WO2019087761A1 - Ferritic stainless-steel sheet and method for manufacturing same - Google Patents

Ferritic stainless-steel sheet and method for manufacturing same Download PDF

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Publication number
WO2019087761A1
WO2019087761A1 PCT/JP2018/038400 JP2018038400W WO2019087761A1 WO 2019087761 A1 WO2019087761 A1 WO 2019087761A1 JP 2018038400 W JP2018038400 W JP 2018038400W WO 2019087761 A1 WO2019087761 A1 WO 2019087761A1
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hot
ferritic stainless
steel sheet
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PCT/JP2018/038400
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French (fr)
Japanese (ja)
Inventor
佳士 井上
英尚 川邉
正崇 吉野
光幸 藤澤
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Ｊｆｅスチール株式会社
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Application filed by Ｊｆｅスチール株式会社 filed Critical Ｊｆｅスチール株式会社
Priority to MX2020004428A priority Critical patent/MX2020004428A/en
Priority to KR1020227016128A priority patent/KR102603113B1/en
Priority to US16/758,551 priority patent/US20200347475A1/en
Priority to JP2019505000A priority patent/JP6536763B1/en
Priority to KR1020207011817A priority patent/KR20200057760A/en
Priority to EP18873329.9A priority patent/EP3666917B1/en
Priority to ES18873329T priority patent/ES2883114T3/en
Priority to CN201880070416.7A priority patent/CN111295458A/en
Publication of WO2019087761A1 publication Critical patent/WO2019087761A1/en

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/002—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working by rapid cooling or quenching; cooling agents used therefor
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/007—Heat treatment of ferrous alloys containing Co
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • 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
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • 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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • 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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • 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
    • C21D8/0278—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular surface treatment
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite

Definitions

  • the present invention relates to a ferritic stainless steel sheet and a method for producing the same, and more particularly to a ferritic stainless steel sheet excellent in toughness and excellent in corrosion resistance, which is useful for using a flange member, and a method for producing the same.
  • the exhaust gas path of a car is composed of various parts such as an exhaust manifold, a muffler, a catalyst, a flexible tube, a center pipe and a front pipe.
  • fastening parts called flanges are often used.
  • the flange applied to such exhaust system components needs to have sufficient rigidity. From this, a thick-walled (for example, 5 mm or more in plate thickness) flange is applied to such an exhaust system component.
  • the flange is manufactured by processing such as punching other than press forming, and ordinary steel has been used.
  • flange materials applied to parts exposed to high temperature exhaust gas such as an EGR (Exhaust Gas Recirculation, EGR) system are required to have sufficient corrosion resistance. Therefore, the application of stainless steel which is superior in corrosion resistance to ordinary steel, in particular, ferritic stainless steel which has a relatively small coefficient of thermal expansion and which hardly generates a thermal stress has been studied. As a result, a ferritic stainless steel plate having a large thickness (for example, 5 mm or more in thickness) applicable to a thick flange is strongly required.
  • EGR exhaust Gas Recirculation
  • a ferritic stainless steel having a large thickness has a problem of low temperature toughness. For example, many press cracks at the time of flange manufacture occur in winter. From these facts, there is a strong demand for improvement in toughness of a ferritic stainless steel having a large thickness.
  • Patent Document 1 For such market requirements, for example, in Patent Document 1, C: 0.02% or less, N: 0.02% or less, Si: 0.005 to 1.0%, Ni: 0 in mass%. 1 to 1.0%, Mn: 0.1 to 3.0%, P: 0.04% or less, S: 0.0100% or less, Cr: 10% or more to 18% or less, and further Ti : 0.05 to 0.30%, Nb: 0.01 to 0.50%, containing one or two kinds, and the total of Ti and Nb is 8 (C + N) to 0.75%, the balance Is composed of Fe and unavoidable impurities, and has a ⁇ p of 70% or more, a ferrite grain size of 20 ⁇ m or less, and a martensite formation amount of 70% or less (a Charpy impact value at ⁇ 40 ° C.
  • a stainless steel sheet excellent in 50 J / cm 2 or more) is disclosed.
  • (gamma) p (%) is evaluated using following (i) Formula (In patent document 1, it describes with (1) Formula).
  • ⁇ p 420 (% C) + 470 (% N) + 23 (% Ni) + 9 (% Cu) + 7 (% Mn)-11.5 (% Cr)-11.5 (% Si)-12 (% Mo) -23 (% V)-47 (% Nb)-49 (% Ti)-52 (% Al) + 189
  • (% X) shows the mass ratio of each component X.
  • An object of the present invention is to provide a ferritic stainless steel sheet which is more excellent in toughness and excellent in corrosion resistance and a method of manufacturing the same.
  • more excellent toughness means that the Charpy impact value at ⁇ 50 ° C. is 100 J / cm 2 or more.
  • having excellent corrosion resistance means that the rusting rate after performing three cycles of the salt spray cycle test defined in JIS H 8502 is 25% or less.
  • the present inventors conducted detailed studies to solve the above problems. As a result, the following findings were obtained.
  • the metal structure is refined and the Charpy impact value at -50 ° C. is 100 J / cm 2 or more.
  • the average grain size of the metal structure it is possible to effectively suppress the occurrence of cracks in the burring portion when processing into a thick flange having the burring portion. It can be fully commercialized to a thick flange having a burring portion.
  • Hot-rolled sheet annealing at a temperature is an effective means for refining the metal structure and obtaining a Charpy impact value of -100 J / cm 2 or more at -50 ° C.
  • the present invention has been made based on the above findings, and the gist of the present invention is as follows. [1] by mass%, C: 0.001 to 0.020%, Si: 0.05 to 0.35%, Mn: 0.05 to 1.00%, P: not more than 0.04%, S: 0.01% or less, Al: 0.001 to 0.300%, Cr: 10.0 to 13.0%, Ni: 0.75 to 1.50%, Ti: 0.05 to 0.35%, N: 0.001 to 0.020%, and ⁇ I [%] of the following formula (1) is 65% or more, and the balance has a component composition consisting of Fe and unavoidable impurities, A ferritic stainless steel sheet having an average grain size of 45 ⁇ m or less in a metal structure.
  • Ni, Mn, Cu, Si, Cr, and Mo in Formula (1) represent content (mass%) of each component, and let the component which is not contained be zero.
  • V 0.01 to 0.20%
  • Nb 0.01 to 0.10%
  • Zr 0.01 to 0.20% in mass%
  • REM 0.001 to 0.100%
  • B 0.0002 to 0.0025%
  • Mg 0.0005 to 0.0030%
  • Ca 0 by mass%
  • a method for producing a ferritic stainless steel sheet comprising: a hot rolling step of performing hot rolling; and a hot rolled sheet annealing step of hot rolled sheet annealing of the hot rolled steel sheet obtained in the hot rolling step at 750 to 1050 ° C.
  • ferritic stainless steel sheet which is more excellent in toughness and excellent in corrosion resistance.
  • the ferritic stainless steel sheet of the present invention can be suitably used for thick flanges and the like.
  • the present inventors used a variety of ferritic stainless steel plates with a thickness of 5.0 mm to form flanges having a 30 mm diameter flange hole with a burred portion that lifts 10 mm from the surface of the steel plate as it is as blank (as punched out).
  • the inventors examined in detail the relationship between the low toughness and the metallographic structure. As a result, it was found that the toughness was lowered as the average grain size of the steel sheet was larger. Then, forming to the above-mentioned flange was tried using various ferritic stainless steel plates (board thickness 5.0 mm). As a result, it was found that, in a steel plate having an average crystal grain size exceeding 45 ⁇ m, the toughness is lowered and a crack is easily generated. When the average crystal grain size is 45 ⁇ m or less, the toughness is excellent and the punching workability of the steel plate is good.
  • the average crystal grain size is 45 ⁇ m or less, and the Charpy impact value at ⁇ 50 ° C. is 100 J / cm 2 or more.
  • the said average grain size can be measured by the measuring method of the Example mentioned later.
  • the Charpy impact value is a value measured in accordance with JIS Z 2242 (2005) as described later.
  • the C content is in the range of 0.001% to 0.020%.
  • the C content is preferably 0.003% or more, more preferably 0.004% or more. Further, the C content is preferably 0.015% or less, more preferably 0.012% or less.
  • Si 0.05 to 0.35%
  • Si has the effect of concentrating on the oxide film formed at the time of welding to improve the corrosion resistance of the welded portion, and is also an element useful as a deoxidizing element in the steel making process. These effects are obtained by containing Si of 0.05% or more, and the effect becomes larger as the content is larger.
  • Si has the effect of promoting the formation of a ferrite phase. If Si is contained in excess of 0.35%, a predetermined amount of austenite phase is not sufficiently formed at the time of heating in the hot rolling step. The desired metallographic structure can not be obtained even if hot rolling and hot rolled sheet annealing are performed under the following conditions. Therefore, the Si content is set to 0.05% or more and 0.35% or less.
  • the Si content is preferably 0.10% or more. Further, the Si content is preferably 0.30% or less.
  • Mn 0.05 to 1.00% Mn has the effect of promoting the formation of the austenite phase. In order to acquire the effect, it is necessary to contain 0.05% or more of Mn. However, if the Mn content exceeds 1.00%, precipitation of MnS, which is a starting point of corrosion, is promoted, and the corrosion resistance is lowered. Therefore, the Mn content is set to 0.05% or more and 1.00% or less.
  • the Mn content is preferably 0.20% or more. Also, the Mn content is preferably 0.80% or less, more preferably 0.70% or less.
  • P 0.04% or less
  • P is an element inevitably contained in steel and is an element harmful to corrosion resistance and workability, and therefore it is preferable to reduce as much as possible. If the P content exceeds 0.04%, the formability is markedly reduced due to solid solution strengthening. Therefore, the P content is 0.04% or less.
  • the P content is preferably 0.03% or less.
  • S 0.01% or less S is also an element inevitably contained in steel like P, and is an element harmful to corrosion resistance and workability, and therefore, it is preferable to reduce as much as possible. In particular, when the S content exceeds 0.01%, the corrosion resistance is significantly reduced. Therefore, the S content is 0.01% or less.
  • the S content is preferably 0.008% or less, more preferably 0.003% or less.
  • Al 0.001 to 0.300%
  • Al is an effective deacidifying agent. Furthermore, since Al has a stronger affinity to nitrogen than Cr, when nitrogen penetrates the weld, it has the effect of precipitating nitrogen as Al nitride instead of Cr nitride to suppress sensitization. These effects are obtained by containing Al 0.001% or more. However, if the Al content exceeds 0.300%, it is not preferable because the penetration during welding decreases and the weldability decreases. Therefore, the Al content is in the range of 0.001% to 0.300%. The Al content is preferably 0.010% or more. Further, the Al content is preferably 0.200% or less, more preferably 0.100% or less, and still more preferably 0.050% or less.
  • Cr 10.0 to 13.0% Cr is the most important element to ensure corrosion resistance. If the content is less than 10.0%, corrosion resistance necessary for automobile exhaust parts can not be obtained. On the other hand, when Cr is contained in excess of 13.0%, a predetermined amount of austenite phase is formed at the time of heating in the hot rolling process even if the steel component is adjusted to ⁇ I represented by predetermined formula (1) described later In order to avoid this, even if hot rolling and hot rolled sheet annealing are performed under the conditions specified by the present invention, the desired metallographic structure can not be obtained. Therefore, the Cr content is in the range of 10.0% to 13.0%. The Cr content is preferably 10.5% or more. Further, the Cr content is preferably 12.0% or less, more preferably 11.7% or less.
  • Ni 0.75 to 1.50%
  • Ni is an austenite-forming element, and has an effect of increasing the amount of austenite generated at the time of heating before rolling in the hot rolling process.
  • a two-phase structure of a ferrite phase and an austenite phase including an austenite phase of 70% or more in volume ratio is obtained at the time of slab heating in the hot rolling process.
  • the metallographic structure is a two-phase structure of a ferrite phase and an austenite phase, the heterophase interface between the ferrite phase and the austenite phase functions as an obstacle to grain growth, so that the metal structure before hot rolling is refined.
  • the Ni content is set to 0.75% or more and 1.50% or less.
  • the Ni content is preferably 0.80% or more. Further, the Ni content is preferably 1.20% or less, more preferably 1.00% or less.
  • Ti 0.05 to 0.35%
  • Ti preferentially combines with C and N to suppress the precipitation of Cr carbonitrides, and has the effect of reducing the recrystallization temperature and suppressing the drop in corrosion resistance caused by the sensitization due to the precipitation of Cr carbonitrides. is there. In order to obtain such an effect, it is necessary to contain 0.05% or more of Ti. On the other hand, if the Ti content exceeds 0.35%, the toughness is significantly reduced due to the formation of coarse TiN, and even if the technology of the present invention is applied, a predetermined toughness can not be obtained. Further, the content of Ti of more than 0.35% is not preferable in production because coarse Ti carbo-nitrides are formed in the casting process to cause surface defects. Therefore, the Ti content is set to 0.05% or more and 0.35% or less. The Ti content is preferably 0.10% or more. Further, the Ti content is preferably 0.30% or less, more preferably 0.15% or less.
  • the N content is in the range of 0.001% to 0.020%.
  • the N content is preferably 0.005% or more, more preferably 0.007% or more. Further, the N content is preferably 0.015% or less, more preferably 0.012% or less.
  • ⁇ I [%] 65% or more
  • ⁇ I [%] is determined using the following equation (1) for evaluating the stability of the austenite phase.
  • ⁇ I [%] 24 Ni + 12 Mn + 6 Cu-18 Si-12 Cr-12 Mo + 188 (1)
  • Ni, Mn, Cu, Si, Cr, and Mo in Formula (1) represent content (mass%) of each component, and let the component which is not contained be zero.
  • the austenite-forming element has a positive coefficient
  • the ferrite-forming element has a negative coefficient, and the respective values were experimentally obtained with reference to the Castro equation.
  • the remainder other than the above is Fe and unavoidable impurities.
  • an unavoidable impurity O (oxygen) etc. are mentioned, and if content of O is 0.01% or less, it is permissible.
  • one or more groups selected from the following groups A to C can be contained.
  • Group A Cu: 0.01 to 1.00%, Mo: 0.01 to 1.00%, W: 0.01 to 0.20%, Co: 0.01 to 0.20% Or two or more
  • group B V: 0.01 to 0.20%, Nb: 0.01 to 0.10%, and Zr: 0.01 to 0.20% one or more
  • group C REM: 0.001 to 0.100%
  • B 0.0002 to 0.0025%
  • Mg 0.0005 to 0.0030%
  • Ca 0.0003 to 0.0030%
  • Cu 0.01 to 1.00%
  • Cu is an element that is particularly effective in improving the corrosion resistance in an aqueous solution or when a weakly acidic water droplet is attached. Furthermore, Cu has the effect of promoting the formation of the austenite phase. This effect is obtained by containing 0.01% or more, and the effect becomes higher as the Cu content is larger. However, if Cu is contained in excess of 1.00%, the hot workability may be reduced to induce surface defects. Furthermore, there are cases where descaling after annealing becomes difficult. Therefore, when it contains Cu, Cu content is made into the range of 0.01% or more and 1.00% or less. When Cu is contained, the Cu content is preferably 0.10% or more. When Cu is contained, the Cu content is preferably 0.50% or less.
  • Mo 0.01 to 1.00%
  • Mo is an element that significantly improves the corrosion resistance of stainless steel. This effect is obtained by containing 0.01% or more of Mo, and the effect improves as the content increases.
  • Mo has the effect of promoting the formation of a ferrite phase, and when the Mo content exceeds 1.00%, a predetermined amount of austenite phase is not sufficiently formed at the time of heating in the hot rolling process. The desired metallographic structure can not be obtained even if hot rolling and hot rolled sheet annealing are performed under the following conditions. Therefore, when it contains Mo, Mo content is made into 0.01% or more and 1.00% or less. When Mo is contained, the Mo content is preferably 0.10% or more, more preferably 0.30% or more. Moreover, when it contains Mo, Mo content is preferably 0.80% or less, more preferably 0.50% or less.
  • W 0.01 to 0.20% Like Mo, W has the effect of improving the corrosion resistance. This effect is obtained by containing 0.01% or more of W. On the other hand, if W is contained in excess of 0.20%, the strength may increase, which may lead to a decrease in manufacturability due to an increase in rolling load or the like. Therefore, when W is contained, the W content is in the range of 0.01% or more and 0.20% or less. When W is contained, the W content is preferably 0.05% or more. When W is contained, the W content is preferably 0.15% or less.
  • Co 0.01 to 0.20%
  • Co is an element that improves the toughness. This effect is obtained by containing 0.01% or more of Co. On the other hand, when the Co content exceeds 0.20%, the processability may be reduced. Therefore, when Co is contained, the Co content is in the range of 0.01% to 0.20%.
  • V 0.01 to 0.20% V forms carbonitrides with C and N, suppresses sensitization during welding, and improves the corrosion resistance of the welded portion. This effect is obtained when the V content is 0.01% or more. On the other hand, when the V content exceeds 0.20%, the processability and the toughness may be significantly reduced. Therefore, when V is contained, V content is made into 0.01% or more and 0.20% or less. When V is contained, the V content is preferably 0.02% or more. Moreover, when V is contained, V content is preferably 0.10% or less.
  • Nb 0.01 to 0.10%
  • Nb has the effect of refining the crystal grains. This effect is obtained by containing 0.01% or more of Nb.
  • Nb also has the effect of raising the recrystallization temperature, and if the Nb content exceeds 0.10%, the annealing temperature required to cause sufficient recrystallization in hot-rolled sheet annealing becomes excessively high. In some cases, it is not possible to obtain a metal structure having an average crystal grain size of 45 ⁇ m or less. Therefore, when Nb is contained, the Nb content is in the range of 0.01% or more and 0.10% or less. When Nb is contained, the Nb content is preferably 0.05% or less.
  • Zr 0.01 to 0.20% Zr combines with C and N and has an effect of suppressing sensitization. This effect is obtained by containing 0.01% or more of Zr. On the other hand, if the content of Zr exceeds 0.20%, the workability may be significantly reduced. Therefore, when Zr is contained, the Zr content is in the range of 0.01% to 0.20%. When containing Zr, the Zr content is preferably 0.10% or less.
  • REM 0.001 to 0.100% REM (Rare Earth Metals: rare earth metal) has the effect of improving the oxidation resistance, and suppresses the formation of an oxide film (welded temper collar) at the weld to suppress the formation of a Cr-deficient region immediately below the oxide film. This effect is obtained by containing 0.001% or more of REM. On the other hand, if the content of REM is more than 0.100%, the productivity such as acid washability at the time of cold rolling annealing may be reduced. Therefore, when REM is contained, the REM content is in the range of 0.001% to 0.100%. When REM is contained, the REM content is preferably 0.050% or less.
  • B 0.0002 to 0.0025%
  • B is an element effective to improve the secondary processing brittleness after deep drawing. This effect is obtained by setting the B content to 0.0002% or more. On the other hand, if B is contained in excess of 0.0025%, processability and toughness may be reduced. Therefore, when it contains B, B content is taken as the range of 0.0002% or more and 0.0025% or less. When B is contained, the B content is preferably 0.0003% or more. When B is contained, the B content is preferably 0.0012% or less.
  • Mg 0.0005 to 0.0030%
  • Mg has the effect of suppressing the coarsening of Ti carbo-nitrides. This effect is obtained by containing 0.0005% or more of Mg.
  • the Mg content exceeds 0.0030%, the surface properties of the steel may be deteriorated. Therefore, when Mg is contained, the Mg content is in the range of 0.0005 to 0.0030%.
  • the Mg content is preferably 0.0010% or more.
  • the Mg content is preferably 0.0020% or less.
  • Ca 0.0003 to 0.0030%
  • Ca is an effective component to prevent the clogging of the nozzle due to the crystallization of Ti-based inclusions that are easily generated during continuous casting. The effect is obtained by containing 0.0003% or more of Ca.
  • the Ca content is more than 0.0030%, the corrosion resistance may be reduced due to the formation of CaS. Therefore, when it contains Ca, Ca content is made into the range of 0.0003% or more and 0.0030% or less.
  • the Ca content is preferably 0.0005% or more.
  • the Ca content is preferably 0.0015% or less, more preferably 0.0010% or less.
  • the present inventors have intensively studied the method of improving the toughness in a ferritic stainless steel sheet, and preferably heat a steel slab having an appropriate steel component at preferably 1050 to 1250 ° C. and then preferably hot roll it in three or more passes.
  • a metal structure having an average crystal grain size of 45 ⁇ m or less is obtained, and the Charpy impact value at 50 ° C. is 100 J
  • the toughness was significantly improved to be at least 2 cm 2 .
  • the desired corrosion resistance can also be obtained.
  • the present inventors diligently studied, from both the steel component and the hot rolling method, an effective method for obtaining a fine structure after hot-rolled sheet annealing.
  • the content of steel components in particular Si, Mn, Cr and Ni, is controlled within an appropriate range, slab heating is performed at an appropriate temperature in the hot rolling process, and austenite phase containing ferrite phase + austenite phase It turned out that it is effective to form a phase structure and perform hot rolling.
  • the heterophase interface between the ferrite phase existing before heating and the austenite phase generated at the time of heating suppresses coarsening of crystal grains, so before hot rolling A fine equiaxed structure is obtained at the stage of. Then, by performing predetermined hot rolling, processing strain to be a recrystallization site is sufficiently accumulated in the hot-rolled sheet annealing in the next step, and a fine metal structure is obtained by the hot-rolled sheet annealing in the next step. Toughness can be expressed.
  • Hot-rolled steel after slab heating at 1050 to 1250 ° C is adjusted for the steels adjusted so that the above-mentioned equation (1) combining the content of elements Si and Cr and negative coefficients to each of Si and Cr holds was devised to do.
  • Hot-rolled sheet annealing is a process of recrystallizing the worked structure formed by hot rolling. Therefore, it is necessary to carry out annealing at a temperature at which sufficient recrystallization occurs.
  • hot-rolled sheet annealing is performed at an excessively high temperature, although recrystallization occurs, significant coarsening of recrystallized grains occurs, and a predetermined fine structure can not be obtained.
  • the inventors investigated in detail the relationship between the grain size of recrystallized grains and the annealing temperature. As a result, it has been found that by suppressing the hot-rolled sheet annealing temperature to 1050 ° C. or less, it is possible to suppress the formation of coarse recrystallized grains that the toughness is reduced.
  • molten steel having the above-described component composition is melted by a known method such as a converter, an electric furnace, a vacuum melting furnace or the like, and made into a steel material (slab) by a continuous casting method or an ingot-bunch method.
  • Heating temperature of steel slab 1050 to 1250 ° C
  • the steel slab is heated at 1050 to 1250 ° C. and subjected to hot rolling.
  • the heating time at the heating temperature is not particularly limited, but heating is preferably performed for 1 to 24 hours.
  • the heating temperature is less than 1050 ° C., the formation ratio of the austenite phase becomes low, and a fine metal structure can not be obtained, so that excellent toughness can not be obtained.
  • the heating temperature of the steel slab is made 1250 ° C. or less.
  • direct feed rolling may be performed without heating the steel material.
  • the rough rolling conditions are not particularly limited. If the cast structure has been effectively broken before the finish hot rolling, it is preferable to set the cumulative rolling reduction in rough rolling to 65% or more, since the refining effect in the subsequent slab heating is further promoted. Thereafter, it is rolled to a predetermined thickness by finish hot rolling.
  • Hot-rolled sheet annealing temperature 750 to 1050 ° C
  • hot-rolled sheet annealing is performed after the completion of the hot rolling.
  • the rolled structure formed in the hot rolling process is recrystallized.
  • rolling strain is effectively applied in the hot rolling step, and coarsening of recrystallization in hot-rolled sheet annealing is suppressed by increasing recrystallization sites. In order to obtain this effect, it is necessary to carry out hot-rolled sheet annealing in the range of 750 to 1050.degree.
  • the hot-rolled sheet annealing temperature is in the range of 750 ° C. or more and 1050 ° C. or less.
  • the hot-rolled sheet annealing temperature is in the range of 750 ° C. or more and 900 ° C. or less.
  • the ferritic stainless steel sheet obtained as described above may be subjected to a descaling treatment by shot blasting or acid washing, if necessary. Furthermore, in order to improve the surface quality, grinding, polishing or the like may be performed. After that, cold rolling and cold rolled sheet annealing may be performed.
  • the metallographic structure of the ferritic stainless steel sheet obtained in the present invention is a ferrite single phase or a total of 3% or less (volume ratio) of one or both of a martensite and a retained austenite phase, and the balance is a ferrite phase.
  • the ferritic stainless steel plate of the present invention has a Charpy impact value at -50 ° C. of 100 J / cm 2 or more.
  • a Charpy impact value at -50 ° C. of 100 J / cm 2 or more.
  • the plate thickness is not particularly limited, but is preferably 5.0 mm or more, and more preferably 8.0 mm or more, because it is desirable that the plate thickness can be applied to a thick flange. Moreover, 15.0 mm or less is preferable and, as for plate
  • the molten stainless steel having the component composition shown in Table 1 was made into a 100 kg steel slab by vacuum induction melting. Subsequently, it hot-rolled on the manufacturing conditions shown in Table 2, and was set as the hot rolled sheet steel of the finish plate thickness shown in Table 2. The hot rolled steel sheet is subjected to hot rolled sheet annealing to obtain a hot rolled annealed steel sheet. In addition, hot-rolled sheet annealing was performed holding the hot-rolled sheet annealing temperature shown in Table 2 for 8 h. The following evaluation was performed about the hot-rolled annealing steel plate obtained by the above.
  • the average grain size was measured by the EBSD (Electron Back Scattering Diffraction) method. The measurement conditions were set to a step of 0.4 ⁇ m at a measurement magnification of 500 times. The obtained data was defined as a grain boundary of 15 ° or more in orientation difference by OIM (Orientation Imaging Microscopy) analysis software manufactured by TSL Solutions, Inc., and the equivalent circle diameter was calculated. The value calculated from the average value of the obtained equivalent circle diameters was taken as the average crystal grain size.
  • OIM Orientation Imaging Microscopy
  • Salt spray cycle test 1 cycle of salt spray (5 mass% NaCl, 35 ° C, spray 2hr) ⁇ drying (60 ° C, 4hr, relative humidity 40%) ⁇ wetting (50 ° C, 2hr, relative humidity) 95%) As, went 3 cycles.
  • the surface of the test piece after 3 cycles of salt spray cycle test is photographed, the rusting area of the test piece surface is measured by image analysis, and the ratio of rusting area to the area of the rusting area measurement portion Rust area / area of the rust area measurement portion) ⁇ 100 [%]) was calculated.
  • the rusted area measurement portion is a portion excluding the portion of the outer periphery 15 mm of the test piece.
  • the rusted area was the area of the rusted portion and the flow rusted portion.
  • the rusting rate of 10% or less is regarded as pass ( ⁇ ) with particularly excellent corrosion resistance, 10% to 25% or less as pass (o), and 25% or more as rejection (x).
  • the steel components, the hot rolling conditions, and the hot-rolled sheet annealing conditions satisfy the range of the present invention.
  • 1 to 32 and 46 fine metal structures having an average crystal grain size of 45 ⁇ m or less were obtained, and a predetermined Charpy impact value was obtained.
  • the rusting rate is 25% or less in any case and also has sufficient corrosion resistance.
  • the corrosion resistance was further improved with a rusting rate of 10% or less.
  • the slab heating temperature exceeds the range of the present invention. 33, and no.
  • the slab heating temperature exceeds the range of the present invention. 33, and no.
  • a predetermined amount of austenite phase is formed at the time of heating in the hot rolling process and rolling is performed at a predetermined cumulative reduction ratio, recovery of working strain occurs because the rolling temperature is excessively high and recrystallization site In the hot-rolled sheet annealing step, coarsening of recrystallized grains is likely to occur, and a predetermined Charpy impact value can not be obtained.
  • the steel sheet A1 and the steel sheet A2 are used, and the hot-rolled sheet annealing temperature exceeds the range of the present invention. 35, and no. In No. 36, as a result of the occurrence of significant coarsening of the formed recrystallized grains, a predetermined Charpy impact value was not obtained.
  • No. 40 although predetermined hot rolling and hot rolled sheet annealing were performed, as austenite phase was not sufficiently generated at the time of heating in the hot rolling process, as a result, the refining of the metal structure is sufficiently performed in the hot rolled sheet annealing process. It did not occur, and a predetermined Charpy impact value was not obtained.
  • the ferritic stainless steel sheet obtained by the present invention is particularly suitable for applications where excellent toughness is required, for example, application to flanges and the like.

Abstract

Provided are a ferritic stainless-steel sheet having superior toughness and exceptional corrosion resistance, and a method for manufacturing the ferritic stainless-steel sheet. This ferritic stainless-steel sheet has a component composition comprising 0.001-0.020% of C, 0.05-0.35% of Si, 0.05-1.00% of Mn, 0.04% or less of P, 0.01% or less of S, 0.001-0.300% of Al, 10.0-13.0% of Cr, 0.75-1.50% of Ni, 0.05-0.35% of Ti, 0.001-0.020% of N, and 65% or more of γI[%], which comprises formula (1), the balance being Fe and unavoidable impurities. The average crystal grain diameter of the metal structure is 45 μm or less. The ferritic stainless-steel sheet is manufactured by subjecting a steel slab having the component composition described above to hot-rolling and then to hot-rolled-sheet annealing at 750-1050°C. Formula (1): γI[%] = 24Ni + 12Mn + 6Cu - 18Si - 12Cr - 12Mo + 188, where the Ni, Mn, Cu, Si, Cr, and Mo in formula (1) represent the content amounts (in percent by mass) for each of these components, and are 0 when the components are not present.

Description

フェライト系ステンレス鋼板およびその製造方法Ferritic stainless steel sheet and method for manufacturing the same
　本発明は、フェライト系ステンレス鋼板およびその製造方法に関し、特にフランジ用部材の使途に有用な、靭性に優れ、かつ、耐食性に優れたフェライト系ステンレス鋼板およびその製造方法に関する。 The present invention relates to a ferritic stainless steel sheet and a method for producing the same, and more particularly to a ferritic stainless steel sheet excellent in toughness and excellent in corrosion resistance, which is useful for using a flange member, and a method for producing the same.
　自動車の排気ガス経路は、エキゾーストマニホールド、マフラー、触媒、フレキシブルチューブ、センターパイプおよびフロントパイプ等、様々な部品から構成されている。これらの部品を接続する場合、フランジと呼ばれる締結部品が使用されることが多い。このような排気系部品に適用されるフランジは十分な剛性を有する必要がある。このことから、このような排気系部品には厚肉（例えば板厚で５ｍｍ以上）のフランジが適用されている。 The exhaust gas path of a car is composed of various parts such as an exhaust manifold, a muffler, a catalyst, a flexible tube, a center pipe and a front pipe. When connecting these parts, fastening parts called flanges are often used. The flange applied to such exhaust system components needs to have sufficient rigidity. From this, a thick-walled (for example, 5 mm or more in plate thickness) flange is applied to such an exhaust system component.
　また、フランジはプレス成形の他、打ち抜き等の加工によって製造されており、普通鋼が用いられてきた。 Further, the flange is manufactured by processing such as punching other than press forming, and ordinary steel has been used.
　さらに、近年では、ＥＧＲ（Ｅｘｈａｕｓｔ　Ｇａｓ　Ｒｅｃｉｒｃｕｌａｔｉｏｎ、ＥＧＲ）システムといった高温の排気ガスに曝される部品に適用するフランジ材には十分な耐食性が求められている。そのため、普通鋼に比べて耐食性に優れるステンレス鋼、特に熱膨張率が比較的小さく熱応力が発生しにくいフェライト系ステンレス鋼の適用が検討されている。結果、厚肉のフランジに適用可能な板厚の大きい（例えば板厚で５ｍｍ以上）フェライト系ステンレス鋼板が強く求められている。 Further, in recent years, flange materials applied to parts exposed to high temperature exhaust gas such as an EGR (Exhaust Gas Recirculation, EGR) system are required to have sufficient corrosion resistance. Therefore, the application of stainless steel which is superior in corrosion resistance to ordinary steel, in particular, ferritic stainless steel which has a relatively small coefficient of thermal expansion and which hardly generates a thermal stress has been studied. As a result, a ferritic stainless steel plate having a large thickness (for example, 5 mm or more in thickness) applicable to a thick flange is strongly required.
　しかしながら、板厚の大きいフェライト系ステンレス鋼は低温靭性の課題がある。例えば、フランジ製造時のプレス割れが冬季に多く発生している。これらのことから、板厚の大きいフェライト系ステンレス鋼の靭性の改善が強く求められている。 However, a ferritic stainless steel having a large thickness has a problem of low temperature toughness. For example, many press cracks at the time of flange manufacture occur in winter. From these facts, there is a strong demand for improvement in toughness of a ferritic stainless steel having a large thickness.
　このような市場要求に対し、例えば、特許文献１には、質量％で、Ｃ：０．０２％以下、Ｎ：０．０２％以下、Ｓｉ：０．００５～１．０％、Ｎｉ：０．１～１．０％、Ｍｎ：０．１～３．０％、Ｐ：０．０４％以下、Ｓ：０．０１００％以下、Ｃｒ：１０％以上～１８％未満を含有し、さらにＴｉ：０．０５～０．３０％、Ｎｂ：０．０１～０．５０％の１種または２種を含有し、ＴｉとＮｂの合計が、８（Ｃ＋Ｎ）～０．７５％であり、残部がＦｅおよび不可避的不純物からなり、γpが７０％以上かつ、フェライト粒径が２０μｍ以下、マルテンサイト生成量が７０％以下となることを特徴とする靭性（－４０℃でのシャルピー衝撃値が５０Ｊ／ｃｍ２以上）に優れたステンレス鋼板が開示されている。
なお、γp（％）は下記（ｉ）式（特許文献１では（１）式と表記）を用いて評価する。
γp＝４２０(％Ｃ)＋４７０(％Ｎ)＋２３(％Ｎｉ)＋９(％Ｃｕ)＋７(％Ｍｎ)－１１．５(％Ｃｒ)－１１．５(％Ｓｉ)－１２(％Ｍｏ)－２３(％Ｖ)－４７(％Ｎｂ)－４９(％Ｔｉ)－５２(％Ａｌ)＋１８９　（ｉ）
なお、（％Ｘ）は、各成分Ｘの質量割合を示す。 For such market requirements, for example, in Patent Document 1, C: 0.02% or less, N: 0.02% or less, Si: 0.005 to 1.0%, Ni: 0 in mass%. 1 to 1.0%, Mn: 0.1 to 3.0%, P: 0.04% or less, S: 0.0100% or less, Cr: 10% or more to 18% or less, and further Ti : 0.05 to 0.30%, Nb: 0.01 to 0.50%, containing one or two kinds, and the total of Ti and Nb is 8 (C + N) to 0.75%, the balance Is composed of Fe and unavoidable impurities, and has a γ p of 70% or more, a ferrite grain size of 20 μm or less, and a martensite formation amount of 70% or less (a Charpy impact value at −40 ° C. A stainless steel sheet excellent in 50 J / cm 2 or more) is disclosed.
In addition, (gamma) p (%) is evaluated using following (i) Formula (In patent document 1, it describes with (1) Formula).
γ p = 420 (% C) + 470 (% N) + 23 (% Ni) + 9 (% Cu) + 7 (% Mn)-11.5 (% Cr)-11.5 (% Si)-12 (% Mo) -23 (% V)-47 (% Nb)-49 (% Ti)-52 (% Al) + 189 (i)
In addition, (% X) shows the mass ratio of each component X.
特開２０１６－１９１１５０号公報JP, 2016-191150, A
　しかし、本発明者らが特許文献１に記載されるステンレス鋼板を用いてバーリング加工部を有する厚肉のフランジ形状への加工を試みたところ、バーリング加工部に割れが生じ、所定のフランジ形状を得ることができない場合があり、厚肉のフランジに適用するには十分ではないことが明らかとなった。 However, when the present inventors tried processing to a thick flange shape having a burring portion using a stainless steel plate described in Patent Document 1, a crack occurs in the burring portion and a predetermined flange shape is formed. It has become apparent that it may not be possible to obtain and is not sufficient to apply to thick flanges.
　本発明はかかる事情に鑑み、より靭性に優れ、かつ、耐食性に優れたフェライト系ステンレス鋼板およびその製造方法を提供することを目的とする。 An object of the present invention is to provide a ferritic stainless steel sheet which is more excellent in toughness and excellent in corrosion resistance and a method of manufacturing the same.
　なお、本発明において、より靭性に優れるとは、－５０℃でのシャルピー衝撃値が１００Ｊ／ｃｍ２以上であることを意味する。また、本発明において、耐食性に優れるとは、ＪＩＳ　Ｈ　８５０２に規定された塩水噴霧サイクル試験を３サイクル実施した後の発錆率が２５％以下であることを意味する。 In the present invention, more excellent toughness means that the Charpy impact value at −50 ° C. is 100 J / cm 2 or more. Further, in the present invention, having excellent corrosion resistance means that the rusting rate after performing three cycles of the salt spray cycle test defined in JIS H 8502 is 25% or less.
　本発明者らは、上記課題を解決するために詳細な検討を行った。その結果、以下の知見を得た。 The present inventors conducted detailed studies to solve the above problems. As a result, the following findings were obtained.
　割れを発生させることなくバーリング加工部を有する厚肉のフランジへ加工するためには、金属組織を微細化し－５０℃でのシャルピー衝撃値が１００Ｊ／ｃｍ２以上であることが有効である。具体的には、金属組織の平均結晶粒径を４５μｍ以下にすることで、バーリング加工部を有する厚肉のフランジへ加工する際のバーリング加工部での割れの発生を効果的に抑制することができ、バーリング加工部を有する厚肉のフランジへ十分に実用化できる。 In order to process into a thick flange having a burring portion without causing a crack, it is effective that the metal structure is refined and the Charpy impact value at -50 ° C. is 100 J / cm 2 or more. Specifically, by setting the average grain size of the metal structure to 45 μm or less, it is possible to effectively suppress the occurrence of cracks in the burring portion when processing into a thick flange having the burring portion. It can be fully commercialized to a thick flange having a burring portion.
　そして、適切な鋼成分、具体的にはＳｉ、Ｍｎ、Ｃｒ、Ｎｉ等を適切な範囲に制御した鋼成分組成を有するスラブを、１０５０～１２５０℃で加熱した後、熱間圧延し、適切な温度で熱延板焼鈍を行うことが、金属組織を微細化し－５０℃でのシャルピー衝撃値が１００Ｊ／ｃｍ２以上を得る上で有効な手段である。 Then, after heating at a temperature of 1050 to 1250 ° C., a slab having a steel composition in which an appropriate steel composition, specifically, Si, Mn, Cr, Ni, etc., is controlled to an appropriate range is hot-rolled and appropriate. Hot-rolled sheet annealing at a temperature is an effective means for refining the metal structure and obtaining a Charpy impact value of -100 J / cm 2 or more at -50 ° C.
　本発明は以上の知見に基づいてなされたものであり、以下を要旨とするものである。
［１］質量％で、Ｃ：０．００１～０．０２０％、Ｓｉ：０．０５～０．３５％、Ｍｎ：０．０５～１．００％、Ｐ：０．０４％以下、Ｓ：０．０１％以下、Ａｌ：０．００１～０．３００％、Ｃｒ：１０．０～１３．０％、Ｎｉ：０．７５～１．５０％、Ｔｉ：０．０５～０．３５％、Ｎ：０．００１～０．０２０％を含有し、かつ、下記式（１）からなるγＩ［％］が６５％以上であり、残部がＦｅおよび不可避的不純物からなる成分組成を有し、金属組織の平均結晶粒径が４５μｍ以下である、フェライト系ステンレス鋼板。
γＩ［％］＝２４Ｎｉ＋１２Ｍｎ＋６Ｃｕ－１８Ｓｉ－１２Ｃｒ－１２Ｍｏ＋１８８　（１）
なお、式（１）中のＮｉ、Ｍｎ、Ｃｕ、Ｓｉ、ＣｒおよびＭｏは、各成分の含有量（質量％）をあらわし、含有しない成分は０とする。
［２］前記成分組成に加えて、質量％で、Ｃｕ：０．０１～１．００％、Ｍｏ：０．０１～１．００％、Ｗ：０．０１～０．２０％、Ｃｏ：０．０１～０．２０％の１種または２種以上を含有する、上記［１］に記載のフェライト系ステンレス鋼板。
［３］前記成分組成に加えて、質量％で、Ｖ：０．０１～０．２０％、Ｎｂ：０．０１～０．１０％、Ｚｒ：０．０１～０．２０％の１種または２種以上を含有する、上記［１］または［２］に記載のフェライト系ステンレス鋼板。
［４］前記成分組成に加えて、質量％で、ＲＥＭ：０．００１～０．１００％、Ｂ：０．０００２～０．００２５％、Ｍｇ：０．０００５～０．００３０％、Ｃａ：０．０００３～０．００３０％の１種または２種以上を含有する、上記［１］～［３］のいずれかに記載のフェライト系ステンレス鋼板。
［５］上記［１］～［４］のいずれかに記載のフェライト系ステンレス鋼板の製造方法であって、前記成分組成を有する鋼スラブに対して、１０５０～１２５０℃で加熱後、熱間圧延を行う熱間圧延工程と、該熱間圧延工程で得られた熱延鋼板を７５０～１０５０℃で熱延板焼鈍する熱延板焼鈍工程とを有する、フェライト系ステンレス鋼板の製造方法。 The present invention has been made based on the above findings, and the gist of the present invention is as follows.
[1] by mass%, C: 0.001 to 0.020%, Si: 0.05 to 0.35%, Mn: 0.05 to 1.00%, P: not more than 0.04%, S: 0.01% or less, Al: 0.001 to 0.300%, Cr: 10.0 to 13.0%, Ni: 0.75 to 1.50%, Ti: 0.05 to 0.35%, N: 0.001 to 0.020%, and γ I [%] of the following formula (1) is 65% or more, and the balance has a component composition consisting of Fe and unavoidable impurities, A ferritic stainless steel sheet having an average grain size of 45 μm or less in a metal structure.
γ I [%] = 24 Ni + 12 Mn + 6 Cu-18 Si-12 Cr-12 Mo + 188 (1)
In addition, Ni, Mn, Cu, Si, Cr, and Mo in Formula (1) represent content (mass%) of each component, and let the component which is not contained be zero.
[2] In addition to the above component compositions, Cu: 0.01 to 1.00%, Mo: 0.01 to 1.00%, W: 0.01 to 0.20%, Co: 0 by mass% The ferritic stainless steel sheet according to the above [1], containing one or more of 01 to 0.20%.
[3] In addition to the above component compositions, one or more of V: 0.01 to 0.20%, Nb: 0.01 to 0.10%, Zr: 0.01 to 0.20% in mass% The ferritic stainless steel sheet as described in said [1] or [2] which contains 2 or more types.
[4] In addition to the above component compositions, REM: 0.001 to 0.100%, B: 0.0002 to 0.0025%, Mg: 0.0005 to 0.0030%, Ca: 0 by mass% The ferritic stainless steel sheet according to any one of the above [1] to [3], which contains one or more of 0003 to 0.0030%.
[5] The method for producing a ferritic stainless steel sheet according to any one of the above [1] to [4], wherein the steel slab having the above-described component composition is heated at 1050 to 1250 ° C. and then hot rolled. A method for producing a ferritic stainless steel sheet, comprising: a hot rolling step of performing hot rolling; and a hot rolled sheet annealing step of hot rolled sheet annealing of the hot rolled steel sheet obtained in the hot rolling step at 750 to 1050 ° C.
　本発明によれば、より靱性に優れ、かつ、耐食性に優れたフェライト系ステンレス鋼板が得られる。本発明のフェライト系ステンレス鋼板は厚肉のフランジ等の使途に好適に用いることができる。 According to the present invention, it is possible to obtain a ferritic stainless steel sheet which is more excellent in toughness and excellent in corrosion resistance. The ferritic stainless steel sheet of the present invention can be suitably used for thick flanges and the like.
　以下、本発明について詳細に説明する。 Hereinafter, the present invention will be described in detail.
　本発明者らは、板厚５．０ｍｍの各種フェライト系ステンレス鋼板を用いて、３０ｍｍφのフランジ孔部をブランクまま（打ち抜いたまま）の鋼板表面から１０ｍｍ持ち上げるバーリング加工部を有するフランジへ成形した際に割れが発生した原因について詳細に検討した。その結果、－５０℃でのシャルピー衝撃値が１００Ｊ／ｃｍ２以上の鋼板では割れが発生せず、割れが発生した鋼板では－５０℃でのシャルピー衝撃値が１００Ｊ／ｃｍ２未満であった。このように、低靭性が割れの原因であることを知見した。 The present inventors used a variety of ferritic stainless steel plates with a thickness of 5.0 mm to form flanges having a 30 mm diameter flange hole with a burred portion that lifts 10 mm from the surface of the steel plate as it is as blank (as punched out). We examined in detail the cause of cracking in the As a result, the Charpy impact value at -50 ° C. does not occur cracks at 100 J / cm 2 or more steel sheets, Charpy impact value at -50 ° C. in a steel sheet cracks occurred were less than 100 J / cm 2. Thus, it was found that low toughness was the cause of cracking.
　さらに、本発明者らは、この低靭性と金属組織の関係を詳細に検討した。その結果、鋼板の平均結晶粒径が大きいほど靭性は低下することがわかった。そこで、種々のフェライト系ステンレス鋼板（板厚５.０ｍｍ）を用いて上述のフランジへの成形を試みた。その結果、平均結晶粒径が４５μｍを上回った鋼板で、靭性が低下し割れが生じやすいことがわかった。平均結晶粒径が４５μｍ以下であれば靭性に優れ鋼板の打ち抜き加工性は良好であった。 Furthermore, the inventors examined in detail the relationship between the low toughness and the metallographic structure. As a result, it was found that the toughness was lowered as the average grain size of the steel sheet was larger. Then, forming to the above-mentioned flange was tried using various ferritic stainless steel plates (board thickness 5.0 mm). As a result, it was found that, in a steel plate having an average crystal grain size exceeding 45 μm, the toughness is lowered and a crack is easily generated. When the average crystal grain size is 45 μm or less, the toughness is excellent and the punching workability of the steel plate is good.
　以上より、本発明において、平均結晶粒径は４５μｍ以下、－５０℃でのシャルピー衝撃値が１００Ｊ／ｃｍ２以上とする。
なお、上記平均結晶粒径は、後述する実施例の測定方法にて測定することができる。また、上記シャルピー衝撃値は、後述するようにＪＩＳ　Ｚ　２２４２（２００５）に準拠して測定した値である。 From the above, in the present invention, the average crystal grain size is 45 μm or less, and the Charpy impact value at −50 ° C. is 100 J / cm 2 or more.
In addition, the said average grain size can be measured by the measuring method of the Example mentioned later. The Charpy impact value is a value measured in accordance with JIS Z 2242 (2005) as described later.
　次に、本発明のフェライト系ステンレス鋼板の成分組成について説明する。
以下、特に断らない限り、成分の含有量の単位である「％」は「質量％」を意味する。 Next, the component composition of the ferritic stainless steel sheet of the present invention will be described.
Hereinafter, unless otherwise indicated, "%" which is a unit of content of a component means "mass%."
　Ｃ：０．００１～０．０２０％
　Ｃを０．０２０％超えて含有すると、加工性および耐食性の低下が顕著になる。Ｃ含有量が少ないほど耐食性および加工性の観点では好ましいが、Ｃ含有量を０．００１％未満にするためには精錬に時間がかかり製造上好ましくない。よって、Ｃ含有量は０．００１％以上０．０２０％以下の範囲とする。Ｃ含有量は、好ましくは０．００３％以上であり、より好ましくは０．００４％以上である。また、Ｃ含有量は、好ましくは０．０１５％以下であり、より好ましくは０．０１２％以下である。 C: 0.001 to 0.020%
When C is contained in excess of 0.020%, the decrease in formability and corrosion resistance becomes remarkable. The smaller the C content, the better in terms of corrosion resistance and processability, but in order to make the C content less than 0.001%, it takes time for refining and is not preferable in production. Therefore, the C content is in the range of 0.001% to 0.020%. The C content is preferably 0.003% or more, more preferably 0.004% or more. Further, the C content is preferably 0.015% or less, more preferably 0.012% or less.
　Ｓｉ：０．０５～０．３５％
　Ｓｉは溶接時に形成される酸化皮膜に濃縮して溶接部の耐食性を向上させる効果があるとともに、製鋼工程における脱酸元素としても有用な元素である。これらの効果は０．０５％以上のＳｉの含有により得られ、含有量が多いほどその効果は大きくなる。一方、Ｓｉはフェライト相の生成を促進する効果があり、０．３５％を超えてＳｉを含有すると、熱間圧延工程における加熱時に所定量のオーステナイト相が十分に生成しないため、本発明が規定する条件で熱間圧延および熱延板焼鈍を行っても、所望の金属組織が得られない。よって、Ｓｉ含有量は０．０５％以上０．３５％以下とする。Ｓｉ含有量は、好ましくは０．１０％以上である。また、Ｓｉ含有量は、好ましくは０．３０％以下である。 Si: 0.05 to 0.35%
Si has the effect of concentrating on the oxide film formed at the time of welding to improve the corrosion resistance of the welded portion, and is also an element useful as a deoxidizing element in the steel making process. These effects are obtained by containing Si of 0.05% or more, and the effect becomes larger as the content is larger. On the other hand, Si has the effect of promoting the formation of a ferrite phase. If Si is contained in excess of 0.35%, a predetermined amount of austenite phase is not sufficiently formed at the time of heating in the hot rolling step. The desired metallographic structure can not be obtained even if hot rolling and hot rolled sheet annealing are performed under the following conditions. Therefore, the Si content is set to 0.05% or more and 0.35% or less. The Si content is preferably 0.10% or more. Further, the Si content is preferably 0.30% or less.
　Ｍｎ：０．０５～１．００％
　Ｍｎはオーステナイト相の生成を促進する効果がある。その効果を得るためには０．０５％以上のＭｎの含有が必要である。しかし、Ｍｎ含有量が１．００％を超えると、腐食の起点となるＭｎＳの析出が促進され、耐食性が低下する。よって、Ｍｎ含有量は０．０５％以上１．００％以下とする。Ｍｎ含有量は、好ましくは０．２０％以上である。また、Ｍｎ含有量は、好ましくは０．８０％以下であり、より好ましくは０．７０％以下である。 Mn: 0.05 to 1.00%
Mn has the effect of promoting the formation of the austenite phase. In order to acquire the effect, it is necessary to contain 0.05% or more of Mn. However, if the Mn content exceeds 1.00%, precipitation of MnS, which is a starting point of corrosion, is promoted, and the corrosion resistance is lowered. Therefore, the Mn content is set to 0.05% or more and 1.00% or less. The Mn content is preferably 0.20% or more. Also, the Mn content is preferably 0.80% or less, more preferably 0.70% or less.
　Ｐ：０．０４％以下
　Ｐは鋼に不可避的に含まれる元素であり、耐食性および加工性に対して有害な元素であるので可能な限り低減することが好ましい。Ｐ含有量が０．０４％を超えると固溶強化により加工性が顕著に低下する。よって、Ｐ含有量は０．０４％以下とする。Ｐ含有量は、好ましくは０．０３％以下である。 P: 0.04% or less P is an element inevitably contained in steel and is an element harmful to corrosion resistance and workability, and therefore it is preferable to reduce as much as possible. If the P content exceeds 0.04%, the formability is markedly reduced due to solid solution strengthening. Therefore, the P content is 0.04% or less. The P content is preferably 0.03% or less.
　Ｓ：０．０１％以下
　ＳもＰと同様に鋼に不可避的に含まれる元素であり、耐食性および加工性に対して有害な元素であるので可能な限り低減するのが好ましい。特に、Ｓ含有量が０．０１％を超えると耐食性が顕著に低下する。よって、Ｓ含有量は０．０１％以下とする。Ｓ含有量は、好ましくは０．００８％以下であり、より好ましくは０．００３％以下である。 S: 0.01% or less S is also an element inevitably contained in steel like P, and is an element harmful to corrosion resistance and workability, and therefore, it is preferable to reduce as much as possible. In particular, when the S content exceeds 0.01%, the corrosion resistance is significantly reduced. Therefore, the S content is 0.01% or less. The S content is preferably 0.008% or less, more preferably 0.003% or less.
　Ａｌ：０．００１～０．３００％
　Ａｌは有効な脱酸剤である。さらに、Ａｌは窒素との親和力がＣｒよりも強いため、溶接部に窒素が侵入した場合に、窒素をＣｒ窒化物ではなくＡｌ窒化物として析出させて、鋭敏化を抑制する効果がある。これらの効果は、Ａｌを０．００１％以上含有することで得られる。しかし、０．３００％を超えるＡｌを含有すると、溶接時の溶け込み性が低下して溶接性が低下するので好ましくない。よって、Ａｌ含有量は０．００１％以上０．３００％以下の範囲とする。Ａｌ含有量は、好ましくは０．０１０％以上である。また、Ａｌ含有量は、好ましくは０．２００％以下であり、より好ましくは０．１００％以下であり、さらに好ましくは０．０５０％以下である。 Al: 0.001 to 0.300%
Al is an effective deacidifying agent. Furthermore, since Al has a stronger affinity to nitrogen than Cr, when nitrogen penetrates the weld, it has the effect of precipitating nitrogen as Al nitride instead of Cr nitride to suppress sensitization. These effects are obtained by containing Al 0.001% or more. However, if the Al content exceeds 0.300%, it is not preferable because the penetration during welding decreases and the weldability decreases. Therefore, the Al content is in the range of 0.001% to 0.300%. The Al content is preferably 0.010% or more. Further, the Al content is preferably 0.200% or less, more preferably 0.100% or less, and still more preferably 0.050% or less.
　Ｃｒ：１０．０～１３．０％
　Ｃｒは耐食性を確保するために最も重要な元素である。その含有量が１０．０％未満では、自動車排気部品に必要な耐食性が得られない。一方、１３．０％を超えてＣｒを含有すると、鋼成分を後述する所定の式（１）で示されるγＩに調整しても、熱間圧延工程における加熱時に所定量のオーステナイト相が生成しないために、本発明が規定する条件で熱間圧延および熱延板焼鈍を行っても、所望の金属組織が得られない。よって、Ｃｒ含有量は１０．０％以上１３．０％以下の範囲とする。Ｃｒ含有量は、好ましくは１０．５％以上である。また、Ｃｒ含有量は、好ましくは１２．０％以下であり、より好ましくは１１．７％以下である。 Cr: 10.0 to 13.0%
Cr is the most important element to ensure corrosion resistance. If the content is less than 10.0%, corrosion resistance necessary for automobile exhaust parts can not be obtained. On the other hand, when Cr is contained in excess of 13.0%, a predetermined amount of austenite phase is formed at the time of heating in the hot rolling process even if the steel component is adjusted to γ I represented by predetermined formula (1) described later In order to avoid this, even if hot rolling and hot rolled sheet annealing are performed under the conditions specified by the present invention, the desired metallographic structure can not be obtained. Therefore, the Cr content is in the range of 10.0% to 13.0%. The Cr content is preferably 10.5% or more. Further, the Cr content is preferably 12.0% or less, more preferably 11.7% or less.
　Ｎｉ：０．７５～１．５０％
　Ｎｉはオーステナイト生成元素であり、熱間圧延工程における圧延加工前の加熱時に生成するオーステナイト量を増加させる効果がある。本発明においては、鋼成分を調整することによって、熱間圧延工程におけるスラブ加熱時に体積率で７０％以上のオーステナイト相を含むフェライト相＋オーステナイト相の二相組織となる。金属組織がフェライト相＋オーステナイト相の二相組織となる場合、フェライト相とオーステナイト相との異相界面が結晶粒成長の障害として機能するため、熱間圧延加工前の金属組織が微細化する。その上で、所定の熱間圧延により再結晶サイトとなる加工ひずみを蓄積させ、次工程の熱延板焼鈍により再結晶を生じさせることにより微細な金属組織が得られ、優れた靭性が発現する。これらの効果は、Ｎｉを０．７５％以上含有することで得られる。一方、Ｎｉ含有量が１．５０％を超えると、結晶粒の微細化による改善効果が飽和するとともに加工性が低下する。さらには、応力腐食割れが発生しやすくなる。よって、Ｎｉ含有量は０．７５％以上１．５０％以下とする。Ｎｉ含有量は、好ましくは０．８０％以上である。また、Ｎｉ含有量は、好ましくは１．２０％以下であり、より好ましくは１．００％以下である。 Ni: 0.75 to 1.50%
Ni is an austenite-forming element, and has an effect of increasing the amount of austenite generated at the time of heating before rolling in the hot rolling process. In the present invention, by adjusting the steel composition, a two-phase structure of a ferrite phase and an austenite phase including an austenite phase of 70% or more in volume ratio is obtained at the time of slab heating in the hot rolling process. When the metallographic structure is a two-phase structure of a ferrite phase and an austenite phase, the heterophase interface between the ferrite phase and the austenite phase functions as an obstacle to grain growth, so that the metal structure before hot rolling is refined. On top of that, processing strain to become a recrystallization site is accumulated by predetermined hot rolling, and recrystallization is caused by the next hot-rolled sheet annealing to obtain a fine metal structure, and excellent toughness is developed. . These effects are obtained by containing Ni 0.75% or more. On the other hand, when the Ni content exceeds 1.50%, the improvement effect due to the refinement of crystal grains saturates and the processability decreases. Furthermore, stress corrosion cracking is likely to occur. Therefore, the Ni content is set to 0.75% or more and 1.50% or less. The Ni content is preferably 0.80% or more. Further, the Ni content is preferably 1.20% or less, more preferably 1.00% or less.
　Ｔｉ：０．０５～０．３５％
　ＴｉはＣ、Ｎと優先的に結合して、Ｃｒ炭窒化物の析出を抑制し、再結晶温度を低下させるとともにＣｒ炭窒化物の析出による鋭敏化に起因した耐食性の低下を抑制する効果がある。このような効果を得るためには０．０５％以上のＴｉの含有が必要である。一方、Ｔｉ含有量が０．３５％を超えると粗大なＴｉＮの生成に起因した著しい靭性の低下が生じ、本発明の技術を適用しても所定の靭性が得られない。また、０．３５％超のＴｉの含有は、鋳造工程において粗大なＴｉ炭窒化物が生成し、表面欠陥を引き起こすため製造上好ましくない。よって、Ｔｉ含有量は０．０５％以上０．３５％以下とする。Ｔｉ含有量は、好ましくは０．１０％以上である。また、Ｔｉ含有量は、好ましくは０．３０％以下であり、より好ましくは０．１５％以下である。 Ti: 0.05 to 0.35%
Ti preferentially combines with C and N to suppress the precipitation of Cr carbonitrides, and has the effect of reducing the recrystallization temperature and suppressing the drop in corrosion resistance caused by the sensitization due to the precipitation of Cr carbonitrides. is there. In order to obtain such an effect, it is necessary to contain 0.05% or more of Ti. On the other hand, if the Ti content exceeds 0.35%, the toughness is significantly reduced due to the formation of coarse TiN, and even if the technology of the present invention is applied, a predetermined toughness can not be obtained. Further, the content of Ti of more than 0.35% is not preferable in production because coarse Ti carbo-nitrides are formed in the casting process to cause surface defects. Therefore, the Ti content is set to 0.05% or more and 0.35% or less. The Ti content is preferably 0.10% or more. Further, the Ti content is preferably 0.30% or less, more preferably 0.15% or less.
　Ｎ：０．００１～０．０２０％
　Ｎ含有量が０．０２０％を超えると、加工性および耐食性の低下が顕著になる。加工性および耐食性の観点からＮ含有量は低いほど好ましいが、Ｎ含有量を０．００１％未満にまで低減するには長時間の精錬が必要となり、製造コストの上昇および生産性の低下を招くため好ましくない。よって、Ｎ含有量は０．００１％以上０．０２０％以下の範囲とする。Ｎ含有量は、好ましくは０．００５％以上であり、より好ましくは０．００７％以上である。また、Ｎ含有量は、好ましくは０．０１５％以下であり、より好ましくは０．０１２％以下である。 N: 0.001 to 0.020%
When the N content exceeds 0.020%, the deterioration of formability and corrosion resistance becomes remarkable. From the viewpoint of processability and corrosion resistance, the lower the N content, the better. However, in order to reduce the N content to less than 0.001%, long-time refining is required, resulting in an increase in manufacturing costs and a decrease in productivity. Unfavorable. Therefore, the N content is in the range of 0.001% to 0.020%. The N content is preferably 0.005% or more, more preferably 0.007% or more. Further, the N content is preferably 0.015% or less, more preferably 0.012% or less.
　γＩ［％］：６５％以上
　下記式（１）で示されるγＩが６５％を下回ると熱間圧延開始前のスラブ加熱温度において、金属組織はオーステナイト量が不十分なため、微細な金属組織が得られない。よって、γＩ［％］は６５％以上とする。なお、γＩ［％］はオーステナイト相の安定度を評価する下記式（１）を用いて求める。
γＩ［％］＝２４Ｎｉ＋１２Ｍｎ＋６Ｃｕ－１８Ｓｉ－１２Ｃｒ－１２Ｍｏ＋１８８　（１）
なお、式（１）中のＮｉ、Ｍｎ、Ｃｕ、Ｓｉ、ＣｒおよびＭｏは、各成分の含有量（質量％）をあらわし、含有しない成分は０とする。
上記式（１）において、オーステナイト生成元素は正の係数、フェライト生成元素は負の係数を持ち、それぞれの値はＣａｓｔｒｏの式を参考にして実験的に求めた。 γ I [%]: 65% or more When γ I shown by the following formula (1) is less than 65%, the metal structure is insufficient in austenite content at the slab heating temperature before the start of hot rolling, so a fine metal I can not get an organization. Therefore, γ I [%] is 65% or more. Here, γ I [%] is determined using the following equation (1) for evaluating the stability of the austenite phase.
γ I [%] = 24 Ni + 12 Mn + 6 Cu-18 Si-12 Cr-12 Mo + 188 (1)
In addition, Ni, Mn, Cu, Si, Cr, and Mo in Formula (1) represent content (mass%) of each component, and let the component which is not contained be zero.
In the above equation (1), the austenite-forming element has a positive coefficient, and the ferrite-forming element has a negative coefficient, and the respective values were experimentally obtained with reference to the Castro equation.
　本発明において、上記以外の残部は、Ｆｅおよび不可避的不純物である。不可避的不純物としては、Ｏ（酸素）等が挙げられ、Ｏの含有量は０．０１％以下であれば許容できる。 In the present invention, the remainder other than the above is Fe and unavoidable impurities. As an unavoidable impurity, O (oxygen) etc. are mentioned, and if content of O is 0.01% or less, it is permissible.
　上記必須成分に加えて、さらに、必要に応じて、下記Ａ群～Ｃ群から選ばれる１群または２群以上を含有することができる。
（Ａ群）Ｃｕ：０．０１～１．００％、Ｍｏ：０．０１～１．００％、Ｗ：０．０１～０．２０％、Ｃｏ：０．０１～０．２０％の１種または２種以上
（Ｂ群）Ｖ：０．０１～０．２０％、Ｎｂ：０．０１～０．１０％、Ｚｒ：０．０１～０．２０％の１種または２種以上
（Ｃ群）ＲＥＭ：０．００１～０．１００％、Ｂ：０．０００２～０．００２５％、Ｍｇ：０．０００５～０．００３０％、Ｃａ：０．０００３～０．００３０％の１種または２種以上 In addition to the above-mentioned essential components, if necessary, one or more groups selected from the following groups A to C can be contained.
(Group A) Cu: 0.01 to 1.00%, Mo: 0.01 to 1.00%, W: 0.01 to 0.20%, Co: 0.01 to 0.20% Or two or more (group B) V: 0.01 to 0.20%, Nb: 0.01 to 0.10%, and Zr: 0.01 to 0.20% one or more (group C) ) REM: 0.001 to 0.100%, B: 0.0002 to 0.0025%, Mg: 0.0005 to 0.0030%, Ca: 0.0003 to 0.0030% One or two of them that's all
　Ｃｕ：０．０１～１．００％
　Ｃｕは水溶液中や弱酸性の水滴が付着した場合の耐食性を向上させるのに特に有効な元素である。さらに、Ｃｕはオーステナイト相の生成を促進する効果がある。この効果は０．０１％以上の含有により得られ、その効果はＣｕ含有量が多いほど高くなる。しかし、１．００％を超えてＣｕを含有すると、熱間加工性が低下して表面欠陥を誘引する場合がある。さらには焼鈍後の脱スケールが困難となる場合もある。そのため、Ｃｕを含有する場合は、Ｃｕ含有量は０．０１％以上１．００％以下の範囲とする。Ｃｕを含有する場合、Ｃｕ含有量は、好ましくは０．１０％以上である。また、Ｃｕを含有する場合、Ｃｕ含有量は、好ましくは０．５０％以下である。 Cu: 0.01 to 1.00%
Cu is an element that is particularly effective in improving the corrosion resistance in an aqueous solution or when a weakly acidic water droplet is attached. Furthermore, Cu has the effect of promoting the formation of the austenite phase. This effect is obtained by containing 0.01% or more, and the effect becomes higher as the Cu content is larger. However, if Cu is contained in excess of 1.00%, the hot workability may be reduced to induce surface defects. Furthermore, there are cases where descaling after annealing becomes difficult. Therefore, when it contains Cu, Cu content is made into the range of 0.01% or more and 1.00% or less. When Cu is contained, the Cu content is preferably 0.10% or more. When Cu is contained, the Cu content is preferably 0.50% or less.
　Ｍｏ：０．０１～１．００％
　Ｍｏはステンレス鋼の耐食性を顕著に向上させる元素である。この効果は０．０１％以上のＭｏの含有によって得られ、その効果は含有量が多いほど向上する。一方、Ｍｏはフェライト相の生成を促進する効果があり、Ｍｏ含有量が１．００％を超えると、熱間圧延工程における加熱時に所定量のオーステナイト相が十分に生成しないため、本発明が規定する条件で熱間圧延および熱延板焼鈍を行っても、所望の金属組織が得られない。よって、Ｍｏを含有する場合は、Ｍｏ含有量は０．０１％以上１．００％以下とする。Ｍｏを含有する場合、Ｍｏ含有量は、好ましくは０．１０％以上であり、より好ましくは０．３０％以上である。また、Ｍｏを含有する場合、Ｍｏ含有量は、好ましくは０．８０％以下であり、より好ましくは０．５０％以下である。 Mo: 0.01 to 1.00%
Mo is an element that significantly improves the corrosion resistance of stainless steel. This effect is obtained by containing 0.01% or more of Mo, and the effect improves as the content increases. On the other hand, Mo has the effect of promoting the formation of a ferrite phase, and when the Mo content exceeds 1.00%, a predetermined amount of austenite phase is not sufficiently formed at the time of heating in the hot rolling process. The desired metallographic structure can not be obtained even if hot rolling and hot rolled sheet annealing are performed under the following conditions. Therefore, when it contains Mo, Mo content is made into 0.01% or more and 1.00% or less. When Mo is contained, the Mo content is preferably 0.10% or more, more preferably 0.30% or more. Moreover, when it contains Mo, Mo content is preferably 0.80% or less, more preferably 0.50% or less.
　Ｗ：０．０１～０．２０％
　ＷはＭｏと同様に耐食性を向上させる効果がある。この効果は０．０１％以上のＷの含有により得られる。一方、０．２０％を超えてＷを含有すると強度が上昇し、圧延荷重の増大等による製造性の低下を招く場合がある。そのため、Ｗを含有する場合は、Ｗ含有量は０．０１％以上０．２０％以下の範囲とする。Ｗを含有する場合、Ｗ含有量は、好ましくは０．０５％以上である。また、Ｗを含有する場合、Ｗ含有量は、好ましくは０．１５％以下である。 W: 0.01 to 0.20%
Like Mo, W has the effect of improving the corrosion resistance. This effect is obtained by containing 0.01% or more of W. On the other hand, if W is contained in excess of 0.20%, the strength may increase, which may lead to a decrease in manufacturability due to an increase in rolling load or the like. Therefore, when W is contained, the W content is in the range of 0.01% or more and 0.20% or less. When W is contained, the W content is preferably 0.05% or more. When W is contained, the W content is preferably 0.15% or less.
　Ｃｏ：０．０１～０．２０％
　Ｃｏは靭性を向上させる元素である。この効果は０．０１％以上のＣｏの含有によって得られる。一方、Ｃｏ含有量が０．２０％を超えると加工性が低下する場合がある。よって、Ｃｏを含有する場合は、Ｃｏ含有量は０．０１％以上０．２０％以下の範囲とする。 Co: 0.01 to 0.20%
Co is an element that improves the toughness. This effect is obtained by containing 0.01% or more of Co. On the other hand, when the Co content exceeds 0.20%, the processability may be reduced. Therefore, when Co is contained, the Co content is in the range of 0.01% to 0.20%.
　Ｖ：０．０１～０．２０％
　ＶはＣ、Ｎと炭窒化物を形成し、溶接時の鋭敏化を抑制して溶接部の耐食性を向上させる。この効果はＶ含有量が０．０１％以上で得られる。一方、Ｖ含有量が０．２０％を超えると加工性および靭性が顕著に低下する場合がある。よって、Ｖを含有する場合は、Ｖ含有量は０．０１％以上０．２０％以下とする。Ｖを含有する場合、Ｖ含有量は、好ましくは０．０２％以上である。また、Ｖを含有する場合、Ｖ含有量は、好ましくは０．１０％以下である。 V: 0.01 to 0.20%
V forms carbonitrides with C and N, suppresses sensitization during welding, and improves the corrosion resistance of the welded portion. This effect is obtained when the V content is 0.01% or more. On the other hand, when the V content exceeds 0.20%, the processability and the toughness may be significantly reduced. Therefore, when V is contained, V content is made into 0.01% or more and 0.20% or less. When V is contained, the V content is preferably 0.02% or more. Moreover, when V is contained, V content is preferably 0.10% or less.
　Ｎｂ：０．０１～０．１０％
　Ｎｂは結晶粒を微細化させる効果がある。この効果は０．０１％以上のＮｂの含有で得られる。一方、Ｎｂは再結晶温度を上昇させる効果もあり、Ｎｂ含有量が０．１０％を超えると熱延板焼鈍にて十分な再結晶を生じさせるために必要な焼鈍温度が過度に高温となって、平均結晶粒径が４５μｍ以下の金属組織を得ることができない場合がある。よって、Ｎｂを含有する場合には、Ｎｂ含有量は０．０１％以上０．１０％以下の範囲とする。Ｎｂを含有する場合、Ｎｂ含有量は、好ましくは０．０５％以下である。 Nb: 0.01 to 0.10%
Nb has the effect of refining the crystal grains. This effect is obtained by containing 0.01% or more of Nb. On the other hand, Nb also has the effect of raising the recrystallization temperature, and if the Nb content exceeds 0.10%, the annealing temperature required to cause sufficient recrystallization in hot-rolled sheet annealing becomes excessively high. In some cases, it is not possible to obtain a metal structure having an average crystal grain size of 45 μm or less. Therefore, when Nb is contained, the Nb content is in the range of 0.01% or more and 0.10% or less. When Nb is contained, the Nb content is preferably 0.05% or less.
　Ｚｒ：０．０１～０．２０％
　ＺｒはＣ、Ｎと結合して鋭敏化を抑制する効果がある。この効果は０．０１％以上のＺｒの含有により得られる。一方、０．２０％を超えてＺｒを含有すると加工性が顕著に低下する場合がある。よって、Ｚｒを含有する場合、Ｚｒ含有量は０．０１％以上０．２０％以下の範囲とする。Ｚｒを含有する場合、Ｚｒ含有量は、好ましくは０．１０％以下である。 Zr: 0.01 to 0.20%
Zr combines with C and N and has an effect of suppressing sensitization. This effect is obtained by containing 0.01% or more of Zr. On the other hand, if the content of Zr exceeds 0.20%, the workability may be significantly reduced. Therefore, when Zr is contained, the Zr content is in the range of 0.01% to 0.20%. When containing Zr, the Zr content is preferably 0.10% or less.
　ＲＥＭ：０．００１～０．１００％
　ＲＥＭ（Ｒａｒｅ　Ｅａｒｔｈ　Ｍｅｔａｌｓ：希土類金属）は耐酸化性を向上させる効果があり、溶接部の酸化皮膜（溶接テンパーカラー）形成を抑制して酸化皮膜直下におけるＣｒ欠乏領域の形成を抑制する。この効果は、ＲＥＭを０．００１％以上含有することで得られる。一方、０．１００％を超えてＲＥＭを含有すると冷延焼鈍時の酸洗性などの製造性を低下させる場合がある。そのため、ＲＥＭを含有する場合、ＲＥＭ含有量は０．００１％以上０．１００％以下の範囲とする。ＲＥＭを含有する場合、ＲＥＭ含有量は、好ましくは０．０５０％以下である。 REM: 0.001 to 0.100%
REM (Rare Earth Metals: rare earth metal) has the effect of improving the oxidation resistance, and suppresses the formation of an oxide film (welded temper collar) at the weld to suppress the formation of a Cr-deficient region immediately below the oxide film. This effect is obtained by containing 0.001% or more of REM. On the other hand, if the content of REM is more than 0.100%, the productivity such as acid washability at the time of cold rolling annealing may be reduced. Therefore, when REM is contained, the REM content is in the range of 0.001% to 0.100%. When REM is contained, the REM content is preferably 0.050% or less.
　Ｂ：０．０００２～０．００２５％
　Ｂは深絞り成形後の耐二次加工脆性を改善するために有効な元素である。この効果はＢの含有量を０．０００２％以上にすることで得られる。一方、０．００２５％を超えてＢを含有すると加工性と靭性が低下する場合がある。よって、Ｂを含有する場合、Ｂ含有量は０．０００２％以上０．００２５％以下の範囲とする。Ｂを含有する場合、Ｂ含有量は、好ましくは０．０００３％以上である。また、Ｂを含有する場合、Ｂ含有量は、好ましくは０．００１２％以下である。 B: 0.0002 to 0.0025%
B is an element effective to improve the secondary processing brittleness after deep drawing. This effect is obtained by setting the B content to 0.0002% or more. On the other hand, if B is contained in excess of 0.0025%, processability and toughness may be reduced. Therefore, when it contains B, B content is taken as the range of 0.0002% or more and 0.0025% or less. When B is contained, the B content is preferably 0.0003% or more. When B is contained, the B content is preferably 0.0012% or less.
　Ｍｇ：０．０００５～０．００３０％
　本発明のようにＴｉを含有する鋼においては、Ｔｉ炭窒化物が粗大化すると靭性が低下する場合がある。この点について、ＭｇはＴｉ炭窒化物の粗大化を抑制する効果を有する。この効果は、０．０００５％以上のＭｇを含有することで得られる。一方で、Ｍｇ含有量が０．００３０％を超えると、鋼の表面性状を悪化させてしまう場合がある。よって、Ｍｇを含有する場合、Ｍｇ含有量は０．０００５～０．００３０％の範囲とする。Ｍｇを含有する場合、Ｍｇ含有量は、好ましくは０．００１０％以上である。また、Ｍｇを含有する場合、Ｍｇ含有量は、好ましくは０．００２０％以下である。 Mg: 0.0005 to 0.0030%
In a steel containing Ti as in the present invention, when the Ti carbo-nitride is coarsened, the toughness may decrease. In this regard, Mg has the effect of suppressing the coarsening of Ti carbo-nitrides. This effect is obtained by containing 0.0005% or more of Mg. On the other hand, if the Mg content exceeds 0.0030%, the surface properties of the steel may be deteriorated. Therefore, when Mg is contained, the Mg content is in the range of 0.0005 to 0.0030%. When Mg is contained, the Mg content is preferably 0.0010% or more. When Mg is contained, the Mg content is preferably 0.0020% or less.
　Ｃａ：０．０００３～０．００３０％
　Ｃａは、連続鋳造の際に発生しやすいＴｉ系介在物の晶出によるノズルの閉塞を防止するのに有効な成分である。その効果は０．０００３％以上のＣａを含有することで得られる。一方、０．００３０％を超えてＣａを含有すると、ＣａＳの生成により耐食性が低下する場合がある。よって、Ｃａを含有する場合、Ｃａ含有量は０．０００３％以上０．００３０％以下の範囲とする。Ｃａを含有する場合、Ｃａ含有量は、好ましくは０．０００５％以上である。また、Ｃａを含有する場合、Ｃａ含有量は、好ましくは０．００１５％以下であり、より好ましくは０．００１０％以下である。 Ca: 0.0003 to 0.0030%
Ca is an effective component to prevent the clogging of the nozzle due to the crystallization of Ti-based inclusions that are easily generated during continuous casting. The effect is obtained by containing 0.0003% or more of Ca. On the other hand, if the Ca content is more than 0.0030%, the corrosion resistance may be reduced due to the formation of CaS. Therefore, when it contains Ca, Ca content is made into the range of 0.0003% or more and 0.0030% or less. When Ca is contained, the Ca content is preferably 0.0005% or more. When Ca is contained, the Ca content is preferably 0.0015% or less, more preferably 0.0010% or less.
　次に本発明のフェライト系ステンレス鋼板の製造方法について説明する。
本発明者らは、フェライト系ステンレス鋼板において靭性を向上させる手法について鋭意検討結果、適切な鋼成分を有する鋼スラブを好ましくは１０５０～１２５０℃で加熱した後、好ましくは３パス以上で熱間圧延し、得られた熱延鋼板に対して、７５０～１０５０℃で熱延板焼鈍を行うことにより、平均結晶粒径が４５μｍ以下の金属組織が得られ、－５０℃でのシャルピー衝撃値が１００Ｊ／ｃｍ２以上と靭性が大幅に向上することを知見した。さらに、所望の耐食性も得られることを知見した。 Next, a method of manufacturing the ferritic stainless steel plate of the present invention will be described.
The present inventors have intensively studied the method of improving the toughness in a ferritic stainless steel sheet, and preferably heat a steel slab having an appropriate steel component at preferably 1050 to 1250 ° C. and then preferably hot roll it in three or more passes. By subjecting the obtained hot rolled steel sheet to hot rolled sheet annealing at 750 to 1050 ° C., a metal structure having an average crystal grain size of 45 μm or less is obtained, and the Charpy impact value at 50 ° C. is 100 J It was found that the toughness was significantly improved to be at least 2 cm 2 . Furthermore, it has been found that the desired corrosion resistance can also be obtained.
　上記により微細な金属組織を有する熱延焼鈍鋼板が得られる理由について以下に説明する。
フェライト系ステンレス鋼は熱間圧延において動的再結晶がほとんど生じず、圧延による加工ひずみの回復が生じやすい傾向がある。そのため、従来技術による熱間圧延では圧延によって導入された加工ひずみの過度な回復が生じて加工ひずみを熱間圧延後まで効果的に維持することができない。その結果、再結晶サイトが不十分となり次工程の熱延板焼鈍において微細な再結晶組織を得ることができない。 The reason why the hot-rolled annealed steel sheet having a fine metal structure is obtained as described above will be described below.
Ferritic stainless steels hardly undergo dynamic recrystallization in hot rolling, and tend to recover from working strain due to rolling. Therefore, in the hot rolling according to the prior art, excessive recovery of the working strain introduced by the rolling occurs, and the working strain can not be effectively maintained until after the hot rolling. As a result, the recrystallization site is insufficient and a fine recrystallized structure can not be obtained in the hot-rolled sheet annealing of the next step.
　そこで本発明者らは、熱延板焼鈍後に微細な組織を得るために有効な手法について、鋼成分および熱間圧延手法の両面から鋭意検討した。その結果、鋼成分、特にＳｉ、Ｍｎ、ＣｒとＮｉの含有量を適切な範囲に制御し、熱間圧延工程において適切な温度でスラブ加熱を行いオーステナイト相を含有したフェライト相＋オーステナイト相の二相組織にして熱間圧延を行うことが有効であることを知見した。 Therefore, the present inventors diligently studied, from both the steel component and the hot rolling method, an effective method for obtaining a fine structure after hot-rolled sheet annealing. As a result, the content of steel components, in particular Si, Mn, Cr and Ni, is controlled within an appropriate range, slab heating is performed at an appropriate temperature in the hot rolling process, and austenite phase containing ferrite phase + austenite phase It turned out that it is effective to form a phase structure and perform hot rolling.
　金属組織がフェライト相＋オーステナイト相の二相組織となった場合、加熱前に存在するフェライト相と加熱時に生成したオーステナイト相との異相界面が結晶粒の粗大化を抑制するため、熱間圧延前の段階で微細な等軸組織が得られる。その上で、所定の熱間圧延を行うことにより次工程の熱延板焼鈍において再結晶サイトとなる加工ひずみを十分に蓄積させ、次工程の熱延板焼鈍により微細な金属組織が得られ優れた靭性が発現することができる。 When the metallographic structure becomes a two-phase structure of a ferrite phase and an austenite phase, the heterophase interface between the ferrite phase existing before heating and the austenite phase generated at the time of heating suppresses coarsening of crystal grains, so before hot rolling A fine equiaxed structure is obtained at the stage of. Then, by performing predetermined hot rolling, processing strain to be a recrystallization site is sufficiently accumulated in the hot-rolled sheet annealing in the next step, and a fine metal structure is obtained by the hot-rolled sheet annealing in the next step. Toughness can be expressed.
　具体的には、熱間圧延前の加熱時に体積率で６５％以上のオーステナイト相が生成するように、オーステナイト生成元素のＮｉ、Ｍｎの含有量とＮｉ、Ｍｎのそれぞれに正の係数、フェライト生成元素のＳｉ、Ｃｒの含有量とＳｉ、Ｃｒのそれぞれに負の係数を組み合わせた前述した式（１）が成立するように調整した鋼について、１０５０～１２５０℃でスラブ加熱した後、熱間圧延を行うことを考案した。 Specifically, the austenite-forming elements Ni and Mn and the positive coefficients of Ni and Mn and ferrite formation so that an austenite phase of 65% or more by volume ratio is generated at the time of heating before hot rolling Hot-rolled steel after slab heating at 1050 to 1250 ° C is adjusted for the steels adjusted so that the above-mentioned equation (1) combining the content of elements Si and Cr and negative coefficients to each of Si and Cr holds Was devised to do.
　また、本発明者らは、次工程の熱延板焼鈍の好適な条件についても鋭意検討した。熱延板焼鈍は熱間圧延によって形成された加工組織を再結晶させる工程である。そのため、十分な再結晶が生じる温度で焼鈍を行う必要がある。しかし、過度な高温で熱延板焼鈍を行った場合、再結晶は生じるものの再結晶粒の著しい粗大化が生じるため、所定の微細な組織が得られなくなる。 In addition, the present inventors diligently studied about suitable conditions for hot-rolled sheet annealing in the next step. Hot-rolled sheet annealing is a process of recrystallizing the worked structure formed by hot rolling. Therefore, it is necessary to carry out annealing at a temperature at which sufficient recrystallization occurs. However, when hot-rolled sheet annealing is performed at an excessively high temperature, although recrystallization occurs, significant coarsening of recrystallized grains occurs, and a predetermined fine structure can not be obtained.
　そこで、本発明者らは、再結晶粒の粒径と焼鈍温度の関係について詳細に調査した。その結果、熱延板焼鈍温度を１０５０℃以下に抑えることによって、靭性が低下するほどの粗大な再結晶粒の生成を抑制できることを見出した。 Therefore, the inventors investigated in detail the relationship between the grain size of recrystallized grains and the annealing temperature. As a result, it has been found that by suppressing the hot-rolled sheet annealing temperature to 1050 ° C. or less, it is possible to suppress the formation of coarse recrystallized grains that the toughness is reduced.
　以下、各製造条件について詳細に説明する。 Each manufacturing condition will be described in detail below.
　まずは、上記した成分組成からなる溶鋼を、転炉、電気炉、真空溶解炉等の公知の方法で溶製し、連続鋳造法あるいは造塊－分塊法により鋼素材（スラブ）とする。 First, molten steel having the above-described component composition is melted by a known method such as a converter, an electric furnace, a vacuum melting furnace or the like, and made into a steel material (slab) by a continuous casting method or an ingot-bunch method.
　鋼スラブの加熱温度：１０５０～１２５０℃
　鋼スラブを、１０５０～１２５０℃で加熱し、熱間圧延に供する。前記加熱温度での加熱時間は、特に限定されないが、好ましくは１～２４時間加熱する。加熱温度が１０５０℃未満では、オーステナイト相の生成割合が低くなって微細な金属組織が得られなくなり、優れた靭性が得られない。一方、加熱温度があまりに高くなると酸化質量の増加に伴うスケールロスの増大につながるため、鋼スラブの加熱温度は１２５０℃以下とする。但し、鋼スラブに熱間圧延を施すに際し、鋳造後の鋼スラブが１０５０℃以上の温度域にある場合には、鋼素材を加熱することなく直送圧延してもよい。 Heating temperature of steel slab: 1050 to 1250 ° C
The steel slab is heated at 1050 to 1250 ° C. and subjected to hot rolling. The heating time at the heating temperature is not particularly limited, but heating is preferably performed for 1 to 24 hours. When the heating temperature is less than 1050 ° C., the formation ratio of the austenite phase becomes low, and a fine metal structure can not be obtained, so that excellent toughness can not be obtained. On the other hand, if the heating temperature becomes too high, it will lead to an increase in scale loss accompanying an increase in the oxidation mass, so the heating temperature of the steel slab is made 1250 ° C. or less. However, when the steel slab is subjected to hot rolling, if the steel slab after casting is in a temperature range of 1050 ° C. or more, direct feed rolling may be performed without heating the steel material.
　粗圧延条件については特に限定されない。仕上熱間圧延前に鋳造組織を効果的に破壊しておいた場合、その後のスラブ加熱における微細化効果が一層促進されるため、粗圧延における累積圧下率を６５％以上とすることが好ましい。その後、仕上熱間圧延により所定板厚まで圧延する。 The rough rolling conditions are not particularly limited. If the cast structure has been effectively broken before the finish hot rolling, it is preferable to set the cumulative rolling reduction in rough rolling to 65% or more, since the refining effect in the subsequent slab heating is further promoted. Thereafter, it is rolled to a predetermined thickness by finish hot rolling.
　熱延板焼鈍温度：７５０～１０５０℃
　本発明では上記熱間圧延終了後に熱延板焼鈍を行う。熱延板焼鈍において、熱間圧延工程で形成させた圧延加工組織を再結晶させる。本発明では熱間圧延工程において効果的に圧延ひずみを付与し、再結晶サイトを増加させることによって熱延板焼鈍における再結晶の粗大化を抑制する。この効果を得るためには熱延板焼鈍を７５０～１０５０℃の範囲で行う必要がある。焼鈍温度が７５０℃未満では再結晶が不十分なため熱延ひずみに起因した残留応力が残存して、熱延焼鈍後の平坦度が保てない。一方、焼鈍温度が１０５０℃を超えると、再結晶粒は、著しい粗大化が生じ、所望の金属組織が得られない。そのため、熱延板焼鈍温度は７５０℃以上１０５０℃以下の範囲とする。好ましくは、熱延板焼鈍温度は７５０℃以上９００℃以下の範囲である。なお、熱延板焼鈍の保持時間および手法に特に限定はなく、箱焼鈍（バッチ焼鈍）、連続焼鈍のいずれで実施してもかまわない。 Hot-rolled sheet annealing temperature: 750 to 1050 ° C
In the present invention, hot-rolled sheet annealing is performed after the completion of the hot rolling. In hot-rolled sheet annealing, the rolled structure formed in the hot rolling process is recrystallized. In the present invention, rolling strain is effectively applied in the hot rolling step, and coarsening of recrystallization in hot-rolled sheet annealing is suppressed by increasing recrystallization sites. In order to obtain this effect, it is necessary to carry out hot-rolled sheet annealing in the range of 750 to 1050.degree. If the annealing temperature is less than 750 ° C., recrystallization is insufficient and residual stress caused by hot rolling distortion remains, and the flatness after hot rolling annealing can not be maintained. On the other hand, if the annealing temperature exceeds 1050 ° C., the recrystallized grains are significantly coarsened, and the desired metal structure can not be obtained. Therefore, the hot-rolled sheet annealing temperature is in the range of 750 ° C. or more and 1050 ° C. or less. Preferably, the hot-rolled sheet annealing temperature is in the range of 750 ° C. or more and 900 ° C. or less. In addition, there is no limitation in particular in the holding time and method of hot-rolled sheet annealing, It may carry out by any of box annealing (batch annealing) and continuous annealing.
　以上により得られたフェライト系ステンレス鋼板には、必要に応じてショットブラストや酸洗による脱スケール処理を行ってもよい。さらに、表面性状を向上させるために、研削や研磨等を施してもよい。また、その後、冷間圧延および冷延板焼鈍を行ってもよい。 The ferritic stainless steel sheet obtained as described above may be subjected to a descaling treatment by shot blasting or acid washing, if necessary. Furthermore, in order to improve the surface quality, grinding, polishing or the like may be performed. After that, cold rolling and cold rolled sheet annealing may be performed.
　以上により、本発明の靭性に優れ、かつ、耐食性にも優れたフェライト系ステンレス鋼板が製造される。 By the above, a ferritic stainless steel sheet excellent in the toughness of the present invention and excellent in corrosion resistance is manufactured.
　本発明で得られるフェライト系ステンレス鋼板の金属組織はフェライト単相、もしくはマルテンサイト、残留オーステナイト相の一方または両方を合計で３％以下（体積率）含み残部がフェライト相である。 The metallographic structure of the ferritic stainless steel sheet obtained in the present invention is a ferrite single phase or a total of 3% or less (volume ratio) of one or both of a martensite and a retained austenite phase, and the balance is a ferrite phase.
　本発明のフェライト系ステンレス鋼板は、－５０℃でのシャルピー衝撃値が１００Ｊ／ｃｍ２以上である。このように低温靭性に優れることで、バーリング加工部を有する厚肉のフランジへ加工する際のバーリング加工部での割れの発生を効果的に抑制することができ、バーリング加工部を有する厚肉のフランジへ十分に実用化できる。 The ferritic stainless steel plate of the present invention has a Charpy impact value at -50 ° C. of 100 J / cm 2 or more. Thus, by being excellent in low-temperature toughness, generation of a crack in a burring part at the time of processing to a thick flange having a burring part can be effectively suppressed, and a thick wall having a burring part Practically applicable to flanges.
　板厚は、特に限定されないが、厚肉のフランジに適用できる板厚であることが望ましいため、５．０ｍｍ以上が好ましく、８．０ｍｍ以上がより好ましい。また、板厚は、１５．０ｍｍ以下が好ましく、１３．０ｍｍ以下がより好ましい。 The plate thickness is not particularly limited, but is preferably 5.0 mm or more, and more preferably 8.0 mm or more, because it is desirable that the plate thickness can be applied to a thick flange. Moreover, 15.0 mm or less is preferable and, as for plate | board thickness, 13.0 mm or less is more preferable.
　以下、本発明を実施例により詳細に説明する。 Hereinafter, the present invention will be described in detail by way of examples.
　表１に示す成分組成を有するステンレス溶鋼を真空誘導溶解により１００ｋｇの鋼スラブとした。次いで、表２に示す製造条件で熱間圧延し、表２に示す仕上げ板厚の熱延鋼板とした。この熱延鋼板に熱延板焼鈍を施し熱延焼鈍鋼板とした。なお、熱延板焼鈍は表２に示す熱延板焼鈍温度に８ｈ保持して行った。
以上により得られた熱延焼鈍鋼板について、以下の評価を行った。 The molten stainless steel having the component composition shown in Table 1 was made into a 100 kg steel slab by vacuum induction melting. Subsequently, it hot-rolled on the manufacturing conditions shown in Table 2, and was set as the hot rolled sheet steel of the finish plate thickness shown in Table 2. The hot rolled steel sheet is subjected to hot rolled sheet annealing to obtain a hot rolled annealed steel sheet. In addition, hot-rolled sheet annealing was performed holding the hot-rolled sheet annealing temperature shown in Table 2 for 8 h.
The following evaluation was performed about the hot-rolled annealing steel plate obtained by the above.
　（１）平均結晶粒径の評価
　平均結晶粒径は、ＥＢＳＤ（Ｅｌｅｃｔｒｏｎ Ｂａｃｋ Ｓｃａｔｔｅｒｉｎｇ Ｄｉｆｆｒａｃｔｉｏｎ）法により測定した。測定条件は、測定倍率５００倍でステップ０．４μｍとした。得られたデータは株式会社ＴＳＬソリューションズ社ＯＩＭ（Ｏｒｉｅｎｔａｔｉｏｎ Ｉｍａｇｉｎｇ Ｍｉｃｒｏｓｃｏｐｙ）解析ソフトにより方位差１５°以上を粒界と定義し、円相当直径を算出した。得られた円相当直径の平均値から算出した値を平均結晶粒径とした。 (1) Evaluation of Average Grain Size The average grain size was measured by the EBSD (Electron Back Scattering Diffraction) method. The measurement conditions were set to a step of 0.4 μm at a measurement magnification of 500 times. The obtained data was defined as a grain boundary of 15 ° or more in orientation difference by OIM (Orientation Imaging Microscopy) analysis software manufactured by TSL Solutions, Inc., and the equivalent circle diameter was calculated. The value calculated from the average value of the obtained equivalent circle diameters was taken as the average crystal grain size.
　（２）シャルピー衝撃値の評価
　熱延焼鈍鋼板の板幅中央部から、ＪＩＳ　Ｚ　２２４２（２００５）に準拠したＶノッチシャルピー試験片を前記鋼板の板厚のままで圧延方向が長手となるように採取し、該試験片についてＪＩＳ　Ｚ　２２４２（２００５）に準拠して－５０℃におけるシャルピー衝撃値を測定した。－５０℃におけるシャルピー衝撃値が１００Ｊ／ｃｍ２以上を合格、１００Ｊ／ｃｍ２未満を不合格とした。 (2) Evaluation of Charpy Impact Value From the central portion of the width of the hot-rolled annealed steel plate, the V-notch Charpy test piece conforming to JIS Z 2242 (2005) is made to have a long rolling direction while maintaining the thickness of the steel plate. The specimen was collected, and the Charpy impact value at −50 ° C. was measured for the test piece in accordance with JIS Z 2242 (2005). The Charpy impact value at −50 ° C. passed 100 J / cm 2 or more and rejected 100 J / cm 2 or less.
　（３）耐食性の評価
　熱延焼鈍鋼板から、６０×８０ｍｍの試験片を採取し、表面を＃６００エメリーペーパーにより研磨仕上げした後に端面部および裏面をシールした試験片を作製し、ＪＩＳ　Ｈ　８５０２に規定された塩水噴霧サイクル試験に供した。塩水噴霧サイクル試験は、塩水噴霧（５質量％ＮａＣｌ、３５℃、噴霧２ｈr）→乾燥（６０℃、４ｈr、相対湿度４０％）→湿潤（５０℃、２ｈr、相対湿度≧９５％）を１サイクルとして、３サイクル行った。塩水噴霧サイクル試験を３サイクル実施後の試験片表面を写真撮影し、画像解析により試験片表面の発錆面積を測定し、発錆面積測定部分の面積との比率から発錆率（試験片中の発錆面積／発錆面積測定部分の面積）×１００［％］）を算出した。発錆面積測定部分とは、試験片の外周１５ｍｍの部分を除いた部分である。なお、発錆面積は発錆部分および、流れ錆部分の面積とした。発錆率１０％以下を特に優れた耐食性で合格（◎）、１０％超２５％以下を合格（○）、２５％超を不合格（×）とした。 (3) Evaluation of corrosion resistance A test piece of 60 × 80 mm is taken from a hot-rolled annealed steel sheet, and the surface is polished and finished with # 600 emery paper, and then a test piece with sealed end face and back is manufactured. Subject to a defined salt spray cycle test. Salt spray cycle test: 1 cycle of salt spray (5 mass% NaCl, 35 ° C, spray 2hr) → drying (60 ° C, 4hr, relative humidity 40%) → wetting (50 ° C, 2hr, relative humidity) 95%) As, went 3 cycles. The surface of the test piece after 3 cycles of salt spray cycle test is photographed, the rusting area of the test piece surface is measured by image analysis, and the ratio of rusting area to the area of the rusting area measurement portion Rust area / area of the rust area measurement portion) × 100 [%]) was calculated. The rusted area measurement portion is a portion excluding the portion of the outer periphery 15 mm of the test piece. The rusted area was the area of the rusted portion and the flow rusted portion. The rusting rate of 10% or less is regarded as pass (◎) with particularly excellent corrosion resistance, 10% to 25% or less as pass (o), and 25% or more as rejection (x).
　以上により得られた試験結果を製造条件と併せて表２に示す。
　 The test results obtained as described above are shown in Table 2 together with the manufacturing conditions.
Figure JPOXMLDOC01-appb-T000001
  
Figure JPOXMLDOC01-appb-T000001
  
Figure JPOXMLDOC01-appb-T000002
  
Figure JPOXMLDOC01-appb-T000002
  
　表１、表２によれば、鋼成分、熱間圧延条件および熱延板焼鈍条件が本発明の範囲を満たすＮｏ．１～３２ならびに４６は、平均結晶粒径が４５μｍ以下の微細な金属組織が得られ、所定のシャルピー衝撃値が得られた。さらに得られた熱延焼鈍鋼板の耐食性を評価した結果、いずれも発錆率は２５％以下であり十分な耐食性も有していることが確認された。特に、Ｃｕを０．９５％含有させた鋼Ａ１７を用いたＮｏ．１７、およびＭｏを０．８８％含有させた鋼Ａ１８を用いたＮｏ．１８では発錆率が１０％以下と一層優れた耐食性が得られた。 According to Tables 1 and 2, the steel components, the hot rolling conditions, and the hot-rolled sheet annealing conditions satisfy the range of the present invention. In 1 to 32 and 46, fine metal structures having an average crystal grain size of 45 μm or less were obtained, and a predetermined Charpy impact value was obtained. Furthermore, as a result of evaluating the corrosion resistance of the obtained hot-rolled annealing steel plate, it was confirmed that the rusting rate is 25% or less in any case and also has sufficient corrosion resistance. In particular, No. 1 using steel A17 containing 0.95% of Cu. No. 17 and No. 18 using steel A18 containing 0.88% of Mo. In No. 18, the corrosion resistance was further improved with a rusting rate of 10% or less.
　また、Ｎｏ．１～３２ならびに４６の本発明例について、バーリング加工部を有する厚肉のフランジ形状への加工を試みたところ、割れは生じず、所定のフランジ形状を得ることできた。なお、本発明例の熱延焼鈍鋼板について組織観察を行ったところ、いずれもフェライト単相組織であるか、または、マルテンサイト、残留オーステナイト相の一方もしくは両方の合計が体積率で３％以下で残部がフェライト相である組織を有していた。 Also, no. When an attempt was made to process a thick flange having a burring portion with respect to Examples 1 to 32 and 46 of the present invention, cracking did not occur, and a predetermined flange shape could be obtained. When the structure of the hot-rolled annealed steel sheet of the present invention example was observed, all had a ferrite single-phase structure, or one or both of martensite and retained austenite phase had a volume ratio of 3% or less The balance had a structure that was a ferrite phase.
　鋼Ａ１、および鋼Ａ２を用い、スラブ加熱温度が本発明の範囲を上回るＮｏ．３３、およびＮｏ．３４では、熱間圧延工程における加熱時に所定量のオーステナイト相が生成し、かつ所定の累積圧下率で圧延したものの、圧延温度が過度に高温であったために加工ひずみの回復が生じて再結晶サイトの導入が不十分であったために、熱延板焼鈍工程において再結晶粒の粗大化が生じやすくなり、所定のシャルピー衝撃値が得られなかった。 Using steels A1 and A2, the slab heating temperature exceeds the range of the present invention. 33, and no. In 34, although a predetermined amount of austenite phase is formed at the time of heating in the hot rolling process and rolling is performed at a predetermined cumulative reduction ratio, recovery of working strain occurs because the rolling temperature is excessively high and recrystallization site In the hot-rolled sheet annealing step, coarsening of recrystallized grains is likely to occur, and a predetermined Charpy impact value can not be obtained.
　鋼Ａ１、および鋼Ａ２を用い、熱延板焼鈍温度が本発明の範囲を上回るＮｏ．３５、およびＮｏ．３６では、生成した再結晶粒の著しい粗大化が生じた結果、所定のシャルピー衝撃値が得られなかった。 The steel sheet A1 and the steel sheet A2 are used, and the hot-rolled sheet annealing temperature exceeds the range of the present invention. 35, and no. In No. 36, as a result of the occurrence of significant coarsening of the formed recrystallized grains, a predetermined Charpy impact value was not obtained.
　鋼の各成分範囲を満たすが、γＩが本発明の範囲を下回る鋼Ｂ１、Ｂ２、およびＢ３を用いたＮｏ．３７、Ｎｏ．３８、およびＮｏ．３９では、所定の熱間圧延および熱延板焼鈍を行ったが、熱間圧延工程の加熱時にオーステナイト相が十分に生成しなかった結果、熱延板焼鈍工程において金属組織の微細化が十分に生じず、所定のシャルピー衝撃値が得られなかった。 No. 1 using steels B1, B2 and B3 which satisfy each component range of steel but γ I is less than the range of the present invention. 37, no. 38, and no. In No. 39, although predetermined hot rolling and hot rolled sheet annealing were performed, as austenite phase was not sufficiently formed at the time of heating in the hot rolling process, as a result, the refining of the metal structure is sufficiently performed in the hot rolled sheet annealing process. It did not occur, and a predetermined Charpy impact value was not obtained.
　Ｃｒ含有量が本発明の範囲を上回る鋼Ｂ４を用いたＮｏ．４０では、所定の熱間圧延および熱延板焼鈍を行ったが、熱間圧延工程の加熱時にオーステナイト相が十分に生成しなかった結果、熱延板焼鈍工程において金属組織の微細化が十分に生じず、所定のシャルピー衝撃値が得られなかった。 The steel No. 4 using steel B4 whose Cr content exceeds the range of the present invention. In No. 40, although predetermined hot rolling and hot rolled sheet annealing were performed, as austenite phase was not sufficiently generated at the time of heating in the hot rolling process, as a result, the refining of the metal structure is sufficiently performed in the hot rolled sheet annealing process. It did not occur, and a predetermined Charpy impact value was not obtained.
　Ｍｎ含有量が本発明の範囲を上回る鋼Ｂ５を用いたＮｏ．４１では、所定の熱間圧延および熱延板焼鈍を行ったが、腐食の起点となるＭｎＳが過剰に析出した結果、所定の耐食性が得られなかった。 No. 1 using steel B5 whose Mn content exceeds the range of the present invention. In No. 41, predetermined hot rolling and hot-rolled sheet annealing were performed, but as a result of excessive precipitation of MnS as a starting point of corrosion, predetermined corrosion resistance was not obtained.
　Ｎｂ含有量が本発明の範囲を上回る鋼Ｂ６を用いたＮｏ．４２では、再結晶温度が上昇したため金属組織の微細化が十分に生じず、所定のシャルピー衝撃値が得られなかった。 No. 4 using steel B6 whose Nb content exceeds the range of the present invention. In No. 42, the recrystallization temperature increased, so that the metal structure was not sufficiently refined, and a predetermined Charpy impact value was not obtained.
　Ｓｉ含有量が本発明の上回る鋼Ｂ７を用いたＮｏ．４３では、金属組織の平均結晶粒径が４５μｍを上回り、所定のシャルピー衝撃値が得られなかった。 No. 1 using steel B7, which has an Si content exceeding that of the present invention. At 43, the average grain size of the metal structure exceeded 45 μm, and a predetermined Charpy impact value was not obtained.
　Ｔｉ含有量が本発明の範囲を上回る鋼Ｂ８を用いたＮｏ．４４では、過剰なＴｉ含有によって粗大なＴｉＮの生成が起き、所定のシャルピー衝撃値が得られなかった。 No. 4 using steel B8 whose Ti content exceeds the range of the present invention. At 44, excessive Ti content resulted in the formation of coarse TiN, and the desired Charpy impact value was not obtained.
　Ｔｉ無添加の鋼Ｂ９を用いたＮｏ．４５では、再結晶温度が上昇したため金属組織の微細化が十分に生じず、所定のシャルピー衝撃値が得られなかった。 No. 4 using Ti-free steel B9. In No. 45, the recrystallization temperature increased, so that refinement of the metal structure did not occur sufficiently, and a predetermined Charpy impact value was not obtained.
　Ｎｉ含有量が本発明の範囲を下回る鋼Ｂ１０を用いたＮｏ．４７では、所定の熱間圧延および熱延板焼鈍を行ったが、熱間圧延工程の加熱時にオーステナイト相が十分に生成しなかった結果、熱延板焼鈍工程において金属組織の微細化が十分に生じず、所定のシャルピー衝撃値が得られなかった。 No. 1 using steel B10 whose Ni content is below the range of the present invention. In No. 47, although predetermined hot rolling and hot rolled sheet annealing were performed, as austenite phase was not sufficiently formed at the time of heating in the hot rolling process, as a result, the refining of the metal structure is sufficiently performed in the hot rolled sheet annealing process. It did not occur, and a predetermined Charpy impact value was not obtained.
　本発明で得られるフェライト系ステンレス鋼板は、優れた靭性が要求される用途、例えばフランジ等への適用に特に好適である。 The ferritic stainless steel sheet obtained by the present invention is particularly suitable for applications where excellent toughness is required, for example, application to flanges and the like.

Claims (5)

  1. 　質量％で、
    Ｃ：０．００１～０．０２０％、
    Ｓｉ：０．０５～０．３５％、
    Ｍｎ：０．０５～１．００％、
    Ｐ：０．０４％以下、
    Ｓ：０．０１％以下、
    Ａｌ：０．００１～０．３００％、
    Ｃｒ：１０．０～１３．０％、
    Ｎｉ：０．７５～１．５０％、
    Ｔｉ：０．０５～０．３５％、
    Ｎ：０．００１～０．０２０％
    を含有し、かつ、下記式（１）からなるγＩ［％］が６５％以上であり、残部がＦｅおよび不可避的不純物からなる成分組成を有し、
    金属組織の平均結晶粒径が４５μｍ以下である、フェライト系ステンレス鋼板。
    γＩ［％］＝２４Ｎｉ＋１２Ｍｎ＋６Ｃｕ－１８Ｓｉ－１２Ｃｒ－１２Ｍｏ＋１８８　（１）
    なお、式（１）中のＮｉ、Ｍｎ、Ｃｕ、Ｓｉ、ＣｒおよびＭｏは、各成分の含有量（質量％）をあらわし、含有しない成分は０とする。     In mass%,
    C: 0.001 to 0.020%,
    Si: 0.05 to 0.35%,
    Mn: 0.05 to 1.00%,
    P: 0.04% or less,
    S: 0.01% or less,
    Al: 0.001 to 0.300%,
    Cr: 10.0 to 13.0%,
    Ni: 0.75 to 1.50%,
    Ti: 0.05 to 0.35%,
    N: 0.001 to 0.020%
    And has a component composition in which γ I [%] consisting of the following formula (1) is 65% or more, and the balance is Fe and unavoidable impurities,
    A ferritic stainless steel sheet having an average grain size of 45 μm or less in a metal structure.
    γ I [%] = 24 Ni + 12 Mn + 6 Cu-18 Si-12 Cr-12 Mo + 188 (1)
    In addition, Ni, Mn, Cu, Si, Cr, and Mo in Formula (1) represent content (mass%) of each component, and let the component which is not contained be zero.
  2. 　前記成分組成に加えて、質量％で、
    Ｃｕ：０．０１～１．００％、
    Ｍｏ：０．０１～１．００％、
    Ｗ：０．０１～０．２０％、
    Ｃｏ：０．０１～０．２０％の１種または２種以上を含有する、請求項１に記載のフェライト系ステンレス鋼板。     In addition to the above component composition, in mass%,
    Cu: 0.01 to 1.00%,
    Mo: 0.01 to 1.00%,
    W: 0.01 to 0.20%,
    The ferritic stainless steel sheet according to claim 1, containing one or more of Co: 0.01 to 0.20%.
  3. 　前記成分組成に加えて、質量％で、
    Ｖ：０．０１～０．２０％、
    Ｎｂ：０．０１～０．１０％、
    Ｚｒ：０．０１～０．２０％の１種または２種以上を含有する、請求項１または２に記載のフェライト系ステンレス鋼板。     In addition to the above component composition, in mass%,
    V: 0.01 to 0.20%,
    Nb: 0.01 to 0.10%,
    3. The ferritic stainless steel sheet according to claim 1, which contains one or more of Zr: 0.01 to 0.20%.
  4. 　前記成分組成に加えて、質量％で、
    ＲＥＭ：０．００１～０．１００％、
    Ｂ：０．０００２～０．００２５％、
    Ｍｇ：０．０００５～０．００３０％、
    Ｃａ：０．０００３～０．００３０％の１種または２種以上を含有する、請求項１～３のいずれかに記載のフェライト系ステンレス鋼板。     In addition to the above component composition, in mass%,
    REM: 0.001 to 0.100%,
    B: 0.0002 to 0.0025%,
    Mg: 0.0005 to 0.0030%,
    The ferritic stainless steel sheet according to any one of claims 1 to 3, which contains one or more of 0.0003 to 0.0030% of Ca.
  5. 　請求項１～４のいずれかに記載のフェライト系ステンレス鋼板の製造方法であって、
    前記成分組成を有する鋼スラブに対して、１０５０～１２５０℃で加熱後、熱間圧延を行う熱間圧延工程と、
    該熱間圧延工程で得られた熱延鋼板を７５０～１０５０℃で熱延板焼鈍する熱延板焼鈍工程とを有する、フェライト系ステンレス鋼板の製造方法。     A method of manufacturing a ferritic stainless steel sheet according to any one of claims 1 to 4,
    A hot rolling step of heating the steel slab having the above component composition at 1050 to 1250 ° C. and then hot rolling;
    A method of producing a ferritic stainless steel sheet, comprising a hot rolled sheet annealing step of hot rolled sheet annealing of the hot rolled steel sheet obtained in the hot rolling step at 750 to 1050 ° C .;
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