Electric arc welding heat-mass-flow-electromagnetic multi-field coupling model containing welding wire pumpback and modeling method

Abstract

The invention discloses an electric arc welding heat-mass-flow-electromagnetic multi-field coupling model containing welding wire pumpback and a modeling method, and belongs to the field of welding numerical simulation. The method comprises the steps that firstly, an electric arc welding three-dimensional calculation domain containing welding wire withdrawing is established, and the calculation domain is composed of a welding wire motion sub-domain, an air sub-domain and a base metal sub-domain; thirdly, constructing a heat-mass-flow-electromagnetic control equation set for simultaneously describing welding wire withdrawing and relative movement of a welding gun and base metal; secondly, coupling welding wire withdrawing and boundary conditions of relative movement of a welding gun and base metal are defined, a material model is established, and the upper surface of a welding wire movement subdomain is defined as a rigid face and a metal speed inlet boundary at the same time; and finally, carrying out grid discretization on the computational domain and setting a solution strategy which comprises a control equation solution sequence and a time step size control scheme. The method is of great significance to deepening the arc characteristics and metal thermodynamic behavior understanding in the welding wire withdrawing process, and can assist in guiding actual welding process optimization and technical improvement.

Description

Technical Field

[0001] The present invention belongs to the technical field of numerical simulation of welding process, and in particular to an arc welding heat-mass-flow-electromagnetic multi-field coupling model including welding wire retraction and a modeling method. Background Art

[0002] In order to achieve low-melting-point lightweight alloys with low heat input and high efficiency welding and effectively control welding deformation, welding equipment manufacturers have innovatively integrated wire retraction into the traditional metal arc gas shielded welding process. The most representative ones are the cold metal transfer process of Furniss and the active welding process of Panasonic. In this process, the welding wire is in a periodic up and down reciprocating motion, accompanied by the periodic evolution of the waveform of the electrical signal (welding current and arc voltage). The interaction of multiple dynamic behaviors such as welding wire movement, transient evolution of current, droplet transition and heat source movement makes the arc thermophysical characteristics and the thermodynamic behavior of the molten pool extremely complex. It is difficult to quantitatively study and deeply understand these physical characteristics directly through experimental testing and other means and methods. The internal related physical mechanism is not clear, which leads to a certain degree of blindness in the optimization of the actual component welding manufacturing process.

[0003] With the rapid development of computer technology and computational fluid dynamics theory, numerical simulation methods have become an effective means to study the heat transfer and flow behavior of welding processes. Numerical simulation methods construct a group of control equations that describe various complex physical processes, equivalent various boundary conditions based on actual states, and use finite volume, finite element or finite difference numerical discretization methods to solve and calculate. They can intuitively and dynamically reproduce the evolution of various physical field quantities in the welding process, thereby revealing the generation mechanism and internal interaction mechanism of various complex physical phenomena in the welding process. At present, there are a large number of multi-physics field coupling numerical models for traditional metal arc welding (MIG) and tungsten inert gas welding (TIG) processes, and in-depth research has been carried out on arc plasma characteristics, droplet transfer behavior and molten pool heat transfer and flow behavior. The relevant theories have basically matured. However, there are few numerical models for the improved MIG process with wire retraction, and most of the reported models are simplified models, that is, the wire retraction movement or the direct heating process of the arc or the transient transfer process of the droplet is ignored, and the error between the simulation results and the actual results is often relatively large. Therefore, in order to accurately simulate and predict multi-physical phenomena such as arc characteristics, droplet transfer behavior and thermodynamic characteristics of the molten pool in the arc welding process including wire retraction, deepen the understanding of the interaction mechanism between wire retraction and arc combustion, droplet transfer and molten pool surface morphology, and guide the improvement of the welding quality of structural parts, it is necessary to explore a reasonable arc welding heat-mass-flow-electromagnetic multi-field coupling numerical modeling method including wire retraction. Summary of the invention

[0004] In order to reproduce the dynamic evolution of various complex physical phenomena of arc welding including wire retraction, accurately predict the arc plasma characteristics and the heat transfer and flow behavior of droplets and molten pool metals, and deepen the understanding of the dynamic interaction mechanism between wire retraction and arc combustion, droplet transition and molten pool surface morphology, the present invention provides an arc welding heat-mass-flow-electromagnetic multi-field coupling model and modeling method including wire retraction. The present invention proposes a numerical modeling method of arc welding heat-mass-flow-electromagnetic multi-field coupling including wire retraction, which is suitable for the numerical study of heat transfer and flow behavior in the welding and additive manufacturing process of materials such as steel, aluminum alloys, magnesium alloys and titanium alloys.

[0005] A modeling method for an arc welding heat-mass-flow-electromagnetic multi-field coupling model including wire retraction, characterized in that it comprises the following steps:

[0006] Step 1: Establish a three-dimensional calculation domain suitable for arc welding including wire retraction, including a wire movement subdomain, an air subdomain and a parent material subdomain. The parent material subdomain is located at the bottom, and the wire movement domain and the air subdomain are located at the top of the parent material subdomain.

[0007] The air subdomain contains a cylindrical hollow area equivalent to the welding wire electrode, and the radius of the hollow area is R a Equal to the wire radius, the hollow area length H a It is the distance from the end of the welding wire to the end of the gas nozzle in the actual welding process;

[0008] Step 2: Construct a set of thermal-mass-fluid-electromagnetic control equations that simultaneously describe the wire retraction and the relative motion between the welding gun and the base material, including the mass conservation equation, momentum conservation equation, energy conservation equation, Maxwell equations, metal vapor transport equation and interface dynamic capture equation;

[0009] Step 3: Define the boundary conditions for the coupled wire retraction motion and the relative motion between the welding gun and the base material and establish the corresponding material model, where: define the upper surface of the wire motion subdomain as a rigid surface, the side surface as a deformation surface, and the rigid surface as a velocity The up and down reciprocating motion is used to describe the dynamic retraction process of the welding wire. At the same time, the upper surface of the welding wire motion subdomain is defined as the velocity inlet boundary, and the relative velocity at the inlet is the wire feeding speed V. wfs , the inlet temperature is the melting point of the welding wire, the inlet metal volume fraction F = 1.0, and the potential satisfies Where z is the axial direction of the welding wire, I is the welding current, and the magnetic potential loss satisfies The side of the wire motion domain is defined as the internal interface, that is, momentum, energy and mass can be coupled and transferred on the interface;

[0010] Step 4: Discretize the three-dimensional computational domain and set the solution strategy. Use the finite volume method to discretize the control equations. Use the pressure implicit partitioning algorithm to decouple and solve the pressure-velocity equations. The spatial discretization format of the control equations is the second-order upwind format.

[0011] Furthermore, in step 1, the three-dimensional calculation domain is a cube as a whole, and the welding wire movement subdomain is a cylinder, whose volume can be dynamically reduced or increased during the simulation process. The radius R of the welding wire movement subdomain cylinder is w Equal to the wire radius, the initial length of the cylinder is H w Greater than the vertical distance that the welding wire moves from the uppermost part to the lowermost part, but less than the vertical distance from the end of the welding wire to the parent material when the welding wire is at the uppermost part; the height H of the parent material subdomain s Slightly larger than the actual thickness of the base material H e The weld height H after welding r The sum of H s =H e +H r +ε, where ε≤2mm; the height of the air subdomain H g The height of the entire calculation domain H minus the height of the parent material subdomain, that is, H g =HH s .

[0012] Furthermore, in step 2, the mass conservation equation that can simultaneously describe the wire retraction motion and the relative motion between the welding gun and the base material is:

[0013]

[0014] Where ρ is density, t is time, is the fluid velocity, is the wire retraction speed, is the speed of the welding gun relative to the base material. In the base material subdomain, The size is equal to the welding speed V T , in other subdomains, is equal to 0;

[0015] Correspondingly, the momentum conservation equation is:

[0016]

[0017] Where p is the pressure, is the stress tensor, is the acceleration due to gravity, is the metal thermal buoyancy, is the electromagnetic force, is the surface tension, For Marangoni, for Darcy's resistance;

[0018] The energy conservation equation is:

[0019]

[0020] Where E is internal energy, H is total enthalpy, k is thermal conductivity, T is temperature, S J is Joule heat, S r is the radiant heat, S a-p Anode sheath heat, S c-p It is cathode sheath heat;

[0021] Maxwell's equations describing electromagnetism are:

[0022]

[0023] Where σ is the conductivity, is the electric potential, is the conductivity, is the magnetic potential loss, μ0 is the vacuum magnetic permeability, is the magnetic induction intensity;

[0024] The metal vapor transport equation is:

[0025]

[0026] in, is the metal vapor mass fraction, is the metal vapor diffusion flux, S M It is the metal vapor mass source.

[0027] The dynamic interface between metal and gas is tracked using the fluid volume fraction method VOF, and the constructed interface dynamic capture equation is:

[0028]

[0029] Where F is the metal volume fraction.

[0030] Furthermore, in step 3, the welding wire is retracted The size is calculated based on the test results. The calculation method is: during the downward movement of the welding wire, Among them, H wi H is the initial height of the welding wire end face from the parent material surface, ws t is the height of the wire end face from the parent material surface when the molten droplet and the molten pool fully short-circuit transition occurs, down is the duration of the downward movement of the welding wire; during the upward movement of the welding wire, Among them, T up It is the duration of the upward movement of the welding wire.

[0031] Furthermore, in step 3, the upper surface of the wire motion domain is defined as the velocity inlet boundary, and the inlet relative velocity is the wire feeding speed V wfs , the inlet temperature is the melting point of the welding wire, the inlet metal volume fraction F = 1.0, and the potential satisfies Where z is the axial direction of the welding wire, I is the welding current, and the magnetic potential loss satisfies

[0032] Furthermore, in step 3, in the air subdomain, the center R of the upper surface in the air subdomain is defined as n The range is the protective gas velocity inlet boundary, where R n is the radius of the welding gun gas nozzle, the inlet velocity is the shielding gas flow rate, and the inlet gas temperature is room temperature; the other areas on the upper surface of the air subdomain are the pressure outlet boundaries, that is, in, is the surface normal vector, p ATM is the ambient pressure; the sides of the air subdomain are also the pressure outlet boundaries, but the magnetic potential loss satisfies The surface of the hollow area in the middle of the air subdomain is the wall boundary, its temperature can be set to a constant value, the fluid flow rate is 0, and the electric potential and magnetic potential satisfy

[0033] Furthermore, in step 3, in the parent material subdomain, the area occupied by the parent material thickness on both sides of the welding direction in the parent material subdomain is defined as the wall boundary, and its temperature is calculated according to the convection heat transfer and radiation equations. The area other than the area occupied by the parent material thickness on both sides of the welding direction is the pressure outlet boundary, and the electric potential and magnetic potential both meet Define the front side perpendicular to the welding direction as the velocity inlet boundary, and the inlet velocity is the welding velocity V T , the metal volume fraction of the inlet in the area occupied by the parent material thickness is F = 1.0, the metal volume fraction of the inlet in the area outside the parent material thickness is F = 0, the inlet temperature is room temperature, and the electric potential and magnetic loss potential both meet The rear side perpendicular to the welding direction is the pressure outlet boundary, and the electric potential and magnetic potential loss also meet The bottom surface of the parent material subdomain is the wall boundary, and its temperature is calculated according to the convection heat transfer and radiation equations. The electric potential and magnetic potential respectively satisfy

[0034] Furthermore, in step 3, the material model includes physical property parameters of the metal and the protective gas and metal vapor mixed gas, wherein each physical property parameter of the metal is a function of temperature, and each physical property parameter of the mixed gas is a function of temperature and metal vapor concentration.

[0035] Furthermore, in step 4, the discrete unit type of the computational domain is a hexahedron or a mixed unit of a hexahedron and a pentahedron, the mesh size of the area near the welding wire electrode is not greater than 0.1 mm, and the maximum mesh size of other areas away from the welding wire does not exceed 1.0 mm.

[0036] Furthermore, the calculation strategy in step 4 is as follows: at the beginning of the calculation, only the mass conservation equation, energy conservation equation, Maxwell equations and interface capture equation are solved, and the time step is small, usually 1×10 -6 After the temperature field reaches a steady state, the momentum conservation equation and the metal vapor transport equation are solved, and the time step is gradually increased, usually up to 1×10 -5 In addition, at the beginning of the calculation, the wire retraction speed And the relative movement speed between welding gun and base material They are all set to 0, and then adjusted to the actual value after the temperature field and flow field are calculated and stabilized.

[0037] The present invention proposes a modeling method for an arc welding heat-mass-flow-electromagnetic multi-field coupling model including wire retraction, which fills the gap in high-fidelity numerical simulation technology of the arc welding process with integrated wire retraction, and can stably and realistically reproduce the evolution details of the thermal field, flow field, and electromagnetic field under multi-physical interactions such as wire retraction, arc burning, droplet transition, and molten pool surface deformation. It is beneficial for relevant practitioners such as welding and additive manufacturing to deepen their understanding of the essence of various physical phenomena in the arc welding process with integrated wire retraction, and to assist in guiding the optimization of actual engineering processes and technical improvements. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A modeling flow chart of the arc welding heat-mass-flow-electromagnetic multi-field coupling model including wire retraction of the present invention;

[0039] Figure 2 Three-dimensional computational domain for arc cladding including wire retraction;

[0040] Figure 3 Transient welding current evolution during wire retraction during arc welding of aluminum alloy;

[0041] Figure 4 Discretization results of computational domain mesh;

[0042] Figure 5 Simulation results of arc shape during arc welding of aluminum alloy and arc morphology during wire retraction process. DETAILED DESCRIPTION

[0043] In order to further illustrate the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0044] The implementation process of the present invention is described below in conjunction with the numerical simulation process of heat-mass-flow-electromagnetic multi-field coupling of arc surfacing welding of aluminum alloy including wire retraction.

[0045] First, the main process parameters and material parameters of aluminum alloy arc surfacing in this embodiment are briefly introduced: the input welding current is 135A, the arc voltage is 18.5V, the welding speed is 10mm / s, the average wire feeding speed is 128mm / s, the shielding gas is high-purity argon, the flow rate is 20L / min, the welding wire radius is 0.6mm, the parent material size is 80mm×20mm×5mm, and the gas nozzle radius is 8.5mm; the material thermophysical properties parameters of the aluminum alloy and the argon-aluminum vapor mixed gas are taken from the material manual and publicly published literature. Except for the density which is a constant, the parameters such as specific heat capacity, thermal conductivity, viscosity, electrical conductivity, and net emissivity are all functions of temperature and aluminum vapor content.

[0046] Next, the present invention is applied to model the heat-mass-flow-electromagnetic multi-field coupling model of arc surfacing welding of aluminum alloy including wire retraction; Figure 1 As shown, it is an implementation flow chart of the present invention, which mainly includes four steps.

[0047] Step 1: Establish a three-dimensional calculation domain suitable for arc surfacing including wire retraction, such as Figure 2 As shown in the figure, the three-dimensional calculation domain has a cube-shaped appearance. The upper part of the center of the cube contains a cylindrical hollow area equivalent to the welding wire electrode. The radius of the hollow area is R a Equal to the wire radius, 0.6mm, the hollow area length H a It is the distance from the end of the welding wire to the end of the gas nozzle in the actual welding process, which is 5mm; the hollow area is located at the upper part of the welding wire movement domain.

[0048] The overall calculation domain consists of the welding wire movement subdomain, the air subdomain and the parent material subdomain. The length L is set to 80 mm, the width W is set to 20 mm, and the height H is set to 15 mm according to the size of the parent material. The welding wire movement subdomain is located in the upper center of the entire calculation domain and is cylindrical in shape. Its volume dynamically shrinks or increases during the simulation process. The radius of the welding wire movement subdomain cylinder R w Equal to the wire radius, 0.6mm, the initial length of the cylinder H wIt is larger than the vertical distance that the welding wire moves from the uppermost part to the lowermost part, but smaller than the vertical distance from the end of the welding wire to the parent material when the welding wire is at the uppermost part. It is set to 4 mm according to the test results. The parent material subdomain is located at the lower part of the entire calculation domain. Its length and width are equal to the length L and width W of the entire calculation domain. Its height H s Slightly larger than the actual thickness of the base material H e And the weld height H after welding r The sum of H s =H e +H r +ε, where ε≤2mm, according to the test results, the weld height H after welding r About 2.9mm, due to the thickness of the base material H e is 5 mm, and ε is 0.1 mm, so H s The air subdomain is located at the top of the entire computational domain. Its length and width are equal to the length L and width W of the entire computational domain. Its height H g The height of the entire calculation domain minus the height of the parent material subdomain, that is, H g =HH s , is 7mm.

[0049] Step 2: Construct a set of heat-mass-fluid-electromagnetic control equations that can describe the wire retraction and the relative motion between the welding gun and the base material, where the mass conservation equations are:

[0050]

[0051] Where ρ is density, t is time, is the fluid velocity, is the wire retraction speed, is the speed of the welding gun relative to the base material. In the base material subdomain, The size is equal to the welding speed V T =10mm / s, in other sub-domains, is equal to 0.

[0052] The momentum conservation equation is:

[0053]

[0054] Where p is the pressure, is the stress tensor, is the acceleration due to gravity, is the metal thermal buoyancy, is the electromagnetic force, is the surface tension, For Marangoni, For Darcy resistance.

[0055] The energy conservation equation is:

[0056]

[0057] Where E is internal energy, H is total enthalpy, k is thermal conductivity, T is temperature, S J is Joule heat, S r is the radiant heat, S a-p Anode sheath heat, S c-p Cathode sheath heat.

[0058] Maxwell's equations are:

[0059]

[0060] Where σ is the conductivity, is the electric potential, is the conductivity, is the magnetic potential loss, μ0 is the vacuum magnetic permeability, is the magnetic induction intensity.

[0061] The metal vapor transport equation is:

[0062]

[0063] in, is the metal vapor mass fraction, is the metal vapor diffusion flux, S M It is the metal vapor mass source.

[0064] The dynamic interface between metal and gas is tracked using the fluid volume fraction method VOF, and the interface dynamic capture equation is:

[0065]

[0066] Where F is the metal volume fraction.

[0067] Step 3: Define the boundary conditions for coupling the wire retraction motion and the relative motion between the welding gun and the base material, and establish the material model; Figure 2 As shown in the figure, the upper surface A2 of the welding wire motion subdomain is defined as a rigid surface, and the side surface A5 is a deformable surface. The rigid surface A2 is The dynamic retraction process of the welding wire is described by the reciprocating motion up and down. According to the test results, when the welding wire is at the highest position, the height H between its unmelted end and the surface of the base material is wi When the molten droplet and the molten pool are fully short-circuited, the height H of the unmelted end of the welding wire from the base material is ws is 1.64mm, the time for the welding wire to move downward is 24ms, and the time for the welding wire to move upward is 8mm. The calculated speed of the welding wire during its upward movement is 0.14m / s, according to Calculated downward speed is 0.42m / s; at the same time, the upper surface A2 of the wire motion domain is defined as the velocity inlet boundary, and the relative velocity at the inlet is the average wire feeding speed V wfs , i.e. 128 mm / s, the inlet temperature is the melting point of the welding wire 906 K, the inlet metal volume fraction F = 1.0, and the potential satisfies Where z is the axial direction of the welding wire, I is the transient welding current, and the welding machine output transient current tested is as follows: Figure 3 As shown; the side A5 of the welding wire motion domain is defined as the internal interface, that is, momentum, energy and mass can be coupled and transmitted at the interface.

[0068] In the air subdomain, the protective gas nozzle area A3 within the radius of 8.5 mm on the upper surface is defined as the velocity inlet boundary. The inlet velocity is obtained by the protective gas flow rate calculation formula, and the inlet gas temperature is room temperature 300K; the other area A4 on the upper surface of the air subdomain is the pressure outlet boundary, that is, p=p ATM , in, is the surface normal vector, p ATM is the ambient pressure; the sides of the air subdomain, AFOP, FGNO, BGNM, and ABMP are also pressure outlet boundaries, but the magnetic potential loss satisfies The surface A1 of the hollow area in the middle of the air subdomain is the wall boundary, its temperature is set to 1000K, the fluid flow rate is 0, and the electric potential and magnetic potential satisfy

[0069] In the parent material subdomain, the areas JKHE and ILCD occupied by the parent material thickness on both sides along the welding direction are wall boundaries, and their temperatures are calculated by the convection heat transfer and radiation equations. Other areas ONKJ and PMLI outside the areas occupied by the parent material thickness on both sides along the welding direction are pressure outlet boundaries, and the electric potential and magnetic loss potential both satisfy The front side MNHC in the vertical welding direction is the velocity inlet boundary, the inlet velocity is the welding speed of 10 mm / s, the inlet metal volume fraction F of the area occupied by the parent material thickness LKHC is 1.0, and the inlet metal volume fraction F of the area outside the parent material thickness MNKL is 0. The inlet temperature is room temperature 300K, and the electric potential and magnetic loss potential both meet The POED on the rear side perpendicular to the welding direction is the pressure outlet boundary, and the electric potential and magnetic potential loss meet The bottom surface of the parent material subdomain DEHC is the wall boundary, and its temperature is also calculated by the convection heat transfer and radiation equations. The electric potential and magnetic potential loss satisfy

[0070] The material model includes physical property parameters of aluminum alloy and a mixed gas of argon and aluminum vapor, wherein the physical property parameters of aluminum alloy are functions of temperature, and the physical property parameters of a mixed gas of argon and aluminum vapor are functions of temperature and metal vapor concentration, all of which are obtained from relevant literature.

[0071] Step 4: Discretize the computational domain into non-uniform units mixed with hexahedrons and pentahedrons, such as Figure 4 As shown, the mesh near the wire electrode is relatively fine, with a minimum mesh size of 0.012 mm, and the mesh far away from the wire electrode is relatively coarse, with a maximum mesh size of 0.6 mm. The finite volume method is used to discretize the control equations, and the pressure implicit segmentation algorithm is used to decouple and solve the pressure-velocity equation. The spatial discretization format of the control equations is the second-order upwind format, and the total solution time is 3 s. At the beginning of the calculation, only the mass conservation equation, energy conservation equation, Maxwell equations and interface capture equation are solved, and the wire retraction motion velocity is And the relative movement speed between welding gun and base material All are preset to 0, and the time step is 1×10 -6 s; after about 200 steps of calculation, the temperature field reaches a steady state, the momentum conservation equation and the metal vapor transport equation are added for solution, and the time step is modified every 100 steps, which is 5×10 -6 s, 1×10 -5 s, 2×10 -5 s, the time step is increased to 2×10 -5 After 50 steps, the velocity residual curve is basically stable. Adjust to the real value, that is, automatically assign 0.14m / s or 0.42m / s according to the cycle, Adjust the welding speed to 10 mm / s; continue to solve the remaining time steps until the simulation is completed.

[0072] The present invention can realize the numerical simulation of arc welding heat-mass-flow-electromagnetic multi-field coupling including wire retraction, and dynamically reproduce the evolution details of physical field quantities including arc shape, arc plasma temperature, arc plasma velocity, metal vapor concentration, arc pressure, droplet size, droplet temperature, droplet metal flow rate, molten pool size, molten pool metal temperature, molten pool metal flow rate, etc. Figure 5 As shown in FIG. 1 , the simulation results of the evolution of the aluminum alloy arc welding weld bead morphology and the arc shape (6000K isotherm) during the wire withdrawal process in this embodiment are shown.

[0073] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A modeling method for arc welding heat-mass-flow-electromagnetic multi-field coupling model including wire retraction, characterized in that The steps include: Step 1: Establish a three-dimensional computational domain suitable for arc welding including wire retraction, including the wire movement subdomain, air subdomain and parent material subdomain. The parent material subdomain is located at the bottom, and the wire movement subdomain and air subdomain are located at the top of the parent material subdomain; the air subdomain contains a cylindrical hollow area equivalent to the wire electrode, and the radius of the hollow area is R a Equal to the wire radius, the hollow area length H a It is the distance from the end of the welding wire to the end of the gas nozzle in the actual welding process; Step 2: Construct a set of thermal-mass-fluid-electromagnetic control equations that simultaneously describe the wire retraction and the relative motion between the welding gun and the base material, including the mass conservation equation, momentum conservation equation, energy conservation equation, Maxwell equations, metal vapor transport equation and interface dynamic capture equation; Step 3: Define the boundary conditions for coupling the wire retraction motion and the relative motion between the welding gun and the base material and establish the corresponding material model, where: define the upper surface of the wire motion subdomain as a rigid surface, the side surface as a deformable surface, and the rigid surface as the wire retraction motion speed. The up and down reciprocating motion is used to describe the dynamic retraction process of the welding wire. At the same time, the upper surface of the welding wire motion subdomain is defined as the velocity inlet boundary, and the relative velocity at the inlet is the wire feeding speed V. wfs , the inlet temperature is the melting point of the welding wire, the inlet metal volume fraction F = 1.0, and the potential satisfies Where z is the axial direction of the welding wire, I is the welding current, and the magnetic potential loss satisfies The side of the wire motion domain is defined as the internal interface, that is, momentum, energy and mass can be coupled and transferred on the interface; Step 4: Discretize the three-dimensional computational domain and set the solution strategy. Use the finite volume method to discretize the control equations. Use the pressure implicit partitioning algorithm to decouple and solve the pressure-velocity equations. The spatial discretization format of the control equations is the second-order upwind format.

2. The modeling method of the arc welding heat-mass-flow-electromagnetic multi-field coupling model including wire retraction according to claim 1 is characterized in that: In step 1, the three-dimensional calculation domain is a cube as a whole, and the wire movement subdomain is a cylinder. Its volume can be dynamically reduced or increased during the simulation process. The radius R of the wire movement subdomain cylinder is w Equal to the wire radius, the initial length of the cylinder is H w Greater than the vertical distance that the welding wire moves from the uppermost part to the lowermost part, but less than the vertical distance from the end of the welding wire to the base material when the welding wire is at the uppermost part; Height H of the parent material sub-domain s Slightly larger than the actual thickness of the base material H e The weld height H after welding r The sum of H s =H e +H r +ε, where ε≤2mm; The height of the air subdomain H g The height of the entire calculation domain H minus the height of the parent material subdomain, that is, H g =HH s .

3. The modeling method of the arc welding heat-mass-flow-electromagnetic multi-field coupling model including wire retraction according to claim 1 is characterized in that: In step 2, the mass conservation equation that can simultaneously describe the wire retraction motion and the relative motion between the welding gun and the base material is: Where ρ is density, t is time, is the fluid velocity, is the wire retraction speed, is the speed of the welding gun relative to the base material. In the base material subdomain, The size is equal to the welding speed V T , in other subdomains, is equal to 0; Correspondingly, the momentum conservation equation is: Where p is the pressure, is the stress tensor, is the acceleration due to gravity, is the thermal buoyancy of the metal, is the electromagnetic force, is the surface tension, For Marangoni, for Darcy's resistance; The energy conservation equation is: Where E is internal energy, H is total enthalpy, k is thermal conductivity, T is temperature, S J is Joule heat, S r is the radiant heat, S a-p Anode sheath heat, S c-p It is cathode sheath heat; Maxwell's equations describing electromagnetism are: Where σ is the conductivity, is the electric potential, is the conductivity, is the magnetic potential loss, μ0 is the vacuum magnetic permeability, is the magnetic induction intensity; The metal vapor transport equation is: in, is the metal vapor mass fraction, is the metal vapor diffusion flux, S M It is the metal vapor mass source; The interface dynamic capture equation is: Where F is the metal volume fraction.

4. The modeling method of the arc welding heat-mass-flow-electromagnetic multi-field coupling model including wire retraction according to claim 1 is characterized in that: In step 3, the wire retraction speed The size is calculated based on the test results. The calculation method is: during the downward movement of the welding wire, Among them, H wi H is the initial height of the welding wire end face from the parent material surface, ws t is the height of the wire end face from the parent material surface when the molten droplet and the molten pool fully short-circuit transition occurs, down is the duration of the downward movement of the welding wire; during the upward movement of the welding wire, Among them, t up It is the duration of the upward movement of the welding wire.

5. The modeling method of the arc welding heat-mass-flow-electromagnetic multi-field coupling model including wire retraction according to claim 1, characterized in that: In step 3, define the center R of the upper surface in the air subdomain n The range is the protective gas velocity inlet boundary, where R n is the radius of the welding gun gas nozzle, the inlet velocity is the shielding gas flow rate, and the inlet gas temperature is room temperature; the other areas on the upper surface of the air subdomain are the pressure outlet boundaries, that is, in, is the surface normal vector, p ATM is the ambient pressure; the sides of the air subdomain are also the pressure outlet boundaries, but the magnetic potential loss satisfies The surface of the hollow area in the middle of the air subdomain is the wall boundary, its temperature can be set to a constant value, the fluid flow rate is 0, and the electric potential and magnetic potential satisfy 6. The modeling method of the arc welding heat-mass-flow-electromagnetic multi-field coupling model including wire retraction according to claim 1, characterized in that: In step 3, in the parent material subdomain, the area occupied by the parent material thickness on both sides along the welding direction is defined as the wall boundary, and the other areas outside the area occupied by the parent material thickness on both sides are defined as the pressure outlet boundary. The electric potential and magnetic potential loss both meet Define the front side perpendicular to the welding direction as the velocity inlet boundary, and the inlet velocity is the welding velocity V T , the metal volume fraction of the entrance area occupied by the parent material thickness on the front side is F = 1.0, the metal volume fraction of the entrance area outside the parent material thickness on the front side is F = 0, and the electric potential and magnetic loss potential both meet Define the rear side perpendicular to the welding direction as the pressure outlet boundary, and the electric potential and magnetic potential loss also satisfy 7. The modeling method of the arc welding heat-mass-flow-electromagnetic multi-field coupling model including wire retraction according to claim 1, characterized in that: In step 3, the material model includes physical property parameters of the metal and the protective gas and metal vapor mixed gas, wherein each physical property parameter of the metal is a function of temperature, and each physical property parameter of the mixed gas is a function of temperature and metal vapor concentration.

8. The modeling method of the arc welding heat-mass-flow-electromagnetic multi-field coupling model including wire retraction according to claim 1, characterized in that: The discrete unit type of the computational domain is a hexahedron or a mixed unit of hexahedron and pentahedron. The mesh size of the area near the welding wire electrode is not greater than 0.1 mm, and the maximum mesh size of other areas far away from the welding wire does not exceed 1.0 mm.

9. The modeling method of the arc welding heat-mass-flow-electromagnetic multi-field coupling model including wire retraction according to claim 1, characterized in that: The solution strategy in step 4 is: before the calculation starts, the wire retraction speed And the relative movement speed between welding gun and base material are all set to 0; after the calculation starts, a smaller time step is first used to solve only the mass conservation equation, energy conservation equation, Maxwell equations and interface capture equation. The time step is usually 1×10 -6 After the temperature field reaches a steady state, the momentum conservation equation and the metal vapor transport equation are solved simultaneously, and the time step is gradually increased to 1×10 -5 order of magnitude; then, the time step remains unchanged, and after the velocity residual curve stabilizes, the wire retraction speed is increased. And the relative movement speed between welding gun and base material Adjust back to the true value and continue calculating until the simulation is complete.

10. An arc welding heat-mass-flux-electromagnetic multi-field coupling model including wire retraction constructed according to the modeling method described in any one of claims 1-9.

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