A molten pool stirring method and a welding device

Abstract

The application discloses a molten pool stirring method and a welding device, which comprises forming a molten pool in a welding area of a workpiece by a first laser beam and scanning the molten pool by a second laser beam; wherein the first laser beam and the second laser beam are projected on the molten pool. The application forms a molten pool by the first laser beam and projects the second laser beam on the first laser beam to accurately scan the molten pool, so that the accuracy is high, sufficient convection can be formed in the liquid molten pool, the stirring in the liquid molten pool is more sufficient, the growth of columnar crystals is effectively inhibited, the weld structure is improved, and the mechanical properties of the weld are greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding, in particular to a molten pool stirring method and welding device. BACKGROUND

[0002] In the welding process, the volume of the molten pool is small, the temperature gradient is large, and the columnar crystal growth in the weld is relatively large, which has adverse effects on the weld structure and mechanical properties; stirring the molten pool can weaken such adverse effects, and existing stirring methods include laser scanning, electron beam scanning, electromagnetic stirring, and ultrasonic oscillation, but the effects of these methods are very limited, for example, laser scanning and electron beam scanning change the solidification state of the molten pool under the original conditions only by dynamic scanning of a single energy beam, the molten pool after scanning still solidifies quickly and cannot form sufficient convection; and electromagnetic stirring and ultrasonic oscillation have a very short liquid duration in the molten pool and cannot fully stir. SUMMARY

[0003] In view of the problems in the prior art, the present application provides a molten pool stirring method and welding device, which can form sufficient convection in the liquid molten pool, stir more fully, effectively inhibit the growth of columnar crystals, and have high accuracy. The technical solution is as follows:

[0004] The present application provides a molten pool stirring method, comprising:

[0005] forming a molten pool in a to-be-welded area of a workpiece by a first laser beam and scanning the molten pool by a second laser beam; wherein the first laser beam and the second laser beam are projected on the molten pool.

[0006] Further, the power of the first laser beam is greater than the power of the second laser beam.

[0007] Further, the power density of the first laser beam is less than the power density of the second laser beam.

[0008] Further, the spot diameter formed by the first laser beam in the to-be-welded area is greater than the spot diameter formed by the second laser beam in the to-be-welded area.

[0009] Further, the scanning speed of the second laser beam is 0.5 m / s to 10 m / s.

[0010] Further, the forming of the molten pool in the to-be-welded area of the workpiece by the first laser beam and the scanning of the molten pool by the second laser beam comprises:

[0011] The first laser beam and the second laser beam are combined by an optical assembly to obtain a composite beam, and the second laser beam in the composite beam scans the molten pool.

[0012] Further, the beam combining process comprises:

[0013] The first laser beam is subjected to a first polarization process to obtain a first polarized beam, and the second laser beam is subjected to a second polarization process to obtain a second polarized beam, so that the first polarized beam and the second polarized beam are combined to obtain the composite beam.

[0014] Further, the beam combining process comprises:

[0015] The first laser beam is subjected to a first polarization process to obtain a first polarized beam, and the second laser beam is subjected to a second polarization process to obtain a second polarized beam, so that the first polarized beam and the second polarized beam are combined to obtain the composite beam.

[0016] The application also provides a welding device, which comprises a laser emission assembly and an optical assembly, the laser emission assembly is used for emitting a first laser beam and a second laser beam to the optical assembly respectively, and the optical assembly is used for receiving the first laser beam and the second laser beam to form a composite beam by beam combining; the laser emission assembly comprises a scanning mirror, and the scanning mirror is used for controlling the second laser beam to scan in a welding area.

[0017] Further, the laser emission assembly comprises a first laser emission mechanism and a second laser emission mechanism, the first laser emission mechanism is used for emitting the first laser beam, and the second laser emission mechanism is used for emitting the second laser beam.

[0018] The application has the following beneficial effects:

[0019] 1. The application forms a molten pool by the first laser beam, and projects the second laser beam on the molten pool to accurately scan the molten pool, so that the energy of the first laser beam and the second laser beam can form sufficient convection in the liquid molten pool, the stirring of the liquid molten pool by the second laser beam is more sufficient, the growth of columnar crystals is effectively inhibited, the weld structure is improved, and the mechanical properties of the weld are greatly improved; the second laser beam is easy to control, and high accuracy can be achieved in a small-volume molten pool, so that the uniformity and sufficiency of the molten pool stirring are further improved.

[0020] 2. The power density of the second laser beam is high, which is beneficial to rapidly increase the temperature in the molten pool, improve the fluidity of the liquid solder in the molten pool, further improve the stirring sufficiency, and also beneficial to slow down the temperature gradient after welding, so that the formation of columnar crystals is inhibited, and the performance of the weld is improved.

[0021] 3、The application can realize larger melting depth and welding speed under lower laser power, is beneficial to save cost, has higher welding accuracy, smaller heat-affected zone and smaller deformation, and is beneficial to improve the mechanical properties of the weld. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the present application, the drawings used in the embodiments will be briefly introduced as follows, wherein the same parts are denoted by the same reference numerals. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0023] Figure 1 A structural diagram of a welding device provided by the embodiment of the present application is shown in the figure.

[0024] Figure 2 A scanning track diagram of the second laser beam in the molten pool provided by the present application is shown in the figure.

[0025] In the figure, the reference numerals correspond to: 1-laser emitting assembly, 11-first laser emitting mechanism, 12-second laser emitting mechanism, 2-optical assembly, 21-focusing mirror, 22-optical beam combining device, 3-first laser beam, 4-second laser beam, 5-composite beam, 6-workpiece. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments, and therefore cannot be understood as limiting the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0027] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than that illustrated below or described below. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or server including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0028] Embodiment

[0029] The present application provides a molten pool stirring method, and also provides a welding device for performing the molten pool stirring method, i.e. the molten pool stirring method is realized based on the welding device, as shown in the figure, the welding device comprises a laser emitting assembly 1 for emitting a first laser beam 3 and a second laser beam 4 so that the first laser beam 3 and the second laser beam 4 are projected on a to-be-welded area of a workpiece 6 for welding; the molten pool stirring method comprises: Figure 1

[0030] forming a molten pool in the to-be-welded area of the workpiece by the first laser beam, and scanning the molten pool by the second laser beam; wherein the first laser beam and the second laser beam are projected on the molten pool.

[0031] In the automatic welding process, the workpiece 6 moves to the welding station at a preset speed, the first laser beam 3 acts as the main welding heat source and is irradiated on the to-be-welded area of the workpiece 6 to form a liquid molten pool; the second laser beam 4 is also irradiated in the molten pool area, and the spot diameter of the second laser beam 4 is smaller than the spot diameter of the first laser beam 3; the second laser beam 4 scans the liquid molten pool at a scanning speed to realize stirring of the molten pool, and sufficient convection is formed in the molten pool, and the stirring is sufficient and uniform; preferably, the scanning speed of the second laser beam 4 is greater than the preset speed of the workpiece 6.

[0032] Specifically, the laser emitting assembly 1 comprises a scanning mirror for controlling the scanning of the second laser beam 4 in the to-be-welded area, wherein the laser emitting assembly 1 emits the second laser beam 4, and the scanning mirror is located on the propagation path of the second laser beam 4 so that the second laser beam 4 is projected on the scanning mirror to realize light path conversion, which includes at least one of the projection direction conversion of the second laser beam 4 and the position conversion of the incident point on the scanning mirror; then by controlling the scanning mirror, the projection position of the second laser beam 4 in the to-be-welded area, i.e. the molten pool, can be changed to realize dynamic scanning; in an optional embodiment, the scanning mirror comprises a plurality of mirror pieces, and by moving or deflecting at least one of the plurality of mirror pieces, the projection position of the second laser beam 4 in the molten pool can be changed; in a preferred embodiment, the scanning mirror is a laser galvanometer mirror, and the control precision is high.

[0033] ​Specifically, the power of the first laser beam 3 is greater than the power of the second laser beam 4, the first laser beam 3 has a high enough energy to melt the solder of the to-be-welded area into a liquid pool, and the power of the second laser beam 4 is low to avoid the second laser beam 4 from being too high to break through the to-be-welded area. In addition, the first laser beam 3 and the second laser beam 4 are projected on the to-be-welded area corresponding to the pool, and the total power is higher than that of the first laser beam 3 or the second laser beam 4 alone, that is, the second laser beam 4 also provides energy input to the pool, which is beneficial to strengthen the solid-liquid convection, and the first laser beam 3 and the second laser beam 4 provide lower power to obtain higher total power, which can save energy and cost while improving the stirring sufficiency.

[0034] Specifically, the power density of the first laser beam 3 is less than the power density of the second laser beam 4; the power density of the laser beam is the power of the laser beam projected on a unit area, and the power density is equal to the power on the preset area divided by the preset area in value, and the unit is W / cm 2 ; the power density of the second laser beam 4 is greater than that of the first laser beam 3, the spot is small and concentrated, which is beneficial to improve the fluidity of the liquid metal solder in the pool, improve the stirring sufficiency, can concentrate energy for accurate stirring, can break the columnar crystal growing in the pool, so that the size of the columnar crystal is reduced, and the formation of the columnar crystal is effectively inhibited; in addition, the detached dendrites grow into equiaxed crystals in the pool, which significantly reduces the grain size of the weld; and the pool volume is small, the power density of the second laser beam 4 is high, the coverage is small, which avoids the influence of the energy of the second laser beam 4 on the workpiece 6 outside the pool, and is also beneficial to improve the scanning accuracy in the pool, so that the coverage of the second laser beam 4 is accurate and easy to adjust, the control accuracy is high, and the accurate stirring in the pool area is accurate, and the stirring accuracy is higher; and the second laser beam 4 cooperates with the first laser beam 3 to slow down the temperature gradient after welding, and improve the high-temperature performance of the weld.

[0035] Specifically, the spot diameter formed by the first laser beam 3 in the to-be-welded area is greater than the spot diameter formed by the second laser beam 4 in the to-be-welded area. Optionally, the spot diameter formed by the first laser beam 3 in the to-be-welded area is 1-10mm. Optionally, the spot diameter formed by the second laser beam 4 in the to-be-welded area is greater than or equal to 0.1mm and less than 1mm. In addition, the power density of the second laser beam 4 is high, the formed spot is small and much smaller than the diameter of the pool, and the second laser beam 4 can have enough moving space for scanning movement in the pool, which is beneficial to improve the uniformity of the metal solder in the pool, effectively reduce the component segregation, and at the same time accelerate the overflow of the gas, greatly reduce the defects such as pores in the weld. In an optional embodiment, as shown in Figure 2As shown, the scanning track of the second laser beam 4 in the molten pool includes at least one of a spiral shape, a linear shape, a wavy shape, a river shape and a well shape, and the present application does not make specific limitation thereon, as long as the scanning track within the range of the molten pool can be within the protection scope of the present application.

[0036] Specifically, in an optional embodiment, the first laser beam 3 can also be scanned by a scanning mirror to improve the sufficiency of the convection in the molten pool; wherein the scanning speed of the first laser beam 3 is less than the scanning speed of the second laser beam 4; the scanning speed of the first laser beam 3 can be selected as 200mm / min-1000mm / min; optionally, the scanning speed of the first laser beam 3 is 300mm / min-1000mm / min; further optionally, the scanning speed of the first laser beam 3 is 500mm / min-1000mm / min.

[0037] Specifically, the scanning speed of the second laser beam 4 is 0.5m / s-10m / s, and the scanning speed of the second laser beam 4 is much greater than that of the first laser beam 3, so that the second laser beam 4 can be dynamically scanned at high speed within the range of the molten pool and be fully stirred; optionally, the scanning speed of the second laser beam 4 is 0.5m / s-5m / s; further optionally, the scanning speed of the second laser beam 4 is 0.5m / s-2m / s; in a specific embodiment, the scanning speed of the second laser beam 4 can be selected as 1m / s.

[0038] Specifically, as shown, Figure 1 The laser emitting assembly 1 includes a first laser emitting mechanism 11 and a second laser emitting mechanism 12, the first laser emitting mechanism 11 is used for emitting the first laser beam 3, and the second laser emitting mechanism 12 is used for emitting the second laser beam 4.

[0039] Optionally, the laser emitting assembly 1 includes a laser emitter, the laser emitter outputs a laser beam, which is divided into the first laser beam 3 and the second laser beam 4 through light splitting processing, and is emitted by the first laser emitting mechanism 11 and the second laser emitting mechanism 12 respectively, which has high integration degree, and can adjust the first laser beam 3 and the second laser beam 4 in the same laser emitter, which is convenient and fast, at this time, the first laser beam 3 and the second laser beam are parallelly emitted to the welding area of the workpiece 6, forming a molten pool and stirring the molten pool.

[0040] Further optionally, as shown, Figure 1As shown, the first laser emitting mechanism 11 and the second laser emitting mechanism 12 are respectively configured as a laser emitter, and the two laser emitters are respectively arranged at different positions, that is, the first laser beam 3 and the second laser beam 4 are respectively emitted by different laser emitters, so that the two laser emitters can be respectively arranged and adjusted to meet the requirements of different welding conditions on the first laser beam 3 and the second laser beam 4, and the flexibility is better; the positions of the first laser emitting mechanism 11 and the second laser emitting mechanism 12 are not specifically limited, as long as the first laser beam 3 and the second laser beam 4 can be projected on the to-be-welded area.

[0041] In one specific embodiment, the second laser emitting mechanism 12 can be selected as a laser galvanometer, which has fast scanning speed, high scanning precision and convenient control, and is also convenient for adjusting the emission direction of the second laser beam 3, so that the welding device can perform high-precision scanning stirring in the molten pool and improve the mechanical properties of the weld.

[0042] Specifically, as shown in the figure, Figure 1 The welding device further comprises an optical assembly 2, the first laser emitting mechanism 11 is used for emitting the first laser beam 3 to the optical assembly 2, the second laser emitting mechanism 12 is used for emitting the second laser beam 4 to the optical assembly 2, and the optical assembly 2 is used for receiving the first laser beam 3 and the second laser beam 4 to combine the beams to form a composite beam 5, the total power of the composite beam 5 is high, and under the same laser power, a larger penetration depth and a faster welding speed can be achieved, the solid-liquid convection in the molten pool is improved, and the power and cost of the laser emitting assembly 1 are saved.

[0043] Specifically, the optical assembly 2 comprises at least one focusing mirror 21, which is arranged in the light path between the laser emitting assembly 1 and the to-be-welded area, that is, the molten pool, so as to enhance the power density of the first laser beam 3 and the second laser beam 4, and improve the accuracy of scanning stirring and welding; in addition, under the condition that the heat required by the molten pool is certain, the power of the laser emitting assembly 1 is further reduced, and energy is saved; in one optional embodiment, the optical assembly 2 comprises one focusing mirror 21, which converges the first laser beam 3 and the second laser beam 4 emitted by the same laser emitter at the same time, thereby saving the number of focusing mirrors 21 and the occupied space; in another optional embodiment, the optical assembly 2 comprises at least two focusing mirrors 21, wherein at least one focusing mirror 21 is arranged in the light path between the first laser emitting mechanism 11 and the to-be-welded area, and at least one focusing mirror 21 is arranged in the light path between the second laser emitting mechanism 12 and the to-be-welded area, so as to focus the first laser beam 3 and the second laser beam 4 respectively, and the focusing mirrors 21 in the respective light paths can also adjust the projection directions of the first laser beam 3 and the second laser beam 4 to a certain extent, thereby further improving the flexibility of the welding device in molten pool stirring.

[0044] Specifically, the forming a molten pool at a region to be welded of a workpiece by a first laser beam and the scanning the molten pool by a second laser beam include:

[0045] The first laser beam and the second laser beam are combined by an optical assembly to obtain a composite beam, and the second laser beam in the composite beam scans the molten pool.

[0046] The optical assembly 2 further comprises an optical combining device 22 for combining the first laser beam 3 and the second laser beam 4, and the first laser beam 3 and the second laser beam 4 are combined by the optical combining device 22 to obtain the composite beam 5. The spot size of the first laser beam 3 in the composite beam 5 is larger than the spot size of the second laser beam 4, so that the second laser beam 4 after combination is wrapped in the range of the first laser beam 3, to ensure that the second laser beam 4 can be scanned and stirred in the molten pool formed by the first laser beam 3. The composite beam 5 has high welding accuracy, small heat-affected zone and small thermal deformation, which is beneficial to improve the mechanical properties of the weld. In addition, the total power of the composite beam is high, which can realize larger penetration and welding speed under lower laser power of the laser emitting assembly 1, which is beneficial to save cost.

[0047] Specifically, in an optional embodiment, the combining processing includes:

[0048] The first laser beam is subjected to first polarization processing to obtain a first polarized beam, and the second laser beam is subjected to second polarization processing to obtain a second polarized beam, so that the first polarized beam and the second polarized beam are combined to obtain the composite beam.

[0049] When the wavelengths of the first laser beam 3 and the second laser beam 4 are the same or similar, the optical combining device 22 is a polarizer for smoothly combining the first laser beam 3 and the second laser beam 4 with similar wavelengths, to avoid interference between the first laser beam 3 and the second laser beam 4 during the combining process, which affects the composite beam 5. The first laser beam 3 is subjected to first polarization processing by the polarizer to obtain a first polarized beam, and the second laser beam is subjected to second polarization processing by the polarizer to obtain a second polarized beam, so that the first polarized beam and the second polarized beam have the same propagation direction, which improves the total power of the composite beam 5 and maintains the incident beam quality of the first laser beam 3 and the second laser beam 4.

[0050] Specifically, in another optional embodiment, the combining processing includes:

[0051] The first laser beam is subjected to first optical path deflection processing to obtain a first deflected beam, and the second laser beam is subjected to second optical path deflection processing to obtain a second deflected beam, so that the first deflected beam and the second deflected beam are combined to obtain the composite beam.

[0052] The optical combining device 22 is a coated optical lens for combining the first laser beam 3 and the second laser beam 4 with different wavelengths into the composite beam 5 by optical path deflection. After the first laser beam 3 is subjected to first optical path deflection processing by the coated optical lens, the optical path of the first laser beam 3 is deflected to obtain a first deflected beam. After the second laser beam 4 is subjected to second optical path deflection processing by the coated optical lens, the optical path of the second laser beam 4 is deflected to obtain a second deflected beam. The propagation directions of the first deflected beam and the second deflected beam are the same, and both are directed to the welding area to form a molten pool and to be stirred, so that the combining is stable and accurate.

[0053] In an optional embodiment, the surface of the coated optical lens is coated with at least one of a transmission film, a reflection film and a refraction film to perform optical path deflection processing on the first laser beam 3 and the second laser beam 4 incident on the coated optical lens to achieve beam combining. For example, in a specific embodiment, the surface of the coated optical lens is provided with a refraction film. The incident directions of the first laser beam 3 and the second laser beam 4 are different, but the refraction directions of the first laser beam 3 and the second laser beam 4 through different refraction films are the same, so that the first laser beam 3 and the second laser beam 4 are combined. In another specific embodiment, the opposite surfaces of the coated optical lens are respectively coated with a transmission film and a reflection film, i.e., the coated optical lens combines by transmission and reflection. The transmission film is used to transmit the first laser beam 3 incident on the coated optical lens, so that the first laser beam 3 directly and smoothly transmits through the coated optical lens to obtain a first deflected beam with an optical path deflection direction of 0°. The reflection film is used to reflect the second laser beam 4 incident on the coated optical lens, so that the second laser beam 4 is reflected on the surface of the coated optical lens to obtain a second deflected beam with an optical path deflection direction of 90°, thereby completing the combining of the first deflected beam and the second deflected beam.

[0054] Specifically, in the present embodiment, the propagation direction of the composite beam 5, i.e., the optical path direction, is perpendicular to the moving direction of the workpiece 6. The moving direction of the workpiece 6 is as shown by the arrow in FIG. 1. Figure 1As indicated by the middle arrow, the propagation path of the composite light beam 5 is reduced, the energy loss of the composite light beam in the propagation process is reduced, the thermal influence area is small, the precision of the molten pool stirring and welding can be greatly improved, and the welding quality is improved. However, the present application does not specifically limit the incident direction of the first laser beam 3 and the second laser beam 4, as long as the first laser beam and the second laser beam have the same direction after being combined by the optical combining device 22 and the second laser beam is within the spot range of the first laser beam. For example, in a preferred embodiment, the first laser beam 3 is emitted perpendicular to the surface of the workpiece 6, the second laser beam 4 is emitted perpendicular to the first laser beam 3, the optical combining device 22 is arranged at an angle of 45°, so that the first laser beam 3 transmits the coated optical lens, and the second laser beam 4 is also emitted perpendicular to the workpiece 6 after being deflected by 90° at the coated optical lens, realizing the combination of the two laser beams. Alternatively, the first laser beam 3 and the second laser beam 4 are interchanged, the first laser beam 3 is emitted perpendicular to the workpiece 6 and transmits the coated optical lens, and the second laser beam 4 is emitted perpendicular to the surface of the workpiece 6 after being reflected at the coated optical lens. The angle adjustment is convenient and easy to control.

[0055] The above only describes some embodiments of the present application and is not used to limit the present application. Those skilled in the art should understand that the present application can have various changes and improvements. Any modification, equivalent replacement and improvement made according to the present application falls within the scope of protection required by the present application.

Claims

1. A molten bath stirring method characterized by, Comprise: Forming a molten pool on a to-be-welded area of a workpiece by a first laser beam, and scanning the molten pool by a second laser beam; wherein the first laser beam and the second laser beam are projected on the molten pool, the power density of the first laser beam is less than the power density of the second laser beam, the spot diameter formed by the first laser beam on the to-be-welded area is greater than the spot diameter formed by the second laser beam on the to-be-welded area, the power of the first laser beam is greater than the power of the second laser beam, and the scanning speed of the second laser beam is 0.5m / s-10m / s; The first laser beam and the second laser beam are combined by an optical assembly to obtain a composite beam, and the second laser beam in the composite beam scans the molten pool.

2. The molten bath stirring method according to claim 1, characterized by, The combining process comprises: The first laser beam is subjected to first polarization processing to obtain a first polarized beam, and the second laser beam is subjected to second polarization processing to obtain a second polarized beam, so that the first polarized beam and the second polarized beam are combined to obtain the composite beam.

3. The molten bath stirring method according to claim 1, characterized by, The combining process comprises: The first laser beam is subjected to first optical path deflection processing to obtain a first deflected beam, and the second laser beam is subjected to second optical path deflection processing to obtain a second deflected beam, so that the first deflected beam and the second deflected beam are combined to obtain the composite beam.

4. A welding apparatus employing the molten pool stirring method as claimed in claim 1, characterized by The welding device comprises a laser emission assembly (1) and an optical assembly (2), the laser emission assembly (1) is used for emitting a first laser beam (3) and a second laser beam (4) to the optical assembly (2) respectively, and the optical assembly (2) is used for combining the first laser beam (3) and the second laser beam (4) to form a composite beam (5); the laser emission assembly (1) comprises a scanning mirror, and the scanning mirror is used for controlling the second laser beam (4) to scan the to-be-welded area.

5. The welding device of claim 4, wherein, The laser emission assembly (1) comprises a first laser emission mechanism (11) and a second laser emission mechanism (12), the first laser emission mechanism (11) is used for emitting the first laser beam (3), and the second laser emission mechanism (12) is used for emitting the second laser beam (4).

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