Appearance of CoCrMo alloy powder

Metal 3D printing VS aviation forging technology

(HY-industry technical centre)

  • Forging technology has been used in the field of aviation manufacturing for many years, and is mainly used to manufacture key and important parts of aircrafts and engines that bear alternating loads and concentrated loads. The weight of parts made of forgings on the aircraft accounts for about 20% to 35% of the weight of the aircraft body structure and 30% to 45% of the weight of the engine structure. It is an important factor that determines the performance, reliability, life and economy of the aircraft and engine First, it can be seen that the development of forging technology plays an important role in the aviation manufacturing industry.

  • With the continuous development of the aviation industry, the pursuit of extreme lightweight and reliability of aviation equipment is becoming more and more urgent, and the bottleneck of forging technology has gradually emerged, especially in the manufacture of large and complex integral structural parts and precision and complex components. At the same time, the new technology called “the third industrial revolution” and “barbaric artifact”-3D printing technology has also brought an impact on the forging technology. Its manufacturing concept is subverted, the processing cycle is greatly shortened, and the material utilization rate is Significantly improved, low-carbon and environmentally friendly manufacturing methods directly threaten the development of the forging industry. Some even believe that 3D printing technology can replace forging technology in the field of aviation manufacturing. Faced with these problems, how the forging industry will develop in the field of aviation manufacturing is currently a subject that needs to be studied urgently.

  • Based on the background and application status of 3D printing technology, HY-Industry analyzes and compares the advantages and disadvantages of this technology and forging technology in the field of aviation manufacturing, and discusses the development of the forging industry in the field of aviation manufacturing based on the author ’s years of management experience in the forging enterprise The direction provides new ideas for the development of the forging industry.

1. Development history of 3D printing

3D printing technology development background: 3D printing technology belongs to an unconventional processing technology, also known as additive manufacturing. It is an advanced technology that integrates light, machine, electricity, computer, numerical control and new materials in the global advanced manufacturing field. Manufacturing technology, the core manufacturing idea of ​​this technology first originated in the United States and has been in existence for more than 120 years. Since the US “Manufacturing Innovation National Network” plan announced by US President Barack Obama on March 9, 2012, “additive manufacturing” is the first research direction, which has caused 3D printing technology to become popular all over the world. Economists will It is called “The Third Industrial Revolution”.

3D printing technology application status: Since the mid-1990s, the use of “3D printing” technology for direct production of metal parts has become the fastest growing direction in this technical field, and a variety of technical methods have been born in just a few years, such as Laser Engineered Net Shaping at Sandia National Laboratory in the United States, Laser Metal Forming at Lausanne Institute of Technology in Switzerland, Directed Light Fabrication at Los-Alamos National Laboratory in the United States, Direct Metal Deposition at the University of Michigan and Liverpool University in the U.S. Manufacturing technology Laser Consolidation, Laser Free-Form Fabrication of the University of Pennsylvania, Laser Forming of Aeromet of the United States, Direct Laser Fabrication of the University of Birmingham, United Kingdom, etc. Although these methods have different names, they are based on the principle of additive manufacturing based on 3D printing technology.

It is worth noting that the US military has paid considerable attention and support to the development of this technology. With its direct support, the United States took the lead in putting this advanced technology into practical use. Among them, the three produced by AeroMet in 1997 Ti-6Al-4V laser rapid prototyping parts are approved for use in actual aircraft. These three parts are a joint on F-22, a wing root eyelet of F / Al8-E / F and F / A-l8E / A connecting rod on F for landing. Recently, the US Air Force and Lockheed Martin have announced that they will become partners with Sciaky, and plan to use the 3D printer produced by the company to make aircraft components and equip the F-35 fighter aircraft being produced . GE has acquired Morris Technologies and 3D printing services rapid quality manufacturing company, plans to use 3D printing technology to produce engine nozzles.

At present, China is at the international advanced level in the field of metal 3D printing technology. The team of Wang Huaming from Beijing University of Aeronautics and Astronautics provided aerospace structural parts for domestically produced C919, J15, J20, and J31. In 2012, he won the first prize of the National Technology Invention Award for his “laser forming manufacturing technology and equipment for large and complex monolithic titanium alloy structural parts.” The team of Northwestern Polytechnical University Huang Weidong successfully trial-produced the upper and lower edge strip members of the wing rib TC4 of the C919 large aircraft. The size of such parts reaches 450mm × 350mm × 3000mm. The team of Shi Yusheng of Huazhong University of Science and Technology used this technology to produce a six-cylinder engine cylinder head, and integrally formed a four-valve six-cylinder engine head sand core within 7 days.

2. Comparison between 3D printing and forging

The aviation industry is an important manifestation of national defense strength, and the degree of development of its manufacturing technology has become an important indicator of a country ’s overall economic strength and technological development level. The application of new manufacturing technology and the transformation of traditional manufacturing technology are important driving forces for the development of aviation manufacturing technology. As a new manufacturing technology, whether metal 3D printing can be widely used in the field of aviation manufacturing, and whether traditional forging technology can meet the needs of the new generation of aviation equipment manufacturing, the author makes a comparative analysis from the following two aspects.

The advantages and disadvantages of 3D printing technology: metal 3D printing technology has outstanding characteristics, that is, free near-net forming without molds, and it is fully digital and highly flexible. The printed parts are fully dense, without macro-segregation and shrinkage, and have high performance. . According to related reports, LSF (laser three-dimensional forming technology, which is a kind of metal 3D printing technology) is used to manufacture aerospace disk-shaped parts. The cycle time, repair rate, and cost are lower, as shown in Table 1. The tensile properties of Ti6Al4V, 316L stainless steel, and Inconel 625 alloy manufactured by LSF technology are superior to forgings.

With the continuous development of the aviation industry, while pursuing high-thrust aircraft, more attention is paid to the stability of the overall quality of the aircraft. Therefore, in aviation manufacturing, the pursuit of quality stability is particularly important. Due to the relatively short development time of metal 3D printing technology, the industrial chain and commercial application system are not perfect, and no quality control specifications suitable for aviation manufacturing, such as metal 3D printing process specifications, acceptance standards, inspection standards, etc., cannot ensure quality. Consistency and stability.

At present, 3D printing technology does not have the advantages of economies of scale; there is no material powder system suitable for metal 3D printing; the size, morphology, and orientation of grains are difficult to control; there is no limit test platform to judge the performance of metal 3D printing parts in the use environment Whether it is excellent; there is no effective way to control internal stress and prevent deformation and cracking of parts.

In summary, metal 3D printing technology still has a long way to go before it is widely used in aerospace manufacturing, but it can be manufactured using small batches, complex shapes, expensive materials, and parts that cannot be processed by conventional methods.

power-nickelThe current status of forging technology application: so far, the development of China’s aviation forging technology has been able to meet the needs of mass production of third-generation military aircraft and its engines. The quality is relatively stable, the forgings are dense and controllable, and the performance is excellent. Different parts of forgings have different microstructure and properties, and have met the occasions where the performance requirements of each part are significantly different, such as the manufacture of TC11 titanium alloy dual performance compressor discs. As the new generation of fighters continue to pursue the extreme lightweight and reliability of aviation equipment, aircraft and engines are constantly developing in the direction of high performance, high weight loss, long life, high reliability, and low cost, that is, aircraft and engines are required. The further integration of the structure and the enlargement of the parts have higher requirements for aviation forging technology and forging equipment.

At present, the forging technology applied in the field of aviation manufacturing is still mainly based on ordinary forging technology, while the precision forging technology is only used in engine blade forgings. According to statistics, the material utilization rate of China’s aviation forgings is about 15% ~ 25%, of which the material utilization rate of large forgings is 10% ~ 15%, the material utilization rate of ring forgings is only 3% ~ 10%, the size of forgings is not easy to control As a result, a large amount of expensive metal materials are turned into waste during machining, the dense layer near the surface of the forgings no longer exists, and the fibrous structure is divided, which affects and reduces the mechanical properties and surface integrity of the parts; and the mold cost is high and the processing cycle is long. Restricted by the tonnage of forging equipment, the size of forgings is restricted. It can be said that the bottleneck of traditional forging technology has gradually emerged in the manufacture of large and complex monolithic structural parts and precision and complex components.

3. The development direction of the forging industry

3.1 With the continuous pursuit of high-quality, precision, high-efficiency, environmental protection and low-cost goals by advanced forging technology, the development of the forging industry in the field of aviation manufacturing should be considered from five aspects.
1. Should meet the needs of large-scale and integrated new-generation aviation equipment manufacturing;
2. Low-cost and highly reliable forging technology should be developed;
3. Low-carbon, environmentally friendly manufacturing methods should be considered;
4. According to the characteristics of new manufacturing technology, combining with forging technology, develop high-efficiency composite manufacturing technology;
5. Circular economy manufacturing should be developed in the forging industry.

3.2. Develop low-cost, R & D highly reliable technologies:
In the field of aviation manufacturing, forging technology is mainly used in the manufacture of aircraft and engine parts. According to its structural characteristics, there are mainly free forging technology, die forging technology and ring rolling technology. It is rarely used directly in the manufacture of parts, often as a process for forging blanks. Therefore, the development of advanced die forging technology and ring rolling technology is the development direction of forging technology in the field of aviation manufacturing.

3.3. Development of isothermal precision forging technology:
Isothermal precision forging technology is a kind of die forging technology, which requires that the mold and the workpiece maintain the same temperature from beginning to end, and a forging method that deforms at a low strain rate. In order to prevent the oxidation of forgings and dies, it is often carried out under vacuum or inert gas protection. It can produce net forgings that do not require machining after forging or forgings that require only a small amount of processing. Better than ordinary forgings.

In recent years, isothermal precision forging technology has developed rapidly in China’s aviation manufacturing field, but it has not yet reached the level of industrialization technology that has been widely promoted and applied. This is mainly because the molds are made of special materials and the cost is much higher than ordinary molds; Even and controllable mold heating system; high lubricant requirements, can be fully used at high temperatures; in order to prevent oxidation of the workpiece and mold, additional vacuum or inert gas protection devices are required. In view of these problems, low-cost high-temperature alloy mold materials should be developed in the future; research on high-temperature mold protective coating and mold repair technology; research on isothermal forging technology under vacuum or protective atmosphere; research on high-temperature alloy mold structure design, mold precision casting, etc. . HY-Industry has taken the lead in purchasing the isothermal forging production line in 2019, and has officially put into production in 2020.

3.4. Development of precision ring rolling technology:
At present, in the research and batch production of various types of aeroengines and other military projects in China, the application of high-temperature alloys, titanium alloys and other hard-deformable material rings is very wide. However, the currently produced aerospace hard-to-deform material rings in China are mostly rectangular or simple shaped cross-sections. The material utilization rate is low, about 5% to 10%, and the problems of poor dimensional accuracy, uneven organization, and severe processing deformation are more prominent. In view of the above problems, how to meet the requirements of the new type of engine on the performance, uniformity and batch stability of the ring of the new engine while reducing the production cost, shortening the development cycle and saving valuable materials while improving the material utilization rate and the dimensional accuracy of the ring And strategic resources are the direction of developing ring rolling technology.

According to the previous research results of HY-Industry, the precision ring can be promoted from the aspects of ring bulging process research, special-shaped ring blank design and preparation process research, rolling / bulging correction / heat treatment process research, and ring production batch stability research. The development of rolling technology focuses on breaking through key technologies such as ring rolling and bulging matching technology, special blank design optimization technology, ring residual stress testing and control technology, etc., and finally meets the high requirements of advanced aviation engines and other weapons on ring parts The needs of performance, low cost, precision, light weight, long life and short cycle manufacturing have made China’s military precision ring production technology reach the international advanced level.

3.5, Development of circular economy manufacturing:

After years of technological innovation and upgrading, as well as the introduction and transformation of international advanced production equipment, China has the ability to produce high-end products such as special steel for aircraft engines. Moreover, China has abundant human resources and low labor costs. Compared with European and American countries, the price should be more competitive. However, the prices of some special steel products in China are nearly double that of similar foreign products, which is a huge cost for the aviation forging industry.

The reason why such a high material cost is formed is that the scrap metal has not been reused. For example, in the international production process, the scrap metal reuse rate has reached 70%, while Chinese special steel production enterprises have Application is zero. According to many years of production experience, in the production process, the recycling of scrap metal can not reach 60%, and the price of the product cannot be reduced. This shows that the development of circular economy manufacturing is one of the effective ways for the aviation forging industry to reduce manufacturing costs.

In aerospace enterprises, strategic metals such as high-temperature alloys and titanium alloys have an effective utilization rate of only 10% to 15% from the material to the final product. Due to the lack of a professional recycling network and professional technology, the material cutting and feed head during processing 3. Corresponding management level, most of the returned materials are degraded and used, a large amount of strategic metals are wasted, and cause pollution. If the waste precious metals such as high-temperature alloys can be recycled and purified, and these materials are re-entered into the raw material supply system, the utilization rate of high-end materials can be effectively improved, and the material costs of forging enterprises can be reduced, which is conducive to enhancing the forging and casting industry The overall competitiveness in the field of aviation manufacturing.

3.6. Introduction of new manufacturing technologies:

In the field of aviation manufacturing, although the current metal 3D printing technology cannot be widely used in the manufacture of high-end equipment, it can make a difference in a small area, such as the integrated manufacturing of aircraft structural parts (integral wing body), large-scale forgings of major equipment (nuclear power Forgings), difficult-to-machine materials and parts forming, repair of high-end parts (repair of blades and casing) and other fields that cannot be achieved by traditional forging techniques.

It can be seen that for the aviation forging industry, metal 3D printing technology can be appropriately introduced, through complementary and cooperative development, to solve the problem of excessive cost caused by the forging of multiple varieties and small batches of military products, and to quickly respond to the urgent technical problems of model development and solve customers. Personalized design needs, etc. HY-Industry has cooperated with Beijing University of Aeronautics and Astronautics and has invested in China Aerospace Geo-Laser Technology Co., Ltd., introducing metal 3D printing technology. In the field of aviation, many metal 3D printing products have been applied to new models, saving costs and improving forging. Industry core competitiveness.

Conclusion

New manufacturing technology-the rapid development of metal 3D printing in the field of aviation manufacturing is a challenge and an opportunity for the aviation forging industry. The development of the forging industry in the field of aviation manufacturing is inseparable from advanced forging technology, so the development of low-cost, high-reliability and advanced forging technology is fundamental, such as isothermal forging technology, advanced precision ring rolling technology, etc., are the development direction of aviation forging technology. The use of high-temperature alloys, titanium alloys and other waste precious metal materials to develop circular economy manufacturing is one of the effective ways for the forging industry to reduce costs. The introduction of metal 3D printing technology and complementary and collaborative development with forging technology are new ideas for the development of the forging industry in the field of aviation manufacturing. It can be said that with the rapid development of China’s aviation manufacturing industry, the introduction of a variety of new manufacturing technologies and coordinated development is the only way for the forging industry to develop in the field of aviation manufacturing. HY management has also recognized the situation and increased investment in scientific research, which will play an important role in the field of additive manufacturing in China.

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