How Does The Sponge Iron In The Electric Arc Furnace Work?

Figure 1 shows the layout sketch of the continuous feeding system in a workshop with two electric furnaces. The incoming sponge iron is transported to the storage bin (2) by the belt conveyor (1). The weighing device (3) places the sponge iron on the conveyor belt as needed, and then conveys it to the electric furnace (4). A feed tube enters the furnace through the top of the furnace and guides the charge into the area between the electrodes. Due to the agitation of the molten pool, the sponge iron immediately comes into contact with the liquid metal and the slag. A large amount of foam slag on the liquid metal plays a good role in protecting the refractory material of the furnace lining from direct electric arc radiation. Before tapping, the slag can be discharged by tilting the electric furnace backward.

（Schematic diagram of the charging system for continuous DRI charging into the electric arc furnace）

　　 For many cast steel and iron castings, it is very important that the residual alloy content is very low because it will have an adverse effect on the mechanical properties of the product. To achieve this goal, the charge must be removed through the following two aspects:

One is to use mechanical separation to remove unqualified scrap steel, which is difficult and expensive; the other is to add sponge iron to the scrap steel charge to reduce the content of residual alloy through dilution. Due to the stable chemical composition and high purity of sponge iron, diluting the residual alloy content in the charge plays an important role.

　　 Figure 2 shows the effect of increasing the proportion of sponge iron on Cu, Sn, Cr, and Ni in a typical charge. This method of adding sponge iron can replace some high-grade steel scraps with relatively low-priced low-grade steel scraps.

（The effect of increasing the percentage of sponge iron in the charge on the content of residual elements in molten steel.）

　　The nitrogen content in molten steel produced from all-scrap charge tends to be relatively high. As a result, brittleness increases, toughness decreases, aging increases, and castings have too many pinholes. As shown in Figure 3, increasing the percentage of sponge iron in the electric arc furnace charge can often cause boiling, which is sufficient to reduce the nitrogen content of the melt.

（The influence of the percentage of sponge iron in the charge on the nitrogen content of the metal）

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