Reliability assessment of cylindrical joints with tensioned roll band of the rolling mill

Abstract

The work addresses to the problem of ensuring the operability of a composite roll made in the form of a cylindrical joint with the tension of a carbide band and a steel axis. When considering the wear processes, all the characteristics related to the surface microgeometry are combined by a dimensionless complex roughness parameter, which, along with the roughness class, includes the features of the surface treatment technology. To determine the contact pressure associated with the tension, the Lame formula for calculating thick-walled cylinders is used. When a hard-alloy bandage is placed on a steel roll with the tension between the contacting surfaces, a plastic unsaturated or saturated contact is performed, for which a method for calculating the tension values shall be proposed. Formulas are given for determining the maximum permissible torque that does not cause a change in the strength of the joint with tension under conditions of plastic saturated and unsaturated contact. In order to test the strength of the connection elements with tension, the theory of the greatest tangential stresses is applied for two dangerous points located on the inner surfaces of the covered and the covering parts: a formula is obtained for determining the maximum permissible calculated value of tension from the strength condition of the covered part. An example of fitting with the tension of a band made of hard alloy VK8 on a working roll made of improved steel 45 with a diameter of d = 100 mm is considered. The band is installed using a press with an H7/p6 fit to transmit a torque of M = 5 kNm. The minimum tension value is obtained from the condition of fixing the contact surfaces without their relative slippage, and the maximum tension value is obtained from the condition of the strength of the steel axis. As a result of the calculations, it was found that the minimum tolerance for this attachment does not provide the transmission of the specified torque since its value is less than the minimum allowable tension. Therefore, to ensure reliable operation of the connection with tension, it is recommended to use the H7/s6 fit, which provides the transmission of the specified torque without the strength of the connection elements.