304H Buttweld Pipe Fittings
ASTM A403 WP304H / EN 1.4948 (X6CrNi18-11) — the controlled higher-carbon version of 304 with coarser grain size for greater creep strength at elevated temperature. Power-boiler superheater piping and high-temperature process lines. EN 10253-2 Type B and ASME B16.9. EN 10204 3.1 standard; 3.2 TPI on request.
½″–48″
Size Range
C 0.04–0.10
Creep Carbon
18Cr-8Ni
304 base, no Mo
EN 10204
3.1 Std / 3.2 On Req.
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304H Grade Equivalents
| ASTM | EN W.Nr. | EN Name | UNS | ASME P-No. |
|---|---|---|---|---|
| A403 WP304H (fittings) | 1.4948 | X6CrNi18-11 | S30409 | 8, Gr 1 |
| A182 F304H (flanges) | 1.4948 | X6CrNi18-11 | S30409 | 8 |
| A312 TP304H (pipe) | 1.4948 | X6CrNi18-11 | S30409 | 8 |
| A240 304H (plate) | 1.4948 | X6CrNi18-11 | S30409 | 8 |
Chemical Composition — 304H / 1.4948
| Standard | C | Cr | Ni | Mo | Mn | Si |
|---|---|---|---|---|---|---|
| ASTM A403 WP304H | 0.04–0.10 | 18.0–20.0 | 8.0–11.0 | — | ≤2.0 | ≤1.0 |
| EN 1.4948 (X6CrNi18-11) | 0.04–0.10 | 18.0–20.0 | 8.0–11.0 | — | ≤2.0 | ≤1.0 |
The controlled carbon (0.04–0.10%) and coarser grain size distinguish 304H from 304L — they raise creep-rupture strength for long-term elevated-temperature service. 304H contains no molybdenum and is not intended for chloride service.
Mechanical Properties — 304H / 1.4948
| Standard | Min. UTS (MPa) | Min. YS (MPa) | Elongation (%) | Grain Size | HT Condition |
|---|---|---|---|---|---|
| ASTM A403 WP304H | 515 | 205 | ≥35% | ASTM No. 7 or coarser | Solution annealed |
| EN 1.4948 (EN 10253-2) | 500–700 | ≥200 | ≥35% | Controlled | Solution annealed |
High-Temperature Service & Welding
✓ No PWHT Required — supplied solution annealed.
304H (ASTM A403 WP304H / EN 1.4948) is austenitic and does not require post-weld heat treatment. It is welded with a matching ER308H / ER308 filler; keep inter-pass temperature ≤150°C. ASME P-No. 8, Group 1.
Why 304H over 304L for High Temperature
- Creep strength: the controlled carbon and coarser grain give higher creep-rupture strength for service above ~525°C.
- Code use: 304H carries ASME B31.1 / B31.3 allowable stresses at elevated temperature where 304L is de-rated.
- Typical service: power-boiler superheater piping and high-temperature process and refinery lines (non-chloride).
304H Fitting Types Available
90° Elbow (LR & SR)
Long Radius & Short Radius
ASME B16.9
45° Elbow
Long Radius
ASME B16.9
Equal Tee
Straight tee, equal branch
ASME B16.9
Reducing Tee
Reduced branch outlet
ASME B16.9
Concentric Reducer
Inline bore reduction
ASME B16.9
Eccentric Reducer
Flat bottom / top configurations
ASME B16.9
End Cap
Pipe end closure
ASME B16.9
Stub End (Lap Joint)
For use with lap joint flanges
ASME B16.9
Cross / Lateral
Four-way and angled branch
ASME B16.9
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