In the common terminology of the aluminum alloy die-casting industry, the so-called cold shut refers to the cracks or seams that appear in the workpiece after casting. These cracks or seams are caused by the incomplete fusion of the molten metal.
What is Aluminum Alloy Die Casting Cold Separation
Cold shut refers to the fact that when filling the casting cavity, the molten metal fails to fully fuse, forming an incompletely connected seam. During the die-casting process, due to the different cooling rates of various parts, the temperature in certain areas will be lower, resulting in the failure of the molten metal to completely solidify. Therefore, during the cooling process, seams or cracks can form, creating a cold shut. The existence of a cold shut will seriously affect the mechanical properties of castings, and will also reduce the quality of castings.
In order to avoid cold shut, the following measures can be taken in aluminum alloy die casting:
- Control the pouring temperature and pouring speed of the alloy to minimize the time that the liquid metal stays in the mold cavity while ensuring sufficient filling of the casting cavity to avoid the formation of a cold shut due to excessive cooling.
- Properly design the cooling system to ensure that the liquid metal can evenly and fully fill the entire casting cavity, and achieve uniform cooling during the cooling process.
- Ensure good venting of the casting cavity to prevent gas from being trapped inside the casting, causing local temperature reduction and resulting in the occurrence of cold shuts.
- Select appropriate pressure and hydraulic parameters to ensure that the liquid metal can smoothly fill the entire cavity and promote complete fusion of the metal liquid.
In addition, it is worth noting that during the aluminum alloy die-casting process, there is a casting defect that is very similar to the cold shut, called "cold slug". Cold slugs refer to metal particles that are not completely melted during the smelting process of aluminum alloy materials.
What is aluminum alloy die-casting cold material?
The material used for aluminum alloy die-casting is put into the furnace in solid form and heated so that it melts into liquid metal for die-casting. However, during the material feeding or melting process, sometimes solid material that is not completely melted remains in the liquid metal. These residual parts are called cold materials.
The existence of cold materials will cause a series of problems. First of all, incompletely melted cold material will cause uneven composition of liquid metal, thus affecting the chemical composition and performance of the casting. Secondly, after the cold material is injected into the mold cavity and solidified, it may form inclusions or produce local cold insulation, further affecting the quality and performance of the casting. In addition, cold materials may cause damage to mold equipment.
To avoid the presence of cold material, the following measures need to be taken:
- Control the furnace temperature and melting time to ensure the raw materials can be fully melted and reach the required melting point.
- Use appropriate mixing equipment to promote even melting and mixing of the materials.
- Regularly clean and maintain the furnace to ensure that there is no accumulation of cold material in the furnace.
Through these methods, the generation of cold slugs can be effectively reduced or avoided, and the quality and performance of aluminum alloy die castings can be improved.