Control device and method for inhibiting collapse of laser mirror image welding pool

Abstract

The invention relates to the technical field of laser manufacturing, discloses a control device and method for restraining collapse of a laser mirror image welding pool, and aims to overcome the common hump-shaped defects of the two sides of a welding seam in laser mirror image transverse welding. In order to solve the problem that molten pools at the upper end and the lower end flow asymmetry due to the fact that liquid metal is segregated towards the position below the axis of a heat source under the action of gravity, the invention provides a composite action scheme integrating adjustable airflow loading and magnetic field regulation and control. An adjusting valve is integrated to realize dynamic control of airflow loading position and speed, so that molten drop collapse is effectively limited, and the defect of non-uniform forming of welding seams on two sides is relieved; and meanwhile, by applying longitudinal magnetic field force, counteracting the segregation effect under liquid metal gravity driving and optimizing the flowing behavior of the molten pool, stable state control of the molten pool is achieved, good material and thickness adaptability is achieved, and dynamic and accurate regulation and control of the molten pool can be achieved under various working conditions.

Description

Technical Field

[0001] The present invention relates to the field of laser manufacturing technology, and in particular to a control device and method for suppressing the collapse of a molten pool in laser mirror welding. Background Art

[0002] Laser manufacturing technology, as an advanced joining process, has been widely used in aerospace, automotive manufacturing, and welding high-performance alloy components due to its advantages such as high energy density, high precision, and concentrated heat input. However, conventional laser welding typically uses a single-sided heat source, resulting in large temperature gradients between the front and back surfaces of the weldment, causing severe weld deformation and making it difficult to meet the requirements of high-precision, high-quality welding. Laser mirror welding, as a new welding method, applies symmetrical laser beams simultaneously on both sides of the workpiece, achieving uniform heating of the weld area, thereby reducing weld deformation and improving weld quality and joint mechanical properties. During laser mirror transverse welding, the weldment is subjected to the action of bilaterally symmetrical laser heat sources, forming a complex interaction of two molten pools. The temperature field and fluid flow in the molten pool are influenced by multiple forces, including surface tension (Marangoni convection), gravity, steam recoil pressure, and fluid dynamic pressure. The symmetry of the molten pool flow is easily affected by gravity, causing the liquid metal to converge below the central axis of the weld under gravity, resulting in molten pool distortion and slump. In laser mirror transverse welding, in particular, due to the horizontally symmetrical distribution of the molten pool, both left and right surfaces are driven by surface tension gradients (the Marangoni effect). Gravity further exacerbates the uneven flow of the liquid metal, leading to excessive accumulation of metal at the bottom of the weld and the formation of a weld collapse defect. This defect not only affects the appearance of the weld but can also lead to uneven microstructure of the weld joint, thereby reducing the mechanical properties of the joint and becoming a potential source of structural failure.

[0003] At present, existing technologies have proposed methods to suppress the hump defect on the back of the weld during the welding process, such as the transverse airflow control method, which is to add a high-speed transverse airflow above the molten pool to form a pressure difference between the top and bottom of the molten pool, thereby changing the flow behavior of the molten pool metal and suppressing the generation of hump defects. This method does not require additional vacuum or electromagnetic auxiliary equipment, the process is relatively simple, and can effectively reduce the excessive accumulation of liquid metal on the back of the weld. However, this method mainly focuses on optimizing the morphology of the back of the weld and cannot effectively suppress the molten pool collapse problem in laser mirror welding. In view of the characteristics of laser mirror transverse welding, it is necessary not only to suppress the hump defects on both sides of the weld, but also to solve the problem of weld collapse caused by the molten pool converging toward the central axis under the action of gravity. Therefore, how to effectively control the stress state and flow behavior of the molten pool during laser mirror welding so that it remains stable during the welding process is a key technical problem in achieving high-quality welding. In order to solve the above problems, the present invention proposes a molten pool control method based on air flow pressure and magnetic field force. The upward airflow support force is provided by the airflow nozzle below the weld, and the magnetic field force at the top and bottom of the workpiece is combined to regulate the flow of molten pool metal, thereby optimizing the force balance of the molten pool, effectively suppressing the hump defects on both sides of the weld and the weld collapse problem, and improving the quality and reliability of laser mirror welding. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies and address the need for improvement, the present invention provides a control device and method for suppressing molten pool collapse during laser mirror welding. This device aims to suppress humps on both sides of the weld by applying an external airflow, while using magnetic field forces to offset gravity-driven concentration of liquid metal below the heat source axis. This provides a solution to the loss of mechanical properties at the origin of laser mirror transverse welding.

[0005] To achieve this goal, according to one aspect of the present invention, a control device and method for suppressing the collapse of the laser mirror welding molten pool are proposed. The weld pool is subjected to multiple forces during the welding process. By controlling the position of the air flow nozzle below the weld and the ejection speed of the air flow pressure F a , combined with the magnetic field force F at the top and bottom of the workpiece m , to achieve dynamic regulation of the stress state of the weld pool, improve the stability of the weld pool and inhibit its downward collapse.

[0006] Preferably, the stress forms of the weld pool include the following: surface tension P in the vertical direction along the tangent direction of the weld pool surface σ , the gravity P of the liquid metal per unit of the keyhole wall g , the vapor pressure P generated by the vaporization of liquid metal in the horizontal direction r , the beam pressure P generated by the laser beam irradiating the metal surface b , the fluid dynamic pressure P caused by the molten pool flowing along the keyhole in the oblique directionc , shear force F caused by fluid tangential velocity s .

[0007] Preferably, the air flow nozzle has an adjustable speed v and direction to control the molten droplet shape, and the intensity B of the magnetic field device can be adaptively adjusted according to changes in the welding state to control the flow field structure of the molten pool and maintain the balance of the molten pool.

[0008] Preferably, the force coupling analysis of different wall surfaces of the keyhole in the confined micro-molten pool is as follows:

[0009] The horizontal force balance equation is:

[0010]

[0011] The vertical force equilibrium equation is:

[0012]

[0013] in:

[0014] are the components of dynamic pressure in the horizontal and vertical directions,

[0015] are the horizontal and vertical components of the shear force, respectively.

[0016] Preferably, the expression of the gas flow pressure is: Among them C a is the air flow pressure coefficient, ρ a is the air flow density, v a is the air flow velocity, A is the surface area of ​​the molten pool affected by the air flow; the expression of the magnetic field force is: F m =JB, J is the current density in the molten pool, and B is the magnetic induction intensity.

[0017] Preferably, the working gas can be selected from compressed air, helium or argon, and is matched according to the welding material, heat input and dynamic characteristics of the molten pool.

[0018] Preferably, the air flow nozzle structure has an adaptive adjustment mechanism, including an adjustable bracket and an electrically controlled regulating valve, which is used to realize dynamic adjustment of the distance and incident angle between the air flow nozzle and the weld, accurately control the loading area and direction of the air flow, and realize control and optimization of the molten droplet morphology.

[0019] Preferably, the mirror image welding base is integrated with the airflow duct system, the magnetic field device is embedded in the welding base structure, and the welding base is made of a metal material with good magnetic conductivity to ensure uniformity and stability of the magnetic field distribution.

[0020] Compared with the laser manufacturing technology in the prior art, the method of the present invention has the following advantages:

[0021] 1. The present invention adopts air flow support to suppress the collapse of the molten pool and improve the quality and uniformity of the weld.

[0022] 2. The present invention uses a controllable magnetic field to act on the upper and lower parts of the weld to improve the stability of the metal flow in the molten pool, reduce the asymmetry of the molten pool temperature field and solidification parameters, and improve the mechanical properties of the joint.

[0023] 3. The present invention can adapt to the welding requirements of different thicknesses and materials by adjusting the air flow velocity, spray angle and magnetic field strength, achieve precise control and improve the applicability of the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a force analysis diagram of a device and method for suppressing molten pool collapse in laser mirror welding provided by a specific embodiment of the present invention;

[0025] Figure 2 Schematic diagram of molten pool morphology adjustment of a device and method for suppressing molten pool collapse in laser mirror welding provided by a specific embodiment of the present invention;

[0026] Figure 3 This is a process flow chart of an apparatus and method for suppressing molten pool collapse in laser mirror welding provided by a specific embodiment of the present invention;

[0027] Among them: 1 is the workpiece, 2 is the laser, 3 is the weld pool, 4 is the air flow nozzle, 5 is the electric control valve, 6 is the air flow pipeline, 7 is the adjustable bracket, 8 is the welding base, and 9 is the magnetic field device. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0029] The embodiment of the present invention provides a control device and method for suppressing the collapse of the laser mirror welding molten pool. Figure 1 As shown, the weld pool (3) is subjected to various forces during the welding process, and the air flow pressure F is controlled by controlling the position of the air flow nozzle (4) below the weld and the ejection speed. a , combined with the magnetic field device (9) at the top and bottom of the workpiece (1) to exert a force F m, to achieve dynamic regulation of the stress state of the weld pool (3), improve the stability of the weld pool, and inhibit its downward collapse. The stress forms of the weld pool (3) include the following: the surface tension P in the vertical direction along the tangent direction of the weld pool surface σ , the gravity P of the liquid metal per unit of the keyhole wall g , the vapor pressure P generated by the vaporization of liquid metal in the horizontal direction r , the beam pressure P generated by the laser beam irradiating the metal surface b , the fluid dynamic pressure P caused by the molten pool flowing along the keyhole in the oblique direction c , shear force F caused by fluid tangential velocity s The air flow nozzle (4) has an adjustable speed v and direction to control the molten droplet shape. The intensity B of the magnetic field device (9) can be adaptively adjusted according to the change of welding state to control the flow field structure of the molten pool and maintain the balance of the molten pool. The force coupling analysis of different wall surfaces of the keyhole in the limited micro molten pool is as follows:

[0030] The horizontal force balance equation is:

[0031]

[0032] The vertical force equilibrium equation is:

[0033]

[0034] in:

[0035] are the components of dynamic pressure in the horizontal and vertical directions respectively;

[0036] are the components of shear force in the horizontal and vertical directions respectively;

[0037] The expression of gas flow pressure is: Among them C a is the air flow pressure coefficient, ρ a is the air flow density, v a is the air flow velocity, A is the surface area of ​​the molten pool affected by the air flow; the expression of the magnetic field force is: F m=JB, J is the current density in the molten pool, B is the magnetic induction intensity, the working gas can be selected from compressed air, helium or argon, and is matched according to the welding material, heat input and dynamic characteristics of the molten pool. The air flow nozzle (4) structure has an adaptive adjustment mechanism, including an adjustable bracket (7) and an electric control valve (5), which is used to realize dynamic adjustment of the distance between the air flow nozzle (4) and the weld and the incident angle, accurately control the loading area and direction of the air flow, and realize the control and optimization of the molten droplet morphology. The mirror welding base (8) and the air flow pipeline (6) system are integrated in design, and the magnetic field device (9) is embedded in the welding base (8) structure. The welding base (8) is made of a metal material with good magnetic conductivity to ensure the uniformity and stability of the magnetic field distribution.

[0038] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. A person skilled in the art would be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A control device and method for suppressing the collapse of the laser mirror welding molten pool, characterized in that: The weld pool (3) is subjected to various forces during the welding process, and the air flow pressure F is controlled by controlling the action position and ejection speed of the air flow nozzle (4) below the weld. a , combined with the magnetic field device (9) at the top and bottom of the workpiece (1) to exert a force F m , realizing dynamic regulation of the stress state of the weld pool (3), improving the stability of the weld pool and inhibiting its downward collapse.

2. A control device and method for suppressing the collapse of the laser mirror welding molten pool according to claim 1, characterized in that: The stress forms of the weld pool (3) include the following: surface tension P in the vertical direction along the tangent direction of the weld pool surface; σ , the gravity P of the liquid metal per unit of the keyhole wall g , the vapor pressure P generated by the vaporization of liquid metal in the horizontal direction r , the beam pressure P generated by the laser beam irradiating the metal surface b , the fluid dynamic pressure P caused by the molten pool flowing along the keyhole in the oblique direction c , shear force F caused by fluid tangential velocity s .

3. A control device and method for suppressing the collapse of the laser mirror welding molten pool according to claim 1, characterized in that: The air flow nozzle (4) has an adjustable speed v and direction to control the molten droplet shape, and the intensity B of the magnetic field device (9) can be adaptively adjusted according to changes in the welding state to control the flow field structure of the molten pool and maintain the balance of the molten pool.

4. A control device and method for suppressing the collapse of the laser mirror welding molten pool according to claim 3, characterized in that: Force coupling analysis of different wall surfaces of the keyhole in the confined micro-molten pool: The horizontal force balance equation is: The vertical force equilibrium equation is: in: are the components of dynamic pressure in the horizontal and vertical directions, are the horizontal and vertical components of the shear force, respectively.

5. A control device and method for suppressing the collapse of the laser mirror welding molten pool according to claim 4, characterized in that: The expression of the gas flow pressure is: Among them C a is the air flow pressure coefficient, ρ a is the air flow density, v a is the air flow velocity, A is the surface area of ​​the molten pool affected by the air flow; the expression of the magnetic field force is: F m =JB, J is the current density in the molten pool, and B is the magnetic induction intensity.

6. A control device and method for suppressing the collapse of the laser mirror welding molten pool according to claim 5, characterized in that: The working gas may be selected from compressed air, helium or argon, and may be matched according to the welding material, heat input and dynamic characteristics of the molten pool.

7. A control device and method for suppressing the collapse of the laser mirror welding molten pool according to claim 5, characterized in that: The airflow nozzle (4) structure is provided with an adaptive adjustment mechanism, including an adjustable bracket (7) and an electrically controlled regulating valve (5), for dynamically adjusting the distance between the airflow nozzle (4) and the weld and the incident angle, accurately controlling the loading area and direction of the airflow, and achieving control and optimization of the molten droplet morphology.

8. The control device and method for suppressing the collapse of the laser mirror welding molten pool according to claim 5, characterized in that: The mirror image welding base (8) and the air flow duct (6) are designed as an integrated system, and the magnetic field device (9) is embedded in the welding base (8) structure. The welding base (8) is made of a metal material with good magnetic conductivity to ensure the uniformity and stability of the magnetic field distribution.

Images