Effect of grain size and phase transformation on fracture toughness in heat-affected zone of reactor pressure vessel steels

原子炉圧力容器熱影響部の破壊靱性に及ぼす粒径及び相変態の影響

勝山 仁哉  ; 飛田 徹; 西山 裕孝 ; 鬼沢 邦雄 

Katsuyama, Jinya; Tobita, Toru; Nishiyama, Yutaka; Onizawa, Kunio

原子炉圧力容器(RPV)鋼の溶接熱影響部(HAZ)における金属組織と破壊靱性の相関を明らかにするため、典型的な多層盛溶接継手のHAZを対象とした金属組織観察と有限要素法熱伝導解析を行い、複数の溶接入熱に伴う粒径及び相分布の非均質性について特徴付けを行った。これをもとに、HAZの熱履歴を模擬した再現熱処理を施して代表的な粒径及び相を有する供試材を多数製作し、破壊靱性等の機械的特性の相違を明らかにした。また、特徴的なHAZ再現熱処理材に対して実施した中性子照射試験について、これまでに得られた結果等を紹介する。

The metallurgical structures and fracture toughness in heat-affected zone (HAZ) of rector pressure vessel (RPV) steels have been studied. Typical RPV plates and their butt-weld joints were produced by multi-pass welding. Inhomogeneity of metallurgical structures such as grain size and phase distribution in HAZ of weld joints has been characterized by microscopic observation and thermal analysis by finite element method. Based on these results, several kinds of simulated HAZ materials varying grain size and microstructure were produced from the plates. Results showed that there were clear differences in mechanical properties such as fracture toughness among typical HAZ materials and the base plate. Preliminary results of neutron irradiation tests are also presented for base metal and some simulated HAZ materials.