Characteristics of die casting
As an advanced metal forming process, die-casting occupies an important position in the manufacturing industry due to its unique technical advantages. However, it also has certain limitations. Understanding its characteristics will help to reasonably select application scenarios in production and maximize the value of the process.
High production capacity is one of the most notable features of die-casting, making it suitable for large-scale production. The die-casting cycle is short, taking only 10 to 60 seconds from mold closing to ejection, far less than the hours or even days required for sand casting. A single die-casting machine can produce thousands to tens of thousands of die-cast parts per day. For example, the die-casting production line for mobile phone mid-frames uses automated loading and unloading, with a single machine capable of producing over 5,000 parts per day. Large parts such as automotive engine brackets can also reach 500 to 1,000 parts per day. This high efficiency stems from the continuous operation mode of die-casting, where metal smelting, injection molding, and cooling can be carried out simultaneously. Combined with automated production lines (such as robot part removal and online testing), it can achieve 24-hour uninterrupted production, significantly reducing the manufacturing cost per unit product. It is particularly suitable for industries that require large-scale production, such as automobiles and home appliances.
Die-cast parts offer high dimensional accuracy and excellent surface quality, reducing subsequent machining steps. The die-casting mold cavity is precision-machined to achieve dimensional tolerances of IT7 to IT10 and a surface roughness of Ra0.8 to 3.2μm. After die-casting, die-cast parts meet assembly requirements without extensive machining. For example, zinc alloy toy parts can be die-cast to within ±0.05mm dimensional tolerances, allowing them to be painted directly without polishing. Aluminum alloy automotive wheels can be die-cast to a surface flatness of 0.1mm/m, requiring only fine milling of the mounting surface. This high-precision feature not only saves processing time and cost, but also improves product consistency and reduces assembly errors, which is particularly important for parts requiring precise fits, such as transmission gearboxes.
Another major advantage of die casting is its ability to form parts with complex structures, breaking through the shape limitations of traditional casting. The high pressure and high speed of die casting enable molten metal to fill complex mold cavities, forming parts with side holes, bosses, thin walls, deep cavities, and other structures, with minimum wall thicknesses of 0.5mm and minimum apertures of 1mm. For example, die casting of laptop computer cases can form complex structures with cooling holes and snap-on slots in a single step, eliminating the multiple steps of traditional stamping. Die casting of automobile engine blocks can integrally form complex internal structures such as water jackets and oil passages, reducing welding and assembly steps. Furthermore, die casting enables lightweight part design. By optimizing wall thickness distribution, weight can be reduced while maintaining strength. For example, aluminum alloy die-cast automobile chassis parts are 30% to 50% lighter than steel parts, in line with the lightweighting trend of modern industry.
High material utilization and a relatively environmentally friendly production process meet the requirements of green manufacturing. During the die-casting process, nearly all of the molten metal is converted into die-cast parts, with only a small amount of flash and sprues requiring remelting. This results in a material utilization rate exceeding 90%, significantly higher than forging (60%-70%) and machining (50%-60%). After processing, the remelted material can be reused for die-casting, further reducing material waste. Regarding environmental protection, modern die-casting production lines utilize closed melting furnaces to reduce flue gas emissions, water-circulating cooling systems to conserve water resources, and water-based release agents to reduce VOC emissions. For example, a large die-casting company, through environmentally friendly renovations, reduced smelting energy consumption by 15% and wastewater emissions by 80%, meeting national Class I environmental standards. Compared to sand casting, die-casting eliminates the need for sand cores, avoiding dust pollution during sand handling and improving the working environment.
Die casting also has certain limitations, primarily high mold costs, a limited range of applicable materials, and a tendency to generate internal pores within die-cast parts. Die-casting molds require high precision manufacturing and require high-quality hot-working die steel (such as H13) to be manufactured through multiple machining steps. A medium-sized mold can cost hundreds of thousands of yuan, while a large, complex mold can cost over a million yuan. Therefore, it is only suitable for large-scale production (typically over 100,000 pieces per year), while small-batch production is less economical. Regarding applicable materials, die casting is primarily suitable for low-melting-point non-ferrous metals such as zinc alloys, aluminum alloys, and magnesium alloys. High-melting-point steel materials are less commonly used because the molds cannot withstand the high temperatures. Furthermore, high-speed filling of the molten metal can easily entrap gases, leading to internal pores within the die-cast part. These pores expand during heat treatment or welding, causing part deformation. Therefore, die-cast parts are generally not suitable for high-temperature heat treatment (such as T6 treatment for aluminum alloys) or welding, limiting their application in applications requiring high strength.
