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Thyssenkrupp Umformtechnik has received an order from a German automotive manufacturer to produce B-pillars for more than 100,000 cars annually by tailored tempering.

Thyssenkrupp’s tailored tempering process was developed on the basis of hot-forming technology.

The safety-relevant components are to be used in compact cars.

The use of hot forming in car manufacturing is currently on the increase, according to the company.

The process permits weight savings of up to 30 per cent in car components.

Hot forming uses special manganese-boron steels.

The sheet material is heated to 880-950C and is then formed into a component and cooled rapidly in the die.

This produces components with strengths of up to 1,500MPa.

These strengths are higher than those produced even with the strongest steels used for cold stamping.

The components are lighter because the high strength of the material means that they can be designed with thinner walls and without additional reinforcements.

While conventional hot forming only enables the production of components with the same strength throughout, tailored tempering produces parts that are not only very strong but also able to yield in specific areas.

These properties are needed in crash-relevant components, for instance, which have to protect vehicle occupants and absorb impact energy in a controlled way.

The B-pillar, for example, is a component with a vertical structural member extending from the door sill to the roof frame.

It has to be able to yield in the lower third to absorb crash energy.

The upper part has to stabilise the passenger cell and protect the occupants in a side impact.

With the process patented by Thyssenkrupp Steel Europe, parts with differing local strength and elongation properties can be produced in a single step from a homogeneous steel sheet.

This is made possible by a newly developed die with flexible heating.

The targeted heating of specific zones of the die gives the finished component elongation properties exactly where they are needed.

As the heated blank cools more slowly in these zones, the steel hardens less.

The technology is said to be cost efficient because it eliminates several process steps.

Depending on sheet thickness, the area of transition between hard and soft zones is extremely narrow – 15-60mm – and this level of accuracy is reproducible.

This means that the properties at every point of the finished component can be accurately predicted, according to the company.

Thyssenkrupp Steel

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