High pressure dies casting is one of the most cost-effective and fastest ways of making big volumes of parts and products in aluminum, magnesium, or zinc. Die casted parts are known for minimal material wastage, maintenance of consistent features, excellent surface finishing.
High pressure die casting is used in a wide variety of industrial applications such as the manufacture of motor housings, appliance parts, heat sinks, fittings, brackets, engine blocks, and a wide range of commercial and industrial products.
For those intending to create parts and products using high-pressure die casting, you must contend with the issue of porosity in your projects. It’s an uncontrollable and unavoidable fact, to mitigate the issue we are going to briefly look at what causes it and ways you can mitigate against it.
What is porosity
Porosity is commonly known as a void or hole in a solid casted metal product or part. Pores can differ in sizes ranging from micropores to larger holes which are measurable in cubic millimeters or larger.
Not only do the pores have to be circular but they also come in the form of irregular linear cracks. There are two main causes of porosity: gas porosity and solidification shrinkage. For this post, we are going to closely look at these two causes and discuss ways in which we can mitigate them.
Solidification Shrinkage
When the molten material is injected onto the mold cavity, they immediately begin to solidify when they come into contact with cooler walls This solidification causes the metal part to shrink, but the rate at which it shrinks depends on the mold tool geometry as well as they type of alloy being used.
The semi-liquified section of the metal that is much further away from the mold tool wall is referred to as slush, this is the area where pores are much more likely to form. Additionally, when the molten materials solidify it blocks all liquid passages to other sections within the mold, this will lead to the creation of pores as a result of lack of full liquification of all the features within the design.
Gas porosity
Gas pockets can form in the following ways, this is the case the hydrogen or aluminum falls out of the suspension and fill it with hydrogen gas. The air pocket can also get trapped in the mold tool when its bot is fully vented or evacuated.
The gas porosity vaporizes forming bubbles, the liquids, and oils which don’t evaporate become contaminants and may form inclusions in the final part or product.
How to prevent porosity
Wall thickness
One of the fastest and easiest ways of tackling porosity is the maintenance of wall thickness, this is the job of a mold tool designer.
Shrink rate
It’s a wise investment decision that a client or manufacturer works closely with high pressure die caster and discusses various options of the raw-materials based on the design and application.
It’s always best to be on the same page with the manufacturers to get everything clear when it comes to the specifications and ideas at the early stages of product development to avoid issues arising from porosity.