報告書番号

Q11005

タイトル（和文）

ボイラ配管溶接部の形状変化部に適用可能な超音波フェーズドアレイ技術の開発―第3報：複雑な余盛形状を有する溶接部への適用―

タイトル（英文）

Development of Ultrasonic Phased Array Technique Applicable to Geometry Variation Regions of Weld Joints in Steam Pipes - Part 3: Application to weld with complex surface profile -

概要 （図表や脚注は「報告書全文」に掲載しております）

本報告では，複雑な余盛形状を有する溶接部の探傷方法を開発した．クリープ損傷を想定して溶接部に模擬き裂を挿入した溶接継手試験体を作製し，受信波形を用いて余盛形状を測定した．その結果，複雑な形状も精度良く測定できることが確認できた．また，幾何光学的回折理論に基づくシミュレーション手法を活用することで，作製した試験体の探傷において，模擬き裂からの最大振幅が得られる条件を選定した．さらに，複雑な表面形状における超音波伝搬経路の計算方法を改良し，余盛形状の測定結果とシミュレーションにより選定した条件をもとに，余盛から超音波を入射して電子走査を実施した．その結果，模擬き裂が想定される位置に明瞭な指示が得られ，本手法が複雑な余盛形状を有する溶接部にも適用できることが確認できた．

概要 （英文）

Creep damage in heat affected zone (HAZ) of welded high-chromium pipes is a serious problem in ultra super critical thermal power plants. Because creep damage progresses at the internal HAZ preferentially rather than surfaces, nondestructive inspection technique is necessary to detect this type of creep damage. The phased array ultrasonic testing has been applied to detection of creep damage in the welded pipes which do not have complex surface profiles, and it can detect about damage of 70% rupture time. In the field inspection, however, testing surfaces are often complex profiles such as a weld crown and a nozzle welding. When a weld crown exists, ultrasonic waves are usually transmitted through a flat surface over the base metal with high refraction angle. Detection sensitivity becomes low because focal length becomes short with increase in the refraction angle. It is possible to obtain high detective sensitivity if ultrasonic waves are transmitted through the surface of weld crown. We developed the phased array ultrasonic inspection technique which measures surface profiles and performs beam steering taking into account surface profiles. In this report, our method is applied to weld crown with complex surface profile. Surface profiles of weld crown of butt welding specimen measured by our method agree well with real shapes. In the sectorial views obtained by waves transmitted through the complex geometry surface over the crown, an indication for simulated crack can clearly be observed.

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