Specialty Steel Plant
The Breitenfeld specialty steel plant is equipped with both an electro slag re-melting (ESR) furnace with a movable inert-gas crucible as well as a modern ESR furnace with a stationary inert-gas crucible. The first furnace has the capacity to produce ingots with a maximum diameter of 1200 mm and length of 4 meters while the second furnace can produce ingots with a maximum diameter of 600 mm and a maximum length of 2.7 meters.
ESR-Technology (Electro Slag Re-melting)
In the process of electro slag re-melting, consumable electrodes are lowered into a resistance-heated active slag bath, which is situated in a water-cooled ingot mould. The superheated slag (1700o C to 2000o C) slowly melts the electrode tip into the bath. Non-metallic impurities are removed via physical-chemical extraction as the drops sink through the slag until they are collected in the refined molten steel bath below. Once there, densification and directional solidification occurs from the bottom to the top of the crucible. The quality of the finished ESR ingot depends upon the electrodes’ characteristics and the accuracy of the process control and especially upon the slag utilized in the process.
The ESR-products are characterized by high purity and a good, low segregation block structure. The ingots can be re-shaped “as cast”.
The specialty steel plant is also equipped with the most modern vacuum arc furnace (VAR), which has the capacity to produce ingots with a maximum diameter of 1000 mm and a maximum length of 3 meters for smelting of high-purity materials.
In the vacuum arc furnace, material is melted under vacuum ( 10-4 mbar) with the energy for melting being produced by a high-current, direct voltage arc ignited between the consumable electrode (cathode) and the molten bath (anode). Small metal drops dissolve from the electrode tip and are captured in the liquid metal pool within a water-cooled ingot mould. The metallurgical improvements result from melting under vacuum as well as the solidification conditions. The main improvements achieved are in purity level, the content of trace elements and dissolved gases, and the block structure.
The surface of VAR-ingots is machined before re-forming.