What is the strongest aluminum

Aluminum has the door to steel

Aluminum alloys are increasingly competing with steel materials in the automotive industry. The largest manufacturer in Germany, Hydro, wants to significantly increase the share of sales in the automotive industry. A visit to the development department in Bonn, where the alloys of tomorrow are made.

When the materials researchers at the hydro company want to show a visitor what they can do, they lead him to the door. It hangs on the wall in an inconspicuous hallway at the Bonn location. Producing the inner part of a car door in one piece, the researchers say, is the supreme discipline for a material developer. The challenge: Particularly high degrees of deformation are necessary.

"If the aluminum material is easy to form," says Henk-Jan Brinkman, program manager for the automotive band at Hydro-Development in Bonn, "the car manufacturer can either keep his design or change it freely." And he immediately declares war on the material competition. "Our goal is to substitute non-aluminum materials used today - steel for example."

The automotive sector is the fastest growing market for the Norwegian aluminum manufacturer Hydro, which employs around 6,000 people in Germany. It currently accounts for around 20% of Hydro's sales in Germany - according to the company, that will be around € 400 million in the current financial year. The proportion is expected to rise to a quarter within a short time.

For the company, this means above all that more capacity is needed. This year the construction of a second line at the Grevenbroich location was announced. In the future, a total of 200,000 t of sheet metal is to be produced annually for the automotive industry, four times as much as today. Hydro invested € 130 million for this.

THE STEEL IS LOSING A UNIQUE PRACTICE

Just five years ago everything looked very bleak. “During the economic crisis in 2009, the aluminum price went down completely,” says Pascal Wagner, head of the Lithography, Automotive and Heat Exchangers business units. During this time, the company "literally burned cash in the electrolysis". It was not certain whether the group would be able to continue operating its raw aluminum plant in Neuss.

Hydro is still not competitive in raw aluminum. When it comes to the finished sheet, you are all the more self-confident. “All materials that contribute to lightweight construction will grow,” says Wagner, “but aluminum grows the most”.

In Bonn, the researchers are constantly working on new aluminum alloys. One of the beacons of hope: the HA 6016-X. "This enables us to achieve degrees of deformation that were previously not possible with aluminum materials - this is particularly important for the so-called side parts," emphasizes Wagner. "The steel thus loses a unique selling point."

High degrees of deformation are the prerequisite for a material manufacturer to be able to produce the large, flat components that are also particularly interesting from an economic point of view: for example the vehicle side wall. Hydro and its competitors are hoping for a kind of industrial domino effect. "If the side wall is made of aluminum, this makes it possible to manufacture the roof from aluminum without additional effort," says Jan-Henk Brinkman. Because the same materials expand in the same way when they are heated - for example when baking paint.

But the material properties are only one aspect in alloy development. A second: processing on the customer's existing production facilities. “The alloys that we develop have to match the production processes of the automaker,” says developer Brinkman.

One example is the age-hardenable alloys: In this case, the material is delivered with a low strength. “This has the advantage that it can still be formed very easily,” explains Brinkman.

During the enamelling process, the alloy loses its formability and, according to Hydro, doubles its strength. "The aim is to get very fine excretions," says Pascal Wagner. “This can only be achieved by quenching after annealing, when the alloying elements are all in solution. The elements then have no time to diffuse. ”The strength-increasing, finely distributed precipitates only arise during the varnish baking at approx. 200 ° C.