Characteristics of hot friction in commercially pure titanium

It is said that in hot-rolling titanium, surface defects are apt to occur by seizures between rolls and products. The authors examined the effects of temperatures and lubricants on the tribological behavior of titanium strip surface contact with rolls using a hot rolling and sliding wear tester with commercially pure titanium disks and a high speed steel. Consequently, in cases of water spray without lubricating oil, fine cracks due to hard layers by oxidation decrease with lower temperature, but the coefficient of friction increases because oxide scales become thin and then metals come easily into contact. The coefficient of friction at 650°C doubles in comparison with that of 850 °C and foil-like overlaps occur. Addition of lubricating oil reduces the coefficient of friction at 650 °C by half and smooth surfaces are obtained. The smooth surface is thought to be due to the lubrication effects of oxide-scales as well as the lubricating oil.