Fe-Ni alloy foil, Fe-Ni alloy foil manufacturing method, and parts

Abstract

The present invention addresses the problem of suppressing deformation such as edge waves, center waves, and warping from occurring in an ultra-thin (50 μm or less in thickness) iron–nickel alloy foil, and the purpose of the present invention is to obtain an iron–nickel alloy foil in which such deformation is suppressed. This iron–nickel alloy foil has a positron annihilation lifetime (PAL) of at least 0.150 ns and can reduce the amount of deformation (the total evaluated amount of deformation such as edge waves, center waves, and warping) relative to conventional products. In order to form a primarily vacant microstructure to achieve a PAL of at least 0.150 ns, an iron–nickel alloy foil can be obtained by manufacturing an alloy block (slab) by HIP treatment and rolling and heat treating the alloy block in accordance with conventional methods.

Description

[Technical Field]

[0001] The present invention relates to an Fe—Ni metal foil, a method for producing the Fe—Ni metal foil, and a part using the Fe—Ni alloy foil. [Background technology]

[0002] As electronic devices become smaller and more densely packed, there is a demand for smaller and lighter electronic components that make up the electronic devices. For example, aluminum foil and stainless steel foil containing Fe-Ni alloy foil are used as cases for secondary batteries. While efforts are being made to reduce the thickness of the case to make secondary batteries lighter and thinner, there is also a demand for maintaining strength. Therefore, efforts are being made to replace the conventional aluminum foil with stainless steel foil, thereby reducing the thickness while maintaining strength (e.g., Patent Document 1).

[0003] Furthermore, there is a demand for thinner materials and components that are essential for manufacturing electronic devices, not just components used in electronic devices themselves. For example, metal masks that are essential for manufacturing organic light-emitting diodes (OLEDs) are made of Fe-Ni alloy foil, which has good etching properties and thermal expansion properties, but thinner masks are being demanded as pixel densities increase (see, for example, Patent Document 2). In response to this demand for thinner Fe-Ni alloy foils, Fe-Ni alloy foils with thicknesses of 100 μm or less are currently available, and there is a demand for Fe-Ni alloy foils with thicknesses of even less than 50 μm. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2015 / 122523 [Patent Document 2] International Publication No. 2020 / 067537 Summary of the Invention [Problem to be solved by the invention]

[0005] When thinning Fe-Ni alloy foil, non-uniform residual stress is likely to occur during the manufacturing process (especially rolling). Although stress relief annealing is performed after rolling to remove the residual stress, the residual stress cannot be completely removed, resulting in deformations such as wavy edges, central elongation, and warpage. This deformation poses a quality issue for Fe-Ni alloy foil. It becomes particularly evident when the foil thickness is less than 50 μm, posing a serious quality and technical problem.

[0006] Therefore, the present invention aims to suppress deformations such as edge undulations, central elongation, and warpage in Fe—Ni alloy foil having a thickness of 50 μm or less, and to obtain Fe—Ni alloy foil (hereinafter sometimes simply referred to as alloy foil) in which such deformations are suppressed. [Means for solving the problem]

[0007] The present inventors have continued their research and development in order to achieve the above object, and have obtained the following findings. (A) It was believed that deformations such as ripples, elongation, and warpage are caused by nonuniform deformation within the alloy foil, and that this nonuniform deformation is due to nonuniform residual stress within the alloy foil. Residual stress is known to be imparted during the manufacturing process of the alloy foil, particularly by rolling. Rolling causes deformation through the movement of dislocations and vacancies in the alloy sheet (although there is no clear standard for the thickness of alloy foil and alloy sheet, for example, a sheet thickness of more than 100 μm may be referred to as an alloy sheet, and a sheet thickness of 100 μm or less may be referred to as an alloy foil. Hereinafter, a plate-shaped Fe-Ni alloy with a thickness of 100 μm or more before being thinned into alloy foil by rolling may be referred to as an Fe-Ni alloy sheet or simply as an alloy sheet). Dislocations themselves are generated by the movement and combination of vacancies. For these reasons, the inventors focused on the behavior of vacancies in the alloy sheet. Note that the vacancies in this invention do not refer to defects such as shrinkage holes or gas vacancies that occur during solidification in cast products, but rather to atomic vacancies and point defects.

[0008] (a) We came up with the idea that if voids are uniformly dispersed in an alloy plate, the movement and bonding of voids will be uniform during rolling of the alloy plate, and the deformation behavior will be uniform within the alloy plate. Therefore, we produced an alloy ingot using, for example, hot powder metallurgy (HIP method, etc.), rolled it to obtain alloy foil, and evaluated its deformation behavior. As a result, we confirmed that edge waves, central elongation, and warpage were suppressed. This confirmed that alloy foil with suppressed deformation can be obtained by rolling an alloy ingot with uniformly dispersed voids.

[0009] (c) We considered using the positron annihilation lifetime (PAL) of vacancies as an index of the uniform dispersion of vacancies in a rolled sheet. PAL is a comprehensive index of the number of vacancies, vacancy size, etc. The larger the vacancy size, the longer the PAL, and the greater the number of vacancies, the greater the detected intensity. As the number of vacancies increases, vacancies bond with each other, resulting in larger vacancy sizes. Through experiments, the inventors found that the larger the PAL, the more the amount of deformation is suppressed.

[0010] (d) Experiments on Fe-Ni alloy foil confirmed that if the PAL is 0.150 ns (nanoseconds) or greater, the amount of deformation is suppressed compared to conventional alloy foil. It was also confirmed that many conventional alloy foils have a PAL of less than 0.150 ns. This is thought to be due to the fact that conventional alloy ingots are manufactured using the ingot manufacturing method. In the ingot manufacturing method, vacancies tend to aggregate during the solidification process, generating edge dislocations, which is thought to hinder the uniformity of vacancies in the alloy ingot after solidification.

[0011] The present invention was made based on the above findings, and the gist of the present invention is as follows.

[0012] [1] The components are in mass%: C: 0 to 0.030%, Si: 0 to 0.21% Mn: 0 to 0.30% Ni: 30.0 to 60.0%, Co: 0-5.00%, P: 0.01% or less, S: 0.01% or less, and The balance is Fe and impurities, An Fe—Ni alloy foil having a thickness of 50 μm or less and a positron annihilation lifetime (PAL) of 0.150 ns or more. [2] The Fe—Ni alloy foil according to [1], wherein the positron annihilation lifetime (PAL) is 0.150 ns to 0.200 ns. [3] The Fe-Ni alloy foil according to [1] or [2], having a thickness of 20 μm or less. [4] The method for producing an Fe—Ni alloy foil according to any one of [1] to [3], The components are in mass%: C: 0 to 0.030%, Si: 0 to 0.21% Mn: 0 to 0.30% Ni: 30.0 to 60.0%, Co: 0-5.00%, P: 0.01% or less, S: 0.01% or less, and preparing an Fe-Ni alloy powder with the balance being Fe and impurities; a step of producing an Fe-Ni alloy ingot by HIPing the Fe-Ni alloy powder; A method for producing an Fe—Ni alloy foil, comprising the step of rolling the Fe—Ni alloy ingot. [5] The method for producing an Fe—Ni alloy foil according to [4], further comprising at least one annealing step between each rolling pass of the rolling step or after final rolling. [6] A part having the Fe—Ni alloy foil according to any one of the above items [1] to [3]. [Effects of the Invention]

[0013] According to the present invention, an Fe—Ni alloy foil can be obtained that is suppressed from deformations such as wavy edges, central elongation, and warpage. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing an example of the relationship between PAL and deformation amount in an Fe—Ni alloy foil. [Figure 2] FIG. 1 is a diagram showing an outline of a vertical hanging test. [Figure 3] FIG. 1 is a conceptual diagram for explaining an example of a method for measuring a gap that occurs between a test piece and a vertical plane in a vertical hanging test. DETAILED DESCRIPTION OF THE INVENTION

[0015] The Fe—Ni alloy foil according to the present invention will be described in detail below. Unless otherwise specified, "%" for components indicates mass % in the steel. When no lower limit is specified or when the lower limit is 0%, this includes the absence of the component (0%).

[0016] [Proton annihilation lifetime (PAL)] Positron annihilation lifetime (PAL) is an index used to evaluate lattice defects, including vacancies, in materials such as metals and polymers. It is also called the average positron annihilation lifetime. PAL can evaluate the type of lattice defect. PAL is a comprehensive index of the number of vacancies in a material, their size, etc. In this specification, vacancies do not refer to defects such as shrinkage holes or gas vacancies that occur during solidification in castings, but rather atomic vacancies and point defects. A detailed explanation of PAL is omitted here, but the larger the vacancy size, the longer the PAL. On the other hand, the greater the number of vacancies, the higher the detected relative intensity (the number of gamma rays counted when a positron annihilates, which corresponds to the probability of existence). Furthermore, as the number of vacancies increases, vacancies bond with each other, resulting in larger vacancy sizes and a longer PAL.

[0017] The positron annihilation lifetime (PAL) can be measured using a PAL measurement device. As the PAL measurement device, a commercially available device such as a positron annihilation lifetime measurement device manufactured by Techno AP Co., Ltd. can be used. The inventors have measured the positron annihilation lifetime of a positron source using the positron annihilation lifetime measurement device manufactured by Techno AP Co., Ltd. 22 Evaluation was performed using Na. For PAL evaluation, Fe-Ni alloy foil, the material to be evaluated, is cut into 10 mm squares, and two sets of three of these are prepared. The positron source is sandwiched between the three Fe-Ni alloy foils, which are then wrapped and fixed in aluminum foil to create a PAL measurement sample. The prepared measurement sample is then placed in a measurement device to measure the positron annihilation lifetime (PAL). It is recommended to use the data analysis software that comes with the measurement device (for example, PALSfit3, developed by the Technical University of Denmark). In order to take into account the effects of the Kapton film lifetime (0.3800 ps) and the epoxy resin lifetime (1.9044 ps), it is recommended to fix these lifetimes when performing the measurement.

[0018] Materials produced using conventional melting methods (ingot materials) are virtually free of vacancies, and the majority of lattice defects are dislocations. Furthermore, in the case of ingot materials, dislocations are not introduced uniformly throughout the material during the solidification process. Simply put, the dislocation state differs between the surface and center of the solidified alloy ingot. When dislocations are the primary defect, if the stress concentration caused by processing exceeds the yield stress, dislocations occur, causing stress relief through plastic deformation, but at the same time, work hardening occurs due to the interaction between dislocations. Therefore, if dislocations are introduced unevenly within the material, stress relief occurs locally, and residual stress is likely to become uneven.

[0019] On the other hand, hot powder metallurgy methods such as HIP can eliminate shrinkage pores and gas voids, but cannot eliminate atomic vacancies. Materials produced by hot powder metallurgy (hot powder metallurgy materials) are produced by isotropically compressing and sintering powder at high temperatures, which is thought to result in numerous vacancies uniformly occurring within the material. In hot powder metallurgy, these vacancies diffuse, causing the necks between particles to grow and sintering to proceed. In other words, materials produced by hot powder metallurgy have a microstructure with vacancies, unlike materials produced by conventional melting methods.

[0020] Vacancies are used for the climbing motion of edge dislocations, and their arrangement also plays a role in forming dislocations. Therefore, the structure of hot powder metallurgy materials, which have a long positron annihilation lifetime and a large proportion (quantity) of vacancies, is thought to be relatively easy for dislocations to move, as vacancies tend to migrate and form dislocations. Dislocations can move while absorbing many vacancies, making the structure relatively easy for dislocations to move. This ease of dislocation formation and movement affects the stress relaxation of the material. Furthermore, remaining vacancies not used for dislocations act similarly to solid-solution strengthening and contribute to the base strength. Therefore, if vacancies are uniformly introduced into a material, they tend to migrate easily during rolling, etc., making it easier to deform even with a relatively light rolling load. Furthermore, stress relaxation is uniform within the material, resulting in uniform residual stress, which is thought to suppress deformation (warping, lateral bending, etc.). On the other hand, ingot materials, due to their short positron annihilation lifetime and small proportion (quantity) of vacancies, edge dislocations are less likely to climb and dislocations are less likely to move. In other words, dislocations are unevenly distributed in the ingot material and are difficult to move, which causes uneven residual stress and makes it easy for shape defects to occur.

[0021] The inventors have confirmed through experiments that the PAL does not exceed 0.150 ns for conventionally produced materials, but does exceed 0.150 ns for hot powder metallurgy materials. Specifically, the PAL is less than 0.150 ns for materials in which dislocations are the main defect, such as conventionally produced materials, while the PAL is 0.150 ns or greater for materials in which point defects such as vacancies are the main defect, such as hot powder metallurgy materials. Therefore, a PAL of 0.150 ns or greater is considered to indicate a microstructure in which lattice defects are primarily point defects such as vacancies. In other words, a PAL of 0.150 ns is considered to be the boundary at which a microstructure changes from one primarily composed of dislocations to one primarily composed of vacancies.

[0022] Deformation Deformations such as wavy edges, elongation, and warpage in Fe-Ni alloy foils occur in a complex manner, making it difficult to evaluate each deformation individually. Therefore, in order to comprehensively evaluate the deformation of the alloy foil, we considered that the maximum deformation amount in the vertical direction of the alloy foil when it is hung vertically could be used to evaluate the deformation amount of the alloy foil.

[0023] The inventors employed the following test method to evaluate the amount of deformation in a vertical hanging test. Specifically, the alloy foil was cut into strips, for example, 40 mm wide and 250 mm long, to serve as test specimens. These were then hung on a vertical surface plate (a surface plate having a plane parallel to the vertical direction (vertical plane)). The gap between the vertical plane and the test specimen was measured, and the maximum value was used to evaluate the amount of deformation. Since undulations and elongation usually occur along the rolling direction, the long side of the test specimen should be oriented in the rolling direction. Furthermore, in some cases, the alloy foil is wound into a coil during production. To eliminate the winding tendency that occurs during this process, a certain tension should be applied. For example, for a test specimen with a thickness of 50 μm or less and a width of 40 mm, a 100 g weight should be attached to the lower end of the test specimen to generate tension. The method for measuring the gap between the test specimen and the vertical plane is not particularly limited, but it can be measured using a gap gauge, laser measurement, or image analysis using photography.

[0024] [Proton annihilation lifetime (PAL)≧0.150ns] Figure 1 shows an example of the relationship between PAL and deformation amount for an Fe-Ni alloy foil shown in the examples. Figure 1 shows the relationship between PAL and deformation amount for a 30 μm thick Fe-Ni alloy foil. As shown in Figure 1, there is a strong correlation between deformation amount and PAL, and it was confirmed that the deformation amount decreases as the PAL increases. In other words, it was confirmed that deformation of the alloy foil can be suppressed by changing the type of lattice defect from a structure mainly composed of dislocations (PAL less than 0.150 ns) to a structure mainly composed of vacancies (PAL 0.150 ns or more).

[0025] That is, it was confirmed that by setting the PAL to 0.150 ns or more, an Fe-Ni alloy with a microstructure mainly composed of voids can be obtained, the non-uniformity of residual stress due to rolling can be reduced, and as a result, an Fe-Ni alloy foil with reduced deformation can be obtained. Since the longer the PAL, the smaller the deformation, the longer the PAL is, so a longer PAL is preferable. Therefore, the lower limit of PAL is preferably 0.151 ns, 0.152 ns, 0.153 ns, 0.154 ns, 0.155 ns, 0.156 ns, 0.157 ns, 0.158 ns, 0.159 ns, 0.160 ns, 0.161 ns, 0.162 ns, 0.163 ns, 0.164 ns, or 0.165 ns.

[0026] On the other hand, the longer the PAL, the smaller the deformation amount. However, when the PAL is long enough, large voids will be present, and these large voids may become the starting point of fracture. Experiments by the inventors have shown that no practical hot powder metallurgy materials have measured PAL values ​​exceeding 0.200 ns. Therefore, although there is no need to particularly limit the upper limit of PAL, if an upper limit is to be set, it should be 0.200 ns, preferably 0.198 ns, 0.196 ns, 0.194 ns, 0.192 ns, 0.190 ns, 0.188 ns, 0.186 ns, 0.184 ns, 0.182 ns, or 0.180 ns.

[0027] [Fe-Ni alloy foil composition] The components of the Fe-Ni alloy foil will be described. As mentioned above, unless otherwise specified, "%" for components indicates mass % in the steel. When no lower limit is specified or when the lower limit is 0%, this includes the case where the component is not contained (0%).

[0028] C: 0 to 0.030%, Carbon (C) increases the strength of the alloy foil. However, excessive C content increases the amount of carbide-derived inclusions in the alloy. Therefore, the C content should be 0.030% or less. Preferably, it should be 0.028%, 0.026%, 0.024%, 0.022%, or 0.020%.

[0029] Si: 0 to 0.21% Silicon (Si) increases the thermal expansion coefficient of the alloy. Fe-Ni alloy foil is an alloy that is originally expected to have a low thermal expansion coefficient, and depending on its application, it may be used in a temperature environment of around 200°C. Furthermore, if the Si content is too high, the strength becomes too high and the workability of the alloy decreases. Therefore, from the viewpoint of suppressing thermal expansion and workability, the Si content should be 0.21% or less. Preferably, it should be 0.20% or less, 0.18% or less, 0.16%, 0.14%, 0.12%, or 0.10% or less.

[0030] Mn: 0 to 0.30% Manganese (Mn) is used as a deoxidizer in place of Mg and Al to prevent the formation of spinel. However, if the Mn content is too high, it segregates at grain boundaries, promoting intergranular fracture and actually worsening hydrogen embrittlement resistance. Therefore, the Mn content should be 0.30% or less. The preferred ranges for the Mn content are 0.28% or less, 0.26% or less, 0.24% or less, 0.22% or less, 0.20% or less, 0.18% or less, or 0.16% or less.

[0031] Ni: 30.0 to 60.0%, Nickel (Ni) is a major component that keeps the thermal expansion coefficient of the alloy low. If the Ni content is too low, the body-centered cubic (bcc) structure increases and dislocation behavior changes. Therefore, the Ni content should be 30.0% or more. On the other hand, if the Ni content is too high, bainite structure is likely to form in the alloy after hot processing (hot rolling or hot forging). Therefore, the Ni content should be 60.0% or less. The preferred ranges of the Ni content are 31.0% or more, 31.5% or more, 32.0% or more, 32.5% or more, 33.0% or more, 33.5% or more, 34.0% or more, 34.5% or more, 35.0% or more, 35.2% or more, or 35.4% or more on the lower limit side, and 59.0% or less, 58.0% or less, 57.0% or less, 56.0% or less, 55.0% or less, 54.0% or less .... It is recommended to set it to 53.0% or less, 52.0% or less, 51.0% or less, 50.0% or less, 49.0% or less, 48.0% or less, 47.0% or less, 46.0% or less, 45.0% or less, 44.0% or less, 43.0% or less, 42.0% or less, 41.0% or less, 40.0% or less, 39.5% or less, 39.0% or less, 38.5% or less, 38.0% or less, 37.5% or less, or 37.0% or less.

[0032] Co: 0-5.00%, Increasing the amount of Co added relative to the amount of Ni can further reduce the thermal expansion coefficient of the alloy. However, because it is a very expensive element, the upper limit of the Co content is set to 5.00%. Preferably, it should be set to 4.50% or less, 4.00% or less, 3.50% or less, 3.00% or less, 2.50% or less, 2.00% or less, 1.50% or less, or 1.00% or less.

[0033] [impurities] In addition to the above elements, the balance is Fe (iron) and impurities. Impurities are elements that are unintentionally contained during the manufacturing process. In particular, impurities include components such as P and S. The contents of P and S are preferably limited to the following ranges.

[0034] P: 0.010% or less, P segregates to grain boundaries during solidification and increases solidification cracking susceptibility. Therefore, it is preferable to keep the P content as low as possible. Therefore, the P content is limited to 0.010% or less. Preferably, it is 0.005% or less, or 0.003% or less. The lower limit of the P content is 0%, but since reducing it too much increases manufacturing costs, it may be 0.001% or more in reality.

[0035] S: 0.010% or less, S segregates to grain boundaries during solidification and increases solidification cracking susceptibility. Therefore, it is preferable to keep the S content as low as possible. Therefore, the S content is limited to 0.010% or less. Preferably, it is 0.005% or less, or 0.002% or less. The lower limit of the S content is 0%, but since excessively lowering it increases manufacturing costs, it may be 0.001% or more in reality.

[0037] Plate Thickness The thickness of the Fe-Ni alloy foil is not particularly limited. Although alloy foils with a thickness of 100 μm or less are referred to as alloy foils, they may also be applied to alloy foils with a thickness of 100 μm or more. However, generally, the thinner the foil, the more likely deformations such as wavy edges, central elongation, and warpage occur. Therefore, it is more effective to apply the present invention to Fe-Ni alloy foils with a thickness of 50 μm or less. The thinner the foil, the more effective the effects of the present invention can be achieved, so a thickness of 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, 10 μm or less, or 5 μm or less is preferable. The lower limit of the foil thickness is not particularly limited, but from the viewpoint of industrial manufacturability, a foil thickness of 1.0 μm or more is also acceptable.

[0038] [Manufacturing method] The method for producing the Fe-Ni alloy foil according to the present invention is not particularly limited. However, the life of the PAL can be extended by making improvements mainly in the alloy ingot production process, rolling process, and annealing process. These methods are described below. However, the Fe-Ni alloy foil according to the present invention is not limited to the production method described here.

[0039] [Fe-Ni alloy ingot manufacturing process] The manufacturing process of Fe-Ni alloy ingots is a process for obtaining ingots (steel billets, slabs, etc.) of Fe-Ni alloy with a predetermined composition. For example, there is a method of refining and solidifying molten Fe-Ni alloy, known as the ingot method. Another example is a method of combining metal powders with a predetermined composition and solid-state bonding them under high temperature and pressure, such as HIP (hot isostatic pressing), known as the hot powder metallurgy method.

[0040] As mentioned above, ingot alloys (ingot alloy ingots) produced using conventional ingot processing methods are virtually free of vacancies, and the majority of lattice defects are dislocations. Furthermore, in the case of ingot alloys, dislocations are not introduced uniformly throughout the entire ingot during the solidification process. Simply put, the way dislocations are introduced differs between the surface and the center of the ingot alloy. When dislocations are the primary defect, if the stress concentration caused by processing exceeds the yield stress, dislocations occur, causing plastic deformation and stress relaxation. Therefore, if dislocations are introduced unevenly within the ingot alloy, stress relaxation occurs locally, and residual stress is likely to occur unevenly.

[0041] On the other hand, hot powder metallurgy methods such as HIP can eliminate shrinkage pores and gas voids, but cannot eliminate atomic vacancies. Materials produced by hot powder metallurgy (hot powder metallurgy materials) are produced by isotropically compressing and sintering powder at high temperatures, which is thought to result in numerous vacancies uniformly generated within the material. In hot powder metallurgy, these vacancies diffuse, causing the necks between particles to grow and sintering to proceed. In other words, materials produced by hot powder metallurgy have a microstructure with vacancies, unlike ingot materials. Therefore, hot powder metallurgy methods such as HIP can produce numerous vacancies uniformly compared to conventional ingot methods, resulting in alloy ingots with longer PAL life.

[0042] [Fe-Ni alloy powder preparation process] When hot powder metallurgy is used, the manufacturing method is not particularly limited. For example, the conventional HIP method can be used. To uniformly generate voids in the resulting alloy ingot, it is preferable that the metal powder used as the raw material for the HIP method be fine-grained. For example, the particle size of the metal powder should be 500 μm or less, 400 μm or less, 300 μm or less, 200 μm or less, or 100 μm or less. The manufacturing method of the metal powder is also not particularly limited. A molten metal adjusted to a predetermined composition by a conventional refining method can be subjected to an atomization method or the like to obtain alloy powder. The refining method is also not particularly limited. At the laboratory level, a vacuum induction furnace can be used. To reduce the carbon content, gas components, and metal inclusions, the argon-oxygen-decarburization (AOD) method, the vacuum-oxygen-decarburization (VOD) method, the V-AOD method, and the like can be used.

[0043] The desired alloy ingot can be obtained by placing the prepared alloy powder in a metal container and performing HIP processing. Hot powder metallurgy methods such as HIP can produce alloy ingots with a near-net shape that is close to the shape of the final product, making it possible to omit subsequent processing steps (such as rolling and forging).

[0044] [Rolling process] The resulting Fe-Ni alloy ingot can be hot-rolled or cold-rolled to obtain alloy foil. Typically, the Fe-Ni alloy ingot is hot-rolled to a Fe-Ni alloy plate with a thickness of 1 mm or less, and then cold-rolled to obtain alloy foil of the desired thickness. Conventional manufacturing methods can be used for both hot and cold rolling. However, to extend the life of PAL, it is preferable not to use too large a total reduction ratio for each cold-rolling pass. This is because too large a total reduction ratio in cold rolling results in a rolled structure with accumulated strain and a high dislocation density, which makes vacancies more likely to be consumed. It is preferable to design the process so that the total reduction ratio in cold rolling is reduced to a mild level without reducing the work hardening capacity.

[0045] [Annealing process] When manufacturing Fe-Ni alloy foil, if the sheet thickness becomes thin (e.g., 100 μm or less), it is recommended to perform at least one annealing between rolling passes (e.g., between each rolling pass or between several passes) in the rolling process (especially cold rolling) or after the final rolling (the period between rolling passes is called intermediate annealing, and the period after the final rolling is called final annealing). Annealing reduces dislocations and vacancies, forming a uniform recrystallized structure. In the case of intermediate annealing, dislocations are reintroduced by subsequent rolling, but the dislocation density is not as high as in the unannealed rolled structure, so dislocations move easily, and dislocation cutting generates vacancies and increases the dislocation density. This results in a longer life for the PAL. Therefore, annealing is preferable, especially intermediate annealing between rolling passes.

[0046] As mentioned above, dislocations can be eliminated by annealing, but dislocation elimination does not progress without recrystallization. Therefore, it is desirable to anneal at a temperature equal to or higher than the recrystallization temperature. For example, in the case of Fe-Ni alloys and stainless steels, annealing at a temperature of 700°C or higher is preferable. Preferably, it is 750°C or higher, or 800°C or higher. Annealing below 700°C involves rolling with dislocations remaining, which makes it easier for dislocations to be introduced during final rolling and reduces the rolling load. However, this results in a high dislocation density, which makes it easier for vacancies to be consumed, resulting in a shorter PAL lifespan.

[0047] [Application to component materials] The Fe—Ni alloy foil according to the present invention can be applied to various parts because deformation is suppressed even when the foil is thinned. In particular, in the field of electronic devices such as battery materials, there is an increasing demand for thin alloy foils due to the need for lighter weight, higher performance, and higher strength, and it is preferable to apply the foil to these parts.

[0048] Furthermore, although not applied to the parts themselves, the present invention can also be applied to parts (components) used in manufacturing parts. For example, the Fe-Ni alloy foil of the present invention can be used for metal masks for OLEDs. Fe-Ni alloy foil is used for metal masks for OLEDs because of its etching properties and low thermal expansion, which allow for high definition. However, to achieve even higher definition, there is a demand for thinner masks and suppression of deformation.

[0049] In the present invention, components (members) used to manufacture electronic components, such as metal masks, are also included in the term "components," rather than electronic or mechanical components themselves.

[0050] Furthermore, the part having an Fe—Ni alloy foil according to the present invention includes not only parts manufactured from an Fe—Ni alloy foil, but also parts having a portion made of an Fe—Ni alloy foil. [Example]

[0051] [Test material] Using an Fe-36Ni alloy as a base, Fe-Ni alloy ingots were adjusted to have the chemical composition shown in Table 1. HIP materials were prepared using the HIP method, and ingot materials were prepared using conventional manufacturing methods. The remainder of the chemical composition shown in Table 1 is Fe and impurities.

[0052] First, for the HIP material, a molten metal (molten alloy) adjusted to the composition shown in Table 1 was gas atomized to form spherical alloy powder. The resulting alloy powder was classified, and the 300 μm undersize was HIP-treated to obtain the HIP material. The HIP treatment was carried out according to the usual procedure, and the HIP material was produced by holding the HIP material under high temperature and high pressure conditions of 1150°C and 120 MPa for 3 hours. As shown in Table 1, HIP1 and HIP2 were prepared as HIP materials with different compositions.

[0053] On the other hand, for comparison, continuous cast slab material conforming to conventional manufacturing methods was prepared by solidifying molten metal adjusted to the chemical composition shown in Table 1, then re-refining it using the ESR method (electroslag remelting) or the VAR method (vacuum arc remelting), and then obtaining a slab according to conventional continuous casting methods. As shown in Table 1, ingot material 1 and ingot material 2 were prepared as ingot materials with different chemical compositions.

[0054] [Table 1]

[0055] The obtained test materials were processed by rolling, annealing, etc. to make alloy foil. Table 2 shows the processing conditions for each test material.

[0056] The HIP1 and HIP2 test materials were machined into rectangular parallelepiped shapes with thicknesses of 1 mm, 3 mm, 10 mm, and 50 mm to obtain alloy plates. The 50 mm thick alloy plates were hot-rolled to 3 mm thick alloy plates. Alloy plates of other thicknesses were not hot-rolled. The 1 mm, 3 mm, and 10 mm thick alloy plates thus obtained were cold-rolled to obtain Fe-Ni alloy foils with a final thickness of 30 μm (0.030 mm). Some samples were subjected to intermediate annealing during cold rolling, while others were not.

[0057] On the other hand, for the ingot material corresponding to the conventional manufacturing method, the slab thickness after continuous casting was 250 mm, which was then hot-rolled into an alloy plate with a thickness of 300 μm (0.300 mm), and then (intermediate) cold-rolled, intermediate annealed, and (final) cold-rolled to obtain an Fe-Ni alloy foil with a final thickness of 30 μm (0.030 mm).

[0058] The deformation of each Fe—Ni alloy foil obtained was evaluated by a vertical hanging test as described above. Figure 2 shows an overview of the vertical hanging test. The alloy foil was cut into strips 40 mm wide and 250 mm long (cut so that the longitudinal direction was the rolling direction) to form test pieces 1, which were then hung on a vertical plane 3 of a vertical surface plate (a surface plate having a plane parallel to the vertical direction (vertical plane)) 2. The gap 5 between the vertical plane 3 and the test piece 1 was measured, and the maximum value was used to evaluate the deformation. In this example, a 100 g weight was attached to the lower end of the test piece to generate tension 4. As shown in Figure 3, the gap 5 (within the dotted frame in the figure) generated between the test piece 1 and the vertical plane 3 of the vertical surface plate 2 was measured using a gap gauge (not shown). While the range 6 for measuring the gap 5 is not particularly limited, it is preferable to use the entire width of the vertical plane 3 as the measurement range 6, as was done in this example. Measurement was made four times for each gap, and the average was taken as the deformation amount of the gap. The maximum value of the deformation amount of each gap was evaluated as the deformation amount of the test piece.

[0059] As mentioned above, the average positron annihilation lifetime (PAL) was measured by cutting the Fe-Ni alloy foil of each test material into 10 mm squares, stacking three of these, and preparing two sets of PAL measurement samples. The positron source was sandwiched between the three stacked Fe-Ni alloy foils, which were then wrapped and fixed in aluminum foil to create PAL measurement samples. The positron annihilation lifetime (PAL) of the prepared measurement samples was measured using a measurement device. A positron annihilation lifetime device manufactured by Techno AP was used as the PAL measurement device, and the positron source was placed in a positron annihilation lifetime measurement device. 22 The evaluation was performed using Na. The data analysis software used was PALSfit3, developed by the Technical University of Denmark. In order to take into account the effects of the Kapton film lifetime (0.3800 ps) and epoxy lifetime (1.9044 ps) during the measurement, these lifetimes were fixed and the average positron annihilation lifetime was analyzed for one component of the material.

[0060] Table 2 shows the manufacturing conditions, deformation amount, and PAL (mean positron annihilation lifetime) measurement results for each test material. The relationship between the deformation amount and PAL shown in Table 2 is shown in Figure 1. In Figure 1, the triangle marks indicate the comparative example (cast material) and the circle marks indicate the example (HIP material).

[0061] [Table 2]

[0062] As can be seen from Table 2 and Figure 1, there is a correlation between the mean positron annihilation lifetime (PAL) and the amount of deformation, and it can be seen that as the PAL increases, the amount of deformation decreases. As can be seen from a comparison with Comparative Example 1, which is equivalent to a conventional product, all of the HIP-treated Examples had a PAL of 0.150 nsec or more, and it was confirmed that the amount of deformation was smaller than that of Comparative Example 1. Furthermore, even when Examples 1 to 6 related to HIP 1, which has approximately the same alloy elements added in terms of component composition, were compared with Comparative Example 3 of ingot material 2, it was confirmed that the HIP material had a longer PAL and a smaller amount of deformation. [Industrial Applicability]

[0063] The present invention can be applied to Fe—Ni alloy foils, and its effects are particularly pronounced when applied to ultra-thin Fe—Ni alloy foils with a thickness of 50 μm or less. [Explanation of symbols]

[0064] 1 test piece 2 Vertical surface plate 3 Vertical plane 4. Tension (direction) 5. Gap 6. Measurement range

Claims

1. The components are in mass%: C: 0 to 0.030%, Si: 0 to 0.21%, Mn: 0 to 0.30%, Ni: 30.0 to 60.0%, Co: 0-5.00%, P: 0.01% or less, S: 0.01% or less, and The balance is Fe and impurities, An Fe—Ni alloy foil having a thickness of 50 μm or less and a positron annihilation lifetime of 0.150 ns or more.

2. 2. The Fe—Ni alloy foil according to claim 1, wherein the positron annihilation lifetime is 0.150 ns to 0.200 ns.

3. The Fe—Ni alloy foil according to claim 1 or 2, wherein the thickness is 20 μm or less.

4. The method for producing an Fe-Ni alloy foil according to claim 1 or 2, The components are in mass%: C: 0 to 0.030%, Si: 0 to 0.21%, Mn: 0 to 0.30%, Ni: 30.0 to 60.0%, Co: 0-5.00%, P: 0.01% or less, S: 0.01% or less, and preparing an Fe—Ni alloy powder with the balance being Fe and impurities; A method for producing an Fe—Ni alloy foil, comprising: a Fe—Ni alloy ingot production step of producing an Fe—Ni alloy ingot from the Fe—Ni alloy powder by a HIP method; and a rolling step of rolling the Fe—Ni alloy ingot.

5. The method for producing an Fe—Ni alloy foil according to claim 4, further comprising at least one annealing step between each rolling pass of the rolling step or after the final rolling.

6. The method for producing an Fe—Ni alloy foil according to claim 4, wherein the thickness of the foil is 20 μm or less.

7. The method for producing an Fe—Ni alloy foil according to claim 5, wherein the thickness of the foil is 20 μm or less.

8. A part comprising the Fe—Ni alloy foil according to claim 1 or 2.

9. 9. The part according to claim 8, wherein the thickness of the Fe—Ni alloy foil is 20 μm or less.

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