4 Common Defects in Aluminum Alloy Die Casting and How to Avoid Them

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Aluminum alloy die casting is a method of producing aluminum alloy components using high temperature and pressure to rapidly flow the liquid aluminum alloy into the mold cavity, which solidifies into a casting after cooling. It is a common process for modern production of aluminum alloy parts, which has advantages such as high dimensional accuracy, good mechanical properties, and high production efficiency. Aluminum alloy die castings have broad application prospects in fields such as automobiles, motorcycles, internal combustion engines, electronics, instruments and meters, aerospace, etc.

Although this production method has various advantages, during the production process, the formation of aluminum alloy die castings is influenced by many factors, making it very easy for final castings to develop defects. For example, the aluminum alloy solution is easily entrained with gas during the flow process, and uneven temperature distribution during casting can cause defects such as porosity, shrinkage cavities, and burns. As a company with decades of experience in aluminum alloy die casting production, Dehui Die Casting is familiar with the defects that are prone to occur in aluminum alloy die castings.

The following are some common defects in aluminum alloy die castings:

Aluminum alloy die casting

Porosity problem and solution

In the actual production of aluminum alloy die castings, the problem of casting porosity is the most typical defect, which manifests as pores and bubbles. Pores mainly refer to smooth holes that appear in the center or thick-walled positions of aluminum alloy castings, which are usually caused by improper exhaust or air trapped in the solution. Bubbles refer to the concentrated gas pockets that appear under the surface of the castings.

To eliminate porosity in aluminum alloy die castings, equipment should be carefully cleaned before production, and clean and dry furnace materials should also be used. Additionally, adding a de-foaming agent is also a good choice. During production, attention should be paid to exhaust, scientific and reasonable die casting process indicators, and well-designed molds. Furthermore, the size of the sprue in the mold should be enlarged, the flow rate of the solution controlled, the filling speed reduced while ensuring complete molding, and turbulence of the solution avoided. If necessary, casting temperature, pressure, and speed can be lowered to prevent bubbles from forming in aluminum alloy die castings.

Surface cracks problem and solution

Surface cracks on aluminum alloy die castings occur because of improper operation during production, which causes flow marks, imprints, scratches, and other phenomena on the surface of the castings. Flow marks mainly refer to concave streaks on the surface of the castings, which generally show the direction of liquid metal flow. Imprints refer to scratches, slag inclusions, or joints produced during production. Scratches refer to the traces left on the casting after demolding, such as tears, scratches, or sticking marks.

To avoid these problems, it is important to control the mold temperature, use mold release agents properly, control the flow rate of the solution, use scientifically designed molds that are thoroughly cleaned, and follow proper mold opening and closing procedures, extended holding times, etc.

Shrinkage cavity problem and solution

Shrinkage cavities (or cold shuts) mainly refer to uneven and rough holes on the surface of aluminum alloy castings, which are usually accompanied by porosity at the site of the shrinkage cavity.

The reason for shrinkage cavity formation is due to inadequate compensation during solidification. This can be caused by a wall thickness that is too thick, high casting temperature, unscientific die casting process, low shot ratio, insufficient overflow slot capacity, insufficient chamber filling, poor residual material compensation effect, or a small inner gate. To prevent shrinkage cavities in aluminum alloy die castings, the part structure should be improved in a timely manner, ensuring that the thickness is the same for all parts and thicker walls are properly cooled. Additionally, strict die casting indicators should be followed to prevent temperature drops, increase shot ratios appropriately, increase overflow slot capacity, and perfect the casting system. For molds with high temperatures, appropriate cooling measures should be used. Adding 0.15%~0.2% metal iron or other grain-refining agents to the alloy solution can help improve its tendency to shrink. Alternatively, using an alloy type with low volume shrinkage or adjusting the alloy liquid to reduce its shrinkage rate, as well as expanding the inner gate cross-sectional area, ensuring that the casting hardens under pressure, and avoiding premature hardening of the inner gate that affects pressure transmission can also be effective.

Aluminum alloy die casting

Flash problem and solution

Flash mainly refers to the thin pieces of aluminum overflow produced during the production of aluminum alloy die castings. If flash occurs in aluminum alloy die castings, it will seriously affect their performance, appearance, and size.

To prevent flash from occurring in castings, the following should be done during production: Before production, check the machine's mold clamping force to ensure it is appropriate, and check the mold for wear and tear. During production, attention should be paid to the pressure and speed of the casting process, the size of the overflow slot, and the design of the mold structure. Additionally, injection speed can be slowed down appropriately, the position and direction of the overflow slot can be adjusted, and other measures can be taken to control flash in aluminum alloy die castings.

In summary

Aluminum alloy die casting production is a complex process that requires strict control of various production indicators to produce high-quality aluminum alloy die castings. As a leading company in the industry, Huayin Precision has many years of experience in the production of aluminum alloy die castings, and we have accumulated a wealth of knowledge and technical expertise. We have a complete quality management system, advanced testing equipment, and a team of professional technicians to provide customers with high-quality aluminum alloy die castings that meet their requirements.

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