Comparison of the Differences Between High Pressure Die Casting and Low Pressure Die Casting

According to GB/T 5611-1998, casting (casting/founding/foundry) refers to the forming method of melting metal, making a mold, pouring the molten metal into the mold and solidifying to obtain a metal part blank with certain shape, size and performance.

There are many kinds of casting, such as sand casting in gravity casting (iron casting brake disc, clutch pressure plate), high pressure die casting, low pressure die casting and investment casting (dewaxing casting), etc. There is also interesting Thixomolding (semi-solid injection molding), which is similar to the injection molding of plastic parts. The metal alloy is made into alloy particles, which are then melted and molded by screw high-pressure injection. As a parts manufacturing company, let us introduce some related knowledge points of high pressure die casting and low pressure die casting.

1. High pressure die casting VS. low pressure die casting

It is established that in the actual working process, the die casting we mentioned in most cases can be directly considered as high pressure die casting.

High pressure die casting refers to the method that molten metal is filled at high speed under high pressure and solidified under pressure.

Low pressure die casting: the mold is placed above the sealed crucible. Compressed air is introduced into the crucible to form a low pressure (generally 60 ~ 150 kPa) on the surface of the molten pool, so that the metal can fill the mold through the riser pipe and control solidification.

2. Advantages and disadvantages of high pressure die casting and low pressure die casting and their applications

(1) Advantages and disadvantages of high pressure die casting:

• The parts are with high dimensional accuracy and good surface quality. It is beneficial to surface treatment, such as anodizing, spraying and so on.

• The casting is with good mechanical properties (tensile strength and elongation), which is suitable for mass production.

• It can produce thin-walled parts with complex structures and shapes.

• Die-casting parts cannot be machined (CNC) in large quantities.

• The castings are prone to produce fine pores and shrinkage porosity, and cannot be subjected to conventional heat treatment.

Common parts: inner and outer shells (turbocharged), base, bracket, steering wheel frame, etc. Because of the low plasticity of die casting, it is not suitable to work under impact or gand vibration.

(2) Advantages and disadvantages of low pressure die casting:

• The manufacturing process is highly automated. Labor cost is controllable and the process is stable.

• The microstructure of the parts is compact with high mechanical properties which can be further improved by heat treatment.

• The utilization rate of raw materials is high, which is generally 90% ~ 98%. The cost advantage of parts increases.

• Although the filling pressure and speed are easy to control, the production efficiency is lower than that of high pressure die casting.

• The lift pipe from crucible to mold is with short service life and large loss, so spare parts need to be prepared.

Common parts: steering knuckle, cast aluminum caliper body, cylinder head, hub, cylinder frame and so on.