Salzgitter Flachstahl has been operating a twin RH degassing facility with two treatment lines since April 2017.
The vacuum treatment in an RH system (Ruhrstahl-Hereaus) is used to produce steels that fulfill the strictest quality requirements. A portion of the liquid steel from the ladle is suctioned under vacuum into a container lined with fireproof materials. This takes place with the help of two immersion snorkels located on the container's underside. Injecting argon into one immersed snorkel causes the liquid steel to rise into the vacuum container where the melt is precisely decarburized before it flows through the other immersed snorkel and back into the steel casting ladle. Setting up very low carbon and silicon levels also allows a significant reduction in the portions of hydrogen and nitrogen.
This new systems technology allows Salzgitter Flachstahl to manufacture very soft deep-drawing steels such as DX57 (hot dipped zinc coated) and DC07 (cold-rolled sheet or zinc-anodized) with the lowest carbon content of 0.002 mass percent. These steels are used for deep drawn parts with complicated shapes, such as inside door panels.
It is also possible to manufacture bake hardening steels (e.g., HC180BD or HC220BD) with improved forming characteristics (r values >1.5) which are used, for example, in automotive body shell elements such as roofs, hoods, and doors.
The dissolved carbon atoms selectively adjusted into the bake-hardening steels diffuse onto the dislocations during the paint baking process. This ultimately leads to the required increase in the component's yield strength. The precise adjustment of the free carbon content that the RH facility allows is required for a defined bake-hardening effect.
This investment puts Salzgitter Flachstahl in a position to continue the rigorous expansion of the target segments in the automotive sector.
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