245kg/mm^2 級および 210kg/mm^2 級マルエージ鋼の延性に及ぼす時効条件と歪速度の影響(<特集>鉄鋼材料の破壊靱性)

概要

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Tensile strength and elongation of 18% Ni-type maraging steels, the nominal strength levels of which are 245 kg/mm^2 and 210 kg/mm^2, have been investigated as a function of aging time. The temperature range in aging was from 575℃ to 400℃. A cross-head speed in the tensile test was varied from 1.0 mm/min to 0.005 mm/min. The change in electrical resistivity at liquid nitrogen temperature has also been measured. Brittle fracture which is caused by decreasing the cross-head speed is observed in the 245 kg/mm^2 grade maraging steel in the early stage of aging in the temperature range from 500℃ to 400℃. The decrease in elongation is also observed in the tensile test of the cross-head speed of 0.005 mm/min in the 210 kg/mm^2 grade maraging steel in the early stage of aging from 425℃ to 400℃. The brittle behavior in low strain rates is reduced by prolonging aging time. Activation energy is calculated to be about 80 kcal/mol for the 245 kg/mm^2 grade maraging steel from the relation between reciprocal absolute aging temperatures and times giving the removal of the brittle behavior at the cross-head speed of 0.005 mm/min. It is noted that aging temperature and time are important for the removal of the brittle behavior in low strain rates.
社団法人日本鉄鋼協会の論文
1978-06-01