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SynopsisIn a high speed cold rolling of tinplate, defects called heat-scratches or heat-streaks appear on the surface of rolled strip. These heat-scratches reduce the rolling efficiency, surface quality of rolled strip, rolling oil cost, and so on. To reduce these defects, we have examined the lubrication in high speed cold rolling and developed rolling oil for high speed cold strip rolling by adding an extreme pressure agent (EP agent) and an emulsifier to palm oil.The main results are as follows :(1) It is suggested that lubrication state in high speed cold rolling is a mixed state of hydrodynamic lubrication and boundary lubrication which is the main part.(2) By the addition of 1 % EP agent and 0.5 % of emulsifier to palm oil, oil film strength is increased 4 times as much as that of neat palm oil, and coefficient of friction is decreased.(3) Lubrication performance of rolling oil is improved by the addition of EP agent and emulsifier, and it becomes possible to use palm oil emulsion of which concentration is lower (15N20 %) than before (25-'30 %). As a result, heat-scratches are eliminated and rolling speed is increased. Still more, the rolling oil cost is decreased.

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