耐熱鋼の研究 (V) : Timken 16-25-6 の析出現象に就いて

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The precipitation phenomena of Timken 16-25-6 heat-resisting alloy were studied in relation to content of nitrogen. There were four grades of nitrogen content in the samples, i. e. 0.16% N, 0.10% N, 0.04% N, and denitrized by Ti addition. They were melted in a high-frequency electric furnace, and hot-forged into bars. Solution treatment was made at 1150℃ for 1 hour in a weak vacuum atmosphere. The influence of the contained nitrogen on precipitation was almost inperceptible at 700℃ (1290°F) aging. However, it was remarkable at 800℃ (1470°F) and 900℃ (1650°F). The intermediate maximum hardness during precipitation at 800℃ (1470°F) was delayed proportionally to decrease of nitrogen content in samples. Besides, the amounts of precipitated particle were varied in parallel with hardness variation at time of the intermediate maximum and minimum hardness. The degree of coagulation in precipitated particles became larger with increasing aging temperature and aging time. On the other hand, the sample of #B4 (containing 0.16% N) had finer particles than other samples of #B5 & 6 (containg 0.10% N) and # B7 (containing 0.04% N) aged at 700℃ (1290°F) and 800℃ (1470°F). But, when they were aged at 900℃. (1650°F), the degree of coagulation in precipitated particle was uniform in the three kinds of samples. The samples of # B8 and # B9 denitrized by Ti., did not show the intermediate maximum and minimum hardness during precipitation process, and their grain-size was very small. Precipitation of # B8 and # B9 was made at a higher speed and to a higher hardness than in other mitrogen containing samples. The lattice parameter of samples was measured by X-ray during precipitation process. The lattice parameter increased in the first stage of precipitation, and then decreased in the late stage. The decrease of lattice parameter was to be expected when the particle was precipitated from iron the base alloy, though the fact that the lattice parameter increased in the first stage of precipitation process was inexplicable. On the other hand, the time when the lattice parameter reached maximum approximately corresponded to the time of intermediate maximum and minimum hardness. This suggested that there must be some relation among the nitrogen content of samples, the intermediate maximum and minimum hardness process, and the variation of lattice parameter from increasing to decreasing. Further, the influence of cold work on subsequent aging at 700℃. (1290°F) was studied. There were three kinds of specimens made from sample # B4 ; (1) cold worked after solution treatment, (2) cold worked after over-aging operation (see Report (IV) of this magazine, Vol 39 (1953) No.5 page 531), (3) only solution treated. Their hardness during aging at 700℃. (1290°F.) was measured, and simultaneously their microstructure was observed.
社団法人日本鉄鋼協会の論文
1954-08-25

耐熱鋼の研究 (V) : Timken 16-25-6 の析出現象に就いて

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