Integrated Die-Cast

With the adoption of "dual carbon" goals, the global automotive industry has placed greater emphasis on energy conservation and environmental protection. To promote energy conservation and reduce emissions, countries are actively recognizing and supporting the development of new energy vehicles. In this context, new energy vehicle companies have steadily increased their investment in research, development, and production to meet consumer demand for lighter, more efficient vehicles. Integrated die-casting technology, which offers notable advantages in production efficiency, cost savings, and weight reduction, is becoming essential for the development of new energy vehicle bodies. Leading new energy vehicle companies like Tesla, NIO, and Xpeng have actively invested in integrated die-casting, suggesting that die-casting machines may gradually replace welding robots as core equipment for manufacturing. The essence of this technology lies in the high performance of large die-casting machines, innovative heat-treatment-free materials, precise mold design, and optimized process parameters. In particular, aluminum alloy integrated die-casting technology, known for its lightweight and efficient production, has become standard among new energy vehicle companies.
 

Die casting (HPDC) stands for high-pressure die casting. It is a molding process in which molten or semi-solid metal is injected into a mold cavity under high pressure (20–120MPa) and at high speed (20–100 m/s), then solidified under continuous pressure. During the die casting process, molten metal rapidly fills the mold cavity. The external pressure not only helps maintain the consistency of the metal’s size and shape in relation to the mold cavity, but also facilitates efficient cooling. The mold's cooling effect, combined with the external pressure, ensures that the molten metal adheres closely to the mold, promoting rapid heat dissipation and allowing for quick solidification. This process produces castings with fine grain structures and uniform properties. Integrated die casting refers to a modern die casting technique that combines multiple traditionally separate small parts into a single, highly integrated design. It utilizes a large die casting machine for one-step molding, eliminating the need for welding and directly producing a complete, large component.

 

Aluminum alloys used in traditional die casting have been in development for a longer period, and the material's process characteristics are well-established and controllable. Structural parts produced through traditional casting can undergo T6 and T7 heat treatments after casting to enhance mechanical properties and corrosion resistance due to their smaller size. ADC12, ADC14, A360, A380, ENAC-43400, and ENAC-4600/SF36 (AlSi10MnMg) are commonly used in the die casting process. Integrated die casting is often used to produce larger and more complex parts. Heat treatment-induced thermal expansion and contraction may cause defects such as dimensional variations and surface cracks. Therefore, aluminum alloys that do not require heat treatment should be selected. The material must also possess high strength, toughness, fluidity, and connection tolerance. Commonly used alloys include C611, 560 alloy, and A152.
 

Because traditional castings are small in size and have a relatively simple structure, the mold design, including the mold splitting scheme, pouring system, exhaust system, ejection system, and mold temperature system, is simpler. Additionally, higher calculation redundancies are built into the early stages of mold design, which makes adjustments easier later. The structure of integrated die-casting molds is larger and more complex, placing greater demands on the design of the pouring system, mold temperature control, ejection system, and vacuum conditions. Sufficient simulation and risk assessments should be conducted early in the design process to reduce the difficulty of subsequent mold adjustments. The selection of mold materials and mechanical processing should also take into account the mold’s service life and reliability.
 

In traditional die-casting, parts are typically small, so the projection area in the mold opening direction is limited, and the clamping force required during the casting process is relatively low. As a result, the performance requirements for the die-casting machine are not particularly demanding, and the required tonnage generally does not exceed 4,500 tons. The size and number of supporting equipment in the die-cast cell are also relatively small. In integrated die-casting, multiple small parts are combined into one, significantly increasing the weight and projection area in the mold opening direction compared to traditional die-cast parts. This results in higher clamping force requirements for the die-cast machine. Currently, die-casting machines used for integrated die-casting typically have a tonnage of no less than 6,000 tons, and the size and number of peripheral equipment have increased accordingly.
 

In traditional die-casting, decisions are often based on experience, with practitioners relying on empirical formulas or charts as industry references. However, there are few comparable products in integrated die-casting, and many process parameters exceed the upper limits of traditional die-casting standards. Therefore, the effectiveness of traditional empirical formulas needs further verification. To ensure the quality of castings, higher process standards must be met in terms of the purity of die-casting alloys, low gas emissions from spraying materials, and the vacuum conditions of the mold cavity before punching.
 

In traditional die-casting for automotive parts, it is mainly used for motor housings, transmission housings, and electronic control enclosures. In contrast, one-piece die-casting is primarily employed for lightweight body components such as torsion beams, front cabin assemblies, rear floors, and side CD-pillar inner panels.