Application and Development of Large-Diameter Titanium Alloy Pipes for Marine Use

In recent years, China has undertaken numerous significant projects, including naval vessels, offshore oil drilling platforms, seawater desalination, and artificial islands. These projects have led to a substantial increase in the demand for high-strength, corrosion-resistant metal pipes used in large-scale equipment within these fields. Due to the complex and harsh marine environment (e.g., strong corrosion, typhoons, strong convection, high temperatures, high pressure, and biological fouling), the corrosion resistance of metal pipes is of utmost importance. Titanium and its alloys, with their high strength, toughness, non-magnetic properties, low density, and excellent corrosion resistance, are ideal materials for such large-scale marine equipment.

Extensive usage has shown that low-alloy steel pipe systems have a lifespan of 1-2 years, and Cu/Ni pipe systems last only 6-8 years, both falling short of the design life requirements for seawater pipelines. Titanium, with its high strength, toughness, specific strength, light weight, non-magnetic properties, and resistance to seawater and marine atmospheric corrosion, has a corrosion life exceeding 120,000 hours and a service life of over 60 years. Under harsh marine conditions, the lifespan of titanium alloy materials far surpasses that of other metal materials. Additionally, they can be 100% harmlessly recycled after their service life ends, making them the best material choice for marine equipment.

Characteristics of Marine Equipment

1. Large Metal Structures: Marine equipment consists of large metal structures with significant tonnage, high investment costs, and substantial damage losses.
2. Complex and Harsh Conditions: These systems are complex, multi-functional, and operate under harsh conditions, requiring high reliability and sophisticated construction techniques.
3. Material Longevity: Extending the lifespan of materials is crucial for ensuring the integrity, reliability, and safety of marine equipment and structures, promoting resource conservation and sustainable development.
4. Enhanced Performance: Improving the performance of marine equipment involves enhancing corrosion resistance, lightweighting, using high-strength and high-toughness materials, reliability, and the economic efficiency of the product's entire life cycle.

Advantages of Titanium Alloy Pipes

Titanium alloys have a series of important properties, including high melting point, low density, high strength, corrosion resistance, superconductivity, shape memory, and hydrogen storage. These properties make titanium alloys widely used in aerospace, marine, nuclear power, medical, chemical, metallurgy, electronics, sports, leisure, and construction fields. Titanium alloys are known as the "third metal," "aerial metal," and "marine metal." Pipes, used for transporting gaseous and liquid media, are fundamental products in various national economic sectors. Titanium alloy pipes, with their lightweight and excellent corrosion resistance, find extensive applications in aviation engines, spacecraft, petroleum pipelines, chemical equipment, marine construction, and offshore platforms. These include coastal power plants, offshore oil and gas extraction and transportation, seawater desalination, marine chemical production, alkali and salt production, and petroleum refining equipment, promising broad prospects.

Technical Development

Promoting the application of titanium materials is a key technological development direction for shipbuilding and marine engineering equipment. Developed countries widely use titanium alloy pipes in marine engineering equipment, enhancing the safety and reliability of these systems, reducing equipment size and weight, and significantly extending service life by reducing equipment damage and maintenance frequency.

Processing Characteristics of Titanium Alloy Pipes

Titanium alloys have two different kinds: Titanium Seamless Tube and Titanium Welded Tube have low plasticity at room temperature and high deformation resistance, but they exhibit good plasticity and lower deformation resistance in the α+β and β phase regions. Therefore, the forming and manufacturing of titanium alloy materials or the preparation of various profiles (plates, rods, Ti Pipe, etc.) require heating to near the phase transition point.

Titanium alloys tend to react chemically with oxygen, nitrogen, carbon, and absorb hydrogen at high temperatures, which sharply decreases their deformation performance and affects their service properties. Additionally, due to the low thermal conductivity of titanium alloys, heating large billets often leads to significant cross-sectional temperature differences, making them prone to cracking during deformation. Furthermore, the deformation temperature range for titanium alloys is narrow and sensitive to strain rates, generally requiring deformation at low rates. The cooling rate after deformation directly impacts the room temperature equilibrium structure and the service properties of components. Therefore, it is crucial to maintain a constant deformation temperature or take measures to reduce the rate of temperature decrease during deformation to ensure sufficient plasticity.