Methodology of creep data analysis for advanced high Cr ferritic steel

Kouichi Maruyama, Kyosuke Yoshimi

Research output: Chapter in Book/Report/Conference proceedingConference contribution

11 Citations (Scopus)

Abstract

Long term creep rupture life is usually evaluated from short term data by a time-temperature parameter (TTP) method. The apparent activation energy Q for rupture life of steels sometimes changes from a high value of short term creep to a low value of long term creep. However, the conventional TTP analyses ignore the decrease in Q, resulting in the overestimation of rupture life recognized recently in advanced high Cr ferritic steels. A multi region analysis of creep rupture data is applied to a creep data set of Gr. 122 steel; in the analysis a creep rupture data is divided into several data sets so that Q value is unique in each divided data set. The multi region analysis provides the best fit to the data and the lowest value of 105 h creep rupture strength among the three ways of data analysis examined. The conventional single region analysis cannot correctly represent the data points and predicts the highest strength. A half of 0.2 % proof stress could not be an appropriate boundary for dividing data to be used in the multi region analysis. In the 2001 Edition of ASME Code an F average concept has been proposed as a substitution for the safety factor of 2/3 for average rupture stress. The allowable stress of Gr. 122 steel may decrease significantly when the F average concept and the multi region analysis are adopted.

Original languageEnglish
Title of host publication2007 Proceedings of the ASME Pressure Vessels and Piping Conference - 8th International Conference on Creep and Fatigue at Elevated Temperatures - CREEP8
Pages631-636
Number of pages6
DOIs
Publication statusPublished - 2008 May 19
Event2007 ASME Pressure Vessels and Piping Conference - 8th International Conference on Creep and Fatigue at Elevated Temperatures, PVP-2007/CREEP8 - San Antonio, TX, United States
Duration: 2007 Jul 222007 Jul 26

Publication series

Name2007 Proceedings of the ASME Pressure Vessels and Piping Conference - 8th International Conference on Creep and Fatigue at Elevated Temperatures - CREEP8

Other

Other2007 ASME Pressure Vessels and Piping Conference - 8th International Conference on Creep and Fatigue at Elevated Temperatures, PVP-2007/CREEP8
CountryUnited States
CitySan Antonio, TX
Period07/7/2207/7/26

Keywords

  • ASME P122
  • Allowable stress
  • Overestimation of rupture life
  • Time-temperature parameter metnod

ASJC Scopus subject areas

  • Mechanical Engineering

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