What Is the Difference between Gravity Casting and High-Pressure Casting


There are many types of mold casting, including gravity casting molds and high-pressure die casting molds (die casting). So what is the difference between these two casting processes?

Gravity Casting

Gravity casting refers to a process in which molten metal enters the mold cavity under the action of gravity and is poured into the mold. It is also called gravity casting. In a broad sense, gravity casting refers to sand casting, metal mold casting, investment casting, lost foam casting, etc. In a narrow sense, gravity casting also refers to metallic pouring.

Characteristics of Gravity Casting

High-pressure Casting

High-pressure casting is a casting method that introduces molten alloy liquid into a pressure chamber, fills the cavity of the steel mold at high speed, and solidifies the alloy liquid under pressure. The main features that distinguish high-pressure die casting from other casting methods are high pressure and high speed.

The molten metal fills the mold cavity, crystallizes, and solidifies under higher pressure. Common pressures are 15-100MPa. The molten metal fills the mold cavity at a high speed, usually 10-50 meters per second, and some can exceed 80 meters per second. Therefore, the filling time of the molten metal is very short, and the mold cavity can be filled in about 0.01-0.2 seconds.

Characteristics of High-pressure Casting

Advantages and Disadvantages of Gravity Casting and High-Pressure Casting

In terms of strength, the strength differences are also large due to the different raw materials of the aluminum alloys involved. Since die-cast products are formed under high pressure, the products have high density and high strength. For example, the strength of A380 die-cast products can reach 360MPa, but its elongation can only reach about 3.7%. Gravity casting products generally have lower strength than die casting. The better material ZL101A can only reach 310MPa after heat treatment, but its elongation is higher, reaching 5-6%. There are also materials whose strength can reach above 380MPa, such as ZL201A and ZL204A.

 CraftsmanshipMold CostMold LifePorosityHeat treatmentMachining AllowanceSmooth SurfaceSuitable ProductProductivity
High Pressure CastingComplexHighShortPoorNoSmallHighThin Wall PartsHigh
Low Pressure CastingSimpleLowLongGoodYesBigHighMiddleMiddle
Gravity CastingSimpleLowLongGoodYesBigLowThick Wall PartsLow

It can be seen from the above that when we choose which process to use for product production, as long as we choose based on the thick wall of the product, high-pressure casting should be the first choice as long as the production process and product performance can meet the requirements because the production efficiency of high-pressure casting is extremely high. . When the thickness of the product is greater than 8mm, the strength of the high-pressure cast product may not meet the expected requirements due to too many internal pores. Gravity casting or low-pressure casting can be considered.

Applications of Gravity Casting and High Pressure Casting in the Automotive Industry

Gravity casting is used for large, complex component housings while high-pressure casting enables more intricate, smaller parts with thinner walls and complex internal features.

Gravity Casting:

High Pressure Casting: