Material selection
Hot Rolled Steel vs Cold Rolled Steel
Hot rolled steel is formed above 1,700 F and cools with mill scale on the surface. Cold rolled is hot rolled stock reduced again at room temperature. Cold rolling buys tighter gauge, a clean finish, and higher yield strength through work hardening, at a premium of roughly 15 to 25 percent per pound.
| Hot Rolled Steel | Cold Rolled Steel | |
|---|---|---|
| Price per pound | $0.40 to $0.55/lb A36 | $0.55 to $0.75/lb 1018 CR |
| Thickness tolerance | ±0.2 to 0.5 mm | ±0.05 to 0.15 mm |
| Surface | Mill scale, Ra 3 to 12 µm | Smooth oiled, Ra 0.8 to 1.5 µm |
| Yield strength | A36 at 36 ksi | 1018 CR at 54 ksi |
| Internal stress | Low, stable when machined | Higher, can move after asymmetric cuts |
| Available sizes | Sheet, plate to 12 in, structural shapes | Sheet and bar, mostly under 0.5 in |
| Paint prep | Blast or pickle scale first | Degrease and go |
Choose Hot Rolled Steel when
- Structural frames and weldments
- Thickness over 12 mm
- Parts machined on all surfaces anyway
Choose Cold Rolled Steel when
- Cosmetic or painted sheet parts
- Gauge tolerance under ±0.15 mm
- Higher strength without heat treating
The verdict
Buy hot rolled for structure and anything fully machined; the 15 to 25 percent savings is free when scale and gauge do not matter. Buy cold rolled for sheet metal work, cosmetic surfaces, and tight forming. Watch cold rolled parts with asymmetric machining: locked in stress makes them move.
Cost comparison
On a 10,000 lb order, hot rolled A36 at $0.48/lb versus cold rolled 1018 at $0.65/lb is a $1,700 spread before processing. But blasting or pickling hot rolled for paint adds $0.05 to $0.12/lb, and holding ±0.1 mm gauge from hot rolled stock means grinding at $40 to $80/hr. When the part needs finish or gauge control, cold rolled is usually cheaper delivered. When it needs neither, hot rolled wins every time.
Common questions
Is cold rolled steel actually stronger?
Yes, but not because the chemistry changed. Cold reduction work hardens the material, raising 1018 yield strength from about 32 ksi hot rolled to around 54 ksi cold drawn, roughly a 50 to 70 percent gain. The trade is lower ductility and residual stress. If the part gets welded or annealed later, that strength gain disappears in the heat affected zone.