Submerged entry nozzle negative pressure mitigation method and apparatus

Abstract

The application relates to a submerged nozzle negative pressure alleviating method and device, which generates upward electromagnetic force on molten steel in a submerged nozzle through a static magnetic field generating device located at a specified height of the submerged nozzle, and comprises the following steps: calculating the molten steel flow rate and internal static pressure of the submerged nozzle under different magnetic field intensity and height according to the on-site casting speed, the submerged nozzle size and the pouring section; obtaining the magnetic induction intensity and the specified height, judging the size of the internal static pressure of the submerged nozzle, and outputting the corresponding magnetic induction intensity as a target value if the internal static pressure is greater than 0; controlling the flow of the submerged nozzle, so that the molten steel in a tundish enters a crystallizer from the submerged nozzle, and the static magnetic field generating device is moved to the specified height of the submerged nozzle after the molten steel flow field is stabilized; and starting the static magnetic field generating device and adjusting the magnetic induction intensity to the target value. Compared with the prior art, the application can balance the pressure difference inside and outside the nozzle under different continuous casting process parameters, and has the advantages of non-contact and non-pollution.

Description

Technical Field

[0001] This invention relates to the field of continuous metal casting technology, and in particular to a method and apparatus for mitigating negative pressure at an immersion nozzle. Background Technology

[0002] In continuous casting, the submerged entry nozzle (SIN) serves as the channel for molten steel to enter the crystallizer from the tundish. It protects the casting process, prevents secondary oxidation of the molten steel, and improves the flow and temperature fields within the crystallizer, significantly contributing to stable continuous casting and improved billet quality. However, in actual continuous casting, non-metallic inclusions in the molten steel can adhere to the nozzle wall, causing blockage. This reduces the flow rate of molten steel within the nozzle, preventing multiple heats from being cast consecutively from the tundish and severely decreasing production efficiency.

[0003] Currently, effective methods to prevent nodule formation or even blockage in submerged entry nozzles mainly include four aspects: introducing inert gas, optimizing nozzle structure, applying inner wall coatings to the nozzle, and applying external fields. Single or combined argon blowing at the nozzle and stopper rod can increase the flotation of inclusions and reduce negative pressure intake; however, the argon bubbles can also easily carry inclusions that adhere to the inner wall of the nozzle or be entangled in the billet, causing quality problems. Simultaneously, it accelerates liquid level fluctuations in the crystallizer, increases the probability of slag entrapment, and deteriorates the service environment of refractory materials. New submerged entry nozzle structures can achieve good results in preventing nozzle blockage, but they may alter the flow state of molten steel entering the crystallizer. Furthermore, specific types of nozzles may only be suitable for one or a few situations and cannot be universally applied to all continuous casting machine production; the manufacturing process is also time-consuming and labor-intensive. Inner wall coatings can effectively prevent the accumulation of inclusions on the inner wall of the nozzle, but they are costly and not suitable for large-scale application. Applying an external field involves applying an electric or electromagnetic field to the nozzle. An electric field reduces the reaction between inclusions and the refractory material on the nozzle's inner wall from a charge perspective. An electromagnetic field generates electromagnetic force within the molten steel, driving the molten steel and inclusions in a specific direction, reducing the probability of them moving towards the wall and mitigating nodule formation in submerged entry nozzles. Of these methods, the first two essentially increase the internal pressure of the nozzle, thus preventing air from being drawn in through gaps in the refractory material or at the connection between the submerged entry nozzle and the tundish nozzle.

[0004] To increase the internal pressure of the sprue, Chinese patent CN109604552B discloses a method and apparatus for stabilizing ladle casting using negative pressure. The core of this method is to increase the internal pressure of the sprue by increasing the argon blowing pressure, thereby reducing air intake. However, the argon blowing pressure is difficult to control, and if the blowing pressure is too high, it may lead to increased bubble breakage inside the sprue, increasing the number of small bubbles and causing subsurface bubble defects in the cast billet. To address this, Chinese patent CN101844220A discloses a vacuum negative pressure suction method and apparatus. When a negative pressure exists inside the sprue, the molten metal in the negative pressure container is sucked into the gating system. This method can effectively ensure that the sprue is filled, but using this method may lead to increased fluctuations at the steel-slag interface, increasing the risk of slag entrapment. Chinese patent CN105195726A proposes applying a traveling wave magnetic field outside the submersible nozzle. The electromagnetic force generated by this magnetic field, opposite to the direction of molten steel flow, reduces the molten steel flow velocity inside the nozzle, thereby increasing the pressure within the nozzle. However, this method cannot use water cooling for the traveling wave magnetic field coil, and prolonged operation at high temperatures may lead to coil overheating. Furthermore, the operating space in the submersible nozzle area is limited. Therefore, based on these issues, this invention proposes a method and apparatus for mitigating negative pressure at the nozzle using a static magnetic field, specifically addressing the problem of nozzle nodule formation. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art by providing an immersion nozzle negative pressure mitigation method and device that can achieve pressure balance between the inside and outside of the nozzle under different continuous casting process parameters, thereby alleviating nozzle blockage problems.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] According to one aspect of the present invention, a method for mitigating negative pressure in an immersion nozzle is provided, which generates an upward electromagnetic force on molten steel inside the immersion nozzle using a static magnetic field generator located at a specified height of the immersion nozzle, comprising the following steps:

[0008] Based on the casting speed, submerged entry nozzle size, and casting cross-section, calculate the molten steel flow velocity v and the static pressure P inside the submerged entry nozzle under different magnetic field strengths B and heights.

[0009] Get the magnetic induction intensity B and the specified height, determine the magnitude of the static pressure P inside the immersion nozzle under the magnetic induction intensity B, and if P is greater than 0, output the corresponding magnetic induction intensity B and use it as the target value.

[0010] The flow of molten steel in the tundish is controlled by the on-site casting speed and the casting section, so that the molten steel enters the crystallizer from the immersion nozzle. After the flow field of the molten steel is stabilized, the static magnetic field generator is moved to the specified height at the immersion nozzle.

[0011] Turn on the static magnetic field generator and adjust the magnetic induction intensity B to the target value.

[0012] According to another aspect of the present invention, an immersion inlet negative pressure mitigation device according to the method described above is provided, comprising an immersion inlet, a static magnetic field generator, and a moving device, wherein the static magnetic field generator is located at the immersion inlet, and the moving device is connected to the static magnetic field generator.

[0013] Furthermore, the outlet of the immersion nozzle is equipped with a flow control device, which is a stopper rod or a sliding nozzle.

[0014] Furthermore, the static magnetic field generating device is a DC magnetic field generator or a neodymium iron boron generator.

[0015] Furthermore, a DC magnetic field generator includes an iron core and a coil.

[0016] Furthermore, the moving device includes a horizontal servo mechanism, a vertical servo mechanism, and a base. The horizontal servo mechanism is connected to the vertical servo mechanism, the vertical servo mechanism is connected to the base, and the base is fixed on the continuous casting equipment where the submerged entry nozzle is located.

[0017] Furthermore, the static magnetic field generator is fixedly installed at the front end of the longitudinal servo mechanism.

[0018] Furthermore, the lifting height of the longitudinal servo mechanism is 0~500mm.

[0019] Furthermore, the static magnetic field generating devices are arranged in pairs at the immersion nozzle.

[0020] Furthermore, the static magnetic field generator produces a magnetic field strength of 0.1~5T.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) Based on the casting speed, submerged entry nozzle size and casting section of the continuous casting site, this invention establishes the relationship between the molten steel flow rate and the static pressure and magnetic field strength inside the submerged entry nozzle at different heights. After controlling the flow of the submerged entry nozzle, the static magnetic field generator is moved to a specified height at the submerged entry nozzle. The magnetic induction intensity of the magnetic field of the static magnetic field generator is adjusted according to the established relationship, and the static pressure at the submerged entry nozzle is controlled to be positive. This solves the problem of secondary oxidation of molten steel caused by the negative pressure of the submerged entry nozzle. At the same time, it can significantly reduce the nozzle blockage rate and improve the continuous casting process.

[0023] (2) The present invention provides a static magnetic field generating device at the submerged entry nozzle. The static magnetic field generated by the static magnetic field generating device generates an upward electromagnetic force on the molten steel at the submerged entry nozzle, thereby reducing the flow velocity of the molten steel in the submerged entry nozzle and increasing the internal pressure of the nozzle. This achieves the beneficial effect of avoiding air intake at the connection between the tundish nozzle and the submerged entry nozzle. The static magnetic field generating device is connected to a moving device including a horizontal servo mechanism and a vertical servo mechanism, so that the installation position of the static magnetic field generating device at the submerged entry nozzle is adjustable. By adjusting the intensity of the static magnetic field and the installation position of the static magnetic field device, the pressure difference inside and outside the nozzle under different continuous casting process parameters can be balanced.

[0024] (3) Compared with traditional argon blowing, the present invention uses the braking force generated by the static magnetic field to fill the inside of the nozzle with molten steel, which has the advantages of no contact and no pollution, and can also avoid subcutaneous bubbles and subcutaneous inclusion defects caused by traditional argon blowing. Attached Figure Description

[0025] Figure 1 This is a flowchart of the method involved in the present invention;

[0026] Figure 2 Schematic diagram of the principle of using static magnetic field to reduce negative pressure at the water inlet;

[0027] Figure 3 This is a schematic diagram of the DC magnetic field generator device in a preferred embodiment of the present invention;

[0028] Figure 4 This is a three-dimensional schematic diagram of the DC magnetic field generator device in a preferred embodiment of the present invention;

[0029] Figure 5 The pressure distribution inside the nozzle with and without a static magnetic field applied;

[0030] Figure 6 This is a schematic diagram of the neodymium iron boron magnetic field generator device in a preferred embodiment of the present invention.

[0031] In the diagram, 1-immersion nozzle, 2-static magnetic field generator, 3-moving device, 4-coil, 5-iron core, 6-stainless steel base, 7-lateral servo mechanism, 8-longitudinal servo mechanism, 9-base, 10-stopper rod, 11-intermediate drum, 12-upper nozzle, 13-upper nozzle-intermediate drum connection area, 14-crystallizer. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0034] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0035] This invention provides a method and apparatus for mitigating negative pressure in a submersible nozzle. It utilizes a static magnetic field to reduce the negative pressure in the submersible nozzle, aiming to decrease the pressure difference between the inside and outside of the nozzle during continuous casting. Figure 1 As shown, the method includes the following steps:

[0036] Step 1: Based on the on-site casting speed, submerged nozzle size and casting cross-section, establish a coupled mathematical model of magnetic field-flow field-temperature field inside the submerged nozzle, and calculate the molten steel flow velocity v and the static pressure P inside the nozzle under different static magnetic field strengths.

[0037] Step 2: Determine the magnitude of the static pressure P inside the immersion nozzle. If P is greater than 0, output the corresponding magnetic induction intensity B and use it as the objective function.

[0038] Step 3: Activate the flow control device according to the on-site casting speed and casting section, so that the molten steel in the tundish enters the crystallizer from the submerged entry nozzle. After the flow field stabilizes, move the static magnetic field generator to a specified height near the submerged entry nozzle.

[0039] Step 4: Turn on the static magnetic field generator and adjust the magnetic induction intensity B to the specified value. According to the principle of electromagnetic induction, the molten steel in the submerged nozzle will generate an upward electromagnetic force, which will reduce the flow rate of the molten steel in the submerged nozzle and increase the internal pressure of the nozzle. This will reduce or prevent air intake at the connection between the tundish nozzle and the submerged nozzle, thereby increasing the internal pressure of the submerged nozzle.

[0040] This invention discloses an immersion-type water inlet negative pressure mitigation device, comprising an immersion water inlet 1, a static magnetic field generator 2, and a moving device 3. The moving device 3 includes a horizontal servo mechanism 7, a vertical servo mechanism 8, and a base 9. The horizontal servo mechanism 7 is connected to the vertical servo mechanism 8, and the vertical servo mechanism 8 is connected to the base 9. The static magnetic field generator 2 is fixedly installed at the front end of the horizontal servo mechanism 7. During water inlet replacement, the static magnetic field generator 2 is moved by the horizontal servo mechanism 7, and the vertical height of the static magnetic field generator 2 is changed by the vertical servo mechanism 8. Preferably, the lifting height of the vertical servo mechanism 8 is 0~500mm.

[0041] In this invention, molten steel passes through the upper nozzle 12 at the tundish 11, through the upper nozzle-tundish connection zone 13 between the tundish 11 and the upper nozzle 12, and enters the crystallizer 14 through the submerged entry nozzle 1. A flow control device is also provided at the outlet of the submerged entry nozzle 1 to control the flow of molten steel from the submerged entry nozzle 1. Preferably, the flow control device can be a stopper rod 10 or a sliding nozzle.

[0042] During use, by applying a static magnetic field, a braking force opposite to the flow direction of the molten steel is generated inside the submerged nozzle 1, thereby reducing the flow velocity of the molten steel inside the submerged nozzle 1 and thus reducing the internal pressure of the submerged nozzle 1. Figure 2 As shown. The static magnetic field generator 2 can be a DC magnetic field generator composed of a coil 4 and an iron core 5, or it can be a neodymium iron boron magnet. The static magnetic field strength is 0.1~1T to meet the magnetic field strength requirements for reducing the negative pressure of the immersion nozzle. The number of static magnetic field generators 2 is an integer multiple of 2, and they are arranged in pairs at the immersion nozzle 1 to ensure a reasonable distribution of the magnetic field and a stable output of the magnetic force. Preferably, the static magnetic field generator 2 is mounted on a stainless steel base 6, which provides protection for the static magnetic field generator 2.

[0043] The specific embodiments of the present invention will be described below through examples.

[0044] Example 1

[0045] In this example, see as follows Figure 3 and Figure 4 As shown, the specific steps to achieve full filling of the submerged entry nozzle during continuous casting production are as follows:

[0046] Step 1: For the continuous casting site conditions of a slab cross-section of 1650×230mm, a casting speed of 1.2m / min, and an 80mm inner diameter of the submerged entry nozzle, a coupled mathematical model of the magnetic field, flow field, and temperature field inside the submerged entry nozzle is established. A static magnetic field with a magnetic induction intensity of 0.5T is applied perpendicular to the direction of the molten steel flow velocity. Figure 5 As shown;

[0047] Step 2: It can be seen that when no static magnetic field is applied, the static pressure inside the submersible nozzle is negative, which may easily cause the intake of external air. After applying a static magnetic field of 0.5T, the pressure inside the submersible nozzle becomes positive. Set 0.5T as the objective function.

[0048] Step 3: Open the stopper rod according to the above working conditions so that the molten steel in the tundish enters the crystallizer from the submerged nozzle. After the flow field stabilizes, align the center of the DC magnetic field generator with the center of the submerged nozzle, and the center of its iron core is 500mm away from the top surface of the crystallizer.

[0049] Step 4: Adjust the magnetic induction intensity to 0.5T through the back-end control cabinet. According to the principle of electromagnetic induction, the molten steel in the submerged nozzle will generate an upward electromagnetic force, which will reduce the flow rate of the molten steel in the submerged nozzle and increase the internal pressure of the nozzle. This will reduce or prevent air intake at the connection between the tundish nozzle and the submerged nozzle, thereby increasing the internal pressure of the submerged nozzle.

[0050] At this point, the pressure P1 at the characteristic point will increase, thereby preventing air from being drawn in at the connection between the tundish top nozzle and the submersible nozzle, thus increasing the internal pressure of the submersible nozzle.

[0051] This embodiment provides a method and apparatus for generating a static magnetic field using a DC magnetic field generator to reduce the negative pressure of an immersion nozzle. It can flexibly adjust the intensity of the static magnetic field, effectively reduce or even alleviate the problem of negative pressure at the nozzle, and has a simple structure and is easy to operate.

[0052] Example 2

[0053] In this example, see as follows Figure 6 As shown, the specific steps to achieve full filling of the submerged entry nozzle during continuous casting production are as follows:

[0054] Steps 1 and 2 are the same as steps 1 and 2 in Embodiment 1 above;

[0055] Step 3: Open the stopper rod according to the above working conditions so that the molten steel in the tundish enters the crystallizer from the submerged nozzle. After the flow field stabilizes, align the center of the NdFeB static magnetic field generator with the center of the submerged nozzle, with the center 500mm away from the top surface of the crystallizer.

[0056] Step 4: Adjust the magnetic induction intensity to 0.5T through the back-end control cabinet. According to the principle of electromagnetic induction, the molten steel in the submerged nozzle will generate an upward electromagnetic force, which will reduce the flow rate of the molten steel in the submerged nozzle and increase the internal pressure of the nozzle. This will reduce or prevent air intake at the connection between the tundish nozzle and the submerged nozzle, thereby increasing the internal pressure of the submerged nozzle.

[0057] At this point, the pressure P1 at the characteristic point will increase, thereby preventing air from being drawn in at the connection between the tundish top nozzle and the submersible nozzle, thus increasing the internal pressure of the submersible nozzle.

[0058] This embodiment provides a device for reducing the negative pressure at the sprue using a neodymium iron boron magnetic field generator. It has a simple structure, is easy to operate, and does not consume energy.

[0059] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for mitigating negative pressure at an immersion inlet, characterized in that, An upward electromagnetic force is generated in the molten steel inside the submerged nozzle (1) by a static magnetic field generating device (2) located at a specified height of the submerged nozzle (1), comprising the following steps: Based on the casting speed, submerged entry nozzle size, and casting cross-section, calculate the molten steel flow velocity v and the static pressure P inside the submerged entry nozzle under different magnetic field strengths B and heights. Get the magnetic induction intensity B and the specified height, determine the magnitude of the static pressure P inside the immersion nozzle (1) under the magnetic induction intensity B, and if P is greater than 0, output the corresponding magnetic induction intensity B and use it as the target value; According to the on-site casting speed and the casting section, the flow of the submerged nozzle is controlled so that the molten steel in the tundish (11) enters the crystallizer (14) from the submerged nozzle (1). After the flow field of the molten steel is stabilized, the static magnetic field generator (2) is moved to the designated height at the submerged nozzle (1). Turn on the static magnetic field generator (2) and adjust the magnetic induction intensity B to the target value; The static magnetic field generating device (2) is a DC magnetic field generator or a neodymium iron boron generator; The DC magnetic field generator includes an iron core (5) and a coil (4). The static magnetic field generating device (2) is arranged in pairs at the immersion water inlet (1); The static magnetic field generating device (2) generates a magnetic field strength of 0.1~5T.

2. A submersible inlet negative pressure mitigation device according to claim 1, characterized in that, It includes an immersion inlet (1), a static magnetic field generator (2) and a moving device (3), wherein the static magnetic field generator (2) is located at the immersion inlet (1) and the moving device (3) is connected to the static magnetic field generator (2).

3. The immersion-type water inlet negative pressure mitigation device according to claim 2, characterized in that, The immersion nozzle (1) is provided with a flow control device at its outlet, which is a stopper rod (10) or a sliding nozzle.

4. The immersion-type water inlet negative pressure mitigation device according to claim 2, characterized in that, The mobile device (3) includes a horizontal servo mechanism (7), a vertical servo mechanism (8) and a base (9). The horizontal servo mechanism (7) is connected to the vertical servo mechanism (8), and the vertical servo mechanism (8) is connected to the base (9). The base (9) is fixed on the continuous casting equipment where the submerged nozzle (1) is located.

5. The immersion-type water inlet negative pressure mitigation device according to claim 4, characterized in that, The static magnetic field generator (2) is fixedly installed at the front end of the longitudinal servo mechanism (8).

6. The immersion-type water inlet negative pressure mitigation device according to claim 4, characterized in that, The lifting height of the longitudinal servo mechanism is 0~500mm.

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