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 ).

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, and   a 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, and   an 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.