310S Buttweld Pipe Fittings
ASTM A403 WP310S / EN 1.4845 (X8CrNi25-21) — 25Cr-20Ni heat-resistant austenitic stainless steel for oxidation resistance in continuous service to ~1150°C. Furnace parts, radiant tubes, kiln components, heat-treatment fixtures and high-temperature gas ducting. EN 10253-2 Type B and ASME B16.9. EN 10204 3.1 standard; 3.2 TPI on request.
½″–48″
Size Range
~1150°C
Max Continuous
25Cr-20Ni
Composition
EN 10204
3.1 Std / 3.2 On Req.
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310S Grade Equivalents
| ASTM | EN W.Nr. | EN Name | UNS | ASME P-No. |
|---|---|---|---|---|
| A403 WP310S (fittings) | 1.4845 | X8CrNi25-21 | S31008 | 8, Gr 3 |
| A182 F310 (flanges) | 1.4845 | X8CrNi25-21 | S31008 | 8 |
| A312 TP310S (pipe) | 1.4845 | X8CrNi25-21 | S31008 | 8 |
| A240 310S (plate) | 1.4845 | X8CrNi25-21 | S31008 | 8 |
Chemical Composition — 310S / 1.4845
| Standard | C | Cr | Ni | Mn | Si | P | S |
|---|---|---|---|---|---|---|---|
| ASTM A403 WP310S | ≤0.08 | 24.0–26.0 | 19.0–22.0 | ≤2.0 | ≤1.5 | ≤0.045 | ≤0.030 |
| EN 1.4845 (X8CrNi25-21) | ≤0.10 | 24.0–26.0 | 19.0–22.0 | ≤2.0 | ≤1.5 | ≤0.045 | ≤0.015 |
The high chromium (24–26%) and nickel (19–22%) form a stable, adherent chromium-oxide scale that resists oxidation and scaling at elevated temperature. 310S contains no molybdenum and is a heat-resistant grade, not an aqueous-corrosion grade.
Mechanical Properties — 310S / 1.4845
| Standard | Min. UTS (MPa) | Min. YS (MPa) | Elongation (%) | Max. Hardness | HT Condition |
|---|---|---|---|---|---|
| ASTM A403 WP310S | 515 | 205 | ≥35% | 217 HBW | Solution annealed |
| EN 1.4845 (EN 10253-2) | 500–700 | ≥210 | ≥30% | 223 HBW | Solution annealed |
High-Temperature Service & Welding
✓ No PWHT Required — supplied solution annealed.
310S (ASTM A403 WP310S / EN 1.4845) is austenitic and does not require post-weld heat treatment. It is delivered in the solution annealed condition and does not undergo martensitic transformation during welding.
Oxidation & Welding Guidance
- Oxidation resistance: continuous service to ~1150°C; ~1035°C under cyclic/intermittent heating (thermal cycling is more demanding than steady heat).
- Filler metal: ER310 (GTAW / TIG) or E310-16 (SMAW). Match filler to base metal.
- ASME P-No.: 8, Group 3. Weld procedure qualification per ASME IX or ISO 15614-1.
- Applications: furnace parts and muffles, radiant and recuperator tubes, kiln and heat-treatment fixtures, high-temperature flue-gas ducting.
⚠ Sigma Phase & Wet Service
Prolonged exposure in the 600–900°C range can precipitate sigma phase, reducing room-temperature ductility — relevant for components that are cooled and handled. 310S is a heat-resistant grade with no molybdenum; it is not suited to aqueous chloride or acid service. For wet corrosion select 316L, 317L, duplex or a nickel alloy. Contact our technical team to confirm material selection.
310S 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
309S vs 310S — Heat-Resistant Grades
| Property | 309S (WP309S / 1.4833) | 310S (WP310S / 1.4845) |
|---|---|---|
| Chromium | 22.0–24.0% | 24.0–26.0% |
| Nickel | 12.0–15.0% | 19.0–22.0% |
| Max continuous service | ~1000°C | ~1150°C |
| Typical use | Furnace, dissimilar welds | Higher-temperature furnace |
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Specify size, schedule, fitting type, standard (ASME B16.9 or EN 10253-2 Type B), and required MTR (EN 10204 3.1 or 3.2). We respond within 1 business day.
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