Metal parts with low thermal expansion coefficient and high mechanical strength

Abstract

The present invention relates to metal parts intended for the manufacture of rubber articles such as tires for wheels, caterpillar tracks, conveyor or power transmission belts, and the manufacture of such parts, based on iron, in particular Fe-Ni alloys, which have a low isobaric thermal expansion coefficient at temperatures up to about 200° C. The commonly used term is coefficient of thermal expansion (CTE).

Description

[Technical Field]

[0001] The present invention relates to metal parts intended for the manufacture of rubber articles such as tires for wheels, caterpillar tracks, conveyor or power transmission belts, and the manufacture of such parts, based on iron, in particular Fe-Ni alloys, which have a low isobaric coefficient of thermal expansion at temperatures up to about 200° C. The commonly used term is coefficient of thermal expansion (CTE). [Background technology]

[0002] Pneumatic or non-pneumatic tires, rubber track tracks, wheels for vehicles, i.e., wheels with a moving function, and / or metal parts used in the manufacture of pneumatic or non-pneumatic tires, rubber track tracks, or parts of such wheels must meet numerous requirements, in particular good mechanical strength to avoid deformation during use and thus ensure an acceptable service life, and the lowest possible thermal expansion to control the geometry of the rubber object formed. It should be noted that the term "pneumatic tire" refers to a tire that can support a load, e.g., a vehicle, using pressurized gas. The term "non-pneumatic tire" refers to a tire that can support a load, e.g., a vehicle, using something other than pressurized gas, for example, using a shroud. For example, a sector-type curing or vulcanizing mold for a vehicle wheel tire mainly comprises two shells, each for molding one of the tire's sidewalls, and a number of sectors for molding the tire's tread, which are radially movable between an open and a closed mold position. The shells and sectors define an interior space intended to come into contact with the unvulcanized tire blank. To form the tread pattern, strips are attached to the mold sectors and protrude into this interior space. For further details of molds with such strips, reference can be made, for example, to EP 1 758 743 and US 2002 / 0139164.

[0003] These elements must not only have sufficient mechanical strength to withstand the stresses associated with forming the molding materials without breaking during use, but also must be as resistant to deformation as possible during the temperature cycles associated with curing (or crosslinking) these materials. A major advantage of manufacturing by selective fusion of overlapping powder layers, more commonly known as "powder bed fusion," is that the technique is well suited to producing small, complex-shaped components that are difficult to manufacture by other processes, such as mold trim strips. When selective melting is performed using a laser beam, the process is called sintering if the powder grains are partially fused, or laser melting. The laser melting technique consists of producing a strip layer by layer by stacking powder layers one on top of the other, consolidated and fused by the laser beam along the stacking direction. The term "powder" refers to powders or mixtures of powders, mainly metallic but also mineral, for example ceramic.

[0004] The first layer is deposited on a production plate and then fused directly to it, after which other layers are successively formed to obtain a laminate from the first layer. Typically, the production of small elements, such as trim strips, is performed horizontally on the production plate, with their length substantially parallel to the production plate. This is called horizontal production. This avoids excessive strip height, thereby reducing production time. Such elements must have good fracture and / or fatigue strength properties to ensure a long service life, and therefore the alloys used in such production are important. Fe—Ni alloys, generally of the 64Fe-36Ni type of composition, which have a low coefficient of thermal expansion at temperatures up to about 200° C., are already known in the art. They are commonly sold under the name INVAR® 36. However, it would be advantageous to improve the mechanical strength and hardness of such alloys while at the same time keeping the coefficient of thermal expansion (CTE) as low as possible, so that they can be used by additive manufacturing.

[0005] It is already a known procedure to improve the mechanical strength of INVAR® 36 by strengthening the alloy through the precipitation of multiple carbides and by severe deformation, especially at low temperatures. This corresponds therefore to patent application WO 03 / 025239, which proposes the production of reinforced and highly cold-deformed wires with Ti, Nb, V, Mo, Hf and Ta carbides. In this way, the authors have achieved a 3.7 × 10 -6 Tensile strengths Rm of up to 1300 MPa are obtained for CTEs of 0.1 / °C. However, the alloys thus obtained cannot be used by additive manufacturing because their carbon content is too high and therefore the presence of carbides would hinder said manufacturing process.

[0006] This also applies to patent application RU2568541, which also proposes strengthening with carbides of Nb, Ti, V, Mo, W and Zr in large amounts. In this way, the authors report that after forging and heat treatment, the steel has a temperature of 7 × 10 -6 Tensile strengths Rm of up to 1900 MPa are obtained for CTEs of less than 1 / °C. However, the alloys thus obtained cannot be used by additive manufacturing due to the presence of cobalt in contents of less than 0.5% by weight, which must be removed from the powder for health and safety reasons. Nakama et al. (Metallogr. Microstruct. Anal. 2, 383-387 (2013)) also proposed strengthening by precipitation of V, Ti, Zr, Nb, or Ta carbides. The authors reported that after forging and heat treatment, the precipitation hardness was 2.5 × 10 -6 Tensile strengths Rm of up to 1010 MPa are obtained for CTEs of 0.1 / °C. However, the alloys thus obtained cannot be used by additive manufacturing because their carbon content is too high and therefore the presence of carbides would hinder said manufacturing process.

[0007] The inventors have surprisingly found that it is possible to improve the mechanical strength of machine components while simultaneously maintaining the lowest possible CTE, allowing them to be manufactured by additive manufacturing. Therefore, the inventors have found that to achieve such a result (the Rm-CTE compromise), it is necessary to adjust the Nb and Ni elements while simultaneously achieving hardening through the precipitation of the γ″ (gamma double prime) phase of the alloy. Specifically, fine intragranular precipitation is thus obtained, which disturbs magnetic order less than coarse precipitates and thus increases the CTE less. Furthermore, since it is not necessary to perform the melt at extremely high temperatures to achieve the desired hardening, it is possible to simplify the heat treatment after additive manufacturing. Furthermore, all additional Nb and Ni elements are found in the precipitates, without any residue in solid solution in austenite that would be detrimental to the CTE, and 36% of the Ni remains in substitution with austenite after precipitation of all possible γ″ (gamma double prime) phases, so as to be within the optimal CTE condition. Carbon is also added to the composition to form some NbC carbides and limit austenite grain growth during heat treatment, but the carbon content is limited so that it can be used by additive manufacturing. Summary of the Invention

[0008] The present invention comprises, in weight percentages of the total composition: - Nickel: 38.0-42.0, advantageously 39.0-42.0, - Niobium: 4.750-5.500, advantageously 5.000-5.500, Carbon: 0.010-0.100, advantageously 0.015-0.070, - Cobalt: not more than 0.400, advantageously not more than 0.100, - Chromium: 0.500 or less, - Silicon: 0.500 or less, - Manganese: 0.500 or less, - Iron: Remaining, and unavoidable impurities The present invention relates to a metal part for manufacturing a rubber article based on an iron-based alloy composition, comprising, advantageously consisting essentially of,

[0009] The present invention also provides a method for producing such a metal part, comprising the steps of: A) producing an iron-based alloy powder having the composition of the alloy composition on which the metal part according to the invention is based, comprising the steps of: a) mixing elemental materials or starting materials before alloying; b) melting the mixture obtained in step a), advantageously in a vacuum induction muffle furnace, c) gas atomization, advantageously with nitrogen, of the product obtained in step b) to obtain a powder; d) screening or sieving the powder obtained in step c) to obtain a desired particle size fraction; e) recovering the resulting powder The steps of: B1) subjecting the powder obtained in step A) to an additive manufacturing process, advantageously selected from the group consisting of selective laser melting in a powder bed (LBM), electron beam melting (EBM), laser melting with powder atomization, such as direct additive laser construction or direct metal deposition (DMD) and binder jetting in a powder bed (MBJ), or to a hot isostatic consolidation process, with the aim of obtaining a part; or B2) subjecting the powder obtained in step A) to a laser melting process with powder atomization, such as direct layer laser building or direct metal deposition (DMD), followed by forging the deposit formed from the molten powder; C) subjecting the part obtained in step B1) or B2) to at least one thermal and / or physical and / or chemical treatment, advantageously selected from the group consisting of a relaxation heat treatment, a hot isostatic pressing treatment if step B1) is not a hot isostatic pressing treatment, a solution treatment, an ageing treatment, a final treatment such as a surface modification treatment or the deposition of a coating for protection against corrosion and oxidation, and a mixture of these treatments, D) Recovering the parts thus obtained. The present invention relates to a method, comprising:

[0010] The present invention also provides a method for producing such a metal part, comprising the steps of: i. mixing elemental materials or starting materials before alloying; ii. Melting the mixture obtained in step i), advantageously in a vacuum induction muffle furnace; iii. An optional step of homogenizing the ingot obtained in step ii) by heat treatment; iv. converting the ingot obtained in step ii) or iii) by forging; v. Recovering the parts thus obtained; vi. Preferentially, subjecting the part obtained in step v) to at least one thermal and / or physical and / or chemical treatment, advantageously selected from the group consisting of a relaxation heat treatment, a hot isostatic compaction treatment, a solution treatment, an ageing treatment, a final treatment such as a surface modification treatment or the deposition of a coating for protection against corrosion and oxidation, and a mixture of these treatments. The present invention relates to a method, comprising:

[0011] The invention also relates to a metal part obtained via one of these methods and further to the use of a metal part according to the invention or obtained via a method according to the invention for manufacturing pneumatic or non-pneumatic tires, rubber track tracks, wheels for vehicles, i.e. with a locomotion function, and / or parts for pneumatic or non-pneumatic tires, rubber track tracks or such wheels. DETAILED DESCRIPTION OF THE INVENTION

[0012] definition In this specification, all percentages (%) given are mass percentages (%) unless otherwise specified. It should be understood that the expression "composition based on" means a composition comprising a mixture of the various constituents used and / or the products of their in situ reactions, some of which may and / or are intended to at least partially react with one another during the various stages of the preparation of the composition. In the more specific case of rubber compositions, the composition may thus be in a fully or partially crosslinked state, or in a non-crosslinked state. The carbon-containing compounds mentioned in the specification may be of fossil or bio-based origin. In the latter case, they may be partially or completely derived from biomass or may be obtained from renewable starting materials derived from biomass. This is particularly true for polymers, plasticizers, fillers, etc.

[0013] Metal parts Thus, the present invention provides a composition comprising, in weight percentage of the total composition: Nickel: 38.0-42.0, advantageously 39.0-42.0; Niobium: 4.750-5.500, advantageously 5.000-5.500; Carbon: 0.010-0.100, advantageously 0.015-0.070; Cobalt: 0.400 or less, advantageously 0.100 or less; Chromium: 0.500 or less, Silicon: 0.500 or less, Manganese: 0.500 or less, Iron: Remaining, and unavoidable impurities The present invention relates to a metal part for manufacturing a rubber article based on an iron-based alloy composition, comprising, advantageously consisting essentially of, in particular consisting of:

[0014] A metal part for producing a rubber article based on a particularly advantageous iron-based alloy composition according to the invention comprises, in mass percentages of the total composition: Nickel: 39.0~42.0, Niobium: 5.000~5.500, Carbon: 0.015~0.070, Cobalt: 0.050 or less, Chromium: 0.100 or less, Silicon: 0.500 or less, Manganese: 0.500 or less, Iron: Remaining, and unavoidable impurities comprising, advantageously consisting essentially of, in particular consisting of,

[0015] In the context of the present invention, the ranges "X to Y%" and "X to Y" are inclusive of the limits X and Y. The range "between X and Y" is exclusive of the limits X and Y.

[0016] In the context of the present invention, the measurement uncertainties shown are typical uncertainties. In particular, the content of unavoidable impurities, in particular those selected from nitrogen (N), oxygen (O), hydrogen (H), sulfur (S), phosphorus (P), aluminum (Al), titanium (Ti), vanadium (V), molybdenum (Mo), calcium (Ca), copper (Cu), magnesium (Mg), and mixtures thereof, is kept as low as possible. These impurities generally result essentially from the manufacturing process and the quality of the furnace loading. Advantageously, the alloy composition on which the metal part according to the invention is based contains not more than 1.00% by weight, preferably not more than 0.75% by weight, and even more advantageously not more than 0.50% by weight of unavoidable impurities relative to the total weight of the composition. Typically, the content of impurities in the alloy is measured with an absolute uncertainty of ±0.08%. In particular, the alloy composition on which the metal part according to the invention is based comprises, in mass percentages of the total composition: Nitrogen less than or equal to 0.030, advantageously less than or equal to 0.020, in particular less than or equal to 0.010, and / or oxygen less than 0.040, advantageously less than 0.035 Includes.

[0017] Limiting the nitrogen content makes it possible to limit the formation of nitrides in the alloy that can be detrimental to the CTE. Nitrogen content is measured with an absolute uncertainty of ±0.0012%. Limiting the oxygen content makes it possible to limit the formation of oxides that can be detrimental to the CTE and ductility of the alloy. While this level of oxygen content may seem surprising compared to conventional processes, fractionation of metals in powder form results in extremely high surface area / volume ratios, which tend to greatly increase the oxygen content of the alloy. This can be further increased if the powder manufacturing process is not well controlled. Oxygen content is measured with an absolute uncertainty of ±0.0019%.

[0018] Advantageously, the alloy composition on which the metal part according to the invention is based has a hydrogen content of less than or equal to 0.0050% by weight relative to the total weight. By limiting the hydrogen content, the brittleness of the alloy can be limited. The hydrogen content is measured with an absolute uncertainty of ±0.0005%. Advantageously, the alloy composition on which the metal part according to the invention is based has a sulfur content of less than or equal to 0.0150% by weight of the total composition, advantageously less than or equal to 0.0050% by weight of the total composition. Limiting the sulfur content makes it possible to limit the formation of low-melting-point phases, such as FeS, which are harmful to the alloy and wet grain joints. In particular, these phases have very low mechanical strength, and therefore their presence reduces the mechanical properties of the alloy. The sulfur content is measured with an absolute uncertainty of ±0.0001%.

[0019] Advantageously, the alloy composition on which the metal part according to the invention is based has a phosphorus content of less than or equal to 0.0150% by weight of the total composition, advantageously less than or equal to 0.0050% by weight of the total composition. Limiting the phosphorus content makes it possible to limit the formation of low-melting-point phases such as Fe3P, which accumulate at grain joints and are therefore detrimental to the alloy by reducing its resilience. The phosphorus content is measured with an absolute uncertainty of ±0.0001%. Advantageously, the aluminum content of the alloy composition on which the metal part according to the invention is based is less than or equal to 0.100% by mass of the total composition. Limiting the aluminum content makes it possible to limit the formation of any intermetallic phases between Ni and Al, such as γ' (gamma prime) phases, which leads to the formation of precipitates potentially larger than γ" (gamma double prime) precipitates and reduces the Ni content in the austenite, which consequently leads to an increase in the CTE. The aluminum content is measured with an absolute uncertainty of ±0.005%. Advantageously, the titanium content of the alloy composition on which the metal part according to the invention is based is less than or equal to 0.100% by mass of the total composition. Limiting the titanium content makes it possible to limit the formation of any intermetallic phases between Ni and Ti, such as γ' (gamma prime) or η (eta) phases, which leads to the formation of precipitates potentially larger than γ" (gamma double prime) precipitates and reduces the Ni content in the austenite, which consequently leads to an increase in the CTE. The titanium content is measured with an absolute uncertainty of ±0.005%.

[0020] Advantageously, the vanadium content of the alloy composition on which the metal part according to the invention is based is less than or equal to 0.100% by weight of the total composition. Limiting the vanadium content makes it possible to limit the formation of crude vanadium carbides, which have a detrimental effect on the CTE. The vanadium content is measured with an absolute uncertainty of ±0.007%. Advantageously, the molybdenum content of the alloy composition on which the metal part according to the invention is based is less than or equal to 0.020% by weight of the total composition. Limiting the molybdenum content makes it possible to limit the formation of coarse molybdenum carbides, which have a detrimental effect on the CTE. The molybdenum content is measured with an absolute uncertainty of ±0.003%. Advantageously, the alloy composition on which the metal part according to the invention is based has a calcium content of less than or equal to 0.015% by weight of the total composition. Limiting the calcium content makes it possible to limit the formation of inclusions harmful to the alloy. The calcium content is measured with an absolute uncertainty of ±0.005%.

[0021] Advantageously, the copper content of the alloy composition on which the metal part according to the invention is based is less than or equal to 0.010% by weight of the total composition. Limiting the copper content makes it possible to limit the formation of copper precipitates at grain junctions, which may be detrimental to the CTE and the mechanical properties of the alloy. The copper content is measured with an absolute uncertainty of ±0.002%. Advantageously, the magnesium content of the alloy composition on which the metal part according to the invention is based is less than or equal to 0.015% by mass of the total composition. Limiting the magnesium content makes it possible to limit the formation of inclusions harmful to the alloy. The magnesium content is measured with an absolute uncertainty of ±0.005%.

[0022] Preferably, the alloy composition on which the metal part according to the invention is based has a content of unavoidable impurities selected from nitrogen (N), oxygen (O), hydrogen (H), sulfur (S), phosphorus (P), aluminum (Al), titanium (Ti), vanadium (V), molybdenum (Mo), calcium (Ca), copper (Cu), magnesium (Mg) and mixtures thereof, which fulfills at least one, preferably at least two, more preferably at least three, and most preferably all of the following conditions: nitrogen≦0.030% by weight of the total composition, oxygen≦0.040% by weight of the total composition, hydrogen≦0.0050% by weight of the total composition, sulfur≦0.0150% by weight of the total composition, phosphorus≦0.0150% by weight of the total composition, aluminum≦0.100% by weight of the total composition, titanium≦0.100% by weight of the total composition, vanadium≦0.100% by weight of the total composition, molybdenum≦0.020% by weight of the total composition, calcium≦0.015% by weight of the total composition, copper≦0.010% by weight of the total composition, Magnesium≦0.015% by weight of the total composition.

[0023] Thus, the alloy composition on which the metal part according to the present invention is based contains nickel (Ni), expressed as a mass percentage content relative to the total mass of the composition, in the range of 38.0 to 42.0, preferably 39.0 to 42.0, and even more preferably 39.5 to 42.0. Specifically, nickel plays two roles in the alloy. First, it imparts its invar properties to the alloy, i.e., a low CTE up to about 200°C, and second, it contributes to hardening the alloy by forming γ″ (gamma double prime) or δ (delta) precipitates, both of which have a NiNb composition. A minimum nickel content of 38.0% is required for 36% Ni substitution to remain in austenite after precipitation of all possible γ″ (gamma double prime) phases, so as to be within the optimum CTE range. Ni contents greater than 42% are undesirable because excessive Ni substitutions may be present in the matrix, which is detrimental to the CTE. The nickel content is measured with an absolute uncertainty of ±0.3%.

[0024] The alloy composition on which the metal part according to the present invention is based also contains niobium (Nb), the content of which, in mass percentage relative to the total mass of the composition, is in the range of 4.750 to 5.500, advantageously 5.000 to 5.500, and even more advantageously 5.100 to 5.300. Specifically, niobium primarily allows the formation of micro-precipitates of the intergranular hardening phase γ″ (gamma double prime), which is highly compatible with additive manufacturing in that it does not cause cracking problems and does not significantly increase the CTE, making it highly compatible for the desired application. Niobium also allows the formation of small amounts of Nb carbide, which can hold the grains together during heat treatment, especially during melting. To obtain the desired strengthening, it is necessary to have a Nb content greater than 4.750. On the other hand, exceeding 5.500 is undesirable, as this would excessively deteriorate the CTE and lead to the precipitation of undesired phases. The niobium content is measured with an absolute uncertainty of ±0.005%.

[0025] The alloy composition on which the metal part according to the present invention is based also contains carbon (C), expressed as a mass percentage of the total mass of the composition, in the range of 0.010 to 0.100, preferably 0.015 to 0.070, and even more preferably 0.015 to 0.050. Specifically, carbon allows the precipitation of Nb carbides at high temperatures, which serves to block grain growth during heat treatment, especially during melting. To achieve high hardening and high yield strength, controlling grain growth is necessary. To be able to perform additive manufacturing, a carbon content of less than 0.100 is necessary. At this content, carbon is present in the precipitates and does not remain in solid solution in the austenite, which is detrimental to the CTE. The carbon content is measured with an absolute uncertainty of ±0.0015%.

[0026] The alloy composition on which the metal part according to the present invention is based has a cobalt (Co) content of 0.400% by weight or less, advantageously 0.100% by weight or less, and more advantageously 0.050% by weight or less, relative to the total weight of the composition. In particular, since cobalt presents HSE (health, safety, and environment) issues when handling powders for additive manufacturing, the cobalt content should be as low as possible. In an advantageous embodiment, the alloy composition on which the metal part is based contains cobalt only as an unavoidable impurity. The term "containing cobalt only as an unavoidable impurity" means that the cobalt content is as low as possible, preferably below a measurement tolerance. Therefore, the alloy composition on which the metal part according to the present invention is based can be said to be "cobalt-free." The cobalt content is measured with an absolute uncertainty of ±0.003%.

[0027] The chromium (Cr) content of the alloy composition on which the metal part according to the invention is based is less than or equal to 0.500% by weight relative to the total weight of the composition, preferably less than or equal to 0.100% by weight relative to the total weight of the composition. In particular, the chromium content should be as low as possible, since chromium can form carbides during heat treatment or become a solid substitute in austenite, which is detrimental to the CTE. The chromium content is measured with an absolute uncertainty of ±0.0015%. The alloy composition on which the metal part according to the invention is based has a silicon (Si) content of not more than 0.500% by weight relative to the total weight of the composition, preferably not more than 0.470% by weight relative to the total weight of the composition. In particular, the content of this element must be as low as possible, since silicon separates in liquids, leading to the formation of oxides or low-melting-point phases, which pose problems for use in additive manufacturing, such as cracks. The silicon content is measured with an absolute uncertainty of ±0.0063%.

[0028] The manganese (Mn) content of the alloy composition on which the metal part according to the invention is based is less than or equal to 0.500% by weight relative to the total weight of the composition, preferably less than or equal to 0.400% by weight relative to the total weight of the composition. In particular, the content of manganese should be as low as possible, since this element can induce the formation of oxides or carbides that are detrimental to the CTE. The manganese content is measured with an absolute uncertainty of ±0.009%.

[0029] In particular, the alloy composition on which the metal part according to the invention is based may be selected from one of the two examples shown in Tables 1 and 3 in the Examples section below. The metal parts according to the invention can be produced from the iron-based alloy composition in the form of powder, forged parts, rolled parts or wire, advantageously in particular powder intended for additive manufacturing, or forged parts. In an advantageous embodiment, the metal part according to the invention can be produced from the alloy composition in the form of a wire intended to be used as such or in the form of a cable formed from the wire, or to be shaped by wire deposition according to various possible processes (by arc, plasma, electron beam or laser). In another advantageous embodiment, the metal part according to the invention may be produced from an alloy composition in the form of a powder intended for shaping by additive manufacturing, advantageously selected from the group consisting of selective laser melting (LBM) in a powder bed, electron beam melting (EBM), laser melting by powder atomization such as direct layer laser buildup (CLAD®) or direct metal deposition (DMD) and binder jetting (MBJ), more particularly selective laser melting (LBM) in a powder bed.

[0030] The powders on which the metal parts according to the invention are preferably based have a particle size distribution (number diameter) in the range of 10 to 60 μm, especially when the parts are intended for production by selective laser melting (LBM) in a powder bed. Traditionally, for this type of particle size cut, the lower limit of 10 μm, characterized by the number D10, is controlled by laser diffraction (ASTM B822-17), while the upper limit, characterized by the number D90 of 60 μm, is controlled by screening. When particle size cut control is implemented according to the standards ASTM B214-16 or ISO 2591-1, which came into force in 1988, screening allows for cuts down to 45 μm. Below this limit, screening is no longer permitted by these standards, and the particles are characterized by the number D10 value of the distribution measured by laser diffraction. The metal parts according to the invention are preferentially selected from curing moulds, injection moulds and components of these moulds, in particular their mechanical properties making them particularly suitable for these uses in which they are subjected to many heating / cooling cycles.

[0031] Manufacturing method The present invention also relates to a method for manufacturing a metal part for the manufacture of a rubber article according to the invention in an iron-based alloy, the method comprising the following steps: A - Preparation of an iron-based alloy powder having the composition of the alloy on which the metal part according to the invention is based, advantageously comprising: a - mixing of elemental materials or starting materials before alloying; b- melting the mixture obtained in step a), advantageously in a vacuum induction muffle (VIM) furnace, c - gas atomization, advantageously with nitrogen, of the product obtained in step b), to obtain a powder that is advantageously predominantly spherical (i.e., without any sharp edges); d - screening or sieving, advantageously under an inert atmosphere, of the powder obtained in step c) to obtain a fraction of the desired particle size; e - Recovering the resulting powder The step of manufacturing by the process of

[0032] The particle size of the powder is therefore adapted depending on the envisaged additive manufacturing technology or powder deposition process. The particle size ranges used for various additive manufacturing or powder deposition processes vary depending on the technology, equipment, and intended application. In general, when all applications are combined, powders used in these processes have a more or less broad particle size distribution between 5 and 150 μm by number (as indicated above, the lower limit of 5 μm, characterized by D10 by number, is controlled by laser diffraction (ASTM B822-17), and the upper cut of 150 μm, characterized by D90 by number, is controlled by screening).

[0033] B1 - subjecting the powder obtained in step A) to an additive manufacturing process, advantageously selected from the group consisting of selective laser melting (LBM) in a powder bed, electron beam melting (EBM), laser melting with powder atomization, such as direct layer laser buildup (CLAD®) or direct metal deposition (DMD) and binder jetting (MBJ) in a powder bed, or hot isostatic consolidation (HIC) processing, with the aim of obtaining a part; or B2 - subjecting the powder obtained in step A) to a laser melting process with powder atomization, such as direct layer laser building (CLAD®) or direct metal deposition (DMD), followed by forging the deposit formed from the molten powder, C - subjecting the part obtained in step B1) or B2) to at least one thermal and / or physical and / or chemical treatment, advantageously selected from the group consisting of a relaxation heat treatment, a hot isostatic compaction (HIC) treatment if step B1) is not a HIC treatment, a solution treatment, an ageing treatment, a final treatment such as a surface modification treatment or the deposition of a coating for protection against corrosion and oxidation, and a mixture of these treatments, D - Recovery of the parts thus obtained.

[0034] Additive manufacturing processes that can be used in the context of the present invention, such as selective laser melting (LBM) in a powder bed, electron beam melting (EBM), laser melting with powder spray such as direct layer laser buildup (CLAD®) or direct metal deposition (DMD) and binder jetting (MBJ) in a powder bed, are well known to those skilled in the art. In an advantageous embodiment, step B1) consists of an additive manufacturing process comprising the layer-by-layer production of the part using an energy source (laser or electron beam) to melt a thin layer of the superalloy powder according to the invention. A second layer of the superalloy powder according to the invention is then deposited and then melted. This process is repeated until the final part is obtained. Advantageously, this is selective laser melting (LBM) in a powder bed.

[0035] In an advantageous embodiment, step C) of the method of the invention comprises a melt treatment at 1050°C to 1150°C, advantageously between 1050°C and 1100°C, in particular at 1050°C for 1 hour to 4 hours, advantageously for 1 hour, followed by an ageing treatment at 600°C to 700°C, advantageously between 600°C to 650°C, in particular at 600°C for 5 hours to 10 hours, advantageously for 5 hours, or a direct ageing treatment without melting at 600°C to 700°C, advantageously between 600°C to 650°C, in particular at 600°C for 5 hours to 10 hours, advantageously for 5 hours. Such treatment conditions can maximize the hardness of the metal part. In a particularly advantageous embodiment, step C) of the method according to the invention consists of direct ageing without melting at 600°C to 700°C, advantageously at 600°C to 650°C, in particular at 600°C for 5 to 10 hours, advantageously 5 hours. Such treatment conditions can maximize the hardness of the metal part when high-temperature heat treatment is not desirable.

[0036] In another advantageous embodiment, step C) of the method according to the invention consists of a melt treatment at 900°C to 1000°C, advantageously at 900°C to 950°C, in particular at 950°C for 30 minutes to 1 hour, followed by an ageing treatment at 600°C to 700°C, advantageously at 600°C to 650°C, in particular at 600°C for 5 hours to 10 hours, advantageously 5 hours. Such treatment conditions allow to maximize the elongation at break of the metal part. The present invention further provides a method for manufacturing a metal part for producing an iron-based alloy rubber article according to the present invention, comprising the steps of: i - mixing the elemental materials or starting materials before alloying, ii - melting the mixture obtained in step i), advantageously in a vacuum induction muffle (VIM) furnace, iii) an optional step of homogenizing the ingot obtained in step ii) by heat treatment, advantageously at a temperature of 1240°C for 4 hours, iv - transformation of the ingot obtained in step ii) or iii) by forging, in particular at high temperature, advantageously with a degree of deformation of 80% to 90%, v - Recovery of the metal parts thus obtained The present invention relates to a method, comprising:

[0037] In an advantageous embodiment, the method according to the invention comprises an additional step vi) of subjecting the part obtained in step v) to at least one thermal and / or physical and / or chemical treatment, advantageously selected from the group consisting of a relaxation heat treatment, a hot isostatic compaction treatment, a solution treatment, an ageing treatment, a final treatment such as a surface modification treatment or the deposition of a coating for protection against corrosion and oxidation, and a mixture of these treatments. In an advantageous embodiment, step vi) of the method of the present invention comprises a melt treatment at 1050°C to 1150°C, advantageously between 1050°C and 1100°C, in particular at 1050°C for 1 hour to 4 hours, advantageously for 1 hour, followed by an ageing treatment at 600°C to 700°C, advantageously between 600°C to 650°C, in particular at 600°C for 5 hours to 10 hours, advantageously for 5 hours, or a direct ageing treatment without melting at 600°C to 700°C, advantageously between 600°C to 650°C, in particular at 600°C for 5 hours to 10 hours, advantageously for 5 hours. Such treatment conditions can maximize the hardness of the metal part.

[0038] In a particularly advantageous embodiment, step vi) of the method according to the invention consists of direct ageing without melting at between 600°C and 700°C, advantageously between 600 and 650°C, in particular at 600°C for 5 to 10 hours, advantageously 5 hours. Such treatment conditions can maximize the hardness of the metal part when high-temperature heat treatment is not desirable. In another advantageous embodiment, step vi) of the method according to the invention consists of a melt treatment at 900°C to 1000°C, advantageously at 900°C to 950°C, in particular at 950°C for 30 minutes to 1 hour, followed by an ageing treatment at 600°C to 700°C, advantageously at 600°C to 650°C, in particular at 600°C for 5 hours to 10 hours, advantageously 5 hours. Such treatment conditions allow to maximize the elongation at break of the metal part.

[0039] The invention also relates to a metal part for manufacturing a rubber article according to the invention from an iron-based alloy advantageously obtained from an alloy powder obtainable via the process of the invention. Advantageously, the metal part according to the invention comprises: - Its linear expansion coefficient is 3.5 x 10 between 30°C and 200°C according to standard ASTM E228-17(2017). -6 / °C, advantageously less than 3.4 × 10 -6 / °C or less, more preferably 3.3 x 10 -6 / °C or less, and / or - have a tensile strength according to standard ISO 6892-1 (2019) of more than 1000 MPa, advantageously of more than 1100 MPa, and / or - have a hardness HV30 according to standard ISO 6507-1 (2018) of more than 350 HV, in particular more than 360 HV, more particularly more than 370 HV, even more particularly more than 375 HV It is characterized by:

[0040] Finally, the invention relates to the use of a metal part according to the invention, or a metal part obtained via one of the methods according to the invention, for manufacturing pneumatic or non-pneumatic tires, rubber track tracks, wheels for vehicles, i.e. with a locomotive function, and / or parts for pneumatic or non-pneumatic tires, rubber track tracks or such wheels. The invention will be more clearly understood on reading the following description of examples, given by way of non-limiting guidance. In the examples, all percentages are given by weight, temperatures are given in degrees Celsius and pressures are atmospheric unless otherwise stated. The metal composition is determined by measuring the infrared absorption and thermal conductivity (LECO) of the combustion gases and by inductively coupled plasma (ICP) mass spectrometry. [Example]

[0041] Various metal parts are manufactured from iron-based alloys whose compositions are shown in Tables 1 and 3. The measured properties are listed in Tables 2 and 4. Table 1 shows Example 1 of an iron-based alloy for metal parts according to the present invention, strengthened by γ″ (gamma double prime) phase precipitation in a proportion sufficient to properly harden the alloy. A standard Invar 36-type alloy containing no hardening elements and with the same level of residuals was produced as a reference, along with four counter-example alloys. Counterexample 1 is an iron-based alloy strengthened with a lower content of γ″ (gamma double prime) phase than that of the alloy of the part according to the invention (the Nb content is less than 4.75 as a percentage by mass of the total composition).

[0042] Counterexample 2 is an iron-based alloy strengthened by the precipitation of molybdenum carbide having a Mo content, as a mass percentage, of 3.97 and a C content, as a mass percentage, of 0.236. Counterexample 3 is an iron-based alloy strengthened by the precipitation of molybdenum carbide and niobium carbide, with a mass percentage content of 3.95 Mo, 0.475 Nb, and 0.212 C. These Mo, Nb, and C contents are within the range claimed in patent application WO 03 / 025239, where the Mo content is 1.5-6, the Nb content is 0.5 or less, and the C content is 0.2-0.4. Counterexample 4 is an iron-based alloy strengthened by the precipitation of vanadium carbides, with a V content of 0.899 and a C content of 0.204. These V and C contents are very close to those of Invar-V in the publication by Nakama et al. (Metallogr. Microstruct. Anal. (2 (2013) 383-387) in which the V content is 0.8 and the C content is 0.203.

[0043] [Table 1]

[0044] Table 2 shows the maximum mechanical strength Rm at room temperature (according to standard ISO 6892-1:2019), the Vickers hardness HV30 at room temperature (according to standard ISO 6507-1:2018), and the coefficient of thermal expansion (CTE) between 30 and 200 °C measured according to standard ASTM E228-17 (2017) for Example 1, the Invar 36 reference, and the four counterexamples after production of 6 kg ingots in a vacuum muffle furnace (VIM), homogenization at 1240 °C for 4 hours, hot forging by punch drawing to a degree of deformation between 80% and 90%, followed by air cooling and heat treatment. The final heat treatment was different for each alloy, and the reported results are the best obtained. Example 1 was subjected to ageing at 600°C for 5 hours followed by air cooling; counterexamples 1, 2 and 3 were subjected to precipitation ageing at 650°C for 5 hours followed by air cooling; the Invar 36 reference alloy was subjected to treatment at 1100°C for 1 hour followed by water cooling; and counterexample 4 was subjected to melting at 1250°C for 1 hour followed by water cooling and air cooling at 650°C for 5 hours.

[0045] The γ″ (gamma double prime) phase precipitation strengthening strategy used to strengthen the alloy allows for the best hardening to be obtained for a limited increase in CTE compared to the reference Invar 36 and four counterexamples produced with the same level of residuals and comparable transformation range. Furthermore, the low hardness level of counterexample 1, which has a Nb content of 2.81, indicates that it is necessary to have a Nb content above 4.75 to obtain the desired strengthening. On the other hand, exceeding 5.5 is not desirable, as this would excessively deteriorate the CTE and may result in the precipitation of undesirable phases.

[0046] Furthermore, these results show the strong influence on hardening of the transformation range and in particular of the cold spinning or drawing step. In particular, counterexample 3, whose Mo, Nb and C contents are within the range claimed by patent WO 03 / 025239, has an Rm equal to 795 MPa, compared to 1300 MPa for wire produced according to patent WO 03 / 025239. Comparing the results obtained for counterexample 4, with an Rm equal to 794 MPa, with those of the publication by Nakama et al. (Metallogr. Microstruct. Anal. 2 (2013) 383-387), which has an Rm of 1010 MPa after the cold transformation step, confirms the contribution of transformation to hardening.

[0047] It can be seen that for the equivalent transformation range, the alloy strengthening strategy with Ni content between 38.0 and 42.0, Nb content between 4.750 and 5.500, and C content between 0.010 and 0.100 provided the best compromise between hardening and low CTE. [Table 2] Example 1 was heat treated in a separate test after forging by melting at 1050°C for 1 hour followed by water cooling, then ageing at 600°C for 5 hours followed by air cooling. In this case, the Rm was equal to 1129 MPa, the elongation was 15.5%, the HV30 hardness measured according to standard ISO6507-1:2018 was 378 HV, and the CTE between 30°C and 200°C was 3.09 × 10 -6 / °C. The CTE was also measured for this sample between 30°C and 100°C, between 30°C and 300°C, and between 30°C and 400°C. The results obtained were 2.47 × 10 -6 / ℃, 5.16×10 -6 / ℃ and 7.49×10 -6 / °C. Therefore, the CTE remains low even in the temperature range of 30°C to 400°C.

[0048] Table 3 shows the compositions of Example 2 of an iron-based alloy for metal parts according to the invention and Counterexample 5 strengthened by the precipitation of vanadium carbide, which were produced under vacuum, then gas atomized and screened in powder form, and formed via an additive manufacturing process of laser melting in a powder bed with a layer thickness of 50 μm and a laser processing strategy of ±45° (i.e., a rotation of 90° between each successive layer), followed by a heat treatment at 1050°C for 1 hour followed by air cooling, and then aging at 600°C for 5 hours followed by air cooling for Example 2, and aging at 650°C for 5 hours followed by air cooling for Counterexample 5.

[0049] [Table 3]

[0050] Table 4 shows the Vickers HV30 hardness obtained for Example 2 and Counter Example 5 after production of parts via the process of laser melting and heat treatment in a powder bed as shown above. [Table 4]

[0051] Example 2 of the alloy according to the invention, produced by powder processing and additive manufacturing, confirms the level of hardness obtained for Example 1 by the forging process. Counterexample 5 confirms that the hardening achieved by strengthening by precipitation of vanadium carbides does not allow such high levels of hardness to be obtained.

[0052] Table 5 shows the tensile strength Rm and elongation at break A% obtained after various heat treatments performed on metal parts based on the alloy of Example 2. The index "H" corresponds to tests performed on horizontally manufactured specimens, while the index "V" corresponds to tests performed on vertically manufactured specimens. It can be seen that it is possible to obtain metal parts by adjusting the heat treatment to favor the hardness or elongation at break of the metal parts.

[0053] [Table 5]

Claims

1. As a percentage by mass of the total composition, Nickel: 38.0 to 42.0, preferably 39.0 to 42.0, niobium: 4.750 to 5.500, preferably 5.000 to 5.500, carbon: 0.010 to 0.100, preferably 0.015 to 0.070, Cobalt: less than or equal to 0.400, advantageously less than or equal to 0.100, - Chromium: 0.500 or less, Silicon: 0.500 or less, Manganese: 0.500 or less, - Iron: remaining, and unavoidable impurities and advantageously consisting essentially of the following, in percentage contents by weight of the total composition: nitrogen≦0.030% by weight of the total composition, oxygen≦0.040% by weight of the total composition, hydrogen≦0.0050% by weight of the total composition, sulfur≦0.0150% by weight of the total composition, phosphorus≦0.0150% by weight of the total composition, aluminum≦0.100% by weight of the total composition, titanium≦0.100% by weight of the total composition, vanadium≦0.100% by weight of the total composition, molybdenum≦0.020% by weight of the total composition, calcium≦0.015% by weight of the total composition, copper≦0.010% by weight of the total composition, Magnesium≦0.015% by weight of the total composition A metal part for manufacturing a rubber article based on an iron-based alloy composition, wherein at least one of the above requirements is satisfied.

2. 2. The metal part according to claim 1, characterized in that the iron-based alloy contains not more than 1.00% by weight, preferably not more than 0.50% by weight, of unavoidable impurities.

3. 3. Metal part according to claim 1 or 2, characterized in that the iron-based alloy contains not more than 0.050% by weight of cobalt relative to the total weight of the composition, preferably containing cobalt only as an unavoidable impurity.

4. The metal part according to any one of claims 1 to 3, which is selected from hardening moulds, injection moulds and components of these moulds.

5. A method for manufacturing a metal part according to any one of claims 1 to 4, comprising: A) producing an iron-based alloy powder having the composition of the alloy composition on which the metal part according to any one of claims 1 to 4 is based, the step comprising: a) mixing the elemental materials or starting materials before alloying; b) melting the mixture obtained in step a), advantageously in a vacuum induction muffle furnace, c) gas atomization, preferably with nitrogen, of the product obtained in step b) to obtain a powder; d) screening or sieving the powder obtained in step c) to obtain a desired particle size fraction; e) recovering the resulting powder The steps of: B1) subjecting the powder obtained in step A) to an additive manufacturing process, preferably selected from the group consisting of selective laser melting in a powder bed (LBM), electron beam melting (EBM), laser melting with powder atomization, such as direct metal deposition laser building or direct metal deposition (DMD) and binder jetting in a powder bed (MBJ), or to a hot isostatic consolidation process, with the aim of obtaining a part; or B2) subjecting the powder obtained in step A) to a laser melting process with powder atomization, such as direct layer laser building or direct metal deposition (DMD), followed by forging the deposit formed from the molten powder; C) subjecting the part obtained in step B1) or B2) to at least one thermal and / or physical and / or chemical treatment, advantageously selected from the group consisting of a relaxation heat treatment, a hot isostatic pressing treatment if step B1) is not a hot isostatic pressing treatment, a final treatment such as a solution treatment, an ageing treatment, a surface modification treatment or the deposition of a coating for protection against corrosion and oxidation, and a mixture of these treatments, D) Recovering the parts thus obtained A method comprising:

6. 6. The method according to claim 5, characterized in that step B1) is selective laser melting (LBM) in a powder bed.

7. 7. A method according to claim 5 or 6, characterized in that step C) consists of a melt treatment between 1050°C and 1150°C for 1 hour to 4 hours, followed by an ageing treatment between 600°C and 700°C for 5 hours to 10 hours, or a direct ageing treatment between 600°C and 700°C for 5 hours to 10 hours without melting.

8. 7. The method according to claim 5 or 6, characterized in that step C) consists of a melt treatment between 900°C and 1000°C for 30 minutes to 1 hour, followed by an ageing treatment between 600°C and 700°C for 5 hours to 10 hours.

9. A method for manufacturing a metal part according to any one of claims 1 to 4, comprising: i. Mixing elemental materials or starting materials before alloying; ii. Melting the mixture obtained in step i), advantageously in a vacuum induction muffle furnace; iii. An optional step of homogenizing the ingot obtained in step ii) by heat treatment; iv. Transforming the ingot obtained in step ii) or iii) by forging; v. Recovering the parts thus obtained; vi) Preferentially, subjecting the part obtained in step v) to at least one thermal and / or physical and / or chemical treatment, advantageously selected from the group consisting of a mild heat treatment, a hot isostatic compaction treatment, a solution treatment, an ageing treatment, a final treatment such as a surface modification treatment or the deposition of a coating for protection against corrosion and oxidation, and a mixture of these treatments. A method comprising:

10. 10. The method of claim 9, wherein step vi) consists of a melt treatment between 1050°C and 1150°C for 1 hour to 4 hours followed by an ageing treatment between 600°C and 700°C for 5 hours to 10 hours or a direct ageing treatment between 600°C and 700°C for 5 hours to 10 hours without melting.

11. 10. The method of claim 9, wherein step vi) consists of a melt treatment between 900°C and 1000°C for 30 minutes to 1 hour, followed by an ageing treatment between 600°C and 700°C for 5 hours to 10 hours.

12. A metal part obtainable via the method according to any one of claims 1 to 4 or any one of claims 5 to 11, its coefficient of linear expansion is 3.5 x 10 between 30 °C and 200 °C according to standard ASTM E228-17 (2017) -6 / °C, and / or - have a tensile strength of more than 1000 MPa according to standard ISO 6892-1:2019, and / or - have a hardness of more than 350 HV HV30 according to standard ISO 6507-1:2018 A metal part characterized by:

13. Use of a metal part according to any one of claims 1 to 4 or obtainable via a method according to any one of claims 5 to 11 for the manufacture of pneumatic or non-pneumatic tires, caterpillar tracks, vehicle wheels and / or parts of pneumatic or non-pneumatic tires, caterpillar tracks or such wheels.

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