村上 敬宜

松岡 三郎; 本間 紳浩; 田中 裕之; 福島 良博; 村上 敬宜

We investigated the effect of hydrogen on the tensile properties of a quenchtempered lowalloy steel, SCM435, with the tensile strength of 930 MPa used for hydrogen storage cylinders. Tensile specimens were machined from a cylinder with the inside and outside diameters of 245 and 315 mm. The specimens were immersed in a 20 mass aqueous solution of ammonium thiocyanate (NH4SCN) at 313 K for 48 hours and then charged with hydrogen. Tensile tests were performed in the air at room temperature. The cross head speed was ranged from 0.01 to 100 mm/min. Hydrogencharged specimens were hold in the air for a period of 1 and 300 hours. The 0.2 proof stress and tensile strength for the hydrogencharged specimens were similar to those for the uncharged specimens, whereas the reduction of area was lower in the hydrogencharged specimens than in the uncharged specimens. Thermal desorption spectroscopy showed that the residual hydrogen contents in the hydrogencharged specimens fractured by tensile tests were between 0.14 and 0.93 mass ppm. The reduction of area of the hydrogencharged specimens decreased linearly with increasing residual hydrogen content. Scanning electron microscopy showed that the cupcorn fracture occurred in the hydrogencharged and the uncharged specimens and that the fracture surfaces were covered with dimples. The normal stress fracture area in the center of the hydrogencharged and uncharged specimens was almost the same. The shear stress fracture area near the specimen surface was wider in the hydrogencharged specimens than in the uncharged specimens. This means that hydrogen enhances slip deformation near the specimen surface and resulted in the lower reduction of area in the hydrogencharged specimen. We therefore concluded that the hydrogen embrittlement behavior of the 900MPaclass SCM435 steel was explained by the hydrogen enhanced localized plasticity model rather than by the lattice decohesion model.

Murakami Yukitaka; 村上 敬宜; 児玉 昭太郎; Kodama Shotaro; Konuma Shizuyo; 小沼 静代

松岡 三郎; 堤 紀子; 村上 敬宜

Murakami Yukitaka; 村上 敬宜; 宇宿 尚史; Usuki Hisafumi

村上 敬宜; 清水 真佐男

松尾 尚; 本間 紳浩; 松岡 三郎; 村上 敬宜

Murakami Yukitaka; 村上 敬宜; 阿部 雅二朗; Abe Masajiro; 清田 高徳; Kiyota Takanori

長田 淳治; 村上 敬宜

Murakami Yukitaka; 村上 敬宜; 堤 一也; Tsutsumi Kazuya; 藤嶋 正博; Fujishima Masahiro

村上 敬宜; Murakami Yukitaka; Uemura Yujiro; 上村 裕二郎; Natsume Yoshitaka; 夏目 喜孝; Miyakawa Susumu; 宮川 進