Forging and casting have replaced cutting and other processes as the main processing methods for high-end aerospace parts. In the aviation field, in the past, even if 80% to 90% of the material was removed when manufacturing important parts such as fuselages, wings, and blades, the cutting method was often used. However, as the complexity of the parts increases, the cost of mass production The requirements for efficiency and efficiency, as well as the advancement of high-performance metal material precision forging and casting capabilities, especially the landing of the concept of net shape and near net shape in recent years, forging and casting have gradually become the mainstream process of forming aerospace metal structural parts, cutting and other processing methods The proportion in the manufacturing process has declined, and it has gradually shifted to post-processing and other auxiliary processing uses.
Near-net shape of parts is the main development trend of the forging and casting industry. Near Net Shape Forming (Near Net Shape Forming) refers to a forming technology that can be used as a mechanical component with a small amount of processing or no processing after the part is formed. Near-net forming technology is based on new materials, new energy, mechatronics, precision molds, automation, numerical analysis and simulation, and other multi-disciplinary high-tech achievements. It has transformed the traditional blank forming technology from rough forming to Forming technology with the advantages of high quality, high efficiency, high precision, light weight, low consumption, low cost and high consistency. Due to the high accuracy of the shape and position of the near-net-shaped parts, the workload of subsequent machining is low, and it can be directly used as an ideal blank for high-precision machining. At present, the main overseas near net shape precision forging and casting technologies include:
Investment casting technology: In the 1940s, due to the development of aviation jet engines, the manufacture of complex, high-precision, heat-resistant alloy parts such as blades, impellers, and nozzles required a new precision molding process. The lost wax casting based on advanced precision casting technology and processes has gradually formed a modern investment casting technology after optimizing materials and processes. The complex and thin-walled high-temperature alloy, titanium alloy, and aluminum alloy integral castings in the aviation industry are key components in the engine and the body, which directly affect various performance and life indicators. Investment casting has obvious advantages when producing such castings, especially for engines For complex hollow parts such as blades, investment casting has become the only technology for its production. At present, all advanced aerospace turbine blades are produced by investment casting. In terms of body structure, compared with composite components, casting components eliminate mechanical fastening connections, thereby reducing weight, improving integrity, shortening the development cycle, and reducing manufacturing costs. In the F-22 airframe structure, titanium alloy castings accounted for 7.1% of the weight. There are about 54 titanium precision castings, which are used at the front and rear sides of the wing. In the field of large transport aircraft and civil aircraft, the instrument panel of a certain Boeing model adopts precision casting, which reduces the weight by 2.24kg, reduces assembly tools by 90%, reduces the time from 180 hours to 20 hours, reduces the number of rivets by 600, and reduces costs by 50%.
Isothermal forging technology: most of the key components in the engines and cabins of advanced military aircraft, strategic and tactical missiles, armored vehicles, naval vessels and other weapons are made of difficult-to-deform material forgings. Among them, aero-engine turbine blades and turbine discs are typical representatives of parts and components in service in harsh environments, and their requirements for strength and toughness, fatigue performance, reliability and durability are very strict. The material selection and forging technology of these parts have become an important indicator of the advanced degree of engines. Early discs and blades were mostly produced by conventional forging technology. In recent years, the use of isothermal forging technology can significantly improve the microstructure and performance of forgings, improve the uniformity of forgings’ structure and performance and streamline integrity, further improve the reliability of parts, increase material utilization, and save scarce strategic resources. Developed countries Isothermal forging technology has been widely used to produce key engine forgings. The high-temperature alloy and titanium alloy precision-forged blades produced by isothermal forging technology have a non-machined surface ≥ 80% and a dimensional accuracy of 0.01mm. More than 90% of the aero engine discs of European countries such as the United States, Britain, France and Germany are produced by isothermal forging technology.
Precision ring rolling technology: Seamless rings are widely used in many military fields such as aviation, aerospace, shipbuilding, weapons, and nuclear industry. Precision ring rolling technology is the preferred process method for producing high-performance seamless rings, and it has an important impact on improving the performance level, service life and research and development capabilities of weapons and equipment. Engine casings, mounting edges, missile compartment joint ring, spaceship reinforcement ring, artillery, tank seat ring, etc. are all processed by rolling ring parts. Industrial developed countries are equipped with a large number of ring rolling production lines of different types and specifications. At present, there are more than 500 ring rolling machines and more than 100 ring rolling production lines worldwide. Since the 1980s, the United States, Russia, Germany, Britain, France and other countries have adopted precision rolling technology for the production of high-quality compressor/turbine casings, combustion chambers, sealing rings, mounting edges and other precision rings. The development of high-performance aircraft engines has made important contributions. GE's IN718 alloy high-tube thin-walled ring for CFM56 engine produced by GE using precision rolling technology has a grain size of ASTM-8 or higher. The dimensional accuracy of the ring has reached 1‰ of the outer diameter of the ring, and the material utilization rate has reached 25%~30%. .
Integral precision forging technology of large complex components: In order to improve the reliability of parts, reduce structural weight, reduce manufacturing costs, and shorten the manufacturing process, developed countries have generally applied the integral precision forging technology of complex components, combining several original components in One body integrally formed. In the aviation field, large integral bulkhead forgings are a typical representative, especially the application of titanium alloy integral structural parts is the most eye-catching. About 40% of the structural weight of advanced foreign military aircraft is made of titanium alloy components, and 10% of the structural weight of advanced civil aviation aircraft is also made of titanium alloy components. The application of titanium alloy integral structural parts can effectively reduce the weight of the aircraft structure, increase the thrust-to-weight ratio of the engine, and significantly improve the overall function of the aircraft. It has become one of the important landmark technologies of the third and fourth generation aircraft production technologies. The United States applies precision hot die forging technology to produce F-22. The four load-bearing bulkheads are made of large-scale integral bulkhead die forgings. The material was originally designed using Ti6Al4V2Sn alloy and later changed to Ti6Al4VELI alloy. The projected area of the forging is 4.06~5.67 square meters. The fuselage integral bulkhead closed die forgings, with a projection area of 5.67 square meters, is currently the world’s largest titanium alloy bulkhead forgings; American F/A-18 fighters use titanium alloy bulkhead precision forgings (projected area is 4 square meters) ) Replace the 368 parts in the original design, reduce the aircraft by 350kg, and save 50% of the machining time. The Russian An-22 transport aircraft uses B95 alloy 20 bulkhead forgings (projected area of 3.5 square meters), which reduces 800 parts, reduces the weight of the aircraft body by 1000 kg, and reduces machining hours by 20%.
Specialized customization is becoming the mainstream of the global precision parts production industry. The downstream applications of special equipment parts are extensive, ranging from aerospace applications to small medical equipment, which need to operate under extreme working conditions such as high and low temperature and corrosion resistance. The traditional production mode of single-variety mass production and internal support for special products has been Can not adapt to the rapid upgrade and professional customization needs of the high-end equipment industry. Large-scale high-end equipment groups are shifting internal support to external specialization. At the same time, taking global industrial integration as an opportunity, starting from core casting technologies, implementing industrial chain extensions and building a professional key component manufacturing system. Some leading specialized forging and casting companies have begun to provide customers with cross-industry, multi-variety, and small-batch customization services for special parts, building a professional key parts manufacturing and design service system, and specialized customization has become the production of aviation supporting parts One of the mainstream trends in the industry.
High-quality one-stop solution providers are expected to gain more market share. The manufacture of special parts needs to go through a series of lengthy processes such as blank forming, heat treatment, finishing, modular manufacturing, etc., due to the process relevance and overall consistency in the manufacturing process, as well as shortening the supply chain process and improving the efficiency of the supply chain After consideration, the integration of the special parts manufacturing industry chain has become an inevitable trend, and high-quality one-stop solution providers are expected to gain more market share. Taking the global automotive forging and casting industry as an example, the delivery share of finished investment casting products increased by about 50% from 2013 to 2018, and this trend will continue in the future. The aerospace industry and other special parts application industries are also facing the same trend. Some leading overseas aviation forging companies have achieved rapid growth in revenue and market share by seizing the opportunity of industrial chain integration, both endogenous and extensional, and this merger and integration process is still continuing.