METHOD AND UNIT FOR MANUFACTURING AN ELONGATE INTERMEDIATE PART BY HOT FORGING

Abstract

Method of manufacturing by forging an intermediate metal alloy part (1) elongate along a longitudinal axis (Z), comprising the following steps: manufacture by hot forging of an elongate blank comprising at least one section of small cross-section variation;shaping of the blank to obtain a semi-finished product elongate along a longitudinal axis comprising a central part and a first and a second part of increased cross-section, extending on both sides of the central part along the direction of the longitudinal axis, the shaping of the blank comprising the production of the first part of increased cross-section of the semi-finished product by hot forging and the production of the second part of increased cross-section of the semi-finished product by hot forging chosen from upsetting, spinning, die forging or backward extrusion techniques;hot stretching of the semi-finished product to obtain the intermediate part (1).

Description

The present invention relates to a method and an installation for the production by hot forging of an intermediate part which is elongate along an axis Z, of total length L, made of a metal alloy, the intermediate part comprising a central part comprising at least one section with a small variation in cross-section and two parts of increased cross-section located on both sides of the central part.

Usually, parts such as aircraft engine shafts are made by carrying out the following successive operations: manufacture of an elongate blank of small cross-section variation by hot extrusion or free-forging drawing, then production by hot forging, e.g. via a hot extrusion, of a part of increased cross-section, called head, located e.g. at one of the ends of the blank, and finally machining to reduce the transverse dimensions of the central part while retaining a part of increased cross-section at an end of the central part opposite the head along the longitudinal direction of the part.

However, such method is not entirely satisfactory. Indeed, the elongate blank of small cross-section variation has transverse dimensions the value of which, over the entire length of the blank, is set by the transverse dimensions of the largest cross-section of the part (excluding the head), and thus, in particular, by the transverse dimensions of the part of increased cross-section of the part opposite the head along the longitudinal direction, machining then being necessary to reduce the transverse dimensions of the central part and to obtain the desired final shape of the central part. Thereof results, given the large length of the central part for the applications mentioned hereinabove, with a relatively high loss of material, and consequently in high production costs, more particularly in the case where the part is made of a so-called noble alloy i.e. including relatively large quantities of expensive alloying elements, such as maraging steels, superalloys or titanium alloys.

A goal of the invention is to provide a method and an installation for the manufacture of elongate intermediate metal alloy parts as described hereinabove, at a reduced cost.

To this end, the invention relates to a method for the production by forging of an intermediate part made of a metal alloy, the intermediate part being elongate along a longitudinal axis, the intermediate part comprising a central part comprising at least one section of small cross-section variation, the surface area of the cross-sections of the or each section with a small variation in cross-section varying by at most 20% along said section, the intermediate part further comprising a first part of increased cross-section and a second part of increased cross-section located on both sides of the central part along the longitudinal axis, the method comprising the following steps:

• • manufacture by hot forging of a blank which is elongate along a longitudinal axis comprising at least one section of small cross-section variation;
  • shaping of the blank to obtain a semi-finished product which is elongate along a longitudinal axis comprising a central part and a first part of increased cross-section and a second part of increased cross-section, extending on both sides of the central part along the direction of the longitudinal axis, shaping of the blank comprising the production of the first part of increased cross-section of the semi-finished product by hot forging and the production of the second part of increased cross-section of the semi-finished product by hot forging chosen from upsetting, spinning, die forging or backward extrusion techniques;
  • hot stretching of the semi-finished product so as to obtain the intermediate part.

The method according to the invention can comprise one or a plurality of the following features, taken individually or according to any technically possible combination:

• • the metal alloy is chosen from a superalloy, a titanium 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 part is greater than or equal to 800 mm and the ratio between the length of the intermediate part and the maximum transverse dimension of the central part of the intermediate part is greater than or equal to 2.5.
  • the surface area of the cross-section of the or each section of small cross-section variation varies by at most 10% along the length of said section, preferably the surface area of the cross-section of the or each section of small cross-section variation is constant along said section.
  • the cumulative length of the section or sections of small cross-section 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 intermediate part, and even more preferably greater than or equal to 70% of the length of the intermediate part.
  • the center of the first part of increased cross-section and/or the center of the second part of increased cross-section, taken along the longitudinal direction of the intermediate part, is located at a distance from the corresponding end of the intermediate part less than or equal to 25% of the length of the intermediate part, preferably less than or equal to 15% of the length of the intermediate part.
  • the first part of increased cross-section of the semi-finished product is produced by upsetting, spinning, die forging or backward extrusion techniques.
  • the second part of increased cross-section of the semi-finished product is produced by upsetting and, preferably, the first part of increased cross-section is produced by upsetting or by die forging.
  • the second part of increased cross-section of the semi-finished product is produced by die forging and, preferably, the first part of increased cross-section is produced by upsetting or by die forging.
  • the production of the first part of increased cross-section of the semi-finished product and the production of the second part of increased cross-section of the semi-finished product are carried out successively.
  • the production of the first part of increased cross-section of the semi-finished product and the production of the second part of increased cross-section of the semi-finished product are carried out simultaneously, more particularly in the same tool.
  • the semi-finished product is not heated between the production of the second part of increased cross-section of the semi-finished product and the hot stretching.
  • the production of the second part of increased section and the hot stretching are carried out in the same tool.

The invention further relates to the method for manufacturing an elongate part made of a metal alloy comprising:

• • the manufacture of an intermediate part by using the method described hereinabove;
  • the finishing of the intermediate part to obtain the part, the finishing comprising more particularly machining.

According to a particular feature of the method, the part is chosen from: an axle, a drive shaft, a part for a landing gear, a riser tube for a pump intended for the extraction of oil or gas, an underwater valve, in particular for a large boat engine, such as a liner or supertanker, and a missile launcher tube.

The invention further relates to an installation for manufacturing by forging an intermediate part made of a metal alloy, the intermediate part being elongate along a longitudinal axis, the manufacturing installation being intended to be used for the implementation of the method, comprising:

• • a housing defining a longitudinal axis intended to receive a blank which is elongate along a longitudinal axis, the blank comprising at least one section of small cross-section variation or a semi-finished part which is elongate along a longitudinal axis, the semi-finished part comprising a rod comprising at least one section of small cross-section variation, and a first part of increased cross-section;
  • a device for shaping the blank or the semi-finished part received in the housing so as to form a semi-finished product which is elongate along a longitudinal axis comprising a central part and a first part of increased cross-section and a second part of increased cross-section, located on both sides of the central part along the direction of the longitudinal axis, the shaping device comprising a device for producing at least the second part of increased cross-section of the semi-finished product by hot forging by die forging, by upsetting, by spinning or by backward extrusion techniques;
  • a hot stretching device configured to hot straighten the semi-finished product to form the intermediate part.

The installation according to the invention can comprise one or a plurality of features, taken individually or according to any technically possible combination:

• • the hot stretching device is configured to hot straighten the semi-finished product received in the housing.
  • the hot stretching device comprises a stretching punch, movable in translation relative to the housing along a direction perpendicular to the longitudinal axis of the housing from a rest position to an end-of-stretching position, the movement of the stretching punch from the rest position to the end-of-stretching position thereof, leading to the hot rectification of the semi-finished product received in the housing to obtain the intermediate part.
  • the installation further comprises a die delimiting the housing, the die comprising a fixed part and a movable part, said movable part of the die being movable in translation relative to said fixed part in the direction of the longitudinal axis of the housing between a closed position, the movable part being in contact with the fixed part, and a spaced apart position, the movable part being spaced from the fixed part by an elongation distance, the movement leading to an elongation of the housing by a length equal to the elongation distance,
  • the hot stretching device further comprising, for each stretching punch, a receiving housing for the stretching punch, configured to receive an end section of the stretching punch when the latter moves from the rest position thereof to the end-of-stretching position thereof, the insertion of the stretching punch into the corresponding receiving housing making the movable part of the die to move in translation relative to the fixed part of the die from the closed position to the spaced away position thereof so as to straighten the semi-finished 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 fastened, the support being movable in translation relative to the housing along a direction parallel to the direction of movement of the or each actuating member and of the or each stretching punch so as to occupy successively the following positions:
  • a rest position, in which the or each actuating member and the or each stretching punch occupies the rest position thereof,
  • an end-of-shaping position, in which the or each actuating member occupies the end-of-shaping position thereof, and
  • an end-of-stretching position, in which the or each stretching punch occupies the end-of-stretching position thereof.
  • the installation is used as a forging press tool.
  • the installation as described hereinabove forms a forging press tool.

The invention further relates to the use of the installation as described hereinabove as a forging press tool.

The invention will be better understood upon reading the following description, given only as an example and making reference to the enclosed drawings, where:

FIG. 1 is a schematic representation of an intermediate part produced by the method according to the invention according to a first embodiment;

FIG. 2 is a schematic representation in section along the plane F-F′ of the intermediate part shown in FIG. 1 according to one embodiment;

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

FIG. 4 is a schematic representation of an intermediate part produced by the method according to the invention according to a variant;

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

FIG. 6 is a schematic representation of a semi-product produced within the framework of the method according to the invention;

FIG. 7 is a schematic representation of a semi-finished part produced within the framework of the method according to the invention;

FIG. 8 is a schematic representation of an intermediate part according to a variant;

FIG. 9 is a schematic perspective view of an installation for manufacturing an intermediate part by forging according to a first embodiment;

FIG. 10 is a schematic longitudinal sectional view along a vertical plane of the installation shown in FIG. 9;

FIG. 11 is a schematic top view of a part of the installation shown in FIG. 9;

FIG. 12 is a schematic perspective view of an installation for manufacturing an intermediate part by forging according to a second embodiment;

FIG. 13 is a schematic longitudinal sectional view along a vertical plane of the installation shown in FIG. 12; and

FIG. 14 is a schematic top view of the elements of a part of the installation shown in FIG. 12.

FIG. 15 is a schematic representation of a shaping of a part of increased cross-section by upsetting from a blank which is hollow at the end.

FIG. 16 is a schematic representation of a shaping of a part of increased cross-section by upsetting with a needle from a blank which is hollow at the end.

FIG. 17 is a schematic representation of a shaping of a section increased by die forging from a solid blank.

FIG. 18 is a schematic representation of a shaping of a part of increased cross-section by backward extrusion from a solid blank.

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

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

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

An example of intermediate part 1 produced by a manufacturing method according to a first embodiment of the invention is shown schematically in FIG. 1.

The intermediate part 1 is elongate 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 small cross-section variation and a first part of increased cross-section 5 and a second part of increased section 5′ located on both sides of the central part 3 along the direction of the longitudinal axis Z.

The central part 3 and the or each section of small cross-section variation are elongate along the longitudinal axis Z.

Throughout the description, the term “cross-section” refers to the cross-section perpendicular to the longitudinal axis Z.

Throughout the description, the term “section of small cross-section variation” refers to in particular a section the surface areas of the cross-sections of which vary by at most 20% along said section, i.e. along the longitudinal axis Z. Such variation is estimated by the ratio between the difference between the surface area of the largest cross-section and the surface area of the smallest cross-section and the average surface areas of the cross-section of the at least one cross-section which varies little. More particularly, the 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 hereinabove is zero. In such case, the term “section of constant cross-section” will be used hereinafter.

The central part 3 has a cumulative length LO of the section or sections the cross-section of which vary little, taken along the longitudinal axis Z, greater than or equal to 40% of the length L of the intermediate part 1. As an example, the cumulative length L0 of the section or sections the cross-section of which vary little 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 part 1.

Preferably, the first part of increased cross-section 5 and the second part of increased cross-section 5′ are each adjacent to a section of small cross-section variation, of the central part 3 along the direction of the longitudinal axis Z, i.e. without interposition of other parts of the part.

According to one embodiment, the central part 3 consists of a section of small cross-section 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, along the direction of the longitudinal axis Z, a plurality of sections the cross-sections of which vary little and at least one intermediate part arranged between the sections the cross-sections of which vary little.

According to another variant (not shown), the central part 3 comprises a plurality of sections of constant cross-section and at least one intermediate part arranged between the sections of constant cross-section.

In the example shown in FIG. 1, the central part 3 consists of a section of constant cross-section and the first and second parts of increased cross-section 5, 5′ are adjacent to the central part 3 along the direction of the longitudinal axis Z.

The first and second parts of increased cross-section 5, 5′ are preferably each located close to a respective end 4, 4′ of the intermediate part 1. More particularly, the center of each part of increased cross-section 5, 5′, taken along the direction of elongation Z of the intermediate part 1, is located at a respective distance L1, L2 from the corresponding end 4, 4′ less than or equal to 25% of the length L of the intermediate part 1. More particularly, the center of each part of increased cross-section 5, 5′ is located at a respective distance L1, L2 from the corresponding end 4, 4′ less than or equal to 15% of the length L of the intermediate part 1.

Each of the parts of increased cross-section 5, 5′ comprises a cross-section of respective minimum surface area Amin, corresponding to the smallest cross-section thereof. For each of the parts of increased cross-section 5, 5′, the surface area Amin of the cross-section is greater than the surface area A of the largest cross-section of at least one of the sections the cross-sections of which vary little, of the central part 3, and in particular of the or each section of the central part 3 of small cross-section variation.

More particularly, the cross-section of minimum surface area Amin of each of the parts of increased cross-section 5, 5′ has a maximum dimension D1, D2 greater than the maximum dimension D of the largest cross-section of at least one of the sections the cross-sections of which vary little, of the central part 3, and in particular of the or each section of the central part 3, of small cross-section variation.

The maximum dimension of a cross-section means in particular the outer diameter of the cross-section in the case of a circular cross-section or the diagonal of the cross-section in the case of a polygonal cross-section, e.g. square or hexagonal cross-section.

According to one embodiment, the first and second parts of increased cross-section 5, 5′ have identical shapes. According to a variant, illustrated in the figures, the first and second parts of increased cross-section 5, 5′ have different shapes, and e.g. different lengths and/or transverse dimensions.

As an example, the first part of increased cross-section 5 and/or the second part of increased cross-section 5′ has a shape chosen from:

• • a shape of constant cross-section, more particularly an annular or cylindrical shape;
  • an axisymmetric shape of variable cross-section along the longitudinal axis Z, more particularly with a shape of a trumpet, a cone or other shape;
  • a non-axisymmetric shape, more particularly a yoke shape, a gimbal shape, or any other suitable complex shape.

In the case of a part of increased cross-section 5, 5′ having a constant cross-sectional shape, i.e. having a constant surface area of the cross-section along said part of increased cross-section, the minimum surface area cross-section Amin corresponds to any cross-section of the part of increased cross-section 5, 5′ considered.

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

In the case of an increased cross-section part 5, 5′ having a cross-sectional shape that varies along the longitudinal axis Z, the minimum surface area of the cross-section Amin corresponds to a particular surface area of the cross-section of the increased surface area of the cross-section part 5, 5′ considered, wherein the surface area of the increased section part 5, 5′ is the smallest.

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

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

According to a first variant, illustrated in FIG. 4, the intermediate part 1 is a hollow part, more particularly a tubular part.

According to a second variant, the central part 3 of the intermediate part 1 is solid and at least the second part of increased cross-section 5′ is hollow and forms one of the ends of the intermediate part 1. As an example, the first part of increased cross-section 5 and the second part of increased cross-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 the patent application WO 2019/141798A1, made of a first metal alloy and a casing made of a second metal alloy.

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

As an example, the central part 3 of the intermediate part 1 is a part of revolution with respect to the axis Z. The central part 3 of the intermediate part 1 is e.g. either 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 straight cross-section. In the case of a hollow cylinder, the diameter of the circular straight cross-section means the outer diameter thereof.

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 outer diagonal of the 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 circumscribing said hexagonal cross-section.

As an example, the length L of the intermediate part 1 is greater than or equal to 800 mm and the ratio L/D between the length thereof 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 e.g. greater than or equal to 20 and/or the length L of the intermediate part 1 is greater than or equal to 1 m, in particular greater than or equal to 1.5m, and e.g. greater than or equal to 2 m, and it is possible to combine the lengths L and ratios L/D listed hereinabove according to the desired final shape of the intermediate part 1.

The intermediate part 1 is made of a metal alloy. In particular, the intermediate part 1 is made of one of the following materials:

• • a steel, and more particularly a steel chosen from the following list:
    • a structural hardening steel, in particular a structural hardening martensitic steel, e.g. 15-5 PH, 17-4 PH, ML340, maraging 250, Marval 18, Maraging 300, Maraging 350, MLX19, or MLX20;
    • an alloy martensitic steel, e.g. a steel 300M;
  • a superalloy, and more particularly a nickel-based superalloy, e.g. an alloy 718;
  • a titanium alloy, e.g. Ti-6-AI-4V, Ti-5333 or Ti 10.2.3.

The steels listed hereinabove are steels with high mechanical properties.

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

• • an axle, e.g. for a railway or motor vehicle,
  • a drive shaft, e.g. for a helicopter rotor or for a pump shaft, more particularly a drive shaft, e.g. for a wind turbine or for the automotive industry: car, truck, tractor, etc. or a shaft for a gas turbine or a turbojet,
  • a landing gear part, such as a landing gear rod or an axle of the landing gear wheels,
  • a riser tube, e.g. for pumps for oil or gas extraction;
  • an underwater valve, in particular for engines of large boats, such as ships or supertankers; or
  • a missile-launcher tube.

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

• • an elongate blank 6 comprising at least one section of small cross-section variation is manufactured by hot forging;
  • the blank 6 is shaped to obtain a semi-finished product 11 comprising a central part 12 and a first part of increased cross-section 13 and a second part of increased cross-section 14, extending on both sides of the central part 12; and
  • the semi-finished product 11 is hot-stretched to obtain the intermediate part 1.

The steps of the method are described in more detail hereinafter in the description.

The hot forging step to obtain the blank 6 is in particular carried out on a billet.

The billet is typically obtained from a forged ingot or a forged ingot which is then rolled, depending on the final diameter of the billet. Prior to hot forging, the billet is heated in a treatment furnace to a temperature and for a period of time suitable for leading to a hot deformation of the material of the billet during shaping. The temperature and the duration of the heating are chosen by a person skilled in the art according to the composition of the alloy. The treatment time is chosen so as to obtain the same temperature between the skin and the core of the billet.

The billet is then transferred into a hot forging tool. The hot forging tool is conventional, and is not described in detail below.

The billet is then subjected to hot forging in the hot forging tool. Hot forging is e.g. carried out by hot extrusion, free forging, radial forging, die forging or rolling.

At the end of said step, an elongate blank 6 of longitudinal axis Z is obtained comprising at least one section of small cross-section variation extending along a longitudinal axis Z. The cross-section of said section is for example circular or polygonal, for example has a square or hexagonal shape.

The blank 6 is more particularly a cylindrical blank of revolution.

The blank 6 is hollow or solid.

An example of blank 6 is shown schematically in FIG. 5. In the example, the blank 6 consists of a section of constant cross-section.

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

The semi-finished product 11 is elongate with a longitudinal axis Z. The semi-finished product 11 comprises a central part 12 and the first and second parts of increased cross-section 13, 14, extending on both sides of the central part 12 along the direction of the longitudinal axis Z. The central part 12 of the semi-finished product 11 comprises at least one section of small cross-section variation. The central part 12 has a longitudinal axis Z.

Each of the first and second parts of increased cross-section 13, 14 comprises a cross-section of minimum surface area, the surface area of which is greater than the surface area of the largest cross-section of at least one section of the central part 12, of small cross-section variation and more particularly of the or each section of the central part 12, of small cross-section variation.

The step of shaping the blank 6 comprises the production of the first part of increased cross-section 13 by hot forging, and in particular by die forging, upsetting, spinning or backward extrusion techniques followed by the production of the second part of increased cross-section 14 by hot forging, and in particular by die forging, upsetting, spinning or backward extrusion.

The term “spinning” refers to the shaping of a blank 6, which is at least hollow at one end, by simple radial movement of the material perpendicular to the longitudinal axis Z of the elongate blank 6.

According to a particular embodiment, the first and second parts of increased cross-section 13, 14 are each hot forged by one of the following methods: upsetting, and in particular upsetting on a needle, spinning, or backward extrusion. The hot forging methods are shown schematically in FIGS. 15 to 20 and described hereinbelow in the case of the second part of increased cross-section 14.

The first part of increased cross-section 13 and the second part of increased cross-section 14 may be made by the same type of hot forging, chosen from upsetting, and in particular upsetting on a needle, spinning, or backward extrusion. More particularly, the first part of increased cross-section 13 and the second part of increased cross-section 14 are produced by upsetting or by die forging.

In a variant, the first part of increased cross-section 13 and the second part of increased cross-section 14 are made by different types of hot forging, chosen from any combination of the types of hot forging mentioned hereinabove. More particularly, the first part of increased cross-section 13 is made by upsetting and the second part of increased cross-section 14 is made by die forging or the first part of increased cross-section 13 is made by die forging and the second part of increased cross-section 14 is made by upsetting.

According to one embodiment, the first part of increased cross-section 13 and the second part of increased cross-section 14 are produced successively, and e.g. in different tools.

In such case, the blank 6 is first transferred into a first hot forging tool, wherein the blank undergoes hot forging, in particular die forging, upsetting, spinning or backward extrusion, in order to obtain a semi-finished part 16.

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

The semi-finished part 16 thereby obtained is then transferred to a shaping tool, wherein the second part of increased cross-section 14 is produced by hot forging, and in particular by die forging, upsetting, spinning or backward extrusion, in order to obtain the semi-finished product 11. The shaping by hot forging to obtain the second part of increased cross-section 14 is carried out in particular by means of an installation which will be described in greater detail hereinafter with reference to FIGS. 9 to 11.

The second part of increased cross-section 14 is preferably made by upsetting or by die forging. In the case of an upsetting, the upsetting ratio during the step of producing the second part of increased cross-section 14 is in particular comprised between 1.20 and 1.25. The upsetting ratio conventionally corresponds to the ratio between the diameter before upsetting and the diameter after upsetting.

According to a variant, the first part of increased cross-section 13 and the second part of increased cross-section 14 of the semi-finished product 11 are produced simultaneously, more particularly in the same tool. In such case, the first part of increased cross-section 13 and the second part of increased cross-section 14 are produced in particular by hot forging such as die forging, upsetting, spinning or backward extrusion techniques. The shaping by hot forging to obtain the first and second parts of increased cross-section 13, 14 is more particularly carried out by means of an installation which will be described in greater detail hereinafter with reference to FIGS. 12 to 14.

The shaping by hot forging to form the second part of increased cross-section 14 of the semi-finished product 11 is followed by hot stretching of the semi-finished product 11 to straighten the semi-finished product 11 and obtain the intermediate part 1.

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

Within the framework of the invention, the main function of hot stretching is to improve the straightness of the semi-finished product 11. Indeed, the shaping steps can give rise to straightness defects in the central part 12 of the semi-finished product 11 which one seeks not to have in the final part. The stretching step serves in particular to reduce, in the central part 12, the transverse deviation, taken perpendicularly to the longitudinal axis Z of the semi-finished product 11, with respect 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 serves to correct the angle between the central part 12 and the parts of increased cross-section 13, 14 of the semi-finished product 11 and, if appropriate, to partially relieve the internal stresses associated with the shaping of the semi-finished product 11.

As an example, in addition to the rectification mentioned hereinabove, the stretching step has the effect of stretching the semi-finished product 11 by a length at most equal to 20 to 30 mm per 2 meters of length of the semi-finished product 11.

Advantageously, the production of the second part of increased cross-section 14 by shaping by hot forging and the hot stretching are carried out in the same tool, and more particularly by means of an installation as described hereinbelow with reference to FIGS. 9 to 11.

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 cross-section 14. More particularly, hot stretching is carried out by means of any tools provided for straightening or rectifying shafts by traction.

Preferably, no intermediate heating is carried out on the semi-finished product 11 before the 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 cross-section 14 by hot forging and the hot stretching.

The invention further relates to a method for manufacturing a finished metal alloy part (not shown), the method comprising:

• • the manufacture of an intermediate part 1 by using the method as described hereinabove; and
  • finishing the intermediate part 1 to obtain the finished part.

The finishing step comprises more particularly 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 solely to eliminate small excess thicknesses, typically less than 10 mm or even a few millimeters of excess thickness, and, if appropriate, in order to obtain functional surfaces.

According to one variant, one of the parts of increased cross-section 5, 5′ of the intermediate part 1 comprises a ring 7 of cross-section with an surface area greater than the surface area of the cross-section of the remainder of the part of increased cross-section 5, 5′, and the machining step comprises the removal of said ring 7. The ring 7 belongs to the corresponding part of increased cross-section 14 of the semi-finished product 11 serves to form a grip at the second part of increased cross-section 14 of the semi-finished product 11 for the use of hot stretching in embodiments wherein the difference between the maximum surface area of the cross-section of the corresponding increased surface area of the cross-section of the finished part and the maximum surface area of the cross-section of the central part of the finished part is small. An example of an intermediate part 1 comprising such a ring 7 in the second part thereof of increased cross-section 5′ is shown in FIG. 8.

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

Optionally, the finishing step further comprises one or a plurality of heat treatments, more particularly to achieve the required mechanical properties of use. The finished part obtained at the end of the method is chosen from:

• • an axle, e.g. for a railway or motor vehicle,
  • a drive shaft, e.g. for a helicopter rotor or for a pump shaft, more particularly a drive shaft, e.g. for a wind turbine or for the automotive industry: car, truck, tractor, etc. or a shaft for a gas turbine or a turbojet,
  • a landing gear part, such as a landing gear rod or an axle of the landing gear wheels,
  • a riser tube, e.g. for pumps for oil or gas extraction;
  • an underwater valve, in particular for engines of large boats, such as ships or supertankers; or
  • a missile-launcher tube.

The method according to the invention is advantageous. Indeed, by means of the production of the second part of increased cross-section 14 of the semi-finished product 11 by hot forging followed by stretching in order to straighten the semi-finished product 11 and obtain the intermediate part 1, it is possible to produce 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. More particularly, in the case of a central part of constant circular cross-section, it is possible to produce the central part 3 of the intermediate part 1 by hot forging directly to an outside diameter very close to the outside diameter thereof in the final part. It is thereby possible to prevent the material losses associated with the machining thereof generated during the implementation of the known methods described in the introduction, and thereby to reduce the costs associated with the manufacture of the part. Such effect is particularly advantageous in the case of noble alloys, i.e. which include expensive alloying elements at relatively high grades, such as steels with high mechanical properties including maraging steels, superalloys and titanium alloys. Indeed, in such case, the effect of reducing material losses on the cost of the part is particularly marked. The stretching step serves to straighten the intermediate part 1 after the production of the second part of increased cross-section 14. Indeed, 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 surface areas and the production of the second part of increased cross-section 14 thereby may lead to a defect of straightness in the central part 12 of the semi-finished part 11, which is corrected by means of the hot stretching step.

FIGS. 9 to 11 show an example of an installation 50 for manufacturing by forging an intermediate part 1 as described hereinabove according to a first embodiment.

The installation 50 is intended to be used for implementing the manufacturing method described hereinabove. The installation serves more particularly to implement the sub-step of producing the second part of increased cross-section 14 of the semi-finished product 11 by hot forging and the step of hot stretching of the semi-finished part 11 to obtain the intermediate part 1.

The installation 50 for manufacturing an intermediate part 1 by forging as described hereinabove comprises:

• • a housing 55 defining a longitudinal axis B intended to receive the elongate blank 6 or the semi-finished part 16 as described hereinabove;
  • 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 11 as described hereinabove, the shaping device 51 comprising a device 52 for making by hot forging, at least the second part of increased cross-section 14 of the semi-finished product 11; and a hot stretching device 54 configured to hot straighten the semi-finished 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 die 100 is fastened in a removable manner on the support table 113. The housing 55 is more particularly formed in the die 53 by being delimited by the lower 100 and upper 102 dies. The relative movement of the upper die 102 with respect to the lower die 100 serves to open the housing 55 over the entire length thereof, in particular for the insertion of the part to be shaped.

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

In the first embodiment, shown in FIGS. 9 to 11, the device 52 is configured to receive the semi-finished part 16 as described hereinabove, i.e. comprising the rod 15 and the first part of increased cross-section 13. More particularly, the housing 55 is intended to receive the semi-finished part 16 coaxially with the longitudinal axis B thereof.

The housing 55 comprises a central part 57 and, on both sides of the central part 57 along the direction of the longitudinal axis B, a first part of increased cross-section 58 and a second part of increased cross-section 59. In the example shown, the first and second parts of increased cross-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. The central part 57 has a shape substantially matching the shape of the central part 12 of the semi-finished product 11. The central part 57 comprises at least one zone of small cross-section variation, intended to receive a corresponding section of small cross-section variation, of the semi-finished product 11.

The first part of increased cross-section 58 of the housing 55 is configured to house the first part of increased cross-section 13 of the semi-finished product 11 and thus of the semi-finished part 16. The first part of increased cross-section 58 comprises in particular at least one part with shape matching a part of the first part of increased cross-section 13 of the semi-finished product 11 and thus of the semi-finished part 16.

The second part of increased cross-section 59 of the housing 55 is configured to contain the second part of increased cross-section 14 of the semi-finished product 11. The second part of increased cross-section 59 comprises in particular at least one part with shape matching a part of the second part of increased cross-section 14 of the semi-finished product 11 to be produced by means of the installation 50.

In such embodiment, the central part 57 and the second part of increased cross-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 onto 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 bear on the upper die 102 so as to push the upper die 102 against the lower die 100. Pressing the upper die 102 against the lower die 100 has the effect of deforming the semi-finished part 16 arranged in the housing 55 so that the semi-finished part 16 is partly shaped in the housing 55 at the parts of the semi-finished part 16 which will not be subsequently shaped. Such shaping results in a wedging of the semi-finished part in the housing 55, preventing in particular the relative movement of the rod 15 of the semi-finished part 16 with respect to the housing 55.

The installation 50 further comprises a locking system 111 for locking the upper die 102 onto the lower die 100, shown in particular in FIG. 9. As an example, the locking system 111 comprises a plurality of locking orifices 120, 121 provided in the upper die 102 and in the lower die 100, respectively, and more particularly in appendages of the upper die 102 and lower die 100, and a locking rod 122. In the closed configuration of the die 53 after shaping, the locking orifices 120, 121 are coaxial and the locking rod 122 is designed to extend through the locking orifices 120, 121 so as to lock the upper die 102 onto the lower die 100. The locking of the upper die 102 on the lower die 100 prevents the relative movement of the rod 15 of the semi-finished part 16 with respect to the housing 55.

The device 52 is configured to produce the second part of increased cross-section 14 of the semi-finished product 11 by hot forging a corresponding part of the rod 15 of the semi-finished part 16 received in the housing 55. Said hot forging is in particular an upsetting, in particular on a needle, a die forging, a spinning or a backward extrusion technique. Preferably, said hot forging is an upsetting or a die forging, more particularly an upsetting.

To this end, 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, along a direction of movement G, shown in FIG. 10, over a maximum movement 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 a crushing, and hence a shaping by upsetting, by spinning, by die forging or by backward extrusion techniques of a part of the stem 15 of the semi-finished part 16 to form in particular the second part of increased cross-section 14.

More particularly, the shaping punch 60 is configured to move in translation along the direction of the longitudinal axis B from a rest position, as shown in FIGS. 9 to 11, to an end-of-shaping position, in which the shaping punch 60 has shaped the semi-finished part 16 to form the second part of increased cross-section 14. More particularly, the shaping punch 60 has then moved over the maximum movement stroke between the rest position and the end-of-shaping position.

In the rest position, the shaping punch 60 exerts no force on the semi-finished part 16. In the example shown, the shaping punch 60 is not in contact with the semi-finished part 16 in the rest position.

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

The shape of the shaping punch 60 is chosen according to the shaping to be carried out, and more particularly of the shape of the part of increased cross-section 14 of the semi-finished product 11 to be produced, and of the type of hot forging to be carried out.

In the example shown in FIGS. 9 to 11, the shaping punch 60 is formed by a rod 62. The rod 62 has more particularly a constant cross-section. The rod 62 has, for example, a shape matching the shape of the part of the housing 55 wherein the rod 62 is inserted, provided the clearances needed for the movement thereof in the housing 55.

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

More particularly, FIG. 15 schematically shows an embodiment of hot forging of a part of increased cross-section 14 from a semi-finished part 16 comprising a hollow end, said hot forging being carried out by spinning using a shaping punch 60 which displaces the material radially perpendicularly 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 performed in a closed cavity.

FIG. 16 schematically shows a variant of the embodiment of FIG. 15 wherein the shaping punch 60 is a needle.

FIG. 17 schematically shows an embodiment of shaping by hot forging a part of increased cross-section 14 from a semi-finished part 16 comprising a hollow end by die forging using a shaping punch 60 which moves the material radially perpendicular to the axis Z and shapes to the geometry of the cavity of the end of housing 53. The shaping punch 60 fits into the end of the housing 53 so that said die forging takes place in a closed cavity.

FIG. 18 schematically represents an embodiment of shaping by hot forging a part of increased cross-section 14 from a solid semi-finished part 16 by backward extrusion using a shaping punch 60 which moves the material along axis B along the opposite direction to the direction of the punch.

FIG. 19 schematically shows an embodiment of shaping by hot forging of a part of increased cross-section 14 from a solid semi-finished part 16 by upsetting using a shaping punch 60 which has a flat end and crushes the material and locally increases the deformed section.

FIG. 20 schematically represents a variant of the embodiment of shaping by hot forging by upsetting shown in FIG. 19 in preparation to forming a part of increased cross-section 14 from a semi-finished part 16 comprising a lost mandrel 17.

In the example shown in FIGS. 9 to 11, the device 52 for producing the second part of increased cross-section 14 further comprises an actuating member 70 that can be moved in translation with respect to the housing 55 in a translation direction F, shown in FIG. 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 is movable in translation along a vertical direction downwards from the rest position thereof to the end-of-shaping position thereof

The actuating member 70 is configured in such a way that the movement of the actuating member 70 from the rest position thereof to the end-of-shaping position thereof leads to the movement of the shaping punch 60 from the rest position thereof to the end-of-shaping position thereof inside the housing 55.

As an example, the actuating member 70 has an elongate 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 main axis C extends along 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.

As an example, the installation 50 comprises an orifice 72 for receiving the actuating member 70, configured to receive the end section 82 of the actuating member 70 when the latter moves to the end-of-shaping position thereof. 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. A longitudinal end of the shaping punch 60 extends into the receiving orifice 72.

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

In the example shown in FIGS. 9 to 11, the angle drive mechanism 75 comprises a cam surface 77 formed on the actuating member 70 and a cam follower surface 79 formed on the shaping punch 60. The cam surface 77 and the cam follower surface 79 are configured so that the translational movement of the actuating member 70 from the rest position thereof to the end-of-shaping position thereof leads to a sliding contact of the cam surface 77 with the cam follower surface 79 and a translation of the shaping punch 60 from the rest position thereof to the end-of-shaping position thereof.

The actuating member 70 is in particular in the form of a blade-shaped shank.

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

In the example shown in FIGS. 9 to 11, the cam surface 77 is formed by an inclined lateral surface of the actuating member 70, the surface forming an angle α with the main axis C of the actuating member 70. The inclined surface is more particularly a flat surface.

The angle α 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 needed to ensure a complete shaping in the second part of increased cross-section 59 of the housing 55 and thereby obtain the desired geometry for the second part of increased cross-section 14 of the semi-finished product 11. The angle α is e.g. comprised between 5° and 20°.

The cam surface 77 and the cam follower surface 79 are configured so that movement in translation of the actuating member 70 from the rest position thereof to the end-of-shaping position thereof pushes the shaping punch 60 toward the second part 59 of the housing 55 along the direction of movement G.

In a variant, any other type of suitable angle drive mechanism may be used as an alternative to the mechanism described with reference to FIGS. 9 to 11.

In the example shown in FIGS. 9 to 11, the device 52 further comprises an elastic return member 85 configured to return the shaping punch 60 toward the rest position thereof when the actuating member 70 moves from the end-of-shaping position thereof to the rest position thereof. As an example, the elastic return member 85 comprises a spring, arranged around the shaping punch 60 and fixedly attached both to the shaping punch 60 and to the housing 55.

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

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

The production of the second part of increased cross-section 14 of the semi-finished product 11 by hot forging serves to obtain a semi-finished product 11 as described hereinabove.

As indicated hereinabove, the installation 50 further comprises a hot stretching device 54 configured to hot straighten the semi-finished product 11 received in the housing 55 and obtained at the end of the step of producing the second part of increased cross-section 14.

The hot stretching device 54 comprises at least one stretching punch 95, visible more particularly in FIG. 10. Preferably, in order to provide a good mechanical balance, the hot stretching device 54 comprises at least two stretching punches 95. The or each stretching punch 95 can be moved in translation relative to the housing 55 along 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 the rest position thereof to the end-of-stretching position thereof leading to 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. The direction of movement H 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 both sides of the housing 55, only one of the punches 95 being visible in FIG. 10.

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

The die 53 comprises a fixed part and a movable part, the movable part being movable in translation relative to the fixed part along the direction of the longitudinal axis B between a closed position, in which the movable part is in contact with the fixed part and a spaced away position, in which the movable part is distant from the fixed part by an elongation distance. The elongation distance is chosen according to the desired degree of stretching.

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

The lower and upper movable parts 108 and 110 are secured to each other in translation along the direction of the longitudinal axis B. To this end, the lower movable parts 108 and upper movable parts 110 comprise e.g. mating locking reliefs, formed in particular in the opposite surfaces thereof.

Advantageously, the lower fixed part 104 and the upper fixed part 106 also comprise mating locking reliefs, formed in particular in the opposite surfaces thereof, serving to improve the fastening thereof along the direction of the longitudinal axis B of the housing 55.

Optionally, the installation 50 comprises locks, configured to lock the moving part of the die 53 to the fixed part of the die 53.

The installation 50 comprises e.g. a guide device 112 configured to guide the translation movement of the movable part of the die 53 with respect to the fixed part of the die 53. The guide device 112 comprises e.g. a rail 114 provided on the support table 113 and a translational guide member (not shown), intended to slide in the rail 114 and formed on the movable part of the die 53. The guide member has a shape matching the shape of the guide rail 114. As an example, the guide member has the shape of a dovetail.

As can be seen in FIG. 11, the upper die 102 comprises, for each stretching punch 95, a housing 115 for receiving the stretching punch 95, with shape matching that of the end section 116 of the stretching punch 95. The housing 115 for receiving the stretching punch 95 is configured to receive the end section 116 of the stretching punch 95 when the latter moves from the rest position thereof to the end-of-stretching position thereof.

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

As an example, and as illustrated in FIG. 11, the receiving housings 115 are arranged on both sides 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 during the movement of the stretching punch 95 from the rest position thereof to the end-of-stretching position thereof leads to a translation movement of the movable part of the die 53 along a direction parallel to the longitudinal axis B of the housing 55 away from the fixed part of the die 53 by a distance equal to the elongation distance.

In the example shown in FIGS. 9 to 11, said movement is obtained by a cam effect, the or each stretching punch 95 comprising a cam surface 117 in the lower section 116 thereof and the or each receiving housing 115 internally delimiting a cam follower surface 119. In the example shown in FIGS. 9 to 11, the cam surface 117 is formed by an inclined lateral surface of the stretching punch 95, the surface forming an angle β with the longitudinal axis E of the stretching punch 95. The inclined surface is more particularly a flat surface. The angle β 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 to the value needed to ensure the desired rectification of the semi-finished product 11.

In the present example, the cam follower surface 119 is formed by an inner surface of the receiving housing 115 having a shape matching the shape of a part of the cam surface 117.

The cam surface 117 and the cam follower surface 119 are configured such that the movement of translation of the stretching punch 95 from the rest position thereof to the end-of-stretching position thereof pushes the movable part of the die 53 away from the fixed part along the direction of the longitudinal axis B of the housing 55.

The movement of translation of the movable part 108, 110 of the die 53 away from the fixed part 104, 106 of the die 53 leads to an elongation of the housing 55, and more particularly of the central part 57 thereof, along the longitudinal axis B of the housing 55, of a length equal to the elongation distance. More particularly, the movement of translation of the movable part 108, 110 of the die 53 away from the fixed part 104; 106 of the die 53 makes the first and second parts of increased cross-section 58, 59 of the housing 55 to move apart. Since the first and second parts of increased cross-section 58, 59 are in engagement with the first and second parts of increased cross-section 13, 14 of the semi-finished product 11, the spacing leads to a stretching, as well as a rectification, of the semi-finished product 11 received in the housing 55.

In the example shown in FIGS. 9 to 11, the or each stretching punch 95 is fixed to the support 90 described hereinabove, so as to extend opposite the receiving housings 115 along the direction of elongation E of the stretching punch 95.

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

More particularly, the support 90 is movable in translation relative to the housing 55 so as to successively occupy the following positions:

• • a rest position, in which the actuating member 70 and each stretching punch 95 occupy the rest position thereof,
  • 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 the end-of-shaping position thereof and has traveled, in relation to the rest position thereof, a stroke resulting in the maximum movement stroke of the shaping punch 60,
  • a start position for hot stretching, wherein each stretching punch 95 begins to perform hot stretching; and
  • an end-of-stretching position, in which each stretching punch 95 occupies the end-of-stretching position thereof, and has traveled, with respect to the rest position thereof, a stroke resulting in the maximum desired spacing between the fixed part and the movable part of the die 53.

In the present example, each stretching punch 95 has a length shorter than the length of the actuating member 70, taken from the support 90, in such a way that each stretching punch 95 leads to the stretching of the semi-finished product 11 by lengthening the housing 55 only after the actuating member 70 has generated the shaping of the semi-finished part 16 to form the second part of increased cross-section 14. As an example, the length of the or each stretching punch 95 is adjusted so that the stretching punch 95 arrives at the entrance of the corresponding receiving housing 115 when the actuating member 70 reaches the end-of-shaping position thereof.

As indicated hereinabove, the device or installation 50 is suitable for use as a hydraulic forging press tool or crankshaft tool. The movement of the press serves to produce the vertical downward movement of the support 90 which leads to the shaping in order to produce the second part of increased section 14 of the semi-finished product 11, as well as to the stretching of the semi-finished product 11.

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

The method comprises the following steps:

• • installation of the lower die 100 fitted with the shaping punch 60 on the support table 113 and installation of the support 90 fitted with the actuating member 70 and the or each stretching punch 95;
  • fitting of the semi-finished part 16 in the part of the housing 55 delimited by the lower die 100,
  • placing the upper die 102 on the lower die 100;
  • installation of the pusher 103;
  • lowering of the press so as to press the upper die 102 onto the lower die 100 by means of the pusher 103 via the support 90 and thereby shape the parts of the semi-finished part 16 which are not intended to be shaped;
  • locking of the upper die 102 on the lower die 100 after shaping and optionally locking of the movable part of the die 53 on the support table 113;
  • removal of the pusher 103;
  • movement of translation of the support 90 from the rest position thereof to the end-of-shaping position thereof resulting in the translation of the actuating member 70 from the rest position thereof to the end-of-shaping position thereof so as to form the second part of increased cross-section 14 by hot forging in the second part of increased cross-section 59 of the housing 55 and obtaining the semi-finished product 11;
  • optionally, unlocking the movable part of the die 53 to allow the movement of translation with respect to the fixed part of the die 53 under the effect of the or each stretching punch 95;
  • continuation of the translation movement of the support 90 to the end-of-stretching position thereof resulting in the translation of the or each stretching punch 95 to the end-of-stretching position thereof so as to straighten the semi-finished product 11 to obtain the intermediate part 1;
  • raising of the support 90, unlocking of the upper die 102 and releasing of the

The installation 50 according to the first embodiment and the associated manufacturing method are advantageous. Indeed, the installation 50 allows making the second part of increased cross-section 14 by hot forging and straightening the semi-finished product 11 by hot stretching in the same tool and by carrying out the steps of the method directly in sequence. It thus allows producing a part having the desired straightness characteristics, without having to carry out intermediate heating between shaping in order to obtain the second part of increased cross-section 14 and the hot stretching. It also results in material savings, and hence saves on the production cost, since the installation 50 serves to manufacture an intermediate part 1 having a central part of external dimensions close to the dimensions in the final part.

Moreover, in the case of the particular example shown in FIGS. 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, which can be moved away from each other substantially perpendicularly to the longitudinal axis B of the housing 55 for the insertion of the blank 6 or the semi-finished part 16 or the extraction of the intermediate part 1. Moreover, an angle drive mechanism 75 serves to transform the vertical movement of the press, and thus of the actuating member 70, into a horizontal movement of the shaping punch 60. Such particular geometry serves to manufacture very long parts with locally larger cross-section zones in a relatively simple and inexpensive manner. In fact, on the one hand, the insertion of the blank 6 or of the semi-finished part 16 or the extraction of the intermediate part 1 requires only a relatively small clearance of the upper die 102 with respect to the lower die 100, and on the other hand, the total height of the installation 50 may be relatively small compared with the length of the intermediate part 1 to be made.

Moreover, the delimitation of the housing 55 between the lower 100 and upper 102 dies, which can easily be moved relative to each other to open the housing 55 throughout the length thereof, permits variations in cross-section without any problem of recovering the parts after hot shaping, which would not be the case with conventional tools having a parting plane of the dies perpendicular to the longitudinal axis Z of the intermediate part 1, and thus to the longitudinal axis B of the housing 55.

FIGS. 12 to 14 illustrate an installation 200 for manufacturing an intermediate part 1 according to a second embodiment of the invention. The installation 200 is intended to be used for implementing the manufacturing method described hereinabove. The installation 200 serves more particularly to implement the steps of shaping the blank 6 to obtain the semi-finished product 11 and of stretching the semi-finished product 11 to obtain the intermediate part 1.

Only the differences with respect to the installation 50 according to the first embodiment are described hereinafter. Furthermore, identical or analogous elements are identified by the same reference number.

The installation 200 according to the second embodiment differs from the installation 50 according to the first embodiment mainly by the fact that the device 52 comprises two parallel actuating members 70, fixed in translation relative to one another, the movement of each actuating member 70 from the rest position thereof to the end-of-forming position thereof leading to the production by upsetting, spinning, die forging or backward extrusion techniques of a respective part of increased cross-section 13, 14 of the semi-finished product 11.

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

The first part of increased cross-section 13 and the second part of increased cross-section 14 may be made by the same type of hot forging, chosen from upsetting, spinning, or backward extrusion techniques, or by different types of hot forging, choose from any combination of said types of hot forging. Preferably, the first part of increased cross-section 13 and the second part of increased cross-section 14 are each produced by upsetting or by die forging.

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

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

The housing 55 has a shape similar to that of the housing 55 described with reference to the first embodiment. However, the housing 55 comprises at the longitudinal end thereof located at the level of the first part of increased cross-section 58, an opening 208 for the insertion of a corresponding shaping punch 60 into the housing 55. In such embodiment, each shaping punch 60 is configured to penetrate into the housing 55 at a longitudinal end thereof, so as to produce the corresponding part of increased cross-section 13, 14.

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

The device 52 thus serves, in said embodiment, to produce the first and second parts of increased cross-section 13, 14 in the same tool, more particularly simultaneously, from the blank 6 received in the housing 55.

In said embodiment, the hot stretching device 54 is not configured to stretch the semi-finished product 11 while the latter is received in the housing 55. The stretching device 54 is not included in the same tool as the device 52 for producing at least one part of increased cross-section 14 of the semi-finished product 11, as is the case in the first embodiment. In such case, the stretching device 54 is formed by a separate tool provided for straightening or rectifying shafts by traction. The stretching device 54 has only been shown schematically in FIG. 14.

According to a particular embodiment, the separate stretching device 54 is analogous to the stretching device 54 described with reference to the first embodiment of the installation shown in FIGS. 9 to 11.

In such case, the stretching device 54 comprises one or a plurality of stretching punches and corresponding receiving housings formed in a die as described hereinabove, the stretching punches being configured to rectify or straighten by traction the semi-finished product 11 received in a housing formed between a lower die and an upper die in the die in a manner similar to that described above with respect to the first embodiment. The die and the receiving housing delimited by the die are distinct from the receiving housing 55 and the die 53 used for shaping the blank 6, and more particularly for producing the first and second parts of increased cross-section 13, 14.

In such case, and as has been described with reference to the first embodiment, the die comprises a fixed part and a movable part, the movement of translation of the movable part of the die away from the fixed part over a stroke equal to an elongation distance under the effect of the insertion of the stretching punch(s) into the corresponding housings, leading to an elongation of the housing for receiving the semi-finished product 11 by one length equal to the elongation distance, and thereby a straightening or rectification of the semi-finished product 11 by traction.

A method for manufacturing an intermediate part 1 from a blank 6 as described hereinabove by means of the installation 200 will now be explained in greater detail.

The method comprises the following steps:

• • installation of the support table 113 and then of the lower die 100 equipped with the shaping punches 60 on the support table 113 and installation of the support 90 equipped with the actuating members 70;
  • placing the blank 6 in the part of the housing 55 delimited by the lower die 100,
  • placing the upper die 102 on the lower die 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 onto 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 translation of the support 90 from the rest position thereof to the end-of-shaping position thereof resulting in the translation of each actuating member 70 from the rest position thereof to the end-of-shaping position thereof so as to form the first part of increased cross-section 13 and the second part of increased cross-section 14 by hot forging, in the first part of increased cross-section 58 and in the second part of increased cross-section 59, respectively, of the housing 55 and obtaining the semi-finished product 11;
  • raising of the support 90, unlocking of the upper die 102 and releasing 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 method, allows the first and second parts of increased cross-section 13 to be produced by hot forging, and in particular by upsetting, spinning, backward extrusion techniques or by any combination of said methods, 14 in a single operation in the same tool, and results in saving material similar to the saving 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 part.

Moreover, since the geometry of the installation 200 is analogous to the geometry of the installation 50, the installation 200 allows obtaining advantages analogous to the advantages described hereinabove, in particular with regard to the possibility of manufacturing long parts.

Claims

1. A method of manufacturing by forging an intermediate part made of a metal alloy, the intermediate part being elongate along a longitudinal axis, the intermediate part comprising a central part comprising at least one section of small cross-section variation, the surface area of the cross-section of the or each section of small cross-section variation varying by at most 20% along said section, the intermediate part further comprising a first part of increased cross-section and a second part of increased cross-section located on both sides of the central part along the longitudinal axis, the method comprising the following steps: manufacture by hot forging of a blank which is elongate along a longitudinal axis comprising at least one section of small cross-section variation;shaping of the blank to obtain a semi-finished product which is elongate along a longitudinal axis comprising a central part and a first part of increased cross-section and a second part of increased cross-section, extending on both sides of the central part along the direction of the longitudinal axis, the shaping of the blank comprising the production of the first part of increased cross-section of the semi-finished product by hot forging and the production of the second part of increased cross-section of the semi-finished product by hot forging chosen from upsetting, spinning, die forging or backward extrusion techniques;hot stretching of the semi-finished product to obtain the intermediate part.

2. The method according to claim 1, wherein the metal alloy is chosen from a superalloy, a titanium alloy and a steel.

3. The method according to claim 1, wherein the length of the intermediate part is greater than or equal to 800 mm and the ratio between the length of the intermediate part and the maximum transverse dimension of the central part of the intermediate part is equal to or greater to 2.5.

4. A method according to claim 1, wherein the surface area of the cross-section of the or each section of small cross-section variation varies by at most 10% along the length of said section.

5. The method according to claim 1, wherein the cumulative length of the at least one section of small cross-section 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 intermediate part.

6. The method according to claim 1, wherein the center of the first part of increased cross-section and/or the center of the second part of increased cross-section, taken along the longitudinal direction of the intermediate part, is located at a distance of the corresponding end of the intermediate part less than or equal to 25% of the length of the intermediate part.

7. The method according to claim 1, wherein the first part of increased cross-section of the semi-finished product is produced by upsetting, spinning, die forging or backward extrusion.

8. The method according to claim 1, wherein the second part of increased cross-section of the semi-finished product is produced by upsetting.

9. The method according to claim 1, wherein the production of the first part of increased cross-section of the semi-finished product and the production of the second part of increased cross-section of the semi-finished product are carried out successively.

10. The method according to claim 1, wherein the production of the first part of increased cross-section of the semi-finished product and the production of the second part of increased cross-section of the semi-finished product are carried out simultaneously, more particularly in the same tool.

11. The method according to claim 1, wherein the semi-finished product is not reheated between the production of the second part of increased cross-section of the semi-finished product and the hot stretching.

12. The method according to claim 1, wherein the production of the second part of increased cross-section and the hot stretching are performed in the same tool.

13. A method for manufacturing an elongate part made of a metal alloy comprising: the manufacture of an intermediate part by using the method according to claim 1;the finishing of the intermediate part to obtain the part.

14. The method according to claim 13, wherein the part is chosen from: an axle, a drive shaft, a part for a landing gear, a riser tube for a pump intended for the extraction of oil or gas, an underwater valve.

15. An installation for manufacturing by forging an intermediate part made of a metal alloy part, the intermediate part being elongate along a longitudinal axis, the manufacturing installation being intended to be used for the implementation of the method according to claim 1, comprising: a housing defining a longitudinal axis intended to receive a blank which is elongate along a longitudinal axis, the blank comprising at least one section of small cross-section variation or a semi-finished part which is elongate along a longitudinal axis, the semi-finished part comprising a rod comprising at least one section of small cross-section variation, and a first part of increased section;a shaping device for shaping the blank or the semi-finished part received in the housing so as to form a semi-finished product which is elongate along a longitudinal axis and which comprises a central part and a first part of increased cross-section and a second part of increased cross-section, located on both sides of the central part along the direction of the longitudinal axis, the shaping device comprising a device for producing at least the second part of increased cross-section of the semi-finished product by hot forging through die forging, upsetting, spinning or backward extrusion;a hot stretching device configured to hot straighten the semi-finished product so as to form the intermediate part.

16. The installation according to claim 15, wherein the device for producing at least the second part of increased cross-section of the semi-finished product comprises at least one actuating member, which is movable in translation relative to the housing along a direction perpendicular to the longitudinal axis of the housing from a rest position to an end-of-shaping position, the movement of the actuating member from the rest position thereof to the end-of-shaping position thereof leading to the production, by hot forging, of at least the second part of increased cross-section of the semi-finished product.

17. The installation according to claim 16, wherein the device for producing at least the second part of increased cross-section of the semi-finished product comprises two actuating members, each actuating member being movable in translation relative to the housing along a direction perpendicular to the longitudinal axis of the housing from a rest position to an end-of-shaping position, the actuating members being fixed in translation relative to one another in the direction perpendicular to the longitudinal axis of the housing, the movement of each actuating member from the rest position thereof to the end-of-shaping position thereof leading to the production, by hot forging, of a respective part of increased cross-section of the semi-finished product.

18. The installation according to claim 16, wherein the device for producing at least the second part of increased cross-section of the semi-finished product comprises: a shaping punch for each actuating member, each shaping punch being configured to move in translation along the direction of the longitudinal axis of the housing, anda angle drive mechanism, configured to transform the movement of the or each actuating member from the rest position thereof to the end-of-shaping position thereof into a movement of translation of the corresponding shaping punch along the direction of the longitudinal axis of the housing in order to produce by hot forging a corresponding part of increased cross-section of the semi-finished product.

19. The installation according to claim 15, wherein the hot stretching device is configured to hot straighten the semi-finished product received in the housing.

20. The installation according to claim 19, wherein the hot stretching device comprises a stretching punch, movable in translation relative to the housing along a direction perpendicular to the longitudinal axis of the housing from a rest position to an end-of-stretching position, the movement of the stretching punch from the rest position to the end-of-stretching position thereof leading to the hot rectification of the semi-finished product received in the housing to obtain the intermediate part.

21. The installation according to claim 19, comprising a die delimiting the housing, the die comprising a fixed part and a movable part, said movable part of the die being movable in translation relative to said fixed part in the direction of the longitudinal axis of the housing between a closed position, in which the movable part is in contact with the fixed part and a spaced apart position, in which the movable part is spaced from the fixed part by an elongation distance, the movement leading to an elongation of the housing by a length equal to the elongation distance, the hot stretching device further comprising, for each stretching punch, a receiving housing for the stretching punch, configured to receive an end section of the stretching punch when the latter moves from the rest position thereof to the end-of-stretching position thereof, the insertion of the stretching punch into the corresponding receiving housing making the movable part of the die move in translation relative to the fixed part of the die from the closed position to the spaced away position thereof so as to straighten the semi-finished product received in the housing.

22. The installation according to claim 20, wherein the device for producing at least the second part of increased cross-section of the semi-finished product comprises at least one actuating member, which is movable in translation relative to the housing along a direction perpendicular to the longitudinal axis of the housing from a rest position to an end-of-shaping position, the movement of the actuating member from the rest position thereof to the end-of-shaping position thereof leading to the production, by hot forging, of at least the second part of increased cross-section of the semi-finished product,the installation further comprising a support on which the or each actuating member and the or each stretching punch are fastened, the support being movable in translation relative to the housing along a direction parallel to the direction of movement of the or each actuating member and of the or each stretching punch so as to occupy successively the following positions:a rest position, in which the or each actuating member and the or each stretching punch occupies the rest position thereof,an end-of-shaping position, in which the or each actuating member occupies the end-of-shaping position thereof, andan end-of-stretching position, in which the or each stretching punch occupies the end-of-stretching position thereof.

23. The installation according to claim 15, which is used as forging press tool.

24. A use of the installation according to claim 15 as a forging press tool.