1.Will oil pollution be generated during the rolling process?
Rolling oil residue: During the cold rolling process, large quantities of rolling oil are used to lubricate, cool, and clean the rolls and strip. If the subsequent cleaning (degreasing) stage is ineffective-for example, due to insufficient lye concentration, low temperature, insufficient spray pressure, or inefficient brushing-then the rolling oil on the strip surface cannot be completely removed, leaving residue. This residual oil may carbonize or form stains during the subsequent annealing and galvanizing processes.
2.Will oil pollution be generated in the annealing furnace process?
Furnace atmosphere contamination: In continuous annealing furnaces, if the shielding gas (usually a nitrogen-hydrogen mixture) is impure and contains hydrocarbons (such as oil vapor), these substances will decompose at high temperatures and deposit on the strip surface.
Grease within the equipment: If the grease in the roller bearings leaks due to poor sealing, or if grease on other components within the furnace evaporates at high temperatures, it can condense and contaminate the strip surface.
3.How big is the impact of oil pollution in the galvanizing line?
Air knife wiping: During the hot-dip galvanizing process, an air knife is used to blow away excess zinc liquid. If the compressed air contains oil or moisture, it can be sprayed directly onto the strip surface, resulting in oily spots or streaks.
Post-galvanizing cooling: In cooling towers, if the cooling fan air contains oil, or if the cooling water used for quenching is contaminated with oil, the strip can become contaminated during the cooling process.
Equipment lubrication leaks: The bearings of many rollers in the production line (such as steering rollers, tension rollers, and stabilizing rollers) require lubrication. If seals fail, grease or oil can leak and directly contact the strip surface. This is a very common source of oil contamination.
Passivation/oiling equipment: This is intentional "oiling," but it can also be a problem if not properly controlled.
Passivation fluid: Some passivation fluids contain organic components. If they are not evenly applied, squeezed out of the rollers, or dried thoroughly, they can leave residue.
Anti-rust oil: Before coiling, a thin layer of anti-rust oil is applied to the strip surface for rust prevention and subsequent processing. If the oiler malfunctions, such as a clogged nozzle resulting in uneven application or an excessively thick oil film, or if the oil itself is of poor quality and easily deteriorates, visible oil stains or spots will form.
4.Will oil pollution be generated during transportation and storage?
Lifting and transport equipment: Oily surfaces such as the C-hooks used to lift coils within the workshop and the platforms of transport vehicles can contaminate the outer ring or edges of the coils during contact.
Environmental contaminants: Oil mist, dust, and other contaminants can also accumulate on surfaces during long-term storage.
5.What impact does surface oil stains have on the subsequent processing of galvanized sheets?
Poor coating: This can lead to decreased paint adhesion, craters, and paint peeling.
Welding difficulties: Oil contamination can affect welding quality and stability.
Appearance defects: Oil spots and color variations can affect product quality and appearance.