Knowledge

Mold Design and Manufacturing

Mold design is a crucial step in the die-casting process, directly influencing the quality of the castings and production efficiency. It requires comprehensive consideration of the casting's shape, size, functional requirements, as well as the fluidity and solidification characteristics of the alloy.

 

Mold material selection: Commonly used mold materials include steel and aluminum alloys, among which H13 steel is widely employed due to its excellent thermal stability and wear resistance. The choice of mold material should be based on the production volume of the castings, the type of alloy, and cost-benefit analysis.

 

Mold structure design: A mold typically consists of two halves, the upper die and the lower die, along with ejection systems, cooling systems, and exhaust systems. Mold design must ensure that the molten metal fills the cavity uniformly, while also taking into account shrinkage rate and draft angle to facilitate the removal of the casting.

 

Mold manufacturing accuracy: The manufacturing accuracy of the mold directly affects the dimensional accuracy and surface quality of the castings. Modern mold manufacturing techniques such as CNC machining, EDM, and laser cutting are widely used to ensure the precision of the molds.

 

 

 

Metal Preparation and Melting

Metal preparation and melting are fundamental steps in the die-casting process, which determine the quality and fluidity of the molten metal.

 

Alloy selection: Commonly used die-casting alloys include aluminum alloys, zinc alloys, and magnesium alloys. Each alloy has its unique physical and chemical properties and is suitable for different application scenarios.

 

Melting temperature control: The melting temperature of the metal is crucial for its fluidity and the quality of the castings. For instance, the melting temperature of aluminum alloys typically ranges from 660°C to 750°C, while that of zinc alloys is between 420°C and 480°C.

 

Charge preparation: The preparation of metal charges involves the proportioning of new and recycled metals, as well as any necessary refining and slag removal processes to ensure the purity of the molten metal.

 

Injection and solidification of molten metal

The injection of molten metal is one of the most critical steps in the die-casting process, as it determines the filling speed and pattern of the casting.

 

Injection speed: The injection speed has a significant impact on the quality of the casting and production efficiency. High injection speed can reduce oxidation and gas entrapment, but it may cause metal splashing and mold wear.

 

Pressure control: Maintaining a constant pressure during injection is crucial to ensure complete filling of the mold cavity. The pressure typically ranges from 10 to 175 megapascals.

 

Filling pattern: The design of the filling pattern needs to consider the flow path and speed of the molten metal to avoid gas traps and cold shuts.

 

Cooling and Solidification of Castings

Cooling and solidification are the key steps that determine the final performance of castings.

Cooling rate: The cooling rate has a significant impact on the microstructure and mechanical properties of castings. Rapid cooling can produce fine grain structures, enhancing the strength and hardness of the castings.

 

Mold cooling system: The design of the mold cooling system must ensure uniform cooling of the molten metal to reduce thermal stress and deformation. The cooling fluid usually circulates through channels within the mold.

 

Solidification time: The solidification time depends on the thickness of the casting, the type of alloy, and the mold temperature. An appropriate solidification time ensures complete solidification of the casting and avoids internal defects.

 

Mold Removal and Post-Processing of Castings

Mold removal and post-processing are the final steps in the die-casting process, and they are crucial for the final quality and appearance of the castings.

 

Mold removal techniques: Mold removal techniques include mechanical ejection and pneumatic ejection. The correct mold removal technique can reduce damage and deformation of the castings.

 

Post-processing procedures: Post-processing procedures include deburring, grinding, cleaning, and heat treatment, etc. These steps can improve the surface quality of the castings, eliminate internal stress, and enhance the performance of the castings.

 

Quality inspection: Strict quality inspection of the castings is carried out, including dimensional measurement, surface inspection, and mechanical property testing, to ensure that the castings meet the design requirements.

 

Vigor team have rich experience on die-castings. If any question or any demands we can help, please feel free to contact us at info@castings-forging.com