HEAT-TRANSFER IN THE HOT-ROLLING OF METALS

The heat-transfer coefficient (HTC) in the roll gap during the hot rol ling of AA5XXX-series (aluminum-magnesium) alloys has been measured in a laboratory mill with the aid of thermocouples attached to the surfa ce and embedded in the interior of test samples. The heat-transfer coe fficient was calculated from the sample temperature response using an implicit finite-difference model over a range of temperatures, strain rates, and pressures. Values of 200 to 450 kW/m(2) degrees C were obta ined by backcalculation. A comparison of the results from this study w ith those measured in a previous investigation on two steel alloys has led to the development of an equation which characterizes the HTC as a function of the ratio of the rolling pressure to the flow stress at the surface of the workpiece. This relationship has been employed to e xplain the apparent differences in the heat-transfer behavior of diffe rent metals at similar rolling pressures.