WO2022049796A1 - Tôle d'acier inoxydable austénitique et procédé de production de ladite tôle - Google Patents

Tôle d'acier inoxydable austénitique et procédé de production de ladite tôle Download PDF

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WO2022049796A1
WO2022049796A1 PCT/JP2021/000471 JP2021000471W WO2022049796A1 WO 2022049796 A1 WO2022049796 A1 WO 2022049796A1 JP 2021000471 W JP2021000471 W JP 2021000471W WO 2022049796 A1 WO2022049796 A1 WO 2022049796A1
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steel sheet
cold rolling
less
stainless steel
heat treatment
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PCT/JP2021/000471
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English (en)
Japanese (ja)
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栄司 土屋
雄太 松村
遼介 小川
修平 蛭田
裕樹 太田
悠太 児玉
正太 廣瀬
愛 ダイアナ 内野
浩志 和田
邦彦 小久保
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株式会社特殊金属エクセル
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Priority to CN202180008100.7A priority Critical patent/CN114901851B/zh
Priority to JP2021571373A priority patent/JP7210780B2/ja
Publication of WO2022049796A1 publication Critical patent/WO2022049796A1/fr

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    • 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
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • 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
    • C22C38/18—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
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F1/00—Electrolytic cleaning, degreasing, pickling or descaling
    • C25F1/02—Pickling; Descaling
    • C25F1/04—Pickling; Descaling in solution
    • C25F1/06—Iron or steel

Definitions

  • the present invention relates to an austenitic stainless steel sheet suitable for automobile parts, electronic devices, springs, and other industrial parts and a manufacturing method thereof, and relates to improvement of corrosion resistance, particularly pitting corrosion resistance.
  • Patent Document 1 describes "a method for producing a ferritic stainless steel for electrical materials having excellent ductility, wear resistance and rust resistance".
  • a method for producing a ferritic stainless steel for electrical materials having excellent ductility, wear resistance and rust resistance In the technique described in Patent Document 1, after finish annealing, cold rolling of 10% or more is performed, reheat treatment is performed, and then nitrate electrolysis in, for example, 10% nitric acid (20 ° C.) is performed on the surface. By removing the scale, it is possible to produce ferritic stainless steel having excellent ductility, wear resistance, and rust resistance without deteriorating corrosion resistance.
  • Patent Document 2 describes "a method for producing a ferritic stainless steel brightly annealed material having excellent rust resistance".
  • a ferritic stainless steel sheet is annealed, descaled using a neutral salt electrolysis method and a nitrate electrolysis method, then cold-rolled, and further annealed by brilliance.
  • the nitric acid electrolysis method was alternately electrolyzed in 15% nitric acid (50 ° C).
  • Patent Document 3 describes "a method for manufacturing stainless steel having good corrosion resistance".
  • an acidic aqueous solution containing an oxidizing agent is used for stainless steel containing Cr: 11 wt% or more and 35 wt% or less, O: 0.01 wt% or less, and S: 0.01 wt% or less. It is said that stainless steel with improved corrosion resistance can be obtained by mechanically polishing using the above as a polishing liquid.
  • lapping polishing and belt polishing are used as mechanical polishing.
  • austenitic stainless steel sheets usually have improved mechanical properties by cold rolling after heat treatment, and have some degree of pitting corrosion resistance.
  • pitting corrosion is likely to occur in an environment containing chloride ions, a gap structure, and an environment such as high temperature and high humidity. Therefore, in such an environment, steel grades with increased Cr and Mo (SUS316L, etc.) are often used.
  • steel grades with increased Cr and Mo SUS316L, etc.
  • Patent Document 1 and Patent Document 2 relate to improving the corrosion resistance of ferritic stainless steel sheets, and Patent Documents 1 and 2 do not describe austenitic stainless steel sheets.
  • Patent Document 3 The technique described in Patent Document 3 is also applied to austenitic stainless steel plates, but in order to improve corrosion resistance, it is a requirement to perform mechanical polishing such as wrapping polishing using an acidic aqueous solution.
  • mechanical polishing such as wrapping polishing using an acidic aqueous solution.
  • the mechanical properties may change when the surface layer is polished, and there is a concern that the corrosion resistance may deteriorate due to the polishing of the surface layer. Further, there is a problem that wrapping polishing cannot deal with products that regulate the roughness of the surface layer.
  • the present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide an austenitic stainless steel sheet having excellent corrosion resistance, particularly pitting corrosion resistance, and a method for producing the same.
  • the present inventors have diligently studied various factors affecting the pitting corrosion resistance of austenitic stainless steel sheets in order to achieve the above-mentioned object.
  • the final cold-rolled cold-rolled steel sheet is manufactured by cold-rolling once or a plurality of times.
  • pore erosion occurs on the surface of the steel sheet by subjecting it to dilute nitrate electrolytic treatment under appropriate conditions. It was found that the rolling-rolling resistance is improved even in an environment where the potential becomes high and cannot be dealt with in the past.
  • the obtained cold-rolled steel sheet was further subjected to dilute nitrate electrolysis treatment, and then the pitting corrosion potential Vc on the surface of each steel sheet was measured in accordance with JIS G0577 without polishing the surface layer.
  • the test solution sodium chloride aqueous solution
  • the reference electrode was an Ag / AgCl (silver chloride) electrode.
  • dilute nitric acid electrolysis treatment was not performed on some steel sheets.
  • the pitting corrosion potential Vc on the surface of the stainless steel sheet becomes higher than the above A value, it is considered that the pitting corrosion resistance is improved.
  • the steel sheet having a pitting corrosion index of less than 15.0 no increase in the pitting corrosion potential was observed beyond the above A value even when the dilute nitric acid electrolysis treatment and the heat treatment were combined. Therefore, the range of X is limited to 15.0 to 50.0.
  • Austenitic stainless steel sheet characterized by satisfying.
  • Ti 0.01 to 1.00%
  • Nb 0.01 to 1.00%
  • Cu 0.01 to 3.00%
  • Al 0.0001 to 1.50%
  • Ca 0.001 to 0.01%
  • Mg. 0.01 to 0.01%
  • V 0.01 to 1.00%
  • Co 0.01 to 0.5%
  • W 0.01 to 1.0%
  • B 0.001 to 0.01%%
  • the dilute nitric acid electrolysis treatment is performed in a dilute nitric acid aqueous solution having a nitric acid concentration of 3 to 10% and a temperature of 40 to 80 ° C., a current density of ⁇ 10 to 80 mA / cm 2 , and a total of cathode and anode electrolysis.
  • the potential for pitting corrosion on the surface is increased, and a stainless steel sheet having excellent pitting corrosion resistance can be obtained, which is extremely effective in industry.
  • a steel sheet having a low pitting corrosion index can be applied even in a corrosive environment that could not be dealt with in the past, and a steel sheet having a high pitting corrosion index causes pitting corrosion.
  • the potential exceeds 1000 mV and corrosion resistance comparable to that of nickel-based superalloys such as Hastelloy can be obtained.
  • the same effect can be obtained not only with austenitic stainless steel sheets but also with precipitation hardening stainless steel sheets and duplex stainless steel sheets specified in JIS G4305.
  • the present invention is an austenitic stainless steel sheet, in mass%.
  • C 0.40% or less
  • Si 1.00% or less
  • Mn 2.00% or less
  • P 0.045% or less
  • S 0.030% or less
  • Cr 15.00 to 30.00%
  • Mo 0 to 7.0%
  • the mass% related to the composition is simply expressed as%.
  • C 0.40% or less
  • C is an element that improves mechanical properties such as strength and wear resistance by containing a small amount. In order to obtain such an effect, it is preferably contained in an amount of 0.001% or more. On the other hand, if the content exceeds 0.40%, Cr carbides are likely to be generated at the grain boundaries, which tends to cause intergranular corrosion. Further, if it is contained in excess of 0.40%, the ductility is lowered and the press workability is impaired. Therefore, C was limited to 0.40% or less. It is preferably 0.01 to 0.20%.
  • Si 1.00% or less
  • Si is an element that acts as a deoxidizing agent for molten steel and contributes to an increase in strength such as elastic limit and tensile strength.
  • it is preferable that Si is contained in an amount of 0.10% or more.
  • Si if it is contained in excess of 1.00%, ear cracks occur during hot rolling and the product yield is lowered. Therefore, Si was limited to 1.00% or less.
  • Mn 2.00% or less
  • Mn is an element that contributes to increasing strength such as tensile strength and improving toughness, and also effectively acts on deoxidation of molten steel. In order to obtain such an effect, it is preferably contained in an amount of 0.10% or more. On the other hand, if the content exceeds 2.00%, inclusions such as MnS increase in the steel and adversely affect workability, so Mn is limited to 2.00% or less.
  • P: 0.045% or less, S: 0.030% or less P and S are elements that are inevitably present in steel and adversely affect the mechanical properties. Therefore, it is desirable to reduce P and S as much as possible, but if P is contained up to 0.045% and S is contained up to 0.030%, there is no practical problem and it is acceptable. Therefore, it was limited to P: 0.045% or less and S: 0.030% or less. It should be noted that P: 0.030% or less and S: 0.010% or less are preferable.
  • Ni 3.5-36.0%
  • Ni is an element that contributes to the improvement of corrosion resistance, toughness, strength, and heat resistance. In order to obtain such an effect, the content of 3.5% or more is required. If the content is less than 3.5%, the structure at room temperature becomes a ferrite phase. On the other hand, if it is contained in excess of 36.0%, the workability is lowered and the weldability is also lowered. Therefore, Ni was limited to the range of 3.5 to 36.0%.
  • Cr 15.00-30.00% Cr, together with Ni, contributes to the improvement of corrosion resistance, and together with Ni, makes the structure at room temperature an austenite phase.
  • Cr must be contained in an amount of 15.00% or more.
  • it is contained in excess of 30.00%, the ductility is lowered and the material cost is increased. Therefore, Cr was limited to the range of 15.00 to 30.00%. It is preferably 16.00 to 30.00%.
  • Mo 0-7.0%
  • Mo is an element that contributes to the improvement of pitting corrosion resistance and also to the improvement of mechanical properties, and contains 0%, and can be contained as needed. When it is contained in order to obtain such an effect, it is preferably contained in an amount of 0.001% or more. If the Mo content is less than 0.001%, the mechanical properties will be slightly reduced. On the other hand, if the content exceeds 7.0%, the precipitation of the ⁇ phase is promoted and the toughness is lowered during the heat treatment. In addition, the inclusion of a large amount causes an increase in material cost. Therefore, when it is contained, Mo is limited to 7.0% or less. It is preferably 0.5 to 3.0%.
  • N 0.25% or less
  • N is an element that stabilizes the austenite phase and at the same time, dissolves in an intrusive form and contributes to an increase in strength by strengthening the solid solution. In order to obtain such an effect, it is preferably contained in an amount of 0.01% or more. On the other hand, if it is contained in excess of 0.25%, it has adverse effects such as promotion of high temperature cracking, deterioration of secondary workability, and promotion of intergranular corrosion. Therefore, N was limited to 0.25% or less. It is preferably 0.20% or less, and more preferably 0.01 to 0.10%.
  • Cr, Mo content of each element (mass%)
  • X is limited to the range of 15.0 to 50.0.
  • the above-mentioned components are the basic components, but in the present invention, in addition to the above-mentioned basic components, as a selective element, Ti: 0.01 to 1.00%, Nb: 0.01 to 1.00%, Cu: as required. 0.01 to 3.00%, Al: 0.0001 to 1.50%, Ca: 0.001 to 0.01%, Mg: 0.001 to 0.01%, V: 0.01 to 1.00%, Co: 0.01 to 0.5%, W: 0.01 to 1.0%, B: 0.001 It may contain one or more selected from ⁇ 0.01%.
  • Ti 0.01 to 1.00%, Nb: 0.01 to 1.00%, Cu: 0.01 to 3.00%, Al: 0.0001 to 1.50%, Ca: 0.001 to 0.01%, Mg: 0.001 to 0.01%, V: 0.01 to 1.00%, Co : 0.01 to 0.5%, W: 0.01 to 1.0%, B: One or more selected from 0.001 to 0.01% Ti, Nb, Cu, Al, Ca, Mg, V, Co, W, B are elements that contribute to increasing the strength and corrosion resistance of steel sheets by dispersing them as fine precipitates in steel, and B is effective in improving high temperature characteristics, so select as necessary. It can contain one kind or two or more kinds.
  • the rest other than the above components consist of Fe and unavoidable impurities.
  • O (oxygen) is inevitably contained and exists as an oxide in steel, which adversely affects the ductility, toughness, etc. Therefore, it is preferable to reduce O (oxygen) as an impurity as much as possible, but up to 0.010% is acceptable. It is preferable that O (oxygen) is 0.001% or more because an excessive reduction of less than 0.001% raises the refining cost.
  • X Cr + 3.3Mo ...... (2)
  • X 15.0-50.0
  • Cr, Mo Content of each element (mass%)
  • the pitting corrosion potential Vc on the surface of the steel sheet shall be a value measured in accordance with JIS G 0577 using a sample without polishing the surface layer.
  • the test solution sodium chloride aqueous solution
  • the reference electrode is an Ag / AgCl (silver chloride) electrode.
  • a hot-rolled steel sheet having the above-mentioned composition and having been annealed and pickled is subjected to cold rolling once or a plurality of times to obtain a cold-rolled steel sheet having a predetermined plate thickness.
  • the heat treatment is performed after the final cold rolling in the plurality of cold rollings or after the cold rolling other than the final in the plurality of cold rollings.
  • the above-mentioned heat treatment is preferably a heat treatment (hereinafter, also referred to as heat treatment A) in which the temperature is maintained in the range of 150 to 600 ° C. for 30 s to 10 min for the purpose of recovering and improving the mechanical properties. If the heat treatment temperature is less than 150 ° C, the recovery of mechanical properties is insufficient, while if it exceeds 600 ° C, the growth of the nitrided layer and the Cr-deficient layer is large, and in order to remove them in the subsequent electrolytic treatment, electrolysis is performed. It is necessary to increase the acid concentration of the treatment liquid and increase the amount of electricity. When such an electrolytic treatment is performed, the surface skin is significantly changed. Therefore, in the heat treatment A, the holding time in the above temperature range is preferably limited to the range of 30 s to 10 min.
  • a heat treatment (hereinafter, also referred to as heat treatment B) in which the temperature is maintained in the range of 150 to 700 ° C. for 15 min to 48 hours may be used for the purpose of recrystallization or reverse transformation. If the heat treatment temperature is less than 150 ° C, recrystallization is insufficient, while if it exceeds 700 ° C, the Cr-deficient layer grows large. Cannot be secured. Therefore, the heat treatment temperature is preferably limited to a temperature in the range of 150 to 700 ° C. Further, if the holding time in the above temperature range is less than 15 min, recrystallization is insufficient, while if it is longer than 48 hr, the Cr-deficient layer grows significantly. Therefore, in the heat treatment B, the holding time in the above temperature range is preferably limited to the range of 15 min to 48 hr.
  • the burning atmosphere is not particularly limited in the present invention, and may be performed in an atmosphere containing, for example, an inert gas atmosphere, combustion gas, oxygen, etc., in addition to the atmospheric atmosphere. Further, the annealing may be performed by bright annealing (sometimes referred to as BA annealing) in a reducing atmosphere containing hydrogen.
  • bright annealing sometimes referred to as BA annealing
  • dilute nitric acid electrolysis treatment is performed as the final step.
  • nitric acid electrolysis treatment in a dilute nitric acid aqueous solution with a nitric acid concentration of 3 to 10% and a temperature of 40 to 80 ° C, a current density of ⁇ 10 to 80 mA / cm 2 and a total of 10 to 60 s for cathode and anode electrolysis. It is preferable to carry out the treatment.
  • the nitric acid concentration of the dilute nitric acid aqueous solution was limited to 3 to 10%.
  • the nitric acid concentration is in the range of 3 to 10%, there is little change in the dissolution amount and there is almost no change in the surface roughness, but it is formed on the surface layer as the nitric acid concentration increases. The passivation film is strengthened and the pitting potential rises.
  • the temperature of the dilute nitric acid aqueous solution is less than 40 ° C.
  • the effect of dilute nitric acid electrolysis is insufficient under the combination of the heat treatment conditions and the dilute nitric acid electrolysis in the present invention, while when the temperature exceeds 80 ° C., the melting of the surface layer of the steel sheet becomes remarkable. .. Therefore, the temperature of the dilute nitric acid aqueous solution was limited to the range of 40 to 80 ° C.
  • the current density is less than 10 mA / cm 2
  • the effect of dilute nitric acid electrolysis is insufficient, while when it is larger than 80 mA / cm 2 , the dissolution of the surface layer becomes too large.
  • the current density was limited to the range of 10 to 80 mA / cm 2 . Further, if the total electrolysis time is less than 10 s, the effect of dilute nitric acid electrolysis is insufficient, while if it is longer than 60 s, the amount of dissolution becomes too large. Therefore, the electrolysis time was limited to the range of 10 to 60 s in total for cathode and anode electrolysis. In the dilute nitric acid electrolysis treatment, from the viewpoint of removing the surface layer, the order of cathode electrolysis and anodic electrolysis may be changed, and the effect is the same even if cathode electrolysis and anodic electrolysis are repeated.
  • the surface roughness Sa is 0.80 ⁇ m or less. If the surface roughness Sa exceeds 0.80 ⁇ m and becomes rough, it is not possible to obtain a glossy surface surface. In the present invention, the surface roughness is 0.80 ⁇ m or less in Sa.
  • the arithmetic mean height Sa measured in accordance with the regulations of ISO 25178 shall be used.
  • Surface roughness is important for products as an index of glossiness, but it also strongly affects corrosion resistance. If the surface roughness exceeds 0.80 ⁇ m in Sa, the corrosion resistance tends to become unstable. From the viewpoint of stabilizing corrosion resistance, it is preferable that the surface roughness is 0.40 ⁇ m or less in terms of Sa. More preferably, Sa is 0.35 ⁇ m or less, and further preferably Sa is 0.30 ⁇ m or less. Further, when stable corrosion resistance is particularly required, it is effective to set the surface roughness to 0.25 ⁇ m or less for Sa, preferably 0.20 ⁇ m or less for Sa, and more preferably 0.15 ⁇ m or less for Sa. be.
  • the dilute nitric acid electrolysis treatment is performed as the final step, and as shown in FIG. 1, after the dilute nitric acid electrolysis treatment as compared with the case before the dilute nitric acid electrolysis treatment (marked with ⁇ ).
  • the pitting corrosion potential Vc (marked with ⁇ ) is improved, and the pitting corrosion resistance is further improved.
  • Cr has a strong affinity for gas components such as O (oxygen) and N. Therefore, it is considered that Cr is concentrated in the vicinity of the surface in contact with the atmospheric gas during the heat treatment. It is considered that the concentrated Cr binds to O, N, C invading from the atmosphere or O, N, C existing in the steel to form a Cr precipitate.
  • solid solution Cr amount the amount of Cr dissolved in the matrix
  • the improvement in corrosion resistance due to Cr is derived from the amount of solid solution Cr, it is considered that a decrease in the amount of solid solution Cr leads to a decrease in the corrosion resistance of the steel sheet itself. Further, when a Cr precipitate is formed, Cr diffuses into the surface layer, so that a Cr-deficient layer is formed inside the Cr precipitate.
  • the thickness of the Cr-deficient layer described above may increase, and the corrosion resistance near the surface of the steel sheet may decrease.
  • the amount of Cr deficiency is smaller and the corrosion resistance is less likely to be impaired as compared with normal annealing (heat treatment) in which heating is performed above 950 ° C. Rather, it is considered that the formation of the C-deficient layer in the vicinity of the surface suppresses the precipitation of Cr carbides and the like inside the outermost surface where the precipitation occurs, and the effective Cr amount (solid solution Cr amount) increases.
  • the layer containing the Cr precipitates formed on the outermost layer is removed by dilute nitrate electrolysis treatment, the amount of Cr precipitates existing inside the layer is small, and the effective Cr amount (solid solution Cr amount) is increased, which is excellent in corrosion resistance. Is exposed, and it is considered that the corrosion resistance of the surface of the steel sheet is improved.
  • the annealing heat treatment
  • the thickness of the Cr-deficient layer becomes even thinner than in the high-temperature region of 700 ° C. or higher, and Cr deficiency occurs.
  • the steel sheet heat-treated in the temperature range of 150 ° C or higher and 700 ° C or lower is more dilute nitric acid electrolyzed than the steel sheet heat-treated in the temperature range of 700 ° C or higher. It is considered that the potential for pitting corrosion after the treatment becomes higher and the pitting corrosion resistance is significantly improved.
  • Cr forms a Cr oxide layer on the outermost layer of the steel sheet, and in the vicinity of the surface, Cr binds to O (oxygen), C, etc., and precipitates as fine Cr oxides, Cr carbides, etc. on the steel sheet side directly below the surface.
  • O oxygen
  • C chemical vapor deposition
  • the effective Cr amount solid solution Cr amount
  • a C-deficient layer in which the C concentration is reduced is formed in the vicinity of the portion where the Cr carbide is formed.
  • the formation of the C-deficient layer increases the effective Cr content in that region. It is considered that if the layer containing the Cr precipitate formed on the outermost surface is removed by the dilute nitric acid electrolysis treatment, the C-deficient layer having improved corrosion resistance is exposed on the surface, and as a result, the corrosion resistance of the steel sheet is improved.
  • the diffusion rate of Cr is further slower than in the high temperature region of 700 ° C. or higher, and the Cr oxide It is considered that the decrease in pitting corrosion resistance (corrosion resistance) due to the formation of the deCr layer is reduced because the formation is smaller. Furthermore, in annealing (heat treatment) at a low temperature of 700 ° C or lower (150 ° C or higher), it is considered that the diffusion of C is slower than in the high temperature region of 700 ° C or higher, and the formation of the C-deficient layer is small. Therefore, it is considered that the effective Cr amount will increase accordingly.
  • Mo also contributes to improving the corrosion resistance (pitting corrosion resistance) of the steel sheet by being in a solid solution state. That is, the corrosion resistance (pitting corrosion resistance) of the steel sheet is improved by increasing the effective Mo amount (solid solution Mo amount).
  • Mo also easily binds to C like Cr, so if gasification of C in steel occurs near the surface during heat treatment, C will decrease and the amount of effective Mo near the surface will increase. Become. Since this increase in the effective Mo content increases as the Mo content increases, it is considered that the steel sheet having a higher Mo content has a greater effect of improving the pitting corrosion resistance.
  • the Cr-deficient layer is reduced and the effective Cr amount is increased as compared with the case of the high temperature region of 700 ° C. or higher.
  • the pitting corrosion potential after dilute nitrate electrolysis will be higher than that of heat treatment in the high temperature range of over 700 °C. Conceivable.
  • a healthy passivation film having excellent corrosion resistance is formed by performing a post-heat treatment at 150 ° C. or lower in an oxygen-enriched atmosphere, and corrosion resistance and pitting corrosion resistance are formed. Eating habits can be improved. Further, the formation of a passivation film can be promoted by immersing in a nitric acid solution. It is also effective to immerse in an oxidizing acid for the purpose of promoting the formation and growth of a passivation film.
  • the corrosion resistance of the matrix should be improved, specifically, the precipitation of carbides should be suppressed, the amount of Cr that works effectively for corrosion resistance should be increased, and the film should be formed during heat treatment. It is effective to remove the coarse oxide film and the dechromium layer that may be formed immediately under the oxide film, and to make the metal surface on which the passivation film is formed smooth.
  • the electrolytic solution is not limited to dilute nitric acid, and may be a treatment using non-oxidizing sulfuric acid, hydrochloric acid or the like.
  • Example 1 The annealed and pickled hot-rolled steel sheet (plate thickness: 2.5 mm) having the composition shown in Table 1 was cold-rolled three times to obtain a cold-rolled steel sheet having a plate thickness of 0.1 mm.
  • heat treatment A was performed mainly for the purpose of recovering and improving the mechanical properties shown in Table 2.
  • the heat treatments shown in Table 2 were performed respectively.
  • Some steel sheets were not heat-treated after the final cold rolling, but were subjected to the heat treatment shown in Table 2 (heat treatment for the purpose of restoring and improving mechanical properties) after the non-final cold rolling.
  • the obtained cold-rolled steel sheet was further subjected to dilute nitrate electrolysis treatment, and then the pitting corrosion potential Vc on the surface of each steel sheet was measured using a sample not polished, in accordance with the provisions of JIS G 0577.
  • the test solution sodium chloride aqueous solution
  • the reference electrode was an Ag / AgCl (silver chloride) electrode.
  • dilute nitric acid electrolysis treatment was not performed on some steel sheets.
  • the conditions for the dilute nitric acid electrolysis treatment were a dilute nitric acid concentration of 3% (liquid temperature: 60 ° C.), a current density of ⁇ 30 mA / cm 2 , and anode / cathode electrolysis for a total of 20 seconds.
  • the electrolysis was performed in the order of the anode and the cathode on the steel plate side.
  • the arithmetic mean height Sa was measured for the steel sheet after the dilute nitric acid electrolysis treatment in accordance with the regulations of ISO 25178.
  • the measurement field of view was 1.0 ⁇ m ⁇ 1.0 ⁇ m, and the measurement interval was 25 ⁇ m.
  • the pitting corrosion potential Vc satisfies the equation (1), and the stainless steel sheet has a high pitting corrosion potential, and it is presumed that the stainless steel sheet has excellent pitting corrosion resistance.
  • the pitting corrosion generation potential Vc does not satisfy the equation (1) and the pitting corrosion resistance is low.
  • the steel sheets No. A5 and No. A6 and No. A7 and No. A8 have the same pitting corrosion index X, but the pitting corrosion potential Vc is the steel sheets No. A7 and No. A8 having a high C content. Shows a higher value. Further, the steel sheets No. A18 and No.
  • Example 2 An annealed and pickled hot-rolled steel sheet (plate thickness: 2.5 mm) having the composition shown in Table 1 is cold-rolled three times, and cold-rolled with a plate thickness of 0.1 mm in the same manner as in Example 1. It was made of steel plate. After the final cold rolling, the heat treatment B for the purpose of recrystallization or reverse transformation shown in Table 3 is performed, and after the cold rolling other than the final, the heat treatment for the purpose of softening shown in Table 3 is performed. provided. Some steel sheets were not heat-treated after the final cold rolling, but were subjected to the heat treatment shown in Table 3 (heat treatment for the purpose of recrystallization or reverse transformation) after the cold rolling other than the final.
  • the obtained cold-rolled steel sheet was further subjected to dilute nitric acid electrolysis treatment, and then the pitting corrosion potential Vc on the surface of each steel sheet was measured using a sample not polished.
  • the test solution sodium chloride aqueous solution
  • dilute nitric acid electrolysis treatment was not performed on some steel sheets. The conditions for the dilute nitric acid electrolysis treatment were the same as in Example 1. The results obtained are shown in Table 3.
  • the pitting corrosion potential Vc satisfies the equation (1), and the stainless steel sheet has a high pitting corrosion potential, and it is presumed that the stainless steel sheet has excellent pitting corrosion resistance.
  • the pitting corrosion generation potential Vc does not satisfy the equation (1) and the pitting corrosion resistance is low.
  • the steel sheets No. B5 and No. B6 and No. B7 and No. B8 have the same pitting corrosion index X, but the pitting corrosion potential Vc is the steel sheets No. B7 and No. B8 having a high C content. Shows a higher value. Further, the steel sheets No. B18 and No.
  • Example 3 A hot-rolled steel sheet (plate thickness: 2.5 mm) having the composition of steel No. D shown in Table 1 is cold-rolled twice under the conditions shown in Table 4, and the cold-rolled steel sheet (plate thickness: 0.1 mm) is subjected to cold rolling. And said. Between the first and second cold rolling, heat treatment (1050 ° C ⁇ 5 min, 1000 ° C ⁇ 2 min) was performed for the purpose of softening. After the final cold rolling, heat treatment A (500 ° C. ⁇ 2 min) was performed for the purpose of recovering mechanical properties, and further, dilute nitric acid electrolysis treatment was performed under the conditions shown in Table 4.
  • the pitting corrosion potential Vc on the surface of each steel sheet was measured in the same manner as in Example 1.
  • the surface roughness (arithmetic mean height) Sa was measured for the surface roughness of the steel sheet in accordance with the ISO 25178 regulations.
  • the pitting corrosion generation potential Vc satisfies the equation (1) and is a stainless steel plate having a high pitting corrosion generation potential, and it is presumed that the pitting corrosion resistance is excellent. Further, all of the examples of the present invention exhibit excellent surface texture with a surface roughness Sa of 0.80 ⁇ m or less.
  • the comparative example in which the pitting corrosion potential Vc does not satisfy the equation (1) and deviates from the present invention has low pitting corrosion resistance. Further, in the comparative example in which the dilute nitric acid electrolysis treatment conditions are low outside the range of the present invention, it is presumed that the pitting corrosion potential Vc does not satisfy the equation (1) and the pitting corrosion resistance is low.
  • the pitting corrosion potential Vc satisfies the equation (1), but the surface roughness (arithmetic mean height) Sa exceeds 0.80 ⁇ m and becomes rough. It is the surface.
  • the pitting corrosion potential Vc does not satisfy the equation (1).
  • the pitting potential Vc is stably 1000 mV or more.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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  • Heat Treatment Of Sheet Steel (AREA)

Abstract

La présente invention concerne une tôle d'acier inoxydable laminée à froid qui présente une excellente résistance à la corrosion par piqûres.　Selon la présente invention, une tôle d'acier inoxydable laminée à froid est produite par réalisation d'un ou de plusieurs tours de laminage à froid sur une tôle d'acier laminée à chaud ayant une constitution de composition qui comprend, en % en masse, pas plus de 0,40 % de C, pas plus de 1,00 % de Si, pas plus de 2,00 % de Mn, pas plus de 0,045 % de P, pas plus de 0,030 % de S, 3,5 à 36,0 % de Ni, 15,00 à 30,00 % de Cr, 0 à 7,0 % de Mo, et pas plus de 0,25 % de N. Dans le laminage à froid, un traitement thermique est effectué après le cycle final de laminage à froid parmi les cycles de laminage à froid ou après un cycle de laminage à froid à l'exception du cycle final de laminage à froid parmi les cycles de laminage à froid, puis un traitement électrolytique dilué à l'acide nitrique est effectué en dernier lieu. En tant que traitement thermique, un traitement thermique consistant à maintenir la tôle d'acier à une température dans une plage de 150 à 600 °C pendant 30 s à 10 min ou un traitement thermique consistant à maintenir la tôle d'acier à une température dans une plage de 150 à 700 °C pendant 15 min à 48 heures est préférable. En conséquence, un potentiel d'initiation de piqûres sur une surface de la tôle d'acier devient élevé et la résistance à la corrosion par piqûres de celle-ci est améliorée.
PCT/JP2021/000471 2020-09-01 2021-01-08 Tôle d'acier inoxydable austénitique et procédé de production de ladite tôle WO2022049796A1 (fr)

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JPS5877555A (ja) * 1981-11-04 1983-05-10 Nippon Yakin Kogyo Co Ltd 耐孔食性・耐候性に優れるオ−ステナイトステンレス鋼
JPH01162786A (ja) * 1987-12-21 1989-06-27 Kawasaki Steel Corp 高強度オーステナイト系ステンレス鋼の酸洗方法
JPH0474900A (ja) * 1990-07-17 1992-03-10 Kawasaki Steel Corp ステンレス鋼表面の酸化物による被覆方法
JPH04120248A (ja) * 1990-09-11 1992-04-21 Nippon Steel Corp アンテナ用ステンレス鋼
JPH0770730A (ja) * 1993-09-06 1995-03-14 Hitachi Metals Ltd 耐孔食性ステンレス鋼
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JP2016188417A (ja) * 2015-03-30 2016-11-04 新日鐵住金ステンレス株式会社 オーステナイト系ステンレス鋼及びその製造法

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