Title: Long-term creep strength and strength reduction factor for welded joints of ASME Grades 91, 92 and 122 type steels

Authors: Kazuhiro Kimura, Masaaki Tabuchi, Yukio Takahashi, Kazuo Yoshida, Koichi Yagi

Addresses: Materials Data Sheet Station, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan. ' Creep Resistant Materials Group, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan. ' Materials Science Research Laboratory, Central Research Institute of Electric Power Industry, 2-6-1 Nagasaka, Yokosuka, Kanagawa 240-0196, Japan. ' Standards and Codes Division, Japan Power Engineering and Inspection Corporation, 2-10-12 Shiba-daimon, Minato, Tokyo 105-0012, Japan. ' 971-33, Higashifukai, Nagareyama, Chiba 270-0101, Japan

Abstract: Creep rupture data of base metal and welded joints of several creep strength enhanced ferritic (CSEF) steels was collected and long-term creep strength of those steels was evaluated by the SHC committee in Japan. The previous allowable tensile stress of those steels regulated in METI Thermal Power Standard Code was reviewed and weld strength reduction factor was investigated. The master creep life equations for not only base metal, but also welded joints were developed. According to the evaluated creep rupture strength, allowable tensile stress of ASME Grade 122 type steels was revised in December 2005 and those of ASME Grade 91 and 92 type steels was revised in August 2007. The creep strength reduction factor obtained from 100,000 hours creep rupture strength of welded joints and base metal was given as a function of temperature.

Keywords: creep strength; ferritic steel; CSEF; welded joints; weld strength reduction factor; allowable stress; tensile stress; Larson-Miller parameter; LMP; post weld heat treatment; PWHT; Type IV; life prediction; region splitting analysis; offset yield stress; creep life equations; temperature.

DOI: 10.1504/IJMMP.2011.040438

International Journal of Microstructure and Materials Properties, 2011 Vol.6 No.1/2, pp.72 - 90

Published online: 27 May 2011 *

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