Aluminum gravity casting vs high pressure die casting vs low pressure casting
Introduction to gravity casting:
Gravity casting refers to the process of injecting molten aluminum into the mold by gravity under the action of the earth's gravity. In a broad sense, gravity casting can be divided into sand mold casting, metal mold (steel mold) casting, lost foam casting, etc.; Gravity casting in narrow sense refers to metal mold casting. Metal mold casting is divided into vertical manual casting, and inclined casting is now the most widely used metal mold (steel mold) casting. The mold is made of heat-resistant alloy steel, and the strength, size and appearance of the cast aluminum castings are higher than those of other casting processes. The aluminum liquid of gravity casting is generally poured into the gate manually, and the mold cavity is filled, vented, cooled and opened to obtain samples by relying on the self weight of the metal liquid. The process flow is generally as follows: aluminum liquid melting, pouring material filling, venting, cooling, mold opening, production clearing, heat treatment and processing.
The characteristics of aluminum alloy gravity casting parts are as follows:
When choosing which process to produce the product, it is mainly based on the wall thickness of the workpiece. When the wall thickness of the product is greater than 8mm, die casting will cause many pores to exist in the wall. Therefore, the products with thick wall thickness can be completed by gravity casting process.
Introduction to die casting:
Pressure die casting is divided into high-pressure casting and low-pressure casting.
High pressure casting is what we usually call die casting. The liquid aluminum is poured into the pressure chamber, the mold cavity is filled with its pressure at high speed, and the liquid aluminum is solidified under pressure to form an aluminum casting.
High pressure die casting: a casting method in which liquid or semi-solid metal or alloy, or liquid metal or alloy containing reinforcement phase, is filled into the cavity of die casting mold at a high speed under high pressure, and the metal or alloy solidifies under pressure to form a casting. The commonly used pressure during die casting is 4 ~ 500MPa, and the metal filling speed is 0.5-120m/s. Therefore, the filling time of liquid metal is very short, and the mold cavity can be filled in about 0.01-0.2 seconds (depending on the size of the casting). Therefore, high pressure and high speed are the fundamental difference and important characteristics between die casting and other casting methods.
Aluminum alloy die castings are characterized by:
Low pressure casting: dry compressed air is introduced into the sealed crucible (or sealed tank). Under the action of gas pressure, the liquid metal rises along the riser into the sprue, enters the mold cavity smoothly through the inner sprue, and maintains the gas pressure on the liquid level in the crucible. Until the casting is completely solidified. Then release the gas pressure on the liquid level to make the non solidified metal liquid in the liquid riser flow back to the crucible. Re open the mold and take out the casting. This casting method has good feeding, dense casting structure, easy to cast large, thin-walled and complex castings without riser, and the metal yield is 95%. No pollution, easy to realize automation. However, the equipment cost is high and the production efficiency is low. Generally used for casting non-ferrous alloys.
The features of aluminum alloy low-voltage parts are:
In short, low pressure is the compromise between high pressure and gravity.
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