. The central part 3 of the intermediate part 1 is for example a solid or hollow cylinder. According to one embodiment, the cross section of the solid or hollow cylinder is circular, the maximum transverse dimension D corresponding to the diameter of the circular cross section. In the case of a hollow cylinder, the diameter of the circular cross section means its exterior diameter.

According to a variant of the invention, the solid or hollow cylinder has a square cross section, the maximum transverse dimension D corresponding to the diagonal of said square cross section. In the case of a hollow cylinder, the diagonal of the square cross section means the exterior diagonal of said square cross section.

According to another variant, the solid or hollow cylinder has a hexagonal cross section, the maximum transverse dimension D corresponding to the diameter of the circle circumscribed by said hexagonal cross section.

For example, the length L of the intermediate part 1 is greater than or equal to 800 mm and the ratio L/D between its length and the maximum transverse dimension D of the central part 3 is greater than or equal to 2.5. More particularly, the ratio L/D is greater than or equal to 5, in particular greater than or equal to 15, and for example greater than or equal to 20 and/or the length L of the intermediate piece 1 is greater than or equal to 1 m, in particular greater than or equal to 1.5 m, and for example greater than or equal to 2 m, the lengths L and ratios L/D listed above can be combined depending on the desired final shape of the intermediate part 1.

The intermediate part 1 is made of metal alloy. It is made in particular from one of the following materials:

- a steel, and more particularly a steel chosen from the following list:

- a structurally hardened steel, in particular a structurally hardened martensitic steel, for example a 15-5 PH, 17-4 PH, ML340, Maraging 250, Marval 18, Maraging 300, Maraging 350, MLX19 or MLX20 steel;

- an alloyed martensitic steel, for example a 300M steel;

- a superalloy, and more particularly a nickel-based superalloy, for example an alloy 718;

- a titanium-based alloy, for example a Ti-6-AI-4V, Ti-5333 or Ti 10.2.3 alloy.

The steels listed above are steels with high mechanical properties.

The intermediate part 1 is intended in particular for the manufacture of a part chosen from:

- an axle, for example for a railway or automobile vehicle,

- a motor shaft, for example for a helicopter rotor or for a pump shaft, in particular a transmission shaft, for example for a wind turbine or for the automotive industry: car, truck, tractor, etc. or a gas turbine or turbojet shaft,

- a landing gear part, such as a landing gear rod or a landing gear wheel axle,

- an extension tube (“riser tube” in English), for example for pumps intended for oil or gas extraction;

- an underwater valve, in particular for the engine of large boats, such as liners or supertankers; Or

- a missile launcher tube.

The method according to the invention comprises the steps according to which:

- an elongated blank 6 is manufactured by hot forging comprising at least one section of cross section with low variation;

- the blank 6 is shaped to obtain a semi-product 11 comprising a central part 12 and a first part of increased section 13 and a second part of increased section 14, extending on either side of the part central 12; And

- the semi-product 1 1 is hot stretched to obtain the intermediate part 1.

These process steps are described in more detail in the remainder of the description.

The hot forging step to obtain the blank 6 is in particular implemented on a plot.

The blank is typically obtained from a forged ingot or an ingot forged then rolled, depending on the final diameter of the blank. Prior to hot forging, the blank is reheated in a treatment oven at a temperature and for a duration adapted to allow hot deformation of the material of the blank during shaping. The temperature and duration of reheating are chosen by those skilled in the art depending on the composition of the alloy. The treatment time is chosen so as to obtain the same temperature between the skin and the heart of the patch.

The blank is then transferred to hot forging tools. Hot forging tools are classic, and are not described in detail below.

The blank is then subjected to hot forging in the hot forging tool. Hot forging is for example carried out by hot spinning, free forging, radial forging, stamping or rolling.

At the end of this step, we obtain an elongated blank 6 of longitudinal axis Z comprising at least one section of cross section with low variation of longitudinal axis Z. The cross section of said section is for example circular or polygonal, for example square or hexagonal in shape.

The blank 6 is in particular a cylindrical revolution blank. The blank 6 is hollow or solid.

An example of blank 6 is shown schematically in Figure 5. In this example, blank 6 consists of a section of constant cross section.

The blank 6 is then shaped to obtain a semi-product 11 as shown schematically in Figure 6.

The semi-finished product 11 is elongated with a longitudinal axis Z. It comprises a central part 12 and the first and second parts of increased section 13, 14, extending on either side of the central part 12 in the direction of the longitudinal axis Z. The central part 12 of the semi-finished product 11 comprises at least one section of cross section with low variation. The central part 12 has a longitudinal axis Z.

Each of the first and second parts of increased section 13, 14 comprises a cross section of minimum area, the area of which is greater than the area of the largest cross section of at least one section of cross section with low variation of the central part 12, and in particular of the or each section of cross section with low variation of the central part 12.

The step of shaping the blank 6 comprises the production of the first part of increased section 13 by hot forging, and in particular by stamping, upsetting, spinning or reverse spinning followed by the production of the second part of increased section 14 by hot forging, and in particular by stamping, upsetting, spinning or reverse spinning.

By spinning, we mean shaping a blank 6, at least hollow at one end, by simple radial displacement of the material perpendicular to the longitudinal axis Z of the elongated blank 6.

According to a particular embodiment, the first and second parts of increased section 13, 14 are each hot forged by one of the following processes: upsetting, and in particular upsetting on a needle, embossing, stamping or reverse spinning. These hot forging modes are shown schematically in Figures 15 to 20 and described below in the case of the second part of increased section 14.

The first part of increased section 13 and the second part of increased section 14 can be produced by the same type of hot forging, chosen from upsetting, and in particular upsetting on a needle, pushing out, stamping or reverse spinning. In particular, the first part of increased section 13 and the second part of increased section 14 are produced by upsetting or by stamping.

Alternatively, the first part of increased section 13 and the second part of increased section 14 are produced by types of hot forging different from each other, chosen from any combination of the types of hot forging mentioned above. In in particular, the first part of increased section 13 is produced by pressing and the second part of increased section 14 is produced by stamping or the first part of increased section 13 is produced by stamping and the second part of increased section 14 is produced by pressing.

According to one embodiment, the first part of increased section 13 and the second part of increased section 14 are produced successively, and for example in different tools.

In this case, the blank 6 is first transferred to a first hot forging tool, in which it undergoes hot forging, in particular stamping, pressing, spinning or reverse spinning, to obtain a semi-worked part. 16.

A semi-finished part 16 according to an example is shown schematically in Figure 7. It comprises a rod 15 comprising at least one section of cross section with low variation and the first part of increased section 13. Each section of cross section with low variation is identical to a corresponding low variation cross section section of the blank 6.

The semi-worked part 16 thus obtained is then transferred to a shaping tool, in which the second part of increased section 14 is produced by hot forging, and in particular by stamping, upsetting, spinning or reverse spinning, to obtain the semi-finished product 11. Shaping by hot forging to obtain the second part of increased section 14 is in particular carried out by means of an installation which will be described in more detail below with reference to Figures 9 to 11.

The second part of increased section 14 is preferably produced by upsetting or by stamping. In the case of a discharge, the discharge ratio during the step of producing the second part of increased section 14 is in particular between 1.20 and 1.25. The discharge ratio classically corresponds to the ratio between the diameter before discharge and the diameter after discharge.

According to a variant, the first part of increased section 13 and the second part of increased section 14 of the semi-finished product 11 are produced simultaneously, in particular in the same tool. In this case, the first part of increased section 13 and the second part of increased section 14 are in particular produced by hot forging of the stamping, upsetting, spinning or reverse spinning type. Shaping by hot forging to obtain the first and second parts of increased section 13, 14 is in particular carried out by means of an installation which will be described in more detail below with reference to Figures 12 to 14. Shaping by hot forging to form the second part of increased section 14 of the semi-product 11 is followed by hot stretching of the semi-product 11 to straighten the semi-product 11 and obtain the intermediate part 1 .

During the hot stretching step, the semi-product 11 is stretched so as to plastically deform the metal alloy, which makes it possible to apply a permanent deformation to the semi-product 11 in order to improve its straightness .

In the context of the invention, the main function of hot stretching is to improve the straightness of the semi-product 1 1. Indeed, the shaping steps can cause straightness defects in the central part 12 of the semi-finished product 11 which we seek to avoid in the final part. The stretching step makes it possible in particular to reduce, in the central part 12, the transverse deviation, taken perpendicular to the longitudinal axis Z of the semi-product 1 1, compared to a perfectly straight geometry. The hot stretching step is preferably carried out so as to reduce in the central part 12 the transverse deviation from a perfectly straight geometry to at most 2 to 5 mm per meter of the central part 12.

The hot stretching step also makes it possible to correct the angle between the central part 12 and the parts of increased section 13, 14 of the semi-finished product 11 and possibly to partially release the internal constraints linked to the shaping of the semi-finished product. -product 11.

By way of example, in addition to the straightening mentioned above, the stretching step has the effect of stretching the half-product 11 by a length at most equal to 20 to 30 mm per 2 meters of length of the half-product 11. product 1 1 .

Advantageously, the production of the second part of increased section 14 by shaping by hot forging and the hot stretching are carried out in the same tool, and in particular by means of an installation as described below with regard to the Figures 9 to 1 1.

According to a variant, the hot stretching is carried out in a tool different from the tool used to produce the second part of increased section 14. In particular, the hot stretching is carried out using any tool intended for straightening or straightening trees by traction.

Preferably, no intermediate heating is carried out on the semi-product 1 1 before hot stretching.

Preferably, the average temperature of the semi-finished product 11 drops by at most 200°C between the production of the second part of increased section 14 by hot forging and hot stretching.

The invention also relates to a method of manufacturing a finished part (not shown) in metal alloy, the method comprising: - the manufacture of an intermediate part 1 by implementing the process as described above; And

- finishing the intermediate part 1 to obtain the finished part.

The finishing step includes in particular a machining step.

According to one embodiment, the geometry of the intermediate part 1 is very close to the geometry of the finished part, and the intermediate part 1 is machined only to remove small excess thicknesses, typically less than 10 mm or even a few millimeters of excess thickness, and possibly to obtain functional surfaces.

According to a variant, one of the parts of increased section 5, 5' of the intermediate piece 1 comprises a ring 7 of cross section of area greater than the area of the cross section of the rest of the part of increased section 5, 5', and the machining step comprises the removal of said ring 7. The ring 7 is part of the part of corresponding increased section 14 of the semi-finished product 1 1 and makes it possible to form a grip at the level of the second part of increased section 14 of the semi-finished product 11 for implementing hot stretching in embodiments in which the difference between the maximum cross-sectional area of the corresponding increased section part of the finished part and the cross-sectional area maximum of the central part of the finished part is low. An example of an intermediate part 1 comprising such a ring 7 in its second part of increased section 5' is shown in Figure 8.

According to one embodiment, in the case where the intermediate part 1 comprises a lost mandrel described above, the machining step comprises the removal by machining of the lost mandrel, resulting in a final hollow part having an external shape close to that of the intermediate piece 1.

Optionally, the finishing step also includes one or more heat treatments, in particular to achieve the required mechanical properties for use.

The finished part obtained at the end of this process is chosen in particular from:

- an axle, for example for a railway or automobile vehicle,

- a motor shaft, for example for a helicopter rotor or for a pump shaft, in particular a transmission shaft, for example for a wind turbine or for the automobile industry: car, truck, tractor, etc. or a gas turbine or turbojet shaft,

- a landing gear part, such as a landing gear rod or a landing gear wheel axle,

- an extension tube (“riser tube” in English), for example for pumps intended for oil or gas extraction; - an underwater valve, in particular for the engine of large boats, such as liners or supertankers; Or

- a missile launcher tube.

The process according to the invention is advantageous. Indeed, thanks to the production of the second part of increased section 14 of the semi-product 1 1 by hot forging followed by stretching to straighten the semi-product 11 and obtain the intermediate part 1, it is possible to achieve the central part 3 of the intermediate part 1 by hot forging directly to external dimensions as close as possible to the dimensions in the final part. In particular, in the case of a central part with a constant circular section, it is possible to produce the central part 3 of the intermediate part 1 by hot forging directly to an exterior diameter very close to its exterior diameter in the final part. This makes it possible to avoid material losses associated with its machining generated during the implementation of the known processes described in the introduction, and thus to reduce the costs associated with the manufacturing of the part. This effect is particularly advantageous in the case of noble alloys, that is to say which include expensive alloying elements at relatively high contents, such as steels with high mechanical properties including maraging steels, superalloys and titanium alloys. Indeed, in this case, the effect of reducing material losses on the cost price of the part is particularly marked. The stretching step makes it possible to straighten the intermediate part 1 after the production of the second part of increased section 14. In fact, when the external dimensions of the central part 3 of the intermediate part 1 are very close to the external dimensions in the final part, the blank 6 or the rod 15 of the semi-finished part 16 has cross sections of relatively small areas and the production of the second part of increased section 14 thus risks generating a lack of straightness in the part central 12 of the semi-product 11, which is corrected thanks to the hot stretching step.

Figures 9 to 11 represent an example of an installation 50 for manufacturing by forging an intermediate part 1 as described above according to a first embodiment.

This installation 50 is intended to be used for implementing the manufacturing process described above. This installation more particularly allows the implementation of the sub-step of producing the second part of increased section 14 of the semi-finished product 11 by hot forging and of the step of hot stretching of the semi-worked part 11 to obtain intermediate piece 1.

The installation 50 for manufacturing by forging an intermediate part 1 as described above comprises: a housing 55 defining a longitudinal axis B intended to receive the elongated blank 6 or the semi-worked part 16 as described above; a device 51 for shaping the blank 6 or the semi-finished part 16 received in the housing 55 so as to form the semi-finished product 1 1 as described above, the shaping device 51 comprising a device 52 for producing, by hot forging, at least the second part of increased section 14 of the semi-product 11; and a hot stretching device 54 configured to hot straighten the half-product 11 so as to form the intermediate part 1.

The installation 50 comprises a die 53 comprising a lower die 100 and an upper die 102 and a support table 113. The lower die 100 is removably fixed on the support table 113. The housing 55 is more particularly formed in the die 53 being delimited by the lower die 100 and upper die 102. The relative movement of the upper die 102 relative to the lower die 100 makes it possible to open the housing 55 over its entire length, in particular for the introduction of the piece to be shaped.

In the example shown in Figures 9 to 11, the longitudinal axis B extends horizontally. In this example, the lower die 100 and the upper die 102 each extend horizontally.

In the first embodiment, shown in Figures 9 to 11, the device 52 is configured to receive the semi-finished part 16 as described above, that is to say comprising the rod 15 and the first part of increased section 13. More particularly, the housing 55 is intended to receive the semi-worked part 16 coaxially with its longitudinal axis B.

The housing 55 comprises a central part 57 and, on either side of the central part 57 in the direction of the longitudinal axis B, a first part of increased section 58 and a second part of increased section 59. In the example shown, the first and second parts of increased section 58, 59 are adjacent to the central part 57.

The central part 57 is configured to house the central part 12 of the semi-finished product 11. It has a shape substantially complementary to the shape of the central part 12 of the semi-finished product 11. It comprises at least one low variation cross section area intended to receive a corresponding low variation cross section section of the semi-finished product 1 1.

The first part of increased section 58 of the housing 55 is configured to house the first part of increased section 13 of the semi-product 11 and therefore of the semi-finished part 16. It comprises for example at least one part of complementary shape of a part of the first part of increased section 13 of the semi-finished product 11 and therefore of the semi-finished part 16.

The second part of increased section 59 of the housing 55 is configured to contain the second part of increased section 14 of the semi-finished product 11. It comprises for example at least one part of shape complementary to a part of the second part of increased section 14 of the semi-finished product 11 to be produced by means of the installation 50.

In this embodiment, the central part 57 and the second part of increased section 59 are intended to receive the rod 15 of the semi-finished part 16.

The installation 50 further comprises a pusher 103 configured to press the upper die 102 on the lower die 100. The pusher 103 is removable. In the example shown, the pusher 103 is in the form of a solid block, configured to rest on the upper die 102 so as to push it against the lower die 100. The pressing of the upper die 102 against the die lower 100 has the effect of deforming the half-worked part 16 placed in the housing 55 so that the half-worked part 16 is partly shaped in the housing 55 at the level of the parts of the half-worked part 16 which do not will not be formatted later. This conformation results in jamming of the half-worked part in the housing 55, preventing in particular the relative movement of the rod 15 of the half-worked part 16 relative to the housing 55.

The installation 50 further comprises a locking system 11 1 of the upper die 102 on the lower die 100, shown in particular in Figure 9. By way of example, the locking system 111 comprises a plurality of locking orifices 120, 121 provided respectively in the upper die 102 and in the lower die 100, and more particularly in appendages of the upper 102 and lower 100 dies, and a locking rod 122. In the closed configuration of the die 53 after shaping, the orifices locking pins 120, 121 are coaxial and the locking rod 122 is intended to extend through the locking holes 120, 121 so as to lock the upper die 102 on the lower die 100. The locking of the upper die 102 on the lower die 100 prevents in particular the relative movement of the rod 15 of the half-worked part 16 relative to the housing 55.

The device 52 is configured to produce the second part of increased section 14 of the semi-finished product 11 by hot forging of a corresponding part of the rod 15 of the semi-worked part 16 received in the housing 55. Said hot forging is in particular a pushing back, in particular on a needle, a stamping, a pushing back or a reverse spinning. Preferably, said hot forging is an upsetting or a stamping, more particularly an upsetting. For this purpose, the device 52 comprises at least one shaping punch 60, received in the housing 55, and configured to move in translation inside the housing 55, and in particular to slide inside the housing 55 , in a direction of movement G, shown in Figure 10, over a maximum travel stroke. The direction of movement G of the shaping punch corresponds to the direction of the longitudinal axis B of the housing 55. The movement of the shaping punch 60 in the housing 55 is configured to cause crushing, and therefore shaping. shaped by upsetting, by pushing back, by stamping or by reverse spinning of a part of the rod 15 of the semi-worked part 16 to form in particular the second part of increased section 14.

More particularly, the shaping punch 60 is configured to move in translation in the direction of the longitudinal axis B from a rest position, shown in Figures 9 to 1 1, to an end position. in shape, in which he carried out the shaping of the semi-worked part 16 to form the second part of increased section 14. In particular, the shaping punch 60 then moved over the maximum displacement stroke between the rest position and the end position of shaping.

In the rest position, the shaping punch 60 does not exert force on the half-worked part 16. In the example shown, the shaping punch 60 is not in contact with the half-worked part. -opened 16 in the rest position.

The housing 55 comprises, at its longitudinal end located on the side of the second part of increased section 59, an opening 61 allowing the insertion of the shaping punch 60 into the housing 55.

The shape of the shaping punch 60 is chosen as a function of the shaping to be carried out, and in particular the shape of the part of increased section 14 of the half-product 11 to be produced, and the type of hot forging to achieve.

In the example shown in Figures 9 to 11, the shaping punch 60 is formed by a rod 62. The rod 62 has in particular a constant cross section. It has for example a shape complementary to that of the part of the housing 55 in which it is inserted, taking into account the clearances necessary for its movement in the housing 55.

However, any other form of shaping punch 60 can be used, depending on the shape of the part of increased section of the semi-finished product 11 and the type of hot forging to be carried out.

More particularly, Figure 15 schematically represents an embodiment of hot forging of a part of increased section 14 from a mid-section part. worked 16 comprising a hollow end, said hot forging being carried out by spinning using a shaping punch 60 which radially moves the material perpendicular to the axis B of the housing 55 of the die 53. More particularly , the shaping punch 60 has a maximum transverse dimension Dp smaller than the maximum transverse dimension Dlog of the end of the housing 55 of the die 53 so that the shaping is not carried out in a closed cavity.

Figure 16 schematically represents a variant of the embodiment of Figure 15 in which the shaping punch 60 is a needle.

Figure 17 schematically represents an embodiment of shaping by hot forging a part of increased section 14 from a semi-worked part 16 comprising a hollow end by stamping using a punch of shaping 60 which moves the material radially perpendicular to the Z axis and shapes to the geometry of the cavity of the end of the housing 53. The shaping punch 60 fits into the end of the housing 53 so that said stamping is produced in a closed cavity.

Figure 18 schematically represents an embodiment of shaping by hot forging of a part of increased section 14 from a solid semi-worked part 16 by reverse spinning using a shaping punch. shape 60 which moves the material along the axis B in the direction opposite to the direction of the punch.

Figure 19 schematically represents an embodiment of shaping by hot forging of a part of increased section 14 from a solid semi-worked part 16 by upsetting using a setting punch in shape 60 which has a flat end and crushes the material and locally increases the deformed section.

Figure 20 schematically represents a variant of the embodiment of shaping by hot forging by upsetting presented in Figure 19 with a view to forming a part of increased section 14 from a semi-worked part 16 comprising a lost mandrel 17.

In the example shown in Figures 9 to 11, the device 52 for producing the second part of increased section 14 further comprises an actuating member 70 movable in translation relative to the housing 55 in a direction of translation F, shown in Figure 10, perpendicular to the longitudinal axis B of the housing 55 from a rest position to an end of shaping position. More particularly, the actuating member 70 can be moved in translation in a vertical direction downwards from its rest position to its end of shaping position. The actuating member 70 is configured such that the movement of the actuating member 70 from its rest position to its end position of shaping causes the movement of the shaping punch 60 from its rest position to its end of shaping position inside housing 55.

By way of example, the actuating member 70 has an elongated shape along a main axis C perpendicular to the longitudinal axis B of the housing 55, and in particular substantially vertical, and defines an end section 82. The axis main C extends in the direction of translation F of the actuating member 70. In the example shown, the end section 82 comprises the lower end of the actuating member 70.

By way of example, the installation 50 comprises a receiving orifice 72 of the actuating member 70, configured to receive the end section 82 of the actuating member 70 when the latter moves up to to its end of formatting position. In the example shown, the receiving orifice 72 of the actuating member 70 is formed in the die 53, more particularly in the lower die 100, and optionally extends into the support table 113. longitudinal end of the shaping punch 60 extends into the receiving orifice 72.

More particularly, the device 52 comprises an angle transmission mechanism 75, configured to transform the translation movement of the actuating member 70 in the translation direction F into a translation of the shaping punch 60 in the direction of displacement G, perpendicular to the direction of translation F.

In the example shown in Figures 9 to 1 1, the angle gear mechanism 75 comprises a cam surface 77 formed on the actuating member 70 and a cam follower surface 79 formed on the setting punch shaped 60. The cam 77 and cam follower 79 surfaces are configured such that the translational movement of the actuating member 70 from its rest position to its end position of shaping generates a sliding contact of the cam surface 77 with the cam follower surface 79 and a translation of the shaping punch 60 from its rest position to its end of shaping position.

The actuating member 70 is in particular in the form of a bladed spindle.

In the example shown, the cam follower surface 79 is formed at one end of the shaping punch 60.

In the example shown in Figures 9 to 1 1, the cam surface 77 is formed by an inclined lateral surface of the actuating member 70, this surface forming an angle a with the main axis C of the member actuation 70. The inclined surface is more particularly a flat surface. The angle a of the cam surface 77 with the main axis C of the actuating member 70 and the stroke of the actuating member 70 are chosen so as to adjust the maximum stroke of the shaping punch 60 to the value necessary to ensure complete shaping in the second part of increased section 59 of the housing 55 and thus obtain the desired geometry for the second part of increased section 14 of the semi-finished product 11. The angle a is for example between 5° to 20°.

The cam surface 77 and the cam follower surface 79 are configured such that the translational movement of the actuating member 70 from its rest position to its end of shaping position pushes the punch shaping 60 towards the second part 59 of the housing 55 in the direction of movement G.

Alternatively, any other type of suitable angle transmission mechanism can be used as an alternative to the mechanism described with reference to Figures 9 to 1 1.

In the example shown in Figures 9 to 1 1, the device 52 further comprises an elastic return member 85 configured to return the shaping punch 60 towards its rest position when the actuating member 70 moves from its end of shaping position to its rest position. For example, the elastic return member 85 comprises a spring, arranged around the shaping punch 60 and secured on the one hand to the shaping punch 60 and on the other hand to the housing 55.

In the example shown in Figures 9 to 11, the installation 50 further comprises a support 90, on which the actuating member 70 is fixed. In this example, the support 90 is arranged above the housing 55 The actuating member 70 is fixed to a longitudinal end 92 of the support 90 by any suitable means, and in particular by bolting or hooping.

The device or installation 50 is suitable for use as hydraulic or crankshaft forging press tools. The movement of the press makes it possible to produce the downward vertical movement of the support 90 and the actuating member 70 which leads to the shaping to produce the second part of increased section 14 of the semi-finished product 11.

Producing the second part of increased section 14 of the semi-product 11 by hot forging makes it possible to obtain a semi-product 11 as described above.

As indicated above, the installation 50 also includes a hot stretching device 54 configured to hot straighten the semi-product 1 1 received in the housing 55 and obtained at the end of the step of producing the second increased section part 14. The hot stretching device 54 comprises at least one stretching punch 95, visible more particularly in Figure 10. Preferably, in order to ensure good mechanical balance, the hot stretching device 54 comprises at least two punches stretching 95. The or each stretching punch 95 can be moved in translation relative to the housing 55 in a direction of movement H from a rest position to an end of stretching position, the movement of the or each stretching punch 95 from its rest position to its end position of stretching causing the hot stretching of the semi-finished product 11 to obtain the intermediate part 1. The direction of movement H is perpendicular to the longitudinal axis B of the housing 55, and in particular vertical. It is parallel to the direction of translation F of the actuating member 70.

In the example shown, the stretching device 54 comprises two stretching punches 95 arranged parallel to each other and on either side of the housing 55, only one of these punches 95 being visible on Figure 10.

The or each stretching punch 95 has an elongated shape along a longitudinal axis E perpendicular to the longitudinal axis B of the housing 55, and in particular parallel to the longitudinal axis C of the actuating member 70, and comprises a end section 116. In the example shown in the Figures, the longitudinal axis E is vertical.

The matrix 53 comprises a fixed part and a movable part, the movable part being movable in translation relative to the fixed part in the direction of the longitudinal axis B between a close position, in which the movable part is in contact with the part fixed and a spaced position, in which the movable part is distant from the fixed part by an elongation distance. The extension distance is chosen based on the desired degree of stretching.

More particularly, in the example shown in Figures 9 to 11, the fixed part comprises a lower fixed part 104 included in the lower die 100 and an upper fixed part 106 included in the upper die 102 and the movable part comprises a movable part lower 108 included in the lower die 100 and an upper movable part 110 included in the upper die 102.

The lower 108 and upper 110 movable parts are secured together in translation in the direction of the longitudinal axis B. For this purpose, the lower 108 and upper 110 movable parts include for example complementary locking reliefs, formed in particular in their surfaces next to it.

Advantageously, the lower fixed parts 104 and upper 106 also include complementary locking reliefs, formed in particular in their facing surfaces, making it possible to improve their connection in the direction of the longitudinal axis B of the housing 55. Optionally, the installation 50 includes locks, configured to lock the movable part of the matrix 53 relative to the fixed part of the matrix 53.

The installation 50 comprises for example a guide device 1 12 configured to guide the translational movement of the movable part of the die 53 relative to the fixed part of the die 53. This guide device 1 12 comprises for example a rail 1 14 provided on the support table 1 13 and a translation guide member (not shown), intended to slide in the rail 1 14 and formed on the movable part of the matrix 53. The guide member has a complementary shape of the shape of the guide rail 114. For example, the guide member has the shape of a dovetail.

As can be seen in Figure 11, the upper die 102 comprises, for each stretching punch 95, a housing 1 15 for receiving the stretching punch 95, of shape complementary to that of the end section 1 16 of the punch stretching 95. The receiving housing 115 of the stretching punch 95 is configured to receive the end section 1 16 of the stretching punch 95 when the latter moves from its rest position to its position of end of stretching.

In the example shown, each receiving housing 115 is formed at the interface between the fixed and mobile parts of the matrix 53 and is delimited partly by the mobile part and partly by the fixed part of the matrix 53.

By way of example, and as illustrated in Figure 11, the receiving housings 115 are arranged on either side of the housing 55 in a direction perpendicular to the direction of elongation B of the housing 55.

The stretching device 54 is configured so that the insertion of the stretching punch 95 into the corresponding receiving housing 115 when moving the stretching punch 95 from its rest position to its end position stretching causes a translational movement of the movable part of the matrix 53 in a direction parallel to the longitudinal axis B of the housing 55 away from the fixed part of the matrix 53 by a distance equal to the distance of elongation.

In the example shown in Figures 9 to 11, this movement is obtained by cam effect, the or each stretching punch 95 comprising a cam surface 117 in its lower section 1 16 and the or each receiving housing 115 delimiting internally a cam follower surface 1 19. In the example shown in Figures 9 to 11, the cam surface 117 is formed by an inclined lateral surface of the stretching punch 95, this surface forming an angle p with the longitudinal axis E of the stretching punch 95. The inclined surface is more particularly a flat surface. The angle p of the cam surface 117 with the longitudinal axis E of the stretching punch 95 and the stroke of the stretching punch 95 are chosen so as to adjust the maximum stroke of the movable part of the die 53 relative to the fixed part at the value necessary to ensure the desired straightening of the semi-product 11.

In this example, the cam follower surface 119 is formed by an interior surface of the receiving housing 115 having a shape complementary to that of a part of the cam surface 117.

The cam surface 1 17 and the cam follower surface 119 are configured such that the translational movement of the stretching punch 95 from its rest position to its end of stretching position pushes the movable part of the matrix 53 away from the fixed part in the direction of the longitudinal axis B of the housing 55.

The translational movement of the movable part 108, 1 10 of the matrix 53 away from the fixed part 104, 106 of the matrix 53 generates an elongation of the housing 55, and more particularly of its central part 57, according to the longitudinal axis B of the housing 55, of a length equal to the extension distance. More particularly, the translational movement of the mobile part 108, 110 of the matrix 53 away from the fixed part 104; 106 of the matrix 53 generates a spacing of the first and second parts of increased section 58, 59 of the housing 55. The first and second parts of increased section 58, 59 being in engagement with the first and second parts of increased section 13, 14 of the half-product 11, this spacing causes a stretching, as well as a straightening of the half-product 11 received in the housing 55.

In the example shown in Figures 9 to 1 1, the or each stretching punch 95 is fixed to the support 90 described previously, so as to extend opposite the receiving housings 115 in the direction of elongation E of the stretching punch 95.

The support 90 is movable in translation relative to the housing 55 in a direction parallel to the direction of translation F of the actuating member 70 and to the direction of movement H of or each stretching punch 95.

More particularly, the support 90 can be moved in translation relative to the housing 55 so as to successively occupy the following positions:

- a rest position, in which the actuator 70 and each stretching punch 95 occupy their rest position,

- a shaping start position, in which the actuating member 70 comes into contact with the shaping punch 60,

- an end of shaping position, in which the actuating member 70 occupies its end of shaping position and has traveled, relative to its rest position, a stroke resulting in the maximum displacement stroke of the shaping punch 60, - a hot stretching start position, in which each stretching punch 95 begins to perform the hot stretching; And

- an end of stretching position, in which each stretching punch 95 occupies its end of stretching position, and has traveled, relative to its rest position, a stroke resulting in the maximum desired spacing between the part fixed and the mobile part of the matrix 53.

In this example, each stretching punch 95 has a length less than that of the actuating member 70, taken from the support 90, so that each stretching punch 95 causes the stretching of the semi-product 1 1 by elongation of the housing 55 only after the actuating member 70 has caused the shaping of the semi-worked part 16 to form the second part of increased section 14. For example, the length of the or of each stretching punch 95 is adjusted such that the stretching punch 95 arrives at the entrance to the corresponding receiving housing 115 when the actuating member 70 reaches its end of shaping position.

As indicated above, the device or installation 50 is suitable for use as hydraulic or crankshaft forging press tools. The movement of the press makes it possible to produce the downward vertical movement of the support 90 which leads to the shaping to produce the second part of increased section 14 of the semi-product 1 1, as well as to the stretching of the semi-product 11 .

A process for manufacturing an intermediate part 1 from a semi-finished part 16 as described above by means of the installation 50 installed in a forging press will now be explained in more detail.

This process includes the following steps:

- installation of the lower die 100 provided with the shaping punch 60 on the support table 113 and installation of the support 90 provided with the actuating member 70 and the or each stretching punch 95;

- installation of the semi-finished part 16 in the part of the housing 55 delimited by the lower die 100,

- placement of the upper matrix 102 on the lower matrix 100;

- installation of pusher 103;

- descent of the press so as to press the upper die 102 on the lower die 100 by means of the pusher 103 via the support 90 and thus conform the parts of the half-worked part 16 which are not intended to be placed in shape; - locking of the upper die 102 on the lower die 100 after shaping and optionally locking of the mobile part of the die 53 on the support table 113;

- removal of the pusher 103;

- movement of the support 90 in translation from its rest position to its end of shaping position resulting in the translation of the actuating member 70 from its rest position to its end of shaping position shape so as to form the second part of increased section 14 by hot forging in the second part of increased section 59 of the housing 55 and obtain the semi-finished product 11;

- optionally, unlocking of the movable part of the die 53 to allow its movement in translation relative to the fixed part of the die 53 under the effect of the or each stretching punch 95;

- continuation of the movement of the support 90 in translation to its end of stretching position resulting in the translation of the or each stretching punch 95 to its end of stretching position so as to straighten the semi-product 11 to obtain intermediate part 1;

- raising of the support 90, unlocking of the upper die 102 and release of the intermediate part 1.

The installation 50 according to the first embodiment and the associated manufacturing process are advantageous. Indeed, the installation 50 allows the production of the second part of increased section 14 by hot forging and the straightening of the semi-finished product 1 1 by hot stretching in the same tool and by linking the stages of the process. It therefore makes it possible to produce a part having the desired straightness characteristics, without having to carry out intermediate heating between shaping to obtain the second part of increased section 14 and hot stretching. It also results in savings in material, and therefore savings in terms of cost price, to the extent that the installation 50 makes it possible to manufacture an intermediate part 1 having a central part of external dimensions close to the dimensions in the final part .

Furthermore, in the case of the particular example shown in Figures 9 to 11, the housing 55 extends along a horizontal longitudinal axis B, coaxial with the direction of elongation of the part to be manufactured, the housing 55 being formed between a lower die 100 and an upper die 102, movable away from each other substantially perpendicular to the longitudinal axis B of the housing 55 for the introduction of the blank 6 or the semi-worked part 16 or the extraction of the intermediate part 1. Furthermore, an angle transmission mechanism 75 makes it possible to transform the vertical movement of the press, and therefore of the actuating member 70, into a horizontal movement of the shaping punch 60. This particular geometry allows the manufacture of very long parts and with locally higher section areas in a relatively simple and inexpensive manner. Indeed, on the one hand, the introduction of the blank 6 or the semi-worked part 16 or the extraction of the intermediate part 1 only requires a relatively small clearance of the upper die 102 relative to the lower die 100, and on the other hand, the installation 50 can have a relatively low total height compared to the length of the intermediate part 1 to be produced.

Furthermore, the delimitation of the housing 55 between the lower 100 and upper 102 dies, which can be easily moved relative to each other to open the housing 55 over its entire length, allows variations in cross section without problems of recovering the parts after hot shaping, which would not be the case with conventional tools having a joint plane of the dies perpendicular to the longitudinal axis Z of the intermediate part 1, and therefore to the longitudinal axis B of the housing 55.

Figures 12 to 14 illustrate a manufacturing installation 200 of an intermediate part 1 according to a second embodiment of the invention. This installation 200 is intended to be used for the implementation of the manufacturing process described above. This installation 200 more particularly allows the implementation of the steps of shaping the blank 6 to obtain the semi-product 1 1 and of stretching the semi-product 11 to obtain the intermediate part 1.

Only the differences compared to the installation 50 according to the first embodiment are described below. Furthermore, identical or similar elements are designated by the same reference number.

The installation 200 according to the second embodiment differs from the installation 50 according to the first embodiment mainly in the fact that the device 52 comprises two parallel actuating members 70, integral in translation, the movement of each member of actuation 70 from its rest position to its end of shaping position generating the production by upsetting, pushing back, stamping or reverse spinning of a part of increased section 13, 14 respectively of the semi-product 1 1.

The installation 200 therefore comprises, for each actuating member 70, an angle transmission mechanism 75, a shaping punch 60, a housing for receiving the actuating member 72 and an elastic return member 85 as described above for each actuating member 70.

The first part of increased section 13 and the second part of increased section 14 can be produced by the same type of hot forging, chosen from upsetting, spinning, stamping or reverse spinning, or by types of hot forging different, chosen from any combination of these types of hot forging. Of preferably, the first part of increased section 13 and the second part of increased section 14 are each produced by upsetting or by stamping.

The shape of the shaping punch 60 is chosen according to the shape of the part of increased section 13, 14 and the type of hot forging to be carried out.

In this embodiment, and as shown in Figures 13 and 14, the housing 55 is intended to receive a blank 6 as described above.

It has a shape similar to that of the housing 55 described with regard to the first embodiment. However, it comprises at its longitudinal end located at the level of its first part of increased section 58, an opening 208 allowing the insertion of a corresponding shaping punch 60 in the housing 55. In this embodiment, each punch shaping 60 is configured to penetrate into the housing 55 at a longitudinal end thereof, so as to produce the corresponding part of increased section 13, 14.

The first part of increased section 58 of the housing 55 is, in this embodiment, configured to house the first part of increased section 13 of the semi-finished product 11 after shaping by hot forging by the shaping device 52.

The device 52 therefore allows, in this embodiment, the production of the first and the second part of increased section 13, 14 in the same tool, in particular simultaneously, from the blank 6 received in the housing 55.

In this embodiment, the hot stretching device 54 is not configured to stretch the semi-finished product 11 while it is received in the housing 55. The stretching device 54 is not not included in the same tool as the device 52 for producing at least one part of increased section 14 of the semi-finished product 11, as is the case in the first embodiment. In this case, the stretching device 54 is formed by a separate tool designed to straighten or straighten trees by traction. The stretching device 54 has only been shown schematically in Figure 14.

According to a particular embodiment, the separate stretching device 54 is similar to the stretching device 54 described with regard to the first embodiment of the installation shown in Figures 9 to 11.

In this case, the stretching device 54 comprises one or more stretching punches and corresponding receiving housings formed in a matrix as described above, the stretching punches being configured to straighten or straighten by traction the half- product 11 received in a housing formed between a lower die and an upper die in the die in a manner analogous to what was described above with regard to the first embodiment. This matrix and the reception housing delimited by this matrix are distinct from the reception housing 55 and the matrix 53 used to the shaping of the blank 6, and more particularly the production of the first and the second part of increased section 13, 14.

In this case, and as has been described with regard to the first embodiment, the matrix comprises a fixed part and a mobile part, the translational movement of the mobile part of the matrix away from the fixed part on a stroke equal to an elongation distance under the effect of the insertion of the stretching punch(s) into the corresponding housings causing an elongation of the housing for receiving the semi-finished product 1 1 by a length equal to the distance of elongation, and thus straightening or straightening of the semi-product 11 by traction.

A process for manufacturing an intermediate part 1 from a blank 6 as described above using the installation 200 will now be explained in more detail.

This process includes the following steps:

- installation of the support table 1 13 then of the lower die 100 provided with shaping punches 60 on the support table 1 13 and installation of the support 90 provided with actuating members 70;

- installation of the blank 6 in the part of the housing 55 delimited by the lower matrix 100,

- placement of the upper matrix 102 on the lower matrix 100;

- installation of the pusher 103 and shaping of the parts of the blank 6 which are not intended to be shaped, by pressing the upper die 102 on the lower die 100 by means of the pusher 103;

- locking of the upper die 102 on the lower die 100 after shaping;

- removal of the pusher 103;

- movement of the support 90 in translation from its rest position to its end of shaping position resulting in the translation of each actuating member 70 from its rest position to its end of shaping position so as to form the first part of increased section 13 and the second part of increased section 14 by hot forging, respectively in the first part of increased section 58 and in the second part of increased section 59 of the housing 55 and thus obtain the half - product 1 1;

- raising of the support 90, unlocking of the upper die 102 and release of the semi-finished product 11;

- stretching of the semi-finished product 11 by means of the separate stretching device 54 to form the intermediate part 1. The installation 200 according to the second embodiment, and the corresponding manufacturing process, allow the production by hot forging, and in particular by upsetting, spinning, stamping, reverse spinning or by any combination of these processes, of the first and second parts of increased section 13, 14 in a single operation in the same tool, and results in material savings similar to those obtained with the installation 50 according to the first embodiment, the central part 3 of the intermediate part 1 having dimensions very close to the dimensions in the final piece.

Furthermore, the geometry of the installation 200 being similar to the geometry of the installation 50, it makes it possible to obtain advantages similar to those described above, in particular with regard to the possibility of manufacturing long parts.

Claims

1. Method of manufacturing by forging an intermediate part (1) of metal alloy elongated along a longitudinal axis (Z), the intermediate part (1) comprising a central part (3) comprising at least one section of low cross section variation, the area of the cross sections of the or of each section of cross section with low variation varying by at most 20% along said section, the intermediate part (1) further comprising a first part of increased section (5) and a second part of increased section (5') located on either side of the central part (3) along the longitudinal axis (Z), the method comprising the following steps:

- manufacture by hot forging of a blank (6) elongated along a longitudinal axis (Z) comprising at least one section of cross section with low variation;

- shaping of the blank (6) to obtain a semi-product (1 1) elongated along a longitudinal axis (Z) comprising a central part (12) and a first part of increased section (13) and a second part of increased section (14), extending on either side of the central part (12) in the direction of the longitudinal axis (Z), the shaping of the blank (6) comprising the production of the first part of increased section (13) of the semi-product (1 1) by hot forging and the production of the second part of increased section (14) of the semi-product (1 1) by hot forging chosen from upsetting , spinning, stamping or reverse spinning; And

- hot stretching of the semi-product (1 1) to obtain the intermediate part (1).

2. Method according to claim 1, in which the metal alloy is chosen from a superalloy, a titanium-based alloy and a steel, more particularly a steel chosen from the following list: a structural hardening steel and an alloyed martensitic steel .

3. Method according to claim 1 or 2, in which the length (L) of the intermediate piece (1) is greater than or equal to 800 mm and the ratio (L/D) between the length (L) of the intermediate piece ( 1) and the maximum transverse dimension (D) of the central part (3) of the intermediate piece (1) is greater than or equal to 2.5.

4. Method according to any one of claims 1 to 3, in which the area of the cross sections of the or of each section of cross section with low variation varies by at most 10% along said section, preferably in which the area of cross sections of the or each section of cross section with low variation is constant along said section.

5. Method according to any one of claims 1 to 4, in which the cumulative length (L _o ) of the section(s) of cross section with low variation, taken along the longitudinal axis (Z), is greater than or equal to 40 % of the length (L) of the intermediate piece (1), preferably greater than or equal to 60% of the length (L) of the intermediate piece (1), and even more preferably greater than or equal to 70% of the length ( L) of the intermediate piece (1).

6. Method according to any one of claims 1 to 5, in which the center of the first part of increased section (5) and/or the center of the second part of increased section (5'), taken in the longitudinal direction (Z) of the intermediate piece (1), is located at a distance (Li, L ₂ ) from the corresponding end (4, 4') of the intermediate piece (1) less than or equal to 25% of the length ( L) of the intermediate piece (1), preferably less than or equal to 15% of the length (L) of the intermediate piece (1) -

7. Method according to any one of the preceding claims, in which the first part of increased section (13) of the semi-finished product (11) is produced by upsetting, spinning, stamping or reverse spinning.

8. Method according to any one of the preceding claims, in which the second part of increased section (14) of the semi-product (1 1) is produced by upsetting and in which, preferably, the first part of increased section is produced by repressing or by stamping.

9. Method according to any one of the preceding claims, in which the production of the first part of increased section (13) of the semi-product (11) and the production of the second part of increased section (14) of the semi-product (11) are carried out successively.

10. Method according to any one of claims 1 to 8, in which the production of the first part of increased section (13) of the semi-product (11) and the production of the second part of increased section (14) of the half -product (11) are carried out simultaneously, in particular in the same tool.

11. Method according to any one of the preceding claims, in which the semi-product (11) is not heated between the production of the second part of increased section (14) of the semi-product (11) and the stretching hot.

12. Method according to any one of the preceding claims, in which the production of the second part of increased section (14) and the hot stretching are carried out in the same tool.

13. Process for manufacturing an elongated metal alloy part comprising:

- the manufacture of an intermediate part (1) by implementing the method according to any one of claims 1 to 12;

- finishing the intermediate part (1) to obtain the part, the finishing including in particular machining.

14. Method according to claim 13, in which the part is chosen from: an axle, a motor shaft, a landing gear part, an extension tube for a pump intended for the extraction of oil or gas, a valve underwater, in particular for the engine of a large boat, such as a liner or a supertanker and a missile launcher tube.

15. Manufacturing installation (50; 200) by forging an intermediate part (1) of metal alloy elongated along a longitudinal axis (Z), the manufacturing installation (50; 200) being intended to be used for the implementation implementing the method according to any one of claims 1 to 12, comprising:

- a housing (55) defining a longitudinal axis (B) intended to receive a blank (6) elongated along a longitudinal axis (Z) comprising at least one section of cross section with low variation or an elongated semi-worked part (16) along a longitudinal axis (Z) comprising a rod (15) comprising at least one section of cross section with low variation, and a first part of increased section (13); a shaping device (51) of the blank (6) or the semi-finished part (16) received in the housing (55) so as to form a half-product (11) elongated along a longitudinal axis ( Z) comprising a central part (12) and a first part of increased section (13) and a second part of increased section (14), located on either side of the central part (12) in the direction of the longitudinal axis (Z), the shaping device (51) comprising a production device (52), by hot forging by stamping, by pressing, by spinning or by reverse spinning, of at least the second part of increased section (14) of the semi-finished product (11); and a hot stretching device (54) configured to hot straighten the half-product (1 1) so as to form the intermediate part (1).

16. Installation (50; 200) according to claim 15, in which the device for producing (52) at least the second part of increased section (14) of the semi-product (1 1) comprises at least one member for actuation (70), movable in translation relative to the housing (55) in a direction perpendicular to the longitudinal axis (B) of the housing (55) from a rest position to an end of shaping position, the movement of the actuating member (70) from its rest position to its end of shaping position generating at least the second part of increased section (14) of the semi-product (1 1) by hot forging.

17. Installation (200) according to claim 16, in which the device for producing (52) at least the second part of increased section (14) of the semi-finished product (1 1) comprises two actuating members (70) , each actuating member (70) being movable in translation relative to the housing (55) in a direction perpendicular to the longitudinal axis (B) of the housing (55) from a rest position to an end position shaping, the actuating members (70) being integral in translation in the direction perpendicular to the longitudinal axis (B) of the housing (55), the movement of each actuating member (70) from its position of rest until its end of shaping position resulting in the production of a part of respective increased section (13, 14) of the semi-finished product (1 1) by hot forging.

18. Installation (50; 200) according to one of claims 16 or 17, in which the device for producing (52) at least the second part of increased section (14) of the semi-finished product (1 1) comprises:

- a shaping punch (60) for each actuating member (70), each shaping punch (60) being configured to move in translation in the direction of the longitudinal axis (B) of the housing ( 55), and

- an angle transmission mechanism (75), configured to transform the movement of the or each actuating member (70) from its rest position to its end of shaping position into a translational movement of the shaping punch (60) corresponding in the direction of the longitudinal axis (B) of the housing (55) to produce by hot forging a corresponding part of increased section (13, 14) of the semi-finished product (11).

19. Installation (50) according to any one of claims 15 to 18, in which the hot stretching device (54) is configured to hot straighten the half-product (1 1) received in the housing (55) .

20. Installation (50) according to claim 19, in which the hot stretching device (54) comprises a stretching punch (95), movable in translation relative to the housing (55) in a direction perpendicular to the longitudinal axis (B) of the housing (55) from a rest position to an end of stretching position, moving the stretching punch (95) from its rest position to its end of stretching position stretching causing the hot straightening of the semi-product (11) received in the housing (55) to obtain the intermediate part (1).

21. Installation (50) according to one of claims 19 or 20, comprising a matrix (53) delimiting the housing (55), the matrix (53) comprising a fixed part (104, 106) and a movable part (108, 110), said movable part (108, 1 10) of the matrix (53) being movable in translation relative to said fixed part (104; 106) in the direction of the longitudinal axis (B) of the housing (55) between a close position, in which the movable part (108; 1 10) is in contact with the fixed part (104; 106) and a spaced position, in which the movable part (108; 110) is distant from the fixed part (104 ; 106) by an elongation distance, this movement causing an elongation of the housing (55) by a length equal to the elongation distance, the hot stretching device (54) further comprising, for each punch stretching (95), a housing (1 15) for receiving the stretching punch (95), configured to receive an end section (1 16) of the stretching punch (95) when the latter moves from its rest position to its end of stretching position, the insertion of the stretching punch (95) into the corresponding receiving housing (115) causing the translational movement of the movable part (108; 1 10) of the die (53) relative to the fixed part (104; 106) of the die (53) from its close position to its spaced position so as to straighten the semi-product (1 1) received in housing (55).

22. Installation (50) according to one of claims 20 or 21, taken in combination with one of claims 15 to 17, further comprising a support (90) on which the or each actuating member (70) is fixed ) and the or each stretching punch (95), the support (90) being movable in translation relative to the housing (55) in a direction parallel to the direction of movement of the or each actuating member (70) and the or each stretching punch (95) so as to successively occupy the following positions:

- a rest position, in which the or each actuating member (70) and the or each stretching punch (95) occupies its rest position,

- an end of shaping position, in which the or each actuating member (70) occupies its end of shaping position, and

- an end of stretching position, in which the or each stretching punch (95) occupies its end of stretching position.

23. Installation (50) according to any one of claims 15 to 22, which is used as forging press tools.

24. Use of the installation (50) according to any one of the claims

15 to 22 as forging press tools.