Abstract
The effect of deformation rate on the ductile-brittle transition behavior of temper embrittled turbine rotor steels has been investigated employing a newly developed dynamic small punch (SP) tester. It is shown that the dynamic SP test produces a clear ductile-brittle transition behavior similar to the Charpy V-notch (CVN) impact test. The ductile-brittle transition temperatures determined by fracture energy measurements and by fracture surface observations are higher about 48-90°C than those obtained from the static SP tests. The effect of deformation rate on the relationship between FATTSP and FATTCVN obtained from SP and CVN tests is examined: it is found that as the deformation rate increases to 103 and 2.5×106 times, the value of a, which is a proportionality coefficient in the relationship given by FATTSP=α×FATTCVN, is increased to 0.45 and 0.54, respectively.
From these experimental results, it is implicated that the use of the dynamic SP testing method enhances the predictability of FATTCVN.
