BYD has disclosed new technical details about the one-piece aluminium frame used in the Yangwang U8L, revealing a development program that began in 2023 and required the creation of China’s largest automotive integrated casting machine, in partnership with aerospace-backed supplier Hantek.

The latest information expands on an earlier breakthrough reported by CarNewsChina, when the world’s first one-piece low-pressure-cast aluminium vehicle frame was revealed on the Yangwang U8L. The structure introduced a 4.2-square-meter integrated casting with wall thicknesses ranging from 4 mm to 50 mm, a manufacturing challenge previously considered beyond the limits of conventional automotive casting processes.

According to BYD engineers, the project targeted a full-size vehicle frame that could exceed traditional steel structures in lightweighting, strength, corrosion resistance, and durability simultaneously.

The team evaluated high-strength steel, hot-formed steel, titanium alloys, and aluminium alloys before selecting aluminium as the only material capable of meeting all objectives within current production constraints.

Unlike conventional automotive aluminium structures, the U8L frame uses extensive aerospace-grade 6-series and 7-series aluminium alloys. Engineers combined these materials with a highly integrated structural layout intended to maximise stiffness while minimising mass.

The challenge extended beyond materials. Engineers determined that achieving the required strength required both large-scale integrated casting and a major reduction in heat-affected zones in welded joints. That pushed the project toward cold-joining methods, including bolting and riveting, which are more commonly used in aerospace structures.

BYD said no supplier had suitable equipment for casting a structure of this size when development began.

After attempts with more traditional multi-piece rear casting solutions failed to meet repeated stress-testing targets, engineers sought solutions outside the automotive industry. The company partnered with Hantek, which has experience in aerospace manufacturing, to develop what BYD described as the largest integrated casting machine currently used in China’s automotive sector.

The resulting process became the first domestic application of integrated low-pressure casting technology for a large vehicle frame. Parts count fell from 251 components to 119, while 67 rear-frame parts were consolidated into a single casting.

Weld length dropped from approximately 100 meters to 9 meters, significantly reducing potential fatigue and deformation points.

Engineers also introduced aerospace-derived dimensional-chain control methods to manage bolt preload distribution and joint reliability under dynamic loading conditions. BYD claims key connection-point performance improved more than fourfold, while tensile performance increased by more than two times compared with earlier development stages.

The finished aluminium frame reduced vehicle weight by 56 kg while increasing structural rigidity.

BYD said the U8L became the first vehicle in the industry to pass a 12-ton lifting test using the integrated frame structure. Vehicle torsional rigidity reportedly exceeds comparable models by more than 50%.

The disclosure comes as Yangwang continues to position itself as BYD’s technology showcase brand. At the 2026 Beijing Auto Show, Yangwang presented special versions of both the U8L and U9 Xtreme, while the limited-production U9 Xtreme later became the most expensive BYD vehicle ever sold, reaching 20 million yuan (2.76 million USD). Yangwang delivered 264 vehicles in April, following 307 units in March and 232 in February, according to China EV DataTracker.