Consideration of Oil Behavior in Hot Rolling Lubrication

In sheet rolling, lubrication oil plays an important role in controlling the rolling condition and improving the sheet surface. However, the lubrication behavior in hot rolling has not been clarified sufficiently in comparison with that in cold rolling. In this work, the difference in oil pit formation and friction behavior at different rolling temperatures was investigated. Although the remaining oil amount was almost constant in the temperature range of 298 K to 973 K, the number of oil pits suddenly decreased in a range below 400 K. Furthermore, lubrication oil behavior was discussed based on the results of a numerical analysis of the oil film behavior at roll-bite. In hot rolling, it is thought that the lubricant oil behaves as follows: The oil film temperature varies greatly in the film thickness direction. Because the viscosity of the oil film on the work roll side remains high and flow is difficult, it does not contribute greatly to decreasing the friction coefficient. In contrast, the oil film on the sheet side has a low viscosity and flows easily, so only small oil pits are formed in the limited thickness with low oil viscosity.