Abstract
The surface roughness of carbon steel sheets is controlled by dull roll surface imprinting in temper rolling. In most cases, a dry condition or a lubricant is applied as a lubrication state in temper rolling. However, the oil film of the lubricant and its lubricating ability of lubricant have not been clarified. In this study, the effect of lubricant on surface imprinting was investigated in temper rolling as three lubrication states. Temper rolling experiments for as-annealed low carbon steel strips and as-annealed high carbon steel strips were conducted in the range of 1 to 3% in reduction, using the 4Hi rolling mill. Non lubricant (dry condition), water soluble lubricant and mineral oil were applied as lubrication states. A shot dull roll and an electric-discharged dull roll were employed. Surface microstructures of temper rolled strips were observed directly, as well as surface textures in terms of mean roughness (Ra), three dimensional textures, cross section profiles, material ratio curves and probability densities applied to compare the lubrication states. As a result, for the high carbon steel, the water soluble lubricant leads to better surface imprinting than the dry condition and the mineral oil. Mineral oil shows the lowest surface imprinting. For the low carbon steel, the water soluble lubricant and dry conditions lead to better surface imprinting than the mineral oil.
