Stainless Steel 314
Stainless Steel 314 (UNS S31400) is a high-alloy austenitic grade with elevated silicon content (1.50-3.00%), along with 23-26% chromium and 19-22% nickel. The silicon addition improves resistance to sulfur-bearing gases and scaling at temperatures up to 1150°C (2100°F).
1. Chemical Composition
The table below shows the elemental composition ranges for Stainless Steel 314. The high silicon specification is what separates it from other 310-series grades and controls its sulfidation and scaling behavior.
| Grade | C | Mn | P | S | Si | Cr | Ni | Mo | Other |
| TP314 | ≤ 0.25 | ≤ 2.00 | ≤ 0.045 | ≤ 0.030 | 1.50–3.00 | 23.00–26.00 | 19.00–22.00 | — | — |
2. Mechanical Properties
The following table gives minimum ambient-temperature mechanical properties for Stainless Steel 314 in the annealed condition. The high silicon content provides some solid-solution strengthening at elevated temperatures.
| Grade | Condition | Tensile Strength Min, MPa (ksi) | Yield Strength Min, MPa (ksi) | Elongation Min, % | Heat Treatment Temp |
| TP314 | Annealed | 550 (80) | 205 (30) | 35 | 1040–1150°C (1900–2100°F) rapid cool |
3. Equivalent Grade
This table aligns Stainless Steel 314 designations with international standards equivalents. This high-silicon grade has limited coverage in some Asian and Russian standards because of its specialised nature.
| GRADE | UNS | GB | JIS | ISO | DIN/EN | GOST | |
| ISC | NEW | ||||||
| 314 | S31400 | S38340 | 1Cr25Ni20Si2 | - | X15CrNiSi25-21 | 1.4841 | 20Kh25N20S2 |
4. Key Technical Advantages
- Better Sulfidation Resistance: Silicon forms a SiO2 layer beneath the chromium oxide scale. This dual-layer structure reduces sulfur diffusion into the alloy under mixed oxidising-sulfidising atmospheres, and it outperforms standard 310 in such conditions.
- Higher Scaling Resistance: Above 1000°C, the silicon-enriched surface oxide adheres better and scales at a lower rate compared to silicon-free grades of similar chromium content. This reduces material loss in cyclic thermal service.
- Resistance to Ash Corrosion: The silica-reinforced oxide resists fluxing by alkali sulfate and vanadium pentoxide deposits better than chromium oxide alone. That makes 314 effective in coal ash and heavy oil combustion environments.
- High-Temperature Structural Retention: With 23-26% Cr and 19-22% Ni, the grade retains an austenitic structure up to its highest service temperatures. Silicon provides additional structure hardening that partially offsets its slight reduction in ductility versus 310.
Technical Note: High silicon content reduces weldability compared to standard 310. Preheat and filler metal selection must be carefully managed to avoid hot cracking in multi-pass welds of thick sections.
5. Common Manufacturing Standards
Stainless Steel 314 is produced under the following manufacturing standards. ASTM coverage for this grade is less extensive than for standard 310 or 316 series:
ASTM A312: Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes — applicable when UNS S31400 is specified.
ASTM A213: Standard Specification for Seamless Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes — referenced with UNS S31400 designation.
ASTM A511: Standard Specification for Seamless Stainless Steel Mechanical Tubing.
DIN EN 10095: Heat-resisting steels and nickel alloys — 1.4841 (EN designation with overlapping Si range covers 314 equivalents).
JIS G4312: Hot-rolled stainless steel strip for heat-resisting applications (SUS314).
JIS G4311: Hot-rolled stainless steel bars for heat-resisting applications.
Standards Comparison Table:
| Standard | ASTM | EN/DIN | JIS | GB/T | GOST |
| Seamless Pipe | A312 (S31400) | EN 10095 (1.4841) | - | - | - |
| Seamless Tube | A213 (S31400) | EN 10095 (1.4841) | - | - | - |
| Bar/Strip | A511 | EN 10095 | G4311 / G4312 | - | - |
6. Primary Applications
- Sulfur-Bearing Combustion Environments: Furnace components, burner assemblies, and thermal shields in oil-fired or coal-fired systems where SO2 and SO3 concentrations create sulfidising conditions alongside an oxidising atmosphere.
- Waste Gas Incinerators: Internal liners and gas-flow diverters in industrial waste incineration units where sulfur and chlorine-bearing combustion gases coexist at temperatures above 900°C.
- Petrochemical Cracking Furnaces: Tube supports, spacers, and fixture components in pyrolysis furnaces where both carburisation and sulfur-contaminated feedstocks are a concern.
- Ore Roasting and Calcining: Kiln liners, rabble arms, and conveyor components in metallurgical roasting operations that process sulfide ore concentrates at high temperatures.
- Glass Industry Furnace Hardware: Muffles, recuperators, and burner blocks in glass tank furnaces, where silicon-containing flue gases and high temperatures create aggressive oxidizing conditions.