S355NL vs S355ML Which is Better?

S355NL vs S355ML: Which is Better?

S355ML vs S355NL is a common comparison in structural steel selection, as both grades are high-strength, low-alloy steels under the EN 10025 standard but differ in processing and performance. S355NL, specified under EN 10025-3, is a normalized fine-grain steel, while S355ML, under EN 10025-4, is thermomechanically rolled (TMCP). This article compares their chemical composition, mechanical properties, weldability, and applications to determine which is better for specific needs, addressing core keywords s355ml vs s355nl, s355nl vs s355ml, s355nl s355ml, and s355ml s355nl. For more details, visit our EN 10025-3 S355NL normalized structural steel plate.

Overview of S355NL and S355ML

S355NL (EN 10025-3)

S355NL is a normalized or normalized rolled fine-grain structural steel with:

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

Its normalization process ensures a refined microstructure, ideal for cold climates like offshore platforms.

S355ML (EN 10025-4)

S355ML is a thermomechanically rolled (TMCP) fine-grain structural steel with:

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

TMCP produces finer grains, enhancing strength and weldability, often at a lower cost than normalization.

Chemical Composition Comparison

The S355NL vs S355ML comparison starts with their chemical compositions, which influence toughness and weldability.

Carbon Equivalent (CEV):

• S355NL: ≤0.43% (≤63 mm).
• S355ML: ≤0.39% (≤40 mm), lower due to reduced carbon and optimized TMCP, enhancing weldability.

The S355NL S355ML difference shows S355ML’s lower carbon content improves weldability and reduces preheating needs.

Mechanical Properties Comparison

The S355ML S355NL comparison highlights similar strength but differences in processing and toughness.

Strength: Both grades offer similar yield strength (355 MPa at ≤16 mm), but S355ML maintains slightly higher yield for thicker sections due to TMCP. S355NL’s tensile strength (470-630 MPa) is marginally higher than S355ML’s (450-610 MPa).
Toughness: Both achieve ≥27 J at -50°C, ensuring excellent performance in cold climates. S355ML’s TMCP may provide finer grain consistency, potentially enhancing toughness in thicker sections.
Thickness Range: S355NL supports up to 250 mm; S355ML up to 120 mm, limiting its use in thicker applications.

Welding and Heat Treatment

• S355NL: CEV ≤0.43% supports GMAW or SAW (EN 1011-2). Preheating (100-150°C) for >20 mm; PWHT (550-650°C) optional. Consumables: ER70S-6 (GMAW), EM12K flux with EH14 wire (SAW).
• S355ML: Lower CEV (≤0.39%) enhances weldability, often requiring less preheating (50-100°C for >20 mm). Same consumables apply.

The S355NL vs S355ML welding comparison favors S355ML for cost-efficient fabrication due to its TMCP process.

Applications

• S355NL:
  • Offshore platforms in cold marine environments.
  • Wind towers in sub-zero climates.
  • Bridges and cranes in northern regions.
    Its normalization ensures reliability across a wide thickness range (up to 250 mm).
• S355ML:
  • Similar applications (offshore, wind towers, bridges) but preferred in projects prioritizing weldability and cost.
  • Limited to thinner sections (≤120 mm), suitable for lighter structures.

The S355ML S355NL application difference highlights S355NL’s versatility for thicker plates and S355ML’s cost-effectiveness for thinner ones.

Which is Better: S355NL or S355ML?

• Choose S355NLfor:
  • Thicker sections (up to 250 mm) requiring consistent properties.
  • Projects needing robust normalization for extreme conditions.
  • Applications where slightly higher tensile strength is beneficial.
• Choose S355MLfor:
  • Thinner sections (≤120 mm) where cost and weldability are priorities.
  • Projects benefiting from TMCP’s finer grain and lower CEV, reducing fabrication costs.
  • Applications with similar low-temperature demands but tighter budgets.

The S355NL vs S355ML choice depends on thickness, budget, and fabrication needs. S355NL is better for heavy-duty, thicker structures; S355ML excels in cost-sensitive, thinner applications.

Equivalent Grades

• S355NL: ASTM A633 Grade E, Q345E (China), StE 355 (DIN).
• S355ML: ASTM A633 Grade E, Q345E (China), StE 355 TM (DIN).

See EN 10025-3 S355N normalized structural steel plate.

Why Choose Gangsteel?

Gangsteel supplies both grades:

• Inventory: Extensive stock in China.
• Sizes: S355NL up to 250 mm, S355ML up to 120 mm; widths 2000/2500/3000 mm; lengths up to 12,000 mm.
• Delivery: 7-30 days globally.
• Certifications: EN 10204 3.1/3.2, 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 is the main difference in S355ML vs S355NL?
S355NL is normalized or normalized rolled, suitable for thicker sections (up to 250 mm) with slightly higher tensile strength (470-630 MPa). S355ML is thermomechanically rolled, optimized for thinner sections (≤120 mm) with lower CEV (≤0.39%) for better weldability and cost efficiency. Both are tested at -50°C for low-temperature toughness.

Which is better for welding in S355NL vs S355ML?
S355ML has a lower CEV (≤0.39% vs ≤0.43%), requiring less preheating (50-100°C vs 100-150°C for >20 mm), making it more cost-effective for welding. However, S355NL’s weldability remains excellent for thicker plates, with minimal risk of cracking using standard GMAW/SAW processes.

Are S355NL S355ML toughness properties the same?
Both achieve ≥27 J at -50°C, ensuring excellent low-temperature performance. S355ML’s TMCP process may provide slightly finer grain consistency, potentially enhancing toughness in thinner sections, while S355NL’s normalization ensures reliable toughness across a wider thickness range.

Which is more cost-effective in S355ML S355NL?
S355ML is generally more cost-effective due to its TMCP process, which reduces production costs and preheating needs, making it ideal for thinner sections (≤120 mm) in cost-sensitive projects. S355NL may be pricier but is better for thicker, heavy-duty structures requiring normalization.

What are applications of S355NL vs S355ML?
S355NL is used in thicker structures like heavy offshore platforms, wind towers, and bridges in cold climates (up to 250 mm). S355ML suits thinner applications (≤120 mm) like lighter wind towers or bridges where weldability and cost are prioritized, both excelling in -50°C environments.

Can S355ML replace S355NL?
S355ML can replace S355NL for thicknesses ≤120 mm where cost and weldability are critical, as both have similar strength and -50°C toughness. However, for thicker sections (>120 mm), S355NL is necessary due to its wider thickness range and consistent properties.

Explore related grades like EN 10025-3 S420NL normalized structural steel plate.