Sakamoto K.,Japan Nuclear Energy Safety Organization |
Furukawa T.,Japan Power Engineering and Inspection Corporation JAPEIC |
Komura I.,JAPEIC |
Kamiyama Y.,JAPEIC |
Mihara T.,University of Toyama
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2012
Japan Nuclear Energy Safety Organization (JNES) has been carrying out the research program entitled "Nondestructive Inspection Technologies for the Cast Stainless Steel Piping" since 2009FY to comprehend the unique ultrasonic wave propagation in the Cast Austenitic Stainless Steel (CASS) and to confirm detection and sizing capability for cracks in the material by currently available ultrasonic testing techniques. The research is also intended to provide inspection staff with the fundamental information of ultrasonic wave propagation in CASS, for educational purpose. In this research program, specimens whose material, size, dimension and welding method are identical to the main coolant piping system in Japanese pressurized water reactors (PWRs) are examined. Results from the study on the capability for inspection of CASS and the unique wave propagation phenomena such as beam skewing are discussed in this paper. Copyright © 2012 by ASME.
Brziak P.,Welding Research Institute |
Lomozik M.,Institute of Welding |
Mizuno R.,Japan Power Engineering and Inspection Corporation JAPEIC |
Matsuda F.,Japan Power Engineering and Inspection Corporation JAPEIC
Archives of Metallurgy and Materials | Year: 2011
SQV2A Manganese-Molybdenum-Nickel ferritic steel has been developed for pressure vessel fabrication. Due to its chemical composition and carefully controlled heat treatment the SQV2A steel consists of fine-grained tempered martensite/lower bainite microstructure, which exhibits well-balanced combination of strength and low temperature toughness. However, this balance is disturbed by the thermal cycles experienced during welding, producing areas of unaccepted mechanical behaviors. Generally, a decrease in toughness of some regions of BM Heat Affected Zone is the most critical aspect of multi-layer (repair) welding. A full scale Post Welding Heat Treatment (PWHT) usually restores the mechanical behaviors to requested levels. Additionally, PWHT removes hydrogen trapped in the microstructure during welding. A situation becomes critical, when on-site local (repair) welding takes place. Harsh environment, difficult access and a presence other facilities make the in-situ PWHT almost inapplicable. In term of cold cracking prevention, a Gas Tungsten arc Welding (GTAW) gives acceptable hydrogen levels in the weld region; and full scale PWHT is unnecessary. This is the main reason why the GTAW has become a leading process for on-site (repair) welding of heavy section components. Moreover, a automatic GTAW process offers better weld geometry controlling which has become out of importance for welding not followed by PWHT. A precisely controlled multiple weld thermal cycles of predefined peak temperatures in particular weld regions can be employed for restoring the mechanical behavior of critical weld areas instead of full scale PWHT.