Low Temperature Carbon Steel Flanges — Charpy V-Notch impact tested to −46°C (−50°F). Forged per ASTM A350, dimensioned to ASME B16.5 / B16.47. Ideal for LNG, cryogenic, arctic pipeline and cold-climate oil & gas service. 30+ years of export to 65+ countries.
ASTM A350 LF2 CL2 is a forged low temperature carbon steel (LTCS) grade engineered specifically for piping components operating in sub-zero environments. Unlike standard carbon steel (ASTM A105), which becomes brittle at low temperatures, A350 LF2 CL2 undergoes mandatory Charpy V-Notch (CVN) impact testing at −46°C (−50°F) to guarantee toughness and fracture resistance in cold service.
Tesco Steel & Engineering manufactures ASTM A350 LF2 CL2 flanges in all standard types — weld neck, blind, slip-on, socket weld, lap joint, threaded, spectacle blind, and long weld neck — conforming to ASME B16.5, ASME B16.47, MSS SP-44, and EN 1092-1. Available from ½″ NB to 60″ NB in pressure classes 150 to 2500.
Our LTCS flanges are backed by full material traceability, mill test certificates (EN 10204 3.1/3.2), third-party inspection, and compliance with PED, NACE MR0175, and major oil & gas client specifications including Shell DEP, Saudi Aramco SAES, and ExxonMobil GP.
ASTM A350 is the Standard Specification for Carbon and Low-Alloy Steel Forgings Requiring Notch Toughness Testing for Piping Components. The "LF" prefix stands for Low-temperature Forging. Grade LF2 covers carbon steel forgings qualified down to −46°C (−50°F), while LF1 is qualified to −29°C (−20°F) and LF3 (3.5% Ni steel) reaches −101°C (−150°F).
The Class designation (CL1 vs CL2) defines the yield strength level within the same grade. CL2 carries a higher minimum yield strength of 52 ksi (360 MPa), making it suitable for demanding pressure applications. Both classes share the same impact test temperature and tensile strength range.
| Property | LF1 | LF2 CL1 | LF2 CL2 ✦ | LF3 CL1 | LF3 CL2 |
|---|---|---|---|---|---|
| Min. Service Temp | −29°C (−20°F) | −46°C (−50°F) | −46°C (−50°F) | −101°C (−150°F) | −101°C (−150°F) |
| Tensile Strength (min) | 415–585 MPa | 485–655 MPa | 485–655 MPa | 450–620 MPa | 450–620 MPa |
| Yield Strength (min) | 205 MPa (30 ksi) | 248 MPa (36 ksi) | 360 MPa (52 ksi) | 241 MPa (35 ksi) | 331 MPa (48 ksi) |
| Elongation (min) | 25% | 22% | 22% | 22% | 22% |
| CVN Impact Test Temp | −29°C | −46°C | −46°C | −101°C | −101°C |
| CVN Energy (avg / min) | 13/10 ft·lbf | 13/10 ft·lbf | 13/10 ft·lbf | 13/10 ft·lbf | 13/10 ft·lbf |
| Ni Content | ≤0.40% | ≤0.40% | ≤0.40% | 3.3–3.7% | 3.3–3.7% |
| Primary Application | Moderate cold service | Cold service, general | Cold service, high-pressure | Cryogenic service | Cryogenic, high-pressure |
The chemical composition of ASTM A350 LF2 is carefully controlled to achieve low-temperature toughness while maintaining weldability. Low carbon content limits hardening, while controlled manganese enhances toughness.
| Element | Composition (wt %) | Role in Performance |
|---|---|---|
| Carbon (C) | ≤ 0.30% | Controlled low to ensure weldability and prevent embrittlement |
| Manganese (Mn) | 0.60 – 1.35% | Strengthening and improved low-temperature toughness |
| Phosphorus (P) | ≤ 0.035% | Kept low to prevent temper embrittlement |
| Sulfur (S) | ≤ 0.040% | Minimised to avoid hot-cracking in welds and improve toughness |
| Silicon (Si) | 0.15 – 0.30% | Deoxidiser; contributes to strength |
| Nickel (Ni) | ≤ 0.40% | Improves toughness at sub-zero temperatures |
| Chromium (Cr) | ≤ 0.30% | Mild hardenability improvement |
| Molybdenum (Mo) | ≤ 0.12% | Temper embrittlement resistance; secondary strengthening |
| Copper (Cu) | ≤ 0.40% | Atmospheric corrosion resistance (minor) |
| Vanadium (V) | ≤ 0.08% | Grain refinement; improved toughness |
| Columbium / Niobium (Cb) | ≤ 0.02% | Grain refinement; fine carbide precipitation |
* Total of Cu + Ni + Cr + Mo + V shall not exceed 1.00%.
| Mechanical Property | A350 LF2 CL1 | A350 LF2 CL2 ✦ | |
|---|---|---|---|
| Tensile Strength (UTS) | 70–95 ksi (485–655 MPa) | 70–95 ksi (485–655 MPa) | |
| Yield Strength (0.2% offset) | 36 ksi min (248 MPa) | 52 ksi min (360 MPa) | |
| Elongation in 2″ (min) | 22% | 22% | |
| Reduction of Area (min) | 30% | 30% | |
| Hardness (max) | 187 HBW (if tested) | ||
| Charpy V-Notch Test Temperature | −46°C (−50°F) | ||
| CVN Impact Energy (avg / individual min) | 13 ft·lbf (18 J) avg / 10 ft·lbf (14 J) individual | ||
| Heat Treatment | Normalize; or Normalize & Temper; or Quench & Temper | ||
| Density | ~7.85 g/cm³ (0.284 lb/in³) | ||
| Minimum Service Temperature | −46°C (−50°F) | ||
This is the most frequently asked question by procurement engineers and piping designers when specifying flanges for low-temperature service. Here is a definitive side-by-side comparison:
| Parameter | ASTM A105 | ASTM A350 LF2 CL2 |
|---|---|---|
| Specification Type | Carbon steel forgings for ambient & elevated temp | LTCS forgings requiring notch toughness testing |
| Impact Testing | Not required | Mandatory CVN at −46°C (−50°F) |
| Min. Service Temp | −29°C (−20°F) — code-dependent | −46°C (−50°F) |
| Yield Strength (min) | 36 ksi (248 MPa) | 52 ksi (360 MPa) |
| Tensile Strength (min) | 70 ksi (483 MPa) | 70 ksi (483 MPa) |
| Heat Treatment | Annealing, Normalizing, or None (optional) | Mandatory: N, N+T, or Q+T |
| Carbon Content (max) | 0.35% | 0.30% |
| Equivalent P-Number | P-No. 1 (Group 1 or 2) | P-No. 1 (Group 1 or 2) |
| PWHT Requirement | Per code (ASME B31.3) | Per code; strongly recommended for weld joints in low-temp service |
| ASME B16.5 Rating | Yes | Yes (same pressure-temperature ratings) |
| Typical Cost | Lower | ~15–25% premium over A105 |
| When to Specify | Ambient to +450°C service without low-temp concern | Any service with design temp below −29°C (−20°F) |
Mandatory Charpy V-Notch impact testing at −46°C (−50°F) ensures the forging resists brittle fracture in arctic, LNG, and cold-climate service — which standard A105 cannot guarantee below −29°C.
Class 2 minimum yield of 52 ksi (360 MPa) — 44% higher than LF2 CL1 — enables use in elevated pressure classes while maintaining the same low-temperature toughness qualification.
All A350 LF2 forgings must be heat treated (Normalize, N+T, or Q+T), refining grain structure and homogenising microstructure to deliver consistent toughness from piece to piece.
The controlled carbon content (≤0.30%) and limited alloying keep the carbon equivalent low, ensuring ease of welding with ER70S-6 / E7018 consumables. PWHT is recommended per ASME B31.3 for P1 welds in cold service.
Each LTCS flange ships with EN 10204 3.1 MTCs, Charpy impact test reports, chemical and mechanical test certificates. Third-party inspection by TÜVR, Bureau Veritas, Lloyds, SGS available on request.
For service temperatures down to −46°C, A350 LF2 CL2 is significantly more cost-effective than austenitic stainless steel (e.g., A182 F316) or 3.5% Ni steel (A350 LF3), while meeting all code requirements.
| Flange Type | Low-Temperature Application Notes | Standard |
|---|---|---|
| Weld Neck (WNRF) | Preferred for high-pressure cryogenic lines; long tapered hub minimises stress concentration; most suitable for thermal cycling service | ASME B16.5 / B16.47 |
| Slip-On (SORF) | Used in moderate pressure low-temperature systems; two fillet welds required; suitable for LNG pump suction headers | ASME B16.5 |
| Blind Flange | Pipeline end closures on cold-service lines; isolates sections for maintenance in LNG terminals and arctic gas plants | ASME B16.5 / B16.47 |
| Socket Weld (SWRF) | Small-bore piping (≤2″ NPS) on cold service utility lines; single fillet weld, suitable for −46°C non-cyclic service | ASME B16.5 |
| Lap Joint (LJRF) | Used with LTCS stub ends; ideal for systems requiring frequent dismantling at cryogenic inspection points | ASME B16.5 |
| Threaded Flange | Instrument and utility connections in low-temperature gas service; no welding required | ASME B16.5 |
| Long Weld Neck (LWN) | Nozzle connections on cryogenic vessels and cold-service pressure vessels; eliminates need for separate nozzle forging | ASME B16.5 / MSS SP-44 |
| Spectacle Blind / Spade | Positive isolation of cold-service lines during maintenance; prevents thermal shock from cross-contamination | ASME B16.48 |
| Orifice Flange | Flow measurement on natural gas transmission and LNG transfer lines at low temperatures | ASME B16.36 |
| Material Standard | ASTM A350 / ASME SA350 Grade LF2 Class 2 |
| Product Form | Forgings (flanges, fittings, valves and piping components) |
| Size Range | ½″ NB to 60″ NB (DN 15 to DN 1500) |
| Pressure Classes (ASME B16.5) | Class 150, 300, 600, 900, 1500, 2500 |
| Large Diameter (ASME B16.47) | Class 75, 150, 300, 400, 600, 900 — Series A & B; NPS 26″ to 60″ |
| Dimensional Standards | ASME B16.5, ASME B16.47, MSS SP-44, EN 1092-1, DIN 2631–2638, BS 4504 |
| Facing Types | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ), Tongue & Groove (T&G), Male & Female (M&F) |
| Finish | 125–250 AARH Raised Face; 63 AARH for RTJ groove |
| Schedule / Wall Thickness | STD, XS, XXS; Sch 20, 40, 80, 160 |
| Testing & Inspection | Charpy CVN (mandatory), Hydrostatic, PMI, Ultrasonic (UT), Magnetic Particle (MT), Radiography (RT) |
| Material Certification | EN 10204 Type 3.1 (MTC by manufacturer); Type 3.2 (witness by third party) |
| Third-Party Inspection | Bureau Veritas, TÜVR, Lloyds Register, SGS, Intertek — on request |
| Client Specifications | Shell DEP, Saudi Aramco SAES, ExxonMobil GP, Norsok M-630 |
| Flange Dimensions Link | View Standard LTCS Flange Dimensions Chart |
| Industry / Sector | Typical A350 LF2 CL2 Applications |
|---|---|
| LNG (Liquefied Natural Gas) | LNG import/export terminal pipelines, loading arms, regasification headers, cryogenic pump suction/discharge lines |
| Oil & Gas (Arctic / Offshore) | Arctic pipelines, cold-climate gas processing facilities, offshore platform topside piping in cold sea environments |
| Petrochemical Plants | Ethylene crackers, propylene refrigeration systems, NGL fractionation units, butadiene extraction units |
| Cryogenic Storage | Cryogenic storage tank nozzles, cold-service pressure vessel piping, liquid CO₂ and nitrogen systems |
| Refrigeration & HVAC | Industrial refrigeration compressor suction/discharge, cold storage plant piping, brine and glycol systems |
| Power Generation | Cold-service auxiliary piping in gas turbine plants; LNG-fired power stations; cold sea water intake piping |
| Air Separation Units (ASU) | Nitrogen and oxygen liquefaction piping, cold box connections, cryogenic distillation column nozzles |
| Natural Gas Transmission | High-pressure gas transmission pipelines through cold-climate regions, compressor station piping |
Every ASTM A350 LF2 CL2 flange from Tesco Steel & Engineering is subject to a comprehensive QA program aligned with ASME, ASTM, and client-specific requirements:
| Test / Inspection | Standard / Method | Frequency |
|---|---|---|
| Charpy V-Notch Impact Test | ASTM A370 at −46°C (−50°F) | Mandatory per heat / lot |
| Chemical Analysis | ASTM E415 / OES Spectroscopy | Per heat |
| Tensile Testing | ASTM A370 | Per lot |
| Hardness Testing | ASTM E18 / E10 (Rockwell / Brinell) | Per piece (if required) |
| Ultrasonic Testing (UT) | ASTM A388 / ASME Section V Art. 5 | As specified |
| Magnetic Particle Testing (MT) | ASTM E709 / ASME Section V Art. 7 | As specified |
| Hydrostatic / Pressure Test | ASME B16.5 / API 598 | As specified |
| Positive Material Identification (PMI) | XRF / OES | Per piece (if required) |
| Dimensional Inspection | ASME B16.5 / B16.47 | 100% per piece |
| Visual Inspection | MSS SP-55 | 100% per piece |
| Standard / System | Designation | Notes |
|---|---|---|
| ASTM / ASME | A350 LF2 CL2 / SA350 LF2 CL2 | Primary standard for flanges and forgings |
| UNS Number | K03011 | Low-alloy carbon steel |
| EN / DIN | P285NH / P285QH (EN 10222-4) | Nearest European equivalent for weldable fine-grain LTCS forgings |
| BS | BS 1503 Grade 221-490 | Approximate British equivalent |
| Weld Filler Wire (MIG/TIG) | ER70S-6 (AWS A5.18) | For GTAW/GMAW; preheat 100–200°C recommended |
| Weld Electrode (SMAW) | E7018 / E7018-1 (AWS A5.1) | Low hydrogen electrode; mandatory for low-temp weld joints |
| Common Name | LTCS Flange, Low Temp Carbon Steel Flange | Used interchangeably in procurement specifications |
Custom sizes, urgent stock, third-party inspection, and full MTC documentation — all available from Tesco Steel & Engineering.