Submersed nozzle for improving flowing stability of molten steel of crystallizer

Abstract

The invention discloses a submersed nozzle for improving the flowing stability of molten steel of a crystallizer, relates to the technical field of continuous casting of ferrous metallurgy, and comprises a nozzle body structure design and an anti-nodulation lining material design. Compared with the scheme of the cross sectional areas of other middle holes and side holes, the submersed nozzle for improving the flowing stability of the molten steel of the crystallizer has remarkable advantages. By means of the structure, the problem that due to the fact that the ratio of the cross section areas of the side holes to the middle holes is too large, the flowing-out speed of molten steel is too high, and the liquid level fluctuates violently is avoided, and the problem that due to the fact that the ratio of the cross section areas of the side holes to the middle holes is too small, sufficient kinetic energy cannot be obtained when the molten steel flows out, and overall flowing of the molten steel is unstable is solved. The curve of the submersed nozzle is gentle, fluctuation consistency is high, molten steel impact energy can be effectively dispersed, fluctuation of the liquid level is restrained, and the risk that casting powder is involved in is reduced. In the aspect of flow field regulation and control, the structure does not have an abrupt peak value of the flow velocity, and also avoids the problem of flow velocity distribution disorder.

Description

Technical Field

[0001] This application belongs to the field of continuous casting technology in iron and steel metallurgy, and particularly relates to an immersion nozzle for improving the stability of molten steel flow in a crystallizer. Background Technology

[0002] The submerged entry nozzle is a core functional component in slab continuous casting production. Installed at the bottom of the tundish, its lower end is immersed in the molten steel within the crystallizer. Its primary function is to smoothly guide the molten steel from the tundish to the crystallizer, preventing secondary oxidation caused by direct contact between the molten steel and air. Simultaneously, through structural design, it regulates the molten steel flow pattern, velocity distribution, and impact depth, directly affecting the flow stability, temperature uniformity, and inclusion flotation efficiency within the crystallizer. It is a crucial component for ensuring the surface quality, internal purity, and production continuity of the cast slab.

[0003] The core development direction of continuous casting technology is to increase casting speed while ensuring product quality, thereby enhancing production efficiency. However, high casting speed will disrupt the original dynamic balance within the crystallizer, leading to a series of technical problems: the heat flux density of the crystallizer increases significantly, resulting in a thinner solidified billet shell at the outlet, and a significant increase in the friction between the billet shell and the crystallizer wall, which can easily cause serious production accidents such as bulging and steel leakage.

[0004] For thin slab continuous casting, the molten pool space inside the crystallizer is small, the copper plates are closely spaced, and the resistance to molten steel flow is relatively large, which places higher demands on the flow field control capability of the submerged entry nozzle. To alleviate the defects caused by high casting speed, the industry generally adopts a combination of funnel-shaped crystallizer and bullnose submerged entry nozzle. The funnel-shaped crystallizer helps melt the protective slag and suppresses turbulence by increasing the surface area of ​​the upper opening, while the bullnose nozzle, as the core component for guiding molten steel, directly determines the molten steel diversion effect and flow field stability.

[0005] However, existing submerged entry nozzles still have many insurmountable defects: First, the outlet area is not precisely matched to the design, resulting in an imbalance between the side and bottom outlet flow rates. Either the side flow rate is insufficient to form a stable backflow, or the bottom flow rate is too large, causing excessive impact and further damaging the flow field stability. Second, the bottom structure design is inappropriate. A convex bottom design cannot buffer the turbulent energy of the molten steel, which will aggravate the surface fluctuations. A concave bottom design causes the molten steel to stay in the nozzle for too long, making it difficult for inclusions to float out, which can easily lead to nozzle nodules or inclusions in the cast billet. Third, the inner wall of the nozzle lacks an effective anti-nodule design. Inclusions and alloying elements in the molten steel are easy to adhere and deposit, which narrows the flow channel and further damages the flow stability and temperature field uniformity of the molten steel. Summary of the Invention

[0006] To address some or all of the technical problems existing in the prior art, this application provides an immersion nozzle for improving the stability of molten steel flow in a crystallizer.

[0007] This application provides an immersion nozzle for improving the stability of molten steel flow in a crystallizer, comprising a nozzle body and an anti-caking liner. The nozzle body adopts a three-outlet diversion structure, with side outlets symmetrically opened on the left and right sides of the nozzle body and a central outlet opened at the bottom center of the nozzle body. The side outlets are inclined downwards, and the anti-caking liner is disposed on the inner wall of the nozzle body.

[0008] Preferably, an inlet is provided at the top of the sprue body, and the inlet communicates with the central hole outlet and the side hole outlet.

[0009] Preferably, the downward tilt angle of the side hole outlet is 25°.

[0010] Preferably, the area ratio of the side hole outlet to the center hole outlet is 1.5.

[0011] Preferably, the size of the side hole outlet is 75×60mm. 2 The size of the central hole outlet is 50×60mm. 2 , .

[0012] Preferably, the size of the inlet is 120×60mm. 2 .

[0013] Preferably, the anti-nodulation liner is made of zirconium oxide-carbon composite material.

[0014] Preferably, the anti-caking liner has a uniform thickness and is tightly bonded to the sprue body.

[0015] The submerged entry nozzle of this application for improving the flow stability of molten steel in a crystallizer has the following advantages and positive effects: The three-outlet submerged nozzle structure adopted in this technical solution has several advantages. Regarding liquid surface stability, this structure avoids the severe fluctuations in the liquid surface caused by excessively high molten steel flow velocity due to an excessively large ratio of the cross-sectional areas of the side holes and the central hole, while also overcoming the problem of insufficient kinetic energy for molten steel flow due to an excessively small ratio, leading to overall instability in the molten steel flow. The submerged nozzle in this patent application exhibits the smoothest flow curve and strong consistency in fluctuations, effectively dispersing the impact energy of the molten steel, suppressing liquid surface fluctuations, and reducing the risk of slag entrapment. In terms of flow field control, this structure avoids both abrupt velocity peaks and disordered velocity distribution. After flowing out, the molten steel forms a symmetrical backflow within the crystallizer, with stable flow in the central region and gradually decreasing velocity on both sides, ensuring a continuous, uniform, and stable flow field.

[0016] In terms of temperature field distribution, it exhibits a state of "stable center and gentle temperature decrease on both sides," without any excessive local temperature differences. This ensures the consistency of heat dissipation and solidification of molten steel within the crystallizer and reduces solidification defects caused by uneven billet shell thickness. Regarding the flow diversion effect, this structure balances the requirements of "smooth flow" and "sufficient residence time," resulting in an appropriate impact depth of molten steel. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are only for further understanding of the embodiments of this application and constitute a part of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the submersible nozzle structure of this application; Figure 2 This is a diagram showing the corresponding dimensions of the three outlets of the submersible nozzle in this application; Figure 3 This is a comparison diagram of the effects of different nozzle structures on liquid level fluctuations in this application; Figure 4 This is a comparison diagram of the effects of different nozzle structures on surface flow velocity in this application; Figure 5 This is a velocity distribution curve along the center line of the top surface of the crystallizer in this application; Figure 6 This is a temperature distribution curve along the center line of the top surface of the crystallizer in this application.

[0018] Attached reference numerals: 1-Water inlet body, 2-Side hole outlet, 3-Central hole outlet, 4-Inlet. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0020] like Figure 1As shown, the submerged nozzle of this application for improving the flow stability of molten steel in a crystallizer includes a nozzle body 1 and an anti-caking liner. The nozzle body 1 adopts a three-outlet diversion structure. Side outlets 2 are symmetrically opened on the left and right sides of the nozzle body 1, and a central outlet 3 is opened at the bottom center of the nozzle body 1. This divides the molten steel into three streams, disperses the impact energy, and avoids flow field turbulence caused by a single outlet or too many outlets. The side outlets 2 are inclined downwards and guide the molten steel to flow smoothly along the narrow wall. The central outlet 3 replenishes the lower molten steel. The anti-caking liner is installed on the inner wall of the nozzle body 1. An inlet 4 is opened at the top of the nozzle body 1, and the inlet 4 is connected to the central outlet 3 and the side outlets 2.

[0021] The anti-nodulation liner is made of zirconium oxide-carbon composite material. The anti-nodulation liner has a uniform thickness and is tightly bonded to the nozzle body 1. It can isolate the high-temperature molten steel from the nozzle body. By utilizing the anti-adhesion properties of the composite material, it reduces the adhesion and deposition of inclusions and alloy elements, thus preventing nodulation.

[0022] Preferably, a suitable electromagnetic braking device can be installed on the outside of the crystallizer. The magnetic induction intensity first increases and then decreases with the height above the free liquid surface. The area of ​​magnetic field action corresponds precisely to the flow field of molten steel. The magnetic induction intensity has a parabolic distribution and can produce a targeted braking effect. The maximum magnetic induction intensity is 0.132 T.

[0023] The downward inclination angle of side outlet 2 is 25°, and the area ratio of side outlet 2 to center outlet 3 is 1.5. This 1.5 area ratio design allows for a more reasonable flow distribution between side outlet 2 and center outlet 3: the slightly larger total area of ​​side outlet 2 guides sufficient molten steel to flow smoothly along the narrow wall of the crystallizer, forming a stable upper backflow; the bottom center outlet 3 ensures sufficient replenishment of molten steel at the bottom of the crystallizer without causing excessive impact due to excessive flow at the bottom.

[0024] like Figure 2 As shown, this application provides an embodiment with specific dimensions; specifically, the dimensions of the side hole outlet 2 are 75 × 60 mm. 2 75mm corresponds to Figure 2 In the middle hole D2, the dimensions of the outlet 3 are 50×60mm. 2 50mm corresponds to Figure 2 In D1, the dimensions of inlet 4 are 120×60mm. 2 120mm corresponds to Figure 2 D3 in the figure. And 60mm is the width dimension of the openings of the side hole outlet 2, the central hole outlet 3, and the inlet 4. Therefore, this application provides applications of slabs with two specific cross-sectional dimensions using this embodiment: Application 1: Applicable cross-section: 120mm×1400mm slab; drawing speed: 5.5m / min; immersion depth: 255mm; Performance effect: Liquid level fluctuation ≤ ±2mm; When used in conjunction with an electromagnetic braking device: the magnetic induction intensity first increases and then decreases with the height above the free liquid surface, and the magnetic induction intensity distribution presents a parabolic shape, with a maximum magnetic induction intensity of 0.132T.

[0025] Application 2: Applicable cross-section: 100mm×1200mm slab; drawing speed: 5m / min; immersion depth: 255mm; Performance effect: Liquid level fluctuation ≤ ±2mm; When used in conjunction with an electromagnetic braking device: the magnetic induction intensity first increases and then decreases with the height above the free liquid surface, and the magnetic induction intensity distribution presents a parabolic shape, with a maximum magnetic induction intensity of 0.132T.

[0026] It is evident that this submersible inlet can effectively reduce liquid level fluctuations.

[0027] Based on the above, experimental tests were conducted, with water inlet number 3 selected. The test results are as follows: like Figure 3 As shown, three monitoring points were set up to measure liquid level fluctuations. The horizontal axis represents the monitoring location in different areas within the crystallizer, used to capture liquid level fluctuations in different regions; the vertical axis represents the liquid level difference, reflecting the stability of the free liquid surface. Numbers 1-9 correspond to nine different nozzle schemes with varying ratios of side and center orifice cross-sectional areas. Each curve represents the liquid level fluctuation performance of one type of outlet at different monitoring locations. Larger curve fluctuations indicate more severe liquid level fluctuations; a smoother curve indicates better liquid level stability.

[0028] like Figure 4 As shown, four points were set up to measure the surface velocity of the free liquid. The horizontal axis represents the lateral position within the crystallizer, and the vertical axis represents the flow velocity of the molten steel. Numbers 1-9 correspond to different nozzle schemes with varying ratios of side and central hole cross-sectional areas. The peak value and uniformity of the curves reflect the flow field state. Excessively high peak values ​​indicate excessively high local velocities, which can easily lead to turbulence; uneven distribution indicates poor molten steel flow distribution, which is detrimental to solidification uniformity.

[0029] like Figure 5 As shown, the horizontal axis represents the lateral distance from both sides of the nozzle to the narrow wall of the crystallizer, extending outwards from the nozzle as the center; the vertical axis represents the flow velocity of the molten steel. The molten steel velocity is relatively flat in the central area where the nozzle is located, gradually increasing towards the narrow walls on both sides without any abrupt peaks. Overall, it exhibits a symmetrical and stable distribution, demonstrating the precise control of the flow velocity by the three-outlet diversion.

[0030] like Figure 6As shown, the horizontal axis represents the lateral distance from both sides of the nozzle to the narrow wall of the crystallizer, extending outwards from the nozzle as the center; the vertical axis represents the temperature of the molten steel. The temperature of the molten steel in the central area of ​​the nozzle is stable, while the temperature changes gently as it extends towards the narrow walls on both sides, without localized sudden cooling or overheating. This reflects the uniformity of the temperature field within the crystallizer, ensuring uniform solidification of the billet shell.

[0031] from Figures 3 to 6 Therefore, the advantages of this application can be deduced as follows: from Figure 3 It can be seen that the curve of the scheme with an excessively large ratio of the cross-sectional area of ​​the side holes to the central hole fluctuates violently, indicating that the flow rate in the side holes is concentrated under this structure, and the impact energy of the molten steel cannot be effectively dispersed, resulting in a significant increase in the fluctuation amplitude of the liquid surface and making it easy to cause slag entrapment. The curve of the scheme with an excessively small ratio of the cross-sectional area of ​​the side holes to the central hole is relatively flat, but there are still local fluctuation peaks. The essence is that the flow diversion capacity of the side holes is insufficient, and the energy of the molten steel is concentrated in the central hole and diffused unevenly, making it impossible to achieve a stable liquid surface state throughout the process. In contrast, the submerged nozzle structure of this application (the cross-sectional area ratio of the side holes to the central hole is 1.5, i.e., nozzle 3) has the flattest curve corresponding to the area ratio applied, and the fluctuation consistency is strong at all monitoring positions. This proves that the submerged nozzle structure of this application can effectively disperse the impact energy, suppress violent fluctuations of the liquid surface, and reduce the risk of slag entrapment.

[0032] As shown in Figure 4, schemes with an excessively large ratio of side-hole to center-hole cross-sectional areas exhibit significant velocity peaks, leading to excessively high local velocities and turbulence. Conversely, schemes with an excessively small ratio result in disordered velocity distribution due to dispersed outlets, with localized areas exhibiting excessively low velocities that negatively impact molten steel circulation. The submerged entry nozzle structure of this application utilizes a curve with no abrupt peaks corresponding to the area ratio, exhibiting a continuous and uniform velocity distribution. Figure 5 The velocity field distribution shows that after the molten steel flows out from the three outlets, it forms a symmetrical backflow. The middle region is stable and the sides gradually change, which avoids the problems of local turbulence and poor flow and ensures the stability of the flow field.

[0033] Compared with other area ratio schemes, the temperature field performance of the submerged nozzle structure in this application, as shown in Figure 6, exhibits a temperature distribution of "stable center and mild variation on both sides," without any excessive local temperature differences. This uniform temperature field ensures consistent heat dissipation and solidification of the molten steel within the crystallizer, avoiding uneven billet shell thickness caused by localized overcooling and reducing solidification defects.

[0034] In designs where the ratio of the side holes to the central hole cross-sectional area is too large, the molten steel flows out at an excessively high velocity, resulting in a deep impact depth and hindering the upward movement of inclusions. Conversely, in designs where the ratio is too small, the molten steel flows out at an excessively low velocity, failing to effectively divert the flow. Furthermore, the residence time of the molten steel becomes unreasonable; excessively long residence times in some areas lead to inclusion deposition, while excessively short residence times prevent proper separation and disrupt the stability of the flow field. This invention's three-outlet structure... Figures 3 to 6The overall performance shows that its diversion effect perfectly balances the requirements of "smooth flow" and "sufficient residence time". The impact depth of the molten steel is appropriate, which creates favorable conditions for the floating of inclusions and improves the purity of the billet.

[0035] The specific workflow is as follows: First, the submerged entry nozzle is installed at the preset position on the crystallizer, and the immersion depth is adjusted to a suitable range to ensure that the molten steel is evenly distributed among the three outlets, and that the distance between the outlets and the narrow wall of the crystallizer is reasonable to avoid direct impact. Then, a protective slag of appropriate thickness is laid to ensure coverage of the free surface. Based on the nozzle structure and crystallizer specifications, an appropriate continuous casting speed is set to ensure the filling rate of the molten steel within the nozzle and the stability of the outflow. After continuous casting production is started, the molten steel flows into inlet 4 through the tundish and is evenly divided into three streams under the guidance of the internal flow channels: the downward-sloping stream from the side outlet 2 flows smoothly downwards along the narrow wall, forming an upper backflow; the stream from the bottom central outlet 3 replenishes the lower molten steel, forming a lower backflow, together constructing a stable and symmetrical flow field. During this process, the anti-caking lining inhibits the adhesion of inclusions to the inner wall of the nozzle, maintaining unobstructed flow; the electromagnetic braking device is activated, precisely braking the molten steel with a parabolic magnetic field force to suppress excessive turbulence, working in conjunction with the three-outlet structure to stabilize the flow and temperature fields. The molten steel flows smoothly and solidifies evenly in the crystallizer, allowing inclusions to float to the surface and be adsorbed by the protective slag, ultimately forming a high-quality billet and completing the continuous casting production.

[0036] It should be noted that, unless otherwise expressly specified and limited, the term "connection" or its synonyms should be interpreted broadly in this document. For example, "connection" can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. Furthermore, expressions such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. At the same time, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. In addition, the terms "front," "rear," "left," "right," "upper," and "lower" in this document refer to the placement states shown in the accompanying drawings.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. An immersion nozzle for improving the stability of molten steel flow in a crystallizer, comprising a nozzle body (1) and an anti-caking liner, wherein the nozzle body (1) adopts a three-outlet diversion structure, side outlets (2) are symmetrically provided on the left and right sides of the nozzle body (1), and a central outlet (3) is provided at the bottom center of the nozzle body (1), wherein the side outlets (2) are inclined downwards, and the anti-caking liner is provided on the inner wall of the nozzle body (1).

2. The submerged entry nozzle for improving the flow stability of molten steel in a crystallizer according to claim 1, characterized in that, An inlet (4) is provided at the top of the water inlet body (1), and the inlet (4) is connected to the central hole outlet (3) and the side hole outlet (2).

3. The submerged entry nozzle for improving the flow stability of molten steel in a crystallizer according to claim 2, characterized in that, The downward inclination angle of the side hole outlet (2) is 25°.

4. The submerged entry nozzle for improving the flow stability of molten steel in a crystallizer according to claim 3, characterized in that, The area ratio of the side hole outlet (2) to the center hole outlet (3) is 1.

5.

5. The submerged entry nozzle for improving the flow stability of molten steel in a crystallizer according to claim 4, characterized in that, The side outlet (2) has a size of 75×60mm. 2 The size of the central hole outlet (3) is 50×60mm. 2 .

6. The submerged entry nozzle for improving the flow stability of molten steel in a crystallizer according to claim 5, characterized in that, The inlet (4) has a size of 120×60mm. 2 .

7. The submerged entry nozzle for improving the flow stability of molten steel in a crystallizer according to claim 1, characterized in that, The anti-nodulation liner is made of zirconium oxide-carbon composite material.

8. The submerged entry nozzle for improving the flow stability of molten steel in a crystallizer according to claim 7, characterized in that, The anti-caking liner has a uniform thickness and is tightly bonded to the main body of the water inlet (1).

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