SS 904L Weld Neck FlangeASTM A182 · ASME B16.5 · Manufacturer, stockist & exporter, India
Alloy 904L · UNS N08904 · WNRF
An SS 904L weld neck flange is a flange with a long tapered hub that is butt-welded to the pipe, made from SS 904L to ASTM A182 F904L. Choose a weld neck flange for high pressure, high or low temperature and cyclic loading. The tapered hub moves stress away from the flange face, and the full-penetration butt weld can be radiographed.
- ASTM A182
- ASME B16.5
- EN 10204 3.1 / 3.2
- Export packing
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is an SS 904L Weld Neck Flange?
- What it is
- A flange with a long tapered hub that is butt-welded to the pipe
- Material
- ASTM A182 F904L
- Dimensions
- ASME B16.5 · B16.47
- Grade
- SS 904L · UNS N08904
- Best at
- Dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water
SS 904L Weld Neck Flange Specification
| Product | SS 904L Weld Neck Flange |
|---|---|
| Material standard | ASTM A182 F904L |
| Dimensional standard | ASME B16.5 · B16.47 |
| Sizes | ½" – 24" (ASME B16.5) · 26" – 60" (ASME B16.47) |
| Pressure class | Class 150, 300, 400, 600, 900, 1500, 2500 · PN 6 – PN 100 |
| Facing | RF · FF · RTJ · tongue & groove |
| Bore | To match pipe schedule (state on order) |
| Testing | PMI · dimensional · NDT and IGC on request |
| Documents | EN 10204 3.1 · 3.2 with third-party inspection |
When to Choose a Weld Neck Flange
Choose a weld neck flange for high pressure, high or low temperature and cyclic loading. The tapered hub moves stress away from the flange face, and the full-penetration butt weld can be radiographed.
- Bore must match the pipe schedule — state it on the order
- Hub length and taper per ASME B16.5 / B16.47 tables
- Most common facing: raised face; RTJ for high-pressure classes
More on choosing: Weld neck flange guide.
SS 904L Weld Neck Flange: Why 904L for weld neck flanges
Choose a weld neck flange for high pressure, high or low temperature and cyclic loading. The tapered hub moves stress away from the flange face, and the full-penetration butt weld can be radiographed. In SS 904L, the choice usually comes down to the medium and temperature — the rows here are the points buyers check for this exact combination.
| Why this grade | Stainless flanges are chosen where carbon steel would rust or contaminate the process. SS 904L is picked for dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water. |
|---|---|
| Typical service | Sulphuric acid plants — Coolers, piping and tanks for dilute sulphuric acid. |
| Bolting | as the project specifies |
| Welding to carbon steel | ER309L (or E309L electrode) is the usual filler when joining it to carbon steel |
| Matching filler | ER385 (AWS A5.9) |
SS 904L Weld Neck Flange Chemical Composition
Under technical review for TDS.
| Element | Current requirement |
|---|---|
| Nickel | As specified |
| Chromium | As specified |
| Molybdenum | As specified |
| Copper | As specified |
| Carbon | As specified |
| Manganese | As specified |
| Silicon | As specified |
| Nitrogen | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification to be verified: ASTM A240 for UNS N08904.
SS 904L Weld Neck Flange Mechanical Properties
Under technical review for TDS.
| Property | Current requirement |
|---|---|
| Tensile strength | As specified |
| Yield strength 0.2% | As specified |
| Elongation | As specified |
| Hardness | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification and condition to be verified: ASTM A240 for UNS N08904 — Annealed plate & sheet.
Full chemistry, properties and equivalents are on the SS 904L grade page.
Other SS 904L flanges
SS 904L Weld Neck Flanges for export
FOB / CIF · Nhava Sheva (JNPT), MumbaiSS 904L Weld Neck Flange dimensions — ASME B16.5 Class 150 & 300
Outside diameter, thickness and bolting are set by size and class. Values in mm; thickness excludes the 1.6 mm raised face.
| NPS | Cl 150 OD | Cl 150 thickness | Cl 150 bolt circle | Cl 150 bolts | Cl 300 OD | Cl 300 thickness | Cl 300 bolt circle | Cl 300 bolts |
|---|---|---|---|---|---|---|---|---|
| ½" | 90 | 9.6 | 60.3 | 4 × ½" | 95 | 12.7 | 66.7 | 4 × ½" |
| 1" | 110 | 12.7 | 79.4 | 4 × ½" | 125 | 15.9 | 88.9 | 4 × ⅝" |
| 1½" | 125 | 15.9 | 98.4 | 4 × ½" | 155 | 19.1 | 114.3 | 4 × ¾" |
| 2" | 150 | 17.5 | 120.7 | 4 × ⅝" | 165 | 20.7 | 127.0 | 8 × ⅝" |
| 3" | 190 | 22.3 | 152.4 | 4 × ⅝" | 210 | 27.0 | 168.3 | 8 × ¾" |
| 4" | 230 | 22.3 | 190.5 | 8 × ⅝" | 255 | 30.2 | 200.0 | 8 × ¾" |
| 6" | 280 | 23.9 | 241.3 | 8 × ¾" | 320 | 35.0 | 269.9 | 12 × ¾" |
| 8" | 345 | 27.0 | 298.5 | 8 × ¾" | 380 | 39.7 | 330.2 | 12 × ⅞" |
| 10" | 405 | 28.6 | 362.0 | 12 × ⅞" | 445 | 46.1 | 387.4 | 16 × 1" |
| 12" | 485 | 30.2 | 431.8 | 12 × ⅞" | 520 | 49.3 | 450.8 | 16 × 1⅛" |
Full chart: ASME B16.5 flange dimensions.
SS 904L Weld Neck Flange — questions buyers ask
Why is the bore important on a weld neck flange?
The flange bore is machined to the inside diameter of the pipe schedule, so the weld is smooth inside. A wrong bore leaves a step that disturbs flow and complicates the weld.
Can SS 904L weld neck flanges be welded to carbon steel?
Yes — ER309L (or E309L electrode) is the usual filler when joining it to carbon steel.
Which standard covers SS 904L weld neck flanges?
The material is ASTM A182 F904L; dimensions follow ASME B16.5 · B16.47. Always state both on your purchase order, with the edition if your project specifies one.
What decides the price of a SS 904L weld neck flange?
The alloy price, the size and pressure class, quantity, and the testing and documents required. Send your list and we quote the same working day.
What documents do you supply?
EN 10204 3.1 mill certificates as standard, 3.2 with third-party inspection on request, plus dimensional and PMI reports.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026