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Why use aluminum for car bodies?
2021-11-22
Many people wonder why cars are not made of stainless steel, so that they can get rid of the trouble of rust? In fact, this is not as simple as imagined at all! Once a British brand used stainless steel for the bodywork, the factory went bankrupt, and some people used titanium alloys and carbon fiber. They were destined to be niche markets and not influential. This is the result of market competition. Stainless steel is not suitable for use. Do the bodywork.
1. First of all, this era is the era of energy saving, emission reduction, and lightweight. Automobile companies all over the world are now engaged in one thing, that is, lightweight. Under the condition of ensuring strength, achieving lighter weight is currently the most important thing. The core idea. Look at the density of aluminum alloy. The density of aluminum alloy is 2.8 g/cm3 (rarely greater than 3), the density of iron is 7.8 g/cm3, and the density of stainless steel is close to 8 g/cm3, which is about It is three times that of aluminum alloy. In this case, with the same material volume, stainless steel has to be three times heavier than aluminum alloy. It is also heavier than DC51D+Z (density about 7.85) of the ordinary galvanized sheet used for most of the current body building. Therefore, if you build a car with the same volume of stainless steel, it will be three times heavier than that made of aluminum and a lot heavier than the galvanized sheet.
2. Stainless steel material has many disadvantages such as "high yield point, high hardness, significant cold hardening effect, and easy cracking". When the cold stamping process of the car body is used, the high hardness of stainless steel, high yield point, and cracks are easy to appear. All of them increase the difficulty of production. If the power is small, the impulse will not move, and the power will be directly crushed. Why use stainless steel for materials that are as easy to handle as aluminum alloy and galvanized sheet?
4. Stainless steel needs to be polished, and it is difficult to paint. It is not that stainless steel is not rusty, but it is not easy to rust. The polished stainless steel surface is easy to bloom. Everyone sees that the stainless steel is transported and processed with layers of film attached, and the film can only be removed after the final product is completed.
5. Let's talk about the frame, the requirement for it is that the strength must be high. After the car receives a collision, the front and back of the frame need to deform and absorb energy, while the frame cannot be deformed, and the door can be opened. This strength cannot be achieved by stainless steel. Generally, the yield strength of stainless steel is about 300MPa. The high-strength steel used for the frame can reach 1000MPa, which can be calculated as how much weight can be reduced while ensuring the rigidity.
6. The deformation trend of stainless steel when it is impacted is unpredictable. To put it bluntly, when a stainless steel car collides, it is impossible to judge the degree of deformation of its body or where the deformation is serious. These can not be judged, so safety There is no guarantee, and naturally no one uses stainless steel to make cars.
7. The price of stainless steel materials is high. From the current market price, the price of ordinary galvanized sheet DC51D+Z is now more than 4,000 yuan per ton, the better double-layer galvanized sheet is more than 6,000, and stainless steel is now 19,000 per ton. On average, a car uses 1.2 tons of steel, and a car body may be 0.5 tons. A car made of stainless steel costs more than 3,000 yuan, and an annual output of one million is 3 billion.
In summary, the most important of the conditions listed above are actually the "high density, high price, and difficult processing" of stainless steel. These three points will inevitably lead to the loss of stainless steel and the automotive industry.
1. First of all, this era is the era of energy saving, emission reduction, and lightweight. Automobile companies all over the world are now engaged in one thing, that is, lightweight. Under the condition of ensuring strength, achieving lighter weight is currently the most important thing. The core idea. Look at the density of aluminum alloy. The density of aluminum alloy is 2.8 g/cm3 (rarely greater than 3), the density of iron is 7.8 g/cm3, and the density of stainless steel is close to 8 g/cm3, which is about It is three times that of aluminum alloy. In this case, with the same material volume, stainless steel has to be three times heavier than aluminum alloy. It is also heavier than DC51D+Z (density about 7.85) of the ordinary galvanized sheet used for most of the current body building. Therefore, if you build a car with the same volume of stainless steel, it will be three times heavier than that made of aluminum and a lot heavier than the galvanized sheet.
2. Stainless steel material has many disadvantages such as "high yield point, high hardness, significant cold hardening effect, and easy cracking". When the cold stamping process of the car body is used, the high hardness of stainless steel, high yield point, and cracks are easy to appear. All of them increase the difficulty of production. If the power is small, the impulse will not move, and the power will be directly crushed. Why use stainless steel for materials that are as easy to handle as aluminum alloy and galvanized sheet?
4. Stainless steel needs to be polished, and it is difficult to paint. It is not that stainless steel is not rusty, but it is not easy to rust. The polished stainless steel surface is easy to bloom. Everyone sees that the stainless steel is transported and processed with layers of film attached, and the film can only be removed after the final product is completed.
5. Let's talk about the frame, the requirement for it is that the strength must be high. After the car receives a collision, the front and back of the frame need to deform and absorb energy, while the frame cannot be deformed, and the door can be opened. This strength cannot be achieved by stainless steel. Generally, the yield strength of stainless steel is about 300MPa. The high-strength steel used for the frame can reach 1000MPa, which can be calculated as how much weight can be reduced while ensuring the rigidity.
6. The deformation trend of stainless steel when it is impacted is unpredictable. To put it bluntly, when a stainless steel car collides, it is impossible to judge the degree of deformation of its body or where the deformation is serious. These can not be judged, so safety There is no guarantee, and naturally no one uses stainless steel to make cars.
7. The price of stainless steel materials is high. From the current market price, the price of ordinary galvanized sheet DC51D+Z is now more than 4,000 yuan per ton, the better double-layer galvanized sheet is more than 6,000, and stainless steel is now 19,000 per ton. On average, a car uses 1.2 tons of steel, and a car body may be 0.5 tons. A car made of stainless steel costs more than 3,000 yuan, and an annual output of one million is 3 billion.
In summary, the most important of the conditions listed above are actually the "high density, high price, and difficult processing" of stainless steel. These three points will inevitably lead to the loss of stainless steel and the automotive industry.
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