1.What is the definition of brushing pressure for cold-rolled coils?
Brushing pressure refers to the combined contact pressure between the brush roller and the strip surface in the brushing section, as well as the spray pressure of the cleaning fluid. These two factors play different roles in the degreasing and cleaning process.
2.How should the brush roller pressing pressure be set? Is there a standardized value?
There is no standardized absolute value for brush roller pressing pressure; instead, it is indirectly controlled and characterized by the pressing amount (mm) or motor current (A).
Control Principle:
The brush roller is driven to rotate by a motor. When the brush roller presses against the strip, the contact resistance increases, and the motor current rises accordingly.
The motor current value is positively correlated with the contact pressure between the brush roller and the strip. Therefore, the pressure can be indirectly controlled by monitoring the motor current.
The goal is to stabilize the current value within a preset range to ensure adequate contact between the brush bristles and the strip.
Influence of Pressing Amount:
Insufficient pressing amount: The brush bristles cannot effectively contact the strip surface, resulting in incomplete removal of residual oil and iron.
Excessive pressing amount: Abnormal wear of the brush bristles, shortened brush roller life, and in severe cases, damage to the strip surface or the formation of brush roller vibration marks.
3.What is the effect of injection pressure?
Insufficient pressure: Weak rinsing ability; sloughed oil and iron powder may remain on the strip surface or be carried back out by the brush roller.
Excessive pressure: May generate excessive foam (especially in the alkaline solution section), affecting the operating environment; in the hot water section, excessive pressure may cause strip vibration or worsen watermarks.
Key points: The nozzle spray angle and nozzle arrangement have a greater impact on rinsing effectiveness than the pressure value alone. It is necessary to ensure that the spray area covers the contact arc between the brush roller and the strip.
4.What quality defects can result from improper brushing pressure control?
Insufficient brush roller pressure:
Insufficient contact between brush bristles and strip steel, incomplete removal of residual oil and iron.
During subsequent annealing, oil stains carbonize, forming "oil spots" and affecting surface quality.
During hot-dip galvanizing, incomplete galvanizing or poor coating adhesion may occur.
Excessive brush roller pressure:
Abnormal wear of brush bristles, shortening brush roller lifespan.
May produce brush roller vibration marks, leaving periodic stripe defects on the strip steel surface.
In severe cases, damage to the strip steel surface, causing scratches or abrasions.
Increased risk of motor overload.
5.How can the brushing pressure be precisely controlled on the production site?
Control methods for brush roller pressing pressure:
Current monitoring method: Real-time acquisition of the current value of the brush roller drive motor, which characterizes the pressure state between the brush roller and the strip.
Closed-loop regulation: The PLC automatically adjusts the cylinder pressure or pressing mechanism based on the deviation between the measured current and the set value, stabilizing the pressure within the preset range.
Pressure pressing mechanism optimization: Employing structures such as worm gear reducers and half-couplings improves adjustment accuracy and avoids jamming during dynamic adjustment.
Control methods for spray pressure:
Pressure sensor monitoring: A pressure transmitter is installed in the main pipeline of the spray nozzle to monitor the spray pressure in real time.
Variable frequency pump control: The cleaning pump frequency is automatically adjusted according to process requirements to maintain stable pressure.
Dynamic adaptation adjustment: For high-pressure cleaning of finishing machines, the cleaning pressure can be dynamically adjusted according to the conductivity of the finishing fluid to achieve pressure adaptation to process conditions.