Secondary metallurgy

SMS group's atmospheric ladle treatment processes are used to set the optimum temperature and chemical analysis of the steel as precisely as possible prior to vacuum treatment or casting. In order to increase the steel temperature, heating can be achieved either by an electric arc with electrical energy or by an oxidation reaction with chemical energy. Slag formers and alloying elements can be added under almost inert conditions if required. The most important units in atmospheric processes are ladle furnaces, chemical heating stations and ladle treatment stations.

In the last 20 years two processes have established themselves at the top of secondary metallurgical vacuum processes: the RH process with the variants RH-TOP (Temperature-Oxygen-Powder) and RH-OB (Oxygen Blowing) as well as the VD process (Vacuum Degassing) with the variants VD-OB and VOD (Vacuum Degassing + Oxygen Blowing or Vacuum Oxygen Decarburization). In VD-OB and VOD processes, oxygen blowing lances are additionally used either to optimize the C-O ratio during decarburization or to blow carbon out of the steel as CO with the aid of oxygen.

In the RH process a stream of liquid steel is continuously circulated under vacuum between vacuum vessel and ladle and unwanted elements are removed as gases.

In the VD process, the entire ladle is placed under vacuum in a tank that is vacuum-tightly closed, and steel circulation within the ladle is enabled by bottom rinsing via plugs in the ladle bottom.

The RH and RH-TOP plants from SMS group are typically installed in steel making plants with batch sizes from 80 to 400 tons. VD and VD-OB plants typically cover batch sizes from 20 to 350 tons, VOD plants from 10 to 180 tons. RH plants and VD plants can be used in both electric and converter steelworks. VOD plants are required in stainless steel production to achieve particularly low carbon contents in an economical way.