With the combination of investment casting technology, automatic control, computer simulation and other advanced technologies, the filling performance of alloy melt can be greatly improved, and the complete filling and precise control of structure and size of castings can be realized, so as to suppress casting defects and improve casting quality.
In order to improve the operational performance of weapon equipment and the overall structural performance and reliability of components, reduce the structural quality, reduce the manufacturing cost and shorten the manufacturing cycle, developed countries have deeply studied and applied the precision casting technology of complex thin-walled castings, and widely used in the development and production of key components such as aeroengine and airframe.
Technical characteristics and technological process of investment casting
In the 1940s, due to the development of Aerojet engine, it is required to manufacture heat-resistant alloy parts with complex shape, precise size and high surface roughness, such as blades, impellers, nozzles, etc. In view of the advanced investment casting technology and the lost wax casting, the modern investment casting technology has developed rapidly through the improvement of materials and technology.
Application status of foreign investment casting technology in aviation industry
Developed countries such as Europe and the United States comprehensively apply new materials and technologies, and constantly research and develop new technology to predict and precisely control the process of precision casting. A one-off precisionhas been widely used in an engine stme in the United States. The number of combustion chamber parts has been reduced by more than 50, the number of welding has been reduced by about 90, and the manufacturing cost has been significantly reduced. Rd-012 is a high-performance liquid hydrogen / liquid oxygen rocket engine of the energy series launch vehicle. The impeller of the inlet combustion chamber stage is formed by precision casting technology and one-time casting of the integral shaft, reducing the mass by about 8%.
The goal of the new generation of US military aircraft is to reduce the mass by 50%, the number of fuselage fasteners by more than 80%, the cost of batch production by more than 25%, and the manufacturing cycle by 1 / 3-1 / 2. In addition to widely using new materials, a large number of large, thin-walled, complex, integrated, high-quality precision castings are also needed. At present, aluminum alloy precision castings have been widely used in the missile body and waveguide of tactical cruise missiles in the United States. In the field of large transport aircraft and civil aviation, the Boeing 767-40er aircraft instrument console frame is manufactured by Sophia investment casting process, which can reduce 27kg of parts, 50% of cost, 89% of cycle time and 90% of tooling cost. In Boeing 737, 747, 757, 767 and 777 aircraft, the instrument framework in the cab, fuel pump shell, integral hatch and A320 cargo door frame, flap guide rail, etc. have all started to adopt the precision casting technology for integral forming.
Application status of investment casting technology in aviation industry in China
With the development of precision components such as Aeroengine Blades, casings, boarding and emergency doors, intake lips, wings and flat tail supports, the industrialization of investment casting in China has been accelerated. In the 1950s, China introduced the wet molding technology of paraffin stearic acid molding material and water glass quartz shell with bauxite cement from the former Soviet Union, and started the research and development process of aviation investment casting.
In 1966, the first generation of hollow nickel base superalloy turbine blades were cast by investment casting technology in China. In 1975, our country introduced the manufacturing technology of Spey aeroengine from Britain. In the process of digestion and absorption, we realized the localization of investment casting process materials. At the end of 1970s, we successfully cast the low-pressure first stage hollow guide vane which meets the performance requirements of the engine. At present, the main aero-engine manufacturing enterprises in China are equipped with investment casting workshops (branches). AVIC group also has Guizhou Anji Aviation Precision Casting Co., Ltd., a professional investment casting chemical factory. In addition, the research institutions at home and abroad have made great progress in the research of investment casting forming theory and technology in recent years.