Development of Model for Formation of Surface Properties in Cold Rolling of Stainless Steels and Application to the Actual Mill

The model "the rolling oil transudation model" by whom the decrease of the sur- face defect and smoothing the surface of the stainless steel cold-rolling was formed were constructed by applying Channel Jacking Mechanism. The surface of the sheet rolled with emulsion oil used this time is not smoothed easily when rolling on the same to neat oil condition, because this emulsion oil becomes a high viscosity under the high pressure, and is not moved easily under high-pressure in the roll byte. How- ever the surface smoothness of the sheet rolled with emulsion oil is the same as one with neat oil with control of the rolling condition based on the rolling oil transuda- tion model. 7-11) proposed what they call the Channel Jacking Mechanism (CJM) as their "micro- pool lubrication model" of the lubrication at the interface of friction between the material and the tool by the lubricant that is mechani- cally trapped in very small dents (micro-pits) in the material surface. This model applies when the lubricant is supplied to the interface of friction between the material and the tool not by the hydrodynamic- based effect but by the effect of the lubricant that is mechanically trapped in micro-pits in the material surface. In the present study, referring to the above CJM model, we con- sidered the transudation behavior of rolling oil which is trapped mechanically in micro-pits in the surface of steel material before cold rolling. Then, we proposed that the transudation behavior in each rolling pass should be evaluated based on the pass characteris- tic value (hereinafter called the F-value) that is calculated from the viscosity of the rolling oil used, rolling conditions and roll surface roughness using said model as a reference. We studied the relation- ship between the pass schedule using the F-value and the change in surface properties after rolling. The study results are described in this paper. In addition, we applied the F-value to smooth the steel surface in the cold rolling process using water-soluble emulsion oil (hereinafter called emulsion oil) which is generally considered infe- rior to neat oil from the standpoint of obtaining the desired steel surface properties. The results are also described in this paper.