316Ti vs 316L: stabilisation and high-temperature knife-line attack
316Ti is titanium-stabilised for long service at 500–800°C and repeated welding; 316L is the lower-carbon general-purpose choice for ambient and normal welded structures.
316Ti (1.4571) and 316L (1.4404) are both molybdenum-bearing austenitic grades; the difference is stabilisation and high-temperature behaviour.
Key points:
• Chemistry: 316Ti adds Ti (typically ≥5×C), which ties up carbon as titanium carbides and reduces chromium depletion at grain boundaries; 316L uses extra-low carbon (≤0.03%) to reduce sensitisation risk.
• High temperature: 316Ti resists sensitisation and knife-line attack better during long service at 500–800°C, and is common in high-temperature piping and furnace parts.
• Ambient and welding: 316L is sufficient for normal welded structures and ambient corrosion, and is more widely available.
• Processing: titanium-stabilised grades can slightly affect polishing and forming; evaluate when surface quality is critical.
Guidance:
1) Long-term high temperature (>500°C) or repeated thermal cycles: prefer stabilised grades such as 316Ti/321.
2) Ambient corrosion and general welding: 316L is the common and cost-effective choice.
3) Do not expect 316L to match 316Ti after long high-temperature service.
State the maximum service temperature and thermal cycling conditions on the purchase order to support correct grade selection.
