Titanium and Titanium Alloy in the Aerospace Sector
Early Applications of Titanium in Aerospace Development
Titanium alloy materials used in aviation and aerospace, known as titanium alloy castings, have extensive applications. These include joints, rivets, and cast parts. In aircraft manufacturing, titanium alloys are primarily used in engine compressor components, rocket development, and certain weapon structural parts. By the mid-21st century, titanium and its alloys had become widely used in general industrial fields.
Innovation in Aircraft Frames with Titanium Alloys
Titanium alloy is a new and significant structural material in the aerospace industry. Its density and operating temperature lie between those of aluminum and steel, but it has a higher strength-to-weight ratio excellent corrosion resistance to seawater, and superb low-temperature performance.
1960s Onwards: The use of titanium alloys expanded from the rear fuselage to the mid-fuselage, partially replacing structural steel to manufacture critical load-bearing components like bulkheads, beams, and flap tracks.
National Defense: With the continuous buildup of national defense, the amount of titanium alloy used in military aircraft rapidly increased. Titanium alloys now account for 20% to 25% of the total weight of aircraft structures.
Civilian Aircraft: Over time, civilian aircraft also began to use titanium alloys extensively. For example, the Boeing 747 uses over 3,600 kg of titanium.
High-Speed Aircraft: The U.S. SR-72 series high-altitude, high-speed reconnaissance aircraft, which flies at Mach 3.0 and reaches an altitude of 26,200 meters, relies heavily on titanium alloys, making up 91% of its structural weight, earning it the nickname “all-titanium” aircraft.
Titanium Alloy Compressors
Increased Temperatures: When the thrust-to-weight ratio of aero-engines increased from 4-6 to 8-10, the temperature at the compressor outlet also increased from 200°C-300°C to 500°C-600°C. Thus, low-pressure compressor discs and blades, previously made of aluminum, had to be replaced with titanium alloys.
Replacement of Stainless Steel: Titanium alloys were used instead of stainless steel to make high-pressure compressor discs and blades, reducing the aircraft’s structural weight.
1970s Onwards: Titanium alloys generally accounted for 20% to 30% of the structural weight of aero-engines, mainly used in compressor components such as forged titanium fans, compressor discs and blades, cast titanium compressor casings, intermediate casings, and bearing housings.
Spacecraft: Titanium alloys are used for their high strength-to-weight ratio, corrosion resistance, and low-temperature performance to manufacture pressure vessels, fuel tanks, fasteners, instrument bands, frames, and rocket shells. Titanium alloy sheets are also used in welded parts of artificial satellites, lunar modules, manned spacecraft, and space shuttles.
Applications of Titanium Alloy Spinning Parts
In aerospace, titanium alloys are used in spacecraft systems not only for their strong structural characteristics and excellent physical properties but also for their lightweight and precision.
New Spinning Parts: The quality and reliability of new titanium alloy spinning parts require multiple experimental data analyses. Due to the complexity of forming titanium alloy sheets, TC4 is used as the base material, combining ordinary and powerful spinning methods to manufacture new semi-spherical titanium alloy parts.
Materials: TC3 and TC4 are also used as materials for titanium alloy sheets, and hot spinning is used to produce two new types of titanium alloy hemispheres.
Applications in Gas Turbine Engines
Another major application of titanium alloys in aerospace is in aircraft engine manufacturing.
Current Usage: About one-third of the structural weight of gas turbine engines used in modern aircraft in China is made up of titanium alloys.
Early Applications: As early as the 1940s and 1950s, industrially advanced countries such as the United States and the United Kingdom applied titanium alloy technology to improve the structural components of jet engines during early aircraft production.
Initial Components: The first titanium alloy engine components were compressor blades, followed by the rapid development of titanium alloy compressor discs. Nowadays, most fan blades used in jet engines are made of new titanium alloys.
Applications of High-Temperature Titanium Alloys
Due to their strong thermal strength and high strength-to-weight ratio, high-temperature titanium alloys are widely used in aero engines.
Primary Uses: They are primarily used in engine fans, blades, precision instruments, and navigation devices.
Replacement of Nickel-Based Superalloys: Replacing existing nickel-based superalloys with titanium alloys reduces the structural weight of compressors by 30% to 35%.
Comprehensive Titanium Alloy System: Over the years, to meet the demands of high-performance engines, a comprehensive titanium alloy system has been developed.
Titanium and Titanium Alloy in Chemical Processing
Applications of Titanium in the Fertilizer Industry
Urea Production:
Corrosive Medium: Ammonium carbamate, excess ammonia, urea, and water at high temperatures and pressures.
Required Equipment: Titanium is used for high-pressure equipment like synthesis towers, CO₂ strippers, and first-stage separators in contact with molten urea due to its superior resistance to localized corrosion compared to stainless steel.
Example: Urea stripping towers are among the heavy-duty titanium-lined equipment designed and manufactured domestically.
Combined Alkali Production:
Corrosive Medium: High concentration ammonium chloride solution.
Required Equipment: Only titanium can effectively solve the corrosion issues in combined alkali production, where coating protection is inadequate.
Applications: Titanium and titanium alloys are used for valve plates, springs in chemical installations like high-pressure compressors for hydrogen and nitrogen, and anode materials for electrochemical cathodic protection to enhance fatigue corrosion resistance and lifespan.
Applications of Titanium in the Chlor-Alkali Industry
Corrosion Resistance: Titanium’s exceptional resistance to wet chlorine gas, chlorides, and chlorine-containing solutions, without pitting or stress corrosion, makes it invaluable in chlor-alkali production.
Key Equipment:
Wet chlorine coolers
Metal anodes in electrolyzers
Dechlorination tower heating tubes
Pumps and valves for vacuum dechlorination of chlorine-containing brine
Benefit: Titanium has resolved long-standing corrosion issues in chlor-alkali plants, making this industry one of the largest users of titanium equipment.
Applications of Titanium in the Synthetic Fiber Industry
Corrosive Medium: Processes involving halogen compounds (chlorides, bromides) as catalysts or intermediates.
Required Equipment: Titanium is used for key equipment to combat severe corrosion.
Examples:
Oxidation towers in polyester production
Photochemical reactors in ε-caprolactam production
Intermediate heaters in disalt hydrolysis
Hydroxylamine heat exchangers
Oxidation reactors in vinyl acetate production
Applications of Titanium in Dye and Pesticide Production
Corrosive Medium: Various acids and alkalis during the production of dyes, pesticides, and intermediates.
Required Equipment: Titanium and titanium alloys are used to overcome severe equipment corrosion, reduce maintenance frequency, and extend service life.
Examples:
Azeotropic towers and evaporators in maleic anhydride production
Titanium and Titanium Alloy in the Marine Engineering
Pressure Hulls
High Specific Strength: Titanium alloys are the preferred material for deep-sea equipment pressure hulls due to their high specific strength, excellent corrosion resistance, and non-magnetic properties.
Early Adoption: Russia was the first country to use titanium alloy pressure hulls in nuclear submarines, with the “Alpha” and “Typhoon” class submarines extensively utilizing titanium.
Chinese Innovation: China’s independently developed “Jiaolong” manned submersible also uses titanium alloy for its pressure hull, underscoring titanium’s critical role in deep-sea exploration.
Propulsion Systems
Corrosion Fatigue Resistance: Titanium alloy propellers are ideal for ships due to their high corrosion fatigue strength and cavitation resistance.
Historical Usage: Since the 1960s, countries like Russia and the UK have used titanium alloy propellers on ships. The US Navy’s experimental submarine hunters and large military hydrofoil boats also adopted titanium alloy propellers.
Engine Applications: Titanium alloys are used in ship engines and waterjet propulsion systems. For instance, Russia’s nuclear-powered icebreakers use steam engines with titanium alloys, while the US SES-100A experimental boat and Japan’s “PT-10” torpedo boat use waterjet propulsion systems made from industrial pure titanium and titanium alloy forgings.
Pumps, Valves, and Pipelines
Marine Environment Challenges: Shipboard pumps, valves, pipelines, and accessories face harsh marine conditions.
Material Requirements: Due to copper alloys’ susceptibility to corrosion in marine environments, titanium alloys are the ideal replacement.
Longevity and Efficiency: Using titanium alloys for these components significantly enhances the ship’s pipeline system’s lifespan and efficiency.
Acoustic Devices
Sonar Systems: Titanium alloys are used to manufacture acoustic devices like sonar systems due to their low density, low sound velocity, and excellent acoustic impedance matching properties.
Improved Detection: These properties enhance the detection accuracy and sensitivity of acoustic devices.
Electronic Information Systems
Component Durability: Titanium alloys play a vital role in shipboard electronic information systems, used for making enclosures, heat sinks, and other parts.
Stable Operation: These components ensure the stable operation of electronic equipment in harsh marine environments.
Structural Materials
High Specific Strength and Lightweight: Titanium alloys are ideal for ship structural materials due to their high specific strength and lightweight properties.
Structural Applications: They can be used to manufacture the ship’s framework, decks, and hull components, effectively reducing the ship’s overall weight and enhancing its navigation performance.
Lightweight: Using titanium alloy for connecting rods is highly rational due to its lightweight properties. Compared to steel connecting rods, titanium alloy rods can reduce weight by 15%-20%.
Early Adopters: The Ferrari 315LV8 was the first car to use titanium alloy connecting rods.
Engine Valves
Lightweight and Durable: Titanium alloy engine valves are lighter, have a longer lifespan, and can reduce fuel consumption.
Comparison to Steel: Titanium alloy valves reduce mass by about 30%-40% compared to steel, allowing the engine’s maximum RPM to increase by approximately 20%.
Valve Spring Retainers
Strength and Fatigue Resistance: The high strength and fatigue resistance of titanium alloy make it ideal for valve spring retainers.
Weight Reduction: Titanium alloy retainers are 30%-40% lighter than steel, reducing the inertia mass of the valve assembly and increasing the engine’s maximum RPM.
Titanium Alloy Springs
Elastic Modulus: Titanium alloy springs have a lower elastic modulus than steel springs.
Space and Weight Savings: They provide the same elasticity at only 40% of the height and 30%-40% of the weight of steel springs, offering more design space and longer lifespan.
Turbocharger Rotors
Heat Resistance and Machinability: Titanium alloy turbocharger rotors perform well under high temperatures and are easy to manufacture.
High-Temperature Performance: These rotors operate efficiently at temperatures up to 850°C, showcasing the capabilities of titanium alloys.
Exhaust Systems and Mufflers
Performance and Lifespan: Titanium alloy exhaust systems enhance performance, longevity, and aesthetics while improving fuel combustion efficiency.
Weight Reduction: Titanium exhaust systems are approximately 40% lighter than steel, reducing the vehicle’s weight by about 5 kilograms.
Vehicle Frame
High Strength and Toughness: Some titanium alloys are ideal for vehicle frames due to their high strength and toughness.
Enhanced Driving Experience: Japanese manufacturers use titanium for vehicle frames to provide a better driving experience.
Titanium Alloy Wheel Hub Bolts
Lightweight and Strong: Essential for modified wheel hubs, titanium alloy bolts are lighter and stronger than steel bolts.
Aesthetic Appeal: Their unique luster enhances the appearance of wheel hubs.
Other Titanium Alloy Components
Diverse Applications: Titanium is also used in various other components, including: