S355MLO EN 10025-4 Weldable Steel Plate Supplier

S355MLO EN 10025-4 Weldable Steel Plate Supplier

Gangsteel – China's Leading Mill-Direct Supplier & Exporter of S355MLO EN 10025-4 Weldable Offshore Structural Steel Plates

Gangsteel is the specialized supplier for S355MLO EN 10025-4 weldable offshore steel plates, delivering the enhanced "offshore package" version of S355ML with mandatory Z35 through-thickness properties, CTOD toughness testing, strain ageing resistance, and full compliance to DNV-OS-B101, Norsok M-120, and API 2W requirements. We maintain the largest dedicated stock of S355MLO in Asia – over 4,000 tons ready for immediate delivery in thickness 6–200 mm, width 1500–4200 mm, length up to 18 meters. All plates are genuine TMCP produced by top mills (HBIS, Shougang) with full European approvals and third-party inspection (DNV, ABS, LR, BV, CCS, KR, TÜV, SGS).

S355MLO is the preferred grade for critical offshore welded joints where standard S355ML is not sufficient. We supply S355MLO with complete offshore certification package (CTOD, strain ageing, higher impact energy, Z35 mandatory) directly from stock – no waiting for mill extras.

Fast delivery worldwide in 3–7 days. Full processing services available.

Explore our complete en 10025 4 High Strength Structural Steel series for all grades.

What is S355MLO EN 10025-4 Weldable Steel Plate?

S355MLO is the offshore-enhanced version of S355ML under EN 10025-4.

The base grade is S355ML – thermomechanically rolled (TMCP) weldable fine-grain structural steel with 355 MPa yield and –50 °C impact toughness.

"S355MLO" is a market designation (the "O" stands for "offshore") used by mills and classification societies to indicate S355ML with additional offshore requirements, typically:

• Z35 through-thickness quality mandatory (≥35% reduction of area EN 10164 Class 3)
• Higher impact energy (often ≥50 J average at –40 °C or –50 °C)
• CTOD (Crack Tip Opening Displacement) toughness testing
• Strain ageing test (impact after 5% strain + ageing)
• PWHT (post-weld heat treatment) simulation testing
• Full compliance with offshore standards (DNV-OS-B101, Norsok M-120, API 2W)

The base material is identical to S355ML – same chemistry, same strength, same TMCP process.

The difference is only in the additional testing and guarantees required for offshore certification.

In practice, when a project specification says "S355MLO", it means S355ML + offshore package.

Most new offshore wind projects (Hornsea, Borkum Riffgrund, Formosa, Baltica) now require S355MLO for critical welds (monopiles, jackets, transition pieces).

Gangsteel supplies both standard S355ML and full S355MLO offshore-certified plates from stock.

For the standard grade explanation, see S355ML Meaning EN 10025-4 Structural Steel Supplier.

Chemical Composition – Identical to S355ML

S355MLO has exactly the same chemical requirements as S355ML per EN 10025-4.

Typical Gangsteel actual values for S355MLO offshore packages: C 0.08–0.11 %, CEV 0.33–0.36, P+S ≤0.025 %.

Full chemical data: S355ML Chemical Composition EN 10025-4 Supplier

Mechanical Properties – Standard vs Offshore Enhanced Requirements

Base mechanical properties are identical to S355ML, but S355MLO has additional offshore guarantees.

S355MLO plates from Gangsteel routinely achieve:

• Impact values 100–200 J at –50 °C
• CTOD 0.4–0.6 mm at –40 °C
• Z35 with ≥40 % reduction of area

Full mechanical tables: S355ML Mechanical Properties EN 10025-4 Plate Supplier

Weldability – Excellent with Offshore Guarantees

Both grades have the same low CEV, but S355MLO's additional testing guarantees superior HAZ properties after high heat input welding (SAW, FCAW).

No preheating required up to 80 mm for both grades. Gangsteel provides welding recommendations and heat-specific data for both S355ML and S355MLO.

Price Difference and Market Reality

The extra cost of S355MLO is easily justified by the additional safety margin and reduced risk of weld failure in offshore environments.

Why Choose Gangsteel for S355ML and S355MLO Plates

• Largest stock of both S355ML and S355MLO in Asia (6,000+ tons combined)
• Factory-direct price – 60–120 USD/ton lower than traders
• Full offshore certification packages for S355MLO in stock
• Z35 quality always available
• Immediate delivery worldwide
• Exported to 90+ countries with perfect documentation
• One-stop service – stock → processing → shipping

FAQ – Detailed Answers

Q1: Is S355MLO a separate grade in EN 10025-4?

A: No – it is S355ML with additional offshore requirements (higher impact, CTOD, Z35 mandatory). The base material is identical to S355ML, but the "O" designation indicates the extra testing package for offshore certification.

Q2: Can I use S355ML instead of S355MLO to save money?

A: Only if the project specification allows it. Most offshore wind and oil & gas projects now require the S355MLO package for the extra safety margin in welded joints, especially for monopiles and jacket nodes where CTOD toughness is critical.

Q3: What is the price difference between S355ML and S355MLO?

A: S355MLO is 120–220 USD/ton higher than standard S355ML (November 2025 market), depending on the exact testing package required (CTOD, strain ageing, higher impact energy).

Q4: Do you have S355MLO in stock right now?

A: Yes – very large stock of S355MLO with full offshore certification (CTOD, strain ageing, Z35) ready for immediate delivery. We can ship within 3–7 days worldwide.

Q5: What additional testing does S355MLO include?

A: Typical S355MLO package includes CTOD toughness testing (≥0.25 mm at –40 °C), strain ageing test (impact after 5 % strain + ageing at 250 °C/1h), higher impact energy (≥50 J average at –40 °C or –50 °C), Z35 mandatory, and PWHT simulation – all included in our S355MLO stock plates.

Q6: Is S355MLO required for all offshore projects?

A: Not all, but 90 % of new offshore wind projects and most oil & gas projects now specify S355MLO for critical welds. Plain S355ML is still accepted for non-critical areas or onshore applications.

Q7: Can you supply dual-certified plates?

A: Yes – many of our plates are supplied with both S355ML (EN 10025-4) and S355MLO offshore certification when the properties meet both standards.

Contact Gangsteel Today

Need S355ML or S355MLO plates? Contact us for quotation within 2 hours.

Email: admin@gangsteel.com WhatsApp/WeChat/Mobile: +86 135 9887 9167 Website: https://gangsteel.net/

Gangsteel – Your Expert for Both Standard and Offshore S355ML Plates.

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