What precautions should be taken during transportation of cold-rolled coils?

What precautions should be taken during transportation of cold-rolled coils?
The key elements of transportation are "securement, protection, and moisture protection":
Security: Coils must be secured to the transport vehicle with wire ropes or special clamps to prevent rolling and collision during transport. Coils must be separated by cushioning pads (such as rubber mats) to prevent scratches.
Protection: During rainy weather, coils must be covered with tarpaulins to prevent them from getting wet. Ordinary cold-rolled coils must be protected from water (if exposed to water, they will rust within 24 hours).
Loading and unloading: Use a crane (with special lifting equipment) for loading and unloading. Do not directly tie the coil surface with wire ropes (this can cause severe scratches).
What should I do if rust appears on the surface of a cold-rolled coil? How can I determine if it is suitable for continued use?
Treatment based on the severity of rust:
Minor rust (small yellow rust spots on the surface, no scale): Use fine sandpaper to remove rust, or clean with an acid-washing passivation solution. Subsequent painting or processing is necessary to prevent further rusting. This will not affect mechanical properties and can continue to be used.
Severe rust (large areas of red rust, scale, or even pitting): Rust removal will result in reduced surface thickness and increased surface roughness. If used for exterior parts (such as appliance housings), the product should be scrapped. If used for non-exterior structural parts (such as brackets), the thickness and mechanical properties must be tested and qualified before use.
What causes "stamping cracking" during cold-rolled coil processing? How can it be resolved?
Common Causes and Solutions:
Incorrect Material Selection: Selecting cold-rolled coil with low elongation (e.g., DC01 for complex stamping). Solution: Switch to a deep-drawing grade (e.g., DC04, DC06).
Work Hardening Not Eliminated: The cold-rolled coil has not been annealed or has been inadequately annealed (yield strength is too high). Solution: Re-anneal (to reduce yield strength and improve plasticity).
Improper Stamping Process: Excessive stamping speed, too small die radius. Solution: Reduce stamping speed, increase die radius (to reduce stress concentration).
Surface Impurities: Oil and scale on the steel plate surface lead to uneven force during stamping. Solution: Clean the surface and remove the scale.
What causes "edge burrs" after slitting cold-rolled coil? How can this be avoided?
Causes and Prevention Measures for Burrs:
Slitting Tool Wear: The tool edge becomes blunt and cannot cut the steel plate, resulting in burrs on the edge. Solution: Replace the slitting tool regularly (usually every 500 tons of slitting).
Improper Tool Clearance: The clearance between the upper and lower tools is too large (resulting in uncut steel plates) or too small (causing the tool to squeeze the steel plates). Solution: Adjust the tool clearance (the clearance should be approximately 10-15% of the steel plate thickness).
Excessive Slitting Speed: Increased friction between the steel plate and the tool leads to rough edges. Solution: Reduce the slitting speed (adjust according to thickness, e.g., ≤100m/min for 0.5mm thick cold-rolled coil).
What impact does "excessive thickness deviation" of cold-rolled coil have on processing? How should it be addressed? Impacts:
Unqualified Stamping Dimensions: Excessive thickness can prevent assembly (e.g., due to insufficient clearance), while excessive thinness can lead to insufficient strength (e.g., deformation).
Poor Welding Quality: Large thickness variations can easily lead to incomplete weld penetration (in thin areas) or burn-through (in thick areas).
Bending Cracking: Stress concentration during bending in areas of localized excessive thickness can lead to cracking.
Resolution:
If the deviation is within the allowable range (e.g., ±0.05mm), the processing technology (e.g., the stamping die clearance) can be adjusted.
If the deviation exceeds the standard, the part must be returned to the manufacturer for re-rolling or used in applications requiring less precise thickness (e.g., simple brackets).