Electric arc furnace's slag-free tapping technology

Siphon tapping method of electric arc steel furnace

In the late 1970s, Krupp Stahl AG developed a simple steel slag separation technology, that is, according to the siphon principle, the original horizontal tapping hole of the electric arc furnace was changed to an inclined type. The inner end is buried in the molten steel to a certain depth, and the outer end of the furnace is higher than the molten steel level. The tapping opening is at an inclination angle of 18°～30° with the horizontal plane, and the furnace body is dumped at about 20°～30° during tapping. The process adopts steel and slag retention operation, and the steel retention is about 10%, and the slag retention effect is generally reachable more than 90 percent. In the 1980s, the siphon tapping technology was widely used in Europe.

Center bottom tapping method of electric arc furnace

In order to expand the water cooling area of the furnace wall and increase the life of the furnace body, MANNES-MANN-DEMAG AG and Thyssen Special Steel Company (Thyssen Edelstahlwerke AG) jointly developed the center bottom tapping technology and succeeded. The first center bottom tapping (CBT) electric arc furnace was put into production in 1979. Its tapping port is located in the center of the furnace bottom, the original tapping trough is cancelled, and the tapping port is downward, so that the horizontal parabolic steel flow during tapping is changed to a vertical downward steel flow. This technology is a major improvement of the electric arc furnace tapping method. Although the furnace body does not need to be shaken during tapping, and the water cooling area of the furnace wall is maximized, it is not widely used because of the eddy current generated during tapping and completely slag-free tapping cannot be achieved.

Eccentric bottom tapping method of electric furnace

Mannesmann-Demark and Thyssen cooperated with Danish special steel mills to develop eccentric bottom tapping (EBT) technology on the basis of center bottom tapping. That is, a nose-shaped tapping box is added at the back of the furnace bottom, and the tapping port system is placed in the lower part of the tapping box. The first eccentric bottom tapping electric arc furnace was put into operation in 1983 in a Danish special steel plant. Because the eccentric furnace bottom tapping electric arc furnace has the characteristics of small shaking furnace angle (about 12°), accurate control of steel retention, and the best slag retention effect, it has been widely used immediately. By 1990, there were more than 50 electric furnaces using this technology in the world.

Other slag-free tapping technology of electric arc furnace

1. The side furnace bottom tapping system (SBT) of Whiting Company in the United States is similar to the siphon tapping method, but the tapping port is opened and closed with a plug rod;

2. The horizontal slag-free tapping system (SF-HOT) developed by Empco in Canada is similar to the eccentric bottom tapping system, but the tapping port is arranged horizontally, and the tapping flow is controlled by sliding Control the nozzle;

3. An eccentric furnace bottom tapping system (OBT) developed by Fuch Company in the United States, which is similar to the center bottom tapping method, but the tap hole deviates from the center line of the furnace bottom by a certain distance, and the tap hole layout is equivalent to The tapping box of the EBT electric furnace is in contact with the furnace bottom, but there is no tapping box.

Application effect of tapping spout electric arc furnace

Various slag-free tapping technologies have different application effects in production, but their main effects can be summarized in six aspects:

1. Because the slag stays in the furnace, the recovery rate of alloy elements added to the ladle is high. Mn can reach 95%, Si can reach 90%, and the refractory life of the ladle slag line is increased by 5%; 

2. The refining effect of the refining furnace is strengthened, the composition of the molten steel is uniform and stable, and the content of impurity elements, gases and non-metallic inclusions Greatly reduced; 

3. The tapping is fast and the steel flow is concentrated. When tapping, the steel flow vertically downwards. When the ladle receives molten steel, it can be covered with a ladle cover with holes, so that the heat loss during tapping is reduced, so the tapping temperature is also It can be reduced;

4. The tilting angle of the electric furnace is reduced during tapping, the water cooling area of the furnace wall is increased, and the consumption of refractories is reduced. And the length of the flexible cable can be shortened; 

5.  Due to the operation of retaining steel and slag, the arc is stable during the melting period; and because the molten pool is formed in advance, the smelting time is shortened;

6. Due to the operation of retaining the slag, the consumption of slag is reduced Slag energy consumption.