S355NL vs S355J2 Weldability

S355NL vs S355J2: Weldability

S355NL vs S355J2 weldability is a critical factor when choosing between these structural steels under the EN 10025 standard. S355NL, specified under EN 10025-3, is a normalized fine-grain steel optimized for low-temperature toughness, while S355J2, under EN 10025-2, is a hot-rolled non-alloy steel for general applications. The difference between S355J2 and S355NL in weldability stems from their chemical compositions and processing, impacting fabrication ease and performance in welded structures.

This article compares their weldability, chemical composition, mechanical properties, and applications, addressing core keywords s355nl vs s355j2 and difference between s355j2 and s355nl. For more details, visit our EN 10025-3 S355NL normalized structural steel plate.

Overview of S355NL and S355J2

S355NL (EN 10025-3)

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

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

Its fine-grain structure enhances weldability and toughness in cold climates.

S355J2 (EN 10025-2)

S355J2 is a non-alloy structural steel, typically hot-rolled, with:

• S: Structural steel.
• 355: Minimum yield strength of 355 MPa (≤16 mm).
• J2: Impact toughness tested at -20°C.

S355J2 is cost-effective for general construction in temperate climates.

Weldability Comparison

The difference between S355J2 and S355NL in weldability is driven by their chemical composition and processing:

• S355NL:
  • Carbon Equivalent (CEV): ≤0.43% (≤63 mm), calculated as CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15.
  • Welding: Supports GMAW (Gas Metal Arc Welding) and SAW (Submerged Arc Welding) per EN 1011-2. Preheating (100-150°C) is recommended for thicknesses >20 mm to prevent hydrogen-induced cracking; no preheat is needed for thinner plates.
  • Consumables: ER70S-6 (GMAW), EM12K flux with EH14 wire (SAW).
  • Advantages: Lower carbon (≤0.18%), sulfur (≤0.015%), and phosphorus (≤0.025%), combined with grain-refining elements (Al, Nb), reduce weld imperfections and enhance toughness in welded joints, especially in cold conditions.
  • Post-Weld Heat Treatment (PWHT): Optional at 550-650°C for critical welds, rarely required due to low CEV.
• S355J2:
  • CEV: ≤0.45% (≤40 mm), slightly higher due to less stringent impurity controls.
  • Welding: Compatible with GMAW and SAW, but requires more preheating (125-175°C for >25 mm) due to higher carbon (≤0.20%) and impurities (P, S ≤0.025%).
  • Consumables: Same as S355NL (ER70S-6, EM12K flux).
  • Challenges: Higher carbon and impurities increase the risk of weld imperfections like cracking, requiring more careful welding procedures.
  • PWHT: Rarely needed, but may be applied for thick sections to reduce stresses.

Key Weldability Difference: S355NL offers superior weldability due to its lower CEV (≤0.43% vs ≤0.45%) and fine-grain structure, reducing preheating needs and weld imperfections compared to S355J2. This makes S355NL vs S355J2 welding more cost-effective and reliable for cold-climate applications.

Chemical Composition Comparison

The S355NL vs S355J2 weldability is influenced by their compositions:

The difference between S355J2 and S355NL includes S355NL’s lower carbon, sulfur, and nitrogen, plus grain-refining elements (Al, Nb, V), which enhance weldability and toughness.

Mechanical Properties Comparison

The S355NL vs S355J2 mechanical properties also influence their weldability and application:

Strength: Both grades have identical yield (355 MPa) and tensile strengths (470-630 MPa) for similar thicknesses, ensuring comparable load-bearing capacity.
Toughness: The primary difference between S355J2 and S355NL is toughness. S355NL’s -50°C testing (≥27 J) makes it ideal for cold climates, while S355J2’s -20°C testing suits milder conditions.
Thickness Range: S355NL supports up to 250 mm with robust low-temperature properties; S355J2 up to 250 mm but with less cold performance.

Applications

• S355NL:
  • Offshore platforms in cold marine environments (e.g., North Sea).
  • Wind towers in sub-zero climates (e.g., northern Europe).
  • Bridges and cranes in arctic regions.
    Its superior weldability and -50°C toughness ensure reliable welds in harsh conditions. See EN 10025-3 S355NL normalized structural steel plate.
• S355J2:
  • Building frameworks in temperate climates.
  • Bridges and machinery in moderate conditions.
  • General welded assemblies where cost is a priority.

The S355NL vs S355J2 application difference highlights S355NL’s advantage in cold environments and S355J2’s affordability for standard conditions.

Equivalent Grades

• S355NL: ASTM A633 Grade E, Q345E (China), TStE 355 (DIN).
• S355J2: ASTM A572 Grade 50, Q345B (China), SM490A (JIS).

Explore EN 10025-3 S420NL normalized structural steel plate.

Why Choose Gangsteel?

Gangsteel supplies both grades:

• 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, 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 between S355J2 and S355NL in weldability?
S355NL has a lower CEV (≤0.43% vs ≤0.45%), lower carbon (0.18% vs 0.20%), and sulfur (0.015% vs 0.025%), requiring less preheating (100-150°C vs 125-175°C for >20 mm), reducing weld imperfections and fabrication costs compared to S355J2.

Which is better for welding in S355NL vs S355J2?
S355NL is better for welding due to its lower CEV and fine-grain structure, minimizing cracking risks and preheating needs, especially for thick plates in cold climates like offshore platforms.

How does toughness affect S355NL vs S355J2 welding?
S355NL’s -50°C toughness (≥27 J) ensures weld integrity in cold climates, reducing brittle fracture risks in welds; S355J2’s -20°C toughness is less suited for sub-zero conditions.

Are S355NL vs S355J2 strengths similar?
Yes, both have identical 355 MPa yield and 470-630 MPa tensile strength for similar thicknesses, but S355NL’s normalization enhances weld quality and cold performance.

What are applications of S355NL vs S355J2?
S355NL is used for cold-climate offshore platforms, wind towers, and bridges with reliable welds; S355J2 suits temperate building frameworks and general fabrication where cost is key.

Can S355J2 replace S355NL in welding?
S355J2 can replace S355NL in temperate climates with careful welding procedures, but its higher CEV and -20°C toughness limit its use in cold environments requiring robust welds.