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Stainless Steel Flanges
Product Overview
R V Metal Corporation offers a full range of Stainless Steel Flanges manufactured and supplied in commercial to critical-service grades including J7, J4, 201, 202, 301, 302, 304, 304L, 304H, 305, 308, 309, 309S, 310, 310S, 316, 316L, 316H, 316Ti, 317, 317L, 321, 321H, 347, 347H, 409L, 410, 410S, 420, 429, 430, 430Ti, 439, 441, 444 and S31803 (Duplex). Stainless steel flanges are used to connect pipes, valves, pumps, and equipment to form a leak-tight, serviceable joint that can be dismantled for inspection and maintenance. Grade selection depends on corrosion, temperature, and strength requirements—J7/J4/201/202 for cost-effective indoor/general fabrication, 304/304L for all-round corrosion resistance, 316/316L/316Ti/316H for chloride and chemical exposure, 317/317L for higher Mo and improved pitting resistance, 321/321H for stabilized high-temperature service, 347/347H for severe thermal cycling, 309/309S and 310/310S for oxidation resistance at elevated temperatures, 409L/410/410S/420 for heat/wear focused applications, 430/430Ti/439/441/444 for oxidation resistance and low-cost corrosion resistance, and S31803 (Duplex) for high strength and superior resistance in chloride-bearing environments. We supply flanges in the most demanded types such as Weld Neck (WN), Slip-On (SO), Socket Weld (SW), Threaded/Screwed, Lap Joint (LJ), Blind (BL), and special isolation variants like Spectacle Blind and Spacer Ring, with facing options including Raised Face (RF), Flat Face (FF), and Ring Type Joint (RTJ) as per pressure class and gasket design. Supplies can be provided with MTC, heat/batch traceability, and project-specific machining and finishing as required.
| Flange Type | Where It’s Used | Why It’s Chosen | Common Grade Options |
|---|---|---|---|
| Weld Neck (WN) | High pressure / high temperature / critical lines | Best stress distribution & fatigue resistance | 304/304L/304H, 316/316L/316H/316Ti, 321/321H, 347/347H, 310/310S, S31803 |
| Slip-On (SO) | Utility piping, general fabrication | Economical & easy alignment | J7, J4, 201, 202, 304/304L, 316/316L, 430/439/441 |
| Socket Weld (SW) | Small-bore, high-pressure services | Strong joint for small sizes | 304/304L, 316/316L/316Ti, 321, 347, S31803 |
| Threaded / Screwed | No-weld areas, maintenance-friendly connections | Easy installation without welding | 304, 316, 410/410S, 420 (as per service) |
| Lap Joint (LJ) | Frequent dismantling, alignment-sensitive lines | Easy rotation and assembly | 304/304L, 316/316L, 317/317L |
| Blind (BL) | Pipeline termination, positive isolation | Strong closure, pressure-test friendly | 304/304L/304H, 316/316L, 310/310S, 347/347H, S31803 |
| Spectacle Blind / Spacer Ring | Isolation points for shutdown & maintenance | Quick visual open/close indication | 304/304L, 316/316L, 321/347, S31803 |
| Facing Options (RF / FF / RTJ) | Sealing interface with gasket | Correct sealing by class and gasket type | RF/FF: most grades; RTJ: commonly 316/310/S31803 for higher classes |
Technical Specifications
| Specification Parameter | Details / Options | Different Types Covered | Grade Applicability (J7, J4, 201–444, S31803) |
|---|---|---|---|
| Product | Stainless Steel Flanges | WN, SO, SW, Threaded, LJ, Blind, Spectacle Blind, Spacer Ring | All listed grades (selection depends on service conditions) |
| Flange Types (Common) | Weld Neck (WN), Slip-On (SO), Socket Weld (SW), Threaded/Screwed, Lap Joint (LJ), Blind (BL), Spectacle Blind, Spacer Ring | All |
J7/J4/201/202: general purpose & non-critical 304/304L: general corrosion-resistant 316/316L/316H/316Ti/317/317L: chloride/chemical & marine exposure 321/321H/347/347H: elevated temp / thermal cycling 309/309S/310/310S: high-temperature oxidation resistance 409L/410/410S/420 & 430/430Ti/439/441/444: heat/oxidation & specific corrosion needs S31803 (Duplex): higher strength & chloride resistance |
| Pressure Rating (Classes) | ASME/ANSI Class 150, 300, 600, 900, 1500, 2500 (as required) | All | All (grade selection as per design pressure/temperature and corrosion) |
| Facing | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ) | WN, SO, SW, Threaded, LJ, Blind | All (RTJ commonly for higher pressure classes and critical service) |
| Size Range | NPS 1/2" to 48" (DN 15 to DN 1200) depending on type and standard | All | All |
| Wall / Bore | Bore matched to pipe schedule (Sch 5S, 10S, 40S, 80S, 160, XXS) or as specified | WN, SW, Threaded (by bore), SO (by OD) | All |
| Standards (Dimensional) | ASME B16.5 (NPS 1/2"–24"), ASME B16.47 Series A/B (NPS 26"–60"), MSS SP-44 (as applicable) | WN, SO, SW, Threaded, LJ, Blind | All |
| Material / Product Standards | ASTM A182 (forged flanges), ASTM A240 (plate for BL / cut flanges), ASTM A351 (cast flanges, if required) | Forged / Plate-cut / Cast (as required) | 304/304L/304H, 316/316L/316H/316Ti, 317/317L, 321/321H, 347/347H, 310/310S, S31803 and other listed grades (availability depends on standard form) |
| Manufacturing Process | Forged (preferred), Plate-cut (BL, large OD), Machined, Heat-treated as per grade & standard | All | All (process depends on flange type and required properties) |
| Heat Treatment Condition | Solution annealed / normalized / quenched & tempered (as per grade family) | All |
Austenitic: solution annealed (typ.) Ferritic/Martensitic: as per grade requirement Duplex: solution annealed (typ.) |
| Surface Finish | Machine finish, serrated finish (gasket seating), pickled, passivated, blasted (as specified) | All | All |
| Gasket Seating | Concentric / spiral serration (typical), smooth (as required for specific gasket types) | RF, FF | All |
| Bolting Compatibility | Compatible with SS bolting or alloy bolting as per pressure class and temperature | All | All (bolting selection is design-dependent) |
| Testing & Inspection | Dimensional checks, visual inspection, PMI (on request), hardness (as applicable), NDT (UT/PT/RT as required), hydro / pneumatic tests as per project spec | All | All |
| Documentation | MTC / Test Certificate as per EN 10204 3.1 (or as specified), heat/batch traceability | All | All |
| Supply Condition | Loose, palletized, export packing; identification marking (grade, size, class, heat no.) | All | All |
| Typical Grade Families |
Austenitic: J7, J4, 201, 202, 301, 302, 304, 304L, 304H, 305, 308, 309, 309S, 310, 310S, 316, 316L, 316H, 316Ti, 317, 317L, 321, 321H, 347, 347H Ferritic/Martensitic: 409L, 410, 410S, 420, 429, 430, 430Ti, 439, 441, 444 Duplex: S31803 |
All | All |
| Common Application Service Notes | General piping & fabrication (J7/J4/201/202/304), chemical & marine (316/317/Duplex), high-temperature (309/310/321/347), heat/oxidation & wear (410/420/430 family) | All | All (choose grade based on corrosion + temperature + pressure + welding needs) |
Chemical Composition
| Grade / Family | UNS / Common Identifier | Typical Flange Types | C (max) | Mn (max) | Si (max) | Cr | Ni | Mo | N | Ti / Nb | Other Key Elements |
|---|---|---|---|---|---|---|---|---|---|---|---|
| J4 (200-series type) | Market grade (approx. 201/J4 variant) | SO, WN, Blind, Threaded (mainly utility / general) | ≤ 0.15 | ≤ 9.00 | ≤ 1.00 | 13.0–16.0 | 1.0–3.0 | — | — | — | Cu (0.8–2.0) typical for formability |
| J7 (200-series type) | Market grade (approx. 202/J7 variant) | SO, WN, Blind, Threaded | ≤ 0.15 | ≤ 9.00 | ≤ 1.00 | 16.0–18.0 | 3.5–5.5 | — | — | — | Cu (0.5–2.0) typical |
| 201 | S20100 (typical) | SO, WN, Blind, Threaded | ≤ 0.15 | ≤ 7.50 | ≤ 1.00 | 16.0–18.0 | 3.5–5.5 | — | — | — | N (up to ~0.25) may be present |
| 202 | S20200 (typical) | SO, WN, Blind, Threaded | ≤ 0.15 | ≤ 10.00 | ≤ 1.00 | 17.0–19.0 | 4.0–6.0 | — | — | — | Cu (up to ~1.5) common |
| 301 | S30100 | SO, WN, Blind, LJ | ≤ 0.15 | ≤ 2.00 | ≤ 1.00 | 16.0–18.0 | 6.0–8.0 | — | — | — | — |
| 302 | S30200 | SO, WN, Blind, LJ | ≤ 0.15 | ≤ 2.00 | ≤ 1.00 | 17.0–19.0 | 8.0–10.0 | — | — | — | — |
| 304 | S30400 | WN, SO, Blind, SW, Threaded, LJ | ≤ 0.08 | ≤ 2.00 | ≤ 1.00 | 18.0–20.0 | 8.0–10.5 | — | — | — | — |
| 304L | S30403 | WN, SO, Blind, SW, Threaded, LJ | ≤ 0.03 | ≤ 2.00 | ≤ 1.00 | 18.0–20.0 | 8.0–12.0 | — | — | — | — |
| 304H | S30409 | WN, SO, Blind (high-temp service) | 0.04–0.10 | ≤ 2.00 | ≤ 1.00 | 18.0–20.0 | 8.0–11.0 | — | — | — | — |
| 305 | S30500 | SO, WN, Blind | ≤ 0.12 | ≤ 2.00 | ≤ 1.00 | 17.0–19.0 | 10.5–13.0 | — | — | — | — |
| 308 (filler-like chemistry) | Commonly referenced (weld deposit family) | Used with 304-series welding (not a base flange grade) | ≤ 0.08 | ≤ 2.00 | ≤ 1.00 | 19.0–21.0 | 9.0–11.0 | — | — | — | Note: typically welding consumable designation |
| 309 | S30900 | WN, SO, Blind (heat resistant) | ≤ 0.20 | ≤ 2.00 | ≤ 1.00 | 22.0–24.0 | 12.0–15.0 | — | — | — | — |
| 309S | S30908 | WN, SO, Blind (heat resistant) | ≤ 0.08 | ≤ 2.00 | ≤ 1.00 | 22.0–24.0 | 12.0–15.0 | — | — | — | — |
| 310 | S31000 | WN, SO, Blind (high temperature) | ≤ 0.25 | ≤ 2.00 | ≤ 1.50 | 24.0–26.0 | 19.0–22.0 | — | — | — | — |
| 310S | S31008 | WN, SO, Blind (high temperature) | ≤ 0.08 | ≤ 2.00 | ≤ 1.50 | 24.0–26.0 | 19.0–22.0 | — | — | — | — |
| 316 | S31600 | WN, SO, Blind, SW, Threaded, LJ | ≤ 0.08 | ≤ 2.00 | ≤ 1.00 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — | — | — |
| 316L | S31603 | WN, SO, Blind, SW, Threaded, LJ | ≤ 0.03 | ≤ 2.00 | ≤ 1.00 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — | — | — |
| 316H | S31609 | WN, SO, Blind (high-temp service) | 0.04–0.10 | ≤ 2.00 | ≤ 1.00 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — | — | — |
| 316Ti | S31635 | WN, SO, Blind | ≤ 0.08 | ≤ 2.00 | ≤ 1.00 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — | Ti: 5×C to 0.70 | — |
| 317 | S31700 | WN, SO, Blind | ≤ 0.08 | ≤ 2.00 | ≤ 1.00 | 18.0–20.0 | 11.0–15.0 | 3.0–4.0 | — | — | — |
| 317L | S31703 | WN, SO, Blind | ≤ 0.03 | ≤ 2.00 | ≤ 1.00 | 18.0–20.0 | 11.0–15.0 | 3.0–4.0 | — | — | — |
| 321 | S32100 | WN, SO, Blind | ≤ 0.08 | ≤ 2.00 | ≤ 1.00 | 17.0–19.0 | 9.0–12.0 | — | — | Ti: 5×C to 0.70 | — |
| 321H | S32109 | WN, SO, Blind (high-temp) | 0.04–0.10 | ≤ 2.00 | ≤ 1.00 | 17.0–19.0 | 9.0–12.0 | — | — | Ti: 4×C to 0.70 | — |
| 347 | S34700 | WN, SO, Blind | ≤ 0.08 | ≤ 2.00 | ≤ 1.00 | 17.0–19.0 | 9.0–13.0 | — | — | Nb+Ta: 10×C to 1.00 | — |
| 347H | S34709 | WN, SO, Blind (high-temp) | 0.04–0.10 | ≤ 2.00 | ≤ 1.00 | 17.0–19.0 | 9.0–13.0 | — | — | Nb+Ta: 8×C to 1.00 | — |
| 409L (Ferritic) | S40900 / S40910 (common) | SO, WN, Blind (heat/auto exhaust service) | ≤ 0.03 | ≤ 1.00 | ≤ 1.00 | 10.5–11.7 | ≤ 0.50 | — | — | Ti stabilized (typ.) | — |
| 410 (Martensitic) | S41000 | WN, SO, Blind | ≤ 0.15 | ≤ 1.00 | ≤ 1.00 | 11.5–13.5 | ≤ 0.75 | — | — | — | — |
| 410S (Ferritic/Martensitic family) | S41008 | WN, SO, Blind | ≤ 0.08 | ≤ 1.00 | ≤ 1.00 | 11.5–13.5 | ≤ 0.60 | — | — | — | — |
| 420 (Martensitic) | S42000 | WN, SO, Blind | 0.15–0.40 | ≤ 1.00 | ≤ 1.00 | 12.0–14.0 | ≤ 1.00 | — | — | — | — |
| 429 (Ferritic) | S42900 | SO, WN, Blind | ≤ 0.12 | ≤ 1.00 | ≤ 1.00 | 14.0–16.0 | ≤ 0.50 | — | — | — | — |
| 430 (Ferritic) | S43000 | SO, WN, Blind | ≤ 0.12 | ≤ 1.00 | ≤ 1.00 | 16.0–18.0 | ≤ 0.75 | — | — | — | — |
| 430Ti (Ferritic stabilized) | S43932 / 430Ti family | SO, WN, Blind | ≤ 0.03 | ≤ 1.00 | ≤ 1.00 | 17.0–19.0 | ≤ 0.50 | — | — | Ti stabilized | — |
| 439 (Ferritic stabilized) | S43035 (common family) | SO, WN, Blind | ≤ 0.03 | ≤ 1.00 | ≤ 1.00 | 17.0–19.0 | ≤ 0.50 | — | — | Ti/Nb stabilized | — |
| 441 (Ferritic stabilized) | S44100 | SO, WN, Blind | ≤ 0.03 | ≤ 1.00 | ≤ 1.00 | 17.5–18.5 | ≤ 0.50 | — | — | Nb/Ti stabilized | — |
| 444 (Ferritic + Mo) | S44400 | SO, WN, Blind | ≤ 0.025 | ≤ 1.00 | ≤ 1.00 | 17.5–19.5 | ≤ 1.00 | 1.75–2.50 | — | Nb/Ti stabilized | — |
| S31803 (Duplex 2205) | S31803 (EN 1.4462 family) | WN, SO, Blind, LJ (chloride / marine) | ≤ 0.03 | ≤ 2.00 | ≤ 1.00 | 21.0–23.0 | 4.5–6.5 | 2.5–3.5 | 0.08–0.20 | — | — |
| Note (read this): The compositions above are typical industry ranges for quick reference and website use. Actual certified limits depend on the exact standard (ASTM A182/A240/EN) and heat. “J4/J7” are market grades and can vary by producer—do not treat them like a guaranteed UNS chemistry unless you control the melt specification. | |||||||||||
UNS Codes & Grades
| Grade (SS) | UNS Code | EN / DIN (Common Equivalent) | JIS (Common Equivalent) | Typical Stainless Family | Common Flange Types Available | Typical Usage / Notes |
|---|---|---|---|---|---|---|
| J4 | — (Market Grade) | — | — | 200-Series (Market Variant) | Slip-On (SO), Weld Neck (WN), Blind (BL), Threaded (TH), Socket Weld (SW) | Cost-focused utility applications; chemistry varies by mill—specify carefully. |
| J7 | — (Market Grade) | — | — | 200-Series (Market Variant) | Slip-On (SO), Weld Neck (WN), Blind (BL), Threaded (TH), Socket Weld (SW) | Higher Ni than J4 typically; still mill-dependent, not a fixed standard grade. |
| 201 | S20100 | 1.4372 (commonly referenced) | SUS201 | Austenitic (200 Series) | SO, WN, BL, TH, SW | General corrosion resistance; economical alternative to 304 where suitable. |
| 202 | S20200 | 1.4373 / 1.4371 (commonly referenced) | SUS202 | Austenitic (200 Series) | SO, WN, BL, TH, SW | Better strength than 201; used where moderate corrosion resistance is acceptable. |
| 301 | S30100 | 1.4310 | SUS301 | Austenitic | SO, WN, BL, Lap Joint (LJ) | High work-hardening; often used in formed parts more than heavy piping flanges. |
| 302 | S30200 | 1.4319 (often cross-referenced) | SUS302 | Austenitic | SO, WN, BL, LJ | Similar to 304 family; used in general corrosion-confirmed environments. |
| 304 | S30400 | 1.4301 | SUS304 | Austenitic | WN, SO, BL, TH, SW, LJ | Most common general-purpose stainless flange grade. |
| 304L | S30403 | 1.4307 | SUS304L | Austenitic (Low Carbon) | WN, SO, BL, TH, SW, LJ | Preferred for welded systems to reduce sensitization risk. |
| 304H | S30409 | 1.4948 (commonly referenced) | — | Austenitic (High Carbon) | WN, SO, BL | High-temperature service; specify standard carefully. |
| 305 | S30500 | 1.4303 | SUS305 | Austenitic | SO, WN, BL | Enhanced formability; less common for flanges versus 304/316. |
| 308 | — (Weld Consumable Family) | — | — | Austenitic (Filler Designation) | — | Primarily a welding consumable designation (308/308L), not a base flange grade. |
| 309 | S30900 | 1.4828 | SUS309 | Austenitic (Heat Resistant) | WN, SO, BL | High-temp oxidation resistance; furnace & hot gas lines. |
| 309S | S30908 | 1.4833 | SUS309S | Austenitic (Heat Resistant) | WN, SO, BL | Low carbon version of 309 for improved weldability. |
| 310 | S31000 | 1.4845 | SUS310 | Austenitic (High Temp) | WN, SO, BL | Excellent high-temperature oxidation resistance. |
| 310S | S31008 | 1.4845 (commonly referenced) | SUS310S | Austenitic (High Temp) | WN, SO, BL | Lower carbon version for weldability in high-temp services. |
| 316 | S31600 | 1.4401 | SUS316 | Austenitic (Mo-Bearing) | WN, SO, BL, TH, SW, LJ | Improved pitting resistance vs 304; chemical/marine service. |
| 316L | S31603 | 1.4404 / 1.4435 | SUS316L | Austenitic (Mo + Low C) | WN, SO, BL, TH, SW, LJ | Most demanded for welded piping in chloride environments. |
| 316H | S31609 | 1.4919 (commonly referenced) | — | Austenitic (Mo + High C) | WN, SO, BL | High-temperature strength variant; specify per project standard. |
| 316Ti | S31635 | 1.4571 | SUS316Ti | Austenitic (Stabilized) | WN, SO, BL | Titanium-stabilized for elevated temperature and welding performance. |
| 317 | S31700 | 1.4449 (commonly referenced) | — | Austenitic (Higher Mo) | WN, SO, BL | Higher corrosion resistance; often specified for aggressive chemicals. |
| 317L | S31703 | 1.4438 / 1.4449 (commonly referenced) | — | Austenitic (Higher Mo + Low C) | WN, SO, BL | Weld-friendly option for severe corrosion services. |
| 321 | S32100 | 1.4541 | SUS321 | Austenitic (Ti Stabilized) | WN, SO, BL | Good for high-temperature and welded systems; resists sensitization. |
| 321H | S32109 | 1.4878 (commonly referenced) | — | Austenitic (Ti Stabilized + High C) | WN, SO, BL | High-temperature strength variant; specify exact standard. |
| 347 | S34700 | 1.4550 | SUS347 | Austenitic (Nb Stabilized) | WN, SO, BL | Excellent for high-temp welded piping; common in refineries. |
| 347H | S34709 | 1.4961 (commonly referenced) | — | Austenitic (Nb Stabilized + High C) | WN, SO, BL | High-temperature strength variant used in critical services. |
| 409L | S40900 / S40910 (common) | 1.4512 (commonly referenced) | SUS409L | Ferritic | SO, WN, BL | Used in heat / exhaust applications; limited corrosion resistance vs 304. |
| 410 | S41000 | 1.4006 | SUS410 | Martensitic | WN, SO, BL | Hardenable; wear resistance; corrosion resistance lower than austenitic. |
| 410S | S41008 | 1.4000 / 1.4003 (commonly referenced) | SUS410S | Ferritic / Low-C Martensitic | WN, SO, BL | Better weldability than 410 due to lower carbon. |
| 420 | S42000 | 1.4021 / 1.4028 (family) | SUS420 | Martensitic | WN, SO, BL | High hardness; used where strength/wear matters more than corrosion. |
| 429 | S42900 | — | — | Ferritic | SO, WN, BL | Ferritic grade with improved corrosion vs lower-Cr ferritics. |
| 430 | S43000 | 1.4016 | SUS430 | Ferritic | SO, WN, BL | Used in architectural/utility; not preferred for marine/chlorides. |
| 430Ti | — (Often sold under 439 family) | 1.4510 (commonly for 439) | — | Ferritic (Stabilized) | SO, WN, BL | Stabilized ferritic; check exact spec (often mapped to 439). |
| 439 | S43035 | 1.4510 | SUS439 | Ferritic (Stabilized) | SO, WN, BL | Improved corrosion vs 430; good for heat & mild corrosion service. |
| 441 | S44100 | 1.4509 | — | Ferritic (Stabilized) | SO, WN, BL | Used in heat exchangers & exhaust; good oxidation resistance. |
| 444 | S44400 | 1.4521 | — | Ferritic (Mo-Bearing) | SO, WN, BL | High pitting resistance among ferritics; used in water/chloride exposure. |
| S31803 (Duplex 2205) | S31803 | 1.4462 | — | Duplex | WN, SO, BL, LJ | Excellent chloride SCC resistance; marine & chemical processing. |
| Reality check: “J4 / J7” are not official UNS grades. If you sell flanges as J4/J7, you must state “market grade” and offer MTC for chemistry. Also, 308 is typically a welding filler designation, not a standard flange base material grade. | ||||||
Mechanical, Physical & Fabrication Properties
| Grade | Family | Typical Flange Types | Mechanical (Typical) | Physical (Typical) | Fabrication / Welding Notes | Service Notes (Practical) |
|---|---|---|---|---|---|---|
| J4 | 200-Series (Market Grade) | SO, WN, BL, TH, SW | Strength varies by mill (MTC required); generally moderate yield with good ductility. | Density ~7.75–7.85 g/cm³ (varies); magnetic: low/variable; thermal expansion similar to 200-series. | Weldable but chemistry varies; control heat input; use proper filler; avoid overheating (sensitization risk). | Cost-driven; not for aggressive chlorides/marine. Treat as “variable grade” unless certified. |
| J7 | 200-Series (Market Grade) | SO, WN, BL, TH, SW | Typically better than J4 but still mill-dependent; verify with MTC. | Density ~7.75–7.90 g/cm³ (varies); magnetic: low/variable. | Weldable; insist on MTC + PMI for critical jobs; passivation recommended after fabrication. | Utility use; specify corrosion environment clearly (avoid seawater/chlorides). |
| 201 | Austenitic (200) | SO, WN, BL, TH, SW, LJ | Good strength, good ductility; lower corrosion resistance than 304 in many environments. | Density ~7.80 g/cm³; magnetic: low (can increase after cold work). | Good formability; weldable; use controlled heat input; pickling/passivation improves corrosion performance. | Indoor/low-chloride service; not ideal for coastal/chemical exposure. |
| 202 | Austenitic (200) | SO, WN, BL, TH, SW, LJ | Strength slightly higher than 201; ductility good. | Density ~7.80 g/cm³; magnetic: low/variable after forming. | Weldable; avoid long dwell in sensitization range; passivation recommended. | General service; not preferred for chloride-rich environments. |
| 301 | Austenitic (300) | SO, WN, BL, LJ | High work-hardening; can achieve high strength after cold work; ductility moderate. | Density ~7.93 g/cm³; magnetic: can become higher after cold work. | Excellent forming; welding is okay but not the most common piping-flange choice vs 304/316. | Used where strength/forming matters; less common for corrosive piping flanges. |
| 302 | Austenitic (300) | SO, WN, BL, LJ | Similar to 304-family; good toughness & ductility. | Density ~7.93 g/cm³; magnetic low. | Good weldability; general fabrication ease. | General-purpose; often substituted by 304 in piping. |
| 304 | Austenitic (300) | WN, SO, BL, TH, SW, LJ | Balanced strength & ductility; excellent toughness. | Density ~7.93 g/cm³; magnetic low; good oxidation resistance. | Excellent fabrication/welding; for thicker sections manage heat input; passivation recommended. | Best for general service; avoid stagnant chlorides (pitting risk). |
| 304L | Austenitic (Low C) | WN, SO, BL, TH, SW, LJ | Similar to 304; slightly lower strength sometimes; very good ductility. | Density ~7.93 g/cm³; magnetic low. | Preferred for welded flanges/piping to reduce sensitization; good for thicker weldments. | General welded systems; still not “marine-safe” like 316 in many cases. |
| 304H | Austenitic (High C) | WN, SO, BL | Higher high-temp strength than 304/304L; good creep resistance. | Density ~7.93 g/cm³; oxidation resistance good. | Weldable, but choose matching filler and procedures; heat-service focus. | Heat exchangers, hot lines; not chosen for chlorides. |
| 305 | Austenitic (300) | SO, WN, BL | Good ductility; lower work-hardening than 304 (better deep drawing). | Density ~7.93 g/cm³; magnetic low. | Very good formability; weldability good. | Special forming grade; less common for standard flanges. |
| 308 / 308L | Welding Filler Designation | — (Used to weld 304/304L) | Not a flange base material grade; properties depend on weld metal & procedure. | — | Used as filler for 304/304L joints; pick correct filler (308L / 316L / duplex fillers as required). | List this under “Welding Consumables”, not as a “flange grade”, unless you want confusion. |
| 309 / 309S | Austenitic (Heat Resistant) | WN, SO, BL | Good high-temp strength; good toughness. | Density ~7.90–7.93 g/cm³; excellent oxidation resistance at high temps. | Weldable; 309 often used as dissimilar metal filler; control heat input. | Furnace parts, hot gas lines; not for chlorides. |
| 310 / 310S | Austenitic (High Temp) | WN, SO, BL | High-temperature strength and oxidation resistance; ductility good. | Density ~7.90 g/cm³; excellent scaling resistance. | Weldable; use correct filler; avoid contamination; good for thermal cycling. | Extreme heat service; overkill for general piping. |
| 316 | Austenitic (Mo Bearing) | WN, SO, BL, TH, SW, LJ | Good strength + ductility; better pitting resistance than 304. | Density ~7.98 g/cm³; magnetic low. | Excellent weldability; passivation recommended; avoid crevice designs in chlorides. | Chemical/marine splash zones; for seawater immersion duplex is usually safer. |
| 316L | Austenitic (Mo + Low C) | WN, SO, BL, TH, SW, LJ | Similar to 316; preferred for weldments. | Density ~7.98 g/cm³; magnetic low. | Best pick for welded process piping in many industries; good fabrication. | Chlorides: better than 304, but still can pit/crevice in harsh seawater. |
| 316H | Austenitic (Mo + High C) | WN, SO, BL | Improved high-temp strength vs 316L. | Density ~7.98 g/cm³. | Weldable with appropriate procedure; heat-service focus. | High-temp lines; specify for creep/strength requirements. |
| 316Ti | Austenitic (Stabilized) | WN, SO, BL | Good high-temp properties; good toughness. | Density ~7.95–8.00 g/cm³. | Stabilized against sensitization; weldable; good for elevated temperature service. | Heat + corrosion service; common in European specifications. |
| 317 / 317L | Austenitic (Higher Mo) | WN, SO, BL | Similar ductility to 316; stronger corrosion resistance in some acids/chlorides. | Density ~7.98 g/cm³. | Weldable; choose filler carefully; passivation recommended. | Used when 316 is marginal; cost higher and availability lower. |
| 321 / 321H | Austenitic (Ti Stabilized) | WN, SO, BL | Good strength at elevated temperature; good toughness. | Density ~7.90–7.93 g/cm³. | Good weldability; stabilized to resist sensitization; 321H for higher temp strength. | Hot exhaust/steam lines; not a “chloride winner”. |
| 347 / 347H | Austenitic (Nb Stabilized) | WN, SO, BL | Excellent creep/high-temp performance; good ductility. | Density ~7.90–7.93 g/cm³. | Weldable; strong choice for high-temp welded piping; 347H for higher temp strength. | Refineries/power plants; high-temp service. |
| 409L | Ferritic | SO, WN, BL | Moderate strength; lower toughness at low temps vs austenitic. | Density ~7.70 g/cm³; magnetic: high; thermal conductivity higher than austenitic. | Good for heat applications; weldable; watch grain growth; stabilize with correct filler if required. | Automotive/exhaust & heat service; not for strong corrosion. |
| 410 | Martensitic (Hardenable) | WN, SO, BL | High strength/hardness after heat treat; ductility lower than austenitic. | Density ~7.75 g/cm³; magnetic: high. | Welding needs control/preheat depending on condition; risk of cracking if mishandled. | Wear/strength applications; corrosion resistance limited. |
| 410S | Low-C Martensitic / Ferritic | WN, SO, BL | Lower hardness than 410; better weldability. | Density ~7.75 g/cm³; magnetic high. | More weld-friendly than 410; still manage heat input. | Heat service & mild corrosion. |
| 420 | Martensitic (Hardenable) | WN, SO, BL | Very high hardness potential; ductility lower. | Density ~7.75 g/cm³; magnetic high. | Weldability is challenging; requires correct procedures. | Wear parts; not common for process flanges. |
| 429 | Ferritic | SO, WN, BL | Moderate strength; fair toughness. | Density ~7.70 g/cm³; magnetic high. | Good formability and weldability typical of ferritics; keep heat input controlled. | Utility and mild corrosion/heat service. |
| 430 | Ferritic | SO, WN, BL | Moderate strength; good formability. | Density ~7.70 g/cm³; magnetic high. | Weldable but heat-affected zone can lose corrosion resistance; passivation helps. | Architectural/utility; avoid marine/chlorides. |
| 430Ti / 439 | Ferritic (Stabilized) | SO, WN, BL | Better high-temp stability than 430; strength moderate. | Density ~7.70 g/cm³; magnetic high. | Stabilized to improve weldability/HAZ behavior; good for heat applications. | Heat exchangers/exhaust; better than 430 for weldments. |
| 441 | Ferritic (Stabilized) | SO, WN, BL | Moderate strength; good oxidation resistance. | Density ~7.70 g/cm³; magnetic high. | Good weldability; avoid excessive heat input to limit grain growth. | High-temp exhaust/heat applications. |
| 444 | Ferritic (Mo Bearing) | SO, WN, BL | Moderate strength; better pitting resistance than 430/439. | Density ~7.70–7.75 g/cm³; magnetic high. | Weldable; use clean procedures; passivation recommended. | Water/chloride exposure where ferritic is preferred; still evaluate crevice conditions. |
| S31803 (Duplex 2205) | Duplex | WN, SO, BL, LJ | High yield strength (typically ~2× austenitic); good toughness when properly heat treated. | Density ~7.80 g/cm³; magnetic: moderate; lower thermal expansion than austenitic. | Welding needs qualified procedure (heat input/interpass control); use duplex filler; avoid overheat & excessive ferrite. | Best for chloride SCC resistance; marine/chemical duty; do PMI + MTC mandatory. |
| No-nonsense warning: If you publish this page, don’t pretend every grade performs the same. Flange performance depends on product form (forged vs plate-cut), heat treatment, and compliance standard (ASTM A182 / A240 / A276 / EN 10222 etc.). For J4/J7 and for any critical service, you must show “MTC required” and ideally offer PMI testing. | ||||||
Common Names & International Identifiers
| Grade | Family | Common / Trade Names | International Identifiers (Typical) | Common Stainless Steel Flange Types | Reality Check |
|---|---|---|---|---|---|
| J4 | 200-series (Market Grade) | J4 SS, Economy Stainless | Not a formal ASTM/EN grade; chemistry varies by mill (MTC-driven) | Slip-On (SO), Weld Neck (WN), Blind (BL), Threaded (TH), Socket Weld (SW) | Only safe to sell with MTC/PMI. Don’t present it as “equivalent to 304”. |
| J7 | 200-series (Market Grade) | J7 SS, Utility Stainless | Not a formal ASTM/EN grade; chemistry varies by mill (MTC-driven) | SO, WN, BL, TH, SW | Same as J4—market naming. If customer is serious, push 304/316 instead. |
| 201 | Austenitic (200) | AISI 201 | UNS S20100 | EN 1.4372 | JIS SUS201 | SO, WN, BL, TH, SW, Lap Joint (LJ) | Lower corrosion resistance than 304; fine for low-chloride environments. |
| 202 | Austenitic (200) | AISI 202 | UNS S20200 | EN 1.4373 (commonly referenced) | JIS SUS202 | SO, WN, BL, TH, SW, LJ | Often used as cost alternative; verify chemistry for welded/critical service. |
| 301 | Austenitic (300) | AISI 301 | UNS S30100 | EN 1.4310 | JIS SUS301 | SO, WN, BL, LJ | More common in sheets/strip than flanges; available on request. |
| 302 | Austenitic (300) | AISI 302 | UNS S30200 | EN family often referenced near 1.4310 (301/302) | JIS SUS302 | SO, WN, BL, LJ | Commonly substituted by 304 for piping/flanges. |
| 304 | Austenitic (300) | 18/8 Stainless, AISI 304 | UNS S30400 | EN 1.4301 | JIS SUS304 | SO, WN, BL, TH, SW, LJ | General purpose; pitting risk in chlorides—don’t oversell “marine”. |
| 304L | Austenitic (Low C) | AISI 304L | UNS S30403 | EN 1.4307 | JIS SUS304L | SO, WN, BL, TH, SW, LJ | Preferred for welded fabrication. |
| 304H | Austenitic (High C) | AISI 304H | UNS S30409 | EN 1.4948 | WN, SO, BL | High-temp service grade; specify when creep strength matters. |
| 305 | Austenitic (300) | AISI 305 | UNS S30500 | EN 1.4303 (commonly referenced) | SO, WN, BL | Less common for flanges; usually special demand. |
| 308 | Welding Consumable (Not Base Grade) | ER308 / E308 (Weld Filler) | AWS filler designation (not a flange base material grade) | — | Technically not a “flange grade”. Keep only if you label it as welding filler. |
| 309 | Austenitic (Heat Resistant) | AISI 309 | UNS S30900 | EN 1.4828 | JIS SUS309 | WN, SO, BL | High-temp oxidation service. |
| 309S | Austenitic (Low C) | AISI 309S | UNS S30908 | EN 1.4833 | JIS SUS309S | WN, SO, BL | Better weldability vs 309 for heat service. |
| 310 | Austenitic (High Temp) | AISI 310 | UNS S31000 | EN 1.4845 | JIS SUS310 | WN, SO, BL | Very high temperature oxidation resistance. |
| 310S | Austenitic (Low C) | AISI 310S | UNS S31008 | EN 1.4845 | JIS SUS310S | WN, SO, BL | Most common 310 family grade for welded heat service. |
| 316 | Austenitic (Mo) | Marine Grade (common term), AISI 316 | UNS S31600 | EN 1.4401 | JIS SUS316 | SO, WN, BL, TH, SW, LJ | Better chloride resistance than 304; not “seawater-proof”. |
| 316L | Austenitic (Mo + Low C) | Marine Grade (common term), AISI 316L | UNS S31603 | EN 1.4404 | JIS SUS316L | SO, WN, BL, TH, SW, LJ | Most specified for welded chemical/process services. |
| 316H | Austenitic (Mo + High C) | AISI 316H | UNS S31609 | EN 1.4919 (commonly referenced) | WN, SO, BL | Heat-service version of 316. |
| 316Ti | Austenitic (Stabilized) | AISI 316Ti | UNS S31635 | EN 1.4571 | JIS SUS316Ti | WN, SO, BL | Common in EN specs for welded/high-temp duty. |
| 317 | Austenitic (Higher Mo) | AISI 317 | UNS S31700 | EN 1.4449 (commonly referenced) | WN, SO, BL | Used where 316 is borderline; confirm availability. |
| 317L | Austenitic (Higher Mo + Low C) | AISI 317L | UNS S31703 | EN 1.4438 / 1.4449 (spec-dependent) | WN, SO, BL | Weld-friendly 317 family; verify EN ID on MTC. |
| 321 | Austenitic (Ti Stabilized) | AISI 321 | UNS S32100 | EN 1.4541 | JIS SUS321 | WN, SO, BL | Good for hot welded lines; stabilized against sensitization. |
| 321H | Austenitic (High C, Stabilized) | AISI 321H | UNS S32109 | EN 1.4878 | WN, SO, BL | Used for heat service requiring higher strength. |
| 347 | Austenitic (Nb Stabilized) | AISI 347 | UNS S34700 | EN 1.4550 | JIS SUS347 | WN, SO, BL | Excellent for welded high-temp service (refineries/power). |
| 347H | Austenitic (High C, Nb Stabilized) | AISI 347H | UNS S34709 | EN 1.4961 | WN, SO, BL | Higher temp strength vs 347. |
| 409L | Ferritic | AISI 409L | UNS S40900 (commonly referenced) | EN family near 1.4512 (MTC-based) | SO, WN, BL | Heat/oxidation service; not for aggressive corrosion. |
| 410 | Martensitic | AISI 410 | UNS S41000 | EN 1.4006 | JIS SUS410 | SO, WN, BL | Strength/wear; welding procedure control needed. |
| 410S | Low-C 410 Type | AISI 410S | UNS S41008 | EN 1.4000 (commonly referenced) | JIS SUS410S | SO, WN, BL | Better weldability than 410. |
| 420 | Martensitic | AISI 420 | UNS S42000 | EN 1.4021 / 1.4034 (condition-dependent) | JIS SUS420 | SO, WN, BL | Hardenable; uncommon as standard flange unless application demands it. |
| 429 | Ferritic | AISI 429 | UNS S42900 | EN equivalent varies by chemistry (MTC-based) | SO, WN, BL | Utility ferritic grade; confirm corrosion expectations. |
| 430 | Ferritic | AISI 430 | UNS S43000 | EN 1.4016 | JIS SUS430 | SO, WN, BL | Architectural/utility; avoid chloride splash zones. |
| 430Ti | Ferritic (Stabilized) | 430Ti | EN commonly referenced near 1.4520 / equivalents vary by standard (MTC-based) | SO, WN, BL | Stabilized ferritic; verify exact EN/UNS on MTC. |
| 439 | Ferritic (Stabilized) | AISI 439 | UNS S43035 | EN 1.4510 | SO, WN, BL | Improved weld/HAZ behavior vs 430. |
| 441 | Ferritic (Stabilized) | AISI 441 | UNS S44100 | EN 1.4509 | SO, WN, BL | Good oxidation resistance; often used in heat duty. |
| 444 | Ferritic (Mo Bearing) | AISI 444 | UNS S44400 | EN 1.4521 | SO, WN, BL | Better pitting resistance than 430/439; still evaluate crevice conditions. |
| S31803 (Duplex) | Duplex (2205 family) | Duplex 2205 (market name) | UNS S31803 / S32205 | EN 1.4462 | Weld Neck (WN), Slip-On (SO), Blind (BL), Lap Joint (LJ) | Excellent SCC resistance; welding must be procedure-controlled (no shortcuts). |
|
Legend (Flange Types):
SO = Slip-On, WN = Weld Neck, BL = Blind, TH = Threaded, SW = Socket Weld, LJ = Lap Joint,
RTJ = Ring Type Joint, LWN = Long Weld Neck, Orifice Flange = Metering/Flow flange.
Note: Grade-to-equivalent mapping can be spec dependent. For critical orders, publish identifiers only where you can supply matching MTC/PMI. |
|||||
Standards & International Equivalents
| Grade / Family | Primary Material Standards (Flange / Forgings) | Common Pipe / Tube / Fitting Standards Used With | International Equivalents (Typical) | Common Stainless Steel Flange Types | Notes (What to Specify) |
|---|---|---|---|---|---|
| J4 / J7 (Market 200-series) | Not formally covered under ASTM A182/A240 as “J4/J7”. Supply against customer chemistry + MTC/PMI. | Project-driven (often matched to 304/201 piping standards, but ONLY if chemistry matches) | No fixed EN/UNS. Must be declared on MTC as actual chemistry. | SO, WN, BL, TH, SW, LJ | Don’t claim equivalence. Quote by chemistry + mechanicals + test certificate. |
| 201 / 202 (Austenitic 200) | ASTM A182 (if supplied as forged flanges) + ASTM A240/A480 (if plate flanges) + ASTM A276 (bars) | ASTM A312 (pipe) | ASTM A403 (fittings) | ASTM A193/A194 (bolting) | 201: UNS S20100 | EN 1.4372 | JIS SUS201 202: UNS S20200 | EN commonly referenced 1.4373 | JIS SUS202 |
SO, WN, BL, TH, SW, LJ | Specify corrosion environment (chlorides). Prefer 304/316 for marine/chemical. |
| 301 / 302 (Austenitic 300) | ASTM A182 (forged) / ASTM A240 (plate) / ASTM A276 (bars) | ASTM A312 | ASTM A403 | ASTM A193/A194 | 301: UNS S30100 | EN 1.4310 | JIS SUS301 302: UNS S30200 | closest EN family near 1.4310 (MTC-based) |
SO, WN, BL, LJ | Less common for flanges; confirm availability and test cert. |
| 304 / 304L / 304H | ASTM A182 (F304/F304L/F304H) | ASTM A240 (plate flanges) | ASME B16.5 / B16.47 (dimensions) | ASTM A312 (TP304/TP304L/TP304H) | ASTM A403 (WP304/WP304L) | ASTM A193 B8/B8M | ASTM A194 8/8M | 304: UNS S30400 | EN 1.4301 | JIS SUS304 304L: UNS S30403 | EN 1.4307 | JIS SUS304L 304H: UNS S30409 | EN 1.4948 |
SO, WN, BL, TH, SW, LJ, RTJ | Always specify pressure class (150/300/600/900/1500/2500) + facing (RF/FF/RTJ). |
| 305 (Austenitic 300) | ASTM A182 / ASTM A240 (where available) | ASME B16.5/B16.47 dimensions | ASTM A312 | ASTM A403 | UNS S30500 | EN 1.4303 (commonly referenced) | SO, WN, BL | Special demand grade; confirm forging availability before listing as stock. |
| 308 (Welding Filler, not flange base) | AWS A5.9 (ER308) / AWS A5.4 (E308) | Used to weld 304/304L systems | Filler designation (not EN/UNS for base metal) | — | Do not show as flange material grade. Keep only under welding consumables. |
| 309 / 309S (Heat Resistant) | ASTM A182 (forgings where applicable) | ASTM A240 (plate) | ASME B16.5/B16.47 | ASTM A312 | ASTM A403 | 309: UNS S30900 | EN 1.4828 | JIS SUS309 309S: UNS S30908 | EN 1.4833 | JIS SUS309S |
WN, SO, BL, RTJ | Specify operating temperature + oxidation environment. |
| 310 / 310S (High Temp) | ASTM A182 / ASTM A240 | ASME B16.5/B16.47 | ASTM A312 | ASTM A403 | 310: UNS S31000 | EN 1.4845 | JIS SUS310 310S: UNS S31008 | EN 1.4845 | JIS SUS310S |
WN, SO, BL, RTJ | High-temp grade; confirm fabrication method (forged vs plate cut). |
| 316 / 316L / 316H / 316Ti | ASTM A182 (F316/F316L/F316H/F316Ti*) | ASTM A240 | ASME B16.5/B16.47 | ASTM A312 (TP316/TP316L/TP316H/TP316Ti) | ASTM A403 (WP316/WP316L) | ASTM A193 B8M | ASTM A194 8M | 316: UNS S31600 | EN 1.4401 | JIS SUS316 316L: UNS S31603 | EN 1.4404 | JIS SUS316L 316H: UNS S31609 | EN often referenced 1.4919 316Ti: UNS S31635 | EN 1.4571 | JIS SUS316Ti |
SO, WN, BL, TH, SW, LJ, RTJ | *316Ti equivalence depends on spec route; verify MTC. For seawater: consider duplex/Cu-Ni instead. |
| 317 / 317L | ASTM A182 / ASTM A240 | ASME B16.5/B16.47 | ASTM A312 | ASTM A403 | 317: UNS S31700 | EN 1.4449 (commonly referenced) 317L: UNS S31703 | EN 1.4438 / 1.4449 (spec dependent) |
WN, SO, BL, RTJ | Confirm availability—317 flanges are often made-to-order. |
| 321 / 321H (Stabilized) | ASTM A182 (F321/F321H) | ASTM A240 | ASME B16.5/B16.47 | ASTM A312 (TP321/TP321H) | ASTM A403 (WP321) | 321: UNS S32100 | EN 1.4541 | JIS SUS321 321H: UNS S32109 | EN 1.4878 |
WN, SO, BL, RTJ | Good for hot welded lines; specify temp + weld procedure requirement. |
| 347 / 347H (Stabilized) | ASTM A182 (F347/F347H) | ASTM A240 | ASME B16.5/B16.47 | ASTM A312 (TP347/TP347H) | ASTM A403 (WP347) | 347: UNS S34700 | EN 1.4550 | JIS SUS347 347H: UNS S34709 | EN 1.4961 |
WN, SO, BL, RTJ | Refinery/power favorite; specify design temperature and NDE if critical. |
| 409L (Ferritic) | ASTM A182 (where applicable) / ASTM A240 (plate) | ASME B16.5/B16.47 | ASTM A268 (ferritic tubes) | ASTM A240 sheets/plate | UNS S40900 (commonly referenced) | EN equivalent varies (MTC-based) | SO, WN, BL | Primarily heat/oxidation service; not for aggressive corrosion duty. |
| 410 / 410S / 420 (Martensitic) | ASTM A182 (forgings as applicable) / ASTM A240 (plate) | ASME B16.5/B16.47 | ASTM A268 / A276 (bars) | project-driven | 410: UNS S41000 | EN 1.4006 | JIS SUS410 410S: UNS S41008 | JIS SUS410S 420: UNS S42000 | EN 1.4021/1.4034 (condition dependent) |
SO, WN, BL | Specify heat treatment condition + welding procedure (preheat/PWHT as needed). |
| 429 / 430 / 430Ti / 439 / 441 / 444 (Ferritic) | ASTM A182 / ASTM A240 (route depends on forging vs plate) | ASME B16.5/B16.47 | ASTM A268 (ferritic tubes) | ASTM A240 sheets/plate | 430: UNS S43000 | EN 1.4016 | JIS SUS430 439: UNS S43035 | EN 1.4510 441: UNS S44100 | EN 1.4509 444: UNS S44400 | EN 1.4521 429/430Ti: equivalents vary by standard (confirm on MTC) |
SO, WN, BL | Ferritic equivalence is chemistry-sensitive. Don’t publish fixed EN unless you can certify it. |
| S31803 (Duplex 2205 family) | ASTM A182 (F51) / ASTM A240 | ASME B16.5/B16.47 | ASTM A790 (duplex pipe) | ASTM A182 (forgings) | ASTM A815 (duplex fittings) | UNS S31803 / S32205 | EN 1.4462 | WN, SO, BL, LJ, RTJ | Specify duplex grade (F51/F60), ferrite control, and welding/NDE requirements. |
| Dimensional & Rating Standards (All Grades) |
ASME B16.5 (NPS 1/2"–24") ASME B16.47 Series A/B (NPS 26"–60") MSS SP-44 (large OD steel flanges, common in industry) |
ASME B31.1 / B31.3 (piping codes, project dependent) EN 1092-1 (flange dimensions & PN rating – European systems) |
ASME Class 150/300/600/900/1500/2500 (pressure classes) EN PN 6/10/16/25/40/63/100 (PN ratings) |
RF, FF, RTJ, Tongue & Groove, Male/Female | Always mention: size (NPS/DN), class/PN, facing, schedule/end prep, and surface finish. |
| Common Flange Types (All Grades) | Weld Neck (WN), Slip-On (SO), Blind (BL), Socket Weld (SW), Threaded (TH), Lap Joint (LJ), Long Weld Neck (LWN), Orifice Flange, Spectacle Blind, Ring Type Joint (RTJ) | Pick types based on pressure, cyclic load, temperature, and maintenance needs. | |||
Applications
| Application / Industry | Why Stainless Steel Flanges | Recommended Grades (Examples) | Common Flange Types Used | Typical Facing / Notes |
|---|---|---|---|---|
| Water Supply, Plumbing & Utilities | Leak-tight joints, corrosion resistance, easy maintenance | 304/304L, 316/316L (better for chlorides), 201/202 (light duty, non-aggressive) | SO, TH, BL | RF/FF depending on gasket system; avoid 201/202 in high-chloride water. |
| HVAC, Chilled Water & Fire Fighting Lines | Clean service, corrosion control, long life | 304/304L, 316/316L; 409L (where heat/oxidation dominates and corrosion is mild) | SO, WN, BL | RF common; specify pressure class and gasket type. |
| Chemical Process & Petrochemical Plants | Chemical compatibility, process safety, code compliance | 316/316L, 317/317L, 321/347 (hot service), Duplex S31803 (chlorides) | WN, BL, RTJ (critical), SO (utility) | RTJ for high pressure/critical duties; confirm NACE/PMI if required. |
| Refineries, Power Plants & High-Temperature Piping | High-temp strength, oxidation resistance, weld integrity | 304H, 316H, 321H, 347H, 309/309S, 310/310S | WN, RTJ, BL | Specify operating temperature, creep/HT requirements, and WPS/PQR. |
| Marine, Shipbuilding & Offshore Platforms | Corrosion resistance in seawater / salt spray, durability | 316/316L (moderate), Duplex S31803 (preferred for chlorides), 304 (non-splash/indoor) | WN, LJ (maintenance), RTJ (high integrity), BL | Use duplex for aggressive chloride exposure; specify PMI + NDT. |
| Food, Dairy, Beverage & Pharmaceuticals | Hygienic joints, cleanability, corrosion resistance | 304/304L, 316/316L (sanitary/chemical cleaning) | SO, WN, LJ, BL | Surface finish requirements may apply; confirm gasket compatibility. |
| Pulp & Paper | Resistance to moisture, mild chemicals, and corrosion under insulation risk | 304/304L, 316/316L, 317/317L (more aggressive) | WN, SO, BL | For chemical bleaching lines, prefer 316/317; verify media. |
| Mining, Slurry & Abrasive Service | Strength + corrosion control; wear depends on media | Duplex S31803 (chlorides), 316/316L; 410/420 (hardness-based, specific cases) | WN, BL | For erosion, material selection must match slurry; don’t assume stainless fixes wear. |
| Oil & Gas (Upstream / Midstream / Downstream) | Pressure containment, corrosion performance, standardization | 316/316L, 321/347 (hot), Duplex S31803; 304 (non-corrosive utilities) | WN, RTJ, BL | RTJ common in high pressure; specify ASME class and NDE. |
| General Fabrication, Structural & Industrial Equipment | Availability, weldability, cost-effective performance | 304/304L, 201/202 (economy, indoor), 430/439/441 (ferritic for mild duty) | SO, BL, WN | Ferritic grades suit mild corrosion/heat; confirm welding procedure. |
| Automotive & Exhaust / Heat Systems | Heat resistance and oxidation performance | 409L, 410S, 430/439/441; 304 (higher corrosion resistance) | SO, WN, BL | Pick based on temperature cycle and road-salt exposure. |
| Valves, Pumps, Heat Exchangers & Pressure Equipment | Leak-tight sealing, compatibility with equipment metallurgy | 316/316L, 304/304L, 321/347, Duplex S31803 | WN, SO, RTJ, BL | Match flange grade to body/nozzle metallurgy; specify facing and gasket. |
| Flange Type Selection (Quick Guide) | WN: high pressure / cyclic / high temp | SO: economy + easy alignment | BL: isolation / pressure testing | TH: low pressure, no welding | SW: small bore, higher pressure | LJ: frequent dismantling, expensive alloy stub-ends | RF most common; RTJ for critical high-pressure; FF for flat-face systems (use carefully). | ||
| Important Note (Reality Check) | Grades like 308 are primarily welding filler designations and are not typically specified as flange base material. Grades like J4/J7 are market grades—use only when you can provide chemistry + MTC/PMI and avoid claiming fixed EN/UNS equivalence. | |||
Common Stainless Steel Flanges Dimensions Chart
| Flange Type | Size Range (NPS / DN) | Pressure Class / Rating | Facing | Typical Thickness / Key Dimensions Controlled By | Common Standards (Dimensional) | Common Grades (Examples) | Notes / Best Use |
|---|---|---|---|---|---|---|---|
| Weld Neck (WN) | 1/2"–24" (DN15–DN600) (larger sizes on request) |
ASME: Class 150–2500 EN: PN6–PN100 |
RF / RTJ (common) FF (by system) |
OD, Bolt Circle (BCD/PCD), Bolt Holes, Hub, Bore, Raised Face/RTJ groove | ASME B16.5 (up to 24"), ASME B16.47 (26"–60"), EN 1092-1, BS 4504 | 304/304L, 316/316L, 304H/316H, 321/347, Duplex S31803 | Best for high pressure/temperature, cyclic loads, vibration. |
| Slip On (SO) | 1/2"–24" (DN15–DN600) | ASME: Class 150–1500 EN: PN6–PN40/PN63 |
RF / FF | OD, BCD/PCD, Bolt Holes, Bore | ASME B16.5, EN 1092-1 | 304/304L, 316/316L, 201/202 (mild duty), 410/420 (special) | Economical; easy alignment. Not ideal for severe cyclic service. |
| Blind (BL) | 1/2"–24" (DN15–DN600) | ASME: Class 150–2500 EN: PN6–PN100 |
RF / RTJ / FF | OD, BCD/PCD, Bolt Holes, Thickness (critical), RF/RTJ details | ASME B16.5, EN 1092-1 | 304/304L, 316/316L, 321/347, Duplex S31803 | Line isolation, pressure testing ends. Thickness increases fast with rating. |
| Threaded (TH) | 1/2"–4" (DN15–DN100) (larger on request) |
ASME: Class 150–600 (typical) | RF / FF | OD, BCD/PCD, Bolt Holes, Thread form (NPT/BSP), RF | ASME B16.5 (where applicable), Thread: ASME B1.20.1 (NPT) / BSP as specified | 304/304L, 316/316L | No welding; used in small-bore utilities. Avoid for high vibration/leak-critical lines. |
| Socket Weld (SW) | 1/2"–3" (DN15–DN80) | ASME: Class 150–1500 (typical) | RF | OD, BCD/PCD, Bolt Holes, Socket depth, Bore | ASME B16.5 | 304/304L, 316/316L | Small bore high-pressure. Not preferred where crevice/corrosion is critical. |
| Lap Joint (LJ) | 1/2"–24" (DN15–DN600) | ASME: Class 150–900 (common) EN: PN10–PN40 |
RF (with stub end) | OD, BCD/PCD, Bolt Holes; works with Stub End (long/short pattern) | ASME B16.5, EN 1092-1 (system dependent) | Backing Flange: 304/316/duplex; Stub End: match pipe material | Frequent dismantling; rotate for easy bolt alignment. Use with stub end. |
| Facing Type | Where Used | Key Dimensional Elements | Standards Reference | Notes |
|---|---|---|---|---|
| Raised Face (RF) | Most process piping | Raised face height, gasket seating diameter, finish/serration | ASME B16.5 / B16.47 | Most common; confirm gasket type (spiral wound, ring, etc.). |
| Ring Type Joint (RTJ) | High pressure / critical service | RTJ groove dimensions (R/RX/BX), groove depth & width | ASME B16.5 / API 6A (as applicable) | Used with metallic ring gaskets; higher integrity, higher cost. |
| Flat Face (FF) | Flat-face systems (often cast iron equipment) | Flat face; full contact area, bolt loads with full-face gaskets | EN 1092-1 / system spec | Don’t mix FF and RF without understanding gasket/bolt loading risks. |
| Standard / System | Typical Size Coverage | Rating System | What It Defines (Dimensions) | Common Use |
|---|---|---|---|---|
| ASME B16.5 | 1/2"–24" | Class 150, 300, 600, 900, 1500, 2500 | Flange OD, BCD, bolt holes, thickness, hub, facing details | Most global industrial piping systems |
| ASME B16.47 (Series A / B) | 26"–60" | Class 75–900 (varies) | Large diameter flange dimensions | Large pipelines / marine / refineries |
| EN 1092-1 | DN10–DN2000 (varies by type) | PN2.5–PN400 (commonly PN6–PN100) | OD, PCD, bolt holes, thickness, facing forms (Type A/B etc.) | European / PN-based systems |
| BS 4504 (legacy) | DN10–DN2000 (legacy) | PN range | Legacy PN flange dimensions | Replacement / maintenance markets |
| Grade Family | Grades Covered (as requested) | Typical Use on Flanges | Practical Note |
|---|---|---|---|
| Austenitic | J7, J4, 201, 202, 301, 302, 304, 304L, 304H, 305, 308, 309, 309S, 310, 310S, 316, 316L, 316H, 316Ti, 317, 317L, 321, 321H, 347, 347H | General purpose, corrosion resistance, high temperature (H grades), stabilized (321/347) | Reality check: “308” is mainly a welding filler designation; avoid listing it as a flange base grade unless you can supply certified material/MTC. |
| Ferritic / Martensitic | 409L, 410, 410S, 420, 429, 430, 430Ti, 439, 441, 444 | Mild corrosion/oxidation, specific heat services, hardness-based cases (410/420) | Welding and corrosion behavior differs from austenitic—don’t treat as drop-in replacements. |
| Duplex | S31803 (Duplex) | Chloride/seawater resistance, higher strength | Often preferred in marine/chloride service vs 316; needs correct welding control. |
