WO2012133506A1 - Acier inoxydable ferritique pour élément de système d'alimentation en biocarburant, élément de système d'alimentation en biocarburant, acier inoxydable ferritique pour unité de récupération de chaleur d'échappement et unité de récupération de chaleur d'échappement - Google Patents

Acier inoxydable ferritique pour élément de système d'alimentation en biocarburant, élément de système d'alimentation en biocarburant, acier inoxydable ferritique pour unité de récupération de chaleur d'échappement et unité de récupération de chaleur d'échappement Download PDF

Info

Publication number
WO2012133506A1
WO2012133506A1 PCT/JP2012/058092 JP2012058092W WO2012133506A1 WO 2012133506 A1 WO2012133506 A1 WO 2012133506A1 JP 2012058092 W JP2012058092 W JP 2012058092W WO 2012133506 A1 WO2012133506 A1 WO 2012133506A1
Authority
WO
WIPO (PCT)
Prior art keywords
less
stainless steel
ferritic stainless
content
mass
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2012/058092
Other languages
English (en)
Japanese (ja)
Inventor
信彦 平出
富美夫 札軒
坂本　俊治
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Steel Stainless Steel Corp
Original Assignee
Nippon Steel and Sumikin Stainless Steel Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP2012057362A external-priority patent/JP5856878B2/ja
Priority claimed from JP2012057363A external-priority patent/JP5856879B2/ja
Application filed by Nippon Steel and Sumikin Stainless Steel Corp filed Critical Nippon Steel and Sumikin Stainless Steel Corp
Priority to CN201280015457.9A priority Critical patent/CN103459636B/zh
Priority to US14/007,807 priority patent/US9611525B2/en
Priority to KR1020137024892A priority patent/KR20130125823A/ko
Publication of WO2012133506A1 publication Critical patent/WO2012133506A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • 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
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/10—Oxidising
    • 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
    • C22C38/004—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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite

Definitions

  • the present invention relates to ferritic stainless steel and biofuel supply system parts suitable for automobile fuel supply system parts for supplying biofuels such as bioethanol and biodiesel.
  • the present invention relates to a ferritic stainless steel suitable for a biofuel supply system component that is close to an engine and tends to be hot, such as a fuel injection system component.
  • the present invention also relates to a ferritic stainless steel for an exhaust heat recovery device of an automobile and an exhaust heat recovery device.
  • the present invention relates to a ferritic stainless steel suitable for an exhaust heat recovery unit in which a heat exchange part is assembled by brazing joint.
  • Bioethanol is ethanol produced from biomass, and bioethanol is mixed with gasoline and used as fuel for gasoline engines.
  • Biodiesel fuel is a fuel in which fatty acid methyl ester is mixed with light oil, and is used as a fuel for diesel engines.
  • ethanol is produced using corn and sugar cane as raw materials.
  • Fatty acid methyl esters are produced by esterification using vegetable oil and waste oil such as rapeseed oil, soybean oil, and palm oil as raw materials.
  • Biofuels such as bioethanol and biodiesel fuel are considered to be more corrosive than metal materials.
  • the influence on the use performance of various members constituting the fuel system parts has been investigated in advance.
  • Manufacturers that guarantee an ultra-long life expectancy demands a more reliable material, and stainless steel is one of the candidates.
  • Patent Document 1 in mass%, C: ⁇ 0.015%, Si: ⁇ 0.5%, Cr: 11.0 to 25.0%, N: ⁇ 0.020%, Ti: 0.05 -0.50%, Nb: 0.10-0.50%, and B: ⁇ 0.0100%, and Mo: ⁇ 3.0%, Ni: ⁇ 2.0%, Cu if necessary
  • a ferritic stainless steel sheet containing one or more selected from: ⁇ 2.0% and Al: ⁇ 4.0% is disclosed. The breaking elongation of the steel sheet is 30% or more, and the Rankford value is 1.3 or more.
  • Patent Document 2 includes mass%, C: ⁇ 0.01%, Si: ⁇ 1.0%, Mn: ⁇ 1.5%, P: ⁇ 0.06%, S: ⁇ 0.03%, Cr: 11 to 23%, Ni: ⁇ 2.0%, Mo: 0.5 to 3.0%, Al: ⁇ 1.0%, and N: ⁇ 0.04%, Cr + 3.3Mo ⁇ 18
  • a ferritic stainless steel sheet satisfying the following relational expression is disclosed.
  • the steel sheet further satisfies one or both of Nb: ⁇ 0.8% and Ti: ⁇ 1.0%, satisfying the relational expression of 18 ⁇ Nb / (C + N) + 2Ti / (C + N) ⁇ 60. contains.
  • the grain number of the ferrite crystal grains of the steel sheet is 6.0 or more, and the average r value is 2.0 or more.
  • Patent Document 3 in mass%, C: ⁇ 0.01%, Si: ⁇ 1.0%, Mn: ⁇ 1.5%, P: ⁇ 0.06%, S: ⁇ 0.03%, Al: ⁇ 1.0%, Cr: 11-20%, Ni: ⁇ 2.0%, Mo: 0.5-3.0%, V: 0.02-1.0%, and N: ⁇ 0
  • a ferritic stainless steel sheet containing 0.04% and containing either one or both of Nb: 0.01 to 0.8% and Ti: 0.01 to 1.0% is disclosed.
  • the surface undulation height generated when deformed by 25% by uniaxial tension is 50 ⁇ m or less.
  • Patent Documents 1 to 3 are techniques dealing with corrosion resistance against ordinary gasoline. As will be described later, since the corrosiveness of biofuels is significantly different from that of gasoline, these technologies have insufficient corrosion resistance to biofuels. Conventionally, the details of the corrosiveness of biofuels to stainless steel are not necessarily clarified, and it is difficult to say that the corrosion resistance of various stainless steel types to biofuels is necessarily clarified.
  • the exhaust heat recovery device is a system that heats engine cooling water with exhaust gas and uses it to warm up a heater or an engine, and is also called an exhaust heat recirculation system.
  • the heat exchange part of the exhaust heat recovery device is required to have good thermal conductivity in order to obtain good thermal efficiency. Further, since the heat exchanging portion is in contact with the exhaust gas, excellent corrosion resistance is required for the exhaust gas condensed water. On the other hand, the outer surface of the exhaust heat recovery device is also required to have excellent corrosion resistance against salt damage. Such corrosion resistance is also required for exhaust system downstream members mainly composed of mufflers. However, corrosion of the exhaust heat recovery device may lead to a serious accident such as leakage of cooling water. Therefore, the exhaust heat recovery device is required to have higher safety and better corrosion resistance.
  • a ferritic stainless steel containing 17% or more of Cr such as SUS430LX, SUS436J1L, SUS436L, or the like, is used for a part that particularly requires corrosion resistance. . Corrosion resistance equal to or better than these is required for the material of the exhaust heat recovery device.
  • the heat exchange part since the structure of the heat exchange part is complicated, it may be assembled by welding joint, but it may be assembled by brazing joint.
  • the material of the heat exchange part assembled by brazing and joining needs to have good brazing properties.
  • the exhaust heat recovery unit since the exhaust heat recovery unit is often installed downstream of the catalytic converter under the floor, the exhaust gas on the inlet side is heated. Further, the exhaust gas is forcibly cooled by heat exchange. Accordingly, the exhaust heat recovery device also requires good thermal fatigue characteristics.
  • Patent Document 4 discloses an automobile exhaust heat recovery device made of ferritic stainless steel.
  • the ferritic stainless steel has C: 0.020% or less, Si: 0.05 to 0.70%, Mn: 0.05 to 0.70%, P: 0.045% or less, S: 0.005 %: Ni: 0.70% or less, Cr: 18.00 to 25.50%, Cu: 0.70% or less, Mo: 2 / (Cr-17.00) to 2.50%, and N: Contains 0.020% or less.
  • the ferritic stainless steel further includes one or both of Ti: 0.50% or less and Nb: 0.50% or less, and a relationship of (Ti + Nb) ⁇ (7 ⁇ (C + N) +0.05) The formula is satisfied, and the balance is Fe and inevitable impurities.
  • corrosion resistance against exhaust gas condensed water is secured by adding Mo to 18% or more of Cr.
  • Patent Document 5 C: 0.05% or less, Si: 0.02 to 1.0%, Mn: 0.5% or less, P: 0.04% or less, S: 0.02% or less, Al : 0.1% or less, Cr: 20 to 25%, Cu: 0.3 to 1.0%, Ni: 0.1 to 3.0%, Nb: 0.2 to 0.6%, and N: A ferritic stainless steel sheet containing 0.05% or less and having excellent crevice corrosion resistance is disclosed.
  • the steel sheet has Nb carbonitride of 5 ⁇ m or less, and the steel sheet has a surface roughness Ra of 0.4 ⁇ m or less.
  • Ni and Cu are added together with 20% or more of Cr to ensure crevice corrosion resistance.
  • Patent Document 6 discloses an automobile exhaust gas passage member made of ferritic stainless steel.
  • the ferritic stainless steel has C: 0.015% or less, Si: 2.0% or less, Mn: 1.0% or less, P: 0.045% or less, S: 0.010% or less, Cr: 16 Containing 25 to 25%, Nb: 0.05 to 0.2%, Ti: 0.05 to 0.5%, N: 0.025% or less, and Al: 0.02 to 1.0%,
  • the steel further contains one or both of Ni: 0.1 to 2.0% and Cu: 0.1 to 1.0% in total (Ni + Cu) of 0.6% or more.
  • Ni + Cu 0.1 to 1.0% in total
  • Patent Document 7 Cr: 16-30%, Ni: 7-20%, C: 0.08% or less, N: 0.15% or less, Mn: 0.1-3%, S: 0.008 %, And Si: 0.1-5%, high temperature exhaust heat recovery satisfying Cr + 1.5Si ⁇ 21 and 0.009Ni + 0.014Mo + 0.005Cu ⁇ (0.085Si + 0.008Cr + 0.003Mn) ⁇ ⁇ 0.25
  • Stainless steel for the heat pipe of the apparatus is disclosed.
  • the technique described in Patent Document 7 relates to an exhaust heat recovery device using heat transfer means called a heat pipe, not a heat exchanger that exchanges heat between exhaust heat and cooling water.
  • Patent Document 7 discloses an austenitic stainless steel suitable for a heat pipe.
  • Waste heat recovery equipment is required to have corrosion resistance equivalent to or better than ferritic stainless steel containing 17% or more of Cr.
  • the corrosion resistance after brazing has not been considered. For this reason, when existing ferritic stainless steel is applied to an exhaust heat recovery device, the corrosion resistance after brazing cannot be sufficiently ensured due to the change in the metal structure of the brazed portion and the progress of oxidation of the steel surface.
  • the gist of the first aspect of the present invention aimed at solving the above problems is as follows. [1] In mass%, C: 0.03% or less, N: 0.03% or less, Si: more than 0.1%, 1% or less, Mn: 0.02% or more, 1.2% or less, Cr: 15% or more, 23% or less, Al: 0.002% or more, 0.5% or less, and any one or both of Nb and Ti, and the balance is composed of Fe and inevitable impurities.
  • a biofuel characterized by satisfying the formulas (1) and (2) and having an oxide film containing Cr, Si, Nb, Ti, and Al in total of 30% or more in total on the surface thereof Ferritic stainless steel for supply system parts.
  • a biofuel supply system component comprising the ferritic stainless steel for a biofuel supply system component as described in any one of [1] to [3].
  • the gist of the second aspect of the present invention aimed at solving the above problems is as follows. [5] By mass%, C: 0.03% or less, N: 0.05% or less, Si: more than 0.1%, 1% or less, Mn: 0.02% or more, 1.2% or less, Cr: 17% or more, 23% or less, Al: 0.002% or more, 0.5% or less, and any one or both of Nb and Ti, Ni: 0.25% or more 5% or less, Cu: 0.25% or more, 1% or less, and Mo: 0.5% or more, containing 2 or 3 types selected from the group consisting of 2% or less, the balance being Fe and inevitable impurities And satisfying the following formulas (3) and (4), and an oxide film containing Cr, Si, Nb, Ti, and Al with a total cation fraction of 40% or more is formed on the surface.
  • Heat recovery dexterity ferritic stainless steel characterized by Rukoto. 8 (C + N) + 0.03 ⁇ Nb + Ti ⁇ 0.6 (3) Si + Cr + Al + ⁇ Nb + Ti-8 (C + N) ⁇ ⁇ 17.5 (4)
  • an element symbol represents content (mass%) of each element.
  • the value of Nb + Ti-8 (C + N) is 0 or more.
  • V 0.5% or less
  • W 1% or less
  • B 0.005% or less
  • Zr 0.5% or less
  • Sn 0.5% or less
  • Co 0 1 or more selected from the group consisting of 2% or less
  • Mg 0.002% or less
  • Ca 0.002% or less
  • REM 0.01% or less
  • a heat exchange part in which members are assembled by brazing joining is provided, and the heat exchange part is made of ferritic stainless steel, and the ferritic stainless steel is C: 0.03% or less in mass%.
  • N 0.05% or less
  • Si more than 0.1%, 1% or less
  • Mn 0.02% or more, 1.2% or less
  • Cr 17% or more, 23% or less
  • Al 0.
  • an element symbol represents content (mass%) of each element.
  • the value of Nb + Ti-8 (C + N) is 0 or more.
  • the ferritic stainless steel further includes, in mass%, V: 0.5% or less, W: 1% or less, B: 0.005% or less, Zr: 0.5% or less, Sn: 0.00. It contains at least one selected from the group consisting of 5% or less, Co: 0.2% or less, Mg: 0.002% or less, Ca: 0.002% or less, and REM: 0.01% or less.
  • the exhaust heat recovery device as described in [8] above.
  • ferritic stainless steel having excellent corrosion resistance against biofuel.
  • This ferritic stainless steel can be suitably used for biofuel supply system parts.
  • this ferritic stainless steel is suitable for biofuel supply system parts that are close to the engine and tend to be hot, such as injection system parts.
  • a ferritic stainless steel for exhaust heat recovery equipment having corrosion resistance against exhaust gas condensed water after brazing.
  • This ferritic stainless steel can be suitably used as a member for an exhaust heat recovery device.
  • this ferritic stainless steel can be suitably used for a heat exchange part assembled by brazing joint.
  • E10 and E22 are fuels in which bioethanol is mixed with gasoline at a ratio of 10% and 22%, respectively, and E100 is 100% bioethanol.
  • RME is a fuel produced by methyl esterifying rapeseed oil. A detailed investigation and analysis of these oxidative degradation behaviors and corrosiveness to stainless steel were conducted in comparison with ordinary gasoline.
  • E10, E22, E100, and RME were evaluated according to JIS K2287 used in the method for evaluating the oxidation stability of gasoline, and compared with the oxidation stability of gasoline. These fuels were sealed in an autoclave, 7 atmospheres of oxygen were introduced, and then the temperature was raised to 100 ° C. and held. In this state, the change in pressure was measured, and the behavior of the pressure decreasing as oxygen was used to oxidize the fuel was evaluated. As a result, the following matters became clear. (1) E10 and E100 are less susceptible to oxidative degradation than gasoline. (2) E22 and RME are more susceptible to oxidative degradation than gasoline, and the degree of oxidative degradation of RME is the greatest.
  • fatty acids such as formic acid, acetic acid, and propionic acid are produced.
  • stainless cold-rolled steel sheets were immersed in oxidized RME and gasoline to examine the presence or absence of corrosion. As a result, no corrosion was observed in either case. This is because the fatty acid that is an oxidation product exists as a dimer in the fuel medium.
  • fatty acids In order for fatty acids to develop corrosive properties, they must dissociate and release hydrogen ions, and for this purpose, the existence of water was considered indispensable. In an actual environment, water is generated by condensation of moisture in the air, so it is extremely important to consider the coexistence of the aqueous phase.
  • the hydrogen ion concentration in water depends mainly on the type of fatty acid in the oxidized fuel, the concentration of the fatty acid, and the partitioning behavior of the fatty acid between the fuel and the aqueous phase. Among these, the distribution behavior of the fatty acid is affected by the temperature, and the higher the temperature, the easier the fatty acid is distributed from the fuel to the water phase.
  • the pH of the aqueous phase is 2.1
  • the pH of the aqueous phase is 3.0
  • this difference is converted into the fatty acid concentration, it corresponds to a difference of about 100 times.
  • corrosion tests using oxidized and deteriorated gasoline have been conducted with a concentration of formic acid and acetic acid in water of about 100 to 1000 ppm. For this reason, it was found that in the corrosion test with biofuels such as RME, it is necessary to increase the concentration of formic acid + acetic acid to 1% to 10% corresponding to a concentration about 100 times that of gasoline.
  • the temperature of fuel injection system parts close to the engine rises to about 90 to 100 ° C., and as the temperature rises, fatty acids are easily distributed from the fuel to the water phase, and the corrosive environment becomes severe.
  • This corrosive environment is a harsh condition compared to a temperature of 40 to 50 ° C. in a corrosion test with oxidized and deteriorated gasoline.
  • the bioethanol in the fuel moves to the aqueous phase and enlarges the aqueous phase, and becomes a factor that hinders maintaining a passive state (passive state) particularly in stainless steel.
  • Nb and / or Ti contained in the stainless steel does not exist as a solid solution, but a part of the Nb and / or Ti is fixed to C and N.
  • the solid solution Nb and / or Ti that is not fixed to C and N is concentrated in the passive film (oxide film) by the heat treatment.
  • Nb and Ti contribute to the corrosion preventing action in the oxide film formed by the heat treatment.
  • the amount of Nb and / or Ti that is fixed to C and N and does not enter into a solid solution state is Nb atomic weight 93, C atomic weight 12, N atomic weight 14 From the ratio, it is considered that the total amount of C and N (C + N) is approximately 8 times. Therefore, in order to form the above oxide film that suppresses the occurrence of corrosion, the total content of Si, Cr, Al, and ⁇ Nb + Ti-8 (C + N) ⁇ contained in the stainless steel is 15.5% or more. It is necessary to make it 17.5% or more.
  • heat treatment by adjusting the process conditions such as pickling to form an oxide film of the above composition.
  • An example of the heat treatment for forming the oxide film having the above cation fraction on the surface of the steel material having the above chemical composition is a heat treatment for brazing and joining members to be parts.
  • fuel injection system parts such as delivery tubes and common rails are parts manufactured by brazing and joining members.
  • heat treatment conditions at the time of brazing for manufacturing such parts in an H 2 atmosphere containing 10 vacuum atmosphere -2 ⁇ 1 torr (reduced pressure atmosphere) or N 2 containing N 2, temperature of 800 ⁇ 1200 ° C. And a condition of holding for 0.5 to 30 minutes. Under these conditions, an oxide film having a desired composition can be suitably formed.
  • the total cation fraction of Cr, Si, Nb, Ti, and Al in the formed oxide film is the desired cation fraction.
  • a vacuum of 10 ⁇ 2 torr or less is evacuated, and then N 2 is introduced to adjust the pressure to 10 ⁇ 2 to 1 torr.
  • N 2 may be introduced in the H 2 atmosphere, but it is not particularly necessary to introduce N 2, and an oxide film having a desired composition can be obtained even with N 2 remaining in the atmosphere.
  • the reason for this is not clear, but heat treatment in an environment containing N 2 produces (Nb, Ti) carbonitrides on the surface of the steel, which promotes reduction of Fe oxide. It may have been done.
  • the content of N 2 in the heat treatment atmosphere is preferably 0.001 to 0.2%, more preferably 0.005 to 0.1%.
  • the heat treatment condition is to hold at 1000 to 1200 ° C. for 5 to 30 minutes in order to form an oxide film enriched with Cr, Si, Nb, Ti and Al with a total cation fraction of 30% or more. Is preferred.
  • the holding temperature is more preferably 1050 to 1150 ° C., and the holding time is more preferably 10 to 20 minutes.
  • the oxide film which has the said cation fraction can be formed by the heat processing at the time of brazing and joining the member which consists of a steel material of the said chemical composition. Therefore, the heat treatment step for forming the oxide film having the cation fraction can also serve as a step of brazing and joining a member made of a steel material having the above chemical composition.
  • the heat treatment step for forming the oxide film having the cation fraction can also serve as a step of brazing and joining a member made of a steel material having the above chemical composition.
  • it is 800 to 1200 ° C. in an environment containing N 2 and a pressure of 10 ⁇ 2 to 1 torr. You may perform the heat processing process hold
  • the above heat treatment process is not added, and in the manufacturing process of steel materials and parts, conditions for heat treatment for forming an oxide film and pickling that removes the oxide film are removed. In this way, an oxide film having a desired cation fraction may be formed.
  • N 2 having a dew point of ⁇ 45 to ⁇ 75 ° C. in final finish annealing in the manufacturing process of steel materials.
  • a mixed gas atmosphere of H 2 and a method of holding 0.5 to 5 minutes at 800 ⁇ 1100 ° C.. In this case, the subsequent pickling is omitted.
  • the oxide film preferably contains Cr, Si, Nb, Ti, and Al in a total of 40% or more of the cation fraction. Further, it is preferable to contain 20% or more of the most important Cr among Cr, Si, Nb, Ti, and Al in terms of cation fraction (the ratio of Cr content to the content of all cations in the oxide film). .
  • the total of the cation fractions of Cr, Si, Nb, Ti, and Al is more preferably 50% or more.
  • the film thickness of the oxide film is preferably 15 nm or less, more preferably 10 nm or less.
  • the increase in film thickness leads to a decrease in the cation fraction of Cr, Si, Nb, Ti, and Al per unit volume, leading to a decrease in corrosion resistance.
  • (Nb, Ti) carbonitride generated by heat treatment in an environment containing N 2 suppresses an increase in film thickness.
  • this embodiment is made in consideration of workability required as a material for biofuel supply system parts, and provides ferritic stainless steel for fuel supply system parts having excellent corrosion resistance against biofuels. To do. The summary is shown below.
  • the ferritic stainless steel of this embodiment comprises a steel main body and an oxide film provided on the surface of the steel main body. Since the thickness of the oxide film is very thin compared to the thickness of the steel body, the composition of the steel material before the oxide film is formed is substantially the same as the composition of the steel body (steel material) after the oxide film is formed. Are identical.
  • the composition of the steel body (steel material) will be described below. In the present specification, unless otherwise specified, the unit “%” indicating the content of a component represents mass%.
  • C (C: 0.03% or less) Since C reduces intergranular corrosion resistance and workability, it is necessary to keep the content low. For this reason, content of C shall be 0.03% or less. However, excessively lowering the C content increases the scouring cost, so the C content is preferably 0.002% or more. The C content is more preferably 0.002 to 0.02%.
  • N (N: 0.03% or less)
  • N is an element useful for pitting corrosion resistance, but it is necessary to keep the N content low in order to reduce intergranular corrosion resistance and workability. For this reason, content of N shall be 0.03% or less. However, excessively reducing the N content increases the scouring cost, so the N content is preferably 0.002% or more. The N content is more preferably 0.002 to 0.02%. Moreover, it is preferable that the total content of C and N is 0.015% or more from the viewpoint of suppressing coarsening of crystal grains during heat treatment by carbonitride and suppressing a decrease in strength.
  • Si more than 0.1%, 1% or less
  • Si concentrates in the surface film after heat treatment and contributes to the improvement of the corrosion resistance of stainless steel. In order to obtain this effect, at least 0.1% of Si is required. Si is useful as a deoxidizing element. However, excessive addition of Si decreases workability, so the Si content is 1% or less. The Si content is preferably more than 0.1% to 0.5%.
  • Mn 0.02% or more, 1.2% or less
  • Mn is an element useful as a deoxidizing element and needs to contain at least 0.02% or more of Mn. However, if an excessive amount of Mn is contained, the corrosion resistance deteriorates, so the Mn content is set to 1.2% or less.
  • the Mn content is preferably 0.05 to 1%.
  • Cr 15% or more, 23% or less
  • Cr is an element serving as a basis for ensuring corrosion resistance in biofuel, and needs to contain at least 15% or more of Cr.
  • the corrosion resistance can be improved as the content of Cr is increased.
  • the addition of an excessive amount of Cr decreases the workability and manufacturability, so the Cr content is 23% or less.
  • the Cr content is preferably 17 to 20.5%.
  • Nb and Ti are elements useful for fixing C and N and improving the intergranular corrosion resistance of the weld. In order to obtain this effect, it is necessary to contain Nb and Ti so that the total amount of Nb and Ti (Nb + Ti) is eight times or more of the total amount of C and N (C + N). Further, Nb and Ti are concentrated in the surface film of stainless steel after the heat treatment and contribute to the improvement of corrosion resistance. In order to obtain this effect, at least 0.03% or more of Nb and / or Ti in a solid solution state that is not fixed to C and N needs to be contained.
  • Nb + Ti is set to 8 (C + N) + 0.03%.
  • the upper limit of Nb + Ti is set to 0.6%.
  • Nb + Ti is preferably ⁇ 10 (C + N) +0.03 ⁇ or more and 0.6% or less.
  • Ti concentrates on the surface film of stainless steel and contributes to improvement of corrosion resistance.
  • Ti has an effect of inhibiting brazing properties.
  • Al 0.002% or more, 0.5% or less
  • Al concentrates in the surface film of stainless steel after heat treatment and contributes to the improvement of corrosion resistance. In order to acquire this effect, it is necessary to contain 0.002% or more of Al.
  • Al has an effect such as a deoxidizing effect, and thus is an element useful in scouring and has an effect of improving moldability.
  • the Al content is set to 0.002 to 0.5%.
  • the Al content is preferably 0.005 to 0.1%.
  • Ni 2% or less
  • Ni may be included as necessary.
  • the Ni content that provides a stable effect is 0.2% or more.
  • the corrosion resistance can be improved as the Ni content is increased.
  • the addition of a large amount of Ni hardens the steel and reduces workability.
  • the Ni content is preferably 0.2 to 2%, more preferably 0.2 to 1.2%.
  • Cu 1.5% or less
  • 1.5% or less of Cu may be included as necessary.
  • the Cu content that provides a stable effect is 0.2% or more.
  • the corrosion resistance can be improved as the Cu content is increased.
  • the addition of a large amount of Cu hardens the steel and decreases the workability. Therefore, Cu content is preferably 0.2 to 1.5% and more preferably 0.2 to 0.8%.
  • Mo 3% or less
  • Mo content 0.3% or more.
  • the corrosion resistance can be improved as the content of Mo is increased.
  • the addition of a large amount of Mo hardens the steel and decreases the workability.
  • Mo since Mo is expensive, it leads to a cost increase. Therefore, the Mo content is preferably 0.3 to 3%, more preferably 1 to 0.5 to 2.0%.
  • Sn 0.5% or less
  • the Sn content that provides a stable effect is 0.01% or more. As the Sn content is increased, the corrosion resistance can be improved. However, the addition of a large amount of Sn hardens the steel and decreases the workability. Therefore, the Sn content is preferably 0.01 to 0.5%, more preferably 0.05 to 0.4%.
  • V 1% or less
  • the content of V that provides a stable effect is 0.05% or more.
  • the addition of an excessive amount of V deteriorates workability.
  • the V content is preferably 0.05 to 1%.
  • W 1% or less
  • the W content that provides a stable effect is 0.3% or more.
  • the addition of an excessive amount of W deteriorates workability.
  • W since W is expensive, it leads to an increase in cost. Therefore, the W content is preferably 0.3 to 1%.
  • B (B: 0.005% or less)
  • B 0.005% or less
  • B may be contained as necessary.
  • the B content is more preferably 0.0002 to 0.001%.
  • Zr 0.5% or less
  • 0.5% or less of Zr may be contained as necessary.
  • Co 0.2% or less
  • 0.2% or less of Co may be included as necessary.
  • Mg is an element useful for scouring because it has effects such as a deoxidation effect. Further, Mg has an effect on the miniaturized improvement in workability and toughness tissue. For this reason, you may contain 0.002% or less of Mg as needed. In order to obtain a stable effect, it is preferable to contain 0.0002% or more of Mg.
  • Ca is an element useful for scouring because it has an effect such as a deoxidation effect. For this reason, you may contain 0.002% or less of Ca as needed. In order to obtain a stable effect, it is preferable to contain 0.0002% or more of Ca.
  • REM 0.01% or less
  • REM is an element useful for scouring because it has effects such as a deoxidation effect. For this reason, you may contain 0.01% or less of REM as needed. In order to obtain a stable effect, it is preferable to contain REM 0.001% or more.
  • the P content is preferably 0.04% or less from the viewpoint of weldability, and the P content is more preferably 0.035% or less.
  • S it is preferable to make S content into 0.02% or less from a corrosion-resistant viewpoint, More preferably, S content is 0.01% or less.
  • the stainless steel of this embodiment is manufactured by the following method, for example.
  • Molten steel having the above chemical composition is converted into a converter or electric furnace, the molten steel is refined in an AOD furnace, a VOD furnace, or the like, and then formed into a steel piece by a continuous casting method or an ingot forming method.
  • the steel slab is subjected to the steps of hot rolling, annealing, pickling, cold rolling, finish annealing, and pickling. Thereafter, H 2 atmosphere including a vacuum atmosphere or N 2 of 10 -2 ⁇ 1 torr comprising N 2, performs heat treatment step of holding 0.5 to 30 minutes at a temperature of 800 °C ⁇ 1200 °C. Thereby, an oxide film having the cation fraction is formed.
  • the stainless steel of the present embodiment may be manufactured by a method in which the heat treatment step is performed after the steps of cold rolling, finish annealing, and pickling.
  • the stainless steel of this embodiment may be manufactured by a method in which the heat treatment process is performed at another stage of the manufacturing process.
  • the biofuel supply system component of this embodiment is made of the stainless steel of this embodiment.
  • the biofuel supply system component of this embodiment is preferably manufactured by a method of performing the step of forming a member having the above chemical composition and the above heat treatment step.
  • the heat treatment step in the method for manufacturing a biofuel supply system component of the present embodiment may be performed before being processed into a shape as a component, or may be performed after being processed into a shape as a component.
  • the heat treatment step is performed after being processed into a shape as a part, it is preferable that the shape is processed without removing the oxide film on the surface and reducing the corrosion resistance.
  • the heat treatment step preferably also serves as a step of brazing the members.
  • the biofuel supply system component can be efficiently manufactured.
  • the biofuel supply system component of this embodiment should just consist of stainless steel of this embodiment, and is not limited to what was brazed and joined.
  • the exhaust gas side is required to have corrosion resistance against the exhaust gas condensed water.
  • exhaust gas condensate has also diversified, increasing chloride ions and sulfuric acid ions (SO 3 2 ⁇ , SO 4 2 ⁇ ), which have a significant effect on corrosion resistance, and a neutral to weak pH. It may change to acidity and the corrosive environment may become severe.
  • the present inventors have intensively studied on improving the perforation resistance of stainless steel in an exhaust gas condensed water environment.
  • the film formed on the surface is composed of Cr, Si, Nb, Ti, and Al with a total cation fraction ( ⁇ (Contains Cr, Si, Nb, Ti, and Al contained in the oxide film) (Total amount) / (content of all cation elements contained in oxide film) ⁇ ⁇ 100 (%)).
  • the oxide film formed on the surface of stainless steel contains these elements in a total of 40% or more of the cation fraction, and is particularly corrosive among the pore resistance in the exhaust gas condensed water environment. It has been found that it acts effectively on the suppression of the occurrence of selenium.
  • the chemical composition of the steel material needs to satisfy the following formula (4).
  • an element symbol represents content (mass%) of each element.
  • the value of Nb + Ti-8 (C + N) is 0 or more.
  • Nb and / or Ti contained in the stainless steel does not exist as a solid solution, but a part of the Nb and / or Ti is fixed to C and N.
  • the solid solution Nb that is not fixed to C and N is concentrated in the passive film (oxide film) during brazing. And Nb contributes to the corrosion prevention effect in the oxide film formed by brazing.
  • the amount of Nb and / or Ti which is fixed to C and N and does not enter into a solid solution state is Nb atomic weight 93, C atomic weight 12, N atomic weight 14 From the ratio, it is considered that the total amount of C and N (C + N) is approximately 8 times. Therefore, in order to form the above oxide film that suppresses the occurrence of corrosion, the total content of Si, Cr, Al, and ⁇ Nb + Ti-8 (C + N) ⁇ contained in the stainless steel is 17.5% or more. There is a need to.
  • the condition of holding for 5 to 30 minutes at is preferable.
  • the heat treatment is simply performed in a vacuum of 10 ⁇ 2 torr or less, the total cation fraction of Cr, Si, Nb, Ti, and Al in the formed oxide film does not reach the desired cation fraction.
  • a vacuum of 10 ⁇ 2 torr or less is evacuated, and then N 2 is introduced to adjust the pressure to 10 ⁇ 2 to 1 torr.
  • the reason for this is not clear, but heat treatment in an environment containing N 2 produces (Nb, Ti) carbonitride on the surface of the stainless steel, which reduces the reduction of Fe oxide. It may have been promoted.
  • the content of N 2 in the heat treatment atmosphere is preferably 0.001 to 0.2%, more preferably 0.005 to 0.1%.
  • the heat treatment condition is to hold at 1050 to 1150 ° C. for 5 to 30 minutes in order to form an oxide film enriched with Cr, Si, Nb, Ti and Al having a total cation fraction of 40% or more. Is more preferable.
  • the holding time is more preferably 10 to 20 minutes.
  • the oxide film which has the said cation fraction can be formed by the heat processing at the time of brazing and joining the member which consists of a steel material of the said chemical composition. Therefore, the heat treatment step for forming the oxide film having the cation fraction can also serve as a step of brazing and joining a member made of a steel material having the above chemical composition.
  • 0.5 is contained at a temperature of 800 to 1200 ° C. in an environment containing N 2 and a pressure of 10 ⁇ 2 to 1 torr. A heat treatment step of holding for ⁇ 30 minutes may be performed.
  • the above heat treatment process is not added, and in the manufacturing process of steel materials and parts, conditions for heat treatment for forming an oxide film and pickling that removes the oxide film are removed. In this way, an oxide film having a desired cation fraction may be formed.
  • N 2 having a dew point of ⁇ 45 to ⁇ 75 ° C. in final finish annealing in the manufacturing process of steel materials.
  • a mixed gas atmosphere of H 2 and a method of holding 0.5 to 5 minutes at 800 ⁇ 1100 ° C.. In this case, the subsequent pickling is omitted.
  • Cr is the most important, and the cation fraction (the ratio of the Cr content to the total cation content in the oxide film) is 20%. It is preferable to contain the above Cr. More preferably, Cr, Si, Nb, Ti, and Al are 50% or more in total of the cation fraction.
  • the film thickness of the oxide film is preferably 15 nm or less, more preferably 10 nm or less. The increase in the film thickness leads to a decrease in the cation of Cr, Si, Nb, Ti, and Al per unit volume, leading to a decrease in corrosion resistance. There is a possibility that (Nb, Ti) carbonitride generated by heat treatment in an environment containing N 2 suppresses an increase in film thickness.
  • the present inventor has focused on Ni, Cu, and Mo.
  • the reason why the perforation resistance is improved by combining stainless steel with two or more selected from Ni, Cu, and Mo is estimated as follows. With the occurrence of corrosion, chloride concentrates in the pits or in the gaps, and the pH decreases. In many of these environments, the material is actively dissolved, but Ni, Cu, and Mo are all effective in reducing the active dissolution rate. Further, since the exhaust heat recovery device is used in an environment in which wetting and drying are repeated, the progress and stop of corrosion are repeated.
  • Ni and Cu having an effect of promoting the cathode reaction are considered to contribute to the promotion of repassivation.
  • Ni mainly contributes to the promotion of repassivation by increasing the cathode current.
  • Cu is thought to contribute to the promotion of repassivation by the action of making the potential noble.
  • Mo has the effect of strengthening the passive, suppresses re-occurrence of corrosion.
  • This embodiment is made in consideration of the thermal fatigue characteristics and workability required as a member of the exhaust heat recovery device in addition to the above knowledge about the perforation resistance, and exhaust heat with excellent corrosion resistance against exhaust gas condensed water. Providing ferritic stainless steel for collectors. The summary is shown below.
  • the ferritic stainless steel of this embodiment comprises a steel main body and an oxide film provided on the surface of the steel main body. Since the thickness of the oxide film is very thin compared to the thickness of the steel body, the composition of the steel material before the oxide film is formed is substantially the same as the composition of the steel body (steel material) after the oxide film is formed. Are identical.
  • the composition of the steel body (steel material) will be described below. In the present specification, unless otherwise specified, the unit “%” indicating the content of a component represents mass%.
  • C (C: 0.03% or less) Since C reduces intergranular corrosion resistance and workability, it is necessary to keep the content low. For this reason, content of C shall be 0.03% or less. However, excessively lowering the C content increases the scouring cost, so the C content is preferably 0.002% or more. The C content is more preferably 0.002 to 0.02%.
  • N (N: 0.05% or less)
  • N is an element useful for pitting corrosion resistance, but its content needs to be kept low in order to reduce intergranular corrosion resistance and workability. For this reason, content of N shall be 0.05% or less. However, excessively reducing the N content increases the scouring cost, so the N content is preferably 0.002% or more. The N content is more preferably 0.002 to 0.02%. Furthermore, from the viewpoint of suppressing crystal grain coarsening during brazing, the total content of C and N is preferably 0.015% or more ((C + N) ⁇ 0.015%).
  • Si more than 0.1%, 1% or less
  • Si concentrates in the surface film of stainless steel after brazing and contributes to the improvement of corrosion resistance. In order to obtain this effect, 0.1% or more of Si is necessary. Si is useful as a deoxidizing element. However, excessive addition of Si decreases workability, so the Si content is 1% or less. The Si content is more preferably more than 0.1% to 0.5%.
  • Mn 0.02% or more, 1.2% or less
  • Mn is an element useful as a deoxidizing element and needs to contain at least 0.02% or more of Mn. However, if an excessive amount of Mn is contained, the corrosion resistance deteriorates, so the Mn content is set to 1.2% or less.
  • the Mn content is more preferably 0.05 to 1%.
  • Cr 17% or more, 23% or less
  • Cr is an element serving as a basis for ensuring corrosion resistance and salt damage resistance to the exhaust gas condensate of stainless steel, and needs to contain at least 17% or more of Cr.
  • the corrosion resistance can be improved as the content of Cr is increased.
  • a large amount of Cr needs to be added in order to obtain the same effect as Ni, Cu, and Mo with respect to the perforation resistance of the gap.
  • the Cr content is set to 23% or less.
  • the Cr content is preferably 17% or more and 20.5% or less.
  • Al 0.002% or more, 0.5% or less
  • Al is concentrated in the surface film of stainless steel after brazing and contributes to the improvement of corrosion resistance. In order to acquire this effect, it is necessary to contain 0.002% or more of Al.
  • Al has an effect such as a deoxidizing effect, and thus is an element useful in scouring and has an effect of improving moldability.
  • the Al content is set to 0.002 to 0.5%.
  • the Al content is preferably 0.003 to 0.1%.
  • the stainless steel needs to contain two or three selected from the group consisting of Ni, Cu, and Mo.
  • Ni 0.25% to 1.5%)
  • the content of Ni that provides a stable effect in a state containing either Cu or Mo is 0.25% or more.
  • the corrosion resistance can be improved as the Ni content is increased.
  • the addition of a large amount of Ni hardens the steel and reduces workability.
  • Ni since Ni is expensive, it leads to a cost increase. Therefore, the Ni content is 1.5% or less.
  • the Ni content is preferably 0.25 to 1.2%, more preferably 0.25 to 0.6%.
  • Cu 0.25% to 1%)
  • Ni and Mo is an important element for improving the corrosion resistance, particularly the perforation resistance.
  • the Cu content that provides a stable effect in a state containing either Ni or Mo is 0.25% or more.
  • the corrosion resistance can be improved as the Cu content is increased.
  • the addition of a large amount of Cu hardens the steel and reduces workability. Therefore, the Cu content is 1% or less.
  • the Cu content is preferably 0.25 to 0.8%, more preferably 0.25 to 0.6%.
  • Mo 0.5% or more, 2% or less
  • Mo is an important element for improving the corrosion resistance, particularly the perforation resistance.
  • the Mo content that provides a stable effect in a state containing either Ni or Cu is 0.5% or more.
  • the corrosion resistance can be improved as the content of Mo is increased.
  • the addition of a large amount of Mo hardens the steel and reduces workability.
  • Mo since Mo is expensive, it leads to a cost increase. Therefore, the Mo content is 2% or less.
  • Mo is a more important element because it improves the perforation resistance by an action different from that of Ni and Cu. Therefore, it is preferable to contain Mo in a range of 0.7% to 2%.
  • the Mo content is more preferably 0.9% or more and 2% or less.
  • Nb and Ti are elements useful for fixing C and N and improving the intergranular corrosion resistance of the weld. In order to obtain this effect, it is necessary to contain Nb and Ti so that the total amount of Nb and Ti (Nb + Ti) is 8 times or more the total amount of C and N (C + N). Moreover, Nb and Ti concentrate on the surface film of stainless steel after brazing and contribute to improving corrosion resistance. In order to obtain this effect, at least 0.03% or more of Nb and / or Ti in a solid solution state that is not fixed to C and N needs to be contained.
  • Nb + Ti is set to 8 (C + N) + 0.03%.
  • the upper limit of the content of Nb + Ti is set to 0.6%.
  • Nb + Ti is preferably ⁇ 10 (C + N) +0.03 ⁇ or more and 0.6% or less.
  • Nb and Ti concentrates on the surface film of stainless steel and contributes to improvement of corrosion resistance.
  • Ti has an effect of inhibiting brazing properties.
  • Nb has the effect of improving the high temperature strength.
  • the exhaust heat recovery device is required to have thermal fatigue characteristics in order to cool high temperature exhaust gas.
  • the stainless steel preferably contains Nb.
  • V 0.5% or less
  • the content of V that provides a stable effect is 0.05% or more.
  • the addition of an excessive amount of V deteriorates workability.
  • the V content is preferably 0.05 to 0.5%.
  • W 1% or less
  • the W content that provides a stable effect is 0.3% or more.
  • the addition of an excessive amount of W deteriorates workability.
  • W since W is expensive, it leads to an increase in cost. Therefore, the W content is preferably 0.3 to 1%.
  • B (B: 0.005% or less)
  • B 0.005% or less
  • B may be contained as necessary.
  • the B content is more preferably 0.0002 to 0.0015%.
  • Zr 0.5% or less
  • 0.5% or less of Zr may be contained as necessary.
  • Sn 0.5% or less
  • 0.5% or less of Sn may be included as necessary.
  • Co 0.2% or less
  • 0.2% or less of Co may be included as necessary.
  • Mg is an element useful for scouring because it has effects such as a deoxidation effect. Further, Mg has an effect on the miniaturized improvement in workability and toughness tissue. For this reason, you may contain 0.002% or less of Mg as needed. In order to obtain a stable effect, it is preferable to contain 0.0002% or more of Mg.
  • Ca is an element useful for scouring because it has an effect such as a deoxidation effect. For this reason, you may contain 0.002% or less of Ca as needed. In order to obtain a stable effect, it is preferable to contain 0.0002% or more of Ca.
  • REM 0.01% or less
  • REM is an element useful for scouring because it has effects such as a deoxidation effect. For this reason, you may contain 0.01% or less of REM as needed. In order to obtain a stable effect, it is preferable to contain REM 0.001% or more.
  • the P content is preferably 0.04% or less from the viewpoint of weldability, and the P content is more preferably 0.035% or less.
  • S it is preferable to make S content into 0.02% or less from a corrosion-resistant viewpoint, More preferably, S content is 0.01% or less.
  • the stainless steel of this embodiment is manufactured by the following method, for example.
  • Molten steel having the above chemical composition is converted into a converter or electric furnace, the molten steel is refined in an AOD furnace, a VOD furnace, or the like, and then formed into a steel piece by a continuous casting method or an ingot forming method.
  • the steel slab is subjected to the processes of hot rolling, hot-rolled sheet annealing, pickling, cold rolling, finish annealing, and pickling. Thereafter, H 2 atmosphere including a vacuum atmosphere or N 2 of 10 -2 ⁇ 1 torr comprising N 2, performs heat treatment step of holding 0.5 to 30 minutes at a temperature of 800 °C ⁇ 1200 °C. Thereby, an oxide film having the cation fraction is formed.
  • the said heat processing process can serve as the process of brazing and joining the member which consists of steel materials of the said chemical composition. If necessary, annealing of the hot-rolled sheet may be omitted, or cold rolling, finish annealing, and pickling may be repeated. Examples of product forms include plates, tubes, bars, and wires.
  • the exhaust heat recovery device of the present embodiment includes a heat exchange part, and this heat exchange part is formed by assembling members by brazing and joining.
  • the heat exchanging portion is made of the ferritic stainless steel of this embodiment, and this ferritic stainless steel has the above-described chemical composition, and Cr, Si, Nb, Ti, and Al on the surface have a cation fraction. An oxide film containing 40% or more in total is formed.
  • the manufacturing method of the exhaust heat recovery device of the present embodiment includes a step of forming a member having the chemical composition of the present embodiment and a step of assembling the member by, for example, a general processing process.
  • the members of the assembly process it is preferable to brazing by heat-treating member in an H 2 atmosphere including a vacuum atmosphere or N 2 of 10 -2 ⁇ 1 torr containing N 2.
  • an oxide film containing Cr, Si, Nb, Ti, and Al in a total cation fraction of 40% or more is formed on the surface of the member made of ferritic stainless steel.
  • the heat exchange part of this embodiment is obtained by the above.
  • brazing and joining are not necessary.
  • the ferritic stainless steel of this embodiment having an oxide film on the surface is processed into a shape as a part. Thereby, a member is formed. Subsequently, a heat exchange part is obtained by assembling a member.
  • Example 1 150 kg of molten steel having the composition shown in Tables 1 and 2 was melted in a vacuum melting furnace and cast into a 50 kg steel ingot to obtain a steel piece. Next, the steel slab was hot rolled to a plate thickness of 4 mm at a heating temperature of 1200 ° C. to obtain a hot rolled sheet. Thereafter, the hot-rolled sheet was annealed at 850 to 950 ° C. Next, the scale was removed by shot blasting and pickling in a nitric hydrofluoric acid solution (mixed solution of nitric acid and hydrofluoric acid). Then, the steel plate was cold rolled to a plate thickness of 2 mm.
  • a nitric hydrofluoric acid solution mixed solution of nitric acid and hydrofluoric acid
  • Test pieces each having a width (W) of 25 mm and a length (L) of 100 mm were cut out from each of the cold rolled steel sheets 1-A to 1-N, and the entire surface of the test piece was wet-polished using emery paper up to # 320. Subsequently, the material No. The test pieces 1-A to 1-N were heat-treated under the conditions 1-1 shown below, Test pieces of 1-1 to 1-10, 1-101 to 1-103, 1-106, 1-201 to 1-203 were obtained. (Condition 1-1) A test piece was placed in the heating furnace. The inside of the furnace was evacuated at 10 ⁇ 3 torr and then N 2 was introduced to adjust the pressure to 10 ⁇ 1 to 10 ⁇ 2 torr.
  • test piece was heated in this atmosphere and held at 1100 ° C. for 10 minutes. Subsequently, it cooled to normal temperature in the furnace. Note that the furnace pressure was maintained at 10 ⁇ 1 to 10 ⁇ 2 torr during the temperature increase and also at 1100 ° C. In addition, the material No.
  • the test pieces 1-D, 1-F, and 1-J were subjected to heat treatment under the conditions 1-2 shown below. Test pieces 1-11 to 1-13 were obtained. (Condition 1-2) The specimen was heated in 100% H 2 with a dew point of ⁇ 65 ° C. and held at 1100 ° C. for 10 minutes.
  • test piece of 1-104 was obtained.
  • Condition 1-3 A test piece was placed in the furnace. The inside of the furnace was evacuated to 10 ⁇ 3 torr. The test piece was heated in this atmosphere and held at 1100 ° C. for 10 minutes. Subsequently, it cooled to normal temperature in the furnace. Material No. The test piece of 1-F, and was heat-treated under the conditions 1-4 below, No. of Table 3 A test piece of 1-105 was obtained.
  • the test piece was heated in the atmosphere and held at 700 ° C. for 30 minutes. Next, it was air cooled to room temperature. In Table 3, numerical values underlined are outside the scope of this embodiment.
  • Corrosion weight loss was calculated as follows. First, it measured using the direct balance which can measure the mass of the test piece before and behind a test to 0.0001g. The decrease in mass calculated from the amount of change was divided by the surface area of the test piece before the test to calculate the corrosion loss. Observation of local corrosion was performed as follows.
  • a magnification of 200 was applied to the entire surface of the test piece regardless of the portion that was in contact with the gas phase (the portion that was not in contact with the aqueous solution), the portion that was in contact with the liquid phase (the portion that was in contact with the aqueous solution), and the gas phase / liquid phase boundary. Observation was carried out using a double optical microscope. Moreover, the corrosion depth was measured by the depth of focus method in the location where local corrosion was observed.
  • Corrosion test 2 In Table 1 and Table 2, the material No. Two test pieces were cut out from each of the cold rolled steel sheets 1-A to 1-N, and the entire surface of the test piece was wet-polished using emery paper up to # 320. Thereafter, each test piece was molded into a cup having an inner diameter of 50 mm and a depth of 35 mm. Next, heat treatment was performed in the same manner as in Conditions 1-1 to 1-4 of Corrosion Test 1 described above. 45 mL of RME was put into one of the cups after the heat treatment, and 45 mL of E22 was put into the other cup.
  • XPS was an X-ray photoelectron spectrometer manufactured by ULVAC-PHI, Inc., using a mono-AlK ⁇ ray as an X-ray source, an X-ray beam diameter of about 100 ⁇ m, and an extraction angle of 45 degrees.
  • Table 3 “A value” indicates the total of the cation fractions of Cr, Si, Nb, Ti, and Al in the oxide film represented by the following formula.
  • a value (Cr + Si + Nb + Ti + Al) / (the total content of cations)
  • Reference Example No. 1-201 to 1-203 showed good corrosion resistance even though the Cr content did not satisfy the conditions of this embodiment. This is because the total concentration of formic acid + acetic acid was less than 1% and the temperature was mild at 45 ° C.
  • Comparative Example No. 1 was heat-treated only in vacuum without introducing N 2 .
  • the A value of 1-104 was 0.22.
  • Comparative Example No. The A value of 1-105 was 0.17. In either case, the composition was within the range of the present embodiment, but the A value did not satisfy the range of the present embodiment and the corrosion resistance was poor.
  • Example 2 30 kg of molten steel having the chemical composition shown in Table 4 and Table 5 below was melted in a vacuum melting furnace to produce a 17 kg flat steel ingot. Subsequently, the steel ingot was hot rolled to a thickness of 4.5 mm at a heating temperature of 1200 ° C. to obtain a hot rolled sheet. Thereafter, the hot rolled sheet was annealed at 900 to 1030 ° C. The scale was then removed by alumina shot blasting. Thereafter, the steel sheet was cold-rolled to a thickness of 1 mm and then subjected to finish annealing at 950 to 1050 ° C. to obtain cold-rolled steel sheets of Material Examples 2-1 to 2-17. Using this cold-rolled steel sheet, the corrosion resistance was evaluated and the surface film was analyzed. In Tables 4 and 5, the numerical values underlined are outside the scope of the present embodiment.
  • Test pieces each having a width of 25 mm and a length of 100 mm were cut out from each of the cold rolled steel sheets of Examples 2-1 to 2-17, and the entire surface of the test pieces was wet-polished with emery paper up to # 320. Next, heat treatment was performed under conditions 2-1 shown below, simulating the atmosphere during brazing, and test pieces of Experimental Examples 2-1 to 2-17 shown in Table 6 were obtained. (Condition 2-1) A test piece was placed in the heating furnace. The inside of the furnace was evacuated at 10 ⁇ 3 torr and then N 2 was introduced to adjust the pressure to 10 ⁇ 1 to 10 ⁇ 2 torr. The test piece was heated in this atmosphere and held at 1100 ° C. for 10 minutes.
  • test pieces of the material examples 2-1 to 2-3 were subjected to heat treatment under the following conditions 2-3, and experimental examples 2-19 to 2-21 shown in Table 6 were obtained.
  • Condition 2-3 The specimen was heated in 100% H 2 with a dew point of ⁇ 65 ° C. and held at 1100 ° C. for 10 minutes.
  • Samples for surface analysis were cut out from the cold rolled steel sheets of Material Examples 2-1 to 2-17.
  • the sample for surface analysis was also heat-treated under the same conditions as the heat treatment of the corrosion test pieces of Experimental Examples 2-1 to 2-2 in Table 6, and the surface analysis test pieces of Experimental Examples 2-1 to 2-2-21 were prepared. did.
  • the oxide film on the surface was analyzed by X-ray photoelectron spectroscopy (XPS), and the cation fraction (A ′ value) of Cr, Si, Nb, Ti, and Al in the oxide film was calculated.
  • XPS X-ray photoelectron spectroscopy
  • XPS was an X-ray photoelectron spectrometer manufactured by ULVAC-PHI, Inc., using a mono-AlK ⁇ ray as an X-ray source, an X-ray beam diameter of about 100 ⁇ m, and an extraction angle of 45 degrees.
  • Experimental Examples 2-1 to 2-12 and 2-19 to 2-21 within the scope of the present embodiment have an A ′ value of 0.4 or more (40% or more).
  • the corrosion resistance in the exhaust gas simulated condensed water is good.
  • Experimental Examples 2-13 to 2-15 are comparative examples containing only one of Ni, Cu, and Mo.
  • Experimental Example 2-17 is a comparative example in which the Cr content and the A ′ value are out of the range of the present embodiment.
  • Experimental Examples 2-13 to 2-15 and 2-17 are inferior in corrosion resistance in exhaust gas simulated condensed water.
  • Experimental Example 2-16 is a comparative example in which the cation fraction (A ′ value) in the oxide film formed by the brazing simulated heat treatment does not satisfy the range of the present embodiment.
  • the A ′ value is less than 0.4 (less than 40%), and the corrosion resistance is poor.
  • Experimental Example 2-18 was heat-treated only in a vacuum without introducing N 2 .
  • the A ′ value was less than 0.4 (less than 40%), and the corrosion resistance in the exhaust gas simulated condensed water was poor.
  • the ferritic stainless steel for biofuel supply system parts of the first embodiment has excellent corrosion resistance against biofuel, it is suitably applied to fuel supply system parts.
  • the present invention is suitably applied to parts in the fuel supply system parts that are close to the engine and are likely to become hot, such as fuel injection system parts.
  • the ferritic stainless steel for exhaust heat recovery device of the second embodiment is suitably used as a member for an exhaust heat recovery device (exhaust heat recirculation system) because it has excellent corrosion resistance against exhaust gas condensed water.
  • it is suitably used as a member of the heat exchange part of the exhaust heat recovery device.
  • it is also suitably used as a member of an exhaust gas passage portion exposed to exhaust gas condensed water such as EGR and muffler.

Landscapes

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

Abstract

D'après un mode de réalisation, un acier inoxydable ferritique contient, en % en masse, 0,03 % ou moins de C, 0,03 % ou moins de N, de 0,1 % (limite non comprise) à 1 % (limite comprise) de Si, entre 0,02 % et 1,2 % de Mn, entre 15 % et 23 % de Cr, entre 0,002 % et 0,5 % d'Al et du Nb et/ou du Ti, le reste étant constitué de Fe et des inévitables impuretés. Les formules (1) et (2) sont satisfaites. Il est formé sur la surface un film d'oxyde contenant au moins 30 % de Cr, Si, Nb, Ti et Al en termes de pourcentage total de cations. 8(C+N)+0.03≤Nb+Ti≤0.6 …(1) Si+Cr+Al+{Nb+Ti-8(C+N)}≥15.5 …(2)
PCT/JP2012/058092 2011-03-29 2012-03-28 Acier inoxydable ferritique pour élément de système d'alimentation en biocarburant, élément de système d'alimentation en biocarburant, acier inoxydable ferritique pour unité de récupération de chaleur d'échappement et unité de récupération de chaleur d'échappement Ceased WO2012133506A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
CN201280015457.9A CN103459636B (zh) 2011-03-29 2012-03-28 生物燃料供给系统部件用铁素体系不锈钢、生物燃料供给系统部件、排热回收器用铁素体系不锈钢以及排热回收器
US14/007,807 US9611525B2 (en) 2011-03-29 2012-03-28 Ferritic stainless steel for biofuel supply system part, biofuel supply system part, ferritic stainless steel for exhaust heat recovery unit, and exhaust heat recovery unit
KR1020137024892A KR20130125823A (ko) 2011-03-29 2012-03-28 바이오 연료 공급계 부품용 페라이트계 스테인리스 강, 바이오 연료 공급계 부품, 배열 회수기용 페라이트계 스테인리스 강 및 배열 회수기

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
JP2011-071372 2011-03-29
JP2011071372 2011-03-29
JP2011071812 2011-03-29
JP2011-071812 2011-03-29
JP2012057362A JP5856878B2 (ja) 2011-03-29 2012-03-14 排熱回収器用フェライト系ステンレス鋼および排熱回収器
JP2012057363A JP5856879B2 (ja) 2011-03-29 2012-03-14 バイオ燃料供給系部品用フェライト系ステンレス鋼およびバイオ燃料供給系部品
JP2012-057363 2012-03-14
JP2012-057362 2012-03-14

Publications (1)

Publication Number Publication Date
WO2012133506A1 true WO2012133506A1 (fr) 2012-10-04

Family

ID=46931215

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2012/058092 Ceased WO2012133506A1 (fr) 2011-03-29 2012-03-28 Acier inoxydable ferritique pour élément de système d'alimentation en biocarburant, élément de système d'alimentation en biocarburant, acier inoxydable ferritique pour unité de récupération de chaleur d'échappement et unité de récupération de chaleur d'échappement

Country Status (1)

Country Link
WO (1) WO2012133506A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105200330A (zh) * 2015-09-24 2015-12-30 宝钢不锈钢有限公司 一种耐高温铁素体不锈钢及其制造方法
JP2017179406A (ja) * 2016-03-28 2017-10-05 新日鐵住金ステンレス株式会社 燃料ポンプ部材用フェライト系ステンレス鋼板および燃料ポンプ部材
EP3428292A1 (fr) * 2017-07-14 2019-01-16 Daido Steel Co.,Ltd. Acier inoxydable ferritique et élément résistant à la chaleur

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60230962A (ja) * 1984-04-27 1985-11-16 Sumitomo Metal Ind Ltd 耐食性に優れたフエライト系ステンレス鋼材
JPH07180001A (ja) * 1993-12-22 1995-07-18 Nippon Steel Corp 加工性と耐銹性に優れたフェライト系ステンレス鋼光輝焼鈍材
JPH08109443A (ja) * 1994-10-07 1996-04-30 Nippon Steel Corp 耐銹性と加工性に優れたフェライト系ステンレス鋼板
JP2006134662A (ja) * 2004-11-04 2006-05-25 Nisshin Steel Co Ltd 自動車の燃料電池システム用熱交換器
JP2008001945A (ja) * 2006-06-22 2008-01-10 Nippon Steel & Sumikin Stainless Steel Corp 耐発銹性と加工性に優れた光輝焼鈍仕上げフェライト系ステンレス鋼板およびその製造方法
JP2008285731A (ja) * 2007-05-18 2008-11-27 Nisshin Steel Co Ltd 表面電気伝導性優れたステンレス鋼板およびその製造方法
JP2009215633A (ja) * 2008-03-12 2009-09-24 Nisshin Steel Co Ltd 給油系部材用フェライト系ステンレス鋼

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60230962A (ja) * 1984-04-27 1985-11-16 Sumitomo Metal Ind Ltd 耐食性に優れたフエライト系ステンレス鋼材
JPH07180001A (ja) * 1993-12-22 1995-07-18 Nippon Steel Corp 加工性と耐銹性に優れたフェライト系ステンレス鋼光輝焼鈍材
JPH08109443A (ja) * 1994-10-07 1996-04-30 Nippon Steel Corp 耐銹性と加工性に優れたフェライト系ステンレス鋼板
JP2006134662A (ja) * 2004-11-04 2006-05-25 Nisshin Steel Co Ltd 自動車の燃料電池システム用熱交換器
JP2008001945A (ja) * 2006-06-22 2008-01-10 Nippon Steel & Sumikin Stainless Steel Corp 耐発銹性と加工性に優れた光輝焼鈍仕上げフェライト系ステンレス鋼板およびその製造方法
JP2008285731A (ja) * 2007-05-18 2008-11-27 Nisshin Steel Co Ltd 表面電気伝導性優れたステンレス鋼板およびその製造方法
JP2009215633A (ja) * 2008-03-12 2009-09-24 Nisshin Steel Co Ltd 給油系部材用フェライト系ステンレス鋼

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105200330A (zh) * 2015-09-24 2015-12-30 宝钢不锈钢有限公司 一种耐高温铁素体不锈钢及其制造方法
JP2017179406A (ja) * 2016-03-28 2017-10-05 新日鐵住金ステンレス株式会社 燃料ポンプ部材用フェライト系ステンレス鋼板および燃料ポンプ部材
EP3428292A1 (fr) * 2017-07-14 2019-01-16 Daido Steel Co.,Ltd. Acier inoxydable ferritique et élément résistant à la chaleur
CN109252088A (zh) * 2017-07-14 2019-01-22 大同特殊钢株式会社 铁素体不锈钢和耐热部件
US10689723B2 (en) 2017-07-14 2020-06-23 Daido Steel Co., Ltd. Ferritic stainless steel and heat-resistant member
CN109252088B (zh) * 2017-07-14 2021-09-14 大同特殊钢株式会社 铁素体不锈钢和耐热部件

Similar Documents

Publication Publication Date Title
CN105296860B (zh) 生物燃料供给系统部件用铁素体系不锈钢以及生物燃料供给系统部件
EP2980274B1 (fr) Tôle d'acier inoxydable ferritique ayant une excellente aptitude au brasage, échangeur de chaleur, tôle d'acier inoxydable ferritique pour des échangeurs de chaleur, acier inoxydable ferritique, acier inoxydable ferritique pour des éléments de systèmes d'alimentation en carburant et élément de système d'alimentation en carburant
US10752973B2 (en) Ferrite-based stainless steel with high resistance to corrosiveness caused by exhaust gas and condensation and high brazing properties and method for manufacturing same
JP5856879B2 (ja) バイオ燃料供給系部品用フェライト系ステンレス鋼およびバイオ燃料供給系部品
JP5856878B2 (ja) 排熱回収器用フェライト系ステンレス鋼および排熱回収器
CA2707518C (fr) Acier inoxydable ferrique presentant une excellente aptitude au brasage
KR102206415B1 (ko) 페라이트계 스테인리스강
JP6379283B2 (ja) ろう付け性に優れたステンレス鋼
JP6157664B1 (ja) フェライト系ステンレス鋼およびその製造方法
JP5684547B2 (ja) 尿素ｓｃｒシステム部品用フェライト系ステンレス鋼板およびその製造方法
WO2016068291A1 (fr) Acier inoxydable à base de ferrite présentant une haute résistance à la corrosivité provoquée par du gaz d'échappement et la condensation et des propriétés au brasage élevées et procédé pour la fabrication de ce dernier
CN109790605B (zh) 用于排气系统热交换器的具有减少的碳渣吸附的铁素体不锈钢及其制造方法
WO2012133506A1 (fr) Acier inoxydable ferritique pour élément de système d'alimentation en biocarburant, élément de système d'alimentation en biocarburant, acier inoxydable ferritique pour unité de récupération de chaleur d'échappement et unité de récupération de chaleur d'échappement
JP6873020B2 (ja) フェライト系ステンレス鋼板およびその製造方法、ならびに燃料改質器および燃焼器の部材
JP5788946B2 (ja) ろう付け性に優れたろう付け接合により組み立てられる部材用フェライト系ステンレス鋼

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 12762842

Country of ref document: EP

Kind code of ref document: A1

DPE1 Request for preliminary examination filed after expiration of 19th month from priority date (pct application filed from 20040101)
ENP Entry into the national phase

Ref document number: 20137024892

Country of ref document: KR

Kind code of ref document: A

WWE Wipo information: entry into national phase

Ref document number: 14007807

Country of ref document: US

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 12762842

Country of ref document: EP

Kind code of ref document: A1