Stainless Steel 316Ti
Stainless Steel 316Ti (UNS S31635) is a titanium-stabilised variant of Grade 316. Titanium is added 5 times the combined carbon and nitrogen content to preferentially form TiC carbides instead of chromium carbides. This prevents chromium carbide precipitation during service in the 425-815°C sensitisation range and offers a stabilised alternative to 316L specifically for long-term service in the sensitisation temperature range, where low-carbon grades alone may not prevent chromium depletion over extended periods.
1. Chemical Composition
The table below shows the elemental ranges for Stainless Steel 316Ti. Titanium is the stabilising addition, tied to the carbon content, while molybdenum provides pitting and crevice corrosion resistance.
| Grade | C | Mn | P | S | Si | Cr | Ni | Mo | Other |
| TP316Ti | ≤ 0.080 | ≤ 2.00 | ≤ 0.045 | ≤ 0.030 | ≤ 0.75 | 16.00–18.00 | 10.00–14.00 | 2.00–3.00 | Ti: 5xC min |
2. Mechanical Properties
The following table gives minimum mechanical properties for Stainless Steel 316Ti in the annealed condition. Titanium does not significantly change room-temperature tensile characteristics compared to standard 316.
| Grade | Condition | Tensile Strength Min, MPa (ksi) | Yield Strength Min, MPa (ksi) | Elongation Min, % | Heat Treatment Temp |
| TP316Ti | Annealed | 515 (75) | 205 (30) | 35 | 1040°C (1900°F) min |
3. Equivalent Grade
This table cross-references Stainless Steel 316Ti with international standard designations. The European 1.4571 designation is widely used in German and broader EU industrial specifications.
| GRADE | UNS | GB | JIS | ISO | DIN/EN | GOST | |
| ISC | NEW | ||||||
| 316Ti | S31635 | S31668 | 06Cr17Ni12Mo2Ti | SUS316Ti | X6CrNiMoTi17-12-2 | 1.4571 | 08X17H13M2T |
4. Key Technical Advantages
- Sensitisation Resistance Through Titanium Stabilisation: Titanium has a much stronger affinity for carbon than chromium does. By tying up carbon as TiC, 316Ti prevents chromium carbides (Cr23C6) from forming during service in the 425–815°C temperature range. Chromium remains evenly distributed in the steel, so it can continue to protect against corrosion. This is a different approach from the low-carbon method used in 316L.
- Suited for Long-Term Elevated-Temperature Service: When components run continuously at elevated temperatures (heat exchanger tubes, boiler components, chemical reactor walls), 316Ti maintains its intergranular corrosion resistance throughout its service life. 316L may eventually sensitise if held at elevated temperatures over long periods.
- European Industrial Specification Prevalence: 316Ti (1.4571) is the standard molybdenum-bearing stabilised grade in European standards (DIN EN). Many European engineering projects and chemical plant specifications default to 1.4571 over 316L where long-term elevated-temperature sensitisation is a concern.
- Maintained Pitting Resistance from Molybdenum: The 2–3% Mo content of 316Ti delivers pitting and crevice corrosion resistance equivalent to standard 316 and 316L, with the added benefit of stabilisation against long-term chromium depletion in the sensitisation temperature range.
Technical Note: The titanium in 316Ti can cause surface quality limitations in some high-finish applications due to TiN and TiC particle effects. For applications requiring ASME BPE or pharmaceutical-grade electropolished surfaces, food-grade (3A sanitary) and semiconductor, confirm surface finish achievability with the mill before specifying 316Ti over 316L.
5. Common Manufacturing Standards
- ASTM A213: Standard Specification for Seamless Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes — UNS S31635 designation.
- ASTM A312: Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes — referenced with UNS S31635 when applicable.
- DIN EN 10216-5: Seamless steel tubes for pressure purposes — Technical delivery conditions for stainless steel (1.4571).
- JIS G3463: Stainless Steel Boiler and Heat Exchanger Tubes (SUS316Ti).
- GB/T 13296: Seamless stainless steel tubes for boiler and heat exchanger (06Cr17Ni12Mo2Ti).
- GOST 9941: Seamless pipes from corrosion-resistant steel (10Kh17N13M2T).
Standards Comparison Table:
| Standard | ASTM | EN/DIN | JIS | GB/T | GOST |
| Seamless Pipe | A312 (S31635) | EN 10216-5 (1.4571) | G3459 | 14976 | 9941 |
| Welded Pipe | A312 (S31635) | EN 10217-7 (1.4571) | G3459 | - | - |
| Heat Exchanger Tube | A213 (S31635) / A249 | EN 10216-5 (1.4571) | G3463 (SUS316Ti) | 13296 | 9941 |
6. Primary Applications
- Chemical Plant Heat Exchangers: Shell-and-tube and plate heat exchangers where metal temperatures may enter the sensitisation range (425–815°C) during service, and where process fluids contain chlorides. In these conditions, sensitisation of 316L would create long-term intergranular corrosion risk.
- Boiler and Superheater Tubes: Industrial boiler components operating in the sensitisation temperature range. Titanium stabilisation provides lasting intergranular protection that low-carbon grades alone cannot guarantee.
- Sulfuric Acid Production Absorbers: Heat exchanger and absorption tower tubes in contact with sulfuric acid and sulfur trioxide-bearing gases at moderate-to-elevated temperatures.
- Petroleum Refinery Heat Recovery: Waste heat recovery units, feed-effluent exchangers, and overhead condensers in crude distillation and hydrocracking units with chloride-contaminated process streams.
- European Chemical Process Vessels: Welded pressure vessel shells and nozzles fabricated to DIN EN standards, where 1.4571 is the standard specification for molybdenum-bearing stabilised austenitic construction.