Transient Thermal Stresses in Hollow Cylinders by the Rapid Heating with Special Application to the Heat Condition of a Hot Roll

Abstract

A cast iron roll formed into a hollow cylinder closed at both ends is used to roll plastics and its inner surface is heated by steam. Recently, a roll was longitudinally cracked owing to the rapid heating. In this paper, it is assumed that the temperature of inner surface of an infinite hollow cylinder is linearly elevated to working temperature, and the transient thermal stresses in an infinite hollow cylinder are caluculated. If the allowable stress of material is given, the heat condition of rolls is determined. Also, when a hollow cylinder is closed at both ends, it is shown that the stresses in the cylinder near the ends become larger than the stresses in an infinite hollow cylinder. In an example, if the allowable tensile stress of material is 4 kg/mm2, it is found that a cylinder of inner radius 200 mm and outer radius 300 mm must be heated to 400°C in about 40 min.