EP0225425A2 - Niedriglegierter Stahl mit guter Beständigkeit gegen Spannungsrisskorrosion - Google Patents

Niedriglegierter Stahl mit guter Beständigkeit gegen Spannungsrisskorrosion Download PDF

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Publication number
EP0225425A2
EP0225425A2 EP86108534A EP86108534A EP0225425A2 EP 0225425 A2 EP0225425 A2 EP 0225425A2 EP 86108534 A EP86108534 A EP 86108534A EP 86108534 A EP86108534 A EP 86108534A EP 0225425 A2 EP0225425 A2 EP 0225425A2
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EP
European Patent Office
Prior art keywords
stress corrosion
corrosion cracking
crystal grain
low alloy
grain size
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Application number
EP86108534A
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English (en)
French (fr)
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EP0225425B1 (de
EP0225425A3 (en
Inventor
Kazutoshi Shimogori
Kazuo Fujiwara
Kiyoshi Sugie
Kikuo Morita
Takenori Nakayama
Mutsuhiro Miyakawa
Yasushi Torii
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Kobe Steel Ltd
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Kobe Steel Ltd
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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
    • C22C38/44—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
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium

Definitions

  • the present invention relates to low alloy steel used as a material for steam turbines or the like, and more specifically to nickel-chrome-molybdenum steel.
  • nickel-chrome-molybdenum steel to which vanadium is added which is high strength steel, is used as a material to meet the aforesaid characteristic.
  • This steel is obtained by adding molybdenum or vanadium which is a fine carbide deposited element to nickel-chrome high strength steel sensitive to temper embrittlement as is known whereby increasing a restraint of softening, that is, a tem- peraing resistance at a high tempering temperature. This steel is well suited for the above-described applications.
  • NiCrMo steel having excellent stress corrosion cracking resistance are as follows:
  • C is an element for securing the strength.
  • this element increases the sensitivity of stress corrosion cracking, and when its content exceeds 0.4 %, toughness is deteriorated in relation to other alloy elements. Therefore, in claims, the upper limit is set to 0.40 %.
  • S is an element which greatly deteriorates hot processing characteristics, and in view of preventing cracking during hot forging, the upper limit is set to 0.030 % in claims.
  • Ni and Cr are elements indispensable to an increase in strength, an improvement of hardenability and an enhancement in toughness. Both the elements have to be added in the amount in excess of 50 %. Preferably, Ni and Cr should be added in the amount in excess of 3.25% and 1.25 %, respectively, in order to win further improvement of hardenability and toughness. When the contents of said elements exceeds 4.00 % and 2.50 %, respectively, the transformation characteristics are greately varied, and it takes a long time for heat treatment to obtain an excellent toughness, which is therefore impractical.
  • Ni content and Cr content are limited in the range of 0.50 to 4.00 % and 0.50 to 2.50 %, respectively in (1) to (5) above and 3.25 to 4.00 % and 1.25 to 2.00 %, respectively, in (6) and (7) above.
  • Mo enhances the corrosion resistance of the prior y grain boundary to materially reduce the sensitivity of intergranular stress corrosion cracking, is deposited in grains as a fine carbide during the tempering and greatly contributes to prevention of temper embrittlement and increase in strength.
  • more than 0.25 % of Mo need to added but when the content thereof exceeds 4.00 %, the aforesaid effects are saturated and the toughness begins to deteriorate.
  • addition of Mo more than as needed is uneconomical. Thereby, in claims, the Mo content is limited to the range of 0,25 % to 4.00 %.
  • V is an effective element in which strength of steel is increased by formation of fine crystals and precipitation hardening .
  • V is added as necessary but when the content thereof exceeds 0.30 %, the effect thereof is saturated, and therefore, in claims, the upper limit is set to 0.30 %.
  • Si, P and Mn are greatly concerned in the sensitivity of intergranular stress corrosion cracking. They are important elements which should be complementarily limited in relation to the size of crystal grain and a small addition of Ti, At, Nb, W, B Ce and Sn.
  • Si is an element necessary for deoxidation during refining.
  • the content of Si exceeds 0.15 %, the corrosion resistance of the prior y grain boundary deteriorates and the sensitivity or intergranular stress corrosion cracking materially increases. Therefore, in claims, the upper limit of Si is set to 0.15 %.
  • P is an impurity element which is segregated in the prior y grain boundary to deteriorate the corrosion resistance and increase the sensitivity of intergranular stress corrosion cracking and promote temper embrittlement.
  • chrome-molybdenum steel and nickel-chrome-molybdenum steel in the JIS Standards the content thereof is limited to 0.030 % or less in view of temper embrittlement .
  • said content is necessary to be further limited, and in claims 1 to 5 the content of P is set to 0.010 % or less.
  • Mn is added for deoxidation and desulfurization during refining.
  • the content of Mn exceeds 0.20 %, the aforesaid segregation of grain boundary is promoted and the sensitivity of stress corrosion cracking materially increases, and in addition, Si and P compositely acts on the stress corrosion cracking and the range of application thereof is greatly concerned in the size of crystal grains and the small addition of Ti, At, Nb, W, B, Ce and Sn, as was made apparent from the results of the inventors own studies.
  • the sensitivity of stress corrosion cracking also depends on the prior austenite crystal grain size, and sufficient reliability cannot be obtained even if the aforesaid alloy composition should be satisfied when the ASTM crystal grain size number is smaller than 3. Accordingly , in claim 1 of the present invention, the prior austenite crystal grain size number is limited to above 4 in addition to the limitation of the aforesaid alloy elements.
  • At, Ti, Nb, Ce, W, B and Sn are addition elements indispensable to enhancement of corrosion resistance of the prior y grain boundary and great contribution to reducing the sensitivity of stress corrosion cracking of the grain boundary type.
  • these six elements i.e., At, Ti, Nb, Ce, W and B
  • more than one kind of these elements need be added in the amount of 0.001 % or more in total.
  • Nb additional set to 0.005 % or more is the most effective to reduce the stress corrosion cracking, relating to the limitations of Si + Mn + 20P ⁇ 0.50 %.
  • the toughness is materially deteriorated.
  • the total amount of addition of these elements is limited to the range of 0.001 to 0.50 %.
  • similar effect to the addition of the aforesaid six elements may be obtained by addition of more than 0.003 % of Sn but when the content thereof exceeds 0.015 %, the temper embrittlement is increased to materially deteriorate the toughness.
  • the content of Sn is limited to the range of 0.003 to 0.015 %.
  • limitation of Mn content and/or range of Si + Mn + 20P or limitation of size of crystal grains are necessary.
  • NiCrMo steel according to the present invention contains optimum alloy elements having the excellent stress corrosion cracking resistance in the range of an optimum composition ratio and or has an appropriate microstructure (crystal grain size), and therefore, even if said steel is used for members subjected to a high load stress under the corrosion environment such as NaOH, OH- or the like, there is less possibility in producing stress corrosion cracking.
  • Table 1 appearing later gives chemical compositions of sample steel used for stress corrosion cracking test and the prior y crystal grain size. These steels were produced by adjusting compositions and melting them in a high frequency induction electric furnace, thereafter making ingots, hot forging them into 25 mm thickness, heating them to a temperature of forming austenite and water quenching them, thereafter heating them up to 620°C and holding them for one hour and then cooling them at a speed of 4°C/min. The crystal grain size was variously varied by adjusting the quenching temperature (heating temperature) and its holding time. The thus produced sample steel was machined to produce a strip of testpiece of 1.5 mm thickness x 15 mm width x 65 mm length.
  • Table 3 appearing later gives chemical composition of sample steel used for stress corrosion cracking test and the prior y crystal grain size.
  • these steels were produced by adjusting compositions and melting them in a high frequency induction electric furnace, thereafter making ingots, hot forging them into 25 mm thickness, heating them to a temperature of forming austenite and water quenching them, thereafter heating them up to 620°C and holding them for one hour and then cooling them at a speed of 4°C/min.
  • the crystal grain size was variously varied by adjusting the quenching temperature - (heating temperature) and its holding time.
  • the thus produced sample steel was machined to produce a strip of testpiece of 1.5 mm thickness x 15 mm width x 65 mm length.
  • the aforesaid testpiece was attached to a four-point bending constant load testing apparatus, bending stress corresponding to 60 % or 100 % of 0.2 % proof stress of the steel was applied thereto, the testpiece was immersed in 30 % NaOH aqueous solution at 150°C for one week or three weeks, and thereafter the presence of cracking and the depth of cracking of the testpiece were measured by observation of an optical microscope.
  • Test III which has the most severe testing conditions, only steels corresponding to Nos. 85 to 94, that is, those which are fulfilled with Si + Mn + 20P ⁇ 0.50 and ASTM crystal grain size number in excess of 4 have no stress corrosion cracking. That is, it is evident that the aforementioned condition is the most effective limitation in prevention of stress corrosion craking that may be achieved by the present invention.

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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)
  • Turbine Rotor Nozzle Sealing (AREA)
EP86108534A 1985-11-06 1986-06-23 Niedriglegierter Stahl mit guter Beständigkeit gegen Spannungsrisskorrosion Expired - Lifetime EP0225425B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP60249707A JPS62109949A (ja) 1985-11-06 1985-11-06 耐応力腐食割れ性に優れたＮｉＣｒＭｏ鋼
JP249707/85 1985-11-06

Publications (3)

Publication Number Publication Date
EP0225425A2 true EP0225425A2 (de) 1987-06-16
EP0225425A3 EP0225425A3 (en) 1988-10-05
EP0225425B1 EP0225425B1 (de) 1991-08-21

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ID=17197003

Family Applications (1)

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EP86108534A Expired - Lifetime EP0225425B1 (de) 1985-11-06 1986-06-23 Niedriglegierter Stahl mit guter Beständigkeit gegen Spannungsrisskorrosion

Country Status (3)

Country Link
EP (1) EP0225425B1 (de)
JP (1) JPS62109949A (de)
DE (1) DE3680995D1 (de)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0384181A2 (de) * 1989-02-03 1990-08-29 Hitachi, Ltd. Dampfturbinenrotor und hitzebeständiger Stahl dafür
EP0505085A1 (de) * 1991-03-20 1992-09-23 Hitachi, Ltd. Stahl für Ankerwellen von Elektromaschinen
FR2748036A1 (fr) * 1996-04-29 1997-10-31 Creusot Loire Acier faiblement allie pour la fabrication de moules pour matieres plastiques
US6224334B1 (en) 1989-02-03 2001-05-01 Hitachi, Ltd. Steam turbine, rotor shaft thereof, and heat resisting steel
EP2159296A1 (de) * 2007-04-13 2010-03-03 Sidenor Investigacion y Desarrollo, S.A. Gehärteter und getemperter stahl und verfahren zur herstellung von teilen aus dem stahl
EP2671959A1 (de) * 2012-06-04 2013-12-11 General Electric Company Nickel-Chrom-Molybdän-Vanadiumlegierung und Turbinenkomponente
DE102014016073A1 (de) 2014-10-23 2016-04-28 Vladimir Volchkov Stahl
DE102016005532A1 (de) 2016-05-02 2017-11-02 Vladimir Volchkov Stahl
EP4008801A1 (de) * 2020-12-01 2022-06-08 CRS Holdings, LLC Hochfeste stahllegierung mit hoher schlagzähigkeit, daraus hergestellter gegenstand und verfahren zu dessen herstellung

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63255344A (ja) * 1987-04-13 1988-10-21 Japan Steel Works Ltd:The 超高純度タ−ビンロ−タ軸材
JPH04362155A (ja) * 1991-06-10 1992-12-15 Japan Steel Works Ltd:The 高低圧一体型タービンロータ用高純度鋼
JP7534102B2 (ja) * 2020-02-27 2024-08-14 日本製鋼所Ｍ＆Ｅ株式会社 ＮｉＣｒＭｏ鋼およびその製造方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1009924A (en) * 1962-06-29 1965-11-17 Republic Steel Corp Steel alloys and methods of making same
US3438822A (en) * 1966-10-31 1969-04-15 United States Steel Corp Method of making fine-grained steel
DE2754524A1 (de) * 1977-12-07 1979-06-13 Jurij Fedorovitsch Balandin Stahl
FR2492846A1 (fr) * 1980-08-05 1982-04-30 N Proizv Ob Tulatschermet Acier

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1009924A (en) * 1962-06-29 1965-11-17 Republic Steel Corp Steel alloys and methods of making same
US3438822A (en) * 1966-10-31 1969-04-15 United States Steel Corp Method of making fine-grained steel
DE2754524A1 (de) * 1977-12-07 1979-06-13 Jurij Fedorovitsch Balandin Stahl
FR2492846A1 (fr) * 1980-08-05 1982-04-30 N Proizv Ob Tulatschermet Acier

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0384181A2 (de) * 1989-02-03 1990-08-29 Hitachi, Ltd. Dampfturbinenrotor und hitzebeständiger Stahl dafür
EP0384181A3 (de) * 1989-02-03 1990-12-05 Hitachi, Ltd. Dampfturbinenrotor und hitzebeständiger Stahl dafür
EP0761836A1 (de) * 1989-02-03 1997-03-12 Hitachi, Ltd. Hitzebeständiger Stahl- und Turbinenrotor
US6224334B1 (en) 1989-02-03 2001-05-01 Hitachi, Ltd. Steam turbine, rotor shaft thereof, and heat resisting steel
EP0505085A1 (de) * 1991-03-20 1992-09-23 Hitachi, Ltd. Stahl für Ankerwellen von Elektromaschinen
US5288455A (en) * 1991-03-20 1994-02-22 Hitachi, Ltd. Steel for rotor shafts of electric machines and method and product thereof
AU708786B2 (en) * 1996-04-29 1999-08-12 Creusot Loire Industrie Low alloy steel for the manufacture of moulds for plastics
US5855845A (en) * 1996-04-29 1999-01-05 Creusot Loire Industrie Societe Anonyme Low alloy steel for the manufacture of molds for plastics
EP0805220A1 (de) * 1996-04-29 1997-11-05 CREUSOT LOIRE INDUSTRIE (Société Anonyme) Niedrig legiertes Stahl für die Herstellung von Pressformen für Plastikwerkstoffen
FR2748036A1 (fr) * 1996-04-29 1997-10-31 Creusot Loire Acier faiblement allie pour la fabrication de moules pour matieres plastiques
EP2159296A1 (de) * 2007-04-13 2010-03-03 Sidenor Investigacion y Desarrollo, S.A. Gehärteter und getemperter stahl und verfahren zur herstellung von teilen aus dem stahl
EP2159296A4 (de) * 2007-04-13 2014-09-10 Sidenor Investigacion Y Desarrollo S A Gehärteter und getemperter stahl und verfahren zur herstellung von teilen aus dem stahl
EP2671959A1 (de) * 2012-06-04 2013-12-11 General Electric Company Nickel-Chrom-Molybdän-Vanadiumlegierung und Turbinenkomponente
DE102014016073A1 (de) 2014-10-23 2016-04-28 Vladimir Volchkov Stahl
DE102016005532A1 (de) 2016-05-02 2017-11-02 Vladimir Volchkov Stahl
EP4008801A1 (de) * 2020-12-01 2022-06-08 CRS Holdings, LLC Hochfeste stahllegierung mit hoher schlagzähigkeit, daraus hergestellter gegenstand und verfahren zu dessen herstellung

Also Published As

Publication number Publication date
EP0225425B1 (de) 1991-08-21
DE3680995D1 (de) 1991-09-26
JPS62109949A (ja) 1987-05-21
EP0225425A3 (en) 1988-10-05

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