Fe-Ni-BASED ALLOY SHEET AND METHOD FOR PRODUCING SAME

Abstract

The present invention pertains to: an Fe-Ni-based alloy sheet comprising, in mass%, C: 0.001-0.05%, Si: 0.05-0.50%, Mn: 0.25-1.00%, P: 0.001-0.030%, S: 0.0001-0.0050%, Ni: 35.0-44.0%, Cr: 0.01-0.50%, Mo: 0.005-0.10%, and Cu: 0.01-2.00%, Al: 0.0001-0.10%, Ti: 0.050% or less, Co: 0.01-2.00%, W: 0.01-0.50%, N: 0.001-0.05%, Sn: 0.0001-0.05%, Mg: 0.050% or less, Zr: 0.0001-0.05%, Ca: 0.0020% or less, and O: 0.0002-0.01%, with the balance being Fe and unavoidable impurities; and a method for manufacturing the same.

Description

Fe-Ni alloy plate and its manufacturing method

[0001] The present invention relates to an Fe—Ni alloy plate and a method for producing the same.

[0002] As specified in JIS C2531 and IEC standards, Fe-Ni-based soft magnetic alloys are broadly classified according to the Ni content into Permalloy C alloy (Ni: 72-83% by mass), Permalloy B alloy (Ni: 45-50% by mass), Permalloy D alloy (Ni: 35-40% by mass), etc. High-grade Permalloy C alloy has high magnetic permeability and low coercive force, and is therefore used in magnetic components such as magnetic shielding materials and magnetic sensor materials. However, because Permalloy C alloy contains a large amount of Ni and is expensive, it has been replaced by the cheaper Permalloy B alloy as a material for magnetic components. Furthermore, because Permalloy B alloy has a high saturation magnetic flux density, it is also used in watch stators, magnetic lens pole pieces, etc.

[0003] In recent years, while demand for soft magnetic materials such as automotive sensors and magnetic shielding materials has been increasing, the price of Ni has been on the rise, and there has been a movement to replace Permalloy B alloys with cheaper alloys such as Alloy 42 and Permalloy D, which have lower Ni contents. However, as the Ni content decreases, problems arise with the deterioration of various magnetic properties and corrosion resistance, and there is a strong demand for maintaining the high saturation magnetic flux density that is characteristic of Permalloy B alloys. In particular, soft magnetic materials with an initial relative permeability of 3,000 or more, a maximum relative permeability of 30,000 or more, and a saturation magnetic flux density of 1.4 T or more are preferably used for automotive sensors and magnetic shielding materials.

[0004] As a method for improving the magnetic properties of permalloy alloys, Patent Document 1 proposes a method for improving the magnetic properties by subjecting a continuously cast slab to a homogenizing heat treatment to reduce segregation, but Patent Document 1 does not mention saturation magnetic flux density.

[0005] Furthermore, Patent Document 2 proposes a method for improving magnetic properties by limiting the temperature and time of magnetic annealing of rolled Fe—Ni alloy material and the amount of A-based (Mn—S-based) inclusions in the Fe—Ni alloy, thereby promoting grain growth. However, this method aims to improve the coercive force, initial relative permeability, and maximum relative permeability of the resulting soft magnetic component material, and does not consider the saturation magnetic flux density.

[0006] JP 2002-173745 A JP 2015-196838 A

[0007] In view of the above circumstances, an object of the present invention is to provide an Fe—Ni-based alloy that can impart excellent initial relative permeability, good maximum relative permeability, and saturation magnetic flux density, and that can be produced with reduced yield, and a method for producing the same.

[0008] As a result of extensive research to solve the above problems, the inventors discovered that by strictly controlling the alloy composition of an Fe—Ni-based alloy, it is possible to improve the magnetic properties of the initial relative permeability, maximum relative permeability, and saturation magnetic flux density, and further to obtain an Fe—Ni-based alloy that can be manufactured with reduced yield, and thus arrived at the present invention.

[0009] The gist of the present invention is as follows. [1] Carbon (C): 0.001 to 0.05 mass%, Silicon (Si): 0.05 to 0.50 mass%, Manganese (Mn): 0.25 to 1.00 mass%, Phosphorus (P): 0.001 to 0.030 mass%, Sulfur (S): 0.0001 to 0.0050 mass%, Nickel (Ni): 35.0 to 44.0 mass%, Chromium (Cr): 0.01 to 0.50 mass%, Molybdenum (Mo): 0.005 to 0.10 mass%, Copper (Cu): 0.01 to 2.00 mass%, Aluminum (Al): 0.0001 to 0.10 mass%, Titanium (Ti): 0.050 mass% or less, Cobalt (Co): 0.01 to 2.00 mass%, Tungsten (W): 0.01 to 0.50 mass%, An Fe-Ni-based alloy plate comprising: 0.001 to 0.05 mass% of nitrogen (N), 0.0001 to 0.05 mass% of tin (Sn), 0.0001 to 0.05 mass% of magnesium (Mg), 0.050 mass% or less of zirconium (Zr), 0.0001 to 0.05 mass% of calcium (Ca), 0.0020 mass% or less of calcium (Ca), 0.0002 to 0.01 mass% of oxygen (O), with the balance consisting of iron (Fe) and unavoidable impurities. [2] The Fe-Ni-based alloy plate according to [1], containing Cu, Co, and W so as to satisfy the following relational formula (A): 1.5≦20[Cu%]+20[Co%]+80[W%]<50.0 ... (A) (In formula (A), % represents mass %) [3] An Fe-Ni alloy plate according to the above [1] or [2], containing Cu, Co, W, Cr, Mo, P and S so as to satisfy the relationship formula of the following formula (B): 10≦50([Cu%]+[Co%])+100[W%]+200[Cr%]+800[Mo%]-100[P%]-1000[S%] ... (B) (In formula (B), % represents mass %).) [4] A method for producing an Fe—Ni-based alloy plate according to any one of the above [1] to [3], characterized by comprising the steps of: subjecting a molten metal containing raw materials of an Fe—Ni-based alloy to oxidation refining in a secondary refining vessel such as an AOD furnace or a VOD furnace; adding Al and / or an FeSi alloy to the molten metal after oxidation refining, and performing deoxidation and desulfurization treatment so that the Al content in the molten metal is 0.0001 to 0.10 mass%, the Si content is 0.05 to 0.50 mass%, the S content is 0.0001 to 0.0050 mass%, and the O content is 0.0002 to 0.01 mass%; continuously casting the molten metal after deoxidation and desulfurization treatment to form a slab; and hot rolling and then cold rolling the obtained slab.

[0010] According to the present invention, by strictly controlling the alloy composition of the Fe—Ni alloy, it is possible to provide an Fe—Ni alloy plate that can be imparted with excellent initial relative permeability, good maximum relative permeability, and saturation magnetic flux density, and that can be produced with reduced yield, and a method for producing the same.

[0011] 1 is a graph showing the relationship between the value of formula (A) and the saturation magnetic flux density and the maximum relative permeability in a magnetic property test.

[0012] The Fe—Ni alloy plate according to the present invention and a method for producing the same are described below. The Fe—Ni alloy plate according to the present invention contains 0.001 to 0.05 mass% of carbon (C), 0.05 to 0.50 mass% of silicon (Si), 0.25 to 1.00 mass% of manganese (Mn), 0.001 to 0.030 mass% of phosphorus (P), 0.0001 to 0.0050 mass% of sulfur (S), 35.0 to 44.0 mass% of nickel (Ni), 0.01 to 0.50 mass% of chromium (Cr), 0.005 to 0.10 mass% of molybdenum (Mo), 0.01 to 2.00 mass% of copper (Cu), and 0.0001 to 0.0050 mass% of aluminum (Al). 10% by mass, titanium (Ti): 0.050% by mass or less, cobalt (Co): 0.01 to 2.00% by mass, tungsten (W): 0.01 to 0.50% by mass, nitrogen (N): 0.001 to 0.05% by mass, tin (Sn): 0.0001 to 0.05% by mass, magnesium (Mg): 0.050% by mass or less, zirconium (Zr): 0.0001 to 0.05% by mass, calcium (Ca): 0.0020% by mass or less, oxygen (O): 0.0002 to 0.01% by mass, with the balance consisting of iron (Fe) and unavoidable impurities. In this way, by strictly controlling the alloy composition of the Fe-Ni alloy, it is possible to provide an Fe-Ni alloy plate that can be imparted with excellent initial relative permeability, good maximum relative permeability and saturation magnetic flux density, and can be manufactured with reduced yield. The Fe--Ni alloy sheet according to the present invention can be endowed with such excellent magnetic properties, and is therefore suitable for use as a soft magnetic material for automobile sensors, magnetic shielding materials, watch stators, and the like.

[0013] In addition, the Fe—Ni alloy plate according to the present invention satisfies the above compositional components, and also satisfies the following formula (A): The Fe—Ni alloy plate preferably contains Cu, Co and W.

[0014] 1.5≦20[Cu%]+20[Co%]+80[W%]<50.0 … (A) (In formula (A), % represents mass %.)

[0015] The above formula (A) expresses as a relational expression the influence of the added amounts of Cu, Co, and W on the maximum relative magnetic permeability and saturation magnetic flux density of an Fe—Ni alloy, with Cu and Co having atomic radii similar to Ni, and W having an ionic radius similar to Ni. Figure 1 is a graph showing the relationship between the maximum relative magnetic permeability and saturation magnetic flux density measured by the following test method (magnetic property test) and the value of formula (A). Figure 2 is a graph showing the relationship between the saturation magnetic flux density and the value of formula (A) in the range where the value of formula (A) is 5.0 or less. Figure 1 shows that when the value of formula (A) is 50.0 or more, the maximum relative magnetic permeability is lower than 30,000, and Figure 2 shows that when the value of formula (A) is less than 1.5, the saturation magnetic flux density is lower than 1.4 T. Therefore, by containing Cu, Co, and W in the Fe—Ni alloy plate so that the value of formula (A) is within the range of 1.5 or more and less than 50.0, it is possible to obtain an Fe—Ni alloy plate that can impart excellent maximum relative magnetic permeability and saturation magnetic flux density.

[0016] <Magnetic Property Test> Fe—Ni alloys containing approximately 39.3 mass% Ni as a basic component were melted in a 10 kg capacity high-frequency induction furnace for testing. During this melting, the amounts of Cu, Co, and W added to each alloy were varied as shown in Table 1 below. The melted alloys were then cast into molds to form steel ingots, which were then hot forged into forged plates with a thickness of 10 mm. Subsequently, the surface was annealed and polished to remove scale, and the plates were cold-rolled to a thickness of 0.8 mm. These cold-rolled plates were processed into ring test pieces with a diameter of 45 mm and a thickness of 33 mm, in accordance with JIS C2531, and subjected to vacuum (≦5.0×10 －３ The wire was magnetically annealed in a 1125°C (1000 Pa) atmosphere for 2.5 hours with a soaking temperature of 1125°C. After that, 50 turns of enameled copper wire specified in JIS C3202 or JIS C3215 were wound on both the primary and secondary sides, and the maximum relative magnetic permeability (μ ｍａｘ ) and saturation magnetic flux density (B ８００ The maximum relative magnetic permeability was measured at a reversal magnetic field of 16 A / m, and the saturation magnetic flux density was measured under a magnetic field of 1600 A / m. The results are shown in Table 2. The numerical values ​​of each component in Table 1 represent "mass %."

[0017]

[0018]

[0019] Thus, Cu, Co, and W are important elements for obtaining an excellent saturation magnetic flux density, and when the value of formula (A), which is the relational expression for the amounts of Cu, Co, and W added, is 1.5 or more, a saturation magnetic flux density of 1.4 T or more can be obtained. On the other hand, when the value of formula (A) is 50.0 or more, the maximum relative magnetic permeability becomes less than 30,000. Therefore, the value of formula (A) is preferably in the range of 1.5 or more and less than 50.0, more preferably in the range of 1.5 or more and 40.0 or less, and even more preferably in the range of 1.5 or more and 25.0 or less.

[0020] In addition, the Fe—Ni alloy plate according to the present invention satisfies the above compositional components, and also satisfies the following formula (B): The Fe—Ni alloy plate preferably contains Cu, Co, W, Cr, Mo, P and S.

[0021] 10≦50([Cu%]+[Co%])+100[W%]+200[Cr%]+800[Mo%]-100[P%]-1000[S%] ... (B) (In formula (B), % represents mass %)

[0022] Rust may occur in Fe—Ni-based soft magnetic materials during the manufacturing process due to changes in temperature, humidity, etc., raising concerns about deterioration of magnetic properties due to rust. Cu, Co, W, Cr, Mo, P, and S are elements that affect rust resistance. In the present invention, by containing Cu, Co, W, Cr, Mo, P, and S in an Fe—Ni-based alloy sheet so as to satisfy formula (B), an Fe—Ni-based alloy sheet can be obtained that not only imparts excellent magnetic properties but also has rust resistance. In this way, the rust resistance of the Fe—Ni-based alloy sheet makes it possible to omit additional steps such as rust removal and handling to prevent rust generation, thereby preventing a decrease in workability and a decrease in productivity due to an increase in the number of steps. The value of formula (B) is preferably 10 or more, more preferably 15 or more, and even more preferably 20 or more.

[0023] C: 0.001 to 0.05% by mass. C contained in Fe—Ni alloy sheets is an element necessary for maintaining the strength of the alloy. If the C content is less than 0.001% by mass, the effect is not fully achieved. On the other hand, if the C content exceeds 0.05% by mass, it reacts with Cr and Ti contained in the alloy to form carbides, which inhibit grain growth and domain wall movement and deteriorate magnetic properties. Therefore, the C content is 0.001 to 0.05% by mass, preferably 0.001 to 0.01% by mass, and more preferably 0.001 to 0.008% by mass.

[0024] Si: 0.05 to 0.50% by mass Si contained in Fe—Ni alloy sheets is an effective element for the deoxidation treatment performed during the production of Fe—Ni alloy sheets. If the Si content is less than 0.05% by mass, this effect is not fully achieved. On the other hand, if the Si content exceeds 0.50% by mass, the ordered lattice of the Fe—Ni alloy is no longer optimal, resulting in deterioration of magnetic properties. Therefore, the Si content is 0.05 to 0.50% by mass, with a preferred lower limit of 0.10% by mass and a preferred upper limit of 0.25% by mass. That is, the Si content is preferably 0.05 to 0.25% by mass, and more preferably 0.10 to 0.25% by mass.

[0025] Mn: 0.25 to 1.00% by mass. Mn contained in the Fe—Ni alloy sheet combines with S, which reduces hot workability, to form MnS. This suppresses the degradation of hot workability due to S, and the formation of MnS is an effective element for improving punchability. If the Mn content is less than 0.25% by mass, this effect cannot be fully achieved. On the other hand, if the Mn content exceeds 1.00% by mass, excessive MnS is formed, which inhibits grain growth and domain wall movement, thereby deteriorating magnetic properties. Therefore, the Mn content is 0.25 to 1.00% by mass, preferably 0.25 to 0.60% by mass, and more preferably 0.25 to 0.57% by mass.

[0026] P: 0.001 to 0.030% by mass. P contained in Fe—Ni alloy sheet is an element that segregates at grain boundaries, thereby suppressing the segregation of S to the grain boundaries, promoting the dispersed precipitation of MnS, and effectively improving punchability. If the P content is less than 0.001% by mass, this effect cannot be fully achieved. On the other hand, if the P content exceeds 0.030% by mass, excessive P segregates at the grain boundaries, not only deteriorating hot workability but also reducing rust resistance. Therefore, the P content is 0.001 to 0.030% by mass, preferably 0.001 to 0.020% by mass, and more preferably 0.001 to 0.019% by mass.

[0027] S: 0.0001 to 0.0050% by mass. S contained in Fe—Ni alloy sheets combines with Mn and Mg to form MnS and MgS, effectively improving punchability. If the S content is less than 0.0001% by mass, this effect is not fully achieved. On the other hand, if the S content exceeds 0.0050% by mass, S segregates at grain boundaries to form low-melting-point compounds, significantly reducing hot workability and rust resistance. Therefore, the S content is 0.0001 to 0.0050% by mass. The lower limit of the S content is preferably 0.0003% by mass, more preferably 0.0005% by mass. The upper limit of the S content is preferably 0.0040% by mass, more preferably 0.0030% by mass. That is, the S content is preferably 0.0003 to 0.0040 mass %, and more preferably 0.0005 to 0.0030 mass %.

[0028] Ni: 35.0 to 44.0% by mass Ni contained in Fe—Ni alloy sheets is an important element for ensuring magnetic properties. If the Ni content is less than 35.0% by mass, the effect is not fully achieved. On the other hand, if the Ni content exceeds 44.0% by mass, scratches may occur on the surface of the rolled sheet during hot rolling, or cracks may occur, resulting in a reduced yield. Therefore, the Ni content is 35.0 to 44.0% by mass, with a preferred lower limit of 35.7% by mass, more preferably 40.5% by mass, and a preferred upper limit of 42.6% by mass, more preferably 41.5% by mass. That is, the Ni content is preferably 35.7 to 42.6% by mass, more preferably 40.5 to 41.5% by mass.

[0029] Cr: 0.01 to 0.50% by mass. Cr contained in the Fe—Ni alloy sheet is an effective element for ensuring rust resistance. If the Cr content is less than 0.01% by mass, this effect is not fully achieved. On the other hand, if the Cr content exceeds 0.50% by mass, Cr bonds with the C present in the Fe—Ni alloy to form Cr-based carbides, which inhibit domain wall movement and deteriorate magnetic properties. Therefore, the Cr content is 0.01 to 0.50% by mass, with a preferred lower limit of 0.02% by mass, more preferably 0.03% by mass, and a preferred upper limit of 0.10% by mass, more preferably 0.08% by mass. That is, the Cr content is preferably 0.02 to 0.10% by mass, more preferably 0.03 to 0.08% by mass.

[0030] Mo: 0.005 to 0.10% by mass Mo contained in the Fe—Ni alloy sheet is an effective element for ensuring rust resistance, and is also an important element for controlling the conditions for forming a superlattice that affects magnetocrystalline anisotropy and magnetostriction. If the Mo content is less than 0.005% by mass, this effect cannot be fully achieved. On the other hand, if the Mo content exceeds 0.10% by mass, the saturation magnetic flux density decreases. Therefore, the Mo content is 0.005 to 0.10% by mass, with a preferred lower limit of 0.01% by mass and a preferred upper limit of 0.05% by mass. That is, the Mo content is preferably 0.01 to 0.05% by mass.

[0031] Cu: 0.01 to 2.00% by mass Cu contained in the Fe—Ni alloy sheet is an important element for ensuring saturation magnetic flux density and rust resistance at the same time. If the Cu content is less than 0.01% by mass, sufficient rust resistance cannot be obtained. On the other hand, if the Cu content exceeds 2.00% by mass, burrs and sagging occur during slitting or punching, resulting in deterioration of the product shape. Therefore, the Cu content is 0.01 to 2.00% by mass, preferably 0.01 to 0.50% by mass, and more preferably 0.01 to 0.40% by mass.

[0032] Al: 0.0001 to 0.10% by mass The Al contained in the Fe-Ni alloy sheet is an effective element for the deoxidation treatment carried out when manufacturing the Fe-Ni alloy sheet. If the Al content is less than 0.0001% by mass, the effect is not fully obtained, and the O concentration in the Fe-Ni alloy increases, increasing the number of oxide-based inclusions and degrading the magnetic properties. On the other hand, if the Al content exceeds 0.10% by mass, the power to reduce MgO in the slag becomes too strong, increasing the Mg concentration in the Fe-Ni alloy and reducing Ni, an intermetallic compound with a low melting point. ２This produces Mg, which reduces hot workability. At the same time, the reducing power of CaO in the slag becomes too strong, increasing the Ca concentration in the steel and degrading magnetic properties. Therefore, the Al content is 0.0001 to 0.10 mass%, preferably 0.0001 to 0.050 mass%, and more preferably 0.0001 to 0.045 mass%.

[0033] Ti: 0.050% by mass or less. Ti contained in the Fe—Ni alloy sheet combines with C and N present in the Fe—Ni alloy to form Ti-based carbides and nitrides. Too much Ti inhibits grain growth and domain wall movement, degrading magnetic properties. On the other hand, Ti forms nitrides, which act as nuclei for MnS, which is effective in improving punchability, and promotes precipitation. Therefore, considering the balance between magnetic properties and punchability, the Ti content is 0.050% by mass or less, with a preferred lower limit of 0.001% by mass and a preferred upper limit of 0.020% by mass. That is, the Ti content is preferably 0.001 to 0.020% by mass.

[0034] Co: 0.01 to 2.00% by mass Co contained in the Fe—Ni alloy sheet is an important element for ensuring saturation magnetic flux density and rust resistance at the same time. If the Co content is less than 0.01% by mass, sufficient rust resistance cannot be obtained. On the other hand, if the Co content exceeds 2.00% by mass, burrs and sagging occur during slitting or punching, resulting in deterioration of the product shape. Therefore, the Co content is 0.01 to 2.00% by mass, preferably 0.01 to 1.00% by mass, and more preferably 0.01 to 0.50% by mass.

[0035] W: 0.01 to 0.50% by mass The W contained in the Fe—Ni alloy sheet is an important element for ensuring saturation magnetic flux density and rust resistance at the same time. If the W content is less than 0.01% by mass, sufficient rust resistance cannot be obtained. On the other hand, if the W content exceeds 0.50% by mass, warping occurs during slitting or punching, resulting in deterioration of the product shape. Therefore, the W content is 0.01 to 0.50% by mass, preferably 0.01 to 0.10% by mass, and more preferably 0.01 to 0.05% by mass.

[0036] N: 0.001 to 0.05% by mass N contained in the Fe—Ni alloy sheet is an element necessary for ensuring the strength of the Fe—Ni alloy. If the N content is less than 0.001% by mass, the effect is not fully achieved. On the other hand, if the N content exceeds 0.05% by mass, when Ti is present in the Fe—Ni alloy, N bonds with Ti to form nitrides, which inhibit grain growth and domain wall movement, thereby deteriorating the magnetic properties. Therefore, the N content is 0.001 to 0.05% by mass, and the preferred upper limit of the Ni content is 0.01% by mass, more preferably 0.006% by mass. That is, the Ni content is preferably 0.001 to 0.01% by mass, more preferably 0.001 to 0.006% by mass.

[0037] Sn: 0.0001 to 0.05% by mass Sn contained in Fe—Ni alloy sheet is an element necessary for ensuring plating properties. If the Sn content is less than 0.0001% by mass, this effect cannot be fully achieved. On the other hand, if the Sn content exceeds 0.05% by mass, hot workability is reduced. Therefore, the Sn content is 0.0001 to 0.05% by mass, with a preferred upper limit of 0.01% by mass, and more preferably 0.005% by mass. That is, the Sn content is preferably 0.0001 to 0.01% by mass, and more preferably 0.0001 to 0.005% by mass.

[0038] Mg: 0.05% by mass or less The Mg contained in the Fe—Ni alloy sheet bonds with the S present in the Fe—Ni alloy to form MgS. If the Mg content is too high, excessive MgS is formed, which inhibits the growth of crystal grains and the movement of domain walls, thereby deteriorating the magnetic properties. However, Mg is inevitably mixed in due to manufacturing reasons. Therefore, from the viewpoint of magnetic properties, the Mg content is 0.05% by mass or less, preferably 0.01% by mass or less, and more preferably 0.005% by mass or less.

[0039] Zr: 0.0001 to 0.05% by mass Zr contained in the Fe—Ni alloy sheet is an element necessary for ensuring the strength of the Fe—Ni alloy. If the Zr content is less than 0.0001% by mass, the effect is not fully obtained. On the other hand, if the Zr content exceeds 0.05% by mass, the magnetic properties are reduced. Therefore, the Zr content is 0.0001 to 0.05% by mass, preferably 0.0001 to 0.01% by mass, and more preferably 0.0001 to 0.008% by mass.

[0040] Ca: 0.0020% by mass or less The Ca contained in the Fe-Ni alloy sheet combines with the Al present in the Fe-Ni alloy to form Ca-Al oxide inclusions. If the Ca content is too high, excessive Ca-Al oxide inclusions are formed, which inhibits the growth of crystal grains and the movement of domain walls, thereby deteriorating the magnetic properties. On the other hand, Ca is a SiO ２ Ca is an important element for suppressing the activity and for reducing the amount of inclusions by controlling the O content. Therefore, from the viewpoint of magnetic properties, the Ca content is 0.0020% by mass or less, with a preferred lower limit of the Ca content being 0.0001% by mass and a preferred upper limit of the Ca content being 0.0010% by mass. That is, the Ca content is preferably 0.0001 to 0.0010% by mass.

[0041] O: 0.0002 to 0.01% by mass. If the O content in the Fe—Ni alloy sheet (molten metal) is less than 0.0002% by mass, CaO in the slag is reduced, increasing the Ca concentration in the molten metal. This leads to the excessive formation of Ca—Al oxide-based inclusions, which inhibit grain growth and domain wall movement and deteriorate magnetic properties. On the other hand, if the O content exceeds 0.01% by mass, oxide-based inclusions are formed with other elements, inhibiting domain wall movement and deteriorating magnetic properties. Therefore, the O content is 0.0002 to 0.01% by mass, with a preferred lower limit of 0.0005% by mass and a preferred upper limit of 0.008% by mass. That is, the O content is preferably 0.0005 to 0.008% by mass.

[0042] In the Fe-Ni alloy plate according to the present invention, the balance other than the above components is Fe and unavoidable impurities, and Fe is contained as the main component.

[0043] The thickness of the Fe-Ni alloy plate is not particularly limited, but is preferably 0.05 mm or more and 6.00 mm or less, and more preferably 0.08 mm or more and 4.00 mm or less.

[0044] Next, a method for producing an Fe—Ni alloy plate according to the present invention will be described. The method for producing an Fe—Ni alloy plate according to the present invention includes the following steps: (a) subjecting a molten metal containing raw materials of an Fe—Ni alloy to oxidative refining in a secondary refining vessel such as an AOD furnace or a VOD furnace (hereinafter also referred to as “step (a)”); (b) adding Al and / or an FeSi alloy to the molten metal after the oxidative refining, and subjecting the molten metal to deoxidation and desulfurization treatment so that the Al content in the molten metal is 0.0001 to 0.10 mass%, the Si content is 0.05 to 0.50 mass%, the S content is 0.0001 to 0.0050 mass%, and the O content is 0.0002 to 0.01 mass% (hereinafter also referred to as “step (b)”); (c) continuously casting the molten metal after the deoxidation and desulfurization treatment to form a slab (hereinafter also referred to as “step (c)”); and (d) hot-rolling and then cold-rolling the obtained slab (hereinafter also referred to as “step (d)”).

[0045] Step (a) In step (a), a molten metal containing raw materials for an Fe—Ni alloy is subjected to oxidation refining using a secondary refining vessel, either an AOD (Argon Oxygen Decarburization) furnace or a VOD (Vacuum Oxygen Decarburization) furnace. The molten metal is obtained by melting raw materials for an Fe—Ni alloy in an electric furnace. Examples of raw materials that can be used include iron scrap, nickel, and ferronickel. Alternatively, Fe—Ni alloy slabs and Fe—Ni scraps may also be used. The obtained molten metal is decarburized using a secondary refining vessel, either an AOD furnace or a VOD furnace, to produce an oxidizing slag after decarburization, i.e., FeO-containing slag, such as FeO—CaO—SiO ２This method allows the removal of oxidizing slag from the system. This slag also contains chromium oxide, tungsten oxide, titanium oxide, and phosphorus oxide, and these oxides can also be removed from the system. This allows the Cr content of the resulting Fe-Ni alloy plate to be controlled within the above-mentioned range. Furthermore, the W and Ti contents can also be easily controlled within the above-mentioned ranges. Furthermore, the content of the harmful impurity element P can be reduced to 0.030 mass% or less. Thus, by performing oxidation refining using either an AOD furnace or a VOD furnace as the secondary refining vessel, it is possible to remove the oxidizing slag from the system. Note that, since a VOD furnace requires the ladle to be temporarily transferred to a slag removal area and the slag removal performed using a slag removal machine, the molten metal temperature is likely to drop. Therefore, the use of an AOD furnace is more effective.

[0046] Furthermore, by the step (a), the contents of Cu, Co, and W can be appropriately controlled so that the obtained Fe—Ni-based alloy plate satisfies the above formula (A). That is, it becomes easy to control the value of the above formula (A) within a range of 1.5 or more and less than 50.0, preferably within a range of 1.5 or more and 40.0 or less, more preferably within a range of 1.5 or more and 25.0 or less.

[0047] In step (b), Al and / or FeSi alloy is added to the molten metal after oxidation refining to perform deoxidation and desulfurization. Even after the oxidizing slag is removed by oxidation refining, about 1 ton of oxidizing slag still remains on the molten metal. Therefore, taking into account the FeO concentration in the remaining oxidizing slag and the oxygen concentration in the molten metal, an amount of Al and / or FeSi alloy commensurate with the concentration is added to the molten metal to deoxidize and desulfurize the molten metal. In particular, by adding Al and an FeSi alloy so that the Al content in the molten metal is adjusted to within the range of 0.0001 to 0.1 mass% and the Si content to within the range of 0.05 to 0.5 mass%, deoxidation and desulfurization proceed in the most preferable manner, and in the resulting Fe—Ni-based alloy plate, the O content can be controlled to within the range of 0.0002 to 0.01 mass% and the S content can be controlled to within the range of 0.0001 to 0.0050 mass%, respectively, and other thermodynamically unstable elements can also be controlled within the above-mentioned ranges. The theory behind this is explained below.

[0048] In the refining process including the above-mentioned steps (a) and (b), the resulting slag plays a very important role. The slag to be formed is not particularly limited, but it may be CaO-SiO ２ -Al ２ O ３ It is preferable to form a slag based on MgO—F. The CaO contained in such a slag is obtained by burning limestone to CO ２ It can be formed by dissociating calcium hydroxide and adding the resulting quicklime as CaO to the molten metal, and SiO ２ can be formed by oxidation after the addition of an FeSi alloy. CaO plays a particularly important role in the slag, and the CaO concentration in the slag is preferably controlled to 40 to 70 mass%. MgO can be formed by using magnesia-containing bricks, such as dolomite-based bricks, magnesia bricks, or MgO-C-based bricks, as the refractory material in the secondary refining vessel of either an AOD furnace or a VOD furnace, and dissolving the MgO in the slag. Furthermore, since such bricks are expensive, it is preferable to extend the life of the bricks as much as possible to reduce costs, and MgO-containing waste bricks may be used. F can be controlled by adding fluorite to the molten metal. F is an important component, ensuring the fluidity of the slag and allowing the following reactions to proceed between the slag and the molten metal, thereby controlling the O content to within a range of 0.0002 to 0.01 mass%, the S content to within a range of 0.0001 to 0.0050 mass%, and the Ca content to 0.0020 mass% or less. Therefore, it is preferable to control the F concentration in the slag to 1 to 10 mass%. In the reactions below, the underlined components are those contained in the molten metal, and the components in parentheses are those contained in the slag.

[0049] Si+2O → (SiO ２ ) (1) 2(CaO)+Si → (SiO ２ )+2Ca (2) Ca+S → (CaS) (3)

[0050] In order to effectively advance the reaction represented by the above formula (1) toward the right side and control the O content within the range of 0.0002 to 0.01 mass%, it is necessary to ２ Activity 10 －２ ~10 －３For this purpose, as mentioned above, CaO is effective, and adding quicklime to the molten metal reduces the amount of SiO ２ Furthermore, when the reaction expressed by the above formula (2) proceeds toward the right side, and then the generated Ca reacts with S in the molten metal to cause the desulfurization reaction expressed by the above formula (3), the S content can be controlled within the range of 0.0001 to 0.0050 mass%, and once the Ca has migrated into the molten metal, it reacts with S, resulting in the Ca being consumed, making it possible to control the Ca content to 0.0020 mass% or less.

[0051] Furthermore, as expressed by the following formula (4), Al can also be used for deoxidation. Generally, industrial FeSi alloys contain about 1 mass% of Al as an impurity. Therefore, by adding FeSi alloy to the molten metal, it is possible to control the Al content within the range of 0.0001 to 0.10 mass%. Furthermore, the Al content in the slag can be controlled to 0.0001 to 0.10 mass%. ２ O ３ Care must be taken because Al may also react with Si in the molten metal. In other words, if the reaction represented by the following formula (5) becomes active, the Al content will exceed 0.10 mass%. In order to control the reaction represented by the following formula (5), the Al content in the slag must be kept at a constant level. ２ O ３ Activity 10 －２ ~10 －３ By controlling the CaO concentration in the slag to a low level, it becomes easier to control the Al content within the range of 0.0001 to 0.10 mass%. To achieve this, as described above, it is preferable to control the CaO concentration in the slag to cause the reaction represented by the above formula (2) to proceed toward the right side, thereby bringing the reaction represented by the following formula (5) into equilibrium and stabilizing the reaction.

[0052] 2Al+3O → (Al ２ O ３ ) (4) 2(Al ２ O ３ )+3Si → 3(SiO ２ ) + 4Al (5)

[0053] In order to control the Mg content to 0.050% by mass or less, it is necessary to suppress the reaction represented by the following formula (6) as much as possible. In this case, it is effective to keep the MgO content in the slag as low as possible, but in consideration of the damage caused by the melting of bricks and the need to add waste bricks, it is preferable to control the MgO concentration in the slag to a range of 5 to 20% by mass. Furthermore, in order to suppress the Mg concentration, it is preferable to control the Si concentration in the molten metal to within the above ranges and the CaO concentration in the slag to within the above ranges. This makes it possible to control the Mg content to 0.050% by mass or less.

[0054] 2(MgO)+Si → (SiO ２ ) + 2Mg (6)

[0055] W is WO during decarburization ３ The oxides of these elements are formed, some of which volatilize, and simultaneously migrate into the slag as represented by the reaction of formula (7) below. The W content can be controlled within the range of 0.01 to 0.50 mass% by adjusting the amount of W added in the ladle refining process, but it is preferable to control the CaO concentration, MgO concentration, and F concentration in the slag within the above ranges, respectively, to bring the reaction represented by formula (7) below into equilibrium and stabilize the reaction.

[0056] W + 3O → (WO ３ ) (7)

[0057] To control the Zr content within the range of 0.0001 to 0.05 mass%, the amount of Zr added can be adjusted in ladle refining, as with W. However, Zr is an element that is easily oxidized, as shown in the following formula (8). Therefore, it is preferable to maintain the equilibrium of the reaction represented by the following formula (7) and stabilize the reaction by controlling the CaO concentration, MgO concentration, and F concentration in the slag within the above ranges, and also by controlling the O content within the range of 0.0002 to 0.01 mass%.

[0058] Zr+2O → (ZrO ２ ) (8)

[0059] In order to control the Ti content to 0.050 mass% or less, the reaction represented by the following formula (9) is effectively advanced toward the right side. Here, the CaO concentration, MgO concentration, and F concentration in the slag are each controlled within the above ranges, and the TiO ２ By reducing the activity and controlling the O content within the range of 0.0002 to 0.01 mass%, the reaction represented by the following formula (9) can be effectively progressed toward the right-hand side, and it is finally possible to control the Ti content to 0.050 mass% or less.

[0060] Ti+2O → (TiO ２ ) (9)

[0061] In order to control the N content within the range of 0.001 to 0.05 mass%, the reaction represented by the following formula (10) is effectively advanced toward the right side. Nitrogen is easily mixed in from the atmosphere when raw materials are melted in an electric furnace. However, by using an AOD furnace or VOD furnace, the reaction represented by the following formula (10) advances toward the right side during decarburization, allowing the N content to be controlled within the above-mentioned range. That is, during oxygen blowing, CO gas is generated by the reactions represented by the following formulas (11) and (12). The CO gas bubbles generated in this manner can capture dissolved nitrogen in the molten metal and transfer it in the form of nitrogen gas into the CO gas. Finally, the CO bubbles are discharged outside the furnace, allowing the nitrogen gas to be removed. However, even if CO gas is removed from the system, the thermodynamic equilibrium value of nitrogen does not fall below 0.001 mass%, making it possible to control the N content within the range of 0.001 to 0.05 mass%.

[0062] 2N → N ２ [Gas] (10) O2 [Gas] + 2Fe → 2FeO [Oxygen gas bubble surface] (11) FeO [Oxygen gas bubble surface] + C → CO [Gas] + Fe [Liquid] (12)

[0063] In step (c), the deoxidized and desulfurized molten metal is continuously cast to form a slab. The conditions for continuous casting are not particularly limited, but continuous casting can be performed using a vertical continuous casting machine.

[0064] Step (d) In step (d), the obtained slab is hot rolled and then cold rolled. A hot section is produced through the hot rolling process of the slab, and then the obtained hot section is cold rolled to produce a cold-rolled sheet. The conditions for hot rolling and cold rolling are not particularly limited, but hot rolling can be performed using a Steckel rolling mill, and cold rolling can be performed using a Sendzimir-type cold rolling mill. Furthermore, before the cold rolling process, annealing and pickling may be performed as necessary to remove surface scale. In this way, the Fe—Ni alloy sheet according to the present invention can be produced.

[0065] By performing magnetic annealing on the cold-rolled sheet obtained by cold rolling, magnetic properties are imparted to the Fe—Ni alloy. The conditions for magnetic annealing are not particularly limited, and magnetic annealing can be carried out appropriately using a conventionally known method. After going through these steps, the initial relative magnetic permeability (μ i ) is 3,000 or more, more preferably 3,500 or more, and preferably the maximum relative permeability (μ ｍａｘ ) is 30,000 or more, more preferably 35,000 or more, and preferably the saturation magnetic flux density (B ８００ ) can be realized as an Fe—Ni alloy sheet exhibiting magnetic properties of 1.4 T or more, more preferably 1.45 T or more.

[0066] Next, examples of the present invention will be described, but the present invention is not limited to these examples as long as they do not depart from the spirit of the present invention.

[0067] Examples 1 to 40, Comparative Examples 1 to 10 Sixty tons of raw materials containing iron scrap, nickel, ferronickel, etc. were melted in an electric furnace. Thereafter, oxidation refining was carried out in an AOD furnace or a VOD furnace for treatments such as decarburization, dechromization, and dephosphorization. Here, the refractories of the secondary refining vessel of the AOD furnace or VOD furnace were lined with dolomite bricks, magnesia bricks, or MgO—C-based bricks for each charge according to the operational cycle. Next, the formed oxidizing slag, i.e., FeO-containing slag FeO—CaO—SiO ２The slag was removed from the system. This slag also contained Cr oxide, W oxide, Ti oxide, and phosphorus oxide, and was removed from the system as much as possible. The molten metal was then deoxidized and desulfurized using Al and / or FeSi alloys while adjusting the contents of Al, Si, S, and O contained in the molten metal. During this process, CaO-SiO ２ -Al ２ O ３ In other words, quicklime was added to the molten metal to form CaO, and SiO ２ was formed by oxidation after the addition of the FeSi alloy. The MgO source was made from MgO-containing waste bricks, which also served the purpose of preventing brick melting damage. The F source was prepared by adding fluorite to the molten metal to ensure the fluidity of the slag. The molten steel was then poured into a ladle, and the temperature was adjusted by ladle refining. At the same time, various components were carefully calculated and added to adjust the alloy composition to the chemical compositions shown in Tables 3 and 4 below. The slag compositions in Table 5 indicate the slag compositions at the end of AOD or VOD refining.

[0068]

[0069]

[0070]

[0071] The deoxidized and desulfurized molten metal was then continuously cast to form a slab, which was then hot-rolled, annealed, and pickled, followed by cold-rolling to produce an Fe—Ni alloy plate having a thickness of 0.8 mm.

[0072] <Magnetic Properties> The obtained Fe—Ni alloy plate was processed into a ring test piece of φ45 mm×33 mm in accordance with JIS C2531, and subjected to vacuum (5.0×10 －３ After magnetic annealing in a 1125°C soaking atmosphere for 2.5 hours, 50 turns of enameled copper wire specified in JIS C3202 or JIS C3215 were wound on both the primary and secondary sides, and the initial relative permeability (μ i ), maximum relative permeability (μ ｍａｘ ) and saturation magnetic flux density (B ８００) were measured. The initial relative permeability and maximum relative permeability were measured with a reversed magnetic field of 16 A / m, and the initial relative permeability was set to a value of 0.8 A / m. The saturation magnetic flux density was measured under a magnetic field of 1600 A / m. A comprehensive evaluation of the magnetic properties was performed based on the measurement results, and if all three of the following criteria for initial relative permeability, maximum relative permeability, and saturation magnetic flux density were met, the magnetic properties were evaluated as excellent (○). If only two of the following criteria for initial relative permeability, maximum relative permeability, and saturation magnetic flux density were met, the magnetic properties were evaluated as good (△), and if only one or none of the criteria were met, the magnetic properties were evaluated as poor (×). The results are shown in Table 6. Initial relative permeability: 3,000 or more Maximum relative permeability: 30,000 or more Saturation magnetic flux density: 1.4 (T) or more

[0073] <Rust Resistance> To evaluate rust resistance, the cold-rolled sheet obtained above was cut into 40 x 50 mm test pieces, and the surfaces were wet-polished with #400 waterproof abrasive paper, followed by an accelerated rust test. The accelerated rust test was performed at a temperature of 70°C and a relative humidity of 100%, and the test pieces were held horizontally in a 1000 ml beaker containing 200 ml of distilled water for 72 hours without getting wet. The degree of rust was then evaluated using the rating number (RN) according to JIS G0595, using the following three-level scale. The results are shown in Table 6. ◯: RN is greater than 2.5 △: RN is 2.0 or greater but not greater than 2.5 ×: RN is less than 2.0

[0074] <Overall evaluation> The above tests were evaluated overall using the following four-point scale. The results are shown in Table 6. ⊚: Both magnetic properties and rust resistance were evaluated as "good". ◯: Magnetic properties were evaluated as "good" and rust resistance was evaluated as "fair". △: Magnetic properties were evaluated as "fair", or magnetic properties were evaluated as "good" and rust resistance was evaluated as "bad". ×: Magnetic properties were evaluated as "bad", or product yield was poor.

[0075]

[0076] As shown in Tables 3 to 6, in Examples 1 to 30 using the Fe-Ni alloy plate that satisfies the range of chemical composition defined in the present invention, the evaluation of both magnetic properties and rust resistance was "○", and the overall evaluation was also "◎".

[0077] In Examples 31 to 34, the obtained Fe-Ni alloy plates satisfied the range of chemical composition defined in the present invention, and the evaluation of magnetic properties was also "○", but the evaluation of rust resistance was "△", and the overall evaluation was "○".

[0078] In Example 35, the obtained Fe—Ni alloy plate satisfied the range of chemical composition defined in the present invention, but the value of formula (A) was 50.4, and the maximum relative magnetic permeability was less than 30,000, so the evaluation of magnetic properties was "△". On the other hand, the evaluation of rust resistance was "〇", so the overall evaluation was "△".

[0079] In Example 36, the obtained Fe—Ni alloy plate satisfied the range of chemical composition defined in the present invention, but the value of formula (A) was 1.4, and the saturation magnetic flux density was less than 1.4 T, so the evaluation of magnetic properties was “△”. On the other hand, the evaluation of rust resistance was “◯”, so the overall evaluation was “△”.

[0080] In Example 37, the obtained Fe—Ni alloy plate satisfied the range of chemical composition defined in the present invention, but the value of formula (A) was 1.3, and the saturation magnetic flux density was less than 1.4 T, so the evaluation of magnetic properties was “△”. On the other hand, the evaluation of rust resistance was “◯”, so the overall evaluation was “△”.

[0081] In Example 38, the obtained Fe—Ni alloy plate satisfied the range of chemical composition defined in the present invention, but the value of formula (A) was 50.1, and the maximum relative magnetic permeability was less than 30,000, so the evaluation of magnetic properties was "△". On the other hand, the evaluation of rust resistance was "〇", so the overall evaluation was "△".

[0082] In Example 39, the obtained Fe—Ni alloy plate satisfies the range of chemical composition defined in the present invention, but the value of formula (B) is 9, and RN is less than 2.0, so the rust resistance is evaluated as "×". On the other hand, the magnetic properties are evaluated as "○", so the overall evaluation is "△".

[0083] In Example 40, the obtained Fe—Ni alloy plate satisfied the range of chemical composition defined in the present invention, but the value of formula (A) was 1.4, and the saturation magnetic flux density was less than 1.4 T. Furthermore, the value of formula (B) was 0, and RN was less than 2.0. Therefore, the evaluation of magnetic properties was "△" and the evaluation of rust resistance was "×", so the overall evaluation was "△".

[0084] In Comparative Examples 1 to 3, the obtained Fe—Ni alloy plates did not satisfy the range of chemical composition specified in the present invention, and the initial relative magnetic permeability was less than 3,000 and the maximum relative magnetic permeability was less than 30,000, so the evaluation of the magnetic properties was "×". Furthermore, the product yield was poor, and one coil of this charge had severe edge cracking and was scrapped. Therefore, the overall evaluation was "×".

[0085] In Comparative Examples 4 and 5, the obtained Fe—Ni alloy plates did not satisfy the range of chemical composition specified in the present invention, and the initial relative permeability was less than 3,000 and the saturation magnetic flux density was less than 1.4 T, so the magnetic properties were evaluated as "×". Furthermore, the value of formula (B) was low, and in particular, in Comparative Example 5, RN was also less than 2.0, so the rust resistance was also evaluated as "×". Therefore, the overall evaluation was "×".

[0086] In Comparative Example 6, the obtained Fe—Ni alloy plate did not satisfy the range of chemical composition specified in the present invention, and the saturation magnetic flux density was less than 1.4 T, so the magnetic properties were evaluated as "△". Furthermore, the value of formula (B) was 7, and RN was less than 2.0, so the rust resistance was evaluated as "×". On the other hand, the product yield was poor, and one coil of this charge had severe edge cracking and was scrapped. Therefore, the overall evaluation was "×".

[0087] In Comparative Examples 7 to 9, the obtained Fe—Ni alloy plates did not satisfy the range of chemical composition defined in the present invention, and the initial relative permeability was less than 3,000 and the saturation magnetic flux density was less than 1.4 T, so the evaluation of magnetic properties was "x". Furthermore, the value of formula (B) was low and RN was less than 2.0, so the evaluation of rust resistance was also "x", and the overall evaluation was all "x".

[0088] In Comparative Example 10, the obtained Fe—Ni alloy plate did not satisfy the range of chemical composition specified in the present invention, and the initial relative magnetic permeability was less than 3,000 and the maximum relative magnetic permeability was less than 30,000, so the evaluation of the magnetic properties was "×". Furthermore, the product yield was poor, and two of the coils in this charge had severe edge cracks and were scrapped. Therefore, the overall evaluation was "×".

[0089] The Fe—Ni alloy plate according to the present invention can be provided with excellent initial relative permeability, good maximum relative permeability and saturation magnetic flux density, and can be manufactured with a low yield, and therefore can be suitably applied as a soft magnetic material for, for example, automobile sensors, magnetic shielding materials, watch stators, etc.

Claims

1. Carbon (C): 0.001 to 0.05 mass%, Silicon (Si): 0.05 to 0.50 mass%, Manganese (Mn): 0.25 to 1.00 mass%, Phosphorus (P): 0.001 to 0.030 mass%, Sulfur (S): 0.0001 to 0.0050 mass%, Nickel (Ni): 35.0 to 44.0 mass%, Chromium (Cr): 0.01 to 0.50 mass%, Molybdenum (Mo): 0.005 to 0.10 mass%, Copper (Cu): 0.01 to 2.00 mass%, Aluminum (Al): 0.0001 to 0.10 mass%, Titanium (Ti): 0.050 mass% or less, Cobalt (Co): 0.01 to 2.00 mass%, Tungsten (W): 0.01 to 0.50 mass%, An Fe-Ni based alloy plate comprising: 0.001 to 0.05 mass% nitrogen (N), 0.0001 to 0.05 mass% tin (Sn), 0.0001 to 0.05 mass% magnesium (Mg) or less, 0.0001 to 0.05 mass% zirconium (Zr), 0.0020 mass% or less calcium (Ca), 0.0002 to 0.01 mass% oxygen (O), with the balance being iron (Fe) and unavoidable impurities.

2. The Fe-Ni alloy sheet according to claim 1, containing Cu, Co and W so as to satisfy the following relational formula (A): 1.5≦20[Cu%]+20[Co%]+80[W%]<50.0 … (A) (In formula (A), % represents mass %).

3. The Fe-Ni alloy sheet according to claim 1 or 2, containing Cu, Co, W, Cr, Mo, P and S so as to satisfy the following relational formula (B): 10≦50([Cu%]+[Co%])+100[W%]+200[Cr%]+800[Mo%]-100[P%]-1000[S%] ... (B) (In formula (B), % represents mass %).

4. A method for producing an Fe-Ni alloy plate according to claim 1 or 2, comprising the steps of: oxidizing and refining a molten metal containing raw materials of an Fe-Ni alloy in a secondary refining vessel, which is either an AOD furnace or a VOD furnace; adding Al and / or an FeSi alloy to the molten metal after the oxidizing and refining process to deoxidize and desulfurize the molten metal so that the Al content in the molten metal is in the range of 0.0001 to 0.10 mass%, the Si content in the range of 0.05 to 0.50 mass%, the S content in the range of 0.0001 to 0.0050 mass%, and the O content in the range of 0.0002 to 0.01 mass%; continuously casting the molten metal after the deoxidizing and desulfurizing process to form a slab; and hot rolling and then cold rolling the obtained slab.

5. A method for producing an Fe-Ni alloy plate according to claim 3, comprising the steps of: subjecting a molten metal containing raw materials of an Fe-Ni alloy to oxidation refining in a secondary refining vessel, which is either an AOD furnace or a VOD furnace; introducing Al and / or an FeSi alloy into the molten metal after oxidation refining, and subjecting the molten metal to deoxidation and desulfurization treatment so that the Al content in the molten metal is in the range of 0.0001 to 0.10 mass%, the Si content is in the range of 0.05 to 0.50 mass%, the S content is in the range of 0.0001 to 0.0050 mass%, and the O content is in the range of 0.0002 to 0.01 mass%; continuously casting the molten metal after deoxidation and desulfurization treatment to form a slab; and hot rolling and then cold rolling the obtained slab.

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