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ASTM A350 / ASME SA-350 · UNS K03011

ASTM A350 LF2
carbon steel forged flanges

Low‑temperature service · Charpy V‑notch tested · Class 1 (−46 °C) & Class 2 (−18 °C) · N/NT/QT delivery

CL1 −46 °C
CL2 −18 °C
HBW 197 max

ASME B16.5 / B16.47

NPS 1/2 – 60 · Class 150–2500

✓ Charpy V-notch

✓ MTC EN 10204 3.1

✓ NACE option

UNS

K03011

A350 LF2

Tensile

485–655

MPa

Yield min.

250

MPa

Charpy CL1

20 J

avg. −46 °C

Charpy CL2

27 J

avg. −18 °C

Density

7.86

g/cm³

Scope & distinctive features

ASTM A350 LF2 (UNS K03011) is a forged carbon/low‑alloy steel intended for flanges, fittings and valve bodies in low‑temperature service. The specification mandates Charpy V‑notch testing. Two classes differ only in impact test temperature: Class 1 at −46 °C (−50 °F) and Class 2 at −18 °C (0 °F). Both share identical composition and tensile properties. LF2 is supplied in normalized (N), normalized and tempered (NT) or quenched and tempered (QT) condition. It is not suitable for cryogenic LNG (−162 °C).

Service range: −46 °C to +425 °C. Typical pairing: ASTM A333 Gr.6 pipe + ASTM A420 WPL6 fittings.

Chemical composition (heat analysis, %)

Element	Range / Max	Element	Range / Max
C	≤ 0.30	Ni	≤ 0.40
Si	0.15 – 0.30	Cr	≤ 0.30
Mn	0.60 – 1.35	Mo	≤ 0.12
P	≤ 0.035	Cu	≤ 0.40
S	≤ 0.040	Nb	≤ 0.02 (0.05 by agreement)
V	≤ 0.08	Σ(Cu+Ni+Cr+Mo+V)	≤ 1.00
CE (IIW)	C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 ≤ 0.47 (≤0.48 for t > 2″)
(Cr+Mo)	≤ 0.32

*By agreement Nb may be increased to 0.05% heat / 0.06% product. Leaded steels not permitted. Si ≤ 0.12% for vacuum carbon deoxidation.

Mechanical & impact properties

Property	CL1	CL2
Tensile strength, MPa	485 – 655	485 – 655
Yield strength Rp0.2, min MPa	250	250
Elongation A%, min (50 mm)	22	22
Reduction of area Z%, min	30	30
Charpy test temp.	−46 °C (−50 °F)	−18 °C (0 °F)
Avg. impact energy (3 spec.), min	20 J (15 ft·lbf)	27 J (20 ft·lbf)
Single specimen min.	16 J	20 J
Hardness, max HBW	197 (after heat treatment)

ELs min 30% (strip specimen, 2″ gauge). ELc = 48t + 15 for thin strip. Yield by 0.2% offset. Hardness after heat treatment.

Sub‑size Charpy equivalent energy (J)

Specimen	10×10	10×7.5	10×6.6	10×5	10×3.3	10×2.5
Min. avg. (CL1)	20	16	14	11	7	6
Min. single (CL1)	16	13	12	10	7	5
Min. avg. (CL2)	27	22	19	15	10	8
Min. single (CL2)	20	16	14	11	8	6

Linear interpolation permitted. When sub‑size, test temperature may be lowered (down to 28 °C below class temperature for 1/4 size).

Equivalent / similar grades

Standard	Equivalent grade	Remarks
USA (ASTM/ASME)	ASTM A350 LF2	Original specification
Germany (DIN/EN)	1.0566 (P355NL1), 1.0460 (C22.8)	Low‑temperature pressure vessel
Europe (EN 10222-4)	P245GH, P280GH, P355NH	Pressure vessel steels
UK (BS 1503)	1503-223-490	Similar low‑temp performance
Japan (JIS)	SFVC2 / SFVC2A	Forged carbon steel
China (GB)	16MnR, ZG16Mn	Pressure vessel substitutes
Russia (GOST)	20ГЛ / 09Г2С	Low‑temperature carbon steel

Heat treatment & delivery conditions

N
Normalized
Austenitize, air cool.

NT
Norm. + tempered
Temper ≥ 590 °C, air cool.

QT
Quenched + tempered
Quench oil/polymer, temper ≥590 °C.

Tempering: ≥ 590 °C (1100 °F), holding ≥ 30 min per 25 mm and ≥ 30 min minimum, air cooling. Hardness max 197 HBW.

Typical physical properties

Density	7.85 – 7.86 g/cm³
Elastic modulus	210 GPa (≈ 30×10⁶ psi)
Coeff. thermal expansion (20–100 °C)	10.4 – 11.5 μm/m·°C
Thermal conductivity	≈ 34 – 50 W/(m·K)
Specific heat	0.46 – 0.50 kJ/(kg·K)
Electrical resistivity	≈ 0.16 μΩ·m

Flange range & dimensional standards

Material	ASTM A350/A350M LF2, Class 1 or 2 as specified
ASME B16.5 size range	NPS 1/2 – 24 (Class 2500: NPS 1/2 – 12)
ASME B16.47 size range	NPS 26 – 60 (Series A / B)
Facing	RF, FF, RTJ
Pressure class	150 – 2500 (per NPS and standard)
Bore	Matched to pipe schedule on request

Typical applications & service environments

Oil & gas / LNG
Low‑temperature storage tanks, receiving terminals, transport vessels, long‑distance pipelines.

Petrochemical
Ethylene/propylene separation, refrigeration piping, flanges and valve bodies.

Power generation
Natural gas power plant low‑temperature piping, auxiliary systems.

Cold climate infrastructure
Arctic offshore platforms, compressor stations, process skids.

Comparison with adjacent materials

Material	Product form	Key notes
ASTM A350 LF2	Forgings (flanges, fittings, valves)	Charpy −46 °C / −18 °C; N/NT/QT
ASTM A105	Forgings general service	No low‑temperature impact requirement
ASTM A352 LCB/LCC	Castings	Cast equivalent for low‑temp valves

Hardness & quality control

Hardness is mandatory: 197 HBW max after heat treatment, tested on at least two forgings per lot. For sour service, NACE MR0175/ISO 15156 compliance must be documented on MTC. Hardness depends on tempering, thickness and quench severity.

✓ MTC EN 10204 3.1/3.2 · ✓ Charpy records · ✓ Heat treatment charts

Typical mechanical values (reference)

Condition	Ø mm	Rm MPa	Rp0.2 MPa	A%	Z%	KV −46°C J	KV −18°C J
Q+T 880°C water / 640°C air	95	600	480	24.6	58	68-66-64	112-114-110
Normalizing 900°C air	210	580	400	32.6	64.4	22-24-18	70-74-70
Normalizing 900°C air	50	548	320	28.6	64.0	30-42-36	78-80-84
As‑rolled (reference)	95	526	302	28.6	62.0	6-6-4	16-10-8

*Lucefin Group experience, for reference only. Actual values depend on heat treatment and section size.

Carbon equivalent (CE) & weldability

CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15. For LF2, CE ≤ 0.47 for thickness ≤ 2″ and ≤ 0.48 for > 2″. This controls preheat and PWHT. Low carbon and moderate Mn ensure toughness after normalizing or quenching.

Preheating generally recommended for thickness > 25 mm. PWHT may be applied if specified, but must be evaluated for impact toughness.

Manufacturing, inspection & testing

✓ Forging from ingot/bloom, controlled reduction
✓ Heat treatment per ASTM A350
✓ Tensile test per lot
✓ Charpy V-notch at class temperature
✓ Hardness survey on 2 forgings per lot
✓ Dimensional inspection per B16.5/16.47

NDE available: UT, MT, PT upon request. PMI and hardness mapping.

Pipeun flange product line

Carbon steel flanges
A105, A350 LF2, A694

Stainless steel flanges
A182, A479

Monel / Hastelloy
B564, C276, C22

Inconel / Incoloy
600, 625, 800H, 825

Send inquiry for LF2 forged flanges →

Common heat‑treatment defects & corrective actions

Defect	Typical cause	Corrective action
Quench cracks / distortion	Non‑uniform austenitizing, severe medium	Improve uniformity, less aggressive quench, prefer NT
Insufficient Charpy toughness	Tempering below 590 °C or insufficient time	Repeat tempering ≥ 590 °C, re‑test; normalize if needed
Over‑tempering (low Rm)	Furnace overshoot, excessive time	Bring within range, verify hardness and Charpy
Non‑uniform hardness	Thermal gradients in thick sections	Double tempering, prefer QT, multi‑position hardness

CE limits by maximum thickness

Maximum thickness	CE max (heat analysis)	Notes
≤ 2″ (50 mm)	0.47	Standard
> 2″ (50 mm)	0.48	Supplementary requirement

Geographic / regional use

Region	Typical applications
North America	Oil & gas pipelines, LNG storage, refineries, chemical plants
Middle East	Petrochemical plants, LNG facilities (Aramco, QatarEnergy)
Europe	North Sea oil & gas, low‑temperature chemical plants
Asia	LNG receiving terminals, shipyards, petrochemical projects
South America / Africa	Offshore platforms, LNG projects

Certification & documentation

Material test certificate	EN 10204 3.1 / 3.2 as specified
Charpy test records	Included in MTC
Heat treatment charts	Available on request
NACE MR0175 compliance	Case‑by‑case, documented on MTC
Traceability	Heat number, batch, forging ID

ASTM A350 LF2 forged flanges — UNS K03011 · ASME B16.5 / B16.47 · Charpy tested · N/NT/QT · MTC EN 10204 3.1

All data is indicative and subject to order specification. Rev. 2025-03.