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The furnace chamber is full of charging
14/01/2020 09:31
furnaceelectrode

Melting period

In the EAF steelmaking process, the melting period is from the start of energization to the melting of all the charge. The melting period accounts for about half of the entire smelting time, and the power consumption accounts for about 2/3 of the total power consumption.


The task of the melting period is to ensure the furnace body life, quickly melt the furnace charge with the least power consumption, and make the slag during the firing period, so as to stabilize the arc, prevent gas absorption and dephosphorization in advance.


(1) Arc starting stage. The furnace chamber is full of charging materials when the arc is turned on. The distance between the arc and the furnace roof is very close. If the input power is too high, the furnace roof will be easily burned out. Therefore, the intermediate voltage and the rated power of the input transformer are generally selected at about 2/3.


(2) through-hole stage. At this stage, the arc is completely surrounded by the charge, and almost all of the heat is absorbed by the charge, which will not burn the lining. Therefore, the maximum power is used. Generally, the penetration time is about 20 minutes, which accounts for about 1/4 of the total melting time.


(3) Rising stage of graphite electrode. After the graphite electrode "goes through the well", the bottom of the furnace has formed a molten pool. The lime and some elements of the bottom of the furnace have been oxidized, so that a layer of molten slag is formed on the molten steel surface. As the liquid level rises, the graphite electrode rises gradually. At this stage, the maximum power is still used to transport electrical energy, which takes about 1/2 of the total melting time.


(4) Melt the last class. After the charge is melted more than 3/4, the arc can no longer be shielded by the charge, and the high temperature area under the three graphite electrodes has been connected into one piece. At this time, if the maximum power is used for a long time, the arc will strongly damage the furnace cover and furnace wall.


The main task of the melting period is to melt the charge, but during the melting period, it is not only to make the slag, but also an important operation content of the melting period. It is enough, but considering the requirements of dephosphorization, the molten slag must have certain oxidation, alkalinity and slag amount.


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