During metallurgical production and treatment processes, non-ferrous melt residues occur (figure 1). This slag usually consists of alkaline and acidic oxides.

A typical slag analysis of acidic cupola furnaceslag flow may have the following componsition:

45-55 % SiO2
25-35 % CaO
8-15 % Al2O3
1-3 % MgO
1-4 % MnO
1-3 % FeO

In long-term furnaces without feed, approximately 40-80 kg/t liquid iron slag. Most slags are insoluble in water. Therefore, they can be used by the cement industry, for road construction and also as abrasive to clean components from corrosion.

In comparison to cupola furnaces, the slag rate in induction furnaces is relatively low. As it has no importance for the metallurgical process, it should be kept as low as possible. On average, it lies at 20 kg/t liquid iron and even below 10 kg/t liquid iron for blasted charge material.

Approximate composition of slag in induction crucible furnaces:

40-70 % SiO2
0-3 % CaO
2-12 % Al2O3
0-3 % MgO
2-10 % MnO
10-30 % FeO

Additional references:

Slag inclusions
Neutral slag

  • Fig. 1: Iron slag (according to Michael Kreuter and Max Linn, early iron smelting in the Saarkohlenwald region)