316Ti з нержавеючай сталі / ЗША S31635 / У 1.4571

1. Рэзюмэ

316Ti is an austenitic stainless steel based on the 300-series (316) хіміі з наўмысным даданнем тытан to stabilize carbon.

The titanium ties up carbon as stable titanium carbides, preventing chromium-carbide precipitation at grain boundaries when the alloy is exposed to temperatures in the sensitization range.

The result is an alloy with the corrosion resistance of 316 plus improved resistance to intergranular corrosion after high-temperature exposure.

316Ti is commonly specified for components that must operate or are fabricated in the ~425–900 °C temperature window (welded assemblies, heat-exposed plant components) where low-carbon grades alone may be insufficient.

2. Што ёсць 316Ti з нержавеючай сталі?

316Ti is a titanium-stabilized, molybdenum-bearing austenitic з нержавеючай сталі developed to enhance resistance to intergranular corrosion after welding or prolonged exposure to elevated temperatures.

By adding titanium in controlled proportions, carbon is preferentially tied up as stable titanium carbides rather than chromium carbides.

This stabilization mechanism preserves chromium at grain boundaries and significantly reduces sensitization risks in the temperature range of approximately 425–850 °C (800–1560 °F).

У выніку, 316Ti is particularly suitable for components that will be welded and placed into service without post-weld solution annealing, or for applications involving cyclic or sustained thermal exposure.

It combines the chloride corrosion resistance of conventional 316 stainless steel with improved structural stability at elevated temperatures. Common international identifiers include ЗША S31635 і У 1.4571.

Standard Designations & Глабальныя эквіваленты

Key Variants and Related Grades

• 316Аб (ЗША S31635 / У 1.4571)
  The titanium-stabilized form of 316 з нержавеючай сталі, intended for welded structures or components exposed to intermediate and elevated temperatures where sensitization resistance is critical.
• 316 (ЗША S31600 / У 1.4401)
  The base molybdenum-alloyed grade without stabilization. Suitable when post-weld heat treatment is feasible or when thermal exposure is limited.
• 316L (ЗША S31603 / У 1.4404)
  A low-carbon alternative to reduce sensitization risk through carbon control rather than stabilization. Commonly used in pressure vessels, трубы, and pharmaceutical equipment.
• 321 (У 1.4541)
  A titanium-stabilized alloy based on the 304 stainless steel chemistry. Used when molybdenum is not required but stabilization is still necessary.
• 347 (Nb-stabilized stainless steel)
  Uses niobium instead of titanium for carbide stabilization. Offers similar intergranular corrosion resistance, often preferred in certain high-temperature pressure equipment codes.
• 316Ч / 316LN
  Variants optimized for higher-temperature strength (316Ч) or increased nitrogen content (316LN). These grades improve mechanical performance but do not replace titanium stabilization.

3. Typical Chemical Composition of 316Ti Stainless Steel

Values are representative engineering ranges for wrought, solution-annealed material (ЗША S31635 / У 1.4571 сям'я).

4. Microstructure and metallurgical behaviour

• Austenitic matrix (γ-Fe): stable at room temperature due to Ni. Microstructure is ductile, немагнітны (in annealed state) and work-hardening.
• Stabilization mechanism: Ti reacts to form titanium carbides (TiC) or carbonitrides which remove C from matrix and prevent Cr₂₃C₆ precipitation at grain boundaries during exposure in ~425–900 °C.
• Sensitization window and limits: even with Ti, extremely long exposure in the sensitization range or improper Ti:C ratio can still permit chromium carbide formation or other intermetallics. Proper melt practice and heat treatment control are essential.
• Intermetallic phases: prolonged exposure in certain intermediate ranges (especially 600–900 °C) can encourage sigma (а) or chi (χ) phase formation in austenitic grades enriched in Mo/Cr;
  316Ti is not immune—designers must avoid prolonged dwell in these ranges or specify stabilised steels with controlled composition and thermomechanical history.
• Precipitation after service: Ti-stabilized alloys may show fine Ti-rich precipitates; these are benign or beneficial compared with Cr carbides as they do not deplete Cr at grain boundaries.

5. Mechanical properties — 316Ti stainless steel

The figures below are прадстаўнік values for wrought 316Ti supplied in the solution-annealed / адпачываў стан.

Actual values depend on product form (ліст, талерка, труба, забараняць), таўшчыня, supplier processing and heat lot.

6. фізічны & thermal properties and high-temperature behaviour

• Цеплаправоднасць: relatively low (≈ 14–16 W·m⁻¹·K⁻¹ at 20 ° С).
• Coefficient of thermal expansion: ~16–17 ×10⁻⁶ K⁻¹ (20–100 ° С) — higher than ferritic steels.
• Melting range: падобны на 316 (solidus ~1375 °C).
• Service temperature window: 316Ti is selected specifically for intermediate temperature exposure (прыблізна. 400–900 ° С) where stabilization prevents intergranular attack.
  Аднак, prolonged exposure in the 600–900 °C window can risk sigma-phase formation and reduction in toughness — avoid continuous exposure to those temperatures unless metallurgical data confirm safety.
• Creep: for sustained loads at high temperature, 316Ti is not a creep-resistant alloy; use high-temperature grades (e.g., 316Ч, 309/310, або нікелевых сплаваў).

7. Corrosion behaviour — strengths and limitations

Моцныя бакі

• Resistance to intergranular corrosion after thermal exposure in the sensitization range, provided Ti:C and Ti:available C ratios and heat treatment are correct.
• Добрая агульная ўстойлівасць да карозіі in oxidizing and many reducing media; Mo contributes pitting/crevice resistance similar to 316.
• Preferred for welded structures that will see intermittent high-temperature service or where post-weld solution anneal is impractical.

Абмежаванні

• Аплавоў & crevice corrosion in high-chloride environments: 316Ti has similar pitting resistance to 316; for severe seawater or warm chloride service consider duplex or higher-PREN alloys.
• Хларыд SCC: not immune—SCC can occur in chloride + напружанне расцяжэння + temperature environments; duplex alloys or super-austenitics may be required where SCC risk is high.
• Sigma phase and intermetallics: long dwell at certain high temperatures can cause embrittling phases independent of Ti stabilization—design to avoid those thermal histories or test.
• Industrial contaminants: like all stainless steels, агрэсіўныя хімікаты (моцныя кіслоты, chlorinated solvents at high T) may attack; perform compatibility checks.

8. Апрацоўка & Manufacturing Characteristics

316Ti’s austenitic microstructure + TiC precipitates enable excellent processability, with minor adjustments needed for titanium’s effects:

Welding Performance (Ключавая перавага)

316Ti retains superior weldability, compatible with GMAW (Мне), GTAW (Зрадак), SMAW (stick), and FCAW – with the critical advantage of no post-weld heat treatment (Pwht) required for IGC resistance:

• Разагрэчэнне: Not required for sections ≤25 mm thick; раздзелы >25 mm may preheat to 80–150°C to reduce HAZ cracking risk.
• Welding consumables: Use ER316Ti (GTAW/GMAW) or E316Ti-16 (SMAW) to match titanium content and ensure stabilization in the weld metal.
• Pwht: Optional stress relief annealing (600–650°C for 1–2 hours) for thick-walled components, but not mandatory for corrosion resistance (unlike 316, which requires PWHT for IGC protection after welding).
• Welded joint performance: Tensile strength ≥460 MPa, elongation ≥35%, and passes ASTM A262 IGC test – weld metal corrosion resistance equivalent to base metal.

Фарміраванне & Выдумка

• Cold forming: Excellent ductility allows deep drawing, выгін, і пракаткі. Minimum bend radius: 1× thickness for cold bending (≤12 mm thick), same as 316L – TiC precipitates do not impair formability.
• Hot forming: Performed at 1100–1250°C, followed by water quenching to retain austenitic microstructure and TiC distribution. Avoids the 450–900°C range during cooling to prevent accidental sensitization.
• Апрацоўванне: Moderate machinability (rated 55–60% vs. Асі 1018 сталь) – TiC precipitates are harder than austenite, causing slightly more tool wear than 316L.
  Recommended cutting speed: 90–140 m/min (цвёрдасплаўныя інструменты) with cutting fluid to reduce heat buildup.

Тэрмічная апрацоўка

• Адпал раствора: Primary heat treatment (1050-1150°C, hold 30–60 minutes, гартаванне вадой) – dissolves residual carbides (if any), refines grains, and ensures uniform TiC distribution. Critical for maximizing corrosion resistance and toughness.
• Адпал для зняцця напружання: 600–650°C for 1–2 hours, air cooling – reduces residual stress by 60–70% without affecting TiC stability or corrosion resistance.
• Avoid over-annealing: Тэмпературы >1200°C may cause TiC coarsening and grain growth, reducing high-temperature strength – limit solution annealing temperature to ≤1150°C.

Апрацоўка паверхні

• Саленне & пасівацыя: Post-fabrication treatment (ASTM A380) to remove oxide scale and restore the Cr₂O₃ passive film – TiC precipitates do not interfere with passivation.
• Шмарка: Achieves surface finishes ranging from Ra 0.02–6.3 μm. Mechanical or electropolishing improves hygiene and corrosion resistance, suitable for medical and food applications.
• Слой: Rarely required due to inherent corrosion resistance; galvanizing or epoxy coating may be used for extreme high-chloride environments (e.g., marine offshore platforms).

9. Typical Applications of 316Ti Stainless Steel

316Ti’s unique combination of high-temperature stability, IGC resistance, and corrosion resistance makes it ideal for demanding environments where 316L or 316 may fail:

Хімічны & Нафтахімічная прамысловасць (35% of Demand)

• Core applications: High-temperature chemical reactors, цеплаабменнікі, рэктыфікацыйныя калоны, and piping for handling chlorides, кіслоты, and organic solvents.
• Ключавая перавага: Resists IGC during repeated welding (e.g., maintenance repairs) and high-temperature operation (up to 850°C) – used in ethylene crackers and sulfuric acid plants.

Аэракасмічная

• Core applications: Aircraft exhaust systems, turbine components, and rocket engine parts.
• Ключавая перавага: High-temperature oxidation resistance (≤900°C) and non-magnetic properties – compatible with avionics and radar systems.

Nuclear Energy

• Core applications: Nuclear reactor cooling system components, steam generators, and fuel cladding (non-radioactive structural parts).
• Ключавая перавага: IGC resistance in high-temperature, high-pressure water (280° С, 15 МПА) and compliance with nuclear safety standards (e.g., ASME Section III).

High-Temperature Furnace Manufacturing

• Core applications: Furnace liners, прамяністыя трубкі, and heating elements for industrial furnaces (тэрмічная апрацоўка, спяканне).
• Ключавая перавага: Retains strength and corrosion resistance at 800–900°C, with a service life 2–3 times longer than 316L in continuous high-temperature operation.

Медычны & Фармацэўтычная прамысловасць

• Core applications: Sterilizable medical devices, абсталяванне для фармацэўтычнай апрацоўкі, and cleanroom components.
• Ключавая перавага: IGC resistance after repeated autoclaving (121° С, 15 PSI) and compliance with FDA 21 Частка CFR 177 – no risk of corrosion-induced contamination.

Марская & Offshore Industry

• Core applications: Offshore platform piping, seawater desalination plants, and subsea components.
• Ключавая перавага: Resists seawater corrosion and SCC, with NACE MR0175 compliance for sour service (H₂S-containing well fluids).

10. Перавагі & Абмежаванні

Core Advantages of 316Ti Stainless Steel

• Superior IGC resistance: Titanium stabilization eliminates Cr₂₃C₆ precipitation, making it ideal for high-temperature or repeated welding scenarios – outperforming 316L/316H.
• Enhanced high-temperature performance: Retains strength, вынослівасць, and oxidation resistance up to 900°C, 50–100°C higher than 316L.
• Выдатная свариваемость: No mandatory PWHT for corrosion resistance, reducing manufacturing costs and lead time.
• Шырокая ўстойлівасць да карозіі: Inherits 316’s resistance to chlorides, кіслоты, and sour service, with extended temperature limits for NACE compliance.
• Дапрацоўка збожжа: TiC precipitates inhibit grain growth, improving mechanical properties and dimensional stability.

Key Limitations of 316Ti Stainless Steel

• Больш высокі кошт: 15–20% more expensive than 316L (due to titanium addition), increasing material costs for large-scale non-critical applications.
• Reduced machinability: TiC precipitates cause more tool wear than 316L, requiring specialized tools or slower cutting speeds – increasing machining costs by ~10–15%.
• TiC coarsening risk: Prolonged exposure to >900°C causes TiC coarsening, reducing high-temperature strength and toughness.
• Limited super-high-temperature resistance: Not suitable for continuous service above 900°C – use super austenitic stainless steels (e.g., 254 МЫ) or nickel-based alloys (e.g., Умова 600) замест гэтага.
• Lower strength than duplex stainless steels: Трываласць на расцяжэнне (485–590 MPa) is lower than duplex grades (e.g., 2205: 600-800 Мпа), requiring thicker sections for structural loads.

11. Comparative analysis — 316Ti vs 316L vs 321 vs Duplex 2205

12. Conclusion

316Ti is a pragmatic stabilized variant of the 316 сям'я, engineered to preserve austenitic stainless steel corrosion resistance in welded and heat-exposed components.

When titanium content and heat-treatment are properly controlled, 316Ti prevents intergranular chromium depletion and is a robust choice for welded plant components, heat-exposed assemblies and moderate chloride environments where post-weld annealing cannot be guaranteed.

Proper procurement, MTR verification, welding procedure control and periodic inspection are essential to realize the alloy’s advantages.

 

FAQ

What is the difference between 316Ti and 316L?

316Ti is titanium-stabilized (Ti added to form TiC), while 316L is low-carbon (L = low C).

Both routes reduce sensitization risk; 316Ti is specifically selected when components will see intermediate-temperature exposure and post-weld anneal is impractical.

Does titanium make 316Ti more corrosion resistant than 316L?

Titanium’s role is to prevent intergranular corrosion after thermal exposure; 316Ti’s bulk pitting resistance is similar to 316/316L (Mo in all gives comparable localized corrosion resistance).

For harsher chloride environments, duplex or higher-PREN alloys are preferred.

Do I need different filler metals to weld 316Ti?

Not necessarily—matching filler alloys (e.g., ER316L/ER316Ti where available) are used.

Ensure filler chemistry and welding procedure maintain stabilization in the HAZ and weld metal; consult welding codes and metallurgical guidance for critical parts.