Carbon Steel Flat Bar
Product Overview
Carbon steel flat bar is a rectangular-section hot-rolled steel product with width greater than thickness — the most versatile structural steel shape for fabrication, manufacturing, and construction. From machine base frames to trailer chassis, from grating to stiffeners, flat bar is the workhorse of steel fabrication shops worldwide.
Huaxia-Steel supplies carbon steel flat bar in thicknesses from 3mm to 100mm and widths from 12mm to 300mm in standard lengths of 6m and 12m (custom lengths available). Grades cover all major international standards — ASTM A36, S235JR/S275JR/S355J2 (EN 10025-2), SS400 (JIS G3101), and GB/T 700 Q235B.
Dimension, Weight, and Tolerance Table
| Thickness × Width (mm) | Weight (kg/m) | Thickness Tolerance | Width Tolerance |
|---|---|---|---|
| 3 × 20 | 0.47 | ±0.20mm | ±0.75mm |
| 5 × 30 | 1.18 | ±0.25mm | ±0.75mm |
| 6 × 40 | 1.88 | ±0.25mm | ±1.0mm |
| 8 × 50 | 3.14 | ±0.30mm | ±1.0mm |
| 10 × 60 | 4.71 | ±0.35mm | ±1.2mm |
| 12 × 80 | 7.54 | ±0.40mm | ±1.2mm |
| 16 × 100 | 12.56 | ±0.45mm | ±1.5mm |
| 20 × 150 | 23.55 | ±0.50mm | ±1.8mm |
| 25 × 200 | 39.25 | ±0.60mm | ±2.0mm |
| 30 × 250 | 58.88 | ±0.70mm | ±2.2mm |
| 40 × 300 | 94.20 | ±0.80mm | ±2.5mm |
Edge condition: Mill edge (standard) with natural radius from hot rolling. Sheared edge and machined edge (square cut) available for tighter width tolerances. Straightness: Maximum camber 0.4% of length per EN 10058 for standard commercial quality.
Available Carbon Steel Grades
| Standard | Grade | Yield (MPa) | Tensile (MPa) | Elongation (%) |
|---|---|---|---|---|
| ASTM A36 | A36 | 250 min | 400–550 | 20 min |
| EN 10025-2 | S235JR | 235 min | 360–510 | 26 min |
| EN 10025-2 | S275JR | 275 min | 410–560 | 23 min |
| EN 10025-2 | S355J2 | 355 min | 470–630 | 22 min |
| JIS G3101 | SS400 | 245 min | 400–510 | 17 min |
| GB/T 700 | Q235B | 235 min | 370–500 | 26 min |
| GB/T 1591 | Q345B | 345 min | 470–630 | 21 min |
Manufacturing Process and Standards
Carbon steel flat bar is produced by hot rolling continuously cast billets through a series of grooved rolls that progressively reduce the cross-section to the finished dimensions. Key manufacturing controls include:
- Reheating temperature: 1,150–1,250°C — ensures uniform austenitic structure before rolling
- Finishing temperature: 850–950°C — controls final grain size and mechanical properties
- Cooling bed: Controlled air cooling on walking-beam or rake-type cooling beds to minimize residual stress and distortion
- Straightening: Multi-roll straightening (5–9 rolls) for flatness and camber control before cutting
Applicable dimensional standards: EN 10058 (hot-rolled flat steel bars for general purposes), EN 10059 (hot-rolled square steel bars), ASTM A6/A6M (general requirements for rolled structural steel bars).
Common Applications
- Steel fabrication: Base plates, stiffeners, gussets, bracing, connection plates
- Machine building: Frame components, rails, guides, mounting brackets
- Trailer and vehicle manufacturing: Chassis components, cross members
- Grating industry: Bearing bars for welded and press-locked grating
- Agricultural equipment: Plow frames, harrow tines, cultivator components
- Construction: Lintels, ties, anchors, formwork components
- Mining and quarrying: Screen decks, crusher frames, wear strips
- General manufacturing: Die sets, fixtures, jigs, tooling plates
Quality Assurance and Testing
Every flat bar shipment from Huaxia-Steel is backed by:
- Mill Test Certificate (EN 10204 3.1) with heat-by-heat traceability
- Chemical composition verified by OES spectrometer
- Tensile test: yield, tensile strength, and elongation
- Bend test (180° cold bend) for ductility verification where specified
- Dimensional check: thickness, width, straightness per statistical sampling (AQL 2.5)
- Visual surface inspection for laminations, scabs, seams, and rolled-in scale
Optional services: ultrasonic testing for internal soundness, Charpy impact testing at specified temperature, third-party witnessed testing and inspection.
Packaging, Marking, and Shipping
Flat bar is bundled by size and heat number in rectangular stacks, secured with steel strapping (4–6 straps per bundle depending on length). Each bundle is tagged with:
- Bundle ID number
- Grade and standard designation
- Heat number
- Dimensions (thickness × width × length)
- Weight (gross, net, and piece count)
- Purchase order reference
Shipping: Containerized (20ft/40ft) for bundles up to 6m length; breakbulk vessel for 12m and longer material. Weather protection available for sea freight: VCI (volatile corrosion inhibitor) paper or anti-rust oil coating on request.
Request a Quotation
For carbon steel flat bar pricing, stock availability, and delivery schedules, contact our sales team. Please specify thickness, width, length, grade, standard, quantity, and destination port for an accurate quotation. We respond to all RFQs within 24 hours.
