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A steel flat bar is a long, rectangular cross-section solid steel product, hot-rolled or cold-drawn to precise dimensional tolerances. In shipbuilding and marine engineering, flat bars are among the most fundamental structural components โ used in hull frames, deck stiffeners, keel plates, bulkhead reinforcement, bracket connections and countless other load-bearing applications.
Marine-grade flat bars must meet rigorous standards for tensile strength, yield strength, impact toughness (especially at low temperatures), weldability and corrosion resistance. Common material grades include AH32, AH36, DH32, DH36, EH36 (IACS/classification society grades), as well as ASTM A36, ASTM A131, EN S355J2 and Chinese GB/T standards.
โ Key Insight: In a typical mid-sized cargo vessel (50,000โ80,000 DWT), flat bars account for 8โ14% of total structural steel tonnage โ making them one of the highest-volume structural profiles in any shipbuilding project.
BAOLF STEEL GROUP supplies hot-rolled flat bars from 10mm ร 3mm up to 600mm ร 100mm, with lengths customizable from 3m to 12m, all compliant with classification society requirements including ABS, DNV GL, Lloyd's Register, BV, CCS and NK.
| Width (mm) | Thickness (mm) | Grade | Standard |
|---|---|---|---|
| 20 โ 100 | 3 โ 12 | A36 / AH32 | ASTM / IACS |
| 100 โ 200 | 8 โ 30 | AH36 / DH36 | ABS / DNV |
| 200 โ 400 | 12 โ 60 | EH36 / FH36 | LR / BV / CCS |
| 400 โ 600 | 20 โ 100 | S355J2 / Q345B | EN / GB |
| Custom | Custom | As Required | Multi-standard |
Global newbuild orders surged to over 120 million CGT in 2023โ2024, driven by fleet renewal, LNG carrier demand and post-pandemic trade recovery. This directly propels demand for marine-grade flat bars and structural steel profiles across Asian and European shipyards.
IMO 2050 decarbonization targets are accelerating orders for LNG-powered, methanol-fueled and ammonia-ready vessels. These ship types require cryogenic-grade steel flat bars (DH36, EH36, FH36) capable of withstanding temperatures as low as โ60ยฐC in tank structures and piping supports.
The offshore wind industry is projected to install over 380 GW of capacity by 2030. Each offshore wind foundation structure (monopile, jacket or tripod) consumes hundreds of tons of flat bar stiffeners, gussets and connection brackets โ creating massive sustained demand.
Governments in Asia-Pacific, Europe and the Middle East are investing heavily in naval fleet expansion. Naval vessel construction demands ultra-high-strength flat bars (AH40, DH40, EH40) with strict Charpy impact test requirements and certified mill test reports for classification society approval.
Modern shipyards are adopting BIM, robotic welding and CNC plasma cutting for flat bar fabrication. This demands tighter dimensional tolerances (ยฑ0.5mm width, ยฑ0.3mm thickness), consistent surface quality and traceable heat numbers โ all of which BAOLF STEEL delivers with ISO-certified production lines.
Post-pandemic supply chain disruptions have pushed global shipyards toward dual-sourcing and regional supplier diversification. BAOLF STEEL's proximity to Tianjin Port (only 20 km) and 800,000-ton annual capacity make it an ideal strategic partner for both Asian and international shipbuilding procurement teams.
The hull's longitudinal and transverse frame system relies extensively on flat bars as web stiffeners, bracket gussets and frame end connections. In double-hull tankers and bulk carriers, flat bars are welded to shell plating at regular intervals (typically 600โ800mm spacing) to resist hydrostatic pressure, wave-induced bending and slamming loads. Grade AH36 or DH36 flat bars with Charpy V-notch impact energy โฅ31J at โ20ยฐC are standard for these applications.
Flat bars welded perpendicular to deck plating function as deck transverses and longitudinal deck girder stiffeners, distributing cargo loads and preventing plate buckling. Around hatch openings of container ships and bulk carriers, heavy flat bars (width 200โ400mm, thickness 20โ50mm) form the coaming reinforcement structure that withstands green water loading and container stack forces exceeding 1,000 tons.
Watertight and structural bulkheads in all vessel types use flat bar vertical stiffeners at 600โ750mm spacing. These flat bars must be precisely straightened and cut to exact lengths to ensure proper fit-up during block assembly. BAOLF STEEL's CNC leveling and precision cutting service ensures flatness tolerance within 1mm/m โ critical for automated welding line compatibility in modern block-assembly shipyards.
Fixed offshore platforms (oil & gas, wind) use massive quantities of flat bars in conductor guide frames, caisson stiffeners, mudmat gussets and brace node reinforcements. These components face simultaneous wave, current, wind and earthquake loading, requiring EH36 or S355G10+M grade flat bars with through-thickness (Z35) properties to prevent lamellar tearing during welding.
Throughout the machinery spaces, engine rooms and accommodation modules of vessels and FPSOs, flat bars form the pipe support brackets, cable tray hangers and HVAC duct frames. Galvanized or epoxy-coated flat bars (typically 50ร6mm to 100ร10mm) are used here, providing corrosion resistance in the high-humidity, salt-laden marine atmosphere.
Rudder frames, horn plates, pintle brackets and propeller shaft brackets incorporate heavy flat bars and plates machined to precise tolerances. The rudder stock housing uses flat bar flanges welded to cylindrical forgings, requiring full-penetration welds with UT/RT examination per classification society rules โ a quality standard that BAOLF STEEL fully supports with third-party inspection coordination.
ABS, DNV GL, LR, BV, CCS, NK certified mill test reports available for every heat number.
20km from Tianjin Port. Stock items ship within 3โ7 days. Custom orders in 15โ25 days.
Heat number, chemical composition, mechanical test results โ all documented and traceable per ISO 9001:2015.
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