As the first third-generation fighter independently developed by Asian countries, is also one of China's most successful fighter . J-10 is a milestone, and it marks that the development of modern fighter is no longer exclusive to the aviation powers of the United States, Russia and Europe.
However, the development process of the J-10 aircraft was not smooth. It encountered a lot of technical difficulties in the early stages of development, one of which was the fastener problem.
Due to the harsh working conditions of aviation fasteners, we must follow the aircraft to experience multiple harsh environments, from 0 altitude to 20,000 meters above sea level, from 50℃ above zero to -40℃ below zero, and accompanied by rain, snow, wind, frost weather, salt spray, humid environment, plus high load, impact, vibration and other stressed environments, these superimposed become special labels for aerospace fasteners: high load, high reliability, corrosion resistance, and long life. However, in the 1990s, my country could not produce high-performance aviation fasteners.
The so-called aviation fasteners are small parts such as bolts, nuts, rivets, washers and other small parts used on the aircraft. Don’t underestimate these small parts. It is the big trouble caused by these small parts that brought considerable difficulties to the development of the aviation industry at that time.
To summarize, there are mainly three types of problems:
- has low processing accuracy, and fasteners in each batch vary by thousands to tens of thousands of thousands of times. The tolerance range of the size fluctuates greatly, and good interchangeability cannot be guaranteed. There are often problems in the installation process and you have to choose from it from time to time.
- material performance is poor, mainly carbon steel and alloy steel fasteners. In addition to poor corrosion resistance and low specific strength, it is also plagued by the problem of hydrogen embrittlement . At that time, after decades of exploration, European and American aviation powers had formed a complete material system of aviation fasteners titanium alloys, high-temperature alloys, etc., with excellent performance, complete types, and full coverage of strength ranges. my country has a huge gap in the development and production of aviation fasteners materials. The quality of plating is not up to standard. The surface treatment method is mainly traditional electroplating methods such as galvanizing and cadmium plating. In addition to polluting the environment, the anti-corrosion ability and lubrication performance are average. An aircraft will take 20 years to fly. If the fastener coating is not up to standard, the life is short and corrosion-resistant, the aircraft also faces the risk of elimination. At that time, domestic surface treatment technology was the same as heat treatment technology, and it was still a long way behind the world's advanced level.
The fundamental reason is that due to the constraints of traditional ideas, our country does not pay enough attention to the development and production of fasteners. It believes that fasteners are shelf products, which are positioned at low end and cheap, and can be taken as you use, without investing huge manpower and material resources to study.
This leads to the fact that when my country designed high-performance aircraft, there were no high-performance aviation fasteners to match it. Therefore, the J-10 aircraft used a large number of imported fasteners in the early stages of the development of the J-10 aircraft, but the price of imported fasteners ranged from dozens of dollars to hundreds of dollars. It consumed a lot of foreign exchange every year, and there was a risk of being "bottled" by European and American countries at any time.
With the establishment of the J-10, the country has increased its attention to fasteners, and has also carried out the imitation and replacement of high-performance fasteners. After nearly 20 years of development, the localization rate of fasteners has been greatly improved, basically ensuring that the quality and life of the aircraft have not declined much.
and a batch of high-end fasteners represented by titanium alloy have been popularized and promoted, and have been used on more and more models, promoting the development and progress of the entire industry, which is mainly reflected in the following three aspects:
- A large number of high-end aviation equipment have been introduced to China, such as high-performance multi-station temperature upsetting equipment, CNC centerless grinders, CNC threaded wire rolling equipment, CNC temperature wire rub equipment, hole punching and square punching machine, bottom-head rounded corner strengthening machine, etc., which has continuously strengthened domestic aviation fastener manufacturing equipment in digitalization and automation, so the product has greatly improved processing accuracy and dimensional consistency.
- However, in the design and application of new fasteners, it is still mainly imitated, and there is no perfect standard system that can be formed in combination with the development of its own model.
- strengthens basic research on fastener materials and completes the upgrade of fastener raw materials. In recent years, a number of domestic major aviation material manufacturers such as Northwest Nonferrous Metals Research Institute , Baoji Titanium Industry , Western Superconductor, Western Supercrystal, Fushun Special Steel , etc., have actively explored in-depth cooperation with aviation fastener manufacturers to carry out the development and trial of high-performance fasteners materials.
- For example, the successful application of domestic TC4 silk material marks the phased success of my country's imitation of American Ti-6Al-4V material and will also be used on more and more models. However, domestic materials still have a considerable gap with imported materials in terms of performance stability, cost, etc.
- , and my country has not made substantial progress in high-temperature and ultra-high-strength materials, and it is still very dependent on imported materials from abroad.
- With the continuous improvement of domestic coating performance and the continuous optimization of coating and plating technology, the coating technology of domestic aviation fasteners has also made great progress. The popularization of
- cyanide-free electroplating and ion plating has greatly improved the environmental friendliness of the plating, improved the anti-corrosion ability of the fasteners, and increased the salt spray test time from the initial 96h to 500h or even higher.
- However, the current high-end fasteners still rely on imported coatings, and domestic coatings have a big gap in coating bonding strength, surface hardness, appearance, etc.
To sum up, the domestic aviation fastener industry has developed rapidly in the past 20 years, but there is still a big gap in design prospects and standard system construction. In addition, there is still a big gap in the research of basic processes such as raw materials and coatings with developed countries. In this regard, the country still needs to continue to increase investment.
China's self-developed civilian C919 passenger aircraft also faces the same problem. A C919 uses about 1.1 million fasteners, but at present, more than 90% of fasteners rely on imports. Wu Guanghui, chief designer of
C919, once praised fasteners for "ten thousand, group division, connecting structure, connecting system, and large objects", which shows the importance of fasteners. With the increasing trade friction between China and the United States and the consideration of national strategic security, the calls for localization of civilian aircraft fasteners are becoming increasingly high.
However, aviation fasteners are a high-end technology-intensive product and cannot catch up overnight. Therefore, the aviation fastener industry must continue to work hard and make greater developments in the future with the help of "Industry 4.0" and " Made in China 2025".
Today's topic is all about sharing. If there are any inappropriate points, criticism and correction are welcome. If you have any questions or suggestions, or if you need source files, or if you need to join the group to communicate, you can follow the WeChat official account of Screw Jun: GAF Screw Jun (GAF-luosijun)
