Effect of NB on the proof strength of ferritic stainless steels at elevated temperatures

Atsushi Miyazaki, Kenji Takao, Osamu Furukimi

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

The effect of Nb on the high temperature proof strength of 0.46 % Nb-added ferritic stainless steel was studied from the viewpoints, of solid solution strengthening, precipitation strengthening, and precipitation strengthening during tensile test and/or preceding hold time. The results obtained were as follows. (1) The increase in high temperature proof strength in Nb-added ferritic stainless steel is particularly remarkable at around 700°C in comparison with that in Ti-added steels. (2) After aging treatment for 2 h at 700°C, in addition to the approximately 0.14 % content of coarse Nb carbides and nitrides which had precipitated before this aging treatment, fine Fe2Nb Laves phase particles with a size of 0.02 μm precipitated out in an amount of approximately 0.3 %, and virtually no solid solution Nb existed in the steel. The 700°C proof strength in this condition showed a value near the 700°C proof strength before the aging treatment, that is, when approximately 0.3 % solid solution Nb was present. (3) When aging treatment is performed at 700°C for 2 h or more, virtually all the added Nb precipitates out. The coarsening of the Fe2Nb laves phase particles within the range of 0.02-0.05 μm during aging at 700°C greatly decreases the high temperature proof strength at 700°C. (4) Cold rolled steel sheets of Nb-added ferritic stainless steel are normally manufactured by annealing at a temperature of 900°C or higher in order to cause recrystallization. Accordingly, before measurement of the proof strength at 700°C, the steel contains a large quantity of solid solution Nb. The phenomenon of particularly high strength at 700°C is considered to be attributable to the precipitation of this solid solution Nb as a fine Fe2Nb Laves phase during the tensile test and/or preceding hold time.

Original languageEnglish
Pages (from-to)916-920
Number of pages5
Journalisij international
Volume42
Issue number8
DOIs
Publication statusPublished - Jan 1 2002

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Stainless Steel
Ferritic steel
Solid solutions
Stainless steel
Aging of materials
Steel
Temperature
Coarsening
Steel sheet
Nitrides
Carbides
Precipitates
Annealing

All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

Cite this

Effect of NB on the proof strength of ferritic stainless steels at elevated temperatures. / Miyazaki, Atsushi; Takao, Kenji; Furukimi, Osamu.

In: isij international, Vol. 42, No. 8, 01.01.2002, p. 916-920.

Research output: Contribution to journalArticle

Miyazaki, Atsushi ; Takao, Kenji ; Furukimi, Osamu. / Effect of NB on the proof strength of ferritic stainless steels at elevated temperatures. In: isij international. 2002 ; Vol. 42, No. 8. pp. 916-920.
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abstract = "The effect of Nb on the high temperature proof strength of 0.46 {\%} Nb-added ferritic stainless steel was studied from the viewpoints, of solid solution strengthening, precipitation strengthening, and precipitation strengthening during tensile test and/or preceding hold time. The results obtained were as follows. (1) The increase in high temperature proof strength in Nb-added ferritic stainless steel is particularly remarkable at around 700°C in comparison with that in Ti-added steels. (2) After aging treatment for 2 h at 700°C, in addition to the approximately 0.14 {\%} content of coarse Nb carbides and nitrides which had precipitated before this aging treatment, fine Fe2Nb Laves phase particles with a size of 0.02 μm precipitated out in an amount of approximately 0.3 {\%}, and virtually no solid solution Nb existed in the steel. The 700°C proof strength in this condition showed a value near the 700°C proof strength before the aging treatment, that is, when approximately 0.3 {\%} solid solution Nb was present. (3) When aging treatment is performed at 700°C for 2 h or more, virtually all the added Nb precipitates out. The coarsening of the Fe2Nb laves phase particles within the range of 0.02-0.05 μm during aging at 700°C greatly decreases the high temperature proof strength at 700°C. (4) Cold rolled steel sheets of Nb-added ferritic stainless steel are normally manufactured by annealing at a temperature of 900°C or higher in order to cause recrystallization. Accordingly, before measurement of the proof strength at 700°C, the steel contains a large quantity of solid solution Nb. The phenomenon of particularly high strength at 700°C is considered to be attributable to the precipitation of this solid solution Nb as a fine Fe2Nb Laves phase during the tensile test and/or preceding hold time.",
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AB - The effect of Nb on the high temperature proof strength of 0.46 % Nb-added ferritic stainless steel was studied from the viewpoints, of solid solution strengthening, precipitation strengthening, and precipitation strengthening during tensile test and/or preceding hold time. The results obtained were as follows. (1) The increase in high temperature proof strength in Nb-added ferritic stainless steel is particularly remarkable at around 700°C in comparison with that in Ti-added steels. (2) After aging treatment for 2 h at 700°C, in addition to the approximately 0.14 % content of coarse Nb carbides and nitrides which had precipitated before this aging treatment, fine Fe2Nb Laves phase particles with a size of 0.02 μm precipitated out in an amount of approximately 0.3 %, and virtually no solid solution Nb existed in the steel. The 700°C proof strength in this condition showed a value near the 700°C proof strength before the aging treatment, that is, when approximately 0.3 % solid solution Nb was present. (3) When aging treatment is performed at 700°C for 2 h or more, virtually all the added Nb precipitates out. The coarsening of the Fe2Nb laves phase particles within the range of 0.02-0.05 μm during aging at 700°C greatly decreases the high temperature proof strength at 700°C. (4) Cold rolled steel sheets of Nb-added ferritic stainless steel are normally manufactured by annealing at a temperature of 900°C or higher in order to cause recrystallization. Accordingly, before measurement of the proof strength at 700°C, the steel contains a large quantity of solid solution Nb. The phenomenon of particularly high strength at 700°C is considered to be attributable to the precipitation of this solid solution Nb as a fine Fe2Nb Laves phase during the tensile test and/or preceding hold time.

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