S355NL Z35 and Z25 Grades

S355NL Z35 and Z25 Grades

S355NL Z35, S355NL Z25, and S355NL-Z35 refer to specific quality designations of S355NL, a high-strength, low-alloy structural steel under EN 10025-3, with enhanced through-thickness properties for demanding structural applications. The Z35 and Z25 grades indicate guaranteed through-thickness tensile strength, reducing the risk of lamellar tearing in welded structures.

 This article explores the properties, chemical composition, mechanical characteristics, and applications of these grades, addressing core keywords s355nl z35, s355nl z25, and s355nl-z35. For more details, visit our EN 10025-3 S355NL normalized structural steel plate.

What are S355NL Z35 and Z25 Grades?

S355NL is a fine-grain structural steel under EN 10025-3, with:

• S: Structural steel.
• 355: Minimum yield strength of 355 MPa (≤16 mm).
• NL: Normalized or normalized rolled, with impact toughness tested at -50°C.

The S355NL Z35 and S355NL Z25 designations add a "Z" quality class per EN 10164, indicating through-thickness properties:

• Z35: ≥35% reduction of area in through-thickness tensile testing, ensuring resistance to lamellar tearing in heavy welds.
• Z25: ≥25% reduction of area, a slightly less stringent requirement.

S355NL-Z35 is synonymous with S355NL Z35, emphasizing the highest Z-quality for critical applications like offshore platforms.

Chemical Composition of S355NL Z35 and Z25

The chemical composition of S355NL Z35 and S355NL Z25 is identical to standard S355NL, with low impurities to support Z-quality:

Carbon Equivalent (CEV): ≤0.43% (≤63 mm), calculated as CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15, ensures weldability. Low sulfur (≤0.015%) minimizes inclusions, critical for Z35/Z25 quality.

Mechanical Properties

The mechanical properties of S355NL Z35 and S355NL Z25 match standard S355NL, with added through-thickness guarantees:

• Z-Quality: S355NL-Z35 ensures ≥35% reduction in through-thickness testing (EN 10164), reducing lamellar tearing risk; Z25 requires ≥25%.
• Yield Strength: ≥355 MPa (≤16 mm) for load-bearing.
• Tensile Strength: 470-630 MPa for durability.
• Impact Toughness: ≥27 J at -50°C for cold climates.

Through-Thickness Testing (Z-Test)

The Z-test per EN 10164 measures through-thickness tensile strength to ensure resistance to lamellar tearing in thick welds:

• Z35: ≥35% reduction of area, ideal for heavy welded joints in offshore structures.
• Z25: ≥25% reduction, suitable for less critical welds.
• Testing: Conducted on plate samples, ensuring no internal defects like inclusions.

Welding and Heat Treatment

S355NL Z35 and S355NL Z25 are weldable:

• Welding: GMAW or SAW per EN 1011-2. Preheating (100-150°C) for >20 mm; Z-quality reduces cracking.
• PWHT: Optional at 550-650°C for critical welds.
• Consumables: ER70S-6 (GMAW), EM12K flux with EH14 wire (SAW).

Applications

S355NL Z35 and S355NL Z25 are used in:

• Offshore Platforms: Z35 for thick welded joints in cold marine environments.
• Wind Turbine Towers: Z25/Z35 for heavy structural welds in sub-zero climates.
• Bridges: Z35 for critical load-bearing welds in northern regions.
• Pressure Vessels: Z25/Z35 for low-temperature storage with robust welds.

Explore EN 10025-3 S420NL normalized structural steel plate.

Why Choose Gangsteel?

Gangsteel supplies S355NL-Z35:

• Inventory: Extensive stock in China.
• Sizes: Thickness 6–250 mm, widths 2000/2500/3000 mm, lengths up to 12,000 mm.
• Delivery: 7-30 days globally.
• Certifications: EN 10204 3.1/3.2, Z-test (EN 10164), UT testing (EN 10160), ABS/LR/BV/DNV approvals.
• Processing: Cutting, welding, bending.

Contact us for EN 10025-3 S355NL normalized structural steel plate.

FAQ

What are S355NL Z35 and S355NL Z25?
S355NL Z35 and S355NL Z25 are S355NL steel grades with guaranteed through-thickness properties (≥35% or ≥25% reduction of area, EN 10164), ensuring resistance to lamellar tearing in heavy welded structures like offshore platforms.

What does S355NL-Z35 mean?
S355NL-Z35 indicates S355NL steel with a Z35 quality class, offering ≥35% reduction in through-thickness tensile testing, ideal for critical welds in thick plates, ensuring high weld integrity in cold climates.

How do S355NL Z35 and Z25 differ?
S355NL Z35 requires ≥35% reduction of area, offering superior resistance to lamellar tearing for heavy welds in offshore structures; S355NL Z25 requires ≥25%, suitable for less critical welds, both maintaining -50°C toughness.

Are S355NL Z35 and Z25 weldable?
Yes, both S355NL Z35 and S355NL Z25 are highly weldable (CEV ≤0.43%), using GMAW/SAW with preheating (100-150°C for >20 mm). Their Z-quality reduces lamellar tearing risks in thick welded joints.

What are applications of S355NL Z35?
S355NL Z35 is used in critical welded structures like offshore platforms, wind towers, and bridges in cold climates, leveraging its -50°C toughness and ≥35% through-thickness strength for heavy welds.

How does S355NL Z25 compare to standard S355NL?
S355NL Z25 adds ≥25% through-thickness reduction per EN 10164, enhancing weld reliability compared to standard S355NL, which lacks specific Z-quality guarantees, while maintaining identical strength and toughness.