High-speed rolling by hybrid-lubrication system in tandem cold rolling mills

Lubrication is one of the most important factors for improving the productivity of tandem cold rolling mills, as it is possible to increase the rolling speed of thin gauge steel strips and prevent chatter when rolling materials with high deformation resistance. In this study, a new hybrid lubrication system is proposed and its effectiveness is clarified. The system is based on a lubricant recirculation system combined with a system for flexible lubrication control. The key to realizing the new lubricant system is control of plate-out oil film formation on the strip surface under high-speed rolling conditions. The plate-out oil film formation of emulsions is investigated, and the conditions for achieving a sufficient plate-out oil film are clarified. The time-dependent property, oil droplet size, and emulsion concentration are found to have significant effects on plate-out behavior. In addition, the conditions for practical application of hybrid lubrication systems are discussed from the viewpoint of realizing effective plate-out control. A new hybrid lubrication system was investigated, and it successfully enabled flexible controllability of lubrication conditions and achieved the high-speed stable rolling, while maintaining an oil consumption rate equal to that of recirculation systems.