7 Ways to Reduce Scrap in Your Aluminum Foundry

Every aluminum foundry produces scrap. The question is: how much?

While rates vary widely, the consensus across the industry is clear: scrap represents a significant drain on profitability. When you consider that common defects like porosity, shrinkage cavities, and inclusions are among the leading causes of casting rejection, the scale of the problem becomes clear.

But here’s the good news: scrap is preventable. Most of it comes from controllable factors in your melt preparation, casting process, and quality control. Here are seven practical ways to reduce scrap in your aluminum foundry.

Start with Melt Control

Many aluminum foundries invest considerable resources controlling operations after the casting is poured, while giving only token attention to what happens prior to pouring. This is backwards. As one industry expert puts it, “it is nearly impossible to solve downstream scrap issues in the foundry without first controlling the melt”.

What to do:

• Specify pouring temperatures and procedures for each part

• Implement standard operating procedures for melt preparation

• Monitor and document melt quality at each stage

The good news? “Controlling the melt is not that complicated: Just follow these basic, common-sense foundry practices”.

Use Quality Raw Materials

All aluminum is not created equal. The small amount saved per pound by using a questionable aluminum supplier can cost you far more in casting scrap.

Quality ingot producers take many steps in the smelting process to ensure the raw material does not contribute to casting scrap. Your ingot producer should use:

• In-line filters – fine ceramic filters remove impurities such as oxides during ingot production. Without these filters, impurities become part of the ingot and ultimately the castings, increasing the scrap rate.

• In-line degassing – quality smelters degas the melt while producing the ingot. When degassing is not performed, an incoming ingot has a much higher quantity of hydrogen gas, which may increase production costs by creating porosity scrap.

• Chemical control – chemical variations from lot to lot can significantly affect the mechanical properties of your casting.

What to do:

• Verify the quality of your raw material suppliers

• Request accurate chemistry certifications with each shipment

• Don’t compromise on ingot quality for short-term savings

Control Scrap Remelt

Most aluminum foundries re-melt casting scrap. But the maximum amount of scrap used for each melt should be controlled.

The percentage of scrap allowed should be based on the customer specification of the casting. The larger the percentage of scrap allowed, the greater the chance of introducing oxides and other inclusions into the cast part.

What to do:

• Set limits on scrap remelt percentage based on casting requirements

• Ensure scrap is dry and clean before remelting

• Remove dross from scrap by sawing, grinding, or blasting

• Never add scrap with sand and dross on the surface—this will result in oxides and inclusions, increasing scrap rate and customer reject rates for hard spots and other defects found during machining

Filter the Molten Metal

Ceramic foam filtration is one of the most effective tools for scrap reduction.

Ceramic foam filters remove non-metallic inclusions from molten aluminum—oxide films, slag, refractory particles, and other impurities that cause defects. By effectively removing inclusions, these filters reduce trapped gas and provide laminar flow—meaning the filtered metal becomes significantly cleaner.

The result? Cleaner metal produces higher-quality castings, less scrap, and fewer inclusion defects—all of which contribute to bottom-line profit.

What to do:

• Install ceramic foam filters in your gating system or filter box

• Choose the right PPI for your application (coarser for large castings, finer for precision work)

• Preheat filters to the proper temperature before use

• Ensure proper sealing around the filter to prevent bypass flow

Degas the Melt

Hydrogen porosity—small, round, smooth-surfaced internal cavities—is one of the most frequent internal defects in aluminum die casting. It forms when dissolved hydrogen comes out of solution during solidification.

The solution? Degassing. This involves introducing an inert gas (argon or nitrogen) into the molten aluminum to remove dissolved hydrogen before it can form pores.

What to do:

• Use rotor degassing for thorough hydrogen removal

• Extend refining time—research has shown that extending refining time positively impacts the reduction of porosity

• Monitor hydrogen levels with reduced pressure testing (RPT)

• Keep furnace atmospheres dry to prevent re-absorption of hydrogen

Maintain Crucible and Ladle Cleanliness

This is one of the most overlooked sources of scrap—and one of the easiest to fix.

Allowing aluminum and dross to build up on crucible walls should not be acceptable in any aluminum foundry. This build-up of oxide-saturated material frequently breaks loose and releases oxide inclusions into the melt, which end up in the casting as inclusions and hard spots.

Similarly, the aluminum skin that forms on the walls of a pouring ladle should be removed prior to each pour. The surface of this skin contains an oxide layer that remelts when combined with new molten aluminum, creating an oxide-rich ladle of molten aluminum that is transferred to the mold.

What to do:

• Implement cleaning procedures to ensure crucibles and melt furnaces are free of dross build-up

• Remove ladle skins before each pour

• Train operators on proper cleaning techniques

• Schedule regular equipment inspections

Optimize Your Gating and Process Design

Poor gating design leads to turbulent filling, which entraps gas and creates oxides—both of which cause scrap.

Ceramic foam filters don’t just remove inclusions—they also rectify flow, converting turbulent flow into laminar flow. This reduces gas entrapment and re-oxidation during filling, preventing defects before they form.

What to do:

• Design gating systems to minimize turbulence

• Place filters strategically in the gating system

• Use simulation software to optimize filling patterns

• Monitor and document process parameters for each casting

Summary: Your Scrap Reduction Action Plan

The Bottom Line

Scrap isn’t just a production problem—it’s a profitability problem. Every defective casting represents wasted energy, wasted labor, wasted material, and lost revenue.

The good news is that most scrap is preventable through disciplined melt control, proper filtration, effective degassing, and good housekeeping. These aren’t expensive, high-tech solutions—they’re fundamental best practices that every aluminum foundry should implement.

Start with melt control. Add ceramic foam filtration. Degas properly. Keep your equipment clean. Optimize your process.

Your scrap rate—and your bottom line—will thank you.

Ready to reduce scrap in your foundry? Our technical team can help you select the right ceramic foam filtration solution for your specific casting application. Contact us for a consultation.

Email: info@sf-foundry.com
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