ASTM A350 LF2 Weld Neck Flanges (WNRF) | NACE MR0175 Low Temperature Flanges ASME B16.5
ASTM A350 LF2 weld neck flanges (WNRF) are forged low-temperature carbon steel flanges designed for pressure piping systems operating in sub-zero and sour (H₂S) environments. Manufactured to ASME B16.5 and compliant with NACE MR0175 / ISO 15156, they provide excellent toughness, impact resistance, and reliable sealing performance in LNG, oil & gas, and petrochemical applications.
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ASTM A350 LF2 flange is usually used for a general low temperature enviorement,it can withstand continuous service down to -46°C [-50°F],and A350 LF2 Flanges (low-temperature carbon steel) is used in the pipeline to match ASTM A333 Grade 6 pipes and A420 WL6 Pipe fittings.
What is ASTM A350 LF2?
ASTM A350 LF2 is a low-temperature carbon steel forging material specifically developed for piping components requiring high notch toughness at sub-zero temperatures (down to -46°C / -50°F).
It is widely used for:
- Flanges
- Valves
- Pipe fittings
Ideal for cryogenic and low-temperature service environments
ASTM A350-A350M-18
Standard Specification for Carbon and Low-Alloy Steel Forgings, Requiring Notch Toughness Testing for Piping Components
Key Features of A350 LF2 WNRF Flanges
- Excellent impact toughness at low temperatures
- High resistance to brittle fracture
- Good weldability
- Suitable for sour service (H₂S environments)
- NACE MR0175 / ISO 15156 compliant
Product Range
We manufacture a full range of ASTM A350 LF2 flanges:
- Weld Neck Flange (WNRF)
- Blind Flange
- Slip-On Flange
Standards:
- ASME B16.5
- ASME B16.47 (Series A / B)
Chemical Composition – ASTM A350 LF2 (%)
| Element | Composition |
|---|---|
| C | ≤ 0.30 |
| Mn | 0.60 – 1.35 |
| Si | 0.15 – 0.30 |
| P | ≤ 0.035 |
| S | ≤ 0.040 |
| Cr | ≤ 0.30 |
| Mo | ≤ 0.12 |
| Ni | ≤ 0.40 |
Carbon Equivalent (CE)
👉 CE control ensures good weldability and structural integrity
Mechanical Properties
- Yield Strength: ≥ 250 MPa
- Tensile Strength: 485 – 655 MPa
- Elongation: ≥ 22%
Impact Test (Charpy V-Notch)
- Test temperature: -46°C (-50°F) for Class 1
- Ensures toughness under low-temperature conditions
| Grade | Avg Energy |
|---|---|
| LF2 Class 1 | ≥ 20 J |
| LF2 Class 2 | ≥ 27 J |
Manufacturing Process
- Hot forging: 900 – 1200°C
- Controlled soaking time
- Air cooling after forging
Heat Treatment Options:
- Normalized
- Normalized & Tempered
- Quenched & Tempered
👉 Ensures optimal strength and toughness balance
Applications
ASTM A350 LF2 flanges are widely used in:
- LNG plants
- Oil & gas pipelines
- Sour gas systems (H₂S service)
- Petrochemical plants
- Cryogenic piping systems
Commonly used with:
- ASTM A333 Gr.6 pipes
- ASTM A420 WPL6 fittings
Quick Summary of ASTM A350 LF2 Flanges
- Material: ASTM A350 LF2 (LTCS)
- Type: Weld Neck Flange (WNRF)
- Temp: down to -46°C
- Standard: ASME B16.5 / B16.47
- Feature: High toughness + impact resistance
- Application: LNG, oil & gas
ASTM A350 Grade LF2 Flange Heat Treatment condition.
ASTM A350 Grade LF2 is a general Carbon steel usually supplied in the Normalised, Normalised and Tempered or. Quench and Tempered condition
Normalising – Heat to 860 – 920°C for a time commensurate with ruling section, Air cool (If Required)
Hardening – Heat to 890 – 960oC for a time commensurate with ruling section and quench in Water.
Tempering – Re-heat to 590oC Minimum as required, dependent on final required properties. Hold for a time
commensurate with the ruling section and cool in still in air.
ASTM A350 LF2 Flange Hardness requirement
the hardness to be 197 HB maximum and this meets the requirements for carbon steel forgings in NACE MR0175/ISO 15156-2.
A350 LF2 Flange with Charpy V-Notch Impact Test,comply with NACE MR 0175 requirement
Charpy V-notch impact test is required for ASTM A350 LF2 Flange to determine the notch toughness of the work piece. The Charpy V-notch impact test shall be conducted in accordance with ASTM A370 or ASTM A1058. Standard test specimens shall be prepared first, the cross section of which shall be 10 mm x 10 mm. Three pieces of test specimens of each heat lot shall be prepared. Generally, theminimum applicable temperaturefor Class 1 of ASTM A350 LF2 is -46°C [-50°F], while it is 0°C [-18°F] for Class 2 of ASTM A350 LF2. The minimum applicable temperatures are also the standard impact test temperatures for standard-size specimens.
| Grade & Class | Eavmin. ft*lbf [J] |
Eeamin. ft*lbf [J] |
|---|---|---|
| LF2 Class 1 | 15 [20] | 12 [16] |
| LF2 Class 2 | 20 [27] | 15 [20] |
*Eav: minimum average impact energy required for each set of 3 specimens; *Eea: minimum impact energy for each specimen.
We also provide ASTM A105 & ASTM A350-LF2 Flanges DUAL CERTIFIED.
- A105 and A350-LF2 are standard specifications for forged carbon steel piping components. A105 for ambient and higher-temperature service; A350-LF2 for low-temperature service with Charpy V-Notch impact energy testing. Components include
- flanges, various fittings and valves.
ASTM A350 LF2 Flange product specificiations:
- Product Name: RF WN FLANGE SCH STD ASTM A350 LF2 /RTJ WN FLANGE ASTM A350 LF2
- Size:2in/4in/6inch/8in/10in/12in/16in/18in/20in/24in/28in/30in/32in
- Bore: STD/SCH80/SCH XS/SCH160
- Class: 150/300/600/900/1500 lbs
- Face: Raised face/Ring joint RTJ
- Material: Low temperature steel ASTM A350 LF2 CL1 & ASTM A350 LF2 CL1
- standard:ASME B16.5 ASME B16.47 A series /B series
FAQ: ASTM A350 LF2 Flanges
Q1: What is ASTM A350 LF2 used for?
Used for low-temperature piping systems requiring high impact toughness.
Q2: What temperature can LF2 used for?
Typically suitable for service down to -46°C (-50°F).
Q3: What is the difference between A350 LF2 and A105?
A350 LF2 is for low-temperature service, while A105 is used for ambient and higher temperatures.
Q4: Is LF2 suitable for sour service?
Yes, it can comply with NACE MR0175 / ISO 15156 requirements.
How to order our A350 LF2 Flanges?
Example#1,ASTM A350 LF2 WN RF Flange,NACE 300# SCH.STD DN300(12″)
Example#2, ASTM A350 LF2 CL 1 BLIND FLANGE, NACE,RF CL150, 12 INCH
FlgWN, A350LF2, CL2500, RTJ, 16IN 2.375W, B16, Flange – Weld Neck Carbon Steel Per ASTM A350 Grade LF2 ASME Class 2500 Ring Type Joint 2.375 Inch
6IN FlgBlnd, A350LF2, CL2500, RTJ, B16.5, Flange – Blind Carbon Steel Per ASTM A350 Grade LF2 ASME Class 2500 Ring Type Joint Per ASME B16.5 Material Shall Meet the Requirements of NACE MR0175 Marked per MSS SP 25
Want to know the difference between ASTM A350 LF2 and ASTM A105?
Pls click ASTM A350 LF2 vs ASTM A105
