US3615904A - Method of improving nitride-strengthened stainless steel properties - Google Patents

Method of improving nitride-strengthened stainless steel properties Download PDF

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Publication number
US3615904A
US3615904A US803214*A US3615904DA US3615904A US 3615904 A US3615904 A US 3615904A US 3615904D A US3615904D A US 3615904DA US 3615904 A US3615904 A US 3615904A
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United States
Prior art keywords
nitride
dispersoid
stainless steel
particles
less
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Expired - Lifetime
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US803214*A
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English (en)
Inventor
Lynn E Kindlimann
Alexander B Greene
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Allegheny Ludlum Corp
Pittsburgh National Bank
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Allegheny Ludlum Steel Corp
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Assigned to ALLEGHENY LUDLUM CORPORATION reassignment ALLEGHENY LUDLUM CORPORATION CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). 8-4-86 Assignors: ALLEGHENY LUDLUM STEEL CORPORATION
Assigned to PITTSBURGH NATIONAL BANK reassignment PITTSBURGH NATIONAL BANK SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ALLEGHENY LUDLUM CORPORATION
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Assigned to PITTSBURGH NATIONAL BANK reassignment PITTSBURGH NATIONAL BANK ASSIGNMENT OF ASSIGNORS INTEREST. RECORDED ON REEL 4855 FRAME 0400 Assignors: PITTSBURGH NATIONAL BANK
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • 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
    • 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
    • C23C8/80—After-treatment

Definitions

  • a compressed nitride-strengthened, stainless steel article substantially free of pores and containing as a dispersoid therein particles of metal nitride which are present at an interparticle spacing of less than about 10 microns and which have a free energy of formation of greater than about 2l,000 cal/moi,
  • the present invention relates to a nitride-strengthened, stainless steel with improved properties and to a process for attaining them and more particularly to a nitridestrengthened, stainless steel with improved high-temperature rupture strength characteristics and to a process for attaining them.
  • a method for producing nitridestrengthened, stainless steel comprises, the steps of providing stainless steel containing a metal component capable of forming a nitride having a free energy of formation of greater than about 21,000 cal./mole in an amount sufficient to provide, after nitriding, nitride particles as a dispersoid in the steel with an interparticle spacing of less than about 10 microns and heating the steel at a temperature between l,600 F. and its melting point in a nitrogen or nitrogen containing atmosphere, such as ammonia.
  • the figure shows a plot of rupture time versus stress for members processed according to this invention and for members not processed in accordance with this invention.
  • Chromium nitride formation removes chromium from solid solution thus reducing the material's corrosion and oxidation resistance.
  • chromium nitrides will soften on exposure to high temperatures, e.g. l,200l,500 F.
  • the removal of excess nitrogen can be effected in a vacuum or by the use of a purging gas nonreactive with the steel, e.g. hydrogen.
  • a purging gas nonreactive with the steel e.g. hydrogen.
  • the removal causes pores to form within the steel. These pores increase the materials tendency to fail, as does a notch insofar as they are areas of pronounced stress concentration. Therefore, it is advantageous to compress the material after removal of excess nitrogen so as to close the pores.
  • material should be heated prior to compressing. Heat gives the material a degree of plasticity which enables a pressing force to compress it without causing nitride dispersoids to break loose from the matrix.
  • Heat gives the material a degree of plasticity which enables a pressing force to compress it without causing nitride dispersoids to break loose from the matrix.
  • a preferred temperature range is l,800-2 ,200 F.
  • the roll-pressed members exhibit a flatter slope than the members which were not compressed. They clearly show in the general direction of rolling better long-time high-temperature rupture strength characteristics than the noncompressed members. For hours at 2,000 F. they show a rupture strength of no less than 4 K.s.i.
  • the poorer high-temperature rupture strength characteristics at shorter times are attributed to the high temperatures employed for roll pressing and can be avoided by roll pressing at lower temperatures. Higher temperatures although increasing plasticity, cause nitrides to grow at the expense of small interparticle spacings upon which strength is dependent. Accordingly, the member represented by line CC should have shown better rupture strength characteristics than the member represented by line DD since it was pressed at a lower temperature but contrarily it did not. This is because it was compressed to a greater degree through additional roll passes and hence was at an elevated temperature for a longer time, thus allowing further nitride growth.
  • the compressed members had a nominal composition of 18 percent Cr, 12 percent Ni and 2 percent Ti but could have had other nominal compositions, i.e. 25 percent Cr, 32 percent Ni and 2 percent Ti.
  • the members were heated to temperatures of 2, 100 and 2,200" F. but could have been heated to lower temperatures, i.e. 800 F.
  • Rolling was used to supply pressure but other forms of pressure application could be employed, e.g. platens.
  • several members can be simultaneously pressed as long as a separating compound is placed between them so as to prevent bonding therebetween. The number is only limited by the capabilities of the pressing and handling equipment.
  • a method of improving the properties of nitridestrengthened, stainless steel comprising the following steps:
  • a method of improving the high-temperature rupture strength characteristics of nitride-strengthened, stainless steel comprising the following steps:
  • nitride-strengthened stainless steel member containing as a dispersoid therein particles of metal nitride of a metal from the group consisting of titanium, aluminum, vanadium, and columbium, said nitride particles being present at an interparticle spacing of less than about 2 microns;
  • a compressed nitride-strengthened, stainless steel article having a rupture strength of no less than about 4 K.s.i. for I30 hours at 2,000 F; said steel article being substantially free of pores and containing as a dispersoid therein particles of a metal nitride having a free energy of formation of greater than about -2l,000 caL/mole, said nitride particles being present at an interparticle spacing of less than about 10 microns.
  • dispersoid is a nitride of a metal from the group consisting of titanium, aluminum, vanadium and columbium.
  • An article according to claim 8 wherein said dispersoid particles are present at an interparticle spacing of less than about 20 microns.
  • a roll-pressed nitride-strengthened, stainless steel article substantially free of pores; said steel article containing as a dispersoid therein particles of a metal nitride of a metal from the group consisting of titanium, aluminum, vanadium and columbium, said nitride particles being present at an interparticle spacing of less than about 2 microns.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Powder Metallurgy (AREA)
  • Heat Treatment Of Steel (AREA)
  • Rolling Contact Bearings (AREA)
  • Compositions Of Oxide Ceramics (AREA)
US803214*A 1969-02-28 1969-02-28 Method of improving nitride-strengthened stainless steel properties Expired - Lifetime US3615904A (en)

Applications Claiming Priority (1)

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US80321469A 1969-02-28 1969-02-28

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US3615904A true US3615904A (en) 1971-10-26

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US803214*A Expired - Lifetime US3615904A (en) 1969-02-28 1969-02-28 Method of improving nitride-strengthened stainless steel properties

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US (1) US3615904A (enrdf_load_stackoverflow)
DE (1) DE2009700A1 (enrdf_load_stackoverflow)
FR (1) FR2037475A5 (enrdf_load_stackoverflow)
GB (1) GB1269016A (enrdf_load_stackoverflow)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3773500A (en) * 1970-03-26 1973-11-20 Nippon Steel Corp High tensile steel for large heat-input automatic welding and production process therefor
US4046601A (en) * 1976-06-01 1977-09-06 Armco Steel Corporation Method of nitride-strengthening low carbon steel articles
US4047981A (en) * 1976-06-30 1977-09-13 Armco Steel Corporation Internally nitrided ferritic stainless steel strip, sheet and fabricated products and method therefor
US4464207A (en) * 1978-08-14 1984-08-07 The Garrett Corporation Dispersion strengthened ferritic stainless steel
US5614039A (en) * 1995-09-29 1997-03-25 The Boc Group, Inc. Argon employing heat treating process

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1330966A (fr) * 1962-06-18 1963-06-28 Lasalle Stell Company Procédé de durcissement de l'acier par vieillissement et déformation
FR1413549A (fr) * 1963-11-22 1965-10-08 Sandvikens Jernverks Ab Acier allié
FR93081E (fr) * 1966-01-13 1969-02-07 Ugine Kuhlmann Aciers améliorés.
FR91370E (fr) * 1966-01-13 1968-05-31 Electro Chimie Soc D Aciers améliorés
FR91296E (fr) * 1966-01-13 1968-05-17 Electro Chimie Soc D Aciers améliorés
FR1481703A (fr) * 1966-06-01 1967-05-19 Mannesmann Ag Procédé pour la fabrication d'alliages de métal, de fer ou d'acier à haute teneur en azote, ainsi qu'alliages conformes à ceux obtenus par ledit procédé ou procédé similaire
SE362445B (enrdf_load_stackoverflow) * 1968-06-07 1973-12-10 Allegheny Ludlum Steel

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3773500A (en) * 1970-03-26 1973-11-20 Nippon Steel Corp High tensile steel for large heat-input automatic welding and production process therefor
US4046601A (en) * 1976-06-01 1977-09-06 Armco Steel Corporation Method of nitride-strengthening low carbon steel articles
US4047981A (en) * 1976-06-30 1977-09-13 Armco Steel Corporation Internally nitrided ferritic stainless steel strip, sheet and fabricated products and method therefor
US4464207A (en) * 1978-08-14 1984-08-07 The Garrett Corporation Dispersion strengthened ferritic stainless steel
US5614039A (en) * 1995-09-29 1997-03-25 The Boc Group, Inc. Argon employing heat treating process

Also Published As

Publication number Publication date
DE2009700A1 (de) 1970-09-24
GB1269016A (en) 1972-03-29
FR2037475A5 (enrdf_load_stackoverflow) 1970-12-31

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AS Assignment

Owner name: ALLEGHENY LUDLUM CORPORATION

Free format text: CHANGE OF NAME;ASSIGNOR:ALLEGHENY LUDLUM STEEL CORPORATION;REEL/FRAME:004779/0642

Effective date: 19860805

AS Assignment

Owner name: PITTSBURGH NATIONAL BANK

Free format text: SECURITY INTEREST;ASSIGNOR:ALLEGHENY LUDLUM CORPORATION;REEL/FRAME:004855/0400

Effective date: 19861226

AS Assignment

Owner name: PITTSBURGH NATIONAL BANK

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST. RECORDED ON REEL 4855 FRAME 0400;ASSIGNOR:PITTSBURGH NATIONAL BANK;REEL/FRAME:005018/0050

Effective date: 19881129