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  Title Ultrasonic inspection for scattered oxides in ERW pipe welds
  Author(s) Dr Yukinori Iizuka, Dr Takatoshi Okabe, Shintaro Kumazawa, and Shigeto Sakashita  
  Abstract IN RECENT YEARS, quality improvement of the welded part of ERW pipe has progressed, and as a result, the size of the oxides that affect quality has been reduced and their density is low. In this research, the authors developed an ultrasonic inspection technology which makes it possible to detect such scattered type oxides. First, the area density of the scattered type oxides was clarified to be about 3% by analysing the results of ultrasonic C-scan testing using a point focused probe. Next, the detection level of the scattered oxides for artificial flaws was analysed, and it was found that the requirement to detect the echo level is -32 dB from a drilled hole with a diameter of 1.6 mm. Based on the results, the authors developed a high sensitivity ultrasonic inspection technology using a point focused tandem method applying a phased array technique. The signal-to- noise ratio of the developed ultrasonic inspection technology reached 38 dB for the drilled hole with a diameter of 1.6 mm. Thus, the new technology has sufficiently high sensitivity for detection of scattered type oxides. The detection results of the ultrasonic inspection technology and the results of the Charpy impact test showed good agreement. Full-length inspection for the scattered type oxides that cause deterioration of weld quality has been achieved.  
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