Grade 316 (UNS S31600) is the second most widely specified stainless steel in the world and the most commonly used grade for flanges in corrosive service environments. Its defining characteristic — a 2–3% molybdenum addition not present in Grade 304 — dramatically improves resistance to pitting and crevice corrosion in chloride-bearing media, seawater, process acids, and pharmaceutical solutions. This is why 316 is referred to as "marine grade" stainless steel and why it is the default specification for offshore, coastal, and chemical processing piping systems worldwide. The low-carbon variant, Grade 316L (UNS S31603), limits carbon to 0.03% maximum, eliminating the risk of sensitisation in the heat-affected zone during welding — making it the preferred choice for fabricated flange assemblies in corrosive service without the need for post-weld heat treatment.
Tesco Steel & Engineering manufactures 316 and 316L Stainless Steel Flanges across all standard types — Weld Neck (WNRF), Slip-On (SORF), Blind (BFF), Socket Weld (SWRF), Lap Joint (LJRF), Threaded (TRFF), Long Weld Neck (LWN), and Orifice — in sizes from ½" NB to 56" NB and pressure classes from 150# through 2500# (PN 6 to PN 400). Every flange is produced to ASTM A182 Grade F316 or F316L and dimensioned to ASME B16.5, ASME B16.47, ANSI, EN 1092-1, DIN, JIS B2220, and GOST standards. Our ISO-certified facility in Mumbai is equipped with open-die forge presses, CNC machining centres, and in-house heat treatment, supported by third-party inspection by Lloyd's, Bureau Veritas, TÜV, and SGS. We hold ready stock of standard 316/316L flanges and export to customers across 96 countries on 6 continents.
| 316 / 316L SS Flange Specifications at a Glance | |
|---|---|
| Material Standard | ASTM A182 Grade F316 / F316L / F316H |
| UNS Numbers | S31600 (316) | S31603 (316L) | S31609 (316H) |
| 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, 60, 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 Continuous Service Temp | 870 °C (oxidising) | 925 °C intermittent |
| Pitting Resistance Equiv. (PREN) | ~25 (316) vs ~18 (304) |
All 316 and 316L flanges are machined to published dimensional tolerances. Bore diameters, bolt circle, number of holes, flange thickness, and raised face height conform to ASME B16.5 (½" to 24" NB) and ASME B16.47 Series A & B (26" NB and above).
| View Full 316 Stainless Steel Flange Dimension Tables → |
The addition of 2–3% molybdenum is what separates Grade 316 from Grade 304. Molybdenum stabilises the passive oxide film on the steel surface in the presence of chloride ions, preventing the localised breakdown that leads to pitting and crevice corrosion. Grade 316L reduces carbon content to 0.03% maximum to prevent sensitisation during welding. Grade 316H increases carbon to a minimum of 0.04% for improved creep strength in high-temperature pressure vessel applications.
| Element | 316 (S31600) | 316L (S31603) | 316H (S31609) |
|---|---|---|---|
| Chromium (Cr) | 16.00 – 18.00% | 16.00 – 18.00% | 16.00 – 18.00% |
| Nickel (Ni) | 10.00 – 14.00% | 10.00 – 14.00% | 10.00 – 14.00% |
| Molybdenum (Mo) | 2.00 – 3.00% | 2.00 – 3.00% | 2.00 – 3.00% |
| Carbon (C) | 0.08% max | 0.03% max | 0.04 – 0.10% |
| Manganese (Mn) | 2.00% max | 2.00% max | 2.00% max |
| Silicon (Si) | 0.75% max | 0.75% max | 0.75% max |
| Phosphorus (P) | 0.045% max | 0.045% max | 0.045% max |
| Sulfur (S) | 0.030% max | 0.030% max | 0.030% max |
| Nitrogen (N) | 0.10% max | 0.10% max | — |
| Mechanical Property | 316 (F316) | 316L (F316L) |
|---|---|---|
| Tensile Strength (min) | 515 MPa (75 ksi) | 485 MPa (70 ksi) |
| Yield Strength 0.2% offset (min) | 205 MPa (30 ksi) | 170 MPa (25 ksi) |
| Elongation in 2" (min) | 30% | 30% |
| Hardness (max) | 217 HBW / 95 HRB | 217 HBW / 95 HRB |
| Density | 7.99 g/cm³ | 7.99 g/cm³ |
| International Equivalent Grades | |
|---|---|
| UNS (USA) | S31600 (316) / S31603 (316L) / S31609 (316H) |
| EN / DIN (Europe) | 1.4401 (316) / 1.4404 (316L) / 1.4919 (316H) |
| JIS (Japan) | SUS 316 / SUS 316L |
| BS (UK) | 316S31 / 316S11 |
| GOST (Russia) | 03Kh17N14M3 (316L) |
| IS (India) | FG 316 / FG 316L (IS 6911) |
316 / 316L SS Weld Neck Flange (WNRF) — The weld neck is the standard choice for high-pressure, high-cycle, and corrosive 316 piping systems. Its long tapered hub provides a smooth bore transition and distributes stress away from the flange face, minimising fatigue risk in systems subject to thermal cycling or vibration. Specified in ASME B16.5 Class 150 through 2500. The 316L variant is standard for all welded assemblies to avoid sensitisation.
316 / 316L SS Slip-On Flange (SORF) — Widely used in 316 piping for moderate-pressure corrosive service where installation speed matters. The pipe slides through the bore and is secured with two fillet welds. Common in offshore topside piping, chemical plant secondary lines, and food & beverage connections where 304 is insufficient due to chloride content.
316 / 316L SS Blind Flange (BFF) — Used to seal pipeline ends and vessel nozzles in corrosive service systems. In offshore and marine environments, 316L blind flanges are the default specification for capped nozzles on process vessels, heat exchangers, and seawater piping headers. Available in raised face, flat face, and ring type joint face finishes.
316 / 316L SS Socket Weld Flange (SWRF) — Specified for small-bore 316 instrument and sample connections (typically ½" to 2" NB) in chemical, pharmaceutical, and food processing plants. The pipe inserts into the counter-bore and is welded with a single fillet. Suitable for ASME B16.5 Class 150 to 3000 in small diameters.
316 / 316L SS Lap Joint Flange (LJRF) — Used with a 316L stub end where the piping must be frequently disassembled for cleaning, inspection, or lining replacement. Common in pharmaceutical hygienic piping, dairy processing, and food-grade installations where CIP (clean-in-place) access is required. The rotating backing ring allows bolt hole alignment without rotating the pipe.
316 / 316L SS Threaded Flange (TRFF) — Screwed onto externally threaded pipe in low-to-moderate pressure 316 instrument connections, sampling points, and utility headers. Suitable for ASME B16.5 Class 150 to 2500 in ½" to 4" NB where welding is not practical. Not recommended for service above 260 °C due to thread relaxation under thermal cycling.
316 / 316L SS Long Weld Neck Flange (LWN) — Used as extended nozzles on pressure vessels, columns, and reactor shells in chemical and pharmaceutical plants. The extended neck acts as a pipe spool and eliminates the need for a separate weld-on nozzle. Available in 316 and 316L to ASTM A182 and ASME B16.5.
316 / 316L SS Orifice Flange — Paired orifice flanges with tapped pressure ports are specified in 316L for flow measurement in corrosive, pharmaceutical, and food processing lines. The material ensures the orifice plate bore and pressure taps remain accurate over time without chloride-induced pitting that would distort differential pressure readings.
The table below compares the three grades most commonly evaluated when specifying stainless steel flanges for corrosion-resistant service.
| Property | 316 (S31600) | 316L (S31603) | 304 (S30400) | 304L (S30403) |
|---|---|---|---|---|
| Molybdenum | 2–3% | 2–3% | None | None |
| Carbon Max | 0.08% | 0.03% | 0.08% | 0.03% |
| Chloride Resistance | Excellent | Excellent | Moderate | Moderate |
| Pitting Resistance (PREN) | ~25 | ~25 | ~18 | ~18 |
| Sensitisation Risk After Welding | Possible | Minimal | Possible | Minimal |
| Tensile Strength (min) | 515 MPa | 485 MPa | 515 MPa | 485 MPa |
| Max Continuous Service Temp | 870 °C | 870 °C | 870 °C | 870 °C |
| ASTM Flange Grade | A182 F316 | A182 F316L | A182 F304 | A182 F304L |
| Relative Material Cost | Higher (Mo) | Higher (Mo) | Lower | Lower |
| Best For | Corrosive service, marine, chemical | Welded corrosive assemblies | General service, food | Welded general assemblies |
Specify 316L over 316 for all welded flange assemblies. For non-welded, flanged-only connections, 316 and 316L are interchangeable. Always verify chloride concentration and temperature before downgrading to 304.
Tesco Steel & Engineering supplies 316 / 316L flanges with Mill Test Certificates (MTC) to EN 10204 Type 3.1 as standard, or Type 3.2 (third-party witnessed) on request.
| Standard | Scope |
|---|---|
| ASTM A182 / ASME SA182 | Material standard for forged alloy and stainless steel flanges — Grade F316, F316L, F316H |
| 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, material 1.4401 (316) / 1.4404 (316L) |
| DIN 2631 – 2638 | German DIN flanges — PN 6 to PN 160 |
| JIS B2220 | Japanese flanges — 5K to 63K, material SUS 316 / 316L |
| 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) — 316L commonly qualified |
| 3-A Sanitary Standards | Hygienic flanges for dairy and food processing — 316L required |
Grade 316 and 316L are readily weldable by all standard arc welding processes. The key fabrication considerations are sensitisation prevention and maintaining corrosion resistance at the weld joint.
Filler Metal: Use ER316L (AWS A5.9) wire for GTAW/GMAW or E316L-15/16/17 (AWS A5.4) electrodes for SMAW on both 316 and 316L base metal. The "L" grade filler limits carbon pickup in the weld bead, preserving corrosion resistance in the heat-affected zone. For joining 316L to carbon steel or dissimilar stainless grades, ER309L is the standard buffer layer filler.
Sensitisation: Sensitisation occurs when carbon precipitates as chromium carbide at grain boundaries, depleting the surrounding matrix of chromium and leaving it susceptible to intergranular corrosion. This happens between 425–870 °C — the danger zone for standard Grade 316. Grade 316L, with carbon limited to 0.03%, is immune to sensitisation in most welding conditions, making it the specification of choice for welded pressure piping.
Preheat: No preheat is required for 316 or 316L under standard conditions. Avoid preheat temperatures that would hold the weld in the sensitisation range. A light warm-up to 30–50 °C in cold ambient conditions is acceptable to remove surface moisture.
Post-Weld Heat Treatment (PWHT): PWHT is not required for 316L and is generally avoided for 316 in corrosive service. If sensitisation has occurred in Grade 316 weld joints, solution annealing at 1040–1120 °C followed by rapid water quench restores full corrosion resistance. Stress relief at 600–800 °C is in the sensitisation range for 316 and must be avoided unless 316L is specified.
Hygienic & Pharmaceutical Welding: For 316L flanges in pharmaceutical, food, and biotech piping, full-penetration orbital TIG welds with argon back-purging are standard, with internal weld beads ground to Ra ≤ 0.8 µm. Tesco Steel can supply flanges with polished bore and face finishes to 3-A and EHEDG hygienic standards.
316 and 316L flanges are the default specification wherever chloride corrosion, chemical resistance, or hygienic cleanliness is the primary design driver.
| Industry | Specific Application |
|---|---|
| Offshore & Marine | Seawater cooling piping, ballast water systems, subsea jumpers, topside process headers, firewater ring mains |
| Chemical Processing | Chloride-bearing process lines, acetic acid piping, sulphate and phosphate chemical plant, absorber columns |
| Pharmaceutical & Biotech | WFI (water for injection) piping, CIP/SIP circuits, fermentation vessel nozzles, sterile process connections |
| Food & Beverage | Dairy processing (CIP lines, pasteurisation loops), brewery piping, food-grade heat exchanger connections |
| Oil & Gas | Sour service piping (NACE MR0175), platform process piping, chemical injection headers, methanol injection |
| Desalination | Reverse osmosis (RO) pressure vessels, high-pressure seawater feed piping, brine discharge lines |
| Pulp & Paper | Bleach plant piping (chlorine dioxide, hypochlorite), black liquor lines, digester nozzles |
| Power Generation | Condensate polishing, cooling water systems in coastal power plants, feedwater heater nozzles |
| Water Treatment | Chlorinated potable water mains, wastewater treatment plant piping, UV treatment vessel nozzles |
| Architecture & Construction | Exposed coastal structural connections, curtain wall anchor flanges in marine environments |
The choice between 316 and 316L is almost always made on the basis of welding requirements, not mechanical performance. Use the following decision logic:
Choose 316L when: The flanges will be welded to pipe or fittings, and the assembly will operate in corrosive service (chloride environments, acids, marine). 316L is immune to sensitisation during welding, ensuring the weld heat-affected zone retains the same corrosion resistance as the base metal. This is the most common selection in practice — most flanges leave the project in a welded assembly.
Choose 316 when: The flange is installed without welding (threaded or lap joint connections), or when higher tensile and yield strength is required. Grade 316 offers slightly higher strength figures than 316L. For elevated temperature service above 500 °C where creep strength matters, specify Grade 316H instead.
Choose 316H when: The piping system operates above 550 °C and long-term creep resistance is required. 316H has a minimum carbon content of 0.04% which improves creep rupture strength at elevated temperature. It is specified in ASME Section VIII pressure vessel and B31.3 process piping codes for high-temperature service.
Consider upgrading to duplex (2205) when: Chloride concentrations exceed 1,000 ppm at temperatures above 50 °C, or stress corrosion cracking is a documented risk. Duplex 2205 offers roughly twice the pitting resistance of 316L and is resistant to chloride stress corrosion cracking — a failure mode that 316L is susceptible to in warm chloride environments.
What is a 316 stainless steel flange?
A 316 stainless steel flange is a pipe fitting manufactured from Grade 316 or 316L austenitic stainless steel (UNS S31600 / S31603). The addition of 2–3% molybdenum distinguishes it from Grade 304 and gives it superior resistance to pitting and crevice corrosion in chloride-bearing environments. Flanges are forged to ASTM A182 F316/F316L and machined to ASME B16.5 or B16.47 dimensional standards. They are used to connect, terminate, or control flow in corrosive and hygienic piping systems.
What is the difference between 316 and 316L stainless steel flanges?
The only difference is carbon content. Grade 316 allows up to 0.08% carbon; Grade 316L limits it to 0.03% maximum. The lower carbon in 316L prevents sensitisation — chromium carbide precipitation at grain boundaries — during welding. In service, 316L weld heat-affected zones retain full corrosion resistance without post-weld heat treatment. For non-welded applications, 316 and 316L are essentially interchangeable. For welded assemblies, 316L is always preferred.
What is the difference between 304 and 316 stainless steel flanges?
Grade 316 contains 2–3% molybdenum; Grade 304 contains none. Molybdenum significantly improves resistance to pitting and crevice corrosion in chloride environments — seawater, salt spray, acids, and bleach solutions. The pitting resistance equivalent (PREN) of 316 is approximately 25 versus 18 for 304. In dry, non-chloride environments (inland, food contact, general service), 304 performs comparably to 316 at lower cost. Where chlorides or marine exposure are present, 316 is the correct choice.
Can 316 stainless steel flanges be used in seawater?
Grade 316 provides acceptable corrosion resistance in seawater for short-term or intermittent exposure, but is susceptible to pitting and crevice corrosion in stagnant seawater or under crevice conditions (under gaskets, at threaded connections) over extended service. For continuous seawater piping, super duplex (2507) or 6Mo stainless steel flanges are more appropriate. 316L is used extensively in seawater systems with appropriate flow velocity to prevent stagnation, and with impressed current cathodic protection in submerged applications.
What is the maximum temperature for 316 stainless steel flanges?
Grade 316 can withstand continuous service up to 870 °C in oxidising atmospheres and up to 925 °C intermittently. However, 316 is not primarily a high-temperature grade — it is selected for corrosion resistance, not heat resistance. For continuous service above 870 °C, Grade 310S (UNS S31008) should be specified. The ASME B16.5 pressure-temperature rating for F316 flanges drops significantly with increasing temperature and must be verified against Table 2-1.1 for the specific pressure class.
Is 316 stainless steel magnetic?
Grade 316 is austenitic and therefore non-magnetic in its annealed (solution-treated) condition. However, cold working during forming and machining can induce a small degree of ferrite transformation, resulting in slight magnetic permeability. This is not a structural or corrosion issue but should be noted for applications in sensitive electromagnetic environments. If strict non-magnetic behaviour is required, verify with the manufacturer that permeability is within the acceptable range, or specify a fully annealed condition.
What standard applies to 316 stainless steel flanges?
The material standard is ASTM A182 / ASME SA182 Grade F316 or F316L. Dimensional standards depend on flange size: ASME B16.5 covers ½" to 24" NB in all pressure classes; ASME B16.47 covers 26" NB and above. European projects use EN 1092-1 with material to EN 10222-5 Grade X2CrNiMo17-12-2 (1.4404 for 316L). Hygienic applications reference 3-A Sanitary Standards or EHEDG guidelines, which mandate 316L as minimum.
What filler metal is used to weld 316L flanges?
ER316L (AWS A5.9) wire is standard for GTAW (TIG) and GMAW (MIG), and E316L-15/16/17 (AWS A5.4) for SMAW (stick). Using the L-grade filler on both 316 and 316L base metal ensures the deposited weld metal also has low carbon, preserving corrosion resistance across the joint. For joining 316L to carbon steel or low-alloy steel, ER309L is used as a transitional filler layer.
What certifications come with 316 flanges from Tesco Steel?
Standard supply includes Mill Test Certificates (MTC) to EN 10204 Type 3.1 with chemical analysis, mechanical test results, and heat traceability. On request: EN 10204 Type 3.2 (third-party witnessed), PMI (Positive Material Identification) test reports, hydrostatic pressure test certificates, radiographic (RT) or ultrasonic (UT) inspection reports, NACE MR0175 compliance declarations, and 3-A or EHEDG hygienic certification for food-grade flanges.
What is the price of 316 stainless steel flanges in India?
The price of 316 stainless steel flanges varies based on size (NB), pressure class, schedule, quantity, flange type, and current nickel and molybdenum raw material surcharges. Because 316 contains 2–3% molybdenum and 10–14% nickel — both more expensive than 304's composition — 316 flanges carry a 15–25% premium over equivalent 304 items in most market conditions. Tesco Steel & Engineering offers competitive ex-works prices from Mumbai with export documentation for all destinations. Request a current price list and stock availability here.
Who manufactures 316 stainless steel flanges in India?
Tesco Steel & Engineering, based in Mumbai, India, is an ISO-certified manufacturer and exporter of 316 and 316L Stainless Steel Flanges to ASTM A182, ASME B16.5, B16.47, EN 1092-1, DIN, JIS B2220, and GOST standards. The company supplies to EPC contractors, oil & gas majors, pharmaceutical plant builders, and process plant operators across 96 countries worldwide.
Tesco Steel & Engineering maintains ready stock of 316 and 316L Stainless Steel Flanges in the most commonly specified sizes, pressure classes, and flange types, enabling fast delivery for urgent requirements. Custom sizes, special schedules, and dual-certified 316/316L flanges are produced to order with full material traceability.
To receive a current price list, ready stock confirmation, and lead time for your specific requirement, submit an enquiry with the following details: grade (316 or 316L), flange type, size (NB), pressure class or PN rating, quantity, delivery port, and any inspection or certification requirements. Our technical sales team responds within 24 hours.
Global Export: Tesco Steel & Engineering exports 316 & 316L 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.