Operating Procedures for 100-ton DC Electric Arc Furnace Smelting Technology (5)

Operating Procedures for 100-ton DC Electric Arc Furnace Smelting Technology (5)

VI. Heating and Decarbonization Operations

1. Operate the C-O gun to maximize its firing range, with the gun position at its lowest, and continuously move it left and right.

2. Intermittently or continuously inject carbon powder at a rate of 10-60kg/min (with a preference for the lower limit due to high carbon content). Adjust the furnace wall gun according to the oxygen flow rate for oxygen production, with an oxygen pressure ranging from 0.9MPa to 1.5MPa. Simultaneously, tilt the furnace body to perform slagging operations based on the dephosphorization situation inside the furnace. The power supply should be at full capacity, using gears 8-9 for power supply.

3. When sampling and temperature measurement, it is necessary to withdraw the C-O lance (or raise the C-O lance to one side) for temperature measurement and sampling. It is strictly prohibited to measure temperature or take samples at the oxygen blowing part of the C-O lance.

4. Adjust the number of furnace wall guns in a timely manner based on the composition of the molten steel, intermittently spray carbon powder, and determine the power supply according to the temperature of the steel water in the furnace. If the temperature is low, continue to supply power at high power. If the temperature is appropriate or slightly high, reduce the power or shut off the power.

5. If the phosphorus content in the steel water is high, appropriate slag materials (CaO) should be added, and an appropriate amount of CaF2 should be added to adjust the slag fluidity and create foam slag.

6. Once the carbon, phosphorus, and temperature in the steel meet the required standards, observe the situation inside the furnace. It is strictly prohibited to discharge the steel with materials attached.

VII. Stone Ash Addition System

In principle, the addition of slag during DC electric arc furnace smelting should be carried out according to the following method, based on the actual smelting process and steel requirements

The requirements for phosphorus content can be adjusted appropriately. The addition of lime should be carried out as early as possible and in batches. When electricity is required, it must be applied for at least 3000 kWh after the scrap steel is added before adding lime to prevent non-conductivity and electrode breakage.

Ⅷ. EBT Tapping and Ladle Alloying 

1. Tapping Preparation

(1) Ladle Preparation

 
a. Due to the high gas content in a new ladle during its first use, it is not suitable for smelting steel grades that are highly sensitive to gas. It can be used to smelt plain carbon steel or undergo degassing treatment through VD. 

b. The interior of the ladle should be clean and free of residue.

c. Before using the ladle, inspect the lining bricks, bottom bricks, permeable bricks, seat bricks, ladle shell, and shaft to ensure they are normal. If any abnormalities are found, the ladle should be stopped immediately for overhaul, excavation, or repair. The mechanism for sliding the water port must be sturdy, flexible, and well-matched. When installing the upper sliding plate of the sliding water port, refractory mud must be applied to ensure levelness. When installing the lower sliding plate and the lower water port, it should be ensured that it can be opened and closed tightly without leaking steel.

e. The ladle baking system.
f. Place the baked ladle onto the ladle car and drive it to the sand filling position. Add filler, connect the argon gas pipe, drive it to the electric furnace EBT position, and position it.

(2) Preparation of Deoxidizer, Alloy, and Slag Materials in the Ladle

a. Weigh the alloy according to the requirements of the process card for each steel type and bake it in an oven for more than 30 minutes.
b. Carburizer: The addition amount is adjusted according to the carbon content requirements of different steel types specified in the process card. The yield of carburizer is calculated as 100%. c. Slagging materials: Use limestone, premelted slag, etc., and the amount used is added according to the production process card for each steel type.

d. The sequence for adding alloy materials at the EBT position is as follows: deoxidizer, carburizer, alloy material, slagging material, etc. The deoxidizer is added in the order of strength from high to low, and its addition amount is shown on the smelting process card for different steel grades.

2. Tapping Conditions

(1) Chemical composition: Carbon, phosphorus (taking into account alloy carburization and phosphorization) meeting the lower limit requirements specified in the steel smelting process card for the respective steel grade. Other residual elements comply with the internal control requirements of the steel grade.

(2) Tapping temperature: 1610℃～1700℃. For steel grades with a higher alloy content, the tapping temperature can be appropriately increased by about 20℃.

3. Tapping Process and Ladle Alloying

(1) Automatic Tilting Furnace Tapping

Place the function selection switch of the shaking furnace at the automatic tapping position, push the operating handle, tilt the furnace towards the tapping side by 3°, open the EBT tapping port support plate, and the molten steel and filler will flow out automatically. Tilt the furnace by about 10°, and when the weight of the ladle reaches the set value, the furnace will automatically and quickly tilt back.

(2) Manual Tilting Furnace Tapping

Place the function selection switch of the shaking furnace in the manual tapping position, push the operating handle, tilt the furnace body 10° towards the tapping side, and when the ladle weight scale displays 100t, pull back the handle to quickly reverse the tilt of the furnace body.

(3) Before Tapping, the Ladle should be Filled with Argon Gas First. 

When nearly 20 tons of steel water flows out, the ladle begins to undergo alloying and slagging. The order of adding additives to the ladle is deoxidizer, carburizer, alloying material, and slagging material. The addition process should be completed before the tapping volume reaches 80 tons.

4. If the molten steel cannot flow out automatically from the EBT taphole due to sintering of the filler, oxygen can be used to burn the sinter at the lower part of the taphole.

5. During the operation of retaining steel and slag, when the electronic scale indicates a difference of 5 tons in the required amount of steel for the steel water volume measurement, the furnace should be quickly returned to the zero position to prevent oxidized slag from entering the ladle. During the process of retaining steel and slag, the furnace should be tilted to a maximum of 10° when tapping.

6. When the expected tapping quantity is not reached, slag will flow into the ladle, and the furnace should be quickly tilted back to 0°.

7. When all steel slag needs to be discharged, the furnace can be tilted to 11°. If slag is found flowing out after the molten steel is basically discharged, quickly return the tilt to 0°, open the ladle car, and send it into the slag pot, after positioning, remove the clean steel slag.