A multiple laser spot welding method

Abstract

The present invention is applicable to the field of laser welding technology, and provides a multiple laser spot welding method, which gradually melts the laser spot welding molten pool by sequentially emitting multiple laser beams with different pulse waveforms at the welding position. It includes: emitting a first pulse laser beam (peak + constant) to melt the surface of the welding base material; when the molten pool is about to cool, emitting a second pulse laser beam (slow rise + constant + slow fall), and the radiation position is the same as the first pulse laser beam, so as to expand the upper layer of the welding base material laser spot welding molten pool; referring to the setting of the second pulse laser beam, emitting the Nth pulse laser beam until the overlapping surface is melted to form a heat conduction type laser weld point (depth-to-width ratio is less than 1) with the overlap area maximized. Compared with conventional laser single spot welding, this method increases the overlapping area, improves the welding quality, and retains the advantages of single spot welding such as small size and good accessibility. It reduces welding deformation, simplifies equipment, reduces costs, has high flexibility, and has broad application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of laser welding, and in particular relates to a multiple laser spot welding method. Background Art

[0002] Laser spot welding is a new type of single-sided non-contact spot welding technology that uses the heat generated by the interaction between the laser beam and the base material as a heat source. This method has the characteristics of small spot size, short welding time (measured in milliseconds), good accessibility and strong adaptability. It is widely used in precision manufacturing fields such as electronic components, biological implants and battery boxes.

[0003] However, the high energy density and strong recoil pressure of the laser beam easily lead to the formation of keyholes in the molten pool (deep fusion welding type). Under the action of the contact thermal resistance in the overlap area, the weld presents a deep and narrow shape (similar to a wine glass shape), resulting in a small bonding area of ​​the parent material, thereby reducing the bonding force of the laser weld and affecting the welding quality. In order to increase the area of ​​the overlap area of ​​laser spot welding, researchers have tried a variety of methods. Among them, although the use of spiral, circular, and special-shaped welding paths can expand the area of ​​the welding area, it does not effectively increase the bonding area of ​​the overlap area, thereby weakening the advantages of laser spot welding and limiting its scope of application. Another method is to use a laser galvanometer system, but the expensive optical path components of the system significantly increase the cost of use, which also limits the application scenarios of laser spot welding. In view of the need to improve welding quality, how to effectively increase the area of ​​the overlap area of ​​laser spot welding without expanding the welding area and increasing the cost of use has always been a key problem to be solved in the field of welding technology. To this end, the present invention proposes a multiple laser spot welding method. Summary of the invention

[0004] The object of the present invention is to provide a multiple laser spot welding method, aiming to solve the problems raised in the above background technology.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A multiple laser spot welding method comprises the following steps:

[0007] Step 1: Pretreatment and fixation of welding base material;

[0008] After pretreatment, the welding base material is fixed on the welding fixture in an overlapping manner;

[0009] Step 2: Welding parameter setting;

[0010] Use Nd:YAG pulse laser welder as welding equipment, adjust the defocus, turn on the shielding gas, and set the pulse peak power and pulse time;

[0011] Step 3: emitting a first pulse laser beam;

[0012] The first pulse laser beam is emitted to melt the surface of the welding base material, and the pulse waveform is a peak and a constant pulse, wherein the maximum pulse power of the peak band is 1.5p, and the pulse time is 0.5t; the pulse peak power of the constant band is p, and the pulse time is t;

[0013] Step 4: emitting a second pulse laser beam;

[0014] When the first pulse laser beam is closed and the laser spot welding molten pool is about to cool, the second pulse laser beam is emitted. The radiation position of the second pulse laser beam is the same as that of the first pulse laser beam, which is used to expand the laser spot welding molten pool of the upper welding base material. The pulse waveform is a slow-rising, constant and slow-falling pulse, wherein the peak power of the constant band is 1.2p, and the pulse time is t; the pulse time of the slow-rising band and the slow-falling band are both 0~0.5t, so as to control the depth-to-width ratio of the laser spot welding molten pool to be less than 1;

[0015] Step 5: emitting a subsequent pulsed laser beam;

[0016] Referring to the setting of the second pulse laser beam, an Nth pulse laser beam is emitted, where N is an integer greater than or equal to 3, and the peak power of the constant band of the Nth pulse laser beam is 1.2 N-1 ×p, and the other parameters remain unchanged until the laser spot welding molten pool melts the overlapping surface to form a heat conduction type laser weld with the maximized overlapping area.

[0017] Furthermore, in the step 2, the defocusing amount is ±3m, the protective gas flow rate is 5-15L / min, the pulse peak power is 1-10kW, and the pulse time is 1-15ms.

[0018] Furthermore, the interval time between the second pulse laser beam and the first pulse laser beam is no more than 0.3t.

[0019] Furthermore, in the step 1, the thickness of the welding base material is 0.1-3 mm, and the upper and lower welding base materials are made of homogeneous or heterogeneous metal materials.

[0020] Furthermore, in step 1, the pretreatment includes sandpaper polishing and chemical cleaning.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The multiple laser spot welding method proposed in the present invention sequentially emits multiple laser beams with different pulse waveforms at the same position to gradually form a laser spot welding molten pool with a depth-to-width ratio of less than 1. Compared with conventional laser single spot welding, the present invention can increase the overlap area several times, thereby improving the welding quality.

[0023] 2. Compared with the galvanometer welding system, the multiple laser spot welding method proposed in the present invention does not require a complex galvanometer mechanical structure and control system. The present invention simplifies the welding equipment, thereby increasing its applicability and diversity of operating conditions, and also reducing equipment cost investment.

[0024] 3. The present invention realizes multiple laser spot welding by sequentially emitting multiple pulsed laser beams. This method has the characteristics of a wide range of weldable base material thickness and flexible adjustment of welding parameters. Therefore, it can be applied to a variety of materials and working conditions and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Flow chart of the method of the present invention.

[0026] Figure 2 Schematic diagram of pulse laser spot welding process.

[0027] Figure 3 Schematic diagram of a conventional pulse laser waveform - a rectangular pulse.

[0028] Figure 4 This is the cross section of the pulse laser weld obtained in Example 1.

[0029] Figure 5 Schematic diagram of the peak and constant pulse of the first pulse laser beam.

[0030] Figure 6 Schematic diagram of the slowly rising, constant and slowly falling pulses of the second pulse laser beam.

[0031] Figure 7 Schematic diagram of the slowly rising, constant and slowly falling pulses of the Nth pulse laser beam.

[0032] Figure 8 This is the cross section of the multi-pulse laser weld obtained in Example 2.

[0033] In the figure: 1- pulse laser beam; 2- cross section of pulse laser weld spot; 3- welding base material; 4- constant wave band; 5- peak wave band; 6- slowly rising wave band; 7- slowly falling wave band. DETAILED DESCRIPTION

[0034] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0035] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0036] like Figure 2 , Figure 5-Figure 7As shown, a multiple laser spot welding method provided by an embodiment of the present invention specifically includes: sequentially emitting multiple pulsed laser beams 1 to gradually melt the laser spot welding molten pool, specifically including: emitting a first pulsed laser beam 1 (peak and constant) to melt the surface of the welding base material 3; when the molten pool is about to cool, emitting a second pulsed laser beam 1 (slow rise, constant and slow fall), the radiation position of which is the same as that of the first pulsed laser beam 1, to expand the laser spot welding molten pool of the upper welding base material 3; referring to the setting of the second pulsed laser beam 1, emitting the Nth pulsed laser beam 1, the peak power of which in the constant band 4 is 1.2 N-1 ×p, until the overlapping surface is melted, forming a heat conduction type laser weld with maximized overlapping area (depth-to-width ratio less than 1), thereby improving the bonding strength of the weld.

[0037] like Figure 1 As shown, the specific steps of the method are as follows:

[0038] Step 1: Pretreatment and fixation of welding base material 3;

[0039] After pretreatment (sandpaper polishing, chemical cleaning), the welding base material 3 is fixed on the welding fixture in an overlapping form; the width of the overlapping area of ​​the upper and lower welding base materials 3 is not less than 2mm;

[0040] Step 2: Welding parameter setting;

[0041] Use Nd:YAG pulse laser welder as welding equipment, adjust the defocus (±3mm), turn on the shielding gas (5~15L / min), set the pulse peak power (1~10kW) and pulse time (1~15ms);

[0042] Step 3: emitting a first pulse laser beam 1;

[0043] The first pulse laser beam 1 is emitted to melt the surface of the welding base material 3, and the pulse waveform formed by the combination of the peak power and the pulse time is a peak and a constant pulse, wherein the maximum pulse power of the peak band 5 is 1.5p, and the pulse time is 0.5t; the pulse peak power of the constant band 4 is p, and the pulse time is t;

[0044] Step 4: emitting a second pulse laser beam 1;

[0045] When the first pulse laser beam 1 is closed and the laser spot welding molten pool is about to cool, the second pulse laser beam 1 is emitted (the interval between two adjacent pulse laser beams is not greater than 0.3t). The radiation position of the second pulse laser beam 1 is the same as that of the first pulse laser beam 1, and is used to expand the laser spot welding molten pool of the upper welding base material 3. The pulse waveform composed of its peak power and pulse time is a slowly rising, constant and slowly falling pulse, wherein the peak power of the constant band 4 is 1.2p, and the pulse time is t; the pulse times of the slowly rising band 6 and the slowly falling band 7 are both 0~0.5t, so as to control the depth-to-width ratio of the laser spot welding molten pool to be less than 1;

[0046] Step 5: emitting a subsequent pulse laser beam 1;

[0047] Referring to the setting of the second pulse laser beam 1, the Nth pulse laser beam 1 is emitted, where N is an integer greater than or equal to 3, and the peak power of the constant wave band 4 is 1.2 N-1 ×p, and the other parameters remain unchanged until the laser spot welding molten pool melts the overlapping surface to form a heat conduction type laser weld with the maximized overlapping area.

[0048] Through the above steps, a multiple laser spot welding process with significantly increased overlapping area and significantly improved welding quality can be achieved.

[0049] Embodiment 1, conventional laser single spot welding;

[0050] In this embodiment, the welding base material 3 is made of TC4 titanium alloy material with a size of 60 mm × 60 mm × 1 mm, and the overlap area is 30 mm × 30 mm. Before welding, the surface oxide layer of the welding base material 3 is removed with 400# sandpaper, and grease is removed by wiping with acetone / alcohol.

[0051] The welding parameters were set as follows: the defocus was +1.5 mm, and the flow rate of the shielding gas (99.999% Ar) was 8 L / min. Figure 3 The conventional pulse laser waveform shown is in the form of a rectangular pulse, and is a single-beam pulse laser spot welding, with a pulse peak power P=3kW in a constant band 4 and a pulse time t=5ms.

[0052] After the above welding process, the cross section of the pulse laser weld point is obtained as shown in FIG. Figure 4 The observation results show that the overlapping area is relatively small.

[0053] Embodiment 2: Multiple laser spot welding method proposed by the present invention;

[0054] In this embodiment, the welding base material 3 is also made of TC4 titanium alloy material with a size of 60 mm × 60 mm × 1 mm, and the overlap area is 30 mm × 30 mm. Before welding, the surface oxide layer of the welding base material 3 is removed with 400# sandpaper, and grease is removed by wiping with acetone / alcohol.

[0055] The welding parameters were set as follows: defocus was +1.5 mm, and the flow rate of shielding gas (99.999% Ar) was 8 L / min.

[0056] In terms of the configuration of the pulsed laser beam, this embodiment adopts a multiple pulse strategy. Specifically:

[0057] The first pulse laser beam 1 is used as Figure 5 The peak and constant pulse forms shown in the figure, where: the maximum peak power P of the peak band 5 is 3kW, and the pulse time t is 2ms; the pulse peak power P of the constant band 4 is 2kW, and the pulse time t is 4ms. The second pulse laser beam 1 is emitted at an interval of 0.05ms, and the beam is Figure 6 The form of the slow-rise, constant and slow-fall pulses shown in the figure, wherein: the pulse time of the slow-rise stage 6 is 0.8ms; the pulse peak power P of the constant band 4 is 2.4kW, and the pulse time t is 4ms; the pulse time of the slow-fall band 7 is 0.8ms. The third pulse laser beam 1 is emitted at intervals of 0.06ms, using Figure 7 The forms of slowly rising, constant and slowly falling pulses are shown, wherein: the pulse time of the slowly rising stage 6 is 0.6ms; the pulse peak power P=2.88kW and the pulse time t=4ms of the constant band 4; the pulse time of the slowly falling band 7 is 0.6ms.

[0058] After the above multiple laser spot welding process, the cross section 2 of the multiple pulse laser weld spot is obtained. Figure 8 As shown, the observation results show that the overlap area is smaller than that of conventional laser single spot welding ( Figure 4 ) has increased several times, and the welding quality has also been greatly improved.

[0059] The multiple laser spot welding method proposed by the present invention is highly flexible and can adjust multiple welding pulse laser parameters according to the characteristics of the welding base material, thereby determining the optimal welding process parameters. At the same time, for technicians in the field of optics, there is no difficulty in implementing such multi-pulse laser remelting spot welding through the setting of optical and control devices.

[0060] The above are only preferred embodiments of the present invention. It should be pointed out that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These should also be regarded as the protection scope of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A multiple laser spot welding method, characterized in that: The following steps are involved: Step 1: Pretreatment and fixation of welding base material; After pretreatment, the welding base material is fixed on the welding fixture in an overlapping manner; Step 2: Welding parameter setting; Use Nd:YAG pulse laser welder as welding equipment, adjust the defocus, turn on the shielding gas, and set the pulse peak power and pulse time; Step 3: emitting a first pulse laser beam; The first pulse laser beam is emitted to melt the surface of the welding base material, and the pulse waveform is a peak and a constant pulse, wherein the maximum pulse power of the peak band is 1.5p, and the pulse time is 0.5t; the pulse peak power of the constant band is p, and the pulse time is t; Step 4: emitting a second pulse laser beam; When the first pulse laser beam is closed and the laser spot welding molten pool is about to cool, the second pulse laser beam is emitted. The radiation position of the second pulse laser beam is the same as that of the first pulse laser beam, which is used to expand the laser spot welding molten pool of the upper welding base material. The pulse waveform is a slow-rising, constant and slow-falling pulse, wherein the peak power of the constant band is 1.2p, and the pulse time is t; the pulse time of the slow-rising band and the slow-falling band are both 0~0.5t, so as to control the depth-to-width ratio of the laser spot welding molten pool to be less than 1; Step 5: emitting a subsequent pulsed laser beam; Referring to the setting of the second pulse laser beam, an Nth pulse laser beam is emitted, where N is an integer greater than or equal to 3, and the peak power of the constant band of the Nth pulse laser beam is 1.2 N-1 ×p, and the other parameters remain unchanged until the laser spot welding molten pool melts the overlapping surface to form a heat conduction type laser weld with the maximum overlapping area; In the step 1, the pretreatment includes sandpaper polishing and chemical cleaning; In the step 2, the defocusing amount is ±3m, the protective gas flow rate is 5-15L / min, the pulse peak power is 1-10kW, and the pulse time is 1-15ms; The interval time between the second pulse laser beam and the first pulse laser beam is no more than 0.3t.

2. The multiple laser spot welding method according to claim 1, characterized in that: In the step 1, the thickness of the welding base material is 0.1-3 mm, and the upper and lower welding base materials are made of homogeneous or heterogeneous metal materials.

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