Aluminum Gravity Casting VS High Pressure VS Low Pressure Die Casting

die casting process

Die casting is one of the most widely used casting processes, but what is the difference between gravity die casting and pressure die casting (high pressure die casting and low pressure die casting)? What are their definitions, and what are the different characteristics of aluminum alloy applications? Follow our professional V1 die casting team. This article will take you to understand the difference between gravity die casting, high pressure die casting, and low pressure die casting.

Table of Contents

What is Gravity Casting?

Gravity casting is a process in which aluminum liquid is injected into the casting mold by gravity under the action of the earth’s gravity. Gravity casting is divided into sand casting, metal casting (steel mold) casting, disappearing mold casting, etc. The narrow sense of gravity casting refers exclusively to metal casting. Metal type casting is divided into vertical hand casting; tilting casting is now the most used metal mold (steel mold). Its mold is made of heat-resistant alloy steel, and the cast aluminum casting’s strength, size, and appearance are higher than those of other casting processes. The aluminum liquid of gravity casting is generally poured into the gate by hand, relying on the self-weight of the metal liquid to fill the cavity, exhausting, cooling, opening the mold to get the sample, and its process flow is as follows:

  • Aluminum liquid melting
  • Pouring filling, exhausting, cooling
  • Opening the mold
  • Clearing the production
  • Heat treatment
  • Processing

The aluminum alloy gravity casting parts characteristics include:

1、The surface finish of the die casing product is not high, and craters are quickly produced after shot blasting.

2、 Aluminum castings with few internal pores can be heat-treated.

3、Low denseness and slightly poor strength, but high elongation.

4、Lower mold cost and extended mold life.

5、Low production efficiency, thus increasing the production cost.

6、The process is more straightforward and not suitable for producing thin-walled parts.

7、Low fluidity special aluminum alloy can be used.

In the product selection of what process production, mainly according to the workpiece wall thickness to make a choice, product wall thickness greater than 8mm, die-casting will cause a lot of pores in the wall, so the thicker wall thickness of the product can choose gravity casting process to complete.

What is High Pressure Die casting?

High pressure die casting: a kind of liquid or semi-solid metal or alloy, or liquid metal or alloy containing enhanced phase, under high pressure with high speed filling into the cavity of the die-casting type, and make the metal or alloy solidify under pressure to form the casting method. Die casting commonly used pressure for 4 ~ 500MPa, metal filling speed for 0.5-120m/s. Therefore, the metal liquid filling time is very short, about 0.01-0.2 seconds (depending on the size of the casting and different) can fill the cavity. Therefore, high pressure, high speed is the fundamental difference between die-casting method and other casting methods, is also an important feature.

The aluminum alloy die casting parts characteristics include:

1、The product surface finish is good, generally up to Ra6.3 or even up to Ra1.6.

2、Product airtightness, casting strength, and surface hardness, but low elongation, wall thickness is too thick easy to produce porosity.

3、 No heat treatment.

4、High mold cost and short service life.

5、High production efficiency.

6、It can produce thin-walled parts with a small machining allowance.

7、Can’t use special aluminum alloy.

 

What is Low Pressure Die Casting?

In a sealed crucible (or sealed tank), dry compressed air is introduced. The metal liquid, under the action of gas pressure, rises along the rising tube into the straight sprue, enters the cavity smoothly through the inner sprue, and maintains the gas pressure on the liquid surface in the crucible until the casting is completely solidified. Then the gas pressure on the liquid surface is lifted, and the unconsolidated liquid flows back to the crucible. The casting is then opened and removed. This casting method has good shrinkage, dense castings, easy-to-cast large thin-walled complex castings, no bubble, and a metal yield of 95%. No pollution, easy to achieve automation. However, the equipment cost is high, and the production efficiency is low. Generally used for casting non-ferrous alloys.

The characteristics of aluminum alloy low pressure parts are:

1、The product surface than die casting poorly stronger than gravity parts

2、Aluminum castings with fewer internal pores can be heat-treated.

3、Product airtightness is high, casting strength and surface hardness is higher than die casting, but the elongation is lower than gravity.

4、Mold cost is lower, and the service life is low.

5、Production efficiency is lower than gravity and much lower than die-casting.

6、The process is complex and used to produce high requirements and high quality castings.

7、Low fluidity special aluminum alloy can be used.

All die casting methods are suitable for different situations, which means that the choice depends on the requirements of your next project.

At V1 Diecast, we will work with you according to your requirements and help provide the best advice to get the best out of your products and components. Contact Us Now.

 

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