Aluminum Die Castings

Article Guide:

1. What is aluminum die castings?

2. Advantages of aluminum die castings;

3. Application of aluminum die castings;

4. Process of aluminum die castings.

What are Aluminum Die Castings?

Aluminum die castings mean the parts made of pure aluminum or aluminum alloys obtained by die casting. Generally, aluminum or aluminum alloys heated to a liquid state are pressed into a metal cavity by a die casting machine, and aluminum parts or aluminum alloy parts of various shapes and sizes are obtained after cooling. These parts are usually called aluminum die castings.

Advantages of Aluminum Die Castings:

Aluminum die castings have some advantages that other castings cannot match.

1. Aluminum die castings are widely favored by users, Because of their beautiful appearance, lightweight, corrosion resistance, and other advantages.

2. The density of aluminum die castings is lower than that of cast iron and cast steel, while the specific strength is higher. Therefore, using aluminum die castings under the same load conditions can reduce the structure's weight.

3. Aluminum die castings have a good surface gloss and corrosion resistance in the atmosphere and fresh water.

4. Pure aluminum die castings have good corrosion resistance in oxidizing acid media such as nitric and acetic acid.

5. Pure aluminum and aluminum alloy die castings have good thermal conductivity. They are also suitable for heat exchange devices used in chemical production and parts that require good thermal conductivity in power machineries, such as cylinder heads and pistons of internal combustion engines made of aluminum alloy.

6. Due to the high latent heat of solidification of aluminum alloy, under the same weight conditions, the solidification process of aluminum liquid lasts much longer than that of cast steel and cast iron, and the fluidity is good, which is conducive to casting thin-walled and complex castings.

Application of Aluminum Die Casting:

The aluminum die casting process can be used to produce auto parts, auto engine parts, engine cylinders, valve rocker arms, valve bearings, power parts, motor end caps, reducer housings, construction parts, and guardrail accessories, wheel hubs, etc.

Aluminum die castings have been widely used in automobile manufacturing, internal combustion engine production, motorcycle manufacturing, motor manufacturing, transmission machinery manufacturing, precision instruments, landscaping, power construction, and other industries.

Process of Aluminum Die Castings:

1. Die-casting machine commissioning

Commissioning the die-casting machine ensures that it can work stably and continuously.

2. Die-casting mold design and manufacture

According to the drawings of the aluminum die casting, the 3D model of the die is designed using the die design software, the die steel is used as the material, and the machining center is used to complete the manufacture of the die casting die.

3. Die-casting mold design and manufacture

According to the drawings of the aluminum die casting, design the 3D model of the mold using the mold design software,  use the die steel as the material, and use the machining center to complete the manufacture of the die casting mold.

4. Die-casting die installation

Install the finished metal mold on the die-casting machine and complete the commissioning work.

5. Paint formulation and application

In the die-casting process, to avoid welding the aluminum die-casting part and the die-casting mold, reduce the frictional resistance of the casting ejection and avoid the excessive heating of the die-casting mold. Requirements for coatings:

1) At high temperatures, it has good lubricity;

2) Low volatilization point, the diluent can volatilize quickly at 100-150℃;

3) No corrosive effect on die-casting molds and die-castings;

4) The performance is stable in the air, and the diluent should not be excessively volatilized and thickened;

5) No harmful gas release at high temperatures;

6) No fouling will occur on the surface of the die-casting cavity.

6. Mold cleaning

The cleaning of the mold needs to be completed before starting processing. To ensure the cleanliness of the mold.

7. Mold preheating and coating

Before Using die-casting molds, should preheat them to a particular temperature. Usually, using gas, blowtorch, electrical or induction heating.

In continuous production, the temperature of die casting molds tends to increase, especially for die casting high melting point alloys, which rise rapidly. In addition to making the liquid metal sticky, The higher temperature will cause the casting to cool slowly and the grains coarse. So when the die-casting mold's temperature is too high,  shall adopt cooling measures. Usually perform cooling with compressed air, water, or chemical media.

8. Die casting mold clamping

9. Aluminum Alloy smelting and heat preservation

The die-cast alloy is heated to a predetermined temperature and kept stable.

10. Die casting injection

The pouring temperature refers to the average temperature of the liquid aluminum alloy when it enters the cavity from the pressing chamber. Because it is inconvenient to measure the temperature of the liquid metal in the pressing chamber, it is usually shown by the temperature in the holding furnace.

The too high pouring temperature will cause the die casting to shrink seriously. Aluminum die castings are prone to cracks, large grains and can also cause stickiness; too low pouring temperature can easily cause cold insulation, surface patterns, and insufficient pouring of die castings. Therefore, we should consider the pouring temperature, the pressure, the temperature of the die casting mold, and the filling speed at the same time.

The time it takes for the liquid metal to fill the cavity from entering the cavity is called the filling time. The length of filling time depends on the casting volume's size and complexity. Large and simple aluminum die castings will have relatively long filling times; complex and thin-walled castings will have shorter filling times. The filling time is closely related to the cross-sectional area of the gate, the width and thickness of the gate, and these three parameters, must be determined correctly.

11. Inserts preparation

Inserts can improve local mechanical properties on castings, such as strength, hardness, wear resistance, etc.

Some parts of aluminum die castings are too complex for the core to come out and require the aid of inserts.

12. Pressure holding

The duration from the liquid aluminum alloy filling the cavity to the complete solidification of the inner gate is called the pressure holding time. The length of the holding time depends on the material and wall thickness of the aluminum die casting.

13. Mold opening and core pulling

We should complete the opening and take out the aluminum die casting at an accurate time after the pressure holding. The time from the pressure injection to the opening mold is called the opening time. We need to accurately control the opening time. Because if the opening time is too short, the strength of the aluminum dies casting will be much lower, which may cause deformation when it is ejected and dropped from the mold; if the opening time is too long, the temperature of the aluminum die casting will decrease, lead to high shrinkage rate, and the resistance of core pulling and ejection of castings will increase accordingly. The general calculation method of opening time is: every 1 mm increase in the wall thickness of the casting takes 3 seconds and then adjusts after the on-machine test.

14. Clean up (refurbishment)

Casting cleaning is hard work, and its workload is often 10 to 15 times that of die casting. Therefore, it is important to realize the mechanization and automation of the casting cleaning work to increase the die casting machine productivity and output.

15. Casting infiltration and shot penning

The surface cleaning of aluminum die castings adopt ordinary polygonal rollers and vibration buried cleaning devices. For simple and small batches of small parts, often use the polygonal cleaning roller; for decorations with high surface requirements, often use the cloth or leather polishing wheel to complete the polishing; for mass-produced die-casting parts, often use the screw-shell vibration cleaning machine.

The cleaned aluminum die castings can also be surface treated and impregnated according to users' requirements to increase luster, prevent corrosion and improve air tightness.

16. Final inspection

Ensure that the shape, size, corrosion resistance, mechanical properties, and other parameters of the die casting meet the requirements.

Summary

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