S355NL vs P355NL Pressure Vessel Steel

S355NL vs P355NL: Pressure Vessel Steel

S355NL vs P355NL is a vital comparison for selecting steels in pressure vessel applications, where low-temperature toughness and weldability are paramount. S355NL, under EN 10025-3, is a normalized fine-grain structural steel, while P355NL, under EN 10028-3, is specifically designed for pressure vessels with similar low-temperature properties. This article compares their chemical composition, mechanical properties, weldability, and applications in pressure vessels, addressing core keywords s355nl vs p355nl and p355nl vs s355nl. For more details, visit our EN 10025-3 S355NL normalized structural steel plate.

Overview of S355NL and P355NL

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.

It's versatile for structural use but can be applied in pressure vessels requiring low-temperature performance.

P355NL (EN 10028-3)

P355NL is a pressure vessel steel under EN 10028-3, normalized or normalized rolled, with:

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

It's optimized for welded pressure vessels, such as boilers and storage tanks, with stricter quality controls for safety.

Chemical Composition Comparison

The S355NL vs P355NL chemical compositions are similar, but P355NL has tighter limits for pressure vessel safety.

Carbon Equivalent (CEV):

• S355NL: ≤0.43% (≤63 mm).
• P355NL: ≤0.41% (≤63 mm).

The P355NL vs S355NL composition shows P355NL’s lower P (0.020% vs 0.025%), S (0.010% vs 0.015%), and N (0.012% vs 0.015%) enhance weldability and toughness for pressure vessels.

Mechanical Properties Comparison

Both grades share similar strength, but P355NL has stricter testing for pressure vessel use.

Strength: Identical yield (355 MPa) and comparable tensile strength.
Toughness: Both ≥27 J at -50°C, but P355NL requires transverse testing and stricter quality controls for vessels.
Thickness Range: S355NL up to 250 mm; P355NL up to 250 mm, with normalized condition mandatory.

Welding and Heat Treatment

• S355NL: CEV ≤0.43% supports GMAW or SAW (EN 1011-2). Preheating (100-150°C) for >20 mm; PWHT optional (550-650°C). Consumables: ER70S-6 (GMAW), EM12K flux with EH14 wire (SAW).
• P355NL: CEV ≤0.41% enhances weldability; stricter PWHT requirements for pressure vessels (e.g., 620°C for stress relief). Preheating similar, but ultrasonic testing mandatory.

The S355NL vs P355NL welding favors P355NL for vessel-specific certifications.

Applications in Pressure Vessels

• S355NL:
  • Structural components in pressure vessels, bridges, wind towers in cold climates.
  • Versatile for non-vessel pressure applications with -50°C toughness.
• P355NL:
  • Welded pressure vessels, boilers, storage tanks for gases/liquids in cold conditions.
  • Compliant with PED (Pressure Equipment Directive) for safety-critical use.

The P355NL vs S355NL application difference: P355NL for certified vessels; S355NL for structural pressure components.

Which is Better for Pressure Vessels?

• Choose S355NLfor:
  • Structural pressure vessel components in cold climates.
  • Applications needing versatility beyond vessels (e.g., bridges).
  • Cost-effective for non-certified use.
• Choose P355NLfor:
  • Full pressure vessel fabrication requiring PED compliance.
  • Stricter weld quality and transverse toughness testing.
  • Safety-critical storage tanks in cold environments.

The S355NL vs P355NL choice depends on certification needs; P355NL is better for dedicated vessels.

Equivalent Grades

• S355NL: ASTM A633 Grade E, Q345E.
• P355NL: ASTM A516 Grade 70, 16MnDR (China).

See EN 10025-3 S355N normalized structural steel plate.

Why Choose Gangsteel?

Gangsteel supplies both:

• Inventory: Extensive stock in China.
• Sizes: Thickness 6–250 mm, widths 2000/2500/3000 mm.
• Delivery: 7-30 days globally.
• Certifications: EN 10204 3.1/3.2, UT testing, ABS/LR/BV/DNV.
• Processing: Cutting, welding, bending.

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

FAQ

What is the main difference in S355NL vs P355NL?
S355NL is a structural steel under EN 10025-3 for general use with -50°C toughness; P355NL is a pressure vessel steel under EN 10028-3 with stricter weld quality, lower S/P/N, and PED compliance for safety-critical vessels.

How do P355NL vs S355NL welding requirements differ?
P355NL requires stricter PWHT (620°C stress relief) and ultrasonic testing for vessels; S355NL has optional PWHT (550-650°C), with both using GMAW/SAW, but P355NL's lower CEV (≤0.41%) enhances weldability.

Which is better for pressure vessels in S355NL vs P355NL?
P355NL is better for certified pressure vessels (boilers, tanks) due to EN 10028-3 specs and transverse toughness testing; S355NL suits structural components in vessels with similar -50°C performance but less certification.

Are S355NL vs P355NL strengths the same?
Yes, both have 355 MPa yield and 450-630 MPa tensile strength, but P355NL has tighter elongation (22%) and impact testing for vessel safety.

What are applications of P355NL vs S355NL?
P355NL: Welded pressure vessels, boilers in cold climates; S355NL: Structural pressure components, bridges, offshore platforms with -50°C toughness.

Can S355NL be used in pressure vessels?
Yes, S355NL can be used for non-certified vessel components in cold environments, but P355NL is preferred for full compliance and safety-critical use. See EN 10025-3 S355N normalized structural steel plate.