1.What are the most critical protective requirements when packaging cold-rolled coils?
Rust Prevention: Cold-rolled coils have a very smooth surface and no coating, making them extremely prone to rust. During packaging, it is essential to ensure the steel coil is tightly wrapped with rust-proof paper and waterproof material, creating a temporary sealed environment. The built-in vapor-phase rust-preventive paper releases rust-preventive gases that adhere to the surface, preventing oxidation.
Prevention of Mechanical Damage: Steel coils are extremely heavy; even the slightest relative displacement can cause friction between layers, resulting in black spots or scratches. Packaging must ensure that the inner and outer coils, as well as the coils themselves, do not loosen or shift during lifting and transportation.
2.Why must corner protectors be used when packaging cold-rolled coils? What is their function?
Protective Steel Straps: Packing steel straps (bundles) generate significant tension when tightened. Without corner protectors, the sharp edges of the steel straps can embed directly into or damage the edges of the steel coil, causing burrs or indentations. This damaged material often needs to be downgraded or removed.
Protective Straps: The edges of steel coils are very sharp. During transport and vibrations, without corner protectors, the strapping may be cut by the edges of the coil, causing it to break and leading to a safety accident. Corner protectors are usually right-angled and fit around the outer edge of the steel coil, allowing the strapping to pass over the smooth surface of the corner protector, protecting both the steel coil and the strapping itself.
3.What are the considerations regarding the number of binding passes and the method (circumferential vs. radial)?
Radial strapping (perpendicular to the axis): This is the most common strapping method, typically using 3-5 straps. It acts like several tight bands to secure the steel coil, primarily preventing interlayer shifting and collapse during rolling or side-laying. For wider coils, the number of radial straps needs to be increased.
Circumferential strapping (parallel to the axis, passing through the core): This method is usually used in conjunction with radial strapping. Its main function is to firmly secure the steel coil to the underlying support frame (bracket) or wooden blocks, preventing the coil from rolling back and forth during transport.
Key principles: Straps must be symmetrically distributed, and the locking buckles (joints) must be secure and preferably facing inwards or in the same direction to avoid snagging during lifting.
4.What are the special requirements for packaging cold-rolled coils with precision surface requirements (such as automotive panels)?
Contactless Packaging: The inner ring uses a paper sleeve for support, and the outer ring is fully wrapped with composite cardboard/plastic protective panels, ensuring that no straps or hard objects directly contact the steel strip surface.
Internal Cleanliness: Packaging materials (rust-proof paper, plastic film) must be dust-free and halogen-free to avoid chemical reactions with the steel plate in high-temperature or humid environments, which could cause white spots or corrosion.
Vacuuming or Inert Gas Filling: For export or sea-freighted products, vacuuming or filling with dry air/nitrogen will be performed between the inner and outer packaging to minimize oxygen and moisture within the packaging.
Strict Humidity Control: All wooden pallets must undergo drying and fumigation treatment to prevent the evaporation of moisture from the wood itself from causing the steel coil to rust.
5.After packaging, what precautions should be taken during the labeling and stacking process?
Clear and Secure Labeling: A secure label containing information such as material, specifications, weight, and furnace batch number must be affixed or hung on the outer packaging. The label must be waterproof and not easily detached, ideally placed in a recessed area on the outer surface of the packaging to prevent scratching during lifting. For export coils, attention must also be paid to the accuracy of the shipping marks and language requirements.
Stacking Limits: Even when packaged, cold-rolled coils cannot be stacked indefinitely. Generally, the main coil (large coil) can only be placed in a single layer, or at most two layers, and they must be aligned vertically using dedicated anti-slip wooden pads. Excessive stacking can cause the bottom coils to deform due to gravity, and may even damage the packaging and the internal strip steel.
Lifting Gear Matching: The packaging design must consider the lifting method (e.g., C-hooks, horizontal lifting gear). If the coils require vertical lifting, the circumferential straps must be strong enough to withstand the significant shear force during turning.