In the cold-rolling process, oil and other foreign materials adhere to the surface of the tin-plated original plate after the rolling of the rolling oil. If the oil is not washed off and directly annealed, the oil will not completely burn and carbonaceous stains will remain on the steel strip. To produce tin plate can not meet the quality requirements. Therefore, the tin plate must be electrolytically cleaned to remove these oils before annealing.
The commonly used tin plate cleaning method is chemical degreasing and electrolytic degreasing in a degreasing liquid.
(1) Chemical degreasing is a degreasing process in which a tin-plated original plate is soaked in a caustic washing solution. The animal and vegetable oils attached to the surface of the original plate are saponified in a hot alkaline washing solution and become soluble soaps and glycerol to be dissolved and removed.
(2) Electrolytic degreasing is a degreasing method in which electrolysis is performed by electrifying an original sheet on the basis of chemical degreasing. During electrolysis, hydrogen and oxygen bubbles are generated from the surface of the original plate, and the oil film adhering to the surface of the original plate is mechanically washed away. The temperature of the alkaline wash is generally maintained at 80-100°C.
In addition, the mechanical cleaning method is that the brush roller is installed before and after the alkali cleaning tank, and the surface of the original plate is brushed to remove oil stains.
The washing water remaining on the strip of the cleaning unit will cause defects in the subsequent processes. The water must be squeezed out and fully dried.
After the electrolytic cleaning line is an annealing step. According to the coiling requirements of the annealing equipment, both ends of the rolled coil must be very neat.