Pickling steel coils: This refers to the process of pickling steel coils in acidic media. Pickling is designed to remove the oxide layer and rust on the steel surface to improve surface quality. This process usually uses strong acids such as hydrochloric acid, which are then rinsed and treated to make the steel surface smooth and clean. Pickling can be done after cold rolling or hot rolling and is used to prepare the surface for further coating, processing or welding.
1. Composition of the surface layer of acid rolled coils
The surface layer of acid rolled coils is mainly composed of rolling oil layer, pollutants and oxide film. Among them, the contaminated layer is the most difficult to clean. (100~300mg/m2)
2. Cleaning method
Mainly used cleaning methods:
chemical cleaning method
Physical cleaning method
Electrolytic cleaning method
Desalted water rinse
Corresponding process flow:
Alkaline pre-cleaning (spray cleaning)
Lye scrubbing + hot water scrubbing
Electrolytic cleaning
hot water rinse
1 Chemical cleaning method
Various greases on the surface of the strip and NaOH in the degreasing agent are hydrolyzed under heating (60-80°C) conditions to generate sodium stearate and glycerin, which dissolve into an alkaline solution to form water-soluble soap salts. The surfactant in the degreasing agent is adsorbed on the grease interface, with the hydrophobic group facing the metal matrix and the hydrophilic group facing the solution, which reduces the interfacial tension between the metal and the solution. Under the action of fluid dynamics and other factors, the oil film breaks into small particles. The oil droplets detach from the metal surface, disperse and emulsify, and disperse into the solution to form an emulsion.
2 Physical cleaning method
The physical cleaning method mainly adopts the brushing method: it consists of a brush roller and a support roller. With the spray cleaning of alkali solution, the brush roller rotates in the opposite direction to the running speed of the strip, which can effectively remove more than 75% of the residues (in the form of iron) on the surface of the strip. Mainly powder).
3 point cleaning method
The mechanism of electrolytic cleaning is that when the strip is used as a cathode or anode, hydrogen or oxygen bubbles are precipitated on the surface of the strip accordingly, destroying the oil film attached to the surface of the strip, and the bubbles detach from the strip where the oil droplets are attached and remain in the oil. On the surface of the droplet, it stays at the interface between the oil and the alkali wash solution. As new bubbles continue to precipitate and the bubbles gradually become larger, the oil droplets break away from the surface of the strip under the action of the bubbles and are carried to the alkali wash solution by the bubbles. Go in.
