Last week, during a visit to a new energy vehicle (NEV) factory, the workshop director pointed to a chassis bracket on the assembly line and said, “A decade ago, this part required 5 forging processes; now, it’s made in one go with aluminum die casting. Costs have dropped by 40%, and there haven’t been any quality issues yet.”
This is not an isolated case. Open a car chassis or disassemble an engine compartment—from small sensor housings to large battery trays, over 80% of parts are die castings. For traditional fuel-powered cars, this ratio can even reach 90%. Many people wonder: auto parts have extremely high requirements for strength and precision, so why do they “favor” die castings? Today, we’ll break down the 3 “counterintuitive” core advantages behind this trend. After reading, you’ll understand why car manufacturers prioritize suppliers with die casting capabilities when switching partners.
Advantage 1: “One-Time Molding for Complex Parts” – Solving the “Integration Dilemma” of Auto Parts
The biggest challenge with auto parts is their “irregular shapes.” Take a transmission housing, for example: it needs oil passage holes and boss structures for bolt installation. Traditional processing methods first require forging a blank, then milling and drilling—there are 8 to 10 processes in total, and dimensional deviations often occur due to repeated clamping.
Die castings, however, can “get it right in one go”: molten aluminum or zinc alloy is poured into a die-casting machine, pressed into a prefabricated mold under high pressure, and then cooled to form the part. Even parts with complex internal cavities or multiple sets of holes can be “integrally molded.”
Consider the battery tray of a certain automaker. Previously, it was welded from 3 steel plates, weighing 35kg and prone to water leakage at the welds. After switching to an aluminum die casting, the weight dropped to 22kg. The one-piece molding eliminated welds, improving water resistance by 3 levels and saving labor costs for the welding process.
What’s more critical is “controllable precision” – die casting molds can achieve a tolerance of ±0.1mm (equivalent to 1/5 the diameter of a human hair). Once the part is formed, it rarely needs secondary processing and can be directly installed in the vehicle. For car manufacturers, “fewer processes = shorter production cycles.” Especially in the current era where NEVs are “competing for production capacity,” the efficiency advantage of die castings is almost irreplaceable.
Advantage 2: “Lightweight + High Strength” – Perfectly Matching the “Weight Reduction Demand” of Automobiles
Nowadays, both fuel-powered cars and NEVs are “crazy about weight reduction”: a 10% weight reduction for fuel-powered cars can lower fuel consumption by 5% to 8% per 100km; for NEVs, it can increase range by 30 to 50 kilometers. However, weight reduction cannot come at the cost of strength. For example, auto chassis parts must withstand the vehicle’s weight and road impact, creating a “dilemma” for material selection.
Die castings perfectly balance these two needs. Currently, the most widely used “aluminum die casting alloys” (such as ADC12 and 6061) have a density only 1/3 that of steel (lightweight), and after T6 heat treatment, their tensile strength can exceed 290MPa—meaning 1 square centimeter can withstand over 300kg of force, stronger than ordinary low-carbon steel.
Take an example: the engine bracket of a joint-venture automaker used to be a cast iron part weighing 12kg. After switching to an aluminum die casting, the weight dropped to 5.8kg, while strength increased by 15% and fuel consumption per 100km decreased by 0.3L. Today, almost all battery trays for NEVs are aluminum die castings, as they can “reduce weight” while protecting the battery from impact. Last year, an NEV was rear-ended: the aluminum die-cast battery tray deformed but did not crack, and the battery pack remained intact—this is a testament to the material’s strength.
Additionally, die castings have an “excellent material utilization rate”: traditional forging generates over 30% waste, while die casting keeps waste below 5%. The remaining waste can be remelted and reused, which is another hidden cost saving for car manufacturers.
Advantage 3: “Low Cost for Mass Production” – A “Hidden Tool” for Automakers to Reduce Costs
Many people think die castings are “expensive because of high mold costs”—it’s true that a die casting mold for auto parts can cost hundreds of thousands or even millions of yuan. However, as production volume increases, costs drop sharply.
The “unit cost” of die castings mainly comes from three parts: materials, labor, and equipment depreciation. The larger the production volume, the less equipment depreciation and labor costs are allocated to each part. For example, the unit cost of a car door hinge was 85 yuan when the production volume was 100,000 units; when the volume increased to 500,000 units, the unit cost dropped to 52 yuan, a decrease of over 38%.
Compared with traditional processing: producing a transmission housing via traditional forging + machining takes 40 minutes per unit and requires 3 workers; die casting takes only 3 minutes per unit, and 1 worker can operate 2 die-casting machines—labor costs are reduced by 2/3.
More importantly, there’s “supply chain stability”: die castings can be “produced locally.” For example, if an automaker builds a factory in the Yangtze River Delta, it can find local die casting suppliers, shortening logistics time from 7 days to 2 days and reducing collision damage during transportation. Last year, due to the pandemic, an automaker’s out-of-town forged parts were out of stock; fortunately, a local die casting factory urgently replenished the order, preventing production line delays—this is the advantage of a die casting supply chain.
A Sincere Final Note:
Choosing die castings for auto parts is not a “compromise” but the “optimal solution.” They can simultaneously meet the four core needs of “complex molding, lightweight design, high strength, and low cost”—something other processing methods (forging, casting, machining) struggle to achieve.
Today, many automakers ask suppliers, “Do you have die casting capacity?” and “Can you do integrated die casting?” For instance, Tesla’s “4680 battery case” uses integrated aluminum die casting, integrating over 70 original parts into 1, increasing production efficiency by 70%.
If you work in auto parts or want to learn about the selection and processes of specific automotive die castings, feel free to leave a comment below—whether you’re asking, “How to choose between aluminum and zinc die castings?” or “Which surface treatment is best for die castings?” I’ll reply to each question and break down more practical insights in future articles.