Aluminum die-casting is a metal casting process, which is characterized by using a die-casting machine to apply high pressure to a molten liquid metal aluminum alloy, allowing metal aluminum to be injected into a designed mold cavity at a high speed, and casting a mold-limited shape and size of aluminum. Alloy parts, this casting process is called aluminum die casting.
The main process steps are as follows:
First step. Melting aluminum alloy
usually heating the aluminum ingot by an electric furnace or a coke oven to a liquid state, and the temperature is maintained at about 600-700 ℃.
Step 2. Loading the molding
When melting the metal aluminum, the corresponding die-casting mold is synchronously assembled on the die-casting machine and pre-heated, and the die-casting machine is adjusted to ensure the ideal working condition.
Step 3. Filling the mold cavity
To pour the molten aluminum into the compression chamber, and then the press system injects the aluminum water into the cavity of the mold through the piston at a high speed, and the specific path is first through the compression chamber. Then enters the flow path and ingate of the mold and then fills the entire cavity.
Step 4. Removing the casting
After the aluminum water fills the entire mold cavity, it starts to cool and solidify in a very short time, and the mold is opened within a set time to take out the casting.
Step 5. Spraying the mold
Simplify production process and high scale manufacturing efficiency
Each casting cycle of the aluminum die-casting process is about a few seconds to a dozen seconds, and can be continuously produced in 24 hours.
Together with advanced automatic production equipment, it can complete all production actions from pouring, injection, mold cooling, mold opening, picking, spraying, etc., without manual operation.
Therefore, the production capacity of each production line is huge. It can produce hundreds of thousands of products in a normal shift of 8 hours, and these characteristics are unmatched by other metal casting processes.
Can produce complex shapes, almost net shape, and high precision
The complex shape of the product can be achieved by designing a plurality of sliders on the die-casting mold, and the corresponding cylinder or cylinder is added to the slider to drive, and the operation speed is very fast.
The blanks that have just been cast, except for some feed heads, runners, slag packs, exhausts, flashing, and the rest are net finished products. The casting grade of die casting can reach CT5-CT4, and it can only be kept at CT7-CT9 level whether it is sanding or gravity casting.
Parts with lightweight, good chemical and mechanical properties.
Aluminum die castings are a collection of high-quality features of many other metal parts, easy to cut, high strength, corrosion resistant, can do a variety of surface treatments.
The quality is also light, equal to the same product size, can save a lot of material costs. This is where the company manufactures parts and customers value products.
Aluminum alloy material supply is stable and affordable
Since aluminum is the third element on the earth, its output is huge. Nowadays, the process and equipment for refining aluminum alloy are advanced, and the supply of aluminum alloy raw materials is generally stable for a long time. The price is much cheaper than copper and stainless steel.
The die casting equipment is generally divided into a hot chamber die casting machine and a cold chamber die casting machine.
The difference between the hot chamber die casting machine and the cold chamber die casting machine is that the injection chamber and the injection punch of the hot chamber die casting machine are immersed in the molten metal, and the cold chamber die casting machine is separated from the crucible of the molten metal.
Aluminum die casting usually uses cold chamber die casting process, with cold chamber die casting machine. This is mainly because the melting point of the aluminum alloy is relatively high, and the crucible of the molten aluminum alloy is kept at more than 600 degrees. If the injection chamber and the injection punch are immersed in the high-temperature metal aluminum liquid for a long time, it is very easy to be corroded, which is greatly shorten the life of these die casting machine components.
Cold chamber die casting machines can be divided into horizontal die casting machines and vertical die casting machines. Horizontal die casting machines are generally more common; however, in the die casting industry, the name of the die casting machine is usually divided according to the tonnage of the clamping force.
At present, there are roughly the following tonnage models in the Chinese die-casting industry.
－Small model: 160 tons / 200 tons / 280 tons / 300 tons / 400 tons / 450 tons / 500 tons,
－Medium model: 600 tons / 700 tons / 800 tons / 1000 tons / 1250 tons,
－Large model: 1600 tons / / 2000 tons / 2500 tons / / 3000 tons / 3500 tons ;
－Extra-large model: 4000 tons / 4500 tons
－Products: that can be cast range from a few grams to tens of kilograms.
• Casting design
These factors must be taken into account in the design of aluminum die castings, draft angle, fillets, ribs, parting line, bosses, uniform wall.
• Draft angle
is a slope set on the contact surface between the product and the mold. When the molten aluminum alloy solidifies in the mold cavity, the surface will adhere to the inner wall of the mold, and sufficient draft angle contributes to the casting easily removed from the mold, to ensure a smooth surface without dragging.
• Fillets
The fillets setting has many advantages. First, it avoids sharp corners and sharp edges on the part, saving subsequent processing. Secondly, it helps to make the aluminum water flow more freely in the mold cavity. If it is a sharp corner, it may block the flow of aluminum water at the corner. Finally, some material costs can be saved. Normally, 0.5X45℃ fillets are more common.
• Ribs
While some area of the casting is weak or the strength of somewhere need higher, it is often considered to increase the strength by generally adding ribs. This way does not require an increase in the overall surface thickness, which not only saves a lot of material costs, but also saves more space. Generally, the number of reinforcing ribs is an odd number.
• Parting line
Casting must be opened by the upper and lower molds to be taken out. There is usually a gap between the upper and lower molds (closed). The aluminum water fills the entire cavity and fills the gap. When the casting solidifies, a line made of casting is formed at this place. This line is the parting line.
• Bosses
Many products need to be installed. In most cases, the bosses are designed on the casting. The position and size of the bossed will be set according to the needs of the installation, but ribs and fillets are usually placed around the bossed to ensure sufficient fixing strength.
• Uniform wall
Die-casting product design must consider the same wall thickness. The purpose is to allow each part to cool down while cooling, reducing the generation of pores. The material texture is also more uniform and the strength will be better.
If these major factors are missed, the cast parts may lack integrity, causing subsequent functional problems.
• Mold design
In addition to considering the above factors, the mold design also considers the setting of the fixed and moving molds, the feeding position and the position of the ram, and the direction of the cooling system, and also considers the demand of the product and the complexity of the shape to consider the cavity. Quantity, number and type of mold sliders. Mold material is also one of the most important factors in the design process. Good materials have a relatively high service life.
Well-designed molds usually produce high precision, smooth surfaces, fewer problems, and high mold life.
• Die cast parameter setting
There are good products and mold designs, but if the die cast press parameters are not properly set, it is difficult to make good products. The time and the speed of injection,; the time when the mold is cooled; the uniformity of the spray; the power of the ejecting.
Generally, the reasonable range of these parameters can be roughly calculated according to the size of the product and the structure of the mold. Of course, the experienced die-casting master combines the situation on the spot, the result of the parameter setting can be more accurate, and the obtained product will be better.
• Material selection
The final working environment and function of the castings are different. Some require that the castings can withstand higher pressures, that is, the mechanical properties are more demanding, and some may require the castings to have corrosion resistance and require special chemical properties. So the right material choice is an important step in getting quality products.
According to NADCA report, the two most widely used materials in the world are the A380 and ADC-12. Their overall performance is very good.
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