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Aluminum alloy castings for transportation
Aluminum is one of the most commonly used light metals. It is also one of the most widely distributed and stored elements in the earth's crust. Aluminum alloy materials have excellent characteristics, such as small specific gravity, high specific strength, good formability, mechanical properties, physical properties, process properties and recycling value. In the global metal industry, the application of aluminum ranks second only to steel. It is widely used in various departments of industrial production, especially in the automotive engine, automotive gearbox, rail vehicle and aerospace parts market in the transportation industry.
Aluminum alloy castings for transportation
At present, aluminum alloy casting for transportation molding process is mainly divided into die casting process, low pressure casting process, sand casting process, vacuum suction casting process and metal mold casting process. Among them, die casting process, low pressure casting process and vacuum suction casting process are widely used.
Die casting process
Die casting process is a method to make liquid or semi liquid metal fill the die casting cavity at a high speed under the action of high pressure, and form and solidify under pressure to obtain castings. It has many advantages, such as high production efficiency, good product surface quality and high dimensional accuracy. It is widely used in the production of automobile castings. The general process flow is as follows: batching - smelting - flow transfer - heat preservation and refining standing - ladle refining - ladle flow transfer - die casting - parts taking - Inspection - slag removal - cooling - purging - cutting cake, sprue - removing flaring, burr - aging - machining - Cleaning - air tightness testing (poor workpieces undergo air tightness testing again after infiltration) - Inspection - packaging.
In actual production, due to the high cost of die-casting die, the die-casting process is more suitable for mass production (to dilute the high cost of die-casting die).
2 low pressure casting and vacuum suction casting process
Low pressure casting is a method in which liquid metal fills the mold cavity under the action of air pressure or inert gas pressure of 0.01Mpa ~ 0.05Mpa higher than atmospheric pressure to form castings. Because the pressure used is low, it is called low-pressure casting. Vacuum suction casting is a casting method that creates a vacuum in the mold cavity, sucks the metal into the mold cavity from bottom to top and solidifies. Due to the complex structure of aluminum alloy castings for transportation and the thin wall thickness in local areas, the production processes of low-pressure casting and vacuum suction casting are widely used in the world. The general process flow is: proportioning of aluminum ingot, master alloy and returned waste for remelting - melting in aluminum melting furnace - refining in furnace refining device - casting by vacuum suction casting machine or low-pressure casting machine - Cleaning - grinding - rough machining - Welding desanding process hole - X-ray flaw detection - heat treatment - semi finishing - air tightness detection - finishing - spraying - packaging. Aluminum alloy castings for rail transit vehicles and aerospace are produced by low pressure casting and vacuum suction casting, which has the advantages of high dimensional accuracy, good surface quality, excellent microstructure and high mechanical properties.
Aluminum alloy castings for transportation are widely used in rail vehicles. Aluminum castings are widely used in vehicles, such as various suspension seats and sleeper beams (Fig. 4). The 350 km / h high-speed train bogies in Germany and France adopt cast aluminum alloy sleeper beams, which are designed by Swiss AMG company according to the technical requirements of German Siemens company and French Alstom company. Although China has begun to engage in the technical research and development of aluminum alloy casting for transportation and has been able to produce finished products, the aluminum alloy sleeper and beam castings for high-speed trains are still mainly imported from Switzerland.
By the end of 2015, the operating mileage of China's high-speed railway reached 19000 km. According to the national plan for future cities, it is predicted that by 2020, the operating mileage of China's high-speed railway will exceed 30000 km, and the annual average demand of domestic passenger rail trains will be more than 13000. If the axle weight of a single domestic crh380 high-speed EMU is 17T, cast aluminum alloy sleepers and cranes will be used on each vehicle body.
If the weight of seat, transmission gearbox, motor end cover and motor fan reaches more than 0.5T, the average annual demand of aluminum alloy castings will reach 6500t by 2020.