5 Steps of Die Casting Material Treatment

Does your die-casting process run perfectly, yet the final parts still end up with defects? In many cases, the real problem starts much earlier—during the material treatment stage. If you want high-quality die casting parts, strict quality control has to begin right from material selection. The following article will tell you the 5 steps of die casting treatment.

Material Report

A material report is a document issued by the supplier or testing institution of die-casting raw materials, detailing the chemical composition of the material.

Typically, die-casting raw materials are various alloys, primarily aluminum alloys, as well as zinc alloys, magnesium alloys, and copper alloys. An alloy means that, in addition to the primary metallic element, the material contains small amounts of other metallic or non-metallic elements.

Although these non-primary elements are present in low concentrations, they can influence the castability properties of the material, such as fluidity and melting point.

Through this report, you can understand the mechanical properties of the die casting alloy, such as tensile strength, yield strength, and elongation. And you can determine whether the alloy is suitable for casting the product you require through the material report. 

You can also find information about the material’s physical properties in this report, such as hardness and density.

For example, if you require die-cast structural components such as housings, cylinders, and frames, aluminum-silicon alloys are your top choice. These alloys contain 10%-25% silicon, imparting excellent casting properties and wear resistance. Sometimes, 0.2%-0.6% magnesium is added to enhance the mechanical properties and heat resistance of your die casting parts.

This material report plays an important role in tracking. If you need to trace the source of the material in the future, it will serve as excellent proof.

Material Inspection

After entering the die casting workshop, metal materials must undergo further inspection to ensure that the die casting materials to be put into production are consistent with the reports provided. Generally speaking, the materials inspection includes the following items.

From an external perspective, you need to observe whether there are any obvious inclusions, cracks, or oxide scales on the surface of the casting material (such as aluminum ingots). 

However, it is impossible to determine whether the composition of the casting alloy meets the standards by visual inspection alone, so spectral analysis and metallographic testing are required.

Spectral Analysis

Spectral analysis is one of the most widely used and efficient methods for inspecting die-casting raw materials. The process involves preparing a polished metal surface from the raw material and analyzing it with specialized instruments. 

It can accurately measure the content of elements such as aluminum, silicon, copper, magnesium, and manganese. By comparing these results with the material report, manufacturers can verify whether the die-casting material meets the required melting standards.

Metallographic Testing

Metallographic testing is essentially a close look at the microstructure of metallic materials. 

In practice, a small metal sample is taken, carefully ground and polished, and then treated with a corrosive agent to reveal the metal’s grains and structural details. Under the microscope, you’ll be able to see the size and distribution of those grains, as well as internal defects like pores or inclusions. 

In this way, metallographic analysis gives us a clear microscopic view of whether a material truly meets casting standards.

Material Melting

Die casting is a forming process that involves high-temperature liquid metal, so the melting of the material is an essential step. As the name suggests, the melting of the material involves heating the die casting alloy in a melting furnace until it becomes liquid. 

The raw materials are typically aluminum ingots, zinc ingots, etc. The melting process requires strict temperature control to ensure that the die-casting alloy does not solidify due to low temperatures or oxidize or absorb other gases due to high temperatures. 

Taking aluminum alloy as an example, its temperature generally needs to be controlled between 680-750℃. 

Of course, for semi-solid die casting, the temperature control requirements during the melting process are different. Semi-solid die casting requires the temperature of the die casting alloy to be between the solidus and liquidus lines. For more details, you can search our website, where we have articles providing specific explanations.

After melting the die casting alloy, it can undergo refining treatment to achieve a purer die-casting material.

Degassing Process

Degassing is the process of removing hydrogen from molten metal during die casting. You might be asking, why does hydrogen even show up in molten metal in the first place? Well, when metals shift from a solid to a liquid state, their ability to absorb hydrogen goes up.

Take aluminum, for example: as molten aluminum gets hotter, it absorbs more hydrogen. But once it cools and solidifies, that hydrogen is pushed out. Because die casting solidifies so quickly, the hydrogen doesn’t have enough time to escape and ends up trapped inside the part as pores.

These pores can seriously hurt the quality of the die casting part, reducing its strength, ductility, and even leaving the surface less smooth. So, you could say that degassing is one of the most crucial steps in preparing materials for die casting.

As one of the die-cast metals refining steps, the degassing process usually means injecting an inert gas—most commonly nitrogen—into the melt through a rotating hollow tube. 

Once the nitrogen enters the melt, it doesn’t react with the aluminum itself. Instead, it grabs onto the hydrogen and carries it up to the surface, where it can escape from the aluminum melt.

Sometimes, die casting engineers use Flow-3D Cast to simulate the degassing process. By tweaking parameters like the design of the hollow shaft and the rotation speed, they can achieve better degassing results and, in turn, improve the overall quality of the die cast.

Remove Slag in Die Casting Process

Removing slag is almost the last step of die casting material treatment.

Slag removal is all about cleaning up the molten metal by getting rid of unwanted impurities. In die casting, once the metal has melted, this step is a must. The slag typically consists of impurities or oxides. It doesn’t just generate on the surface of the molten metal—it can also be found within the liquid itself.

Take aluminum as an example. At elevated temperatures, aluminum readily reacts with oxygen, making oxide formation almost unavoidable. As a result, oxides are commonly observed during the smelting process.

Beyond aluminum’s inherent properties, moisture in the crucible and poor flux also promote oxide formation. For die-cast parts, the presence of oxides leads to shrinkage, pores, and inclusions.

Therefore, removing metal slag, which means eliminating impurities and contaminants from the molten metal, is an indispensable step.

To remove impurities from molten metal, fluxing agents are often added. Some of these agents create a protective layer on the surface of molten aluminum, helping to minimize oxidation. Others work by gathering oxide particles together, making them float to the surface for easier removal. 

Additionally, the nitrogen gas introduced into the molten metal during degassing can also adsorb oxide slag, carrying it to the surface as the bubbles rise.

Conclusion

From inspection to slag removal, every step in material treatment ensures compliance with die-casting standards and guarantees part quality. At Sunrise, we enforce strict raw material control so your components stand out with lasting reliability and market competitiveness. If you are looking for a die casting manufacturer in China, please feel free to contact us!