WO2018043310A1 - フェライト系ステンレス鋼 - Google Patents
フェライト系ステンレス鋼 Download PDFInfo
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- WO2018043310A1 WO2018043310A1 PCT/JP2017/030439 JP2017030439W WO2018043310A1 WO 2018043310 A1 WO2018043310 A1 WO 2018043310A1 JP 2017030439 W JP2017030439 W JP 2017030439W WO 2018043310 A1 WO2018043310 A1 WO 2018043310A1
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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
- C22C38/18—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
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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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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- 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
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- 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
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- 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
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- 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
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- 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
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- 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
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- 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%
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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- 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
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- 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
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- 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
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- 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
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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
- C22C38/18—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
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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
- C22C38/18—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
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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
- C22C38/18—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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2101/00—Articles made by soldering, welding or cutting
- B23K2101/04—Tubular or hollow articles
- B23K2101/14—Heat exchangers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/24—Selection of soldering or welding materials proper
- B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550 degrees C
- B23K35/3053—Fe as the principal constituent
- B23K35/308—Fe as the principal constituent with Cr as next major constituent
- B23K35/3086—Fe as the principal constituent with Cr as next major constituent containing Ni or Mn
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working
Definitions
- the present invention relates to a ferritic stainless steel used in an automobile exhaust gas condensate environment. More specifically, the present invention relates to a ferritic stainless steel used in an exhaust gas recirculation device such as an exhaust heat recovery unit or an EGR (Exhaust Gas Recirculation) cooler.
- an exhaust gas recirculation device such as an exhaust heat recovery unit or an EGR (Exhaust Gas Recirculation) cooler.
- the exhaust heat recovery device is a device that recovers and reuses the heat of exhaust gas, and is mounted mainly on hybrid vehicles.
- the heat of the exhaust gas is transmitted to the engine cooling water through the heat exchanger, so that the engine warm-up is promoted and the fuel consumption and the heating performance are improved.
- the EGR cooler is a device for recirculating exhaust gas.
- high-temperature exhaust gas on the exhaust side is cooled by a heat exchanger, and the cooled exhaust gas is re-intaken to lower the combustion temperature of the engine, thereby suppressing NOx generation.
- ⁇ Condensate is generated in the heat exchange part of such an exhaust heat recovery unit or EGR cooler, and is exposed to a severe corrosive environment.
- exhaust gas and cooling water are in contact with each other through stainless steel, and if perforation occurs due to corrosion, it leads to leakage of cooling water, so high resistance to condensed water corrosion is required.
- Patent Document 1 discloses an austenitic stainless steel for an EGR cooler and an exhaust heat recovery device in the case of using a fuel having a high S concentration and insufficient purification.
- austenitic stainless steel is expensive because it contains a large amount of Ni, as well as fatigue characteristics in environments where it is restrained by intense vibrations at high temperatures, such as parts around exhaust manifolds, and heat at high temperatures. There was a problem in that the fatigue characteristics were low.
- Patent Document 2 discloses an automobile exhaust heat recovery device configured using ferritic stainless steel as a material.
- Mo molecular weight
- crevice corrosion resistance in an exhaust gas condensation-evaporation environment are secured.
- brazing joining is applied to the joining of the above-mentioned EGR cooler such as a heat exchange part, and these members are required not only to improve the resistance to condensed water corrosion but also to have excellent brazing ability. It has been.
- Patent Document 3 discloses EGR cooler ferritic stainless steel.
- Cu to Cr so as to satisfy Cr + 2.3Cu ⁇ 18
- excellent brazing property and corrosion resistance against exhaust gas condensed water are ensured.
- Patent Document 4 discloses a ferritic stainless steel for an exhaust heat recovery device having corrosion resistance against exhaust gas condensate after brazing.
- the cation fraction in the film formed after brazing heat treatment is defined.
- an object of the present invention is to provide a ferritic stainless steel having excellent brazing properties and excellent resistance to condensed water corrosion in an environment used for an exhaust heat recovery device or an EGR cooler.
- excellent brazeability means that 1.2 g of a brazing material BNi-5 (Ni-19Cr-10Si) is applied to one end face of two stacked steel plates, and a vacuum atmosphere of 10 ⁇ 2 Pa, After the brazing treatment is performed under a heating condition of 1170 ° C. ⁇ 600 s, it indicates that the penetration of the brazing material is 50% or more of the overlapping length of the two plates.
- Excellent corrosion resistance to condensed water means that the test piece is fully immersed in a 200 ppm Cl ⁇ +600 ppm SO 4 2- solution at pH 8.0, maintained at 80 ° C., immersed for 24 hours in an evaporation test, and in a furnace at 250 ° C. After 24 cycles of heating and holding for 4 hours (hereinafter also referred to as a condensed water corrosion test), the maximum corrosion depth is less than 100 ⁇ m.
- the present inventors have conducted the above-mentioned condensed water corrosion test and found that excellent condensed water corrosion resistance can be obtained by adding an appropriate amount of Si in addition to Cr, Mo, Ni, C, and N. Furthermore, it discovered that brazing property was securable by adjusting Al content.
- the gist of the present invention aimed at solving the above problems is as follows.
- a ferritic stainless steel characterized in that the balance has a composition comprising Fe and inevitable impurities.
- a ferrite system having excellent brazing resistance and excellent condensate corrosion resistance when used for automobile parts exposed to a condensate corrosive environment such as an exhaust heat recovery unit or an EGR cooler.
- Stainless steel can be provided.
- the exhaust gas side of the heat exchange part of the exhaust heat recovery unit or EGR cooler is in an environment where the exhaust gas is repeatedly condensed and evaporated as in the case of a conventional muffler.
- the produced condensed water is heated by the exhaust gas, and moisture is evaporated, and ionic species are concentrated and pH is lowered to promote corrosion of stainless steel.
- exhaust gas has been diversified with the diversification of fuels. Corrosion environment such as increase of chloride ion and sulfate ion that greatly affect corrosion resistance, pH change from neutral to weak acid, etc. Is expected to be harsh.
- the corrosion form of the condensed water corrosion is pitting corrosion.
- the resistance to condensed water corrosion is improved by suppressing the occurrence of pitting corrosion, reducing the growth rate of pitting corrosion, and stopping the growth of pitting corrosion.
- the suppression effect is reinforce
- the growth rate of the second pitting corrosion is reduced by containing an appropriate amount of Ni.
- the growth is stopped more effectively by adding appropriate amounts of Si and Ni in addition to the inclusion of Cr and Mo.
- brazability can be secured by adjusting the Al content.
- the ferritic stainless steel of the present invention is, in mass%, C: 0.025% or less, Si: 0.40 to 2.0%, Mn: 0.05 to 1.5%, P : 0.05% or less, S: 0.01% or less, Cr: 16.0-30.0%, Mo: 0.60-3.0%, Ni: 0.10-2.5%, Nb: 0.20 to 0.80%, Al: 0.001 to 0.15%, N: 0.025% or less, and satisfying the following formulas (1) and (2), the balance being Fe
- it has a composition consisting of inevitable impurities, has excellent brazing properties, and has excellent resistance to resistance when used for automobile parts exposed to a condensed water corrosive environment such as an exhaust heat recovery unit or an EGR cooler. Condensed water corrosive.
- 2Si + Ni ⁇ 1.0% (2) (C, N, Si, and Ni in Formula (1) and Formula (2) indicate the content (mass%) of each element.)
- C 0.025% or less C is an element inevitably contained in steel.
- the C content is large, the strength is improved, and when it is low, the workability is improved. In order to improve the strength, it is preferable to contain 0.001% or more of C.
- the C content exceeds 0.025%, the workability is remarkably reduced, and Cr carbide precipitates, and the resistance to condensed water corrosion due to local Cr deficiency is likely to occur. Therefore, the C content is 0.025% or less.
- the C content is preferably 0.020% or less, more preferably 0.015% or less, and still more preferably 0.010% or less. Further, the C content is more preferably 0.003% or more, and further preferably 0.004% or more.
- Si 0.40 to 2.0% Si is an important element for improving the resistance to condensed water corrosion in the present invention.
- the effect is acquired by containing 0.40% or more of Si.
- the Si content is preferably more than 0.60%.
- the Si content is set to 0.40 to 2.0%.
- the Si content is preferably more than 0.60%, more preferably 0.80% or more, and further preferably 1.00% or more.
- Si content becomes like this. Preferably it is 1.80% or less, More preferably, it is 1.60% or less, More preferably, it is 1.40% or less.
- Mn 0.05 to 1.5% Mn has a deoxidizing action, and the effect is obtained with a Mn content of 0.05% or more. However, if Mn exceeds 1.5%, workability is impaired by solid solution strengthening. Further, when Mn is contained in excess of 1.5%, precipitation of MnS which is a starting point of corrosion is promoted, and the resistance to condensed water corrosion is reduced. Therefore, the Mn content is in the range of 0.05 to 1.5%.
- the Mn content is preferably 0.10% or more. Further, the Mn content is preferably 0.50% or less, and more preferably 0.30% or less.
- P 0.05% or less
- P is an element inevitably contained in steel, and the inclusion of P in excess of 0.05% reduces weldability and easily causes intergranular corrosion. Therefore, the P content is limited to 0.05% or less.
- the P content is 0.04% or less. More preferably, the P content is 0.03% or less.
- S 0.01% or less S is an element inevitably contained in steel, and the inclusion of S in excess of 0.01% promotes precipitation of MnS and lowers the resistance to condensed water corrosion. Therefore, the S content is 0.01% or less. Preferably, the S content is 0.008% or less. More preferably, the S content is 0.005% or less.
- Cr 16.0-30.0% Cr is an important element for ensuring the resistance to condensed water corrosion.
- the Cr content is in the range of 16.0 to 30.0%.
- the Cr content is preferably 18.0% or more, more preferably 19.0% or more, and further preferably 20.5% or more.
- Cr content becomes like this.
- it is 24.0% or less, More preferably, it is 23.0% or less, More preferably, it is 22.0% or less.
- Mo 0.60 to 3.0%
- Mo has the effect of stabilizing the passive film of stainless steel and improving the resistance to condensed water corrosion.
- the exhaust heat recovery device and the EGR cooler are effective in preventing internal corrosion due to condensed water and external corrosion due to a snow melting agent. Furthermore, it has an effect of improving thermal fatigue characteristics, and is a particularly suitable element when used for an EGR cooler attached directly under an exhaust manifold. These effects can be obtained with a Mo content of 0.60% or more.
- Mo is an expensive element, the cost increases. Furthermore, if the Mo content exceeds 3.0%, the workability decreases. Therefore, the Mo content is in the range of 0.60 to 3.0%. Mo content becomes like this.
- it is 0.80% or more, More preferably, it is 1.00% or more, More preferably, it is 1.20% or more, More preferably, it is 1.50% or more. Moreover, Mo content becomes like this. Preferably it is 2.50% or less, More preferably, it is 2.00% or less.
- Ni 0.10 to 2.5%
- Ni is an element that effectively contributes to the improvement of the resistance to condensed water corrosion and toughness with a content of 0.10% or more.
- the Ni content exceeds 2.5%, the stress corrosion cracking sensitivity becomes high. Therefore, the Ni content is in the range of 0.10 to 2.5%.
- the Ni content is preferably 0.50% or more, more preferably more than 0.80%, even more preferably 1.00% or more, even more preferably 1.20% or more, Preferably it is 1.50% or more.
- Si content effective for improving the resistance to condensed water corrosion is 0.60% or less, it is desirable to contain Ni in excess of 0.80% in order to ensure the resistance to condensed water corrosion.
- Nb 0.20 to 0.80%
- Nb is an element that suppresses a decrease in resistance to condensed water corrosion due to precipitation of Cr carbonitride by preferentially bonding with C and N. It also has the effect of increasing the high temperature strength and improving thermal fatigue properties. These effects are obtained when the content of Nb is 0.20% or more. On the other hand, if the Nb content exceeds 0.80%, the toughness decreases. Therefore, the Nb content is in the range of 0.20 to 0.80%.
- the Nb content is preferably 0.25% or more.
- Nb content becomes like this. Preferably it is 0.60% or less, More preferably, it is 0.50% or less, More preferably, it is 0.40% or less.
- Al 0.001 to 0.15%
- Al is an element useful for deoxidation, and the effect can be obtained by containing 0.001% or more of Al.
- the Al content is set to 0.001 to 0.15%.
- the Al content is preferably 0.10% or less, more preferably 0.050% or less, still more preferably 0.025% or less, and even more preferably 0.015% or less. Preferably it is 0.010% or less, Most preferably, it is 0.008% or less.
- N 0.025% or less
- N is an element inevitably contained in steel like C, and has the effect of increasing the strength of steel by solid solution strengthening. The effect is acquired by containing N 0.001% or more.
- the N content is 0.025% or less. N content becomes like this. Preferably it is 0.020% or less, More preferably, it is 0.015% or less, More preferably, it is 0.010% or less. Further, the N content is preferably 0.001% or more, more preferably 0.003% or more, and further preferably 0.005% or more.
- C + N 0.030% or less (1)
- C and N in the formula (1) indicate the content (mass%) of each element.
- An excessive content of C and N decreases the resistance to condensed water corrosion and workability. Therefore, C + N (the sum of C content and N content) is set to 0.030% or less after setting each of the C content and the N content within the ranges described above.
- C + N is 0.025% or less. More preferably, C + N is 0.020% or less.
- each of Si and Ni is made a predetermined content in order to improve the resistance to condensed water corrosion. Furthermore, the present inventors have intensively studied and found that when 2Si + Ni (the sum of twice the Si content and Ni content) is less than 1.0%, the desired condensate corrosion resistance cannot be obtained. did. Therefore, in the present invention, the Si content and the Ni content are set in the above-described ranges, and 2Si + Ni is set to 1.0% or more. More preferably, 2Si + Ni is 1.5% or more.
- the balance consists of Fe and inevitable impurities.
- ferritic stainless steel of the present invention can further contain one or more selected from Cu, W, and Co in the following ranges.
- Cu 0.01 to 1.0%
- Cu is an element having an effect of increasing the resistance to condensed water corrosion. The effect is acquired by containing 0.01% or more of Cu.
- the Cu content exceeds 1.0%, the hot workability may decrease. Therefore, when Cu is contained, the Cu content is preferably in the range of 0.01 to 1.0%.
- the Cu content is more preferably 0.05% or more. Further, the Cu content is more preferably 0.50% or less.
- W 0.01 to 1.0% W, like Mo, has the effect of improving the resistance to condensed water corrosion. The effect is acquired by containing 0.01% or more of W. On the other hand, if the W content exceeds 1.0%, productivity may be reduced. Therefore, when W is contained, the W content is preferably 0.01 to 1.0%. More preferably, the W content is 0.50% or less.
- Co 0.01 to 1.0%
- Co is an element that improves the resistance to condensed water corrosion and toughness. The effect is acquired by containing 0.01% or more of Co. On the other hand, if the Co content exceeds 1.0%, productivity may be reduced. Therefore, when Co is contained, the Co content is preferably 0.01 to 1.0%.
- the Co content is more preferably 0.02% or more, and further preferably 0.04% or more. Further, the Co content is more preferably 0.50% or less, and still more preferably 0.20% or less.
- the ferritic stainless steel of the present invention can further contain one or more selected from Ti, V, Zr, B, Ca, Mg, and REM within the following range.
- Ti 0.01 to 0.10% Ti combines with C and N contained in the steel and has an effect of preventing sensitization. The effect is obtained when the Ti content is 0.01% or more.
- Ti is an element active against oxygen, and the content of Ti exceeding 0.10% generates a dense and continuous Ti oxide film on the surface of the steel during the brazing process, thereby reducing the brazing property. There is a case to let you. Therefore, the Ti content is preferably 0.01 to 0.10%.
- the Ti content is more preferably 0.02% or more, and further preferably 0.03% or more. Further, the Ti content is more preferably 0.05% or less, and further preferably 0.04% or less.
- V 0.01 to 0.50% V, like Ti, combines with C and N contained in the steel and has the effect of preventing sensitization. The effect is acquired by containing V 0.01% or more. On the other hand, if the V content exceeds 0.50%, workability may be reduced. Therefore, when V is contained, the V content is preferably in the range of 0.01 to 0.50%. The V content is more preferably 0.03% or more, and even more preferably 0.05% or more. Further, the V content is more preferably 0.40% or less, and still more preferably 0.25% or less.
- Zr 0.01 to 0.30%
- Zr combines with C and N and has the effect of suppressing sensitization. The effect is acquired by containing 0.01% or more of Zr.
- the Zr content is preferably 0.01 to 0.30%.
- the Zr content is more preferably 0.05% or more. Further, the Zr content is more preferably 0.20% or less.
- B 0.0003 to 0.005%
- B is an element that improves secondary work brittleness. The effect is acquired by containing B 0.0003% or more. On the other hand, if the B content exceeds 0.005%, the ductility may decrease due to solid solution strengthening. Therefore, when B is contained, the B content is preferably in the range of 0.0003 to 0.005%. The B content is more preferably 0.0005% or more. Further, the B content is more preferably 0.0030% or less.
- Ca 0.0003 to 0.003% Ca improves the weldability by improving the penetration of the weld. The effect is acquired by containing 0.0003% or more of Ca. On the other hand, if the Ca content exceeds 0.003%, it combines with S to produce CaS, which may reduce the resistance to condensed water corrosion. Therefore, when Ca is contained, the Ca content is preferably in the range of 0.0003 to 0.003%. The Ca content is more preferably 0.0005% or more. Further, the Ca content is more preferably 0.0020% or less.
- Mg 0.0003 to 0.003%
- Mg is an element useful for refining such as a deoxidizing effect, and is also useful for improving the workability and toughness by refining the structure. If necessary, it can contain 0.003% or less of Mg. .
- the Mg content is preferably 0.0003% or more so that a stable effect is obtained. That is, when Mg is contained, the Mg content is preferably 0.0003 to 0.003%.
- the Mg content is more preferably 0.0020% or less.
- REM 0.001 to 0.10% REM (rare earth element) improves oxidation resistance, suppresses the formation of oxide scale, and suppresses the formation of a Cr-deficient region immediately below the temper collar of the weld. The effect is acquired by containing REM 0.001% or more. On the other hand, when the REM content exceeds 0.10%, the productivity such as pickling properties is lowered and the cost is increased. Therefore, when REM is contained, the REM content is preferably 0.001 to 0.10%.
- the method for producing stainless steel of the present invention can be suitably used as long as it is an ordinary method for producing ferritic stainless steel, and is not particularly limited.
- the steel having the above-described composition of the present invention is obtained by melting steel in a known melting furnace such as a converter or electric furnace, or further through secondary refining such as ladle refining or vacuum refining. It is made into a steel slab (slab) by the ingot-bundling rolling method, and then made into a cold-rolled annealed plate through processes such as hot-rolling, hot-rolled sheet annealing, pickling, cold-rolling, finish annealing, pickling. It can be manufactured in a manufacturing process.
- the cold rolling may be performed once or two or more cold rollings with intermediate annealing interposed therebetween, and the steps of cold rolling, finish annealing, and pickling may be repeated. Furthermore, hot-rolled sheet annealing may be omitted, and skin pass rolling may be performed after cold rolling or after finish annealing when surface gloss or roughness adjustment of the steel sheet is required.
- the steel melted in a converter or an electric furnace is secondarily refined by a VOD method or the like, and the steel contains the above essential components and components added as necessary.
- the molten steel can be made into a steel material by a known method, it is preferable to use a continuous casting method in terms of productivity and quality.
- the steel material is preferably heated to 1050 to 1250 ° C., and hot rolled into a desired thickness by hot rolling.
- hot working can be performed in addition to the plate material.
- the hot-rolled sheet is preferably subjected to continuous annealing at a temperature of 900 to 1150 ° C. as necessary, and then descaled by pickling or the like to obtain a hot-rolled product. If necessary, the scale may be removed by shot blasting before pickling.
- the hot-rolled annealed sheet may be a cold-rolled product through a process such as cold rolling.
- the cold rolling may be performed once, but may be performed twice or more with intermediate annealing in view of productivity and required quality.
- the total rolling reduction of one or more cold rollings is preferably 60% or more, more preferably 70% or more.
- the cold-rolled steel sheet is then preferably subjected to continuous annealing (finish annealing) at a temperature of preferably 900 to 1150 ° C., more preferably 950 to 1150 ° C., pickling, and forming a cold-rolled product.
- finish annealing continuous annealing
- pickling may be omitted by performing continuous annealing by bright annealing.
- skin pass rolling or the like may be performed to adjust the shape, surface roughness, and material quality of the steel sheet.
- the ferritic stainless steel of the present invention described above is suitably used for exhaust gas recirculation devices such as automobile exhaust heat recovery devices and EGR coolers.
- Condensed water corrosion resistance was evaluated by a cycle test simulating a real environment.
- the cold-rolled annealed plate was cut into a size of 25 mm ⁇ 100 mm and used for the test.
- For the test solution referring to the analysis example of the condensed water collected from the exhaust heat recovery system of the actual vehicle, only chloride ions and sulfate ions that contribute particularly to corrosion were used.
- a solution of 200 ppm Cl ⁇ +600 ppm SO 4 2 ⁇ was prepared using hydrochloric acid and sulfuric acid as reagents, and then the pH was adjusted to 8.0 using aqueous ammonia.
- test piece was immersed in the above-described solution controlled at 80 ° C., and the immersion solution was evaporated in 24 hours while the test piece was immersed. This process was performed 5 times. Subsequently, the test piece was put in a furnace at 250 ° C. and kept heated for 24 hours. This was taken as one cycle, and a total of 4 cycles were performed. After completion of the test, the corrosion products were removed and the corrosion depth was measured with a 3D macroscope.
- the brazing property was evaluated by the permeability of the brazing material into the gap.
- a 30 mm square and a 25 mm ⁇ 30 mm plate were cut out for each cold-rolled annealed plate, and the two plates were stacked and clamped using a clamp jig with a constant torque force (170 kgf).
- 1.2 g of brazing material BNi-5 (Ni-19Cr-10Si) was applied to one end face, and brazing was performed in a vacuum atmosphere of 10 ⁇ 2 Pa.
- the heat treatment temperature pattern is: temperature rising temperature 10 ° C./s, soaking time 1 (step of making the whole temperature uniform): 1060 ° C.
- the steel No. of the present invention example. Nos. 1 to 20, 31 to 34, and 37 to 45 all show excellent resistance to condensed water corrosion and brazing.
- Nos. 3, 13, 31, 37 to 40, 42, 44, and 45 were particularly excellent in resistance to condensed water corrosion.
- the ferritic stainless steel of the present invention is suitable as a member used in exhaust gas recirculation devices such as exhaust heat recovery devices and EGR coolers exposed to condensed water generated from automobile exhaust gas.
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Abstract
Description
[1]質量%で、
C:0.025%以下、
Si:0.40~2.0%、
Mn:0.05~1.5%、
P:0.05%以下、
S:0.01%以下、
Cr:16.0~30.0%、
Mo:0.60~3.0%、
Ni:0.10~2.5%、
Nb:0.20~0.80%、
Al:0.001~0.15%、
N:0.025%以下を含有し、
かつ、以下の式(1)および式(2)を満たし、
残部がFeおよび不可避的不純物からなる組成を有することを特徴とするフェライト系ステンレス鋼。
C+N≦0.030% ・・・(1)
2Si+Ni≧1.0% ・・・(2)
(式(1)、式(2)中のC、N、Si、Niは、各元素の含有量(質量%)を示す。)
[2]さらに質量%で、
Cu:0.01~1.0%、
W:0.01~1.0%、
Co:0.01~1.0%
のうちから選ばれる1種または2種以上を含有することを特徴とする前記[1]に記載のフェライト系ステンレス鋼。
[3]さらに質量%で、
Ti:0.01~0.10%、
V:0.01~0.50%、
Zr:0.01~0.30%、
B:0.0003~0.005%、
Ca:0.0003~0.003%、
Mg:0.0003~0.003%
REM:0.001~0.10%
のうちから選ばれる1種または2種以上を含有することを特徴とする前記[1]または[2]に記載のフェライト系ステンレス鋼。
[4]自動車の排熱回収器用または排気ガス再循環装置用であることを特徴とする前記[1]~[3]の何れかに記載のフェライト系ステンレス鋼。
C+N≦0.030% ・・・(1)
2Si+Ni≧1.0% ・・・(2)
(式(1)、式(2)中のC、N、Si、Niは、各元素の含有量(質量%)を示す。)
Cは、鋼に不可避的に含まれる元素である。C含有量が多いと強度が向上し、少なくなると加工性が向上する。強度を向上させるためには0.001%以上Cを含有することが好ましい。一方、C含有量が0.025%を超えると加工性の低下が顕著となるうえ、Cr炭化物が析出して局所的なCr欠乏による耐凝縮水腐食性の低下を起しやすくなる。よって、C含有量は0.025%以下とする。C含有量は、好ましくは0.020%以下であり、より好ましくは0.015%以下であり、さらに好ましくは0.010%以下である。また、C含有量は、より好ましくは0.003%以上であり、さらに好ましくは0.004%以上である。
Siは、本発明において耐凝縮水腐食性向上のために重要な元素である。その効果は、0.40%以上Siを含有することで得られる。より優れた耐凝縮水腐食性を必要とする場合は0.60%超えのSiの含有が望ましい。ただし、Siを2.0%超えで含有すると加工性を低下させる。よって、Si含有量は0.40~2.0%とする。Si含有量は、好ましくは0.60%超であり、より好ましくは0.80%以上であり、さらに好ましくは1.00%以上である。また、Si含有量は、好ましくは1.80%以下であり、より好ましくは1.60%以下であり、さらに好ましくは1.40%以下である。
Mnは、脱酸作用があり、その効果は0.05%以上のMnの含有で得られる。しかし、Mnの1.5%超えの含有は、固溶強化により加工性を損なわせる。また、Mnの1.5%超えの含有は、腐食の起点となるMnSの析出を促進して、耐凝縮水腐食性を低下させる。よって、Mn含有量は0.05~1.5%の範囲とする。Mn含有量は、好ましくは0.10%以上である。また、Mn含有量は、好ましくは0.50%以下であり、より好ましくは0.30%以下である。
Pは、鋼に不可避的に含まれる元素であり、0.05%超えのPの含有は溶接性を低下させ、粒界腐食を生じさせ易くする。そのため、P含有量は0.05%以下に限定する。好ましくは、P含有量は0.04%以下である。さらに好ましくは、P含有量は0.03%以下である。
Sは、鋼に不可避的に含まれる元素であり、0.01%超のSの含有は、MnSの析出を促進し、耐凝縮水腐食性を低下させる。よって、S含有量は0.01%以下とする。好ましくは、S含有量は0.008%以下である。より好ましくは、S含有量は0.005%以下である。
Crは、耐凝縮水腐食性を確保するために重要な元素である。Cr含有量が16.0%未満では、耐凝縮水腐食性を十分に得られない。一方で、Crを30.0%超えで含有すると、加工性、製造性が低下する。よって、Cr含有量は16.0~30.0%の範囲とする。Cr含有量は、好ましくは18.0%以上であり、より好ましくは19.0%以上であり、さらに好ましくは20.5%以上である。また、Cr含有量は、好ましくは24.0%以下であり、より好ましくは23.0%以下であり、さらに好ましくは22.0%以下である。
Moは、ステンレス鋼の不動態皮膜を安定化させて、耐凝縮水腐食性を向上させる効果を有する。排熱回収器やEGRクーラーでは、凝縮水による内面腐食や融雪剤などによる外面腐食を防止する効果がある。さらに、熱疲労特性の向上効果があり、エキゾーストマニホールド直下に取り付けられるEGRクーラーに使用する場合には、特に好適な元素である。これらの効果は、0.60%以上のMoの含有で得られる。しかし、Moは高価な元素であるためコストの増大を招く。さらに、Mo含有量が3.0%を超えると、加工性が低下する。よって、Mo含有量は0.60~3.0%の範囲とする。Mo含有量は、好ましくは0.80%以上であり、より好ましくは1.00%以上であり、さらに好ましくは1.20%以上であり、さらにより好ましくは1.50%以上である。また、Mo含有量は、好ましくは2.50%以下であり、より好ましくは2.00%以下である。
Niは、0.10%以上の含有で、耐凝縮水腐食性および靭性の向上に有効に寄与する元素である。しかし、Ni含有量が2.5%を超えると、応力腐食割れ感受性が高くなる。そのため、Ni含有量は0.10~2.5%の範囲とする。Ni含有量は、好ましくは0.50%以上であり、より好ましくは0.80%超であり、さらに好ましくは1.00%以上であり、さらにより好ましくは1.20%以上であり、特に好ましくは1.50%以上である。また、耐凝縮水腐食性向上に有効なSiの含有量が0.60%以下の場合は、耐凝縮水腐食性を確保するためにNiを0.80%を超えて含有することが望ましい。
Nbは、CおよびNと優先的に結合することにより、Cr炭窒化物の析出による耐凝縮水腐食性の低下を抑制する元素である。また、高温強度を高めて、熱疲労特性を向上させる効果を有する。これらの効果は、Nbの0.20%以上の含有で得られる。一方、Nb含有量が0.80%を超えると、靱性が低下する。そのため、Nb含有量は0.20~0.80%の範囲とする。Nb含有量は、好ましくは0.25%以上である。また、Nb含有量は、好ましくは0.60%以下であり、より好ましくは0.50%以下であり、さらに好ましくは0.40%以下である。
Alは脱酸に有用な元素であり、その効果は0.001%以上のAlの含有で得られる。一方、Alの0.15%超えの含有はろう付け性を低下させることから、Al含有量は0.15%以下とする。よって、Al含有量は0.001~0.15%とする。Al含有量は、好ましくは0.10%以下であり、より好ましくは0.050%以下であり、さらに好ましくは0.025%以下であり、さらにより好ましくは0.015%以下であり、特に好ましくは0.010%以下であり、最も好ましくは0.008%以下である。
Nは、Cと同様に鋼に不可避的に含まれる元素であり、固溶強化により鋼の強度を上昇させる効果がある。その効果は、Nを0.001%以上含有することで得られる。一方、Nを0.025%超えで含有し、Cr窒化物として析出した場合には耐凝縮水腐食性を低下させる。よって、N含有量は0.025%以下とする。N含有量は、好ましくは0.020%以下であり、より好ましくは0.015%以下であり、さらに好ましくは0.010%以下である。また、N含有量は、好ましくは0.001%以上であり、より好ましくは0.003%以上であり、さらに好ましくは0.005%以上である。
(式(1)中のC、Nは、各元素の含有量(質量%)を示す。)
CおよびNの過剰含有は、耐凝縮水腐食性および加工性を低下させる。そのため、C含有量およびN含有量の夫々を前述した範囲とした上で、C+N(C含有量とN含有量の和)は0.030%以下とする。好ましくは、C+Nは0.025%以下である。より好ましくは、C+Nは0.020%以下である。
(式(2)中のSi、Niは、各元素の含有量(質量%)を示す。)
前述したように、本発明では、耐凝縮水腐食性の向上のためにSiおよびNiの夫々を所定の含有量にする。さらに本発明者らは、鋭意検討し、2Si+Ni(Si含有量の2倍とNi含有量の和)が1.0%未満であると、所望の耐凝縮水腐食性が得られないことも知見した。そのため、本発明では、Si含有量およびNi含有量の夫々を前述した範囲とした上で、2Si+Niを1.0%以上とする。より好ましくは、2Si+Niは1.5%以上である。
Cuは、耐凝縮水腐食性を高める効果を有する元素である。その効果は、Cuを0.01%以上含有することで得られる。一方、Cu含有量が1.0%を超えると、熱間加工性が低下する場合がある。そのため、Cuを含有する場合は、Cu含有量は0.01~1.0%の範囲とすることが好ましい。Cu含有量は、より好ましくは0.05%以上である。また、Cu含有量は、より好ましくは0.50%以下である。
Wは、Moと同様に、耐凝縮水腐食性を向上させる効果がある。その効果は、Wを0.01%以上含有することで得られる。一方、W含有量が1.0%を超えると、製造性を低下させる場合がある。よって、Wを含有する場合は、W含有量は0.01~1.0%とすることが好ましい。より好ましくは、W含有量は0.50%以下である。
Coは、耐凝縮水腐食性および靭性を向上させる元素である。その効果は、Coを0.01%以上含有することで得られる。一方、Co含有量が1.0%を超えると、製造性を低下させる場合がある。よって、Coを含有する場合は、Co含有量は0.01~1.0%とすることが好ましい。Co含有量は、より好ましくは0.02%以上であり、さらに好ましくは0.04%以上である。また、Co含有量は、より好ましくは0.50%以下であり、さらに好ましくは0.20%以下である。
Tiは、鋼中に含まれるCおよびNと結合し、鋭敏化を防止する効果を有する。その効果はTiの0.01%以上の含有で得られる。一方、Tiは酸素に対して活性な元素であり、0.10%超えのTiの含有はろう付け処理時に緻密で連続的なTi酸化皮膜を鋼の表面に生成して、ろう付け性を低下させる場合がある。よって、Ti含有量は0.01~0.10%とすることが好ましい。Ti含有量は、より好ましくは0.02%以上であり、さらに好ましくは0.03%以上である。また、Ti含有量は、より好ましくは0.05%以下であり、さらに好ましくは0.04%以下である。
Vは、Ti同様に、鋼中に含まれるCおよびNと結合し、鋭敏化を防止する効果を有する。その効果は、Vを0.01%以上含有することで得られる。一方、V含有量が0.50%を超えると、加工性が低下する場合がある。そのため、Vを含有する場合は、V含有量は0.01~0.50%の範囲とすることが好ましい。V含有量は、より好ましくは0.03%以上であり、さらに好ましくは0.05%以上である。また、V含有量は、より好ましくは0.40%以下であり、さらに好ましくは0.25%以下である。
Zrは、C、Nと結合して、鋭敏化を抑制する効果がある。その効果は、Zrを0.01%以上含有することで得られる。一方、Zr含有量が0.30%を超えると、加工性を低下させるうえ、非常に高価な元素であるためコストの増大を招く場合がある。よって、Zrを含有する場合は、Zr含有量は0.01~0.30%とすることが好ましい。Zr含有量は、より好ましくは0.05%以上である。また、Zr含有量は、より好ましくは0.20%以下である。
Bは、二次加工脆性を改善する元素である。その効果は、Bを0.0003%以上含有することで得られる。一方、B含有量が0.005%を超えると、固溶強化により延性が低下する場合がある。よって、Bを含有する場合は、B含有量は0.0003~0.005%の範囲とすることが好ましい。B含有量は、より好ましくは0.0005%以上である。また、B含有量は、より好ましくは0.0030%以下である。
Caは、溶接部の溶け込み性を改善して溶接性を向上させる。その効果は、Caを0.0003%以上含有することで得られる。一方、Ca含有量が0.003%を超えると、Sと結合してCaSを生成し、耐凝縮水腐食性を低下させる場合がある。よって、Caを含有する場合は、Ca含有量は0.0003~0.003%の範囲とすることが好ましい。Ca含有量は、より好ましくは0.0005%以上である。また、Ca含有量は、より好ましくは0.0020%以下である。
Mgは、脱酸効果等精錬上有用な元素であり、また、組織を微細化し、加工性、靭性の向上にも有用であり、必要に応じてMgを0.003%以下含有させることができる。Mgを含有させる場合、Mg含有量は、安定した効果が得られる0.0003%以上とすることが好ましい。すなわち、Mgを含有させる場合、Mg含有量は0.0003~0.003%とすることが好ましい。Mg含有量は、より好ましくは0.0020%以下である。
REM(希土類元素)は耐酸化性を向上させて、酸化スケールの形成を抑制し、溶接部のテンパーカラー直下のCr欠乏領域の形成を抑制する。その効果は、REMを0.001%以上含有することで得られる。一方、REM含有量が0.10%を超えると、酸洗性などの製造性を低下させるうえ、コストの増大を招く。よって、REMを含有する場合は、REM含有量は0.001~0.10%とすることが好ましい。
耐凝縮水腐食性は、実環境を模擬したサイクル試験で評価した。冷延焼鈍板を25mm×100mmの大きさに切り出し、試験に供した。試験液は実車の排熱回収装置から採取した凝縮水の分析例を参考にし、腐食に特に寄与する塩化物イオンと硫酸イオンのみを用いた。試薬に塩酸、硫酸を用いて、200ppmCl-+600ppmSO4 2-の溶液を調整した後、アンモニア水を用いてpHを8.0に調整した。80℃に一定管理した上記溶液に試験片を浸漬させ、試験片を浸漬したまま浸漬溶液を24時間で蒸発させた。本工程を5回行った。続いて試験片を250℃の炉に入れて24時間加熱保持を行った。これを1サイクルとし、計4サイクル行った。試験終了後、腐食生成物を除去して、3Dマクロスコープにより腐食深さを測定した。最大腐食深さが80μm未満の場合を◎(合格、特に優れている)、最大腐食深さが80μm以上100μm未満の場合を○(合格)、100μm以上の場合を×(不合格)と評価した。
ろう付け性は、ろう材のすき間部への浸透性で評価した。各冷延焼鈍板について30mm角と25mm×30mmの板を切出し、この2枚の板を重ねて、一定のトルク力(170kgf)でクランプ冶具を用いてはさみ止めした。片側の端面にろう材BNi-5(Ni-19Cr-10Si)を1.2g塗布し、10-2Paの真空雰囲気でろう付け処理を行った。
熱処理温度パターンは、昇温温度10℃/s、均熱時間1(全体の温度を均一にする工程):1060℃×1800s、昇温温度10℃/s、均熱時間2(実際にろう材の融点以上の温度でろう付けを行う工程):1170℃×600sの処理を順に行った後、炉冷し、200℃に温度が下がったときに外気(大気)でパージするものとした。ろう付け処理後に板間にろう材がどの程度浸透したかを、重ねた板の側面部にて目視により確認し、以下の基準で評価した。ろう材の浸透が2枚の板の重なり長さの50%以上の場合を○(合格)、ろう材の浸透が2枚の板の重なり長さの50%未満の場合を×(不合格)とした。
特に、Si含有量が0.60%を超えている鋼No.1、2、4~8、11、12、14~20、32~34、41、43、Si含有量は0.60%以下であるがNi含有量が0.80%を超えている鋼No.3、13、31、37~40、42、44、45は、耐凝縮水腐食性が特に優れていた。
Claims (4)
- 質量%で、
C:0.025%以下、
Si:0.40~2.0%、
Mn:0.05~1.5%、
P:0.05%以下、
S:0.01%以下、
Cr:16.0~30.0%、
Mo:0.60~3.0%、
Ni:0.10~2.5%、
Nb:0.20~0.80%、
Al:0.001~0.15%、
N:0.025%以下を含有し、
かつ、以下の式(1)および式(2)を満たし、
残部がFeおよび不可避的不純物からなる組成を有することを特徴とするフェライト系ステンレス鋼。
C+N≦0.030% ・・・(1)
2Si+Ni≧1.0% ・・・(2)
(式(1)、式(2)中のC、N、Si、Niは、各元素の含有量(質量%)を示す。) - さらに質量%で、
Cu:0.01~1.0%、
W:0.01~1.0%、
Co:0.01~1.0%
のうちから選ばれる1種または2種以上を含有することを特徴とする請求項1に記載のフェライト系ステンレス鋼。 - さらに質量%で、
Ti:0.01~0.10%、
V:0.01~0.50%、
Zr:0.01~0.30%、
B:0.0003~0.005%、
Ca:0.0003~0.003%、
Mg:0.0003~0.003%、
REM:0.001~0.10%
のうちから選ばれる1種または2種以上を含有することを特徴とする請求項1または2に記載のフェライト系ステンレス鋼。 - 自動車の排熱回収器用または排気ガス再循環装置用であることを特徴とする請求項1~3の何れかに記載のフェライト系ステンレス鋼。
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US20190177824A1 (en) | 2019-06-13 |
CN109563596A (zh) | 2019-04-02 |
JPWO2018043310A1 (ja) | 2019-06-24 |
KR20190028785A (ko) | 2019-03-19 |
EP3508598A1 (en) | 2019-07-10 |
EP3508598A4 (en) | 2019-08-28 |
MX2019001947A (es) | 2019-05-15 |
US11261512B2 (en) | 2022-03-01 |
KR102206415B1 (ko) | 2021-01-22 |
JP6699670B2 (ja) | 2020-05-27 |
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