Stainless Steel 310S (UNS S31008) is one of the most demanding grades in the austenitic stainless steel family, engineered specifically for high-temperature service where standard grades like 304 or 316 fall short. With a chromium content of 24–26% and nickel of 19–22%, Grade 310S delivers exceptional resistance to oxidation and scaling at continuous operating temperatures up to 1100 °C and intermittent peaks of 1150 °C. This makes 310S flanges the go-to choice for piping systems in furnaces, kilns, heat exchangers, radiant tubes, and other thermal processing environments where both structural integrity and oxidation resistance must be maintained simultaneously. The low carbon variant designation ("S" in 310S) also minimises carbide precipitation during welding, preserving corrosion resistance at weld joints — a critical advantage in fabricated high-temperature assemblies.
Tesco Steel & Engineering manufactures 310S Stainless Steel Flanges across all standard types — Weld Neck, Slip-On, Blind, Socket Weld, Lap Joint, Threaded, and Long Weld Neck — in sizes from ½" NB to 56" NB and pressure classes from 150# through 2500# (PN 1 to PN 400). Every flange is produced to ASTM A182 Grade F310S and conforms to dimensional standards including ASME B16.5, ASME B16.47, ANSI, DIN, EN 1092-1, JIS B2220, and GOST, ensuring full compatibility with global piping systems. Our ISO-certified facility is equipped with forge presses, CNC machining centres, and third-party inspection capabilities, allowing us to meet stringent quality requirements for projects in the oil & gas, petrochemical, power generation, and high-temperature process industries. With a ready stock of standard items and export coverage across 96 countries on 6 continents, Tesco Steel delivers 310S flanges with short lead times and full material traceability.
| 310S SS Flange Specifications at a Glance | |
|---|---|
| Material Standard | ASTM A182 Grade F310S |
| UNS Number | S31008 |
| Size Range | ½" NB to 56" NB (DN 15 to DN 1400) |
| ANSI Pressure Classes | 150#, 300#, 600#, 900#, 1500#, 2500# |
| DIN Pressure Ratings | PN 6, PN 10, PN 16, PN 25, PN 40, PN 64, PN 100, PN 160, PN 250, PN 320, PN 400 |
| Bore Schedule | STD, XS, XXS, SCH 10, 20, 40, 80, 120, 160 |
| Flange Types | Weld Neck (WNRF), Slip-On (SORF), Blind (BFF), Socket Weld (SWRF), Lap Joint (LJRF), Threaded (TRFF), Long Weld Neck (LWN), Orifice |
| Flange Faces | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ) |
| Max Service Temperature | 1100 °C continuous / 1150 °C intermittent |
All 310S flanges supplied by Tesco Steel & Engineering conform to published dimensional standards. Bore diameters, bolt circle diameters, number of bolt holes, and flange thickness are machined to ASME B16.5 (up to 24" NB) and ASME B16.47 Series A & B (26" NB and above) tolerances.
| View Full 310S Stainless Steel Flange Dimension Tables → |
Grade 310S (UNS S31008) is an austenitic stainless steel with the highest chromium and nickel content in the standard 3xx series. The "S" designation signifies a controlled carbon maximum of 0.08%, which reduces the risk of sensitisation — intergranular carbide precipitation — during and after welding. This is critical for flanges that are welded into high-temperature piping loops.
| Chemical Composition — ASTM A182 F310S | |
|---|---|
| Chromium (Cr) | 24.00 – 26.00% |
| Nickel (Ni) | 19.00 – 22.00% |
| Carbon (C) | 0.08% max |
| Manganese (Mn) | 2.00% max |
| Silicon (Si) | 1.50% max |
| Phosphorus (P) | 0.045% max |
| Sulfur (S) | 0.030% max |
| Iron (Fe) | Balance |
| Mechanical Properties — ASTM A182 F310S | |
|---|---|
| Tensile Strength (min) | 515 MPa (75 ksi) |
| Yield Strength 0.2% offset (min) | 205 MPa (30 ksi) |
| Elongation in 2" (min) | 30% |
| Hardness (max) | 217 HBW / 95 HRB |
| Density | 7.90 g/cm³ |
| International Equivalent Grades | |
|---|---|
| UNS (USA) | S31008 |
| EN / DIN (Europe) | 1.4845 / X8CrNi25-21 |
| JIS (Japan) | SUS 310S |
| BS (UK) | 310S24 |
| GOST (Russia) | 10Kh23N18 |
310S SS Weld Neck Flange (WNRF) — The weld neck is the preferred flange type for high-temperature and high-pressure 310S piping systems. Its long tapered hub transfers stress from the flange to the pipe wall, minimising stress concentrations at the weld joint — critical in systems cycling between ambient and operating temperatures above 800 °C.
310S SS Slip-On Flange (SORF) — Slip-on flanges are used where moderate temperatures and pressures are encountered. In 310S, they are common in secondary high-temperature ducting, heat exchanger inlet piping, and low-pressure furnace exhaust connections. Two fillet welds secure the pipe, making installation faster than weld neck configurations.
310S SS Blind Flange (BFF) — Blind flanges in Grade 310S are used to seal the end of high-temperature pipelines, pressure vessels, and furnace penetrations. They provide full access for inspection and maintenance of thermal systems without requiring pipe removal.
310S SS Socket Weld Flange (SWRF) — Used in smaller bore 310S piping (typically up to 2" NB) in high-temperature instrument connections, bypass lines, and pilot piping within furnaces and kilns. The socket bore accepts the pipe and is sealed with a single fillet weld.
310S SS Lap Joint Flange (LJRF) — Used with a 310S stub end in systems where the flanged joint must be frequently disassembled for inspection, replacement of internal components, or cleaning. The rotating back ring allows bolt holes to be aligned independently of the pipe orientation.
310S SS Threaded Flange (TRFF) — Threaded 310S flanges are used in low-to-moderate pressure high-temperature connections where welding is not feasible — such as instrumentation taps and sample connections on furnace walls. They are not recommended for service above 300 °C due to thread relaxation risk.
310S SS Long Weld Neck Flange (LWN) — An extended version of the weld neck, used as a nozzle on pressure vessels, reactors, and autoclaves. In 310S, LWN flanges are specified for high-temperature reactor inlet/outlet nozzles in petrochemical and refinery applications.
310S SS Orifice Flange — Paired orifice flanges in Grade 310S are used for flow measurement in high-temperature gas and process lines. They include tapped pressure ports on either side of the orifice plate to enable differential pressure measurement.
Choosing between stainless steel grades is the most critical material decision in high-temperature piping design. The table below compares 310S against the most common alternative grades engineers consider for elevated-temperature flange applications.
| Property | 310S (S31008) | 316L (S31603) | 321 (S32100) | 347 (S34700) |
|---|---|---|---|---|
| Max Continuous Temp | 1100 °C | 870 °C | 900 °C | 900 °C |
| Chromium % | 24–26 | 16–18 | 17–19 | 17–19 |
| Nickel % | 19–22 | 10–14 | 9–12 | 9–13 |
| Oxidation Resistance | Excellent | Good | Good | Good |
| Sulphidation Resistance | Moderate | Low | Low | Low |
| Weldability (low carbon) | Good (0.08% C max) | Excellent (0.03% C max) | Good (Ti-stabilised) | Good (Nb-stabilised) |
| Typical Flange Standard | ASTM A182 F310S | ASTM A182 F316L | ASTM A182 F321 | ASTM A182 F347 |
| Best For | Furnaces, kilns, high-temp piping | Marine, food, pharma | Creep resistance, cryogenic | Nuclear, high-temp corrosion |
Note: 310S is not recommended for service in strongly reducing, sulphur-rich, or carburising atmospheres above 500 °C without additional protective measures.
Tesco Steel & Engineering manufactures 310S flanges to all major international standards. Every order is supported by mill test certificates (MTC) to EN 10204 3.1 or 3.2, confirming chemical composition, mechanical properties, and heat treatment records.
| Standard | Scope |
|---|---|
| ASTM A182 / ASME SA182 | Material standard for forged alloy and stainless steel flanges — Grade F310S |
| ASME B16.5 | Pipe flanges and flanged fittings — ½" to 24" NB, Class 150 to 2500 |
| ASME B16.47 | Large diameter flanges — 26" to 60" NB (Series A: MSS SP-44, Series B: API 605) |
| ASME B16.36 | Orifice flanges — Class 300 to 2500 |
| EN 1092-1 | European flanges — PN 6 to PN 400, Type 01 to Type 13 |
| DIN 2631 – 2638 | German DIN flanges — PN 6 to PN 160 |
| JIS B2220 | Japanese flanges — 5K to 63K |
| BS 4504 / BS 10 | British Standards flanges |
| GOST 12820 / 12821 | Russian standard flanges |
| MSS SP-44 | Steel pipeline flanges — large diameter |
| NACE MR0175 / ISO 15156 | Sour service (H₂S) compatibility requirements |
310S stainless steel is generally considered weldable using standard austenitic stainless techniques, but several precautions specific to the grade are essential to maintain performance at elevated temperatures.
Filler Metal: ER310 (AWS A5.9) or E310-15/16 (AWS A5.4) are the standard consumables for welding 310S flanges to pipe. For joints to dissimilar stainless steels, ER309L is typically used as a buffer layer. Avoid over-dilution with lower-alloy base metals, as this reduces high-temperature oxidation resistance at the weld.
Preheat: No preheat is required for 310S under normal conditions. However, when welding heavy section flanges (wall thickness above 25 mm) in cold ambient conditions, a light preheat to 50–80 °C is advisable to eliminate moisture.
Interpass Temperature: Limit interpass temperature to 175 °C maximum. 310S is prone to sigma-phase formation if held in the 600–900 °C range for extended periods, which can embrittle the weld heat-affected zone.
Post-Weld Heat Treatment (PWHT): PWHT is generally not required for 310S and can be detrimental. If sensitisation is a concern, solution annealing at 1040–1180 °C followed by rapid quench restores corrosion resistance. Standard stress-relief at 600–700 °C should be avoided as it falls within the sigma-phase formation range.
Inspection: Tesco Steel can supply 310S flanges with third-party inspection (TPI) by Lloyd's, Bureau Veritas, TÜV, SGS, or any nominated agency, with PMI (Positive Material Identification) confirmation on request.
310S flanges are specified wherever piping systems must maintain structural and oxidation resistance above the limits of standard 304 or 316 grades. Key application areas include:
| Industry | Specific Application |
|---|---|
| Furnace & Heat Treatment | Combustion air piping, burner connections, radiant tube flanges, atmosphere retort nozzles |
| Petrochemical & Refining | Fired heater piping, regeneration gas lines, catalyst feed nozzles, cracking unit piping |
| Power Generation | Gas turbine exhaust ducts, waste heat recovery units (WHRU), superheater piping |
| Cement & Lime | Kiln shell piping, preheater cyclone connections, clinker cooler ducting |
| Chemical Processing | Sulphuric acid plant converter piping, nitric acid plant absorber connections |
| Food Processing | High-temperature sterilisation lines, pasteurisation loop piping (where 316 is insufficient) |
| Steel & Metallurgy | Annealing furnace piping, bell furnace atmosphere lines, sintering plant connections |
| Waste Incineration | Flue gas piping, secondary combustion chamber connections, heat recovery connections |
| Aerospace & Defence | Engine test cell exhaust piping, high-temperature test rig flanges |
Use the following checklist when specifying 310S stainless steel flanges for a new or replacement project:
1. Confirm Operating Temperature — If continuous service exceeds 870 °C, 310S is one of very few austenitic grades that will perform reliably. For temperatures between 500 °C and 870 °C, evaluate whether 321 or 347 may offer equivalent performance at lower cost.
2. Define Pressure Class — Specify pressure class per ASME B16.5 (150# to 2500#) or DIN PN rating based on the system's design pressure and temperature combination. Remember that allowable pressure at elevated temperature drops significantly — consult ASME B16.5 Table 2-1.1 for F310S pressure-temperature ratings.
3. Select Flange Type — Weld neck flanges are preferred for high-pressure, high-temperature cycling service. Slip-on or threaded flanges are acceptable for moderate-pressure secondary systems. Blind flanges are specified at inspection points and end-of-line terminations.
4. Specify Flange Face — Raised Face (RF) is standard for most 310S applications. Ring Type Joint (RTJ) is required for Class 900 and above, or where zero-leak sealing is critical. Flat Face (FF) is used when mating with cast iron or non-metallic components.
5. Check Atmosphere Compatibility — 310S performs best in oxidising atmospheres. In strongly sulphidising (H₂S above 500 °C), carburising (carbon-rich reducing gas), or halide-contaminated environments, specify a more resistant alloy such as Alloy 601, 310MoLN, or a nickel-based superalloy.
6. Verify Certification Requirements — For EPC, oil & gas, and power plant projects, specify ASTM A182 F310S with EN 10204 3.1 or 3.2 MTC, heat traceability, and PMI. NACE MR0175 compliance may also be required for sour service locations.
What is a 310S stainless steel flange?
A 310S stainless steel flange is a pipe fitting made from Grade 310S (UNS S31008) austenitic stainless steel, used to connect, terminate, or control flow in high-temperature piping systems. The grade contains 24–26% chromium and 19–22% nickel, giving it superior oxidation resistance up to 1100 °C. Flanges are manufactured to ASTM A182 F310S and dimensioned to ASME B16.5 or B16.47 standards.
What is the maximum temperature for 310S flanges?
310S stainless steel flanges can withstand continuous service temperatures up to 1100 °C and intermittent peaks of up to 1150 °C in oxidising atmospheres. This is the highest operating temperature among standard austenitic stainless grades, making 310S the first choice for furnace, kiln, and high-temperature process piping applications.
What is the difference between 310 and 310S stainless steel?
Grade 310 and Grade 310S share the same chromium (24–26%) and nickel (19–22%) composition, but differ in carbon content. Grade 310 allows up to 0.25% carbon, while Grade 310S limits carbon to 0.08% maximum. The lower carbon in 310S reduces the risk of sensitisation — carbide precipitation at grain boundaries — making it more suitable for welded applications in high-temperature service.
What standard applies to 310S stainless steel flanges?
The material standard for 310S flanges is ASTM A182 / ASME SA182 Grade F310S. Dimensional standards depend on the flange size: ASME B16.5 covers ½" to 24" NB in all pressure classes, while ASME B16.47 covers 26" NB and above. European projects use EN 1092-1 with material to EN 10222-5 Grade X8CrNi25-21 (1.4845).
Is 310S suitable for sulphur-rich or carburising environments?
310S performs well in oxidising and mildly sulphidising atmospheres, but it is not recommended for strongly sulphidising (H₂S above 500 °C) or carburising (carbon-rich reducing gas) environments without additional protective coatings or alloying. In those conditions, nickel-based alloys such as Alloy 601, 625, or 310MoLN are preferred.
What filler metal is used to weld 310S flanges?
ER310 (AWS A5.9) wire is the standard filler for GTAW/GMAW, and E310-15/16 (AWS A5.4) electrodes for SMAW. Interpass temperature must be kept below 175 °C to avoid sigma-phase embrittlement. Post-weld heat treatment is generally not applied; if sensitisation must be corrected, solution annealing at 1040–1180 °C with rapid water quench is specified.
What is the price of 310S stainless steel flanges?
The price of 310S stainless steel flanges depends on size (NB), pressure class, flange type, wall schedule, quantity, and current nickel and chromium surcharges. Because 310S contains significantly more nickel (19–22%) and chromium (24–26%) than 304 or 316, it carries a material premium. Tesco Steel & Engineering offers competitive ex-works and CIF pricing. Request a current price list and ready stock details here.
What certifications does Tesco Steel provide with 310S flanges?
Tesco Steel & Engineering supplies 310S flanges with Mill Test Certificates (MTC) to EN 10204 Type 3.1 as standard, or Type 3.2 (third-party witnessed) on request. Additional documentation available includes: heat and lot traceability, PMI (Positive Material Identification) reports, hydrostatic test certificates, radiographic (RT) or ultrasonic (UT) test reports, and NACE MR0175 compliance declarations.
Can 310S flanges be used in cryogenic service?
310S is not optimised for cryogenic service. Its austenitic structure remains stable at low temperatures and it will not become brittle, but grades such as 304L, 316L, or 347 are more commonly specified for cryogenic applications due to their better documented low-temperature impact properties and lower cost.
Who manufactures 310S stainless steel flanges in India?
Tesco Steel & Engineering, based in Mumbai, India, is an ISO-certified manufacturer and exporter of 310S Stainless Steel Flanges to ASTM A182, ASME B16.5, B16.47, DIN, JIS, and GOST standards. The company supplies to EPC contractors, oil & gas majors, and process plant operators across 96 countries worldwide.
Tesco Steel & Engineering maintains ready stock of 310S Stainless Steel Flanges in the most commonly specified sizes and pressure classes, enabling fast delivery for urgent project requirements. For non-stock sizes, custom forgings and machined flanges are produced to order with full material traceability.
To receive a current price list, ready stock availability, and lead time for your specific requirement, please submit an enquiry with the following details: flange type, size (NB), pressure class or PN rating, quantity, delivery port, and any applicable third-party inspection or documentation requirements. Our technical team will respond within 24 hours.
Global Export: Tesco Steel & Engineering exports 310S Stainless Steel Flanges to customers across the UAE, Saudi Arabia, USA, UK, Germany, Australia, Canada, Singapore, Malaysia, Oman, Qatar, Kuwait, Bahrain, South Africa, Nigeria, Kenya, Indonesia, Thailand, Vietnam, Brazil, and 76 other countries worldwide.