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After 1990's, Chinese die casting industry made amazing development, has been developed as a new industry. At present, aluminum alloy die-casting technology has become a car USES aluminium alloy forming process in one of the most widely used technique in various kinds of car molding process, the method of 49%.
China's existing die casting enterprise to 3000 or so, die casting production from 1995 to 2005 26.6 tons up 87 million tons, the annual growth rate of 20 per cent or more, which remain in aluminum alloy die casting die casting yield of all the 3/4 above. Chinese die casting a diverse variety of products, including automobile, motorcycle, communication, electric appliance, metal products, electric tools, IT, lighting, escalator cascade, toys lamp, etc. Along with the technical level and product development ability the enhancement, die-casting products types and application fields continuously expanding, its die-casting equipment, die casting die, and die casting technology are changed greatly. Die-casting aluminum alloy die casting aluminum alloy since 1914 commercial production of the past, with the developing automobile industry and cold room casting invention, get a rapid development.
Die casting aluminum alloy according to performance is divided into low intensity (such as China's Y102) and high strength (such as China's Y112) two kinds. Current industrial application of the die casting aluminum alloy basically has the following several big series: Al - Si, Al - Mg, Cu and Al - Si - Al - Si - Mg, Al - Si - Cu Al, Zn, Mg - - etc. Die casting aluminum alloy mechanics performance enhancement usually accompanied by casting property reduce, because of its high pressure casting rapid solidification characteristics make this kind of contradiction in some ways more prominent, so difficult for general die-casting solid solution heat treatment, it is restricted the die casting aluminum alloy mechanics performance improvement, although oxygen-rich die-casting, vacuum die-casting alloy etc is improving mechanical properties of effective ways, but widely adopted still has the certain difficulty, so new die casting aluminum alloy of development have been in progress. Advanced die-casting technology early horizontal cold room casting die casting process is only one speed pressure of a liquid metal into the mold, injection speed only 1-m ~ 2m/s. Using this technique, casting internal stomatal much, organization osteoporosis, soon improvement for the 2nd level injection, injection process simply decomposed to slow and fast for the two stages, but fast speed also but 3m/s, later in order to increase the densify, die-casting in slow and fast after added a pressure ascension stage, become slow injection, quick injection and supercharged 3 stages, this is classic 3 pieces injection.
In the 1960's, the middle grade 3 injection has generally away, and fast injection phase speed has been raised to was not/s. After more than 40 years, world leading during casting manufacturers of the ejection process was studied test, thus developed some new processes, such as the 1970s parabolic injection system, the 1980s without flash die casting system, in the 1990s without flash injection system, some from three stages of each stage to pressure shot again decomposition, this is exactly this classic three phases injection of continued development of extension. Now ejection velocity, pressure already by original artificially handwheel adjustment control instead of computer control. In recent years, people in order to solve the die casting internal existing pore and shrinkage problem, can produce the high strength, high-density sex, weldability can heat treatment, can distort, etc. Various kinds of high requirements of the die casting, in addition to continue to perfect vacuum die-casting outside and development of squeeze casting and semi-solid casting and so on the new technology, and generalize the land called "high-density die-casting method". Vacuum die-casting technology vacuum die-casting method is the cavity of gas time or part time, reduce the pressure, so as to facilitate the mold filling mould and alloy melt gas excluded, and make alloy melt in pressure under the action of mold filling, and under pressure solidification and obtain the density of die-casting pieces.
Vacuum die-casting die casting method compared with common law has the following features: (1) the blowhole rate reduced greatly, (2) vacuum die-casting of casting hardness, microstructure tiny, (3) vacuum die-casting mechanics performance of the higher. Recently, vacuum die-casting to surking cavity of gas is given priority to, basically have two kinds of forms: (1) from the mold directly suction, (2) both in really empty containers in mold suction.
Apply the vacuum die-casting, mould exhaust tao position and exhaust tao area of design is very important. Exhaust word in a "critical area", its and cavity in spare gas quantity, suction time and filling time related. When the area of the exhaust way than the critical area, vacuum die-casting, obvious effects Conversely, is not obvious. The vacuum system choice is very important, the requirement in vacuum pump before shutting, within the vacuum cavity can maintain to filling mold finished. Oxygen-rich die-casting technology die-casting stomatal the gases in the predominantly N2 and H2, almost no O2, the main reason is the O2 and active metal happening reaction generated the solid oxide, such as oxygen filling die-casting technology provides theory basis. Oxygen-rich die-casting is in die casting before filling cavity, replace oxygen of air. When the liquid metal into cavity, part of the oxygen from air exhaust slot eduction, residual oxygen react with liquid metal oxide particles generated diffuse shape in casting, formed in flash vacuum, thus obtained without stomatal die-casting pieces. Oxygen-rich die casting process of vacuum is within the cavity, from the chemical reactions of generation. Production to ensure safety, shall be strictly controlled filling oxygen amount, lower cavity pressure, make its and oxygen-rich pressure match. Will vacuum die-casting combined with oxygen filling process, make the cavity is in negative state, we can obtain a better effect.
The liquid metal mould filling process, should make liquid metal to diffuse injection state during the filling. Runner size of also to oxygen-rich die-casting effect has greater influence, proper runnet size can satisfy the liquid metal in the form of turbulent flow and full of casting, can avoid the liquid metal temperature drop too fast. The height of the oxide on castings dispersion distribution will not produce adverse effect, but can improve casting hardness, and make after heat-treatment organization refined. Oxygen-rich die-casting can be used with oxygen reaction of Al, Zn, Mg and alloy. At present, adopt oxygen-rich die-casting can produce all kinds of aluminium alloy castings, such as: hydraulic gearbox shell, heater with heat exchangers, hydraulic transmission body, computer use pipe for heating or compound, requirement need high gas tightness and used in a higher temperature of die casting, oxygen-rich die-casting has technology and economic advantages. Semi-solid casting technology semi-solid casting during solidification is conducted in the liquid metal stirring, in a certain cooling velocity gain about 50% or higher solid-phase components of slurry, then use the slurry for die-casting technology. Semi-solid casting technology now have two kinds of forming process: rheological forming technology and touch into shape craft. The former is the liquid metal into special design of the injection forming barrel by spiral device exert shearing makes its cooling into semi-solid pulp, and then die casting. The latter is solid metal grain or debris into spiral injection forming machine, heating and the shear conditions make metal particles into slurry after whole-coasting. Semi-solid forming technology of die casting key is effective producing semi-solid alloys slurry, precise control of solid-liquid components of proportion and semi-solid forming process automation control of research and development.
To realize the automatic production semi-solid forming, American scientists think need to vigorously develop the following kinds: (1) which has the technical eligibility, flexibility of bar feeders transport; (2) precision die casting lubrication and maintenance, (3) controllable casting cooling system; (4) plasma except gas and processing.
Extrusion die casting technology extrusion die casting, say again "liquid metal mould". Its casting density and the mechanical performance is high, and has no watering riser. Some of our country enterprise has applied to the actual production. Extrusion die casting technology has excellent craft advantage, it can substitute the traditional die-casting, squeeze casting, low pressure casting, vacuum die-casting technology, as well as to the differential pressure casting, forging, semi-solid casting even processing of rheological casting process compatible. Experts think, extrusion die casting technology is a new technology, drilling.it across multiple technology field, rich connotation, innovation, strong, challenging.
Electromagnetic pump low pressure casting electromagnetic pump low pressure casting is a kind of new up-and-coming low-pressure casting process, and gas type low pressure casting technology, compared to the pressure mode is completely different. Its use of non-contact electromagnetic force direct role in the liquid metal, and greatly reduce the due to the compressed air is pure and compressed air oxygen high differential pressure caused by oxidation and inspiratory, etc, to carry out the liquid aluminum of smooth transportation and filling mold, can prevent because turbulent flow caused by the secondary pollution. Other electromagnetic pump system completely using computer numerical control, process execution very accurate, reproducible and make al-alloy castings in yield, mechanical properties and surface quality and metal utilization has obvious advantages. This technique with the deepening of the research, the craft is also getting mature.
Die-casting equipment development after years of development, China die-casting machine design level, technical parameters, performance index, mechanical structure and manufacturing quality to wait to have different degrees of improvement, especially cold room die-casting machine, by original full hydraulic rated-locking institutions to curve elbow type rated-locking institutions, but also increase automatic feeding, automatic spraying, pack automatic pick-up, automatic cutting material side, electric power control by ordinary also changed to computer control, handling level has been greatly improved, and some had been at or near the international level, are toward large-scale, automation and ChanYuanHua march. During this period, the domestic new casting enterprise in succession, including Hong Kong force galerie jingang company is a typical representative, this company has developed many leading domestic die-casting machine, for example, horizontal cold room casting largest empty ejection velocity 6m/s (1997) and 8m/s (early 2000), magnesium alloy die-casting machine (hot room in early 2000) acceleration in the injection system (2002), largest empty ejection velocity 10m/s and more sections die casting system (June 2004), real-time control injection system (August 2004) and clamping force of 30000kN large-scale die-casting machine (July 2004), etc.
In recent years, Shanghai die-casting depots, guannan die-casting depot etc backbone enterprises are developed largest empty injection speed for 8m/s above horizontal cold room casting and clamping force in 10000kN above large-scale die-casting machine, In 2005, the production of guangdong shun wei yi force of pure pressure technology co., ltd. Will produce 10000kN ~ 30000kN large-scale die-casting machine. Obviously China are forming a strength, with independent intellectual property rights of the die-casting machine manufacturing industry. China's total 1.2 million existing die casting machines, including domestic casting accounts for approximately 85% imported casting about 15%. Last year China casting in 1800 sales are above, including Taiwan 10000kN and above casting 8000kN ~ 2%, 9000kN casting 5% 5000kN ~ 7000kN casting 13%, 4000kN casting 3500kN ~ 20%, 3000kN and below casting 60%. In 3000kN below die-casting machine, hot room casting accounted for about 30%.
Small and medium-sized die-casting machine still with domestic-made equipment primarily. Homebred die-casting machine with foreign advanced die-casting equipment gap is mainly manifested in the following aspects: (1) the whole structure design backward, (2) oil leakage is serious; (3) poor reliability: this is homebred die-casting machine's most prominent defects, it is understood that the average trouble-free operation homebred casting time is less than 3000 hour, and even reach foreign 50 and the 1960s level. But foreign average more than 20,000 hours; (4) variety specification is not complete, supporting ability difference: although horizontal cold room die-casting machine has basic become series, but still have the individual DuanDang, as from 28000kN between 16000kN to has no products. Hot room die-casting machine also lacks 4000kN more products. The development of die-casting molds the earliest die-casting die die cores of material selection is 45 ﹟ steel, steel casting and forging steel, etc, due to its high temperature resistant badly-impactive poor, so when using life also is relatively short. With the development of science and technology, die-casting die core material also significant changes have occurred, are now using high temperature, high intensity of 3Cr2N8VH13 hot forging steel as punch materials in recent years, and adopts the imported 8407 material, make mould service life greatly improved, especially in recent years, domestic large factory has adopted computer design and simulation filling technique, make die-casting die production quality greatly improved, campaign shortens greatly.
China mold and die industry is developing rapidly, 1996 and 2004 mold production at an average annual rate of 14%, 2003 die-casting die when output is 38 billion yuan. At present, China's domestic die on the market satisfaction rate is only 80%, in which low-standard mould give priority to, large, complex precision mould, in production technology, mould quality and life and production capacity are cannot meet the needs of economic development. Research and development direction of automobile, motorcycle industry and auto accessories consumption and accessory products demand, to die casting production provides a broad market, die casting aluminum alloy in automotive applications will also expands unceasingly.
In future die-casting technology research and development, aluminum alloy die-casting deepening is still one of the main die-casting technology development direction. In order to meet the market demand, we should further solving the following questions: (1) the promotion application type high strength, high wear resistance of die-casting alloy die-casting, study can be shaded alloy, and for a special safety requirements of castings aspects of new die-casting alloy, (2) developing stable performance, easy to control the die casting aluminum alloy composition, (3) simplifying alloying, reduce alloy nameplate, provides the basis for realizing green production, (4) further perfect die-casting new technologies (vacuum die-casting, oxygen-rich die-casting, semi-solid casting, extrusion); foundry etc. (5) improve the ability of fast reaction to market, promote the concurrent engineering (CE) and rapid prototyping manufacturing technology (RPM); (6) in CAD/CAM/CAE system research and development; (7) development and application more die casting aluminum alloy parts of the car.
