Steel Coils
Product Overview
Steel coil refers to flat-rolled steel products wound into a coil form for easier handling, storage, and transportation. Steel coils serve as the fundamental raw material for countless downstream industries, including construction, automotive manufacturing, appliance production, pipe manufacturing, and general engineering.
Steel coils are categorized primarily by production method (hot-rolled or cold-rolled), surface treatment (bare, galvanized, or coated), and material composition (carbon steel or stainless steel). The coil format enables efficient high-volume processing and continuous manufacturing operations.
Product Types
1 Hot-Rolled Steel Coils
Hot-rolled coils are produced by rolling steel at elevated temperatures, typically above 1,000°C, which softens the material for shaping. After rolling, the hot steel strip is cooled and wound into coils.
| Attribute | Description |
|---|
| Thickness | Typically 1.2 mm and above |
| Surface Finish | Rough, bluish-gray scale finish |
| Key Characteristics | Lower production cost, high strength, structural durability, looser dimensional tolerances |
| Applications | Construction, roofing, car frames, shipbuilding, welded pipes, cold-rolled coil feedstock |
2 Cold-Rolled Steel Coils
Cold-rolled coils start as hot-rolled coils and undergo additional rolling at room temperature. This process reduces thickness, improves surface quality, and tightens dimensional tolerances.
| Attribute | Description |
|---|
| Thickness | 0.15 – 4.0 mm |
| Surface Finish | Smooth, bright, with sharp and precise edges |
| Key Characteristics | Higher strength, excellent surface finish, tight dimensional accuracy, may require annealing to restore ductility |
| Applications | Automotive body panels, appliances, furniture, precision components |
3 Galvanized Steel Coils
Galvanized coils are steel coils coated with a layer of zinc to provide corrosion protection. The zinc coating acts as a sacrificial barrier against atmospheric exposure.
| Attribute | Description |
|---|
| Thickness | 0.12 – 3.2 mm |
| Width | 600 – 1,500 mm |
| Zinc Coating | 20 – 300 g/m² |
| Surface Structure | Zero spangle, minimized spangle, regular spangle, big spangle |
| Coil Weight | 2.5 – 20 tons per coil |
| Applications | Roofing, structural frames, automotive parts, pipes, guardrails, appliances |
- Galvanized Steel Grades and Properties:
| Grade | Yield Strength (MPa) | Typical Use |
|---|
| SGCC / DX51D+Z | ≥205 | Commercial quality, general forming |
| DX52D+Z | — | Drawing quality |
| SGCD / DX53D+Z | ≥270 | Deep drawing quality |
| SGCE / DX54D+Z | — | Extra deep drawing quality |
| S220GD | ≥220 | Structural quality |
| S250GD | ≥250 | Structural quality |
| S280GD | ≥280 | Structural quality |
| S320GD | ≥320 | Structural quality |
| S350GD | ≥350 | Structural quality |
4 Pre-Painted / Polymer-Coated Steel Coils
Pre-painted coils (also known as color-coated coils or PPGI - Pre-Painted Galvanized Iron) consist of a steel base (hot-rolled, cold-rolled, or galvanized) with a decorative and protective painted layer applied through chemical preparation, roller coating, and heat curing.
| Attribute | Description |
|---|
| Base Metal | Galvanized steel or cold-rolled steel |
| Color Coating Thickness | 15 – 35 μm (top coat) / 5 – 30 μm (back coat) |
| Zinc Coating (base) | 40 – 275 g/m² |
| Applications | Metal roofing, sandwich panels, household appliances, automotive components, furniture |
5 Stainless Steel Coils
Stainless steel coils are produced from corrosion-resistant alloys containing a minimum of 10.5% chromium, offering excellent resistance to corrosion, oxidation, and chemical attack.
- 2.2.2.2.5.1 Austenitic Stainless Steels
| Grade | Characteristics | Typical Applications |
|---|
| 304 / 304L | Excellent formability and corrosion resistance; "18-8" alloy (18% Cr, 8% Ni) | Food processing equipment, kitchen sinks, heat exchangers, chemical containers |
| 316 / 316L | Molybdenum addition for enhanced chloride resistance; superior pitting resistance | Marine environments, medical equipment, chemical processing |
| 201 | Manganese substitutes for some nickel; cost-effective, good strength | Decorative tubes, cookware, transit panels |
| 309S / 310S | High chromium and nickel for extreme oxidation resistance | High-temperature furnace components |
| 321 | Titanium stabilized to prevent intergranular corrosion | High-temperature service, thermal cycling applications |
- 2.2.2.2.5.2 Ferritic Stainless Steels
| Grade | Characteristics | Applications |
|---|
| 430 | Nickel-free; cost-effective; magnetic; good polishability | Appliance trim, automotive components, shallow-draw parts |
- 2.2.2.2.5.3 Stainless Steel Coil Specifications
| Attribute | Details |
|---|
| Thickness (Cold Rolled) | 0.1 – 4.0 mm |
| Thickness (Hot Rolled) | 3.0 – 120 mm |
| Width | 100 – 2,500 mm |
| Surface Finishes | 2B, BA, No.1, No.3, No.4, HL, Mirror, Embossed |
- Stainless Steel Surface Finishes:
| Finish | Description | Applications |
|---|
| 2B | Cold-rolled, annealed, pickled, and lightly rolled on polished rolls; bright and reflective | Medical equipment, food industry, construction, kitchen utensils |
| BA (Bright Annealed) | Bright heat treatment after cold rolling; mirror-like shine | Kitchen utensils, electrical equipment, building construction |
| No.1 | Hot-rolled, heat-treated and pickled; industrial finish | Chemical tanks, pipes |
| No.4 | Polished with fine abrasives; brushed finish | Kitchen utensils, building construction, medical equipment |
| HL (Hairline) | Continuous polishing streaks | Building construction, architectural trim |
| Mirror / 8K | Highly reflective polished surface | Decorative applications |
Applicable Standards
1 Chinese Standards (GB)
| Standard | Description |
|---|
| GB/T 3274 | Carbon structural steels and low-alloy high-strength structural steels for general use |
| GB/T 11253 | Cold-rolled steel sheets and strips for general use |
2 International Standards
| Standard | Description |
|---|
| ASTM A36 / A36M | Carbon structural steel |
| ASTM A283 / A283M | Low and intermediate tensile strength carbon steel plates |
| ASTM A588 | High-strength low-alloy structural steel with atmospheric corrosion resistance |
| ASTM A653 | Hot-dipped galvanized steel sheets |
| ASTM A1008 / A1011 | Cold-rolled / hot-rolled steel sheets for general use |
| EN 10025 | Hot-rolled structural steel products |
| EN 10111 | Hot-rolled low-carbon steel sheets for cold forming |
| EN 10130 | Cold-rolled low-carbon steel flat products for cold forming |
| EN 10346 | Continuously hot-dip coated steel flat products |
| EN 10149-2 | Hot-rolled high-strength steel for cold forming |
| JIS G3101 | General structure hot-rolled steel |
| JIS G3131 | Hot-rolled mild steel sheets and strips |
| JIS G3302 | Hot-dipped galvanized steel sheets and strips |
| ISO 630 | Structural steels |
3 Key Grade Equivalents
| Application | Chinese Grade | ASTM Equivalent | EN Equivalent | JIS Equivalent |
|---|
| Commercial/Drawing | — | CS Type A/B/C | DD11 | SPHC / SPHD |
| Structural | Q235 | A36 / SS Grade 230 | S235JR | SS400 |
| Structural | Q345 | A572 Gr.50 | S355JR | SM490 |
| Galvanized | — | ASTM A653 | DX51D+Z | SGCC |
Manufacturing Processes
1 Steelmaking and Casting
Iron ore, coal, and limestone are processed in a blast furnace to produce molten steel, which is continuously cast into flat slabs.
2 Hot Rolling
Slabs are heated above recrystallization temperature and passed through rollers to reduce thickness and form long sheets, then cooled and wound into coils.
3 Pickling
Acid baths remove iron oxide scale from hot-rolled surfaces, preparing the steel for cold rolling or coating applications.
4 Cold Rolling
Pickled hot-rolled coils are rolled at room temperature through tight rollers to achieve thinner gauges, smoother surfaces, and tighter dimensional tolerances.
5 Annealing
Cold-rolled coils may undergo heat treatment to relieve internal stresses and restore ductility for forming operations.
6 Galvanizing
Steel coils pass through a bath of molten zinc, or zinc is applied via electroplating. Coating thickness varies based on the required corrosion protection level.
- Galvanizing Coating Classes:
- Z80 – Z450: Standard zinc coating classes per EN 10346
- 20 – 300 g/m²: Typical coating weight range
7 Surface Treatment (Galvanized Coils)
| Treatment | Description |
|---|
| Chromated / Passivated (C) | Chemical surface treatment for corrosion resistance |
| Oiled (O) | Application of protective oil film |
| Skin-Passed | Light rolling to improve surface finish and flatness |
| Anti-Fingerprint | Special coating to prevent surface marking |
Dimensions and Specifications
1 Hot-Rolled Coils
| Dimension | Range |
|---|
| Thickness | 1.2 – 25 mm+ |
| Width | 600 – 1,500 mm |
| Coil Weight | Varies by mill specifications |
2 Cold-Rolled Coils
| Dimension | Range |
|---|
| Thickness | 0.15 – 4.0 mm |
| Width | 600 – 1,250 mm |
3 Galvanized Coils
| Dimension | Range |
|---|
| Thickness | 0.12 – 3.2 mm |
| Width | 500 – 1,500 mm |
| Coil ID | 508 mm or 610 mm |
| Coil Weight | 3 – 20 tons per coil |
4 Stainless Steel Coils
| Dimension | Cold Rolled | Hot Rolled |
|---|
| Thickness | 0.1 – 4.0 mm | 3.0 – 120 mm |
| Width | 100 – 2,500 mm | 100 – 2,500 mm |
Packaging and Protection
Steel coils require specialized packaging to ensure product integrity during storage and transportation:
| Packaging Element | Description |
|---|
| Steel Straps / Bundling | Strong steel bands securing the coil to prevent unwinding |
| Waterproof Wrapping | Moisture-resistant paper or plastic sheeting for corrosion protection |
| Edge Protection | Plastic caps or edge protectors to prevent damage to coil edges |
| Wooden Racks / Crates | For protection during road, rail, and ocean transport |
| Protective Oiling | Anti-rust oil applied to bare coil surfaces |
Key Applications and Industries
1 Construction and Infrastructure
- Roofing sheets and corrugated panels
- Structural beams, columns, and frames
- Guardrails and highway barriers
- Ventilation ducts and gutters
2 Automotive Manufacturing
- Car bodies and frames
- Engine components and exhaust systems
- Interior and structural parts
3 Appliances and Consumer Goods
- Refrigerators, washing machines, ovens
- Heating equipment casings
- Furniture and shelving
4 Industrial and Manufacturing
- Pipe and tube manufacturing (welded pipes)
- Storage tanks and pressure vessels
- Machinery components and equipment frames
