THE IMPROVEMENT OF COLD ROLLED COIL QUALITY THROUGH ELIMINATION OF SCRATCH DEFECT IN ELECTROLYTIC CLEANING LINE

摘要

PT Krakatau Steel has an integrated production technology from iron and steel making, hot rolling and cold rolling. Researches improving the quality and productivity are always launched in order to fulfil the customer demands that becomes more and more severe. Electrolytic Cleaning Line No 2 (ECL-2) is new facility in Cold Rolling Mill to enhance the existing facilities. The function of the line is to clean strip from any rolling oil or grease left on the surface of the strip as the strip is rolled out from TCM. Since 1998, several modification and improvement has been made in this line including increasing line speed from 160 mpm to 320 mpm. As the production speed increased, the quality problem emerged during operation. Scratch on the surface of the strip was formed due to slip/friction between strip and chromatic roll in the degreasing tank. As the population of scratch defect was so high therefore immediate actions were taken in order to reduce the number of coil rejected in ECL-2 due to scratch defects. The most important action to reduce scratch was to install a motor drive in the chromatic roll.