Views: 0 Author: Site Editor Publish Time: 2025-06-16 Origin: Site
The key differences between 1.4404 (316L) and 1.4571 (316Ti) lie in their composition, stabilization method, and suitability for specific applications, particularly welding and high-temperature service. Both are austenitic stainless steels derived from the basic 316 grade but modified to address sensitization (carbide precipitation).
1.4404 (316L): The "L" stands for Low Carbon (typically ≤ 0.03% C). This ultra-low carbon content directly minimizes the formation of chromium carbides (Cr23C6) at grain boundaries during welding or exposure to high temperatures (450-850°C). This prevents chromium depletion around the carbides, maintaining corrosion resistance.
1.4571 (316Ti): This grade has a higher carbon content (typically ≤ 0.08% C) but adds Titanium (Ti) as a stabilizing element (Ti content typically ≥ 5 x C%, min 0.40%). Titanium has a stronger affinity for carbon than chromium. It forms stable titanium carbides (TiC) preferentially over chromium carbides, thereby preventing chromium depletion at grain boundaries.
316L (1.4404): Designed primarily to resist sensitization (intergranular corrosion - IGC) during welding , especially in sections that cannot be solution annealed afterward. It's the go-to choice for welded fabrications operating in corrosive environments.
316Ti (1.4571): Designed to resist sensitization during prolonged exposure to high temperatures (within the sensitization range of 450-850°C) in service. While also weldable, its stabilization is often more relevant for high-temperature applications than just welding.
316L (1.4404): Excellent weldability.The low carbon content inherently prevents significant chromium carbide formation in the heat-affected zone (HAZ). Post-weld heat treatment is generally not required for corrosion resistance in typical applications.
316Ti (1.4571):Weldable, but requires more care. Titanium can oxidize during welding, potentially reducing its effectiveness. The weld metal itself doesn't contain titanium unless specifically matched filler is used. While stabilized, the base metal HAZ is generally more resistant to sensitization than standard 316, but 316L is often preferred for critical welded joints due to its inherent low carbon approach. Use of low-carbon filler metals (like 316L) is common.
316L (1.4404): Suitable for intermittent high-temperature exposure. However, prolonged service within the sensitization range (450-850°C) can still lead to some carbide precipitation over time because carbon, although low, is still present. Not ideal for sustained high-temp service.
316Ti (1.4571):Superior for prolonged high-temperature service (within the austenitic range, up to ~800°C). The titanium effectively "locks up" the carbon, providing long-term resistance to sensitization and intergranular corrosion/attack in this temperature regime. Also offers slightly better creep strength than 316L.
General & Pitting/Corrosion Resistance: The base corrosion resistance (pitting, crevice, general corrosion in various media like acids, chlorides) is very similar for both grades, as they share similar levels of Chromium (Cr), Nickel (Ni), and Molybdenum (Mo). Titanium itself does not enhance pitting resistance.
Intergranular Corrosion (IGC): Both are highly resistant to IGC, but through different mechanisms (low C vs. Ti stabilization). 316L achieves this inherently for welding, while 316Ti achieves it via stabilization for sustained high temps.
Specific Environments: 316Ti can show better resistance in certain aggressive environments like concentrated **sulfuric and phosphoric acids at elevated temperatures due to its stabilization.
Room Temperature: Properties (tensile strength, yield strength, elongation) are very similar and typical for austenitic stainless steels.
Elevated Temperature: 316Ti generally has slightly higher strength (especially creep strength) at sustained high temperatures compared to 316L due to the titanium carbide dispersion.
316L (1.4404) is generally less expensive than 316Ti (1.4571) due to the simpler production process (controlling low carbon) vs. the cost of adding and controlling titanium content.
| Feature | 1.4404 (316L) | 1.4571 (316Ti) |
| Key Modification | Low Carbon (≤ 0.03% C) | Titanium Stabilized (Ti ≥ 5xC%, min 0.4%) |
| Carbon Content | Very Low (≤ 0.03%) | Higher (≤ 0.08%) but stabilized |
| Primary Purpose | Resist sensitization during welding | Resist sensitization during prolonged high-temp service |
| Welding | Excellent, preferred for critical welds | Good, but low-carbon filler often used; Ti can oxidize |
| High-Temp Service | Limited for prolonged exposure | Superior for sustained exposure (up to ~800°C) |
| orrosion Resistance (General/Pitting) | Very Good, same as 316Ti base | Very Good, same as 316L base |
| Corrosion Resistance (IGC) | Inherent via low C (welding focus) | Via Ti stabilization (high-temp focus) |
| Mechanical Props (RT) | Similar to 316Ti | Similar to 316L |
| Mechanical Props (HT) | Slightly Lower Strength/Creep | Slightly Higher Strength/Creep |
| Relative Cost | Lower | Higher |
Choose 316L (1.4404) if:
Your application involves welding and the component will operate in a corrosive environment.
The component experiences only intermittent or short-term exposure to the sensitization temperature range.
Cost is a significant factor.
Choose 316Ti (1.4571) if:
The component will operate under sustained high temperatures (within 450-850°C) in a corrosive environment where sensitization is a major risk.
Slightly improved creep strength at high temperatures is needed.
Superior performance in specific aggressive acids (e.g., hot conc. H2SO4, H3PO4) is required.
The material might be subject to slow cooling through the sensitization range after fabrication (e.g., heavy sections).
In essence: 316L is the king for welded corrosion resistance, while 316Ti excels in high-temperature corrosion resistance.
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