12Cr-Mo-W-V鋼および19-9DL鋼の長時間応力リラクセーション特性 : (<小特集>高温強度小特集)

概要

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Long-time stress relaxation tests up to one year have been carried out 500°, 550°, and 600℃ on 12 Cr-Mo-W-V steel and at 600°, 650°, and 700℃ on 19-9 DL steel for high temperature bolts of a steam turbine for total strains ranging from 0.10% to 0.25%. The stress relaxation curves of both steels showed an inflection of convex nature in a certain time range on the longer time and higher temperature side. The inflection of the curves for 12 Cr-Mo-W-V steel at 550° and 600℃ might be due to the decrease of nitrogen of content in solid solution, which was mainly caused by the formation nitride. For 19-9 DL steel the inflection was considered to be caused by the decrease of the alloying elements in solid solution, such as tungsten, molybdenum and chromium, together with the coarsening of carbide precipitates. The comparison of the present relaxation strength with the published data was made. The influence of the total strain on the residual stress and the correlation of the observed stress relaxation curves with the estimated ones obtained from the creep data applying the creep constitutive equations were discussed.
社団法人日本材料学会の論文
1977-03-15