Method for calculating the motion of inclusions across the slag / metal interface during a vidp melting process

Abstract

The present application relates to the technical field of metal processing, and particularly relates to a method for calculating the movement of inclusions across a slag / gold interface in a VIDP smelting process. The method comprises the following steps: S1: establishing a geometric model of a vacuum induction degassing pouring furnace to be solved; S2: assigning material physical property parameters in the geometric model; S3: adding physical fields and setting initial values and boundary conditions of the geometric model; the physical fields include a magnetic field, a turbulent flow field and a fluid flow particle tracking physical field; S4: adding a Lorentz force to couple the magnetic field and the turbulent flow field; S5: performing mesh division on the geometric model; and S6: solving to obtain the movement trajectory of the inclusion particles. The present application establishes a model of the VIDP under physical fields such as a magnetic field and a flow field by using finite element simulation software, ensures the accuracy of the coupling, and performs simulation calculation on fluid flow particle tracking in the VIDP smelting process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal processing, in particular to a method for calculating the motion of inclusions across a slag / metal interface in a VIDP smelting process. BACKGROUND

[0002] With the rapid development of modern science and technology, people's quality requirements for metal materials are increasingly strict. Controlling non-metallic inclusions in alloys has a huge impact on improving material quality and performance. Among them, using slag / metal reaction to remove inclusions is an effective method to control inclusions in molten metal. Vacuum induction degassing pouring smelting (VIDP) is a method of using eddy current generated in a metal conductor by electromagnetic induction to heat the furnace charge for smelting under vacuum conditions. It is mainly applied to the production of special alloys such as special steel, precision alloy, electrothermal alloy, high-temperature alloy and corrosion-resistant alloy. Therefore, studying the motion behavior of inclusions across the slag / metal interface in the VIDP smelting process is of great significance to the removal of inclusions and the improvement of material quality and performance.

[0003] VIDP smelting is carried out in a high-temperature sealed space, so the reaction in the furnace cannot be directly observed during smelting. The method of finite element numerical simulation can be used to calculate and analyze the electromagnetic field, temperature field, flow field and other multi-physical fields in the VIDP smelting process, which can provide data that are difficult to obtain in the test process, reduce test costs, shorten test cycle and optimize process parameters. On the basis of multi-physical field coupling, fluid flow particle tracking analysis can be carried out to accurately understand the motion behavior of inclusions across the slag / metal interface in the VIDP smelting process, which can theoretically guide practice and has important practical significance for controlling inclusions in alloys and improving alloy performance.

[0004] Therefore, the present application is proposed. SUMMARY

[0005] The purpose of the present application is to provide a method for calculating the motion of inclusions across the slag / metal interface in the VIDP smelting process, to fill the gap in the simulation of the motion behavior of inclusions across the slag / metal interface in the VIDP smelting process, to complete the model establishment of VIDP under multi-physical fields by using finite element simulation software, and to ensure the accuracy of coupling, so as to realize the control of inclusions in alloy materials.

[0006] In order to achieve the above purpose of the present application, the following technical scheme is adopted:

[0007] The method for calculating the motion of inclusions across the slag / metal interface in the VIDP smelting process comprises the following steps:

[0008] S1: a geometry model of a vacuum induction degassing casting furnace to be solved is established by using Comsol Multiphysics;

[0009] S2: physical property parameters of materials in the geometry model are given;

[0010] S3: a physical field is added in the geometry model, and initial values and boundary conditions of the geometry model are set; wherein the physical field includes a magnetic field, a turbulent flow field and a fluid flow particle tracking physical field;

[0011] In the magnetic field, the simulated vacuum induction degassing casting furnace model is a two-dimensional axisymmetric model, the left boundary is set as an axisymmetric boundary, the edge of the furnace wall is set as an infinite element domain, and the furnace wall boundary is set as a magnetic insulation; the magnetic field is set in a coil current excitation or coil voltage excitation mode, and a single wire coil group is used for the coil;

[0012] In the turbulent flow, a k-ε turbulent flow model is used to analyze the flow of the fluid in the vacuum induction degassing casting furnace, all the fluids are set as incompressible fluids, the boundary condition of the crucible wall is set as no slip, and the wall function is used for wall treatment of the crucible wall; the initial values of the slag and alloy liquid velocity field are set as 0, and the fluids are subjected to gravity and volume force, and the calculated Lorentz force in the magnetic field is input into the volume force as a calculation result; a dynamic mesh is used to simulate the change of the contact surface between the protective gas and the slag and the alloy liquid with time;

[0013] In the fluid flow particle tracking physical field, the inclusion particles are released at a random position in the alloy liquid from 0 s, the fluid motion velocity calculated in the turbulent flow process is input into the calculation as the particle motion velocity; the symmetry axis and the wall condition of the bottom of the crucible are set as rebound, and the wall condition of the side wall of the crucible is set as frozen; the interfaces of the inclusion particles and the alloy liquid and the slag are set as wall conditions, wherein the wall condition of the upper surface of the slag is frozen, and the wall condition of the interface between the slag and the alloy liquid is through; the inclusion particles are subjected to the action of gravity, lift, drag and additional mass force when moving in the alloy liquid and the slag, and are subjected to the action force of the interface when crossing the slag / gold interface, and it is set that the inclusion particles are subjected to the action force of the interface only when the distance between the position of the inclusion particles and the interface is less than the radius of the inclusion particles;

[0014] S4: a Lorentz force is added to couple the magnetic field and the turbulent flow process through the Lorentz force;

[0015] S5: the geometry model is meshed;

[0016] S6: the motion trajectory of the inclusion particles is calculated.

[0017] In the specific embodiment of the present application, in S1, the calculation domain of the geometric model comprises an alloy liquid calculation domain, a slag calculation domain, a crucible calculation domain, an insulating material calculation domain, an induction coil calculation domain, a magnetic yoke calculation domain, a protective gas calculation domain and a cooling water calculation domain.

[0018] In actual operation, according to the vacuum induction degassing casting furnace smelting process and the physical map of the experimental device, the geometric model of the vacuum induction degassing casting furnace to be solved is established.

[0019] In the specific embodiment of the present application, in S2, the material comprises an alloy liquid, a slag, a crucible, an insulating material, an induction coil, a magnetic yoke, a protective gas and cooling water; and the physical property parameter comprises a thermal conductivity, a constant-pressure heat capacity, an electrical conductivity, a density, a relative magnetic permeability, a relative dielectric constant, a dynamic viscosity and a specific heat rate.

[0020] In the specific embodiment of the present application, in the geometric model, all the calculation domains satisfy the Ampere's law. Further, force calculation is added in the alloy liquid calculation domain and the slag calculation domain.

[0021] In the specific embodiment of the present application, in S5, the grid type is a triangular grid. Further, the grid division is performed in a multi-region and multi-scale manner.

[0022] In the specific embodiment of the present application, small-size grids are used for the slag, the alloy liquid, the coil and the magnetic yoke, and the remaining regions are divided by large grids. Further, the grid division method comprises: performing grid division on all the regions, with the unit size being super-fined, and further refining the grids of the slag, the alloy liquid, the coil and the magnetic yoke.

[0023] In the specific embodiment of the present application, S6 comprises: solving to obtain the magnetic flux density, the turbulent flow velocity field distribution and the motion trajectory of the inclusion particles. Further, in S6, frequency domain-transient research is added to calculate the turbulent flow field; in the research, time step, frequency, tolerance are set, the magnetic field, the turbulence and the dynamic grid are selected in the physical field interface, the magnetic field and the turbulent flow field are coupled by selecting the Lorentz force in the multi-physical field; the transient solver selects MUMPS, and the magnetic flux density and the turbulent flow velocity field distribution are calculated.

[0024] The grid division is performed again on the geometric model;

[0025] Transient research is added to calculate the motion trajectory of the inclusion across the slag / gold interface; in the research, time step is set, and the fluid flow particle tracking is selected in the physical field interface; the transient solver selects MUMPS, and the motion trajectory of the inclusion particles is calculated.

[0026] The application also provides application of the method for calculating the movement of inclusions across a slag / gold interface in a VIDP smelting process to a powder high-temperature alloy VIDP smelting process.

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

[0028] (1) The application establishes a model of VIDP under physical fields such as a magnetic field and a flow field by using finite element simulation software, ensures the accuracy of coupling, and simulates and calculates the flow of fluid and particle tracking in the VIDP smelting process, thereby filling the gap in the simulation of the movement behavior of inclusions across a slag / gold interface in the VIDP smelting process.

[0029] (2) The method for simulating and calculating the movement trajectory of inclusions across a slag / gold interface in the VIDP smelting process based on finite elements can provide theoretical guidance for VIDP smelting process design, so as to remove inclusions in alloy materials, improve the quality and performance of materials, and has important significance for controlling inclusions in alloys and improving the performance of alloys. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the specific embodiments or the prior art, the drawings needed in the description of the specific embodiments or the prior art will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0031] Figure 1 A simulation calculation flowchart provided by the application;

[0032] Figure 2 A geometric model of a vacuum induction degassing casting furnace provided by the embodiment of the application;

[0033] Figure 3 A mesh division result graph provided by the embodiment of the application;

[0034] Figure 4 A magnetic flux density distribution graph provided by the embodiment of the application;

[0035] Figure 5 A turbulent flow velocity field distribution cloud graph when the smelting time is 300s provided by the embodiment of the application;

[0036] Figure 6 A position graph of inclusions at different times provided by the embodiment of the application; wherein (a), (b), (c) and (d) are position graphs of inclusions when the smelting time is 0s, 10s, 50s and 100s, respectively;

[0037] Figure 7 A curve of the adsorption rate of the slag, the alloy liquid surface and the crucible wall surface to the inclusion particles in the VIDP smelting process is provided for the embodiments of the present application. DETAILED DESCRIPTION

[0038] The technical solutions of the present application will be described clearly and completely in combination with the drawings and specific embodiments, but those skilled in the art will understand that the following described embodiments are part of the embodiments of the present application, not all the embodiments, and are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The specific conditions are not specified in the embodiments, and are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, and are conventional products that can be purchased on the market.

[0039] The method for calculating the motion of inclusions crossing the slag / metal interface in the VIDP smelting process comprises the following steps:

[0040] S1: using Comsol Multiphysics to establish a geometric model of the vacuum induction degassing casting furnace to be solved;

[0041] S2: giving the material property parameters in the geometric model;

[0042] S3: adding physical fields in the geometric model and setting the initial values and boundary conditions of the geometric model; wherein the physical fields include magnetic field, turbulent flow field and fluid flow particle tracking physical field;

[0043] In the magnetic field, the simulated vacuum induction degassing casting furnace model is a two-dimensional axisymmetric model, the left boundary is set as an axisymmetric boundary, the edge of the furnace wall is an infinite element domain, and the furnace wall boundary is magnetically insulated; the magnetic field is set in a coil current excitation or coil voltage excitation mode, and the coil adopts a single wire coil group;

[0044] In the turbulent flow, the k-ε turbulent flow model is used to analyze the flow of the fluid in the vacuum induction degassing casting furnace, all the fluids are set as incompressible fluids, the crucible wall boundary condition is set as no slip, and the wall function is used for wall treatment of the crucible wall; the initial values of the slag and alloy liquid velocity field are set as 0, subjected to gravity and body force, and the calculated Lorentz force in the magnetic field is input into the body force as a calculation result; the dynamic mesh is used to simulate the changes of the contact surfaces of the protective gas and the slag, and the slag and the alloy liquid with time;

[0045] In the fluid flow particle tracking physical field, the inclusion particles are released from the random position in the alloy liquid at 0s, the turbulent flow process is calculated to obtain the fluid motion velocity as the inclusion particle motion velocity input into the present calculation; during the VIDP smelting, part of the inclusion particles in the alloy liquid will cross the slag / gold interface into the molten slag, and be adsorbed by the molten slag, and the remaining inclusion particles cannot cross the slag / gold interface and remain in the alloy liquid, the part of the inclusion particles may be captured by the crucible wall and removed or continue to stay in the alloy liquid, the wall condition of the symmetry axis and the bottom of the crucible is set to be rebound, and the wall condition of the side wall of the crucible is set to be frozen; since the inclusion particles are solid, and the alloy liquid and the molten slag are liquid, the interface of the inclusion particles and the alloy liquid and the inclusion particles and the molten slag is set as a wall condition, wherein the upper surface wall condition of the molten slag is frozen, and the wall condition of the interface between the molten slag and the alloy liquid is crossed; the inclusion particles are affected by gravity, lift, drag and additional mass force when moving in the alloy liquid and the molten slag, and the inclusion particles are affected by the interface force when crossing the slag / gold interface, the interface tension points to the particle center of gravity along the normal direction, therefore, the existence of the interface tension will hinder the crossing of the inclusion particles through the interface, and the inclusion particles are set to be affected by the interface force only when the distance between the position of the inclusion particles and the interface is less than the radius of the inclusion particles;

[0046] S4: adding Lorentz force, coupling the magnetic field and the turbulent flow process through the Lorentz force;

[0047] S5: meshing the geometric model;

[0048] S6: solving to obtain the motion trajectory of the inclusion particles.

[0049] In order to study the motion behavior of the inclusion particles crossing the slag / gold interface, the electromagnetic field, the flow field, the temperature field and the force condition of the inclusion particles need to be studied; the Comsol Multiphysics finite element software and the built-in solver are used to solve the electromagnetic field problem, and the direct coupling analysis of multiple physical fields is realized, and the distribution diagram of the physical parameters such as the magnetic field, the flow field and the ion motion trajectory is obtained, which is beneficial to the analysis of the results.

[0050] In the present research, each physical field is symmetrically distributed in the circumferential direction, the charge is assumed to be uniform and continuous, and the model is an axisymmetric graph, so that the three-dimensional problem can be simplified into a two-dimensional problem; in the software model wizard, the two-dimensional axisymmetric space dimension and the physical fields such as magnetic field (mf), turbulent flow k-ε (spf) and fluid flow particle tracking (fpt) are selected to enter the research.

[0051] In actual operation, according to the vacuum induction degassing casting furnace smelting process and the actual diagram of the experimental device, the geometric model of the vacuum induction degassing casting furnace to be solved is established.

[0052] In the specific embodiment of the present application, in S1, the calculation domain of the geometric model comprises an alloy liquid calculation domain, a slag calculation domain, a crucible calculation domain, an insulation material calculation domain, an induction coil calculation domain, a magnetic yoke calculation domain, a protective gas calculation domain and a cooling water calculation domain.

[0053] In the establishment of the geometric model, the height of the alloy liquid, the height of the slag, the size and wall thickness of the crucible, the size and wall thickness of the insulation material, the inner and outer circle size of the induction coil, the size of the magnetic yoke and the like are included but not limited to.

[0054] In the specific embodiment of the present application, in S2, the materials comprise the alloy liquid, the slag, the crucible, the insulation material, the induction coil, the magnetic yoke, the protective gas and the cooling water; the physical property parameters comprise the thermal conductivity, the constant-pressure heat capacity, the electrical conductivity, the density, the relative magnetic permeability, the relative dielectric constant, the dynamic viscosity and the specific heat rate. The corresponding parameters correspond to the actual VIDP smelting process and the actual device.

[0055] In the specific embodiment of the present application, the alloy liquid can be the alloy liquid of FGH4096 powder high-temperature alloy; the slag can be three-seven slag (30% CaF2+70% Al2O3); the crucible can be magnesium oxide material; the insulation material is asbestos; the induction coil material is red copper; the magnetic yoke material is silicon steel; and the protective gas is argon.

[0056] In the specific embodiment of the present application, in the geometric model, all the calculation domains satisfy the Ampere's law. Further, the force calculation is added in the alloy liquid calculation domain and the slag calculation domain.

[0057] In the specific embodiment of the present application, the Ampere's law has the formula:

[0058] E=-jωA

[0059]

[0060]

[0061] J=σE+jωD

[0062] wherein,

[0063] E—induced electromotive force, V / m;

[0064] J—current density, A / m 2 ;

[0065] ω—angular frequency, rad / s;

[0066] A—magnetic potential, Wb / m;

[0067] H—magnetic field intensity, A / m;

[0068] B - magnetic induction, T;

[0069] σ - electrical conductivity, S / m;

[0070] D - electric flux density, C / m 2 .

[0071] In the specific embodiments of the present application, the Lorentz force is met in the alloy liquid calculation domain and the slag calculation domain. Further, the Lorentz force is:

[0072] F = J x B

[0073] Wherein F - Lorentz force, N / m 3 .

[0074] In the specific embodiments of the present application, the k-ε turbulence model in the RANS turbulence model type is used to analyze the flow of the fluid in the vacuum induction degassing casting furnace, and the fluid properties are all from the material.

[0075] Since the contact interfaces of the protective gas and the slag and the slag and the alloy liquid will fluctuate in the actual smelting process, the present application uses a dynamic grid to simulate the changes of the contact interfaces of the protective gas and the slag and the slag and the alloy liquid with time. The grid uses Yeoh smoothing type, and the hardening factor can be 10 or the like.

[0076] In the specific embodiments of the present application, the fluid flow meets the k-ε turbulence model in the RANS turbulence model type, and the formulas involved include:

[0077] Momentum conservation equation:

[0078]

[0079]

[0080] Wherein ρ - solution density, kg / m 3 ;

[0081] u - velocity, m / s;

[0082] p - pressure, Pa;

[0083] F - body force, N / m 3 ;

[0084] g - gravitational acceleration, m / s 2 ;

[0085] μ - solution viscosity, Pa·s;

[0086] μ T - turbulence viscosity coefficient, Pa·s;

[0087] Continuity equation:

[0088]

[0089] Equation of turbulent kinetic energy k:

[0090]

[0091]

[0092]

[0093] Equation of turbulent dissipation rate ε:

[0094]

[0095] where k—turbulent kinetic energy, m2 / s2 2 / s 2 ;

[0096] p k —turbulent kinetic energy due to average velocity gradient, m2 / s2 2 / s 2 ;

[0097] σ k —turbulent Prandtl number of the equation of turbulent kinetic energy k, dimensionless

[0098] σ ε —turbulent Prandtl number of the equation of turbulent dissipation rate ε, dimensionless

[0099] C ε1 ,C ε2 —empirical constants

[0100] Equations involved in the simulation of the slag and alloy liquid (slag / gold) interface and the slag and protective gas (slag / protective gas) interface using dynamic mesh include:

[0101]

[0102] u mesh ·n=u·n

[0103]

[0104] where n—direction vector, dimensionless

[0105] p ext —external pressure, Pa

[0106] u mesh —mesh displacement velocity vector, m / s

[0107] In the detailed description of the present application, the force of slag / metal interface on the inclusion particle in the fluid flow particle tracking physical field is expressed as:

[0108]

[0109] where F s — interfacial tension, N;

[0110] V p — volume of the inclusion particle, m 3 ;

[0111] σ— electrical conductivity, S / m;

[0112] k— thermal diffusivity, kJ / m 3 ·s;

[0113] α— fluid phase fraction.

[0114] The drag force calculation formula is:

[0115]

[0116] where F D — drag force, N;

[0117] d p — particle diameter, m;

[0118] v— particle movement speed, m / s;

[0119] The lift force calculation formula is:

[0120]

[0121] where F L — lift force, N;

[0122] The gravity calculation formula is:

[0123]

[0124] where F g — gravity, N;

[0125] m p — particle mass, kg;

[0126] g— gravitational acceleration, m / s 2 ;

[0127] ρ p — particle density, kg / m 3 .

[0128] The added mass force calculation formula is:

[0129]

[0130] where F m — additional mass force, N;

[0131] r p — particle radius, m;

[0132] p s — slag density, kg / m 3 ;

[0133] a— acceleration during particle motion, m / s 2 .

[0134] In the specific embodiment of the present application, in the fluid flow particle tracking physical field, the freezing probability and the crossing probability of the particle are calculated according to the following formula (in which the adsorption rate mentioned in the formula corresponds to the corresponding freezing probability or crossing probability) :

[0135] The adsorption rate of the inclusion particle at the wall surface can be calculated by the following formula:

[0136]

[0137]

[0138]

[0139] where η WA — inclusion wall adsorption rate;

[0140] d— turbulent boundary layer thickness, m;

[0141] y— distance from the wall, m;

[0142] y + — dimensionless distance from the wall;

[0143] v l — dynamic viscosity of the solution, m 2 / s;

[0144] T0— shear stress, kg / (m·s 2 ) ;

[0145] p l — density of the solution, kg / m 3 ;

[0146] k— turbulent kinetic energy, m 2 / s 2 .

[0147] In the specific embodiment of the present application, in S5, the grid type is a triangular grid. Further, the grid division is performed in a multi-region and multi-scale manner.

[0148] In the specific embodiment of the present application, since the skin effect is obvious on the surface of the charge and the inner surface of the coil, small-size grids are used for the molten slag, the alloy liquid, the coil and the magnetic yoke, and the rest of the area is divided by large grids. Further, the grid division method comprises: dividing the grids in all regions, with the cell size being super-fined; and further refining the grids of the molten slag, the alloy liquid, the coil and the magnetic yoke, with the cell size being super-fined.

[0149] In the specific embodiment of the present application, in the grid division, the maximum cell size can be 6-7 mm, such as 6.6 mm; and the minimum cell size can be 0.02-0.03 mm, such as 0.0247 mm, etc.

[0150] In the specific embodiment of the present application, S6 comprises: solving to obtain the magnetic flux density, the turbulent flow velocity field distribution and the motion trajectory of the inclusion particles. Further, in S6, a frequency domain-transient study is added to calculate the turbulent flow field; in the study, the time step, the frequency and the tolerance are set, the magnetic field, the turbulence and the dynamic mesh are selected in the physical field interface, the magnetic field and the turbulent flow field are coupled by selecting the Lorentz force in the multi-physical field; the transient solver is selected as MUMPS, and the magnetic flux density and the turbulent flow velocity field distribution are calculated.

[0151] The grid division is performed again on the geometric model;

[0152] A transient study is added to calculate the motion trajectory of the inclusion particles across the slag / gold interface; in the study, the time step is set, and the fluid flow particle tracking is selected in the physical field interface; the transient solver is selected as MUMPS, and the motion trajectory of the inclusion particles is calculated.

[0153] In actual operation, in S6, the solving process comprises solving the magnetic flux density and the turbulent flow velocity field distribution (study A) and solving the motion trajectory of the inclusion particles across the slag / gold interface (study B).

[0154] In the study A, the frequency domain-transient study is used to calculate the turbulent flow field in the VIDP smelting process, the time step, the frequency and the tolerance are set, the magnetic field, the turbulence and the dynamic mesh are selected in the physical field interface, the magnetic field and the turbulent flow field are coupled by selecting the Lorentz force in the multi-physical field; the initial values of the variables to be solved and the variables not to be solved in the dependent variable are set as the physical field control, and the transient solver is selected as MUMPS; the magnetic flux density and the turbulent flow velocity field distribution are calculated.

[0155] In the study A, the dynamic mesh is used, the shape of the result domain changes, so it is necessary to redivide the mesh on the basis of the study A, redivide the mesh in the result for the deformed configuration, redivide the mesh of the area obtained in the study A, and obtain mesh 2.

[0156] In the study B, on the basis of the study A, the transient study is used to calculate the motion behavior of the inclusions crossing the slag / gold interface. In the study setting, the time step is set, and the fluid flow particle tracking is selected in the physical field interface. The initial value of the variable to be solved in the dependent variable value is set as the physical field control, and the variable value not to be solved is set as the user control (i.e. the result calculated in the study A), the study is the study A, the frequency domain-transient, the time setting is the last one; the mesh is selected as mesh 2, and the transient solver is selected as MUMPS; the motion trajectory of the inclusion particle is calculated.

[0157] In the specific embodiment of the application, the result analysis is further included. Further, the result analysis includes: drawing the magnetic flux density distribution nephogram and the velocity field distribution nephogram in the VIDP smelting process, drawing the motion trajectory graph of the inclusion particle in the VIDP smelting process, and statistically analyzing the adsorption rate of the molten slag, the alloy liquid surface and the crucible wall surface to the inclusion particle.

[0158] In the application, the inclusion particle in the study is the inclusion in the VIDP smelting process.

[0159] The application further provides the application of the method for calculating the motion of the inclusion crossing the slag / gold interface in the VIDP smelting process to the powder high-temperature alloy VIDP smelting process.

[0160] Embodiment 1

[0161] The embodiment provides a method for calculating the motion of the inclusion crossing the slag / gold interface in the VIDP smelting process, and a calculation flowchart is as shown in Figure 1 The method comprises the following steps:

[0162] (1) selecting a physical field

[0163] In the study of the embodiment, each physical field is symmetrically distributed in the circumferential direction, the charge is assumed to be uniform and continuous, the model is an axisymmetric graph, and therefore the three-dimensional problem can be simplified as a two-dimensional problem. In the software model wizard, the two-dimensional axisymmetric space dimension and the physical fields such as the magnetic field (mf), the turbulent flow k-ε (spf) and the fluid flow particle tracking (fpt) are selected, and the study is entered.

[0164] (2) establishing a geometric physical model to be solved

[0165] According to the VIDP melting process and the physical map of the experimental device, a finite element geometric model is established, including: alloy liquid, slag, crucible, insulation layer, induction coil, magnetic yoke, etc. The geometric model is shown in Figure 2 , and the dimensions of each part are as follows: alloy liquid height 110 mm; slag height 10 mm; crucible size wall thickness 7 mm; insulation material (insulation layer) size wall thickness 10 mm; induction coil outer size 12.8 x 18 mm, inner size 9 x 14 mm; magnetic yoke size 8 mm x 235 mm.

[0166] (3) Set the material properties of the model

[0167] The materials include: alloy liquid, slag, crucible, insulation material, induction coil, magnetic yoke, protective gas, cooling water, etc., among which the alloy liquid is FGH4096 powder superalloy alloy liquid, the slag is three-seven slag (30% CaF2+70% Al2O3), the crucible is magnesium oxide material, the insulation material is asbestos, the induction coil material is red copper, the magnetic yoke material is silicon steel, and the protective gas is argon.

[0168] The material physical property parameters include: thermal conductivity, constant pressure heat capacity, electrical conductivity, density, relative permeability, relative dielectric constant, dynamic viscosity, specific heat rate, etc. The material physical property parameters are shown in Table 1.

[0169] Table 1 Material physical property parameters

[0170]

[0171] (4) Set the initial value and boundary condition of the model

[0172] ① Magnetic field (mf)

[0173] The simulated vacuum induction degassing casting furnace model is a two-dimensional axisymmetric model, so the left boundary is set as an axisymmetric boundary, the edge of the furnace wall is assumed to be an infinite element domain, and the furnace wall boundary is set as a magnetic insulator, the initial magnetic potential of each direction is 0, and all regions of the model satisfy Ampere's law. The coil uses a single wire coil group, the coil excitation is voltage, the size is 40V, and force calculation is added in the alloy liquid and slag domain.

[0174] ② Turbulent flow, k-ε (spf)

[0175] The k-ε turbulence model in the RANS turbulence model type was used to analyze the fluid flow in the VIDP furnace. All fluids were incompressible flow, the initial velocity was 0, and the fluid properties were from the material. The volume reference temperature of the alloy liquid and the slag was 1673 K, and the volume reference temperature of the protective gas was 300 K. The protective gas above the slag was set as an open boundary. The assumption of the crucible wall boundary condition was no slip, and the wall function was used for the wall treatment of the crucible wall. The slag and the alloy liquid were subjected to gravity and volume force, and the calculated Lorentz force in the magnetic field was input into the volume force. The surface tension coefficient of the alloy liquid and the slag fluid interface was 1.758 N / m, and the contact angle of the fluid interface and the crucible wall was 90°. The surface tension coefficient of the slag and the protective gas fluid interface was 2 N / m, and the contact angle of the fluid interface and the crucible wall was 120°. In the actual smelting process, the contact interface between the protective gas and the slag and the contact interface between the slag and the alloy liquid would fluctuate, so the dynamic mesh was used to simulate the changes of the slag and the alloy liquid interface with time. The Yeoh smoothing type was used for the mesh, and the hardening factor was 10.

[0176] ③Fluid flow particle tracking (fpt)

[0177] The inclusion particles were released from the random position of the alloy liquid at 0 s, the particle properties were solid particles, the density was 3900 kg / m 3 , and the diameter was 20 μm. The fluid flow velocity calculated by the turbulence process was input into the particle motion velocity in this calculation. The wall condition of the symmetry axis and the bottom of the crucible was rebound. The wall condition of the side of the crucible was frozen, and the primary particle freezing probability was 77%, otherwise rebound. Since the inclusion was solid and the alloy liquid and the slag were liquid, the interface between the inclusion and the alloy liquid or the slag was set as a wall condition considering the requirement of the dynamic mesh technology. The wall condition of the slag and the alloy liquid interface was through, and the primary particle through probability was 80%, otherwise rebound. The wall condition of the slag and the protective gas interface was frozen, and the primary particle freezing probability was 88%, otherwise rebound. The gravity, lift, drag and additional mass force and surface tension were added in the alloy liquid and slag domain, and all inclusion particles were subjected to these forces. Since the particle crossed the slag / gold interface and was also subjected to the force of the interface, a self-defined surface tension was applied to the inclusion particle, and it was considered that only when the distance between the particle position and the interface was less than the particle radius, the particle would be subjected to the action of the surface tension.

[0178] wherein the force of the slag / gold interface on the particle can be expressed as:

[0179]

[0180] wherein F s is the interface tension, N;

[0181] Vp Volume of inclusion particle, m 3

[0182] σ - electrical conductivity, S / m

[0183] k - thermal diffusivity, kJ / m 3 · s

[0184] a - fluid fraction

[0185] (5) Add multi-physics field

[0186] Add Lorentz force (lf1) in multi-physics field, couple electromagnetic field and flow field together by Lorentz force.

[0187] (6) Divide grid

[0188] The grid division adopts the method of multi-region and multi-scale division. Since the skin effect is obvious on the surface of the charge and the inner surface of the coil, small-size grids are used for the regions of molten slag, alloy liquid, coil, and magnetic yoke, and larger grids are used for other regions. First, grid division is performed for all regions using physical field control, with the cell size being super-fine, and then the grid of the regions of molten slag, alloy liquid, coil, and magnetic yoke is further refined using user control, with the cell size being super-fine, and the grid type being triangular grid. The grid number is 54201, the maximum cell size is 6.6 mm, and the minimum cell size is 0.0247 mm. The grid division result is shown in Figure 3 .

[0189] (7) Add research and calculation

[0190] ① Research A: Add "frequency domain-transient" research to calculate the turbulent flow field in the VIDP smelting process. In the research setting, set the time step as (0, 0.1, 300) s, the frequency as 3400 Hz, the tolerance as physical field control, select magnetic field (mf), turbulent flow k-ε (spf), and dynamic mesh in the physical field interface, and select Lorentz force in the multi-physics field to couple the magnetic field and the flow field. The initial values of the dependent variables to be solved and the variables not to be solved are set as physical field control, and the transient solver is selected as MUMPS. The magnetic flux density and turbulent flow velocity field distribution are calculated, and the results are shown in Figure 4 and 5 .

[0191] ② In research A, dynamic mesh is used, and the shape of the result domain changes, so it is necessary to re-divide the grid based on research A. In the result, the deformed configuration is selected to re-divide the grid, and the regions obtained in research A are re-divided to obtain grid 2.

[0192] ​③On the basis of research A, add "transient" research to calculate the motion behavior of inclusions crossing the slag / gold interface. Set the time step as (0, 0.1, 100) s in the research setting, select fluid flow particle tracking (fpt) in the physical field interface. The initial value of the dependent variable to be solved is set as the physical field control, and the variable value not to be solved is set as the user control (i.e. the results calculated by research A are adopted), the research is research A, the frequency domain-transient, the time is set as the last one. The grid is selected as grid 2, and the transient solver is selected as MUMPS. The motion trajectory of the inclusion particles in 0-100 s is calculated.

[0193] (8) Result analysis

[0194] The position diagram of the inclusions in VIDP smelting at 0 s, 10 s, 50 s and 100 s is drawn, as shown in the figure. Figure 6 The inclusion adsorption rates of the molten slag, the molten pool liquid surface and the crucible wall surface are counted, and the counting results are shown in the table. Figure 7

[0195] The present application establishes the model of VIDP under the physical fields such as magnetic field and flow field by the finite element simulation software, ensures the accuracy of coupling, and simulates and calculates the fluid flow particle tracking in the VIDP smelting process, fills the blank of the simulation and simulation of the motion behavior of inclusions crossing the slag / gold interface in the VIDP smelting process. And the method for calculating the motion trajectory of inclusions crossing the slag / gold interface in the VIDP smelting process based on finite element simulation can provide theoretical guidance for VIDP smelting process design, so as to realize the removal of inclusions in alloy materials, improve the quality and performance of materials, and has important significance.

[0196] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.​

Claims

1. A method of calculating the motion of inclusions across the slag-metal interface during a VIDP smelting process, characterized by, The method comprises the following steps: S1: a geometric model of a vacuum induction degassing casting furnace to be solved is established by using Comsol Multiphysics; S2: physical property parameters of materials in the geometric model are given; S3: a physical field is added in the geometric model, and initial values and boundary conditions of the geometric model are set; wherein the physical field comprises a magnetic field, a turbulent flow field and a fluid flow particle tracking physical field; In the magnetic field, the simulated vacuum induction degassing casting furnace model is a two-dimensional axisymmetric model, the left boundary is set as an axisymmetric boundary, the edge of the furnace wall is set as an infinite element domain, and the furnace wall boundary is set as a magnetic insulation; the magnetic field is set in a coil current excitation or coil voltage excitation mode, and a single wire coil group is used for the coil; In the turbulent flow, a k-ε turbulent flow model is used to analyze the flow of fluid in the vacuum induction degassing casting furnace, all the fluids are set as incompressible fluids, the boundary condition of the crucible wall is set as no slip, and the wall function is used for wall treatment of the crucible wall; the initial values of the slag and alloy liquid velocity field are set as 0, subjected to gravity and volume force, and the calculated Lorentz force in the magnetic field is input into the volume force as a calculation result; a dynamic mesh is used to simulate the change of the contact surface between the protective gas and the slag and the alloy liquid with time; In the fluid flow particle tracking physical field, the inclusion particles are released at random positions in the alloy liquid from 0 s, the fluid motion speed calculated in the turbulent flow process is input into the calculation as the particle motion speed; the symmetry axis and the wall condition of the bottom of the crucible are set as rebound, and the wall condition of the side wall of the crucible is set as frozen; the interfaces of the inclusion particles and the alloy liquid and the slag are set as wall conditions, wherein the wall condition of the upper surface of the slag is frozen, and the wall condition of the interface between the slag and the alloy liquid is through; the inclusion particles are subjected to the action of gravity, lift, drag and additional mass force when moving in the alloy liquid and the slag, and the interface force is exerted when the inclusion particles pass through the slag-gold interface, and the interface force is set to be exerted only when the distance between the position of the inclusion particle and the interface is less than the radius of the inclusion particle, S4: a Lorentz force is added, and the magnetic field and the turbulent flow process are coupled through the Lorentz force; S5: the geometric model is meshed; S6: the motion trajectory of the inclusion particle is calculated; The force of the slag-gold interface on the inclusion particle is represented as: wherein - interfacial tension, N / m; Volume of inclusion particles, m 3 ; - conductivity, S / m; - thermal diffusivity, kJ / m 3 s; - fluid phase fraction.

2. The method of claim 1, wherein, In S1, the calculation domain of the geometric model comprises an alloy liquid calculation domain, a slag calculation domain, a crucible calculation domain, an insulation material calculation domain, an induction coil calculation domain, a magnetic yoke calculation domain, a protective gas calculation domain and a cooling water calculation domain.

3. The method of claim 1, wherein, In S2, the materials comprise alloy liquid, slag, crucible, insulation material, induction coil, magnetic yoke, protective gas and cooling water; the physical property parameters comprise thermal conductivity, constant pressure heat capacity, electrical conductivity, density, relative magnetic permeability, relative dielectric constant, dynamic viscosity and specific heat rate.

4. The method of claim 1, wherein, In the geometric model, all the calculation domains satisfy Ampere's law.

5. The method of claim 4, wherein, The force calculation is added in the alloy liquid calculation domain and the slag calculation domain.

6. The method of claim 1, wherein, In S5, the mesh type is a triangular mesh.

7. The method of claim 6, wherein, The mesh division is performed in a multi-region and multi-scale mode.

8. The method of claim 1, wherein, S6 comprises: The magnetic flux density, the turbulent flow velocity field distribution and the motion trajectory of the inclusion particles are calculated.

9. The method of claim 8, wherein, In S6, a frequency domain-transient study is added to calculate the turbulent flow field; time step, frequency, tolerance are set in the study, magnetic field, turbulence, dynamic mesh are selected in the physical field interface, Lorentz force is selected in the multi-physical field to couple the magnetic field and the turbulent flow field; MUMPS is selected as the transient solver, and the magnetic flux density and the turbulent flow velocity field distribution are calculated. The geometric model is re-meshed; A transient study is added to calculate the motion trajectory of the inclusion across the slag-gold interface; time step is set in the study, fluid flow particle tracking is selected in the physical field interface; MUMPS is selected as the transient solver, and the motion trajectory of the inclusion particles is calculated.

10. The method of claim 1, wherein, The result analysis is further included; The result analysis includes: drawing the magnetic flux density distribution nephogram and the velocity field distribution nephogram in the VIDP smelting process, drawing the motion trajectory diagram of the inclusion particles in the VIDP smelting process, and counting the adsorption rate of the molten slag, the alloy liquid surface and the crucible wall to the inclusion particles.

11. The application of the method for calculating the motion of the inclusion across the slag-gold interface in the VIDP smelting process according to any one of claims 1-10 in the powder high-temperature alloy VIDP smelting process.

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