1.What is a suitable range for the brushing pressure of cold-rolled coils?
Under normal circumstances, the contact pressure (or indentation) between the brush roller and the strip is recommended to be controlled between 2.0 mm and 5.0 mm (expressed as indentation), corresponding to a working pressure (hydraulic or pneumatic) of approximately 1.5 bar to 3.5 bar.
For applications requiring high surface quality (such as automotive steel sheets or mirror panels), the pressure will be biased towards the lower end to ensure a "wiping" effect rather than a "cutting" effect on the strip surface, thus avoiding brush marks.
2.What are the main factors that affect the setting of scrubbing pressure?
Brush Roller Condition: New brush rollers have sharp, hard bristles, so the initial pressure should be relatively low (e.g., 2.0~3.0mm infeed). Older brush rollers have worn, softened bristles, requiring increased pressure or infeed to compensate for the reduced cleaning power.
Strip Steel Specifications: Thin strips (e.g., below 0.3mm) are prone to wrinkling or breakage under pressure, so the pressure needs to be reduced. Thicker strips or high-strength steel can have their pressure increased to enhance cleaning ability.
Process Speed: The faster the production line speed, the shorter the contact time between the strip and the brush roller, usually requiring increased pressure to ensure cleaning effectiveness.
Cleaning Objectives: Use lower pressure to remove only rolling oil residue; if removing fine iron powder or slight oxide scale is required, higher pressure combined with high-pressure spraying is necessary.
3.What quality problems can arise from improper brushing pressure settings?
Insufficient pressure: Insufficient contact between the brush roller and the strip fails to effectively remove residual rolling oil and iron powder from the surface, leading to "oil spots," carbide accumulation, or poor adhesion of subsequent coatings after annealing.
Excessive pressure:
Brush marks: Excessive pressure from the brush bristles leaves regular streaks or scratches on the surface, damaging its gloss.
Strip damage: For thin plates, excessive pressure can cause edge wrinkles, waviness, or even strip breakage.
Brush roller wear: Abnormal wear of the brush bristles drastically reduces the service life of the brush roller and may also burn out the brush roller motor (overcurrent).
4.In actual production, how can we quickly determine whether the current scrubbing pressure is appropriate?
**Observe the Current:** Observe the load current of the brush roller motor. The current should be stable between 60% and 80% of the rated value. Drastic current fluctuations indicate unstable pressure or poor strip shape; too low a current indicates insufficient pressure, while too high a current close to the rated value indicates excessive pressure.
**Listen to the Sound:** During normal brushing, the sound should be uniform and continuous. If you hear obvious periodic impact sounds or sharp friction sounds, it may indicate excessive pressure or a problem with the brush roller bearings.
**Touch the Surface:** After brushing and before drying, briefly pause the machine and touch the strip surface (be careful). Under appropriate pressure, the surface should be uniformly moist and smooth to the touch; if it feels rough or has obvious texture, the pressure may be too high.
**Check the Results:** Observe the spread of the water film on the strip surface after brushing. A uniform, continuous water film without shrinkage indicates thorough degreasing; the appearance of water droplets or broken water film indicates insufficient pressure or the condition of the brush roller.
5.Are there any recommendations for different washing pressures for cold-rolled coils of different materials or for different applications?
There is no absolute "standard value" for cold rolling brushing pressure. The core principle is to use the lowest possible pressure while ensuring cleaning effectiveness (no oil stains, no iron powder residue) to protect the surface quality of the strip and the life of the brush rollers. In actual production, dynamic fine-tuning is required based on the brush roller wear cycle and process speed.