Fluoro iron - Flußeisen
The term flußeisen (today: flussseisen )  was coined in the 19th century, around the wrought iron ( welding iron ) , which was still commonly used at that time and produced in the puddling process , from the new, in the Bessemer or Thomas process or in a Siemens-Martin - Distinguish furnace produced liquid iron.
This fluvial iron was later called steel in the early 20th century . Steel used to describe only a small group of special products with a carbon content of 0.4% to 1.2%, which could be forged, welded and, above all, hardened. All other products made from refined pig iron were referred to as malleable iron, wrought iron, or fresh iron.
In the puddle created by refining one of slag particles interspersed carbon doughy Luppe . In several work steps it was cut into strips and in the forge by multiple rolling together of individual strips ( welding ) to a usable product.
In the new process, the pig iron melted in the blast furnace was used in the converters or in the Siemens-Martin furnace to produce liquid and homogeneous iron with a likewise low carbon content, which was called fluoro iron to distinguish it and which is now called steel .
Fluorescent iron has a grainy break in contrast to welding iron, which has a sinewy break.
When the puddling process was finally superseded by the new process at the beginning of the 20th century and only fluent iron was produced, the distinction became superfluous. A little later, only the terms steel on the one hand and cast iron for carbon-rich, non-plastically deformable iron on the other hand were used.
- Bernhard Osann : Textbook of the iron and steel foundry , 5th edition, Verlag von Wilhelm Engelmann, Leipzig 1922, Chapter I ( online )
- A. Schulenburg (Ed.) Giesserei-Lexikon , Verlag Schiele und Schön, Berlin 1958, p. 180