Tundish electromagnetic purifying device and method with additional ring-shaped embedded continuous casting nozzle electrode

Abstract

The present application belongs to the technical field of metal melt purification, and discloses a tundish electromagnetic purification device and method with an additional annular embedded continuous casting nozzle electrode. The tundish electromagnetic purification device comprises a tundish and a pulse current device; further comprises a submerged nozzle arranged at the outlet position of the tundish, a stopper rod arranged in the tundish and above the submerged nozzle, and a crystallizer arranged below the tundish and in communication with the submerged nozzle; the stopper rod is connected to the positive electrode of the pulse current device; the outlet position of the tundish is embedded with an annular electrode surrounding the submerged nozzle, and the annular electrode is connected to the negative electrode of the pulse current device. The present application adds an embedded annular electrode surrounding the nozzle at the bowl opening where the tundish and the submerged nozzle meet, and under the action of the pulse current, an invisible "electromagnetic net" is formed at the submerged nozzle, which can drive the inclusions at the bowl opening where the stopper rod and the submerged nozzle meet in the tundish away from the nozzle, and realize the purification of the molten steel.

Description

Technical Field

[0001] This invention belongs to the technical field of molten metal purification, and relates to an electromagnetic purification device and method for an intermediate ladle with an added annular embedded electrode for continuous casting nozzles. Background Technology

[0002] The tundish plays a crucial role in the production of high-quality steel. Through tundish metallurgy, secondary oxidation and gas absorption of molten steel can be prevented, the flow state of the molten steel can be improved, slag entrapment can be prevented, inclusions can be promoted to float, and their morphology can be controlled, thus achieving the goal of purifying the molten steel. The tundish supplies molten steel to the crystallizer through a submerged entry nozzle. If a large amount of non-metallic inclusions from the tundish enter the crystallizer, it will deteriorate the quality of the cast billet, and in severe cases, even cause nozzle blockage, leading to a casting stoppage. Therefore, effective control of non-metallic inclusions in the tundish directly affects the quality of the final steel product.

[0003] In existing technologies, common methods for purifying molten steel in the tundish include: ① Tundish internal structure design: By installing flow control elements such as turbulence suppressors, slag weirs, and slag dams in the tundish, the flow field in the tundish is improved, promoting the flotation and removal of inclusions; ② Argon gas injection at the bottom of the tundish: By injecting inert gas at the bottom of the tundish to form an air curtain, the flotation and removal of inclusions is promoted; ③ Adsorption of inclusions by protective slag: Using alkaline linings and high-alkalinity tundish covering slag to reduce pollution and absorb inclusions; ④ Development of physical filtration devices: By installing a filter sleeve directly above the submerged entry nozzle to purify the molten steel, the filter sleeve changes the flow direction of the molten steel near the stopper rod body, suppresses the formation of converging vortices, and prevents slag entrapment from contaminating the molten steel in the crystallizer.

[0004] The aforementioned methods for controlling inclusions in the tundish all utilize the density difference between inclusions and molten steel to achieve separation. However, for small inclusions or inclusions with densities close to those of the molten steel, it is difficult to achieve separation by simply encouraging them to float. Furthermore, traditional techniques for controlling molten steel in the tundish have limitations such as complex equipment structures, high production costs, and insignificant purification effects. These methods can still result in non-metallic inclusions entering the continuous casting nozzle, causing nozzle blockage and deteriorating billet quality. Summary of the Invention

[0005] To address the problems of current methods for purifying non-metallic inclusions in tundish melt, such as inability to drive small-sized non-metallic inclusions, insignificant purification effects, and easy clogging of the tundish nozzle, an electromagnetic purification device for tundish is provided, which adds an annular embedded electrode to the continuous casting nozzle. This device forms an invisible "electromagnetic mesh" in the immersion nozzle, driving inclusions away from the nozzle opening, preventing inclusions from entering the continuous casting nozzle, suppressing nozzle clogging, and achieving billet purification.

[0006] Another objective of this invention is to provide an electromagnetic purification method for intermediate packages based on the above-described apparatus.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0008] The present invention provides an electromagnetic purification device for an intermediate tundish with an added annular embedded continuous casting nozzle electrode, which includes an intermediate tundish and a pulse current device; it also includes an immersion nozzle disposed at the outlet of the intermediate tundish, a stopper rod disposed inside the intermediate tundish and above the immersion nozzle, and a crystallizer disposed below the intermediate tundish and communicating with the immersion nozzle.

[0009] The stopper rod is connected to the positive terminal of the pulse current device; an annular electrode surrounding the immersion nozzle is embedded at the outlet of the intermediate tundish, and the annular electrode is connected to the negative terminal of the pulse current device.

[0010] Furthermore, the inner diameter of the immersion nozzle ranges from 20 to 60 mm, and the outer diameter ranges from 60 to 200 mm.

[0011] Furthermore, the annular electrode is formed by sequentially connecting several parallel rod-shaped electrodes via wires, with one rod-shaped electrode connected to the negative terminal of the pulse current device. All rod-shaped electrodes have the same structure, with a diameter of 10-20 mm and a length of approximately 25-50 mm. The rod-shaped electrodes are made of pure iron, steel, or a conductive, high-temperature resistant material that does not react with molten steel (e.g., tungsten alloy, titanium alloy). The spacing between adjacent rod-shaped electrodes remains consistent. To ensure the effectiveness of the current density distribution in the bowl-shaped region, the number of rod-shaped electrodes is 6-12.

[0012] Furthermore, the shape of the annular electrode coverage area has no special requirements and can be circular, polygonal (e.g., triangular, rectangular, etc.), elliptical, or arc-shaped, etc.; the area of ​​the annular electrode coverage area is 1-2 times the cross-sectional area of ​​the submersible nozzle.

[0013] Furthermore, the annular electrode can be directly embedded or clamped into the bottom of the tundish at the outlet position, or it can be integrated with the bottom of the tundish. The length of the annular electrode inserted into the molten steel is 10-20 mm. Furthermore, both the stopper rod and the annular electrode are connected to the pulse current device via metal wires. The metal wires are pure copper wire, nickel-plated copper wire, or pure nickel wire.

[0014] The electromagnetic purification device for tundish with an added annular embedded electrode for continuous casting nozzle provided by the present invention adds an embedded annular electrode around the nozzle at the bowl-shaped junction of the tundish and the submerged entry nozzle. Under the action of pulsed current, an invisible "electromagnetic mesh" is formed at the submerged entry nozzle, which can drive the inclusions at the bowl-shaped junction of the stopper rod in the tundish and the submerged entry nozzle away from the nozzle and promote the floating of the inclusions. On the one hand, this will improve the nozzle blockage caused by inclusions entering the nozzle, and on the other hand, it will also purify the molten steel to obtain a cleaner billet.

[0015] The present invention further provides an electromagnetic purification method for tundishes, which uses the above-mentioned device to perform the following steps: while pouring molten steel into the tundish, a pulse current device is turned on, and the molten steel treated by the pulse current enters the crystallizer through an immersion nozzle, thereby obtaining an ingot with inclusions removed from the molten steel.

[0016] The aforementioned electromagnetic purification method for the tundish requires continuous and stable pulsed current treatment to ensure that the current remains in a closed loop during the molten steel casting process. This creates a non-uniform electric field distribution at the tip of the stopper rod and the top of the submerged entry nozzle, generating an invisible "electromagnetic net" around the nozzle opening. This effectively inhibits inclusions from entering the nozzle and drives them to float to the tundish surface for removal. By setting appropriate pulsed current parameters (including pulse frequency and current intensity), the skin effect around the electrodes can be strengthened, increasing the range of the non-uniform electric field distribution to cover the entire nozzle area, effectively inhibiting inclusions from entering the nozzle and driving them to float to the tundish surface for removal. The selection of pulse current parameters is related to the type of steel and inclusions in the molten steel to be cast. After research, the pulse current parameters are set as follows: current 50-500A, frequency 1000-50000Hz, pulse width 1-1000μs, voltage 1-24V; in the preferred implementation mode, the current is 140-300A, frequency 5000-40000Hz, pulse width 15-110μs, and voltage 15-24V.

[0017] The aforementioned electromagnetic purification method for tundishes primarily refers to non-metallic inclusions in the molten steel, specifically at least one of the following: alumina, titanium oxide, titanium nitride, manganese sulfide, calcium sulfide, aluminosilicates, calcium aluminates, magnesium oxide, and rare earth oxides. This is only a partial list of non-metallic inclusions; other non-metallic inclusions in the molten steel not listed can also be removed using the method provided by this invention.

[0018] Compared with the inclusions in the untreated billet, the inclusions in the billet prepared by the method of the present invention have a significantly reduced number and density of large-sized inclusions, and the operating state of the stopper rod during the pulsed current treatment process is more stable than that during the process without pulsed current treatment. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the tundish electromagnetic purification device with an added annular embedded continuous casting nozzle electrode provided in Embodiment 1 of the present invention.

[0020] Figure 2 for Figure 1 Top view of the bowl-shaped area;

[0021] Figure 3This is a comparison diagram of inclusion distribution between ingots obtained by pulsed current treatment and sulfur-containing steel ingots obtained without pulsed current treatment in Embodiment 2 of the present invention.

[0022] Figure 4 This is a comparison diagram of inclusion distribution between ingots obtained by pulsed current treatment and sulfur-containing steel ingots obtained without pulsed current treatment in Embodiment 3 of the present invention.

[0023] Figure 5 This is a comparison diagram of inclusion distribution between ingots obtained by pulsed current treatment and titanium-containing steel ingots obtained without pulsed current treatment in Embodiment 4 of the present invention.

[0024] Figure 6 This is a comparison diagram of inclusion distribution between ingots obtained by pulsed current treatment and titanium-containing steel ingots obtained without pulsed current treatment in Embodiment 5 of the present invention.

[0025] In the diagram, 1-intermediate jar; 2-stopper rod; 3-ring electrode; 4-immersion nozzle; 5-crystallizer; 6-metal wire; 7-pulse current device. Detailed Implementation

[0026] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0027] Example 1

[0028] The electromagnetic purification device for the tundish with an added annular embedded continuous casting nozzle electrode provided in this embodiment is as follows: Figure 1 , Figure 2 As shown, it includes an intermediate package 1, a stopper rod 2, an immersion nozzle 4, a crystallizer 5, and a pulse current device 7.

[0029] The stopper rod 2 is placed inside the intermediate package 1 and located above the outlet of the intermediate package.

[0030] The submersible nozzle 4 is located at the outlet of the tundish and is directly opposite the stopper rod 2. Below the submersible nozzle 4 is the crystallizer 5, and the submersible nozzle 4 is connected to the crystallizer 5. The submersible nozzle 4 has an inner diameter of 50 mm and an outer diameter of 140 mm.

[0031] An annular electrode 3, surrounding the submersible nozzle, is directly embedded at the outlet of the tundish. The annular electrode 3 consists of eight parallel rod-shaped electrodes connected sequentially in a circle by wires. All rod-shaped electrodes have the same structure, with a diameter of 20 mm and a length of 40 mm; the distance between adjacent rod-shaped electrodes is 34 mm. The length of the annular electrode inserted into the molten steel is 10 mm.

[0032] Both the stopper rod 2 and the annular electrode 3 are connected to the positive and negative terminals of the pulse current device 7 respectively via metal wires 6.

[0033] Example 2

[0034] This embodiment uses the tundish electromagnetic purification device with an added annular embedded electrode for continuous casting provided in Embodiment 1 to remove inclusions in the molten steel. In this embodiment, the annular electrode is made of pure iron, and the metal wire is nickel-plated copper wire.

[0035] This embodiment focuses on molten steel containing sulfur (S: 0.041 wt.%), in which the inclusions are mainly alumina, calcium sulfide, manganese sulfide, titanium nitride, calcium aluminate, aluminosilicate, etc.

[0036] Using the aforementioned electromagnetic purification device for intermediate packaging, the following steps are performed:

[0037] S1 sets the pulse current parameters of the pulse current device, specifically: current 300A, frequency 8000Hz, pulse width 85μs, and voltage 15V.

[0038] While pouring molten steel into the tundish, S2 activates the pulse current device. The molten steel treated by the pulse current enters the crystallizer through the immersion nozzle, thereby obtaining ingot A with inclusions removed from the molten steel.

[0039] To conduct a control experiment, molten steel was poured into the tundish without turning on the pulse current device and entered the crystallizer through the immersion nozzle to obtain ingot B, in which the pulse current did not act on the molten steel in the tundish.

[0040] Analysis of the stopper rod floating data during the casting process shows that the stopper rod operated smoothly throughout the entire experiment.

[0041] Ingot A and Ingot B were taken, their surfaces were ground and polished, and the distribution of inclusions in Ingot A and Ingot B was observed. The size and quantity of inclusions were counted using an ASPEX inclusion automatic scanner. The results are as follows. Figure 3 As shown.

[0042] from Figure 3 It can be seen that, compared with the untreated billet, the size and number of inclusions in the ingot after pulse treatment in this embodiment are significantly reduced. According to statistics, the inclusion number density in the obtained billet is reduced by 51.6% compared with the inclusions in the untreated billet.

[0043] Example 3

[0044] This embodiment uses the tundish electromagnetic purification device with an added annular embedded electrode for continuous casting provided in Embodiment 1 to remove inclusions in the molten steel. In this embodiment, the annular electrode is made of pure iron, and the metal wire is nickel-plated copper wire.

[0045] This embodiment focuses on molten steel containing sulfur (S: 0.037 wt.%), in which the inclusions are mainly alumina, calcium sulfide, manganese sulfide, titanium nitride, calcium aluminate, aluminosilicate, etc.

[0046] Using the aforementioned electromagnetic purification device for intermediate packaging, the following steps are performed:

[0047] S1 sets the pulse current parameters of the pulse current device, specifically: current 180A, frequency 20kHz, pulse width 27μs, and voltage 24V.

[0048] While pouring molten steel into the tundish, S2 activates the pulse current device. The molten steel treated by the pulse current enters the crystallizer through the immersion nozzle, thereby obtaining ingot A with inclusions removed from the molten steel.

[0049] To conduct a control experiment, molten steel was poured into the tundish without turning on the pulse current device and entered the crystallizer through the immersion nozzle to obtain ingot B, in which the pulse current did not act on the molten steel in the tundish.

[0050] Analysis of the stopper rod floating data during the casting process shows that the stopper rod operated smoothly throughout the entire experiment.

[0051] Ingot A and Ingot B were taken, their surfaces were ground and polished, and the distribution of inclusions in Ingot A and Ingot B was observed. The size and quantity of inclusions were counted using an ASPEX inclusion automatic scanner. The results are as follows. Figure 4 As shown.

[0052] from Figure 4 It can be seen that, compared with the untreated billet, the size and number of inclusions in the ingot after pulse treatment in this embodiment are significantly reduced. According to statistics, the inclusion number density in the obtained billet is reduced by 80.5% compared with the inclusions in the untreated billet.

[0053] Example 4

[0054] This embodiment uses the tundish electromagnetic purification device with an added annular embedded electrode for continuous casting provided in Embodiment 1 to remove inclusions in the molten steel. In this embodiment, the annular electrode is made of pure iron, and the metal wire is nickel-plated copper wire.

[0055] This embodiment focuses on titanium-containing steel (Ti: 0.028 wt.%) molten steel, in which the inclusions are mainly titanium oxide, titanium nitride, aluminum oxide, manganese oxide, manganese sulfide and aluminosilicates.

[0056] Using the aforementioned electromagnetic purification device for intermediate packaging, the following steps are performed:

[0057] S1 sets the pulse current parameters of the pulse current device, specifically: current 250A, frequency 40kHz, pulse width 15μs, and voltage 22V.

[0058] While pouring molten steel into the tundish, S2 activates the pulse current device. The molten steel treated by the pulse current enters the crystallizer through the immersion nozzle, thereby obtaining ingot A with inclusions removed from the molten steel.

[0059] To conduct a control experiment, molten steel was poured into the tundish without turning on the pulse current device and entered the crystallizer through the immersion nozzle to obtain ingot B, in which the pulse current did not act on the molten steel in the tundish.

[0060] Analysis of the stopper rod floating data during the casting process shows that the stopper rod operated smoothly throughout the entire experiment.

[0061] Ingot A and Ingot B were taken, their surfaces were ground and polished, and the distribution of inclusions in Ingot A and Ingot B was observed. The size and quantity of inclusions were counted using an ASPEX inclusion automatic scanner. The results are as follows. Figure 5 As shown.

[0062] from Figure 5 It can be seen that, compared with the untreated billet, the size and number of inclusions in the ingot after pulse treatment in this embodiment are significantly reduced. The inclusion number density in the obtained billet is reduced by 91.5% compared with the inclusions in the untreated billet.

[0063] Example 5

[0064] This embodiment uses the tundish electromagnetic purification device with an added annular embedded electrode for continuous casting provided in Embodiment 1 to remove inclusions in the molten steel. In this embodiment, the annular electrode is made of pure iron, and the metal wire is nickel-plated copper wire.

[0065] This embodiment focuses on titanium-containing steel (Ti: 0.033 wt.%) molten steel, in which the inclusions are mainly titanium oxide, titanium nitride, aluminum oxide, manganese oxide, manganese sulfide and aluminosilicates.

[0066] Using the aforementioned electromagnetic purification device for intermediate packaging, the following steps are performed:

[0067] S1 sets the pulse current parameters of the pulse current device, specifically: current 140A, frequency 5000Hz, pulse width 110μs, and voltage 24V.

[0068] While pouring molten steel into the tundish, S2 activates the pulse current device. The molten steel treated by the pulse current enters the crystallizer through the immersion nozzle, thereby obtaining ingot A with inclusions removed from the molten steel.

[0069] To conduct a control experiment, molten steel was poured into the tundish without turning on the pulse current device and entered the crystallizer through the immersion nozzle to obtain ingot B, in which the pulse current did not act on the molten steel in the tundish.

[0070] Analysis of the stopper rod floating data during the casting process shows that the stopper rod operated smoothly throughout the entire experiment.

[0071] Ingot A and Ingot B were taken, their surfaces were ground and polished, and the distribution of inclusions in Ingot A and Ingot B was observed. The size and quantity of inclusions were counted using an ASPEX inclusion automatic scanner. The results are as follows. Figure 6 As shown.

[0072] from Figure 6 It can be seen that, compared with the untreated billet, the size and number of inclusions in the ingot after pulse treatment in this embodiment are significantly reduced. The inclusion number density in the obtained billet is reduced by 82.2% compared with the inclusions in the untreated billet.

[0073] In summary, the electromagnetic purification device and method for tundish with added annular embedded continuous casting nozzle electrodes provided by the present invention have the following advantages:

[0074] (1) This invention involves arranging an embedded annular electrode at the upper end of the submersible nozzle, connecting the stopper rod to the positive terminal of the pulse current device via a metal wire, and connecting the embedded annular electrode to the negative terminal of the pulse current device via a metal wire. This creates a non-uniform electric field at the rim of the nozzle where the stopper rod meets the submersible nozzle, forming an invisible "electromagnetic net" to prevent inclusions from flowing into the nozzle with the molten steel. By setting a reasonable pulse frequency and current intensity, the skin effect around the electrode is strengthened, increasing the range of the non-uniform electric field distribution and covering the entire rim area, effectively suppressing inclusions from entering the nozzle and driving them to float to the surface of the tundish for removal.

[0075] (2) The tundish electromagnetic purification device and method provided by the present invention are simple in structure and method, low in cost and high in efficiency. It adopts an embedded ring electrode to form a non-uniform electric field in the bowl area at the junction of the stopper rod and the submerged nozzle, and generates an invisible electromagnetic net on the outside of the stopper rod and the bowl to drive the purification of the tundish molten steel by removing inclusions. The application method is simple and convenient, does not interfere with the steelmaking and continuous casting production process, and can also inhibit nozzle blockage and prepare clean billets.

[0076] (3) The present invention utilizes the geometry of the stopper rod-bowl region to form a non-uniform electric field distribution under pulsed current. The skin effect coverage around the annular electrode includes the entire bowl region. For different intermediate tundish and nozzle sizes, it is necessary to adjust the pulse parameters (frequency, current intensity, pulse width, duty cycle) to expand the range of the pulsed current to cover the entire bowl region.

[0077] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for electromagnetic purification of intermediate packages, characterized in that, The electromagnetic purification device for tundishes with added annular embedded continuous casting nozzle electrodes is used in the following steps: while pouring molten steel into the tundish, the pulse current device is turned on. After being treated by the pulse current, the molten steel enters the crystallizer through the immersion nozzle, thereby obtaining an ingot with inclusions removed from the molten steel. The intermediate tundish electromagnetic purification device includes an intermediate tundish and a pulse current device, and further includes an immersion nozzle located at the outlet of the intermediate tundish, a stopper rod placed inside the intermediate tundish and above the immersion nozzle, and a crystallizer located below the intermediate tundish and communicating with the immersion nozzle; the stopper rod is connected to the positive electrode of the pulse current device; an annular electrode surrounding the immersion nozzle is embedded at the outlet of the intermediate tundish, and the annular electrode is connected to the negative electrode of the pulse current device; The annular electrode is formed by connecting several parallel rod-shaped electrodes sequentially with wires, one of which is connected to the negative terminal of the pulse current device; the diameter of the rod-shaped electrode is 10-20mm and the length is 25-50mm; the number of annular electrodes is 6-12; the length of the annular electrode inserted into the molten steel is 10-20mm. The pulse current parameters are set as follows: current 50-500A, frequency 1000-50000Hz, pulse width 1-1000μs, voltage 1-24V.

2. The electromagnetic purification method for intermediate packages according to claim 1, characterized in that, The rod-shaped electrode material is pure iron, steel, or a conductive and high-temperature resistant material that does not react with molten steel.

3. The electromagnetic purification method for intermediate packages according to claim 1, characterized in that, The shape of the area covered by the annular electrode is circular, polygonal, elliptical, or arc-shaped.

4. The electromagnetic purification method for intermediate packages according to claim 1, characterized in that, The ring electrode can be directly embedded in the bottom of the intermediate package at the outlet position, or it can be clamped in place, or it can be integrated with the bottom of the intermediate package.

5. The electromagnetic purification method for intermediate packages according to any one of claims 1 to 4, characterized in that, The inclusions in the molten steel mainly refer to non-metallic inclusions contained in the molten steel, which are at least one of alumina, titanium oxide, titanium nitride, manganese sulfide, calcium sulfide, aluminosilicate, calcium aluminate, magnesium oxide, and rare earth oxides.

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