Study on the Heat Indication Test of Steam Turbine Rotor Forgings : 1st Report, The Representation of Type A, B, C and D Deflections with the Model Tests and the Introduction of Type C' Deflection

Abstract

The causes of deflections of turbine rotor forgings at the heat indication test were studied experimentally. Using a model apparatus of heat indication test, the deflections of type A, B, C and D as well as a deflection of type C' newly proposed by the authors were presented. It was confirmed that the tangential non-uniformity in heat treatment could be a direct cause for the origination of type B and C deflections in rotor forgings. It was found, futher, that the deflections of types A, C' and D, which were reproduced in model rotors having had no deflections when their surface uniformly treated in some ways, could be referred to the asymmetric thermal emissivity of surfaces. (It is known that there are two kinds of the tangential non-uniform thermal emissivity, i.e., one capable of improvement by a short time tempering and the other which scarcely admits the improvement.) Thus, it could be said that the heat indication test primarily intended for the inspection of metallurgical quality of rotor forgings has been utilized, for the most part, for the examination of surface condition. The authors wish to draw much attention to this point, with particular remarks to the view that the type D deflection is one of the surface phenomena and with the proposal of type C' deflection as well. The study of the origin of each deflection and the experiments with real rotor forgings demonstrated for confirming the conclusion derived from the model test results will be presented later in the coming paper.