LF furnace refining process

Source: | Author:ChangXing | Published time: 1735 days ago | 961 Views | Share:

1. Slag removing
The primary furnace slag has a great influence on the refining process. One is the erosion of the ladle lining, and the other is the high FeO, SiO2, P2O5 and other components in the slag will seriously affect the refining process. For this reason, it is necessary to remove the slag from the primary smelting furnace.

2. Heating
The reducing atmosphere and high alkalinity slag were produced by arc heating and argon stirring. When the furnace cover is lowered at the ladle mouth, the electrode is lowered and inserted into the slag for submerged arc heating. The temperature drop of molten steel entering the refining furnace from the primary refining furnace is supplemented, heat loss of molten steel in the ladle furnace caused by the addition of slag and alloy during the refining process, heat taken away by bottom blowing argon and vacuum pumping, etc., ensures that the molten steel can be refined smoothly and finally meet the temperature required for steel production.

3. Argon gas mixing
It has great influence on desulphurization, dehydrogenation, denitrification and inclusion floating. In fact, argon blowing begins when the ladle furnace receives steel. The flow rate of bottom argon blowing during heating is generally 40% ~ 45% of that during vacuum operation.

4. Slag forming
Slagging is an important step in refining process. Lime and fluorite were added to the liquid steel in two times according to different proportions (e.g. 5:1 or 4:1). The amount of addition was 1% ~ 2% of the liquid steel. Then, ferrosilicon powder, calcium silicon powder and aluminum powder or carbon powder are mixed directly into the molten steel in a certain proportion or are added into the molten steel by injection.

5. Liquid steel composition adjustment
When the heating temperature reaches ≥1600℃, the alloy can be added to the liquid steel to adjust the composition. Ladle furnace refining allowed a wide range of alloy composition, easy to uniform and high yield. All alloys that are easily oxidized during alloying in the primary furnace can be moved to the ladle furnace during the refining process.

6. Thermal insulation
Complete insulation and narrow range alloy fine tuning. At this time it is still necessary to bottom blow the argon at an appropriate flow rate to uniform temperature and composition. Finally, temperature measurement (pouring method is different, steel temperature is different), sampling for full analysis (including steel, slag sample), etc., all meet the requirements of steel, steel can be produced.

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