Comparison of P355GH, P355N, and P355NH Pressure vessel Steel Grades

2025-06-04 | More News

1. Grade Designation

P355GH:

“P” = Pressure vessel steel;”355″ = Minimum yield strength of 355 Mpa;”G” = Special requirements for other properties;”H” = Steel for elevated temperature service.

Overall: Pressure vessel steel with specified elevated temperature properties.

P355N:

“P” = European standard pressure vessel steel;”355″ = Minimum yield strength of 355 Mpa;”N” = Normalized delivery condition.

Overall: Normalized steel for ambient temperature service.

P355NH:

“P” and “355” = Same as above;”N” = Normalized or normalized rolled;”H” = Steel for elevated temperature service.

Overall: Normalized steel for elevated temperature applications.

2. Standards Compliance

P355GH: Complies with EN 10028-2(Steels for pressure purposes – Part 2: Non-alloy and alloy steels with specified elevated temperature properties).
P355Nand P355NH: Comply with EN 10028-3 (Steels for pressure purposes – Part 3: Normalized/normalized rolled weldable fine grain steels).

3. Chemical Composition (wt%)

Element	P355GH	P355N	P355NH
C	0.10-0.22	≤0.18	0.18-0.22
Si	≤0.60	≤0.50	≤0.50
Mn	1.10-1.70	1.10-1.70	1.10-1.70
P	≤0.025	≤0.025	≤0.025
S	≤0.010	≤0.010	≤0.015
N	≤0.012	≤0.012	–
Cr	≤0.30	≤0.30	0.30-1.70
Ni	≤0.30	≤0.50	≤0.30
Cu	≤0.30	≤0.30	≤0.30
Mo	≤0.08	≤0.08	–
Nb	≤0.040	≤0.05	0.05-0.10
Ti	≤0.03	≤0.03	–
V	≤0.02	≤0.10	0.05-0.10
Al	Total ≥0.020	For N-binding	–

4. Mechanical Properties

Property	P355GH	P355N	P355NH
Yield Strength (MPa)	355 (8-16mm) 345 (16-40mm) 315 (60-100mm)	355 MPa (all thicknesses)	355-510 MPa
Tensile Strength (MPa)	510-650 (8-40mm) 490-630 (60-100mm)	490-630	490-630
Elongation (%)	≥20	≥22	~22
Impact Energy (J)	≥27 (-20°C)	Good toughness at low temperatures	–

5. Applications

P355GH:High-temperature pressure vessels (e.g., boilers, storage tanks, furnace components).Suitable for moderate to high-temperature environments.
P355N:Ambient-temperature pressure vessels (e.g., reactors, heat exchangers, separators) in industries such as oil, gas, and power generation.
P355NH:High-temperature applications (e.g., reactors, heat exchangers, spherical tanks) in industries like oil, chemical, and power plants.

6. Processing Characteristics

P355GH:

Weldability: Excellent (low carbon equivalent, minimal risk of cracking).
Formability: Suitable for cold forming (e.g., bending, rolling) with controlled deformation rates.
Cutting: Can be cut using flame or plasma methods.

P355N:

Weldability: Good (normalized condition improves homogeneity).
Formability: High plasticity, ideal for complex shapes.

P355NH:

Weldability: Good (suitable for manual arc welding, gas shielded welding).
High-Temperature Resistance: Maintains strength and toughness at elevated temperatures.
P355GH, P355N, and P355NH

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