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Products and solutions, 2000-03-20, 01:00 AM

Steel segment: Krupp VDM GmbH invests in innovative remelting technology

Krupp VDM GmbH is investing some 15 million marks in innovative processes for the production of high-purity metals. At the Unna, Germany plant - center of the company's melting and casting activities - an ESR furnace (electro-slag remelting) and a VAR furnace (vacuum-arc remelting) are being installed. Each of these furnaces has an annual capacity of around 4,000 tonnes. Construction work is already in full progress: the ESR plant is planned to commence operation in June of this year, with start-up for the VAR furnace scheduled for the first quarter of 2001. Krupp VDM GmbH is targeting new markets with these investments, in particular the aerospace and electronics sectors.

Alloys melted in the electric furnace are remelted in the two new furnaces to remove non-metallic inclusions such as residues from deoxidization processes and create an extremely homogeneous metallic matrix. In sectors such as the aircraft industry, for example, such high metal purity is essential to eliminate quality fluctuations in safety-relevant components. The new Krupp VDM furnaces can also be used to produce materials with particularly high magnetic characteristics, e.g. for the electronics industry.

In the ESR process, this purity is achieved by passing the alloy through a special cleansing slag. First of all an electrode is cast from the alloy to be remelted and submerged in the slag. Electrical current is passed through the electrode, causing the slag to heat up and melting the electrode under controlled conditions. The purified metal solidifies into an ingot beneath the slag. This process is carried out in a closed atmosphere using argon as the protective gas.

The first step in the VAR process also involves casting an electrode which is then melted by an electric arc in a vacuum. Some of the non-metallic inclusions are destroyed by the high melting temperatures, the rest are deposited on the surfaces of the ingots and ground off in subsequent treatment steps. The new VAR furnace at Krupp VDM will be the biggest of its kind in the world.

The first step in the VAR process also involves casting an electrode which is then melted by an electric arc in a vacuum. Some of the non-metallic inclusions are destroyed by the high melting temperatures, the rest are deposited on the surfaces of the ingots and ground off in subsequent treatment steps. The new VAR furnace at Krupp VDM will be the biggest of its kind in the world.

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