1.What are the effects of oxidation and corrosion on surface quality?
Cause: Cold-rolled coils have a very smooth surface and are usually coated with rust-preventive oil (commonly known as "minimum order quantity oil"). However, over time, especially in humid environments or environments with large temperature fluctuations, the rust-preventive oil will gradually evaporate and become ineffective.
Consequence: If stored for too long (more than 36 months), rust and white spots may appear on the surface of the steel plate. Once rusted, this batch of material may need to be downgraded or even scrapped, resulting in significant economic losses. First-in, first-out (FIFO) ensures that coils with shorter storage life are released first, avoiding oxidation due to prolonged storage.
2.What are the effects on physical and processing properties?
Reason: Cold-rolled sheets have high requirements for yield strength and elongation during subsequent processing (such as stamping and deep drawing). Although cold-rolled coils do not exhibit significant natural aging at room temperature (unlike some aluminum alloys), long-term storage can lead to slight changes in sheet shape (flatness) due to the release of residual stress.
Consequence: If old inventory is subjected to slight compression or changes in internal stress during storage, it may crack or exhibit unstable springback when stamped by the user. Using a first-in, first-out (FIFO) system ensures that the materials leaving the warehouse are from more stable, "newer" batches.
3.Why avoid physical deformation caused by "overloading"?
Reason: Cold-rolled coils are coiled. Although the steel coil itself has high strength, if a coil is pressed at the bottom of a stack for several years, it will be subjected to the pressure of several tons or even tens of tons above it for an extended period.
Consequence: The steel coil may undergo slight deformation (change in ellipticity) or damage to its inner diameter, making it impossible to smoothly uncoil on an uncoiler. First-in, first-out (FIFO) processing speeds up turnover and reduces the time a single coil is subjected to pressure.
4.How to prevent quality accidents caused by confusion between steel types and batches?
Cause: Cold-rolled coils are typically available in various grades (such as DC01, DC03, SPCC, SGCC, etc.) and specifications. The chemical composition may vary slightly between different batches.
Consequence: If old materials are left unattended for a long time while new materials are continuously piled on top, it's easy to send or use the wrong material when rummaging through the old coils. Sending high-grade material as low-grade material results in a loss, while sending low-grade material as high-grade material to demanding customers (such as automotive OEMs) can lead to serious batch quality incidents.
5.How can we meet the traceability requirements of downstream customers?
Reason: Industries such as automotive and home appliances require strict quality traceability. Once a product has a problem, it's crucial to quickly pinpoint which batch of raw materials caused it.
Consequence: If warehouses issue goods out in a random order, with batches A and B mixed together, it becomes impossible to accurately locate the source of a quality issue. This necessitates expanding the recall scope, resulting in extremely high costs.