316Ti Stainless Steel Titanium-Stabilized Molybdenum-Containing

316Ti is a titanium-stabilized molybdenum-containing austenitic stainless steel. Titanium preferentially combines with carbon to form TiC, eliminating intergranular corrosion and improving high-temperature stability. It is suitable for high-temperature welding components requiring both corrosion resistance and intergranular corrosion resistance.

Chemical Composition (wt%): C≤0.08, Cr=16.00-18.00, Ni=10.00-14.00, Mo=2.00-3.00, Ti=4×C-0.70, Si≤1.00, Mn≤2.00, P≤0.045, S≤0.030, Fe=Balance

Mechanical Properties (Annealed): Tensile Strength ≥515MPa, Yield Strength ≥205MPa, Elongation ≥40%, Hardness ≤217HB

Performance Advantages: Excellent intergranular corrosion resistance after welding, no post-weld heat treatment required; high-temperature stability (continuous service temperature up to 900℃); good resistance to high-temperature chloride corrosion; excellent weldability and formability.

Applications: Aero-engine auxiliary components, high-temperature heat exchanger tubes (800-900℃), nuclear power plant auxiliary equipment pipelines, high-temperature furnace liners, petrochemical cracking furnace auxiliary parts.

Equivalent Grades: UNS S31635, JIS SUS316Ti, EN 1.4571, GB 06Cr17Ni12Mo2Ti

Q&A

Q1: What is the stabilization mechanism of titanium in 316Ti? A1: The stabilization mechanism of titanium in 316Ti is based on the preferential combination of titanium and carbon to form stable titanium carbides (TiC), thereby preventing the formation of chromium carbides and avoiding intergranular corrosion. At high temperatures or during welding, carbon in stainless steel has a stronger affinity for titanium than for chromium. In 316Ti, the titanium content is controlled at 4×C-0.70wt%, ensuring that all carbon combines with titanium to form TiC instead of combining with chromium to form Cr₂₃C₆. Cr₂₃C₆ precipitation at grain boundaries will consume chromium in the grain boundary area, forming a chromium-depleted zone and leading to intergranular corrosion. In contrast, TiC is extremely stable and does not decompose easily, and its formation does not consume chromium, thus maintaining the integrity of the chromium-rich passivation film at grain boundaries. This stabilization mechanism enables 316Ti to have excellent intergranular corrosion resistance after welding without post-weld heat treatment.

Q2: Can 316Ti replace 316L in welding-intensive components? A2: Yes, 316Ti can replace 316L in welding-intensive components, and it has advantages in high-temperature applications. Both 316Ti and 316L have excellent intergranular corrosion resistance after welding; 316L achieves this through ultra-low carbon content, while 316Ti relies on titanium stabilization. In room-temperature corrosion environments, their corrosion resistance is similar, both having good resistance to chloride corrosion due to molybdenum content. However, in high-temperature environments (above 800℃), 316Ti has obvious advantages: its continuous service temperature (up to 900℃) is 30℃ higher than 316L's (870℃), and it has better high-temperature oxidation resistance and creep strength. For high-temperature welding-intensive components (such as aero-engine exhaust pipes), 316Ti is more suitable. However, 316Ti is 10-15% more expensive than 316L and has slightly worse machinability due to titanium content, so 316L is still preferred in low-temperature or general corrosion environments with strict cost control.

Q3: What welding materials are used for 316Ti stainless steel? A3: The suitable welding materials for 316Ti stainless steel are mainly ER316Ti welding wire and E316Ti electrodes. ER316Ti welding wire is preferred for gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) because it contains the same titanium content as the base metal, ensuring that the weld has the same stabilization mechanism and corrosion resistance as 316Ti. During welding, it is important to control the heat input to ≤180J/mm to avoid overheating, which can cause excessive grain growth and reduce the mechanical properties of the weld. High-purity argon (≥99.99%) should be used as shielding gas to prevent weld oxidation. Post-weld passivation treatment is recommended to enhance the corrosion resistance of the weld surface, but post-weld annealing is not required due to titanium stabilization. It is not recommended to use ER316L welding wire for 316Ti, as the lack of titanium in the weld may lead to intergranular corrosion in high-temperature environments.

Q4: What is the difference in high-temperature performance between 316Ti and 316? A4: The high-temperature performance of 316Ti is significantly better than that of 316, mainly reflected in high-temperature stability, oxidation resistance, and creep strength. First, service temperature: 316Ti's continuous service temperature can reach 900℃, 30℃ higher than 316's 870℃. Second, high-temperature oxidation resistance: at 850℃, 316Ti forms a more dense and stable oxide film, which is not easy to peel off, while 316's oxide film may age and peel off after long-term service. Third, high-temperature creep strength: at 800℃, the 1000h creep rupture strength of 316Ti is 20-30% higher than that of 316, enabling it to maintain structural stability under long-term high-temperature and high-stress conditions. Fourth, high-temperature corrosion resistance: in high-temperature environments containing chloride ions or sulfur dioxide, 316Ti's titanium-stabilized structure reduces the risk of intergranular corrosion, while 316 is prone to sensitization at 450-850℃. These differences make 316Ti more suitable for high-temperature applications, while 316 is limited to medium-temperature environments.

Q5: What are the machining characteristics of 316Ti stainless steel? A5: 316Ti stainless steel has specific machining characteristics due to the addition of titanium. First, machinability is slightly worse than 316: titanium carbides (TiC) in 316Ti are hard and brittle, increasing tool wear during cutting, so tools with high hardness and wear resistance (such as cemented carbide tools) should be used. Second, higher cutting force is required: compared to 316, 316Ti has higher cutting resistance, so the machine tool should have sufficient power and rigidity. Third, good chip control: during cutting, 316Ti produces continuous chips, which need to be broken by using tools with appropriate chip breakers to avoid chip entanglement affecting processing. Fourth, low cutting speed: to reduce tool wear, the cutting speed of 316Ti should be 10-20% lower than that of 316. Fifth, sufficient cooling and lubrication: during machining, use cutting fluids with good cooling and lubricating properties to reduce cutting temperature, prevent tool bonding, and improve surface quality. Despite these characteristics, with proper tool selection and processing parameters, 316Ti can still achieve high-precision machining, meeting the requirements of aerospace and nuclear power components.