Hot Rolled and Cold Rolled Steel Coil Compared

Where the Two Routes Split

Both products start as the same carbon steel. Hot rolling forms the strip at temperature, so the coil comes off with mill scale on the surface and looser dimensional control. Cold rolling takes that material and reduces it further at room temperature, which cleans up the surface, tightens the gauge and work hardens the strip until it is annealed back to a usable temper.

Carbon steel coil is quoted here in both techniques, hot rolled and cold rolled, from the same grade family. That means a fabricator can hold one grade across two thickness bands instead of managing two suppliers.

• Hot rolling forms the strip at temperature and leaves mill scale
• Cold rolling reduces the strip at room temperature for a clean surface
• Cold rolled strip is annealed to recover formability after reduction
• Both routes supplied from the same carbon steel coil range
• Processing covering bending welding decoiling cutting and punching on either

Gauge Ranges You Can Actually Order

This is the decision that makes itself. Cold rolled steel coil is listed from 0mm to 3mm thickness with width to 1500mm or customized. Carbon steel coil covering the hot rolled route is listed from 0.1mm to 300mm or customized, and the plate and sheet specification block carries 0 to 100mm.

If the part needs 6mm it is a hot rolled job. If it needs 0.8mm with a clean face it is a cold rolled job. The overlap in the thin gauges is where surface finish and tolerance decide instead of thickness.

• Cold rolled coil listed 0mm to 3mm thick and to 1500mm wide
• Hot rolled carbon steel coil listed from 0.1mm and customized as required
• Plate and sheet specification block carried at 0 to 100mm
• Steel sheet cut widths 1000 1219 1500 1800 2000 2500 3000 and 3500mm
• Steel sheet cut lengths 2000 2400 3000 5800 and 6000mm

Grade Designations by Route

The two routes carry different designation families and mixing them up is the most common mistake on an inquiry. Cold rolled coil is quoted in SPCC, SPCD, SPCE, Q195, DC01, DC02, DC03, DC04 and ST12 to JIS G3141, DIN1623 and EN10130. Hot rolled carbon steel coil is quoted in Q195, Q215, Q235B, Q345B, S235JR, S355JR, SS400, SS490, SM400 and SM490 to EN10025, ASTM A573, ASTM A283, GB/T 700-2006, GB/T711-2008, JIS G3101, JIS G3131 and JIS G3016.

The DC and SPC families are drawing grades and step from DC01 up to DC04 as the forming demand rises. The Q and S families are structural grades where the number is a yield level. Quoting a structural grade for a deep drawn part, or a drawing grade for a load bearing member, is a specification error rather than a price question.

• Cold rolled drawing grades DC01 DC02 DC03 and DC04
• Cold rolled Japanese designations SPCC SPCD and SPCE
• Hot rolled structural grades Q195 Q215 Q235B and Q345B
• European designations S235JR and S355JR on the hot rolled route
• Japanese hot rolled designations SS400 SS490 SM400 and SM490

Surface Finish and Oiling

Cold rolled coil is supplied in general, bright, dull and mirror finish, oiled or non oiled. That choice runs straight into your downstream process. A part that gets painted or powder coated wants a finish the coating will key to. A part that is visible in service wants the bright or mirror end. Oiling protects the surface in transit but has to be removed before coating.

Hot rolled material is supplied natural or painted and carries mill scale unless it is processed further. If the part is welded and then painted, the scale is a process step you are inheriting, and it belongs in the cost estimate.

• Cold rolled finishes general bright dull and mirror
• Oiled or non oiled supplied on the cold rolled route
• Hot rolled supplied natural or painted
• Mill scale removal is a downstream cost on hot rolled parts
• State the coating process so the finish and oil match it

Forming Welding and Downstream Work

Carbon steel coil in this range has good plasticity and toughness, a bending strength that is not high so it falls into the easily bendable category, and it welds and shapes easily. Those properties are what make it the default for building work, bridges, road repair platforms, structural members and general fabrication.

Cold rolled material adds dimensional consistency to that. When a press tool is set and every coil feeds the same, scrap and setup time drop. That consistency, not raw strength, is usually what justifies the cold rolled price.

• Good plasticity and toughness on both routes
• Bending strength not high which puts it in the easily bendable category
• Easy to weld and easy to shape
• Cold rolled feeds a press consistently coil to coil
• Hot rolled suits welded fabrication where the surface is worked afterwards

Applications That Settle the Choice

Hot rolled coil and plate go into buildings, bridges, road repair platforms, structural members and general fabrication work. Cold rolled coil goes into automotive parts, construction materials and mechanical components where the surface and the gauge are seen or measured.

Where a job needs both, order them against the same grade family and the same certificate so the stores and the inspector see one specification rather than two.

• Hot rolled for structural members bridges and platforms
• Cold rolled for automotive parts and mechanical components
• Cold rolled where the face is visible or painted in service
• Hot rolled where the section is welded into a heavy structure
• Decoiling and cutting to sheet available on either route

What to Confirm Before Ordering

Name the route, the grade in the designation on your drawing, the thickness and width, the finish and the oiling condition, and whether you want coil, decoiled sheet or cut parts. Samples are available where a forming trial has to be run before a production order.

Ask for the mill test certificate so the grade and the route are documented. Certificates for ISO9001, BV, SGS and RoHS can be supplied with the paperwork.

• Route stated as hot rolled or cold rolled
• Grade in the designation printed on your drawing
• Thickness and width with the coil dimensions your line accepts
• Finish and oiled or non oiled condition
• Coil decoiled sheet or cut parts against a cutting list
• Mill test certificate requested with the shipment