What are the main reasons for cold insulation in aluminum die-casting?

The main causes of cold shut defects in the aluminum die casting process include the following:

1. Low Mold Temperature: If the mold temperature is too low, the molten aluminum can cool rapidly during flow, preventing it from flowing smoothly and fusing properly within the cavity, leading to cold shuts.

2. Low Pouring Temperature: When the molten aluminum has a low temperature, its fluidity decreases, causing it to cool quickly in the mold and preventing proper fusion with the aluminum that flowed earlier, resulting in cold shuts.

3. Slow Filling Speed: If the filling speed of the molten aluminum is too slow, the front part of the aluminum may stay in the mold cavity for too long, cool down, and not fuse well with the subsequent flow, leading to cold shuts.

4. Poor Mold Design: Improper design of the gates, runners, or overflow channels can cause the aluminum to flow unevenly, creating split flows or turbulence, which hinders proper fusion of different parts of the molten aluminum, resulting in cold shuts.

5. Poor Venting: Inadequate venting in the mold cavity can trap air, obstructing the flow of molten aluminum and leading to cold shut defects.

What are the main appearance phenomena of poor cold insulation?

Cold shut defects primarily lead to the following appearance issues:

1. Surface Cracks: Cold shut areas may develop noticeable linear or web-like cracks, usually due to incomplete fusion of the molten aluminum, creating weak zones prone to cracking.

2. Depressions: The presence of cold shuts can cause uneven shrinkage during cooling, leading to surface depressions or pits.

3. Incomplete Molding: Cold shuts can result in areas of the product's surface that are not fully filled or have irregular edges, affecting the product's integrity.

4. Uneven Color: Due to the uneven cooling of materials at the cold shut areas, color variations may occur, causing the surface to appear mottled or uneven in color.

These appearance defects not only affect the aesthetic quality of the product but may also compromise its structural integrity and mechanical performance.

How to improve poor cold insulation in die-casting?

To improve the issue of cold shut defects, the following measures can be taken:

1. Increase Mold Temperature:

   - Raise the preheating temperature of the mold appropriately, ensuring the mold temperature is within the optimal range. This allows the molten aluminum to flow and fill the cavity more effectively, reducing the risk of rapid cooling.

2. Increase the Pouring Temperature of the Molten Aluminum:

   - Elevate the pouring temperature of the molten aluminum to enhance its fluidity. This ensures that the aluminum can fully merge during the filling process in the mold.

3. Optimize Filling Speed and Pressure:

   - Adjust the parameters of the die-casting machine to increase the filling speed and pressure. This helps the molten aluminum to quickly and evenly fill the mold cavity, avoiding issues where slower speeds cause the aluminum to not fuse properly.

4. Improve Mold Design:

   - Optimize the design of the gate, overflow channels, and venting systems to ensure smooth flow paths for the molten aluminum in the mold, reducing flow resistance and potential turbulence.

5. Enhance Venting Effectiveness:

   - Strengthen the design of the mold's venting system to ensure that air trapped in the cavity can be expelled promptly. This prevents air entrapment from affecting the flow and filling of the molten aluminum.

6. Adjust the Cooling System:

   - Modify the cooling system of the mold to achieve a more uniform temperature distribution. This helps avoid cold spots in the mold that could lead to cold shut defects.

By implementing these measures, cold shut defects can be significantly reduced or eliminated, resulting in higher quality aluminum die-cast products.