1.What are the specific functions and principles of ingredient design?
Adopting ultra-low carbon or micro carbon design
Controlling the carbon content in steel to an extremely low level (e.g., 0.01%–0.03%) reduces the number of freely moving carbon and nitrogen interstitial atoms at the source, which is fundamental to eliminating the risk of aging.
2.What are the specific functions and principles of the hot rolling process?
High-temperature final rolling and high-temperature coiling
By controlling the hot rolling and coiling temperatures, the precipitation behavior of carbides can be altered, thereby indirectly improving the aging resistance of the final product.
3.What are the specific functions and principles of the cold rolling process?
This is the most direct means of eliminating existing aging tendencies or preventing potential aging:
• Ensure sufficient elongation at the flattening point: Through minute cold deformation of 0.5% to 3%, pinned dislocations are freed, eliminating the yield plateau.
• Strictly control the flattening temperature: Ensure the temperature of the steel coil being flattened is below 45℃. Excessively high temperatures (e.g., exceeding 40-45℃) will accelerate aging, leading to unstable performance after flattening.
4.How to manage storage and transportation?
Control the storage environment: Store steel coils in cool, dry warehouses whenever possible, avoiding prolonged exposure to high temperatures. Higher temperatures accelerate atomic diffusion and the aging process.
Shorten the inventory cycle: Implement the "first-in, first-out" lean production management principle to shorten the inventory time of steel coils, especially for ordinary low-carbon steel coils that have not undergone anti-aging treatment. Practice has shown that reducing the production cycle from 18 days to 13 days helps reduce the risk of performance fluctuations caused by natural aging.
5.What are the remedies and usage recommendations for aged steel coils?
Production-side remedial measures: Over-aging treatment: This is a specific heat treatment process. The already aged steel coil is reheated to a higher temperature (e.g., above 300°C) and held for a short time (e.g., 3-5 minutes). This temperature allows carbon and nitrogen atoms to gain enough energy to "dissipate" from their pinned positions, thus eliminating or inhibiting strain aging. However, this treatment usually needs to be performed on specific continuous annealing or hot-dip galvanizing units.
User-side response: Minor leveling before use: If downstream users (such as stamping plants) find that the material has a slight tendency to age before processing, a minor supplementary leveling (applying a small elongation of about 0.5%-1.5%) can be performed on a dedicated leveling machine to temporarily eliminate the yield plateau. However, this needs to be done with caution, as improper control of the leveling amount may lead to new problems.