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

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

[0001] Method and installation for manufacturing by hot forging an elongated intermediate part

[0002] The present invention relates to a method and an installation for manufacturing by hot forging an intermediate part elongated along a Z axis, of total length L, made of metal alloy, the intermediate part comprising a central part comprising at least one section of low variation section and two parts of increased section located on either side of the central part.

[0003] Usually, parts such as aircraft engine shafts are produced by implementing the following successive operations: manufacturing an elongated blank of low variation section by hot extrusion or drawing in open forging, then production by hot forging, 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 retaining a part of increased section at one end of the central part opposite the head in the longitudinal direction of the part.

[0004] This method is not, however, entirely satisfactory. In fact, the elongated blank of low variation section 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 (excluding the head), 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 to obtain the desired final shape of the central part.This results, given the significant length of the central part for the applications mentioned above, in a relatively high loss of material, and consequently in significant production costs, in particular in the case where the part is made from a so-called noble alloy, i.e. including relatively large quantities of expensive alloying elements, such as maraging steels, superalloys or titanium alloys.

[0005] An aim of the invention is to provide a method and an installation allowing the manufacture of elongated intermediate parts made of metal alloy as described above at a reduced cost price.

[0006] To this end, the invention relates to a method of manufacturing by forging an intermediate part made of metal alloy elongated along a longitudinal axis, the intermediate part comprising a central part comprising at least one section of cross-section with 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 increased section located on either side of the central part along the longitudinal axis, the method comprising the following steps:

[0007] - manufacture by hot forging of a blank elongated along a longitudinal axis comprising at least one section of cross-section with low variation;

[0008] - shaping the blank to obtain a semi-finished 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 central part 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-finished product by hot forging and the production of the second part of increased section of the semi-finished product by hot forging chosen from upsetting, spinning, die-stamping or reverse extrusion; and

[0009] - hot stretching of the semi-finished product to obtain the intermediate part.

[0010] The method according to the invention may comprise one or more of the following characteristics, taken in isolation or in any technically possible combination:

[0011] - 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 structurally hardened steel and an alloyed martensitic steel.

[0012] - 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.

[0013] - the area of ​​the cross-sections of the or each section of low-variation cross-section varies by at most 10% along said section, preferably the area of ​​the cross-sections of the or each section of low-variation cross-section is constant along said section.

[0014] - the cumulative length of the section(s) with low variation in cross-section, 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.

[0015] - 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 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.

[0016] - the first part of increased section of the semi-finished product is produced by upsetting, spinning, die-stamping or reverse spinning.

[0017] - the second part of increased section of the semi-finished product is produced by upsetting and, preferably, the first part of increased section is produced by upsetting or by stamping.

[0018] - the second part of increased section of the semi-finished product is produced by die-stamping and, preferably, the first part of increased section is produced by upsetting or die-stamping.

[0019] - the production of the first part of increased section of the semi-finished product and the production of the second part of increased section of the semi-finished product are carried out successively.

[0020] - the production of the first part of increased section of the semi-finished product and the production of the second part of increased section of the semi-finished product are carried out simultaneously, in particular in the same tool.

[0021] - the semi-finished product is not reheated between the production of the second part of increased section of the semi-finished product and the hot stretching.

[0022] - the production of the second part of increased section and the hot stretching are carried out in the same tool.

[0023] The invention also relates to a method of manufacturing an elongated part made of metal alloy comprising:

[0024] - the manufacture of an intermediate part by implementing the method described above;

[0025] - finishing the intermediate part to obtain the part, the finishing including in particular machining.

[0026] According to a particular characteristic of the method, the part is chosen from: an axle, a drive 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 the engine of a large boat, such as a cruise ship or a supertanker and a missile launch tube.

[0027] The invention also relates to an installation for manufacturing by forging an intermediate part made of metal alloy elongated along a longitudinal axis, the manufacturing installation being intended to be used for implementing the method, comprising:

[0028] - 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-finished 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;

[0029] - a device for shaping the blank or semi-finished part received in the housing so as to form a semi-finished 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 device for producing, by hot forging by stamping, by upsetting, by spinning or by reverse extrusion, at least the second part of increased section of the semi-finished product; and

[0030] - a hot stretching device configured to hot straighten the semi-finished product so as to form the intermediate part.

[0031] The installation according to the invention may comprise one or more of the following characteristics, taken in isolation or in any technically possible combination:

[0032] - the hot stretching device is configured to hot straighten the semi-finished product received in the housing.

[0033] - 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, the movement of 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.

[0034] - 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 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 the latter moves from its rest position to its end-of-stretching position,the insertion of the stretching punch into the corresponding receiving housing causing the translational movement of the movable part 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-finished product received in the housing.,

[0035] - 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 each actuating member and the or each stretching punch so as to successively occupy the following positions:

[0036] - a rest position, in which the or each actuating member and the or each stretching punch occupies its rest position,

[0037] - an end-of-shaping position, in which the or each actuating member occupies its end-of-shaping position, and

[0038] - an end-of-stretch position, in which the or each stretching punch occupies its end-of-stretch position.

[0039] - the installation is used as a forging press tool.

[0040] - the installation as described above constitutes a forging press tool.

[0041] The invention also relates to the use of the installation as described above as forging press tooling.

[0042] The invention will be better understood on reading the following description, given solely by way of example, and made with reference to the appended drawings, in which:

[0043] Figure 1 is a schematic representation of an intermediate part obtained by the method according to the invention according to a first embodiment;

[0044] Figure 2 is a schematic representation in section along the plane F-F' of the intermediate part of Figure 1 according to one embodiment;

[0045] Figure 3 is a schematic representation similar to that of Figure 2 of an intermediate part according to a variant;

[0046] Figure 4 is a schematic representation of an intermediate part obtained by the method according to the invention according to a variant;

[0047] Figure 5 is a schematic representation of a blank used in the process according to the invention;

[0048] Figure 6 is a schematic representation of a semi-finished product obtained in the context of the process according to the invention;

[0049] Figure 7 is a schematic representation of a semi-finished part obtained within the framework of the method according to the invention;

[0050] 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;

[0051] Figure 10 is a schematic representation in section along a vertical plane of a part of the installation of Figure 9;

[0052] Figure 11 is a schematic top view of part of the installation of Figure 9;

[0053] Figure 12 is a schematic perspective representation of an installation for manufacturing by forging an intermediate part according to a second embodiment;

[0054] Figure 13 is a schematic representation in section along a vertical plane of the installation of Figure 12; and

[0055] Figure 14 is a top schematic representation of part of the installation of Figure 12.

[0056] Figure 15 is a schematic representation of shaping a portion of increased section by spinning from a blank hollow at the end.

[0057] Figure 16 is a schematic representation of shaping a portion of increased section by needle spinning from a blank hollow at the end.

[0058] Figure 17 is a schematic representation of a forming of an increased section portion by die-stamping from a solid blank.

[0059] Figure 18 is a schematic representation of shaping a portion of increased section by reverse spinning from a solid blank.

[0060] Figure 19 is a schematic representation of shaping a portion of increased section by upsetting from a solid blank.

[0061] Figure 20 is a schematic representation of shaping a portion of increased section by upsetting from a hollow blank including a lost mandrel.

[0062] The invention relates to a method of manufacturing by forging an elongated intermediate part 1 made of metal alloy.

[0063] An example of an intermediate part 1 obtained by the manufacturing method according to a first embodiment of the invention is shown schematically in Figure 1.

[0064] 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 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.

[0065] The central part 3 and the or each section of low variation section are elongated along the longitudinal axis Z.

[0066] Throughout the description, cross-section means the section perpendicular to the longitudinal axis Z.

[0067] Throughout the description, a section with a low variation cross-section is understood in particular to mean a section whose cross-sectional areas vary by at most 20% along said section, i.e. along 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 cross-sectional areas of the at least one section with a low variation cross-section. 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 refer to a section with a constant cross-section in the following.

[0068] The central part 3 has a cumulative length L oof the section(s) of cross-section with low variation, taken along the longitudinal axis Z, greater than or equal to 40% of the length L of the intermediate part 1. For example, the cumulative length Lo of the section(s) of cross-section with low variation 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.

[0069] 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, that is to say without interposition of other parts of the part.

[0070] According to one embodiment, the central part 3 consists of a section with a cross-section with low variation, and more particularly, the central part 3 consists of a section with a constant cross-section.

[0071] 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.

[0072] 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.

[0073] The first and second parts of increased section 5, 5' are, preferably, each located near a respective end 4, 4' of the intermediate part 1. In particular, the center of each part of increased section 5, 5', taken along the direction of elongation Z of the intermediate part 1, is located at a respective distance Li, 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 section 5, 5' is located at a respective distance Li, L2 from the corresponding end 4, 4' less than or equal to 15% of the length L of the intermediate part 1.

[0074] Each of the increased section parts 5, 5' comprises a cross-section of minimum area A min respective, corresponding to its smallest cross-section. For each of the parts of increased section 5, 5', the area A minof this cross-section is greater than the area A of the largest cross-section of at least one of the cross-section sections with low variation of the central part 3, and in particular of the or each cross-section section with low variation of the central part 3.

[0075] In particular, the minimum area cross-section A min of each of the parts of increased section 5, 5' has a maximum dimension Di, D2 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 the or each section of cross-section with low variation of the central part 3.

[0076] The maximum dimension of a cross-section is understood to mean, in particular, 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, for example a square or hexagonal one.

[0077] 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.

[0078] By way of example, the first part of increased section 5 and / or the second part of increased section 5' has a shape chosen from:

[0079] - a constant cross-sectional shape, in particular an annular or cylindrical shape;

[0080] - an axisymmetric shape with a 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 gimbal shape, or any other suitable complex shape.

[0081] In the case of a portion of increased section 5, 5' having a constant cross-sectional shape, i.e. the area of ​​the cross-sections along said portion of increased section is constant, the minimum area cross-section A min corresponds to any cross-section of the part of increased section 5, 5' considered.

[0082] 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 away 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.

[0083] In the case of a portion of increased section 5, 5' having a variable cross-sectional shape along the longitudinal axis Z, the cross-section of minimum area A min corresponds to a particular cross-section of the increased section part 5, 5' considered, in which the area of ​​the increased section part 5, 5' is the smallest.

[0084] 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.

[0085] The intermediate part 1 illustrated in Figure 1 is a solid part.

[0086] According to a first variant, illustrated in Figure 4, the intermediate part 1 is a hollow part, in particular tubular.

[0087] 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. By way of 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 piece 1.

[0088] 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 from a first metal alloy and an envelope made from a second metal alloy.

[0089] According to one embodiment of the invention, the intermediate part 1 is a part of revolution relative to the Z axis.

[0090] For example, the central part 3 of the intermediate part 1 is of revolution relative to the Z axis. 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 is understood to mean its external diameter.

[0091] 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 is understood to mean the external diagonal of said square cross-section.

[0092] 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 to said hexagonal cross-section.

[0093] 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 part 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 being able to be combined depending on the desired final shape of the intermediate part 1.

[0094] The intermediate part 1 is made of a metal alloy. It is made in particular of one of the following materials:

[0095] - a steel, and more particularly a steel chosen from the following list:

[0096] - 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;

[0097] - an alloyed martensitic steel, for example a 300M steel;

[0098] - a superalloy, and more particularly a nickel-based superalloy, for example an alloy 718;

[0099] - a titanium-based alloy, for example a Ti-6-AI-4V, Ti-5333 or Ti 10.2.3 alloy.

[0100] The steels listed above are steels with high mechanical properties.

[0101] The intermediate part 1 is intended in particular for the manufacture of a part chosen from:

[0102] - an axle, for example for a railway or automobile vehicle,

[0103] - a drive 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, ... or a gas turbine or turbojet shaft,

[0104] - a landing gear part, such as a landing gear rod or a landing gear wheel axle,

[0105] - a riser tube, for example for pumps intended for extracting oil or gas;

[0106] - an underwater valve, particularly for engines of large boats, such as cruise ships or supertankers; or

[0107] - a missile launcher tube.

[0108] The method according to the invention comprises the steps according to which:

[0109] - an elongated blank 6 is produced by hot forging, comprising at least one section of cross-section with low variation;

[0110] - the blank 6 is shaped to obtain a semi-finished 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 central part 12; and

[0111] - the semi-finished product 1 1 is hot stretched to obtain the intermediate part 1 .

[0112] These process steps are described in more detail in the remainder of the description.

[0113] The hot forging step to obtain the blank 6 is in particular carried out on a billet.

[0114] The billet is typically obtained from a forged ingot or a forged and then rolled ingot, depending on the final diameter of the billet. Prior to hot forging, the billet is reheated in a treatment furnace at a temperature and for a time suitable for allowing hot deformation of the billet material during shaping. The temperature and duration of reheating are chosen by a person 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 core of the billet.

[0115] The billet is then transferred to a hot forging tool. The hot forging tool is conventional and is not described in detail below.

[0116] The billet is then hot forged in the hot forging tool. Hot forging is carried out, for example, by hot drawing, open die forging, radial forging, drop forging or rolling.

[0117] At the end of this step, an elongated blank 6 with longitudinal axis Z is obtained comprising at least one section with a cross-section with a small variation in longitudinal axis Z. The cross-section of said section is for example circular or polygonal, for example square or hexagonal in shape.

[0118] Blank 6 is in particular a cylindrical blank of revolution. Blank 6 is hollow or solid.

[0119] An example of a blank 6 is shown schematically in Figure 5. In this example, the blank 6 consists of a section of constant cross-section.

[0120] The blank 6 is then shaped to obtain a semi-finished product 11 as shown schematically in Figure 6.

[0121] 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 little variation. The central part 12 has a longitudinal axis Z.

[0122] Each of the first and second increased section portions 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 low-variation cross-section section of the central portion 12, and in particular of the or each low-variation cross-section section of the central portion 12.

[0123] 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 die-forging, upsetting, spinning or reverse extrusion followed by the production of the second part of increased section 14 by hot forging, and in particular by die-forging, upsetting, spinning or reverse extrusion.

[0124] By spinning is meant a shaping of 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.

[0125] According to a particular embodiment, the first and second parts of increased section 13, 14 are each hot forged by one of the following methods: upsetting, and in particular needle upsetting, spinning, die-forging or reverse spinning. These hot forging methods are shown schematically in Figures 15 to 20 and described below in the case of the second part of increased section 14.

[0126] 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 needle upsetting, spinning, die-forging 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 die-forging.

[0127] Alternatively, the first portion of increased section 13 and the second portion of increased section 14 are produced by different types of hot forging, chosen from any combination of the types of hot forging mentioned above. In particular, the first portion of increased section 13 is produced by upsetting and the second portion of increased section 14 is produced by die-stamping or the first portion of increased section 13 is produced by die-stamping and the second portion of increased section 14 is produced by upsetting.

[0128] 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.

[0129] In this case, the blank 6 is first transferred into a first hot forging tool, in which it undergoes hot forging, in particular die-forging, upsetting, spinning or reverse spinning, to obtain a semi-finished part 16.

[0130] 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 low variation cross-section and the first part of increased cross-section 13. Each section of low variation cross-section is identical to a corresponding section of low variation cross-section of the blank 6.

[0131] The semi-finished part 16 thus obtained is then transferred into a shaping tool, in which the second part of increased section 14 is produced by hot forging, and in particular by die-forging, upsetting, spinning or reverse spinning, to obtain the semi-finished product 11. The 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 later with reference to Figures 9 to 11.

[0132] The second part of increased section 14 is preferably produced by upsetting or by stamping. In the case of upsetting, the upsetting ratio during the step of producing the second part of increased section 14 is in particular between 1.20 and 1.25. The upsetting ratio conventionally corresponds to the ratio between the diameter before upsetting and the diameter after upsetting.

[0133] 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 extrusion type. The 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 later with reference to Figures 12 to 14. The shaping by hot forging to form the second part of increased 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.

[0134] During the hot stretching step, the semi-finished product 11 is stretched so as to plastically deform the metal alloy, which makes it possible to apply permanent deformation to the semi-finished product 11 in order to improve its straightness.

[0135] In the context 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 cause straightness defects in the central part 12 of the semi-finished product 11 which one seeks 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-finished product 11, 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 compared to a perfectly straight geometry to at most 2 to 5 mm per meter of the central part 12.

[0136] 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 stresses linked to the shaping of the semi-finished product 11.

[0137] For example, in addition to the straightening mentioned above, 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.

[0138] 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 such as described below with regard to Figures 9 to 11.

[0139] 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 shafts by traction.

[0140] Preferably, no intermediate heating is carried out on the semi-finished product 1 1 before hot stretching.

[0141] 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 the hot stretching.

[0142] The invention also relates to a method for manufacturing a finished part (not shown) made of a metal alloy, the method comprising: - manufacturing an intermediate part 1 by implementing the method as described above; and

[0143] - finishing of the intermediate part 1 to obtain the finished part.

[0144] The finishing stage includes in particular a machining stage.

[0145] 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.

[0146] According to a variant, one of the increased section portions 5, 5' of the intermediate part 1 comprises a ring 7 with a cross-section of greater area than the cross-sectional area of ​​the rest of the increased section portion 5, 5', and the machining step comprises the removal of said ring 7. The ring 7 is part of the corresponding increased section portion 14 of the semi-finished product 11 and makes it possible to form a grip at the second increased section portion 14 of the semi-finished product 11 for the implementation of hot drawing in embodiments in which the difference between the maximum cross-sectional area of ​​the corresponding increased section portion of the finished part and the maximum cross-sectional area of ​​the central part of the finished part is small. An example of an intermediate part 1 comprising such a ring 7 in its second increased section portion 5' is shown in Figure 8.

[0147] 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 hollow final part having an external shape close to that of the intermediate part 1.

[0148] Optionally, the finishing step also includes one or more heat treatments, in particular to achieve the required mechanical properties for use.

[0149] The finished part obtained at the end of this process is notably chosen from:

[0150] - an axle, for example for a railway or automobile vehicle,

[0151] - a drive 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, ... or a gas turbine or turbojet shaft,

[0152] - a landing gear part, such as a landing gear rod or a landing gear wheel axle,

[0153] - a riser tube, for example for pumps intended for the extraction of oil or gas; - an underwater valve, in particular for the engine of large boats, such as cruise ships or supertankers; or

[0154] - a missile launcher tube.

[0155] The method according to the invention is advantageous. Indeed, by producing the second part of increased section 14 of the semi-finished product 11 by hot forging followed by stretching 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. 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 external diameter very close to its external diameter in the final part. This makes it possible to avoid the material losses associated with its machining generated during the implementation of the known methods described in the introduction, and thus to reduce the costs associated with the manufacture of the part.This effect is particularly advantageous in the case of noble alloys, i.e. alloys which include expensive alloying elements in relatively high amounts, 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.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 areas and the production of the second part of increased section 14 thus risks generating a defect in straightness in the central part 12 of the semi-finished product 11, which is corrected thanks to the hot stretching step.

[0156] 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.

[0157] This installation 50 is intended to be used for the implementation of the manufacturing method 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 the step of hot drawing of the semi-finished part 11 to obtain the intermediate part 1.

[0158] 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-finished part 16 as described above; a shaping device 51 of 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 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-finished product 11; and a hot stretching device 54 configured to straighten the semi-finished product 11 while hot so as to form the intermediate part 1.

[0159] 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 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 makes it possible to open the housing 55 over its entire length, in particular for the introduction of the part to be shaped.

[0160] 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.

[0161] 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-finished part 16 coaxially to its longitudinal axis B.

[0162] 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.

[0163] The central portion 57 is configured to house the central portion 12 of the semi-finished product 11. It has a shape substantially complementary to the shape of the central portion 12 of the semi-finished product 11. It comprises at least one area of ​​low variation cross-section intended to receive a corresponding section of low variation cross-section of the semi-finished product 11.

[0164] 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-finished product 11 and therefore of the semi-finished part 16. It comprises for example at least one part of a shape complementary to a part of the first part of increased section 13 of the semi-finished product 11 and therefore of the semi-finished part 16.

[0165] 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 a 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.

[0166] 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.

[0167] 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 it 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 level of the parts of the semi-finished part 16 which will not be shaped subsequently. This shaping results in the semi-finished part being jammed in the housing 55, in particular preventing the relative movement of the rod 15 of the semi-finished part 16 relative to the housing 55.

[0168] The installation 50 further comprises a locking system 111 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 locking orifices 120, 121 are coaxial and the locking rod 122 is provided to extend through the locking orifices 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 displacement of the rod 15 of the semi-finished part 16 in relation to the accommodation 55.

[0169] The device 52 is configured to produce the second portion of increased section 14 of the semi-finished product 11 by hot forging a corresponding portion 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 reverse extrusion. Preferably, said hot forging is an upsetting or a die-forging, 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. 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 by pushing back, by pushing back, by stamping or by reverse spinning of a part of the rod 15 of the semi-finished part 16 to form in particular the second part of increased section 14.

[0170] More particularly, the shaping punch 60 is configured to move in translation along the direction of the longitudinal axis B from a rest position, shown in Figures 9 to 11, to an end-of-shaping position, in which it has carried out the shaping of the semi-finished part 16 to form the second portion of increased section 14. In particular, the shaping punch 60 has then moved over the maximum travel between the rest position and the end-of-shaping position.

[0171] In the rest position, the shaping punch 60 does not exert any 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.

[0172] 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.

[0173] The shape of the shaping punch 60 is chosen according to the shaping to be carried out, and in particular the shape of the increased section part 14 of the semi-finished product 11 to be produced, and the type of hot forging to be carried out.

[0174] 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. For example, it has a shape complementary to that of the part of the housing 55 in which it is inserted, with the clearances necessary for its movement in the housing 55.

[0175] However, any other form of shaping punch 60 may be used, depending on the shape of the increased section portion of the semi-finished product 11 and the type of hot forging to be carried out.

[0176] More particularly, Figure 15 schematically represents an embodiment of the hot forging of a portion of increased 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 radially displaces 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.

[0177] Figure 16 schematically represents a variation of the embodiment of Figure 15 in which the shaping punch 60 is a needle.

[0178] Figure 17 schematically represents an embodiment of shaping by hot forging of a portion of increased 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 Z axis and shapes it 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 die-forging is carried out in a closed cavity.

[0179] Figure 18 schematically represents an embodiment of shaping by hot forging of a portion of increased section 14 from a solid semi-finished part 16 by reverse extrusion using a shaping punch 60 which moves the material along the axis B in the direction opposite to the direction of the punch.

[0180] Figure 19 schematically represents an embodiment of shaping by hot forging of a part of increased section 14 from a solid semi-finished part 16 by upsetting using a shaping punch 60 which has a flat end and comes to crush the material and locally increase the deformed section.

[0181] Figure 20 schematically represents a variant of the embodiment of hot forging by upsetting presented in Figure 19 in order to form a part of increased section 14 from a semi-finished part 16 comprising a lost mandrel 17.

[0182] In the example shown in Figures 9 to 11, the device 52 for producing the second portion of increased section 14 further comprises an actuating member 70 movable in translation relative to the housing 55 in a translation direction 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 is movable in translation in a vertical downward direction 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-of-shaping position causes the movement of the shaping punch 60 from its rest position to its end-of-shaping position inside the housing 55.

[0183] 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 main axis C extends along the translation direction F of the actuating member 70. In the example shown, the end section 82 comprises the lower end of the actuating member 70.

[0184] By way of example, the installation 50 comprises a receiving orifice 72 for the actuating member 70, configured to receive the end section 82 of the actuating member 70 when the latter moves to its end-of-forming position. In the example shown, the receiving orifice 72 for 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.

[0185] More particularly, the device 52 comprises an angle return 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 movement direction G, perpendicular to the translation direction F.

[0186] In the example shown in Figures 9 to 11, the angle transmission 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 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-of-shaping position causes 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.

[0187] The actuating member 70 is in particular in the form of a bladed pin.

[0188] In the example shown, the cam follower surface 79 is formed at one end of the shaping punch 60.

[0189] In the example shown in Figures 9 to 11, the cam surface 77 is formed by an inclined lateral surface of the actuating member 70, this 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 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 α is for example between 5° and 20°.

[0190] 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 shaping punch 60 towards the second part 59 of the housing 55 in the direction of movement G.

[0191] Alternatively, any other type of suitable angle drive mechanism may be used as an alternative to the mechanism described with respect to Figures 9 to 11.

[0192] In the example shown in Figures 9 to 11, 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. By way of 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.

[0193] 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.

[0194] The device or installation 50 is suitable for use as a hydraulic or crankshaft forging press tool. 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.

[0195] The production of the second part of increased section 14 of the semi-finished product 11 by hot forging makes it possible to obtain a semi-finished product 11 as described above.

[0196] As indicated above, the installation 50 also 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 section 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 stretching punches 95. The or each stretching punch 95 is movable 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-of-stretching position 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.

[0197] 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 in Figure 10.

[0198] 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 an end section 116. In the example shown in the Figures, the longitudinal axis E is vertical.

[0199] 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 fixed part and a spaced 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.

[0200] 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 lower movable part 108 included in the lower die 100 and an upper movable part 110 included in the upper die 102.

[0201] The lower 108 and upper 110 movable parts are secured to each other in translation in the direction of the longitudinal axis B. For this purpose, the lower 108 and upper 110 movable parts comprise, for example, complementary locking reliefs, formed in particular in their facing surfaces.

[0202] Advantageously, the lower 104 and upper 106 fixed parts also comprise complementary locking reliefs, formed in particular in their facing surfaces, making it possible to improve their securing in the direction of the longitudinal axis B of the housing 55. Optionally, the installation 50 comprises locks, configured to lock the movable part of the die 53 relative to the fixed part of the die 53.

[0203] The installation 50 comprises for example a guide device 112 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 112 comprises for example 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 complementary to the shape of the guide rail 114. By way of example, the guide member has the shape of a dovetail.

[0204] As can be seen in Figure 11, the upper die 102 comprises, for each stretching punch 95, a receiving housing 115 for the stretching punch 95, of a shape complementary to that of the end section 116 of the stretching punch 95. The receiving housing 115 for the stretching punch 95 is configured to receive the end section 116 of the stretching punch 95 when the latter moves from its rest position to its end-of-stretching position.

[0205] 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.

[0206] 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.

[0207] 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 its rest position to its end-of-stretching position causes a translational movement of the movable part of the die 53 in 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.

[0208] 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 116 and the or each receiving housing 115 internally delimiting a cam follower surface 119. 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 to the value necessary to ensure the desired straightening of the semi-finished product 11.

[0209] In this example, the cam follower surface 119 is formed by an inner surface of the receiving housing 115 having a shape complementary to that of a portion of the cam surface 117.

[0210] The cam surface 117 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-stretch position pushes the movable part of the die 53 away from the fixed part in the direction of the longitudinal axis B of the housing 55.

[0211] The translational movement of the movable part 108, 110 of the die 53 away from the fixed part 104, 106 of the die 53 causes an elongation of the housing 55, and more particularly of its central part 57, along the longitudinal axis B of the housing 55, by a length equal to the elongation distance. More particularly, the translational movement of the movable part 108, 110 of the die 53 away from the fixed part 104; 106 of the die 53 causes a separation 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 engaged with the first and second parts of increased section 13, 14 of the semi-finished product 11, this separation causes a stretching, as well as a straightening of the semi-finished product 11 received in the housing 55.

[0212] In the example shown in Figures 9 to 11, 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.

[0213] The support 90 is movable in translation relative to the housing 55 in a direction parallel to the translation direction F of the actuating member 70 and to the direction of movement H of the or each stretching punch 95.

[0214] More particularly, the support 90 is movable in translation relative to the housing 55 so as to successively occupy the following positions:

[0215] - a rest position, in which the actuating member 70 and each stretching punch 95 occupy their rest position,

[0216] - a shaping start position, in which the actuating member 70 comes into contact with the shaping punch 60,

[0217] - 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 carry out the hot stretching; and

[0218] - 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 desired maximum spacing between the fixed part and the movable part of the die 53.

[0219] 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 semi-finished product 11 to be stretched by lengthening the housing 55 only after the actuating member 70 has caused the semi-finished part 16 to be shaped to form the second portion of increased section 14. By way of example, the length of the or each stretching punch 95 is adjusted so that the stretching punch 95 arrives at the inlet of the corresponding receiving housing 115 when the actuating member 70 reaches its end-of-shaping position.

[0220] As indicated above, the device or installation 50 is suitable for use as a tool for a hydraulic or crankshaft forging press. 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-finished product 11, as well as to the stretching of the semi-finished product 11.

[0221] A method of 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.

[0222] This process includes the following steps:

[0223] - 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;

[0224] - placing the semi-finished part 16 in the part of the housing 55 delimited by the lower die 100,

[0225] - placing the upper die 102 on the lower die 100;

[0226] - installation of pusher 103;

[0227] - lowering 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 thus conform the parts of the semi-finished part 16 which are not intended to be shaped; - locking the upper die 102 onto the lower die 100 after conforming and optionally locking the movable part of the die 53 onto the support table 113;

[0228] - removal of pusher 103;

[0229] - displacement 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 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;

[0230] - optionally, unlocking of the movable part of the die 53 to allow its translational movement relative to the fixed part of the die 53 under the effect of the or each stretching punch 95;

[0231] - continuing 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-finished product 11 to obtain the intermediate part 1;

[0232] - raising of the support 90, unlocking of the upper die 102 and release of the intermediate part 1.

[0233] The installation 50 according to the first embodiment and the associated manufacturing method 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 11 by hot drawing in the same tool and by chaining the steps of the method. It therefore makes it possible to produce a part having the desired straightness characteristics, without having to carry out intermediate heating between the shaping to obtain the second part of increased section 14 and the hot drawing. It also results in savings in material, and therefore savings in terms of production cost, insofar as the installation 50 makes it possible to manufacture an intermediate part 1 having a central part with external dimensions close to the dimensions in the final part.

[0234] 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-finished part 16 or the extraction of the intermediate part 1. Furthermore, an angle return 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 larger cross-section areas in a relatively simple and inexpensive manner.Indeed, on the one hand, the introduction of the blank 6 or the semi-finished part 16 or the extraction of the intermediate part 1 only requires a relatively small movement 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 relative to the length of the intermediate part 1 to be produced.

[0235] 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 any problem of recovering the parts after hot forming, 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.

[0236] 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 implementing the manufacturing method described above. This installation 200 more particularly allows the implementation of 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.

[0237] Only the differences from the installation 50 according to the first embodiment are described below. Furthermore, identical or similar elements are designated by the same reference number.

[0238] 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, integral in translation, the movement of each actuating member 70 from its rest position to its end of shaping position causing the production by upsetting, pushing back, stamping or reverse spinning of a respective part of increased section 13, 14 of the semi-finished product 11.

[0239] The installation 200 therefore comprises, for each actuating member 70, an angle return 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.

[0240] The first increased section portion 13 and the second increased section portion 14 may be made by the same type of hot forging, selected from upsetting, spinning, die-forging or reverse extrusion, or by different types of hot forging, selected from any combination of these types of hot forging. Preferably, the first increased section portion 13 and the second increased section portion 14 are each made by upsetting or die-forging.

[0241] The shape of the shaping punch 60 is chosen according to the shape of the increased section part 13, 14 and the type of hot forging to be carried out.

[0242] In this embodiment, and as shown in Figures 13 and 14, the housing 55 is intended to receive a blank 6 as described above.

[0243] 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 its first part of increased section 58, an opening 208 allowing the insertion of a corresponding shaping punch 60 into the housing 55. In this 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 section 13, 14.

[0244] 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.

[0245] The device 52 therefore allows, in this embodiment, the production of the first and second parts of increased section 13, 14 in the same tool, in particular simultaneously, from the blank 6 received in the housing 55.

[0246] In this 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 portion 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 intended for straightening or straightening shafts by traction. The stretching device 54 has only been shown schematically in Figure 14.

[0247] According to a particular exemplary embodiment, the separate stretching device 54 is analogous to the stretching device 54 described with respect to the first embodiment of the installation shown in Figures 9 to 11.

[0248] In this case, the stretching device 54 comprises one or more stretching punches and corresponding receiving housings formed in a die as described above, the stretching punches being configured to straighten 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 regard to the first embodiment. This die and the receiving housing delimited by this 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 section 13, 14.

[0249] In this case, and as described with regard to the first embodiment, the die comprises a fixed part and a movable part, the translational movement 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 causing an elongation of the housing for receiving the semi-finished product 11 by a length equal to the elongation distance, and thus a straightening or straightening of the semi-finished product 11 by traction.

[0250] A method of manufacturing an intermediate part 1 from a blank 6 as described above by means of the installation 200 will now be explained in more detail.

[0251] This process includes the following steps:

[0252] - installation of the support table 1 13 then of the lower die 100 equipped with the shaping punches 60 on the support table 1 13 and installation of the support 90 equipped with the actuating members 70;

[0253] - placing the blank 6 in the part of the housing 55 delimited by the lower die 100,

[0254] - placing the upper die 102 on the lower die 100;

[0255] - 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;

[0256] - locking the upper die 102 on the lower die 100 after shaping;

[0257] - removal of pusher 103;

[0258] - displacement 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 semi-finished product 11;

[0259] - raising of the support 90, unlocking of the upper die 102 and release of the semi-finished product 1 1;

[0260] - 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, allow the production by hot forging, and in particular by upsetting, spinning, die-stamping, reverse spinning or by any combination of these methods, 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 part.

[0261] 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

DEMANDS 1. A method for manufacturing by forging an intermediate part (1) of a metal alloy elongated about a longitudinal axis (Z), the intermediate part (1) comprising a central part (3) including at least one section of low cross-section, the cross-sectional area of ​​the or each section of low cross-section varying by no more than 20% along said section, the intermediate part (1) further comprising a first section of increased cross-section (5) and a second section of increased cross-section (5') situated on either side of the central part (3) along the longitudinal axis (Z), the method comprising the following steps: - manufacturing by hot forging of a blank (6) elongated along a longitudinal axis (Z) comprising at least one section of low variation cross-section; - shaping the blank (6) to obtain a semi-finished product (11) elongated along a longitudinal axis (Z) comprising a central part (12) and a first part with an increased cross-section (13) and a second part with an increased cross-section (14), extending on either side of the central part (12) along the direction of the longitudinal axis (Z), the shaping of the blank (6) comprising producing the first part with an increased cross-section (13) of the semi-finished product (11) by hot forging and producing the second part with an increased cross-section (14) of the semi-finished product (11) by hot forging selected from upsetting, spinning, die forging or reverse drawing; and - hot stretching of the semi-product (1 1 ) to obtain the intermediate piece (1 ).

2. A method according to claim 1, wherein the metal alloy is selected from a superalloy, a titanium-based alloy and a steel, more particularly a steel selected from the following list: a structurally hardening steel and an alloyed martensitic steel.

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

5.

4. A method according to any one of claims 1 to 3, wherein the cross-sectional area of ​​the segment or each segment with a low cross-sectional variation varies by at most 10% along said segment, preferably wherein the area of cross-sections of the or each segment of cross-section with low variation is constant along said segment.

5. A method according to any one of claims 1 to 4, wherein the cumulative length (L o ) of the section(s) of low variation cross section, 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. A method according to any one of claims 1 to 5, wherein the center of the first increased cross-sectional part (5) and / or the center of the second increased cross-sectional part (5'), taken along the longitudinal direction (Z) of the intermediate piece (1), is located at a distance (Li, L2) 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. A method according to any one of the preceding claims, wherein the first increased cross-sectional part (13) of the semi-product (11) is produced by upsetting, spinning, die forging or reverse spinning.

8. A method according to any one of the preceding claims, wherein the second increased cross-section part (14) of the semi-product (11) is produced by upsetting and wherein, preferably, the first increased cross-section part is produced by upsetting or by forging.

9. A method according to any one of the preceding claims, wherein the realization of the first increased section part (13) of the semi-product (11) and the realization of the second increased section part (14) of the semi-product (11) are carried out successively.

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

11. A method according to any one of the preceding claims, wherein the semi-product (11) is not reheated between the making of the second part of increased section (14) of the semi-product (11) and hot stretching.

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

13. Method for manufacturing an elongated part made of a metal alloy comprising: - the manufacture of an intermediate part (1) by implementing the process according to any one of claims 1 to 12; - the finishing of the intermediate part (1) to obtain the part, the finishing including in particular machining.

14. Method according to claim 13, wherein the part is selected from: an axle, a drive shaft, a landing gear part, an extension tube for a pump intended for the extraction of oil or gas, a subsea valve, in particular for a large boat engine, such as a cruise ship or a supertanker, and a missile launch tube.

15. Manufacturing installation (50; 200) for forging an intermediate part (1) made of metal alloy elongated along a longitudinal axis (Z), the manufacturing installation (50; 200) being intended to be used for carrying out the process according to any one of claims 1 to 12, comprising: - a housing (55) defining a longitudinal axis (B) for receiving a blank (6) elongated along a longitudinal axis (Z) comprising at least one section with a low cross-sectional variation, or a semi-finished part (16) elongated along a longitudinal axis (Z) comprising a rod (15) comprising at least one section with a low cross-sectional variation, and a first part with an increased cross-section (13); a shaping device (51) for the blank (6) or the semi-finished part (16) received in the housing (55) so as to form a semi-finished product (11) elongated along a longitudinal axis (Z) comprising a central part (12) and a first part with an increased cross-section (13) and a second part with an increased cross-section (14), located on either side of the central part (12) along the direction of the longitudinal axis (Z), the shaping device (51) comprising a forming device (52), by hot forging by die forging, upsetting, spinning or reverse spinning, of at least the second increased section part (14) of the semi-product (11); and a hot drawing device (54) configured to hot straighten the semi-product (11) so as to form the intermediate part (1).

16. Installation (50; 200) according to claim 15, wherein the device for producing at least the second increased section part (14) of the semi-product (11) comprises at least one actuating member (70), which can be moved 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 a final forming position, the movement of the actuating member (70) from its rest position to its final forming position resulting in the production of at least the second increased section part (14) of the semi-product (11) by hot forging.

17. Installation (200) according to claim 16, wherein the device for producing at least the second increased cross-sectional part (14) of the semi-product (11) comprises two actuating members (70), each actuating member (70) being translationally movable relative to the housing (55) in a direction perpendicular to the longitudinal axis (B) of the housing (55) from a rest position to a final forming position, the actuating members (70) being translationally fixed in the direction perpendicular to the longitudinal axis (B) of the housing (55), the movement of each actuating member (70) from its rest position to its final forming position resulting in the production of a respective increased cross-sectional part (13, 14) of the semi-product (11) by hot forging.

18. Installation (50; 200) according to any one of claims 16 or 17, wherein the embodiment device (52) of at least the second increased cross-sectional part (14) of the semi-product (11) comprises: - a forming punch (60) for each actuating member (70), each forming punch (60) being configured to move in translation along the direction of the longitudinal axis (B) of the housing (55), and - an angle transfer mechanism (75), configured to transform the displacement of the actuating member or members (70) from its rest position to its final forming position into a translational displacement of the corresponding forming punch (60) along 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-product (11).

19. Installation (50) according to any one of claims 15 to 18, wherein the hot stretching device (54) is configured to hot straighten the half-product (11) received in the housing (55).

20. Installation (50) according to claim 19, wherein the hot stretching device (54) comprises a stretching punch (95), which can be moved 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, the movement of the stretching punch (95) from its rest position to its end-of-stretching position 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 any one of claims 19 or 20, comprising a die (53) delimiting the housing (55), the die (53) comprising a fixed part (104, 106) and a movable part (108, 110), said movable part (108, 110) of the die (53) being translationally movable relative to said fixed part (104; 106) along the direction of the longitudinal axis (B) of the housing (55) between a close position, in which the movable part (108; 110) is in contact with the fixed part (104; 106) and a distant position, in which the movable part (108; 110) is distant from the fixed part (104;106) of an elongation distance, this displacement causing an elongation of the housing (55) of a length equal to the elongation distance, the hot stretching device (54) further comprising, for each stretching punch (95), a receiving housing (115) for the stretching punch (95), configured to receive an end section (116) of the stretching punch (95) when it 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 displacement of the moving part (108; 110) of the die (53) relative to the fixed part (104; 106) of the die (53) from its close position to its distant position so as to straighten the semi-product (11) received in the housing (55).; 22. Installation (50) according to any one of claims 20 or 21, taken in combination with any one of claims 15 to 17, further comprising a support (90) on which are fixed the actuating member or members (70) and the stretching punch or members (95), the support (90) being movable in translation relative to the housing (55) along a direction parallel to the direction of movement of the actuating member(s) (70) and of the stretching punch(s) (95) so as to successively occupy the following positions: - a rest position, in which the actuating member(s) (70) and the stretching punch(s) (95) are in their rest position, - a final forming position, in which the actuating member(s) (70) occupies its final forming position, and - an end-of-stretch position, in which the stretch punch or each stretch punch (95) occupies its end-of-stretch position.

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

24. Use of the installation (50) according to any one of the claims 15 to 22 as forging press tooling.

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