Manufacturing method of large seamless dome and corresponding dome

Abstract

The method comprises the following steps: providing a semi-finished product (11); -hot forging by upsetting the semi-finished product (11) to form a blank (13), the expanded area of which is larger than the expanded area of the semi-finished product (11) and smaller than the expanded area of the wall (3) of the dome; -thermoforming the blank (13) in order to form a preform (15) having an expanded area less than or equal to the expanded area of the wall (3), the preform (15) comprising at least two continuous portions (19, 21) joined to each other in the radial direction and extending outwardly away from the central axis (A-A), such that, for all portions (19, 21), the two continuous portions (19, 21) are connected to each other in the radial direction and extend outwardly away from the central axis (A-A). 21) are different from each other in terms of average thickness and / or convexity; thermally deforming the preform (15) between the die and the punch by means of the press in order to form the wall (3).

Description

[0001] The present application relates to a method for manufacturing a large hollow component in a dome shape.

[0002] Some large pressure vessels are composed of two domes assembled by welding or adding a cylindrical ring between them. The ends are composed of a bottom or a lid in the shape of a dome, which is fixed to the cylindrical body by bolts or welding.

[0003] For example, these pressure vessels are high-pressure cryogenic storage tanks for liquefied gases (such as liquid hydrogen, liquid oxygen or liquid nitrogen), which are used in the fields of space launchers, land or mobile storage, or aviation.

[0004] To manufacture such components, it is known to shape a multi-petal-shaped metal sheet through a stamping process, then assemble it into a corolla structure, and then weld them together to form a complete component.

[0005] The disadvantage of this technique is that it requires a series of expensive operations. In particular, welding components require special large-scale equipment. In addition, strict ultrasonic inspections need to be carried out on the welds to ensure that the weld areas are intact.

[0006] A single-piece in the shape of a dome can also be manufactured by closed-die forging. The advantage of this technique is that it only requires one forming operation, but the disadvantage is that it is limited to small components because the size of existing forging presses is limited, and a great deal of force is required to deform the material and fill the final part.

[0007] The object of the present application is to remedy the above defects by proposing a method for manufacturing a component in the shape of a dome (such as a dome of a cryogenic storage tank), which method does not require welding and can be implemented on an existing forging press with limited size and / or bearing capacity.

[0008] To this end, the object of the present application is to provide a method for manufacturing a hollow component, which hollow component includes a seamless, single (integral) dome-shaped wall extending around a central axis, the wall being made of a metal alloy material with an average thickness of less than 50 mm and having dimensions between 1500 mm and 3700 mm in a direction perpendicular to the central axis, and the method includes the following consecutive steps:

[0009] - Providing a semi-finished product of the material;

[0010] - Performing hot forging on the semi-finished product by upset forging to form a blank, the developed area of which is larger than the developed area of the semi-finished product but smaller than the developed area of the wall surface;

[0011] - Performing hot forming on the blank to form a preform, the developed area of which is less than or equal to the developed area of the wall, the preform including at least two consecutive parts that are radially connected to each other and extend outward from the central axis, such that in all parts, the average thickness and / or convexity of the two consecutive parts are different;

[0012] - Thermally deforming the preform under pressure between the die and the punch to form the wall.

[0013] Preferably, the method according to the present application may include one or more of the following features, which may be employed individually or in any technically possible combination:

[0014] - The portion includes a central portion and at least one intermediate annular portion, and the central portion and the intermediate annular portion have different convexities.

[0015] - Further, the portion includes an outer peripheral annular portion, and the outer peripheral annular portion has a convexity different from that of the adjacent intermediate annular portion;

[0016] - The developed area of the preform is substantially equal to the developed area of the wall;

[0017] The ratio of the projected area of the preform in the cross-section to its developed area is less than 90%, and the maximum dimension of the projected area of the preform in the cross-section is less than or equal to 150% of the maximum dimension of the punch (in the direction perpendicular to the central axis);

[0018] - The step of deforming the preform under the press includes unfolding the preform between the die and the punch such that, after unfolding, the surface of the portion facing the punch is concave;

[0019] - The surface of the central portion facing the punch has a concave shape;

[0020] - The step of thermoplastically forming the blank includes:

[0021] · A first forming stage, hot die forging the blank to produce a first concave blank;

[0022] · A second forming stage, hot die forging the first concave blank to produce the preform;

[0023] - The second forming stage includes a first intermediate forming stage and a second intermediate forming stage: the first intermediate forming stage hot die forges the first concave blank to produce a second blank with a concave portion in the center and convex portions radially continuous with the central portion around it; the second intermediate forming stage hot die forges the second blank to produce the preform;

[0024] - The portion includes a central portion and at least one intermediate annular portion, the average thickness of the central portion and the intermediate annular portion is different, and the developed area of the preform is less than the developed area of the wall;

[0025] - In addition, the part includes an outer peripheral annular part, and the intermediate annular part is a thickened part, and the average thickness of the intermediate annular part is greater than the average thickness of the central part and the average thickness of the outer peripheral annular part;

[0026] - The deformation step of the preform includes a shaping stage and a die forging stage. In the shaping stage, at least a part of the intermediate annular part contacts the die through a punch; in the die forging stage, corresponding to the expansion stage, at least a part of the preform does not contact the punch during this period;

[0027] - In the expansion stage, the thickened intermediate annular part of the preform is compressed between the die and the punch, and at least a part of the central part and / or the outer peripheral annular part does not contact the punch, so that the material plastically flows from the intermediate annular part to the central part and the outer peripheral annular part, and then exceeds the outer peripheral annular part to increase the unfolded area of the preform and form a wall;

[0028] - The material is an aluminum alloy, specifically 2XXX or 7XXX alloy.

[0029] This application also relates to a hollow component, which includes a single seamless wall in the shape of a dome, the wall extends around a central axis, the wall is made of a metal alloy material, the average thickness of the wall is less than 50 mm, and in the direction perpendicular to the central axis, it has a large size between 1500 mm and 3700 mm.

[0030] Preferably, the wall presents a uniform fibrous distribution around the central axis, and the grain (also called fiber) orientation of the metal alloy forms a substantially constant angle between the elongation direction of the grains seen in any cross-section and the tangent of the wall at the position of the grains.

[0031] This application also relates to a cryogenic storage tank, which includes the component described above or the component manufactured by the method described above.

[0032] Figure 1 is a schematic perspective view of a dome-shaped hollow component according to an embodiment;

[0033] Figure 2 Schematically shows a method according to an embodiment;

[0034] Figure 3 is a schematic diagram of a cross-section in the axial plane of a preform according to the first embodiment;

[0035] Figure 4 Schematically shows the steps of shaping a blank to form Figure 3 the preform;

[0036] Figure 5is a schematic perspective view of a preform according to the second embodiment before thermal deformation under pressure;

[0037] Figure 6 is according to Figure 3 a schematic cross-sectional view of an axial plane at the initial stage of the thermal deformation step of the preform;

[0038] Figure 7 shows Figure 1 the orientation of the grains in the hollow part.

[0039] An axial cross-section according to an embodiment Figure 1 represents a domed hollow part 1.

[0040] The hollow part 1 includes a single seamless wall 3 of domed shape. The "wall" referred to here means a single integral thickness, rather than the terms "surface" or "face".

[0041] The wall 3 includes a convex outer surface facing the outside of the dome and a concave inner surface.

[0042] The wall 3 is seamless and without welding, and is thus made of a single piece of material integrally.

[0043] For example, the hollow part 1 is intended to form the end dome of a generally cylindrical pressure vessel.

[0044] The wall 3 extends between two planes perpendicular to the central axis A-A and axially defines the wall 3.

[0045] Hereinafter, as shown in the figure, we will consider the axial direction such that, when viewed from top to bottom, the wall is concave. In addition, a plane perpendicular to the central axis A-A will be referred to as "transverse", and a plane including the central axis A-A will be referred to as "axial".

[0046] Therefore, referring to Figure 1 , the wall 3 extends between a lower cross-section 5 and an upper cross-section 7.

[0047] For example, the wall 3 is in a rotational form, in other words, the cross-section of the wall 3 in any axial plane A remains constant.

[0048] For example, the wall 3 is substantially hemispherical or in the form of a spherical cap.

[0049] Alternatively, the wall 3 is in the form of an oval cap, or in the form of a Cassini dome, a Cassini cap, or more generally in the form of an oval cap.

[0050] The wall 3 has a cross-section in a curved form (in other words, in a plane perpendicular to the central axis A-A), such as circular, elliptical, in particular a Cassini oval or an ellipse.

[0051] According to one embodiment, the wall 3 includes a curved surface portion, such as an elliptical cap, a Cassini dome, a Cassini cap or an ovoid cap; and a cylindrical or frustoconical portion that continues the curved surface portion.

[0052] The wall 3 is made of a metal alloy material.

[0053] For example, the metal alloy is an aluminum alloy, specifically an alloy of the 2XXX series, such as alloy 2050 or alloy 2219; or an alloy of the 7XXX series, such as alloy 7020.

[0054] Alternatively, the metal alloy is a titanium alloy or steel.

[0055] The average thickness of the wall 3 is less than 50 mm, and generally greater than 25 mm, particularly greater than 30 mm.

[0056] The wall 3 has a relatively large dimension, perpendicular to the central axis A-A, between 1500 mm and 3700 mm. The relatively large dimension refers to the largest dimension in any cross-section, in other words, in Figure 1 the example shown, the relatively large dimension in the upper cross-section 7.

[0057] For example, if the wall 3 has a circular cross-section, the largest dimension of the wall 3 is the diameter of the outer circle in the upper cross-section 7. If the wall 3 has an elliptical cross-section, the largest dimension of the wall 3 is the major diameter of the outer ellipse in the upper cross-section 7.

[0058] The wall 3 optionally includes features arranged thereon. For example, these features are intended to connect devices, such as pipes. These features include, for example, openings, reliefs on the outer surface of the wall 3, attachments, protrusions, bosses, faucets and / or ribs. These features are preferably integrated into the wall 3, and the material thereof is the same as that of the wall, so they are formed during the manufacturing process of the wall 3.

[0059] In particular, the wall 3 preferably includes a feature in its lower part, such as a tubular opening 9 on the central axis A-A. The cross-section of the opening 9 is, for example, circular, elliptical or ovoid.

[0060] For example, the opening 9 is bounded by an edge whose thickness is greater than the average thickness of the wall 3.

[0061] Referring to Figures 2 to 6 , a method for manufacturing such a hollow component 1 according to an embodiment of the present application will now be described.

[0062] The method first includes the step of providing a semi-finished product 11 made of the material of the hollow part 1.

[0063] The semi-finished product 11 (e.g., a billet or slab of the material (as shown in top view in Figure 2 )) can be obtained, for example, by casting the material.

[0064] Then, the method includes a hot forging step of forming a blank 13 by upset forging the semi-finished product 11. For example, in the Figure 2 example, a substantially circular blank 13 is formed from the semi-finished product 11 by applying pressure between the lower surface and the upper surface of the semi-finished product 11.

[0065] The developed area of the blank 13 is larger than the developed area of the semi-finished product 11 and smaller than the developed area of the wall 3 to be manufactured.

[0066] The temperature of the hot forging step depends on the material used. For example, if the material is an aluminum alloy, the hot forging step is generally carried out at a temperature of 300°C to 500°C. If the material is a titanium alloy, the hot forging step is generally carried out at a temperature of 700°C to 1300°C.

[0067] If the hollow part 1 to be manufactured includes the opening 9 as described above, then in this step, a circular opening 14 is formed in the blank 13.

[0068] Then, the blank 13 is hot formed to form a preform 15.

[0069] The temperature of the hot forming step depends on the material used. For example, if the material is an aluminum alloy, the hot forming step is generally carried out at a temperature of 300°C to 500°C. If the material is a titanium alloy, the hot forming step is generally carried out at a temperature of 700°C to 1300°C.

[0070] The developed surface area of the preform 15 is less than or equal to the developed surface area of the wall 3.

[0071] The preform 15 includes at least two continuous radially extending portions that extend outward from the central axis A-A such that for all portions, the average thickness of the first and second continuous portions is different; and / or the first portion is convex, concave, or flat, while the second portion is respectively concave or flat, convex or flat, or convex or concave. (In other words, if the first portion is convex, the second portion is concave or flat; if the first portion is concave, the second portion is also convex or flat; if the first portion is flat, the second portion is convex or concave).

[0072] As described below, the preform 15 is then hot deformed under pressure between a die and a punch to form the wall 3 of the hollow part 1.

[0073] For a convex or concave shape, it means a region of the part under consideration, the surface of which faces the punch during the thermoforming process and is convex or concave respectively, while the opposite surface is concave or convex respectively.

[0074] Furthermore, hereinafter, only when one part is concave and the other part is convex, or one part is flat and the other part is convex, or if one part is concave and the other part is flat, are the two parts considered to have a significant convexity.

[0075] Thus, the preform 15 includes at least two consecutive parts that extend radially in sequence in a direction away from the central axis A-A, such that for all parts, the average thickness and / or convexity of two consecutive parts are different.

[0076] By the so-called different average thicknesses, it means that according to at least one axial cross-section, there is a significant difference between the average thicknesses of the first part and the second part, such that the ratio of the maximum average thickness to the minimum average thickness is greater than or equal to 1.2, preferably greater than or equal to 1.3, more preferably greater than or equal to 1.5, and even more preferably greater than or equal to 2. Usually, this ratio is less than or equal to 5. In other words, the maximum average thickness is greater than or equal to 120% of the minimum thickness, preferably 130%, more preferably 150%, or even 200%, but still needs to remain less than or equal to 500% of the minimum thickness.

[0077] Thus, the preform 15 includes a central part 19 and at least one annular part 21 that extends radially outward from the central axis A-A and are interconnected, and the central part 19 and the annular part 21 have different convexities and / or different average thicknesses.

[0078] If the central part 19 and the annular part 21 have different convexities, then the central part 19 is usually concave and the adjacent annular part 21 is convex.

[0079] If the average thicknesses of the central part 19 and the annular part 21 are different, then the average thickness of the central part 19 is usually lower than the average thickness of the adjacent annular part 21.

[0080] If the hollow component 1 to be manufactured includes an opening 9, then the central part 19 is an annular part. Thus, the central part 19 includes a recess 22. The recess 22 is used to form the opening 9 of the hollow component 1.

[0081] Preferably, the preform 15 includes a plurality of successive portions 19, 21, 23..., which are successive with each other and extend radially outward from the central axis A-A, so that for all portions, the average thickness and / or convexity of any two successive portions are different.

[0082] The developed area of the central portion 19 is generally 5% to 90% of the developed area of the preform 15.

[0083] If the preform includes only two portions, the developed area of the annular portion 21 is 10% to 95% of the developed area of the preform 15.

[0084] Furthermore, if N is the number of portions constituting the preform 15 and N≥3, the developed area of each annular portion is 10% / (N - 1) to 100% / (N - 1) of the developed area of the preform 15.

[0085] Each portion considered is different from its adjacent portion in that the average thickness of the portion considered is different from the average thickness of this adjacent portion, and / or the convexity of the portion considered is different from the convexity of the portion adjacent to it.

[0086] For example, the portions exhibit different successive convexities.

[0087] Preferably, the preform 15 includes a series of at least three alternating concave and convex portions 19, 21, 23, which form a wavy pattern. In this case, the developed area of the central portion is preferably 10% to 90% of the developed area of the preform 15, and the developed area of each annular portion is preferably 10% / (N - 1) to 50% / (N - 1) of the developed area of the preform 15.

[0088] According to another example, the portions exhibit different successive average thicknesses.

[0089] According to another example, at least one portion has the same convexity as the first adjacent portion, but its average thickness is different from the average thickness of the first adjacent portion; and the convexity of this portion is different from the convexity of the second adjacent portion, but its average thickness is the same as the average thickness of the second adjacent portion.

[0090] In particular, the preform includes a central portion 19, an intermediate annular portion 21, and an outer peripheral annular portion 23; wherein the intermediate annular portion 21 extends radially from the central portion 19 and away from the central axis A-A; the outer peripheral annular portion 23 continues from the intermediate annular portion 21 and extends radially away from the central axis A-A; wherein the average thickness of the intermediate annular portion 21 is different from the average thicknesses of the central portion 19 and the outer peripheral annular portion 23, and / or the convexity is different from the convexities of the central portion 19 and the outer peripheral annular portion 23.

[0091] In the first embodiment, wherein Figure 3 An example is shown, where a portion of the preform 15 includes a central portion 19 and at least one intermediate annular portion 21, and the central portion 19 and the intermediate annular portion 21 have different convexities.

[0092] Preferably, as Figure 3 shown, the portion further includes an outer peripheral annular portion 23, and the convexity of the outer peripheral annular portion 23 is significantly different from that of the adjacent intermediate annular portion 21. Thus, the preform 15 includes a series of at least three alternating concave and convex portions, which form a wavy pattern.

[0093] In Figure 3 the example shown, the preform 15 includes a single intermediate annular portion 21.

[0094] Thus, the central portion 19, the intermediate annular portion 21, and the outer peripheral annular portion 23 extend radially in a direction away from the central axis A-A and are connected to each other, where the central portion 19 is adjacent to the intermediate annular portion 21, and the intermediate annular portion 21 is adjacent to the central portion 19 and the outer peripheral annular portion 23.

[0095] For example, the developed area of the central portion 19 is 50% to 90% of the developed area of the preform 15.

[0096] For example, the developed area of the intermediate annular portion 21 is 5% to 25% of the developed area of the preform 15.

[0097] For example, the developed area of the outer peripheral annular portion 23 is 5% to 25% of the developed area of the preform 15.

[0098] In this example, the central portion 19 is an annular portion and includes a recess 22.

[0099] In an alternative, the preform includes at least two intermediate annular portions. In this first embodiment, for all portions, the convexities of two consecutive portions are different. For example, if the preform includes a central portion, a first intermediate annular portion, a second intermediate annular portion, and an outer peripheral annular portion, which extend radially and continuously from the central axis A-A, then the convexity of the first intermediate annular portion is different from that of the central portion and the second intermediate annular portion, and the convexity of the outer peripheral annular portion is different from that of the second intermediate annular portion.

[0100] Preferably, in this first embodiment, as Figure 3 shown, the surface of the central portion 19 facing the punch (in other words, when viewed from top to bottom) has a concave shape.

[0101] In Figure 3 the example shown, the middle annular part 21 is convex, while the central part 19 and the outer peripheral annular part 23 are concave.

[0102] In this example, the average thicknesses of the central part 19, the middle annular part 21, and the outer peripheral annular part 23 are substantially the same, in other words, such that the ratio between the maximum average thickness and the minimum thickness is less than 1.2.

[0103] In this first embodiment, the developed area of the preform 15 is generally substantially equal to the developed area of the wall 3.

[0104] Therefore, by thermally deforming the preform 15 to form the wall 3, this process does not cause thickness changes, and thus the required force is limited.

[0105] Furthermore, due to the alternation of the concave and convex parts, the projected area of the preform 15 in the cross-section is smaller than its developed area.

[0106] The ratio between the projected area and the developed area of the preform 15 in the cross-section is generally less than 90%, preferably less than 80%, more preferably less than 50%; the maximum dimension of the projected area of the preform in the cross-section is less than or equal to 150% of the maximum dimension of the punch perpendicular to the central axis A-A, particularly less than or equal to 135% of the maximum dimension of the punch perpendicular to the central axis A-A, preferably less than or equal to 120% of the maximum dimension of the punch perpendicular to the central axis A-A.

[0107] Therefore, large-sized hollow components 1 can be manufactured using a press of limited size, particularly at least 10% smaller in size, preferably at least 20% smaller, and more preferably at least 50% smaller than that required for stamping a flat preform having a developed area equal to the developed area of the wall 3.

[0108] Figure 4 Steps for shaping the blank 13 according to this first embodiment to form the preform 15 are shown.

[0109] In Figure 4 the example shown, the step of thermally shaping the blank to form the preform 15 includes a first shaping stage: hot die forging or stamping the blank 13 to produce a first concave blank 27.

[0110] The first shaping stage is preferably a stage of shaping by upset forging the material towards the outer periphery of the blank 13, such that the developed area of the first concave blank 27 is larger than the developed area of the blank 13.

[0111] Then, the thermally shaping step includes a second stage of thermally shaping, by hot die forging or hot stamping the first concave blank 27 to produce the preform 15.

[0112] In this step, the outer peripheral portion of the first concave blank 27 is deformed to form an intermediate annular portion 21 and an outer peripheral annular portion 23.

[0113] Preferably, in this second shaping stage, the material is again upset towards the periphery of the first concave blank 27 such that the developed area of the preform 15 is greater than the developed area of the first concave blank 27.

[0114] Preferably, the first and second shaping stages are respectively implemented by a first auxiliary press 29 and a second auxiliary press 37.

[0115] As Figure 4 shown, the first auxiliary press 29 includes a first die 33 and a first punch 31.

[0116] The first shaping stage is preferably implemented by hot die forging or stamping the blank 13 between the first die 33 and the first punch 31.

[0117] The second shaping stage takes place between a second die 35 and a second punch 39 in the second auxiliary press 37.

[0118] The shapes of the second die 35 and the second punch 39 are capable of shaping the preform 15, in particular the intermediate annular portion 21 and the outer peripheral annular portion 23.

[0119] Then, the second shaping stage is carried out by die forging or stamping the first concave blank 27 between the second die 35 and the second punch 39.

[0120] According to an alternative, the second shaping stage includes a first intermediate shaping stage and a second intermediate hot shaping stage; the first intermediate shaping stage is by hot die forging or stamping the first concave blank to produce a second blank which includes a concave central portion and a convex outer peripheral portion extending in a continuation of the central portion; the second intermediate hot shaping stage is by die forging or stamping the second blank to form the preform.

[0121] Figure 5 An example of the preform 15 according to the second embodiment is shown. In accordance with the perspective view, this figure only shows a part of the preform 15. Furthermore, in Figure 5 it, a press 47 before the hot deformation of the preform 15 is shown, including a die 49 and a punch 51.

[0122] In this second embodiment, the part of the preform 15 includes a central portion 19 and at least one intermediate annular portion 21, and the average thicknesses of the central portion 19 and the intermediate annular portion 21 are different.

[0123] The developed area of the preform 15 is smaller than the developed area of the wall 3.

[0124] In addition, the ratio between the projected area of the preform 15 in cross-section and its developed area is generally greater than 90%. In addition, the maximum dimension of the projected area of the preform 15 in cross-section is less than or equal to 150% of the maximum dimension of the punch 51, preferably less than or equal to 120% of the maximum dimension of the punch 51 perpendicular to the central axis A-A.

[0125] These portions include at least one thickened portion, which is intended to provide excess material that will be used in the hot deformation step to increase the developed area of the preform 15 by plastic flow.

[0126] Preferably, as Figure 5 shown, the portion further includes an outer peripheral annular portion 23, and the average thickness of the outer peripheral annular portion 23 is different from the average thickness of its adjacent intermediate annular portion 21. The preform 15 then includes at least three consecutive portions with different consecutive average thicknesses.

[0127] In Figure 5 the example shown, the preform 15 includes a single intermediate annular portion 21.

[0128] Therefore, the central portion 19, the intermediate annular portion 21, and the outer peripheral annular portion 23 radially extend in a direction away from the central axis A-A and are connected to each other, where the central portion 19 is adjacent to the intermediate annular portion 21, and the intermediate annular portion 21 is adjacent to the central portion 19 and the outer peripheral annular portion 23.

[0129] For example, the developed area of the central portion 19 is 5% - 90% of the developed area of the preform 15.

[0130] For example, the developed area of the intermediate annular portion 21 is 5% - 50% of the developed area of the preform 15.

[0131] For example, the developed area of the outer peripheral annular portion 23 is 5% - 50% of the developed area of the preform 15.

[0132] In this example, the central portion 19 is an annular portion and includes a recess 22.

[0133] In addition, in this example, the average thickness of the intermediate annular portion 21 is different from the average thickness of the central portion 19 and the average thickness of the outer peripheral annular portion 23.

[0134] In particular, the intermediate annular portion 21 is a thickened portion, in other words, its average thickness is greater than the average thickness of the central portion 19 and the average thickness of the outer peripheral annular portion 23.

[0135] In this example, the average thicknesses of the central portion 19, the intermediate annular portion 21, and the outer peripheral annular portion 23 are such that the ratio between the maximum average thickness and the minimum thickness is greater than or equal to 1.2, preferably greater than or equal to 1.3, more preferably greater than or equal to 1.5, and even more preferably greater than or equal to 2. Preferably, the ratio is less than or equal to 5.

[0136] The preform 13 is formed into the preform 15 by, for example, upset forging, using a die ring or a flat disk.

[0137] After the step of thermoforming the preform 13 into the preform 15, the method includes a step of thermally deforming the preform 15 under a press 47 between a die 49 and a punch 51 to form the wall 3.

[0138] The thermally deforming step is carried out at a temperature depending on the material used. For example, if the material is an aluminum alloy, the thermally deforming step is typically carried out at a temperature between 300 °C and 500 °C. If the material is a titanium alloy, the thermally deforming step is typically carried out at a temperature between 700 °C and 1300 °C.

[0139] Generally, the die 49 has a larger diameter, but less than the maximum diameter of the unfolded area of the wall 3.

[0140] The thermally deforming step includes stamping, and optionally forging the preform 15 to form the wall 3.

[0141] During stamping, the shape of the preform 15 is modified to present the contour shape of the die 49 and / or the punch 51, without a significant change in thickness.

[0142] During forging, the wall 3 is shaped and the local and average thicknesses are modified.

[0143] In the above first embodiment, wherein the preform 15 includes at least two portions with different convexities, the thermally deforming step includes stamping.

[0144] In particular, if the unfolded area of the preform 15 is equal to the unfolded area of the wall 3, the thermally deforming step includes stamping.

[0145] In particular, the thermally deforming step includes unfolding the preform 15 between the die 49 and the punch 51 in such a way that, after unfolding, the surface of the convex portion of the preform facing the punch 51 becomes concave.

[0146] In particular, in Figure 3 the example shown, the preform 15 is unfolded during the thermally deforming step such that the surface of the intermediate annular portion 21 facing the punch 51 becomes concave.

[0147] If the developed area of the preform 15 is equal to the developed area of the wall 3, this thermoforming step does not involve any change in thickness. Thus, this step requires less pressure.

[0148] Furthermore, the projected area of the preform 15 in cross-section is smaller than its developed area, and in this step, large-sized hollow parts 1 can be manufactured using a press of limited size, in particular at least 50% smaller than the size required for stamping a flat preform having a developed area equal to the developed area of the wall 3.

[0149] Figure 6 is schematically shown by way of example Figure 3 the initial stage of the thermoforming step of the preform 15 in

[0150] As shown in this figure, the deformation step includes an initial stage in which the punch 51 contacts the preform 15, in particular the central part 19.

[0151] Then, the punch 51 continues its stroke, unfolding the preform 15 such that the convexity of the intermediate annular part 21 is reversed and the intermediate annular part 21 becomes concave. At the end of the punch stroke, the surface of the wall 3 in contact with the punch is concave.

[0152] In the second embodiment described above, the preform 15 includes at least two parts with different average thicknesses, and the thermoforming step includes, for example, forging and stamping the preform 15 between the die 49 and the punch 51.

[0153] In particular, the stamping of the preform 15 includes a shaping stage during which the preform 15 contacts the die 49 through the punch 51.

[0154] For example, at the end of this stage, at least a part of the lower surface of the preform 15, preferably all parts of the preform 15, contacts the die 49, and the upper surface of at least this part does not contact the punch 51. Preferably, at the end of this stage, at least a part of the intermediate annular part 21 contacts the die 49 and the punch 51.

[0155] Alternatively, at the end of this stage, the upper surface of at least one part (preferably all parts of the preform 15) of the preform 15 contacts the punch 51, and at least a part of the lower surface does not contact the die 49.

[0156] Forging is an expansion stage during which the material is upset until the material takes the shape of the surfaces of the punch 51 and the die 49.

[0157] According to one embodiment, during this stage, as long as the expansion is not complete, at least a part of the preform 15 does not contact the punch 51.

[0158] Thus, the force applied by the press is reduced. In addition, the projected area of the preform 15 in cross-section is smaller than its unfolded area, so that large-sized hollow components 1 can be manufactured using a press of limited size, in particular at least 50% smaller than the size required for stamping a flat preform having an unfolded area equal to the unfolded area of the wall 3.

[0159] In Figure 5 In the example shown, during the expansion phase, the thickened intermediate annular portion 21 of the preform 15 is compressed between the die 49 and the punch 51, wherein at least a portion of the central portion 19 and / or the outer peripheral annular portion 23 does not contact the punch 51. Thus, the material flows from the intermediate annular portion 21 to the central portion 19 and the outer peripheral annular portion 23, and then outside the outer peripheral annular portion 23 to increase the unfolded area of the preform 15 and form the wall 3.

[0160] Thus, the method according to the present application allows the manufacture of large dome-shaped components, such as domes of cryogenic storage tanks without welding, which can be achieved on existing forging presses of limited size, in particular when the maximum diameter thereof is smaller than the maximum diameter of the unfolded area of the wall 3, and / or when the force application capacity of the forging press is limited.

[0161] In addition, by this method, components with uniform grains can be achieved, such that the mechanical properties of the components are uniform around the central axis A-A and along the wall 3, from the lower cross-section 5 to the upper cross-section 7, as Figure 7 shown.

[0162] In particular, the orientation of the grains is uniform both around the central axis and in any axial plane including the axis A-A, and in any plane perpendicular to the axis A-A.

[0163] Generally, in any cross-section, as Figure 7 shown, the angle α formed between the elongation direction (long direction) of the grains seen in the cross-section and the tangent to the wall surface at that grain remains substantially constant (e.g., + / - 10°).

[0164] In fact, due to the deformation applied by the method according to the present application, the grains elongate in a preferred direction.

[0165] The elongation direction of the grains observed in the cross-section refers to the direction in which the maximum dimension (length) of the grains seen in the cross-section extends.

[0166] The paper "Comportement et endommagement des alliages d'aluminium 6061-T6:Approche micromécanique", Yang Shen, 2012, specifically describes the microstructural characteristics of the grains, especially the elongation direction.

[0167] In terms of fibration, the tangential direction is more unobstructed than the axial direction, and the axial direction is more unobstructed than the radial direction. This means that generally, the grains are elongated more in the tangential direction than in the axial direction, and more in the axial direction than in the radial direction. Here, the "radial direction" generally refers to the direction extending through the wall thickness, in other words, perpendicular to the plane tangent to the wall according to the thickness (so not necessarily perpendicular to the axis A-A).

[0168] Generally speaking, if the grains are observed from a three-dimensional perspective, the maximum direction of grain elongation is the tangential direction, which is included in the cross-section and tangent to the surface of the wall 3 (in other words, the angle α formed between the grain elongation direction observed in this cross-section and the tangent of the wall surface at this grain is basically zero).

[0169] The mechanical properties of the obtained component are higher in the tangential direction, which is the highest stress mode of such components.

[0170] The grains are preferably symmetric about the central axis A-A.

[0171] Generally speaking, those skilled in the art will be able to adjust the geometry of the preform and the dimensions of its different parts, especially the diameter and thickness, as well as the number of parts, according to the shape and size of the wall to be manufactured, and the maximum size and capacity of the press.

[0172] In addition, the method is not limited to manufacturing the domes of large pressure vessels. It can be applied to any large component that can be manufactured by stamping / die forging.

[0173] The components manufactured by this method are usually of revolution, but not necessarily all. The wall can also include other features, such as openings, surface reliefs, especially protrusions, pits and ribs.

[0174] In addition, the above two embodiments can be combined. In particular, referring to the first embodiment, the average thickness of at least one part is different from the average thickness of the other part.

Claims

1. A method for manufacturing a hollow component (1), the hollow component (1) comprising a single seamless wall (3) in the shape of a dome extending around a central axis (A-A); the wall (3) is made of a metal alloy material, has an average thickness of less than 50 mm, and its large dimension perpendicular to the central axis (A-A) is from 1500 mm to 3700 mm; the method comprises the following successive steps: - Providing a semi-finished product (11) of the material; - Upsetting and hot forging the semi-finished product (11) to form a blank (13), the developed area of the blank being larger than the developed area of the semi-finished product (11) and smaller than the developed area of the wall (3); - Thermoforming the blank (13) to form a preform (15), the developed area of the preform being smaller than or equal to the developed area of the wall (3), the preform (15) comprising at least two successive parts (19, 21), the two successive parts being joined to each other and extending radially away from the central axis (A-A), such that for all parts (19, 21), the average thickness and / or convexity of the two successive parts (19, 21) are different; - Thermally deforming the preform (15) between a die (49) and a punch (51) by means of a press (47) to form the wall (3).

2. The manufacturing method according to claim 1, wherein the parts comprise a central part (19) and at least one intermediate annular part (21), the central part (19) and the intermediate annular part (21) having different convexities.

3. The manufacturing method according to claim 2, wherein the parts further comprise an outer peripheral annular part (23), the outer peripheral annular part (23) having a convexity different from that of the adjacent intermediate annular part (21).

4. The manufacturing method according to any one of claims 2 to 3, wherein the ratio of the projected area of the preform (15) in cross-section to its developed area is less than 90%, and the maximum dimension of the projected area of the preform (15) in cross-section is less than or equal to 150% of the maximum dimension of the punch (51) perpendicular to the central axis (A-A).

5. The manufacturing method according to any one of claims 2 to 4, wherein the step of deforming the preform (15) under the press comprises unfolding the preform (15) between the die (49) and the punch (51) such that, after unfolding, the surface of the part facing the punch (51) is concave.

6. The manufacturing method according to any one of claims 2 to 5, wherein the surface of the central part (19) facing the punch (51) has a concave shape.

7. The manufacturing method according to claim 1, wherein the parts comprise a central part (19) and at least one intermediate annular part (21), the average thickness of the central part (19) and the intermediate annular part (21) being different, and the developed area of the preform (15) being smaller than the developed area of the wall (3).

8. The manufacturing method according to claim 7, wherein the portion further includes an outer peripheral annular portion (23), and the intermediate annular portion (21) is a thickened portion, and the average thickness of the intermediate annular portion (21) is greater than the average thickness of the central portion (19) and the average thickness of the outer peripheral annular portion (23).

9. The manufacturing method according to any one of claims 7 or 8, wherein the deformation step of the preform (15) includes a shaping stage and a die forging stage. In the shaping stage, at least a part of the intermediate annular portion (21) contacts the die (49) through a punch (51); in the die forging stage corresponding to the expansion stage, at least a part of the preform (15) does not contact the punch (51).

10. The manufacturing method according to claim 9, wherein in the expansion stage, the thickened intermediate annular portion (21) of the preform (15) is compressed between the die (49) and the punch (51), and at least a part of the central portion (19) and / or the outer peripheral annular portion (23) does not contact the punch (51), so that the material plastically flows from the intermediate annular portion (21) to the central portion (19) and the outer peripheral annular portion (23), and then exceeds the outer peripheral annular portion (23) to increase the unfolded area of the preform and form the wall (3).

11. The method according to any one of claims 1 to 10, wherein the material is an aluminum alloy, specifically 2XXX or 7XXX alloy.

12. A hollow component (1) comprising a single seamless wall (3) in a dome shape, the wall (3) extending around a central axis (A - A), the wall (3) being made of a metal alloy material, the average thickness of the wall being less than 50 mm, and its large dimension perpendicular to the central axis (A - A) being 1500 mm to 3700 mm.

13. The hollow component according to claim 12, wherein the wall (3) exhibits a uniform fibrous distribution around the central axis (A - A), and the orientation of the grains of the metal alloy is such that in any cross-section, the angle formed between the elongation direction of the grains seen in the cross-section and the tangent of the wall (3) at that grain is substantially constant.

14. The hollow component according to any one of claims 12 or 13, wherein the material is an aluminum alloy, specifically 2XXX or 7XXX alloy.

15. A cryogenic storage tank comprising the hollow component (1) according to any one of claims 12 to 14 or a hollow component (1) manufactured by the method according to any one of claims 1 to 11.

Images