According to materials from UTMK's Technical Department
Hot-rolled or cold-rolled — this is the first question that arises when choosing sheet metal. Both types are manufactured from the same steel but using different methods, and this determines everything: surface quality, dimensional accuracy, allowable loads, and price. Let's analyze it in detail.
The Main Difference: Rolling Temperature
Hot-Rolled Steel (HR)
The steel billet is heated to 1100–1250 °C and rolled while in a plastic state. After cooling, an oxide film (mill scale) forms on the surface — hence the dark color and rough texture. In accordance with EN 10025 standards (which govern technical delivery conditions), thickness tolerances for standard precision are ±0.3 mm and more.
The advantage of this method is the ability to manufacture thick plates (up to 200 mm) and large-sized structural profiles. After cooling, the metal does not have high internal stresses, so it behaves well during cutting and welding.
Cold-Rolled Steel (CR)
Previously cooled hot-rolled metal is re-rolled at room temperature. The process is more complex and expensive (by 15–30%), but the result is a smooth, shiny surface and minimal tolerances: according to EN 10131, thickness accuracy is ±0.05–0.15 mm. The method is applied only to thin metal — usually 0.3–6 mm.
An important technical nuance: cold deformation strengthens the metal (work hardening or strain hardening), but simultaneously creates internal stresses. If CR steel is cut or welded without prior normalization, warping (deformation) is possible.
Comparison Table: HR vs CR Steel
| Parameter | Hot-Rolled (HR) | Cold-Rolled (CR) |
|---|---|---|
| Rolling Temperature | 1100–1250 °C | Room temperature (no heating) |
| Surface | Rough, dark, with mill scale | Smooth, shiny, without scale |
| Dimensional Accuracy | ±0.3 mm and more (EN 10025, contextually EN 10029/EN 10051) | ±0.05–0.15 mm (EN 10131) |
| Thickness | 1.5–200 mm | 0.3–6 mm |
| Strength | High, no internal stresses | Higher due to work hardening, but has stresses |
| Corrosion Resistance | Better (oxide film protection) | Lower without coating |
| Price | Lower | Higher by 15–30% |
| Typical Application | Construction, beams, frames, pipes | Appliances, automotive, cladding, decor |
Tolerances are provided in accordance with contextually implied EN 10025 context (structural properties) with tolerance standards like EN 10051/10029 and EN 10131 (CR).
Marking and Designations
The marking of sheet steel indicates four mandatory elements:
| Marking Element | Value | Example | Explanation |
|---|---|---|---|
| Product Type | HR / CR | HR = Hot-rolled | CR = Cold-rolled |
| Accuracy Class | A, B, C | A = High | B = Ordinary (most common) |
| Steel Grade | S235JR, 08kp, DC01 | 08kp — for stamping | S235JR (analogue of St3) — structural steel |
| Dimensions | thk×wid×len | 2.0×1250×2500 | in millimeters |
Exactly such a sheet — Cold-rolled sheet 2.0×1250×2500 08kp steel — is available in the UTMK range.
Regulatory Base in Europe
Both types of steel are manufactured and supplied in accordance with European and international standards. The key difference: for HR steel, EN 10025 (which replaces GOST 16523 context for engineering grades) standards apply; for CR steel, EN 10130 and EN 10131 are used, which set significantly stricter requirements for dimensional accuracy and surface quality.
| Standard | Product Type | What it Regulates |
|---|---|---|
| EN 10025 | Hot-Rolled | Mechanical properties, tolerances, and supply conditions for structural steels (analogous context of replaced DSTU 16523, DSTU 8540, GOST 380) |
| EN 10130:2009 | Cold-Rolled | Requirements for CR steel for stamping: surface quality, accuracy classes, deep drawing (analogous of replaced DSTU 19904 context for deep draw) |
| EN 10131 | Cold-Rolled | Tolerances on thickness (±0.05–0.15 mm), width, and flatness |
| ISO 404 | HR & CR | General technical delivery requirements for steel products |
ISO 404 establishes general technical delivery requirements for steel — valid for both types of steel. European EN standards largely replace older GOST/DSTU technical regulations in the EN market.
Where Each Type is Applied
Hot-Rolled Steel — For Strength and Large Loads
- Construction: load-bearing beams, frames, trusses, foundation embeds
- Bridge and Shipbuilding: requirements for thickness and ductility
- Heavy Machinery: frames, traverses, support structures
- Pipe Production: billets for welded and seamless pipes
- Sections and Profiles: channels, angles, I-beams
The UTMK range of hot rolled sheet includes various steel grades and thicknesses in stock.
Cold-Rolled Steel — For Precision and Aesthetics
- Automotive Industry: body parts, trim elements
- Household Appliances and Electronics: enclosures, panels
- Profiled Sheets and Metal Tiles: a perfect surface is needed for coating
- Ventilation Systems and Air Ducts: thin metal of precise dimensions
- Furniture Production: visible surfaces without defects
- Galvanizing and Painting: a level surface ensures coating adhesion
The UTMK range of cold rolled sheet features steel grades optimized for stamping, forming, and coating.
How to Choose: Decision Table
If you are in doubt — check your task against this table:
| Task / Condition | What to Choose | Why |
|---|---|---|
| Load-bearing structures, frames, beams | HR | Thickness and strength are required; precision is non-critical |
| Stamping, forming, bending | CR | High precision and ductility of CR steel (EN 10130) |
| Decor, facade, visible surfaces | CR | Smooth surface without scale, suitable for coating |
| Galvanizing or painting the sheet | CR | Even surface ensures superior coating adhesion |
| Welded structures without surface requirements | HR | No internal stresses — less deformation during welding |
| Thickness > 6 mm | HR | Cold rolling is not applied for thick plate metal |
A rule that simplifies the choice in 80% of cases: if the surface will be hidden or welded — take HR. If the surface is visible or the part will be stamped — take CR.
Pre-order Checklist for Sheet Steel
- Determine thickness: up to 6 mm — both options are possible; over 6 mm — HR only
- Assess surface requirements: visible / decorative → CR; hidden / welded → HR
- Check accuracy: if tolerance is critical (stamping, precision bending) → CR according to EN 10131
- Specify the steel grade: for stamping — 08kp, DC01; for structures — S235JR, S355J2
- Consider welding: CR steel may warp if not normalized after welding
You can find the right hot rolled or cold rolled sheet with the required steel grade and size in the UTMK catalog. Our technical department will assist with the choice of grade and supply standard.
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