How to choose between low pressure casting and gravity casting

Force casting and low-pressure casting are two different casting methods. They have significant differences in implementation principles, process characteristics, and product applications.

First of all, from the perspective of implementation principle, gravity casting is a traditional casting method that relies on the gravity of the earth to inject molten metal into the mold. During the gravity casting process, the molten metal naturally flows into the mold cavity through the gate, where it cools and solidifies, eventually forming the desired casting. Low-pressure casting is a more advanced casting technology that pushes molten metal into the mold cavity by applying low gas pressure in a sealed crucible. This method of applying pressure allows the molten metal to fill the mold more evenly and stably, and effectively reduces casting defects such as pores and shrinkage porosity.

Secondly, in terms of process characteristics, gravity casting has the advantages of simple process and low cost. However, since it relies on natural gravity for filling, the flow rate and pressure of the molten metal are relatively low, which may result in the internal structure of the casting being not dense enough and the mechanical properties being lacking. In contrast, low-pressure casting applies additional pressure during the molten metal filling stage, allowing the molten metal to fill the mold cavity more fully, resulting in higher casting density and better mechanical properties. In addition, low-pressure casting can effectively control the solidification process of molten metal, further reducing defects in castings.

1. High-pressure casting uses a hydraulic cylinder to drive the injection head to press the metal liquid into the mold cavity at high speed. Because it uses oil pressure, the pressure is high, so it is commonly known as high-pressure casting; while low-pressure casting uses air pressure to hydraulically press the metal into the mold. In the cavity, the air pressure is generally 0-2Kg/cm2, so it is generally called low-pressure casting.

2. However, the cost of high-pressure casting equipment is high, the mold manufacturing cycle is long, and the requirements for molds are high. Low-pressure casting and high-pressure casting are two common casting processes, and they have their own application fields and characteristics in production. Low-pressure casting is suitable for producing parts with complex shapes and high precision requirements, while high-pressure casting is suitable for large-scale, batch production.

 

3. But we must clearly realize that although low-pressure casting has a dense structure and good mechanical properties, its productivity is low.

 

Finally, in terms of product applications, gravity casting is mostly used to produce castings with relatively simple shapes and low requirements on mechanical properties, such as some ordinary mechanical parts and building components. Low-pressure casting is more suitable for the production of castings with complex shapes and high requirements on mechanical properties and surface quality, such as automobile wheels, aerospace engine parts, etc. Taking automobile wheels as an example, low-pressure casting technology can be used to produce wheel hub products with higher strength and better surface quality, thus improving the safety performance and driving stability of automobiles.