EVALUATION OF INTERFACIAL HEAT-TRANSFER AND ITS EFFECTS ON HOT FORMING PROCESSES

The heat transfer at the tool/workpiece interface governs the temperat ure development of the workpiece and tools during non-isothermal formi ng of metals and alloys and, consequently, has a critical influence on microstructural evolution and power requirements. In the present stud y, numerical models of heat transfer and experimental measurements by inserted thermocouples have been used to evaluate the temperature chan ges of the specimens during hot rolling and forging of steels. Emphasi s has been given to the effects of the oxide scales formed on the heat ed carbon and stainless steel specimens and of the percentage reductio n on interfacial heat transfer. On the basis of computer analysis and experimental observations, the variation of interfacial heat transfer coefficient with scale thickness, pressure, and percentage reduction i s established. (C) 1996 The Institute of Materials.