How to reduce the surface scratches of hot-rolled aluminum discs?

Reducing Scratching on Hot-Rolled Aluminum Discs: The core approach involves strict raw material control, process optimization, equipment maintenance, standardized handling & protection, implementing full-process control from source to finished product.

1. Raw Material & Billet Control (Source Prevention)

• Ingot Surface Pre-treatment

  Thoroughly clean the ingot surface before hot rolling to remove scale, oil stains, burrs, and handling damage; employ sandblasting/shot blasting + cleaning​ to ensure a clean, contaminant-free billet surface.

• Billet Quality Screening

  Strictly inspect ingots for surface cracks, scabs, inclusions, and other defects; reject non-conforming billets. Control ingot thickness deviation to ≤ ±0.3mm​ to prevent misalignment and scraping during rolling.

• Billet Heating Protection

  Control furnace atmosphere with oxygen content <5% and humidity 20%–30%; use a protective atmosphere if necessary to minimize scale formation. Remove surface scale promptly after furnace discharge to prevent it from entering the mill.

2. Rolling Process Optimization (In-Process Control)

• Work Roll Management (Core)
  • Regularly grind work rolls to maintain a surface roughness Ra ≤ 0.8μm, free of cracks, pits, and aluminum pick-up.
  • Establish a roll surface cleaning routine: use high-pressure air + felt/nylon brushes​ during rolling to continuously remove metal fines and scale.
  • Properly control roll cooling to avoid abnormal thermal crown which leads to poor shape and edge scraping.
• Lubrication System Upgrade

  Use high-temperature anti-wear rolling lubricants​ to maintain a stable friction coefficient between 0.08–0.12. Employ precision metered oil application​ to ensure a uniform oil film forms between the roll gap and billet surface, reducing dry friction.

• Rolling Parameter Matching
  • Rationalize pass reduction distribution: 60%–70%​ for roughing, 30%–40%​ for finishing. Avoid excessive single-pass reduction which causes severe friction between the billet and rolls/guides.
  • Control rolling speed and tension to prevent billet misalignment, vibration, and interlayer sliding. Excessively high speed increases friction and scratching risk.
• Guide/Optimization
  • Maintain guide contact surface roughness Ra ≤ 0.8μm, free of sharp edges or worn protrusions.
  • Install guides precisely to ensure proper alignment and gap, avoiding hard contact and scraping against the billet. Replace immediately if severely worn.

3. Equipment & Table Roller Maintenance (Hardware Assurance)

• Table Roller Management

  Inspect table rollers regularly; promptly replace rollers with cracks, wear, or rough surfaces. Keep roller surfaces clean, free of adhered aluminum or debris. Match roller spacing and height to prevent disc bouncing and scraping during transfer.

• Equipment Component Protection

  Install rubber/nylon protective pads​ at key points like mill entry/exit, shears, and transfer tables to isolate metal-to-metal contact. Round off sharp equipment edges to eliminate scraping risks.

• Regular Equipment Cleaning

  Clean aluminum fines and scale from the mill, rollers, and guides per shift. Periodically check lubrication and cooling systems to prevent leaks, contamination, and increased friction.

4. Handling, Stacking & Post-Processing (Finished Product Protection)

• Handling Specifications

  Use specialized lifting tools/suction cups​ for gentle handling to avoid impact or dragging. Line transfer pallets/racks with rubber mats/felt​ to isolate metal contact.

• Stacking Protection

  Place separator paper/plastic film​ between discs to prevent interlayer friction and scratching. Control stacking height to avoid deformation and surface scratches on the bottom layers.

• Post-Processing & Inspection

  Perform surface cleaning/passivation​ promptly after hot rolling to remove residual oil and scale. Implement online visual inspection​ to identify scratches in real-time for immediate process adjustment.

5. Management & Operation (Human Factors)

• Establish Surface Quality Control Standards, defining limits for scratch depth (e.g., ≤0.03mm) and area.
• Enhance operator training on standardized procedures to reduce handling-induced scratches from impacts or dragging.
• Implement a defect traceability system to analyze scratch root causes and continuously optimize processes and equipment maintenance.