Why Do Cars Rarely Use Stainless Steel For Their Bodies?

Some time ago, Tesla released the Cybertruck electric pickup truck, and its unique stainless steel body also attracted people's attention. On Tesla's official website, this material is defined as ULTRA-HARD30X cold rolled stainless steel.

In fact, stainless steel, which is widely used in daily life, is rarely used as a car body material. Automobile manufacturers usually use high-strength steel, aluminum alloy and other materials to make their bodies. Stainless steel can have good anti-corrosion and anti-rust properties. Why is stainless steel rarely used?

In terms of anti-corrosion and anti-rust performance, other methods, such as the use of galvanizing, high-quality primers and paint, can prevent rust well, and the cost is not high. The main function of the original car paint is anti-corrosion. Today, car paint has become an important element in the field of automotive styling design. It can be said that as the paint process has been strengthened, the advantages of stainless steel have been gradually weakened. However, stainless steel is not friendly to paint spraying, which makes the covering parts unable to achieve many beautiful colors, and the single color cannot meet the diverse needs of consumers.

In terms of cost, the price of stainless steel is much higher than that of ordinary steel plates, generally three times that of galvanized steel plates. Stainless steel is also more difficult to process and difficult to weld. This further increases the cost. It is more common in high-end models. The aluminum body seen also has good corrosion resistance and is lighter.

The strength of 304 stainless steel plate is 205-400MPa, and the strength cannot be satisfied for safety parts such as A-pillar and B-pillar. In addition, due to the limitation of tensile strength, stainless steel is not suitable for stamping and forming. The physical properties of stainless steel are inferior to carbon steel, and the cost is high. Of course, no manufacturer is willing to use it.

Regarding Cybertruck30X cold rolled stainless steel, Elon clarified on Twitter that this is a new alloy developed by Tesla that belongs to the stainless steel 30 series. In an interview, Elon mentioned an important reason for choosing 30x stainless steel: 30x stainless steel has very good fracture toughness. Fracture toughness is a characteristic of the propagation of material structure cracks and other sharp defects. In addition, most steel materials become very brittle at low temperatures, and materials with poor fracture toughness, such as ceramics and glass, once cracks appear, it is difficult to prevent the cracks from becoming larger. This is not the case with 30x stainless steel. As for the cost, ElonMusk previously mentioned that the cost of 30x stainless steel is only $2500/ton.

Historically, Ford used stainless steel to build cars in 1936, known as Ford Tudor. In 1963, Porsche built three all-stainless 911S sports cars. However, the more widely known stainless steel car is the DMC-12, which is famous for the "Back to the Future" series. It uses a fiberglass body structure, stainless steel panels, a unique gull-wing door and a rear engine, and a high-gloss mirror. Body.

At present, ordinary cars use double-sided galvanized steel sheets, which are mainly low cost, light weight, and high reliability.

High-end cars use lightweight aluminum alloy plates, which are much more expensive than double-sided galvanized steel plates, but have lighter weight, better corrosion resistance and rigidity, no light deformation, better impact resistance, and better safety .

As for why stainless steel is not used for the body, there are three reasons: first, the weight of stainless steel is greater, which will increase fuel consumption; second, it is not easy to cold-roll, and the durability is not good; third, the deformation after impact is large and difficult to control, so it is used as a body Material safety is poor.

Therefore, although stainless steel is good, it must not be used as a body material. This is the conclusion drawn by automotive engineers after repeated experiments during the design.