0.5Mo 鋼の水素アタック抵抗性におよぼす熱処理の影響

概要

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In order to evaluate hydrogen attack resistance and to manifest factors contributing to intergranular cracking of 0.5 Mo steels, metallurgical studies were carried out relating to manifestation of the cause of many damage due to hydrogen attack in 0.5 Mo steel heat exchangers, pipes and its fittings which had been used in a hydrogen environment below the operating limit curve shown in the NELSON chart revised in 1983. Effects of stress relief heat treatment, normalizing and tempering conditions on susceptibility to intergranular cracking and critical temperatures in methane generation of materials taken from a heat exchanger head and a reactor shell plate were investigated by conducting hydrogen exposure tests at 300 to 440℃ under 9.81 MPa (100kgf/cm^2). Identification of carbides in residue extracted from the heat-treated materials was also performed by using X-ray diffraction method. It was confirmed that high resistance to intergranular cracking due to hydrogen attack and higher critical temperatures in methane generation could be obtained by elevating temperatures in heat treatment for stress relief and tempering after normalizing, owing to precipitation of such stable carbides as M_<23>C_6 and Mo_2C. Normalization at temperatures below 950℃ and tempering at 625 to 650℃ were found to be beneficial for ensuring higher resistance to hydrogen attack of 0.5 Mo steels.
社団法人日本鉄鋼協会の論文
1985-09-01