1. Die Casting: Widely Applied Automotive Aluminum Alloy Forming Process

Die casting, abbreviated as die casting technology, is a specialized casting technique. This technique refers to a precision casting method where liquid or semi-liquid metal is filled into a die casting mold cavity under high-speed and high-pressure conditions, rapidly solidifying under specific pressure to form a casting. With a history of over a century, this casting technology finds widespread use in the automotive manufacturing industry.

Currently, die-cast aluminum alloy products comprise approximately 54% to 70% of aluminum used in automobiles. Manufacturers classify automotive aluminum alloys into cast aluminum alloys and deformable aluminum alloys based on their different processing properties. Cast aluminum alloys, the most widely used type in automobiles, find extensive applications in structural components such as wheels, engine parts, chassis, shock absorber brackets, and space frames.

Currently, the application scope of aluminum alloy die-castings for automotive purposes is classified according to usage functions, including structural parts, stress parts, safety parts, and decorative parts. It mainly includes the following application scenarios:

• Power system: cylinder block, cylinder head, cylinder head cover, crankcase, oil pan, piston, pump body, pump cover, shell, and various engine brackets.
• Transmission system: gearbox housing, gearbox oil circuit board, clutch housing, shift fork, gearbox bracket, etc.;
• Steering system: chain cover, rack body and turbocharger body.
• Chassis assembly: suspension bracket and crossbeam;
• Body: wheel hubs, body structural components, and decorative products;
• Others: lower end cover of shock absorber, compressor bracket, clutch pedal, and brake pedal, etc.

The development of the new energy vehicle industry has driven continuous innovation in aluminum alloy die casting technology. With the continuous improvement of technical indicators such as power, safety, comfort, and lightweighting in the new energy vehicle industry, the required automotive aluminum alloy products are gradually developing towards thin-walled, high-strength, low-cost, and integrated structural directions, providing an application basis and driving force for the development of die casting technology.

The advancement of aluminum alloy die casting technology for automotive applications in recent years has largely depended on the ongoing refinement and modification of the composition of automotive aluminum alloy materials. This is coupled with the use of high-vacuum die casting technology and the tweaking of heat treatment process parameters. The aim is to fully exploit the process features of automotive aluminum alloy materials and consistently enhance the overall mechanical properties of die-cast aluminum alloy materials through high-pressure injection and slow-speed filling. In the field of new energy vehicles, aluminum alloy die casting has been applied in battery pack shells, electric drive housings, motors, and reducer integrated machine shells.

 2. Integrated Die Casting: Tesla Leads the New Transformation of Die Casting Technology

Integrated die casting technology is a new transformation of die casting technology. Integrated die casting technology redesigns multiple independent parts that originally needed to be assembled in the design and uses oversized die casting machines to directly cast the entire parts in one shot to achieve the original functions.

Tesla was the first to apply integrated die casting to the rear floor. At Battery Day in September 2020, Tesla announced that the Model Y would adopt an integrated die-cast rear floor assembly, which would reduce 79 components and manufacturing costs by 40% compared to the original stamping and welding assembly. This marks the formal implementation of the design concept of assembling entire large castings instead of assembling individual components.

Integrated die casting molding of the lower body assembly is the direction of Tesla’s development. Tesla announced plans to replace the entire lower body assembly, consisting of 370 parts, with 2-3 large castings, further reducing weight by 10%, which corresponds to an increase in range of 14%.

Tesla may potentially achieve one-time die-casting of the car body-in-white, thereby completely eliminating assembly production lines. In July 2019, Tesla released a patent titled “Multi-Faced Integral Forming Casting Machine for Automobile Chassis and Related Casting Methods.” According to the patent information, the die-casting machine comprises a central part with a body shell mold and multiple protruding mold parts that can be translated relative to the shell mold. Multiple protruding molds can converge in the central area to be responsible for die-casting different components, ultimately completing either the entire or partial monolithic chassis casting.

 3 Integrated die-casting: Innovating Traditional Automobile Manufacturing Processes

The traditional manufacturing processes of automobiles mainly include stamping, welding, painting, and assembly. The main process involves stamping steel sheets into different individual parts, which are then assembled into a body shell assembly through welding, riveting, gluing, and other methods. Subsequently, anti-corrosion and painting treatments are applied, followed by the assembly of interior and exterior trims, powertrains, chassis assemblies, and other components to complete the vehicle assembly.

Integrated die-casting technology represents an innovation in traditional automobile manufacturing processes. Tesla’s Model Y rear body was originally stamped and welded from 70 parts, but integrated die-casting consolidates it into a single component. The consolidation of 70 parts into one offers multiple advantages, including lightweighting the vehicle body, cost savings, efficiency improvements, shortened supply chains, reduced manufacturing and transportation times, decreased reliance on manual labor and robots, and enhanced manufacturing scale.