A method for preventing stopper rod clogging using electrical pulses

Abstract

The present application belongs to the field of continuous casting and refractory material, and relates to a method for preventing clogging of a stopper by using an electric pulse, which comprises the following specific steps: fixing a metal round hoop with an external extension wire on the outside of a water gap seat brick and the outside of a top end of a stopper respectively; double-layer coating and anti-oxidation treatment: mixing zirconium sol, graphite powder and aluminum oxide powder in a mass ratio of 1:3-5:3-5, uniformly coating the round hoop surface and the connecting gap, and using hot air to dry quickly, so as to increase the electrical conductivity of the connecting part; then mixing the zirconium sol and the aluminum oxide powder in a mass ratio of 1:8-15, and uniformly coating the coating surface containing graphite again; constructing an electric field: connecting the water gap seat brick and the stopper with a pulse power by using an external wire to construct an electric field loop; the present application effectively avoids the aggregation, adhesion and growth of inclusions on the surface of the stopper; and solves the problem of clogging of the stopper itself.

Description

Technical Field

[0001] This invention belongs to the field of continuous casting and refractory materials, and specifically relates to a method for preventing stopper rod nodule formation using electrical pulses. Background Technology

[0002] Continuous casting, as a crucial part of steel production, plays a central role in optimizing steel industry processes and product structure. With societal development, the requirements for steel performance are becoming increasingly stringent. To produce higher-quality steel, in addition to adopting new processes and technologies in continuous casting, the improvement and development of refractory material properties are also essential.

[0003] Taking the stopper rod as an example, it is an important functional refractory material installed in the tundish to control and regulate the flow of molten steel from the tundish into the nozzle and the crystallizer. It mainly plays a role in controlling the flow rate, flow field and safe casting of molten steel. However, at present, the stopper rod head is prone to nodule formation during continuous casting, which leads to excessive opening of the stopper rod and many other problems such as uneven control of molten steel flow rate and flow field.

[0004] To prevent stopper rod bridging, existing technologies mainly involve adjusting smelting processes and casting parameters, optimizing the stopper rod itself and its head structure, selecting different types of carbon-containing refractory materials (such as magnesia-carbon, spinel-carbon, aluminum-carbon, and zirconium-carbon materials) based on different cast steel grades, and using novel anti-bridging coatings. However, these measures can only moderately alleviate the bridging problem of the stopper rod itself. Once the continuous casting time is extended or the cast steel grade is changed, the bridging problem of the stopper rod itself will worsen again. Therefore, finding a highly adaptable and effective technology to prevent stopper rod bridging is of great significance. Summary of the Invention

[0005] To address the aforementioned technical problems, the purpose of this invention is to propose a method for preventing plug rod nodule formation using electrical pulses.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preventing plug rod nodule formation using electrical pulses, the specific steps of which are as follows:

[0008] (1) Tightening the connection: Fix the metal hoop with the extended wire to the outside of the water inlet seat brick and the outside of the top of the stopper rod respectively;

[0009] Double-layer coating and anti-oxidation treatment: Zirconium sol, graphite powder, and alumina powder are mixed in a mass ratio of 1:3-5:3-5 and uniformly coated onto the surface of the circular hoop and the connecting gaps. Hot air is used to quickly dry the mixture, thereby increasing the conductivity of the connection. The coating thickness does not exceed 5 mm. Then, zirconium sol and alumina powder are mixed in a mass ratio of 1:8-15 and uniformly coated again onto the graphite-containing surface to prevent oxidation of the circular hoop and its wiring during high-temperature continuous casting and energization. The coating thickness of zirconium sol and alumina powder is 10-25 mm.

[0010] Constructing the electric field: An electric field circuit is constructed by connecting the nozzle seat brick and stopper rod to the pulse power supply using external wires. During continuous casting, the applied electric field strength, pulse frequency, and electric field polarity are adjusted in a timely manner according to the corresponding steel grade and continuous casting parameters. Specifically, when the molten steel contains a high content of metallic alloys, the electric field applied to the stopper rod is a positive electric field; when the molten steel contains a high content of inclusions, especially alumina inclusions, the electric field applied to the stopper rod is a negative electric field. During continuous casting, the applied electric field strength and pulse frequency also need to be adjusted according to the steel throughput and the growth rate of nodules at the stopper rod head.

[0011] The metal hoop is made of a metal wire with good conductivity and high temperature resistance, such as iron, copper, molybdenum, platinum, or tungsten.

[0012] The metal hoop is made of copper or iron.

[0013] The thickness of the metal hoop should be 3mm or more.

[0014] The applied pulsed electric field strength is 20-300A, and the pulse frequency is 5000-120000Hz.

[0015] The present invention proposes a method for preventing plug rod nodule formation using electrical pulses. Compared with other technologies, the advantages of the present invention are as follows:

[0016] (1) The technical method described in this invention is simple, convenient, highly operable and applicable to the problem of plug rod nodules and blockages in any continuous casting steel grade; and the technology described in this invention will not bring any changes to the original production process and steel grade composition, nor will it bring any burden or interference to on-site production;

[0017] (2) Double coating and anti-oxidation treatment can effectively improve the connection effect and conductivity between the metal hoop, the sprue seat brick and the stopper rod; and during the high-temperature continuous casting process, the coated zirconium sol, graphite powder and alumina powder mixture will also promote and strengthen the contact effect between the metal hoop, the sprue seat brick and the stopper rod; at the same time, the externally coated zirconium sol and alumina powder can protect the internal metal conductors such as the metal hoop, the sprue seat brick and the stopper rod and carbon-containing materials from being oxidized; and these enhancement effects will also effectively prevent local overheating, poor contact and high resistance when the electric field is applied, and effectively ensure the application effect and stability of the electric field.

[0018] (3) During continuous casting, the problem of nodule formation on the stopper rod not only stems from the adhesion of inclusions in the steel flowing through the stopper rod surface to the rod head surface; at the same time, as a carbonaceous refractory material, the decarburization of the stopper rod itself leads to the exposure of its surface refractory material in the molten steel, which further promotes the adhesion and growth of inclusions on the surface of the stopper rod; in addition, the nodule formation problem on the stopper rod is also directly related to factors such as the reaction between the alloy in the steel and the refractory material in the stopper rod area; therefore, this invention uses an electric pulse to form a high-energy, high-current-density pulsed electric field between the stopper rod, molten steel, and nozzle seat brick; on the one hand, under the influence of the electric pulse, various inclusions flowing through the surface of the stopper rod will migrate, effectively avoiding the aggregation, adhesion, and growth of inclusions on the surface of the stopper rod; even if a small number of inclusions still adhere to the surface of the stopper rod, under the influence of the electric pulse Under the influence of this technology, unstable substances in these adherents will detach from the stopper rod surface again, leaving only a very small amount of adherents remaining on the stopper rod surface. These stable nodules are extremely thin and will not affect the growth of nodules on the stopper rod surface or the stability of continuous casting. On the other hand, the technology described in this invention can also adjust and switch the polarity of the applied electric field in a timely manner according to the alloy composition of different cast steel grades. Furthermore, it can effectively regulate the decarburization of the stopper rod itself and the original chemical reaction between the refractory material on the stopper rod surface and the alloy components in the steel by utilizing the differences in electrochemical reactions generated under different polarity electric fields, thereby further limiting and preventing the generation of nodules and growth problems on the stopper rod. Finally, with the combined effect of the above technologies, the nodule problem of the stopper rod itself will be completely solved. Attached Figure Description

[0019] Appendix Figure 1 This is a schematic diagram illustrating the application of the method for preventing plug rod nodulation using electrical pulses as described in this invention, which mainly includes electric field construction and double-layer coating and anti-oxidation treatment on the outer side of the metal hoop.

[0020] In the diagram: 1. Immersion nozzle, 2. Pulse power supply, 3. Stopper rod, 4. Intermediate liner, 5. Metal hoop, 6. Inner coating, 7. Outer coating. Detailed Implementation

[0021] The invention will be described in detail with reference to the accompanying drawings and specific embodiments: Example

[0022] This embodiment uses a billet continuous casting platform in a steel plant as an example. First, metal hoops with extended conductors are fixed to the outside of the nozzle seat brick and the top of the stopper rod, respectively. The metal hoops are made of copper and have a thickness of 3mm. Then, zirconium sol, graphite powder, and alumina powder are mixed in a mass ratio of 1:3:4 and uniformly coated onto the surface of the hoop and the connecting seams. Hot air is used to quickly dry the mixture, thereby increasing the conductivity of the connection points. The coating thickness is 3mm. After drying, zirconium sol and alumina powder are mixed in a mass ratio of 1:10 and uniformly coated again onto the graphite-containing coating surface to prevent oxidation of the hoop and its connections during high-temperature continuous casting and energization. The coating thickness is 15mm. Finally, the nozzle seat brick and stopper rod are connected to the pulse power supply using external wires to construct an electric field circuit. Since the low-carbon aluminum killed steel being cast has a high content of acid-soluble aluminum and alumina inclusions, it was decided to use the stopper rod as the positive electrode and the nozzle seat brick as the negative electrode for regulation during continuous casting. The pulse electric field intensity is 50A and the pulse frequency is 30000Hz.

[0023] Throughout the casting process, the stopper rod remained under stable control without significant fluctuations. After casting was completed, the stopper rod was removed as a whole, and no obvious nodules formed on its surface. Furthermore, sampling and analysis of the resulting cast billet revealed no changes in the steel quality. Example

[0024] This embodiment uses a slab continuous casting platform in a steel plant as an example. First, metal hoops with extended conductors are fixed to the outside of the nozzle seat brick and the top of the stopper rod, respectively. The metal hoops are made of copper and have a thickness of 4mm. Then, zirconium sol, graphite powder, and alumina powder are mixed in a mass ratio of 1:3:4 and uniformly coated onto the surface of the hoops and the connecting seams. Hot air is used to quickly dry the mixture, increasing the conductivity of the connection points; the coating thickness is 3mm. After drying, zirconium sol and alumina powder are mixed in a mass ratio of 1:10 and uniformly coated again onto the graphite-containing coating surface to prevent oxidation of the hoops and their connections during high-temperature continuous casting and energization. The coating thickness is 15mm. Finally, external conductors are used to connect the nozzle seat brick and the stopper rod to a pulse power supply, thus constructing an electric field circuit. Because the cast steel contains a large amount of alloys and rare earth compounds, during the continuous casting process, it was decided to use a stopper rod as the positive electrode and the sprue holder as the negative electrode for control in the early stage of continuous casting, with a pulsed electric field intensity of 120A and a pulse frequency of 80,000Hz. In the middle and later stages, the sprue holder was used as the positive electrode and the stopper rod as the negative electrode for control, with a pulsed electric field intensity of 70A and a pulse frequency of 50,000Hz.

[0025] Throughout the casting process, the stopper rod remained under stable control without significant fluctuations. After casting was completed, the stopper rod was removed as a whole, and no obvious nodules formed on its surface. Furthermore, sampling and analysis of the resulting cast billet revealed no alteration in the steel quality.

Claims

1. A method for preventing plug rod nodule formation using electrical pulses, characterized in that: The specific steps are as follows: (1) Tightening the connection: Fix the metal hoop with the extended wire to the outside of the water inlet seat brick and the outside of the top of the stopper rod respectively; (2) Double-layer coating and anti-oxidation treatment: Zirconium sol, graphite powder and alumina powder are mixed in a mass ratio of 1:3-5:3-5 and then uniformly coated on the surface of the hoop and the connection gap. Hot air is used to dry it quickly to increase the conductivity of the connection. The coating thickness does not exceed 5 mm. Then, zirconium sol and alumina powder are mixed in a mass ratio of 1:8-15 and uniformly coated again on the surface of the coating containing graphite to prevent oxidation of the hoop and its wiring during high-temperature continuous casting and energization. The coating thickness of zirconium sol and alumina powder is 10-25 mm. (3) Constructing an electric field: Connect the sprue seat brick and stopper rod to the pulse power supply using external wires to construct an electric field circuit; During continuous casting, adjust the applied electric field strength, pulse frequency and electric field polarity in a timely manner according to the corresponding steel grade and continuous casting parameters; Specifically, when casting low carbon aluminum killed steel, during continuous casting, use the stopper rod as the positive electrode and the sprue seat brick as the negative electrode for regulation, wherein the pulse electric field applied strength is 50A and the pulse frequency is 30000Hz.

2. The method for preventing plug rod nodulation using electrical pulses as described in claim 1, characterized in that: The metal hoop is made of iron, copper, molybdenum, platinum, or tungsten.

3. The method for preventing plug rod nodule formation using electrical pulses as described in claim 1, characterized in that: The thickness of the metal hoop should be 3mm or more.

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