A study of water-based lubricant with a mixture of polyphosphate and nano-TiO2 as additives for hot rolling process

Hot rolling is one of the most widely used hot metal forming processes by shaping the hot workpiece with cylindrical rolls. Its harsh working conditions, including high loading (up to 0.5 GPa), elevated temperature (600–1100 °C) and high speed (above 10 m/s), lead to the problems of high friction, severe wear, oxidation at the tool/workpiece rubbing surfaces. Lubricants are essential to reduce the rolling force, prolong the service life of work rolls, and improve overall process efficiency. In this work, the mixture of sodium polyphosphate and nano-TiO as water-based hot rolling lubricants were studied using a laboratory hot rolling mill. Aqueous lubricant with 2 wt.% TiO in 20 wt.% sodium polyphosphate demonstrates an excellent lubrication performance with a reduction of a rolling force of 10% compared to pure water lubrication condition. The sodium polyphosphate can not only act as a surfactant to improve the dispersibility of TiO nanoparticles in water, but also form an easily sheared glass melt at high temperature to lubricate the workpiece/roller. Focused ion beam and transmission electron microscope analysis of the sliding interface demonstrate that some nano-TiO were contained in the polyphosphate melt. The concept that combines the inorganic polymer with nanoparticles to produce the synergy effects of glass lubrication and nanoparticle lubrication can provide new insight into the design of lubricants for the hot metal forming process. 2 2 2 2