Numerical simulation method of laser welding between molybdenum-rhenium alloy and stainless steel dissimilar materials

Abstract

The application discloses a numerical simulation method for laser welding of molybdenum-rhenium alloy and stainless steel dissimilar materials, prepares a joint of laser welding of molybdenum-rhenium alloy and stainless steel dissimilar materials, and obtains a molten pool pattern of the joint; each thermal physical property parameter and mechanical property parameter of molybdenum-rhenium alloy base material, stainless steel base material and weld metal is obtained through experiment and calculation; a thermal-structure calculation model of the laser welding process of the molybdenum-rhenium alloy and stainless steel dissimilar materials is established; initial conditions, boundary conditions and a heat source model of the laser welding model are set; a laser welding analysis task is established, and a temperature field and a stress field of the laser welding process of the molybdenum-rhenium alloy and stainless steel dissimilar materials are solved. The method converts the yield strength of the weld metal by using the Vickers hardness of the weld metal, obtains the component proportion of the weld by means of energy spectrum analysis, and calculates the high-temperature property parameter of the weld metal by means of a calculation software. High-precision calculation of the temperature field and the stress field of the laser welding process of the molybdenum-rhenium alloy and stainless steel dissimilar materials is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to a numerical simulation method for laser welding of molybdenum-rhenium alloy and stainless steel dissimilar materials, and belongs to the technical field of laser welding and numerical simulation. BACKGROUND

[0002] Molybdenum-rhenium alloy has excellent high-temperature mechanical properties, low linear expansion coefficient and good thermal conductivity, and is applied to advanced reactors such as fast neutron reactors and nuclear fusion reactors as a nuclear reactor structural material. The application range of molybdenum-rhenium alloy is limited due to its high cost, while stainless steel is a cheap alloy with excellent comprehensive performance and is widely used in many fields. The composite structure of molybdenum-rhenium alloy and stainless steel will help to increase design flexibility, reduce manufacturing difficulty and save material cost.

[0003] Compared with traditional welding methods, laser welding has the advantages of high energy density, small heat-affected zone and small welding deformation, which is beneficial to the welding of dissimilar metals. Due to the different physical and chemical properties of molybdenum-rhenium alloy and stainless steel, the linear expansion coefficient and thermal conductivity are quite different, and attention should be paid to the control of residual stress and welding deformation. With the help of numerical simulation method, the temperature field distribution, joint residual stress and welding deformation characteristics of molybdenum-rhenium alloy and stainless steel laser welded joint can be theoretically analyzed, and the welding process can be optimized under the condition of saving test cost.

[0004] The metallurgical reaction in the weld zone of dissimilar materials is relatively complex, and it is usually difficult to accurately obtain the material constitutive model, especially for laser welding which has a narrow weld zone. It is difficult to obtain the thermophysical performance parameters and mechanical performance parameters of the weld metal by using traditional experimental methods. SUMMARY

[0005] The purpose of the present application is to provide a numerical simulation method for laser welding of molybdenum-rhenium alloy and stainless steel dissimilar materials, which solves the problem that the material performance parameters of dissimilar material weld metal are difficult to accurately obtain, and the temperature field change, residual stress after welding and welding deformation during the laser welding process of molybdenum-rhenium alloy / stainless steel are difficult to predict.

[0006] The technical scheme adopted by the present application is a numerical simulation method for laser welding of molybdenum-rhenium alloy and stainless steel dissimilar materials, comprising the following steps:

[0007] Step 1, preparing a joint for laser welding of molybdenum-rhenium alloy / stainless steel dissimilar materials, and obtaining the molten pool morphology of the joint;

[0008] Step 2, obtaining the thermal physical performance parameters and mechanical performance parameters of the molybdenum-rhenium alloy base material, stainless steel base material and weld metal through experiments and calculations;

[0009] Step 3, establishing a thermal-structure calculation model of the laser welding process of the molybdenum-rhenium alloy / stainless steel dissimilar materials;

[0010] Step 4, setting initial conditions, boundary conditions and heat source model of the laser welding model;

[0011] Step 5, establishing a laser welding analysis task, and solving the temperature field and stress field of the laser welding process of the molybdenum-rhenium alloy / stainless steel dissimilar materials.

[0012] Further, the step 2 is implemented according to the following steps:

[0013] Step 2-1, obtaining the thermal physical property parameters and mechanical property parameters of the molybdenum-rhenium alloy base material and the stainless steel base material;

[0014] Step 2-2, performing Vickers hardness test on the obtained joint to obtain the average value of the microhardness of the weld metal, and converting the room temperature yield strength of the weld metal by using an empirical formula:

[0015]

[0016] In the formula, σ y represents the yield strength, and the unit is MPa; H v is the Vickers hardness, and the unit is HV; and m is the Meyer hardness coefficient.

[0017] Step 2-3, performing energy spectrum analysis on the weld area of the obtained joint to obtain the composition proportion of the weld metal, and calculating the high-temperature performance parameters of the weld metal by using JMatPro calculation software.

[0018] Further, the step 3 is implemented according to the following steps:

[0019] Step 3-1, establishing a joint finite element grid model of the joint molten pool shape by using Hypermesh finite element pre-processing software, and the grid is dense to sparse from the weld to the molybdenum-rhenium alloy base material side and from the weld to the stainless steel base material side. The weld and the heat-affected zone are encrypted; the area away from the weld is relatively sparse; and the established joint finite element grid model is imported into MSC.Marc finite element software.

[0020] Step 3-2, assigning the thermal physical property parameters and mechanical property parameters of the molybdenum-rhenium alloy base material, the stainless steel base material and the weld metal to the corresponding parts of the joint in the form of a table in the MSC.Marc finite element software.

[0021] Further, the step 4 is implemented according to the following steps:

[0022] Step 4-1, in the MSC.Marc finite element software, set the initial temperature of the molybdenum-rhenium alloy base material, the stainless steel base material and the weld metal in the initial condition as the ambient temperature; set the temperature field boundary condition, including convection and thermal radiation, set the joint displacement constraint to limit the rigid displacement during the welding process;

[0023] Step 4-2, according to the joint molten pool morphology obtained in step 1 experiment, a combination heat source of double ellipsoid + cylinder is selected as the heat source model for simulating the heat input in the laser welding process.

[0024] Further, the step 5 is implemented according to the following steps:

[0025] Step 5-1, the welding analysis task is divided into two analysis working conditions of welding and cooling, the convergence criterion and the time step are set, the output results are set, and the establishment of the laser welding analysis task is completed, and the output results include the element type, the temperature, the stress and the displacement.

[0026] Step 5-2, in the MSC.Marc finite element software, the welding analysis task is submitted, the thermal analysis is carried out: the joint temperature field is solved, and the temperature field of each node in the joint finite element grid model is obtained; the structure analysis is carried out: each node temperature field is loaded to the thermal-structure calculation model structure analysis finite element model as a thermal load, so that the stress and displacement of the whole welding process are solved; then the calculation result postprocessor is entered, and the temperature field and stress field of the molybdenum-rhenium alloy / stainless steel dissimilar material laser welding process are obtained.

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

[0028] 1, the present application obtains the thermal physical and mechanical performance parameters of the weld metal by combining experiment and calculation. The yield strength of the weld metal is converted by using the Vickers hardness, the component proportion of the weld is obtained by energy spectrum analysis, and the high temperature performance parameters of the weld metal are calculated by using the calculation software. The problem that the material constitutive model is difficult to accurately obtain is solved, the accuracy of the material constitutive model is greatly improved, and the calculation accuracy of the temperature field and stress field of the molybdenum-rhenium alloy and stainless steel dissimilar material laser welding process is improved;

[0029] 2, by the numerical simulation method of the molybdenum-rhenium alloy / stainless steel dissimilar material laser welding of the present application, a thermal-structure calculation model is adopted, and a double ellipsoid + cylinder combination heat source is selected to simulate the laser welding heat input. Through the numerical simulation method, the stress distribution and deformation of the molybdenum-rhenium alloy / stainless steel welded joint can be obtained, the failure position of the joint in the service process can be predicted, and the engineering application is guided. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application.

[0031] Figure 1 Molymet alloy / stainless steel dissimilar material laser welding joint molten pool shape.

[0032] Figure 2 Molymet alloy / stainless steel dissimilar material laser welding joint microhardness test results.

[0033] Figure 3 Molymet alloy / stainless steel dissimilar material laser welding joint energy spectrum element analysis results.

[0034] Figure 4 Molymet alloy / stainless steel dissimilar material laser welding joint weld metal material performance parameters.

[0035] Figure 5 Molymet alloy / stainless steel dissimilar material laser welding numerical simulation finite element grid model.

[0036] Figure 6 Molymet alloy / stainless steel dissimilar material laser welding joint weld metal material performance parameters.

[0037] Figure 7 Molymet alloy / stainless steel dissimilar material laser welding joint weld metal material performance parameters.

[0038] Figure 8 Molymet alloy / stainless steel dissimilar material laser welding joint weld metal material performance parameters.

[0039] Figure 9 Molymet alloy / stainless steel dissimilar material laser welding joint weld metal material performance parameters. DETAILED DESCRIPTION

[0040] The detailed content of the present application and its specific implementation mode will be further explained below in combination with the drawings.

[0041] In the present application, the "molymet alloy / stainless steel" refers to the molymet alloy and the stainless steel two materials.

[0042] In the present application, the "molymet alloy / stainless steel" refers to the molymet alloy and the stainless steel two materials.

[0043] The application discloses a numerical simulation method for laser welding of molybdenum-rhenium alloy and stainless steel dissimilar materials, and is realized according to the following steps:

[0044] Step 1, a molybdenum-rhenium alloy / stainless steel dissimilar material laser welding joint is prepared, and a molten pool morphology of the joint is obtained.

[0045] The existing laser welding process is used to prepare the molybdenum-rhenium alloy / stainless steel dissimilar material laser welding joint. After the metallographic sample at a proper position of the joint is cut by using a wire cut electrical discharge machine, the sample is polished and observed by using an optical microscope, and the molten pool morphology of the joint is obtained.

[0046] Step 2, performance parameters of base materials and weld metal are obtained through experiments and calculations.

[0047] Step 2-1, each thermophysical property parameter and mechanical property parameter of the molybdenum-rhenium alloy base material, the stainless steel base material and the weld metal are obtained, including density, thermal conductivity, specific heat capacity, yield strength, elastic modulus, Poisson's ratio and linear expansion coefficient, and each thermophysical property parameter and mechanical property parameter is obtained by using an existing method.

[0048] Step 2-2, Vickers hardness testing is performed on the joint, the average value of the microhardness of the weld metal is obtained, and the yield strength of the weld metal at room temperature is converted by using the following formula:

[0049]

[0050] In the formula, σ y represents the yield strength, that is, the stress value at which plastic deformation of the material begins, and the unit is megapascal (MPa) ; H v is the Vickers hardness, and the unit is Vickers hardness unit (HV) ; and m is a Meyer hardness coefficient, and different materials have different Meyer hardness coefficients.

[0051] Step 2-3, energy spectrum analysis is performed on the weld area of the joint, the component proportion of the weld metal is obtained, and the high-temperature performance parameters of the weld metal are calculated by using JMatPro calculation software, the high-temperature performance parameters of the weld metal including density, thermal conductivity, specific heat capacity, yield strength, elastic modulus, Poisson's ratio and thermal expansion coefficient.

[0052] Step 3, a thermal-structure calculation model of the laser welding process of the molybdenum-rhenium alloy / stainless steel dissimilar material is established.

[0053] Step 3-1, according to the joint molten pool shape in the experiment, the finite element mesh model of the joint was established by using Hypermesh finite element pre-processing software. In order to improve the calculation efficiency while ensuring the calculation accuracy, the mesh was dense to sparse from the weld to the molybdenum-rhenium alloy base metal side and from the weld to the stainless steel base metal side. During the welding process, the temperature gradient of the weld and the heat affected zone changed greatly, so the dense mesh was used in this part; while the temperature gradient of the area far away from the weld changed relatively small, so the relatively sparse mesh was used. The established joint finite element mesh model was exported in the form of.inp file, and this file was imported into MSC.Marc finite element software;

[0054] Step 3-2, the thermal physical property parameters and mechanical property parameters of the molybdenum-rhenium alloy base metal, the stainless steel base metal and the weld metal were respectively assigned to the corresponding parts of the joint in the form of table.

[0055] Step 4, the initial conditions, boundary conditions and heat source model of the laser welding model were set;

[0056] Step 4-1, the initial temperature of the welded joint was set to the ambient temperature in the initial conditions; the boundary conditions of the temperature field were set, including convection and thermal radiation. The displacement constraint of the joint was set to limit the rigid displacement of the joint during the welding process;

[0057] Step 4-2, according to the actual molten pool shape, the upper molten pool of the molybdenum-rhenium alloy / stainless steel dissimilar material laser welding joint was wide, and the lower molten pool was narrow. Therefore, the welding heat source model of the combination of double ellipsoid heat source and cylindrical heat source was selected. According to the welding conditions in the experiment, the related heat source parameters were set, including the welding path, the laser power, the welding heat efficiency, the welding speed, etc.

[0058] Step 5, the analysis task of laser welding was established and submitted for solving.

[0059] Step 5-1, the whole welding analysis task was divided into two analysis conditions of welding and cooling. According to the actual welding process, the corresponding load and time of the two conditions were set, the convergence criterion and time step were set. The unit type was set, and the temperature, stress, displacement and other required output results were selected to complete the establishment of the laser welding analysis task.

[0060] Step 5-2, the laser welding analysis task was submitted. First, the temperature field of the joint was solved, and the temperature field of each node was obtained. The stress field calculation used the thermal-elastic-plastic finite element calculation method, that is, the temperature field results of each node were loaded as thermal load to the structure analysis finite element model, so as to solve the stress and displacement of the whole welding process. After the calculation was completed, the calculation result post-processor was entered to obtain the temperature field and stress field of the molybdenum-rhenium alloy / stainless steel dissimilar material laser welding process.

[0061] Embodiment

[0062] A numerical simulation method for laser welding of molybdenum-rhenium alloy and stainless steel dissimilar materials is described in combination with the accompanying drawings, taking the calculation of laser welding of Mo-5Re molybdenum-rhenium alloy and 316L stainless steel dissimilar materials as an example.

[0063] The chemical composition (wt.%) of Mo-5Re molybdenum-rhenium alloy is as follows:

[0064]

[0065] The chemical composition (wt.%) of 316L stainless steel is as follows:

[0066]

[0067] The following steps are specifically implemented:

[0068] Step 1, prepare Mo-5Re molybdenum-rhenium alloy / 316L stainless steel dissimilar material laser welding joint, and obtain the molten pool morphology of the joint;

[0069] Under the welding process of laser power of 2200W and welding speed of 2m / min, the Mo-5Re molybdenum-rhenium alloy / 316L stainless steel dissimilar material laser welding joint is prepared. Mo-5Re and 316L are respectively corroded using corresponding corrosion reagents, and then microstructure observation is performed to obtain the molten pool morphology of the Mo-5Re molybdenum-rhenium alloy / 316L stainless steel laser welding joint as shown in Figure 1

[0070] Step 2, obtain the performance parameters of Mo-5Re molybdenum-rhenium alloy base metal, 316L stainless steel base metal and weld metal through experiments and calculations;

[0071] Step 2-1, obtain the thermal physical performance parameters and mechanical performance parameters of Mo-5Re molybdenum-rhenium alloy and 316L stainless steel with temperature change, including density, thermal conductivity, specific heat capacity, yield strength, elastic modulus, Poisson's ratio and thermal expansion coefficient, by means of tensile property test experiment, linear expansion test experiment, thermal physical property test experiment and related literature materials.

[0072] Step 2-2, Vickers hardness test is performed on the joint obtained in this example, the Vickers hardness values of 20 point positions on both sides of the weld center are measured, and the interval between each point is 0.1mm. The loading force is 200gf during measurement, and the holding time is 10s. The microhardness test results of the Mo-5Re molybdenum-rhenium alloy / 316L stainless steel dissimilar material laser welding joint are shown in Figure 2

[0073] ​​

[0074] wherein σ y represents the yield strength, i.e. the stress value at which the material begins to plastically deform, in units of mega pascal (MPa); H v is the Vickers hardness, in units of Vickers hardness units (HV); m is the Meyer hardness coefficient, which is different for different materials. The Meyer hardness coefficient of the dissimilar material welded joint metal in the present example is the sum of the Meyer hardness coefficients of the two base metals, which is 4.3, and the yield strength σy of the welded joint metal at room temperature is 359 MPa.

[0075] Step 2-3, energy spectrum analysis was performed on the welded joint area of the joint obtained in the experiment in the present example, and the analysis results are shown in Table 2. Figure 3 The mass proportions of the chemical components of the welded joint metal were introduced into the JMatPro calculation software to calculate the high-temperature performance parameters of the welded joint metal, including density, thermal conductivity, specific heat capacity, yield strength, elastic modulus, Poisson's ratio, and thermal expansion coefficient, and the calculation results are shown in Table 3. Figure 4

[0076] Step 3, a thermal-structure calculation model of the Mo-5Re molybdenum-rhenium alloy / 316L stainless steel dissimilar material laser welding process was established.

[0077] Step 3-1, the finite element mesh model of the joint was established by using the Hypermesh finite element pre-processing software in combination with the actual morphology of the molten pool obtained in the experiment in the present example, wherein the sizes of the Mo-5Re molybdenum-rhenium alloy and the 316L stainless steel were all 100 mm x 50 mm x 3 mm. In order to improve the calculation efficiency while ensuring the calculation accuracy, the mesh was dense to sparse from the weld to the base metal side. During the welding process, the temperature gradient of the weld and the heat-affected zone changes greatly, and this part needs to use the encrypted mesh; while the area far away from the weld, the temperature gradient changes relatively small, and relatively sparse mesh can be used. The obtained mesh model is shown in Table 4, the mesh element type of the whole joint is 8-node hexahedral element, the total number of nodes is 111957, and the total number of elements is 94400. The established joint mesh model was exported in the.inp file format, and this file was imported into the MSC.Marc finite element software. Figure 5

[0078] Step 3-2, the obtained thermal physical performance parameters and mechanical performance parameters of the Mo-5Re molybdenum-rhenium alloy, the 316L stainless steel and the welded joint metal were respectively assigned to the corresponding joint parts in the form of a table.

[0079] Step 4, the initial conditions, boundary conditions and heat source model of the laser welding model were set.

[0080] ​​Step 4-1, set the initial temperature of the welded joint as the ambient temperature 25℃ in the initial condition; set the boundary condition of the temperature field, comprehensively consider the convection and thermal radiation, load in the form of convection, and set the total heat transfer coefficient as 3.3×10 -5 According to the actual welding conditions, the displacement constraint of the joint is set to limit the rigid displacement of the joint during the welding process. In this example, as shown in Figure 5 three-point constraints and vertical constraints are applied to the Mo-5Re molybdenum-rhenium alloy and 316L stainless steel two base materials far from the weld edge to prevent displacement of the joint during the welding process;

[0081] Step 4-2, according to the actual molten pool morphology, a combined heat source of double ellipsoid + cylinder as shown in Figure 6 is established in this example to simulate the heat input in the laser welding process. The total heat input Q of the combined heat source is:

[0082] Q = ηP = n1Q + n2Q

[0083] n1 + n2 = 1

[0084] In the formula, η is the welding thermal efficiency, which is 0.9; P is the laser power; n1 and n2 are the distribution coefficients of the double ellipsoid and the cylindrical heat source, respectively, n1 is 0.4, and n2 is 0.6.

[0085] The heat flux density (q1 and q2) distribution of the upper part of the double ellipsoid heat source is defined as:

[0086]

[0087] In the formula, H1 is the action height of the double ellipsoid in the plate thickness direction; a1, a2, b, and c are ellipsoid shape parameters; f1 and f2 are front and rear ellipsoid heat distribution functions, and f1 + f2 = 2.

[0088] The heat flux density (q V ) of the lower part of the cylindrical heat source is defined as:

[0089]

[0090] H = d - H1

[0091] In the formula, H is the action height of the cylindrical heat source; d is the plate thickness; r0 is the action radius; r is the distance of a certain point in the arc coverage area from the center of the heat source.

[0092] The welding path of this example is a straight line path for ordinary butt joint, the laser power P used is 2200W, and the welding speed is 2m / min.

[0093] Step 5, establish the analysis task of laser welding and submit the solution;

[0094] Step 5-1, the whole welding analysis task is divided into two analysis conditions of welding and cooling, the welding condition time is 3s, and the cooling condition is 4000s. The convergence criterion method is residual stress or displacement, and the convergence tolerance is 0.1. The unit type is set to No. 7 thermal-structural analysis entity unit. After selecting the required output results such as temperature, stress and displacement, the establishment of the analysis task is completed.

[0095] Step 5-2, submit the analysis task, first solve the joint temperature field to obtain the temperature field of each node.

[0096] During welding, heat spreads from the high-temperature part of the workpiece to the low-temperature part in the form of heat conduction. The heat transfer phenomenon during welding can be calculated and analyzed by Fourier's law:

[0097]

[0098] In the formula, T is the temperature field to be solved (℃); λ is the thermal conductivity (J·mm -1 ·s -1 ·℃ -1 ); q v is the heat generation power of the internal heat source (J·mm -3 ); ρ is the density (g·mm -3 ); c P is the constant-pressure heat capacity (J·g -1 ·℃ -1 ); t is the heat transfer time (s).

[0099] The stress field calculation adopts the thermal-elastic-plastic finite element calculation method, that is, the temperature field results of each node are loaded to the structural analysis finite element model as thermal load, so as to solve the stress and displacement of the whole welding process.

[0100] After calculation, enter the calculation result postprocessor to obtain the temperature field and stress field of the Mo-Re / 316L dissimilar material laser welding process.

[0101] From Figure 7 (a) The temperature field cloud chart during welding can be seen that with the movement of the welding heat source, the temperature field on both sides of the welding test plate is asymmetrically distributed. The isotherm on the Mo-5Re side is relatively sparse compared with the 316L side. Because the thermal conductivity of Mo-5Re is greater than that of 316L, the high-temperature area on the Mo-5Re side is wider. Figure 7 (b) is the temperature field distribution cloud chart of Mo-5Re / 316L weld cross section. The gray area in the figure is the area with temperature higher than the melting point of Mo-5Re (2500℃), that is, the welding pool. The white dotted line is the shape of the actual welding joint pool. It can be seen that the calculated and experimental pool shapes are basically consistent.

[0102] From Figure 8It can be seen that the residual stress distribution of Mo-5Re molybdenum-rhenium alloy / 316L stainless steel laser welded joint on the left and right sides has significant difference, the transverse ( Figure 8 (a)) and longitudinal ( Figure 8 (b)) residual stress is mainly concentrated near the fusion zone on the Mo-5Re molybdenum-rhenium alloy side, the longitudinal residual peak stress is 490 MPa, and the transverse residual peak stress is 345 MPa. The fusion zone on the Mo-5Re molybdenum-rhenium alloy side will be the weak position of the whole joint, which should be paid attention to during service.

[0103] The displacement distribution cloud map of Mo-5Re molybdenum-rhenium alloy / 316L stainless steel laser welded joint after 10 times amplification in the plate thickness direction (Y) is shown in Figure 9 The Mo-5Re molybdenum-rhenium alloy / 316L stainless steel welded joint produces small overall deformation, and due to the uneven distribution of transverse shrinkage in the plate thickness direction, the joint produces certain angular deformation, and the maximum deformation is only 0.312 mm.

[0104] The above is only the preferred example of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made to the present application shall be included in the protection scope of the present application.

Claims

1. A numerical simulation method of laser welding of molybdenum-rhenium alloy and stainless steel dissimilar materials, characterized by, It comprises the following steps: Step 1, preparing a joint of laser welding of molybdenum-rhenium alloy / stainless steel dissimilar materials, and obtaining the molten pool morphology of the joint; Step 2, obtaining the thermal physical property parameters and mechanical property parameters of the molybdenum-rhenium alloy base material, the stainless steel base material and the weld metal through experiments and calculations; Step 3, establishing a thermal-structure calculation model of the laser welding process of the molybdenum-rhenium alloy / stainless steel dissimilar materials; The step 3 is implemented according to the following steps: Step 3-1, using the Hypermesh finite element pre-processing software to establish a joint finite element grid model of the joint molten pool morphology, from the weld to the molybdenum-rhenium alloy base material side and from the weld to the stainless steel base material side, the grid is dense to sparse, and the weld and the heat-affected zone adopt the encrypted grid; the area away from the weld adopts the relatively sparse grid; the established joint finite element grid model is imported into the MSC.Marc finite element software; Step 3-2, in the MSC.Marc finite element software, the thermal physical property parameters and mechanical property parameters of the molybdenum-rhenium alloy base material, the stainless steel base material and the weld metal are respectively assigned to the corresponding parts of the joint in the form of a table; Step 4, setting the initial conditions, boundary conditions and heat source model of the laser welding model; The step 4 is implemented according to the following steps: Step 4-1, in the MSC.Marc finite element software, setting the initial temperature of the molybdenum-rhenium alloy base material, the stainless steel base material and the weld metal as the ambient temperature in the initial conditions; setting the temperature field boundary conditions, including convection and thermal radiation, setting the joint displacement constraint to limit the rigid displacement during the welding process; Step 4-2, according to the joint molten pool morphology obtained in step 1, selecting a combined heat source of double-ellipsoid + cylinder as the heat source model of the heat input in the simulation of the laser welding process; Step 5, establishing a laser welding analysis task, and solving the temperature field and stress field of the laser welding process of the molybdenum-rhenium alloy / stainless steel dissimilar materials; The step 5 is implemented according to the following steps: Step 5-1, the welding analysis task is divided into two analysis conditions of welding and cooling, the convergence criterion and time step are set, the output results are set after the establishment of the laser welding analysis task, and the output results include the element type, the selection of temperature, stress and displacement; Step 5-2, in the MSC.Marc finite element software, the welding analysis task is submitted, the thermal analysis is carried out: the joint temperature field is solved, the temperature field of each node in the joint finite element grid model is obtained; the structure analysis is carried out: the stress and displacement of the whole welding process are solved; then entering the calculation result post-processor, the temperature field and stress field of the laser welding process of the molybdenum-rhenium alloy / stainless steel dissimilar materials are obtained.

2. The numerical simulation method of laser welding of a molybdenum-rhenium alloy and a stainless steel dissimilar material according to claim 1, characterized in that, The step 2 is implemented according to the following steps: Step 2-1, obtaining the thermal physical property parameters and mechanical property parameters of the molybdenum-rhenium alloy base material and the stainless steel base material; Step 2-2, Vickers hardness test is conducted on the obtained joint, the average value of the microhardness of the weld metal is obtained, and the room temperature yield strength of the weld metal is converted by using the empirical formula: wherein σ y represents the yield strength, in MPa; H v is the Vickers hardness, in HV; m is the Meyer hardness coefficient; Step 2-3, energy spectrum analysis is conducted on the weld area of the obtained joint, the composition proportion of the weld metal is obtained, and the high temperature performance parameters of the weld metal are calculated by means of JMatPro calculation software.

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