Abstract
A small punch creep(SP-Creep) test using miniaturized specimen(10×10×0.5mm) has been described for the development of the new creep test method for structural components operated at high-temperature and pressure. The SP-Creep test technique has been applied to 9CrlMoVNb steel used as valve material in boiler components. The creep test temperatures were varied at 575℃〜625℃, and the applied loads at 40kg〜100kg. The overall deformations of SP-Creep curve were definitely depended on creep test conditions and showed the creep behaviors of three regions like those of conventional uniaxial tensile creep curve. The steady state creep rate (ε^・_<qf-ss>) in SP-Creep test increased with increase of applied load and creep temperature. Furthermore, the power law's exponent decreased with increase of creep temperature, and the activation energy(Q_<SPC>) obtained from SP-Creep test decreased as applied load increases. These behaviors were similar to those of conventional uniaxial creep test. Also, a predicting equation of SP-Creep rate was suggested and a good agreement between experimental and calculated values was shown. And several creep results of 9CrlMoVNb steel were compared with those of 2.25Cr-1Mo and 1Cr-0.5Mo steels that has been widely used as boiler tube and header materials, respectively.
