Titanium and its alloys have low density (4.51g/cm3), high strength (some up to 1000MPa), high specific strength, high and low temperature performance (-250℃～500℃) and fatigue resistance (the fatigue limit is that of steel). Twice) excellent and other characteristics, so it is very suitable for use on high-speed aircraft such as aircraft, missiles, and rockets. The weight reduction effect produced by the application of titanium alloy fasteners will have a huge effect on improving the propulsion of aircraft and spacecraft, increasing the range, saving fuel, and reducing launch costs. In modern aircraft manufacturing, the connecting fasteners used in an aircraft range from hundreds of thousands to millions. Titanium alloy fasteners account for up to 90% of threaded fasteners.Today Titanium alloy fasteners have become the most important variety of "aerospace fasteners".

Titanium alloy fasteners have excellent corrosion resistance, especially its positive potential properties just match with carbon fiber composite materials, effectively preventing the galvanic corrosion of fasteners. Therefore, not only titanium structures, aluminum structures, but even some composite materials can be connected with titanium alloy fasteners. This characteristic cannot be replaced by any other material, which is another reason for the rapid development of titanium alloy fasteners and the increase in usage year by year. Titanium alloy fasteners not only have strong demand in the fields of aviation and aerospace, but also have great application potential in shipbuilding (including submarines, etc.) and some industrial fields with heavy corrosive environments such as petroleum, chemical industry, light industry, electric power, metallurgy, etc. .

Marine equipment manufacturing field.

Since titanium has better resistance to seawater corrosion than all metals, it has special stability in static or high-speed flowing seawater. In addition, fasteners made of titanium alloys are ideal for use on submarines, warships, civilian vessels, and desalination plants.

Industrial areas with heavy corrosive environments.

In the relevant facilities and equipment in the petroleum, chemical, metallurgical, electric power and other industries, fasteners and connectors not only have to bear a certain load, but also are strongly corroded by a variety of acid and alkali media. The working conditions are very harsh, and the use of titanium Alloy fasteners are the best choice. Because, titanium has strong corrosion resistance in high temperature and humid chlorine environment. For example, in normal temperature chlorine water, the corrosion rate of titanium is 0.000565mm/a; in 80°C chlorine water, the corrosion rate is 0.00431mm/a; in 95% wet chlorine water, the corrosion rate is 0.00096mm/a. Therefore, titanium alloy fasteners are the best substitute for stainless steel fasteners

Medical and pharmaceutical production fields.

Because titanium can resist liquid corrosion inside the human body, is non-magnetic, has good biocompatibility, and is harmless to the human body, titanium alloy fasteners are increasingly used in pharmaceutical equipment, medical equipment, surgical instruments and Artificial bones.

High-end sports equipment field

In the field of high-end sports equipment (such as golf clubs), high-end bicycles and high-end cars, titanium alloy fasteners have considerable application prospects. According to preliminary statistics, in 2010, the titanium used in automobiles and motorcycles in my country reached nearly 8000t. Since the automobile industry is the largest user of fastener products, its demand accounts for about 18%-20% of the total fastener sales. Therefore, it is of great significance to further expand the market space of titanium alloy fasteners for automobiles.

In 2011, as one of the seven strategic new industries, titanium and tungsten deep processing products (tungsten carbide) have been selected into the national new material catalog. Nowadays, global titanium products are exploring new application fields, and in the future, they will continue to deepen in the fields of automobiles, energy and power, sports and leisure, and medical care. It is estimated that by 2013, the amount of titanium used in new applications will increase from 10% of the world's 1.5×105t to 20% or more.

Aviation titanium alloy fastener varieties

The tensile strength of titanium alloy fasteners is generally 1000-1500MPa, which is equivalent to the strength level of 30CrMnSiA steel after quenching and tempering. The shear strength of titanium alloy fasteners is also of the same level as alloy steel, but the density is only 58% of steel. . Therefore, in foreign advanced aircraft, 30CrMnSiA steel fasteners have been basically replaced by titanium alloy fasteners. Due to the high specific strength (up to the specific strength of high-strength aluminum alloys), the temperature resistance can reach 350 °C. A variety of titanium alloy fasteners are used in modern aircraft materials, mainly including ordinary titanium bolts, interference bolts, special bolts, etc.

Ordinary titanium fasteners mainly include: ordinary titanium bolts, high-lock bolts, Eddy bolt systems, etc.

Ordinary titanium bolts: according to the head type, it is divided into countersunk head (100°, 130°) bolts, hexagon bolts, twelve angle bolts, twelve angle flange bolts, etc. 100° countersunk head bolts have a variety of groove shapes, such as Phillips cross groove, high torque cross groove, three-wing groove, high torque flat groove and so on. There are gap type and interference type for rod diameter.

High Lock Bolt: It is a threaded fastener that can be installed on one side and is one of the fasteners widely used in aircraft. According to the force, it can be divided into tensile type and shear type. The bolts have 100° countersunk head and flat raised head, aluminum high lock nuts for shear type, stainless steel nuts for tension type bolts. The rod diameter is divided into clearance type, interference type, and short thread interference type. Nuts are divided into ordinary high-lock nuts, sealed high-lock nuts (with nylon washers inside), and self-aligning high-lock nuts according to their uses.

Eddy Bolt Fastening System: It is the fourth generation nut system. The thread of the bolt has five grooves, and the nut has three protrusions. After the interlayer reaches a certain preload, it is filled into the threaded groove of the bolt. The load of the system can be controlled, the parts are not easily damaged, and it is suitable for the connection of composite materials.

Interfering fasteners: The fatigue life of modern aircraft is getting higher and higher. The life of military aircraft is 5000-8000 flight hours; civil aircraft is 50,000 flight hours. Therefore, an interference fit connection in addition to hole wall reinforcement is required to improve the fatigue life of the structure. Almost 100% of non-removable shear fasteners on commercial aircraft use interference fit technology. Interference fasteners used in metal structures, such as MD pins, interference high lock bolts, 70° interference bolts, interference ring grooved nails, etc., can be installed by riveting guns or pulling guns. The use of bushed interference ring grooved nails and the recently developed HI-LEX fastener system on composites.

Special fasteners include titanium ring grooved nails, single-sided thread pulling nails, etc.

Titanium ring grooved nails: Mainly used for high load transfer joints. There are two types of 100° countersunk head and convex head used for metal structures, and the rod diameter has gap type, interference type, and enlarged type. There are three types of titanium ring grooved nails for composite structures: 100° countersunk head, 130° countersunk head and convex head. Among them, the interference type is a ring grooved nail with a bushing, and the connection is completed with a pull gun with a controllable preload. Single-sided fasteners: It is one of the commonly used fasteners for aircraft installation. It is used to install the open parts of the structure. The titanium alloy outsole single-sided fasteners used are mainly used for composite material structures. There are two types of thread, such as TIMATIC single-sided pull stud, COMPOSI-LOKⅡ thread puller, COMPOSI-BOLT thread puller, etc. In recent years, foreign countries have also developed interference-type screw-pulling screws with bushings, and the largest interlayer single-sided screw-pulling screws. Soft core construction can use aluminum collar grooved nails and MAF adjustable fasteners.

According to my non-ferrous network analysis, the production technical requirements of aviation titanium alloy fasteners are almost demanding. In addition to high specific strength, high temperature resistance, low temperature resistance, corrosion resistance, corrosion resistance, and pursuit of the highest possible fatigue life, it also requires anti-loosening, self-locking, shape memory and other functions. The advanced nature, reliability and rationality of installation and connection should reach a very ideal situation. That is, after the assembly process is completed, the clamping force, self-locking force and interference amount should be reliably guaranteed. The threads of titanium alloy fasteners are mostly enlarged arc bottoms, MJ threads (metric) or UNJ threads (imperial) with high precision and high precision, and their technical content is much higher than that of general-purpose fasteners