A low-energy baking method for immersion tubes used in the RH production of aluminum-killed steel

Abstract

The invention discloses a low-energy consumption baking method for an immersion tube used in RH production of aluminum-killed steel. The baking steps are as follows: after the RH cycle treatment of molten steel is completed, move the gunning trolley to directly below the RH immersion tube, gun the inside and outside of the immersion tube, and wait for the RH treatment of molten steel after the gunning is completed. Before the RH treatment of molten steel, according to the service life of the immersion tube, lift the slag in the ladle to stay below the immersion tube for 1 to 5 minutes, then place the immersion tube above the slag for 0.5 to 3 minutes, and repeat 0 to 3 times, and then perform normal vacuum treatment. It can be seen from the method of the invention that by repairing the immersion tube from the outside to the inside and then baking the immersion tube by using the temperature of the slag, the baking effect of the immersion tube with low energy consumption can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel smelting, and more specifically, it relates to a low - energy - consumption baking method for immersion tubes used in the RH production of aluminum - killed steel. Background Art

[0002] With the progress and development of industry, the quality requirements for steel materials are getting higher and higher, especially the control level of inclusions in steel is becoming more and more strict. During the smelting of many special steel grades, RH vacuum circulation treatment is adopted to ensure the cleanliness of steel. The immersion tube is a device in the steel - making process. It mainly inserts into the molten steel in the ladle, and the molten steel enters and exits the vacuum chamber through the immersion tube channel for the circulation of molten steel. During the production and application of RH, due to the erosion of the immersion tube by molten steel, after the molten steel is processed, the surface of the immersion tube needs to be sprayed with refractory materials containing a certain amount of moisture. At present, during the production operation of many steel mills' RH furnaces, after the spraying of the immersion tube is completed, a baking gun is used to perform combustion baking operation on the vacuum chamber (immersion tube) to ensure that the sprayed immersion tube is dry and free of moisture.

[0003] When using gas combustion baking, oxygen and natural gas (coal gas) are burned in a certain proportion. For example, currently, oxygen and natural gas are burned in a ratio of 2.2:1 to 1.8:1 for baking. The oxygen used is in excess, and there is a certain oxidation atmosphere and oxygen source in the vacuum chamber, which causes secondary oxidation of the molten steel during the treatment process, resulting in a decrease in the aluminum content in the molten steel, causing more aluminum loss and a reduction in the purity of the steel. The existing immersion tube baking method will lead to a decrease in the utilization rate of aluminum, deteriorate the cleanliness of steel, and increase production costs. Therefore, there is an urgent need for a low - energy - consumption baking method for immersion tubes used in the RH production of aluminum - killed steel that can solve the above problems. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a low - energy - consumption baking method for immersion tubes used in the RH production of aluminum - killed steel to solve the problems of low cleanliness and high production costs in the existing immersion tube using gas combustion baking as mentioned in the above background art.

[0005] The purpose of the present invention is to provide a low - energy - consumption baking method for immersion tubes used in the RH production of aluminum - killed steel, and to reduce the aluminum loss of molten steel during the RH treatment process. By quickly spraying and patching using the waste heat of the immersion tube after the RH treatment is completed, and baking the immersion tube again using the temperature of the molten steel before the treatment, effective baking of the immersion tube can be achieved under the condition of no gas baking. The baking effect of the RH vacuum chamber can be controlled at the following level: the consumption of the baking medium is reduced to 0, and under the treatment process conditions of maintaining a vacuum degree < 100 Pa for 20 min, the aluminum loss in the steel ≤ 0.006%.

[0006] To achieve the above object, the present invention provides the following technical solutions: A low-energy baking method for the immersion tube used in the RH production of aluminum-killed steel, and the adopted technical solution is:

[0007] A low-energy baking method for the immersion tube used in the RH production of aluminum-killed steel, characterized by comprising the following steps:

[0008] 1) After the RH circulation treatment of the molten steel is completed and the ladle leaves the treatment station within ≤ 3 minutes, move the gunning trolley to directly below the RH immersion tube, and immediately spray the gunning material onto the surface of the immersion tube. The dosage of the gunning material is 0 - 190 kg / furnace. Within ≤ 5 minutes after the gunning is completed, move the heat preservation cover to below the RH immersion tube;

[0009] 2) During the waiting period from the end of the previous RH treatment to the start of the next treatment, the vacuum chamber does not use gas combustion for baking;

[0010] 3) Before the RH treatment of the molten steel, according to the life of the immersion tube, raise the ladle to a position < 5 cm below the immersion tube and stay for 1 - 5 minutes, then insert the immersion tube into the liquid slag in the ladle, and then immediately leave the slag, repeating 0 - 3 times;

[0011] 4) After the baking of the immersion tube is completed, perform normal vacuum treatment using the temperature of the slag in the ladle.

[0012] A further improvement of the present invention is: In the step 1), first spray the outer surface of the immersion tube, and then spray the inner surface of the immersion tube.

[0013] A further improvement of the present invention is: In the step 1), the dosage of the gunning material is: when the life of the immersion tube < 20 furnaces, the dosage of the gunning material < 100 kg / furnace; when the life of the immersion tube is 21 - 50 furnaces, the dosage of the gunning material < 120 kg / furnace; when the life of the immersion tube is 51 - 80 furnaces, the dosage of the gunning material < 150 kg / furnace; when the life of the immersion tube > 80 furnaces, the dosage of the gunning material < 190 kg / furnace.

[0014] A further improvement of the present invention is: In the step 3), when the life of the immersion tube < 20 furnaces, raise the ladle to a position < 5 cm below the immersion tube and stay for 1 - 3 minutes; when the life of the immersion tube is 21 - 50 furnaces, raise the ladle to a position < 5 cm below the immersion tube and stay for 2 - 5 minutes; when the life of the immersion tube is 51 - 80 furnaces, raise the ladle to a position < 5 cm below the immersion tube and stay for 2 - 5 minutes, then insert the immersion tube into the liquid slag in the ladle, and then immediately leave the slag, repeating 1 - 2 times; when the life of the immersion tube > 80 furnaces, raise the ladle to a position < 5 cm below the immersion tube and stay for 2 - 5 minutes, then insert the immersion tube into the liquid slag in the ladle, and then immediately leave the slag, repeating 2 - 3 times.

[0015] A further improvement of the present invention is that the speed of the immersion tube inserting into and leaving the molten slag in the ladle is 25 - 35 mm / s.

[0016] A further improvement of the present invention is that in the step 1), the distance between the heat preservation cover and the bottom end of the immersion tube is 10 - 30 cm.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The low - energy - consumption baking method of the immersion tube for RH production of aluminum - killed steel in the present invention cancels the use of gas combustion baking in the vacuum chamber during the production gap.

[0019] 2. The low - energy - consumption baking method of the immersion tube for RH production of aluminum - killed steel in the present invention preliminarily bakes the gunning material on the surface of the immersion tube by using the waste heat of the immersion tube.

[0020] 3. The low - energy - consumption baking method of the immersion tube for RH production of aluminum - killed steel in the present invention uses a heat preservation cover to semi - enclose the RH vacuum chamber to reduce heat dissipation.

[0021] 4. The low - energy - consumption baking method of the immersion tube for RH production of aluminum - killed steel in the present invention uses the temperature of the slag in the ladle to bake the immersion tube again, and adopts different residence times for baking under different service furnace times of the immersion tube, ensuring the high temperature drop caused by gunning and waiting time and the drying and moisture - free of the gunning material.

[0022] 5. The low - energy - consumption baking method of the immersion tube for RH production of aluminum - killed steel in the present invention reduces the consumption of the baking medium to 0 during production; when w([Al])% in the steel at the RH arrival station is 0.015 - 0.045 and the vacuum degree < 100 Pa is maintained for 20 min in the treatment process conditions, the aluminum loss in the steel ≤ 0.006%. Specific embodiments

[0023] The present invention provides a low - energy - consumption baking method of an immersion tube for RH production of aluminum - killed steel.

[0024] The technical solution of the present invention will be described in detail below through specific embodiments. Example 1

[0025] A low - energy - consumption baking method of an immersion tube for RH production of aluminum - killed steel includes the following steps:

[0026] (1)After the RH circulation treatment of the molten steel is completed and the ladle leaves the treatment station within ≤3 min, after the molten steel treatment is completed, the initial temperature on the surface of the immersion tube is 1000 - 1250 °C. Move the gunning device to directly below the RH immersion tube and immediately spray the gunning material onto the surface of the immersion tube. First gun the outer surface of the immersion tube, and then gun the inner surface of the immersion tube. The consumption of the gunning material is as follows: when the life of the immersion tube is <20 furnaces, the consumption of the gunning material is <100 kg / furnace; when the life of the immersion tube is 21 - 50 furnaces, the consumption of the gunning material is <120 kg / furnace; when the life of the immersion tube is 51 - 80 furnaces, the consumption of the gunning material is <150 kg / furnace; when the life of the immersion tube is >80 furnaces, the consumption of the gunning material is <190 kg / furnace. When the life of the immersion tube is <20 furnaces, raise the ladle top to a position 5 cm below the immersion tube and stay for 1 - 3 min; when the life of the immersion tube is 21 - 50 furnaces, raise the ladle top to a position 5 cm below the immersion tube and stay for 2 - 5 min; when the life of the immersion tube is 51 - 80 furnaces, raise the ladle top to a position 5 cm below the immersion tube and stay for 2 - 5 min, then insert the immersion tube into the liquid slag in the ladle, and then immediately leave the slag, repeat 1 - 2 times; when the life of the immersion tube is >80 furnaces, raise the ladle top to a position 5 cm below the immersion tube and stay for 2 - 5 min, then insert the immersion tube into the liquid slag in the ladle, and then immediately leave the slag, repeat 2 - 3 times. Within ≤5 min after the gunning is completed, move the heat preservation cover to below the RH immersion tube, and the distance between the heat preservation cover and the bottom end of the immersion tube is 10 - 30 cm.;

[0027] (2)During the waiting period from the end of the previous RH treatment to the start of the next treatment, the waiting time is 30 - 70 min, and the surface temperature of the immersion tube is controlled at 550 - 800 °C;

[0028] (3)Before the RH treatment of the molten steel, according to the life of the immersion tube, raise the ladle top to a position 5 cm below the immersion tube and stay for 1 - 5 min, then insert the immersion tube into the liquid slag in the ladle, and then immediately leave the slag, repeat 0 - 3 times. The speed of inserting and leaving the immersion tube into / from the liquid slag in the ladle is 25 - 35 mm / s, and the molten steel temperature is controlled at 1600 - 1670 °C;

[0029] (4)After baking the immersion tube with the temperature of the slag in the ladle, perform normal vacuum treatment.

[0030] For the process conditions not specified in the above production method, the conventional techniques in the art can be referred to.

[0031] Through steps (1) - (3), the energy consumption of the baking medium during the continuous production of the RH furnace is 0; under the process conditions of w([Al])% = 0.015 - 0.045 in the steel arriving at the station and a vacuum degree <100 Pa maintained for 20 min, the aluminum loss in the steel is ≤0.006%.

Claims

1. A low - energy - consumption baking method for the immersion tube used in RH production of aluminum - killed steel, characterized in that, it includes the following steps: (1) After the RH cycle treatment of the molten steel is completed and the ladle leaves the treatment station within ≤ 3 min. After the molten steel treatment is completed, the initial temperature on the surface of the immersion tube is 1000 - 1250 °C. Move the gunning device to directly below the RH immersion tube and immediately spray the gunning material onto the surface of the immersion tube. Within ≤ 5 min after the gunning is completed, move the heat - preservation cover to below the RH immersion tube; (2) During the waiting period from the end of the previous RH treatment to the start of the next treatment, the waiting time is 30 - 70 min, and the surface temperature of the immersion tube is controlled at 550 - 800 °C; (3) Before the RH treatment of the molten steel, according to the life of the immersion tube, raise the ladle to a position < 5 cm below the immersion tube and stay for 1 - 5 min, then insert the immersion tube into the liquid slag in the ladle, and then immediately leave the slag, repeat 0 - 3 times. The temperature of the molten steel is controlled at 1600 - 1670 °C; (4) Further bake the immersion tube using the temperature of the slag in the ladle, and after completion, conduct normal vacuum treatment.

2. The low - energy - consumption baking method for the immersion tube used in RH production of aluminum - killed steel according to claim 1, characterized in that, in step 1, first spray - gun the outer surface of the immersion tube, and then spray - gun the inner surface of the immersion tube.

3. The low - energy - consumption baking method for the immersion tube used in RH production of aluminum - killed steel according to claim 1, characterized in that in step 1, the dosage of the gunning material is as follows: when the life of the immersion tube < 20 furnaces, the dosage of the gunning material < 100 kg / furnace; when the life of the immersion tube is 21 - 50 furnaces, the dosage of the gunning material < 120 kg / furnace; when the life of the immersion tube is 51 - 80 furnaces, the dosage of the gunning material < 150 kg / furnace; when the life of the immersion tube > 80 furnaces, the dosage of the gunning material < 190 kg / furnace.

4. The low - energy - consumption baking method for the immersion tube used in RH production of aluminum - killed steel according to claim 1, characterized in that, in step 3, when the life of the immersion tube < 20 furnaces, raise the ladle to a position < 5 cm below the immersion tube and stay for 1 - 3 min; when the life of the immersion tube is 21 - 50 furnaces, raise the ladle to a position < 5 cm below the immersion tube and stay for 2 - 5 min; when the life of the immersion tube is 51 - 80 furnaces, raise the ladle to a position < 5 cm below the immersion tube and stay for 2 - 5 min, then insert the immersion tube into the liquid slag in the ladle, and then immediately leave the slag, repeat 1 - 2 times; when the life of the immersion tube > 80 furnaces, raise the ladle to a position < 5 cm below the immersion tube and stay for 2 - 5 min, then insert the immersion tube into the liquid slag in the ladle, and then immediately leave the slag, repeat 2 - 3 times.

5. The low - energy - consumption baking method for the immersion tube used in RH production of aluminum - killed steel according to claim 4, characterized in that, the speed of the immersion tube inserting into and leaving the liquid slag in the ladle is 25 - 35 mm / s.

6. The low - energy - consumption baking method for the immersion tube used in RH production of aluminum - killed steel according to claim 1, characterized in that, in step 1, the distance between the heat - preservation cover and the bottom - most end of the immersion tube is 10 - 30 cm.