Session: MF-16-01 Creep and Creep-Fatigue Interaction-1

Paper Number: 122999

122999 - Revision of Long-Term Creep Strength Evaluation of Base Metal of Asme Grade 91 Type Steel 

In preliminary study on creep rupture life scatter estimation of base metal of ASME Grade 91 type steel under actual service conditions performed by one of authors, it was pointed out that the creep rupture life curves and allowable stress of Grade 91 type pipe steel, which were determined in Japan in 2015, may not be appropriate. Therefore, a re-evaluation of those was conducted in this work by the Assessment Committee on Creep Data of High Chromium Steels, which consists of the Federation of Electric Power Companies of Japan, materials producers, power plant manufacturers and institutes in Japan, which had conducted the evaluation of the material in 2015. Creep rupture data were again provided for the re-evaluation by each organization of the Assessment Committee and creep rupture strength was assessed using the latest data set of Grade 91 type steel by means of region splitting analysis method in the same manner in the previous study. It was suggested that the assessment should be performed all at once regardless of product forms such as pipe, plate and tube. As a result, creep rupture life curves and allowable stresses of Grade 91 type pipe steel was revised towards a lower strength side compared with those in 2015. Furthermore, on the basis of the latest data and knowledge regarding the effect of chemical composition on the creep life of Grade 91 type steel, revisions to Japanese material standards regarding the chemical composition of Grade 91 type steel were proposed to prevent low-strength Grade 91 type steel from being produced.

Presenting Author: Masatsugu Yaguchi Central Research Institute of Electric Power Industry

Presenting Author Biography: Educational Background: Doctor in Mechanical Engineering in 1995 , University of Tokyo
Organization : Central Research Institute of Electric Power Industry since 1995
Division/Dept.: Materials Science Division, Energy Transformation Research Laboratory
Position : Associate Vice President

Authors:

Kazuhiro Kimura National Institute for Materials Science
Masatsugu Yaguchi Central Research Institute of Electric Power Industry