Voestalpine : What is special steel

voestalpine BÖHLER Edelstahl has begun operating the new special steel plant in Kapfenberg. With state-of-the-art melting facilities and extensive metallurgical expertise, the plant will produce around 250 exceptional steel grades. So what makes this steel special?

It is highly likely you have already used special steel today, although you may not have realized it. Indirectly, using your toothbrush which was manufactured using injection molding in a mold made from special steel-plastic mold steel to be precise. Or you selected an attractive-looking package of cream cheese-the packaging was produced in molds made from special steel. Special steel was also involved in the manufacture of your smartphone, as well as the paper knives which cut your daily newspaper into a manageable size.

Special steel often plays a role in the background. But what makes it special?

As so often in life, when it comes to special steel it is the intrinsic values that count. Including those which are absent. What makes these steel grades special is their purity. That means an exceptionally low sulfur and phosphorus content: no more than 0.025%, or 25 parts in a thousand. That is comparable to two tiny pinches of salt in a liter of water, which is why extreme precision is required to achieve the chemical compositions of special steel grades. It is the same level of precision as demanded in their subsequent processing.

The exceptional properties of special steel, such as resistance to corrosion and heat, strength, wear resistance, workability, and polishability, all depend on its composition and the care with which it is produced. This is where special additives, so-called alloys, come into play. The manufacturers' "recipe books" include a variety of ingredients:

• Chrome: for resistance to corrosion and heat
• Tungsten and cobalt: increase wear resistance which is important for milling tools and drills
• Chrome and nickel: increase weld strength
• Molybdenum: increases heat resistance and makes steel rust-proof
• Titanium, niobium: creates resistance to intergranular corrosion
• Manganese: increases tensile strength

Perhaps you are aware of cutlery and kitchen utensils made from 18/10 stainless steel. This may sound like a precious material, but you won't find it in our portfolio. We are specialized in producing far higher quality materials for extremely demanding use in almost all industrial applications.

We use state-of-the-art technology at the voestalpine BÖHLER Edelstahl special steel plant in Kapfenberg to produce this material with the highest levels of metallurgical purity. The process is supported by digital planning and control programs.

Around 8,000 measurements are permanently recorded and used to drive the corresponding processes. Even the selection of input materials is subject to precise analysis to ensure the purity of the special steel. This is because the composition of the scrap used in the melt depends on the nature of its previous use, and so must be considered during the production process. Production starts in the electric arc furnace (EAF) which melts the scrap, removing a part of the undesired attendant materials from the steel together with the slag. The following processing steps involve an extensive series of additions and removals before the final product is special steel. Any carbon and other elements which could negatively impact the steel properties, including sulfur, phosphorus, nitrogen, and hydrogen, must be removed. This is achieved using equipment such as a vacuum converter which combines decarburization with vacuum degassing. This "draws out" the gases released in the melt.

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In turn, alloys are added to improve the steel, giving it its desired properties: chrome, nickel, vanadium, molybdenum, and many others. In secondary metallurgy, the chemical composition of the special steel is finely adjusted to meet specific standards or customer requirements, while the vacuum degasser removes any remaining nitrogen and hydrogen.

At voestalpine BÖHLER Edelstahl our production processes are extremely precise, from start to finish. Once the special steel has achieved the required composition, it is brought to an optimal temperature for pouring and then cast into molds. Once cool, the blocks will be prepared for further processing in the rolling mill or forge. Key customers are other voestalpine companies, including local subsidiaries voestalpine Böhler Aerospace and voestalpine Böhler Bleche. They work the special steel into products such as turbine blades, chassis components, or extremely high load-bearing sheets for use in aircraft construction.