EP0337846B1 - Austenitisch-ferritischer rostfreier Stahl - Google Patents

Austenitisch-ferritischer rostfreier Stahl Download PDF

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Publication number
EP0337846B1
EP0337846B1 EP89400888A EP89400888A EP0337846B1 EP 0337846 B1 EP0337846 B1 EP 0337846B1 EP 89400888 A EP89400888 A EP 89400888A EP 89400888 A EP89400888 A EP 89400888A EP 0337846 B1 EP0337846 B1 EP 0337846B1
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Prior art keywords
alloy
stainless steel
heat treatment
copper
austeno
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EP89400888A
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English (en)
French (fr)
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EP0337846A1 (de
Inventor
Jacques Charles
Pierre Soulignac
Daniel Catelin
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Creusot Loire Industrie SA
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Creusot Loire Industrie SA
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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
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper

Definitions

  • the present invention relates to an austenitic-ferritic stainless steel.
  • Austeno-ferritic stainless steels are known having good mechanical properties, good corrosion resistance and good weldability.
  • Patent application EP 0.156.778 thus describes an austenitic-ferritic stainless steel alloy whose austenitic phase remains stable allowing cold deformation between 10 and 30%, good weldability and good corrosion resistance.
  • Patent application GB-A-1 456 634 discloses an austeno-ferritic steel with the composition in percentage by weight: 0.01-0.1% C, 0.2-2% Si, 0.2-4% Mn, 23-30% Cr, 4 -7% Ni, 0.06-0.4% N, 1-5% Mo, 1.3-4% Cu, the balance being Fe.
  • the copper content allows an improvement in resistance to rupture and corrosion.
  • the object of the present invention is to produce an austeno-ferritic alloy whose corrosion resistance is improved compared to existing alloys and which has a high machinability index.
  • Such an alloy has a low percentage of molybdenum but a high copper content, the latter being dissolved by heat treatment above 900 ° C. and followed by rapid cooling to ambient, the composition of this alloy being the next, expressed as a percentage by weight. the balance being Fe.
  • the composition is balanced to obtain between 38 and 70% of ferrite at 300 K (27 ° C).
  • compositions have been summarized as elements of addition to Fe for the alloys A and B according to the invention and the known alloys.
  • the alloys of the invention are produced by melting to a minimum of 1600 ° C. and reheated to approximately 1180 ° C. after solidification. They undergo sheet metal rolling. Samples are taken in order to determine the structural stability as a function of the heat treatments and more particularly the hardening, the mechanical and physical characteristics, the corrosion resistance as well as the aptitude for machinability.
  • Carbon is reduced to lower lower contents to 0.06% in order to reduce the risks of carbide formation during heat treatments which would be detrimental to the resistance to certain forms of corrosion.
  • the silicon is reduced to low contents lower than 1.2% in order to reduce the risks of formation of intermetallic compounds which weaken the alloy.
  • Manganese makes it possible to increase the solid dissolution of nitrogen in the alloy but its content must be limited to 3% so as not to become detrimental to the resistance to generalized and localized corrosion in certain cases.
  • the chromium is controlled so that the volume fractions of the ferritic and austenitic phases are close. Too low a content does not allow a sufficient volume fraction of ferrite to be obtained.
  • Too high a content may require significant additions of nickel and nitrogen, which, given the price of nickel, should be avoided.
  • the alloy has an increased tendency to precipitate embrittling intermetallic phases during heat treatments.
  • chromium contents between 21 and 25% are used, more precisely a content of 23.5%. At such a percentage, the alloy has excellent corrosion resistance.
  • Such a chromium content associated with a low nickel and molybdenum content makes it possible to avoid, even for heat treatments of a few hours, the formation of an ⁇ 'phase, by demixing of the ⁇ phase, hardening and embrittling.
  • Nickel is an element which stabilizes the austenitic phase so as to optimize the austenite / ferrite balance. Given its price, its addition is limited to 3 to 6%, in particular 4.2%. Nitrogen is involved in maintaining the austenite / ferrite balance and, moreover, such an addition makes it possible to increase the mechanical characteristics and the resistance to pitting corrosion. The addition of nitrogen is limited to 0.30 and often close to 0.13%.
  • Molybdenum is limited to a percentage of 1% maximum so as to reduce the manufacturing costs of the alloy and limit the formation of intermetallic phases. Molybdenum improves the corrosion resistance of the alloy.
  • Copper unlike known alloys, is present in relatively large percentages between 1 and 3.5%. This element is generally present in small quantities in known alloys because its solubility in austeno-ferritic alloys during cooling is limited.
  • This hardening is proportional for a heat treatment given to the copper content.
  • hardened alloy B it is alloy B which has been subjected to a heat treatment of 5 h at 400 ° C.
  • the alloys according to the invention have improved mechanical properties, in particular the values of the conventional elastic limit (Re 0.2%) and the elastic limit at 1% (Re 1%) while retaining a resilience value on a V-notch test piece (KCV) and sufficient ductility (Elongation A).
  • the machinability index of the alloys according to the invention is significantly improved compared to known alloys and in particular to the alloy of patent application EP 0.156.778.
  • the three parameters studied are Brinnel hardness (HB), the machinability index for a cutting speed of 0.5 m / min and a drilling test in number of holes corresponding to a cumulative length of 500mm (0.5 m).
  • the known alloys have hardness values which frame the hardness value of sample A of the alloy according to the invention and all of the two machinability tests clearly show performance. of alloy A.
  • the starting potential is -600 mV relative to a saturated calomel electrode (DHW) and for a scanning speed of 0.25 mV / sec.
  • the return was made for a current of 100 ⁇ A up to -1100 mV / DHW.
  • the passivation current Ip is reduced while the breaking potential is increased, which makes it possible to extend the field of use of the alloy according to the invention in terms of redox potential.
  • the alloy according to the invention solves the problem posed, by improving the mechanical characteristics, the machinability without these improvements being detrimental to the qualities of corrosion resistance.
  • the Cu content must be limited to 3.5% in order to avoid the major risks of tearing of products during processing.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Catalysts (AREA)
  • Glass Compositions (AREA)

Claims (6)

  1. Austenoferritische rostfreie Stahllegierung mit sehr gutem Korrosionsverhalten und guter Abspanbarkeitszahl, welche einen geringen Gehalt an Molybdän und einen hohen Gehalt an Kupfer, welches durch Wärmebehandlung der Legierung oberhalb 900°C und gefolgt von einem raschen Abkühlen auf Raumtemperatur gelöst ist, aufweist, wobei die Zusammensetzung die folgende ist:
    Figure imgb0009
    Rest Eisen.
  2. Rostfreie Stahllegierung nach Anspruch 1, dadurch gekennzeichnet, daß sie die folgende Zusammensetzung hat:
       C = 0,02 Gew.-%
       Si = 0,6
       Mn = 1,9
       Ni = 4,1
       Cr = 23,5
       Mo = 0,13
       N = 0,1
       Cu = 1,6.
  3. Rostfreie Stahllegierung nach Anspruch 1, dadurch gekennzeichnet, daß sie die folgende Zusammensetzung hat:
       C = 0,02
       Si = 0,5
       Mn = 2
       Ni = 3,9
       Cr = 24,3
       Mo = 0,14
       N = 0,09
       Cu = 2,8.
  4. Rostfreie Stahllegierung nach irgendeinem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß das Kupfer durch einen Schmelzvorgang bei mindestens 1600°C gefolgt von einer Nachbehandlung bei 1180°C nach Erstarrung solubilisiert ist.
  5. Stahllegierung nach Anspruch 4, dadurch gekennzeichnet, daß derart, daß das solubilisierte Kupfer partiell ausgeschieden wird, die Legierung eine Wärmebehandlung zwischen 300 und 500°C durchmacht.
  6. Rostfreie Stahllegierung nach Anspruch 5, dadurch gekennzeichnet, daß die Wärmebehandlung fünfstündig bei 400°C ist.
EP89400888A 1988-04-15 1989-03-30 Austenitisch-ferritischer rostfreier Stahl Expired - Lifetime EP0337846B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT89400888T ATE89874T1 (de) 1988-04-15 1989-03-30 Austenitisch-ferritischer rostfreier stahl.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8805045A FR2630132B1 (fr) 1988-04-15 1988-04-15 Acier inoxydable austeno-ferritique
FR8805045 1988-04-15

Publications (2)

Publication Number Publication Date
EP0337846A1 EP0337846A1 (de) 1989-10-18
EP0337846B1 true EP0337846B1 (de) 1993-05-26

Family

ID=9365363

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89400888A Expired - Lifetime EP0337846B1 (de) 1988-04-15 1989-03-30 Austenitisch-ferritischer rostfreier Stahl

Country Status (6)

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EP (1) EP0337846B1 (de)
AT (1) ATE89874T1 (de)
CA (1) CA1340030C (de)
DE (1) DE68906708T2 (de)
FI (1) FI93126C (de)
FR (1) FR2630132B1 (de)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0750053B1 (de) * 1994-12-16 2001-10-10 Sumitomo Metal Industries, Ltd. Rostfreier duplexstahl mit hervorragendem korrosionswiderstand
JP3508095B2 (ja) * 1999-06-15 2004-03-22 株式会社クボタ 耐熱疲労性・耐腐食疲労性およびドリル加工性等に優れたフェライト−オーステナイト二相ステンレス鋼および製紙用サクションロール胴部材
KR20090005252A (ko) * 2004-01-29 2009-01-12 제이에프이 스틸 가부시키가이샤 오스테나이트·페라이트계 스테인레스 강
TWI394848B (zh) * 2007-10-10 2013-05-01 Nippon Steel & Sumikin Sst 雙相不銹鋼線材、鋼線及螺釘以及其製造方法
SE533635C2 (sv) 2009-01-30 2010-11-16 Sandvik Intellectual Property Austenitisk rostfri stållegering med låg nickelhalt, samt artikel därav

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1158614A (en) * 1967-03-16 1969-07-16 Langley Alloys Ltd Improvement in Stainless Steels
GB1456634A (en) * 1972-09-13 1976-11-24 Langley Alloys Ltd High strength stainless steel having a high resistance to corro sive and abrasive wear in corrosive environments particularly chloride environments
CA1242095A (en) * 1984-02-07 1988-09-20 Akira Yoshitake Ferritic-austenitic duplex stainless steel
SE451465B (sv) * 1984-03-30 1987-10-12 Sandvik Steel Ab Ferrit-austenitiskt rostfritt stal mikrolegerat med molybden och koppar och anvendning av stalet
US4612069A (en) * 1984-08-06 1986-09-16 Sandusky Foundry & Machine Company Pitting resistant duplex stainless steel alloy

Also Published As

Publication number Publication date
ATE89874T1 (de) 1993-06-15
FR2630132A1 (fr) 1989-10-20
FI891783A (fi) 1989-10-16
EP0337846A1 (de) 1989-10-18
FI891783A0 (fi) 1989-04-14
FR2630132B1 (fr) 1990-08-24
FI93126B (fi) 1994-11-15
FI93126C (fi) 1995-02-27
DE68906708T2 (de) 1993-09-16
DE68906708D1 (de) 1993-07-01
CA1340030C (fr) 1998-09-08

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