Method for establishing heat source for circular path laser deep penetration welding of thick-walled circular tube workpiece

Abstract

A method for establishing a heat source for annular path laser deep penetration welding of thick-walled circular tube workpieces belongs to the technical field of laser deep penetration welding. The present invention addresses the problem that the existing heat source model for circumferential weld laser welding is limited to a Gaussian surface heat source or a double ellipsoid heat source model, and lacks the embodiment of the large radial penetration characteristics of the thick-walled circular tube workpiece, resulting in low simulation calculation accuracy. It includes establishing a three-dimensional finite element workpiece mesh model of the thick-walled circular tube workpiece; establishing a laser deep penetration welding heat source model for the corresponding flat workpiece; performing coordinate transformation on the laser deep penetration welding heat source model of the flat workpiece according to the annular path of the thick-walled circular tube workpiece to obtain a laser deep penetration welding heat source model for the thick-walled circular tube workpiece; loading the laser deep penetration welding heat source model of the thick-walled circular tube workpiece onto a three-dimensional finite element workpiece mesh model, setting model parameters, calculating the temperature field of the three-dimensional finite element workpiece mesh model, and obtaining a final heat source model. The present invention can realize numerical simulation of laser welding with different penetration depths in annular paths.

Description

Technical Field

[0001] The invention relates to a method for establishing a heat source for annular path laser deep penetration welding of a thick-walled circular tube workpiece, and belongs to the technical field of laser deep penetration welding. Background Art

[0002] As one of the high-energy beam welding methods, laser welding has the advantages of high energy density, good weld formation, high welding efficiency, good penetration, and small post-weld deformation. It has been widely used in shipbuilding engineering, aerospace, transportation industry, machinery manufacturing, and micro-nano processing.

[0003] In the aerospace sector, Airbus has replaced traditional riveting with laser welding technology for fuselage panels on the A318 aircraft. Currently, the C919 uses laser welding technology for aluminum alloy trusses and skins, significantly reducing fuselage weight and processing costs while ensuring reliable fuselage connections. With the continuous development of industry, there is an increasing demand for laser deep penetration welding, and even laser penetration welding, for medium- and thicker metal plates. Increasing weld penetration while ensuring weld quality has become a research focus for scholars both domestically and internationally. Experimental research on laser deep penetration welding faces high processing costs, time, and material consumption. Consequently, numerical simulation is increasingly being used to study laser deep penetration welding. Compared to empirical judgment and physical testing, numerical simulation can significantly save material and human resources, production costs, and research cycles, and offers advantages such as ease of control and high flexibility.

[0004] Currently, there is little research on the numerical simulation of girth welds in laser deep penetration welding. The development of a heat source for annular laser deep penetration welding is a primary challenge in this field. The heat sources for girth welds described in current literature are limited to Gaussian surface heat sources or double ellipsoid heat source models, lacking the ability to account for the deep penetration characteristic along the radial direction of thick-walled circular tubes. This can severely reduce the computational accuracy of numerical simulations of laser deep penetration welding of thick-walled circular tubes. Summary of the Invention

[0005] In view of the problem that the existing heat source model of circumferential weld laser welding is limited to Gaussian surface heat source or double ellipsoid heat source model, which lacks the embodiment of the large radial penetration feature of thick-walled circular tube workpieces, resulting in low simulation calculation accuracy, the present invention provides a method for establishing a heat source for annular path laser deep penetration welding of thick-walled circular tube workpieces.

[0006] The present invention provides a method for establishing a heat source for annular path laser deep penetration welding of a thick-walled circular tube workpiece, comprising:

[0007] Step 1: Use 3D modeling software to establish a 3D finite element numerical model of the thick-walled circular tube workpiece, and then use meshing software to mesh the 3D finite element numerical model to obtain a 3D finite element workpiece mesh model;

[0008] Step 2: Establish a laser deep penetration welding heat source model for the corresponding flat workpiece based on the thick-walled circular tube workpiece, wherein the laser deep penetration welding heat source model includes a surface heat source and a body heat source;

[0009] Step 3: performing coordinate transformation on the laser deep penetration welding heat source model of the flat workpiece according to the circular path of the thick-walled circular tube workpiece to obtain the laser deep penetration welding heat source model of the thick-walled circular tube workpiece;

[0010] Step 4: Load the laser deep penetration welding heat source model of the thick-walled circular tube workpiece onto the three-dimensional finite element workpiece mesh model, set the model parameters, and use finite element calculation software to calculate the temperature field of the three-dimensional finite element workpiece mesh model to obtain the final heat source model.

[0011] According to the method for establishing a heat source for annular path laser deep penetration welding of a thick-walled circular tube workpiece of the present invention, in step one, the three-dimensional finite element numerical model is a 1:1 geometric model of the thick-walled circular tube workpiece; the thickness of the thick-walled circular tube workpiece is at least 5 mm.

[0012] According to the method for establishing a heat source for annular path laser deep penetration welding of thick-walled circular tube workpieces of the present invention, in the heat source model for laser deep penetration welding of flat workpieces, the surface heat source and body heat source formulas are:

[0013]

[0014]

[0015] Where Q s1 (x, y, t) is the heat flux density distribution of the surface heat source on the surface of the flat workpiece, x is the horizontal coordinate of the movement of the heat source center over time, y is the vertical coordinate of the movement of the heat source center over time, t is time, α is the heat flux concentration coefficient of the surface heat source, P s is the surface heat source power, η s is the surface heat source energy distribution coefficient, R s is the effective action radius of the surface heat source, (x0, y0) is the initial action point of the surface heat source on the flat workpiece;

[0016] Q v (x, y, z, t) is the heat flux density distribution of the body heat source inside the flat workpiece, z is the vertical coordinate of the heat source center in the three-dimensional space based on the xy plane coordinate system that changes with time, β is the heat flux concentration coefficient of the body heat source, P v is the body heat source power, η v is the energy distribution coefficient of the body heat source, ηs +η v =1, H is the effective depth of body heat source, R v is the effective action radius of the body heat source, and (x0, y0, z0) is the initial action point of the body heat source inside the flat workpiece.

[0017] According to the method for establishing a heat source for annular path laser deep penetration welding of thick-walled circular tube workpieces of the present invention, in step three, coordinate transformation includes transforming the coordinate points on the flat workpiece into the coordinate points of the annular path of the thick-walled circular tube workpiece. The coordinate transformation formula is:

[0018]

[0019] Where x1 is the horizontal coordinate of the circular motion path of the thick-walled circular tube workpiece, y1 is the vertical coordinate of the circular motion path of the thick-walled circular tube workpiece, and z1 is the vertical coordinate of the circular motion path of the thick-walled circular tube workpiece; (x1, y1) is the point where the surface heat source moves along the circular path of the thick-walled circular tube workpiece, (x1, y1, z1) is the point where the body heat source moves along the circular path of the thick-walled circular tube workpiece, and θ is the arc that the laser deep penetration welding heat source model of the flat workpiece rotates through over time with the center of the thick-walled circular tube workpiece as the rotation center.

[0020] According to the method for establishing a heat source for annular path laser deep penetration welding of thick-walled circular tube workpieces of the present invention, in step 3, the heat source model for laser deep penetration welding of thick-walled circular tube workpieces obtained includes a surface heat source and a body heat source:

[0021]

[0022]

[0023] Where Q s2 (x, y, t) is the heat flux density distribution of the surface heat source on the surface of the thick-walled circular tube workpiece, Q v (δ,h,t) is the heat flux density distribution of the body heat source inside the thick-walled circular tube workpiece, δ is the heat source position factor after coordinate transformation, and h is the radial projection depth of the body heat source along the thick-walled circular tube;

[0024]

[0025]

[0026] For intermediate variables:

[0027]

[0028] According to the method for establishing a heat source for annular path laser deep penetration welding of thick-walled circular tube workpieces of the present invention, formulas (1) to (8) are programmed offline to realize the programming of the laser heat source; the offline programming is written in Fortran language.

[0029] According to the method for establishing a heat source for annular path laser deep penetration welding of thick-walled circular tube workpieces of the present invention, in step four:

[0030] Setting the model parameters includes: setting the convection heat transfer coefficient between the thick-walled circular tube workpiece and the environment to 40W / (m 2 ·℃), the emissivity is 0.85, and the initial temperature of the thick-walled circular tube workpiece is 20 degrees Celsius; the convection and radiation heat transfer formula of the thick-walled circular tube workpiece is:

[0031]

[0032] Where k is the thermal conductivity of the thick-walled circular tube workpiece material, is the normal vector of the outer surface of the thick-walled circular tube workpiece, P is the total laser power, h0 is the convection heat transfer coefficient, T is the surface temperature of the thick-walled circular tube workpiece, T0 is the ambient temperature of the thick-walled circular tube workpiece, ε is the emissivity of the thick-walled circular tube workpiece material; σ is the Stefan-Boltzmann constant, which is always equal to 5.67×10 -8 W / (m 2 ·K 4 );

[0033] temperature difference

[0034] In the heat source model of laser deep penetration welding of thick-walled circular tube workpiece, the surface heat source is applied to the outer surface of the thick-walled circular tube workpiece, and the body heat source is applied to the entire thick-walled circular tube workpiece;

[0035] Then, the heat source model of the laser deep penetration welding of the thick-walled circular tube workpiece is loaded onto the three-dimensional finite element workpiece mesh model for calculation to obtain the temperature field of the three-dimensional finite element workpiece mesh model and obtain the final heat source model.

[0036] The present invention has the following beneficial effects: The heat source model established by the present method can be moved along a circular path on a thick-walled circular tube workpiece, enabling butt welding of thick-walled circular tubes. The heat source model is concise, and shape parameters such as penetration depth and heat source radius, as well as motion parameters such as rotational angular velocity, can be easily modified. It offers high controllability and can replace physical testing in production workshops with high precision, minimizing the blindness and repetitiveness of research.

[0037] The method of the present invention not only achieves numerical simulation of circumferential welding of circular tubes, but also highlights the characteristic of large radial penetration depth. The main shape parameters of the heat source model are the effective heat source depth and effective heat source radius. The shape is easily adjustable, enabling numerical simulation of laser welding with varying penetration depths along an annular path. The main motion parameter of the heat source model is the circumferential rotational angular velocity, allowing for flexible selection of the welding speed based on the welding cycle or weld length, resulting in high controllability.

[0038] The present invention realizes the establishment of a heat source model for annular path laser deep penetration welding of thick-walled circular tube workpieces with freely adjustable shape and high calculation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a three-dimensional finite element workpiece mesh model obtained in the method for establishing a heat source for annular path laser deep penetration welding of thick-walled circular tube workpieces described in the present invention;

[0040] Figure 2 This is the heat flux density diagram of the heat source model for laser deep penetration welding of thick-walled circular tube workpieces;

[0041] Figure 3 This is an overall rendering of the molten pool morphology in the longitudinal section of a thick-walled circular tube workpiece at the initial moment of laser deep penetration welding using the final heat source model established by the method of the present invention. In the figure, the annular end face of the thick-walled circular tube is the xy plane of the three-dimensional coordinate system, and the length direction is the z-axis direction of the three-dimensional coordinate system.

[0042] Figure 4 yes Figure 3 A partial enlarged view of

[0043] Figure 5 This is an overall rendering of the molten pool morphology in the longitudinal section of a thick-walled circular tube workpiece at the middle moment of laser deep penetration welding using the final heat source model established by the method of the present invention;

[0044] Figure 6 yes Figure 5 A partial enlarged view of

[0045] Figure 7 The invention discloses a molten pool morphology in a transverse section of a thick-walled circular tube workpiece obtained by laser deep penetration welding using the final heat source model established by the method of the invention. DETAILED DESCRIPTION

[0046] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0047] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0048] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0049] Specific implementation method 1. Combination Figures 1 to 7 As shown, the present invention provides a method for establishing a heat source for annular path laser deep penetration welding of thick-walled circular tube workpieces, comprising:

[0050] Step 1: Use 3D modeling software to build a 3D finite element numerical model of the thick-walled circular tube workpiece, and then use meshing software to mesh and verify the 3D finite element numerical model to obtain a 3D finite element workpiece mesh model;

[0051] Step 2: Establish a laser deep penetration welding heat source model for the corresponding flat workpiece based on the thick-walled circular tube workpiece, wherein the laser deep penetration welding heat source model includes a surface heat source and a body heat source;

[0052] Step 3: performing coordinate transformation on the laser deep penetration welding heat source model of the flat workpiece according to the circular path of the thick-walled circular tube workpiece to obtain the laser deep penetration welding heat source model of the thick-walled circular tube workpiece;

[0053] Step 4: Load the laser deep penetration welding heat source model of the thick-walled circular tube workpiece onto the three-dimensional finite element workpiece mesh model, set the model parameters, and use finite element calculation software to calculate the temperature field of the three-dimensional finite element workpiece mesh model to obtain the final heat source model.

[0054] Furthermore, in step 1, the three-dimensional finite element numerical model is a 1:1 geometric model of a thick-walled circular tube workpiece; the thickness of the thick-walled circular tube workpiece is at least 5 mm.

[0055] Taking into account the calculation accuracy, calculation time cost and calculation CPU cost, the mesh division of the three-dimensional finite element numerical model adopts the method of dense in the middle and sparse on both sides, with a total of 98748 mesh units. While ensuring the calculation accuracy near the weld, it can significantly reduce the calculation cost. The mesh type is assigned to the DC3D8 heat transfer type, and the resulting mesh model is as follows: Figure 1 shown.

[0056] As an example, the dimensional parameters of a thick-walled round tube workpiece may be: outer diameter 15 mm, inner diameter 10 mm, total length 20 mm, and the material is Q235 steel.

[0057] Furthermore, in the heat source model of laser deep penetration welding of flat workpieces, the surface heat source and body heat source formulas are:

[0058]

[0059]

[0060] Where Q s1 (x, y, t) is the heat flux density distribution of the surface heat source on the surface of the flat workpiece, x is the horizontal coordinate of the movement of the heat source center over time, y is the vertical coordinate of the movement of the heat source center over time, t is time, α is the heat flux concentration coefficient of the surface heat source, P s is the surface heat source power, η s is the surface heat source energy distribution coefficient, R s is the effective action radius of the surface heat source, (x0, y0) is the initial action point of the surface heat source on the flat workpiece;

[0061] Q v (x, y, z, t) is the heat flux density distribution of the body heat source inside the flat workpiece, z is the vertical coordinate of the heat source center in the three-dimensional space based on the xy plane coordinate system that changes with time, β is the heat flux concentration coefficient of the body heat source, P v is the body heat source power, η v is the energy distribution coefficient of the body heat source, η s +η v =1, H is the effective depth of body heat source, R v is the effective action radius of the body heat source, and (x0, y0, z0) is the initial action point of the body heat source inside the flat workpiece.

[0062] In step 3, the coordinate transformation includes transforming the coordinate points on the flat workpiece into the annular path coordinate points of the thick-walled circular tube workpiece. The coordinate transformation formula is:

[0063]

[0064] Where x1 is the horizontal coordinate of the circular motion path of the thick-walled circular tube workpiece, y1 is the vertical coordinate of the circular motion path of the thick-walled circular tube workpiece, and z1 is the vertical coordinate of the circular motion path of the thick-walled circular tube workpiece; (x1, y1) is the point where the surface heat source moves along the circular path of the thick-walled circular tube workpiece, (x1, y1, z1) is the point where the body heat source moves along the circular path of the thick-walled circular tube workpiece, and θ is the arc that the laser deep penetration welding heat source model of the flat workpiece rotates through over time with the center of the thick-walled circular tube workpiece as the rotation center.

[0065] In step 3, the heat source model of laser deep penetration welding of thick-walled circular tube workpiece obtained includes surface heat source and body heat source:

[0066]

[0067]

[0068] Where Q s2(x, y, t) is the heat flux density distribution of the surface heat source on the surface of the thick-walled circular tube workpiece, Q v (δ,h,t) is the heat flux density distribution of the body heat source inside the thick-walled circular tube workpiece, δ is the heat source position factor after coordinate transformation, and h is the radial projection depth of the body heat source along the thick-walled circular tube;

[0069]

[0070]

[0071] For intermediate variables:

[0072]

[0073] Furthermore, formulas (1) to (8) are programmed offline to realize the programming of the laser heat source; the offline programming is written in Fortran language.

[0074] The laser combined circumferential rotating heat source model established in steps 1 to 3 is only an analytical model and cannot be recognized and run by the computer. Therefore, it is necessary to program the above heat source model and perform offline programming on formulas (1) to (8). In the process of writing the program in Fortran language, all welding process parameters need to be defined: the laser power is 2kW, the effective action radius of the heat source is 0.7mm, the effective action depth of the heat source is 5mm, the welding angular velocity is 0.314159rad / s, and the welding cycle is 20s. The heat flux density distribution of the laser heat source is obtained as follows: Figure 2 shown.

[0075] Furthermore, in step 4, the temperature field of the numerical model is solved and calculated using finite element calculation software:

[0076] Setting the model parameters includes: setting the convection heat transfer coefficient between the thick-walled circular tube workpiece and the environment to 40W / (m 2 ·℃), the emissivity is 0.85, and the initial temperature of the thick-walled circular tube workpiece is 20 degrees Celsius; the convection and radiation heat transfer formula of the thick-walled circular tube workpiece is:

[0077]

[0078] Where k is the thermal conductivity of the thick-walled circular tube workpiece material, is the normal vector of the outer surface of the thick-walled circular tube workpiece, P is the total laser power, h0 is the convection heat transfer coefficient, T is the surface temperature of the thick-walled circular tube workpiece, T0 is the ambient temperature of the thick-walled circular tube workpiece, ε is the emissivity of the thick-walled circular tube workpiece material; σ is the Stefan-Boltzmann constant, which is always equal to 5.67×10 -8 W / (m 2 ·K 4 );

[0079] temperature difference

[0080] In the heat source model for laser deep penetration welding of thick-walled circular tubes, a surface heat source is applied to the outer surface of the thick-walled circular tube, and a body heat source is applied to the entire thick-walled circular tube. Both the surface heat source and the body heat source are set to "User Defined" with a value of 1. In the three-dimensional finite element numerical model, the convection and radiation heat transfer coefficient between the thick-walled circular tube and the environment is set, the initial temperature of the workpiece is 20 degrees Celsius, and the heat source load application position is set. Then, the heat source model for laser deep penetration welding of thick-walled circular tubes established in step 3 is loaded onto the three-dimensional finite element workpiece mesh model established in step 1 through the Dflux subroutine for calculation. A job is created and the subroutine is called. The operation is submitted to obtain the temperature field of the three-dimensional finite element workpiece mesh model, resulting in the final heat source model.

[0081] Finally, extract and post-process the results:

[0082] When laser welding starts, take the longitudinal section of the round tube workpiece for observation. Figure 3 As shown in Figure 2, a "nail-shaped" molten pool has been formed with a melting depth of about 5 mm. The effect of the observation after the partial magnification of the molten pool is as follows: Figure 4 When the laser welding process is halfway through, take the longitudinal section of the round tube workpiece for observation, as shown in Figure 5 As shown, the morphology of the molten pool is basically the same as that at the initial moment, and is also a "nail shape" of the same size. The effect observed after the partial enlargement of the molten pool is as follows Figure 6 As shown in Figure 2, the molten pool morphology remains highly stable throughout the laser welding process. In order to further observe the depth-to-width ratio of the final weld, a cross-section of the round tube workpiece is taken during post-processing. Figure 7 As shown, the depth-to-width ratio is about 4:1, which meets the basic characteristics of laser deep penetration welding.

[0083] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in conjunction with other described embodiments.

Claims

1. A method for establishing a heat source for annular path laser deep penetration welding of thick-walled circular tube workpieces, characterized in that include: Step 1: Use 3D modeling software to establish a 3D finite element numerical model of the thick-walled circular tube workpiece, and then use meshing software to mesh the 3D finite element numerical model to obtain a 3D finite element workpiece mesh model; Step 2: Establish a laser deep penetration welding heat source model for the corresponding flat workpiece based on the thick-walled circular tube workpiece, wherein the laser deep penetration welding heat source model includes a surface heat source and a body heat source; Step 3: performing coordinate transformation on the laser deep penetration welding heat source model of the flat workpiece according to the circular path of the thick-walled circular tube workpiece to obtain the laser deep penetration welding heat source model of the thick-walled circular tube workpiece; Step 4: Loading the laser deep penetration welding heat source model of the thick-walled circular tube workpiece onto the three-dimensional finite element workpiece mesh model, setting model parameters, and calculating the temperature field of the three-dimensional finite element workpiece mesh model using finite element calculation software to obtain the final heat source model; In step 3, the heat source model of laser deep penetration welding of thick-walled circular tube workpiece obtained includes surface heat source and body heat source: Where Q s2 (x, y, t) is the heat flux density distribution of the surface heat source on the surface of the thick-walled circular tube workpiece, Q v (δ,h,t) is the heat flux density distribution of the body heat source inside the thick-walled circular tube workpiece, δ is the heat source position factor after coordinate transformation, and h is the radial projection depth of the body heat source along the thick-walled circular tube; For intermediate variables: Where x is the horizontal coordinate of the heat source center over time, y is the vertical coordinate of the heat source center over time, t is time, α is the heat flux concentration coefficient of the surface heat source, P s is the surface heat source power, η s is the surface heat source energy distribution coefficient, R s is the effective action radius of the surface heat source, x1 is the horizontal coordinate of the annular motion path of the thick-walled circular tube workpiece, y1 is the vertical coordinate of the annular motion path of the thick-walled circular tube workpiece; β is the heat flux concentration coefficient of the body heat source, P v is the body heat source power, η v is the energy distribution coefficient of the body heat source, η s +η v =1, H is the effective depth of body heat source, R v is the effective action radius of the body heat source; z is the vertical coordinate of the heat source center in the three-dimensional space based on the xy plane coordinate system that changes with time, z0 belongs to (x0, y0, z0), and (x0, y0, z0) is the coordinate of the initial action point of the body heat source inside the flat workpiece.

2. The method for establishing a heat source for annular path laser deep penetration welding of thick-walled circular tube workpieces according to claim 1 is characterized in that: In step 1, the three-dimensional finite element numerical model is a 1:1 geometric model of a thick-walled circular tube workpiece; the thickness of the thick-walled circular tube workpiece is at least 5 mm.

3. The method for establishing a heat source for annular path laser deep penetration welding of thick-walled circular tube workpieces according to claim 2 is characterized in that: In the heat source model of laser deep penetration welding of flat workpieces, the surface heat source and body heat source formulas are: Where Q s1 (x, y, t) is the heat flux density distribution of the surface heat source on the flat workpiece surface; Q v (x, y, z, t) is the heat flux density distribution of the body heat source inside the flat workpiece.

4. The method for establishing a heat source for annular path laser deep penetration welding of thick-walled circular tube workpieces according to claim 3 is characterized in that: In step 3, the coordinate transformation includes transforming the coordinate points on the flat workpiece into the annular path coordinate points of the thick-walled circular tube workpiece. The coordinate transformation formula is: Where z1 is the vertical coordinate of the circular motion path of the thick-walled circular tube workpiece; (x1, y1) is the point where the surface heat source moves along the circular path of the thick-walled circular tube workpiece, (x1, y1, z1) is the point where the body heat source moves along the circular path of the thick-walled circular tube workpiece, and θ is the arc that the laser deep penetration welding heat source model of the flat workpiece rotates through over time with the center of the thick-walled circular tube workpiece as the rotation center.

5. The method for establishing a heat source for annular path laser deep penetration welding of thick-walled circular tube workpieces according to claim 4 is characterized in that: Formulas (1) to (8) are programmed offline to realize the programming of the laser heat source; the offline programming is written in Fortran language.

6. The method for establishing a heat source for annular path laser deep penetration welding of thick-walled circular tube workpieces according to claim 5, characterized in that: In step 4: Setting the model parameters includes: setting the convection heat transfer coefficient between the thick-walled circular tube workpiece and the environment to 40W / (m 2 ·℃), the emissivity is 0.85, and the initial temperature of the thick-walled circular tube workpiece is 20 degrees Celsius; the convection and radiation heat transfer formula of the thick-walled circular tube workpiece is: Where k is the thermal conductivity of the thick-walled circular tube workpiece material, is the normal vector of the outer surface of the thick-walled circular tube workpiece, P is the total laser power, h0 is the convection heat transfer coefficient, T is the surface temperature of the thick-walled circular tube workpiece, T0 is the ambient temperature of the thick-walled circular tube workpiece, ε is the emissivity of the thick-walled circular tube workpiece material; σ is the Stefan-Boltzmann constant, which is always equal to 5.67×10 -8 W / (m 2 ·K 4 ); temperature difference In the heat source model of laser deep penetration welding of thick-walled circular tube workpiece, the surface heat source is applied to the outer surface of the thick-walled circular tube workpiece, and the body heat source is applied to the entire thick-walled circular tube workpiece; Then, the heat source model of the laser deep penetration welding of the thick-walled circular tube workpiece is loaded onto the three-dimensional finite element workpiece mesh model for calculation to obtain the temperature field of the three-dimensional finite element workpiece mesh model and obtain the final heat source model.

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