Frequently asked questions \

The slag adhered to the silicon lining carries an inefficient running of the furnace. It can be low or high melting point.

Low melting point. When the furnace works at low temperatures silicon oxide is formed and it sticks to the walls of the lining as:

Si metal + O2 -> SiO2 slag

High melting point. Slag difficult to eliminate are formed because these have higher melting point than the own lining:

2 FeO oxidized load + Si metal -> 2 Fe + Si O2 slag

Al metal-> Al2O3 + SiO2 lining -> Al2O3.SiO2 mullitic slag

What can happen?

In any of two cases the furnace loses capacity, increases the risk of cracks forming, presents an irregular melting with distinct areas of magnetic behaviour, in short the life of the furnace decreases.

What to do?

It is indispensable to analyse the reason of this regrowth.

With low point of melting slag, raise the metal level and proceed to raise the temperature up to eliminate it.

With high point of melting slag, it is indispensable to analyse the load and used additives. Often high concentrations of Si appear in FeSi causing of this problem.

When melting with the foot of bath the most frequent wear takes place in the bottom part of the furnace. This type of wear it is known as elephant leg. By adding a new load for melting and putting power, a part of this one warms the metal of the bottom doing that this raises its temperature favouring the natural chemical wear of the silicon lining.

What can happen?

Refractory wall gets lost and it must be controlled with regular inspections.

What to do?

If it is possible, avoid working with foot of bath.

The carbon reduction of the silica is a natural reaction accentuated with temperature.

SiO2 lining + 2 C metal -> Si metal + 2CO gas

It is impossible to avoid this reaction and the silicon lining of the induction furnace will be getting worn out naturally.

Yes. The electromagnetic agitation provokes the movement of the metal inside the crucible. The speed thereof is responsible for the erosion on the wall of the lining.

• To verify the correct melting of the metallic load realized in the sintered one.
• Indispensable to have maintained for 1 hour, 50 ºC above the nominal temperature of strain.
• Check that the vent-wall is in good condition and there is no crack formation. If any, apply a plastic mass in the zone as INSEPLAST-70PF.
• To verify that quartzite expansion has been corrected
• Do not recarburate with low feet of baths in the nascent linings.
• In the first strain and successive strains, empty the furnace and verify the superficial aspect of the lining. It must be homogeneous and exempt from cracks.
• To assure that in the deslagging practice, the permanency time of the slag coagulant is the strictly necessary.

• Do not raise the temperature beyond what is strictly necessary.
• To control the melting process.
• Keep the metal molten for the shortest possible time.
• Maintain the shortest possible time the furnace in a sloping position or spillage with molten metal.
• Perform the necessary strain and return the furnace to its work position.
• If it is possible, empty the furnace completely, without leaving feet of baths.
• Not desulfurize in the furnace with a silicon lining.
• Minor degree of sintering.
• Impacts of the metallic load.
• Regrowth of slag
• Avoid loading dirty and rusty scrap.
• To verify that the returns are exempt from moulding sand.
• To make sure that no scraps contain aluminium.
• To avoid the additions of ferrosilicon with high aluminium content.
• Abrade the furnace after every load.
• Not work with full power with low levels of bath.
• Assure that the whole load penetrates in the broth before covering the furnace.
• To verify that there are no anomalous vertical expansions in the lining.