Key points of dephosphorization and desulfurization in the process of medium frequency smelting electric furnace

According to the metallurgical reaction mechanism of dephosphorization, the dephosphorization operation of medium frequency electric furnace equipment should be arranged in the melting period. In the smelting process of medium frequency electric furnace of Xinda Electric Furnace in Weifang, attention should be paid to the four links of liquid steel oxidation, preparation of primary slag, slag raking and secondary slag making.

(1) oxidation of liquid steel

In order to achieve the purpose of dephosphorization as soon as possible, so that the molten steel can effectively participate in the dephosphorization reaction in the whole process of melting, the scale or iron ore can be put into the furnace together with the scrap steel for melting when adding the furnace charge before melting, 8-10kg of scale or iron ore can be prepared for each ton of molten steel, and half of the scale or iron ore required for the total scrap steel can be added in advance. If there is no scale or iron ore, oxygen can be blown at the early stage of melting to oxidize the liquid steel.

(2) preparation of primary slag of medium frequency smelting electric furnace

After the scrap begins to melt, the primary slag can be produced. Weigh about 0.6-0.8% lime and fluorite (the ratio of lime and fluorite is 10:1) of the total charge, melt and add them together with the scrap steel, when the scrap steel reaches 70% of the required total amount, prepare to pick up the slag, so as to make the secondary slag better dephosphorization. Note that the lime used for slagging must be dry and of particle size. It is forbidden to use powdery lime due to moisture absorption, so lime must be used as soon as it is baked. Iron oxide scale and fluorite must be dried for use.

(3) slagging

When the steel is liquefied to 60-70%, stop feeding and reduce the power, maintain the melting state, stir the slag liquid, and pour out the slag.

(4) secondary slagging

After the slag is basically cleaned, scrap steel shall be added again, power shall be increased for melting, and 0.5% of the total slag and the remaining iron oxide scale or iron ore shall be weighed and added into the furnace. After the scrap is completely melted, tilt the furnace to remove the slag, and take samples to test whether P is within the allowable range. Generally speaking, the dephosphorization effect of carbon scrap can reach 50% after the above operations.