In Marine engineering, due to the high salinity, high corrosiveness and complex stress characteristics of the seawater environment, commonly used titanium and titanium alloy grades need to have excellent corrosion resistance, good mechanical properties and processing performance. The followings are the commonly used titanium grades in Marine engineering, along with their characteristics and application scenarios:
Industrial pure titanium (α type)
Gr.1, Gr.2, Gr.3
- Characteristics:High purity (Ti≥99%), excellent resistance to seawater corrosion, good plasticity and weldability, but relatively low strength (tensile strength approximately 240-500 mpa).
- Application: Components such as seawater heat exchangers, condensers, pipes, valves, and seawater desalination equipment that have high corrosion resistance requirements but relatively low loads.
α -type titanium alloy
1.Ti-4Al-0.05Si
- Characteristics: It has good high-temperature strength (operating temperature ≤350℃), is resistant to seawater corrosion, and has excellent welding performance.
- Application: High-temperature structural components in Marine environments, such as oil and gas pipeline fittings and ship engine parts.
2.Ti - 5-2.5 Sn
- Characteristics: It has excellent low-temperature toughness (can be used at -253 ℃), is resistant to stress corrosion from seawater, and has medium strength (tensile strength approximately 700-850 mpa).
- Application: Deep-sea cryogenic equipment and components related to liquefied natural gas (LNG).
3. Ti - 0.3-0.8 Ni
- Characteristics: By adding Mo and Ni to industrial pure titanium, the resistance to crevice corrosion and pitting corrosion is significantly enhanced, making it particularly suitable for seawater environments containing chloride ions.
- Application: Components for harsh corrosive environments such as seawater heat exchanger tubes, evaporators, and salt water pump impellers.
α+β type titanium alloy
1.Ti-6Al-4V, Gr.5
- Features: The titanium alloy with the best comprehensive performance, high strength (tensile strength ≥895MPa), resistance to seawater corrosion, fatigue resistance, heat-treatable for strengthening, and the most widely used.
- Applications: Marine platform structural components (bolts, flanges, brackets), ship propeller shafts, deep-sea riser joints, underwater connectors, etc.
2.Ti-6Al-6V-2Sn
Features: High strength (tensile strength ≥1030MPa), resistance to seawater corrosion, good weldability and processing performance, suitable for high-load environments.
Application: High-strength components in Marine oil and gas extraction equipment, such as wellhead devices and sucker rods.
β -type titanium alloy
1. Ti-5Mo-5V-8Cr-3Al
- Features: Ultra-high strength (tensile strength ≥1300MPa), good toughness and fatigue resistance, and can be strengthened through aging treatment.
- Application: Deep-sea high-strength structural components, such as pressure-resistant shells of submarines and key components of deep-sea robots.
2.Ti-10V-2Fe-3Al
- Features: High strength (tensile strength ≥1000MPa), good processing performance, resistant to seawater stress corrosion, suitable for complex load conditions.
- Application: High-load connection components and fasteners in Marine engineering.
Other special-purpose grades
3.Ti-0.2Pd (Gr.7) : By adding Pd on the basis of TA2, it has extremely strong resistance to crevice corrosion and is used for precision components in seawater cooling systems.
4.Ti-31 (Ti-3Al-2.5V) : Resistant to seawater corrosion, with excellent plasticity and weldability, it is often used in ship pipelines and corrosion-resistant structures.
China's independent research and development in the field of titanium alloys for Marine engineering has formed a complete system centered on Ti60, Ti600, Ti70, Ti80, etc., covering multiple directions such as corrosion resistance, high strength, high temperature, and additive manufacturing. It has achieved full-chain breakthroughs from material research and development to engineering application in fields such as deep-sea equipment, Marine oil and gas, and seawater desalination.
When choosing titanium grades in Marine engineering, the following aspects need to be comprehensively considered:
- Corrosive environment: seawater flow rate, temperature, chloride ion concentration, and whether there is a risk of crevice corrosion;
- Mechanical properties: strength, toughness, fatigue performance, impact resistance;
- Processing technology: Weldability, formability, heat treatment requirements;
- Cost: Industrial pure titanium has a relatively low cost, while β -type alloys have a higher cost but excellent strength.
