MEASUREMENT AND ANALYSIS OF HEAT-TRANSFER AND FRICTION DURING HOT-FORGING

An investigation of heat transfer antifriction during hot forging has been performed using experimental and analytical techniques. The interface heat transfer coefficient was measured in experiments in which two flat H-13 tool steel dies were heated to different initial temperatures and brought together under varying pressure levels, or the two dies were heated to the same temperature and used to upset aluminum alloy 2024-0 rings under both isothermal as well as nonisothermal conditions. The cou pling between heat transfer and friction during hot forging has been studied by analysis of data from the ring experiments and the generation of heat transfer coeffi cient and friction shear factor calibration curves derived from finite element simula tions. By this means, the effects of forging pressure, deformation rate, and lubrica tion on the heat transfer coefficient and the friction shear factor were established. It was sho wn that, for the geometry studied, the value of the friction shear factor is in dependent of the heat transfer coefficient and vice versa, at least to a first order. results suggest that the heat transfer coefficient varies little during a given experiment and that essentially the same value of h 0 is predicted by both the near-surface and deeper ther mocouple measurements: the latter observation adds credibili ty to the measurements. This general behavior was mirrored by all of the other results as well.