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WO2025225030A1 - Tôle d'acier fe-cr-ni et son procédé de production - Google Patents

Tôle d'acier fe-cr-ni et son procédé de production

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Publication number
WO2025225030A1
WO2025225030A1 PCT/JP2024/016602 JP2024016602W WO2025225030A1 WO 2025225030 A1 WO2025225030 A1 WO 2025225030A1 JP 2024016602 W JP2024016602 W JP 2024016602W WO 2025225030 A1 WO2025225030 A1 WO 2025225030A1
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WO
WIPO (PCT)
Prior art keywords
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content
steel sheet
temperature
annealing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2024/016602
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English (en)
Japanese (ja)
Inventor
睦子 吉井
純一 濱田
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Steel Corp
Original Assignee
Nippon Steel Corp
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Filing date
Publication date
Application filed by Nippon Steel Corp filed Critical Nippon Steel Corp
Priority to PCT/JP2024/016602 priority Critical patent/WO2025225030A1/fr
Publication of WO2025225030A1 publication Critical patent/WO2025225030A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • C22C30/02—Alloys containing less than 50% by weight of each constituent containing copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur

Definitions

  • the present invention relates to Fe-Cr-Ni steel sheet, which is used as a material for heat-resistant parts that require heat resistance, and is particularly applicable to exhaust manifolds, converters, and turbocharger parts for automobiles and motorcycles, as well as boilers, power plants, chemical plants, etc.
  • the Fe-Cr-Ni steel sheet of the present invention is an austenitic stainless steel sheet or a superalloy.
  • Automobile exhaust manifolds, front pipes, center pipes, mufflers, and other environmentally friendly parts for purifying exhaust gases use materials with excellent heat resistance, including oxidation resistance, high-temperature strength, and thermal fatigue properties, in order to ensure stable ventilation of high-temperature exhaust gases. Furthermore, because they are exposed to the corrosive environment of condensed water, they also require excellent corrosion resistance.
  • Stainless steel is widely used in these parts due to factors such as stricter exhaust gas regulations, improved engine performance, and lighter vehicle weight. Furthermore, in recent years, exhaust gas regulations have become even stricter, and with trends toward improved fuel economy and downsizing, the temperature of exhaust gases passing through the exhaust manifold directly below the engine is on the rise. In addition, the number of vehicles equipped with superchargers such as turbochargers is increasing, so the stainless steel used in exhaust manifolds and turbochargers must have even greater heat resistance. With regard to rising exhaust gas temperatures, they are expected to rise from the previous level of around 900°C to around 1000°C.
  • Patent Document 1 discloses high-Cr and Mo-added steels.
  • Patent Document 2 discloses exhaust guide parts for nozzle vane-type turbochargers made from austenitic stainless steel with an added amount of 2-4% Si.
  • the steel composition is specified taking into account hot workability during steel manufacturing, but it cannot be said that it fully satisfies the high-temperature properties required for the above-mentioned parts. Furthermore, while it is considered important to maintain the hole expandability of punched holes, the steel composition specified based on hot workability does not provide sufficient hole expandability. Furthermore, stainless steel cast steel is used for turbocharger housings, but due to their thick walls, there is a need to make them thinner and lighter.
  • Patent Document 3 discloses that the high-temperature strength and creep properties of heat-resistant austenitic stainless steel plate are improved by determining the optimum ranges for the contents of Nb, V, C, N, Al, and Ti and optimizing the manufacturing process.
  • the technical challenge with the invention disclosed in Patent Document 3 is improving high-temperature strength and creep properties at 800°C, and the invention disclosed in Patent Document 3 is insufficient for use with exhaust gases exceeding 900°C.
  • Patent Document 5 also discloses that by controlling the low ⁇ CSL grain boundary frequency and average crystal grain size, it is possible to achieve improved intergranular corrosion resistance and high-temperature strength with small-grain-size materials.
  • the "high-temperature strength" in Patent Document 5 refers to high-temperature strength in water, and does not disclose any specific solutions for achieving strength against exhaust gas temperatures exceeding 900°C.
  • Patent Document 6 is characterized by ensuring excellent resistance to intergranular corrosion in high-temperature water by increasing the twin grain boundary ratio in the steel.
  • Patent Document 6 does not disclose the high-temperature strength of the nuclear stainless steel, nor does it disclose any specific solutions for achieving strength against exhaust gases exceeding 900°C.
  • the corrosion-resistant austenitic alloy disclosed in Patent Document 7 is characterized by being obtained by subjecting an austenitic alloy to more than 30% cold working and heat treatment, thereby forming twin boundaries within the austenitic grains and dispersing precipitates on the austenitic grain boundaries and/or twin boundaries. These characteristics suppress grain boundary sliding and increase grain boundary strength, so the corrosion-resistant austenitic alloy has higher stress corrosion cracking growth resistance.
  • the stress corrosion cracking growth resistance disclosed in Patent Document 7 is a characteristic in high-temperature water, and Patent Document 7 does not disclose any specific solutions for achieving strength against exhaust gases above 900°C.
  • Patent documents 8 to 14 also contain various descriptions of the steel composition and manufacturing conditions for this purpose.
  • the steel composition covers SUS304 and SUS316-based austenitic stainless steels, and there is no mention of superalloy Fe-Cr-Ni steels or materials with added Si, Nb, and Co, as featured in this application.
  • Rolling conditions are based on low reduction rates, such as 2-15% in Patent document 9 and 2-5% in Patent documents 12 and 13.
  • Subsequent heat treatment conditions call for relatively long periods of time, such as 5 hours or more at 900-1000°C in Patent document 9, 1-60 minutes at 927-1227°C in Patent document 13, and 10-48 hours at 900-950°C in Patent document 11.
  • Patent document 12 calls for a temperature of 1052°C or higher for no more than 2 minutes.
  • the frequency of twin boundaries decreases. Therefore, in order to increase the frequency of twin boundaries, it is thought that heat treatment at a relatively low temperature for a long period of time, as described above, is carried out to prevent recrystallization from progressing and to allow the high-angle boundaries that were originally present to migrate.
  • Patent Documents 16 and 17 disclose that the austenitic stainless steel sheets disclosed have a frequency of 70% or more or 80% or more of coincidence grain boundaries by performing cold rolling and annealing processes once or twice, and that austenitic stainless steel sheets with good creep properties at 900-950°C can be obtained with a holding time of 120 seconds to 20 minutes.
  • Nb, Mo, Cu, and Co which are characteristic of the present invention, are listed as essential or optional additional elements, there is no description of their effects on coincidence grain boundaries or stacking fault energy, making them unclear. Furthermore, there is room for improvement in high-temperature strength.
  • the object of the present invention is to solve the above problems and improve the heat resistance of Fe-Cr-Ni steel sheets, including austenitic stainless steel sheets, used in heat-resistant parts by controlling the structure. More specifically, the object is to provide Fe-Cr-Ni steel sheets that have excellent 0.2% yield strength and creep properties at 900°C, as well as excellent room-temperature ductility.
  • grain boundaries form after cold rolling and annealing, resulting in polycrystalline bodies.
  • the atomic arrangement at the grain boundaries can be regular or irregular. When the atomic arrangement at the grain boundaries is regular with few gaps, the structure becomes low-energy and grain boundary degradation is less likely to occur.
  • a representative example of this special grain boundary is the correspondence boundary.
  • the atomic arrangement at the grain boundary is not regular, it is called a random grain boundary and has a high-energy structure.
  • Correspondence orientation relationships occur in many geometric combinations, but grain boundaries formed by correspondence orientation relationships between ⁇ 3 and ⁇ 29 are called correspondence boundaries. This ⁇ value is an odd number, and the smaller this value, the higher the density of correspondence lattice points and the stronger the characteristics of a low-energy grain boundary.
  • Patent Document 9 suppresses intergranular corrosion by increasing the frequency of ⁇ 29 or less to 75% or more for SUS304, which has a Si content of 0.59% and an unknown Nb and Co content.
  • Patent Document 9 requires heat treatment at 900-1000°C for 5 hours or more, which is inefficient for industrial mass production.
  • the invention disclosed in Patent Document 9 increases the frequency of coincidence boundaries to suppress precipitation at grain boundaries and improve corrosion resistance, but the effect on mechanical properties at high temperatures was unknown.
  • the inventors conducted detailed research into the relationship between the metal structure and high-temperature properties of Fe-Cr-Ni steel sheet. As a result, they discovered that for materials that require heat resistance in components exposed to extremely harsh thermal environments, such as turbochargers, heat resistance can be ensured by the steel's composition, and by controlling the characteristics of the grain boundaries in the metal structure through the cold rolling process and subsequent annealing process, significantly superior high-temperature strength can be achieved.
  • annealing time required to increase the frequency of corresponding grain boundaries can be shortened by using steel compositions that reduce the stacking fault energy (SFE), calculated using the following formula in D. DULIEU and J. NUTTING, Iron and Steel Inst. Special report, 86 (1964) 140.
  • SFE stacking fault energy
  • the KAM value when the KAM value is the average value of the crystal orientation difference between the target measurement point and its surrounding measurement points, the KAM value must be a ratio (area ratio) of 1 to 2 degrees, and the proportion of high-angle boundaries (HAGB), calculated by dividing the length of grain boundaries with a relative orientation difference of 15 degrees or more by the total grain boundary length (i.e., the length of grain boundaries with a relative orientation difference of 2 degrees or more), must satisfy the condition KAM/HAGB ⁇ 0.01. Furthermore, it was discovered that high-temperature strength and creep strength can be improved by creating a structure in which the total frequency of coincidence boundaries with a ⁇ value of 3 to 29 is 50% or more.
  • HAGB proportion of high-angle boundaries
  • the present invention which aims to solve the above problems, was made based on the above findings and includes the following aspects.
  • [4] A method for manufacturing the Fe-Cr-Ni steel sheet of [1], comprising, by mass%, C: 0.300% or less, Si: 5.00% or less, Mn: 10.00% or less, P: 0.050% or less, S: 0.0100% or less, Ni: 2.00 to 40.00%, Cr: 14.00 to 30.00%, N: 0.400% or less, Al: 0.001 to 1.000%, V: 0.02 to 1.00%, Nb: 0.001 to 1.000%, Co: 0.001 to 1.00 0%, Cu: 0-4.00%, Mo: 0-5.00%, Ti: 0-1.000%, B: 0-0.0100%, Ca: 0-0.0100%, W: 0-3.00%, Zr: 0-0.30%, Sn: 0-0.50%, Mg: 0-0.0100%, Sb: 0-0.300%, REM: 0-0.200%, Ga: 0-0.3000%, Ta: 0-1.00%, Hf: 0-1.00%, Bi: 0-0.02
  • the present invention makes it possible to provide Fe-Cr-Ni steel sheet with excellent high-temperature properties, and when applied to automotive exhaust parts in particular, it significantly contributes to weight reduction and high exhaust temperature.
  • the Fe-Cr-Ni steel sheet of the present invention is described in detail below.
  • C (C: 0.300% or less) C may be added to ensure austenite structure formation and improve high-temperature strength and creep life.
  • C is not an essential element, and the C content may be 0%.
  • the C content is preferably 0.001% or more.
  • the C content may be 0.005% or more, 0.010% or more, 0.015% or more, 0.030% or more, 0.045% or more, or 0.050% or more.
  • the C content is set to 0.300% or less.
  • the C content may be 0.270% or less, 0.250% or less, 0.210% or less, 0.170% or less, or 0.150% or less.
  • Si acts as a deoxidizing element. It may be added to improve oxidation resistance, steam oxidation resistance, and high-temperature sliding properties through internal oxidation of Si, and to improve high-temperature strength and creep life by increasing the frequency of corresponding grain boundaries. Deoxidation can also be achieved with other elements, and Si is not an essential element, so the Si content may be 0%. To achieve the above effects, the Si content is preferably 0.01% or more. In consideration of hot workability during steel sheet production, the Si content may be 0.20% or more, or 0.50% or more. In terms of reducing stacking fault energy, the Si content may be 1.00% or more, 1.20% or more, or 1.50% or more.
  • the Si content may be 1.80% or more, 1.90% or more, or 2.00% or more.
  • the Si content is set to 5.00% or less.
  • the Si content may be 4.80% or less, 4.50% or less, or 4.00% or less.
  • the Si content may be 3.50% or less, 3.40% or less, or 3.30% or less.
  • Mn acts as a deoxidizing element and may be added to ensure austenite structure formation and improve scale adhesion. Deoxidation can also be performed with other elements, and Mn is not an essential element, so the Mn content may be 0%. To achieve the above effects, the Mn content is preferably 0.01% or more. The Mn content may be 0.10% or more, 0.40% or more, 0.70% or more, 1.50% or more, 2.00% or more, or 2.50% or more. On the other hand, if the Mn content is high, the inclusion cleanliness significantly deteriorates, workability and hole expandability decrease, and pickling ability significantly deteriorates, resulting in a rough surface of the Fe—Cr—Ni steel sheet.
  • the Mn content is set to 10.00% or less. From the viewpoint of effectively reducing stacking fault energy, the Mn content may be 9.40% or less, 8.80% or less, 8.00% or less, 7.50% or less, 7.00% or less, or 6.50% or less. In consideration of pickling properties and oxidation characteristics during steel sheet production, the Mn content may be 6.00% or less, or 5.00% or less.
  • P is an impurity that promotes hot workability and solidification cracking during manufacturing, and also hardens and reduces ductility, so the P content is set to 0.050% or less.
  • the P content may be 0.045% or less, 0.040% or less, 0.035% or less, or 0.030% or less. The lower the P content, the better, and it may be 0%.
  • the P content may be 0.001% or more, 0.002% or more, 0.005% or more, 0.010% or more, 0.015% or more, or 0.020% or more.
  • S is an impurity and an element that not only reduces hot workability during manufacturing but also degrades corrosion resistance. Furthermore, the formation of coarse sulfides (MnS) significantly reduces inclusion cleanliness and degrades room-temperature ductility, so the S content is set to 0.0100% or less.
  • the S content may be 0.0090% or less, 0.0080% or less, 0.0065% or less, 0.0050% or less, 0.0040% or less, or 0.0030% or less. The lower the S content, the better, and it may be 0%. Taking refining costs into consideration, the S content may be 0.0001% or more, 0.0002% or more, 0.0003% or more, 0.0004% or more, or 0.0005% or more.
  • Ni is added to form an austenite structure and ensure corrosion resistance and oxidation resistance. Since a low Ni content significantly coarsens grains, the Ni content is set to 2.00% or more. Considering manufacturability, room-temperature ductility, and corrosion resistance, the Ni content may be 3.20% or more, 3.50% or more, 4.50% or more, 5.00% or more, 8.00% or more, or 10.00% or more. Since a high Ni content increases costs and also increases stacking fault energy, the Ni content is set to 40.00% or less. From the viewpoint of reducing stacking fault energy and effectively increasing the frequency of coincidence grain boundaries, the Ni content may be 37.50% or less, or 35.00% or less. From the standpoint of cost, the Ni content may be 30.00% or less, 25.00% or less, 22.00% or less, 20.00% or less, 16.00% or less, or 14.00% or less.
  • Cr 14.00-30.00%
  • Cr is an element that improves corrosion resistance, oxidation resistance, and high-temperature sliding properties, and is an element necessary from the perspective of suppressing abnormal oxidation in consideration of the exhaust component environment. Cr is also an element that is effective in improving high-temperature strength. To achieve this effect, the Cr content is set to 14.00% or more. From the perspective of steel sheet manufacturability and workability, the Cr content may be 14.50% or more, 15.00% or more, 16.00% or more, 17.00% or more, 18.50% or more, or 20.00% or more. A high Cr content makes the steel hard, degrading formability and increasing costs. The Cr content is set to 30.00% or less. In consideration of manufacturing costs and stacking fault energy, the Cr content may be 29.00% or less, 28.00% or less, 26.00% or less, 25.00% or less, or 24.00% or less.
  • N is an effective element for forming austenite structure and ensuring high-temperature strength, creep, and high-temperature sliding properties, and may be added.
  • N is not an essential element, and the N content may be 0%.
  • N is known as a solid-solution strengthening element for high-temperature strength, and N is also effective for twin formation. To achieve this effect, the N content is preferably 0.001% or more.
  • N also exerts the effect of improving high-temperature strength by forming clusters with Cr, so the N content may be 0.005% or more, or 0.010% or more. From the viewpoint of suppressing softening of the steel, the N content may be 0.020% or more, or 0.030% or more.
  • the N content may be 0.040% or more, 0.050% or more, 0.070% or more, 0.100% or more, or 0.150% or more.
  • a high N content significantly hardens the room-temperature material, degrading cold workability during steel plate manufacturing and also impairing formability and part precision during part processing, so the N content is set to 0.400% or less.
  • the N content may be 0.370% or less or 0.360% or less.
  • the N content may be 0.350% or less, 0.345% or less, 0.340% or less, 0.320% or less, 0.300% or less, 0.280% or less, 0.250% or less, or 0.200% or less.
  • V 0.02-1.00%
  • V is an element that improves corrosion resistance and also promotes the formation of V carbides and ⁇ phases, thereby improving high-temperature strength.
  • the V content is set to 0.02% or more.
  • the V content may be 0.04% or more, 0.07% or more, 0.10% or more, 0.12% or more, 0.15% or more, 0.18% or more, or 0.25% or more. Since a high V content increases alloy costs and decreases the abnormal oxidation limit temperature, the V content is set to 1.00% or less.
  • the V content may be 0.90% or less, 0.80% or less, 0.70% or less, 0.60% or less, or 0.50% or less.
  • the Nb content may be 0.011% or more, 0.015% or more, 0.020% or more, or 0.030% or more.
  • a high Nb content significantly deteriorates hot workability during steel sheet manufacturing, and also leads to deterioration of ductility and fatigue properties due to coarse Nb carbonitrides, and an increase in stacking fault energy.
  • the Nb content is set to 1.000% or less.
  • the Nb content may be 0.900% or less, 0.800% or less, 0.700% or less, 0.600% or less, or 0.500% or less.
  • stacking fault energy the Nb content may be 0.400% or less, 0.300% or less, 0.200% or less, 0.100% or less, 0.080% or less, or 0.050% or less.
  • Co (Co: 0.001-1.000%) Co is added because it contributes to improving high-temperature strength and increasing the frequency of twinning by reducing stacking fault energy, thereby contributing to improving high-temperature properties.
  • the Co content is set to 0.001% or more.
  • the Co content may be 0.010% or more, 0.030% or more, 0.050% or more, 0.070% or more, or 0.100% or more. Since a high Co content leads to hardening, deterioration of toughness during steel plate production, and increased costs, the Co content is set to 1.000% or less. In consideration of manufacturability, the Co content may be 0.900% or less, 0.800% or less, 0.650% or less, 0.500% or less, 0.400% or less, 0.300% or less, or 0.250% or less.
  • the Fe-Cr-Ni steel sheet of the present invention may contain the following elements in addition to the elements mentioned above.
  • Mo Mo may be added as needed to improve corrosion resistance and high-temperature strength. Since Mo is not an essential element, the Mo content may be 0%. While the improvement in high-temperature strength is primarily due to solid solution strengthening, Mo also contributes to fine precipitation strengthening at twin boundaries of Mo carbides because it is an element that promotes precipitation of ⁇ phases and the like. To achieve this effect, the Mo content is preferably 0.001% or more. Considering the strengthening stability due to precipitation, the Mo content may be 0.005% or more, 0.01% or more, 0.05% or more, 0.10% or more, 0.20% or more, 0.30% or more, 0.40% or more, or 0.50% or more.
  • the Mo content is set to 5.00% or less.
  • the Mo content may be 4.50% or less, 4.00% or less, 3.50% or less, or 3.00% or less.
  • the Mo content may be 2.50% or less, 2.00% or less, or 1.50% or less.
  • Ti may be added as needed to improve corrosion resistance and intergranular corrosion resistance by bonding with C and N. Since Ti is not an essential element, the Ti content may be 0%. Although the effects of Ti can be obtained even with trace amounts, if Ti is added, the Ti content is preferably 0.001% or more. In consideration of high-temperature strength and intergranular corrosion resistance of welds, the Ti content may be 0.005% or more, 0.010% or more, 0.015% or more, 0.020% or more, or 0.025% or more. From the viewpoint of creep properties, the Ti content may be 0.030% or more, 0.035% or more, or 0.040% or more.
  • the Ti content is set to 1.000% or less. Considering alloy costs, the Ti content may be 0.900% or less, 0.800% or less, 0.650% or less, 0.500% or less, 0.400% or less, or 0.300% or less.
  • B is an element that improves hot workability during steel sheet production and may be added as needed. Since B is not an essential element, the B content may be 0%. Furthermore, twin boundary segregation of B also increases strength. Although the effect of B can be obtained even in small amounts, if B is added, the B content is preferably 0.0001% or more. Considering refining costs, the B content may be 0.0002% or more, 0.0003% or more, or 0.0005% or more. Since a high B content leads to the formation of borocarbides, resulting in a decrease in cleanliness and ductility and a deterioration in intergranular corrosion resistance, the B content is set to 0.0100% or less. Considering the decrease in ductility, the B content may be 0.0090% or less, 0.0080% or less, 0.0060% or less, 0.0030% or less, 0.0020% or less, or 0.0010% or less.
  • Ca 0-0.0100%
  • Ca is added as needed for desulfurization. Since Ca is not an essential element, the Ca content may be 0%. Although the effect of Ca inclusion can be obtained even with a small amount, when Ca is added, the Ca content is preferably 0.0001% or more. From the viewpoint of manufacturability, the Ca content may be 0.0002% or more, 0.004% or more, 0.006% or more, or 0.0010% or more. Since a high Ca content generates water-soluble inclusions CaS, which leads to a decrease in cleanliness and a significant decrease in corrosion resistance, the Ca content is set to 0.0100% or less. From the viewpoint of surface quality, the Ca content may be 0.0080% or less, 0.0060% or less, 0.0050% or less, 0.0040% or less, 0.0030% or less, or 0.0020% or less.
  • W contributes to improving corrosion resistance and high-temperature strength, so it may be added as needed. Since W is not an essential element, the W content may be 0%. Although the effect of containing W can be obtained even in small amounts, when W is added, the W content is preferably 0.001% or more. Furthermore, in consideration of refining costs, the W content may be 0.005% or more, 0.01% or more, 0.02% or more, 0.05% or more, 0.08% or more, or 0.10% or more. Since a high W content leads to hardening, deterioration of toughness during steel plate production, and increased costs, the W content is set to 3.00% or less.
  • Zr 0-0.30%) Zr may be added as needed to improve the intergranular corrosion resistance and oxidation resistance of welds by bonding with C and N. Since Zr is not an essential element, the Zr content may be 0%. Although the effect of containing Zr can be obtained even in small amounts, if Zr is contained, the Zr content is preferably 0.001% or more. In consideration of refining costs, the Zr content may be 0.005% or more, 0.01% or more, 0.02% or more, 0.05% or more, 0.08% or more, or 0.10% or more. Since a high Zr content not only increases costs but also significantly deteriorates manufacturability and hole expandability, the Zr content is set to 0.30% or less. In consideration of manufacturability, the Zr content may be 0.28% or less, 0.26% or less, 0.23% or less, 0.20% or less, or 0.18% or less.
  • Sn contributes to improving corrosion resistance and high-temperature strength, so it may be added as needed. Since Sn is not an essential element, the Sn content may be 0%. Although the effect of Sn inclusion can be obtained even with a small amount, when Sn is contained, the Sn content is preferably 0.001% or more. In consideration of refining costs, the Sn content may be 0.005% or more, 0.01% or more, 0.02% or more, 0.03% or more, 0.05% or more, or 0.08% or more. Since a high Sn content may cause slab cracking during steel plate production, the Sn content is set to 0.50% or less. In consideration of manufacturability, the Sn content may be 0.45% or less, 0.40% or less, 0.35% or less, 0.30% or less, or 0.25% or less.
  • Mg may be added as a deoxidizing element, and also contributes to improving the cleanliness of inclusions and refining the structure of the slab by refining and dispersing oxides. Since Mg is not an essential element, the Mg content may be 0%. Although the effect of containing Mg can be obtained even in small amounts, when Mg is contained, the Mg content is preferably 0.0001% or more. In consideration of refining costs, the Mg content may be 0.0002% or more, 0.0003% or more, 0.0004% or more, 0.0005% or more, or 0.0007% or more.
  • the Mg content is set to 0.0100% or less.
  • the Mg content may be 0.0090% or less, 0.0080% or less, 0.0065% or less, 0.0050% or less, 0.0035% or less, or 0.0025% or less.
  • Sb is an element that segregates at grain boundaries to increase high-temperature strength and may be added as needed. Since Sb is not an essential element, the Sb content may be 0%. Although the effect of Sb inclusion can be obtained even in small amounts, if Sb is included, the Sb content is preferably 0.001% or more. In consideration of high-temperature properties, the Sb content may be 0.002% or more, 0.005% or more, 0.010% or more, 0.020% or more, 0.030% or more, or 0.035% or more. Since a high Sb content causes Sb segregation and cracks during welding, the Sb content is set to 0.300% or less. In consideration of manufacturing cost and toughness, the Sb content may be 0.280% or less, 0.250% or less, 0.200% or less, 0.150% or less, or 0.100% or less.
  • the REM content may be 0.180% or less, 0.160% or less, 0.130% or less, 0.100% or less, 0.080% or less, or 0.060% or less.
  • REM rare earth element
  • Y scandium
  • Y yttrium
  • 15 elements lanthanoids
  • La lanthanum
  • Lu lutetium
  • Ga may be added as needed to improve corrosion resistance and suppress hydrogen embrittlement. Since Ga is not an essential element, the Ga content may be 0%. The effect of Ga inclusion can be obtained even in small amounts, but if Ga is included, the Ga content is preferably 0.0001% or more from the viewpoint of sulfide and hydride formation.
  • the Ga content may be 0.0002% or more, 0.0005% or more, 0.0010% or more, 0.0020% or more, 0.0050% or more, 0.1000% or more, or 0.1500% or more. Since a high Ga content generates coarse sulfides and deteriorates the r-value, the Ga content is set to 0.3000% or less.
  • the Ga content may be 0.2900% or less, 0.2800% or less, 0.2600% or less, 0.2500% or less, or 0.2400% or less.
  • Ta and Hf may be added in amounts of 0.01% to 1.00% to improve high-temperature strength. Since Ta and Hf are not essential elements, their contents may be 0%.
  • the Ta and Hf contents may be 0.02% or more, 0.05% or more, 0.10% or more, or 0.20% or more, respectively.
  • the Ta and Hf contents may be 0.80% or less, 0.60% or less, 0.50% or less, or 0.40% or less, respectively.
  • Bi may be contained in an amount of 0.001 to 0.020% if necessary.
  • the Bi content may be 0.002% or more, 0.003% or more, or 0.005% or more.
  • the Bi content may be 0.018% or less, 0.016% or less, or 0.015% or less.
  • the As and Pb contents may be 0%.
  • the As and Pb contents may be 0.010% or less, 0.008% or less, 0.006% or less, 0.004% or less, or 0.002% or less, respectively.
  • unavoidable impurities refer to components that are mixed in during the industrial production of steel plate due to various factors in the manufacturing process, including raw materials such as ore and scrap, and do not adversely affect the properties of the hot-rolled steel material of the present invention, i.e., are contained in a range that allows the desired properties, such as workability, required of the hot-rolled steel plate of the present invention to be obtained.
  • the SFE value may be -35 or greater, -20 or greater, -5 or greater, 0 or greater, 5 or greater, 10 or greater, or 20 or greater. Taking into account creep properties, oxidation properties, etc., the SFE value may be 45 or less, 40 or less, 35 or less, or 30 or less.
  • Fe-Cr-Ni steel sheet used for heat-resistant applications are high-temperature strength and creep properties.
  • complex shapes such as turbocharger housings
  • excessive deformation can cause contact between parts and poor gas flow, leading to damage and reduced thermal efficiency, which in turn reduces the reliability of part performance.
  • the precipitation of chromium carbides and other precipitates at random grain boundaries, and the propagation of creep voids along random grain boundaries, resulting in agglomeration and coarsening are considered to be grain boundary degradation, both of which cause deterioration of creep properties and high-temperature properties.
  • the Fe-Cr-Ni of the present invention requires that the frequency of coincidence boundaries with ⁇ values of 3 to 29 be a total of 50% or more, taking into account the relationship between KAM and HAGB, which will be described later.
  • grain boundaries where the relative misorientation between two adjacent crystal grains is 15 degrees or more and the atomic arrangement is irregular and high energy are prone to grain boundary degradation.
  • grain boundaries where the relative misorientation between two adjacent crystal grains is less than 15 degrees are defined as low-angle grain boundaries
  • grain boundaries where the relative misorientation between two adjacent crystal grains is 15 degrees or more are defined as high-angle grain boundaries
  • high-angle grain boundaries other than coincidence boundaries are defined as random grain boundaries. Since the sum of the low-angle grain boundary frequency and the high-angle grain boundary frequency is 100%, in order to increase the coincidence boundary frequency, it is preferable to reduce the low-angle grain boundary frequency and increase the high-angle grain boundary frequency to reduce the random grain boundary frequency.
  • the ⁇ 3 grain boundary which is the lowest ⁇ grain boundary among the correspondence grain boundaries, is made up of annealing twins.
  • Annealing twins are generated during heat treatment and are closely related to stacking fault energy caused by the steel components. Therefore, from the perspective of preventing grain boundary degradation, it is preferable that the proportion of correspondence grain boundaries, and in particular the proportion of annealing twins, among the crystal grain boundaries of the entire material be high.
  • the frequency of coincidence grain boundaries is determined as the ratio of the length of the coincidence grain boundaries to the total length of the grain boundaries in the cross section of the material. Specifically, a length x thickness cross section of a plate-shaped sample measuring approximately 10 mm long x 5 mm wide x 5 mm thick is colloidally finished, and a FE-SEM (manufactured by JEOL)/EBSD (Electron Back-Scattering Diffraction pattern)/OIM (manufactured by TSL) is used to perform crystal orientation analysis on a 100 ⁇ m long x 300 ⁇ m thick region within a range of approximately 1/4 to 1/2 of the plate thickness from the center of the plate thickness of the material at an acceleration voltage of 25 kV, a working distance of 14 mm, a measurement magnification of 500 times, and a measurement interval of 1.0 ⁇ m.
  • the total length of the crystal grain boundaries present within the observed range and the length of the coincidence grain boundaries are measured.
  • the thickness of the plate-shaped sample may be, for example, 2 mm or less depending on the thickness of the Fe—Cr—Ni steel plate. Even when the thickness of the Fe-Cr-Ni steel plate is 0.3 ⁇ m or less, the sample may be taken so that the total measurement area of a plurality of fields is 100 ⁇ m long ⁇ 300 ⁇ m thick.
  • KAM/HAGB ⁇ 0.010 The structure of the Fe—Cr—Ni steel sheet of the present invention satisfies KAM/HAGB ⁇ 0.010.
  • KAM in the above formula is the ratio of KAM values of 1 to 2 degrees to all measurement points.
  • HAGB in the above formula is the proportion of high-angle grain boundaries, which is calculated by dividing the length of grain boundaries with a relative misorientation of 15 degrees or more by the total grain boundary length, i.e., the length of grain boundaries with a relative misorientation of 2 degrees or more.
  • a small KAM means that there is little residual strain and that recrystallization has been completed normally. This is thought to result in less high-temperature deformation and higher high-temperature strength.
  • the smaller the KAM/HAGB ratio the less residual strain there is in the Fe-Cr-Ni steel sheet, and the higher the high-temperature strength.
  • KAM/HAGB is large and recrystallization has not been completed normally, the steel may harden and its elongation may deteriorate.
  • KAM and HAGB are measured using the following procedure.
  • a cross section (L cross section) parallel to the rolling direction and thickness direction of an Fe-Cr-Ni steel sheet is used as the observation surface, and mechanical polishing and mechanochemical polishing using a colloidal silica suspension or the like are performed to remove surface strain.
  • the surface is observed and measured using a field-emission scanning electron microscope (manufactured by JEOL, hereinafter referred to as "FE-SEM") equipped with an EBSD (Electron Back-Scattering Diffraction pattern) measurement device.
  • FE-SEM field-emission scanning electron microscope
  • KAM and HAGB are then analyzed and determined using an OIM (Orientation Imaging Microscopy, manufactured by TSL).
  • OIM Orientation Imaging Microscopy
  • the software used is "OIM Analysis.”
  • the measurement range is the region from the center of the sheet thickness to one-quarter of the sheet thickness, with one field of view covering a maximum of 1 mm2 .
  • Ten fields of view are measured at a magnification of 200x and a measurement interval of 1.5 ⁇ m.
  • the method for manufacturing steel sheet of the present invention consists of steelmaking - hot rolling - annealing and pickling - first cold rolling - first annealing and pickling - second cold rolling - second annealing and pickling. Annealing after hot rolling may be omitted if necessary.
  • a suitable method is to melt steel containing the essential elements and any additional elements required in an electric furnace or converter, followed by secondary refining.
  • the resulting molten steel is formed into slabs using a known casting method (continuous casting), and the slabs are heated to a predetermined temperature and continuously hot-rolled to a predetermined thickness using a known hot-rolling method.
  • manufacturing conditions are set in the processes following hot rolling to ensure the desired grain size, cross-sectional hardness, and surface roughness according to known methods. In this application, the following manufacturing conditions are specified to ensure that the frequency of coincidence boundaries with ⁇ values of 3 to 29 is 50% or more, and that KAM/HAGB is 0.010 or less.
  • the hot-rolled steel sheet obtained in the hot rolling step is cold-rolled at a rolling reduction of 80% or less to obtain a cold-rolled steel sheet. If the rolling reduction in this step exceeds 80%, grain growth is suppressed in the subsequent recrystallization, making it difficult to increase the frequency of coincidence boundaries with a ⁇ value of 3 to 29. In addition, the strain introduced during processing increases, reducing elongation. On the other hand, if the rolling reduction is excessively low, recrystallization is difficult to occur, so a rolling reduction of 3% or more is preferable. Taking into account the material and sheet shape, the rolling reduction may be 50% or more, 60% or more, 65% or more, 70% or more, or 75% or more.
  • the cold-rolled steel sheet is annealed at a temperature range of 950 to 1300°C, with a holding time of 120 seconds or less at 950°C or higher.
  • the metal structure after the first cold rolling, annealing, and pickling process be as fine-grained as possible.
  • the holding time at 950°C or above may be 5 seconds or more, 10 seconds or more, 15 seconds or more, or 20 seconds or more. Also, taking into account the stability of the material, the holding time at 950°C or above may be 110 seconds or less, 100 seconds or less, 90 seconds or less, 80 seconds or less, or 70 seconds or less.
  • the annealing temperature is set to 1300°C or less.
  • the annealing temperature is set to 950°C or higher.
  • the annealing temperature may be 1000°C or higher, 1050°C or higher, or 1100°C or higher.
  • the annealing temperature may be 1250°C or lower, 1230°C or lower, or 1180°C or lower.
  • the reduction ratio in cold rolling is set to 10% or less. If the reduction ratio in this step exceeds 10%, recrystallization will proceed in the subsequent annealing step, and new random grain boundaries will be formed, thereby reducing the frequency of coincidence grain boundaries. An excessive reduction in the reduction ratio will result in a poor steel sheet shape, so the reduction ratio is preferably 1% or more. Taking into consideration manufacturability and the formation of annealing twins, the reduction ratio may be 2% or more, or 3% or more. Furthermore, taking into consideration manufacturability and the formation of annealing twins, the reduction ratio may be 8% or less, or 7% or less.
  • the first stage of heat treatment is performed at a maximum temperature of 900-1000°C, with a heating rate of 10°C/sec or more up to 900°C, and a holding time at the maximum temperature of less than 60 seconds.
  • the second stage of heat treatment is performed at a maximum temperature of 1000-1200°C, with a heating rate of less than 10°C/sec up to the maximum temperature, and a holding time from 1000°C to the maximum temperature of 60 seconds or more but less than 50 hours.
  • the first and second stages of heat treatment are performed consecutively.
  • the first stage heat treatment in the second annealing after cold rolling is intended to suppress the formation of precipitates that inhibit the formation of correspondence boundaries, and to raise the temperature to the temperature range where correspondence boundaries begin to form.
  • the subsequent second stage heat treatment is intended to promote the formation of correspondence boundaries through grain growth, suppress the formation of random grain boundaries due to new recrystallization, and obtain a metal structure with a high frequency of correspondence boundaries.
  • the heating rate is increased in the temperature range up to 900°C to suppress the formation of ⁇ phase and Cr carbonitrides, which precipitate at relatively low temperatures. These precipitates not only inhibit the formation of coincidence grain boundaries but also serve as nuclei for newly formed random grain boundaries. Furthermore, if the number of precipitates becomes too large, elongation deteriorates. From the above technical viewpoint, the heating rate is set to 10°C/sec or more. From the viewpoint of manufacturability, a heating rate of 100°C/sec or less is preferable. The heating rate may be 15°C/sec or more, or 20°C/sec or more. The heating rate may also be 90°C/sec or less, 80°C/sec or less, or 70°C/sec or less.
  • the maximum temperature may be 950°C or higher. If the maximum temperature is above 1000°C, the formation and coarsening of precipitates will be promoted during the first-stage heat treatment.
  • a long holding time at the maximum temperature promotes coarsening of precipitates and inhibits grain growth during the second heat treatment, so a shorter holding time is preferable.
  • the holding time at the maximum temperature may be 0.5 seconds or more, 1 second or more, 5 seconds or more, 7 seconds or more, or 10 seconds or more.
  • the holding time at the maximum temperature may be 50 seconds or less, 40 seconds or less, or 30 seconds or less.
  • the heating rate to the maximum temperature is set to less than 10°C/sec.
  • the heating temperature is preferably 0.1°C/sec or higher, and may be 0.5°C/sec or higher, 1°C/sec or higher, 2°C/sec or higher, 3°C/sec or higher, or 5°C/sec or higher.
  • random grain boundaries migrate and grow during holding at 1000°C to the maximum temperature, reducing the random grain boundary frequency, while forming correspondence grain boundaries such as annealing twins, increasing the correspondence grain boundary frequency.
  • the holding time at 1000°C or higher at the maximum temperature should be at least 60 seconds but less than 50 hours. If the holding time is too long or too short, the elongation of the steel will deteriorate. Furthermore, if the holding time is too short, the formation of correspondence grain boundaries will not be promoted, resulting in a low frequency of correspondence grain boundaries. From the perspective of productivity, the holding time at 1000°C or higher at the maximum temperature may be less than 30 hours, less than 24 hours, less than 18 hours, less than 12 hours, less than 10 hours, or less than 5 hours. From the perspective of promoting the formation of correspondence grain boundaries and improving the material properties through softening, the holding time may be at least 90 seconds, at least 120 seconds, at least 180 seconds, at least 300 seconds, or at least 600 seconds.
  • the alloy elements are selected to have an SFE value of 50 mJ/ m or less.
  • an even smoother surface can be obtained by cold rolling after hot-rolled sheet annealing and pickling, followed by cold-rolled sheet annealing and pickling.
  • the cold rolling process can be performed by tandem rolling, Sendzimir rolling, cluster rolling, etc. 2B or 2D products are generally used for functional applications such as automotive exhaust parts, but if high surface smoothness and gloss are required, bright annealing can be performed after cold rolling to produce a BA product.
  • slab thickness and hot-rolled sheet thickness can be designed as needed.
  • roll roughness, roll diameter, rolling oil, number of rolling passes, rolling speed, and rolling temperature can be selected as needed.
  • Intermediate annealing can be performed during cold rolling, and either batch or continuous annealing can be used.
  • pretreatment before pickling can involve neutral salt electrolysis or salt bath immersion, or it can be omitted.
  • the pickling process can involve treatment using nitric acid, nitric acid electrolytic pickling, sulfuric acid, or hydrochloric acid.
  • shape and material adjustment can be performed using temper rolling or a tension leveler.
  • Fe-Cr-Ni steel sheet can be coated with a lubricating coating to further improve press formability; the type of lubricating film can be selected as needed.
  • special surface treatments such as nitriding and carburizing can be used after part processing to further improve heat resistance.
  • the Fe-Cr-Ni steel sheet obtained in this way can be suitably used for, for example, exhaust parts, precision internal parts of turbochargers, wastegate valves, or turbo housings.
  • the frequency of coincident grain boundaries (%) and the frequency of random grain boundaries (%) were measured using the methods described above, and creep tests and high-temperature tensile tests were also conducted at 900°C.
  • a flanged test piece with a test width of 8 mm and a distance between marks of 35 mm was cut out from a 2.0 mm thick Fe-Cr-Ni steel plate so that the load was applied in the rolling direction.
  • a constant load creep test was conducted at 900°C and 20 MPa using a creep testing machine with a heating furnace. During this test, the no-load period at the test temperature was set to one hour, and a load was applied after one hour.
  • JIS No. 13B test pieces were cut from 2.0 mm thick Fe-Cr-Ni steel plates so that tension was applied in the rolling direction, and tensile tests were conducted at room temperature in accordance with JIS Z2241:2011 to determine the elongation at break.
  • a flanged test piece with a test width of 10 mm and a gauge length of 35 mm was cut out from a 2.0 mm thick Fe-Cr-Ni steel plate so that a load was applied in the rolling direction.
  • a tensile test was conducted in accordance with JIS G 0567:2020 to determine the 0.2% yield strength.
  • a Shimadzu Autograph AG-100kNX equipped with an infrared heating furnace was used for the test.
  • the "Correspondence boundary frequency” item in the table indicates the total frequency (%) of coincidence boundaries with ⁇ values of 3 to 29
  • the "Random grain boundary frequency” item indicates the frequency (%) of random grain boundaries, i.e., the difference (%) between the frequency of high-angle boundaries, which are grain boundaries where the relative misorientation between adjacent crystal grains is 15 degrees or more, and the frequency of coincidence boundaries with ⁇ of 3 to 29.
  • the "KAM/HAGB” item indicates the ratio between the proportion of high-angle boundaries and the proportion with KAM values of 1 to 2 degrees.
  • Comparative Example 1 had a high Cr content, which hardened the steel, resulting in poor fracture elongation. It is also thought that the stacking fault energy was high, resulting in little annealing twin formation. As a result, the frequency of coincidence grain boundaries was low, making it more susceptible to grain boundary degradation at high temperatures, resulting in a shorter creep rupture life.
  • Comparative Example 2 is an example with a low Cr content.
  • the maximum temperature of the first annealing stage after the second cold rolling was low, which is thought to have prevented recrystallization from completing normally and resulted in a large amount of residual strain.
  • KAM increased and KAM/HAGB increased.
  • the high-temperature strength was poor.
  • Comparative Example 3 had a high Ni content, which resulted in reduced ductility and poor fracture elongation. It is also believed that the stacking fault energy was high, resulting in little annealing twin formation. As a result, the frequency of coincidence grain boundaries was low, making it more susceptible to grain boundary degradation at high temperatures, resulting in a shorter creep rupture life.
  • Comparative Example 4 had a high Nb content, which resulted in reduced ductility and poor fracture elongation. It is also believed that the stacking fault energy was high, resulting in little annealing twin formation. As a result, the frequency of coincidence grain boundaries was low, making it more susceptible to grain boundary degradation at high temperatures, resulting in a shorter creep rupture life.
  • Comparative Example 5 had a high Cu content, resulting in poor fracture elongation. It is also believed that the stacking fault energy was high, resulting in little annealing twin formation. As a result, the frequency of coincidence grain boundaries was low, making it more susceptible to grain boundary degradation at high temperatures, resulting in a shorter creep rupture life.
  • Comparative Example 6 had a high Mo content, resulting in excessively high strength and poor fracture elongation. It is also believed that the stacking fault energy was high, resulting in little annealing twin formation. As a result, the frequency of coincidence grain boundaries was low, making it more susceptible to grain boundary degradation at high temperatures, resulting in low high-temperature strength and a shorter creep rupture life.
  • Comparative Example 7 had a high Si content, which is thought to have hardened the steel. This resulted in poor breaking elongation.
  • Comparative Example 8 had a high Co content, which is thought to have hardened the steel. This resulted in poor breaking elongation.
  • Comparative Examples 10 to 25 are examples in which the steel compositions were within the range of the present invention, but the manufacturing method was inappropriate, and the Fe-Cr-Ni steel sheet of the present invention could not be obtained.
  • Comparative Example 10 is an example that underwent the combination of cold rolling and annealing only once. As a result, the frequency of coincident grain boundaries decreased, making it more susceptible to grain boundary degradation at high temperatures, resulting in a shorter creep rupture life.
  • Comparative Example 11 is an example in which, after the second cold rolling, only annealing was performed at a maximum temperature in the range of 900 to 1000°C. It is believed that this prevented random grain boundaries from migrating and growing, preventing the formation of coincidence boundaries such as annealing twins. As a result, the frequency of coincidence boundaries decreased, making it easier for grain boundary degradation to occur at high temperatures, resulting in a shorter creep rupture life.
  • Comparative Example 12 is an example in which, after the second cold rolling, only annealing was performed at a maximum temperature in the range of 1000 to 1200°C. As a result, precipitates were formed before annealing, which is thought to have inhibited an improvement in the frequency of coincidence boundaries. As a result, the frequency of coincidence boundaries decreased, making it easier for grain boundary degradation to occur at high temperatures, resulting in a shorter creep rupture life.
  • Comparative Example 14 the reduction ratio in the second cold rolling was high, and it is thought that recrystallization progressed during the subsequent annealing, resulting in the formation of new random grain boundaries. As a result, the frequency of coincident grain boundaries decreased, making it more susceptible to grain boundary degradation at high temperatures, and therefore shortening the creep rupture life.
  • the present invention makes it possible to provide Fe-Cr-Ni steel sheets with excellent properties for exhaust parts that require heat resistance.
  • materials incorporating the present invention particularly for automotive exhaust manifolds and turbochargers, significant weight reductions can be achieved compared to conventional castings, leading to compliance with exhaust gas regulations, weight reduction, and improved fuel efficiency. It also makes it possible to omit cutting and grinding processes for parts and surface treatments, significantly contributing to cost reductions.
  • the present invention can be applied to any of these parts.
  • these include the housing that forms the outer frame of the turbocharger and precision parts inside nozzle vane turbochargers (e.g., back plates, oil deflectors, compressor wheels, nozzle mounts, nozzle plates, nozzle vanes, drive rings, drive levers, etc.).
  • nozzle vane turbochargers e.g., back plates, oil deflectors, compressor wheels, nozzle mounts, nozzle plates, nozzle vanes, drive rings, drive levers, etc.
  • the fuel used in automobiles equipped with turbochargers can be any of gasoline, diesel, synthetic fuels such as ethanol or methanol, or hydrogen, or a mixture of these, and is not limited to these.
  • the invention is not limited to automobiles and motorcycles; it can also be applied to components used in high-temperature environments, such as various boilers (e.g., incinerator boilers, next-generation boilers, sheath heaters, combustion burners, etc.), fuel cell systems, and chemical plants (e.g., ethylene plants, hydrogen production plants, polysilicon production plants, steel plants, reduction iron manufacturing facilities, nuclear power plants, thermal power plants, oil mining plants, etc.), making it extremely useful industrially.
  • various boilers e.g., incinerator boilers, next-generation boilers, sheath heaters, combustion burners, etc.
  • fuel cell systems e.g., ethylene plants, hydrogen production plants, polysilicon production plants, steel plants, reduction iron manufacturing facilities, nuclear power plants, thermal power plants, oil mining plants, etc.

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Abstract

La présente invention aborde le problème de la fourniture d'une tôle d'acier Fe-Cr-Ni présentant une résistance à la chaleur améliorée. Une tôle d'acier Fe-Cr-Ni selon la présente invention présente une composition chimique prescrite. La valeur de 0,5 × Cr + 1,4 × Ni + 3,2 × Nb + 0,1 × Mo + 3,6 × Cu − 3,4 × Si − 0,6 × Co (les symboles d'élément dans la formule représentent les quantités contenues (% en masse) des éléments correspondants, et zéro est substitué lorsque l'élément n'est pas contenu) est inférieure ou égale à 50. La fréquence de limite de grain correspondante de joints de grain correspondants ayant une valeur Σ de 3-29 est supérieure ou égale à 50 % au total. KAM représentant la proportion pour laquelle des valeurs KAM sont de 1 à 2°, et HAGB représentant le rapport entre des longueurs de limite de grain cristallin pour lesquelles la différence d'orientation relative est de 15° ou plus et la longueur de limite de grain totale pour laquelle la différence d'orientation relative est de 2° ou plus, satisfont KAM/HAGB ≤ 0,010.
PCT/JP2024/016602 2024-04-26 2024-04-26 Tôle d'acier fe-cr-ni et son procédé de production Pending WO2025225030A1 (fr)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2019218588A (ja) * 2018-06-18 2019-12-26 日鉄ステンレス株式会社 オーステナイト系ステンレス鋼板およびその製造方法
WO2024043080A1 (fr) * 2022-08-24 2024-02-29 日鉄ステンレス株式会社 Acier inoxydable austénitique
JP2024047464A (ja) * 2022-09-26 2024-04-05 日鉄ステンレス株式会社 オーステナイト系ステンレス鋼板

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2019218588A (ja) * 2018-06-18 2019-12-26 日鉄ステンレス株式会社 オーステナイト系ステンレス鋼板およびその製造方法
WO2024043080A1 (fr) * 2022-08-24 2024-02-29 日鉄ステンレス株式会社 Acier inoxydable austénitique
JP2024047464A (ja) * 2022-09-26 2024-04-05 日鉄ステンレス株式会社 オーステナイト系ステンレス鋼板

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