CN117473891A - Molten pool flow field simulation method for thick plate narrow gap point ring laser filler wire welding - Google Patents
Molten pool flow field simulation method for thick plate narrow gap point ring laser filler wire welding Download PDFInfo
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- 238000003466 welding Methods 0.000 title claims abstract description 104
- 238000000034 method Methods 0.000 title claims abstract description 75
- 239000000945 filler Substances 0.000 title claims abstract description 46
- 238000004088 simulation Methods 0.000 title claims abstract description 32
- 230000008569 process Effects 0.000 claims abstract description 27
- 230000008878 coupling Effects 0.000 claims abstract description 14
- 238000010168 coupling process Methods 0.000 claims abstract description 14
- 238000005859 coupling reaction Methods 0.000 claims abstract description 14
- 239000012530 fluid Substances 0.000 claims description 22
- 239000000463 material Substances 0.000 claims description 21
- 238000005429 filling process Methods 0.000 claims description 10
- 230000008859 change Effects 0.000 claims description 9
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 8
- 239000010953 base metal Substances 0.000 claims description 6
- 238000010586 diagram Methods 0.000 claims description 6
- 239000002131 composite material Substances 0.000 claims description 5
- 238000004134 energy conservation Methods 0.000 claims description 5
- 229910052786 argon Inorganic materials 0.000 claims description 4
- 230000004927 fusion Effects 0.000 claims description 4
- 239000007789 gas Substances 0.000 claims description 4
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- 230000001133 acceleration Effects 0.000 claims description 3
- 230000000694 effects Effects 0.000 claims description 3
- 229910001338 liquidmetal Inorganic materials 0.000 claims description 3
- 239000002184 metal Substances 0.000 claims description 3
- 238000012795 verification Methods 0.000 claims description 2
- 238000004364 calculation method Methods 0.000 abstract description 8
- 230000007547 defect Effects 0.000 abstract description 7
- 238000011161 development Methods 0.000 abstract description 4
- 230000002401 inhibitory effect Effects 0.000 abstract description 3
- 238000002844 melting Methods 0.000 abstract description 2
- 230000008018 melting Effects 0.000 abstract description 2
- 238000009826 distribution Methods 0.000 description 5
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- 238000005516 engineering process Methods 0.000 description 4
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- 230000009286 beneficial effect Effects 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/20—Bonding
- B23K26/21—Bonding by welding
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
- G06F30/28—Design optimisation, verification or simulation using fluid dynamics, e.g. using Navier-Stokes equations or computational fluid dynamics [CFD]
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2113/00—Details relating to the application field
- G06F2113/08—Fluids
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- G—PHYSICS
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- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
- G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
Abstract
The invention discloses a molten pool flow field simulation method for thick plate narrow gap point ring laser filler wire welding, which comprises the steps of establishing a three-dimensional model for thick plate narrow gap laser filler wire welding, carrying out secondary development on CFD simulation software to solve the loading of a point ring laser heat source and further coupling the filler wire process, solving a control equation based on the CFD simulation software, and adopting a VOF method to track an interface and obtain a result. The thick plate narrow gap point ring laser filler wire welding simulation method aims at a thick plate narrow gap structure under point ring laser welding, simultaneously considers a filler wire process and a melting and solidifying process, obtains accurate dynamic flow field details through solving a flow field model, and has good matching of a calculation result and an experimental result, so that theoretical guidance can be provided for welding operation for inhibiting unfused defects, and the operation of thick plate narrow gap laser filler wire welding is further optimized.
Description
Technical Field
The invention relates to the technical field of narrow-gap laser welding industry, in particular to a molten pool flow field simulation method for thick plate narrow-gap point ring laser filler wire welding.
Background
With the continuous progress of scientific technology, large thick-wall components are increasingly applied to the industrial production fields of ship manufacturing, marine equipment, aerospace and the like. Because the components are difficult to mold at one time, welding technology is needed to connect the components, and the service performance and service life of the components are directly affected by the welding quality.
Compared with the traditional thick plate welding, the narrow-gap laser welding has a series of advantages of high energy density, large depth-to-width ratio, high welding speed, small welding deformation and the like, and has great advantages in the thick plate welding. Narrow gap laser welding can be divided into three main categories, namely narrow gap laser self-welding, narrow gap laser filler wire welding and narrow gap laser-arc hybrid welding. At present, more and more researchers adopt a narrow-gap laser filler wire welding method to carry out thick plate welding experiments, and good results are obtained. However, the observation of dynamic behavior changes of a molten pool of narrow gap laser filler wire welding is difficult due to the following reasons: the laser spot size is small, so that bridging property is poor, the assembly tolerance of the welding seam is small, and the defect of unfused after welding is easy to occur. The formation of defects is closely related to the dynamic behavior of a molten pool, but the action area of laser and a workpiece is small, so that the volume of the molten pool is small and is always in dynamic change; meanwhile, the welding is a process of rapid heating and rapid cooling, and the existence time of a molten pool is short; furthermore, the laser welding process is accompanied by intense light and heat radiation.
At present, numerical simulation developed by means of computer technology and numerical analysis technology provides a new thought for researching heat transfer and fluid flow in the welding process, and many students deeply research the dynamic behavior of a molten pool by adopting a numerical simulation method and obtain good results. However, the following problems still exist in the numerical simulation research on the dynamic behavior of the thick plate narrow gap laser filler wire welding molten pool: firstly, most of the existing laser welding flow field simulation research focuses on the deep fusion welding process, and a blank exists in the aspects of flow field simulation and molten pool dynamic evolution of laser filler wire welding; secondly, the defect mechanism of the spot ring laser for improving the narrow gap laser filler wire welding is not elucidated yet, and the dynamic simulation research of a molten pool of the spot ring laser under the restraint of a narrow gap is not reported yet. Therefore, a method for simulating the flow field of a molten pool for thick plate narrow gap point ring laser filler wire welding is needed to clarify the influence of point ring laser on the flow of the molten pool and the formation of defects in the narrow gap filler wire welding process, so as to provide theoretical guidance for the welding operation of inhibiting unfused defects and further optimize the operation of thick plate narrow gap laser filler wire welding.
In view of this, the present invention has been made.
Disclosure of Invention
The invention aims to provide a molten pool flow field simulation method for thick plate narrow gap point ring laser filler wire welding, so as to improve the technical problems.
The invention is realized in the following way:
the invention provides a molten pool flow field simulation method for thick plate narrow gap point ring laser filler wire welding, which comprises the following steps:
the method comprises the steps of respectively establishing a thick plate narrow gap geometric workpiece model and a point ring laser three-dimensional heat source model based on CFD simulation software, wherein the point ring laser three-dimensional heat source model is obtained by programming based on a rotating Gaussian heat source model, and an equation of the rotating Gaussian heat source is as follows:
based on a CFD simulation platform, simulating a wire filling process by adopting a mass momentum source method and realizing coupling with a heat source loading process;
and importing the coupled composite model for filling wires and thermally loading the geometric tool model into CFD simulation software, setting model boundary conditions in the CFD simulation software, determining the spatial position of a heat source and the position for simulating the filling wires, calculating by adopting laminar flow simulation, and solving a hydrodynamic basic equation for iterative solution until the result is converged to obtain the related information of the temperature field, the speed field and the molten pool size in the welding process.
The invention has the following beneficial effects: the method comprises the steps of loading a thick plate narrow gap geometric workpiece model by establishing a plurality of three-dimensional body heat source models of a point ring, correctly coupling a wire filling process, solving and obtaining accurate dynamic flow field details based on a hydrodynamic basic equation, providing a simple, convenient and effective modeling and calculating method for molten pool flow field simulation of thick plate narrow gap point ring laser wire filling welding, and ensuring that a calculation result and an experimental result are well matched, thereby providing theoretical guidance for welding operation for inhibiting unfused defects and further optimizing the operation of thick plate narrow gap laser wire filling welding.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a thick plate narrow gap three-dimensional model and grid division situation according to the embodiment 1 of the present invention;
FIGS. 2-3 are graphs showing the physical property parameters of the material according to the embodiment 1 of the present invention with temperature;
FIG. 4 is a schematic view showing the energy distribution of the point ring heat source according to the embodiment 1 of the present invention;
FIG. 5 shows that the energy ratio between the inside and outside of the dot ring of example 1 of the present invention is 1.0: a weld morphology comparison chart at 0;
FIG. 6 shows that the energy ratio between the inside and outside of the dot ring of example 1 of the present invention is 0.5: a weld morphology comparison graph at 0.5;
FIG. 7 is a schematic diagram of droplet transition according to example 1 of the present invention;
FIG. 8 is a schematic diagram of boundary conditions of a narrow gap three-dimensional model of a thick plate according to example 1 of the present invention;
FIG. 9 is a schematic view of the melt pool flow field of example 1 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
The method for simulating the flow field of the molten pool for welding the thick plate narrow gap point ring laser filler wire is specifically described below.
Computational fluid dynamics (Computational Fluid Dynamics, CFD) is an analysis of systems involving physical phenomena such as fluid flow and thermal conduction through computer numerical calculations and image display. It can be seen as a numerical simulation of flow under the control of the basic method of hydrodynamics. By such numerical simulation, the distribution of basic physical quantities at various positions in the flow field of the complex problem and the change of these physical quantities with time can be obtained. The inventors have proposed the following technical solutions based on CFD simulation software through research and practice.
Some embodiments of the invention provide a molten pool flow field simulation method for thick plate narrow gap point ring laser filler wire welding, which comprises the following steps:
the method comprises the steps of respectively establishing a thick plate narrow gap geometric workpiece model and a point ring laser three-dimensional heat source model based on CFD simulation software, wherein the point ring laser three-dimensional heat source model is obtained by programming based on a rotating Gaussian heat source model, and an equation of the rotating Gaussian heat source is as follows:
based on the CFD simulation platform, a mass momentum source method is adopted to simulate the wire filling process and realize the coupling with the heat source loading process.
And importing the coupled composite model for filling wires and thermally loading the geometric tool model into CFD simulation software, setting model boundary conditions in the CFD simulation software, determining the spatial position of a heat source and the position for simulating the filling wires, calculating by adopting laminar flow simulation, and solving a hydrodynamic basic equation for iterative solution until the result is converged to obtain the related information of the temperature field, the speed field and the molten pool size in the welding process.
Specifically, in some embodiments, the molten pool flow field simulation method for thick plate narrow gap point ring laser filler wire welding specifically comprises the following steps:
s1, establishing a thick plate narrow gap geometric workpiece model.
Specifically, a thick plate narrow gap geometric workpiece model is built based on CFD simulation software, for example, a thick plate narrow gap point ring laser filler wire welding model is built in three-dimensional modeling software (such as 3ds Max, maya, C4D, blender, sketchUp, CAD and the like), and is stored as an intermediate file in stl format, and is imported into the CFD simulation software.
In some embodiments, the thick plate narrow gap point ring laser filler wire welding model has dimensions of 25-35 mm x 15-25 mm x 25-35 mm, groove bottom dimensions of 3-4 mm, thickness of 4-6 mm, and slope of 3-5 °. Illustratively, the thick plate narrow gap spot ring laser filler wire welding model may have dimensions of 30mm by 20mm by 30mm, groove bottom dimensions of 3.4mm, thickness of 5mm, and a slope of about 4 °. It should be noted that the model size may be designed according to the specific size of the workpiece actually welded.
The method comprises the steps of carrying out targeted grid division on different areas of a workpiece, wherein the 'targeted grid division' refers to fine and thick division of a welding line area and an area close to the welding line and thick division of an area far away from the welding line. Specifically, the welding line is divided into grids within a range of 5mm at two sides of the center of the welding line according to a grid size of 0.25mm, and the rest is divided into grids according to a size of 0.5 mm. For the above model sized workpiece, the total mesh count is 1000000 ～ 1200000, the maximum aspect ratio is 2.5-3, e.g., the total mesh count is 1092000, and the maximum aspect ratio is 2.8.
Through the grid division and the selection of the total grid number and the aspect ratio, the calculation accuracy can be ensured, the calculation time can be reduced, and the efficient convergence of the calculation can be ensured.
Further, based on the selection of the base metal and the welding wire of the workpiece to be simulated, the change values of important thermophysical parameters such as the density, specific heat, thermal conductivity and the like of the base metal and the welding wire with temperature are calculated, and then the performance of the base metal and the welding wire is built into a material library of CFD simulation software.
It should be noted that the CFD simulation software used in the embodiment of the present invention may be existing common CFD simulation software, such as ANSYS Fluent, phoenics, cfx, STAR-CCM, or OpenFOAM.
S2, constructing a point ring body heat source model and loading heat sources to the workpiece model.
Specifically, the point-ring laser three-dimensional heat source model is obtained by programming based on a rotating Gaussian heat source model, and the equation of the rotating Gaussian heat source is as follows:
the programming mode is to perform secondary development on the subprogram of CFD simulation software, and the point and the energy of the ring of the point-ring laser three-dimensional body heat source model respectively follow Gaussian distribution.
In some embodiments, after the point ring body heat source model is built, the built point ring laser three-dimensional heat source model can be verified, the verification method is that welding entities with the same size as the thick plate narrow gap geometric workpiece model are welded, and the obtained welding seams are compared with a simulated molten pool to judge whether the welding seams are matched.
In some embodiments, when welding the welding entity, the welding speed is 20-30 mm/s, the laser power is 2500-3500W, the defocusing amount is +20-30 mm, the diameter of the defocused laser spot is 2.5-3.5 mm, the shielding gas adopts argon, and the flow is 15-25L/min. For example, the welding speed is 25mm/s, the laser power is 3000W, the defocusing amount is about +25mm, the diameter of a defocused laser spot is about 3mm, the shielding gas adopts argon, and the flow is 20L/min.
S3, simulating a wire filling process by adopting a mass momentum source method based on the CFD simulation platform and realizing coupling with a heat source loading process.
Specifically, in some embodiments, the mass momentum source method is used to simulate the wire filling process and achieve coupling with the heat source loading process based on calculated values of the base metal and wire metal densities, specific heat and thermal conductivity as a function of temperature. I.e., determining the relevant parameters of the wire filling process, equating the wire filling process to an increase in puddle mass and momentum.
S4, importing the coupled composite model for filling wires and thermally loading the geometric tool model into CFD simulation software, setting model boundary conditions in the CFD simulation software, determining the space position of a heat source and the position of the simulated filling wires, calculating by adopting laminar flow simulation, solving a hydrodynamic basic equation, and carrying out iterative solution until the result converges, thereby obtaining the related information of the temperature field, the speed field and the size of a molten pool in the welding process.
Specifically, the setting of the model boundary conditions is as follows: two face boundary conditions in the z direction are set as specified pressure boundary conditions, and the remaining four faces are all continuous boundary conditions.
In some embodiments, the hydrodynamic basis equations include a mass continuous equation, a momentum conservation equation, and an energy conservation equation, the mass continuous equation being:
for incompressible fluids, the mass continuous equation is:
wherein ρ represents the density of the fluid, t is time, (u) x ,u y ,u z ) And (u, v, w) each correspond to a velocity component in the (x, y, z) direction; v (V) F Representing the volume fraction of material in the mesh, (A) x ,A y ,A z ) Representing the area percentage of the material in the grid in the plane of the corresponding coordinate system, i.e. A x Representing the percentage of material in the grid in the yz plane as area of the cell.
The conservation of momentum equation is:
where ρ is the density of the fluid, u, v, w is the velocity component of the fluid at point (x, y, z) at time t, (G) x ,G y ,G z ) The gravity acceleration in each direction on the rectangular coordinate axis is represented, mu represents the viscosity of liquid metal, K represents the drag coefficient of a solid-liquid two-phase region, and tau represents the shear stress.
According to the established physical model, the coupling considers the influence of convection and conduction heat transfer of a molten pool, and the energy conservation equation is as follows:
wherein,representing the change in the internal energy of the cell volume material, +.>Represents the energy of the fluid per unit mass, c (T) is the specific heat of the material, h sl Is the latent heat of fusion of the material.
S5, capturing a free interface of the welding molten pool by adopting a VOF method based on the temperature field, the speed field and the related information of the size of the molten pool in the welding process, establishing a free interface tracking model, and simulating a flow state effect diagram in the molten pool.
The features and capabilities of the present invention are described in further detail below in connection with the examples.
Example 1
The embodiment provides an operation example of a molten pool flow field simulation method for thick plate narrow gap point ring laser filler wire welding, which specifically comprises the following steps:
the first step: and establishing a three-dimensional model of thick plate narrow-gap laser filler wire welding.
And constructing a thick plate narrow gap point ring laser filler wire welding model in three-dimensional modeling software CATIA, wherein the model size is 30mm multiplied by 20mm multiplied by 30mm, the groove bottom size is 3.4mm, the thickness is 5mm, the gradient is about 4 degrees, and the model is stored as an intermediate file in stl format and is imported into CFD simulation software Flow-3D. The model is subjected to grid division, structured grids are uniformly adopted as grids, grid division is performed according to the grid size of 0.25mm within the range of 5mm on two sides of the center of a welding line, grid division is performed according to the size of 0.5mm on the other parts, the total grid number is 1092000, the maximum aspect ratio is 2.8, and the built model is shown in figure 1.
And calculating the change values of important thermophysical performance parameters such as the density, specific heat, thermal conductivity and the like of the base metal of the workpiece and the metal of the welding wire along with the temperature, and then constructing the performance of the parameters into a CFD software material library, wherein the change conditions are shown in figures 2-3.
And a second step of: and constructing a point ring body heat source model and loading a heat source to the workpiece model.
Performing secondary development on the rotating Gaussian heat source model by a subroutine of CFD simulation software (computational fluid dynamics software), establishing a point ring laser three-dimensional heat source model, and loading and moving a point ring heat source; the equation for the rotating gaussian heat source is as follows:
the energy distribution pattern of the dot-loop heat source is shown in fig. 4, wherein the energy of the dot and loop respectively follow gaussian distribution.
And a third step of: and (5) verifying a heat source model.
The welding entity geometric model is cuboid, the length is 200mm, the width is 100mm, the thickness is 30mm, a 25mm deep groove is formed, the bottom width is about 3mm, the side wall inclination degree is about 4 degrees, the welding speed is 25mm/s, the laser power is 3000W, the defocusing amount is about +25mm, the diameter of a laser spot after defocusing is about 3mm, the shielding gas adopts argon, and the flow is 20L/min. The obtained weld and simulated weld pool are shown in fig. 5 and 6, wherein fig. 5 shows that the energy ratio between the inside and outside of the spot ring is 1.0: FIG. 6 is a graph showing the weld morphology at 0, wherein the energy ratio between the inside and outside of the spot ring is 0.5: and the weld morphology comparison chart at 0.5 shows that the matching degree of the simulation result and the actual experimental result is higher by comparing the depth and the width of the molten pool, and the model precision meets the requirement.
Fourth step: and coupling the wire filling process by adopting a mass momentum source method.
Based on a CFD simulation platform, simulating a wire filling process by adopting a mass momentum source method and realizing coupling with a heat source loading process; the mass momentum source method is to give physical parameters such as density, thermal conductivity, specific heat, viscosity, etc. to the material, so that liquid droplets with a diameter of 1.2mm and a temperature of about 2000K are generated at a designated position of a welding path in space, and the droplets fall into a molten pool under the action of gravity, and the process is shown in fig. 6.
Fifth step: and importing the coupled composite model for filling wires and thermally loading the geometric tool model into CFD simulation software, and setting model boundary conditions in the CFD simulation software, wherein the boundary conditions of the upper surface and the lower surface in the z direction are set as specified pressure boundary conditions, the rest four surfaces are continuous boundary conditions, and the setting of the boundary conditions is shown in figure 8. And determining the space position of the heat source and the simulated filler wire position, calculating by adopting laminar flow simulation, solving a hydrodynamic basic equation, carrying out iterative solution until the result converges, obtaining the related information of the temperature field, the speed field and the molten pool size in the welding process, and deriving a calculation result.
The fluid mechanics basic equation comprises a mass continuous equation, an energy continuous equation and a mass continuous equation, and the specific form of the equation is as follows:
the mass continuous equation is:
for incompressible fluids, the mass continuous equation is:
wherein ρ represents the density of the fluid, t is time, (u) x ,u y ,u z ) And (u, v, w) each correspond to a velocity component in the (x, y, z) direction; v (V) F Representing the volume fraction of material in the mesh, (A) x ,A y ,A z ) Representing the area percentage of the material in the grid in the plane of the corresponding coordinate system, i.e. A x Representing the percentage of material in the grid in the yz plane as area of the cell.
The conservation of momentum equation is:
where ρ is the density of the fluid, u, v, w is the velocity component of the fluid at point (x, y, z) at time t, (G) x ,G y ,G z ) The gravity acceleration in each direction on the rectangular coordinate axis is represented, mu represents the viscosity of liquid metal, K represents the drag coefficient of a solid-liquid two-phase region, and tau represents the shear stress.
According to the established physical model, the coupling considers the influence of convection and conduction heat transfer of a molten pool, and the energy conservation equation is as follows:
wherein,representing the change in the internal energy of the cell volume material, +.>Represents the energy of the fluid per unit mass, c (T) is the specific heat of the material, h sl Is the latent heat of fusion of the material.
Sixth step: based on CFD simulation software, a mainstream VOF method is adopted to capture the free interface of a welding pool, a free interface tracking model is established, and a simulated pool internal flow state effect diagram is shown in fig. 9.
In summary, by establishing a three-dimensional model of thick plate narrow gap laser filler wire welding, secondary development is performed on CFD simulation software (computational fluid dynamics software) to solve the loading of a point ring laser heat source and further couple the filler wire process, a control equation is solved based on the CFD simulation software, and an interface is tracked by adopting a VOF method to obtain a result. The thick plate narrow gap point ring laser filler wire welding simulation method aims at a thick plate narrow gap structure under point ring laser welding, simultaneously considers a filler wire process and a melting solidification process, obtains accurate dynamic flow field details through solving a convection field model, and has a good calculation result and an experimental result.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A molten pool flow field simulation method for thick plate narrow gap point ring laser filler wire welding is characterized by comprising the following steps:
the method comprises the steps of respectively establishing a thick plate narrow gap geometric workpiece model and a point ring laser three-dimensional heat source model based on CFD simulation software, wherein the point ring laser three-dimensional heat source model is obtained by programming based on a rotating Gaussian heat source model, and an equation of the rotating Gaussian heat source is as follows:
based on a CFD simulation platform, simulating a wire filling process by adopting a mass momentum source method and realizing coupling with a heat source loading process;
and importing the coupled composite model for filling wires and thermally loading the geometric tool model into CFD simulation software, setting model boundary conditions in the CFD simulation software, determining the spatial position of a heat source and the position for simulating the filling wires, calculating by adopting laminar flow simulation, and solving a hydrodynamic basic equation for iterative solution until the result is converged to obtain the related information of the temperature field, the speed field and the molten pool size in the welding process.
2. The method for simulating a molten pool flow field for thick plate narrow gap point ring laser filler wire welding, according to claim 1, is characterized in that when a thick plate narrow gap geometric workpiece model is established, the workpiece is meshed according to a mesh size of 0.25mm within a range of 5mm on two sides of the center of a welding line, and the rest is meshed according to a size of 0.5 mm.
3. The method for simulating a molten pool flow field for thick plate narrow gap point ring laser filler wire welding according to claim 2, wherein the total grid number is 1000000 ～ 1200000, and the maximum aspect ratio is 2.5-3.
4. The method for simulating a molten pool flow field for thick plate narrow gap point ring laser filler wire welding according to claim 2, wherein the thick plate narrow gap point ring laser filler wire welding model has the dimensions of 25-35 mm×15-25 mm×25-35 mm, the groove bottom has the dimensions of 3-4 mm, the thickness of 4-6 mm and the gradient of 3-5 °.
5. The molten pool flow field simulation method for thick plate narrow gap point ring laser filler wire welding according to claim 2, wherein the hydrodynamic basic equation comprises a mass continuous equation, a momentum conservation equation and an energy conservation equation, and the mass continuous equation is:
for incompressible fluids, the mass continuous equation is:
wherein ρ represents the density of the fluid, t is time, (u) x ,u y ,u z ) And (u, v, w) each correspond to a velocity component in the (x, y, z) direction; v (V) F Representing the volume fraction of material in the mesh, (A) x ,A y ,A z ) Representing the area percentage of the material in the grid in the plane of the corresponding coordinate system, i.e. A x Representing the area percentage of the material in the grid accounting for the unit cell on the yz plane;
the momentum conservation equation is:
where ρ is the density of the fluid, u, v, w is the velocity component of the fluid at point (x, y, z) at time t, (G) x ,G y ,G z ) The gravity acceleration in each direction on the rectangular coordinate axis is represented, mu represents the viscosity of liquid metal, K represents the drag coefficient of a solid-liquid two-phase region, and tau represents the shear stress.
According to the established physical model, the coupling considers the influence of convection and conduction heat transfer of a molten pool, and the energy conservation equation is as follows:
wherein,representing the change in the internal energy of the cell volume material, +.>Represents the energy of the fluid per unit mass, c (T) is the specific heat of the material, h sl Is the latent heat of fusion of the material.
6. The method for simulating the molten pool flow field for thick plate narrow gap point ring laser filler wire welding, which is characterized by adopting three-dimensional modeling software to construct a thick plate narrow gap geometric workpiece model, storing the thick plate narrow gap geometric workpiece model as an intermediate file in stl format, and importing the thick plate narrow gap geometric workpiece model into CFD modeling software.
7. The method for simulating a molten pool flow field for thick plate narrow gap point ring laser filler wire welding according to claim 1, further comprising verifying the established point ring laser three-dimensional body heat source model, wherein the verification method is to weld welding entities with the same size as the thick plate narrow gap geometric workpiece model, and comparing the obtained welding seams with a simulated molten pool to judge whether the welding seams are matched.
8. The method for simulating a molten pool flow field for thick plate narrow gap point ring laser filler wire welding, which is characterized in that when welding a welding entity, the welding speed is 20-30 mm/s, the laser power is 2500-3500W, the defocusing amount is +20-30 mm, the diameter of a defocused laser spot is 2.5-3.5 mm, argon is adopted as shielding gas, and the flow is 15-25L/min.
9. The method for simulating a molten pool flow field for thick plate narrow gap point ring laser filler wire welding according to claim 1, wherein the mass momentum source method is adopted to simulate the filler wire process and realize the coupling with the heat source loading process, and the coupling is performed based on calculated values of the density, specific heat and thermal conductivity of the base metal and the metal of the welding wire along with the change of temperature.
10. The method for simulating a molten pool flow field for thick plate narrow gap point ring laser filler wire welding according to claim 1, further comprising capturing a free interface of a welding pool by a VOF method based on the temperature field, the speed field and the relevant information of the size of the molten pool in the welding process, establishing a free interface tracking model, and simulating a flow state effect diagram in the molten pool.
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