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

Abstract

The invention relates to an iron-nickel alloy having the following composition in percent by weight: 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%, the remainder being iron and unavoidable impurities resulting from production.

Description

Technical Field

[0001] This invention relates to an iron-nickel (Fe-Ni) alloy, particularly intended for cryogenic applications, especially for manufacturing workpieces or assemblies designed to contain liquefied gases (e.g., transport pipes or transport / storage tanks for transporting or storing liquefied gases). These workpieces or assemblies are particularly suitable and adapted to receive liquid hydrogen. Background Technology

[0002] Currently, materials used for transporting liquefied gases are typically designed for transporting and storing liquid methane with a boiling point of -162°C. However, there is a need to produce components or parts suitable for transporting and storing liquid hydrogen with a boiling point of -253°C.

[0003] The inventors of this invention have noted that using materials typically used for transporting liquefied gases (e.g., Invar M93) to transport and store liquid hydrogen can present difficulties, partly due to the low boiling point of liquid hydrogen and partly due to the risk of hydrogen embrittlement of the alloy.

[0004] More specifically, the inventors of this invention have discovered that when a material undergoes plastic deformation at low temperatures, the austenitic structure of materials such as Invar M93 may undergo a martensitic transformation. The more severe the deformation and the lower the temperature, the higher the martensite content. Therefore, for Invar M93, in the event of minor mechanical accidents (impact, breakage, bending, etc.) during operation in cryogenic pipelines or tanks, the risk of martensitic transformation within the microstructure increases significantly at the temperature of liquid hydrogen (-253°C). The martensite generated and loaded with hydrogen within the microstructure of Invar M93 may then cause hydrogen embrittlement. Summary of the Invention

[0005] Therefore, one object of the present invention is to provide an alloy that exhibits good mechanical properties at the temperature of liquid hydrogen (-253°C) while having a low average coefficient of thermal expansion between 0°C and -196°C. This alloy is particularly suitable for manufacturing workpieces designed for the transport and storage of liquid hydrogen, such as pipes or tanks designed for the transport and storage of liquid hydrogen.

[0006] Therefore, the present invention relates to an iron-nickel alloy having the following composition by weight percentage:

[0007] 36.5% ≤ Ni ≤ 38.5%

[0008] 0.50% ≤ Mn ≤ 1.25%

[0009] 0.001% ≤ Cu ≤ 0.85%

[0010] 0.040% ≤ C ≤ 0.150%

[0011] 0.10% ≤ Si ≤ 0.35%

[0012] The remainder consists of iron and unavoidable impurities produced during manufacturing.

[0013] Specific characteristics of the alloy according to the present invention:

[0014] - Carbon content, by weight, is between 0.040% and 0.075%;

[0015] -Unavoidable impurities resulting from manufacturing, by weight percentage, include:

[0016] Cr≤0.5%

[0017] Co ≤ 0.5%

[0018] S≤0.0035%

[0019] P≤0.01%

[0020] Mo < 0.5%

[0021] O≤0.0025%

[0022] Ca ≤ 0.0015%

[0023] Mg≤0.0035%

[0024] Al ≤ 0.0085%;

[0025] The alloy exhibits an average coefficient of thermal expansion α greater than or equal to 2.0 × 10⁻⁶ between -196°C and 0°C. -6 ℃ -1 And less than or equal to 3.0 × 10 -6 ℃ -1 This is especially true when the alloy is in the form of a hot-rolled product.

[0026] The present invention also relates to a cold strip made of the above-mentioned alloy.

[0027] The present invention also relates to a method for manufacturing a cold strip as described above, comprising the following sequential steps:

[0028] - Producing alloys as described above;

[0029] - A semi-finished product forming the alloy;

[0030] -Hot-roll the semi-finished product to obtain a tropical strip;

[0031] - Cold rolling one or more passes of the hot strip to obtain a cold strip.

[0032] The present invention also relates to the use of the alloy as defined above for manufacturing tanks or pipes intended to receive liquefied gases.

[0033] The present invention also relates to a filler wire made of the alloy as defined above.

[0034] The present invention also relates to a method for manufacturing a metal wire for producing the filled metal wire as defined above, the method comprising the following steps:

[0035] - Provide semi-finished products made of the alloys specified above;

[0036] - The semi-finished product is thermally converted to form an intermediate metal wire; and

[0037] - The intermediate metal wire is transformed into a filler metal wire with a diameter smaller than that of the intermediate metal wire. This transformation includes a drawing step.

[0038] The present invention also relates to a workpiece or part thereof made of the alloy as defined above, which is obtained by metal additive manufacturing.

[0039] The present invention also relates to a manufacturing method for manufacturing a workpiece or a portion thereof, comprising the step of manufacturing the workpiece or portion thereof by means of a metal additive manufacturing process using filler wires made of the alloys defined above and / or powders made of the alloys defined above as filler materials.

[0040] The present invention also relates to the use of the filler wire as defined above in a metal additive manufacturing process.

[0041] The present invention also relates to a metal powder made of the alloy as defined above.

[0042] The present invention also relates to a powder manufacturing method for producing the metal powder as defined above, the method comprising the steps of providing the filler metal wire as defined above, and plasma atomizing the filler metal wire to obtain the metal powder.

[0043] The present invention also relates to a pipe segment made of the alloy as defined above, wherein the pipe segment is preferably seamless.

[0044] Based on specific characteristic features, the pipe segment comprises a sheet bent into a pipe shape and made of an alloy as defined above, the sheet having longitudinal edges joined together by welds.

[0045] The present invention also relates to a pipe manufacturing method for manufacturing the pipe segment as defined above, comprising the following sequential steps:

[0046] -Provide a sheet material made of the alloy as defined above and having two longitudinal edges; and

[0047] - Weld the longitudinal edges of the sheets together to form a tube segment.

[0048] The invention also relates to a pipe comprising at least two pipe segments as defined above, wherein the two consecutive pipe segments are joined together by a weld.

[0049] The present invention also relates to a method for manufacturing a tube, comprising the following sequential steps:

[0050] - Provide a first pipe segment as defined above and a second pipe segment as defined above, the first pipe segment and the second pipe segment extending along a longitudinal axis;

[0051] - Position the first pipe segment and the second pipe segment such that the longitudinal end of the first pipe segment is arranged to face the longitudinal end of the second pipe segment along the longitudinal axis of the first and second pipe segments; and

[0052] - Weld the two facing longitudinal ends of the first and second pipe sections together.

[0053] The present invention also relates to a tank portion comprising at least one part made of the alloy as defined above. The tank portion is intended for transporting or storing liquefied gases, particularly liquid hydrogen.

[0054] The present invention also relates to a tropical material made of the alloy described above.

[0055] The present invention also relates to a method for manufacturing a tropical strip as described above, comprising the following sequential steps:

[0056] - Produce alloys as specified above;

[0057] - A semi-finished product forming the alloy;

[0058] -Hot rolling the semi-finished product to obtain a hot strip. Attached Figure Description

[0059] The invention will be better understood by reading the following description, which is provided by way of example only and with reference to the accompanying drawings, in which:

[0060] Figure 1 This is a schematic perspective view of a pipe segment according to a first embodiment of the present invention;

[0061] Figure 2 This is a schematic perspective view of a pipe segment according to a second embodiment of the present invention;

[0062] Figure 3 This is a schematic top view of the sheet material used during the implementation of the method for manufacturing the pipe segment according to the second embodiment;

[0063] Figure 4This is a schematic perspective view of a tube according to the present invention; and

[0064] Figure 5 This is a schematic perspective view of a workpiece obtained by additive manufacturing process according to the present invention. Detailed Implementation

[0065] Throughout the instruction manual, the content is given as a percentage by mass.

[0066] The alloy according to the present invention is an iron-based alloy, comprising, by weight percentage:

[0067] 36.5% ≤ Ni ≤ 38.5%

[0068] 0.50% ≤ Mn ≤ 1.25%

[0069] 0.001% ≤ Cu ≤ 0.85%

[0070] 0.040% ≤ C ≤ 0.150%

[0071] 0.10% ≤ Si ≤ 0.35%

[0072] The remainder consists of iron and unavoidable impurities produced during manufacturing.

[0073] The term 'unavoidable impurities resulting from manufacturing' is used to refer to elements present in the raw materials used to produce the alloy or from the equipment used to produce the alloy (e.g., refractory materials from a furnace). These impurities have no metallurgical effect on the alloy.

[0074] Impurities arising from manufacturing, by weight percentage, particularly include:

[0075] Cr≤0.5%

[0076] Co ≤ 0.5%

[0077] S≤0.0035%

[0078] P≤0.01%

[0079] Mo < 0.5%

[0080] O≤0.0025%

[0081] Ca ≤ 0.0015%

[0082] Mg≤0.0035%

[0083] Al ≤ 0.0085%.

[0084] The alloys according to the invention exhibit an average coefficient of thermal expansion α greater than or equal to 2.0 × 10⁻⁶, particularly between -196°C and 0°C. -6 ℃-1 And less than or equal to 3.0 × 10 -6 ℃ -1 .

[0085] In the alloy according to the invention, the content levels of Ni, Mn, C and Cu (i.e., Ni ≥ 36.5%, Mn ≥ 0.50%, C ≥ 0.040%, Cu ≥ 0.001%) enhance the alloy's stability against martensitic transformation at -253°C (20K) (i.e. at the temperature of liquid hydrogen), thereby providing the alloy with the ability to maintain its austenitic structure in the event of minor mechanical accidents (impact, breakage, bending, etc.) occurring at the temperature of liquid hydrogen.

[0086] The inventors of this invention have noted that if the content levels of Ni, Mn, C, and Cu are below the aforementioned lower limits, the alloy has an increased risk of hydrogen embrittlement in the event of minor mechanical accidents (impact, breakage, bending, etc.) occurring at the temperature of liquid hydrogen, characterized by low elongation at break A (A≤10%) and excessively low shrinkage Z (Z%≤50%).

[0087] Elongation at break (A) is determined according to standard ASTM A370, July 2019.

[0088] Shrinkage rate Z was determined according to French standard NF EN ISO 6892-1, December 2019.

[0089] Furthermore, the upper limits selected for Ni, Mn, and Cu (i.e., Ni ≤ 38.5%, Mn ≤ 1.25%, Cu ≤ 0.85%) can keep the average coefficient of thermal expansion α between -196℃ and 0℃ less than or equal to 3.0 × 10⁻⁶. -6 ℃ -1 This allows the thermal stress to be limited to a critical value evaluated at 110 MPa. This critical stress is equal to approximately 15% of the alloy's yield strength at temperatures in liquid hydrogen (Rp(-253℃)~800 MPa).

[0090] The inventors of this invention discovered that if the content levels of Ni, Mn, and Cu are higher than the aforementioned upper limit, the average coefficient of thermal expansion α between -196°C and 0°C has a value greater than 3.0 × 10⁻⁶. -6 ℃ -1 The value is therefore too high for the intended application.

[0091] Furthermore, when the carbon content exceeds 0.150%, the alloy loses its weldability during tungsten inert gas (TIG) welding without filler wire through the formation of pores. In fact, the presence of carbon levels above 0.150% during TIG welding operations without filler wire generates foam. In this case, the weldability of the alloy decreases.

[0092] Preferably, the carbon content is between 0.040% and 0.075% by weight. In this case, the weldability of the alloy is further enhanced.

[0093] Preferably, the Mn content is greater than or equal to 0.7% by weight. Such a manganese content level further enhances the alloy's stability against martensitic transformation at -253°C (20K).

[0094] In the alloy according to the invention, the silicon content is between 0.10% and 0.35% by weight. This level of silicon content is used to achieve deoxidation of the alloy. At content levels greater than 0.35% by weight, there is a risk of excessively high thermal expansion between -196°C and 0°C when adjusting the content levels of Ni, Mn, and Cu according to the invention.

[0095] The alloys according to the invention can be produced by any suitable method known to those skilled in the art. For example, it is produced in an electric arc furnace or induction furnace, and then refined in a ladle by conventional methods, particularly including a vacuum oxygen decarburization or VOD type ladle refining step, followed by an ASV type hot ladle metallurgical step. As a variation, the alloys according to the invention are produced in a vacuum induction furnace from low-residue feedstock.

[0096] The production method used to produce the alloy is provided by way of example only. All other methods known to those skilled in the art for producing alloys can be used for this purpose.

[0097] The invention also relates to a cold strip having the composition defined above. The thickness of the cold strip is particularly between 0.5 and 10 mm. In cases where the cold strip is intended for use in the manufacture of cryogenic tubes, the thickness is advantageously between 2 mm and 10 mm. In cases where the cold strip is intended for use in the manufacture of transport / storage tanks for transporting or storing liquefied gases, the thickness is advantageously between 0.5 mm and 2 mm.

[0098] For example, the following method is used to manufacture this type of cold strip.

[0099] The alloys described above are cast into semi-finished products, such as ingots, remelted electrodes, slabs (especially thin slabs with a thickness of less than 180 mm) or billets.

[0100] When the alloy is cast into the form of a remelted electrode, the latter is advantageously remelted under vacuum or by a conductive slag remelting process to obtain a semi-finished product with higher purity and more uniformity.

[0101] The semi-finished product obtained by direct casting is then hot-rolled at a temperature between 950°C and 1300°C to obtain a hot strip.

[0102] The thickness in tropical regions is particularly between 2mm and 20mm, and more specifically between 2mm and 10mm.

[0103] When the manufactured metal sheet is intended for use in liquefied gas transport or storage tanks, the final thickness after hot rolling is, for example, approximately 3.5 mm.

[0104] According to one embodiment, prior to hot rolling, the semi-finished product undergoes a chemical homogenization heat treatment process at a temperature between 950°C and 1300°C for a duration between 30 minutes and 24 hours.

[0105] The tropical material is cooled to ambient temperature to form a cooling strip, which is then wound into a coil.

[0106] The cooled strip is then cold-rolled to obtain a final thickness advantageously between 0.5 mm and 10 mm. The cold rolling process can be performed once or multiple times consecutively.

[0107] When the manufactured metal sheet is intended for use in cryogenic tubes, the final thickness after cold rolling is advantageously between 2 mm and 10 mm.

[0108] When the manufactured metal sheet is intended for use in liquefied gas transport or storage tanks, the final thickness after cold rolling is advantageously between 0.5 mm and 2 mm.

[0109] Optionally, the hot strips can be chemically pickled and then shot peened to remove any scrap before cold rolling.

[0110] Optionally, the pickled and shot-peened sheets are polished to remove oxide penetration at the grain boundaries before cold rolling, with a desired roughness Ra of less than 50 μm according to standard ISO 4287.

[0111] At the final thickness, the cold strip can optionally undergo a recrystallization heat treatment process in a static furnace at temperatures exceeding 700°C for 10 minutes to several hours. As a variation, it can be subjected to a recrystallization heat treatment process in a continuous annealing furnace at temperatures exceeding 800°C in the furnace holding zone and in a protective atmosphere of N2 / H2 type (30% / 70%) with frosting temperatures between -50°C and -15°C for several seconds to approximately 1 minute. The frosting temperature defines the partial pressure of water vapor contained in the heat treatment atmosphere. This treatment process is particularly performed after the pickling, shot peening, and polishing steps described above.

[0112] During cold rolling, at an intermediate thickness between the initial thickness (corresponding to the thickness of the hot strip) and the final thickness, a recrystallization heat treatment process can optionally be performed under the same conditions as the recrystallization heat treatment process described above. For example, when the final thickness of the cold strip is 1.0 mm, the intermediate thickness is selected to be equal to 1.5 mm.

[0113] The method for manufacturing cold-rolled strips made of this alloy is described by way of example only. Any other methods known to those skilled in the art for manufacturing cold-rolled strips may be used for this purpose.

[0114] The present invention also relates to cryogenic pipe sections made of the aforementioned alloys. These pipe sections are particularly suitable for transporting liquefied gases, especially liquid hydrogen.

[0115] According to the first embodiment, pipe segment 1 is in Figure 1 As shown in the figure. This pipe segment 1 does not include longitudinal welds. Therefore, it is a pipe segment without welds. This pipe segment 1 is obtained, for example, by extruding a billet made of the alloy described above.

[0116] According to the second embodiment, pipe segment 7 is in Figure 2 As shown in the figure. The pipe section 7 comprises a sheet 9 made of the alloy described above and bent into a tube shape, the longitudinal edges 12 of which are joined together by welds 15. The wall thickness of the pipe section 7 is, for example, between 2 mm and 10 mm.

[0117] The weld is specifically obtained by gas welding, that is, by using filler wire made of the aforementioned alloy.

[0118] As a variation, a filler wire with a different composition than those described above is used. The composition of the filler wire is selected based on the desired properties, specifically to obtain a coefficient of thermal expansion α between -196℃ and 0℃ that is less than or equal to 5.5 × 10⁻⁶. -6 ℃ -1 Furthermore, the welding process yields mechanical properties superior to those of metal sheets.

[0119] The present invention also relates to a pipe manufacturing method for manufacturing such pipe segment 7.

[0120] The method includes providing a sheet 9 made of the alloy described above. Such a sheet 9... Figure 3 As shown in the figure. It extends along the longitudinal direction L and has a longitudinal edge 12 that is substantially parallel to the longitudinal direction L. Its thickness is, for example, between 2 mm and 10 mm.

[0121] The method also includes the step of bending the sheet 9 so that the two longitudinal edges 12 face each other, followed by the step of welding the two longitudinal edges 12 together by using a suitable filler wire, and in particular a filler wire made of the alloy described above.

[0122] The weld obtained during this step is a longitudinal weld. Preferably, it is a butt weld.

[0123] At the end of the process, pipe segment 7 is obtained, such as Figure 2As shown, sheet 9 is bent into the shape of a tube, and the longitudinal edges 12 of sheet 9 are joined together by weld 15.

[0124] The present invention also relates to a cryogenic tube 20 manufactured by assembling cryogenic tube sections 1 and 7 according to the invention. Tube 20 is particularly used for transporting liquefied gases, especially liquid hydrogen.

[0125] For example, the cryogenic pipe 20 includes at least two pipe segments 1 and 7 as described above, which are joined to each other by a weld 22. The weld 22 extends along the circumference of the pipe 20 to join the pipe segments 1 and 7 to each other.

[0126] Weld 22 is specifically obtained by gas welding, that is, by using a filler wire having the above composition.

[0127] Welds, especially butt welds, are preferred to be rail welds. The term 'rail weld' is used to refer to welds produced by rotating the welding tool (i.e., in particular the welding torch) around the pipe segments 1 and 7 to be welded.

[0128] The wall thickness of the cryogenic tube 20 is, for example, between 2 mm and 10 mm.

[0129] exist Figure 4 The above reference is shown in the diagram. Figure 2 The cryogenic tube 20 obtained according to the tube segment 7 of the second embodiment.

[0130] As a variant, tube 20 is assembled according to the above reference. Figure 1 The pipe segment 1 obtained according to the first embodiment.

[0131] The present invention also relates to a method for manufacturing the cryogenic tube 20 as described above.

[0132] In this process, at least two pipe segments 1 and 7 are provided. Each pipe segment 1 and 7 is generally cylindrical with an axis M and has two longitudinal ends 24 spaced apart along the direction of the axis M.

[0133] Then, the two pipe segments 1 and 7 are positioned such that their longitudinal ends 24 are arranged to face each other in the direction of the axis M of these pipe segments 1 and 7; thereafter, the facing longitudinal ends 24 of the two pipe segments 1 and 7 are welded together using filler wire (in particular, wire made of the alloy described above).

[0134] Advantageously, during this step, a butt weld is formed between the facing longitudinal ends 24 of pipe segments 1 and 7. The weld is preferably a track weld.

[0135] Preferably, the welding step includes a process of chamfering the ends 24 of the pipe segments 1 and 7 to be welded together before joining them together.

[0136] Repeat the welding steps, the number of times equal to the number of pipe segments 1 and 7 to be welded together to form pipe 20 minus 1.

[0137] According to one embodiment, the pipe segment is pipe segment 1 according to the first embodiment described above. As a variation, the pipe segment is pipe segment 7 according to the second embodiment described above.

[0138] At the end of the one or more welding steps, a cryogenic tube 20 is obtained. The cryogenic tube 20 comprises at least two consecutive tube segments 1 and 7 assembled to each other by a weld 22.

[0139] The present invention also relates to a portion of a tank made of the aforementioned alloy for transporting or storing liquefied gases.

[0140] The present invention also relates to a filler wire made of the above-described alloy.

[0141] This filler wire is particularly intended for use in additive manufacturing processes, or as a filler wire for welding two workpieces or workpiece parts together, the workpieces or workpiece parts being made, for example, of the alloy described above.

[0142] This type of filler wire is produced in particular by implementing the following method.

[0143] The method includes: in a first step, providing a semi-finished product made of the aforementioned alloy.

[0144] Therefore, the alloy produced according to the above method is cast into ingots or directly cast into billets, particularly by continuous casting, especially rotary casting. Thus, the semi-finished product obtained at the end of this step is advantageously an ingot or billet, and has a diameter, for example, between 130 mm and 230 mm, and more particularly equal to about 150 mm.

[0145] Subsequently, the semi-finished product is transformed through thermal conversion to form an intermediate metal wire.

[0146] Specifically, during this thermal conversion step, the semi-finished product (that is, in particular ingots or billets) is heated to a temperature between 1150°C and 1250°C.

[0147] They are then subjected to a hot roughing process, followed by a hot rolling process, particularly on a wire rod mill, at a temperature between 950°C and 1150°C, and then a hyper-quenching process at the mill exit. The intermediate wire can be, in particular, a wire rod. For example, its diameter is between 5 mm and 21 mm, particularly approximately 5.5 mm.

[0148] Superquenching, in particular, is superquenching in a 20°C bath following a heat treatment process in a gas furnace at temperatures between 1050°C and 1150°C for a duration between 20 and 120 minutes.

[0149] The central metal wire is then peeled off and wound into a roll.

[0150] Optionally, the intermediate metal wire or wire rod thus obtained is drawn using a drawing device of a known type to obtain a filler wire. This filler wire has a smaller diameter than the initial metal wire. Specifically, its diameter is between 0.5 mm and 3.5 mm. Advantageously, it is between 0.8 mm and 2.4 mm.

[0151] Depending on the desired final diameter, the drawing process includes one or more drawing passes, preferably with an annealing process between two consecutive drawing passes. This annealing is, for example, performed during the drawing process at a temperature of around 1150°C in a reducing atmosphere.

[0152] After the drawing step, it is preferable to clean the surface of the drawn wire, and then to wind the wire.

[0153] The drawing pass is a cold drawing pass.

[0154] Specifically, for the manufacture of filler wire with a diameter of approximately 1.6 mm, two drawing passes are used, with the second drawing pass producing a final diameter of approximately 1.6 mm.

[0155] For the manufacture of filler wire with a diameter of approximately 1.2 mm, for example, three drawing passes are used, where the second drawing pass produces a diameter of approximately 1.6 mm and the third drawing pass produces a final diameter of 1.2 mm.

[0156] The method for manufacturing a filler wire is described by way of example only. All other suitable methods known to those skilled in the art for manufacturing filler wires can be used for this purpose.

[0157] The present invention also relates to a metal powder for additive manufacturing produced from the alloy described above, wherein the screened metal powder has an advantageous particle size between 10 μm and 200 μm.

[0158] For example, this powder is produced by plasma atomization of a metal wire made of the alloy described above, which specifically has a diameter of approximately 3 mm.

[0159] Specifically, the powder particle size was determined using the following measurement method. Powder batches were separated into multiple powder size distributions using an ultrasonically vibrating stainless steel sieve. The powder size distributions obtained after the sieving process were analyzed according to standard ASTM B214-07. Sieving yielded five size grades: <20μm - 20μm to 45μm - 45μm to 75μm - 75μm to 105μm -> 105μm.

[0160] The plasma atomization process itself is known, so it will not be described in detail.

[0161] The filler wire is also intended to be used as a filler wire, for example, in metal additive manufacturing processes.

[0162] Additive manufacturing processes, for example, use electric arcs, laser beams, and / or electron beams as energy sources to cause the melting of filler wires.

[0163] In particular, additive manufacturing is a directional energy deposition additive manufacturing process. During this process, the filler material is deposited, specifically by means of a nozzle, and is immediately melted by concentrated thermal energy, particularly by a laser beam, electron beam, and / or electric arc.

[0164] For example, additive manufacturing processes are based on wire-arc (in recognized terms, "wire-arc additive manufacturing" or "WAAM"), wire-laser, wire-electron beam (in recognized terms, "electron beam freeform manufacturing" or "electron beam additive manufacturing"), or hybrid additive manufacturing processes that combine wire-arc and powder-laser or combine wire-arc and wire-laser technologies.

[0165] In these processes, the metal wire used is the filled metal wire as described above.

[0166] In the case of hybrid wire-arc and powder-laser processes, the powder used has the same composition as the wire.

[0167] The present invention also relates to a method for manufacturing alloys as described above. Figure 5 A method for manufacturing a workpiece 40 or a portion thereof, schematically shown in the figure, comprising:

[0168] - Provide filler wire made of this alloy; and

[0169] - To manufacture workpiece 40 or workpiece portion using filler wire made of the alloy as described above and / or powder made of the alloy as described above as filler material by means of metal additive manufacturing process.

[0170] Additive manufacturing processes, for example, use electric arcs, laser beams, and / or electron beams as energy sources to cause the melting of filler materials.

[0171] Specifically, additive manufacturing is a “directional energy deposition” additive manufacturing process. During this process, filler material is deposited, particularly through a nozzle, and immediately melted by concentrated thermal energy, particularly by means of a laser beam, electron beam, and / or electric arc.

[0172] For example, additive manufacturing processes are based on wire-arc (in recognized terms, "wire-arc additive manufacturing" or "WAAM"), wire-laser, wire-electron beam (in recognized terms, "electron beam freeform manufacturing" or "electron beam additive manufacturing"), or hybrid additive manufacturing processes that combine wire-arc and powder-laser or combine wire-arc and wire-laser technologies.

[0173] In the case of using a hybrid additive manufacturing process that combines wire-arc and powder laser or wire-arc and wire-laser technologies, the powder and filler wire are made of alloys as described above.

[0174] The additive manufacturing process described above is known and therefore will not be described in detail here.

[0175] The present invention also relates to a workpiece 40 or a portion thereof made of an alloy as described above, obtained by a metal additive manufacturing process.

[0176] This metal additive manufacturing process specifically uses filler wires made of alloys as described above and / or powders made of alloys as described above as filler materials.

[0177] The workpiece or part of a workpiece (e.g., workpiece 40) obtained by a metal additive manufacturing process is a solidified workpiece. Therefore, it has the typical solidification microstructure of the alloy under consideration, which typically includes columnar dendrites that grow epitaxially on top of each other, and the orientation of the columnar dendrites depends on the width and height of the resulting metal walls. Furthermore, the workpiece obtained by the additive manufacturing process has a series of superimposed solidified layers due to its additive manufacturing process. Each layer obtained by the solidification of deposited molten metal droplets causes the surface of the previous layer to remelt to create metallurgical continuity, and thus reheats the remainder of the lower layer. The further the layer in question is from the region of melting and solidification, the lower the reheating temperature. This particular microstructure can be observed through metallographic observation on a metallographic cross-section of the workpiece.

[0178] Therefore, the workpiece 40 or part of the workpiece obtained by the metal additive manufacturing process can be distinguished from the workpiece obtained by other processes, especially from the workpiece obtained by conventional metallurgy that produces a uniform grain recrystallized structure.

[0179] Workpiece 40 or workpiece part, especially special workpieces or workpiece parts, such as valves, pipe connectors or some other workpieces, which are particularly used in cryogenic applications and more specifically in the temperature of liquid hydrogen, such as in the transportation and storage of liquid hydrogen.

[0180] As an example, part 40 is a tubular connector intended to be used as a connector between multiple coaxial tubes, particularly, for example, between double-walled and single-walled tubes in a pipeline. Such a connector is known by accepted terminology as a "blind end." Blind ends are well-known components in the piping industry.

[0181] test

[0182] The alloys used in tests numbered 1 to 22 were produced under vacuum and cast into small ingots weighing approximately 2 kg. These ingots were machined into strips measuring 35 mm on each side and 100 mm in height. These strips were then reheated to 1220°C under argon atmosphere for 8 hours, and subsequently hot-rolled at approximately 1150°C to obtain sheet strips measuring 750 mm × 35 mm × 4 mm.

[0183] Table 1 below defines the chemical composition of the alloying elements in the obtained sheet strips by weight (%). The approximate mass content of impurities in the sheet strips produced by the manufacturing process is shown in Table 2 below.

[0184]

[0185]

[0186] Table 1: Composition of Sheet Strips (by weight %) In Table 1 above, items not based on embodiments of the present invention are underlined.

[0187] S P Al Mg Ca Cr Co O Mo 0.0003 0.0080 0.0050 0.0015 0.0004 <0.5 <0.5 <0.0025 <0.5

[0188] Table 2: Approximate mass content levels (by weight) of impurities in sheet strips caused by the manufacturing process

[0189] Then, cylindrical expansion test specimens (one of each composition) with a measuring diameter of 3 mm and a length of 50 mm and prismatic planar tensile test specimens (two of each composition, according to standard ASTM A370, July 2019) with a measuring diameter of 3 mm and a length of 50 mm are processed from the sheet strips to form test specimens for hydrogen embrittlement sensitivity studies and thermal expansion measurements.

[0190] In the initial stage, the tensile specimens were heat-treated at 1100°C with 99.999% pure hydrogen for 4 hours, followed by rapid cooling in the cold zone of the furnace. The cooling time was approximately 45 seconds. The purpose of this heat treatment was to load the specimens with atomic hydrogen (H).

[0191] In the subsequent stage, the tensile specimen (loaded with hydrogen) was subjected to two different temperatures at 5 × 10⁻⁶ ℃. -3 s -1 Deformation rate pre-strain:

[0192] - Sample A was pre-strained by 10% at the temperature of liquid helium (-268°C). The purpose of pre-straining at -268°C was to ensure the stability of the alloy and to generate more or less martensite under thermal conditions more severe than liquid hydrogen (-253°C).

[0193] - Specimen B, pre-strained at ambient temperature (20°C) with a strain of 10%. The purpose of the 10% pre-strain at ambient temperature is to provide a reference specimen free of martensite, but the reference specimen has the same strain rate as at -268°C and may contain martensite. These specimens will provide a non-brittle reference state.

[0194] Finally, samples A and B were subjected to a temperature of -50℃ (+ / -5℃) at 5×10⁻⁶. -5 s -1 A planar tensile strain test is performed at a slow strain rate until fracture. This test, conducted in this manner, is known as the "slow tension and fracture at -50°C" test. The time between hydrogen loading and the slow tension test at -50°C must never exceed 48 hours.

[0195] The hydrogen sensitivity of specimens subjected to slow tensile and fracture tests at -50°C was assessed by measuring the total elongation at break, A%, and the shrinkage, Z%, = (S0 - S) / S0 (measured using a 25x optical microscope). S0 and S are the initial cross-section before pre-strain and the final cross-section with the narrowest diameter, respectively. These measurements are shown in the “A%” and “Z%” columns for specimens A and B in Table 3 below.

[0196] Furthermore, the expansion ΔL of the alloy was measured when cooled between 0°C and -196°C (liquid nitrogen temperature), and the average coefficient of thermal expansion α[-196°C_0°C] between -196°C and 0°C was calculated according to the following expression: α[-196°C_0°C]=1 / L0×ΔL / ΔT, where ΔT=0-(-196), and L0 is the initial length of the sample (50mm). The results of these measurements and calculations are shown in column “α” of Table 3 below.

[0197] The results are shown in Table 3 below.

[0198]

[0199]

[0200] Table 3: Experimental Results

[0201] In Table 3 above, items not based on embodiments of the present invention are underlined.

[0202] For compositions numbered 3 to 7, the reference for tensile testing is specimen B corresponding to composition number 3. In fact, for this group of compositions, the ductility after "slow tension and fracture at -50°C" is considered composition-independent.

[0203] Similarly, for components numbered 8 to 13, the reference for tensile testing is specimen B corresponding to component number 8; for components numbered 14 to 17, the reference for tensile testing is specimen B corresponding to component number 14; and for components numbered 18 to 22, the reference for tensile testing is specimen B corresponding to component number 18.

[0204] In cases 1, 2, 3 and 8, where the content levels of Ni, Mn, C and / or Cu are below the lower limits of these elements described above, test specimen A exhibits hydrogen embrittlement, characterized by low elongation at break (A≤10%) and excessively low shrinkage (Z≤50%).

[0205] Reference specimen B, pre-strained at ambient temperature with 15% strain, exhibits normal ductility, with A% of ~18% and Z% of ~88%.

[0206] In experiments 7, 13, and 17, where the content levels of Ni, Mn, and / or Cu were higher than the upper limits described above for these elements, it was observed that the average coefficient of thermal expansion α between -196°C and 0°C exhibited a value greater than 3.0 × 10⁻⁶. -6 ℃ -1 The degradation value.

[0207] Test number 22 did not meet the requirements because the carbon content was too high (C > 0.150%). In this case, the inventors have noted that the alloy loses its weldability during TIG welding without filler wire through the formation of pores. In fact, the presence of carbon generates foam during TIG welding operations without filler wire.

[0208] In the cases of test numbers 4 to 6, 9 to 12, 14 to 16 and 18 to 21 according to the present invention, the average coefficient of thermal expansion α under low thermal expansion (between -196°C and 0°C) is greater than or equal to 2.0 × 10⁻⁶. -6 ℃ -1 And less than or equal to 3.0 × 10 -6 ℃ -1A satisfactory performance trade-off was achieved between resistance to hydrogen embrittlement (elongation at break A > 10% and shrinkage Z > 50%).

[0209] Therefore, these alloys exhibit good mechanical properties at temperatures of liquid hydrogen (-253°C), while having a low average coefficient of thermal expansion α between -196°C and 0°C.

[0210] Therefore, the alloys according to the invention are particularly suitable for applications using liquid hydrogen (-253°C), and especially for manufacturing components designed to contain hydrogen, particularly transport pipes or transport / storage tanks for transporting or storing liquid hydrogen. Needless to say, these alloys can also be used in cryogenic applications with lower limitations than those concerning liquid hydrogen, such as for transporting or storing liquefied gases with boiling points higher than liquid hydrogen.

Claims

1. An iron-nickel alloy having the following composition by weight 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% The remainder consists of iron and unavoidable impurities produced during manufacturing. The alloy exhibits an average coefficient of thermal expansion α greater than or equal to 2.0 × 10⁻⁶ between -196°C and 0°C. -6 ℃ -1 And less than or equal to 3.0 × 10 -6 ℃ -1 .

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

3. The alloy according to claim 1 or 2, wherein, by weight percentage, unavoidable impurities resulting from manufacturing comprise: 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%。 4. A cold strip made of the alloy according to claim 1 or 2.

5. A method for manufacturing the cold strip according to claim 4, comprising the following sequential steps: - To manufacture the alloy according to claim 1 or 2; - A semi-finished product forming the alloy; - The semi-finished product is hot-rolled to obtain a hot strip; - The tropical strip is cold rolled in one or more passes to obtain a cold strip.

6. Use of an alloy according to claim 1 or 2 for manufacturing a tank or pipe intended to receive liquefied gas.

7. A filler wire made of an alloy according to claim 1 or 2.

8. A method for manufacturing the filled metal wire according to claim 7, the method comprising the following steps: - Provide a semi-finished product made of the alloy according to claim 1 or 2; - The semi-finished product is thermally transformed to form an intermediate metal wire; as well as - The intermediate metal wire is transformed into a filler metal wire with a diameter smaller than that of the intermediate metal wire, the transformation including a drawing step.

9. A workpiece (40) or a portion thereof made of an alloy according to claim 1 or 2, said workpiece (40) or a portion thereof being obtained by metal additive manufacturing.

10. A method for manufacturing a workpiece (40) or a portion thereof, comprising the step of manufacturing the workpiece (40) or a portion thereof by means of a metal additive manufacturing process using filler wires made of an alloy according to claim 1 or 2 and / or powder made of an alloy according to claim 1 or 2 as filler materials.

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

12. A metal powder made from the alloy according to claim 1 or 2.

13. A method for manufacturing the metal powder according to claim 12, the method comprising the steps of providing a filler wire according to claim 7, and plasma atomizing the filler wire to obtain the metal powder.

14. A pipe section (1; 7) made of the alloy according to claim 1 or 2.

15. The pipe segment (7) according to claim 14, comprising a sheet (9) bent into the shape of a pipe and made of an alloy according to claim 1 or 2, the sheet (9) having longitudinal edges (12) joined together by a weld (15).

16. A method for manufacturing a pipe segment (7) according to claim 15, comprising the following sequential steps: - Provide a sheet (9) made of the alloy according to claim 1 or 2 and having two longitudinal edges (12); and - Weld the longitudinal edges (12) of the sheet (9) together to form the tube segment (7).

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

18. A method for manufacturing a tube (20), comprising the following sequential steps: - Provides a first pipe segment (1; 7) and a second pipe segment (1; 7), the first pipe segment being the pipe segment according to claim 14, the second pipe segment (1; 7) being the pipe segment according to claim 14, the first pipe segment (1; 7) and the second pipe segment (1; 7) extending along a longitudinal axis (M), - Position the first pipe segment and the second pipe segment (1; 7) such that the longitudinal end (24) of the first pipe segment (1; 7) is arranged to face the longitudinal end (24) of the second pipe segment (1; 7) along the longitudinal axis (M) of the first pipe segment and the second pipe segment (1; 7); and - Weld the two facing longitudinal ends (24) of the first pipe segment and the second pipe segment (1; 7) together.

19. A can portion comprising at least one portion made of an alloy according to claim 1 or 2.

20. A tropical material made of an alloy according to claim 1 or 2.

21. A method for manufacturing a tropical fruit according to claim 20, comprising the following sequential steps: - To produce the alloy according to claim 1 or 2; - A semi-finished product forming the alloy; - The semi-finished product is hot-rolled to obtain a hot strip.

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