Patent Publication Number: US-2023138062-A1

Title: Process for manufacturing a metal part

Description:
BACKGROUND 
     The present invention relates to a process for manufacturing a metal part extending in a first direction and having a section comprising a central member and at least a first side member extending in a second direction, the first and second directions being different to each other. 
     The invention is particularly applicable to structural members, for example in the field of aeronautics. 
     Manufacturing processes for such metal parts are known, for example in patent U.S. Pat. No. 3,713,205. However, this process includes a welding step at the junction zone, which potentially causes lower mechanical strength in the obtained part. 
     The purpose of the present invention is to provide an improved process for making such a metal part. 
     SUMMARY 
     To this end, the invention concerns a manufacturing process of the aforementioned type, comprising the following steps: supply of a metal blank of substantially rectangular cross-section, said blank extending in the first direction; at least one step involving removing material from the metal blank, so as to form an intermediate part comprising the central member, extending in the first direction; a junction zone and at least a first and a second intermediate side member, extending in parallel substantially in the first direction from said junction zone, opposite the intermediate central member; a space being provided between the first and second intermediate side members; at least a first hot forming of the intermediate part, said first forming comprising heating of the intermediate part, followed by a step of spreading the first and second intermediate side members by inserting a first punch between said first and second members, the central member being clamped in a die to block movement of the intermediate part in at least one transverse direction perpendicular to the first direction; so as to obtain the metal part. 
     Among other advantageous aspects of the invention, the process comprises one or more of the following features, taken individually or in accordance with all technically possible combinations:
         the first punch has a V-shaped section defined by an angular sector delimited by first and second planar surfaces intersecting at an apex, the angular sector having an angle α of between 10° and 160°;   the manufacturing process comprises at least a second hot forming, the second forming using at least a second punch, the at least second punch having an angular sector greater than the angular sector of the first punch;   at least a first or second punch used during a hot forming step comprises three angular sectors, one angular sector being smaller than the other two angular sectors and disposed between said other two angular sectors;   the die has a planar bearing surface, and at least the second punch has an angular sector substantially equal to 180°;   the die has a non-planar bearing surface, and at least one first or second punch has an angular sector substantially different from 180°;   the metal part is made of titanium alloy, heating being carried out at a temperature of between 600° C. and 950° C., and preferably close to 900° C.;   the metal part is made of an aluminum alloy, heating being carried out at a temperature of between 400° C. and 550° C., and preferably of between 450° C. and 480° C.;   in a hot forming step, at least one of the first punch and the die is heated to a temperature at least 50° C. lower than the heating temperature of the blank or an intermediate part;   the heating of the first punch and/or the die is carried out at 350° C. to 450° C.       

     The invention further relates to a process for manufacturing a metal angle, comprising the following steps: supply of a T-shaped metal part made by a process as described above; then cutting said metal part according to a plane passing through the central member, the first and a second side members being arranged on either side of said plane. 
     The invention further relates to a process for manufacturing an X-shaped metal section, comprising the following steps: supply of a metal part made by a process as described above, said metal part having a Y-shaped cross-section; then a second step of removing material from the free end of the central member so as to create third and fourth side members, and then at least one step of hot forming the third and fourth side members, so as to obtain an X-shaped metal part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood upon reading the following description, which is presented only as a non-limiting example, and with reference to the drawings, in which: 
         FIG.  1    is a perspective view of a metal part according to one embodiment of the invention; 
         FIG.  2    is a schematic representation of a process for manufacturing the metal part in  FIG.  1   ; 
         FIG.  3    is a schematic representation of a process for manufacturing a metal part according to a second embodiment of the invention, starting from the metal part of  FIG.  1   ; 
         FIG.  4    is a schematic representation of a process for manufacturing a metal part according to a third embodiment of the invention, starting from a metal part analogous to the part in  FIG.  1   ; 
         FIG.  5    is a schematic representation of a device used in a process for manufacturing a metal part according to a first embodiment of the invention; and 
         FIG.  6    is a schematic representation of a process for manufacturing a metal part according to a fourth embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows a T-shaped metal part  10  obtained according to a first embodiment of the invention. Said part  10  is intended to be used as a structural member, for example in an aircraft. 
     An orthonormal basis (X, Y, Z), associated with the part  10 , is shown. 
     The part  10  extends in one main direction, corresponding to the Y direction. As seen in  FIG.  1   , the part  10  has a substantially T-shaped cross-section perpendicular to said main direction. 
     In particular, the part  10  comprises a junction zone  12 , a central member  14 , and first  16  and second  18  side members. 
     The central member  14  extends in a first transverse direction, corresponding to the Z-direction, from the junction zone  12 . The first  16  and second  18  side members extend away from each other in a second transverse direction, corresponding to the X direction, from said junction zone  12 . 
     Preferably, the part  10  is substantially symmetrical with respect to a plane (Y, Z) ( FIG.  2   ) passing through the central member  14 , the first  16  and second  18  side members being mirror images of each other with respect to said plane. 
     In the embodiment shown, the first  16  and second  18  side members have comparable thicknesses. In the embodiment shown in  FIG.  1   , a thickness  20  along X of the central member  14  is substantially equal to three times the thickness  22  along Z of each of the first  16  and second  18  side members. As a variant, a ratio between thickness  20  and thickness  22  is between 1 and 3. 
     Preferably, the part  10  is made of titanium or a Ti-6Al-4V type titanium alloy. As a variant, the part  10  is made of another metal such as steel or aluminum, a superalloy or a steel or aluminum alloy. 
       FIG.  2    schematically represents a process  100  for making the above-described part  10  according to one embodiment of the invention. 
     A first step of said process is the supply of a metal blank  30  (view  2 A of  FIG.  2   ). Said blank  30  extends in the main Y direction. 
     The blank  30  has a substantially parallelepiped shape, a section of said blank perpendicular to Y preferably having a rectangular shape. 
     In the next step  102  (view  2 B of  FIG.  2   ), the metal blank  30  is split, so as to form a first intermediate part  32 . The slot thus formed extends in the main Y direction. 
     Specifically, the first intermediate part  32  comprises the junction zone  12 , the central member  14 , and a first  116  and a second  118  intermediate side members, intended to form the first  16  and second  18  side members of the part  10 . 
     In the first intermediate part  32 , the first  116  and second  118  intermediate side members extend substantially in the first transverse direction Z from the junction zone  12  away from the central member  14 . A gap  34  is formed by removing material between said first  116  and second  118  intermediate side members. 
     Preferably, the material removal step is performed using a digitally-controlled milling machine. As a variant, the material removal step is performed by electro-erosion. 
     The metal blank  30  material removal step defines a thickness  120  of the central member  14  and a thickness  122  of the first  116  and second  118  side members. Preferably, the thickness  120  is about three times the thickness  122 . The said thicknesses  120  and  122  are preferably slightly greater than the corresponding thicknesses  20  and  22 , in order to compensate for thickness variations related to the following process steps, described below. 
     In the next step  104  (view  2 C of  FIG.  2   ), the first intermediate part  32  is heated in a furnace for the first time, at a temperature preferably around 900° C. for a titanium alloy, and in any case below the beta-transus temperature of the titanium alloy in question. Heating is followed by insertion of the central member  14  of the first intermediate part  32  in a die  200 . Said die comprises two mobile elements  202  and  204 , capable of clamping the central member  14  between them. Preferentially, the mobile elements  202  and  204  are configured to allow the clamping of the central member  14  without clamping the junction zone  12  nor the first  116  and second  118  side members, the ends of said side members being free. 
     In this example, the two elements  202  and  204  define a substantially planar bearing surface  206 . When the central member  14  is disposed between the elements  202  and  204 , the bearing surface  206  is disposed in a plane (X, Y) according to the orthonormal basis associated with the metal part. 
     When the central member  14  of the first intermediate part  32  is inserted between the elements  202  and  204  and clamped, the junction zone  12  is disposed above the bearing surface  206  in order the side members  116  and  188  may be deformed on all their length until coming in abutment on the bearing surface  206 . 
     With the central member  14  of the first heated intermediate part  32  held in a locking position by the two elements  202  and  204 , a first punch  212  is inserted between the first  116  and second  118  intermediate side members so as to move them apart in a (X, Z) plane. 
     The first punch  212  preferably has a V-shaped profile. More specifically, the first punch includes first  216  and second  218  substantially planar surfaces. The surfaces  216  and  218  intersect at an edge  220  disposed along Y and define an angular sector with an angle α. The surfaces  216  and  218  are intended to make contact with the first  116  and second  118  intermediate side members, respectively. The first  216  and second  218  surfaces are in this example substantially symmetrical with respect to a plane (Y, Z) passing through the edge  220 . The angle α is between between 10° and 160°. 
     After cooling, a second intermediate part  36 , shown in view  2 C of  FIG.  2   , is obtained. The first  116  and second  118  intermediate side members of said second intermediate part  36  extend in different and divergent directions from each other. 
     In the next step  106 , the second intermediate part  36  undergoes a second furnace heating, preferably of the order of 900° C. for a titanium alloy. After heating, the central member  14  of said second intermediate part  36  is clamped back into the die  200 . 
     With the central member  14  held tight by members  202  and  204 , a second punch  222  is applied to the first  116  and second  118  intermediate side members ( 2 D view of  FIG.  2   ). This second punch has a planar surface  224  that is applied opposite the bearing surface  206  of the die  200 . A force is applied between the second punch  222  and the die  200 . For example, for a titanium alloy metal part of 1 to 3 meters long, a force of about 3,300 tons is applied. The second punch may be held for a few seconds or minutes on the first  116  and second  118  intermediate side members against the die  200 , depending on the force applied and the surface area of the intermediate side members. 
     Preferably, during this second hot forming, the die  200  and the punch  222  are heated to a temperature between 350° C. and 450° C. and more preferably around 400° C. 
     The hot forming step can be repeated several times, with identical or different punches, preferably with increasingly large angular sectors. 
     In particular, according to one embodiment, the step  106  is repeated a second time with the same second punch  222 , in order to ensure the coplanarity of the first  116  and second  118  side members, especially after the second intermediate part  36  has cooled. The heating temperatures of each intermediate part, each punch and the die may be the same as or different to those in the previous step. 
     In another embodiment, the step  106  is performed using a punch with a V-shaped profile and a larger angular sector than the first punch  212  used for the first forming step  104 . 
     The hot forming step can thus be repeated several times, with identical and/or different punches, the angular sector of the punch progressing from an acute angle to an obtuse angle. 
     As a variant, at least one punch  500  has a so-called ‘broken’ V-profile, comprising three angular sectors, namely a central angular sector as and two lateral angular sectors α 51  and α 52 , the central angular sector as being smaller than the two lateral angular sectors and disposed between said lateral angular sectors α 51  and α 52 . Such a punch is shown in  FIG.  5   . In one embodiment, the central angular sector as is greater than 10° and less than the lateral angular sectors α 51  and α 52 . Preferably, the lateral angular sectors α 51  and α 52  are greater than or equal to 100° and less than or equal to 160°. 
     In the example described, the bearing surface  206  of the die  200  is planar, and the profile of the punch varies from a V-shaped profile having an acute angular sector to a planar profile having an angular sector of 180° . As a variant, the die bearing surface has an acute or obtuse V-shaped profile. The angular sectors of the punch(es) must of course be adapted accordingly. 
     After cooling, the metal part  10  described above is obtained. 
       FIG.  3    schematically represents a process  300  for making a curved part  302  according to a second embodiment of the invention, from the part  10  described above. 
     The process  300  uses a bending tool  306 . Said bending tool includes a support element  308  and a press element  310 . 
     The support element  308  includes a top surface  312  and a slot  314  formed in said top surface. 
     The top surface  312  is shaped like a portion of a circular cylinder. The slot  314  follows a circular arc path, a radius of said circle corresponding to the desired curvature of the curved part  302 . As a variant, the top surface  312  has a non-circular curved shape, such as a curved base formed by a succession of radii and/or flat sections. 
     On either side of the slot  314 , the walls of the support element  308  may be moved toward each other. 
     The press element  310  has a concave surface substantially complementary to the top surface  312  of the support element. 
     In the first step of the process  300 , the metal part  10  undergoes a first heating in a furnace at a temperature preferably of around 900° C. for a titanium alloy. After heating, the part  10  is transferred to the bending tool  306 . More specifically, the central member  14  of the part  10  is eased into the slot  314  and clamped between the walls of the support element  308 . In addition, the hot part  10  is optionally held in the support element  308  using flanges (not shown). Other holding devices may be used. 
     The press element  310  is then lowered toward the support element  308  so as to bend the part  10 , at a speed of between 1 and 20 mm/s. 
     The press element  310  may be held against the support element  308  for between  10  seconds and  30  minutes. At the end of the bending step, the press element  310  is raised and the resulting curved profile  302  is removed from the support element  308 . 
     A stress relieving step may be performed to relieve the residual stresses induced by the previous forming steps by performing a heat treatment on the curved part  302 . 
     A final machining step may be performed to bring the curved part  302  to the desired dimensions. 
       FIG.  4    illustrates a process  400  for producing angles  402  according to an embodiment of the invention. 
     The process  400  includes making a metal part  410  with a T-shaped cross-section, similar to the metal part  10  described above. The part  410  extends along the main Y direction and comprises, among other things, a junction zone  412 , a central member  414 , and first  416  and second  418  side members. The part  410  is made according to the process  100  described above. 
     The process  400  then includes a step of cutting the part  410  along a plane of symmetry  419  of said part, passing through the central member  414 . The first  416  and second  418  side members are disposed on opposite sides of said plane. 
     Two substantially identical angles  402  are obtained, each of the two angles having an L-shaped cross-section perpendicular to the main direction. 
     A difference between the part  410  of  FIG.  4    and the part  10  of  FIG.  1    is that the thickness  420  of the central member  414  is defined by considering that said part  410  is cut along the plane of symmetry  419 . The said thickness  420  is thus chosen according to the desired dimensions of the angles  402 . 
     According to variant embodiments of the invention, processes similar to the processes described above are used to manufacture metal parts with a Y- or X-section. 
     To make a Y-shaped part, the process described above for forming a T-shaped part is used, but no punch has a 180° angular sector. The die may have a planar or non-planar bearing surface, for example in the shape of a V, corresponding to the angular sector between the two side members, the hot forming step(s) being carried out with at least one punch having an angular sector substantially different from 180° . The Y-shaped part is, for example, analogous to the second intermediate part  36 , shown in view  2 C of  FIG.  2   . 
     A process for manufacturing an X-shaped part  600  is schematically shown in  FIG.  6   . Said process comprises making a second intermediate Y-shaped part  36 , as described above, and then a second material removal step performed at the free end of the central member  14  of said part. Third  140  and fourth  142  side members are thus formed. 
     One or more hot forming steps are then performed to distort the third  140  and fourth  142  side members into a V shape, preferably by clamping the first  116  and second  118  side members in a die of suitable shape. 
     As a variant, the metal blank  30  of rectangular cross-section, visible in  FIG.  2   , may be split at each end, before the side members of each end are distorted in turn to form an X-shaped profile. 
     Alternatively, the metal part can be later cut into the plane (X, Z) into slices to provide a semi-finished part. The thickness of the semi-finished part in the Y direction can be between a few centimeters, and two meters. The semi-finished part can later be stamped and/or machined to obtain a finished part, such as, for example, a Y-shaped landing gear scissor, a C-shaped hinge, an L-shaped flange, a structural tee or a T-shaped junction tee. 
     For example, the process for manufacturing a finished part such as a landing gear scissor includes the following steps: manufacturing a Y-shaped metal part as described earlier; then a step of cutting into slices the Y-shaped metal part so as to obtain at least one semi-finished part having a section in Y; then a step of stamping or machining the semi-finished part so as to obtain the landing gear scissor. 
     The method of the invention has a significant material gain compared to the billet machining process. 
     The method of the invention requires less power than a forging press.