Cr-Mo-V鋼高温ロータの経年脆化の非破壊推定法

概要

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The temper embrittlement in low-alloy steels, one of the typical material degradations, occurs in service and it is important to detect this embrittlement by means of a nondestructive technique. In order to develop the nondestructive evaluation method of embrittlement for the Cr-Mo-V rotors, a study was conducted using 1ab-charged steels of P dope and Sn dope. P-doped steels showed evident embrittlement by the segregation of P at grain boundaries. On the other hand, Sn-doped steels showed little embrittlement when compared with P-doped steels. Various testing methods were investigated and compared in terms of their sensitivity and the factors detected, using these steels. The chemical etching test was found to be a very good measure of the embrittlement. That is, it was found that there is a good correlation between the width W of the etched grain boundary measured by the penetration of replicas and FATT. The correlation between W and FATT was also recognized for the samples taken from long-term serviced rotots. The relation had the same slope as that found for the lab-charged steels. From this, the multiple regression was conducted in order to express FATT using W and the variables which are known or nondestructively measurable. As a result, a regression equation which can estimate the actual FATT with the scatter of ±20℃ was obtained.
社団法人日本機械学会の論文
1991-05-25