A method of RH nozzle baking

Abstract

The application discloses a RH suction nozzle baking method, comprising the following steps: step one, offline baking; step two, online baking; and step three, slag washing operation; after the vacuum tank is assembled and connected to the line, the application uses small fire to preheat the vacuum tank, then carries out temperature rising treatment and secondary temperature rising after the preheating, when the secondary temperature rising reaches 700-800 DEG C, compressed air is sprayed to the lower part of the suction nozzle, and the spraying flow of the compressed air is controlled to be 80-120 Nm 3 / h, the heat flow density of the suction nozzle part is increased, the heat energy utilization rate of the suction nozzle part is improved, the baking efficiency and baking temperature of the suction nozzle are improved, and finally, the heat preservation treatment is carried out after the secondary temperature rising, so that the moisture in the refractory material is fully dried, the refractory material of the suction nozzle part is fully dried during the use of the suction nozzle, the service life of the suction nozzle is ensured to be synchronous with the lower tank, the consumption cost of the refractory material in the vacuum refining process is reduced, and the production efficiency of the vacuum refining is improved.

Description

Technical Field

[0001] This invention relates to the field of vacuum refining technology, specifically to an RH nozzle baking method. Background Technology

[0002] Vacuum refining is a widely used refining method in steel production. It can produce high-quality steel with ultra-low carbon content and high purity, meeting increasingly stringent requirements. RH vacuum refining equipment is the fastest and best refining device among many vacuum equipment options, and has received widespread attention and vigorous development from metallurgists in recent years. The RH vacuum refining method is characterized by two suction nozzles connected to the lower part of the vacuum chamber. During degassing, the nozzles are inserted into the molten steel. The pressure difference created by the vacuum chamber being evacuated forces the molten steel into the vacuum degassing chamber through the riser pipe. Simultaneously, inert gases (such as argon and nitrogen) are continuously blown into the riser pipe. These inert gases expand rapidly under the high temperature of the molten steel and the low pressure in the upper part of the vacuum chamber. Driven by the buoyancy of the argon bubbles, the molten steel moves upward. After reaching the vacuum chamber, the molten steel flows back to the ladle through the downcomer pipe due to gravity, rushing towards the bottom and wall of the ladle, forming a circulation between the vacuum pool and the ladle. This achieves degassing, decarburization, and deoxidation of the molten steel. The RH suction nozzle is a crucial component of the RH vacuum refining equipment. It comprises an ascending pipe and a descending pipe, with a main steel structure internally constructed of magnesia-chrome bricks. The space between the magnesia-chrome bricks and the steel structure is filled with RH-impregnated corundum self-flowing castable. During use, the RH suction nozzle is welded to the bottom of the lower tank of the vacuum chamber and assembled with the middle tank before operation. Before use, the entire vacuum chamber must be baked to above 1050℃. However, the suction nozzle is located at the very bottom of the vacuum chamber, far from the end of the baking flame. Often, due to insufficient baking, the refractory material at the nozzle area is not fully dried. After only a few uses, the nozzle becomes severely corroded and unusable, requiring replacement of the lower tank and the nozzle. This increases refractory consumption and significantly impacts production organization. Therefore, designing an RH suction nozzle baking method to ensure sufficient drying of the refractory material at the nozzle area during use, reducing refractory consumption costs, and improving the production efficiency of vacuum refining is essential. Summary of the Invention

[0003] The purpose of this invention is to provide an RH nozzle baking method to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: an RH nozzle baking method, comprising the following steps: Step 1, offline baking; Step 2, online baking; Step 3, residue washing operation;

[0005] In step one above, after the vacuum tank is assembled and put into operation, it is in standby position and the overall refractory material is baked. The overall refractory material baking process is as follows: first, a small flame is used for baking and preheating. After baking and preheating, a heating treatment is performed. After the heating treatment, a second heating is performed. During the second heating process, compressed air is sprayed from the lower part of the nozzle. After the second heating, a heat preservation treatment is performed.

[0006] In step two above, the nozzle is baked online before online use;

[0007] In step three above, the ladle is raised to the liquid level before production, and the new suction nozzle is preheated using the high temperature of molten steel and slag, followed by slag washing.

[0008] Preferably, in step one, the baking preheating temperature is 25°C and the baking preheating time is 24-32 hours. During the baking preheating process, the moisture contained in the refractory needs to be dried. The heating rate during the heating treatment is 50-60°C / h, and the heating treatment raises the temperature in the vacuum chamber to 300-400°C.

[0009] Preferably, in step one, the heating rate during the second heating is 20-40℃ / h, and the duration of the second heating is 35-50h. The temperature during the heat preservation treatment is 1200-1300℃, and the heat preservation treatment time is 8-15h.

[0010] Preferably, in step one, the temperature in the vacuum chamber during compressed air injection is 700–800°C, and the injection flow rate is 80–120 Nm. 3 / h.

[0011] Preferably, in step two, during online baking, the gas flow rate is 400–500 Nm³. 3 The coal-oxygen ratio is 0.95, the gun position is 600-650mm, and the gun position is changed every 2 hours, with a change of 100-200mm.

[0012] Preferably, in step two, the temperature of the vacuum chamber is maintained above 1050℃ during online baking, and the pre-production temperature of the vacuum chamber needs to be ≥1050℃, while the gas flow rate is increased to ≥30Nm during the online baking process. 3 / h.

[0013] Preferably, in step three, the preheating time for the new suction nozzle is 0.25 to 0.5 hours, and the slag washing operation is performed by repeatedly immersing the suction nozzle in molten steel, and the slag washing operation is performed 3 to 5 times.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: This RH nozzle baking method involves preheating the nozzle in a vacuum chamber using a small flame after assembly and production line setup. Following preheating, a second heating process is performed. When the second heating reaches 700–800°C, compressed air is injected into the lower part of the nozzle, and the compressed air flow rate is controlled to be 80–120 Nm. 3 / h, increasing the heat flux density at the nozzle, improving the heat energy utilization rate of the nozzle, and increasing the nozzle baking efficiency and baking temperature. Finally, after the second heating, heat preservation treatment is carried out to fully dry the moisture in the refractory material. This ensures that the refractory material at the nozzle is fully dry during the use of the nozzle, ensuring that the service life of the nozzle is synchronized with that of the lower tank, reducing the consumption cost of refractory material during vacuum refining, and improving the production efficiency of vacuum refining. Attached Figure Description

[0015] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Please see Figure 1 The present invention provides an embodiment of an RH nozzle baking method, comprising the following steps: Step 1, offline baking; Step 2, online baking; Step 3, residue washing operation;

[0018] In step one above, after the vacuum tank is assembled and put into operation, it stands by and undergoes overall refractory baking. The overall refractory baking process is as follows: First, preheating is performed using a low flame at a temperature of 25°C for 30 hours, during which the moisture in the refractory needs to be dried. After preheating, a heating process is performed at a rate of 55°C / hour, raising the temperature in the vacuum tank to 350°C. A second heating process is then performed at a rate of 30°C / hour for 40 hours. During the second heating process, compressed air is sprayed from below the nozzle at a temperature of 750°C and a flow rate of 100 Nm³. 3 / h, after the second heating, it is kept at 1250℃ for 12h;

[0019] In step two above, the nozzle undergoes online baking before use, and the gas flow rate during online baking is 450 Nm. 3 The gas flow rate is 35 Nm³ / h, the coal-oxygen ratio is 0.95, the nozzle position is 630 mm, and the nozzle position is changed every 2 hours with a variation of 150 mm. During online baking, the vacuum chamber temperature is maintained at 1200℃, and the pre-production temperature of the vacuum chamber needs to be 1100℃. Simultaneously, the gas flow rate during online baking is 35 Nm³ / h. 3 / h;

[0020] In step three above, before production, the ladle is raised to the liquid level, and the new suction nozzle is preheated using the high temperature of molten steel and slag. The preheating time for the new suction nozzle is 0.3 hours. After that, the slag washing operation is carried out. The rules for the slag washing operation are: the suction nozzle is repeatedly immersed in molten steel, and the number of slag washing operations is 4 times.

[0021] Based on the above, the advantages of the present invention are that it uses a small flame for baking and preheating in a vacuum chamber, followed by a heating process and then a second heating process. When the second heating reaches 700°C to 800°C, compressed air is injected into the lower part of the suction nozzle, and the injection flow rate of the compressed air is controlled to be 80 to 120 Nm. 3 / h, increasing the heat flux density at the nozzle, improving the heat energy utilization rate of the nozzle, and increasing the nozzle baking efficiency and baking temperature. Finally, after the second heating, heat preservation treatment is carried out to fully dry the moisture in the refractory material. This ensures that the refractory material at the nozzle is fully dry during the use of the nozzle, ensuring that the service life of the nozzle is synchronized with that of the lower tank, reducing the consumption cost of refractory material during vacuum refining, and improving the production efficiency of vacuum refining.

[0022] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for baking an RH nozzle, comprising the following steps: Step 1, offline baking; Step 2, online baking; Step 3, residue washing operation; characterized by: In step one above, after the vacuum tank is assembled and put into operation, it is in standby position and the overall refractory material is baked. The overall refractory material baking process is as follows: first, a small flame is used for baking and preheating. After baking and preheating, a heating treatment is performed. After the heating treatment, a second heating is performed. During the second heating process, compressed air is sprayed from the lower part of the nozzle. After the second heating, a heat preservation treatment is performed. In step two above, the nozzle is baked online before online use; In step three above, the ladle is raised to the liquid level before production, and the new suction nozzle is preheated by the high temperature of molten steel and slag, followed by slag washing.

2. The RH nozzle baking method according to claim 1, characterized in that: In step one, the baking preheating temperature is 25°C and the baking preheating time is 24-32 hours. During the baking preheating process, the moisture contained in the refractory needs to be dried. The heating rate during the heating treatment is 50-60°C / h, and the heating treatment raises the temperature in the vacuum chamber to 300-400°C.

3. The RH nozzle baking method according to claim 1, characterized in that: In step one, the heating rate during the second heating is 20-40℃ / h, and the duration of the second heating is 35-50h. The temperature during the heat preservation treatment is 1200-1300℃, and the heat preservation treatment time is 8-15h.

4. The RH nozzle baking method according to claim 1, characterized in that: In step one, the temperature in the vacuum chamber is 700–800°C when compressed air is injected, and the injection flow rate is 80–120 Nm. 3 / h.

5. The RH nozzle baking method according to claim 1, characterized in that: In step two, during online baking, the gas flow rate is 400–500 Nm³. 3 The coal-oxygen ratio is 0.95, the gun position is 600-650mm, and the gun position is changed every 2 hours, with a change of 100-200mm.

6. The RH nozzle baking method according to claim 1, characterized in that: In step two, the temperature of the vacuum chamber is maintained above 1050℃ during online baking, and the pre-production temperature of the vacuum chamber must be ≥1050℃. Simultaneously, the gas flow rate is increased to ≥30 Nm³ during the online baking process. 3 / h.

7. The RH nozzle baking method according to claim 1, characterized in that: In step three, the preheating time for the new suction nozzle is 0.25 to 0.5 hours, and the slag washing operation is as follows: the suction nozzle is repeatedly immersed in molten steel, and the slag washing operation is performed 3 to 5 times.

Images