EN 1.0566 P355NL1 EN 10028-3 LTCS −50°C Charpy ≈ ASTM WPL3

P355NL1 (1.0566) High-Yield LTCS Pipe Fittings

High-yield low-temperature normalised carbon steel buttweld fittings to EN 10028-3. Charpy impact tested at −50°C with 40 J average requirement. European equivalent to ASTM A420 WPL3 — used for LNG satellite station piping, cold gas headers, and cryogenic process plant where high wall thickness would otherwise be needed with the lower-yield P275NL1.

Chemical Composition — P355NL1 (EN 10028-3)

Element	Range / Max %
Carbon (C)	≤0.18
Silicon (Si)	≤0.60
Manganese (Mn)	1.00–1.70
Phosphorus (P)	≤0.025
Sulphur (S)	≤0.010
Aluminium (Al)	≥0.020
Nb (optional)	≤0.05
V (optional)	≤0.12

Higher Mn content (up to 1.70%) compared to P275NL1 provides the increased yield strength. Al deoxidation for fine-grained microstructure essential for sub-zero Charpy performance.

Mechanical Properties — P355NL1

Property	Value
Yield Strength (Rp0.2, min)	355 MPa
Tensile Strength (Rm)	490–630 MPa
Elongation (A, min)	22%
Charpy Test Temperature	−50°C
Charpy KV (avg, min)	40 J (longitudinal)
Charpy KV (individual min)	28 J
Heat Treatment	Normalised (N)

P355NL1 vs ASTM A420 WPL3

Property	ASTM WPL3	EN P355NL1
Standard	ASTM A420	EN 10028-3
Ni content	3.18–3.82%	None (Mn-based)
Charpy temp	−101°C (−150°F)	−50°C
Min YS	275 MPa	355 MPa
Charpy avg	27 J	40 J

Important: P355NL1 is NOT a direct substitute for ASTM WPL3 at temperatures below −50°C. For services requiring −101°C (e.g. LNG at full-scale terminals), specify either ASTM A420 WPL3 (3.5Ni) or EN 10028-4 nickel alloy steel grades (13MnNi6-3 or X10Ni9 for LNG).

When to Choose P355NL1 over P275NL1

›Wall thickness reduction: 355 MPa yield vs 275 MPa reduces required wall by ~22% at the same operating pressure — significant for large-bore cold headers
›LNG satellite and regasification: Required where design pressure is high and −50°C MDMT is sufficient (not going below −50°C)
›Offshore cold service: Arctic platforms where MDMT is −46°C to −50°C and higher yield strength is needed for weight reduction
›Cold gas high-pressure headers: Compressor station headers and pig launchers/receivers in cold climate installations

Related grades: P275NL1 (1.0488) — lower yield LTCS · ASTM WPL3 (−101°C, 3.5Ni) · WPL6

P355NL1 (1.0566) High-Yield LTCS Pipe Fittings

Chemical Composition — P355NL1 (EN 10028-3)

Mechanical Properties — P355NL1

P355NL1 vs ASTM A420 WPL3

When to Choose P355NL1 over P275NL1

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