スモールパンチ試験法による長期使用2.25Cr-1Mo鋼製ボイラ配管のクリープ特性評価

抄録

The small punch (SP) creep testing technique was applied to the long-term service-exposed 2.25Cr-1Mo steel, which had been actually used as a boiler piping in the fossil power plant for long periods of time, to investigate the applicability of this technique to the remaining-life assessment. The SP creep tests were carried out at the temperatures of 580 and 650°C and under the load range from 150 to 400 N using small disk-type specimens removed from the piping. In order to compare the results obtained from the SP creep test with those from the uniaxial creep test, the SP load (F) was converted to the stress (σ) with the load/stress conversion coefficient (F/σ) determined by the high temperature SP test, that is, the central displacement to the maximum load. The experimental results revealed that the SP creep rupture life was slightly shorter in the outer surface than the inner surface. Additionally, the F/σ were determined to be around 2.9 irrespective of temperature, and the SP creep rapture data were well correlated with the uniaxial ones using this F/σ.