ボロン鋼における脱ボロン現象とその計算モデル

概要

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Deboronization behavior during austenitizing of 0.2%C-0.85%Mn boron-treated steels was investigated in the various atmospheres. A considerable amount of boron removal was observed during the heat treatment in the air, and neither an atmosphere of argon nor a nickel-plating on metal surfaces had detectable effect in preventing this phenomenon. Deboronization could be eliminated only in the vacuum of 10^<-4> Torr with a zirconium oxygen getter. Boron concentration profiles after deboronization occasionally showed some anormalous appearances which were unexplainable by a diffusion control mechanism. One was a two-step fashion in a boron concentration profile and the other was an enhancement of deboronization at a certain temperature range. The latter, for instance, involved a lower residual boron concentration at 850℃ rather than at 950℃. A probable model for deboronization kinetics was discussed taking a dissolution of fixed boron as precipitates together with a diffusion of free boron into consideration. In addition, the effect of formation of ferrite owing to a simultaneous occurrence of decarburization was also taken into consideration. A finite-difference method was applied to the calculation of boron profile and it was shown that the above-mentioned anormalous phenomena were predictable.
社団法人日本鉄鋼協会の論文
1983-09-01