The aluminum material that is touted as sweet and delicious may not be so "pure"
When it comes to aluminum, PTJ can’t help but think of the motto of Lotus founder Colin Chapman. If you want to make your car faster and easier to handle, “simplify the structure, and then reduce the weight”, there is no doubt that aluminum is like this. Kind of material. As an automotive machining material, aluminum alloy has good machinability, beautiful appearance, and light weight, and can play a very important role in driving control and environmental sustainability.
Although it is favored by automakers, the key issue is cost. The biggest advantage of aluminum is of course its light weight. The density of alloy steel is about 7.8g/cm3, while the density of aluminum alloy is only about 2.7g/cm3. Therefore, under the same volume, the weight of aluminum alloy is lighter, which is one of the reasons why aluminum alloy materials are widely used in the aerospace field. But at the same time, the strength of industrial high-strength aluminum alloy can reach 400-500MPa. Although it can not catch up with the ultra-high-strength steel that can achieve more than 1000MPa, it is completely aluminum alloy except for anti-collision beams, A-pillars, B-pillars and other body parts. Can be competent for the role of ordinary steel. Moreover, in the front of the car, such as the position of the engine cover, the more flexible aluminum material can absorb the impact energy and collapse during the collision. Therefore, while the aluminum alloy is light, it will not be compromised in terms of safety.
It is generally believed that the use of 50%-60% by weight of aluminum alloy instead of steel can make the car achieve the same performance. In addition, aluminum alloy has the advantages of corrosion resistance and wear resistance. Therefore, the idea of “substituting aluminum for iron” has always existed in the minds of the bosses of major auto companies. Even if aluminum alloys cannot be used to build the entire frame, many models on the market currently have suspensions, engine blocks, and other parts. Applied aluminum alloy technology.
Let’s not talk about supercars, the Jaguar that has always been known for its all-aluminum body. Jaguar has always been obsessed with the research and development of all-aluminum bodies, gradually expanding from the flagship model XJ/XJL to lower-position models. On the first domestic Jaguar model XFL just launched, the application rate of aluminum alloy reached 75%, which is also the model with the highest application rate of aluminum alloy among domestic models. After the wheelbase increased by 140mm, the weight of the vehicle remained almost unchanged. . Compared with the previous XF model, the weight of the 2016 XF has been reduced by 190kg, and the weight has been reduced by 40%. The weight of the white body is only 297kg, but the body stiffness has increased by 28%.
In addition, Audi A8, Cadillac CT6, and even Ford’s 2015 F150 pickup trucks have begun to use all-aluminum bodies. The plates and profiles of the Audi A8 use 7 types of aviation aluminum alloys, and the connectors are vacuum die-casting. The Cadillac CT6 is an all-aluminum body with 11 different metal materials. After a variety of complex and advanced processing techniques, the weight of the CT6’s body-in-white is not only lower than the standard wheelbase BMW 7 series, but even lighter than the long axle 5 series.
Therefore, the use of more aluminum materials can greatly improve the safety, operability, ride comfort, fuel economy, rigidity, etc. of automobiles, but the biggest reason hindering its popularity is cost. What I’m talking about here is not only the production cost, but also the Cnc Machining cost and complexity of the related processes when the automobile manufacturing is involved in the follow-up.
Aluminum materials have poor toughness. To achieve aluminum sheet stamping, better materials and finer processes are required. The new aluminum plate developed by the material industry makes this kind of production possible, but the transformation of the production line, the experience of the engineer team, and the control of the process are equally indispensable.
The connection of steel to steel is not a problem, and the welding process of aluminum to aluminum is more demanding, but it is also acceptable. But to connect these two materials with different physical and chemical properties together, it will face more technical difficulties. The welding of aluminum to iron has not yet been realized. At present, it is only possible to make the parts into a whole piece or use the method of riveting, but this also requires a more precise design and manufacturing level.
The torsion resistance of aluminum alloy is excellent, but the impact resistance is relatively weak, and it needs to be strengthened design and treatment. If the body is damaged and needs to be replaced, the repair cost will be a more difficult issue.
Because the aluminum plate is relatively rigid, it is more difficult to knock, and the deformation may be too large, and there may be a risk of cracking, and it is impossible to use the methods of repairing ordinary steel plates. Therefore, in terms of after-sales vehicles, maintenance and time costs will increase accordingly.
Therefore, this is also one of the main reasons why the all-aluminum body is still only used for high-end models. The target consumers are relatively less sensitive to price and car cost. From a technical point of view, the body structure of mixed materials mainly made of aluminum and high-strength steel, supplemented by other materials, is a more ideal and pragmatic body structure than all-aluminum.
The birth of aluminum may not be so “pure”. At present, the price of aluminum alloy is almost several times that of steel, and it takes almost 10 times more energy to manufacture. What exactly does this “energy” mean? Aluminum extracted from bauxite ore is also called “solidified electricity”. Especially after the method of electrolytic alumina is applied, 45% of the value of aluminum materials needs to be created by a lot of electricity. However, under the same energy consumption, aluminum has a better recyclable value. Recycling aluminum materials only need to use 5% of the energy required for new aluminum ingots, while reducing greenhouse gas emissions by 92%. If the production process uses renewable energy to generate electricity, then aluminum is an impeccable green metal. However, if the number of manufacturing processes is wrong, it will also be stained with many labels related to “environmental pollution”.
Some foreign colleagues believe that the correct method of producing aluminum should be all around renewable energy, hydropower, solar, wind, geothermal, etc. to generate electricity. So correspondingly, the places where aluminum is produced should also be those places that rely more on these new energy sources. For example, Iceland, Siberia, and Quebec, Canada, are all using hydropower and geothermal power to produce aluminum parts. At the same time, inland areas of Australia, which have sufficient bauxite and sunlight resources, also have the advantage and potential for the development of solar power.
But in reality, more than half of the world’s aluminum is still refined by domestic coal-fired thermal power generation. Of course, due to various reasons, our production costs are lower. Perhaps when people are still worried about the radiation impact of the Fukushima nuclear power plant accident, the pollution it brings may not be as much pollution as the sulfur dioxide, nitrogen oxides, dust and coal ash that are produced by burning coal due to the production of aluminum each year.
Perhaps in the future, when car companies promote all-aluminum bodies, words like “geothermal energy from nature” and “luxury solar texture” should be added, just like the soil and climate of the origin are to red wine. However, expecting to see this kind of propaganda in the country, this “later” period is still quite long.
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