Comparison of the Performance of Lubricants in Rolling Based on Temperature Measurement

Abstract

Lubricants are used in rolling process mainly to reduce the friction. Thus, the measurement of friction can give the idea about the performance of a lubricant. However, the measurement of friction by no means is an easy task. In the past, various methods have been employed for measuring the friction in rolling. Some of these methods require damaging of the surface of the rolls. The methods based on the measurement of roll force, roll torque and the slip can be easily used, but their reliability is dependent on reliability of measuring devices and the mathematical model. A possible way of measuring the average coefficient of friction in rolling is to measure the exit temperature of the strip. It can be easily done by means of temperature sensors. In this work, an inverse method of estimating the approximate value of friction coefficient is proposed based on the exit temperature measurement. The inverse model makes use of a direct model of temperature determination, which is based on finite element analysis and analytical models available in the literature. For a given exit temperature, the inverse model searches the appropriate value of friction coefficient using golden section search algorithm. The methodology is tested by carrying out a number of numerical experiments on the cold strip rolling. Some preliminary experiments have been conducted. It is planned to carry out more experiments in future. Although the direct model used in this work is highly approximate, the entire methodology displays its high potentiality in an industrial setting. In any case, the methodology can compare two lubricants with respect to their ability to reduce the coefficient of friction, even if the estimated coefficient of friction may be approximate.

An approximate method for computing the temperature distributions in roll and strip during rolling process

“…The model described in this section is same as that used by Yadav et al 3 Yadav et al 3 have carried out deformation analysis by an FEM code developed by Dixit and Dixit 36 and thermal analysis based on the work of Kim et al 37 In this work, further approximations are introduced to reduce the computational time. First, only four iterations of FEM are carried out instead of eight iterations in the work of Yadav et al 3 This reduced the FEM computational time by 50%. Due to this, the effect on the accuracy of the plastic deformation power was less than 5%, as even an approximate velocity field provides a reasonable estimation of power, thanks to upper bound theorem.…”

“…The roll-strip interface temperature is compared from the experiments of Jeswiet and Rice. 40 The material of the strip is Alloy 1100-H141 of dimensions (28032339:8) mm 3 . The material properties of Alloy 1100-H141 and the roll are taken from Wilson et al 16 Roll radius and exit speed of strip are 75 mm and 0.096 m/s, respectively.…”

“…2 Measurement of temperature in cold rolling can be useful for inverse determination of friction and strip material parameters, provided a theoretical model for the estimation of temperature is available. For example, recently, Yadav et al 3 proposed that the performance of lubricants can be assessed based on the temperature measurement. Yadav et al 4 also presented a methodology for inverse determination of strip material parameters and friction based on the temperature and forward slip measurements.…”