The development trend of titanium alloy screws for aviation
Titanium alloy screws, as an important general-purpose basic component, play a pivotal role in the industry, and are called "the rice of industry". According to the type, titanium alloy screws can be divided into 13 categories such as bolts, screws, studs, nuts, wood screws, self-tapping screws, washers, rivets, pins, retaining rings, link pairs, and titanium alloy screws-assemblies; according to the application In the field, titanium alloy screws are divided into general-purpose titanium alloy screws and aerospace titanium alloy screws. In the aviation field, the connection method of the aircraft is still mainly mechanical connection, and the connection assembly of the aircraft relies on a large number of various titanium alloy screws; in the aerospace field, the connection between the aircraft sections also relies on the connection of titanium alloy screws. With the development of lightweight equipment, more and more aerospace titanium alloy screws favor titanium alloy materials. In foreign countries, the application history of titanium alloy screws can be traced back to the 1950s. The United States took the lead in applying Ti-6Al-4V alloy bolts to the B-52 bomber and achieved significant weight reduction effects. Titanium alloy screws are used in the aerospace field. The application starts here.
The history of the development of titanium alloy screws in China can be traced back to 1965. In the 1970s, relevant units carried out research work on titanium alloy rivets and applications; in the 1980s, a small amount of titanium such as rivets and bolts began to be used on some second-generation military aircraft in China. Alloy screws; In the late 1990s, with the introduction of foreign third-generation heavy fighter production lines and the development of domestic third-generation fighters, China began to use some titanium alloy screws; in recent years, with the development of China's aerospace industry, Various units have successively carried out the research and development of titanium alloy materials for titanium alloy screws and the research and development of titanium alloy screw manufacturing technology. Titanium alloy screws have taken the lead in a large number of applications in the aerospace field, and their consumption on civil aircraft is also very considerable. According to data, each domestic C919 aircraft needs about 200,000 pieces of titanium alloy screws. If the planned annual production of 150 large aircraft in 2018 is calculated, 30 million pieces of titanium alloy screws are needed each year. Regarding the future development trend of titanium alloy screws for aviation, Zhongyang Metals combines relevant materials as follows:
1. Ultra-high-strength titanium alloy screws
With the development of my country's aerospace industry, the level of connection technology used in new aircraft and space vehicles has continued to improve, and new requirements have been put forward for new titanium alloy screws. The future development of ultra-high-strength titanium alloy screws with a tensile level of 1 200~1 500 MPa and a shear strength of ≥750 MPa is one of the future development trends.
2. High temperature resistant titanium alloy screws
At present, the use temperature of titanium alloy materials for titanium alloy screws is not high. In the field of aerospace, due to the continuous increase in the flight speed of new models of aircraft and aircraft, the service temperature of the required materials has also increased. Therefore, high temperature resistant titanium alloy screws are also the future development trend, especially in the aerospace field, requiring new high temperature titanium alloy materials to be able to serve for a short time at 600~800 ℃. Usually Ti2AlNb alloy is used to replace heavier high-temperature alloys, and its deformation is more serious, while the use of Ti2AlNb alloy to replace other titanium alloy materials is still heavier and cannot meet the weight reduction requirements; Ti-Al-based intermetallic compounds have poor process plasticity and relatively high maturity difference. Therefore, in the future, high-temperature titanium alloy materials for titanium alloy screws will still be mainly two-phase titanium alloys with near-α type and high aluminum equivalent. At high temperatures, the improvement of the strength and creep resistance of titanium alloys mainly depends on the solid solution strengthening effect of Al, Sn, and Zr. However, due to the limitation of aluminum equivalent, the content of these elements cannot be increased indefinitely, so it is appropriate to In the case of controlling the content of Al, Sn, and Zr, the titanium alloy is designed by supplementary strengthening by multi-element composite alloying. The β-stabilizing element Mo has a solid solution strengthening effect on the high-temperature strength and creep strength of high-temperature titanium alloys. Nb, Cr and V also have similar effects. The addition of a small amount of β-stabilizing elements can also prevent alloy embrittlement. In addition, the content of Si in the titanium alloy is very important to the performance. After adding about 0.2% of the mass fraction of Si, the ellipsoidal silicide will be non-uniformly and discontinuously precipitated on the boundary of the alpha sheet, which can effectively hinder the movement of dislocations. , Produce dispersion strengthening effect, greatly improve the creep resistance of the alloy. However, the appearance of silicide also has a harmful effect on the thermal stability of the alloy structure. It not only reduces the plasticity of the alloy, but also enhances the degree of ordering of the alloy and promotes the formation of Ti3Al phase. Therefore, the Si content should be controlled at a low level, generally the mass fraction is not more than 0.5%. Therefore, multi-element composite strengthening is still the development direction of new high-temperature titanium alloy material design. titanium square bar Gr3 Pure Titanium Plate titanium sheet Titanium Bike Rack
