Fe-Ni alloys, in particular, for the transport and storage of liquid hydrogen

Abstract

The present invention relates to an iron-nickel alloy having the following composition in mass percentages: 36.5%≦Ni≦38.5%, 0.50%≦Mn≦1.25%, 0.001%≦Cu≦0.85%, 0.040%≦C≦0.150%, 0.10%≦Si≦0.35%, with the balance being iron and unavoidable impurities resulting from production.

Description

[Technical Field]

[0001] The present invention relates particularly to iron-nickel (Fe-Ni) alloys intended for use in cryogenic applications, and especially to alloys for manufacturing works or assemblies designed to contain liquefied gases, such as transport pipes or transport / storage tanks for transporting or storing liquefied gases. These works or assemblies are particularly suitable and adapted for receiving liquid hydrogen. [Background technology]

[0002] The materials currently used for transporting liquefied gases are generally designed for the transport and storage of liquid methane, which has a boiling point of -162°C. However, there is an increasing need to manufacture structures or assemblies that are also appropriately adapted for the transport and storage of liquid hydrogen, which has a boiling point of -253°C.

[0003] The inventors of the present invention have noticed that the transport and storage of liquid hydrogen using materials commonly used for transporting liquefied gases, such as Invar M93, may present problems, on the one hand, due to the low boiling point of liquid hydrogen, and on the other hand, due to the risk of the alloy becoming brittle due to hydrogen.

[0004] More specifically, the inventors of this invention have found that austenitic structures, such as those made of Invar M93, can undergo martensitic transformation when the material is subjected to plastic strain at cryogenic temperatures. The more severe the strain and the lower the temperature, the higher the martensite content. In the case of Invar M93, therefore, the risk of martensitic transformation within the microstructure during minor mechanical incidents (collisions, crashes, bending, etc.) in cryogenic lines or tanks increases significantly at the temperature of liquid hydrogen (-253°C). The martensite that develops within the microstructure of INVAR M93 and is then hydrogenated can subsequently induce hydrogen embrittlement. [Overview of the project] [Problems that the invention aims to solve]

[0005] Therefore, one object of the present invention is to provide an alloy that exhibits a low average coefficient of thermal expansion between 0°C and 196°C, and at the same time good mechanical properties at the temperature of liquid hydrogen (-253°C), and is particularly usable for the manufacture of works designed for the transport and storage of liquid hydrogen, for example, for the manufacture of pipes or tanks designed for the transport and storage of liquid hydrogen. [Means for solving the problem]

[0006] For this purpose, the present invention has the following composition in mass percent: 36.5% ≤ Ni ≤ 38.5% 0.50% ≤ Mn ≤ 1.25% 0.001% ≤ Cu ≤ 0.85% 0.040% ≤ C ≤ 0.150% 0.10% ≤ Si ≤ 0.35% This invention relates to an iron-nickel alloy having [a certain component], with the remainder being iron and unavoidable impurities arising from the manufacturing process.

[0007] According to the specific characteristics of the alloy according to the present invention, - The carbon content is between 0.040% by mass and 0.075% by mass. - Inevitable impurities arising from manufacturing are expressed in mass percent: Cr ≤ 0.5% Co ≤ 0.5% S ≤ 0.0035% P ≤ 0.01% Mo<0.5% 0 ≤ 0.0025% Ca ≤ 0.0015% Mg ≤ 0.0035% Al ≤ 0.0085% Includes, - The alloy, especially if it is a hot-rolled product, is 2.0 × 10 -6 ℃ -1 The above is 3.0 × 10 -6 ℃ -1 The following is the average thermal expansion coefficient α between -196°C and 0°C.

[0008] The present invention further relates to a cold-rolled strip made of the above alloy.

[0009] The present invention further relates to the following continuous process for manufacturing the above cold-rolled strip: - A step of generating the alloy defined above, - A step of forming a semi-finished product of the alloy, - A step of hot rolling this semi-finished product to obtain a hot-rolled strip, - A step of cold rolling the hot-rolled strip in one or more passes to obtain a cold-rolled strip, relates to a method for manufacturing a strip comprising the above.

[0010] The present invention further relates to the use of the alloy defined above for manufacturing a tank or pipe intended to receive liquefied gas therein.

[0011] The present invention further relates to a filler wire made of the alloy defined above.

[0012] The present invention further relates to a wire manufacturing method for manufacturing the filler wire defined above, the method comprising the following steps: - A step of preparing a semi-finished product made of the alloy defined above, - A step of hot transforming this semi-finished product to form an intermediate wire, and - A step of transforming the intermediate wire into a filler wire having a diameter smaller than the diameter of the intermediate wire, the step including a wire drawing step. comprising.

[0013] The present invention further relates to a workpiece or a part of a workpiece made of the alloy defined above, the workpiece or part of the workpiece being obtained using additive manufacturing.

[0014] The present invention further relates to a manufacturing method for producing a workpiece or a part of a workpiece, the method comprising the step of producing the workpiece or part of a workpiece by a metal additive manufacturing process using, as a filler material, a filler wire made from the alloy defined above and / or a powder made from the alloy defined above.

[0015] The present invention further relates to the use of the filler wire defined above as a filler wire in the context of a metal addition manufacturing process.

[0016] The present invention further relates to metal powders made from the alloys defined above.

[0017] The present invention further relates to a powder manufacturing method for producing the metal powder defined above, the method comprising the steps of preparing the filler wire defined above, and plasma spraying the filler wire to obtain the metal powder.

[0018] The present invention further relates to a tube segment made from the alloy defined above, wherein the tube segment is preferably seamless.

[0019] According to certain characteristic properties, the tube fragment comprises sheets made from the alloy defined above, bent into the shape of a tube, the sheets having longitudinal edges joined to each other by weld seams.

[0020] The present invention further comprises the following sequential steps: - A step of preparing a sheet made from the alloy defined above and having two longitudinal edges, and - A process of welding the longitudinal edges of sheets together to form a pipe segment, The present invention relates to a method for manufacturing pipes for the production of pipe segments as defined above, including the above.

[0021] The present invention further relates to a tube comprising at least two tube segments as defined above, wherein the two continuous tube segments are joined to each other by a weld seam.

[0022] The present invention further comprises the following sequential steps: - A step of preparing a first pipe segment and a second pipe segment as defined above, wherein the first pipe segment and the second pipe segment extend along their longitudinal axes. - The steps of positioning the first and second pipe fragments such that the longitudinal end of the first pipe fragment faces the longitudinal end of the second pipe fragment, and aligning them along the longitudinal axes of the first and second pipe fragments, - The process of welding together the two opposing longitudinal ends of the first and second pipe segments, This relates to a manufacturing method for producing pipes, including the production of pipes.

[0023] The present invention further relates to a tank portion comprising at least one part made from the alloy defined above. The tank portion is intended for the transport and storage of liquefied gases, particularly liquid hydrogen.

[0024] The present invention further relates to a hot-rolled strip made of the above alloy.

[0025] The present invention further comprises the following sequential steps: - The process of producing the alloy described above, - A step of forming a semi-finished product of the aforementioned alloy, - A process to obtain a hot-rolled strip by hot-rolling this semi-finished product, The present invention relates to a method for manufacturing strips for producing the above-mentioned hot-rolled strips.

[0026] The present invention will be better understood by reading the following description, which is provided merely as an example and refers to the accompanying drawings. [Brief explanation of the drawing]

[0027] [Figure 1] This is a schematic perspective view of a pipe fragment according to a first embodiment of the present invention. [Figure 2] This is a schematic perspective view of a pipe fragment according to a second embodiment of the present invention. [Figure 3] This is a schematic top view of a sheet used in the implementation of a method for manufacturing pipe fragments according to a second embodiment. [Figure 4] This is a schematic perspective view of a pipe according to the present invention. [Figure 5] This is a schematic perspective view of a workpiece obtained by means of an additive manufacturing process according to the present invention. [Modes for carrying out the invention]

[0028] Throughout the explanation, the content is expressed as a mass percentage.

[0029] The alloy according to the present invention is, in mass percent: 36.5% ≤ Ni ≤ 38.5% 0.50% ≤ Mn ≤ 1.25% 0.001% ≤ Cu ≤ 0.85% 0.040% ≤ C ≤ 0.150% 0.10% ≤ Si ≤ 0.35% Includes, The remainder consists of iron and iron-based alloys, which are unavoidable impurities resulting from the manufacturing process.

[0030] The term "unavoidable impurities arising from manufacturing" is used to refer to components present in the raw materials used to produce the alloy, or originating from the equipment used in their production, such as the refractory materials of a furnace. These impurities do not have a metallurgical effect on the alloy.

[0031] Impurities resulting from manufacturing, especially in mass percentage: Cr ≤ 0.5% Co ≤ 0.5% S ≤ 0.0035% P ≤ 0.01% Mo<0.5% 0 ≤ 0.0025% Ca ≤ 0.0015% Mg ≤ 0.0035% Al ≤ 0.0085% Includes.

[0032] The alloy according to the present invention, in particular, has an average coefficient of thermal expansion α between -196 °C and 0 °C, which is 2.0×10 -6 °C -1 or more and 3.0×10 -6 °C -1 or less.

[0033] In the alloy according to the present invention, the content levels of Ni, Mn, C and Cu, namely Ni≥36.5%, Mn≥0.50%, C≥0.040% and Cu≥0.001%, are such that they enhance the stability of the alloy against martensitic transformation at -253 °C (20 K), i.e., the temperature of liquid hydrogen. As a result, an alloy is provided that has the ability to retain an austenite structure in minor mechanical incidents (collisions, crashes, bending, etc.) that occur at the temperature of liquid hydrogen.

[0034] The inventors of the present invention have noticed that when the content levels of Ni, Mn, C and Cu are below the above lower limits, in minor mechanical incidents (collisions, crashes, bending, etc.) that occur at the temperature of liquid hydrogen, which are characterized by a low elongation at break A (A≤10%) and an overly low striction Z (Z≤50%), the alloy presents an increased risk of hydrogen embrittlement.

[0035] The elongation at break A was determined using the ASTM A370 standard (July 2019).

[0036] The striction Z was determined using the French standard, NF EN ISO 6892-1 (December 2019).

[0037] In addition, the upper limits selected for Ni, Mn and Cu, namely Ni≤38.5%, Mn≤1.25% and Cu≤0.85%, make the average coefficient of thermal expansion α 3.0×10 -6 °C -1It is possible to maintain the temperature between -196°C and 0°C, thereby providing the ability to limit the thermal stress to the critical value evaluated at 110 MPa. The critical stress is approximately equal to 15% of the yield strength of the alloy at the temperature of liquid hydrogen (Rp(-253°C)~800 MPa).

[0038] The inventors of this invention have found that when the content levels of Ni, Mn, and Cu exceed the above upper limit, the average thermal expansion coefficient α between -196°C and 0°C is 3.0 × 10⁻⁶. -6 ℃ -1 Because it has a larger value than [the specified value], we found that it is too large for the intended application.

[0039] In addition, if the carbon content is higher than 0.150%, the alloy loses its weldability through void formation during tungsten inert gas (TIG) welding without filler wire. In fact, the presence of carbon at levels higher than 0.150% causes foaming during TIG welding without filler wire. In this case, the weldability of the alloy decreases.

[0040] Preferably, the carbon content is between 0.040% by mass and 0.075% by mass. In this case, the weldability of the alloy is further improved.

[0041] Preferably, the Mn content is 0.7% by mass or more. This manganese content level further improves the stability of the alloy against martensitic transformation at -253°C (20K).

[0042] In the alloy according to the present invention, the silicon content is 0.10 mass% to 0.35 mass%. Silicon at these content levels helps to enable deoxygenation of the alloy. At content levels higher than 0.35 mass%, if the content levels of Ni, Mn, and Cu are adjusted according to the present invention, there is a risk that the coefficient of thermal expansion between -196°C and 0°C will become too high.

[0043] The alloys according to the present invention can be produced by any suitable method known to those skilled in the art. For example, the alloys are produced in an electron arc furnace or induction furnace and then ladle-refined by conventional methods, which include, in particular, a step of ASV-type high-temperature ladle-refining technique following a vacuum oxygen decarburization or VOD-type ladle-refining step. As a variation, the alloys according to the present invention are produced in a vacuum induction furnace from low-residue raw materials.

[0044] The methods for producing alloys are provided merely as examples. All other methods for producing alloys known to those skilled in the art can also be used for this purpose.

[0045] The present invention further relates to cold-rolled strips having the composition defined above. The cold-rolled strips have a thickness of 0.5 to 10 mm in particular. When the cold-rolled strips are intended to be used for the manufacture of cryogenic tubes, the thickness of the cold-rolled strips is preferably 2 mm to 10 mm. When the cold-rolled strips are intended to be used for the manufacture of transport / storage tanks for transporting or storing liquefied gases, the thickness is preferably 0.5 mm to 2 mm.

[0046] As an example, the following method is used for the production of such cold-rolled strips.

[0047] The above alloy is cast into semi-finished products, such as ingots, remelted electrodes, slabs, especially thin slabs with a thickness of less than 180 mm, or billets.

[0048] When casting alloys in the form of remelting electrodes, the latter is advantageously remelted under vacuum or by a conductive slag melting process, thereby obtaining a semi-finished product of higher purity and greater homogeneity.

[0049] The semi-finished product thus obtained by the direct casting method is then hot-rolled at a temperature between 950°C and 1300°C to obtain a hot-rolled strip.

[0050] The thickness of the hot-rolled strip is, in particular, 2 mm to 20 mm, and more specifically, 2 mm to 10 mm.

[0051] If the sheet metal being manufactured is intended for transporting or storing liquefied gases, the final thickness after hot rolling is, for example, approximately 3.5 mm.

[0052] According to one embodiment, hot rolling precedes a chemical homogenization heat treatment process performed on the semi-finished product at a temperature between 950°C and 1300°C for 30 minutes to 24 hours.

[0053] The hot-rolled strip is cooled to room temperature, forming the cooled strip, and then it is wound into a coil.

[0054] The cooled strip is then cold-rolled to obtain a cold-rolled strip having a final thickness of, advantageously, 0.5 mm to 10 mm. The cold-rolling process is carried out in one pass or multiple consecutive passes.

[0055] When the sheet metal being manufactured is intended for cryogenic tubes, the final thickness after cold rolling is advantageously between 2 mm and 10 mm.

[0056] When the sheet metal being manufactured is intended for transporting or storing liquefied gases, the final thickness after cold rolling is preferably 0.5 mm to 2 mm.

[0057] If necessary, the hot-rolled strip is chemically pickled and then shot-blasted to remove any mill scale present before cold rolling.

[0058] If necessary, the sheets that have been pickled and shot blasted are polished to remove oxidised penetration at the grain boundaries prior to cold rolling, thereby achieving the desired roughness Ra, specifically less than 50 μm, based on ISO standard 4287.

[0059] For the final thickness, the cold-rolled strip is subjected to a recrystallization heat treatment process in an electrostatic furnace at a temperature exceeding 700°C for a range of 10 minutes to several hours, as needed. As a variation, the cold-rolled strip is subjected to a recrystallization heat treatment process in a continuous annealing furnace at a temperature exceeding 800°C in the holding zone of the furnace for a range of several seconds to approximately 1 minute, under a protective atmosphere of N2 / H2 type (30% / 70%), at a freezing temperature of -50°C to -15°C. The freezing temperature defines the partial water vapor pressure contained within the heat treatment atmosphere. Prior to carrying out such treatment processes, the pickling, shot blasting, and polishing steps described above are performed in particular.

[0060] The recrystallization heat treatment process is carried out as needed during cold rolling, under the same conditions as the recrystallization heat treatment process described above, at the intermediate thickness between the initial thickness (corresponding to the thickness of the hot-rolled strip) and the final rolling thickness. For example, if the final thickness of the cold-rolled strip is 1.0 mm, the intermediate thickness is selected to be equal to 1.5 mm.

[0061] A method for producing cold-rolled strips made from this alloy is described only as an example. Any other method for producing cold-rolled strips known to those skilled in the art can be used for this purpose.

[0062] The present invention further relates to cryogenic tube fragments made from the above-mentioned alloys. The tube fragments are intended, in particular, for transporting liquefied gases, especially liquid hydrogen.

[0063] A pipe segment 1 according to the first embodiment is shown in Figure 1. This pipe segment 1 does not include longitudinal welding. Therefore, it is a weldless pipe segment. This pipe segment 1 can be obtained, for example, by extrusion molding of a billet made from the above alloy.

[0064] A tube segment 7 according to a second embodiment is shown in Figure 2. The tube segment 7 includes a sheet 9 made of the above alloy, bent into the shape of a tube, and the longitudinal edges 12 of the tube are joined to each other by a weld seam 15. The walls of the tube segment 7 have a thickness of, for example, between 2 mm and 10 mm.

[0065] The weld seam is obtained, in particular, by self-sharpening welding, i.e., by means of using a filler wire made from the above-mentioned alloy.

[0066] As a variation, filler wires with a different composition than those described above are used, and the composition of the filler wires is selected based on the desired properties, and in particular, thereafter 5.5 × 10 -6 ℃ -1 The following is obtained: an average thermal expansion coefficient α between -196°C and 0°C, and a weld with superior mechanical properties compared to sheet metal.

[0067] The present invention further relates to a method for manufacturing a tube for producing such a tube fragment 7.

[0068] The method includes preparing a sheet 9 made from the above alloy. Such a sheet 9 is shown in Figure 3. The sheet 9 extends along the longitudinal direction L and has a longitudinal edge 12 substantially parallel to the longitudinal direction L. The sheet 9 has a thickness of, for example, between 2 mm and 10 mm.

[0069] The method further comprises the steps of bending the sheet 9 so that the two longitudinal edges 12 are joined together and face each other, and subsequently welding the two longitudinal edges 12 to each other using a suitable filler wire, in particular a filler wire made of the above alloy.

[0070] The weld obtained during this process is a longitudinal weld. Preferably, it is a butt weld.

[0071] At the end of this process, a pipe segment 7 is obtained as shown in Figure 2, in which the sheet 9 is bent into the shape of a pipe, and the longitudinal edges 12 of the sheet 9 are joined to each other by a weld seam 15.

[0072] The present invention further relates to a cryogenic tube 20 manufactured by assembling cryogenic tube segments 1 and 7 according to the present invention. The tube 20 is intended in particular for transporting liquefied gases, and more particularly, liquid hydrogen.

[0073] As an example, the cryogenic tube 20 includes at least two of the above-mentioned tube segments 1, 7, which are joined to each other by a weld seam 22. The weld seam 22 extends along the outer circumference of the tube 20 in such a manner that it joins the tube segments 1, 7 to each other.

[0074] The weld seam 22 is obtained, in particular, by self-sharpening welding, i.e., by means of using a filler wire having the above composition.

[0075] The welding is, in particular, butt welding, and preferably circumferential welding. The term “circumferential welding” is used to refer to a weld produced by rotating the welding tool, i.e., the welding torch, around the periphery of the pipe segments 1, 7.

[0076] The walls of the cryogenic tube 20 have a thickness of, for example, between 2 mm and 10 mm.

[0077] The cryogenic tube 20 obtained by assembling the tube fragments 7 according to the second embodiment described above, with reference to Figure 2, is shown in Figure 4.

[0078] As a variation, the pipe 20 is obtained by assembling the pipe fragment 1 according to the first embodiment described above, with reference to Figure 1.

[0079] The present invention further relates to a manufacturing method for producing the above-mentioned cryogenic tube 20.

[0080] During this process, at least two tube segments 1, 7 are prepared. Each tube segment 1, 7 is substantially cylindrical with a centerline M and has two longitudinal ends 24 that are separated along the centerline M.

[0081] Next, the two tube segments 1 and 7 are positioned such that their longitudinal ends 24 face each other in the direction of the centerline M of these tube segments 1 and 7, and then the opposing longitudinal ends 24 of the two tube segments 1 and 7 are welded to each other using a filler wire, in particular a wire made of the alloy described above.

[0082] Advantageously, during this process, butt welds are formed between the opposing longitudinal ends 24 of the pipe segments 1 and 7. The weld is preferably a circumferential weld.

[0083] Preferably, the welding process includes a machining process for chamfering the ends 24 of the pipe segments 1 and 7 for welding them together before joining them together.

[0084] The welding process is carried out repeatedly, and the number of repetitions is equal to one less than the number of pipe fragments 1, 7 to be welded together to form pipe 20.

[0085] According to one embodiment, the pipe fragment is pipe fragment 1 according to the first embodiment described above. As a modification, the pipe fragment is pipe fragment 7 according to the second embodiment described above.

[0086] At the end of one or more of the welding steps, a cryogenic tube 20 is obtained. This cryogenic tube 20 includes at least two continuous tube segments 1, 7 assembled together by a welding seam 22.

[0087] The present invention further relates to a part of a tank for transporting or storing liquefied gas, made from the above-mentioned alloy.

[0088] The present invention further relates to a filler wire made from the above-mentioned alloy.

[0089] Such filler wires are intended for use in particular under additive manufacturing conditions or as filler wires for welding two workpieces or parts of workpieces together, where the workpieces or parts of workpieces are made of, for example, the alloy described above.

[0090] Such filler wires are produced, in particular, by the following method.

[0091] This method includes, in the first step, providing a semi-finished product made from the above-mentioned alloy.

[0092] For this purpose, the alloy produced by the above method is either cast into an ingot or directly into a billet, particularly using continuous casting, especially rotary casting. Thus, the semi-finished product obtained at the end of this process is advantageously an ingot or a billet, having a diameter of, for example, between 130 and 230 mm, more specifically, approximately 150 mm.

[0093] Subsequently, the semi-finished product is deformed using thermal deformation to form an intermediate wire.

[0094] In particular, during this thermal deformation process, the semi-finished product, i.e., ingots or billets in particular, is heated to a temperature between 1150°C and 1250°C, especially in a gas furnace.

[0095] Next, the semi-finished product is subjected to a hot rough rolling process, followed by a hot rolling process, particularly on a wire mill, at a temperature between 950°C and 1150°C, and then a super-quench process at the outlet of the rolling mill. The intermediate wire may be a wire rod in particular. For example, the intermediate wire has a diameter between 5 mm and 21 mm, and in particular, is approximately equal to 5.5 mm.

[0096] A superquench is a superquench in a 20°C bath following a heat treatment process in a gas furnace at temperatures between 1050°C and 1150°C for 20 to 120 minutes.

[0097] The intermediate wire was then stripped and wound into a spool.

[0098] If necessary, the intermediate wire or wire rod thus obtained was drawn using a known type of wire drawing apparatus to obtain a filler wire. This filler wire has a smaller diameter than the initial wire. In particular, its diameter is between 0.5 mm and 3.5 mm. Advantageously, its diameter is between 0.8 mm and 2.4 mm.

[0099] Depending on the final diameter to be achieved, the wire drawing process includes one or more wire drawing passes, preferably with an annealing process between two consecutive wire drawing passes. This annealing is performed during wire drawing, for example, in a reducing atmosphere at a temperature of about 1150°C.

[0100] The wire drawing process is preferably followed by a cleaning process of the surface of the drawn wire, and then winding the wire.

[0101] The wire drawing path is a path for cold wire drawing.

[0102] In particular, two drawing passes are used to produce filler wire with a diameter of approximately 1.6 mm, and the second drawing pass results in a final diameter of approximately 1.6 mm.

[0103] For the production of a filler wire with a diameter of approximately 1.2 mm, for example, three drawing passes are used, with the second drawing pass resulting in a diameter of approximately 1.6 mm, and the third drawing pass resulting in a final diameter of approximately 1.2 mm.

[0104] A wire manufacturing method for the production of filler wire is described only as an example. All other suitable methods for manufacturing filler wire known to those skilled in the art can be used for this purpose.

[0105] The present invention further relates to a metal powder for additive manufacturing produced from the above-mentioned alloy, wherein the particle size of the metal powder after screening is preferably between 10 μm and 200 μm.

[0106] Such powder is produced, for example, by plasma spraying from a wire made from the above alloy, the wire having a diameter of approximately 3 mm.

[0107] The particle size of the powder is determined, in particular, according to the following measurement method. The powder batch is separated into several particle size distributions using an ultrasonically vibrating stainless steel sieve. The powder particle size distribution obtained after the screening process is analyzed according to ASTM standard B214-07. Screening yields five size classifications: <20μm - 20μm to 45μm - 45μm to 75μm - 75μm to 105μm ->105μm.

[0108] The plasma spraying process is well-known and therefore will not be described in detail.

[0109] The filler wire is also intended to be used as a filler wire in situations such as metal additive manufacturing processes.

[0110] Additive manufacturing processes are those that use, for example, arc discharge, laser beams, and / or electron beams as energy sources, thereby resulting in the melting of filler wires.

[0111] In particular, the additive manufacturing process is a directed energy deposition additive manufacturing process. In this process, the filler material is deposited, in particular by a nozzle, and instantly melted by high-concentration thermal energy, in particular by a laser beam, electron beam, and / or arc discharge.

[0112] For example, additive manufacturing processes are based on wire-arc ("wire-arc additive manufacturing" or "WAAM" are recognized technical terms), wire-laser, wire-electron beam ("Electron Beam Free Form Fabrication" or "Electron Beam Additive Manufacturing" are recognized technical terms), or hybrid additive manufacturing processes that combine wire-arc and powder-laser or wire-arc and wire-laser technologies.

[0113] The wire used under these process conditions is the filler wire described above.

[0114] Hybrid wire-arc and powder-laser processes use powders that have the same composition as the wire.

[0115] The present invention further relates to a method for manufacturing a workpiece for producing a workpiece 40 schematically shown in Figure 5 or a part of a workpiece made from the above alloy, wherein the manufacturing method is as follows: - The process of preparing filler wires made from this alloy, and - A process of manufacturing a workpiece 40 or a workpiece part by a metal additive manufacturing process using filler wire and / or powder made from the above alloy as filler material. Includes.

[0116] Additive manufacturing processes, for example, use arc discharge, laser beams, and / or electron beams as energy sources to melt filler materials.

[0117] In particular, the additive manufacturing process is a "directed energy deposition" additive manufacturing process. In this process, the filler material is deposited, in particular by a nozzle, and immediately melted by high-concentration thermal energy, in particular by a laser beam, electron beam, and / or arc discharge.

[0118] For example, additive manufacturing processes are based on wire-arc ("wire-arc additive manufacturing" or "WAAM" are recognized technical terms), wire-laser, wire-electron beam ("Electron Beam Free Form Fabrication" or "Electron Beam Additive Manufacturing" are recognized technical terms), or hybrid additive manufacturing processes that combine wire-arc and powder-laser or wire-arc and wire-laser technologies.

[0119] When using a hybrid additive manufacturing process that combines wire-arc and powder-laser or wire-arc and wire-laser technologies, the powder and filler wires are made from the alloys described above.

[0120] The additive manufacturing process described above is publicly known and therefore will not be described in detail herein.

[0121] The present invention further relates to a workpiece 40 or a part of a workpiece obtained by a metal addition process, which is made from the above-mentioned alloy.

[0122] This metal addition process, in particular, uses filler wires and / or powders made from the above-mentioned alloys as filler materials.

[0123] A workpiece or part of a workpiece obtained by an additive manufacturing process, for example, workpiece 40, is a solidified workpiece. Therefore, workpiece 40, in consideration, has a solidified microstructure characteristic of alloys, such microstructure typically includes columnar dendrites that grow on top of one another by epitaxy, the arrangement of which depends on the width and height of the resulting metal wall. Furthermore, a workpiece obtained by an additive manufacturing process has a series of overlapping solidified layers as a result of that process. Each layer is obtained by the solidification of deposited droplets of molten metal, but remelts the surface of the previous layer, thereby creating metallurgical continuity and consequently reheating the rest of the lower layer. The further the layer in question is from the zone during the melting and solidification process, the lower the reheating temperature will be. This particular microstructure can be observed by metallographic observation on a metallographic cross-section of the workpiece.

[0124] A workpiece 40 or workpiece portion obtained by a metal addition process can thus be distinguished from workpieces obtained by other processes, and in particular from workpieces obtained by conventional refining methods that produce a recrystallized structure having homogeneous particles.

[0125] The workpiece 40 or workpiece part, especially special workpieces or workpiece parts, such as valves, pipe connectors, or any other workpiece, are used particularly under cryogenic application conditions, more specifically, under the temperature of liquid hydrogen, for example, under the conditions of transporting and storing liquid hydrogen.

[0126] According to one embodiment, the workpiece 40 is a cylindrical connector intended to function as a connector between multiple coaxial pipes, particularly between a double-layer pipe and a single-layer pipe, for example, in a pipeline. Such a connector is referred to as a “bulkhead” in accepted technical terms. Bulkheads are well-known components in the field of pipelines.

[0127] test The alloys used in test numbers 1-22 were produced under vacuum, and small ingots weighing approximately 2 kg were cast. These ingots were machined into rods with dimensions of 35 mm on each side and 100 mm in height. These rods were then hot-rolled at approximately 1150°C before being reheated to 1220°C over 8 hours under argon gas, thereby obtaining sheet bars with dimensions of 750 × 35 × 4 mm.

[0128] The chemical composition of alloying elements in the obtained sheet bar is defined in mass percent in Table 1 below. The approximate mass content of impurities in the sheet bar resulting from the manufacturing process is shown in Table 2 below.

[0129] [Table 1]

[0130] In Table 1 above, examples that do not conform to the present invention are underlined.

[0131] [Table 2]

[0132] Specimens for planar tensile testing of prismatic prisms (two per composition, based on ASTM A370 standard (July 2019)) and cylindrical specimens for thermal expansion testing with a diameter of 3 mm and a length of 50 mm (one per composition) were machined from the sheet bars thus obtained, thereby producing specimens for hydrogen embrittlement susceptibility studies and thermal expansion measurements.

[0133] In the initial stage, tensile test specimens were subjected to heat treatment at 1100°C for 4 hours under 99.999% pure hydrogen, followed by rapid cooling in the low-temperature range of the furnace. The cooling period was approximately 45 seconds. The purpose of this heat treatment was to add atomic hydrogen (H) to the test specimens.

[0134] In the next stage, the tensile test specimen (hydrogenated) was subjected to strain rate 5 × 10 at two different temperatures. -3 S -1 Then, pre-distortion was applied. - Specimen A was pre-strained to 10% at the temperature of liquid helium (-268°C). The purpose of pre-straining at -268°C is to induce more or less martensite formation under more severe thermal conditions than those of liquid hydrogen (-253°C), depending on the stability of the alloy. - Specimen B was pre-strained to 10% at room temperature (20°C). The purpose of pre-straining to 10% at room temperature is to prepare a reference specimen that does not contain martensite but has the same strain rate as a specimen that was strained at -268°C and is likely to contain martensite. These specimens will result in a non-brittle reference state.

[0135] Finally, test specimens A and B were subjected to a low strain rate of 5 × 10⁻⁶. -5 s -1 A tensile strain test was performed on a planar sample at -50°C (+ / -5°C) until fracture. This type of test is called a "slow tensile fracture test at -50°C". The period between hydrogenation and the slow tensile test at -50°C never exceeded 48 hours.

[0136] The hydrogen susceptibility of the specimens subjected to low-speed tensile and fracture tests at -50°C was evaluated by measuring the total elongation at fracture A% and reduction of area Z% = (S0-S) / S0 using a 25× optical microscope. S0 and S are the initial cross-sectional view before pre-strain and the final cross-sectional view with the shortest diameter, respectively. The results of these measurements are shown in the A% and Z% columns for specimens A and B in Table 3 below.

[0137] Furthermore, the expansion coefficient ΔL of the alloy was measured during cooling between 0°C and -196°C (the temperature of liquid nitrogen), and then the average thermal expansion coefficient α[-196°C_0°C] between -196°C and 0°C was calculated based on the formula: α[-196°C_0°C] = 1 / L0 × ΔL / ΔT, where ΔT = 0 - (-196) and L0 are the initial length of the test specimen (50 mm). The results of these measurements and calculations are shown in the "α" column of Table 3 below.

[0138] The results are presented in Table 3 below.

[0139] [Table 3]

[0140] In Table 3 above, examples that do not conform to the present invention are underlined.

[0141] Regarding composition numbers 3 to 7, the standard material for tensile testing is test specimen B, which corresponds to composition number 3. Indeed, it was concluded that within this group of compositions, the ductility after "low-speed tensile fracture at -50°C" was not dependent on the composition.

[0142] Similarly, for composition numbers 8-13, the standard material for tensile testing is test specimen B corresponding to composition number 8. For composition numbers 14-17, the standard material for tensile testing is test specimen B corresponding to composition number 14, and for composition numbers 18-22, the standard material for tensile testing is test specimen B corresponding to composition number 18.

[0143] In the cases of test numbers 1, 2, 3, and 8, where the content levels of Ni, Mn, C, and / or Cu are lower than the lower limit levels mentioned above for those elements, it can be observed that test specimen A exhibits hydrogen embrittlement, characterized by a low elongation at break A (A ≤ 10%) and an excessively low reduction of area (Z ≤ 50%).

[0144] At room temperature, reference specimen B, pre-strained by 15%, exhibited normal ductility, with A% approximately 18% and Z% approximately 88%.

[0145] In the cases of test numbers 7, 13, and 17, where the content levels of Ni, Mn, and / or Cu are higher than the upper limits mentioned above for those elements, the average thermal expansion coefficient α between -196°C and 0°C is 3.0 × 10⁻⁶. -6 ℃ -1 It can be observed that the values ​​presented are significantly lower than the previous values.

[0146] Test number 22 is unsuitable as long as the carbon content is too high (C > 0.150%). In this case, the inventors found that the alloy loses its weldability through void formation during TIG welding without filler wire. In fact, the presence of carbon causes foaming during subsequent TIG welding operations without filler wire.

[0147] For test numbers 4-6, 9-12, 14-16, and 18-21, the trade-off that satisfies the conditions based on the present invention is a low coefficient of thermal expansion (2.0 × 10⁻¹⁰). -6 ℃ -1 The above is 3.0 × 10 -6 ℃ -1 The following properties are obtained in relation to the average thermal expansion coefficient α) between -196°C and 0°C and hydrogen embrittlement resistance (elongation at break A greater than 10% and reduction of area Z greater than 50%).

[0148] Therefore, these alloys exhibit good mechanical properties at the temperature of liquid hydrogen (-253°C) while simultaneously having a low average coefficient of thermal expansion α between -196°C and 0°C. [Industrial applicability]

[0149] Accordingly, the alloys according to the present invention are particularly suitable for use in applications using liquid hydrogen (-253°C), especially in assemblies designed to contain hydrogen, and especially in the manufacture of transport pipes or transport / storage tanks for transporting or storing liquid hydrogen. Needless to say, these alloys can also be used for cryogenic applications with even fewer restrictions than those relating to liquid hydrogen, for example, for the transport or storage of liquefied gases having boiling points higher than the boiling point of liquid hydrogen. [Explanation of Symbols]

[0150] 1 tube fragment 7 tube fragment 9 sheets 12 Longitudinal edge 15 Weld seam 20 Cryogenic tubes 20 tubes 22 Weld seams 24 Longitudinal ends 40 Workpiece L Longitudinal direction M center line

Claims

1. The composition is as follows, in mass percentage: 36.5% ≤ Ni ≤ 38.5% 0.50% ≤ Mn ≤ 1.25% 0.001% ≤ Cu ≤ 0.85% 0.040% ≤ C ≤ 0.150% 0.10% ≤ Si ≤ 0.35% An iron-nickel alloy, the remainder being iron and unavoidable impurities arising from the manufacturing process.

2. The alloy according to claim 1, wherein the carbon content is between 0.040% by mass and 0.075% by mass.

3. The unavoidable impurities resulting from the above manufacturing process, in mass percent, are: Cr ≤ 0.5% Co ≤ 0.5% S ≤ 0.0035% P ≤ 0.01% Mo < 0.5% O ≤ 0.0025% Ca ≤ 0.0015% Mg ≤ 0.0035% Al ≤ 0.0085% The alloy according to claim 1 or 2, comprising:

4. A cold-rolled strip made from the alloy described in any one of claims 1 to 3.

5. A manufacturing method for producing the cold-rolled strip described in claim 4, comprising the following consecutive steps: - A step of manufacturing the alloy according to any one of claims 1 to 3, - A process for forming a semi-finished product of the alloy, - A step of hot-rolling the aforementioned semi-finished product to obtain a hot-rolled strip, - A step of cold-rolling the hot-rolled strip in one or more passes to obtain a cold-rolled strip. A manufacturing method that includes this.

6. Use of the alloy according to any one of claims 1 to 3 for the manufacture of a tank or pipe intended to receive liquefied gas inside.

7. A filler wire made from the alloy described in any one of claims 1 to 3.

8. A manufacturing method for producing the filler wire described in claim 7, comprising the following steps: - A step of preparing a semi-finished product made from an alloy according to any one of claims 1 to 3, - A step of thermally deforming the aforementioned semi-finished product to form an intermediate wire, and - A process of transforming the intermediate wire into a filler wire having a diameter smaller than the diameter of the intermediate wire, including a step of drawing the wire. A manufacturing method that includes this.

9. A workpiece (40) or a part of a workpiece, made from an alloy according to any one of claims 1 to 3, obtained by metal addition manufacturing.

10. A method for manufacturing a workpiece (40) or a part of a workpiece, comprising the step of manufacturing the workpiece (40) or a part of a workpiece by a metal addition process using a filler wire made from an alloy according to any one of claims 1 to 3 and / or powder made from an alloy according to any one of claims 1 to 3 as a filler material.

11. Use of the filler wire according to claim 7 as a filler wire in a metal additive manufacturing process.

12. Metal powder made from the alloy described in any one of claims 1 to 3.

13. A method for producing the metal powder described in claim 12, comprising the steps of preparing the filler wire described in claim 7, and plasma spraying the filler wire to obtain the metal powder.

14. A tube segment (1; 7) made from the alloy described in any one of claims 1 to 3.

15. A pipe fragment (7) according to claim 14, comprising a sheet (9) made from an alloy according to any one of claims 1 to 3, which is bent into the shape of a pipe, wherein the sheet (9) has longitudinal edges (12) joined to each other by a weld seam (15).

16. A method for manufacturing the tube fragment (7) described in claim 15, comprising the following sequential steps: - A step of preparing a sheet (1) made from an alloy according to any one of claims 1 to 3, having two longitudinal edges (3), - A step of welding the longitudinal edges (3) of the sheet (1) to each other to form the pipe fragment (7), A manufacturing method that includes this.

17. A pipe (20) comprising at least two pipe segments (1;7) according to claim 14 or 15, wherein the two continuous pipe segments (1;7) are joined to each other by a weld seam (22).

18. A manufacturing method for producing a pipe (20), comprising the following series of steps: - A step of preparing a first tube segment (1;7) and a second tube segment (5) according to claim 14 or 15, wherein the first tube segment (1;7) and the second tube segment (1;7) extend along a longitudinal axis (M), - A step of positioning the first and second pipe segments (1;7) such that the longitudinal end (24) of the first pipe segment (1;7) faces the longitudinal end (24) of the second pipe segment (1;7), and the first and second pipe segments (1;7) are positioned along the longitudinal axis (M) of the first and second pipe segments (1;7), and - A step of welding together the two opposing longitudinal ends (24) of the first and second pipe segments (1; 7), A manufacturing method that includes this.

19. A tank portion comprising at least one portion made from the alloy described in any one of claims 1 to 3.

20. A hot-rolled strip made of the alloy described in any one of claims 1 to 3.

21. A manufacturing method for producing the hot-rolled strip described in claim 20, comprising the following consecutive steps: - A step of producing the alloy according to any one of claims 1 to 3, - A process for forming a semi-finished product of the alloy, - A step of hot-rolling the aforementioned semi-finished product to obtain a hot-rolled strip, A manufacturing method that includes this.

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