Submersed nozzle negative pressure retarding method and device

Abstract

The invention relates to a method and a device for relieving negative pressure of a submersed nozzle, which are characterized in that upward electromagnetic force is generated on molten steel in the submersed nozzle through a static magnetic field generating device positioned at the specified height of the submersed nozzle, and the method comprises the following steps of: according to the on-site pulling speed of continuous casting, the size of the submersed nozzle and a pouring section; calculating the flow velocity of molten steel in the submersed nozzle and the static pressure in the nozzle under different magnetic field intensities and heights; magnetic induction intensity and specified height are obtained, the size of static pressure in the submersed nozzle is judged, and if the size is larger than 0, the corresponding magnetic induction intensity is output and serves as a target value; flow control is conducted on the submersed nozzle, molten steel in the tundish enters the crystallizer from the submersed nozzle, and after a molten steel flow field is stable, the static magnetic field generating device is moved to the designated height of the submersed nozzle; starting the static magnetic field generating device, and adjusting the magnetic induction intensity to a target value. Compared with the prior art, the balance of the internal and external pressure difference of the collector nozzle in different continuous casting process parameters can be realized, and the device has the advantages of no contact and no pollution.

Description

Technical Field

[0001] The invention relates to the technical field of metal continuous casting, and in particular to a method and a device for alleviating negative pressure of an immersed nozzle. Background Art

[0002] During continuous casting, the submerged nozzle is the channel for molten steel to enter the crystallizer from the tundish. It protects pouring, prevents secondary oxidation of molten steel, improves the flow field and temperature field in the crystallizer, and has significant effects on stabilizing continuous casting and improving the quality of ingots. However, in the actual continuous casting process, non-metallic inclusions in the molten steel will adhere to the nozzle wall, causing the nozzle to be blocked, thereby reducing the flow rate of molten steel in the nozzle, making it impossible to perform multi-furnace continuous casting in the tundish, and seriously reducing production efficiency.

[0003] At present, the effective means to prevent the agglomeration or even blockage of the submerged nozzle mainly include the introduction of inert gas, optimization of nozzle structure, nozzle inner wall coating and application of external field. Single or combined argon blowing of nozzle and stopper can increase the floating of inclusions and reduce the suction of negative pressure, but the blown argon bubbles are also easy to carry inclusions to adhere to the inner wall of the nozzle, or roll into the steel billet to cause quality problems, and accelerate the fluctuation of the crystallizer liquid level, increase the probability of slag roll, and deteriorate the service environment of refractory materials. The new submerged nozzle structure can achieve good results from the perspective of preventing nozzle blockage, but it may change the flow state of molten steel entering the crystallizer, and a specific type of nozzle may only be applicable to one or several situations, and cannot be universally applicable to all continuous casting machine production, and the production process is time-consuming and labor-intensive. The inner wall coating of the nozzle can effectively prevent the accumulation of inclusions on the inner wall of the nozzle, but it is costly and not suitable for large-scale use. Applying an external field applies an electric field or an electromagnetic field to the nozzle. Applying an electric field can reduce the reaction between inclusions and the refractory material on the inner wall of the nozzle from the perspective of charge. Applying an electromagnetic field generates electromagnetic force in the molten steel, driving the molten steel and inclusions to move in a specific direction, reducing the probability of moving to the wall, and also reducing the nodule of the submerged nozzle. Among the above-mentioned methods, the essence of the first two is to increase the internal pressure of the nozzle, thereby preventing air from being sucked in from the gaps in the refractory material or the connection between the submerged nozzle and the upper nozzle of the tundish.

[0004] In order to increase the internal pressure of the nozzle, Chinese patent CN109604552B discloses a method and device for stabilizing ladle pouring by negative pressure. The core of the method is to increase the internal pressure of the nozzle by increasing the argon blowing pressure to reduce the intake of air. However, the argon blowing pressure is difficult to control. At the same time, if the argon blowing pressure is too high, it may cause the bubbles to break more severely inside the nozzle, increase the number of small bubbles, and cause subcutaneous bubble defects in the casting. For this reason, Chinese patent CN101844220A discloses a vacuum negative pressure suction method and device, that is, when there is a negative pressure inside the nozzle, the molten metal in the negative pressure container will be sucked into the runner system. This method can effectively ensure that the nozzle is full, but the use of this method may cause the slag interface to fluctuate more severely and increase the risk of slag rolling. Chinese patent CN105195726A proposes to apply a traveling wave magnetic field to the outside of the submerged nozzle, and reduce the flow rate of the molten steel in the submerged nozzle through the electromagnetic force generated by the traveling wave magnetic field in the opposite direction of the flow direction of the molten steel, thereby increasing the pressure in the nozzle. However, the traveling wave magnetic field coil in this method cannot be water-cooled. If it is operated at high temperature for a long time, it may cause the coil to overheat. At the same time, the operating space in the submerged nozzle area is also limited. To this end, based on the above-mentioned problem, the present invention proposes a method and device for reducing the negative pressure of the nozzle by using a static magnetic field to solve the problem of nozzle nodules. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide an immersed nozzle negative pressure reduction method and device which can achieve the pressure difference balance inside and outside the nozzle under different continuous casting process parameters, thereby alleviating the nozzle blockage problem.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] According to one aspect of the present invention, a method for alleviating negative pressure of an immersion nozzle is provided, wherein an upward electromagnetic force is generated on molten steel in the immersion nozzle by a static magnetic field generating device located at a specified height of the immersion nozzle, and the method comprises the following steps:

[0008] According to the on-site casting speed, the size of the submerged nozzle and the casting section of the continuous casting, the flow velocity v of the molten steel in the submerged nozzle and the static pressure P inside the nozzle under different magnetic field strengths B and heights are calculated;

[0009] Obtain the magnetic induction intensity B and the specified height, determine the size of the static pressure P inside the submerged nozzle under the magnetic induction intensity B, and if P is greater than 0, output the corresponding magnetic induction intensity B as the target value;

[0010] The flow of the submerged nozzle is controlled according to the on-site casting speed and the pouring section, so that the molten steel in the tundish enters the crystallizer from the submerged nozzle. After the flow field of the molten steel is stable, the static magnetic field generating device is moved to the specified height of the submerged nozzle;

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

[0012] According to another aspect of the present invention, there is provided an immersed water inlet negative pressure relief device according to the foregoing method, comprising an immersed water inlet, a static magnetic field generating device and a moving device, wherein the static magnetic field generating device is located at the immersed water inlet, and the moving device is connected to the static magnetic field generating device.

[0013] Furthermore, a flow control device is provided at the water outlet of the immersion nozzle, and the flow control device 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.

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

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

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

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

[0019] Furthermore, the static magnetic field generating devices are arranged in pairs at the submerged water inlet.

[0020] Furthermore, the static magnetic field generating device generates a magnetic field strength of 0.1 to 5T.

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

[0022] (1) The present invention establishes the relationship between the flow rate of molten steel in the submerged nozzle at different heights and the static pressure inside the nozzle and the magnetic field strength according to the on-site pulling speed of continuous casting, the size of the submerged nozzle and the casting section. After the submerged nozzle is controlled, the static magnetic field generating device is moved to a specified height at the submerged nozzle, and the magnetic induction intensity of the magnetic field of the static magnetic field generating device is adjusted according to the established relationship, and the static pressure at the submerged nozzle is controlled to be positive, thereby solving the problem of secondary oxidation of molten steel caused by the negative pressure of the submerged nozzle. At the same time, the nozzle blockage rate can be greatly reduced, thereby improving the smooth process of continuous casting.

[0023] (2) The present invention sets a static magnetic field generating device at the immersed water nozzle, and the static magnetic field generated by the static magnetic field generating device generates an upward electromagnetic force on the molten steel at the immersed water nozzle, thereby reducing the flow rate of the molten steel in the immersed water nozzle, increasing the internal pressure of the water nozzle, and achieving the beneficial effect of avoiding air inhalation at the connection between the upper water nozzle of the tundish and the immersed water nozzle; the static magnetic field generating device is connected to a moving device including a transverse servo mechanism and a longitudinal servo mechanism, so that the installation position of the static magnetic field generating device at the immersed water nozzle is adjustable. By adjusting the strength of the static magnetic field and the installation position of the static magnetic field device, the balance of the pressure difference inside and outside the water nozzle can be achieved under different continuous casting process parameters.

[0024] (3) Compared with conventional argon blowing, the present invention utilizes the braking force generated by the static magnetic field to fill the nozzle with molten steel, which has the advantages of being contact-free and pollution-free, and can also avoid the subcutaneous bubbles and subcutaneous inclusion defects caused by conventional argon blowing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A flow chart of the method involved in the present invention;

[0026] Figure 2 The schematic diagram of using static magnetic field to mitigate negative pressure at water outlet;

[0027] Figure 3 This is a schematic diagram of a DC magnetic field generator device in a preferred embodiment 1 of the present invention;

[0028] Figure 4 It is a schematic diagram of a three-dimensional device of a DC magnetic field generator in a preferred embodiment 1 of the present invention;

[0029] Figure 5 The pressure distribution in the nozzle when a static magnetic field is applied or not;

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

[0031] In the figure, 1-immersed water nozzle, 2-static magnetic field generating device, 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-tundish, 12-upper water nozzle, 13-upper water nozzle-tundish connecting area, 14-crystallizer. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0035] The present invention provides a method and device for alleviating negative pressure of an immersion nozzle, which utilizes a static magnetic field to alleviate the negative pressure of the immersion nozzle, with the purpose of reducing the pressure difference between the inside and outside of the immersion nozzle during the continuous casting process. Figure 1 As shown, the method comprises the following steps:

[0036] Step 1: According to the on-site casting speed, the size of the immersion nozzle and the casting section, a coupled mathematical model of the magnetic field, flow field and temperature field in the immersion nozzle is established to calculate the flow velocity v of the molten steel in the immersion nozzle and the static pressure P inside the nozzle under different static magnetic field intensities;

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

[0038] Step 3: Open 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 nozzle. After the flow field is stable, move the static magnetic field generating device to a specified height near the submerged nozzle;

[0039] Step 4: Turn on the static magnetic field generating device 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, thereby reducing or avoiding the air inhalation at the connection between the upper nozzle of the tundish and the submerged nozzle, thereby achieving the purpose of increasing the internal pressure of the submerged nozzle.

[0040] An immersion nozzle negative pressure relief device of the present invention comprises an immersion nozzle 1, a static magnetic field generating device 2, and a moving device 3. Among them, the moving device 3 comprises a transverse servo mechanism 7, a longitudinal servo mechanism 8 and a base 9. The transverse servo mechanism 7 is connected to the longitudinal servo mechanism 8, and the longitudinal servo mechanism 8 is connected to the base 9. The static magnetic field generating device 2 is fixedly installed at the front end of the transverse servo mechanism 7. During the process of replacing the nozzle, the static magnetic field generating device 2 is moved by the transverse servo mechanism 7, and the longitudinal height of the static magnetic field generating device 2 is changed by the longitudinal servo mechanism 8. Preferably, the lifting height of the longitudinal servo mechanism 8 is 0 to 500 mm.

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

[0042] During use, a static magnetic field is applied to generate a braking force in the molten steel inside the immersion nozzle 1 in the opposite direction of the flow direction of the molten steel, thereby reducing the flow rate of the molten steel inside the immersion nozzle 1 and achieving the purpose of reducing the internal pressure of the immersion nozzle 1. Figure 2 As shown. The static magnetic field generating device 2 can be a DC magnetic field generator composed of a coil 4 and an iron core 5, or it can be neodymium iron boron. The magnetic field strength of the static magnetic field is 0.1 to 1 T to meet the magnetic field strength requirement of the static magnetic field to mitigate the negative pressure of the immersed water outlet. The number of static magnetic field generating devices 2 is an integer multiple of 2, and they are arranged in pairs at the immersed water outlet 1 to ensure a reasonable distribution of the magnetic field and a stable output of the magnetic field force. Preferably, the static magnetic field generating device 2 is mounted on a stainless steel base 6, and the stainless steel base 6 is used to provide protection for the static magnetic field generating device 2.

[0043] The specific implementation modes of the present invention are described below by way of examples.

[0044] Example 1

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

[0046] Step 1: For the continuous casting field conditions with a slab section of 1650×230mm, a casting speed of 1.2m / min, and an immersion nozzle inner diameter of 80mm, a coupled mathematical model of magnetic field, flow field, and temperature field in the immersion 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 rate, such as Figure 5 As shown;

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

[0048] Step 3: According to the above working conditions, the stopper rod is opened to allow the molten steel in the tundish to enter the crystallizer from the submerged nozzle. After the flow field is stable, the center of the DC magnetic field generator is aligned with the center of the submerged nozzle, and the center of the iron core is 500 mm away from the top surface of the crystallizer;

[0049] Step 4: Adjust the magnetic induction intensity to 0.5T through the background 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, thereby reducing or avoiding the air inhalation at the connection between the upper nozzle of the tundish and the submerged nozzle, thereby achieving the purpose of increasing the internal pressure of the submerged nozzle.

[0050] At this time, the pressure P1 at the characteristic point will increase, thereby avoiding the air inhalation at the connection between the tundish upper water inlet and the submerged water inlet, thereby achieving the purpose of increasing the internal pressure of the submerged water inlet.

[0051] This embodiment provides a method and device for using a DC magnetic field generator to generate a static magnetic field to reduce the negative pressure of an immersed water outlet, which can realize flexible adjustment of the static magnetic field strength, can effectively reduce or even alleviate the negative pressure problem of the water outlet, and has a simple structure and is easy to operate.

[0052] Example 2

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

[0054] Step 1 and step 2 are the same as step 1 and step 2 of the above embodiment 1;

[0055] Step 3: According to the above working conditions, the stopper rod is opened to allow the molten steel in the tundish to enter the crystallizer from the submerged nozzle. After the flow field is stable, the center of the NdFeB static magnetic field generator is aligned with the center of the submerged nozzle, with the center 500 mm away from the top surface of the crystallizer;

[0056] Step 4: Adjust the magnetic induction intensity to 0.5T through the background 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, thereby reducing or avoiding the air inhalation at the connection between the upper nozzle of the tundish and the submerged nozzle, thereby achieving the purpose of increasing the internal pressure of the submerged nozzle.

[0057] At this time, the pressure P1 at the characteristic point will increase, thereby avoiding the air inhalation at the connection between the tundish upper water inlet and the submerged water inlet, thereby achieving the purpose of increasing the internal pressure of the submerged water inlet.

[0058] This embodiment provides a device for reducing negative pressure at a water outlet by using a NdFeB magnetic field generator, which has a simple structure, is easy to operate and does not consume energy.

[0059] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for alleviating negative pressure of an immersed nozzle, characterized in that: An upward electromagnetic force is generated on the molten steel in the immersion nozzle (1) by a static magnetic field generating device (2) located at a specified height of the immersion nozzle (1), comprising the following steps: According to the on-site casting speed, the size of the submerged nozzle and the casting section of the continuous casting, the flow velocity v of the molten steel in the submerged nozzle and the static pressure P inside the nozzle under different magnetic field strengths B and heights are calculated; Obtaining the magnetic induction intensity B and the specified height, determining the magnitude of the static pressure P inside the submerged nozzle (1) under the magnetic induction intensity B, and if P is greater than 0, outputting the corresponding magnetic induction intensity B as the target value; The submerged nozzle is controlled according to the on-site casting speed and the pouring section, so that the molten steel in the tundish (11) enters the crystallizer (14) through the submerged nozzle (1), and after the flow field of the molten steel is stabilized, the static magnetic field generating device (2) is moved to a specified height at the submerged nozzle (1); The static magnetic field generating device (2) is turned on, and the magnetic induction intensity B is adjusted to the target value.

2. An immersion nozzle negative pressure relief device according to the method of claim 1, characterized in that: It comprises an immersion water inlet (1), a static magnetic field generating device (2) and a moving device (3), wherein the static magnetic field generating device (2) is located at the immersion water inlet (1), and the moving device (3) is connected to the static magnetic field generating device (2).

3. The device for reducing negative pressure of an immersion nozzle according to claim 2, characterized in that: A flow control device is provided at the water outlet of the submerged nozzle (1), and the flow control device is a stopper rod (10) or a sliding nozzle.

4. The device for reducing negative pressure of an immersion nozzle according to claim 2, characterized in that: The static magnetic field generating device (2) is a DC magnetic field generator or a neodymium iron boron.

5. The device for alleviating negative pressure of an immersion nozzle according to claim 4, characterized in that: The DC magnetic field generator comprises an iron core (5) and a coil (4).

6. The device for reducing negative pressure of an immersion nozzle according to claim 2, characterized in that: The moving device (3) comprises a transverse servo mechanism (7), a longitudinal servo mechanism (8) and a base (9), wherein the transverse servo mechanism (7) is connected to the longitudinal servo mechanism (8), the longitudinal servo mechanism (8) is connected to the base (9), and the base (9) is fixed on the continuous casting equipment where the submerged nozzle (1) is located.

7. The device for alleviating negative pressure of an immersion nozzle according to claim 6, characterized in that: The static magnetic field generating device (2) is fixedly mounted on the front end of the longitudinal servo mechanism (8).

8. The device for alleviating negative pressure of an immersion nozzle according to claim 6, characterized in that: The lifting height of the longitudinal servo mechanism is 0 to 500 mm.

9. The device for alleviating negative pressure of an immersion nozzle according to claim 2, characterized in that: The static magnetic field generating devices (2) are arranged in pairs at the submerged water inlet (1).

10. The device for alleviating negative pressure of an immersion nozzle according to claim 2, characterized in that: The static magnetic field generating device (2) generates a magnetic field strength of 0.1 to 5T.

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