Fe-ni alloy having excellent air release characteristics and method for producing the same

Abstract

The present invention relates to an Fe-Ni alloy consisting of C: 0.001 to 0.2 mass%, Si: 0.001 to 0.30 mass%, Mn: 0.005 to 0.7 mass%, Ni: 30.0 to 45.0 mass%, Cr: 0.30 mass% or less, Al: 0.001 to 0.1 mass%, Ti: 0.020 mass% or less, Mg: 0.0050 mass% or less, O: 0.007 mass% or less, Ca: 0.0015 mass% or less, Na: 0.00005 to 0.001 mass%, and the balance being Fe and unavoidable impurities, wherein, among all non-metallic inclusions, the number ratio of CaO-SiO2-Al2O3-MgO-MnO-Na2O inclusions is 40% or more, the number ratio of CaO inclusions, Na2O inclusions, MgO-Al2O3 inclusions, and MnO-SiO2 inclusions is 20% or less, respectively, the CaO-SiO2-Al2O3-MgO-MnO-Na2O inclusions consist of CaO: 20 to 60 mass%, SiO2: 10 to 40 mass%, Al2O3: 30 mass% or less, MgO: 5 to 50 mass%, Na2O: 0.001 to 1 mass%, and the balance being MnO, and the MgO-Al2O3 inclusions are MgO: 10 to 40 mass% and Al2O3: 60 to 90 mass%, thereby producing an Fe-Ni alloy having excellent outgassing characteristics and suitable for use in a vacuum environment.

Description

TECHNICAL FIELD

[0001] The present application relates to an Fe-Ni alloy having excellent outgassing properties suitable for use in a vacuum environment and a manufacturing method thereof. BACKGROUND

[0002] Among metals, Fe-Ni alloys have a low thermal expansion rate near room temperature, and Fe-42Ni alloys are used as electrode materials for electronic parts sealed with glass, IC lead frames, terminals for quartz resonators, and the like. Fe-36Ni alloys are used in precision equipment, precision measuring instruments, timepieces or experimental apparatuses, fuel tanks for LNG tankers, press molds for CFRP (Carbon Fiber Reinforced Plastics), and the like, because the size changes little with temperature.

[0003] In particular, Fe-Ni alloys used in electronic parts are used in a vacuum environment depending on their use. For example, terminals for quartz resonators, small vacuum tubes, and the like can be cited. In a vacuum environment of about 1 x 10 -5 ~ 1 x 10 -7 In a vacuum environment of about 1 x 10

[0004] Regarding outgassing, in Patent Literature 1, it is disclosed that in a rolling bearing used in a vacuum environment or the like, by forming a lubricating film composed of a lubricant containing a specific fluorine-based lubricant and a fluorine resin, outgassing due to the fluorine-based lubricant is suppressed.

[0005] In addition, regarding metal materials, in Patent Literature 2, it is disclosed that in a titanium alloy used as a container material for ultra-high vacuum, oxygen is fixed as an oxide with Y or a mixed rare earth metal, hydrogen is physically adsorbed as H atoms on the alloy surface with a platinum-based metal such as Pd, and further hydrogen is fixed as a metal compound with transition metals such as Ti and Co, and gas outgassing from the material is suppressed.

[0006] In addition, regarding stainless steel, in Patent Literature 3 and Patent Literature 4, it is disclosed that the non-metallic inclusions in the steel of the stainless steel used in structural members such as chambers, pipes, valves, and the like of an ultra-high vacuum device are extremely reduced to suppress gas outgassing.

[0007] As described in the report by Tosoh (Non-Patent Literature 1), the surface of carbon steel is easily covered with an iron oxide layer (so-called rust), in which a large number of voids exist, in which water vapor or gas molecules are easily adsorbed. Therefore, it is not suitable to use carbon steel as a vacuum container material, and in order to provide a vacuum of extremely low pressure, container materials mainly employ stainless steel, or aluminum alloy or titanium alloy. However, as described above, in applications in which low thermal expansion characteristics are required, Fe-Ni alloy is employed even in a vacuum environment.

[0008] Regarding outgassing of Fe-Ni alloy, in Patent Literature 5, it is reported that the dissolved gas component is fixed as a carbide or nitride or the like with Group IVa elements (Ti, Zr, Hf) and Group Va elements (V, Nb, Ta), and the amount of gas emission in a vacuum is reduced.

[0009] However, in Patent Literature 5, only the emission of the dissolved gas component of the Fe-Ni alloy is reduced, and outgassing due to fine non-metallic inclusions present on the surface of the Fe-Ni alloy cannot be reduced.

[0010] In addition, in Patent Literature 6, it is reported that by applying a metallized coating or a polymer coating to a substrate of a high-heat amorphous polymer material used in a hard disk drive housing or the like, an excellent covering effect on outgassing is obtained.

[0011] However, applying a plating layer or various coatings to the Fe-Ni alloy, although effective in suppressing outgassing, increases the manufacturing cost, and in applications in which low thermal expansion characteristics are required, deteriorates the characteristics of the product.

[0012] Prior Art Documents

[0013] Patent Literature

[0014] Patent Literature 1: Japanese Patent Application Laid-Open (JP-A) No. 2019-27545,

[0015] Patent Literature 2: Japanese Patent Application Laid-Open (JP-A) No. H6-65661,

[0016] Patent Literature 3: Japanese Patent Application Laid-Open (JP-A) No. H1-316439,

[0017] Patent Literature 4: Japanese Patent Application Laid-Open (JP-A) No. H3-31451,

[0018] Patent Literature 5: Japanese Patent Application Laid-Open (JP-A) No. H2-171401,

[0019] Patent Literature 6: Japanese Patent Application Laid-Open (JP-A) No. 2016-508896.

[0020] Non-Patent Literature

[0021] Non-Patent Literature 1: Journal of the Vacuum Society of Japan, Vol. 57, No. 8, 2014. SUMMARY

[0022] PROBLEMS TO BE SOLVED BY THE INVENTION

[0023] In the present invention, by controlling the form of non-metallic inclusions in Fe-Ni alloy, an Fe-Ni alloy suitable for use in a vacuum environment, which is excellent in outgassing characteristics, and a manufacturing method are provided.

[0024] MEANS FOR SOLVING THE PROBLEMS

[0025] In order to solve the problems as described above, the inventors observed the surface of Fe-Ni alloy for use in a vacuum environment in detail with an electron microscope, analyzed the composition of non-metallic inclusions by SEM / EDS, and as a result, found that there is a hydroxide in the fine non-metallic inclusions present on the surface of Fe-Ni alloy.

[0026] Further, a plurality of test pieces of a plate thickness of 1 mm x 10 cm x 10 cm of Fe-Ni alloy manufactured by various manufacturing methods in a manner different in the composition of non-metallic inclusions were mirror-polished, the composition of non-metallic inclusions was analyzed by SEM / EDS, after confirming that the non-metallic inclusions were oxides, the test pieces were left in an atmosphere of humidity of 60% and temperature of 40°C for 24 hours, and then the composition of fine non-metallic inclusions on the surface of the test pieces was measured again by SEM / EDS, and as a result, it was confirmed that the non-metallic inclusions originally oxides changed to hydroxides in some of the test pieces. That is, it was found that the fine non-metallic inclusions present on the surface layer changed from oxides to hydroxides in an atmospheric atmosphere depending on the composition of non-metallic inclusions.

[0027] Further, the Fe-Ni test pieces in which the non-metallic inclusions changed to hydroxides were surface-cleaned with an organic solvent, and in a stream of high-purity Ar gas of 6N, baking treatment at 98°C x 1 hour was performed while suppressing oxidation. In Figure 1 A mode diagram of an apparatus for outgassing amount measurement and composition analysis of a sample of the present invention is shown in FIG. 1. An Fe-Ni test piece 1 in which non-metallic inclusions changed to hydroxides was disposed in a vacuum chamber 2 connected with a rotary pump 5 and a turbo molecular pump 4 by a valve 3, and the chamber was brought to a vacuum state of 3 x 10 -6 Pa, and the gas components remaining in the chamber were measured with a quadrupole mass spectrometer 6, and as a result, H2O was detected as a main component.

[0028] That is, in the case of using Fe-Ni alloy in a vacuum environment, as Figure 2As shown, the fine non-metallic inclusions 10 originally present on the surface as oxides are changed to hydroxides 11 in an atmospheric atmosphere, and water vapor is emitted as outgassing from the non-metallic inclusions that have become hydroxides. In the case where the composition of the non-metallic inclusions is CaO, reactions of formula (1), formula (2) occur.

[0029] Atmospheric atmosphere: CaO + H2O → Ca(OH)2... Formula (1)

[0030] Under vacuum: Ca(OH)2→ CaO + H2O (outgassing)... Formula (2)

[0031] Oxide-based non-metallic inclusions are generated in the Fe-Ni steel liquid during the refining process. Since CaO-SiO2-Al2O3-MgO-MnO-Na2O-based oxides have low melting points, they exist in the Fe-Ni steel liquid in a liquid phase. Furthermore, during solidification of the Fe-Ni steel liquid by continuous casting and ordinary ingot casting, CaO-SiO2-Al2O3-MgO-MnO-Na2O-based oxides solidify in a glassy state. Glassy non-metallic oxides do not react with moisture in the atmosphere and exist stably as oxides. In particular, it was found that oxide-based non-metallic inclusions containing a small amount of Na2O tend to become glassy and stable. On the other hand, non-metallic inclusions composed of CaO have a melting point of 2613°C and exist in a solid state in the Fe-Ni steel liquid, and even during solidification of the Fe-Ni steel liquid by continuous casting and ordinary ingot casting, non-metallic inclusions of CaO exist in an amorphous state. In addition, CaO forms Ca(OH)2as a hydrate in an atmospheric atmosphere.

[0032] Therefore, non-metallic inclusions in Fe-Ni alloys manufactured by various manufacturing methods were intensively studied, and as a result, a composition in which non-metallic inclusions do not become hydrates and do not emit outgassing in a vacuum environment was successfully found by controlling the composition of non-metallic inclusions. That is, it was found that in the case where non-metallic inclusions are CaO, they tend to change to hydroxides due to moisture in the atmosphere, and conversely, CaO-SiO2-Al2O3-MgO-MnO-Na2O-based oxides do not change to hydroxides. That is, it was found that by controlling the composition of non-metallic inclusions, non-metallic inclusions do not become hydrates, and an Fe-Ni alloy having excellent outgassing characteristics in a vacuum environment can be provided. Based on the insights obtained through this analysis, the present application was completed.

[0033] That is, the present application is an Fe-Ni alloy having excellent outgassing properties and suitable for use in a vacuum environment, characterized by containing, as essential components, non-metallic inclusions of CaO-SiO2-Al2O3-MgO-MnO-Na2O system, and further containing, as optional components, one or more non-metallic inclusions selected from the group consisting of CaO, MgO, MgO-Al2O3, MnO-SiO2, and Na2O, wherein the number ratio of CaO-SiO2-Al2O3-MgO-MnO-Na2O inclusions is 40% or more in all non-metallic inclusions.

[0034] In the alloy of the present application, it is further preferable to contain N: 0.010 mass% or less, and H: 0.0020 mass% or less, and it is preferable to contain Nb: 0.01 mass% to 1.00 mass%.

[0035] Further, in the non-metallic inclusions, it is further characterized in that the number ratio of CaO and Na2O inclusions is 20% or less, the number ratio of MgO-Al2O3 inclusions is 20% or less, and the number ratio of MnO-SiO2 inclusions is 20% or less.

[0036] Further, in the non-metallic inclusions, it is further characterized in that the CaO-SiO2-Al2O3-MgO-MnO-Na2O system oxide is composed of CaO: 20 to 60 mass%, SiO2: 10 to 40 mass%, Al2O3: 30 mass% or less, MgO: 5 to 50 mass%, Na2O: 0.001 to 1 mass%, and the balance being MnO, and the MgO-Al2O3 is composed of MgO: 10 to 40 mass%, and Al2O3: 60 to 90 mass%.

[0037] Further, in the case where a slab having a plate thickness of 200 mm is hot-rolled to a plate thickness of 1 mm, in these non-metallic inclusions, in the area of 200 mm 2 from the surface of the alloy, non-metallic inclusions dispersed in parallel with the rolling direction, having a width of 5 μm or more and arranged continuously for 40 μm or more are preferably 10 or less.

[0038] Furthermore, this invention also provides a method for manufacturing the Fe-Ni alloy. The manufacturing method is a method for manufacturing Fe-Ni alloys with excellent outgassing characteristics suitable for use in a vacuum environment. Its features include: melting raw materials in an electric furnace; then, after decarburization in AOD and / or VOD, adding lime, fluorite, ferrosilicon alloy, and / or Al; using a CaO-SiO2-MgO-Al2O3-Na2O-F system slag composed of CaO: 50-70 wt%, SiO2: 3-30 wt%, MgO: 3-15 wt%, Al2O3: less than 5 wt%, Na2O: 0.001-1 wt%, with the balance being F; simultaneously refining with Ar while stirring to perform deoxidation, desulfurization, and denitrification; adjusting temperature and composition while using LF to promote the flotation of inclusions caused by Ar stirring; strictly managing the moisture content of lime and fluorite to suppress the increase in H concentration; then, casting to produce ingots using a continuous casting machine or ordinary ingot casting method; the ingots are then forged to produce slabs; followed by hot rolling and, in the case of thin plates, cold rolling. Attached Figure Description

[0039] [ Figure 1 [Schematic diagram of the apparatus for measuring the outgassing volume and analyzing the composition of the sample according to the present invention.]

[0040] [ Figure 2 A schematic diagram depicting the release and degassing state of oxide nonmetallic inclusions present on the surface of Fe-Ni alloys. Detailed Implementation

[0041] First, the rationale for limiting the chemical composition of the Fe-Ni alloy of the present invention is explained.

[0042] C: 0.001~0.2% by mass

[0043] Carbon (C) is an essential element for maintaining the strength of an alloy. If the amount of C is less than 0.001% by mass, sufficient strength cannot be obtained; on the other hand, if it exceeds 0.2% by mass, the coefficient of thermal expansion increases. Therefore, the C content is specified as 0.001 to 0.2% by mass, preferably 0.002 to 0.1% by mass, and more preferably 0.003 to 0.05% by mass.

[0044] Si: 0.001–0.30% by mass

[0045] Si is an element effective for deoxidization, and has an effect of controlling the composition of non-metallic inclusions to CaO-SiO2-Al2O3-MgO-MnO-Na2O system. If the amount of Si is less than 0.001 mass%, deoxidization effect cannot be sufficiently obtained, and the composition of non-metallic inclusions cannot be controlled to CaO-SiO2-Al2O3-MgO-MnO-Na2O system. On the other hand, if the amount of Si exceeds 0.30 mass%, the thermal expansion rate becomes large, the required characteristics of Fe-Ni alloy sheet are not satisfied, and MgO in the slag is reduced to supply Mg to the Fe-Ni molten steel. Mg reacts with Al, and thus the non-metallic inclusions become MgO-Al2O3spinel which easily clusters, causing surface defects. Surface defects deteriorate the yield of products, and in addition, gaps are generated at the joints when used under vacuum, thus the degree of vacuum is reduced, and further, foreign matters attached to fine surface defects pollute the inside of the vacuum chamber, and thus are not preferable. Therefore, in the present application, the amount of Si is specified to be 0.001 to 0.30 mass%. It is preferable to be 0.010 to 0.28 mass%. It is more preferable to be 0.05 to 0.24 mass%.

[0046] Mn: 0.005 to 0.7 mass%

[0047] Mn is an element effective for deoxidization, and has an effect of controlling the composition of non-metallic inclusions to CaO-SiO2-Al2O3-MgO-MnO-Na2O system. However, it is also an element having an effect of increasing the thermal expansion rate of Fe-Ni alloy, and from this viewpoint, it is desirable to be as low a concentration as possible. That is, if the amount of Mn is less than 0.005 mass%, the composition of non-metallic inclusions cannot be controlled to CaO-SiO2-Al2O3-MgO-MnO-Na2O system. On the other hand, if it exceeds 0.7 mass%, the thermal expansion rate of Fe-Ni alloy becomes large, and the required quality of Fe-Ni alloy sheet cannot be satisfied. Therefore, in the present application, the amount of Mn is specified to be 0.005 to 0.7 mass%. It is preferable to be 0.02 to 0.65 mass%. It is more preferable to be 0.1 to 0.50 mass%.

[0048] Ni: 30.0 to 45.0 mass%

[0049] Ni is an element having a large influence on the thermal expansion rate, and it is known that the thermal expansion rate reaches a minimum around 36 mass% at 200°C and around 42 mass% at 500°C. However, if the amount of Ni is less than 30 mass% or exceeds 45 mass%, the thermal expansion rate becomes large, and the required characteristics cannot be satisfied. Therefore, the amount of Ni is specified to be 30.0 to 45.0 mass%. It is more preferable to be 32.0 to 43.0 mass%. It is more preferable to be 35.0 to 42.0 mass%.

[0050] Cr: 0.30 mass% or less

[0051] Cr is an element that increases the thermal expansion rate, and from this viewpoint, it is desirable to be as low a concentration as possible. Therefore, the content of Cr is specified to be 0.30 mass% or less. It is preferable to be 0.25 mass% or less. It is more preferable to be 0.10 mass% or less.

[0052] Al: 0.001 to 0.1 mass%

[0053] Al is a deoxidizing element, and is an element that plays a very important role in the present application. If the amount of this Al is less than 0.001 mass%, deoxidization is insufficient, and thus the O concentration increases to more than 0.007 mass%, and the number of oxide inclusions increases. On the other hand, if the amount of this Al exceeds 0.1 mass%, the ability to reduce MgO and CaO in the slag is too strong, and Mg and Ca in the Fe-Ni alloy exceed 0.001 mass%. Therefore, the inclusion composition is dominated by CaO, MgO-Al2O3. For this reason, Al is specified to be 0.001 to 0.1 mass%. It is preferable to be 0.0015 to 0.05 mass%. It is more preferable to be 0.0020 to 0.02 mass%.

[0054] Ti: 0.020 mass% or less

[0055] Ti is an element that increases the thermal expansion rate, and from this viewpoint, it is desirable to be as low a concentration as possible. Therefore, the content of Ti is specified to be 0.020 mass% or less. It is preferable to be 0.010 mass% or less. It is more preferable to be 0.005 mass% or less.

[0056] Mg: 0.0050 mass% or less

[0057] If Mg exceeds 0.0050 mass%, non-metallic inclusions easily become MgO, MgO-Al2O3. MgO forms a hydrate Mg(OH)2 in an atmospheric environment, but compared to CaO, it takes time to change to a hydroxide, and furthermore, in a baking treatment at around 100°C or a low vacuum degree of 1 x 10 -3 Pa, H2O gas is emitted and returns to an oxide, and thus does not affect the use of the present application. On the other hand, MgO-Al2O3 easily aggregates into a cluster and becomes a large inclusion in the refining process of the Fe-Ni steel liquid, and causes surface defects of the product. Surface defects deteriorate the yield of the product, and furthermore, in use under vacuum, a gap is generated at the joint, and thus the vacuum degree decreases, and furthermore, foreign matter attached to fine surface defects contaminates the inside of the vacuum chamber and causes a decrease in the vacuum degree, and thus is not preferable. Therefore, in the present application, it is specified to be 0.0050 mass% or less. It is preferable to be 0.0030 mass% or less. It is more preferable to be 0.0010 mass% or less.

[0058] O: 0.007 mass% or less

[0059] O combines with the constituent components in the alloy to generate non-metallic inclusions. If these non-metallic inclusions are coarse, surface properties deteriorate, and thus it is desirable to reduce them as much as possible. If it exceeds 0.007 mass%, coarse inclusions of MnO-SiO2-based oxides are generated, and thus O is specified to be 0.007 mass% or less. It is preferable to be 0.005 mass% or less, and more preferable to be 0.003 mass% or less.

[0060] N: 0.010 mass% or less

[0061] N, when used in a vacuum environment, becomes outgassing as N2gas by being solid-solved in the Fe-Ni alloy, and thus is an element that is best as low as possible. Thus, in the present application, it is specified to be 0.010 mass% or less. It is preferable to be 0.008 mass% or less, and more preferable to be 0.006 mass% or less.

[0062] H: 0.0020 mass% or less

[0063] H, when used in a vacuum environment, becomes outgassing as H2gas by being solid-solved in the Fe-Ni alloy, and thus is an element that is best as low as possible. Thus, in the present application, it is specified to be 0.0020 mass% or less. It is preferable to be 0.0015 mass% or less, and more preferable to be 0.0010 mass% or less.

[0064] Ca: 0.0015 mass% or less

[0065] Ca is an element that is useful for controlling non-metallic inclusions to be CaO-SiO2-Al2O3-MgO-MnO-Na2O-based non-metallic inclusions. However, if this Ca exceeds 0.0015 mass%, the CaO concentration in the inclusions rises, and becomes a hydrate, which is not preferable for use in a vacuum environment. From this viewpoint, the content of Ca is specified to be 0.0015 mass% or less. It is preferable to be 0.0010 mass% or less, and more preferable to be 0.0008 mass% or less.

[0066] Na: 0.00005 to 0.001 mass%

[0067] Na is a very important component in controlling non-metallic inclusions to CaO-SiO2-Al2O3-MgO-MnO-Na2O system glassy inclusions. If less than 0.00005 mass%, the effect cannot be exerted, and if 0.001 mass% or more, Na2O inclusions are generated. Na2O also hydrates, which is not preferable for use in a vacuum environment. For this reason, Na is specified to be 0.00005 to 0.001 mass%. It is preferable to be 0.00008 to 0.0005 mass%. It is more preferable to be 0.00010 to 0.0003 mass%. Note that Na can be supplied to the Fe-Ni steel liquid by reducing Na2O in the slag.

[0068] Nb: 0.01 to 1.00 mass%

[0069] In the Fe-Ni alloy of the present application, in addition to the above components, it is further preferable to add Nb as needed. If Nb is in a trace amount, it has the effect of reducing the coefficient of thermal expansion, and if it is in the range of 0.01 to 1.00 mass%, it is an element effective for improving the strength of the Fe-Ni alloy sheet. If the strength of the Fe-Ni alloy sheet with low thermal expansion properties is improved, the thickness of the Fe-Ni alloy sheet can be made thinner, achieving material weight reduction, space saving, and suitability for fine electronic parts. However, if it exceeds 1.00 mass%, the coefficient of thermal expansion increases. For this reason, when Nb is added, it is specified to be 0.01 to 1.00 mass%. It is preferable to be in the range of 0.02 to 0.50 mass%. It is more preferable to be 0.10 to 0.30 mass%.

[0070] Non-metallic inclusions

[0071] In the present application, it is preferable that non-metallic inclusions containing CaO-SiO2-Al2O3-MgO-MnO-Na2O system complex oxides be included as essential components, and further that non-metallic inclusions containing one or more of CaO, MgO, MgO-Al2O3, MnO-SiO2, and Na2O be included as optional components, and that the number ratio of CaO-SiO2-Al2O3-MgO-MnO-Na2O inclusions be 40% or more in all non-metallic inclusions. Hereinafter, the basis for limiting the number ratio of non-metallic inclusions is shown.

[0072] Non-metallic inclusions containing CaO-SiO2-Al2O3-MgO-MnO-Na2O system complex oxides are included as essential components, and further non-metallic inclusions containing one or more of CaO, MgO, MgO-Al2O3, MnO-SiO2, and Na2O are included as optional components, and the number ratio of CaO-SiO2-Al2O3-MgO-MnO-Na2O inclusions is 40% or more in all non-metallic inclusions

[0073] The Fe-Ni alloy according to the present application contains, as an essential component, non-metallic inclusions of CaO-SiO2-Al2O3-MgO-MnO-Na2O system oxides according to the content of Si, Al, Mg, Ca, Na in the alloy, and further contains inclusions of one or more of CaO, MgO, MgO-Al2O3, MnO-SiO2, and Na2O. Of these, the CaO-SiO2-Al2O3-MgO-MnO-Na2O oxides are glassy and are very stable oxides, and thus do not become hydrates even in the atmosphere, and are stable even in a vacuum environment, and do not emit out gas. If the content of the CaO-SiO2-Al2O3-MgO-MnO-Na2O oxides is 40% or more in terms of number ratio, it is suitable for use in a vacuum environment, and thus is specified to be 40% or more in terms of number ratio. It is preferably 45% or more, and more preferably 50% or more.

[0074] The number ratio of CaO and Na2O inclusions is 20% or less

[0075] CaO and Na2O react with moisture in the atmosphere to become hydrates. CaO reacts with H2O in the atmosphere to become Ca(OH)2, which emits out H2O as gas in a vacuum environment. Similarly, Na2O becomes NaOH in the atmosphere, and furthermore, NaOH not only emits out H2O as gas, but also is highly deliquescent, and becomes fine powder in a vacuum environment, polluting the vacuum environment. CaO and Na2O are thus preferably as little as possible. Therefore, the number ratio of CaO and Na2O inclusions is specified to be 20% or less. It is preferably 15% or less, and more preferably 10% or less.

[0076] The number ratio of MgO-Al2O3 inclusions is 20% or less

[0077] MgO-Al2O3 inclusions agglomerate and become coarse, causing surface defects, and thus are preferably as little as possible. Surface defects deteriorate the yield of products, and in addition, when used in a vacuum, gaps are generated at the joints, thus reducing the degree of vacuum, and furthermore, foreign matter adhering to fine surface defects pollutes the inside of the vacuum chamber and causes a reduction in the degree of vacuum, and thus are not preferable. Therefore, the number ratio of MgO-Al2O3 inclusions is specified to be 20% or less. It is preferably 15% or less, and more preferably 10% or less.

[0078] The number ratio of MnO-SiO2 inclusions is 20% or less

[0079] The MnO-SiO2 inclusions lack ductility even in the process of hot working and cold working of the Fe-Ni alloy, so they do not disperse finely and remain in a coarse shape in the product of the Fe-Ni alloy. Coarse MnO-SiO2 non-metallic inclusions easily become a cause of surface defects, and as non-metallic inclusions of a raw material used in a vacuum environment, it is preferable to have as few as possible. Therefore, the number ratio of the MnO-SiO2 inclusions is specified to be 20% or less. It is preferable to be 15% or less, and more preferable to be 10% or less.

[0080] Next, the reason for specifying each component of the CaO-SiO2-Al2O3-MgO-MnO-Na2O system oxide is explained.

[0081] CaO: 20 to 60 mass%, SiO2: 10 to 40 mass%, Al2O3: 30 mass% or less, MgO: 5 to 50 mass%, Na2O: 0.001 to 1 mass%, and the balance being MnO

[0082] Basically, the ranges are set so that the melting point of the CaO-SiO2-Al2O3-MgO-MnO-Na2O oxide reaches about 1300°C or less, and becomes an oxide of glass quality. Note that if CaO is less than 20 mass%, the melting point increases, and if CaO exceeds 60%, CaO inclusions coexist. If SiO2 is less than 10 mass% and exceeds 40 mass%, the melting point increases. Furthermore, if Al2O3 exceeds 30 mass%, MgO-Al2O3 inclusions coexist. If MgO is less than 5 mass% and exceeds 50 mass%, the melting point increases. In particular, if Na2O is present in a small amount, it is preferable for the generation of non-metallic inclusions of the oxide of glass quality. If Na2O is less than 0.001 mass%, the effect of becoming an oxide of glass quality is small, and if it exceeds 1 mass%, independent oxides of Na2O are generated. In addition, MnO is preferable to contain because it has the effect of lowering the melting point of inclusions.

[0083] For the above reasons, CaO is set to 20 to 60 mass%, SiO2 is set to 10 to 40 mass%, Al2O3 is set to 30 mass% or less, MgO is set to 5 to 50 mass%, Na2O is set to 0.001 to 1 mass%, and the balance is MnO.

[0084] The reason for specifying the constituent components of MgO-Al2O3 is explained.

[0085] MgO-Al2O3 is MgO: 10 to 40 mass%, Al2O3: 60 to 90 mass%

[0086] MgO-Al2O3 is a compound that has a wide solid solution. Since it becomes a solid solution within the above range, it is specified as such.

[0087] Next, the reason for specifying the number and size of non-metallic inclusions on the surface will be explained.

[0088] Non-metallic inclusions having a width of 5 μm or more and arranged continuously for 40 μm or more are 10 or less in the area of 200 mm 2 of the surface of the alloy

[0089] Inclusions present on the surface of the alloy have a great influence on the surface properties. Deterioration of the surface properties causes surface defects, which deteriorate the yield of the product, and in addition, when used in a vacuum, gaps are generated at the joints, thereby reducing the vacuum degree, and further, foreign matter adhering to fine surface defects contaminates the inside of the vacuum chamber, and thus is not preferable. In particular, non-metallic inclusions having a width of 5 μm or more and arranged continuously for 40 μm or more become the starting point of surface defects such as linear defects, and thus it is desirable to be as few as possible. However, if non-metallic inclusions having a width of 5 μm or more and arranged continuously for 40 μm or more are less than 10 in the area of 200 mm 2 of the surface of the alloy, surface defects will not be caused, and thus the above specification is made. It is preferable to be 8 or less, and more preferable to be 5 or less. Note that inclusions having an interval of 20 μm or less are counted as one block, and inclusions having an interval exceeding 20 μm are counted as other blocks.

[0090] Manufacturing method

[0091] In the present application, a manufacturing method of Fe-Ni alloy is also proposed. The method is, first, melting raw materials, melting Fe-Ni having a prescribed composition, then, after decarburization in AOD and / or VOD, adding lime, fluorite, ferrosilicon and / or Al, using CaO-SiO2-MgO-Al2O3-Na2O-F system slag consisting of CaO: 50 to 70 mass%, SiO2: 3 to 30 mass%, MgO: 3 to 15 mass%, Al2O3: 5 mass% or less, Na2O: 0.001 to 1 mass%, and the balance being F, performing deoxidation, desulfurization and denitrification while stirring by blowing Ar for refining, promoting temperature and composition adjustment by LF while promoting inclusion floating caused by Ar stirring; in order to suppress H concentration rise, strictly performing moisture management of lime and fluorite; then, performing casting by continuous casting machine or ordinary ingot casting method to manufacture slab or ingot, manufacturing slab by forging the ingot; performing grinding of the manufactured slab surface, performing hot rolling by heating at 1200°C, rolling to a prescribed thickness, performing annealing, pickling, removing the surface scale, finally manufacturing a plate having a prescribed thickness. Thus, the following Fe-Ni alloy can be obtained, wherein non-metallic inclusions contain CaO-SiO2-Al2O3-MgO-MnO-Na2O system complex oxide as an essential component, and further contain one or more of CaO, MgO, MgO-Al2O3, MnO-SiO2, Na2O as optional components, and the number ratio of CaO-SiO2-Al2O3-MgO-MnO-Na2O inclusions is 40% or more in all non-metallic inclusions. In the manufacturing method of Fe-Ni alloy according to the present application, the slag composition is characterized as described above.

[0092] Hereinafter, the basis for prescribing the slag composition as described above in the present application is described.

[0093] CaO: 50 to 70 mass%

[0094] CaO concentration in the slag is an important element for effectively performing deoxidation and desulfurization, and performing non-metallic inclusion control. The concentration is adjusted by adding lime. If CaO concentration exceeds 70 mass%, the activity of CaO in the slag rises, and reaction of formula (3) is excessively performed.

[0095] CaO (in the slag) → Ca (in Fe-Ni molten steel) + O (in Fe-Ni molten steel) … formula (3)

[0096] Therefore, the concentration of Ca in the Fe-Ni molten steel is increased to more than 0.001 mass% by reduction, and independent non-metallic inclusions of CaO are generated, which are not preferable for use in a vacuum atmosphere. Therefore, the upper limit is set to 70 mass%. On the other hand, if the concentration of CaO is less than 50 mass%, deoxidation and desulfurization cannot be performed, and the range of the S concentration and the O concentration in the present application cannot be controlled. Therefore, the lower limit is set to 50 mass%. Thus, the concentration of CaO is set to 50 to 70 mass%. It is preferable that it be 52 to 68 mass%. It is more preferable that it be 55 to 65 mass%.

[0097] SiO2: 3 to 30 mass%

[0098] SiO2in the molten slag is an important component for ensuring optimum fluidity, and therefore needs to be 3 mass%. However, if SiO2is too high to more than 30 mass%, the oxygen concentration is also increased to more than 0.007 mass%. Note that the addition of SiO2and the SiO2concentration can be adjusted by the amount of ferrosilicon added. As described above, the SiO2concentration is specified to be 3 to 30 mass%. It is preferable that it be 3 to 28 mass%. It is more preferable that it be 3 to 25 mass%.

[0099] MgO: 3 to 15 mass%

[0100] MgO in the molten slag is an important component for controlling the Mg concentration contained in the molten steel to the concentration range described in the claims, and is also an important element for controlling the non-metallic inclusions to the preferable composition of the present application. Therefore, the lower limit is set to 3 mass%. On the other hand, if the MgO concentration is more than 15 mass%, the Mg concentration in the Ni molten steel is increased, and it cannot be controlled to 0.001 mass% or less in the Mg concentration range in the present application. Therefore, the upper limit of the MgO concentration is set to 15 mass%. It is preferable that it be 4 to 14 mass%, and it is more preferable that it be 5 to 12 mass%. MgO in the molten slag reaches the specified range by being dissolved into the molten slag from dolomite bricks or magnesia-chrome bricks used when AOD refining or VOD refining is performed. Alternatively, in order to control to the specified range, waste bricks of dolomite bricks or magnesia-chrome bricks can also be added.

[0101] Al2O3: 5 mass% or less

[0102] If Al2O3in the molten slag is high, the number ratio of non-metallic inclusions of MgO-Al2O3exceeds 20%. It is necessary to reduce the Al2O3concentration in the molten slag as much as possible. Therefore, the upper limit is set to 5 mass% or less. It is preferable that it be 4 mass% or less, and it is more preferable that it be 3 mass% or less.

[0103] Na2O: 0.001 to 1 mass%

[0104] Adjusting the Na2O concentration of the slag to the appropriate range is the best method for precisely controlling the Na2O concentration in the non-metallic inclusions of the CaO-SiO2-Al2O3-MgO-MnO-Na2O system in the low concentration range. If it exceeds 1%, Na2O non-metallic inclusions are generated, so the upper limit is set to 1 mass%, and if it is less than 0.001 mass%, the Na2O concentration in the non-metallic inclusions is less than the range of 0.001 mass% of the present application. For the above reasons, the Na2O concentration in the slag is specified to be 0.001 to 1 mass%. It is preferably 0.005 to 0.9 mass%. It is more preferably 0.010 to 0.5 mass%. Note that the Na2O concentration of the slag is controlled by adding sodium carbonate.

[0105] Example

[0106] The following examples are given to further clarify the constitution and effects of the present application, but the present application is not limited to the following examples. An electric furnace with a capacity of 60 tons was used to melt raw materials such as ferronickel, pure nickel, iron chips, and Fe-Ni alloy chips. Then, oxygen blowing refining (oxidation refining) for removing C was performed in an AOD and / or VOD, limestone, fluorite, and sodium carbonate were charged, a CaO-SiO2-Al2O3-MgO-Na2O-F system slag was generated, and further FeSi and / or Al were charged to perform deoxidation, and then Ar stirring was performed to perform desulfurization and denitrification. Then, the molten steel was tapped into a ladle, temperature adjustment and composition adjustment were performed, and a slab was manufactured using a continuous casting machine.

[0107] The surface of the manufactured slab was ground, and hot rolling was performed by heating at 1200°C to manufacture a hot strip coil. A slab with a thickness of 200 mm was hot rolled to a sheet thickness of 3 mm, then, after an annealing pickling process, cold rolling was performed to a sheet thickness of 1 mm, and then annealing, pickling were performed, and after removing the surface scale, cold rolling was performed to a specified thickness to manufacture a cold rolled coil. The chemical composition of the obtained Fe-Ni alloy, the steel making process (EF: electric furnace, AOD: argon oxygen decarburization device, VOD: vacuum oxygen decarburization device, LF: ladle refining device, CC: continuous casting machine, IC: ordinary ingot casting method), the slag composition at the end of AOD or VOD refining are shown in Table 1, and the non-metallic inclusion composition, the morphology of the inclusions, the amount of gas generation, and the gas composition are shown in Table 2.

[0108] The evaluation method is shown below.

[0109] (1) Chemical composition of the alloy and slag composition: quantitative analysis was performed using a fluorescent X-ray analysis device, and the oxygen concentration of the alloy was quantitatively analyzed using an inert gas pulse melting infrared absorption method.

[0110] (2) Non-metallic inclusion composition: In the case of continuous casting, a Fe-Ni alloy sample was collected with a tundish immediately after the start of casting, and in the case of ordinary ingot casting, a Fe-Ni alloy sample was collected with a sprue connected to a mold, and the solidified sample was mirror-polished, and non-metallic inclusions of 5 μm or more in size were randomly measured at 20 points using SEM-EDS.

[0111] (3) Number ratio of each non-metallic inclusion: The number ratio was evaluated based on the measurement results of (2) above.

[0112] (4) Number distribution of each non-metallic inclusion: The obtained slab was hot-rolled from a thickness of 200 mm to a sheet thickness of 3 mm (reduction: 98.5%), and after an annealing and pickling process, further cold-rolled from a sheet thickness of 3 mm to 1 mm (reduction: 66.7%). A Fe-Ni alloy sheet sample of sheet thickness 1 mm thus obtained was cut into 10 mm x 20 mm, and the surface of the test piece was polished and mirror-finished. The number of non-metallic inclusions of 40 μm or more in size dispersed and arranged continuously in parallel with the rolling direction in an area of 10 mm x 20 mm was measured at a magnification of 200 times using an optical microscope.

[0113] (5) Outgassing amount: The entire surface of the test piece of sheet thickness 1 mm x 10 mm x 20 mm subjected to mirror finishing in (4) above was further mirror-polished, and after being left in an atmosphere of 60% humidity and 40°C for 24 hours, the test piece was placed in a beaker containing an organic solvent, washed with an ultrasonic cleaner for 5 minutes, and dried, and subjected to a baking treatment at 98°C for 1 hour in a stream of 6N high-purity Ar gas while suppressing oxidation, to remove contaminants and adhering water from the surface. The outgassing amount was measured using a device shown in Figure 1 . The test piece was placed in a vacuum chamber connected to a rotary pump and a turbo molecular pump, and the chamber was brought to a vacuum state of 1 x 10 -7 Pa or less, and after the valve connected to the pump was closed, the outgassing amount (Pa-m 3 / s) was measured based on the pressure change in the chamber and the volume of the chamber after 3600 seconds. The outgassing amount generated by the chamber device itself without the test piece was also measured in advance, and the outgassing amount generated by the test piece was calculated from the difference. The outgassing amount was measured at room temperature of 20 to 25°C.

[0114] (6) The gas components remaining in the chamber were further measured using a quadrupole mass spectrometer. Data on the reduction in the life of electronic parts used in a vacuum environment and the malfunction thereof were applied to the outgassing measurement method (5) above, and the outgassing characteristics were evaluated as follows.

[0115] A: Outgassing amount < 0.3 x 10-7 Pa-m 3 / s

[0116] B: 0.3 x 10 -7 Pa-m 3 / s < outgassing amount < 1.0 x 10 -7 Pa-m 3 / s

[0117] C: 1.0 x 10 -7 Pa-m 3 / s < outgassing amount < 20.0 x 10 -7 Pa-m 3 / s

[0118] D: 20.0 x 10 -7 Pa-m 3 / s < outgassing amount

[0119] [Table 1]

[0120]

[0121] [Table 2]

[0122]

[0123] Examples 1 to 21 of the Invention have good outgassing characteristics because they satisfy the range of the Invention. In particular, Examples 1 to 14 of the Invention have extremely little or no outgassing, and have good outgassing characteristics, because they are in the preferred range, and are rated A or B. The quality is suitable for use in a vacuum environment.

[0124] Example 15 of the Invention has a high N concentration of 0.012 mass%, and although the non-metallic inclusions are CaO-SiO2-Al2O3-MgO-MnO-Na2O-based, a small amount of outgassing of 3.9 x 10 -7 Pa-m 3 / s is generated, and the outgassing characteristics are rated C. N2is detected from the outgassing. The N dissolved in the Fe-Ni alloy is released as outgassing.

[0125] Example 16 of the Invention has a high H concentration of 0.0028% because it uses lime containing moisture during the refining of the Fe-Ni alloy, and although the non-metallic inclusions are CaO-SiO2-Al2O3-MgO-MnO-Na2O-based, outgassing of 8.2 x 10 -7 Pa-m 3 / s is generated, and the outgassing characteristics are rated C. H2is detected from the outgassing. The H dissolved in the Fe-Ni alloy is released as outgassing.

[0126] Reference Examples 17 to 21 are within the scope of the present application, but since the proportion of the number of non-metallic inclusions is not within the preferable range, although within the allowable range, outgassing was detected, and the outgassing characteristics were evaluated as C.

[0127] On the other hand, Comparative Examples 22 to 26 are outside the scope of the present application. Each of the examples is described below.

[0128] The Si concentration of Comparative Example 22 was as high as 0.372 mass%, and the Al concentration was as high as 0.2230 mass%, and the deoxidation reaction was excessively performed, as a result of which Ca was excessively supplied from the slag phase to the molten steel, and the Ca concentration reached 0.0018 mass%. As a result, a large amount of 89.0 x 10 -7 Pa-m 3 of outgassing was generated, and the outgassing characteristics were evaluated as D. H2O was detected from the outgassing.

[0129] The Si concentration of Comparative Example 23 was as low as 0.0004 mass%, the Mn concentration was as low as 0.003 mass%, and the Al concentration was as low as 0.0004 mass%, and the deoxidation could not be performed, and the oxygen concentration was as high as 0.0121 mass%. As a result, a large amount of the non-metallic inclusions were formed as large MnO-SiO2inclusions, and the number of non-metallic inclusions on the surface of 40 μm or more in length was as many as 38, and 23.2 x 10 -7 Pa-m 3 of outgassing was generated, and the outgassing characteristics were evaluated as D. H2O and hydrocarbons were detected from the outgassing. Moisture, organic solvents, and the like penetrated into the gap between the large MnO-SiO2inclusions present on the surface and the Fe-Ni alloy, and could not be removed by etching, and were emitted as outgassing.

[0130] Comparative Example 24 was supplied with excessive Na2O to the slag, and as a result, the Na concentration in the molten steel was as high as 0.00172 mass%. As a result, the non-metallic inclusions were dominated by Na2O, and the Na2O concentration in the CaO-SiO2-Al2O3-MgO-MnO-Na2O system non-metallic inclusions was as high as 1.811 mass%, and a large amount of 69.7 x 10 -7 Pa-m 3 of outgassing was generated, and the outgassing characteristics were evaluated as D. H2O and Na were detected from the outgassing. The detected Na was obtained by deliquescence and fine pulverization of Na2O.

[0131] Comparative Example 25 directly supplied Mg to the Fe-Ni molten steel, and the Mg was as high as 0.0065 mass%. As a result, a large amount of MgO-Al2O3 inclusions were generated by reacting with Al2O3 in the slag. As a result, the MgO-Al2O3 ratio increased, and there were as many as 42 non-metallic inclusions of 40 μm or more on the surface, resulting in 28.8 x 10 -7 Pa-m 3 / s of outgassing, and the outgassing characteristic was evaluated as D. H2O and hydrocarbons were detected from the outgassing. The moisture, organic solvent, and the like penetrated into the gap between the large MgO-Al2O3 inclusions present on the surface and the Fe-Ni alloy, and could not be removed by etching, and was emitted as outgassing.

[0132] Comparative Example 26 did not supply Na2O to the slag, and the Na concentration in the molten steel was as low as 0.00002 mass%, and the non-metallic inclusions were CaO-SiO2-Al2O3-MgO-MnO system not containing Na2O. There were 21.6 x 10 -7 Pa-m 3 / s of outgassing, and the outgassing characteristic was evaluated as D. H2O and hydrocarbons were detected from the outgassing. The moisture, organic solvent, and the like penetrated into the gap between the large MgO-Al2O3 inclusions present on the surface and the Fe-Ni alloy, and could not be removed by etching, and was emitted as outgassing.

[0133] Industrial Applicability

[0134] The technology of the present application can obtain an Fe-Ni alloy having excellent outgassing characteristics suitable for use in a vacuum environment by controlling the morphology of non-metallic inclusions.

[0135] Legend

[0136] 1: Fe-Ni alloy sample, 2: SUS vacuum chamber, 3: valve, 4: turbo molecular pump, 5: rotary pump, 6: quadrupole mass spectrometer, 7: pressure gauge, 10: oxide non-metallic inclusion, 11: hydroxide non-metallic inclusion.

Claims

1. A Fe-Ni alloy with excellent outgassing characteristics suitable for use in a vacuum environment, characterized in that, Composed of C: 0.001–0.2 wt%, Si: 0.001–0.30 wt%, Mn: 0.005–0.7 wt%, Ni: 30.0–45.0 wt%, Cr: less than 0.30 wt%, Al: 0.001–0.1 wt%, Ti: less than 0.020 wt%, Mg: less than 0.0050 wt%, O: less than 0.007 wt%, Ca: less than 0.0015 wt%, Na: 0.00005–0.001 wt%, with the balance being Fe and unavoidable impurities, containing CaO-SiO2- The composite oxide system of Al2O3-MgO-MnO-Na2O contains non-metallic inclusions as essential components, and further includes one or more non-metallic inclusions selected from CaO, MgO, MgO·Al2O3, MnO·SiO2, and Na2O as optional components. Among all non-metallic inclusions, the proportion of CaO-SiO2-Al2O3-MgO-MnO-Na2O inclusions is more than 40%, while the proportions of CaO inclusions, Na2O inclusions, MgO·Al2O3 inclusions, and MnO·SiO2 inclusions are all less than 20%. The CaO-SiO2-Al2O3-MgO-MnO-Na2O system oxide is composed of CaO: 20-60% by mass, SiO2: 10-40% by mass, Al2O3: less than 30% by mass, MgO: 5-50% by mass, Na2O: 0.001-1% by mass, with the balance being MnO. The MgO·Al2O3 is composed of MgO: 10-40% by mass and Al2O3: 60-90% by mass.

2. The Fe-Ni alloy with excellent outgassing characteristics and suitable for use in a vacuum environment as described in claim 1, characterized in that, Contains less than 0.010% by mass of N and less than 0.0020% by mass of H.

3. The Fe-Ni alloy with excellent outgassing characteristics and suitable for use in a vacuum environment as described in claim 1 or 2, characterized in that, Contains Nb: 0.01% to 1.00% by mass.

4. The Fe-Ni alloy with excellent outgassing characteristics and suitable for use in a vacuum environment as described in claim 1 or 2, characterized in that, When a 200mm thick slab is hot-rolled to a 1mm thickness, a 200mm thick alloy surface is formed. 2 Within the area, there are fewer than 10 non-metallic inclusions that are dispersed parallel to the rolling direction, have a width of more than 5 μm, and are continuously arranged for more than 40 μm.

5. The Fe-Ni alloy with excellent outgassing characteristics and suitable for use in a vacuum environment as described in claim 3, characterized in that, When a 200mm thick slab is hot-rolled to a 1mm thickness, a 200mm thick alloy surface is formed. 2 Within the area, there are fewer than 10 non-metallic inclusions that are dispersed parallel to the rolling direction, have a width of more than 5 μm, and are continuously arranged for more than 40 μm.

6. A method for manufacturing a Fe-Ni alloy with excellent outgassing characteristics suitable for use in a vacuum environment, wherein the method for manufacturing the Fe-Ni alloy as described in claim 1 or 2 is characterized in that, The raw materials are melted in an electric furnace. Then, after decarburization in AOD and / or VOD, lime, fluorite, ferrosilicon alloy and / or Al are added. A CaO-SiO2-MgO-Al2O3-Na2O-F slag system is used, consisting of CaO: 50-70% by mass, SiO2: 3-30% by mass, MgO: 3-15% by mass, Al2O3: less than 5% by mass, Na2O: 0.001-1% by mass, with the balance being F. Deoxidation, desulfurization and denitrification are carried out while stirring by Ar refining. Temperature and composition are adjusted by using LF to promote the flotation of inclusions caused by Ar stirring. For the lime and fluorite, the increase of H concentration is suppressed by strict moisture management. The ingots are manufactured by casting using a continuous casting machine or ordinary ingot casting method. The ingots are hot forged to manufacture slabs, followed by hot rolling and, in the case of thin plates, cold rolling.

7. A method for manufacturing a Fe-Ni alloy with excellent outgassing characteristics suitable for use in a vacuum environment, wherein the method for manufacturing the Fe-Ni alloy as described in claim 3 is characterized in that, The raw materials are melted in an electric furnace. Then, after decarburization in AOD and / or VOD, lime, fluorite, ferrosilicon alloy and / or Al are added. A CaO-SiO2-MgO-Al2O3-Na2O-F slag system is used, consisting of CaO: 50-70% by mass, SiO2: 3-30% by mass, MgO: 3-15% by mass, Al2O3: less than 5% by mass, Na2O: 0.001-1% by mass, with the balance being F. Deoxidation, desulfurization and denitrification are carried out while stirring by Ar refining. Temperature and composition are adjusted by using LF to promote the flotation of inclusions caused by Ar stirring. For the lime and fluorite, the increase of H concentration is suppressed by strict moisture management. The ingots are manufactured by casting using a continuous casting machine or ordinary ingot casting method. The ingots are hot forged to manufacture slabs, followed by hot rolling and, in the case of thin plates, cold rolling.

8. A method for manufacturing a Fe-Ni alloy with excellent outgassing characteristics suitable for use in a vacuum environment, wherein the method for manufacturing the Fe-Ni alloy as described in claim 4 is characterized in that, The raw materials are melted in an electric furnace. Then, after decarburization in AOD and / or VOD, lime, fluorite, ferrosilicon alloy and / or Al are added. A CaO-SiO2-MgO-Al2O3-Na2O-F slag system is used, consisting of CaO: 50-70% by mass, SiO2: 3-30% by mass, MgO: 3-15% by mass, Al2O3: less than 5% by mass, Na2O: 0.001-1% by mass, with the balance being F. Deoxidation, desulfurization and denitrification are carried out while stirring by Ar refining. Temperature and composition are adjusted by using LF to promote the flotation of inclusions caused by Ar stirring. For the lime and fluorite, the increase of H concentration is suppressed by strict moisture management. The ingots are manufactured by casting using a continuous casting machine or ordinary ingot casting method. The ingots are hot forged to manufacture slabs, followed by hot rolling and, in the case of thin plates, cold rolling.

9. A method for manufacturing a Fe-Ni alloy with excellent outgassing characteristics suitable for use in a vacuum environment, comprising the method for manufacturing the Fe-Ni alloy as described in claim 5, characterized in that, The raw materials are melted in an electric furnace. Then, after decarburization in AOD and / or VOD, lime, fluorite, ferrosilicon alloy and / or Al are added. A CaO-SiO2-MgO-Al2O3-Na2O-F slag system is used, consisting of CaO: 50-70% by mass, SiO2: 3-30% by mass, MgO: 3-15% by mass, Al2O3: less than 5% by mass, Na2O: 0.001-1% by mass, with the balance being F. Deoxidation, desulfurization and denitrification are carried out while stirring by Ar refining. Temperature and composition are adjusted by using LF to promote the flotation of inclusions caused by Ar stirring. For the lime and fluorite, the increase of H concentration is suppressed by strict moisture management. The ingots are manufactured by casting using a continuous casting machine or ordinary ingot casting method. The ingots are hot forged to manufacture slabs, followed by hot rolling and, in the case of thin plates, cold rolling.

Images