A method and system for optimizing design of a crystallizer arc-shaped nozzle for suppressing slag entrapment

Abstract

The application discloses a kind of crystallizer arc-shaped nozzle optimization design method and system for inhibiting slag winding, related to steel continuous casting production technical field, the method includes: nozzle area calculation is carried out, to ensure that the area of arc-shaped nozzle side outlet after optimization is equal with before optimization;Based on preset bending curvature parameter, the long side and the wide side of nozzle side outlet are respectively designed with arc bending, to form arc curved surface structure;Round corner transition is set at the intersection of arc-shaped edge;Three-dimensional model is constructed and sample piece is made to carry out hydraulics physical simulation experiment;The optimization effect is verified by comparing liquid level fluctuation and slag winding frequency.The application transforms straight edge rectangular side hole into arc curved surface outlet with equal area, significantly improves the flow field distribution in crystallizer, effectively inhibits the winding of protective slag and liquid level fluctuation, and the experimental results show that the fluctuation amplitude is reduced by an average of 31.9%, and the slag winding frequency is reduced by an average of 62.4%, which provides reliable technical support for high-quality steel continuous casting production.

Description

Technical Field

[0001] This invention relates to the field of steel continuous casting production technology, and in particular to a method and system for optimizing the design of arc-shaped nozzles in crystallizers to suppress slag entrapment. Background Technology

[0002] In continuous casting, the crystallizer, as the core equipment for solidification and forming of molten steel, has a decisive influence on the quality of the cast billet due to the flow behavior of the molten steel inside. The submerged entry nozzle is a key functional component connecting the tundish and the crystallizer; its outlet structure directly determines the flow field distribution, surface fluctuation, and slag entrapment behavior of the molten steel within the crystallizer. A reasonable flow field distribution helps reduce the amplitude of slag-metal interface fluctuations, decrease slag entrapment frequency, promote the flotation and removal of non-metallic inclusions in the molten steel, and avoid subsurface and internal defects in the cast billet.

[0003] Currently, most conventionally used submerged entry nozzles for crystallizers employ rectangular or straight-edged side hole structures. In production practice, the kinetic energy of the molten steel stream output from these straight-edged nozzles is relatively concentrated, easily forming strong impacts and backflows near the narrow face of the crystallizer. This leads to severe local fluctuations in the liquid surface, resulting in a significant increase in the frequency of slag entrapment. Simultaneously, the flow channel structure inside traditional straight-edged nozzles has limited guiding effect on the molten steel, making it difficult to precisely control the ratio of "upper circulating flow" to "lower returning flow" within the crystallizer, which is detrimental to the effective removal of inclusions. Furthermore, under high-speed production conditions, the aforementioned flow field instability and slag entrapment problems become more prominent, becoming one of the bottlenecks restricting the high-efficiency and high-quality production of continuous casting.

[0004] To address the aforementioned issues, while the industry has attempted improvements such as adjusting the inclination angle of the nozzle side holes and altering the outlet shape, most solutions only involve adjusting a single parameter and fail to propose a systematic optimization design method from the perspective of flow channel surface geometry and overall flow field control. Therefore, it is necessary to develop a novel nozzle structure and its design method that can significantly improve the flow field within the crystallizer, suppress liquid surface fluctuations and mold flux entrapment, thereby enhancing billet production quality and reducing overall production costs. Summary of the Invention

[0005] To address these issues, this invention provides a method and system for optimizing the design of arc-shaped nozzles in crystallizers to suppress slag entrapment. This system solves the technical problems of unstable flow field, severe liquid surface fluctuations, and high slag entrapment frequency in crystallizers caused by straight-edge nozzles in the prior art.

[0006] To address the aforementioned technical problems, embodiments of the present invention provide a method for optimizing the design of an arc-shaped nozzle in a crystallizer to suppress slag entrapment, comprising: The area of ​​the water inlet is calculated to ensure that the side outlet area of ​​the optimized arc-shaped water inlet is equal to the side outlet area of ​​the unoptimized straight-edge water inlet. Based on the preset curvature parameters, the long and short sides of the rectangle of the sprue outlet are respectively designed to be curved, so that the optimized side outlet forms an arc surface structure. A rounded corner transition is provided at the intersection of the long side and the wide side of the arc; Based on the above design parameters, a three-dimensional geometric model of the water inlet is constructed, and a physical sample is made based on the model to conduct hydraulic physical simulation experiments. By comparing the liquid surface fluctuation characteristics and protective slag entrainment behavior in the crystallizer before and after the optimization of the nozzle structure, the performance of the arc-shaped nozzle in suppressing slag entrainment and stabilizing the flow field is verified.

[0007] Preferably, the method for calculating the water inlet area includes: Ensure that the total flow area of ​​the side outlet of the optimized arc-shaped water inlet remains consistent with the flow area of ​​the side outlet of the straight-edge water inlet before optimization, and that the outlet area of ​​the main channel at the bottom of the water inlet remains unchanged before and after optimization.

[0008] Preferably, the method for designing the rectangular long side and wide side of the sprue outlet with arc bending includes: designing the long side of the sprue outlet as an arc segment on a circle with a diameter of a preset multiple of the chord length calculated from the long side; and designing the wide side of the sprue outlet as an arc segment on a circle with a diameter of a preset multiple of the initial sprue outlet width.

[0009] Preferably, the arc chord length corresponding to the wide side of the optimized sprue is equal to the width of the initial sprue; the arc chord length corresponding to the long side of the optimized sprue is obtained by inverse calculation with the constraint of equal side outlet areas.

[0010] Preferably, the side outlet area of ​​the optimized water inlet is calculated by subtracting the corresponding arc area of ​​each side from the virtual area of ​​the rectangle formed by the chord length. The mathematical relationship satisfies: total side outlet area = long side chord length × wide side chord length - (wide side corresponding arc area × 2 + long side corresponding arc area × 2).

[0011] Preferably, the arc area corresponding to the wide side is determined as a constant based on the chord length of the wide side and a set diameter multiple; the arc area corresponding to the long side is expressed as a function with the chord length of the long side as a variable, and the numerical solution of the chord length of the long side is obtained by iteratively solving the equation constraint of the total area of ​​the side exit.

[0012] Preferably, the rounded corner transition is located at the sharp corner where the long side and the wide side of the arc meet, and the radius of the rounded corner transition is selected as a preset suitable process value.

[0013] Preferably, the reduction in side outlet area caused by the rounded corner transition is within a preset allowable range of engineering errors relative to the total outlet area, and this area loss is ignored during the calculation of the water inlet area.

[0014] Preferably, the verification indicators of the hydraulic physics simulation experiment include at least: Under different continuous casting speeds, the fluctuation amplitude data at multiple preset monitoring points on the liquid surface of the crystallizer were measured; The frequency of slag entrapment events in protective slag under different structural nozzles and corresponding operating conditions was statistically analyzed.

[0015] This invention also provides a crystallizer arc-shaped nozzle optimization design system for suppressing slag entrapment. This system is used to implement the above-mentioned crystallizer arc-shaped nozzle optimization design method for suppressing slag entrapment, specifically including: The area conservation calculation module is used to calculate the area of ​​the water inlet and determine that the side outlet area of ​​the optimized arc-shaped water inlet is equal to the side outlet area of ​​the unoptimized straight-edge water inlet. The arc surface construction module is used to design the long and wide sides of the rectangle of the sprue side outlet to be curved based on preset curvature parameters, so that the optimized side outlet forms an arc surface structure. A rounded corner transition module is used to set a rounded corner transition at the intersection of the long arc side and the wide arc side; The model building and sample preparation module is used to build a three-dimensional geometric model of the sprue according to the above design parameters, and to make physical samples based on the model to conduct hydraulic physical simulation experiments. The hydraulic verification and performance evaluation module is used to verify the performance of the arc-shaped nozzle in suppressing slag entrainment and stabilizing the flow field by comparing the liquid surface fluctuation characteristics and protective slag entrainment behavior in the crystallizer before and after the optimization of the nozzle structure.

[0016] As can be seen from the above technical solutions, this invention application has the following beneficial effects: (1) By transforming the straight rectangular side outlet into an arc-shaped curved side outlet with equal area and combining it with the rounded corner transition, the present invention effectively changes the shape of the molten steel jet, reduces the impact kinetic energy of the jet on the narrow surface of the crystallizer, and fundamentally suppresses the entrapment of protective slag caused by violent fluctuations in the liquid surface.

[0017] (2) The present invention adopts an arc bending design method with area conservation, which realizes the optimization and control of the flow field under the premise of ensuring that the steel flow rate at the sprue remains unchanged. It can be directly replaced without changing the existing continuous casting process parameters, and has strong engineering applicability.

[0018] (3) The present invention induces the steel liquid jet to generate radial velocity and form a fan-shaped divergent flow state at the moment of outflow by designing an arc-shaped flow guide structure at the outlet corner, which promotes the rapid dissipation of high turbulent kinetic energy at the outlet of the water nozzle with the diffusion of the jet, and significantly reduces the actual impact velocity reaching the liquid surface and narrow surface.

[0019] (4) Water model experiments show that the optimized arc nozzle can reduce the average fluctuation amplitude of liquid surface by 31.9% and the average slag entrapment frequency by 62.4%, which significantly improves the stability of the flow field in the crystallizer and the purity of the billet, providing reliable technical support for high-speed continuous casting production of high-quality steel grades. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Referring to the drawings will make the features and advantages of the present invention clearer. The drawings are illustrative and should not be construed as limiting the present invention in any way. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a flowchart of an optimized design method for an arc-shaped nozzle in a crystallizer to suppress slag entrapment, provided by the present invention. Figure 2 This is a schematic diagram of a three-hole water inlet; Figure 3 This is a schematic diagram of water inlet calculation; Figure 4 This is a schematic diagram for solving the area S2 of the arc; Figure 5 This is a schematic diagram of the optimized sprue; Figure 6 This is a schematic diagram of the measurement points; Figure 7 These are schematic diagrams of the original water inlet fluctuations, where (a) is a schematic diagram of measurement point 1, (b) is a schematic diagram of measurement point 2, and (c) is a schematic diagram of measurement point 3. Figure 8 These are schematic diagrams of the optimized water inlet fluctuation, where (a) is a schematic diagram of measurement point 1, (b) is a schematic diagram of measurement point 2, and (c) is a schematic diagram of measurement point 3. Figure 9 These are schematic diagrams of the average fluctuation, where (a) is a schematic diagram of the original water inlet and (b) is a schematic diagram of the optimized water inlet; Figure 10 This is a schematic diagram showing the slag entrainment frequency at different water inlets; Figure 11 These are schematic diagrams of sprue outlets with different shapes, where (a) is a front view of a square sprue outlet, (b) is a side view of a square sprue outlet, (c) is a front view of an arc-shaped sprue outlet, and (d) is a side view of an arc-shaped sprue outlet. Figure 12 These are schematic diagrams of flow field tracers for different nozzle types, where (a) is a square nozzle and (b) is an arc-shaped nozzle; Figure 13This is a schematic diagram showing the influence of different nozzle types on the flow field velocity, where (a) is a square nozzle and (b) is an arc-shaped nozzle; Figure 14 These are schematic diagrams of slag entrapment at different shaped nozzles, where (a) is a schematic diagram of slag entrapment at a square nozzle and (b) is a schematic diagram of slag entrapment at an arc-shaped nozzle. Figure 15 This is a schematic diagram showing the slag entrainment frequency of two types of nozzles at different drawing speeds; Figure 16 These are flow field velocity contour maps for different types of nozzles, where (a) is a square nozzle and (b) is an arc-shaped nozzle; Figure 17 This is a schematic diagram showing the flow distribution of different streams in different directions under different shaped nozzles, where (a) represents the flow rate of different streams and (b) represents the percentage of flow rate in different directions. Figure 18 This is a schematic diagram of the impact velocity of sprue nozzles of different shapes; Figure 19 This is a schematic diagram of the maximum speed of the slag-metal interface at various drawing speeds; Figure 20 This is a diagram comparing the number of slag droplets with different nozzle shapes; Figure 21 This is a block diagram of an optimized design system for an arc-shaped nozzle of a crystallizer to suppress slag entrapment, provided by the present invention. Detailed Implementation

[0021] 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, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1: This embodiment provides an optimized design method for the arc-shaped nozzle of a crystallizer to suppress slag entrapment, addressing the technical problems of unstable flow field, severe liquid surface fluctuations, and high slag entrapment frequency in the crystallizer caused by straight-edge nozzles in existing technologies. Figure 1 As shown, the method includes the following steps: Step S1: Calculate the area of ​​the water inlet to ensure that the side outlet area of ​​the optimized arc-shaped water inlet is equal to the side outlet area of ​​the unoptimized straight-edge water inlet.

[0023] In this step, when calculating the inlet area, ensure that the total flow area of ​​the side outlet of the optimized arc-shaped inlet is consistent with the flow area of ​​the side outlet of the straight-edge inlet before optimization, and that the outlet area of ​​the main channel at the bottom of the inlet remains unchanged before and after optimization.

[0024] The calculation process will be explained in detail below using a specific example of water inlet design.

[0025] See Figure 2 The diagram shows a conventional three-hole nozzle side outlet. Before optimization, the straight-edge nozzle side outlet is rectangular, with a wide side dimension of 40mm and a long side dimension of 85mm. Therefore, the area of ​​the unoptimized side outlet is S0 = 40mm × 85mm = 3400mm². The optimization design objective of this invention is to transform the rectangular outlet into an arc-shaped curved surface outlet while maintaining the total flow area of ​​the side outlet at 3400mm².

[0026] See Figure 3 This is a schematic diagram of the sprue calculation. The optimized sprue's side outlet is formed by two pairs of oppositely arranged arc-shaped sides, where the wide side and long side are each composed of arcs of different diameters. In this embodiment, the chord length of the arc corresponding to the wide side is set to remain at the initial sprue's wide side dimension, i.e., the wide side chord length Lw = 40mm; simultaneously, according to preset curvature parameters, the wide side is designed as an arc segment on a circle with a diameter that is a preset multiple of the initial sprue's wide side dimension. In this embodiment, this preset multiple is exemplarily taken as 4 times, so the diameter of the circle containing the wide side is Dw = 4 × 40mm = 160mm.

[0027] Based on the diameter and chord length, the area S1 of the arc corresponding to the wider side can be calculated as a constant. The formula for calculating the arc area is well known to those skilled in the art, and the specific value can be obtained through geometric relationships or measurement using CAD software. Calculations show that in this example, the arc area S1 of the wider side is 67.96 mm².

[0028] For the longer side, its chord length L1 is an unknown variable, denoted as X. In this embodiment, the longer side is also designed to bend according to a preset multiple, for example, the diameter is taken as 4 times the chord length, that is, the diameter D1 of the circle containing the longer side is 4X. At this time, the area S2 of the arc corresponding to the longer side can be expressed as a function with the chord length X as the variable. Figure 4 As shown, based on the geometric relationship of the area of ​​the arc, S2 can be expressed as: .

[0029] The total area S of the optimized arc-shaped side exit can be calculated by subtracting the sum of the areas of the corresponding segments on each side from the virtual area of ​​the rectangle formed by the chord lengths. The mathematical relationship should satisfy: ; Substitute the known values ​​into: .

[0030] By substituting the expression for S2 into the above equation and iteratively solving the equation, the length of the long chord X = 117.9 mm is obtained.

[0031] Thus, all the geometric parameters of the optimized nozzle side outlet were determined: the chord length of the wide side is 40mm, and the diameter of the circle is 160mm; the chord length of the long side is 117.9mm, and the diameter of the circle is 471.6mm.

[0032] Step S2: Based on the preset curvature parameters, the long and wide sides of the rectangle of the sprue outlet are designed to be curved, so that the optimized outlet forms an arc-shaped surface structure.

[0033] After determining the chord length and curvature (i.e., arc diameter) of the sprue outlet in step S1, this step is specifically implemented as follows: the long side of the sprue outlet is designed as an arc on a circle with a diameter of a preset multiple of the chord length calculated from the long side; the wide side of the sprue outlet is designed as an arc on a circle with a diameter of a preset multiple of the initial sprue width.

[0034] It should be noted that the aforementioned preset multiplier (e.g., 4 times) is merely illustrative and not intended to limit the invention. In practical applications, any reasonable multiplier can be selected based on the initial aspect ratio of the nozzle, the target flow field characteristics, and process requirements. By adjusting this multiplier, the curvature of the arc-shaped edge can be changed, thereby adjusting the diffusion angle and kinetic energy distribution of the outlet stream to achieve different flow field control effects. The core of this invention lies in transforming the originally straight rectangular outlet into an arc-shaped curved surface outlet composed of two pairs of circular arcs, while ensuring area conservation, to change the shape and direction of the molten steel jet stream.

[0035] Step S3: Set a rounded corner transition at the intersection of the long side and the wide side of the arc.

[0036] After completing the design of the curved long and wide sides, a rounded transition is set at the sharp corner where they meet to avoid stress concentration and flow dead zones. The radius of this rounded transition is selected from a preset suitable process value. In this embodiment, a rounded corner with a radius of 5mm is used as an example.

[0037] Since the reduction in side outlet area caused by the rounded corner transition is extremely small relative to the total outlet area, calculations show that the area reduction due to the rounded corner in this embodiment is less than 2% of the total area, which is within the preset allowable engineering error range. Therefore, in the aforementioned step S1 of the water inlet area calculation process, this part of the area loss is ignored, thereby simplifying the complexity of the design calculation.

[0038] Step S4: Construct a three-dimensional geometric model of the water inlet based on the above design parameters, and make a physical sample based on the model to conduct a hydraulic physical simulation experiment.

[0039] Based on the geometric parameters of the sprue determined in steps S1 to S3, an optimized 3D geometric model of the sprue is constructed in 3D modeling software (such as SOLIDWORKS). A schematic diagram of the completed model is shown below. Figure 5 As shown in the figure, the curved surface features of the side exit and the rounded corner transition are clearly displayed.

[0040] Based on this 3D model, a physical prototype of the sprue was fabricated using 3D printing technology for subsequent hydraulic physics simulation experiments (i.e., water model experiments). Water model experiments are a widely used similar simulation method in continuous casting process research. Water is used to simulate molten steel and oil is used to simulate protective slag, allowing for a direct study of the flow field and liquid surface behavior within the crystallizer at room temperature.

[0041] Step S5: By comparing the liquid surface fluctuation characteristics and protective slag entrainment behavior in the crystallizer before and after the optimization of the nozzle structure, the performance of the arc-shaped nozzle in suppressing slag entrainment and stabilizing the flow field is verified.

[0042] The verification indicators for the hydraulic physical simulation experiment include at least the following: measuring the fluctuation amplitude data at multiple preset monitoring points on the liquid surface of the crystallizer under different continuous casting speed conditions; and statistically analyzing the frequency of slag entrapment events in protective slag under corresponding operating conditions for different sprue structures.

[0043] See Figure 6 This is a schematic diagram of the liquid level fluctuation measurement points in the water model experiment. In this embodiment, three representative monitoring points are set: measurement point 1 is located 20cm away from the center of the inlet, used to monitor the liquid level stability in the area near the inlet; measurement point 2 is located at the 1 / 4 width of the crystallizer, used to monitor the fluctuation of the main stream backflow zone; and measurement point 3 is located 5cm away from the narrow face, used to monitor the fluctuation of the area near the narrow face where slag entrapment is prone to occur.

[0044] The experiment tested the original straight-edge nozzle and the arc-shaped nozzle optimized by the present invention under different pulling speed conditions. Figure 7 The liquid level fluctuations at three measurement points are shown, where (a) is the fluctuation curve at measurement point 1, (b) is the fluctuation curve at measurement point 2, and (c) is the fluctuation curve at measurement point 3. Figure 8 The optimized sprue shows the liquid level fluctuation at the corresponding measurement points. Similarly, (a), (b), and (c) correspond to the three measurement points respectively.

[0045] contrast Figure 7 and Figure 8 It is evident that, at different pulling speeds, the liquid level fluctuation amplitude at each measuring point of the optimized nozzle is significantly reduced compared to the original nozzle. Figure 9 The statistical comparison of the average fluctuation values ​​is further illustrated, where (a) is the average fluctuation value of the original nozzle and (b) is the average fluctuation value of the optimized nozzle. Calculations show that using the optimized arc-shaped nozzle of this invention reduces the average fluctuation amplitude of the crystallizer liquid surface by 31.9%, fully demonstrating that the optimized nozzle can effectively reduce the fluctuation magnitude at the slag-gold interface and improve flow field stability.

[0046] Figure 10 The comparison of slag entrainment frequency with different nozzle structures is presented. Experimental statistics show that the slag entrainment frequency of the optimized nozzle is significantly lower than that of the original nozzle, with an average decrease of 62.4%. This data strongly verifies that the arc-shaped nozzle designed in this invention has excellent slag entrainment suppression capabilities.

[0047] Example 2: Arc-shaped nozzle structure obtained based on optimization design method and its verification This embodiment provides an arc-shaped nozzle structure obtained by the optimization design method described in Embodiment 1, along with further verification data.

[0048] (a) Water inlet structure like Figure 11 As shown, (a) and (b) are the front and side views of the existing square nozzle, and (c) and (d) are the front and side views of the improved arc-shaped nozzle of the present invention. The arc-shaped nozzle obtained by the optimization design method described in Embodiment 1 includes a nozzle body and an outlet disposed on the side wall of the nozzle body. The cross-sectional profile of the outlet is formed by an inwardly concave arc segment. Specifically, while keeping the total area of ​​the original nozzle outlet basically unchanged, the outlet is based on a square outlet, with outwardly extending arc-shaped flow guiding structures at the four corner vertices, so that the original square outlet cross-section is transformed into an arc-shaped cross-section, forming a flared shape with flow guiding structures at the four corners, inducing the molten steel jet to flow out in a fan shape.

[0049] Furthermore, the included angles of the tangent directions at the four corner vertices are all less than 90°. This structure forces the molten steel to generate flow separation and eddies inside the nozzle, weakening the concentrated kinetic energy of the jet upon reaching the outlet and dissipating the turbulent kinetic energy impacting the liquid surface upwards. This mechanism reduces the outlet jet velocity and causes the jet stream to exhibit a more divergent shape.

[0050] The arc-shaped guide structure at the outlet provides a radial velocity component at the moment the molten steel flows out, which increases the contact area between the jet and the stationary molten steel in the crystallizer, transforming the originally single square jet into a fan-shaped flow with divergent characteristics, promoting the dissipation of turbulent kinetic energy to reduce the core velocity of the jet.

[0051] (II) Experimental Verification of Physical Simulation of Crystallizer Flow Field To verify the optimization effect of the arc-shaped nozzle on the flow field of the crystallizer in this embodiment, a water model experiment was conducted. Five different casting speeds of 0.9 m / min, 1.0 m / min, 1.1 m / min, 1.2 m / min and 1.3 m / min were selected for the experiment. The flow velocity, liquid surface fluctuation amplitude and slag entrainment frequency inside the crystallizer were collected and analyzed.

[0052] 1. Flow field morphology analysis Based on the results of the tracer flow field colorimetric experiment using the crystallizer water model, such as Figure 12 As shown, the arc-shaped (upward-sloping) nozzle of this invention still exhibits a typical "three-roller flow" field within the crystallizer, retaining the core advantage of the upward-sloping nozzle in preventing the protective slag from forming a crust. Compared to the square nozzle, the streamline morphology displayed by the tracer is more divergent and gentler. This indicates that the arc-shaped design does not disrupt the original main flow pattern of the nozzle, but rather fine-tunes the local fluid movement to better meet the requirements of stability and uniformity.

[0053] The curved cross-section effectively diverts the originally singular and concentrated impact kinetic energy of the jet into multiple streams. At the moment of exiting the nozzle, the fluid is no longer a unidirectional columnar jet, but is forced to diffuse in all directions. This diversion significantly homogenizes the flow distribution within the crystallizer, eliminates the high-speed jet that might have been generated by the original square nozzle, makes the velocity distribution within the crystallizer flow field more gradual, and increases the impact range of the upward flow on the liquid surface, reducing the impact force on the liquid surface and thus reducing the disturbance to the liquid surface.

[0054] 2. Flow velocity monitoring and kinetic energy dissipation analysis Figure 13 The study demonstrates the velocity variations at the outlet, liquid surface impact point, and narrow face impact point for different nozzle types under varying casting speeds. It is clearly evident that the velocity at the outlet of the optimized curved nozzle is significantly higher than that of the unoptimized nozzle. This result indicates that the flaring and corner guiding design of the curved nozzle does not hinder the increase in outlet flow rate; on the contrary, it maintains a strong steel flow capacity. This is of significant engineering importance for preventing the adhesion and blockage of inclusions inside the nozzle during actual production.

[0055] By comparing the measured velocity difference between the outlet and the impact point on the liquid surface, it can be found that the arc-shaped nozzle of this invention exhibits an extremely high kinetic energy attenuation rate. Although its initial kinetic energy at the outlet is high, the measured velocity at the impact point on the liquid surface is generally lower than that of the square nozzle. This physical experimental result directly confirms that the arc-shaped structure successfully induces high-intensity internal energy dissipation at the moment the fluid leaves the nozzle through strong turbulent diffusion and multi-directional flow splitting. This dissipation mechanism effectively eliminates excess kinetic energy, making the originally high-impact jet gentler when it reaches the slag-metal interface.

[0056] Measurement data at the narrow impact point show that the overall flow velocity at this location is still slightly lower than that at the square impact point. The reduced impact velocity at the narrow impact point, captured in the physical experiments, indicates that the upward backflow formed after the jet impacts the narrow surface lacks sufficient momentum support, thus physically weakening the driving force for slag entrainment. Physical water model experimental data conclusively demonstrate that the nozzle of this invention possesses excellent rheological characteristics of high outlet kinetic energy, high internal dissipation, and low surface impact.

[0057] 3. Analysis of the effect of inhibiting slag-carrying behavior Figure 14 The paper presents a comparison of slag droplet entrainment patterns in two nozzle types under extreme operating conditions, where (a) is a square nozzle and (b) is the arc-shaped nozzle of this invention. At a high casting speed of 1.3 m / min, the square nozzle exhibited a large amount of slag entrainment within the crystallizer, with numerous fine oil droplets being captured by the deep flow and carried deep into the crystallizer, making it difficult for them to float to the surface. In contrast, while the arc-shaped nozzle also entrained slag droplets, the droplets were relatively larger, making them easier to float back to the slag-gold interface, and their number was significantly less than that of the square nozzle.

[0058] Figure 15 The slag entrainment frequency under various casting speeds was statistically analyzed. The data shows that at all casting speeds from 0.9 to 1.3 m / min, the slag entrainment frequency of the curved nozzle was consistently lower than that of the square nozzle. At 0.9 m / min, the slag entrainment frequency of the curved nozzle was only 1.5 times / min, less than half the frequency of the square nozzle under the same conditions (approximately 3 times / min); even under the harsh condition of 1.3 m / min, the curved nozzle still maintained a performance advantage of approximately 20%.

[0059] Example 3: Numerical simulation verification of the flow field in a crystallizer based on an arc-shaped nozzle To explore in depth the impact of nozzle structure optimization on the flow behavior of molten steel in the crystallizer, this embodiment uses numerical simulation to quantitatively analyze key indicators such as velocity distribution, impact point velocity, surface fluctuation, and slag entrainment severity, intuitively revealing the improved flow field morphology, stability, and uniformity after optimization.

[0060] 1. Analysis of macroscopic morphology of the flow field and jet characteristics Figure 16 The diagram shows the velocity contour maps of the flow field inside the crystallizer for different types of nozzles under the same process parameters (pulling speed 1.1 m / min, immersion depth 120 mm). Figure 16 As shown in (b), the jet exhibits a clear divergence characteristic. Thanks to the arc-shaped guide design at the outlet corner, the jet generates a significant radial velocity component the instant it leaves the nozzle, causing the stream to spread rapidly in the horizontal direction. This blooming flow pattern greatly increases the contact area between the jet and the surrounding stationary molten steel, promoting momentum exchange and energy dissipation, thereby diluting the high-speed region of the jet core. Simulation results show that the flow field symmetry on both sides of the arc-shaped nozzle is significantly better than that of the square nozzle, which improves the stability of the flow field and reduces surface fluctuations caused by asymmetric flow.

[0061] 2. Flow distribution analysis Figure 17The diagram shows the upward and downward flow distribution of molten steel after exiting the nozzle, where (a) represents the flow rate of the streams in different directions, and (b) represents the percentage of flow in each direction. Compared to a square nozzle, the upward flow rate of the curved nozzle slightly decreased from 0.53 L / min to 0.51 L / min, and the upward flow ratio slightly decreased from 23% to 22%; the downward flow rate increased from 1.76 L / min to 1.79 L / min, and the downward flow ratio increased from 77% to 78%. Although the flow distribution ratio of the nozzle did not change significantly, due to the divergent characteristics of its jet, the increased fluid was dispersed over a wider spatial area, resulting in a decrease in the impact force per unit area. Simultaneously, the increased downward flow enhanced the overall momentum of the downward return flow, which is beneficial for eliminating the flow dead zone at the bottom of the crystallizer and promoting the cleaning and flotation of deep inclusions.

[0062] 3. Narrow-face impact velocity analysis Figure 18 The transient changes in the narrow-face impact velocity of the square nozzle and the arc-shaped nozzle of this invention under the same operating conditions (pulling speed 1.3 m / min) were monitored and statistically analyzed. The results showed that the average impact velocity of the square nozzle was as high as 0.156 m / s, while the average impact velocity of the arc-shaped nozzle decreased to 0.134 m / s, a reduction of approximately 14.1%. While maintaining a constant total outlet flow rate, the arc-shaped guide structure of this invention causes the jet to exhibit a divergent flow pattern, resulting in a reduction of the average narrow-face impact velocity of more than 10% compared to the square nozzle under the same operating conditions.

[0063] 4. Analysis of the speed of the gold interface Figure 19 The study demonstrates the variation of the maximum velocity at the slag-gold interface under various casting speeds. Statistical results show that the average maximum velocity at the square nozzle interface remained at a high level, reaching 0.23 m / s; while the average maximum velocity at the curved nozzle interface decreased significantly to 0.19 m / s, a decrease of approximately 17.4%. Observation of the square nozzle reveals extremely drastic velocity fluctuations, with instantaneous peak values ​​even exceeding 0.40 m / s. Such sudden high-speed fluctuations correspond to strong turbulent events within the crystallizer, often a direct cause of severe slag entrapment. In contrast, the curved nozzle exhibits a gentler velocity trend with less turbulence, and its velocity never exceeded 0.23 m / s throughout the entire simulation period.

[0064] 5. Analysis of Slag Rolling Quantity and Slag Rolling Index Figure 20The evolution of the number of slag droplets entrained in the molten steel within the crystallizer over time was statistically analyzed during numerical simulation. Statistical data shows that the average number of slag droplets entrained in a square nozzle was 6.84, while the average number in an arc-shaped nozzle decreased to 4.2, a reduction of approximately 38.6%. The nozzle of this invention, through its arc-shaped flow guiding structure, reduces the average number of slag droplets entrained per unit time by more than 35% compared to a square nozzle under the same operating conditions. Observation of the square nozzle reveals that its slag droplet count is not only high but also extremely unstable, exhibiting explosive slag entrainment phenomena; conversely, the arc-shaped nozzle shows a smooth overall trend, maintaining between 2 and 6 droplets for most of the time, never exceeding 8 droplets.

[0065] Example 4: Optimized Design System for Arc-Shaped Inlet of Crystallizer to Suppress Slag Entrainment like Figure 21 As shown, this invention provides a crystallizer arc-shaped nozzle optimization design system for suppressing slag entrapment. This system is used to implement the crystallizer arc-shaped nozzle optimization design method for suppressing slag entrapment described in Embodiment 1 above, specifically including: The area conservation calculation module 100 is used to calculate the area of ​​the water inlet, ensuring that the side outlet area of ​​the optimized arc-shaped water inlet is equal to the side outlet area of ​​the unoptimized straight-edge water inlet. The specific calculation logic of this module is consistent with the description of step S1 in Example 1, including keeping the bottom outlet area unchanged and solving for the long side chord length using a mathematical model that subtracts the arc area from the chord length rectangle area.

[0066] The arc-shaped surface construction module 200 is used to design the long and short sides of the rectangle of the sprue side outlet to be curved in an arc shape based on preset curvature parameters, so that the optimized side outlet forms an arc-shaped surface structure. This module receives the chord length and curvature parameters output by the area conservation calculation module 100 and generates the arc-shaped profile curve of the sprue side outlet.

[0067] The sharp corner rounded corner transition module 300 is used to set a rounded corner transition at the intersection of the long side and the wide side of the arc. This module rounds the sharp corners generated by the arc surface construction module 200 according to a preset suitable process radius value, and ensures that the area error is within the allowable range.

[0068] The model building and sample preparation module 400 is used to construct a three-dimensional geometric model of the sprue based on the above design parameters, and to fabricate a physical sample based on the model for hydraulic physical simulation experiments. This module can call a 3D modeling software interface or a built-in geometry engine to generate a digital model of the sprue and output a file format that can be recognized by 3D printing equipment.

[0069] The hydraulic verification and performance evaluation module 500 is used to verify the performance of the arc-shaped nozzle in suppressing slag entrapment and stabilizing the flow field by comparing the liquid surface fluctuation characteristics and protective slag entrapment behavior in the crystallizer before and after optimization of the nozzle structure. This module can receive sensor data from water model experiments, automatically calculate quantitative indicators such as fluctuation amplitude and slag entrapment frequency, and generate a comparative analysis report.

[0070] This embodiment provides a crystallizer arc-shaped nozzle optimization design system for suppressing slag entrapment. This system is used to implement the aforementioned crystallizer arc-shaped nozzle optimization design method for suppressing slag entrapment. Therefore, the specific implementation of the crystallizer arc-shaped nozzle optimization design system for suppressing slag entrapment can be found in the embodiment section of the crystallizer arc-shaped nozzle optimization design method for suppressing slag entrapment described above. For example, the area conservation calculation module 100, the arc-shaped surface construction module 200, the sharp corner rounded corner transition module 300, the model construction and sample preparation module 400, and the hydraulic verification and performance evaluation module 500 are respectively used to implement steps S1, S2, S3, S4, and S5 in the above-mentioned crystallizer arc-shaped nozzle optimization design method for suppressing slag entrapment. Therefore, the specific implementation can be referred to the description of the corresponding embodiment. To avoid redundancy, it will not be repeated here.

[0071] In summary, the present invention provides an optimized design method and system for an arc-shaped nozzle in a crystallizer to suppress slag entrapment. By transforming the straight-sided rectangular side outlet into an arc-shaped curved side outlet of equal area and setting rounded transitions at the sharp corners, the flow pattern of molten steel ejected from the nozzle side hole is significantly altered, reducing the impact intensity of the flow on the narrow face of the crystallizer and improving the flow field distribution within the crystallizer. The corner arc-shaped flaring design constructs an energy dissipation mechanism, inducing significant fan-shaped divergence in the jet, transforming the originally concentrated columnar jet into a diffuse flow state. This ensures high outlet velocity while achieving rapid attenuation of the jet's core kinetic energy during transmission. It exhibits excellent flow stabilization throughout the crystallizer flow field, significantly suppressing liquid surface fluctuations, reducing the impact velocity at the narrow face and the maximum velocity at the slag-metal interface, and cutting off the power supply for slag entrapment at its source. The consistency between physical experiments and numerical simulations proves that this invention can significantly reduce slag entrainment, effectively suppress the risk of sudden large-scale slag entrainment, and solve the problem of slag entrainment at high casting speeds while retaining the advantages of upward angled slag formation. This provides reliable technical support for achieving high-quality and high-stability slab continuous casting production.

[0072] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for optimizing the design of an arc-shaped nozzle in a crystallizer to suppress slag entrapment, characterized in that, include: The area of ​​the water inlet is calculated to ensure that the side outlet area of ​​the optimized arc-shaped water inlet is equal to the side outlet area of ​​the unoptimized straight-edge water inlet. Based on the preset curvature parameters, the long and short sides of the rectangle of the sprue outlet are respectively designed to be curved, so that the optimized side outlet forms an arc surface structure. A rounded corner transition is provided at the intersection of the long side and the wide side of the arc; Based on the above design parameters, a three-dimensional geometric model of the water inlet is constructed, and a physical sample is made based on the model to conduct hydraulic physical simulation experiments. By comparing the liquid surface fluctuation characteristics and protective slag entrainment behavior in the crystallizer before and after the optimization of the nozzle structure, the performance of the arc-shaped nozzle in suppressing slag entrainment and stabilizing the flow field is verified.

2. The method for optimizing the design of the arc-shaped nozzle of the crystallizer to suppress slag entrapment according to claim 1, characterized in that, The method for calculating the water inlet area includes: Ensure that the total flow area of ​​the side outlet of the optimized arc-shaped water inlet remains consistent with the flow area of ​​the side outlet of the straight-edge water inlet before optimization, and that the outlet area of ​​the main channel at the bottom of the water inlet remains unchanged before and after optimization.

3. The method for optimizing the design of the arc-shaped nozzle of the crystallizer to suppress slag entrapment according to claim 1, characterized in that, The method for designing the rectangular long and short sides of the outlet on the water inlet side by respectively making arc bends includes: The long side of the sprue outlet is designed as an arc on a circle with a diameter equal to a preset multiple of the chord length calculated from the long side; the wide side of the sprue outlet is designed as an arc on a circle with a diameter equal to a preset multiple of the initial sprue width.

4. The method for optimizing the design of the arc-shaped nozzle of a crystallizer to suppress slag entrapment according to claim 3, characterized in that, The chord length of the arc corresponding to the wide side of the optimized sprue is equal to the width of the initial sprue; the chord length of the arc corresponding to the long side of the optimized sprue is obtained by back-calculation with the constraint that the side outlet areas are equal.

5. The method for optimizing the design of the arc-shaped nozzle of a crystallizer to suppress slag entrapment according to claim 4, characterized in that, The optimized side outlet area is calculated by subtracting the area of ​​the corresponding arc shape on each side from the virtual area of ​​the rectangle formed by the chord length. The mathematical relationship satisfies: Total side outlet area = Long side chord length × Wide side chord length - (Wide side corresponding arc shape area × 2 + Long side corresponding arc shape area × 2).

6. The method for optimizing the design of the arc-shaped nozzle of a crystallizer to suppress slag entrapment according to claim 5, characterized in that, The arc area corresponding to the wide side is determined as a constant based on the chord length of the wide side and a set diameter multiple; the arc area corresponding to the long side is expressed as a function with the chord length of the long side as a variable, and the numerical solution of the chord length of the long side is obtained by iteratively solving the equation constraint of the total area of ​​the side exit.

7. The method for optimizing the design of the arc-shaped nozzle of a crystallizer to suppress slag entrapment according to claim 1, characterized in that, The rounded corner transition is set at the sharp corner where the long side and the wide side of the arc meet, and the radius of the rounded corner transition is selected as a preset suitable process value.

8. The method for optimizing the design of the arc-shaped nozzle of a crystallizer to suppress slag entrapment according to claim 1, characterized in that, The reduction in side outlet area caused by the rounded corner transition is within the preset allowable range of engineering error, and this area loss is ignored in the process of calculating the water inlet area.

9. The method for optimizing the design of the arc-shaped nozzle of a crystallizer to suppress slag entrapment according to claim 1, characterized in that, The verification indicators for the hydraulic physics simulation experiment include at least the following: Under different continuous casting speeds, the fluctuation amplitude data at multiple preset monitoring points on the liquid surface of the crystallizer were measured; The frequency of slag entrapment events in protective slag under different structural nozzles and corresponding operating conditions was statistically analyzed.

10. A crystallizer arc-shaped nozzle optimization design system for suppressing slag entrapment, characterized in that, The system is used to implement the crystallizer arc nozzle optimization design method for suppressing slag entrapment as described in any one of claims 1 to 9, specifically including: The area conservation calculation module is used to calculate the area of ​​the water inlet and determine that the side outlet area of ​​the optimized arc-shaped water inlet is equal to the side outlet area of ​​the unoptimized straight-edge water inlet. The arc surface construction module is used to design the long and wide sides of the rectangle of the sprue side outlet to be curved based on preset curvature parameters, so that the optimized side outlet forms an arc surface structure. A rounded corner transition module is used to set a rounded corner transition at the intersection of the long arc side and the wide arc side; The model building and sample preparation module is used to build a three-dimensional geometric model of the sprue according to the above design parameters, and to make physical samples based on the model to conduct hydraulic physical simulation experiments. The hydraulic verification and performance evaluation module is used to verify the performance of the arc-shaped nozzle in suppressing slag entrainment and stabilizing the flow field by comparing the liquid surface fluctuation characteristics and protective slag entrainment behavior in the crystallizer before and after the optimization of the nozzle structure.

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