ASTM A350 LF2 is a commonly used low-temperature carbon steel forging material standard, primarily employed for the manufacture of flanges, forged fittings, valves, and other pressure-containing components. Its core advantage is excellent low-temperature impact toughness, combined with good strength and weldability, making it widely applied in low-temperature pressure pipelines and fittings.
ASTM A350 LF2 – Low Temperature Carbon Steel Forging Material
- Full Name: ASTM A350 Grade LF2 (Low Temperature Carbon Steel Forgings)
- Category: Low-temperature carbon steel, suitable for service down to -46°C
- Typical Applications: Flanges, fittings, valves, pressure vessel components, widely used in petroleum, natural gas, chemical, and low-temperature storage/transport systems
- Delivery Condition: Usually supplied normalized or normalized + tempered
Chemical Composition (Typical Range, %)
- C ≤ 0.30
- Mn: 0.60 – 1.35
- Si: 0.15 – 0.30
- P ≤ 0.035
- S ≤ 0.040
Mechanical Properties (Typical Values at Room Temperature)
- Ultimate Tensile Strength (UTS): 485 – 655 MPa
- Yield Strength (YS): ≥ 250 MPa
- Elongation: ≥ 22%
- Impact Toughness (Charpy V-notch): ≥ 20 J at -46°C
Why ASTM A350 LF2 Exhibits Low-Temperature Performance
LF2 maintains excellent low-temperature impact toughness and ductility due to low carbon, low impurities, moderate Mn/Si content, heat treatment, and uniform microstructure.
Chemical Composition Design
- Low carbon content (C ≤ 0.30%) → reduces carbide formation, improves low-temperature toughness
- Moderate manganese (Mn 0.60–1.35%) → enhances hardenability and impact toughness
- Silicon (Si 0.15–0.30%) → increases strength without significantly reducing low-temperature toughness
- Very low phosphorus and sulfur (P ≤ 0.035%, S ≤ 0.040%) → minimizes brittleness and prevents low-temperature cracking
Heat Treatment
- Normalized or normalized + tempered
- Normalizing → refines grains, improves toughness
- Tempering → reduces internal stress, stabilizes structure, increases impact absorption
Microstructure Control
- Mainly ferrite + pearlite / minor bainite
- Fine grains and minimal inclusions allow energy absorption at low temperature, preventing brittle fracture
Equivalent Grades Across Different Countries/Standards
| Standard / Country | Equivalent or Similar Grade | Remarks |
| USA (ASME/ASTM) | ASTM A350 LF2 | Original standard, low-temperature carbon steel forging |
| Germany / DIN / EN | 1.0566 (P355NL1 / P355NL2), 1.0460 (C22.8) | Commonly used for pressure vessels and flanges, low-temperature toughness ensured |
| Europe (EN 10222-4) | P245GH, P280GH, P355NH, P355NL1, P355NL2 | Low-temperature pressure vessel steels, equivalent to LF2 |
| UK (BS 1503) | 1503-223-490 | Pressure vessel steel, low-temperature performance similar to LF2 |
| France (AFNOR) | A48CP, A52CP | Pressure vessels and low-temperature applications |
| Japan (JIS) | JIS G3204 SFVC2 / SFVC2A | Forged carbon steel, low-temperature impact requirements similar to LF2 |
| Russia (GOST) | 20ГЛ / 09Г2С (20GL / 09G2S) | Low-temperature carbon steel for oil, gas, and energy applications |
| China (GB / JB) | 16MnR / 20MnR, ZG16Mn / ZG20Mn | Pressure vessel steel or cast steel, commonly used as LF2 substitutes |
| International (ISO 9329 / ISO 3183) | L245NB / L290NB | Low-temperature pressure pipeline steels, can replace LF2 in piping systems |
Typical Applications of ASTM A350 LF2
Geographic / Regional Use
Since LF2 is an ASME/ASTM standard material, it is mainly used in countries and regions following the American standard system:
- North America (USA, Canada): Oil & gas pipelines, LNG storage tanks, refineries, chemical plants
- Middle East (Saudi Arabia, UAE, Qatar, Kuwait): Petrochemical plants, LNG facilities (e.g., QatarEnergy, Aramco projects)
- Europe (UK, Norway, Netherlands): North Sea oil & gas, low-temperature chemical plants
- Asia (China, Korea, Singapore, India): LNG receiving terminals, shipyards, petrochemical projects (e.g., Sinopec, CNOOC, Samsung, Hyundai Heavy Industries)
- South America / Africa (Brazil, Nigeria): Offshore platforms, LNG projects
Typical Service Environments
LF2 is designed for low-temperature service (-46°C) and is mainly applied in:
- Low-Temperature Storage & Transport Systems
- LNG storage tanks, receiving stations, transport vessels
- LPG facilities
- Oil & Gas Industry
- Long-distance natural gas pipelines, compressor stations
- Offshore oil platforms (cold seawater, high impact toughness required)
- Petrochemical & Chemical Industry
- Low-temperature separation units (ethylene, propylene, methanol processes)
- Refrigeration system pressure pipelines and flanges
- Power & Energy
- Natural gas power plant low-temperature piping
- Nuclear power low-temperature auxiliary systems (some substitute materials)
In summary, ASTM A350 LF2 is a reliable low-temperature carbon steel forging material widely used for flanges, fittings, valves, and pressure components, offering excellent toughness, strength, and weldability for demanding low-temperature applications.
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