In the past decade, the United States has paid much attention to the development of precision thermal processing and improve the performance of integrated technology. Such as: aluminum-lithium alloy powder parts precision thermoforming can make parts than the stiffness increased by 30%; silicon carbide / aluminum composite materials can make parts than the stiffness increased by 30% to 75%; single crystal blade precision casting can increase the turbine temperature of 55 ℃, fuel savings of 10%; fast solidification of powder laminated turbine blades, can make the engine turbine temperature increased by 220 ℃, fuel consumption reduced by 8.4%, the aircraft take-off quality reduced by 7.4%, the engine thrust-to-weight ratio increased by 30%, the engine thrust-weight ratio increased by 7.5%. 4%, the engine thrust-to-weight ratio of 30% to 50%. The development of precision thermal processing technology, and improve the performance of parts and components research integration, in line with China's national defense science and technology development of key basic processing technology research requirements.
A, precision casting
Precision casting molding process can not only shorten the development cycle of new weapons, reduce costs, but also improve the flexibility and reliability of weapons. Such as the U.S. Boeing Company produced cruise missile cabin using aluminum alloy precision casting process, the cost of the bomb body to reduce 30%, each missile required hours from 8000 hours to 5500 hours, and improve reliability, weight has been reduced.
The United States Oak Ridge National Laboratory, the United States precision casting company and NASA Lewis Research Center and other units of the A1 system of intermetallic compounds and Ti, Ni-based special alloys, such as precision casting conducted a lot of research. They use the whole once the molding precision casting process processing turbojet, turbofan guide, reduce machining time 40%, cost reduction of 30%. China's military industrial system of precision casting process compared with foreign countries have a large gap. Such as missile hull is mainly used low, differential pressure casting method. Ordinary clay sand casting production cabin, low dimensional accuracy, poor surface quality, internal defects, more than the second oxidation of the alloy liquid serious mechanical properties are not high, the scrap rate of up to 20% to 30%, the current domestic casting only 1.4m below the cabin. In addition, such as missile tail, aircraft parts of the device is still using machining methods, not only the long production cycle, high cost, and poor reliability. Precision casting process in special alloys, there is also a big gap, such as single product hollow without margin blade precision casting process, has been applied to military production in foreign countries, while the domestic is still in the research stage. As for the A1 system of intermetallic compounds precision casting process research has not yet begun.
In summary, compared with foreign countries, our country in the precision casting process is about 10-15 years behind. In order to shorten the development and production of new weapons cycle, reduce costs, improve reliability, must strengthen the research of precision casting process.
Two, precision plastic forming
Precision plastic processing technology in industrialized countries by a high degree of attention, and invested a lot of money to give priority to the development of the 70's U.S. Air Force presided over the development of the "modernization of the forging process plan", the purpose is to make the forging of this important process to achieve modernization, and more use of CAD / CAM, so that the new forgings In 1992, the U.S. Department of Defense put forward a "list of key military technologies", which contains the isobaric molding process, CNC computer-controlled spinning, plastic change and shear molding machinery, super-plastic molding / diffusion connection process, hydraulic extension molding process and other precision plastic molding process. In addition, in recent years, foreign countries have also developed to aerospace products as the object of application of "large die forging parts of the forging and blade precision forging process", "fast solidification powder lamination process", "large and complex structural parts of the strong spinning forming Process", "difficult to deform the material superplastic molding process", "advanced materials (such as metal matrix composites, ceramic matrix composites, etc.) forming process" and so on. Recently, with the penetration of computer and automation technology on the hot forming process, plate forming flexible manufacturing system has also begun to emerge.
(a) super-plastic forming
U.S. Hughes, BAE and other companies in the super-plastic forming technology at the forefront of the world. Currently Chin alloy superplastic forming process has been widely used in the manufacture of missile shells, propellant storage tanks, fairings, spherical cylinders, corrugated plates and engine components. Aluminum alloy, magnesium alloy, nickel-based high-temperature alloys, metal matrix composites and other superplastic forming process is also being studied. China's superplastic forming technology in aerospace and machinery industry has been applied, such as satellite components in the aerospace industry, missiles and rocket cylinders, and the use of superplastic forming method to manufacture reconnaissance satellites Chin alloy recycling capsule. At the same time, but also basically mastered the zinc, copper, aluminum, Chin alloy superplastic forming process, the minimum forming thickness of up to 0.3mm, the shape is also more complex. But the wall thickness uniformity problem has yet to be solved.
(II) strong spinning
The United States use strong spinning technology. Has been able to produce a diameter of 3.9m, radial dimensional accuracy of 0.05mm, surface roughness RaO.16-0.32μm, wall thickness <0.03mm of the missile shell. Almost all kinds of metal can be spinning forming, and process stability, and has realized the equipment large-scale, multi-purpose and automation. Staggered spinning, CNC and other advanced spinning process and equipment has also been popularized.
China now has hundreds of kinds, millions of parts using spinning process, which has a bullet, tail pipe, head, combustion chamber, shell, nozzle and so on. And has developed a variety of external spinning process, including low-temperature and high-temperature spinning technology and equipment, can spin the maximum diameter of 5m head pieces, the largest spinning bed up to 60 tons. Aerospace system has used the strong spinning process to produce a large solid engine high-strength steel head and aluminum alloy head, diameter 2.5m; liquid rocket silver alloy tube. Export diameter 0.28m; tactical missile aluminum alloy shell, diameter 0.46m; engine spherical container of Chin alloy hemisphere, diameter 0.53m, thinning rate of 50% a 75%. The gap between our country and foreign countries is mainly manifested in our country basically can only spin cylindrical parts, conical parts and simple curved surface shape of the parts, most of the large-size shell is still using the rolled plate welding process, there are often residual stress in the component, in the weld heat-affected zone is also prone to delayed cracking; large-scale spinning parts of the size of the accuracy is poor, to the subsequent assembly of the welding caused great difficulties; with shallow tendons and cylindrical pieces of the internal spinning process has made some achievements, but can spin cylinder diameter is small, but the spinning process is very easy. But the spinning cylinder diameter is small, the tendon is very shallow; spinning equipment is mostly obsolete, staggered spinning, CNC spinning and recording back spinning and so on are just starting.
(C) thin plate precision molding
Thin plate class of complex components of precision molding of new technology has been widely used in Russia, the United States and other countries. Russia, the United States and other countries of the discharge molding equipment has been serialized, the maximum energy of the equipment up to 500KJ. Russia has been able to produce dozens of missile parts, including A1-Li alloy difficult to deform the material, the maximum size of 1,200mm × 1,000mm × 6mm (diameter × height × thickness). At present, the polyurethane soft mold forming technology has become an important forming means in the aerospace industry, the Russian TY-154 aircraft factory has used the technology to produce more than 10,000 parts. The United States, France and other countries have been widely used CNC pull the shape of the skin and wall plate, shaped cross-section box parts rolling process has been widely used, large launch vehicles commonly used as a whole aluminum alloy ring forgings.
China's complex components in thin-plate molding, but also follow the traditional process. Electromagnetic forming has just been used for production, and low energy equipment, coil technology has not yet passed; electric water forming is still a blank, polyurethane soft mold forming technology only a small number of simple applications, the technology is not mature; CNC skin pulling shape and the engine has stringent requirements of the space towards the conduit application is still a blank.
(D) precision molding
Foreign countries have been widely used precision molding technology to manufacture weapons. Alcoa used isothermal forming manufacturing F-14 fighter frame Chin alloy reinforcing plate and support seat parts, the former projected area of 10320mm2, forging weight 0.32Kg, reinforcing the minimum wall thickness of 3.17mm. The latter projected area of 13545mm2, forging weight O.82kg, minimum thickness of 2.67mm. Pratt - Whitney used isothermal forging process to produce F100 engine turbine disk, the weight of the original ordinary die forging parts of 112.5kg down to 56.7kg. commonly used precision molding technology, such as occlusion forging, the use of the principle of shunt precision molding and isothermal forming, etc. foreign countries have been used in military production. China, the first two technologies have just started, isothermal forming has been applied. At present, the precision molding technology in China is still less application, accuracy is also poor, foreign precision of ± 0.05-0.10mm, our country for ± 0.1-0.25mm.
Three, special heat treatment
Specialty heat treatment process is the national defense industry system is one of the key manufacturing technology. The United States in order to accelerate the development of its space shuttle by five companies to form a consortium *** with the development of new materials for five kinds of molding and heat treatment process, namely, high-temperature Ti-Al compounds, C / C and ceramic-based composites, high creep strength materials and high thermal conductivity of materials. The United States by a special process. Treatment of 8089 alloy, the use of temperature can reach 400 ℃. Intermetallic compounds toughened by the treatment can significantly improve the toughness, more suitable for use at high temperatures, Ti3A1 can be in 816 ℃, TiAl can be used in 1083 ℃; is the space shuttle and aircraft engine ideal materials. The United States has been shape memory alloys used for satellite antenna and tube joints, for the missile since the spreading tail research has also made great progress. The University of Wisconsin in the United States, headed by the PSII surface thermal modification processing technology for aero-engine and satellite shaft parts and bearings, and has made significant progress, President Clinton has personally inspected the process technology.
Vacuum and atmosphere heat treatment is widely used in aerospace structural parts processing, such as carburizing or nitriding on the surface of gear structural parts, de-stressing, strengthening or toughening of various alloys or steel parts of missiles and spacecrafts with the advantages of its unique non-fouling beams, no oxidation, small deformation of the workpiece and a wide range of advantages, etc. Typical structures, such as: instrumentation parts, transmission parts and bearings. Typical structures such as: instrumentation parts, transmission structures, fuel storage tanks, engine shells, etc.; U.S. heat treatment furnace about 50% more than the vacuum heat treatment furnace. Complete specifications, complete sets. The fourth generation of the latest type of gas quenching furnace - double chamber high-pressure vacuum air quenching furnace has also begun to apply. In addition, vacuum heat treatment furnace has been widely used in computer control. It has been developed to vacuum chemical heat treatment and vacuum air quenching heat treatment, including high-pressure vacuum air quenching, high-flow rate vacuum air quenching and high-pressure high-flow rate vacuum air quenching technology.
Laser heat treatment technology in foreign countries has been widely used in aviation, aerospace, electronics, instrumentation and other fields, such as a variety of complex surfaces, miniature components, need to be locally strengthened components, microelectronic devices, large-scale integrated circuits, production and repair, precision optics, precision measurement components. Among them, laser quenching is the earliest and most widely used laser processing technology, can deal with Chin alloy, aluminum alloy, alloy steel and carbon steel and other materials. Such as MKlO guided rocket launch system ignition area of the blocking cam, the use of AISl4340 steel, with 1.2KW laser surface treatment instead of the original nitriding treatment, the highest hardness from the original 55Rc to 62Rc, hardening layer depth from 0.01-0.02in to 0.015-0.030in, and the hardening layer depth from 0.01-0.02in, and 0.030in. 0.030in, and each group of 4 pieces of cam processing guide by the original 60 days shortened to 1 hour, the surface of the Chin alloy parts laser hardening hardness can be increased by 75% to 125%. The current level of research has reached the hardness of the laser surface treatment than ordinary quenching 5-20% higher than the laser coating combined with a solid, molten layer of only 0.05-0.13mm, laser alloying and amorphous treatment, the melting layer of only 1-10μm; the world's major research units are the United States IBM Corporation, Battelle Research Institute, Naval Research Laboratory, Laser Applications, etc.; Rolls-Royce, Imperial University of the United Kingdom, etc.; Japan's Osaka University Thermal Spraying Research Center, Murata, etc.. Domestic research in this field has also carried out the corresponding research work, and achieved remarkable results. However, due to the late start, coupled with insufficient funding, so compared with foreign countries there is still a gap. Therefore, the "Ninth Five-Year Plan" period should increase efforts to carry out research to further narrow the gap with foreign countries.
Four, special welding technology
Special working environment of aerospace products and requirements dictate the need to continue to use some of the new structural materials, special structural forms and connection technology, which requires a new welding process and equipment to adapt to the requirements of the weapon system. The facts show that it is impossible to manufacture any spacecraft without the use of welding technology. Therefore, the world's countries in the aerospace industry sector of the highest level of welding technology, hair stock speed is also the fastest.
The United States and Russia, two developed countries in the space industry, the development of each new type of space products are always accompanied by a series of special welding technology development to ensure that the new type of product manufacturing needs. For example, the United States in the development of Saturn V launch vehicle, Russia in the development of energy launch vehicle, aluminum alloy storage box diameter reached 10m and 8m, wall thickness of 25mm and 42mm, conventional welding technology has been unable to adapt to this new type of product manufacturing needs, the U.S. and Russia have coincidentally developed a suitable vertical assembly and welding of special welding technology. The United States developed the VPPA (variable polarity plasma arc) welding process and equipment to complete the manufacture of large aluminum alloy storage tanks. Russia has developed a local vacuum in the beam welding process and equipment to complete the energy number of large aluminum alloy storage tank manufacturing. Special welding technology research scope is very broad, the following are only a few directional research areas specifically introduced at home and abroad the current state of development:
(a) automated intelligent welding technology
Modern aerospace products in the manufacture of precision, quality assurance (quality stability and reliability) are extremely high requirements, the urgent need to use a complete alternative to manual operation of the automated intelligent welding technology. Technology. For example, the U.S. Marshall Space Flight Center is organizing NASA's some institutions of higher learning and industrial sectors to develop to meet the needs of manufacturing large-scale aluminum alloy storage tanks, automated intelligent welding system, the end of 1993, the system has been nearly completed. It is said to be composed of a variety of quality sensors, mathematical models of the welding process and computer-controlled welding devices are estimated to have been put into operation. China in the medium-sized aluminum alloy storage tank welding automation has made some achievements and has been used in the production, but in the intelligent aspect there is still a big gap. Hope that in the "Ninth Five-Year Plan" period can be used part of the hardware introduced from abroad, some key technologies and software from their own research and development policy, to overcome this "automated intelligent welding technology" to meet the needs of China's new aerospace products manufacturing technology, in the "Ninth Five-Year Plan". "Ninth Five-Year Plan" period close to or catch up with the level of advanced countries.
(B) new materials and heterogeneous materials welding technology
many parts of aerospace products almost without exception require the quality as light as possible, the performance is as good as possible, so many new structural materials (ceramics, composite materials, intermetallic compounds, amorphous materials, directional crystalline materials, refractory metal materials, functional materials, etc.), which gives the new material or heterogeneous materials connection This brings difficulties to the connection of new materials or dissimilar materials. Developed countries in the aerospace industry have carried out a lot of research work on the requirements for the connection of these new and dissimilar materials, and according to different combinations of materials, the required connection joints can be obtained through solid-state connection or melting connection methods to meet the working requirements of the components. For example, Russia has successfully manufactured by the copper a stainless steel a Chin a combination of different metal materials welded high-pressure refueling sandwich structure liquid engine thrust chamber. The process is novel, advanced, reasonable, to meet the structural design requirements. U.S. and Russian aerospace sector using special pre-treatment, and then brazing or diffusion welding, successfully welded B / A1 composite tube and aluminum alloy tube or titanium alloy tube, the successful manufacture of space vehicles within the load-bearing diffraction frame. In addition, we have successfully solved the welding technology of metal and ceramics. There are various methods of welding, but the more ideal method is to Ag-Cu-Ti alloy as the active brazing material, supplemented by strain relief transition material for brazing.
China's 703, HIT, 621 and other units of the new materials and dissimilar materials welding technology to carry out research, but also achieved some results, but with the advanced countries than there is still a big gap. The main reason is that we are in this area of basic research and applied basic research is too weak, the means are too backward, invested in manpower and material resources is too little.
(C) micro-connection technology
Spacecraft control circuits and payloads of high reliability, high density and micro-miniaturization of the aerospace industry is the goal of long-term efforts. Solving these problems can not only significantly reduce the spacecraft launch costs, but also can greatly improve the reliability of the control system and operating frequency, to extend the life of the satellite has an important impact. The United States, Russia and other advanced countries have adopted a large number of advanced electronic device assembly technologies such as surface assembly technology, micro-assembly technology and multi-chip assembly in the control system of spacecraft, so that the control system and satellites have achieved the purpose of miniaturization and lightweight. As the micro-connection technology in China is still backward, the control system of spacecraft still mainly adopts jack assembly, which is difficult to achieve sufficient miniaturization and lightweight. The State Key Laboratory of Welding of Harbin Institute of Technology has the earliest micro-connection research laboratory established in China, which has carried out years of research in micro-connection technology of surface assembly, and now cooperates with relevant units of the Ministry of Electricity and Industry, 504 institutes of the Ministry of Aerospace, and the Shanghai Space Administration to carry out research on micro-connection technology in conjunction with the needs of spacecraft.
(D) advanced melting welding process
Large fuel tanks of aluminum alloy for high-thrust launch vehicles and spacecraft or the space shuttle, spacecraft aluminum alloy pressure shell manufacturing is mainly used in melting welding technology. For different structures and sizes of large fuel tanks or pressure shell manufacturing needs. Foreign countries have developed different melt welding process and equipment, successfully completed the manufacture of aerospace products.
The United States, Russia developed advanced melt welding process technology are: narrow gap helium shielded fused electrode welding process, can be multi-layer welding, welding thickness is not limited, Russia has successfully welded the thickness of 40mm and 80mm aluminum alloy storage tank; DC positive helium helium shielded tungsten tungsten arc welding, Russia has successfully completed the single-pass welding process 3-8mm thick workpiece production tasks; local vacuum tungsten arc welding, Russia has successfully completed the manufacturing tasks of aerospace products. Russia has successfully completed the production of 3-8 mm thick workpieces with a single welding process; local vacuum electron beam welding technology, Russia has been successfully used for welding aluminum alloy storage boxes with a thickness of 42 mm; flash butt welding technology. Russia has been successfully used to produce large cross-section (50-80 × 103mm2) aluminum alloy ring frame or longitudinal joint welding; variable polarity plasma arc perforation welding. The United States has been successfully developed and used to weld large aluminum alloy containers with a thickness of 16mm, is a kind of no internal defects in the most ideal aluminum alloy welding process. Domestic research in the above new welding process are almost in the blank or just start stage, need to carry out research work as soon as possible.
In addition, for a variety of spacecraft stainless steel, titanium alloy, aluminum alloy conduit welding U.S. and Russia have developed an advanced automatic welding process, but also the corresponding development of the joints to prevent leakage inspection methods to ensure the safe operation of the conduit system. China in the conduit welding is still in the manual welding situation. After welding quality inspection means also backward.
There is an urgent need to carry out research to change this seriously backward situation. The United States and Russia have successfully applied C02 laser welding technology in the missile air rudder in the Chin alloy skin and casting skeleton welding, weld quality and reduce deformation have obtained ideal results. Our country in this regard is basically in the blank or just starting stage. State Key Laboratory of Welding at the Harbin Institute of Technology has introduced a power of 2KW CO2 laser processing system is being carried out in conjunction with the needs of the aerospace industry research work.