Iron–nickel alloy foil, method for manufacturing iron–nickel alloy foil, and component

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

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

[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.

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

[0003] Furthermore, there is a demand for thinner materials and components essential for the manufacture of electronic devices, not just components used in electronic devices themselves. For example, Fe—Ni alloy foil, which has good etching properties and thermal expansion properties, is used for metal masks essential for the manufacture of organic light-emitting diodes (OLEDs). However, as pixel density increases, thinner foils are being required (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.

[0004] International Publication No. WO 2015 / 122523 International Publication No. WO 2020 / 067537

[0005] When thinning Fe—Ni alloy foil, non-uniform residual stress is likely to occur during the manufacturing process (particularly rolling). Although stress relief annealing or other treatments are performed after rolling to remove the residual stress, the residual stress cannot be ultimately removed, resulting in deformations such as wavy edges, central elongation, and warpage. This deformation poses a quality problem for Fe—Ni alloy foil. In particular, this deformation becomes apparent when the foil thickness is less than 50 μm, posing a significant quality and technical problem.

[0006] Therefore, the present invention aims to suppress deformation such as edge undulation, center elongation, and warpage in an Fe—Ni alloy foil having a thickness of 50 μm or less, and to obtain an Fe—Ni alloy foil (hereinafter sometimes simply referred to as alloy foil) in which such deformation is suppressed.

[0007] The present inventors have conducted extensive research and development to achieve the above-mentioned objectives, and have discovered the following. (A) They believe that deformations such as wavy edges, central elongation, and warpage are caused by non-uniform deformation within the alloy foil, and that this non-uniform deformation is due to non-uniform residual stress within the alloy foil. It is known that residual stress is imparted during the manufacturing process of the alloy foil, particularly by rolling. Rolling causes deformation due to the movement of dislocations and vacancies in the alloy plate (although there is no clear standard for the thickness of alloy foil and alloy plate, for example, a plate with a thickness of more than 100 μm may be referred to as an alloy plate, and a plate with a 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 by rolling to form an alloy foil may be referred to as an Fe—Ni alloy plate or simply as an alloy plate). Dislocations themselves are generated by the movement and combination of vacancies. Based on these findings, the inventors focused on the behavior of vacancies in the alloy plate. It should be noted that the voids in the present invention do not refer to defects such as shrinkage holes or gas voids that occur during solidification in a casting, but rather refer to atomic vacancies or point defects.

[0008] (a) It was conceived 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, resulting in uniform deformation behavior within the alloy plate. Therefore, an alloy ingot was manufactured, for example, by hot powder metallurgy (such as the HIP method), and rolled to obtain alloy foil, and the deformation behavior was evaluated. As a result, it was confirmed that edge waviness, 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 foils have confirmed that when the PAL is 0.150 ns (nanoseconds) or greater, the amount of deformation is suppressed compared to conventional alloy foils. It has also been 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 impair 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] An Fe—Ni alloy foil having, in mass %, the following components: C: 0-0.030%, Si: 0-0.21%, Mn: 0-0.30%, Ni: 30.0-60.0%, Co: 0-5.00%, P: 0.01% or less, S: 0.01% or less, and the balance being Fe and impurities, the 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], wherein the foil has a thickness of 20 μm or less. [4] A method for producing an Fe—Ni alloy foil according to any one of [1] to [3], comprising the steps of preparing an Fe—Ni alloy powder containing, in mass %, C: 0-0.030%, Si: 0-0.21%, Mn: 0-0.30%, Ni: 30.0-60.0%, Co: 0-5.00%, P: 0.01% or less, S: 0.01% or less, and the balance being Fe and impurities, 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] A method for producing an Fe—Ni alloy foil according to [4], further comprising at least one annealing step between rolling passes or after final rolling in the rolling step. [6] A part having the Fe—Ni alloy foil according to any one of [1] to [3].

[0013] According to the present invention, it is possible to obtain an Fe—Ni alloy foil in which deformations such as wavy edges, central elongation, and warpage are suppressed.

[0014] 1 is a diagram showing an example of the relationship between PAL and deformation amount in an Fe—Ni alloy foil. 2 is a diagram showing an outline of a vertical hanging test. 3 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.

[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 case where the component is not contained (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, vacancy size, etc. In this invention, 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). 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 by 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 PAL of a positron source using a positron annihilation lifetime measurement device manufactured by Techno AP Co., Ltd. ２２ The PAL was evaluated using Na. For PAL evaluation, the Fe-Ni alloy foil to be evaluated was cut into 10 mm squares, and two sets of three stacked sheets were prepared. The positron source was sandwiched between the three stacked Fe-Ni alloy foils, which were then wrapped and secured in aluminum foil to create a PAL measurement sample. The prepared measurement sample was then loaded into a measurement device to measure the positron annihilation lifetime (PAL). It is recommended to use the data analysis software provided with the measurement device (e.g., PALSfit3, developed by the Technical University of Denmark). 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 during 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 plastic deformation and stress relaxation, but at the same time, work hardening occurs due to the interaction between dislocations. Therefore, if dislocations are introduced unevenly within the material, stress relaxation 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 holes 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 the generation of numerous vacancies uniformly throughout 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 will move more easily during rolling, etc., making it easier to deform even with a relatively light rolling load. Furthermore, uniform stress relaxation within the material results 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 conventional ingot materials, but does exceed 0.150 ns for hot powder metallurgy materials. That is, for materials in which dislocations are the main defect, such as conventional ingot materials, the PAL is less than 0.150 ns, while for materials in which point defects such as vacancies are the main defect, such as hot powder metallurgy materials, the PAL is 0.150 ns or greater. Therefore, a PAL of 0.150 ns or greater is considered to indicate a structure in which lattice defects are mainly point defects such as vacancies. That is, a PAL of 0.150 ns is considered to be the boundary at which a microstructure changes from one dominated by dislocations to one dominated by vacancies.

[0022] [Amount of deformation] Deformations such as edge undulation, center elongation, and warpage of Fe—Ni alloy foil 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 amount of deformation of the alloy foil in the vertical direction when the alloy foil was hung vertically could be used to evaluate the amount of deformation of the alloy foil.

[0023] The inventors adopted 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 center elongation usually occur along the rolling direction, the long side of the test specimen should be oriented in the rolling direction. Furthermore, alloy foils may be 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) ≧ 0.150 ns] 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 amount of deformation 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 has been confirmed that by setting the PAL to 0.150 ns or more, an Fe—Ni alloy with a void-dominated microstructure 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 amount of deformation. 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 of the present invention 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] [Composition of Fe—Ni Alloy Foil] The composition of the Fe—Ni alloy foil will be described. As mentioned above, unless otherwise specified, "%" regarding the composition 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%).

[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 about 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: 0-0.30% 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, so the Mn content should be 0.30% or less. The preferred range of the Mn content is 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: 30.0-60.0% 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, so 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 working (hot rolling or hot forging). Therefore, the Ni content should be 60.0% or less. The preferred range of the Ni content is, on the lower limit side, 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, and on the upper limit side, 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 preferable to set the value 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 in relation to the Ni content 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 should be set at 5.00%. Preferably, it should be set at 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 at grain boundaries during solidification and increases solidification cracking susceptibility. Therefore, it is preferable that the P content be as low as possible. Therefore, the P content is limited to 0.010% or less. It is preferably set to 0.005% or less, or 0.003% or less. The lower limit of the P content is 0%, but since an excessive reduction increases the manufacturing cost, it may be set to 0.001% or more in reality.

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

[0036] Other elements may also be contained as impurities within a range that does not impair the effects of the present invention, such as Cr, Al, Cu, Nb, Mo, Ti, Mg, Ca, Sn, V, W, Zr, B, and Bi.

[0037] [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 the effects of the present invention can be enjoyed, so the foil thickness is preferably 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. The lower limit of the foil thickness is not particularly limited, but from the viewpoint of industrial manufacturability, the foil thickness may be 1.0 μm or more.

[0038] [Manufacturing Method] The manufacturing method of 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 manufacturing process, rolling process, and annealing process. This method is described below. However, the Fe—Ni alloy foil according to the present invention is not limited to the manufacturing method described here.

[0039] [Fe—Ni Alloy Ingot Manufacturing Process] The Fe—Ni alloy ingot manufacturing process is a process for obtaining an ingot (steel billet, slab, etc.) of an Fe—Ni alloy having a predetermined composition. For example, there is a method of refining and solidifying a molten Fe—Ni alloy, which is called an ingot manufacturing method. Another example is a method of combining metal powders of a predetermined composition and solid-state bonding them under high temperature and high pressure, such as HIP (Hot Isostatic Press), which is called a hot powder metallurgy method.

[0040] As mentioned above, ingot alloys (molten alloy ingots) produced using conventional melting 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 material of an ingot alloy, localized stress relaxation occurs, and residual stress is likely to occur unevenly.

[0041] On the other hand, hot powder metallurgy methods such as HIP can eliminate shrinkage holes 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 the generation of numerous vacancies uniformly throughout 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 in which vacancies exist, unlike ingot materials. Therefore, hot powder metallurgy methods such as HIP can produce numerous vacancies uniformly compared to conventional ingot methods, resulting in an alloy ingot with a longer PAL life.

[0042] [Fe—Ni Alloy Powder Preparation Process] When producing Fe—Ni alloy powder by hot powder metallurgy, the production method is not particularly limited. For example, the conventionally used HIP method can be applied. To uniformly generate voids in the produced 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 may be 500 μm or less, 400 μm or less, 300 μm or less, 200 μm or less, or 100 μm or less. The production 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, or the like can be applied.

[0043] The prepared alloy powder is placed in a metal container and subjected to HIP treatment to obtain the desired alloy ingot. 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, thereby omitting subsequent processing steps (such as rolling and forging).

[0044] [Rolling Process] The obtained Fe—Ni alloy ingot can be hot-rolled or cold-rolled to obtain an alloy foil. Generally, the Fe—Ni alloy ingot is hot-rolled to form an Fe—Ni alloy plate having a thickness of 1 mm or less, and then cold-rolled to obtain an alloy foil of the desired thickness. Conventional manufacturing methods can be used for both hot and cold rolling. However, to extend the life of the PAL, it is preferable that the total reduction rate of each cold-rolling pass is not too large. This is because if the total reduction rate of cold rolling is too large, the rolling will result in a rolled structure with a high dislocation density in which strain accumulates, making vacancies more likely to be consumed. It is preferable to design the process so that the total reduction rate of cold rolling is reduced to a mild level within a range that does not reduce 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 the intersecting dislocations generates vacancies while increasing the dislocation density. This results in a longer life for the PAL. Therefore, annealing is preferable, and intermediate annealing between rolling passes is particularly preferable.

[0046] As mentioned above, dislocations can be eliminated by annealing, but dislocation elimination does not progress without recrystallization. Therefore, it is desirable to perform annealing 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, the temperature is 750°C or higher, or 800°C or higher. When annealing is performed at a temperature lower than 700°C, rolling is performed with dislocations remaining, and dislocations are more likely to be introduced in the final rolling, reducing the rolling load. However, the dislocation density becomes high, and vacancies are more likely to be consumed, resulting in a shorter lifespan of the PAL.

[0047] [Application to component materials] The Fe—Ni alloy foil according to the present invention can be applied as a material for all kinds of components because deformation is suppressed even when the foil is thinned. In particular, in 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 component materials.

[0048] Furthermore, although not applied to the component itself, it can also be applied to the component (member) used in the component manufacturing. For example, the Fe—Ni alloy foil according to the present invention may be applied to a metal mask for an OLED. For metal masks for OLEDs, Fe—Ni alloy foil is used due to its etching property and low thermal expansion, which allows for high definition. However, for 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 the Fe—Ni alloy foil according to the present invention includes not only parts made from the Fe—Ni alloy foil but also parts having a portion made of the Fe—Ni alloy foil.

[0051] [Test Materials] Fe-Ni alloy ingots were prepared by HIP using an Fe-36Ni alloy as a base, with the composition adjusted to that shown in Table 1. HIP materials were prepared by the HIP method, and ingot materials were prepared according to a conventional manufacturing method. The remainder of the components in Table 1 is Fe and impurities.

[0052] First, for the HIP materials, a molten metal (molten alloy) adjusted to the composition shown in Table 1 was gas atomized to form spherical alloy powder. The obtained alloy powder was classified, and the 300 μm undersize was subjected to HIP treatment to obtain the HIP materials. The HIP treatment was performed according to the usual procedure, and the HIP materials were produced by holding the HIP materials 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 materials conforming to conventional manufacturing methods were prepared by solidifying molten metal adjusted to the chemical composition shown in Table 1, re-refining it by the ESR method (electroslag remelting) or the VAR method (vacuum arc remelting), and then obtaining slabs according to conventional continuous casting methods. As shown in Table 1, ingot materials 1 and 2 with different chemical compositions were prepared.

[0054]

[0055] The obtained test materials were processed by rolling, annealing, etc. to form alloy foils. 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 plate was hot-rolled to a 3 mm thick alloy plate. Alloy plates with 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 plates 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 having 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 having a final thickness of 30 μm (0.030 mm).

[0058] The deformation amount 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 from 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 amount. In this example, a 100 g weight was attached to the lower end of the test piece to generate tension 4, and 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 with a gap gauge (not shown) as shown in Figure 3. The range 6 for measuring the gap 5 is not particularly limited, but 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 described above, the average positron annihilation lifetime (PAL) was measured by cutting the Fe-Ni alloy foil of each test material into 10 mm squares, preparing two sets of three stacked sheets, sandwiching the positron source between the three stacked Fe-Ni alloy foils, and wrapping and fixing them in aluminum foil to prepare PAL measurement samples. The prepared measurement samples were placed in a measuring device to measure the positron annihilation lifetime (PAL). A positron annihilation lifetime analyzer manufactured by Techno AP was used as the PAL measuring device, and the positron source was placed in a measuring device. ２２ The evaluation was performed using Na. PALSfit3, developed by the Technical University of Denmark, was used as the data analysis software. In order to take into account the influence 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 (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, triangle marks indicate comparative examples (cast materials), and circle marks indicate examples (HIP materials).

[0061]

[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 equivalent to the 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 contains approximately the same alloy elements 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.

[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.

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

Claims

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

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. A method for producing an Fe-Ni alloy foil according to claim 1 or 2, comprising the steps of: preparing an Fe-Ni alloy powder containing, in mass %, C: 0-0.030%, Si: 0-0.21%, Mn: 0-0.30%, Ni: 30.0-60.0%, Co: 0-5.00%, P: 0.01% or less, S: 0.01% or less, and the remainder being Fe and impurities; producing an Fe-Ni alloy ingot from said Fe-Ni alloy powder by HIP; and rolling said 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 is 20 μm or less.

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

8. A part having the Fe-Ni alloy foil according to claim 1 or 2.

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