IF steel

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An IF steel has only a very low content of interstitially embedded alloying elements such as carbon or nitrogen . This prevents the formation of so-called Cottrell clouds , which hinder the dislocation movement and thus the plastic deformation . IF steels are very soft and have very good forming properties. They are mainly used for complex deep-drawn parts in the automotive industry. The abbreviation IF stands for Interstitial Free ( i nterstitiell f rei).

The IF steels are divided into the ULC steel category. The abbreviation ULC denotes the typically low carbon content of such steels (ULC = Ultra Low Carbon):

The low content of carbon (C) and nitrogen (N) is achieved by a decarburization treatment of the steel melt in a vacuum before casting. The remaining C and N atoms are bound by alloying with titanium or niobium in carbides and nitrides and precipitate at the latest during the slow cooling after the last hot forming .

There are also higher-strength IF steels. The desired and increased strength is achieved through solid solution strengthening and the deliberate addition of phosphorus, silicon and manganese. Phosphorus plays a key role in solid solution strengthening; as little as 0.01 mass percent can lead to an increase in the yield strength of approx. 8 MPa.

The higher-strength IF steels are z. B. called HX180YD, HX220YD, HX260YD. The numerical value indicates the yield point in N / mm². These steels are defined in EN 10346 Continuously hot-dip coated steel flat products - Technical delivery conditions .

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