What Is ASTM A350 LF2 Flange?
ASTM A350 LF2 flange is a forged carbon steel flange specifically designed for low-temperature piping systems. Manufactured according to ASTM A350 / ASME SA350 standards, these flanges provide excellent toughness and impact resistance in sub-zero environments.
ASTM A350 flanges are widely used in industries where pipelines operate at low or cryogenic temperatures, including LNG plants, oil and gas pipelines, petrochemical facilities, and offshore platforms.
The most commonly used grade is ASTM A350 LF2 Class 1, which is typically used together with:
- ASTM A333 Grade 6 pipes
- ASTM A420 WPL6 pipe fittings
ASTM A350 LF2 flanges offer a minimum yield strength of 240 MPa and tensile strength between 480 MPa and 655 MPa, with Charpy V-notch impact testing conducted at −46°C (-50°F) to ensure toughness in low temperature conditions.
ASTM A350 LF2 Flange Specifications
| Item | Specification |
|---|---|
| Standard | ASTM A350 / ASME SA350 |
| Material Grade | LF2 |
| Product Type | Forged Steel Flange |
| Size Range | 1/2″ – 24″ (ASME B16.5) |
| Large Diameter | Up to 60″ (ASME B16.47) |
| Pressure Class | Class 150 – Class 2500 |
| Manufacturing Standard | ASME B16.5 / ASME B16.47 |
| Service | Low Temperature / Cryogenic |
Types of ASTM A350 LF2 Flanges
ASTM A350 LF2 flanges are available in several common flange types used in industrial piping systems.
Weld Neck Flange
The ASTM A350 LF2 weld neck flange features a long tapered hub that reduces stress concentration and provides excellent reinforcement for high-pressure pipelines. These flanges are widely used in critical and high-pressure systems.
Blind Flange
ASTM A350 LF2 blind flanges are solid flanges used to seal the ends of pipelines or pressure vessels. They are commonly installed for pipeline isolation, inspection, and pressure testing.
Slip On Flange
Slip on flanges slide over the pipe and are welded on both sides. This design makes installation easier and reduces fabrication costs.
Socket Weld Flanges
Threaded Flanges
Chemical Composition of ASTM A350 LF2
ASTM A350 specifies strict chemical composition requirements to ensure proper toughness and weldability.
Typical elements include:
- Carbon (C)
- Manganese (Mn)
- Silicon (Si)
- Phosphorus (P)
- Sulfur (S)
Leaded steels are not permitted under ASTM A350 standards.
Chemical heat analysis and product analysis must comply with ASTM A961/A961M requirements.
Mechanical Properties
ASTM A350 LF2 forged flanges must meet the following minimum mechanical properties:
| Property | Requirement |
|---|---|
| Yield Strength | ≥ 240 MPa |
| Tensile Strength | 480 – 655 MPa |
| Elongation | ≥ 22% |
| Impact Test | Charpy V-Notch |
These mechanical properties ensure reliable performance in low-temperature service environments.
Impact Test Requirements
ASTM A350 flanges require Charpy V-notch impact testing to verify notch toughness at low temperatures.
| Grade | Impact Test Temperature |
|---|---|
| LF1 | −29°C |
| LF2 Class 1 | −46°C |
| LF2 Class 2 | −18°C |
| LF3 | −101°C |
| LF5 | −59°C |
| LF6 | −51°C |
| LF9 | −73°C |
Minimum impact energy requirements are defined to guarantee toughness under low-temperature conditions.
Manufacturing Process of ASTM A350 Flanges
Steel Melting
Steel used for ASTM A350 forgings may be produced using:
- Electric furnace
- Basic oxygen furnace
- Vacuum induction melting (VIM)
Secondary refining processes may include:
- Electroslag remelting (ESR)
- Vacuum arc remelting (VAR)
Forging Process
Forgings may be produced from:
- Ingots
- Billets
- Blooms
- Bars
Sufficient discard is required to remove internal defects and segregation.
Heat Treatment
ASTM A350 LF2 forgings are typically heat treated using:
- Normalized
- Normalized and tempered
- Quenched and tempered
Heat treatment ensures proper microstructure, strength, and toughness for low-temperature service.
Inspection and Testing
ASTM A350 forged flanges undergo strict quality inspection including:
- Chemical composition analysis
- Mechanical testing
- Charpy V-notch impact testing
- Dimensional inspection
- Visual inspection
Hydrostatic testing may be performed when required by Supplementary Requirement S57 of ASTM A961/A961M.
ASTM A350 LF2 vs ASTM A105 Flanges
| Property | ASTM A350 LF2 | ASTM A105 |
|---|---|---|
| Service Temperature | Low Temperature | Ambient Temperature |
| Impact Test | Required | Not Required |
| Typical Application | LNG / Cryogenic Systems | General Piping |
ASTM A350 LF2 flanges are specifically designed for low-temperature applications, while ASTM A105 flanges are typically used in standard temperature piping systems.
Applications of ASTM A350 LF2 Flanges
ASTM A350 LF2 low temperature flanges are widely used in industries including:
LNG and Cryogenic Systems
- LNG pipelines
- Cryogenic storage facilities
Oil and Gas Industry
- Offshore pipelines
- Gas processing plants
Petrochemical Industry
- Low-temperature process piping
Power Generation
- Cryogenic fluid pipelines
- Industrial pressure vessels
Related Products
- ASTM A333 Grade 6 Pipe
- ASTM A420 WPL6 Pipe Fittings
- ASTM A105 Carbon Steel Flange
- ASTM A182 Stainless Steel Flange
These materials are commonly used together in low-temperature piping systems.
FAQ – ASTM A350 LF2 Flanges
What is ASTM A350 LF2 flange used for?
ASTM A350 LF2 flanges are used in low temperature and cryogenic piping systems, including LNG plants, offshore pipelines, and gas processing facilities.
What temperature is ASTM A350 LF2 rated for?
ASTM A350 LF2 Class 1 flanges are typically impact tested at −46°C (-50°F) to ensure toughness in low temperature environments.
What is the difference between ASTM A350 LF2 and ASTM A105?
ASTM A350 LF2 flanges are designed for low temperature service, while ASTM A105 flanges are used for general temperature piping systems.
ASTM A350 LF2 Flange Supplier
We supply high-quality ASTM A350 LF2 forged flanges manufactured according to ASTM and ASME standards.
All flanges can be supplied with EN 10204 3.1 Mill Test Certificates.
