Why is the car shell made of steel instead of iron?

As we all know, iron can't avoid rusting, only because of different treatment methods, it will rust after a long time, and many steel products on cars are rusted by manufacturers who cut corners before long! A friend said, in this case, why not use aluminum alloy and stainless steel directly? The cost has not increased much.

First of all, talk about aluminum alloy. Let's talk about other advantages of aluminum alloy. Aluminum alloy has the same or even better strength as steel, but it is also very light. But why are there so few cars with aluminum alloy shells now?

One reason: the cost is too expensive. This is not only the high cost of the material itself, but also the cost brought by the manufacturing process with higher threshold. Therefore, the all-aluminum body model may not reach the level of super-running, but it is not "economical". Therefore, most of the all-aluminum bodies we see are used by luxury brands or pure electric vehicles (the cost of luxury brands is easier, and the price of Tesla Model S equipped with all-aluminum bodies is 70.89-1399,800 yuan, and that of jaguar xj is 79.8-1278,000 yuan, including140.27-265438 of Audi R8.

For example, more than 2,000 rivets are needed for the whole car in jaguar XE with all-aluminum body, and the surface oxide layer needs to be treated to ensure the bonding effect when using adhesive, which has higher requirements for the environment and thus brings higher costs.

Generally, an all-aluminum fuselage will use several or even all processes, such as self-piercing rivets, hot-melt self-tapping screws, aluminum resistance spot welding, cold metal welding, laser welding, adhesive bonding and so on. The complexity and automation of the production process is much higher than that of the traditional car body.

The second reason: the maintenance cost of aluminum alloy parts is high and the maintenance is difficult. The general small collision 4S shop can't handle it, and it needs special equipment to repair it, which is very expensive. Some netizens broke the news that their own 7 series is all aluminum except the tailgate cover. Last year, there was a small accident at the front of the car. The headlights scratched the bumper and the hood was slightly deformed at the headlight position.

4S shop maintenance costs more than 5W. Do you think it is expensive? Single cover 1W+ almost 2W 4S store said that it would only be replaced but not repaired!

Then why not use stainless steel? Stainless steel has low cost!

First of all, the stamping performance of stainless steel is not good, and the fuselage material is mainly deep drawing, so the material requires good calendaring, strong rigidity and no rebound. Although the ductility of stainless steel is very good, its resilience is high, which can not meet the processing requirements, not to mention the difficulty of welding and drilling stainless steel. Moreover, once the technology fails, the car body is likely to crack, which is one of the reasons why stainless steel is not suitable as an automobile manufacturing material at this stage.