Characteristics and Development of Die Casting
In recent years, China's aluminum alloy die-casting production continues to rise, the industry is developing very rapidly, mainly due to China's unique market advantage.
As we all know, the application of aluminum alloy Die-casting is very extensive, especially in the automotive
industry, the demand for aluminum die casting is very large. China's automobile industry in recent years, rapid
development and expansion of aluminum alloy die-casting rapid increase in demand, which greatly promoted
the development of China's aluminum die-casting industry.
Especially in the light of the trend driven by the automobile, the global aluminum die-casting market have
emerged a huge demand, China's auto industry, not to mention the needs of this.
At the same time, due to internal optimization and upgrading of the automotive industry in recent years,
aluminum casting is gradually replaced by gray iron castings, which continue to stimulate demand for
aluminum die casting growth. The automotive industry for China, is still in the stage of development
and growth, driven by the above trends,China's aluminum die-casting industry, the advantages
of development and expansion is very obvious.
Die casting is a method of casting liquid forging, the completion of the A special die forging machine technology. The basic process is: first low or high speed liquid metal casting filling into the cavity of the mold, the mold has a cavity surface activity, cooling it with liquid metal forging pressure, which eliminates blank Shrinkage pine defects, but also to achieve the internal organization of the blank forging state of broken grains. Blank mechanical properties has been significantly improved.
Die Casting Structure and composition
(1) casting mold structures
Scheduled to die: die casting machine is fixed in the fixed mold mounting plate, straight runner nozzle or pressure chamber coupled Movable mold: fixed-casting mold motor mounting plate, and with the movable die mounting plate
for the opening movement when the mold clamping, closed cavity and constituting the casting system, the cavity
filled with liquid metal under high pressure; mold opening, the movable die and separated from the fixed mold by means provided on the movable die casting agencies will launch soon.
(2) the role of classification according to the structure of die-casting mold
Cavity: the outer surface of the sprue (sprue bushing)
Core: inner surface of the gate
(3) the quasi conductive parts
Pillar; guide sleeve
(4) Release mechanism
Putter (thimble), the reset lever, putting the fixed plate, push plate, push plate guide posts, guide sleeve push plate.
(5) side core bodies
Boss; cavity (side), wedge tight block, limit springs, screws.
(6) overflow discharge system
Overflow water tank, exhaust ducts.
(7) the cooling system
(8) the supporting parts
Fixed mold; movable mold base plate, spacer (assembly, positioning, installation effect)
Compared with other metal forming processes, the characteristics of die casting are:
(1) the productivity is extremely high, the production process is easy to realize the mechanization and the
automation. General cold chamber Die casting machine every eight hours can be 600 to 700 times the die-casting,
hot-pressing Die-casting machine every eight hours to die-casting 3 000 to 7 000 times. And a die-casting mold
cavity often more than one,so that the number of die-casting production will also exponentially increased.
(2) high dimensional accuracy of the casting, the size of stability, consistency, and less processing allowance
and a good assembly. Die-casting of the accuracy of up to IT11 ~ IT13 level, sometimes up to IT9 level.
Surface roughness values are generally Ra0.8 ~ 3.2, the lowest up to Ra0.4. General Die castings only a
few parts of the size of machining, and some parts without even mechanical processing can be directly
assembled to use.This high utilization of materials, up to 60% to 80%, rough utilization rate of 90%.
(3) casting dense organization, with high strength and hardness. Because the metal liquid is solidified under
pressure,and because of high-speed filling, the cooling rate is very fast, so that the surface of the castings to
produce a layer of cold hard layer (about 0.3 ~ 0.8mm), the layer of metal grain is small, dense organization.
Therefore, high strength and hardness of Die-casting, solid wear-resistant. When the die wall thickness is
appropriate and uniform,its intensity is higher.
(4) can be complex casting shape, clear-cut thin-walled deep cavity casting, because the metal under high
pressure to maintain high mobility. The minimum wall thickness of zinc alloy die-casting parts can reach
0.3 mm, aluminum alloy is about 0.5 mm. The minimum casting diameter is 0.7 mm and the minimum
pitch of the castable thread is 0.75 mm.
(5) Inlay casting method eliminates the assembly process, simplify the manufacturing process. Parts of other
materials such as magnets, brass sleeves and insulating materials can be embedded directly into specific
parts of the die casting to meet specific requirements, eliminating the need for assembly processes and
simplifying the manufacturing process.
(6) casting the existence of porosity, but generally still meet the requirements. As the filling of liquid metal is
extremely fast,it is difficult to completely remove the gas entrained in the cavity during filling, which results in
the presence of pores and oxidized inclusions in the die castings, thereby reducing the quality of the die
castings.Therefore, the general die casting can not be heat treatment, and should not work at high
temperatures.Similarly,do not want to machining, so as not to expose the pores under the casting surface.
(7) Die-casting machine pressure chamber and die casting mold cavity material limits the type of Die-casting
alloys.High melting point ferrous metal die casting die because of its short life and difficult to die in the actual
production.In the same alloy, there are grades restrictions, which is due to the characteristics of the
die-casting process, such as chilling, shrinkage stress, filling conditions, such as molding.
(8) Die-casting process is only suitable for mass production. As the high price of Die-casting machine,
Die-casting mold manufacturing costs are high, long hours, maintenance costs are high, so the total cost
of production, not small batch production.
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