What are the rust prevention measures for long-term storage of cold-rolled coils?
A: Apply rust-preventive grease to form a protective layer, and check and reapply regularly; seal with anti-oxidation packaging film to prevent moisture intrusion; avoid exposing the packaging film to direct sunlight, which can cause cracking or evaporation of the rust inhibitor.
How to avoid surface damage during handling of cold-rolled coils?
A: Use soft slings or special hooks when using lifting equipment to avoid direct metal-to-metal contact; ensure the handling surface is dry and flat, plan a reasonable route, reduce turns and height differences, and avoid impacts between the coils and hard objects.
How are roll marks formed on cold-rolled coils?
A: Excessively high and unevenly cleaned strip welds can cause sticking to the rolls during continuous rolling; weld beads, metal shavings, and other hard objects may adhere to the rolls; and the work rolls may have chipped material. These conditions will leave periodic pits or bumps on the surface of the cold-rolled coil during rolling or leveling, i.e., roll marks.
What are the characteristics and causes of pyramidal defects in cold-rolled coils? A: The characteristic is that the end face of the steel coil is progressively higher (or lower) than the previous coil, resembling a pagoda, mostly appearing on the inner or outer coil. Causes include coiler malfunction, crescent-shaped bends in the strip, large edge waviness due to poor strip shape, and improper operation and adjustment.
What is the main purpose of annealing cold-rolled coils?
A: To eliminate work hardening caused by cold rolling, restore the strip to good mechanical properties, especially improving the plasticity required for deep drawing, and meeting the requirements of subsequent processing.