Marine Welded Steel Pipe

Marine Welded Steel Pipe · High Durability Series

Engineered for the Deep Sea – Built to Endure

In extreme marine environments-offshore platforms, subsea pipelines, port infrastructure, and cross-sea crossings-the durability, corrosion resistance, and structural integrity of steel pipes directly determine project lifecycles and operational costs. Our Marine High-Durability Welded Steel Pipe is purpose‑designed to withstand high salinity, strong currents, complex seabed conditions, and thermal cycling. It redefines "long‑term service" through advanced technology and superior performance.

Advanced manufacturing processes are the key to realizing product performance:

Efficient Forming: JCO forming process (pre-bending, J-shape, C-shape, O-shape) ensures precise geometric dimensions, providing an excellent foundation for subsequent welding.

Hybrid Welding Technology: Pre-welding, internal welding, and external welding all employ gas-shielded metal arc welding (50%–70% CO₂ + 30%–50% Ar) with ER70S series welding wire. By precisely controlling welding speed (pre-weld 25–30 cm/min, inner/outer weld 18–23 cm/min) and interpass temperature (130–170°C), the process effectively addresses the common issues of HAZ property inhomogeneity and toughness degradation in high-strength steel welding.

Full-Process NDT Inspection: From steel plate ultrasonic testing to weld X-ray inspection, weld ultrasonic testing, and pipe-end magnetic particle inspection.

The marine environment presents comprehensive corrosion challenges to pipes. Our high-durability series adopts a multi-layer composite protection strategy:

Base Material Corrosion-Resistant Design: Drawing on the concept of chromium-bearing weathering steel, the addition of Cr and other alloying elements to the base metal promotes the formation of a denser rust layer that effectively inhibits oxygen penetration – corrosion rates can be reduced to less than half that of ordinary steel.

High-Performance External Coating Systems: Compliant with international standards including DNV RP F106 and ISO 21809-1, with multiple coating options:

Fusion Bonded Epoxy (FBE): Single or dual-layer, offering excellent adhesion and cathodic disbondment resistance.

Three-Layer Polyethylene/Polypropylene (3LPE/3LPP): Combining the anti-corrosion performance of epoxy, the adhesion of copolymer adhesive, and the mechanical protection of the polyolefin layer – the go-to solution for subsea pipelines and humid environments.

To meet the diverse requirements of marine engineering projects, the product is available in multiple grades:

Standard Strength Grade: Q355B grade available – yield strength ≥355MPa, tensile strength 470–630MPa, carbon equivalent (Ceq) ≤0.40%. Excellent weldability, suitable for offshore platform piles, trestles, and other structural applications.

Ultra-High Strength Grade: For demanding deepwater oil & gas pipelines and self-elevating drilling platform leg supports, EQ70 grade (equivalent to API 5L X100Q) is available, with minimum yield strength of 690MPa. This enables wall thickness reduction and structural lightweighting while maintaining integrity, reducing overall project costs.

Offshore wind foundations (jackets, monopiles)

Subsea oil/gas transmission pipelines, subsea water pipelines

Port and wharf piling systems, trestles, and revetment works

Marine Welded Steel Pipe · High Durability Series – With precision materials, advanced processes, and multi-layer protection, delivering reliable lifecycle protection for your marine assets.

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