Tesco Steel & Engineering manufactures ASTM A350 LF1 LTCS flanges — the entry-level low-temperature carbon steel forging grade of the A350 specification. LF1 is a carbon-manganese-silicon steel similar to A105 but with controlled chemistry and a mandatory Charpy V-notch impact test, supplied in Class 1 and impact tested at -20°F (-29°C) for low-temperature piping. Available in weld neck, slip-on, blind, socket-weld, threaded, lap-joint, spectacle and orifice types to ASTM A350 / ASME B16.5. Class 150 to 2500, NPS 1/2″ to 24″, PN6 to PN400. ISO 9001:2015 certified. Made in India.
ASTM A350 LF1 LTCS Flanges
A350 LF1 Weld Neck & RTJ Flanges
Tesco Steel & Engineering manufactures A350 LF1 flanges in all types from weld neck to orifice, Class 150 to 2500 — supplied normalized with EN 10204 3.1 / 3.2 certification, the impact-test record, and third-party inspection on request. Explore the wider LTCS flange range, the common A350 LF2 flanges and nickel-bearing A350 LF3 flanges, and the flange dimension charts.
| ASTM A350 LF1 flanges are available in the following specifications: | |
|---|---|
| Material Grade | ASTM A350 / A350M Grade LF1, Class 1 (low-temperature carbon steel) |
| Alloy Type | Carbon-manganese-silicon steel (LTCS), no deliberate nickel |
| Impact Test | Charpy V-notch at -20°F (-29°C) |
| Heat Condition | Normalized (or normalized and tempered) |
| Size | 1/2″ NB to 24″ NB (DN 15 to DN 600); larger to ASME B16.47 |
| Class / Rating | 150#, 300#, 600#, 900#, 1500#, 2500# · 3000#, 6000#, 9000# (socket-weld / threaded) |
| Pressure Ratings | PN 6 – PN 400 (PN6, 10, 16, 25, 40, 64, 100, 160, 250, 320, 400) |
| Dimensional Standards | ASME B16.5, ASME B16.47 (Series A & B), MSS SP-44, DIN EN 1092-1 |
| Flange Types | Weld Neck (WNRF), Slip-On (SORF), Blind, Socket Weld (SWRF), Lap Joint, Threaded / Screwed, Spectacle Blind, Long Weld Neck, Orifice, Plate |
| Flange Faces | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ), Tongue & Groove (T&G) |
| Testing | Charpy impact, hydrostatic, UT, MT/PT per spec; EN 10204 3.1 / 3.2 |
A350 LF1 is a plain carbon-manganese steel with controlled chemistry. It contains no deliberate nickel, so its low-temperature toughness limit is moderate — verified by the mandatory Charpy impact test at -20°F. Colder service calls for LF2 or the 3.5%-nickel LF3.
| Element | ASTM A350 LF1 (Class 1) |
|---|---|
| Carbon (C) | 0.30% max |
| Manganese (Mn) | 0.60 – 1.35% |
| Silicon (Si) | 0.15 – 0.30% |
| Phosphorus (P) | 0.035% max |
| Sulphur (S) | 0.040% max |
| Nickel (Ni) | 0.40% max (residual) |
| Chromium / Molybdenum | 0.30% / 0.12% max (residual) |
| Mechanical Property | ASTM A350 LF1 |
|---|---|
| Tensile Strength | 60 – 85 ksi (415 – 585 MPa) |
| Yield Strength (min) | 30 ksi (205 MPa) |
| Elongation | ~22 – 25% |
| Impact Toughness | Charpy V-notch verified at -20°F (-29°C) |
| Min. Design Temperature | ~ -29°C (-20°F) |
| Condition | Normalized / normalized & tempered |
A350 LF1 Weld Neck Flange (WNRF)
A350 LF1 Slip-On Flange (SORF)
A350 LF1 Blind Flange
| Flange Type | Description & LF1-Specific Use |
|---|---|
| Weld Neck (WNRF) | Tapered hub butt-welded to pipe for high-integrity low-temperature piping; weld with impact-rated low-hydrogen consumables. |
| Slip-On (SORF) | Fillet-welded over the pipe; common in low-temperature piping at moderate pressure. |
| Blind | Seals pipe ends and vessel nozzles in low-temperature systems. |
| Socket Weld (SWRF) | Small-bore (1/2″–2″) instrument and branch connections in cold service. |
| Lap Joint (LJRF) | Used with an LF1 stub end where frequent dismantling is required. |
| Threaded (TRFF) | Internal NPT/BSP threads for non-welded low-pressure connections. |
| Spectacle Blind / Long Weld Neck / Orifice | Isolation spades, nozzle/long-neck and flow-metering flanges in A350 LF1 for low-temperature duty. |
| Property | LF1 | LF2 | LF3 |
|---|---|---|---|
| Type | C-Mn steel | C-Mn steel (richer) | 3.5% Nickel steel |
| Impact-test temperature | -20°F (-29°C) | -50°F (-46°C) | -150°F (-101°C) |
| Nickel | None (residual) | None (residual) | ~3.5% |
| Relative cost | Lowest | Low | Higher (Ni) |
| Typical role | Mild low-temperature service | Most common LTCS grade | Deep cryogenic-ish low temperature |
Mandatory Charpy impact test at -20°F confirms notch toughness for cold-service piping.
Plain C-Mn steel with no nickel — the lowest-cost A350 grade for moderate low temperatures.
Standard carbon-steel welding with impact-rated low-hydrogen consumables and procedures.
Meets ASME B31.3 / B16.5 low-temperature requirements with full impact documentation.
| Industry | Typical Application |
|---|---|
| Oil & Gas | Low-temperature wellhead, processing and pipeline flanged connections |
| Refining & Petrochemical | Cold-service process and utility piping flanges |
| Gas Processing | Moderate low-temperature gas handling flanges |
| Cold-Climate Pipelines | Low-ambient-temperature pipeline and station flanges |
| Storage & Terminals | Low-temperature storage and loading flanged connections |
| General Low-Temperature Plant | Sub-ambient pressure-system flanges to -29°C |
Made from certified A350 LF1 with chemistry and Charpy impact results documented on the MTC.
Supplied in the normalized condition with verified impact toughness at -20°F.
WNRF, SORF, blind, socket-weld, threaded, lap-joint, spectacle, LWN, orifice and plate — in RF, FF, RTJ and T&G.
EN 10204 3.1 / 3.2 MTC with impact results, heat/lot traceability, hydrostatic and third-party inspection on request.
A350 LF1 flange prices reflect forged carbon-steel material plus normalizing and impact testing — it is the most economical low-temperature carbon-steel flange grade. Tesco Steel & Engineering offers competitive ex-works pricing from Mumbai with full export documentation and material traceability. Click Ask for Quote or message us on WhatsApp at +91 92233 66922 with flange type, size (NB), pressure class, quantity and documentation requirements.
Q1. What is an ASTM A350 LF1 flange?
An ASTM A350 LF1 flange is a forged low-temperature carbon steel (LTCS) flange in the entry-level grade of the A350 specification. LF1 is a carbon-manganese-silicon steel similar to A105 but with controlled chemistry and a mandatory Charpy V-notch impact test, supplied in Class 1 with impact testing at -20 degrees F (-29 degrees C). It is used for low-temperature piping where mild sub-ambient notch toughness is required. Flanges are made to ASTM A350 and machined to ASME B16.5 / B16.47 dimensions.
Q2. What is the difference between A350 LF1, LF2 and LF3?
All three are forged low-temperature carbon steel grades of ASTM A350, differing in chemistry and minimum impact-test temperature. LF1 is a carbon-manganese steel impact tested at -20 degrees F (-29 degrees C). LF2 is a slightly richer C-Mn steel tested at -50 degrees F (-46 degrees C) and is the most common LTCS grade. LF3 contains about 3.5% nickel for service down to -150 degrees F (-101 degrees C). Choose the grade by the minimum design temperature.
Q3. What is the impact test temperature for A350 LF1?
ASTM A350 LF1 (Class 1) requires a Charpy V-notch impact test at -20 degrees F (-29 degrees C), with minimum average absorbed energy per the specification. This mandatory low-temperature toughness test is what distinguishes A350 LF1 from ordinary A105 carbon-steel flanges, which are not impact tested.
Q4. What is the chemical composition of A350 LF1?
ASTM A350 LF1 nominal composition: carbon 0.30% max, manganese 0.60–1.35%, silicon 0.15–0.30% (Class 1), phosphorus 0.035% max, sulphur 0.040% max, with small limits on residual elements. It is a plain carbon-manganese steel with no deliberate nickel, which is why its low-temperature limit is moderate compared with the nickel-bearing LF3.
Q5. How is A350 LF1 different from A105 flanges?
A105 and A350 LF1 are both forged carbon-steel flange materials with similar chemistry, but A350 LF1 adds mandatory Charpy impact testing at -20 degrees F and tighter control, qualifying it for low-temperature service. A105 is for ambient and higher temperatures and is not impact tested. Where a code requires notch toughness at low temperature, A350 LF1 (or LF2/LF3) is specified instead of A105.
Q6. What standards apply to A350 LF1 flanges?
A350 LF1 flanges are forged to ASTM A350/A350M (Grade LF1, Class 1) and machined to ASME B16.5 (1/2 inch to 24 inch) or ASME B16.47 / MSS SP-44 for larger sizes, with EN 1092-1 for PN-rated flanges. Material is supplied normalized (or normalized and tempered) with EN 10204 3.1 / 3.2 certification including the impact-test record.
Q7. Can A350 LF1 flanges be welded?
Yes. A350 LF1 is a readily weldable carbon-manganese steel, welded with low-hydrogen processes and matching low-temperature-rated consumables (for example E7018-1 / ER70S-x with impact requirements). Preheat and, for thicker sections, post-weld heat treatment may be specified; welding procedures should be impact-tested to confirm low-temperature toughness of the joint.
Q8. What are the mechanical properties of A350 LF1?
Typical ASTM A350 LF1 properties: tensile strength 60–85 ksi (415–585 MPa), yield strength 30 ksi (205 MPa) minimum, elongation about 22–25%, with Charpy V-notch impact toughness verified at -20 degrees F (-29 degrees C). It is supplied in the normalized or normalized-and-tempered condition.
Q9. What industries use A350 LF1 flanges?
ASTM A350 LF1 flanges are used in low-temperature oil & gas, refinery and petrochemical piping, gas processing, cold-climate pipelines and storage, and general low-temperature pressure systems where moderate sub-ambient toughness (down to -29 degrees C) is required at lower cost than nickel-bearing LTCS grades.
Q10. Are A350 LF1 flanges supplied with material test certificates?
Yes. Every A350 LF1 flange is supplied with EN 10204 3.1 (or 3.2) mill test certificates confirming chemistry, mechanical properties, the Charpy impact-test result and heat/lot traceability, with hydrostatic testing and third-party inspection on request. Tesco Steel & Engineering is an ISO 9001:2015 certified manufacturer and exporter from Mumbai, India.