EP1557477B1 - METHOD FOR PRODUCING OXIDATION-RESISTANT HIGH Cr FERRITIC HEAT RESISTANT STEEL - Google Patents

METHOD FOR PRODUCING OXIDATION-RESISTANT HIGH Cr FERRITIC HEAT RESISTANT STEEL Download PDF

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Publication number
EP1557477B1
EP1557477B1 EP03770135A EP03770135A EP1557477B1 EP 1557477 B1 EP1557477 B1 EP 1557477B1 EP 03770135 A EP03770135 A EP 03770135A EP 03770135 A EP03770135 A EP 03770135A EP 1557477 B1 EP1557477 B1 EP 1557477B1
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EP
European Patent Office
Prior art keywords
oxidation
coating film
protective coating
ferritic
working
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.)
Expired - Fee Related
Application number
EP03770135A
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German (de)
English (en)
French (fr)
Other versions
EP1557477A4 (en
EP1557477A1 (en
Inventor
Takehiko National Inst. for Mat. Scie. Itagaki
Shiro National Inst. for Mat. Scie. Torizuka
Hiroyuki c/o National Inst. for Mat Sci Kutsumi
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National Institute for Materials Science
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National Institute for Materials Science
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Filing date
Publication date
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Publication of EP1557477A1 publication Critical patent/EP1557477A1/en
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Classifications

    • 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
    • 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
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • 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
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite

Definitions

  • the invention of this application relates to a method for producing ferritic heat-resistant steel for use in boilers of thermal power plants, chemical industry apparatuses, and the like that are operated at high temperatures and under low oxygen partial pressure atmospheres.
  • Heat resistant steel and heat resistant alloys have been used as materials resisting to high temperatures and high pressures at thermal power plants; in the case of using such heat resistant steel and heat resistant alloys under the atmosphere, dense oxide coating film forms on the surface to function as protective layers.
  • Cr-containing heat resistant steel and heat-resistant alloys having a Cr content of 25 mass% or more show excellent oxidation-resistance because oxidation-resistant protective film is formed even under high temperature water vapor atmospheric condition.
  • chromium (Cr)-containing heat resistant steel and heat-resistant alloys having a Cr content of or about 20 mass% it is possible to modify the surface of the base material by applying a mechanical treatment such as shot peening, or to form an oxidation-resistant protective coating film by a method such as crystal grain refining treatment and the like.
  • the invention of the application provides the invention as follows.
  • the invention of the present application provides a method for producing a steel which is a ferritic heat-resistant steel containing 7-15 mass % of Cr, in which at least the region up to 10 ⁇ m defined by surface depth is made of a worked texture composed of extended ferritic grains or superfine texture composed of ferrites 3 ⁇ m or less in grain diameter, and having a Cr-rich (Cr 2 O 3 ) protective coating film on the surface, said method characterised by applying working at a strain rate of 0.1 sec -1 or higher and at a working ratio of 70% or higher, in the temperature range of from 400 to 800°C to form a worked texture composed of extended ferritic grains or a superfine texture composed of ferrites 3 ⁇ m or less in grain diameter, at least in the region up to 10 ⁇ m defined by surface depth, and by applying pre-oxidation treatment to form a protective coating film wherein the pre-oxidation treatment is carried out by holding the steel for 30 to 90 minutes in the temperature range of from 400 to 800°C under the atmosphere. It further provides a production method
  • the invention of the application is most characterized by that the oxidation resistance is improved by applying a specific working and heat-treatment, and not by increasing the composition of chromium (Cr) or silicon (Si), nor by adding elements such as palladium (Pd) or platinum (Pt) and the like. Accordingly, the high Cr ferritic heat-resistant steel obtained by the method for improving the oxidation resistance according to the invention of the application possesses an advantage in that the physical properties and the chemical properties of the initial composition remain without being impaired.
  • the surface layer of the steel material can be modified by applying mechanical treatment such as shot peening and the like, or an oxidation-resistant protective coating film can be formed by applying relatively mild crystal grain refining treatment with large grains about 10 to 50 ⁇ m in particle diameter, however, in high Cr ferritic heat-resistant steel containing 15 mass % or less Cr, such oxidation-resistant protective coating film cannot be formed even if such treatment should be employed.
  • the keys of the invention of the present application are to accumulate strain energy at high levels by applying warm intensive working to the high Cr ferritic heat-resistant steel, or to form fine texture consisting of crystal grains 2 ⁇ m or less in grain diameter.
  • the reason for accumulating strain energy at high levels or for forming fine texture consisting of crystals grains 3 ⁇ m or less in grain diameter is because, the steel material having the strain energy accumulated in high levels easily undergoes recrystallization to form superfine grain texture.
  • the grain boundary area increases to contribute for the diffusion acceleration of chromium (Cr).
  • chromium Cr
  • Cr 2 O 3 chromium oxide
  • thermomechanical treatment such as the rolling or the forging generally employed in the art, it is not possible to highly accumulate the strain energy or to form a fine texture consisting of ferritic crystal grains 3 ⁇ m or less in grain diameter according to the invention of the present application.
  • warm working treatment is performed at a strain rate of 0.1 sec -1 or higher and at a working ratio (cross section area reduction ratio) of 70 % or higher.
  • the working ratio is lower than 70 %, the accumulation of the desired strain energy remains insufficient, and the generation of protective coating film and the use thereof cannot be fully expected ever after the pre-oxidation treatment.
  • the warm intense working it is preferably carried out in the temperature range of 400 to 800°C. Further, by forming the strain under the conditions above, it is possible to generate the elongated ferritic grains or fine grains.
  • the morphology of the elongated ferritic grains it is preferred that it has a shorter diameter of 5 ⁇ m or less, and most preferably, it has a shorter diameter of 3 ⁇ m or less; otherwise, the ferritic grains has a grain diameter of 3 ⁇ m or less, and most preferably, they are fine grains 1 ⁇ m or less in grain diameter.
  • the invention of the present application comprises accumulating strain energy at high levels by applying warm intensive working to the high Cr ferritic heat-resistant steel, or forming fine texture consisting of crystal grains 3 ⁇ m or less in grain diameter; however, the protective coating film does not always form at high temperatures in the presence of water vapor by simply accumulating the strain energy by warm intensive working or by forming fine crystal texture. It is necessary to form sequentially thereafter the protective coating film by applying pre-oxidation treatment.
  • the pre-oxidation treatment is preferably carried out under the atmosphere or under an inert gas (rare gas or gaseous nitrogen) atmosphere containing gaseous oxygen, but more practical is to perform the treatment in the atmosphere. Further, the pre-oxidation treatment is preferably performed by heat treatment in the atmosphere at 400 - 800°C for about 30 to 90 minutes.
  • Cr chromium
  • the grain diameter is 0.8 ⁇ m or less for the sample held at 660°C or lower, and is 1- 2 ⁇ m for the sample held at 680 - 700°C.
  • the invention of the application enables forming an oxidation-resistant protective coating film on the high Cr ferritic heat-resistant steel having a Cr content of 7-15 mass %, on which an oxidation-resistant protective coating film had never been formed, and this widely increases the usage of high Cr ferritic heat-resistant steel. Furthermore, the invention of the application is advantageous in that it utilizes heat treatment, because it does not make any changes on the composition of the high Cr ferric heat-resistant steel. Moreover, since the protective coating film is thin and is tightly adhered, it hardly peels off; it thereby exhibits effect on greatly reducing the risk of causing clogging of the piping due to the peeled off scales, or of wearing the turbine blades.
  • Mod. 9Cr-1Mo steel was subjected to 70% compression working at 500°C, and was cut and polished in such a manner that the fine texture region and the worked texture region should be exposed on the surface. Then, after applying pre-oxidation treatment at 650°C for 1 h in the atmosphere, the test specimen was oxidized in water vapor at 650°C/100 h.
  • Fig. 1 shows the cross section SEM photograph of the intensively worked part. The formation of the Cr-rich (Cr 2 O 3 ) protective coating film (0.1 ⁇ m or less in thickness) on the surface was observed. Furthermore, the crystal grain diameter of the ferritic grains in the fine texture region under the protective coating film was found to be 1.0 ⁇ m or smaller. Further, the shorter diameter of the elongated ferrite in the worked texture region under the protective coating film was found to be 3 ⁇ m.
  • Mod. 9Cr-1Mo steel was subjected to pre-oxidation treatment at 680°C for 1 h in the atmosphere, and was then subjected to water-vapor oxidation at 650°C/100 h.
  • Fig. 2 shows the cross section SEM photograph of the resulting product, but the growth of an Fe-rich double layer scale (about 60 ⁇ m in thickness) due to accelerated oxidation was observed. The average grain diameter of the ferritic grains was 7 ⁇ m.
  • Mod. 9Cr-1Mo steel was subjected to 70% compression working at 500°C in a manner similar to that of Example 1, and was subjected to water-vapor oxidation at 650°C/3 h thereafter without applying pre-oxidation treatment for observation.
  • Fig. 3 shows the cross section SEM photograph of the intensively worked part. The formation of double layer scale (about 10 ⁇ m in thickness) was observed.
  • the invention of the application enables forming a thin and highly adhesive oxidation-resistant protective coating film, which had been believed impossible, on the high Cr ferritic steel having a Cr content of 7-15%.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Heat Treatment Of Steel (AREA)
EP03770135A 2002-11-01 2003-11-04 METHOD FOR PRODUCING OXIDATION-RESISTANT HIGH Cr FERRITIC HEAT RESISTANT STEEL Expired - Fee Related EP1557477B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2002320568 2002-11-01
JP2002320568A JP4253719B2 (ja) 2002-11-01 2002-11-01 耐酸化性高Ｃｒフェライト系耐熱鋼の製造方法
PCT/JP2003/014066 WO2004040031A1 (ja) 2002-11-01 2003-11-04 耐酸化性高Ｃｒフェライト系耐熱鋼の製造方法

Publications (3)

Publication Number Publication Date
EP1557477A1 EP1557477A1 (en) 2005-07-27
EP1557477A4 EP1557477A4 (en) 2006-05-03
EP1557477B1 true EP1557477B1 (en) 2009-01-21

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP03770135A Expired - Fee Related EP1557477B1 (en) 2002-11-01 2003-11-04 METHOD FOR PRODUCING OXIDATION-RESISTANT HIGH Cr FERRITIC HEAT RESISTANT STEEL

Country Status (8)

Country Link
US (1) US20040250923A1 (ja)
EP (1) EP1557477B1 (ja)
JP (1) JP4253719B2 (ja)
KR (1) KR100619158B1 (ja)
CN (1) CN1329543C (ja)
DE (1) DE60325995D1 (ja)
DK (1) DK1557477T3 (ja)
WO (1) WO2004040031A1 (ja)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9847520B1 (en) * 2012-07-19 2017-12-19 Bloom Energy Corporation Thermal processing of interconnects
DE102018217284A1 (de) * 2018-10-10 2020-04-16 Siemens Aktiengesellschaft Verbesserung des Niedertemperatur-Oxidationswiderstands von Chromstahl, Bauteil und Verfahren

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4331474A (en) * 1980-09-24 1982-05-25 Armco Inc. Ferritic stainless steel having toughness and weldability
JPH07268554A (ja) * 1994-03-28 1995-10-17 Nippon Steel Corp 成形加工性および耐熱性の優れた自動車排気系用フェライト系ステンレス鋼板
JPH09143611A (ja) * 1995-11-21 1997-06-03 Nippon Steel Corp 成形性及び疲労特性に優れた耐熱軟化性を有する熱延 高強度鋼板
DE69827729T2 (de) * 1997-09-22 2005-04-28 National Research Institute For Metals Ferritischer,wärmebeständiger Stahl und Verfahren zur Herstellung
KR100536828B1 (ko) * 1997-09-22 2006-02-28 카가쿠기쥬쯔죠 킨조쿠자이료 기쥬쯔켄큐죠 미세페라이트주체조직강과그제조방법
JP4221518B2 (ja) * 1998-08-31 2009-02-12 独立行政法人物質・材料研究機構 フェライト系耐熱鋼
JP4355782B2 (ja) * 1999-02-26 2009-11-04 独立行政法人物質・材料研究機構 耐酸化性の改善されたフェライト系耐熱鋼
JP2001192730A (ja) * 2000-01-11 2001-07-17 Natl Research Inst For Metals Ministry Of Education Culture Sports Science & Technology 高Ｃｒフェライト系耐熱鋼およびその熱処理方法
CN1482648A (zh) * 2000-03-02 2004-03-17 住友金属工业株式会社 彩色显象管荫罩框及框架构件
DE60200326T2 (de) * 2001-01-18 2005-03-17 Jfe Steel Corp. Ferritisches rostfreies Stahlblech mit hervorragender Verformbarkeit und Verfahren zu dessen Herstellung

Also Published As

Publication number Publication date
DK1557477T3 (da) 2009-05-18
WO2004040031A1 (ja) 2004-05-13
EP1557477A4 (en) 2006-05-03
CN1692171A (zh) 2005-11-02
JP4253719B2 (ja) 2009-04-15
EP1557477A1 (en) 2005-07-27
KR100619158B1 (ko) 2006-08-31
US20040250923A1 (en) 2004-12-16
KR20040089657A (ko) 2004-10-21
DE60325995D1 (de) 2009-03-12
CN1329543C (zh) 2007-08-01
JP2004156075A (ja) 2004-06-03

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