A method for suppressing slag runoff from vortex during ladle pouring

Abstract

This invention provides a method for suppressing slag discharge from vortexes during ladle casting, characterized by the following steps: when the ladle is cast to the first critical slag discharge height, the opening of the sliding nozzle slide is reduced from the initial value K0 to the first adjustment value K1 = 18~23%, held for 20~25s, and then increased back to the initial value K0; when the ladle is cast to the second critical slag discharge height, the opening of the sliding nozzle slide is reduced from the initial value to the second adjustment value K2 = 18~35%, held for 20~25s, and then increased back to the initial value.

Description

Technical Field

[0001] This invention belongs to the field of ladle casting control, specifically relating to a method for suppressing slag runoff during ladle casting vortex. Background Technology

[0002] Slag addition at the end of the continuous casting process is a significant cause of reduced steel cleanliness and deteriorated steel quality. The main components of ladle top slag are generally CaO-SiO2-Al2O3, with high oxidizing properties (FeO-MnO). Due to this high oxidizing property, slag addition from the ladle causes secondary oxidation of the molten steel in the tundish. Furthermore, after ladle slag enters the molten steel in the tundish, slag droplets also form inclusions, typically large in size. Some of these inclusions float to the tundish covering agent slag layer, while others flow with the molten steel in the tundish (especially in cases of short-circuit flow due to poor tundish design). These inclusions are easily captured by the initial shell of the continuously cast billet, adversely affecting the processing and service performance of the steel. For example, during rolling, they can easily cause surface defects in ultra-low carbon steel plates, reducing the fatigue resistance of bearing steel during service.

[0003] Scholars have discovered three slag discharge mechanisms at the end of the continuous casting process: confluence vortices, discharge pits, and slag-steel emulsification. Confluence vortex slag discharge occurs at the end of the unsteady casting process in the continuous casting ladle. When the molten steel in the ladle drops to a certain height, a vortex forms above the nozzle. Molten slag is drawn into the molten steel through the vortex core. As casting continues, the vortex eventually penetrates the nozzle and enters the tundish, causing a large amount of slag discharge. Confluence vortices occur relatively early, when the ladle level is higher. The formation and eventual transition of the confluence vortex into a discharge pit strongly promotes slag-steel emulsification, causing the molten slag to be more diffusely distributed into the molten steel as it enters the tundish. Therefore, slag discharge caused by confluence vortices is the most harmful and the primary cause of slag discharge from the ladle.

[0004] Research on the mechanism and influencing factors of slag runoff from ladle confluence vortexes in steel casting has primarily relied on physical and numerical simulations by scholars both domestically and internationally. The critical slag runoff height (the height of the liquid level when a vortex forms on the fluid surface) is generally used to evaluate the degree of slag runoff from the ladle. Furthermore, the critical slag runoff height is also a crucial parameter in actual production processes and a necessary prerequisite for developing slag runoff control technologies. Current research on slag runoff from ladle confluence vortexes and the critical slag runoff height uses either direct-flow casting (100% slide gate opening) or ball valve control (as used in physical simulations) for setting the ladle nozzle opening. However, in continuous casting production, the slide gate opening of the ladle nozzle dynamically changes to stabilize the tundish level and match the casting speed. Therefore, how to objectively and accurately reflect the actual dynamic changes during ladle casting and improve the predictability of slag runoff from ladle vortexes remains a problem to be solved. Moreover, further suppressing slag runoff from vortexes through regulation, based on the existing slag runoff early warning system, is also an urgent issue that needs to be addressed. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for suppressing slag discharge from the ladle pouring vortex. The method aims to control the opening of the sliding nozzle slide plate by adjusting the timing appropriately to suppress slag discharge, and further ensures the smooth progress of production.

[0006] As one aspect of the present invention, a method for suppressing slag discharge from vortex during ladle casting is provided, comprising the following steps: when the ladle is cast to a first critical slag discharge height, the opening of the sliding nozzle slide is reduced from an initial value K0 to a first adjustment value K1 = 18~23%, held for 20~25s, and then increased back to the initial value K0; when the ladle is cast to a second critical slag discharge height, the opening of the sliding nozzle slide is reduced from an initial value to a second adjustment value K2 = 18~35%, held for 20~25s, and then increased back to the initial value.

[0007] As a preferred embodiment of the method for suppressing slag runoff from vortexes during ladle casting according to the present invention, the initial value of the opening K0 is 50~60%.

[0008] As a preferred embodiment of the method for suppressing slag runoff from vortex during ladle casting according to the present invention, the velocity during the process of decreasing the opening of the sliding nozzle slide plate is 3.5-4.2 mm / s; the velocity during the process of increasing the opening of the sliding nozzle slide plate is 0.16-0.17 mm / s.

[0009] As a preferred embodiment of the method for suppressing slag runoff from vortex during ladle casting according to the present invention, the first adjustment value K0 = 20%, and the second adjustment value K2 = 28~33%.

[0010] As a preferred embodiment of the method for suppressing slag runoff during ladle pouring according to the present invention, the first critical slag runoff height h1 is obtained by the following method:

[0011] 1) Obtain the structural and dimensional parameters of the ladle, establish a three-dimensional model of the ladle and perform mesh generation. The structure of the ladle includes the ladle body, the upper water inlet, the sliding water inlet and the lower water inlet located at the bottom of the ladle. The interfaces of the upper water inlet, the sliding water inlet and the lower water inlet in the three-dimensional model of the ladle are connected by a fluid interface, and the wall surface is set as a no-slip wall boundary condition.

[0012] 2) Obtain the casting speed of the ladle, the initial liquid level of the molten steel in the ladle, and the trajectory of the sliding gate opening during the casting process under the casting speed condition. Use the dynamic layup method to set the dynamic mesh of the sliding gate.

[0013] 3) Select the RNG k-ε turbulence model and the VOF model, set the upper opening of the ladle as the pressure inlet boundary, the inlet material as air, and the inlet pressure as standard atmospheric pressure, set the lower outlet as the pressure outlet boundary, and the outlet pressure as standard atmospheric pressure, and set the interface as a no-slip boundary condition; set the turbulence intensity and hydraulic diameter at the pressure inlet, and the turbulence intensity and hydraulic diameter at the pressure outlet.

[0014] 4) Track the interface between molten steel, slag and air in the ladle according to the model and set conditions in step 3), wherein the sum of the volume fractions of molten steel, slag and air is controlled to be 1.

[0015] 5) Based on the tracking results of step 4), the first critical slag drop height h1 is obtained when the interface between the molten steel surface and the slag layer becomes unstable.

[0016] As a preferred embodiment of the method for suppressing slag runoff during ladle casting according to the present invention, the second critical slag runoff height h2 is obtained by the following method:

[0017] 1) Obtain the structural and dimensional parameters of the ladle, establish a three-dimensional model of the ladle and perform mesh generation. The structure of the ladle includes the ladle body, the upper water inlet, the sliding water inlet and the lower water inlet located at the bottom of the ladle. The interfaces of the upper water inlet, the sliding water inlet and the lower water inlet in the three-dimensional model of the ladle are connected by a fluid interface, and the wall surface is set as a no-slip wall boundary condition.

[0018] 2) Based on the aforementioned method for adjusting the sliding gate slide opening when the pouring height reaches the first critical slag discharge height, the sliding gate slide opening trajectory is obtained, and the sliding gate is set with a dynamic layering method. At this time, the initial liquid level of the molten steel in the ladle is the first critical slag discharge height.

[0019] 3) Select the RNG k-ε turbulence model and the VOF model, set the slag layer surface as the pressure inlet boundary, the inlet material as air, and the inlet pressure as standard atmospheric pressure. Set the outlet as the pressure outlet boundary, the outlet pressure as standard atmospheric pressure, and set the interface as a no-slip boundary condition. Set the turbulence intensity and hydraulic diameter (corresponding to the diameter of the ladle top) at the pressure inlet and the turbulence intensity and hydraulic diameter (corresponding to the diameter of the outlet) at the pressure outlet.

[0020] 4) Track the interface between molten steel, slag and air in the ladle according to the model in step 3), wherein the sum of the volume fractions of molten steel, slag and air is controlled to be 1.

[0021] 5) Based on the tracking results of step 4), the second critical slag height h2 is obtained.

[0022] As a preferred embodiment of the method for suppressing slag fall from vortex during ladle casting according to the present invention, in step 1), the ladle and the sliding nozzle slide body are divided into a hexahedral mesh, and the top and bottom of the ladle and the bottom of the sliding nozzle slide are divided into an O-type mesh; in step 2), the DEFINE_CG_MOTION macro in UDF is used to define the slide mesh motion in FLUENT according to the obtained relationship between the slide opening degree and time of the sliding nozzle slide.

[0023] As a preferred embodiment of the method for suppressing slag runoff during ladle casting according to the present invention, in step 3), the turbulence intensity at the pressure inlet is... Among them, the Reynolds number at the pressure inlet In the formula, ρ is the fluid density, kg / m³. 3 ; The hydraulic diameter at the pressure inlet is in mm; ρ is the kinematic viscosity of the fluid, Pa·s; ρ is the average fluid velocity at the pressure inlet. In the formula, and These represent the cross-sectional areas at the pressure inlet and pressure outlet, respectively, and the average fluid velocity at the pressure outlet. In the formula, g is the acceleration due to gravity, 9.8 m / s². 2 H represents the initial liquid level of molten steel in the ladle, in mm; turbulence intensity at the pressure outlet. Among them, the Reynolds number at the pressure outlet In the formula, The hydraulic diameter at the pressure outlet is in mm.

[0024] As a preferred embodiment of the method for suppressing slag runoff from vortexes during ladle casting according to the present invention, in step 4), the tracking specifically adopts a pressure-velocity coupled implicit algorithm, using the Coulomb number to control the time step, with an initial minimum time step of 0.001s and the Coulomb number being 0.5~1, until casting is completed.

[0025] As a preferred embodiment of the method for suppressing slag runoff during ladle pouring according to the present invention, the critical slag runoff height is the height of the molten steel when a vortex is generated at the steel-slag interface.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. By adjusting the opening of the appropriate sliding plate, slag discharge during the steel pouring process can be effectively suppressed, reducing the amount of slag in the ladle.

[0028] 2. By using the dynamic layering method to set the dynamic mesh for the sliding nozzle, the changing process of the sliding nozzle can be simulated more realistically. On this basis, the RNG k-ε turbulence model and VOF model are used and appropriate boundary conditions are selected to further improve the accuracy of model calculation and further improve the effect of suppressing slag. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a steel ladle modeling according to an embodiment of the present invention;

[0030] Figure 2 This is a diagram showing the change in the opening degree of the sliding gate slide plate in Embodiment 1 of the present invention;

[0031] Figure 3 This is a cloud map showing the changes in the steel slag interface during slag discharge warning in Embodiment 1 of the present invention. Detailed Implementation

[0032] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the 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.

[0033] The ladle size parameters used in the specific embodiments of the present invention are shown in Table 1. The first-class continuous casting machine has a casting cross-section of 1255mm×230mm. The steel throughput is determined based on the cross-section size and the actual production casting speed.

[0034] Table 1 Dimensional parameters of steel ladle

[0035]

[0036] Example 1

[0037] A method for suppressing slag runoff from vortexes during ladle pouring includes the following steps:

[0038] 1) Obtain the structural and dimensional parameters of the ladle, establish a 3D model of the ladle, and perform mesh generation, such as... Figure 1 As shown, the structure of the ladle includes the ladle body, an upper water inlet, a sliding water inlet, and a lower water inlet located at the bottom of the ladle. In the three-dimensional model of the ladle, the interfaces of the upper water inlet, the sliding water inlet, and the lower water inlet are connected by a fluid interface, and the wall surface is set as a no-slip wall boundary condition.

[0039] 2) Obtain the casting speed V during the ladle casting process. casting =1.3m / min, the relationship between the sliding gate opening and time under this pulling speed condition is shown in [reference]. Figure 2The dynamic layering method is used to set the dynamic mesh of the sliding gate. The DEFINE_CG_MOTION macro in UDF is used to define the sliding gate mesh motion in FLUENT according to the relationship between the sliding gate opening and time.

[0040] 3) Select the RNG k-ε turbulence model and the VOF model, set the upper inlet of the ladle as the pressure inlet boundary, the inlet material as air, and the inlet pressure as standard atmospheric pressure, set the lower outlet as the pressure outlet boundary, and the outlet pressure as standard atmospheric pressure, and set the interface as a no-slip boundary condition; set the turbulence intensity at the pressure inlet. and hydraulic diameter Turbulence intensity at the pressure outlet and hydraulic diameter ; Turbulence intensity at the pressure inlet Among them, the Reynolds number at the pressure inlet In the formula, Fluid density, kg / m³ 3 ; The hydraulic diameter at the pressure inlet is 3140 mm. The fluid's kinematic viscosity is 0.0055 Pa·s; the average fluid velocity at the pressure inlet is... In the formula, and These represent the cross-sectional areas at the pressure inlet and pressure outlet, respectively, and the average fluid velocity at the pressure outlet. In the formula, g is the acceleration due to gravity, 9.8 m / s². 2 H represents the initial liquid level of molten steel in the ladle, in mm; turbulence intensity at the pressure outlet. Among them, the Reynolds number at the pressure outlet In the formula, The hydraulic diameter at the pressure outlet is 67 mm.

[0041] 4) The VOF model in Fluent software was used to simulate the ladle casting process. The pressure-velocity coupled implicit algorithm (PISO algorithm) was used to track the interface between molten steel, slag and air in the ladle. The sum of the volume fractions of molten steel, slag and air was controlled to be 1. The time step was controlled by the Coulomb number with an initial minimum time step of 0.001s and the Coulomb number of 0.5 until the casting was completed. The change cloud map of the steel-slag interface was obtained based on the tracking results. According to the obtained change cloud map, when the liquid level drops to a certain height, the molten steel surface layer at the steel-slag interface above the nozzle first shows a depression and begins to develop. At the same time, the free liquid surface begins to change. As the molten steel around the ladle continuously flows towards the center of the nozzle, the velocity gradient accumulation of the molten steel fluid layer near the outlet is aggravated. After a certain degree, it will drive the fluid of the adjacent upper layer to undergo the same evolution. This is transmitted layer by layer to the interface between the molten steel surface and the slag layer, causing the interface to gradually become unstable.

[0042] 5) When the tracking result of step 4) shows that the interface between the molten steel surface and the slag layer becomes unstable, the first critical slag height h1 = 125 mm is obtained.

[0043] 6) When the ladle is poured to the first critical slag height h1=125mm, the opening of the sliding nozzle slide plate is reduced from the initial value K0=55.2% at a speed of 3.5mm / s to the first adjustment value K1=20%, held for 20s, and then increased back to the initial value K0 at a speed of 0.16mm / s.

[0044] 7) Obtain the second critical height: Replace the relationship between the slide opening and time of the sliding gate under the specified pulling speed condition in step 2) with the sliding gate slide opening change trajectory obtained in step 6) (see... Figure 2 ), and repeat steps 2) to 4). At this time, the initial liquid level of the molten steel in the ladle is the first critical height. When the tracking results show that the interface between the molten steel surface and the slag layer becomes unstable, the second critical height for slag removal is obtained as h2 = 105 mm.

[0045] 8) When the ladle is poured to the second critical slag discharge height, the opening of the sliding nozzle slide plate is reduced from the initial value to the second adjustment value K2=20% at a speed of 3.5mm / s, held for 20s, and then increased back to the initial value at a speed of 0.16mm / s until the pouring is completed. At this time, 75mm of steel remains in the ladle, and slag discharge occurs, which cannot be controlled and suppressed by the slide plate.

[0046] The experiment was verified using a 1:3 water simulation. The initial pouring height was 1116 mm and the thickness of the oil layer (i.e., the simulated slag layer) was 35 mm. The first critical height was 41.0 mm and the second critical height was 34.9 mm. The pouring was completed after adjusting the opening of the aforementioned sliding gate slide plate. Compared with the process without dynamic adjustment, the critical height of vortex generation decreased from 46 mm to 25.3 mm, a decrease of 45.00%, which showed a significant suppression effect. At the same time, the tundish dropped by 36 mm.

[0047] Example 2

[0048] A method for suppressing slag runoff from vortexes during ladle pouring includes the following steps:

[0049] 1) Obtain the structural and dimensional parameters of the ladle, establish a 3D model of the ladle, and perform mesh generation, such as... Figure 1 As shown, the structure of the ladle includes the ladle body, an upper water inlet, a sliding water inlet, and a lower water inlet located at the bottom of the ladle. In the three-dimensional model of the ladle, the interfaces of the upper water inlet, the sliding water inlet, and the lower water inlet are connected by a fluid interface, and the wall surface is set as a no-slip wall boundary condition.

[0050] 2) Obtain the casting speed V during the ladle casting process. casting =1.3m / min, initial molten steel level in the ladle 3348mm, the relationship between the sliding gate opening and time under this casting speed condition is described in [reference needed]. Figure 3 The dynamic layering method is used to set the dynamic mesh of the sliding gate. The DEFINE_CG_MOTION macro in UDF is used to define the sliding gate mesh motion in FLUENT according to the relationship between the sliding gate opening and time.

[0051] 3) Select the RNG k-ε turbulence model and the VOF model, set the upper inlet of the ladle as the pressure inlet boundary, the inlet material as air, and the inlet pressure as standard atmospheric pressure, set the lower outlet as the pressure outlet boundary, and the outlet pressure as standard atmospheric pressure, and set the interface as a no-slip boundary condition; set the turbulence intensity at the pressure inlet. and hydraulic diameter Turbulence intensity at the pressure outlet and hydraulic diameter ; Turbulence intensity at the pressure inlet Among them, the Reynolds number at the pressure inlet In the formula, Fluid density, kg / m³ 3 ; The hydraulic diameter at the pressure inlet is in mm; ρ is the kinematic viscosity of the fluid, Pa·s; ρ is the average fluid velocity at the pressure inlet. In the formula, and These represent the cross-sectional areas at the pressure inlet and pressure outlet, respectively, and the average fluid velocity at the pressure outlet. In the formula, g is the acceleration due to gravity, 9.8 m / s². 2 H represents the initial liquid level of molten steel in the ladle, in mm; turbulence intensity at the pressure outlet. Among them, the Reynolds number at the pressure outlet In the formula, The hydraulic diameter at the pressure outlet is in mm.

[0052] 4) The VOF model in Fluent software was used to simulate the ladle casting process. The pressure-velocity coupled implicit algorithm (PISO algorithm) was used to track the interface between molten steel, slag and air in the ladle. The sum of the volume fractions of molten steel, slag and air was controlled to be 1. The time step was controlled by the Coulomb number with an initial minimum time step of 0.001s and the Coulomb number of 0.5 until the casting was completed. The change cloud map of the steel-slag interface was obtained based on the tracking results. According to the obtained change cloud map, when the liquid level drops to a certain height, the molten steel surface layer at the steel-slag interface above the nozzle first shows a depression and begins to develop. At the same time, the free liquid surface begins to change. As the molten steel around the ladle continuously flows towards the center of the nozzle, the velocity gradient accumulation of the molten steel fluid layer near the outlet is aggravated. After a certain degree, it will drive the fluid of the adjacent upper layer to undergo the same evolution. This is transmitted layer by layer to the interface between the molten steel surface and the slag layer, causing the interface to gradually become unstable.

[0053] 5) When the tracking result of step 4) shows that the interface between the molten steel surface and the slag layer becomes unstable, the first critical slag height h1 = 125 mm is obtained.

[0054] 6) When the ladle is poured to the first critical slag height h1=125mm, the opening of the sliding nozzle slide plate is reduced from the initial value K0=55.2% at a speed of 3.5mm / s to the first adjustment value K1=20%, held for 20s, and then increased back to the initial value K0 at a speed of 0.16mm / s.

[0055] 7) Obtain the second critical height: Replace the relationship between the sliding gate opening and time under the pulling speed condition in step 2) with the sliding gate opening change trajectory obtained in step 6), and execute steps 2) to 4) again. At this time, the initial liquid level of the molten steel in the ladle is the first critical height. When the tracking result shows that the interface between the molten steel surface and the slag layer becomes unstable, the second critical height for slag discharge h2 = 105 mm is obtained.

[0056] 8) When the ladle is poured to the second critical slag height, the opening of the sliding nozzle slide plate is reduced from the initial value to the second adjustment value K2=35% at a speed of 3.5mm / s, held for 20s, and then increased back to the initial value at a speed of 0.16mm / s until the pouring is completed. At this time, 95mm of steel remains in the ladle, and slag begins to fall, which cannot be controlled and suppressed by the slide plate.

[0057] The experiment was verified using a 1:3 water simulation. The initial pouring height was 1116 mm and the thickness of the oil layer (i.e., the simulated slag layer) was 35 mm. The first critical height was 41.0 mm and the second critical height was 34.9 mm. The pouring was completed after adjusting the opening of the aforementioned sliding gate slide plate. Compared with the process without dynamic adjustment, the critical height of vortex generation decreased from 46 mm to 31.67 mm, a decrease of 31.15%, which showed a significant suppression effect. At the same time, the tundish dropped by 24 mm.

[0058] Example 3

[0059] A method for suppressing slag runoff from vortexes during ladle pouring includes the following steps:

[0060] 1) Obtain the structural and dimensional parameters of the ladle, establish a 3D model of the ladle, and perform mesh generation, such as... Figure 1 As shown, the structure of the ladle includes the ladle body, an upper water inlet, a sliding water inlet, and a lower water inlet located at the bottom of the ladle. In the three-dimensional model of the ladle, the interfaces of the upper water inlet, the sliding water inlet, and the lower water inlet are connected by a fluid interface, and the wall surface is set as a no-slip wall boundary condition.

[0061] 2) Obtain the casting speed V during the ladle casting process. casting =1.3m / min, initial molten steel level in the ladle 3348mm, the relationship between the sliding gate opening and time under this casting speed condition is described in [reference needed]. Figure 3 The dynamic layering method is used to set the dynamic mesh of the sliding gate. The DEFINE_CG_MOTION macro in UDF is used to define the sliding gate mesh motion in FLUENT according to the relationship between the sliding gate opening and time.

[0062] 3) Select the RNG k-ε turbulence model and the VOF model, set the upper inlet of the ladle as the pressure inlet boundary, the inlet material as air, and the inlet pressure as standard atmospheric pressure, set the lower outlet as the pressure outlet boundary, and the outlet pressure as standard atmospheric pressure, and set the interface as a no-slip boundary condition; set the turbulence intensity at the pressure inlet. and hydraulic diameter Turbulence intensity at the pressure outlet and hydraulic diameter ; Turbulence intensity at the pressure inlet Among them, the Reynolds number at the pressure inlet In the formula, Fluid density, kg / m³ 3 ; The hydraulic diameter at the pressure inlet is in mm; ρ is the kinematic viscosity of the fluid, Pa·s; ρ is the average fluid velocity at the pressure inlet. In the formula, and These represent the cross-sectional areas at the pressure inlet and pressure outlet, respectively, and the average fluid velocity at the pressure outlet. In the formula, g is the acceleration due to gravity, 9.8 m / s². 2 H represents the initial liquid level of molten steel in the ladle, in mm; turbulence intensity at the pressure outlet. Among them, the Reynolds number at the pressure outlet In the formula, The hydraulic diameter at the pressure outlet is in mm.

[0063] 4) The VOF model in Fluent software was used to simulate the ladle casting process. The pressure-velocity coupled implicit algorithm (PISO algorithm) was used to track the interface between molten steel, slag and air in the ladle. The sum of the volume fractions of molten steel, slag and air was controlled to be 1. The time step was controlled by the Coulomb number with an initial minimum time step of 0.001s and the Coulomb number of 0.5 until the casting was completed. The change cloud map of the steel-slag interface was obtained based on the tracking results. According to the obtained change cloud map, when the liquid level drops to a certain height, the molten steel surface layer at the steel-slag interface above the nozzle first shows a depression and begins to develop. At the same time, the free liquid surface begins to change. As the molten steel around the ladle continuously flows towards the center of the nozzle, the velocity gradient accumulation of the molten steel fluid layer near the outlet is aggravated. After a certain degree, it will drive the fluid of the adjacent upper layer to undergo the same evolution. This is transmitted layer by layer to the interface between the molten steel surface and the slag layer, causing the interface to gradually become unstable.

[0064] 5) When the tracking result of step 4) shows that the interface between the molten steel surface and the slag layer becomes unstable, the first critical slag height h1 = 125 mm is obtained.

[0065] 6) When the ladle is poured to the first critical slag height h1=125mm, the opening of the sliding nozzle slide plate is reduced from the initial value K0=55.2% at a speed of 3.5mm / s to the first adjustment value K1=20%, held for 20s, and then increased back to the initial value K0 at a speed of 0.16mm / s.

[0066] 7) Obtain the second critical height: Replace the relationship between the sliding gate opening and time under the pulling speed condition in step 2) with the sliding gate opening change trajectory obtained in step 6), and execute steps 2) to 4) again. At this time, the initial liquid level of the molten steel in the ladle is the first critical height. When the tracking result shows that the interface between the molten steel surface and the slag layer becomes unstable, the second critical height for slag discharge h2 = 105 mm is obtained.

[0067] 8) When the ladle is poured to the second critical slag discharge height, the opening of the sliding nozzle slide plate is reduced from the initial value to the second adjustment value K2=30% at a speed of 3.5mm / s, held for 20s, and then increased back to the initial value at a speed of 0.16mm / s until the pouring is completed. At this time, 83.5mm of steel remains in the ladle, and slag discharge occurs, which cannot be controlled and suppressed by the slide plate.

[0068] The experiment was verified using a 1:3 water simulation. The initial pouring height was 1116 mm and the thickness of the oil layer (i.e., the simulated slag layer) was 35 mm. The first critical height was 41.0 mm and the second critical height was 34.9 mm. The pouring was completed after adjusting the opening of the aforementioned sliding gate slide plate. Compared with the process without dynamic adjustment, the critical height of vortex generation decreased from 46 mm to 28.1 mm, a decrease of 38.91%, which showed a significant suppression effect. At the same time, the tundish height decreased by 31 mm.

[0069] Comparative Example 1

[0070] A method for suppressing slag runoff from vortexes during ladle pouring includes the following steps:

[0071] 1) Obtain the structural and dimensional parameters of the ladle, establish a 3D model of the ladle, and perform mesh generation, such as... Figure 1 As shown, the structure of the ladle includes the ladle body, an upper water inlet, a sliding water inlet, and a lower water inlet located at the bottom of the ladle. In the three-dimensional model of the ladle, the interfaces of the upper water inlet, the sliding water inlet, and the lower water inlet are connected by a fluid interface, and the wall surface is set as a no-slip wall boundary condition.

[0072] 2) Obtain the casting speed V during the ladle casting process. casting =1.3m / min, initial molten steel level in the ladle 3348mm, the relationship between the sliding gate opening and time under this casting speed condition is described in [reference needed]. Figure 3 The dynamic layering method is used to set the dynamic mesh of the sliding gate. The DEFINE_CG_MOTION macro in UDF is used to define the sliding gate mesh motion in FLUENT according to the relationship between the sliding gate opening and time.

[0073] 3) Select the RNG k-ε turbulence model and the VOF model, set the upper inlet of the ladle as the pressure inlet boundary, the inlet material as air, and the inlet pressure as standard atmospheric pressure, set the lower outlet as the pressure outlet boundary, and the outlet pressure as standard atmospheric pressure, and set the interface as a no-slip boundary condition; set the turbulence intensity at the pressure inlet. and hydraulic diameter Turbulence intensity at the pressure outlet and hydraulic diameter ; Turbulence intensity at the pressure inlet Among them, the Reynolds number at the pressure inlet In the formula, Fluid density, kg / m³ 3 ; The hydraulic diameter at the pressure inlet is in mm; ρ is the kinematic viscosity of the fluid, Pa·s; ρ is the average fluid velocity at the pressure inlet. In the formula, and These represent the cross-sectional areas at the pressure inlet and pressure outlet, respectively, and the average fluid velocity at the pressure outlet. In the formula, g is the acceleration due to gravity, 9.8 m / s². 2 H represents the initial liquid level of molten steel in the ladle, in mm; turbulence intensity at the pressure outlet. Among them, the Reynolds number at the pressure outlet In the formula, The hydraulic diameter at the pressure outlet is in mm.

[0074] 4) The VOF model in Fluent software was used to simulate the ladle casting process. The pressure-velocity coupled implicit algorithm (PISO algorithm) was used to track the interface between molten steel, slag and air in the ladle. The sum of the volume fractions of molten steel, slag and air was controlled to be 1. The time step was controlled by the Coulomb number with an initial minimum time step of 0.001s and the Coulomb number of 0.5 until the casting was completed. The change cloud map of the steel-slag interface was obtained based on the tracking results. According to the obtained change cloud map, when the liquid level drops to a certain height, the molten steel surface layer at the steel-slag interface above the nozzle first shows a depression and begins to develop. At the same time, the free liquid surface begins to change. As the molten steel around the ladle continuously flows towards the center of the nozzle, the velocity gradient accumulation of the molten steel fluid layer near the outlet is aggravated. After a certain degree, it will drive the fluid of the adjacent upper layer to undergo the same evolution. This is transmitted layer by layer to the interface between the molten steel surface and the slag layer, causing the interface to gradually become unstable.

[0075] 5) When the tracking result of step 4) shows that the interface between the molten steel surface and the slag layer becomes unstable, the first critical slag height h1 = 125 mm is obtained.

[0076] 6) When the ladle is poured to the first critical slag height h1=125mm, the opening of the sliding nozzle slide plate is reduced from the initial value K0=55.2% at a speed of 3.5mm / s to the first adjustment value K1=20%, held for 20s, and then increased back to the initial value K0 at a speed of 0.16mm / s.

[0077] 7) Obtain the second critical height: Replace the relationship between the sliding gate opening and time under the pulling speed condition in step 2) with the sliding gate opening change trajectory obtained in step 6), and execute steps 2) to 4) again. At this time, the initial liquid level of the molten steel in the ladle is the first critical height. When the tracking result shows that the interface between the molten steel surface and the slag layer becomes unstable, the second critical height for slag discharge h2 = 105 mm is obtained.

[0078] 8) When the ladle is poured to the second critical slag discharge height, the opening of the sliding nozzle slide plate is reduced from the initial value to the second adjustment value K2=40% at a speed of 3.5mm / s, held for 20s, and then increased back to the initial value at a speed of 0.16mm / s until the pouring is completed. At this time, 110mm of steel remains in the ladle, and slag discharge occurs.

[0079] The experiment was conducted using a 1:3 water simulation. The initial pouring height was 1116 mm and the thickness of the oil layer (i.e., the simulated slag layer) was 35 mm. The first critical height was 41.0 mm and the second critical height was 34.9 mm. The pouring was completed after adjusting the opening of the aforementioned sliding gate slide plate. Compared with the process without dynamic adjustment, the critical height of vortex generation decreased from 46 mm to 40.7 mm, a decrease of 11.52%, and the suppression effect was not obvious.

[0080] Comparative Example 2

[0081] A method for suppressing slag runoff from vortexes during ladle pouring includes the following steps:

[0082] 1) Obtain the structural and dimensional parameters of the ladle, establish a 3D model of the ladle, and perform mesh generation, such as... Figure 1 As shown, the structure of the ladle includes the ladle body, an upper water inlet, a sliding water inlet, and a lower water inlet located at the bottom of the ladle. In the three-dimensional model of the ladle, the interfaces of the upper water inlet, the sliding water inlet, and the lower water inlet are connected by a fluid interface, and the wall surface is set as a no-slip wall boundary condition.

[0083] 2) Obtain the casting speed V during the ladle casting process. casting =1.3m / min, initial molten steel level in the ladle 3348mm, the relationship between the sliding gate opening and time under this casting speed condition is described in [reference needed]. Figure 3The dynamic layering method is used to set the dynamic mesh of the sliding gate. The DEFINE_CG_MOTION macro in UDF is used to define the sliding gate mesh motion in FLUENT according to the relationship between the sliding gate opening and time.

[0084] 3) Select the RNG k-ε turbulence model and the VOF model, set the upper inlet of the ladle as the pressure inlet boundary, the inlet material as air, and the inlet pressure as standard atmospheric pressure, set the lower outlet as the pressure outlet boundary, and the outlet pressure as standard atmospheric pressure, and set the interface as a no-slip boundary condition; set the turbulence intensity at the pressure inlet. and hydraulic diameter Turbulence intensity at the pressure outlet and hydraulic diameter ; Turbulence intensity at the pressure inlet Among them, the Reynolds number at the pressure inlet In the formula, Fluid density, kg / m³ 3 ; The hydraulic diameter at the pressure inlet is in mm; ρ is the kinematic viscosity of the fluid, Pa·s; ρ is the average fluid velocity at the pressure inlet. In the formula, and These represent the cross-sectional areas at the pressure inlet and pressure outlet, respectively, and the average fluid velocity at the pressure outlet. In the formula, g is the acceleration due to gravity, 9.8 m / s². 2 H represents the initial liquid level of molten steel in the ladle, in mm; turbulence intensity at the pressure outlet. Among them, the Reynolds number at the pressure outlet In the formula, The hydraulic diameter at the pressure outlet is in mm.

[0085] 4) The VOF model in Fluent software was used to simulate the ladle casting process. The pressure-velocity coupled implicit algorithm (PISO algorithm) was used to track the interface between molten steel, slag and air in the ladle. The sum of the volume fractions of molten steel, slag and air was controlled to be 1. The time step was controlled by the Coulomb number with an initial minimum time step of 0.001s and the Coulomb number of 0.5 until the casting was completed. The change cloud map of the steel-slag interface was obtained based on the tracking results. According to the obtained change cloud map, when the liquid level drops to a certain height, the molten steel surface layer at the steel-slag interface above the nozzle first shows a depression and begins to develop. At the same time, the free liquid surface begins to change. As the molten steel around the ladle continuously flows towards the center of the nozzle, the velocity gradient accumulation of the molten steel fluid layer near the outlet is aggravated. After a certain degree, it will drive the fluid of the adjacent upper layer to undergo the same evolution. This is transmitted layer by layer to the interface between the molten steel surface and the slag layer, causing the interface to gradually become unstable.

[0086] 5) When the tracking result of step 4) shows that the interface between the molten steel surface and the slag layer becomes unstable, the first critical slag height h1 = 125 mm is obtained.

[0087] 6) When the ladle is poured to the first critical slag height h1=125mm, the opening of the sliding nozzle slide plate is reduced from the initial value K0=55.2% at a speed of 3.5mm / s to the first adjustment value K1=20%, held for 20s, and then increased back to the initial value K0 at a speed of 0.16mm / s.

[0088] 7) Obtain the second critical height: Replace the relationship between the sliding gate opening and time under the pulling speed condition in step 2) with the sliding gate opening change trajectory obtained in step 6), and execute steps 2) to 4) again. At this time, the initial liquid level of the molten steel in the ladle is the first critical height. When the tracking result shows that the interface between the molten steel surface and the slag layer becomes unstable, the second critical height for slag discharge h2 = 105 mm is obtained.

[0089] 8) When the ladle is poured to the second critical slag discharge height, the opening of the sliding nozzle slide plate is reduced from the initial value to the second adjustment value K2=15% at a speed of 3.5mm / s, held for 20s, and then increased back to the initial value at a speed of 0.16mm / s until the pouring is completed. At this time, 66mm of steel remains in the ladle, and slag discharge occurs.

[0090] The experiment was conducted using a 1:3 water simulation. The initial pouring height was 1116 mm, and the thickness of the oil layer (i.e., the simulated slag layer) was 35 mm. The first critical height was 41.0 mm, and the second critical height was 34.9 mm. The pouring was completed after adjusting the opening of the sliding nozzle slide plate as described above. Compared with the process without dynamic adjustment, the critical height of the vortex was reduced from 46 mm to 22.2 mm, a decrease of 51.74%, which showed a significant suppression effect. However, under this adjustment mode, the liquid level in the tundish dropped by 54 mm, which significantly affected the stability of the pouring.

[0091] It should be noted that, based on the above embodiments of the present invention, those skilled in the art can fully realize the scope of the independent claims and dependent claims of the present invention, and the implementation process and methods are the same as those in the above embodiments; and the parts of the present invention not described in detail belong to the well-known technology in the art. However, the protection scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.

Claims

1. A method for suppressing slag runoff from vortexes during ladle pouring, characterized in that, The process includes the following steps: When the ladle is poured to the first critical slag discharge height h1, the opening of the sliding nozzle slide is reduced from the initial value K0 to the first adjustment value K1 = 18~23%, held for 20~25s, and then increased back to the initial value K0. When the ladle is poured to the second critical slag discharge height h2, the opening of the sliding nozzle slide is reduced from the initial value to the second adjustment value K2 = 18~35%, held for 20~25s, and then increased back to the initial value. The first critical slag height h1 is obtained by the following method: 1) Obtain the structural and dimensional parameters of the ladle, establish a three-dimensional model of the ladle and perform mesh generation. The structure of the ladle includes the ladle body, the upper water inlet, the sliding water inlet and the lower water inlet located at the bottom of the ladle. The interfaces of the upper water inlet, the sliding water inlet and the lower water inlet in the three-dimensional model of the ladle are connected by a fluid interface, and the wall surface is set as a no-slip wall boundary condition. 2) Obtain the casting speed of the ladle, the initial liquid level of the molten steel in the ladle, and the trajectory of the sliding gate opening change during the casting process under the casting speed condition. Use the dynamic layup method to set the dynamic mesh of the sliding gate. Use the DEFINE_CG_MOTION macro in UDF to define the sliding gate mesh motion in FLUENT according to the obtained relationship between the sliding gate opening and time. 3) Select the RNG k-ε turbulence model and the VOF model, set the upper opening of the ladle as the pressure inlet boundary, the inlet material as air, and the inlet pressure as standard atmospheric pressure, set the lower outlet as the pressure outlet boundary, and the outlet pressure as standard atmospheric pressure, and set the interface as a no-slip boundary condition; set the turbulence intensity and hydraulic diameter at the pressure inlet, and the turbulence intensity and hydraulic diameter at the pressure outlet. 4) Track the interface between molten steel, slag and air in the ladle according to the model and set conditions in step 3), wherein the sum of the volume fractions of molten steel, slag and air is controlled to be 1. 5) Based on the tracking results of step 4), the first critical slag drop height h1 is obtained when the interface between the molten steel surface and the slag layer becomes unstable; The second critical slag height h2 is obtained by replacing steps 2) and 3) of the method for obtaining the first critical slag height h1 with: 2) Based on the adjustment method of the sliding gate slide opening when the pouring height reaches the first critical slag discharge height, the sliding gate slide opening trajectory is obtained, and the dynamic layering method is used to set the dynamic mesh of the sliding gate; the DEFINE_CG_MOTION macro in UDF is used to define the slide mesh motion in FLUENT according to the obtained sliding gate slide opening and time relationship; 3) Select the RNG k-ε turbulence model and VOF model, set the slag layer surface as the pressure inlet boundary, the inlet material as air, and the inlet pressure as standard atmospheric pressure, set the outlet of the sluice gate as the pressure outlet boundary, the outlet pressure as standard atmospheric pressure, and set the interface as no-slip boundary condition; set the turbulence intensity and hydraulic diameter at the pressure inlet, and the turbulence intensity and hydraulic diameter at the pressure outlet. That is, to obtain the method of acquisition.

2. The method as described in claim 1, characterized in that, The initial value of the opening is K0 = 50~60%.

3. The method as described in claim 1, characterized in that, The speed during the process of decreasing the opening of the sliding gate slide plate is 3.5-4.2 mm / s; the speed during the process of increasing the opening of the sliding gate slide plate is 0.16-0.17 mm / s.

4. The method as described in claim 1, characterized in that, The first adjustment value K0 = 20%, and the second adjustment value K2 = 28~33%.

5. The method as described in claim 1, characterized in that, In step 1), the ladle and the sliding gate slide body are divided into a hexahedral grid, while the top and bottom of the ladle and the bottom of the sliding gate slide are divided into an O-shaped grid.

6. The method as described in claim 1, characterized in that, In step 4), the tracking specifically adopts a pressure-velocity coupled implicit algorithm, using the Courant number to control the time step, with an initial minimum time step of 0.001s and the Courant number being 0.5~1, until the casting is completed.

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