フェライト・パーライト鋼の中・常温降伏強度におよぼす結晶粒度の影響

概要

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The influence of grain size on the yield strength at moderate temperature in ferrite-pearlite steels was studied with paying attention to the k_y value in the Petch equation. The lower yield stress of a ferrite-pearlite steel has been considered to depend on the grain size, and is estimated by the Petch equation. The k_y value in the Petch equation is considered as the value which ralates with the dislocation mobility and the Pierce-force. The k_y value is reported to be constant as 2.2 kgf/mm^2/mm^<-1/2> below the room temperature. On the other hand, the investigation on k_y above the room temperature has not been reported. The authors have verified that the k_y value decreased with the increase in temperature above the room temperature. The temperature dependence of k_y is clasified to four ranges between 25℃ and 550℃. The dependence can be explained by the decrease in pinning force of dislocations by carbon and nitrogen, the active multification of dislocations, and I.S. (Interstitial-Substitutional) effect. The k_y value becomes negative, when the grain boundary sliding occurs because of the creep phenomenon under the lower strain rate at relatively high temperatures. The k_y value can not become negative without the creep phenomenon, but the k_y value approaches to zero.
社団法人日本鉄鋼協会の論文
1987-04-01