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

Paper Number: 84220

84220 - Development of Life Estimation Method for Nozzle Welds in Large Scale Piping of Modified 9Cr-1Mo Steel -Part I: Experimental Study 

Creep damage in weld heat-affected zone (type IV damage) has frequently occurred in creep strength-enhanced ferritic (CSEF) steels used in piping and header of ultra-super critical (USC) power plants, and it is required to develop a life evaluation method for this kind of damage. In particular, the type IV damage has been frequently reported in longitudinal welds and nozzle welds. Many studies have been conducted on the longitudinal welds, and the applicability of life evaluation by non-destructive testing and numerical analysis has been examined. On the other hand, there are few studies on the nozzle welds, and the applicability of the existing life evaluation method is not clear. In this study, internal pressure creep test and numerical analysis were carried out on a large diameter pipe specimen which has several welded nozzles in order to clarify the applicability of the creep life evaluation method for the nozzle welds.

This first report describes the experimental part. The internal pressure creep test at 650 °C was performed on the large-diameter pipe specimen of P91 steel. The test was interrupted three times and non-destructive inspections were performed at each interruption. They included phased array ultrasonic testing, magnetic particle testing and replica observation. The test was completed when the test time reached about 20,000 hours. and cross-sectional observations were performed after the specimen was cut in many pieces. Based on these efforts, the location and process of creep damage development in the nozzle welds and the effectiveness of non-destructive inspection were revealed.

Presenting Author: Haruhisa Shigeyama Central Research Institute of Electric Power Industry

Presenting Author Biography: Haruhisa Shigeyama is a research scientist of Central Research Institute of Electric Power Industry, CRIEPI, Japan. He received a doctoral degree in Engineering from Tohoku University in 2014 and joined CRIEPI in the same year. His specialty is high temperature strength and fracture mechanics of metallic materials. Haruhisa is mainly researching on the life evaluation of high temperature components in thermal power plants. In particular, he is actively researching on the creep crack initiation and growth under multiaxial stress state of 9Cr steel used in steam piping of USC power plant. In addition, he is also researching on thermal fatigue life evaluation of gas turbine blades and creep life evaluation of boiler tubes.

Authors:

Haruhisa Shigeyama Central Research Institute of Electric Power Industry
Yukio Takahashi Central Research Institute of Electric Power Industry
Koji Tamura Central Research Institute of Electric Power Industry
Masatsugu Yaguchi Central Research Institute of Electric Power Industry
Satoshi Nishinoiri Central Research Institute of Electric Power Industry