Bending And Forming Technology Of TA18 High-Strength Titanium Alloy Pipe For Aviation

TA18 high-strength titanium alloy has become the material of choice for aviation piping systems for its excellent overall performance. The level of bending and forming technology of pipes is essential to the performance of aircraft. The development of TA18 high-strength titanium alloy pipes in our country is still in its early stages. In order to meet the needs of lean aviation products, there is an urgent need to establish a more comprehensive titanium alloy pipe bending and forming process system and numerical simulation system.

TA18 titanium alloy is a low-aluminum equivalent nearly α-type titanium alloy that evolved from TC4 titanium alloy, and its nominal composition is Ti-3Al-2.5V. The strength of TA18 titanium alloy at room temperature and high temperature is 20 to 50% higher than that of pure titanium. It not only has good mechanical properties and corrosion resistance at room temperature and high temperature, but also has excellent plasticity, formability and welding properties of cold and hot processing processes. The alloy is not sensitive to gaps and has good corrosion resistance, so it has become the material of choice for aerospace piping systems.

The strengthening method of TA18 titanium alloy is mainly through cold processing and deformation. After cold processing, the pipes can reach different strength levels through different heat treatment systems. The most commonly used are the medium-strength grade in the annealed state (Rp0.2≥620MPa) and the high-strength grade in the stress-relieving annealed state (Rp0.2≥860MPa). Among them, medium-strength grade pipes in the annealed state are mainly used in engine piping systems, and high-strength grade pipes in the stress-relieving annealed state are mainly used in aircraft hydraulic piping systems.

The piping system of aerospace aircraft is the lifeline of the aircraft, which mainly includes fuel pipelines, hydraulic oil pipelines, lubricating oil pipelines, air source pipelines, compressed air pipelines, and injection water pipelines. There are a large number of them and complex structural shapes, and the processing quality directly affects the accuracy and stability of their connections. All along, various defects often occur in the bending and forming of pipes, such as cross-section deformation, wrinkling, thinning of the elbow, bending rebound, etc., which not only affects product quality and production and assembly progress, but also brings safety risks to the realization of system functions of aircraft.

The reliability and durability of the piping system are important factors for meeting the requirements of airworthiness, ensuring flight safety and reducing maintenance costs. Therefore, improving the bending and forming technology of pipes is very important to improve aircraft performance.

Application Status Domestic And International

International Application Status

TA18 high-strength titanium tubing is used in hydraulic piping systems, which can not only meet the high strength requirements, but also meet the lightweight requirements of components in aerospace and other fields. Therefore, it has long been valued and widely used abroad. In the mid-20th century, the United States developed TA18 titanium alloy for aircraft pipeline hydraulic systems. The pipes prepared from this alloy have been popularized and applied in the hydraulic and fuel pipeline systems of F-14A, F-15, B-1 and Boeing 747, 757, 767 and other aircraft. The world's major airlines, such as Boeing, General Motors, Mcdonald's, Pratt & Whitney, Luoluo, Airbus, etc., also use TA18 titanium alloy pipes extensively on their means of transportation such as military aircraft and commercial airliners. At present, TA18 titanium alloy has been widely used in pipe fittings (including helicopters) in military projects in many Western countries, and has become the material of choice for piping systems for military and civilian aircraft.

Domestic Application Status

In the mid-1970s, relevant units led by the Northwest Institute of Non-Ferrous Metals began to conduct in-depth research on medium-strength TA18 titanium alloy, and it was widely used in aerospace shuttle piping systems, but the development of high-strength TA18 titanium alloy pipes is still in its infancy. Stage. At present, since the bending and joint technology of titanium alloy pipes is not yet fully mature, titanium alloy pipes have not been widely used in civil and military aircraft. In terms of pipe bending and forming, due to the lack of corresponding equipment, CNC cold bending and forming of pure titanium (such as TA1, TA2) and some low-strength titanium alloy pipes (such as TA16M) and medium-strength titanium alloy pipes (such as TA18M) can only be achieved stably.