PROCESS FOR MANUFACTURING A METAL PART

A process for manufacturing a metal part (10), is described said part extending in a first direction (Y) and having a section comprising a central member (14) and at least a first side member (16) extending in a second direction. The process comprises the following steps: supply of a metal blank (30); removing material from the blank so as to form an intermediate part (32) comprising the central member (14), a junction zone (12) and at least first (116) and second (118) intermediate side members, with a space (34) between the first and second intermediate side members; and hot forming (104) the intermediate part, including spreading the first and second intermediate side members apart by inserting a first punch (212) between said members.

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.

DETAILED DESCRIPTION

FIG.1shows a T-shaped metal part10obtained according to a first embodiment of the invention. Said part10is intended to be used as a structural member, for example in an aircraft.

An orthonormal basis (X, Y, Z), associated with the part10, is shown.

The part10extends in one main direction, corresponding to the Y direction. As seen inFIG.1, the part10has a substantially T-shaped cross-section perpendicular to said main direction.

In particular, the part10comprises a junction zone12, a central member14, and first16and second18side members.

The central member14extends in a first transverse direction, corresponding to the Z-direction, from the junction zone12. The first16and second18side members extend away from each other in a second transverse direction, corresponding to the X direction, from said junction zone12.

Preferably, the part10is substantially symmetrical with respect to a plane (Y, Z) (FIG.2) passing through the central member14, the first16and second18side members being mirror images of each other with respect to said plane.

In the embodiment shown, the first16and second18side members have comparable thicknesses. In the embodiment shown inFIG.1, a thickness20along X of the central member14is substantially equal to three times the thickness22along Z of each of the first16and second18side members. As a variant, a ratio between thickness20and thickness22is between 1 and 3.

Preferably, the part10is made of titanium or a Ti-6Al-4V type titanium alloy. As a variant, the part10is made of another metal such as steel or aluminum, a superalloy or a steel or aluminum alloy.

FIG.2schematically represents a process100for making the above-described part10according to one embodiment of the invention.

A first step of said process is the supply of a metal blank30(view2A ofFIG.2). Said blank30extends in the main Y direction.

The blank30has a substantially parallelepiped shape, a section of said blank perpendicular to Y preferably having a rectangular shape.

In the next step102(view2B ofFIG.2), the metal blank30is split, so as to form a first intermediate part32. The slot thus formed extends in the main Y direction.

Specifically, the first intermediate part32comprises the junction zone12, the central member14, and a first116and a second118intermediate side members, intended to form the first16and second18side members of the part10.

In the first intermediate part32, the first116and second118intermediate side members extend substantially in the first transverse direction Z from the junction zone12away from the central member14. A gap34is formed by removing material between said first116and second118intermediate 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 blank30material removal step defines a thickness120of the central member14and a thickness122of the first116and second118side members. Preferably, the thickness120is about three times the thickness122. The said thicknesses120and122are preferably slightly greater than the corresponding thicknesses20and22, in order to compensate for thickness variations related to the following process steps, described below.

In the next step104(view2C ofFIG.2), the first intermediate part32is 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 member14of the first intermediate part32in a die200. Said die comprises two mobile elements202and204, capable of clamping the central member14between them. Preferentially, the mobile elements202and204are configured to allow the clamping of the central member14without clamping the junction zone12nor the first116and second118side members, the ends of said side members being free.

In this example, the two elements202and204define a substantially planar bearing surface206. When the central member14is disposed between the elements202and204, the bearing surface206is disposed in a plane (X, Y) according to the orthonormal basis associated with the metal part.

When the central member14of the first intermediate part32is inserted between the elements202and204and clamped, the junction zone12is disposed above the bearing surface206in order the side members116and188may be deformed on all their length until coming in abutment on the bearing surface206.

With the central member14of the first heated intermediate part32held in a locking position by the two elements202and204, a first punch212is inserted between the first116and second118intermediate side members so as to move them apart in a (X, Z) plane.

The first punch212preferably has a V-shaped profile. More specifically, the first punch includes first216and second218substantially planar surfaces. The surfaces216and218intersect at an edge220disposed along Y and define an angular sector with an angle α. The surfaces216and218are intended to make contact with the first116and second118intermediate side members, respectively. The first216and second218surfaces are in this example substantially symmetrical with respect to a plane (Y, Z) passing through the edge220. The angle α is between between 10° and 160°.

After cooling, a second intermediate part36, shown in view2C ofFIG.2, is obtained. The first116and second118intermediate side members of said second intermediate part36extend in different and divergent directions from each other.

In the next step106, the second intermediate part36undergoes a second furnace heating, preferably of the order of 900° C. for a titanium alloy. After heating, the central member14of said second intermediate part36is clamped back into the die200.

With the central member14held tight by members202and204, a second punch222is applied to the first116and second118intermediate side members (2D view ofFIG.2). This second punch has a planar surface224that is applied opposite the bearing surface206of the die200. A force is applied between the second punch222and the die200. 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 first116and second118intermediate side members against the die200, depending on the force applied and the surface area of the intermediate side members.

Preferably, during this second hot forming, the die200and the punch222are 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 step106is repeated a second time with the same second punch222, in order to ensure the coplanarity of the first116and second118side members, especially after the second intermediate part36has 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 step106is performed using a punch with a V-shaped profile and a larger angular sector than the first punch212used for the first forming step104.

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 punch500has a so-called ‘broken’ V-profile, comprising three angular sectors, namely a central angular sector as and two lateral angular sectors α51and α52, the central angular sector as being smaller than the two lateral angular sectors and disposed between said lateral angular sectors α51and α52. Such a punch is shown inFIG.5. In one embodiment, the central angular sector as is greater than 10° and less than the lateral angular sectors α51and α52. Preferably, the lateral angular sectors α51and α52are greater than or equal to 100° and less than or equal to 160°.

In the example described, the bearing surface206of the die200is 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 part10described above is obtained.

FIG.3schematically represents a process300for making a curved part302according to a second embodiment of the invention, from the part10described above.

The process300uses a bending tool306. Said bending tool includes a support element308and a press element310.

The support element308includes a top surface312and a slot314formed in said top surface.

The top surface312is shaped like a portion of a circular cylinder. The slot314follows a circular arc path, a radius of said circle corresponding to the desired curvature of the curved part302. As a variant, the top surface312has 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 slot314, the walls of the support element308may be moved toward each other.

The press element310has a concave surface substantially complementary to the top surface312of the support element.

In the first step of the process300, the metal part10undergoes a first heating in a furnace at a temperature preferably of around 900° C. for a titanium alloy. After heating, the part10is transferred to the bending tool306. More specifically, the central member14of the part10is eased into the slot314and clamped between the walls of the support element308. In addition, the hot part10is optionally held in the support element308using flanges (not shown). Other holding devices may be used.

The press element310is then lowered toward the support element308so as to bend the part10, at a speed of between 1 and 20 mm/s.

The press element310may be held against the support element308for between10seconds and30minutes. At the end of the bending step, the press element310is raised and the resulting curved profile302is removed from the support element308.

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 part302.

A final machining step may be performed to bring the curved part302to the desired dimensions.

FIG.4illustrates a process400for producing angles402according to an embodiment of the invention.

The process400includes making a metal part410with a T-shaped cross-section, similar to the metal part10described above. The part410extends along the main Y direction and comprises, among other things, a junction zone412, a central member414, and first416and second418side members. The part410is made according to the process100described above.

The process400then includes a step of cutting the part410along a plane of symmetry419of said part, passing through the central member414. The first416and second418side members are disposed on opposite sides of said plane.

Two substantially identical angles402are obtained, each of the two angles having an L-shaped cross-section perpendicular to the main direction.

A difference between the part410ofFIG.4and the part10ofFIG.1is that the thickness420of the central member414is defined by considering that said part410is cut along the plane of symmetry419. The said thickness420is thus chosen according to the desired dimensions of the angles402.

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 part36, shown in view2C ofFIG.2.

A process for manufacturing an X-shaped part600is schematically shown inFIG.6. Said process comprises making a second intermediate Y-shaped part36, as described above, and then a second material removal step performed at the free end of the central member14of said part. Third140and fourth142side members are thus formed.

One or more hot forming steps are then performed to distort the third140and fourth142side members into a V shape, preferably by clamping the first116and second118side members in a die of suitable shape.

As a variant, the metal blank30of rectangular cross-section, visible inFIG.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.