What are the main tasks and operation points of vacuum induction furnace in refining period?

The main tasks of refining period are deoxidation, denitrification and removal of trace harmful impurity elements, so as to improve the purity of liquid steel and create conditions for alloying period.

There are three operation points in refining period.

Refining vacuum, refining temperature and refining time are three important process parameters in refining period. These three interrelated parameters are related to the important control conditions and operation contents of liquid steel refining effect.

1. The highest vacuum degree in the whole smelting process should be maintained during the refining period.

The vacuum degree in refining period is controlled at 1.0-0.1pa for small furnace and 5-1.0pa for large furnace. For the purpose of denitrification and volatilization, a high vacuum is needed; for the purpose of deoxidation and reduction of oxides, a high vacuum is needed; for the purpose of dehydrogenation and decarbonization, a low vacuum is needed.

2. Keep proper refining temperature

At a certain refining vacuum, increasing the temperature will increase the oxygen supply from crucible to molten steel and increase the oxygen content in steel. However, increasing temperature is beneficial to denitrification, decarbonization and volatilization.

Usually, the refining temperature should match with the vacuum degree, and the appropriate refining temperature should be selected according to the refining purpose. The suitable refining temperature should be about 100 ℃ above the liquid phase point.

3. Keep proper refining time

The refining time is determined according to the refining depth and furnace capacity. The deeper the refining depth, the larger the furnace capacity and the longer the refining time. The dehydrogenation time is the shortest, followed by deoxidation and decarburization, and the denitrification time is long. When the content of carbon and nitrogen reaches a very low level, it needs a longer refining time.

In short, the operation of refining period should be combined with the purpose of refining, and the corresponding process parameters of induction furnace should be flexibly formulated for control.

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