Introduction
This article explains cold-rolled, hot-rolled and galvanized steel sheets and the differences among them. This article covers the basic knowledge of steel products: the difference between hot-rolled and cold-rolled processing, the meaning of common steel terms, and the classification of rolled products. A clear grasp of these basics supports correct specification and purchasing.
Hot Rolling Versus Cold Rolling
Hot rolling is carried out above the recrystallization temperature and produces thick products with a scale surface, used for structural sections, plates and heavy sheet. Cold rolling is done at room temperature on hot-rolled strip after pickling, giving thinner products with a smooth surface and tighter tolerances, used for panels, appliance shells and coated products.
Rolled Product Forms
Plate, sheet and strip differ by thickness and width. Plate is the thickest form, sheet is thinner and usually supplied flat, and strip or coil is the thin continuous product that feeds presses and roll-forming lines. The classification is defined in the relevant standards for each product.
| Form | Thickness | Typical Use |
|---|---|---|
| Plate | Over 3 mm | Structural, heavy fabrication |
| Sheet | 0.4 - 3 mm | Panels, enclosures |
| Strip / coil | 0.1 - 3 mm | Press feed, roll forming |
| Cold-formed sections | 0.4 - 3 mm | Purlins, studs, framing |
Cold Forming and Cold-Formed Steel
Cold-formed steel sections are roll-formed or press-braked from strip at room temperature, which gives high strength-to-weight ratios and precise dimensions. They are used for purlins, studs, framing and many building components, and their advantages are light weight, speed of fabrication and consistent quality.
Equivalent Grades
Similar steels are designated differently in national standards, and equivalents are used in international trade. The equivalence is based on the mechanical properties and chemistry, and it should be verified against the tables in the relevant standards before substitution.
Verification
Specify the product form, grade, dimensions and standard, and verify the mechanical properties and surface quality on the mill certificate before acceptance.
