Device and method for suppressing molten steel level fluctuation in crystallizer

Abstract

The present invention relates to a device and method for suppressing the fluctuation of the liquid level of molten steel in a crystallizer. The liquid level control device is a single-piece frame structure. The body is made of a high-melting-point and high-thermal-conductivity material, and the surface is sprayed with a high-thermal-conductivity refractory coating. The overall density is 4.0-7.0 g / cm 3 , capable of floating at the contact surface between the mold powder and the molten steel; the contact area between the stabilizing liquid level control device and the upper surface of the molten steel accounts for 20% to 80% of the total upper surface area of ​​the molten steel. The present invention effectively suppresses molten steel level fluctuations in the mold by using a stabilizing liquid level control device without changing the existing continuous casting process or affecting the normal addition of mold powder. The stabilizing liquid level control device has the advantages of high thermal conductivity, adjustable specific gravity, large coverage area for molten steel, multiple stabilizing liquid level control points, and no contamination of the molten steel. It is also simple to manufacture and easy to operate.

Description

Technical Field

[0001] The present invention relates to the technical field of continuous casting, and in particular to a device and method for suppressing fluctuation of molten steel level in a crystallizer. Background Art

[0002] High-efficiency continuous casting, characterized by high casting speeds, high quality, high efficiency, and high continuous casting rates, is the primary goal of continuous casting technology development. In all high-efficiency continuous casting operations, the stability of the molten steel level within the mold is crucial. Large fluctuations in the mold's molten steel level inevitably affect the casting speed, significantly limiting the efficient operation of the continuous casting machine and posing numerous quality and safety risks.

[0003] The hazards caused by large fluctuations in the molten steel level in the crystallizer are mainly manifested in the following aspects: (1) As the fluctuation of the crystallizer liquid level intensifies, the content of non-metallic inclusions under the surface of the ingot increases significantly, thereby deteriorating the surface quality of the final product; (2) The fluctuation of the crystallizer liquid level will affect the solidification of the meniscus steel liquid; (3) The liquid level fluctuation will affect the three-layer structure of the crystallizer protective slag, destroying the lubricity and heat transfer balance of the crystallizer protective slag; (4) Large fluctuations in the liquid level will cause slag to roll in the crystallizer molten steel, causing the content of inclusions inside the ingot to exceed the standard. In severe cases, it will cause serious production accidents such as longitudinal cracks in the ingot and steel leakage or slag inclusion and steel leakage. At present, most domestic steel mills have strict requirements on the fluctuation amplitude of the molten steel level in the crystallizer, generally requiring the fluctuation amplitude to be less than ±3mm.

[0004] At present, the research work on suppressing the fluctuation of molten steel in the crystallizer is mainly focused on the parameter design of the submerged nozzle, including the immersion depth, opening angle, etc., as well as the amount of argon blowing in the nozzle. In addition, the nozzle nodules can be improved by improving the purity of the molten steel, reducing the amount of argon blowing, and stabilizing the flow field distribution in the crystallizer; or the crystallizer flow field can be optimized by electromagnetic stirring, and the roller array can be optimized to weaken the impact of the molten steel backflow on the liquid surface and reduce the liquid surface fluctuation. However, the effect obtained by the above methods is not stable. Therefore, under the premise of ensuring that the submerged nozzle does not nodule, how to improve the effect of suppressing the fluctuation of the molten steel liquid level in the crystallizer, further remove the inclusions in the molten steel, stably obtain good ingot quality, and ensure the smooth operation of the continuous casting process is an urgent problem to be solved.

[0005] The Chinese patent application with publication number CN111097886A discloses a “steady-state casting process method for suppressing the fluctuation of the liquid level in a continuous casting mold”. The technical solutions adopted are: (1) controlling the interference amplitude of the superimposed frequency range of the fluctuations caused by the instability of the crystallizer liquid level to be the lowest; (2) controlling the fluctuations in the low-frequency range caused by the unstable bulging of the cast billet; (3) improving the equipment accuracy of the continuous casting machine head; and (4) using a new high-efficiency double-nozzle nozzle or a new pulse control nozzle.

[0006] The Chinese utility model patent with publication number CN217412397U discloses "a control device for suppressing liquid level fluctuations in a continuous casting crystallizer," which can improve the arc accuracy of the bending section and avoid large fluctuations in the molten steel level in the crystallizer due to unstable stress on the high-temperature solidified shell.

[0007] A Chinese patent application with publication number CN109676106A discloses "a method and device for controlling liquid level fluctuations in a continuous casting crystallizer." The method includes: judging whether the ingot in the continuous casting crystallizer has a tendency to bulge based on detection information; if it is judged that there is a tendency to bulge, determining a compensation amount for a stopper rod based on the detection information; and adjusting the position of the stopper rod according to the compensation amount to control the liquid level fluctuations in the continuous casting crystallizer.

[0008] Chinese patent application publication number CN115464130A discloses a "device for regulating mold liquid level fluctuations," comprising an electromagnetic swirl component disposed on the periphery of an immersed nozzle and an electromagnetic stirring component disposed on the periphery of the mold. The electromagnetic swirl component, when energized, controls the molten steel output from the immersed nozzle to rotate into the mold under the influence of its magnetic field. The electromagnetic stirring component controls the molten steel within the mold, which is then subjected to the electromagnetic stirring force, causing it to rotate within the mold. Because electromagnetic stirring generates flow from the outside in, while electromagnetic swirl generates flow from the inside out, the radial flow fields generated by the two balance each other, optimizing the flow and temperature distribution within the mold, reducing the impact depth of the molten steel at the nozzle, balancing the secondary flow within the mold, and thus suppressing mold liquid level fluctuations.

[0009] The Chinese patent application with publication number CN104624995A discloses "a device for suppressing fluctuations in the crystallizer liquid level at high pulling speeds", which includes a flow-gathering mechanism, a flow-dividing mechanism and a connecting mechanism. It can suppress fluctuations in the crystallizer liquid level at high pulling speeds, and can weaken the downward reflux intensity in the crystallizer, allowing most inclusions to move with the liquid flow to the surface of the molten steel and be absorbed by the protective slag. The coating layer on its surface can also absorb some inclusions, which can effectively remove inclusions in the molten steel.

[0010] As mentioned above, to stabilize the fluctuations in the molten steel level within the mold, the aforementioned public documents address various aspects, including reducing the frequency of molten steel level fluctuations, improving the accuracy of the curved section, online control of the stopper opening, optimizing electric field stirring process parameters, and reducing the intensity of molten steel reflux. However, these methods all suffer from difficulties in controlling operational precision and high equipment failure rates.

[0011] A Chinese patent application with publication number CN105798251A discloses a "method for controlling liquid level fluctuations in a continuous casting crystallizer," comprising: placing protective slag on the crystallizer liquid surface to form a protective slag layer; placing a flattening plate on the protective slag layer; wherein the contact surface between the flattening plate and the protective slag layer is flat, and the flattening plate remains on the protective slag layer without sinking into it. This method addresses the problem of excessive liquid level fluctuations in the crystallizer by using the protective slag layer and the flattening plate to achieve buffering and gradual weakening, thereby forcibly suppressing fluctuations. However, the method directly acts on the protective slag liquid surface, making it less efficient in suppressing molten steel level fluctuations and affecting the addition of protective slag. Summary of the Invention

[0012] The present invention provides a device and method for suppressing fluctuations in the liquid level of molten steel in a crystallizer. Without changing the existing continuous casting process operation and without affecting the normal filling of protective slag, a stable liquid level control device is used to effectively suppress fluctuations in the liquid level of molten steel in the crystallizer. The stable liquid level control device has the advantages of high thermal conductivity, adjustable specific gravity, large coverage area of ​​molten steel, multiple stable liquid level control points, and no pollution to the molten steel. The device is simple to manufacture and easy to operate.

[0013] In order to achieve the above object, the present invention adopts the following technical solutions:

[0014] A device for suppressing fluctuations in the liquid level of molten steel in a crystallizer, comprising a liquid level stabilizing control device; the liquid level stabilizing control device is a monolithic frame structure consisting of an outer frame and a fishbone-shaped rack disposed within the outer frame; the device body is made of a high-melting-point, high-thermal-conductivity material, and the surface is sprayed with a high-thermal-conductivity, refractory coating; the overall density of the liquid level stabilizing control device is 4.0 to 7.0 g / cm 3 , able to float on the contact surface between the protective slag and the molten steel in the crystallizer; the contact area between the stable liquid level control device and the upper surface of the molten steel accounts for 20% to 80% of the total area of ​​the upper surface of the molten steel; the horizontal position of the stable liquid level control device is limited by the submerged water nozzle or the inner wall of the crystallizer.

[0015] Furthermore, a positioning hole is provided in the middle of the stable liquid level control device, and the positioning hole is sleeved on the outer side of the immersion water outlet to achieve positioning.

[0016] Furthermore, a plurality of positioning plates are provided on the periphery of the stable liquid level control device, and the positioning plates are supported on the inner wall of the corresponding crystallizer to achieve positioning.

[0017] Furthermore, the width of a single skeleton in the fishbone-shaped rack is ≤20 mm, and the distance between two adjacent skeletons is ≥50 mm.

[0018] Furthermore, the maximum thickness of the stable liquid level control device is 10 mm.

[0019] Furthermore, the high melting point and high thermal conductivity material includes one or more of high temperature alloy, titanium and corundum.

[0020] Furthermore, the high thermal conductivity refractory coating is composed of one or more of molybdenum disilicide, hexagonal boron nitride and titanium diboride.

[0021] A method for suppressing molten steel level fluctuation in a crystallizer comprises the following steps:

[0022] 1) Make a stable liquid level control device;

[0023] First, the device body is manufactured, and then a high thermal conductivity refractory coating is sprayed on the outer surface material of the device body to modify the device body. The spraying process is as follows: the high thermal conductivity refractory material is crushed and sieved, and then high-speed ground at a speed of 4000-5000 r / min for 10-20 minutes to prepare a fine powder. The prepared fine powder is sprayed on the outer surface of the device body by a plasma spraying method or a laser cladding method to obtain a finished product.

[0024] 2) Place a stable liquid level control device into the crystallizer during the continuous casting process;

[0025] Before continuous casting begins, heat the stable liquid level control device to 600-1400℃ and fix it to the bottom of the tundish with steel wire. If the positioning hole is used for limiting, align the positioning hole with the immersed nozzle; if the inner wall of the crystallizer is used for limiting, align the outer end of the positioning plate with the corresponding inner wall of the crystallizer; after continuous casting begins, wait until the height of the molten steel level is stable, cut the steel wire, and let the stable liquid level control device slowly fall to the surface of the molten steel.

[0026] Furthermore, in step 1), the manufacturing process of the device body is as follows: the outer frame and the fishbone-shaped frame are both made of a composite material frame material, and the frame material is composed of a hollow tube made of 2050 high-temperature alloy or metal titanium filled with corundum; the volume ratio of 2050 high-temperature alloy to corundum is less than 3, and the volume ratio of metal titanium to corundum is greater than 0.5.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1) Without changing the existing continuous casting process and affecting the normal filling of mold slag, a stable liquid level control device is adopted to effectively suppress the fluctuation of the molten steel level in the crystallizer;

[0029] 2) The stable liquid level control device has the characteristics of large coverage area, multiple control points and small contact area. It is placed at the contact surface between the mold slag and the molten steel to suppress the formation of peaks in the liquid level fluctuation process. For the peaks that have been formed, the contact points between the skeleton plate and the liquid surface can buffer and weaken them, achieving forced leveling.

[0030] 3) Compared with the existing method for controlling the fluctuation of the molten steel level in the continuous casting crystallizer, the implementation effect of the present invention is more stable and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a front view of a device for suppressing fluctuations in the liquid level of molten steel in a crystallizer according to the present invention.

[0032] Figure 2 yes Figure 1 Top view of .

[0033] Figure: 1. Crystallizer 2. Immersed nozzle 3. Liquid level control device 31. Outer frame 32. Fishbone rack 33. Positioning holes 4. Molten steel 5. Continuous powder 6. Solidified shell DETAILED DESCRIPTION

[0034] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0035] like Figure 1 、 Figure 2 As shown in the figure, the device for suppressing the fluctuation of the liquid level of molten steel in the crystallizer of the present invention mainly includes a liquid level stabilizing control device 3. The body of the liquid level stabilizing control device 3 is made of a high melting point and high thermal conductivity material, and the outer surface is sprayed with a high thermal conductivity refractory material for modification. The overall density of the liquid level control device 3 is 4.0-7.0 g / cm 3 , and can float on the contact surface between the protective slag 5 and the molten steel 4.

[0036] Preferably, the contact area between the stable liquid level control device 3 and the upper surface of the molten steel 4 accounts for 20% to 80% of the total area of ​​the upper surface of the molten steel 4 .

[0037] Preferably, Figure 2 As shown, the stable liquid level control device 3 is a monolithic frame structure consisting of an outer frame 31 and fishbone-shaped frames 32. The width of a single frame in the fishbone-shaped frames 32 is ≤ 20 mm, and the spacing between two adjacent frames is ≥ 50 mm. This design features a large coverage area, multiple control points, and a small contact area, which can minimize the impact on heat transfer between the mold slag 5 and the molten steel 4 and the absorption of inclusions by the mold slag 5.

[0038] Preferably, the maximum thickness of the stable liquid level control device 3 is 10 mm.

[0039] Preferably, the material of the body of the stable liquid level control device 3 includes but is not limited to one or more of high thermal conductivity and high melting point materials such as high temperature alloy, titanium (Ti), and corundum.

[0040] Preferably, the material used to modify the outer surface of the body of the stabilizing liquid level control device 3 includes but is not limited to one or more of high thermal conductivity refractory materials such as molybdenum disilicide (MoSi2), hexagonal boron nitride (HBN), and titanium diboride (TiB2).

[0041] Preferably, a positioning hole 33 is provided in the middle of the stable liquid level control device 3 or a positioning plate is provided on the periphery thereof, so as to limit its position on the surface of the molten steel 4 by means of the submerged nozzle 2 or the inner wall of the crystallizer 1. The stable liquid level control device 3 can be placed at any position on the contact surface between the mold slag 5 and the molten steel 4.

[0042] Preferably, the device for suppressing the fluctuation of the molten steel level in the crystallizer according to the present invention is prepared by the following method:

[0043] (1) The manufacturing process of the device body is as follows: the outer frame 31 and the fishbone-shaped rack 32 are both made of composite material, and the rack is composed of a hollow tube made of 2050 high-temperature alloy or metal titanium filled with corundum; the volume ratio of 2050 high-temperature alloy to corundum is less than 3, and the volume ratio of metal titanium to corundum is greater than 0.5.

[0044] (2) The spraying process of the high thermal conductivity refractory material coating is as follows: the high thermal conductivity refractory material is crushed and sieved, and then high-speed ground at a speed of 4000-5000 r / min for 10-20 minutes to prepare a fine powder; the prepared fine powder is sprayed on the outer surface of the device body by a plasma spraying method or a laser cladding method to obtain a finished product;

[0045] The method for using the device for suppressing fluctuations of the molten steel level in the crystallizer according to the present invention, that is, the method for suppressing fluctuations of the molten steel level in the crystallizer, is as follows:

[0046] Before continuous casting begins, heat the stable liquid level control device 3 and fix it to the bottom of the tundish with a steel wire. If the positioning hole 33 is used for limiting, align the positioning hole 33 with the submerged nozzle 2; if the inner wall of the crystallizer 1 is used for limiting, align the outer end of the positioning plate with the corresponding inner wall of the crystallizer 1; after continuous casting begins, wait until the liquid level of the molten steel 4 is stable, cut the steel wire, and slowly lower the stable liquid level control device 3 to the surface of the molten steel 4.

[0047] Preferably, the liquid level stabilizing control device 3 is heated to 600-1400° C. and then thrown onto the surface of the molten steel 4 .

[0048] Furthermore, the liquid level stabilizing control device 3 is heated to 1000-1400° C. and then thrown onto the surface of the molten steel 4 .

[0049] Furthermore, the liquid level stabilizing control device 3 is heated to 1300-1400° C. and then thrown onto the surface of the molten steel 4 .

[0050] The following examples are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operating processes, but the protection scope of the present invention is not limited to the following examples.

[0051] [Example 1]

[0052] This embodiment uses a double-strand slab continuous casting machine as the carrier, the cross-section of the crystallizer 1 is 1200mm×230mm, and the casting speed is 1m / min. Among them, one stream is conventionally cast, and the second stream is placed on the surface of the molten steel 4 with a stable liquid level control device 3.

[0053] The contact area between the liquid level control device 3 and the upper surface of the molten steel 4 accounts for 50% of the total area of ​​the upper surface of the molten steel 4; the liquid level control device 3 is a single-piece frame structure with a central opening, and its overall dimensions are 860mm×160mm×8mm, and the aperture of the positioning hole is The width of a single frame is 20mm, and the distance between two adjacent frames is 80mm.

[0054] The preparation process of the stable liquid level control device 3 is as follows:

[0055] (1) Manufacturing the device body: 2050 high-temperature alloy is machined to meet the required size, with a thickness of 8 mm, and filled with corundum. The volume ratio of 2050 high-temperature alloy to corundum is 2:1, and the overall density is 6.7 g / cm 3 .

[0056] (2) Powdering: Crush molybdenum disilicide (MoSi2), pass through a 200-mesh sieve, and grind at a high speed of 4500 r / min for 20 minutes to make a fine powder.

[0057] (3) Spraying: The fine powder prepared in step (2) is sprayed onto the surface of the device body prepared in step (1) by plasma spraying, and the surface material is modified to obtain the finished product of the stable liquid level control device 3.

[0058] After heating the stable liquid level control device 3 to 1100℃, fix it to the bottom of the ladle with steel wire, align the positioning hole with the submerged nozzle 2, and after continuous casting starts, wait until the liquid level of the molten steel 4 is stable, cut the steel wire and let the stable liquid level control device 3 slowly fall to the surface of the molten steel 4.

[0059] This embodiment carries out continuous casting production of three tanks of molten steel. During the entire casting process, the fluctuation of the liquid level of stream 1 is ±5mm, and the fluctuation of the liquid level of stream 2 is ±3mm.

[0060] [Example 2]

[0061] This embodiment uses a double-strand slab continuous casting machine as the carrier, the cross-section of the crystallizer 1 is 1200mm×230mm, and the casting speed is 1m / min. Among them, one stream is conventionally cast, and the second stream is placed on the surface of the molten steel 4 with a stable liquid level control device 3.

[0062] The contact area between the liquid level control device 3 and the upper surface of the molten steel 4 accounts for 60% of the total area of ​​the upper surface of the molten steel 4; the liquid level control device 3 is a single-piece frame structure with a central opening, and its overall dimensions are 950mm×175mm×6mm, and the aperture of the positioning hole is The width of a single frame is 18mm, and the distance between two adjacent frames is 60mm.

[0063] The preparation process of the stable liquid level control device 3 is as follows:

[0064] (1) Manufacturing the device body: Titanium metal is machined to the required size, with a thickness of 6 mm, and filled with corundum. The volume ratio of titanium metal to corundum is 2:1, and the overall density is 4.3 g / cm 3 .

[0065] (2) Powdering: Crush molybdenum disilicide (MoSi2), pass through a 200-mesh sieve, and grind at a high speed of 5000 r / min for 15 minutes to make a fine powder.

[0066] (3) Spraying: The fine powder prepared in step (2) is sprayed onto the surface of the device body prepared in step (1) by laser cladding to modify the surface material, thereby obtaining a finished product of the stable liquid level control device 3.

[0067] After heating the stable liquid level control device 3 to 1200℃, fix it to the bottom of the ladle with steel wire, align the positioning hole with the submerged nozzle 2, and after continuous casting starts, wait until the liquid level of the molten steel 4 is stable, cut the steel wire and let the stable liquid level control device 3 slowly fall to the surface of the molten steel 4.

[0068] This embodiment carries out continuous casting production of three tanks of molten steel. During the entire casting process, the fluctuation of the liquid level of stream 1 is ±5mm, and the fluctuation of the liquid level of stream 2 is ±2mm.

[0069] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A device for suppressing fluctuations in the level of molten steel in a crystallizer, characterized in that: The invention comprises a stable liquid level control device; the stable liquid level control device is a single-piece frame structure, consisting of an outer frame and a fishbone-shaped rack arranged inside the outer frame; the device body is made of a high-melting-point and high-thermal-conductivity material, and the surface is sprayed with a high-thermal-conductivity refractory coating; the overall density of the stable liquid level control device is 4.0-7.0 g / cm 3 , able to float on the contact surface between the protective slag and the molten steel in the crystallizer; the contact area between the stable liquid level control device and the upper surface of the molten steel accounts for 20% to 80% of the total area of ​​the upper surface of the molten steel; the horizontal position of the stable liquid level control device is limited by the submerged water nozzle or the inner wall of the crystallizer.

2. The device for suppressing the fluctuation of the molten steel level in the crystallizer according to claim 1, characterized in that: A positioning hole is provided in the middle of the stable liquid level control device, and the positioning hole is sleeved on the outer side of the immersion water outlet to achieve positioning.

3. The device for suppressing the fluctuation of the molten steel level in the crystallizer according to claim 1, characterized in that: A plurality of positioning plates are provided on the periphery of the stable liquid level control device, and the positioning plates are supported on the inner wall of the corresponding crystallizer to achieve positioning.

4. The device for suppressing the fluctuation of the molten steel level in the crystallizer according to claim 1, characterized in that: The width of a single skeleton of the fishbone-shaped rack is ≤20 mm, and the distance between two adjacent skeletons is ≥50 mm.

5. The device for suppressing the fluctuation of the molten steel level in the crystallizer according to claim 1, characterized in that: The maximum thickness of the stable liquid level control device is 10 mm.

6. The device for suppressing the fluctuation of the molten steel level in the crystallizer according to claim 1, characterized in that: The high melting point and high thermal conductivity material includes one or more of high temperature alloy, titanium and corundum.

7. The device for suppressing the fluctuation of the molten steel level in the crystallizer according to claim 1, characterized in that: The high thermal conductivity refractory material coating is composed of one or more of molybdenum disilicide, hexagonal boron nitride and titanium diboride.

8. A method for suppressing fluctuations in the level of molten steel in a crystallizer based on the device according to any one of claims 1 to 7, characterized in that: The steps include: 1) Make a stable liquid level control device; First, the device body is manufactured, and then a high thermal conductivity refractory coating is sprayed on the outer surface material of the device body to modify the device body. The spraying process is as follows: the high thermal conductivity refractory material is crushed and sieved, and then high-speed ground at a speed of 4000-5000 r / min for 10-20 minutes to prepare a fine powder. The prepared fine powder is sprayed on the outer surface of the device body by a plasma spraying method or a laser cladding method to obtain a finished product. 2) Place a stable liquid level control device into the crystallizer during the continuous casting process; Before continuous casting begins, heat the stable liquid level control device to 600-1400℃ and fix it to the bottom of the tundish with steel wire. If the positioning hole is used for limiting, align the positioning hole with the immersed nozzle; if the inner wall of the crystallizer is used for limiting, align the outer end of the positioning plate with the corresponding inner wall of the crystallizer; after continuous casting begins, wait until the height of the molten steel level is stable, cut the steel wire, and let the stable liquid level control device slowly fall to the surface of the molten steel.

9. The method for suppressing the fluctuation of the molten steel level in the crystallizer according to claim 8, characterized in that: In step 1), the manufacturing process of the device body is as follows: the outer frame and the fishbone-shaped frame are both made of a composite material frame material, and the frame material is composed of a hollow tube made of 2050 high-temperature alloy or metal titanium and filled with corundum; the volume ratio of 2050 high-temperature alloy to corundum is less than 3, and the volume ratio of metal titanium to corundum is greater than 0.5.

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