Titanium Alloy Steel UNS 50400 GR7 Heat Exchanger Tube , Chemical Industries
The ASME SB338 standard governs the material specifications for titanium tubes and titanium alloy tubes used in heat exchangers and other high-pressure applications. The "SB" designation indicates that the material is for boiler and pressure vessel applications.
The Grade 7 (Gr. 7) designation refers to a specific titanium alloy with 0.2% palladium for enhanced corrosion resistance.
The alloy is lighter than steel, which is particularly advantageous in aerospace, marine, and other weight-sensitive industries. It provides strong mechanical performance, allowing for the construction of pressure vessels and heat exchangers without excessive material thickness.
Chemical Composition:
- Titanium Grade 7 (Ti-0.2Pd) is an alloy primarily composed of titanium with a small percentage of palladium (0.12-0.25%). This alloy is designed to offer enhanced corrosion resistance, especially in aggressive environments such as in seawater, chemicals, or heat exchangers.
- Titanium (Ti) is known for its excellent strength-to-weight ratio, outstanding corrosion resistance, and ability to perform under high temperatures.
- Palladium (Pd) is added to Grade 7 to improve resistance to general corrosion, particularly in acidic environments.
Manufacturing and Processing:
- Cold Working: Titanium Gr. 7 is typically cold worked into tubes, sheets, and plates through standard manufacturing processes like extrusion, rolling, or drawing.
- Heat Treatment: Though titanium alloys, in general, are not typically heat-treated for hardness, annealing or solution heat treatment can improve the material's ductility and strength in certain applications.
- Welding: The alloy is weldable using processes like TIG (Tungsten Inert Gas) welding, but care must be taken to prevent contamination during the welding process. The presence of palladium enhances its weldability compared to other titanium grades.
- Surface Finish: For heat exchanger applications, smooth surfaces are typically preferred, as this enhances heat transfer efficiency and reduces the risk of fouling or scaling on the surface.
Applications:
- Seawater Heat Exchangers: Titanium Grade 7's outstanding resistance to seawater corrosion makes it ideal for use in heat exchangers onboard ships, offshore oil rigs, and desalination plants where the material will be constantly exposed to saltwater.
- Cooling Systems for Naval Vessels: Used in the cooling systems of naval ships and submarines, where exposure to seawater and high temperatures is common.
- Offshore Oil and Gas Platforms: Heat exchangers in offshore drilling platforms often use titanium alloy tubes to handle the harsh marine environment and the corrosive effects of saltwater and chemicals.
- Petrochemical Refining: In industries like oil refining and natural gas processing, where fluids can be highly corrosive, Grade 7 titanium tubes are used for cooling systems and heat exchangers to avoid corrosion and ensure efficient heat transfer.
- Reverse Osmosis (RO) Systems: Titanium tubes are often used in the cooling systems for RO desalination units, where heat transfer and durability in harsh, saline environments are crucial.
