Long-Term Creep Strength Evaluation of Welded Joint of ASME Grade 91 Type Steel

Abstract

Abstract. Creep rupture data of welded joints of ASME Grade 91 type steel were collected by the Assessment Committee on Creep Data of High Chromium Steels, which consists of electric utilities, manufacturers, and research institutes in Japan. Within this framework, the creep rupture life curves of welded joints were reevaluated using the latest dataset to examine the validity of the long-term creep rupture life curves determined by the committee in 2015. The author independently performed regression analyses using the same methodology as adopted in the 2015 assessment, including newly obtained long-term creep data, some of which were obtained under the author's involvement. This study extends the validation range of the existing evaluation framework to approximately 100,000 h. It was found that the evaluation formula proposed in 2015 remains applicable for appropriately evaluating the newly obtained long-term data. Comparison with estimated creep life under actual service conditions derived from creep data of long-term used materials also showed reasonable agreement. These results confirm that the 2015 evaluation formula remains valid in the long-term region, and revision of the formula is not required.