EP4130322A1 - Acier inoxydable austénitique - Google Patents

Acier inoxydable austénitique Download PDF

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Publication number
EP4130322A1
EP4130322A1 EP21778892.6A EP21778892A EP4130322A1 EP 4130322 A1 EP4130322 A1 EP 4130322A1 EP 21778892 A EP21778892 A EP 21778892A EP 4130322 A1 EP4130322 A1 EP 4130322A1
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Prior art keywords
less
content
ozone
stainless steel
acid
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EP21778892.6A
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German (de)
English (en)
Inventor
Toshihiko Yoshimi
Nobuhiko Hiraide
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Nippon Steel Stainless Steel Corp
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Nippon Steel Stainless Steel Corp
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Publication of EP4130322A1 publication Critical patent/EP4130322A1/fr
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    • 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
    • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
    • 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
    • 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
    • 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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold 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
    • C21D8/0273—Final recrystallisation annealing
    • 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
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of 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
    • C22C38/18—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
    • C22C38/46—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
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel
    • C23G1/081—Iron or steel solutions containing H2SO4
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel
    • C23G1/086—Iron or steel solutions containing HF
    • 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
    • C21D2211/001—Austenite

Definitions

  • the present invention relates to an austenitic stainless steel.
  • stainless steel has been used for various applications as a representative corrosion resistant material
  • steel types with high atmospheric corrosion resistance have been developed in recent years, and applications thereof as construction materials for roofs, exteriors, and the like have been increased.
  • exterior construction materials not only prevention of rusting and pitting due to corrosion but also aesthetic appearance after construction are required.
  • Patent Document 1 discloses a stainless steel sheet with both a glare-proof property and corrosion resistance, and the stainless steel sheet contains, in terms of by % by weight, C: 0.10% or less, Si: 1.0% or less, Mn: 1.0% or less, P: 0.09% or less, S: 0.01% or less, Cr: 20% or more and 40% or less, Mo: 0.5% or more and 6.0% or less, Cr + Mo: 24.5% or more, N: 0.1 % or less, Nb: 0.01% or more and 0.8% or less, Ti: 0.01% or more and 0.8% or less, Al: 0.008% or more and 1.0% or less, and one or more selected from the group consisting of Ni: 0.1% or more and 25% or less, and Cu: 0.01 % or more and 3% or less, with a remainder being Fe and impurities, in which as surface roughness (Ra), arithmetic average roughness is 1.0 ⁇ m or more.
  • Ra surface roughness
  • Patent Document 2 discloses an pickling liquid for stainless steel, and the pickling liquid contains, as main components: 10 to 200 g/L of sulfuric acid or 5 to 150 g/L of hydrochloric acid, 1 to 40 g/L of one or two or more selected from a hydrofluoric acid, a fluorosilicic acid, sodium fluoride; and 5 to 40 g/L of Fe 3+ ions, in which a thickener is added to an aqueous solution that does not contain a nitric acid to obtain the aqueous solution in a paste form.
  • Patent Document 2 further discloses an pickling liquid containing, in terms of concentration converted into 35%, either one or both of 5 to 15 g/L of hydrogen peroxide and 5 to 10 g/L of sodium peroxide in addition to the aforementioned components.
  • Patent Document 1 has relatively high corrosion resistance. However, there is a probability that rusting may occur in a humid environment including chlorides such as seawater and aesthetic appearance is degraded, and there is still room for improvement.
  • so-called super austenitic stainless steel that contains relatively large amounts of Cr, Mo, and N among austenitic stainless steels have more excellent corrosion resistance as compared with other austenitic stainless steels.
  • variations may occur in elution of the surface of the steel sheet due to segregation of components in conventional acid pickling performed for finishing in manufacturing of the super austenitic stainless steel.
  • parts eluted through acid pickling is whitened, and parts that are not eluted has glossiness, there may be cases in which appearance unevenness of the super austenitic stainless steel are observed.
  • Patent Document 2 it is difficult to elute the entire surface of the super austenitic stainless steel, and there may be cases in which appearance unevenness are observed. In cases of applications to exterior construction materials requiring aesthetic appearance, there is room for improvement in super austenitic stainless steel.
  • the present invention was made in view of the aforementioned problem, and an object of the present invention is to provide an austenitic stainless steel with aesthetic appearance.
  • the present inventors achieved, as a result of various studies in regard to acid pickling conditions under which appearance unevenness did not occur, a knowledge that it was possible to suppress appearance unevenness caused by segregation of components of super austenitic stainless steel with segregation of components as long as washing is performed using a predetermined acidic solution with an oxidizing power.
  • an austenitic stainless steel with aesthetic appearance.
  • An austenitic stainless steel according to the present embodiment contains, in terms of % by mass, C: 0.100% or less, Si: 3.00% or less, Mn: 0.01% or more and 5.00% or less, P: 0.100% or less, S: 0.0050% or less, Ni: 7.00% or more and 38.00% or less, Cr: 17.00% or more and 28.00% or less, Mo: 10.00% or less, and N: more than 0.100% and 0.400% or less, with a remainder being Fe and impurities, in which a brightness difference ⁇ L of a surface of a steel sheet is 5 or less.
  • % indicating the component means % by mass.
  • C is an element inevitably contained in a stainless steel and is an element that contributes to stabilization of the austenite phase and improvement in high-temperature strength. Excessive content of C may lead to degradation of welding solidification crack resistance and degradation of corrosion resistance due to precipitation of Cr-based carbides. Therefore, the content of C is set to 0.100% or less.
  • the content of C is preferably 0.06% or less and is more preferably 0.04% or less.
  • a lower limit of the content of C is not particularly limited, the lower limit is preferably 0.005% or more.
  • Si is an element effective for stabilizing the austenite phase.
  • excessive content of Si may promote precipitation of a ⁇ phase. Therefore, the content of Si is set to 3.00% or less.
  • the content of Si is preferably 1.00% or less and is more preferably 0.80% or less.
  • the content of Si is preferably 0.01% or more in order to obtain the effect of stabilizing the austenite phase due to Si.
  • the content of Si is more preferably 0.10% or more.
  • Mn 0.01% or more and 5.00% or less
  • Mn is an element effective for stabilizing the austenite phase.
  • the content of Mn is set to 0.01% or more.
  • the content of Mn is preferably 0.20% or more and is more preferably 0.4% or more.
  • excessive content of Mn may degrade corrosion resistance. Therefore, the content of Mn is set to 5.00% or less.
  • the content of Mn is preferably 2.00% or less and is more preferably 1.50% or less.
  • P is contained as an impurity in a stainless steel. Since P is an element that degrades hot workability, it is preferable to reduce the content as much as possible. Therefore, the content of P is set to 0.100% or less.
  • the content of P is preferably 0.080% or less and is more preferably 0.050% or less. Although a lower limit is not particularly limited, the content of P is preferably 0.005% or more from the viewpoint of cost.
  • the content of S is an element that segregates at austenite grain boundaries during hot working and induces cracking during hot working by weakening a binding force at the grain boundaries. Therefore, it is preferable to reduce the content of S as much as possible.. Therefore, the content of S is set to 0.0050% or less.
  • the content of S is preferably 0.0020% or less and is more preferably 0.0010% or less.
  • the content of S is preferably 0.0001 % or more.
  • the content of S is more preferably 0.0002% or more.
  • Ni 7.00% or more and 38.00% or less
  • Ni is an important element for stabilizing the austenite phase.
  • the content of Ni is set to 7.00% or more.
  • the content of Ni is preferably 16.00% or more and is more preferably 18.00% or more.
  • excessive content of Ni may lead to an increase in material cost and degrade economic efficiency. Therefore, the content of Ni is set to 38.00% or less.
  • the content of Ni is preferably 30.00% or less and is more preferably 25.00% or less.
  • Cr is an extremely important element for improving corrosion resistance of the austenitic stainless steel.
  • Cr is an element that also contributes to an increase in strength of the austenitic stainless steel. Therefore, the content of Cr is set to 17.00% or more.
  • the content of Cr is preferably 18.00% or more and is more preferably 19.00% or more.
  • the content of Cr is set to 28.00% or less.
  • the content of Cr is preferably 25.00% or less and is more preferably 22.00% or less.
  • Mo is an extremely important element for improving corrosion resistance of the austenitic stainless steel.
  • Mo is an element that contributes to an increase in strength.
  • the content of Mo is set to 10.00% or less.
  • the content of Mo is preferably 8.00% or less and is more preferably 7.00% or less.
  • the content of Mo is preferably 3.00% or more in order to stably obtain the effects of improving corrosion resistance and increasing strength due to Mo.
  • the content of Mo is preferably 5.00% or more, is more preferably more than 5.00%, and is most preferably 6.00% or more.
  • N More than 0.100% and less than 0.400%
  • N is an extremely important element for improving corrosion resistance of the austenitic stainless steel.
  • N has an effect as an austenite stabilizing element.
  • the content of N is set to more than 0.100%.
  • the content of N is preferably 0.120% or more and is more preferably 0.150% or more.
  • the content of N is set to 0.400% or less.
  • the content of N is preferably 0.300% or less and is more preferably 0.250% or less.
  • the remainder other than the aforementioned elements is Fe and impurities.
  • impurities described here mean components that are included due to various factors including ingredient materials such as ore and scrap and manufacturing processes when the austenitic stainless steel according to the present embodiment is industrially manufactured and that are accepted within a range in which they do not adversely affect the present embodiment.
  • the austenitic stainless steel according to the present embodiment preferably contains one or more selected from a group consisting of Cu: 3.00% or less, W: 2.00% or less, and V: 1.00% or less instead of a part of Fe. Note that since these elements may not be contained, lower limits of content of these elements are 0%.
  • Cu is an element effective for stabilizing the austenite phase.
  • the content of Cu is preferably set to 3.00% or less.
  • the content of Cu is more preferably 2.00% or less.
  • the content of Cu is preferably 0.10% or more in order to stably obtain the effect of stabilizing the austenite phase due to Cu.
  • the content of Cu is more preferably 0.50% or more.
  • V 1.00% or less
  • the content of W is preferably 1.00% or less.
  • the content of V is more preferably 0.50% or less.
  • the content of V is preferably 0.05% or more.
  • the content of V is more preferably 0.10% or more.
  • the austenitic stainless steel according to the present embodiment preferably contains, in terms of % by mass: one or more selected from a group consisting of Al: 0.001% or more and 0.3% or less, Ca: 0.001% or more and 0.3% or less, B: 0.0001 % or more and 0.1 % or less, Ti: 0.001 % or more and 0.40% or less, Nb: 0.001 % or more and 0.40% or less, Sn: 0.001% or more and 0.5% or less, Zr: 0.001% or more and 0.5% or less, Co: 0.001% or more and 0.5% or less, Mg: 0.001% or more and 0.5% or less, Hf: 0.001 % or more and 0.5% or less, REM: 0.001 % or more and 0.5% or less, Ta: 0.001% or more and 0.5% or less, Ga: 0.001% or more and 0.5% or less, and Sb: 0.001% or more and 0.5% or less, instead of a part of Fe. Note that since these elements may be
  • Al 0.001% or more and 0.3% or less
  • Al is an element having a deoxidizing effect.
  • the content of Al is preferably 0.001% or more.
  • the content of Al is more preferably 0.01% or more.
  • the content of Al is preferably 0.3% or less.
  • the content of Al is further preferably 0.30% or less and is more preferably 0.10% or less.
  • Ca is an element effective for deoxidizing and improving hot workability.
  • the content of Ca is preferably 0.001% or more.
  • the content of Ca is more preferably 0.002% or more.
  • the content of Ca is preferably 0.3% or less.
  • the content of content of Ca is further preferably 0.30% or less and is more preferably 0.01% or less.
  • the content of B is an element that improves hot workability.
  • the content of B is preferably 0.0001% or more.
  • the content of B is more preferably 0.0002% or more.
  • the content of B is preferably 0.1% or less.
  • the content of B is further preferably 0.10% or less and is more preferably 0.001 % or less.
  • Ti is an element that forms carbonitrides and improves corrosion resistance. Therefore, the content of Ti is preferably 0.001% or more. The content of Ti is more preferably 0.005% or more. On the other hand, in the case where an excessive content of Ti is contained, it may also lead to saturation of the effect. Therefore, the content of Ti is preferably 0.40% or less. The content of Ti is more preferably 0.10% or less.
  • Nb 0.001 % or more and 0.40% or less
  • Nb is an element that forms carbonitrides and improves corrosion resistance. Therefore, the content of Nb is preferably 0.001% or more. The content of Nb is more preferably 0.002% or more. On the other hand, in the case where an excessive content of Nb is contained, it may lead to saturation of the effect. Therefore, the content of Nb is preferably 0.40% or less. The content of Ti is more preferably 0.10% or less.
  • Sn is an element effective for improving oxidation resistance.
  • the content of Sn is preferably 0.001 % or more.
  • the content of Sn is more preferably 0.01 % or more.
  • the content of Sn is preferably 0.5% or less.
  • the content of Sn is further preferably 0.50% or less and is more preferably 0.10% or less.
  • Zr is an element that improves strength.
  • the content of Zr is preferably 0.001% or more.
  • the content of Zr is more preferably 0.01% or more.
  • the content of Zr is preferably 0.5% or less.
  • the content of Zr is further preferably 0.50% or less and is more preferably 0.10% or less.
  • Co 0.001% or more and 0.5% or less
  • Co is an element effective for improving corrosion resistance.
  • the content of Co is preferably 0.001 % or more.
  • the content of Co is more preferably 0.01% or more.
  • the content of Co is thus preferably 0.5% or less.
  • the content of Co is further preferably 0.50% or less and is more preferably 0.10% or less.
  • Mg 0.001% or more and 0.5% or less
  • Mg is an element effective for deoxidizing and improving hot workability.
  • the content of Mg is preferably 0.001% or more.
  • the content of Mg is more preferably 0.01% or more.
  • the content of Mg is preferably 0.5% or less.
  • the content of Mg is further preferably 0.50% or less and is more preferably 0.10% or less.
  • Hf 0.001% or more and 0.5% or less
  • Hf is an element that improves corrosion resistance.
  • the content of Hf is preferably 0.001% or more.
  • the content of Hf is more preferably 0.01% or more.
  • the content of Hf is preferably 0.5% or less.
  • the content of Hf is further preferably 0.50% or less and is more preferably 0.10% or less.
  • the content of REM is an element effective for deoxidizing and improving hot workability and corrosion resistance.
  • the content of REM is preferably 0.001% or more.
  • the content of REM is more preferably 0.01% or more.
  • the content of REM is preferably 0.5% or less.
  • the content of REM is further preferably 0.50% or less and is more preferably 0.10% or less.
  • REM is two elements namely Sc and Y and fifteen elements (lanthanoids) from La to Lu, and REM is one or more selected from the above-described elements.
  • the content of REM refers to a total amount of the contained elements.
  • Ta 0.001% or more and 0.5% or less
  • Ta forms carbonitrides and improves corrosion resistance.
  • the content of Ta is preferably 0.001 % or more.
  • the content of Ta is more preferably 0.01% or more.
  • the content of Ta is preferably 0.5% or less.
  • the content of Ta is further preferably 0.50% or less and is more preferably 0.10% or less.
  • Ga 0.001 % or more and 0.5% or less
  • Ga is an element that contributes to an improvement in corrosion resistance and workability.
  • the content of Ga is preferably 0.001 % or more.
  • the content of Ga is more preferably 0.01 % or more.
  • the content of Ga is preferably 0.5% or less.
  • the content of Ga is further preferably 0.50% or less and is more preferably 0.10% or less.
  • Sb is an element effective for improving oxidation resistance.
  • the content of Sb is preferably 0.001 % or more.
  • the content of Sb is more preferably 0.01% or more.
  • the content of Sb is preferably 0.5% or less.
  • the content of Sb is further preferably 0.50% or less and is more preferably 0.10% or less.
  • the austenitic stainless steel according to the present embodiment has a brightness difference ⁇ L of 5 or less.
  • the brightness difference ⁇ L refers to a difference between a maximum value and a minimum value of brightness L obtained in accordance with JIS Z 8730: 2009.
  • the brightness difference ⁇ L is a difference between a maximum value and a minimum value of measured brightness (L value) when the brightness L is continuously measured over a sheet width direction that perpendicularly intersects a rolling direction.
  • L value measured brightness
  • a region where the brightness L is measured is defined as a part other than the removed part.
  • the length in the rolling direction is equally split into ten parts, a brightness difference ⁇ L' in the sheet width direction at a center position of each of the ten sections in the rolling direction is calculated, and the largest numerical value among them is defined as a brightness difference ⁇ L.
  • the length in an axial direction is equally split into ten parts, and brightness L is continuously measured along a circumference at the center positions of the ten sections in the axial direction, thereby calculating the brightness differences ⁇ L'. Then, the largest numerical value among the calculated brightness differences ⁇ L' is defined as a brightness difference ⁇ L.
  • the brightness difference ⁇ L is 5 or less, occurrence of appearance unevenness is not observed in the exterior construction material using it or very slight variations are observed, which is not problematic.
  • the brightness difference ⁇ L is more than 5, it is extremely difficult to stably prevent occurrence of appearance unevenness even if various kinds of processing such as temper rolling, dull rolling, embossing rolling, and polishing is performed.
  • the austenitic stainless steel according to the present embodiment may have various shapes such as a thin sheet, a thick plate, a wire, and a bar material.
  • the austenitic stainless steel according to the present embodiment has been described hitherto.
  • a method for manufacturing the austenitic stainless steel sheet according to the present embodiment is not particularly limited, for example, it is possible to manufacture the austenitic stainless steel sheet by the following method.
  • an example of the method for manufacturing the austenitic stainless steel according to the present embodiment will be described.
  • the manufacturing method of the austenitic stainless steel according to the present embodiment includes: a steel manufacturing step; a hot rolling step; an annealing step after the hot rolling; a hot rolled sheet acid pickling step; a cold rolling step; an annealing step after the cold rolling; and an finishing acid pickling step.
  • Manufacturing conditions for the steps other than the finishing acid pickling step are not particularly limited, and known methods can be applied.
  • the acid pickling solution contains: either one or both of a sulfuric acid with a concentration of 10 to 200 g/L and a hydrochloric acid with a concentration of 5 to 150 g/L; one or two or more selected from a hydrofluoric acid with a concentration of 40 g/L or less, a fluorosilicic acid with a concentration of 40 g/L or less, and sodium fluoride with a concentration of 40 g/L or less, the total of which being 1 g/L or more in terms of F converted amount; and ozone with a dissolved ozone concentration of 0.5 to 2.0 mg/L, with a remainder being water.
  • the acid pickling solution contains either one or both of a sulfuric acid with a concentration of 10 to 200 g/L and a hydrochloric acid with a concentration of 5 to 150 g/L.
  • the concentration of the sulfuric acid is 10 g/L or more.
  • the concentration of the sulfuric acid is preferably 20 g/L or more and is more preferably 50 g/L or more.
  • the concentration of the sulfuric acid is more than 200 g/L, then erosion due to the acid is severe, and the surface nature of the stainless steel after the acid pickling deteriorates.
  • the concentration of the sulfuric acid is 200 g/L or less.
  • the concentration of the sulfuric acid is preferably 150 g/L or less and is more preferably 100 g/L or less.
  • the concentration of the hydrochloric acid is 5 g/L or more.
  • the concentration of the hydrochloric acid is preferably 10 g/L or more and is more preferably 50 g/L or more.
  • the hydrochloric acid concentration is more than 150 g/L, erosion due to the acid is severe, and the surface nature of the stainless steel after acid pickling deteriorates.
  • the concentration of the hydrochloric acid is 150 g/L or less.
  • the concentration of the hydrochloric acid is preferably 120 g/L or less and is more preferably 100 g/L or less.
  • one or two or more selected from a hydrofluoric acid with a concentration of 40 g/L or less, a fluorosilicic acid with a concentration of 40 g/L or less, and sodium fluoride with a concentration of 40 g/L or less are contained such that the total F converted amount thereof is 1 g/L or more.
  • the concentration of the hydrofluoric acid, the fluorosilicic acid, or the sodium fluoride contained in the acid pickling solution is less than 1 g/L in terms of the total F converted amount, it takes a long time to remove scale from the surface of the stainless material. Therefore, in the case where one or two or more selected from the hydrofluoric acid, the fluorosilicic acid, and the sodium fluoride are contained, the concentration of the contained compounds is 1 g/L or more in terms of the total F converted amount. The concentration thereof is preferably 5 g/L or more and is more preferably 10 g/L or more in terms of the total F converted amount.
  • each concentration of the hydrofluoric acid, the fluorosilicic acid, and the sodium fluoride contained in the acid pickling solution is more than 40 g/L, the effect of removing scale is saturated, which leads to an increase in manufacturing cost. Therefore, each concentration of the hydrofluoric acid, the fluorosilicic acid, and the sodium fluoride contained in the acid pickling solution is 40 g/L or less.
  • the concentration is preferably 30 g/L or less and is more preferably 20 g/L or less.
  • the acid pickling solution contains ozone with a dissolved ozone concentration of 0.5 to 2.0 mg.
  • Ozone is an oxidizing agent and uniformly whitens the surface of the austenitic stainless steel after the acid pickling. If the concentration of dissolved ozone is less than 0.5 mg/L, the surface of the austenitic stainless steel after the acid pickling is not uniformly whitened. Therefore, the concentration of dissolved ozone is 0.5 mg/L or more.
  • the concentration of dissolved ozone is preferably 0.8 mg/L or more and is more preferably 1.0 mg/L or more. On the other hand, if the concentration of dissolved ozone is more than 2.0 mg/L, the whitening effect is saturated. Therefore, the concentration of dissolved ozone is 2.0 mg/L or less.
  • the concentration of dissolved ozone is preferably 1.8 mg/L or less and is more preferably 1.5 mg/L or less.
  • the method for adjusting the concentration of dissolved ozone in the acid pickling solution is not particularly limited, and it is only necessary to adjust the concentration of dissolved ozone by causing ozone gas to pass through the acid pickling solution from the lower side.
  • a commercially available dissolved ozone meter for example, may be used to measure the concentration of dissolved ozone.
  • the time for immersion in the acid pickling solution is 10 seconds or more. If the acid pickling time is less than 10 seconds, the surface of the austenitic stainless steel after the acid pickling is not uniformly whitened. In the case where the acid pickling time is excessively long, dissolution of the steel material component leads to degradation of the acid pickling solution, and the acid pickling time is thus preferably 60 seconds or less and is more preferably 20 seconds or less.
  • the acid pickling solution preferably does not contain a nitric acid solution.
  • the austenitic stainless steel obtained through the finishing acid pickling step has a brightness difference ⁇ L of 5 or less and is aesthetic with no appearance unevenness observed therefrom. Moreover, the austenitic stainless steel obtained through the finishing acid pickling step has the aforementioned chemical components and thus has high corrosion resistance.
  • the brightness difference ⁇ L was calculated by the following method.
  • the length of the manufactured stainless steel sheet in the rolling direction was equally split into ten parts, a brightness difference ⁇ L' in the sheet width direction was calculated at the center position of each of the ten sections in the rolling direction, and a maximum value among the calculated brightness differences ⁇ L' was defined as the brightness difference ⁇ L.
  • Brightness L necessary to calculate the brightness difference ⁇ L was measured by a method in accordance with JIS Z 8730: 2009. Also, a measurement interval for the brightness L was set to 10 mm.
  • evaluation was made by the following methods as appearance evaluation.
  • the surface of the stainless steel sheet was masked such that a 50 mm square was exposed, and whether streaky appearance unevenness were observed in the 50 mm square was visually observed. Cases in which variations were observed were evaluated with a point 1, and cases in which no variations were observed were evaluated with a point 0.
  • the aforementioned evaluation was performed at ten locations on the surface of the stainless steel sheet, and evaluation was performed using the total points (0 to 10). If the total point was 3 or less, the appearance was evaluated to be aesthetic enough for practical use.
  • Example 1 100 50 Hydrofluoric acid 20 Ozone 1.0 20 2.09 0
  • Example 2 100 50 Hydrofluoric acid 20 Ozone 1.0 20 3.69 0
  • Example 3 100 50 Hydrofluoric acid 20 Ozone 1.0 20 3.42 0
  • Example 4 100 50 Hydrofluoric acid 20 Ozone 1.0 20 3.03 0
  • Example 5 100 50 Hydrofluoric acid 20 Ozone 1.0 20 3.28 0
  • Example 6 100 50 Hydrofluoric acid 20 Ozone 1.0 20 3.98 0
  • Example 7 100 50 Hydrofluoric acid 20 Ozone 1.0 20 2.97 0
  • Example 8 100 50 Hydrofluoric acid 20 Ozone 1.0 20 3.09 0
  • Example 9 100 50 Hydrofluoric acid 20 Ozone 1.0 20 2.55 0
  • Example 10 100 50 Hydrofluoric acid 20 Ozone 1.0 20 2.55 0
  • Example 10 100 50 Hydrofluoric acid 20 Ozone 1.0 20 2.55 0
  • Example 10 100 50 Hydrofluoric acid 20 Ozone 1.0 20 2.55 0
  • Example 10
  • Example 44 100 150 Hydrofluoric acid 20 Ozone 1.0 20 2.29 0
  • Example 45 100 8 Hydrofluoric acid 20 Ozone 1.0 20 4.22 2 Comparative Example 2 100 2 Hydrofluoric acid 20 Ozone 1.0 20 5.39 7
  • Example 46 100 50 Fluorosilicic acid 20 Ozone 1.0 20 3.09 0
  • Example 47 100 50 Sodium fluoride 20 Ozone 1.0 20 3.12 0
  • Example 48 100 50 Hydrofluoric acid + fluorosilicic acid 20 Ozone 1.0 20 2.99 0
  • Example 49 100 50 Hydrofluoric acid + sodium fluoride 20 Ozone 1.0 20 3.01 0
  • Example 50 100 50 Hydrofluoric acid 40 Ozone 1.0 20 2.01 0
  • Example 51 100 50 Hydrofluoric acid 1 O
  • each obtained steel sheet was substantially the same as the chemical composition of the material of each stainless steel. Also, the stainless steel sheets (invention examples) according to the present embodiments had aesthetic appearance as shown in Tables 1D to 1F.
  • the austenitic stainless steel according to the present embodiment is suitably applied to construction materials for roofs, exteriors, and the like that require aesthetic appearance.
EP21778892.6A 2020-03-30 2021-03-16 Acier inoxydable austénitique Pending EP4130322A1 (fr)

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