Core Viewpoint - The assertion that a higher proportion of hot-formed steel in vehicle bodies directly correlates with increased safety is deemed inaccurate and overly simplistic [3]. Group 1: Reasons for Using Hot-Formed Steel - Hot-formed steel is defined as steel with a strength of 1500MPa to 2000MPa, primarily used for its high strength to prevent excessive deformation during collisions and protect the occupant space [4]. Group 2: Limitations on Increasing Hot-Formed Steel Proportion - The proportion of hot-formed steel in vehicle bodies has not consistently increased due to several factors, including the need for energy absorption during collisions, the requirement for complex shapes in body panels, and the increasing use of aluminum alloys for lightweighting [5][8][10]. - For example, Volvo's hot-formed steel proportion increased to 38% but has not surpassed this level, with only 33% of that being ultra-high-strength steel [7]. Group 3: Optimal Proportion of Hot-Formed Steel - There is no definitive answer to the optimal proportion of hot-formed steel; safety should be evaluated through crash test ratings rather than material percentages [17]. - For instance, Volvo's XC40 has a hot-formed steel proportion of 12%, while the XC90 has 33%, and the newer EX90 has reduced it to 21% due to the need for lightweighting in electric vehicles [19][21]. Group 4: One-Piece Die Casting Structure - The one-piece die casting structure has multiple layers of energy absorption design, which enhances repairability and overall vehicle safety [23][28]. - Advantages of this structure include reduced weight, improved production efficiency, and enhanced vehicle rigidity, while disadvantages involve higher costs and more complex quality control [30].