Key Takeaways & Executive Findings
- •• Dual injection system significantly reduces cold shuts and solidification time compared to single injection in large die-casting. • Scaled model at 1:3 ratio successfully replicated real casting conditions, validating the dual injection approach. • The study provides both theoretical insights and practical guidance for producing integrated bottom car bodies via die casting. • The dual injection system addresses challenges of extended filling time and metal flow distance in large integrated castings.
Abstract
This study investigates the formation feasibility of the integrated bottom car body components with dual die casting injection molding technology. During the production of a die-cast super-large one-piece body part weighing over 10,000 t, a thorough comparison and investigation were conducted on the arising issues, using both single and double injection systems. Particular attention was given to meticulously discussing the die casting filling problems and microstructural defects that originated from the filling process. The research findings indicate that the implementation of a double injection system can significantly minimize cold shuts and reduce the solidification time. The effectiveness of this die casting technique was further confirmed by the production of high-quality castings using a scaled model that replicated real casting conditions at a 1:3 ratio, thereby maintaining a one-to-one correspondence in essential aspects. This successful study offers both theoretical insights and practical applications for the production of integrated bottom car bodies utilizing die casting in conjunction with a dual injection system.
1. Introduction
Aluminum alloys are widely used in the automobile industry due to their low weight and good anti-corrosion properties [1]. However, the current body structure is generally complicated in design for achieving the necessary stiffness and strength, which arouses long processing time, high cost, and low efficiency [2]. Recently, as illustrated in Fig. 1, the appearance of the integrated die-casting technology supports one solution for resolving these problems through utilizing large die-casting machines accompanied with the designed die. This approach successfully replaces the traditional multiple processes, which includes riveting, stamping, and welding. Furthermore, this technology can strongly reduce the part weight and cut the costs [3-8].
Due to these advantages, the integrated die-casting technology is evolving towards higher integration and larger size [4]. For example, the 16,000 t die-casting machine equipped with a die over 200 t has been recently developed in China [9]. As die-casting machine capacities continue to increase, the production of large, integrated die-cast products encounters numerous challenges. These include extended filling time and greater metal flow distances during the die casting filling stage. Such conditions exacerbate issues such as cold shuts and compromised mechanical properties in areas distant from the gate [10, 11].
To resolve these issues, the multi-shot injection technology has emerged. In comparison to the single-shot injection casting system, the multi-shot systems can effectively shorten the metal flow length, which can reduce the filling time and keep the metal at a high temperature during the final filling stage. These advantages strongly reduce the appearance probability of cold shuts [12]. To produce a large integrated structural part, Tesla developed an innovative patent for a multi-shot system. This system consists of a fixed set of central dies and four movable mold sets [12]. Subsequently, several domestic automotive manufacturers and die-casting suppliers proposed similar concepts. At the end of 2023, Chery and LK Tech jointly released the first dual-shot system with locking force over 10,000 tons [13], which significantly stimulates the practical application of multi-shot systems.
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Rong Xiao, Jing-guo Wang, Shao-xing Meng, Wei-dong Mao, Li-geng Yang, Jin Zhang, Lei Song, Wan-tong Chen, Wen-bo Yu (2025). Simulation study on integrated bottom car body formation by high pressure die casting with a dual injection system. China Foundry. https://doi.org/10.1007/s41230-025-4028-y
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Frequently Asked Questions
What is the main advantage of using a dual injection system in die casting?
The dual injection system significantly minimizes cold shuts and reduces solidification time, improving the quality of large integrated castings.
How was the dual injection system validated in this study?
The system was validated by producing high-quality castings using a scaled model at a 1:3 ratio that replicated real casting conditions, maintaining a one-to-one correspondence in essential aspects.
What challenges does the dual injection system address in large die-casting?
It addresses challenges such as extended filling time and greater metal flow distances, which can lead to cold shuts and compromised mechanical properties in areas distant from the gate.
What is the significance of this study for the automotive industry?
The study offers both theoretical insights and practical applications for producing integrated bottom car bodies using die casting with a dual injection system, potentially reducing costs and improving efficiency.
What is the scale of the die-casting machine mentioned in the study?
The study mentions a die-cast super-large one-piece body part weighing over 10,000 t, and references a 16,000 t die-casting machine developed in China.
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