If ever a light metal was able to conquer the automobile sector, Then it's the material aluminum. It has, for a long time now, been the favourite for cylinder heads, intake systems, and gearbox-/final drive casings etc. However, the final breakthrough was only recently achieved by using it for engine blocks (see picture) and particularly, for chassis parts. Then, there are the areas where the use of aluminum cannot be seen (e.g., seat-racks and dashboard support etc.). In addition, (brushed) aluminum is now also often being used, e.g., on the dashboard as a surface material.
The silver-coloured aluminum is the the most abundantly found metal in the world. Of all the chemical elements, it is the 3rd most prolific. In it's pure form, because of the lack of stability, it is hardly ever found in technology. It is nearly always alloyed with silicon and/or magnesium. Once it has developed an oxide layer, it doesn't corrode any further. On the contrary, the oxide layer (anodization) even strengthens the component.
Aluminum is extracted from Bauxite. This is a material which is mixed with, among other things, iron and titanium, it's name comes from the now insignificant, first site of discovery, Le Baux, in the south of France. In the manufacturing process it is ground, dried and thus made into powder form, whose aluminum parts are then disolved in sodium lye. Pressure and heat accelerate this process.
In the first process, aluminum is separated from all substances found in the ore except for iron. Now the, through the iron, slightly reddish, solid components, are extracted in containers with sloping floors. Once the last red-sludge portion has been removed through additional filtering, the aluminum oxide is coagulated in gigantic mixers by adding small amounts of alluminum hydroxide.
Aluminum hydroxide, which is developed after once more being filtered and heated in a rotary kiln at just under 1300°C, is freed from it's water portions. Large amounts of Direct-Current are then necessary, to separate the aluminum from it's oxygen through electrolysis in a temperature sinking cryolite-bath.
Due to the ten-fold higher energy requirements, the aluminum-technology only makes sense in combination with a functioning recycling process (returning the materials into the production process), then this, only requires half the energy. If one compares the density of aluminum (2,7 kg/dm3) with that of steel (7,85 kg/dm³), the target of using as much as possible in vehicles, becomes understandable.
For it to be cast, aluminum must of course be heated. Whereby, it is important to repeatedly remove any dross, e.g., the oxides. Aluminum appears almost exclusively as an alloy with an amount of 10- to 20% silicon and other manufacturer specific components, which among other things, distinctly improves the strength and hardness of the material. Cylinder-blocks are produced in a low pressure process (at 0,8 bar, from the bottom upwards).
Good running characteristics, when paired with aluminum pistons are obtained, when they glide on the silicon crystals. These can be chemically exposed, or prefabricated as a special silicon containing alloy, then recast with the otherwise normal mixture. Before being further processed, the components are X-rayed to ensure a continuous quality standard. The last stages of the process, are the deburring, turning and the milling. Particularly thin iron- or ceramic layers can also be applied through laser- or spraying technology.
There are scientists, Who compare the release of aluminium with the opening of Pandora's box. Any number of things that are needed for our day-to-day life, contain aluminium compounds. Even when being innoculated against illness, is one given a dose. It is also suspected, that aluminium can trigger allergies. Normally, after a while, the aluminium is flushed from the body again. Apparenty however, there are some people whose bodies store the element. The aluminium or it's compounds then, after perhaps a long journey through the body, end up in the brain.
It's not that aluminum causes anything like Alzheimers disease, indeed, there are cases where just that has occurred. Cases are known, where aluminum has got into the drinking water. It is, in fact used, in small amounts in the drinking water, to compound with other elements, which can then be more easily removed. Science tells us, that no living organism voluntarily uses aluminum, and that it has no biological use, in contrast to the enormous technical value.
The manufacturing of aluminum is more of a problem. Recycling requires not only half the energy, one also does not have to deal with the very problematic red-sludge. This is done nowadays, in (developing) countries where the Bauxite is mined. Unfortunately, there are very large deposits in the tropical rain-forest regions.
The bursting of a dam in an aluminum smelting works near to Kolontįr (Hungary), impresively brought to light the terrible results of caustic red-sludge burns. Contact with any part of the skin, led to it's dying off. Apparently, 10 people were suffocated by the sludge-avalanche and a further 150 were injured. The remains of Kolontįr, were flattened. In the meantime, the company is back at work. You can read more about it here.
Under the most favourable conditions, red-sludge makes up about half the Bauxite, more if the quality is poor. It is then dumped and in fact, is a time bomb that's already ticking away. In the manufacture of aluminum-hydroxide, the values are five times as high. Nonetheless, probably because of the environmental dangers, the first processing stages are carried out in the country where it's mined. The high amount of energy required, when converting aluminum-hydroxide into pure aluminum, can be seen by the further five times higher energy requirements. 09/13