High temperature workability behaviour of a modified P92 steel

The high temperature forming behaviour of a modified P92, type 9% Cr, steel is studied by means of torsion tests. The data obtained from these tests allowed correlation of the number of turns to failure, a measure of ductility, as a function of strain rate and temperature. In addition, the data were correlated by the Garofalo equation with a stress exponent of 4.78 and an activation energy of 390 kJ mol(-1). This equation was used to predict the formability behaviour for the rolling process and also to determine the maximum forming efficiency and stability of the steel. A temperature of 1140 degrees C is found to give the optimum forming temperature.