ASTM A105, A350 LF2 & A694 grades. ASME B16.5 / B16.47 / B16.36 / DIN / EN 1092-1. Class 150 to 2500, ½″ to 60″ NB. The most widely specified flange material — high strength, fully weldable, cost-effective, and stocked for immediate export to 65+ countries.
Carbon steel flanges are the most widely used flange type in the global oil & gas, petrochemical, power generation, and general engineering industries. Manufactured from iron-carbon alloy steel, they combine high tensile strength, excellent weldability, and outstanding value — making them the default choice for most piping applications at ambient and moderate elevated temperatures.
Tesco Steel & Engineering manufactures carbon steel flanges to ASTM A105 (standard ambient/elevated service), ASTM A350 LF2 (low-temperature service, Charpy CVN tested to −46°C), and ASTM A694 (high-yield for gas transmission, F42–F70) across all standard dimensional standards — ASME B16.5, B16.47, B16.36, MSS SP-44, EN 1092-1, DIN, BS 4504, and BS 10.
Every carbon steel flange we manufacture is supplied with EN 10204 3.1 material test certificates, full dimensional inspection, and optional third-party inspection by Bureau Veritas, TÜVR, Lloyds Register, SGS, or Intertek.
Standard carbon steel forgings for ambient and elevated temperature piping service. UTS ≥485 MPa, YS ≥250 MPa. Service range: −29°C to +427°C. Used in oil & gas, petrochemical, power, water, and general engineering.
View A105 Flanges →Charpy V-Notch impact tested forgings for sub-zero service. LF2 CL2: −46°C (−50°F) min, YS ≥360 MPa. Mandatory for LNG, cryogenic, arctic O&G, and cold-climate pipelines.
View A350 LF2 CL2 Flanges →High yield strength carbon steel forgings for high-pressure gas transmission and distribution flanges. Grades F42 to F70 (290–480 MPa YS). Conforms to API 6A and high-pressure pipeline specifications.
Enquire for A694 →ASTM A105 carbon steel has a carefully balanced composition that delivers good strength and hardness while keeping the carbon equivalent low enough for reliable field welding without complex preheating procedures.
| Element | Composition (wt %) | Role in Performance |
|---|---|---|
| Carbon (C) | ≤ 0.35% | Primary strengthening element; controlled to maintain weldability |
| Manganese (Mn) | 0.60 – 1.05% | Strengthening and hardening; improves hardenability and toughness |
| Phosphorus (P) | ≤ 0.035% | Kept low to prevent embrittlement and improve ductility |
| Sulfur (S) | ≤ 0.040% | Minimised to prevent hot cracking in welds and inclusions |
| Silicon (Si) | 0.10 – 0.35% | Deoxidiser during steelmaking; contributes to strength |
| Copper (Cu) | ≤ 0.40% | Minor contribution to atmospheric corrosion resistance |
| Nickel (Ni) | ≤ 0.40% | Improves toughness at sub-ambient temperatures |
| Chromium (Cr) | ≤ 0.30% | Mild hardenability and oxidation resistance improvement |
| Molybdenum (Mo) | ≤ 0.12% | Creep resistance at elevated temperatures |
| Vanadium (V) | ≤ 0.08% | Grain refinement; secondary hardening |
* Total of Cu + Ni + Cr + Mo + V shall not exceed 1.00%.
| Property | ASTM A105 ✦ | ASTM A350 LF2 CL2 | ASTM A694 F65 |
|---|---|---|---|
| Tensile Strength (UTS) | ≥ 485 MPa (70 ksi) | 485–655 MPa | ≥ 530 MPa (77 ksi) |
| Yield Strength (0.2% offset) | ≥ 250 MPa (36 ksi) | ≥ 360 MPa (52 ksi) | ≥ 450 MPa (65 ksi) |
| Elongation in 2″ | ≥ 22% | ≥ 22% | ≥ 20% |
| Reduction of Area | ≥ 30% | ≥ 30% | — |
| Hardness (max) | 187 HBW | 187 HBW | — |
| Impact Testing | Not required | Charpy CVN at −46°C (mandatory) | Not required |
| Heat Treatment | Optional (annealing/normalising) | Mandatory (N, N+T, or Q+T) | As required |
| Min. Service Temperature | −29°C (−20°F) | −46°C (−50°F) | −29°C (−20°F) |
| Max. Service Temperature | +427°C (+800°F) | +427°C (+800°F) | +427°C (+800°F) |
| Primary Application | General piping — oil & gas, petrochemical, power | LNG, cryogenic, arctic pipelines | High-pressure gas transmission pipelines |
This is the most common material selection question in piping engineering. Here is a definitive comparison to guide specification:
| Parameter | Carbon Steel (A105) | Stainless Steel (A182 F316) |
|---|---|---|
| Material Cost | Low (baseline reference) | 3–5× higher than A105 |
| Tensile Strength | ≥ 485 MPa | ≥ 515 MPa |
| Corrosion Resistance | Moderate — requires protective coating for wet/corrosive service | Excellent — self-passivating Cr₂O₃ film |
| High-Temperature Oxidation | Up to ~427°C without alloying additions | Up to ~870°C (SS 321/347) |
| Low-Temperature Service | −29°C standard (−46°C with A350 LF2) | Down to −196°C (cryogenic grade) |
| Weldability | Excellent — ER70S-6 / E7018 | Good — requires matching filler wire, no carbon pickup |
| Magnetic Properties | Magnetic | Non-magnetic (austenitic grades) |
| Hygienic Applications | Not suitable | Ideal — food, pharma, chemical |
| Suitable Fluids | Hydrocarbons, steam, compressed air, treated water, non-corrosive gases | Acids, brine, seawater, chlorinated fluids, pharmaceutical |
| When to Specify | Budget-driven projects, non-corrosive service, −29°C to +427°C | Corrosive environments, hygienic service, extreme temperatures |
| Flange Type | Application & Notes | Standard |
|---|---|---|
| Weld Neck (WNRF) | High-pressure, high-temperature, and high-stress service. Tapered hub transfers stress to pipe wall. Most reliable for cyclic and fatigue loading. Preferred for refinery and gas plant service. | ASME B16.5 / B16.47 |
| Slip-On (SORF) | Slides over pipe; double fillet welded. Easier installation than weld neck. Suitable for moderate pressure and temperature. Cost-effective for utilities and water service. | ASME B16.5 |
| Blind Flange | Closes ends of piping systems, vessels, and valves. Used for isolation, hydrostatic testing, and future expansion. Available flat or with raised/RTJ face. | ASME B16.5 / B16.47 |
| Socket Weld (SWRF) | For small-bore piping (NPS ½″–2″) at high pressure. Pipe inserted into socket and fillet welded externally. Used in instrument tubing, chemical injection, and hydraulic lines. | ASME B16.5 |
| Threaded Flange | Screwed onto externally threaded pipe — no welding required. Used for low-pressure, small-bore instrument and utility connections. Can be removed without cutting. | ASME B16.5 |
| Lap Joint (LJRF) | Used with stub ends. Flange rotates freely, simplifying bolt-hole alignment. Ideal for piping requiring frequent maintenance access. Economical when pipe is expensive alloy. | ASME B16.5 |
| Long Weld Neck (LWN) | Extended neck replaces a separate nozzle forging on vessels and heat exchangers. Used on pressure vessel nozzles in refinery and petrochemical plants. | ASME B16.5 / MSS SP-44 |
| Spectacle Blind / Spade | Positive isolation device for piping maintenance and turnaround. Rotated to align blank plate for isolation or open ring for flow. Replaces double-block-and-bleed valves. | ASME B16.48 |
| Orifice Flange | Flow measurement flanges with machined tappings for pressure differential measurement. Used on gas and liquid measurement skids in upstream and midstream O&G. | ASME B16.36 |
| Plate / Flat Flange | Simplified design for low-pressure applications and non-code piping. Common in water treatment, HVAC, and general fabrication. | EN 1092-1 / DIN / BS 10 |
| Standard / System | Flange Types Covered | Pressure Classes / PN Ratings |
|---|---|---|
| ASME / ANSI B16.5 | Weld Neck, Slip-On, Blind, Socket Weld, Lap Joint, Threaded, Ring Type Joint | Class 150, 300, 400, 600, 900, 1500, 2500 (NPS ½″–24″) |
| ASME / ANSI B16.47 | Weld Neck, Blind (Series A & B) | Class 75, 150, 300, 400, 600, 900 (NPS 26″–60″) |
| ASME / ANSI B16.36 | Orifice Weld Neck, Slip-On, Threaded | Class 300, 400, 600, 900, 1500, 2500 |
| MSS SP-44 | Pipeline Weld Neck, Blind | Class 150–2500 (large bore) |
| EN 1092-1 | Weld Neck, Blind, Slip-On, Plate, Lapped | PN 6, PN 10, PN 16, PN 25, PN 40, PN 63, PN 100, PN 160, PN 250, PN 320, PN 400 |
| DIN Flanges | DIN 2527, 2566, 2573, 2576, 2627–2638, 2641, 2642, 2655, 2656, 2673 | PN 6 to PN 100 |
| BS 4504 (Sec 3.1) | Weld Neck, Hubbed Slip-On, Hubbed Threaded, Lapped, Plate, Blank | PN 2.5 to PN 40 |
| BS 4504 (Part 1) | Weld Neck, Hubbed Slip-On, Hubbed Threaded, Plate, Blank | PN 2.5 to PN 400 |
| BS 1560 BOSS | Weld Neck, Socket Weld, Slip-On, Blind, Screwed Boss, Lapped | Class 150, 300, 400, 600, 900, 1500, 2500 |
| BS 10 | Weld Neck, Plate Slip-On, Screwed Boss, Slip-On Boss, Blind | Tables D, E, F, H |
| Face Type | Description | Typical Application |
|---|---|---|
| Raised Face (RF) | Small raised seating surface concentrates bolt load on gasket. Surface finish: 125–250 AARH. | Most common — oil & gas, petrochemical, general piping |
| Flat Face (FF) | Full face contact. Always used with cast iron or non-metallic mating flanges to prevent bolt bending. | Pump flanges, water, low-pressure utility systems |
| Ring Type Joint (RTJ) | Oval or octagonal metal ring gasket seated in machined groove. Superior sealing under high temperature and pressure. | Wellheads, subsea, high-pressure refinery and gas plant |
| Tongue & Groove (T&G) | Male/female mating faces; gasket retained in groove. Prevents gasket blowout. | Heat exchangers, compressor suction/discharge |
| Male & Female (M&F) | Similar to T&G but shallower; gasket exposed on outer edge. | Special services where gasket needs to be contained |
ASTM A105 carbon steel flanges cost 60–75% less than equivalent stainless steel flanges, making them the standard specification for all non-corrosive, non-cryogenic piping service.
UTS ≥485 MPa and YS ≥250 MPa for A105, rising to YS ≥450 MPa for A694 F65. Suitable for Class 150 to 2500 pressure ratings in all standard piping applications.
Carbon equivalent of A105 is well within the weldable range. Field welded with ER70S-6 (GTAW/GMAW) or E7018 (SMAW) without preheat for most wall thicknesses, simplifying installation.
A105 is rated from −29°C to +427°C. When low-temperature service to −46°C is required, A350 LF2 replaces A105 with mandatory Charpy impact testing at no significant size or weight penalty.
ASTM A105 is available globally from multiple mills and stockholders. Tesco Steel maintains ready stock of standard sizes in Class 150–900 for immediate dispatch to 65+ countries worldwide.
A105 flanges are listed in ASME B16.5, B31.3, B31.8, API 6A, PED 2014/68/EU, and all major international piping codes, eliminating approval risks on any project worldwide.
| Industry | Typical Carbon Steel Flange Applications |
|---|---|
| Oil & Gas (Upstream) | Wellhead connections, flowline manifolds, production separators, gas compression trains, slug catchers |
| Oil & Gas (Midstream) | Gas transmission pipelines, pumping station headers, pig launcher/receiver connections, metering skids |
| Petrochemical / Refinery | Crude distillation units, hydrotreaters, reformers, alkylation units, heat exchanger connections |
| Power Generation | Steam pipelines, boiler feed water lines, condensate systems, turbine inlet connections, auxiliary piping |
| LNG & Cryogenic | A350 LF2 specified for LNG terminals, regasification systems, cold-service valves, cryogenic storage nozzles |
| Water & Wastewater | Water distribution mains, pump stations, filtration plant headers, desalination pre-treatment piping |
| Cement & Mining | Compressed air networks, slurry pipelines, cooling water systems, dust suppression piping |
| Chemical Processing | Non-corrosive chemical lines, nitrogen, hydrogen, CO₂ service (dry), process steam and condensate |
| Shipbuilding | Above-waterline piping, fuel oil systems, ballast lines, accommodation utilities, engine room piping |
| Fertiliser & Sugar | Ammonia vapour headers (dry), steam supply lines, product transfer piping, process condensate systems |
| Test / Inspection | Standard / Method | Frequency |
|---|---|---|
| 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) |
| Charpy V-Notch Impact (LF2 only) | ASTM A370 at −46°C (−50°F) | Mandatory per heat / lot for A350 LF2 |
| 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 |
| Positive Material Identification (PMI) | XRF / OES | Per piece (if required) |
| Hydrostatic / Pressure Test | ASME B16.5 / API 598 | As specified |
| Dimensional Inspection | ASME B16.5 / B16.47 | 100% per piece |
| Visual Inspection | MSS SP-55 | 100% per piece |
Third-party inspection by Bureau Veritas, TÜVR, Lloyds Register, SGS, and Intertek available on request. Material test certificates issued to EN 10204 Type 3.1 (standard) or Type 3.2 (witnessed by third party).
ASTM A105, A350 LF2 CL2, A694 — all types, all standards, custom sizes. Ready stock for immediate export. Tell us your size, class & quantity.