阅读说明：本技术 一种适用于高强铝合金平焊的激光-电弧复合焊接方法 (Laser-electric arc hybrid welding method suitable for high-strength aluminum alloy flat welding ) 是由 韩永全 洪海涛 冯一萍 杜茂华 孙振邦 于 2019-09-19 设计创作，主要内容包括：本发明为一种适用于高强铝合金平焊的激光-电弧复合焊接方法,采用双脉冲变极性等离子弧焊接与激光焊接相结合的复合焊接工艺,通过控制实现脉冲变极性等离子弧脉冲电流高中低频率可控,高频脉冲频率200-1000Hz,低频脉冲频率1-5Hz,工频频率40Hz；焊接工艺参数：等离子电流160-220A,电弧电压21-30V,弧高5-6mm,等离子焊枪角度45-60°,高纯氩气体保护；激光功率1.5-2.5kw,激光离焦量-5-5mm,激光束倾于焊枪侧5-10°；电弧在激光束之前,光钨间距3-6mm,焊接速度480-1040mm/min。本发明能够减少焊接热输入,提高焊接效率。(The invention relates to a laser-electric arc hybrid welding method suitable for high-strength aluminum alloy flat welding, which adopts a hybrid welding process combining double-pulse polarity-variable plasma arc welding and laser welding, and realizes the high-medium and low-frequency controllability of pulse polarity-variable plasma arc pulse current through control, wherein the high-frequency pulse frequency is 200 plus materials Hz, the low-frequency pulse frequency is 1-5Hz, and the power frequency is 40 Hz; welding technological parameters are as follows: plasma current 160-220A, arc voltage 21-30V, arc height 5-6mm, plasma welding gun angle 45-60 degrees, high-purity argon gas protection; the laser power is 1.5-2.5kw, the defocusing amount of the laser is-5-5 mm, and the laser beam is inclined to the welding gun side for 5-10 degrees; the electric arc is before the laser beam, the optical tungsten spacing is 3-6mm, and the welding speed is 480-. The invention can reduce welding heat input and improve welding efficiency.)

1. A laser-electric arc hybrid welding method suitable for the high-strength aluminum alloy flat welding is characterized in that a hybrid welding process combining double-pulse polarity-variable plasma arc welding and laser welding is adopted, and the high-frequency, medium-frequency and low-frequency controllability of pulse polarity-variable plasma arc pulse current is realized through control, wherein the high-frequency pulse frequency is 200 plus material frequency 1000Hz, the low-frequency pulse frequency is 1-5Hz, and the power frequency is 40 Hz; the welding process parameters are set as follows:

plasma current 160-220A, arc voltage 21-30V, arc height 5-6mm, included angle of plasma welding gun and workpiece 45-60 degrees, and high-purity argon protection; the laser power is 1.5-2.5kw, the defocusing amount of the laser is defocused by-5-5 mm, and the laser beam is inclined to the side of the welding gun by 5-10 degrees; the electric arc is before the laser beam, the optical tungsten spacing is 3-6mm, and the welding speed is 480-.

2. The laser-arc hybrid welding method suitable for the flat welding of the high-strength aluminum alloy as claimed in claim 1, wherein a stainless steel backing plate is adopted on the back of the welding process, a 5356 diameter 1.2mm aluminum alloy welding wire is adopted as the welding wire, the wire feeding speed is 4.5-6.5m/min, and the wire feeding mode is a push type wire feeding mode.

3. The laser-arc hybrid welding method suitable for high-strength aluminum alloy flat welding according to claim 1, characterized in that the pulse polarity-variable plasma arc positive polarity current 155A, the reverse polarity current 190A, the positive and negative polarity time ratio 21: 4.

Technical Field

The invention belongs to the technical field of welding, and particularly relates to a laser-electric arc hybrid welding method suitable for high-strength aluminum alloy flat welding.

Background

The variable polarity plasma is known as the defect-free welding of light alloy welding such as aluminum alloy and the like, but because the welding efficiency is lower, the welding position is limited, the aluminum alloy flat welding perforation forming is poor, the tungsten electrode burning loss is serious when heavy current is welded on a medium plate, and the softening of a high-strength aluminum alloy welding joint is obvious.

The laser has high energy density, so the laser has strong deep melting capability, and because the aluminum alloy has high reflectivity to light and heat during laser welding, the laser welding has high temperature gradient, so the hot crack defect is serious, the assembly precision requirement is strict, and the high-power laser is expensive.

The laser-pulse variable polarity plasma is combined for welding, the deep melting effect of the laser is utilized, the advantages of variable polarity plasma welding of aluminum alloy are achieved, meanwhile, the welding efficiency is improved, the welding current is reduced, the heat input is reduced, the softening problem of a high-strength aluminum alloy welding joint is further improved, the purposes of aluminum alloy through hole flat welding, single pass welding and single-side welding double-side forming are achieved, and the welding effect of 1+1>2 is achieved.

However, the existing single-pass laser-arc hybrid welding method has the following disadvantages: 1) the penetration capability to the welding plate is weak; the problems of undercut, weld toe crack and the like are easily caused when the opening is broken; when the groove is not formed, the welding current needs to be increased, so that the heat input is high, and the joint strength is reduced; 2) the high-strength aluminum alloy welding joint is seriously softened, a non-compression electric arc is relatively diffused, and the welding heat input is relatively large; 3) the back of the welding seam is poor in forming, and is often not fully welded, and the surplus height is large in fluctuation. 4) Slag inclusions, porosity and cracking tend to be severe.

The above problems restrict industrial production and application, so that it is necessary to provide a more economical and efficient welding means for overcoming the disadvantages of the laser-arc hybrid welding method.

Disclosure of Invention

The invention aims to provide a laser-electric arc hybrid welding method suitable for high-strength aluminum alloy flat welding, which aims to reduce welding heat input, improve welding efficiency and ensure welding quality, thereby providing an economical and efficient welding method and means for industrial manufacturing.

In order to achieve the purpose, the invention adopts the following technical scheme:

a laser-electric arc hybrid welding method suitable for the flat welding of high-strength aluminum alloy is characterized in that a hybrid welding process combining double-pulse polarity-variable plasma arc welding and laser welding is adopted, the high, medium and low frequency of pulse polarity-variable plasma arc pulse current is controllable through control, the high-frequency pulse frequency is 200-1000Hz, the low-frequency pulse frequency is 1-5Hz, and the power frequency is 40 Hz; the welding process parameters are set as follows:

plasma current 160-220A, arc voltage 21-30V, arc height 5-6mm, included angle of plasma welding gun and workpiece 45-60 degrees, and high-purity argon protection; the laser power is 1.5-2.5kw, the defocusing amount of the laser is defocused by-5-5 mm, and the laser beam is inclined to the side of the welding gun by 5-10 degrees; the electric arc is before the laser beam, the optical tungsten spacing is 3-6mm, and the welding speed is 480-.

The invention is also characterized in that the back of the welding process adopts a stainless steel backing plate, the welding wire adopts 5356 aluminum alloy welding wire with the diameter of 1.2mm, the wire feeding speed is 4.5-6.5m/min, and the wire feeding mode is a push type wire feeding mode.

The invention is also characterized in that the positive polarity current 155A of the pulse variable polarity plasma arc, the reverse polarity current 190A, the time ratio of positive polarity to reverse polarity is 21: 4.

compared with the prior art, the invention has the following advantages:

the invention combines the advantages of pulse plasma arc molten pool stirring cleaning, laser deep melting penetration and the like, can realize welding with larger plate thickness compared with the traditional composite welding, improves the welding efficiency, obviously improves the welding quality, obtains a welding joint with beautiful shape, less welding defects and high welding seam quality; according to the laser-electric arc hybrid welding method adopted by the invention, the medium plate aluminum alloy can be welded through in a single pass, the double-sided forming is realized, the heat source is concentrated, the deformation after welding and the joint softening are improved, and the advantages of the welding of the medium plate aluminum alloy are obvious.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic view of a welding structure of a composite heat source according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a pulse polarity-changing plasma current waveform in an embodiment of the present invention, where positive and negative polarities of a pulse alternate once to form a power frequency cycle, and high and low energy pulses alternate once to form a low frequency pulse cycle;

FIG. 3 is a graph of a polarity-changing plasma arc electrical signal and an arc shape acquired by the arc detection system in the embodiment of the present invention, where the left side is the arc electrical signal and the right side is the plasma arc shape, where a is the detection data of laser-polarity-changing plasma arc hybrid welding without pulse implantation, and where b, c, and d are the monitoring data of high-frequency pulse hybrid welding with 200Hz, 500Hz, and 1000Hz respectively;

fig. 4 is a forming diagram of a fiber laser-pulse VPPA composite welding seam, wherein a is a forming diagram of the front side of the welding seam, and b is a forming diagram of the back side of the welding seam.

Description of reference numerals: 1. the plasma welding machine comprises a pulse polarity-changing plasma welding machine, 2, a plasma welding gun, 3, a fiber laser, 4, a wire feeding system, 5, a workpiece and 6, a laser head.

Detailed Description

Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but it should be understood that the scope of the present invention is not limited to the specific embodiments.

The embodiment of the invention provides a laser-electric arc hybrid welding method suitable for high-strength aluminum alloy flat welding, which adopts a hybrid welding process combining double-pulse polarity-variable plasma arc welding and laser welding, realizes the high-medium frequency controllability of pulse polarity-variable plasma arc pulse current through control, the high-frequency pulse frequency is 200 plus 1000Hz, the low-frequency pulse frequency is 1-5Hz, and the power frequency is 40 Hz; the welding process parameters are set as follows:

plasma current 160-220A, arc voltage 21-30V, arc height 5-6mm, included angle of plasma welding gun and workpiece 45-60 degrees, and high-purity argon protection; the laser power is 1.5-2.5kw, the defocusing amount of the laser is defocused by-5-5 mm, and the laser beam is inclined to the side of the welding gun by 5-10 degrees; the electric arc is before the laser beam, the optical tungsten spacing is 3-6mm, and the welding speed is 480-.

In the embodiment of the invention, the back of the welding process adopts the stainless steel backing plate, the stainless steel backing plate is mainly used for considering that the welding seam is easy to collapse under the condition of flat welding of the aluminum alloy through holes, and the backing plate is adopted at the back of the welding process, so that the forming is stable. Meanwhile, the aluminum alloy perforation composite welding can solve the problems of air holes and stress formed by laser welding.

The 5356 aluminum alloy welding wire with the diameter of 1.2mm is adopted as the welding wire, if the diameter of the welding wire is large, the heat required by the welding wire during melting is increased, the energy of electric arc is easy to be insufficient, the laser deep melting effect is weakened, the back surface is not fused, and the like. In addition, the wire feeding speed is 4.5-6.5m/min, and the wire feeding mode is a push type wire feeding mode. The over-small wire feeding speed can cause the defects of insufficient filling amount of a molten pool, sunken welding seams after welding, untimely melting of welding wires and poor fluidity if the wire feeding is too fast, and uneven welding seams and the like are easy to cause.

In the embodiment of the invention, the positive polarity current 155A and the reverse polarity current 190A of the pulse variable polarity plasma arc, the positive and reverse polarity time ratio is 21: 4.

in the invention, the high frequency of the pulse variable polarity plasma arc is 200Hz and 1000Hz, the high frequency pulse has a compression effect on the plasma arc, so that the action area of the arc is reduced, the arc force is enhanced, and the problem of joint softening caused by large current is solved. The low-frequency pulse frequency is 1-5Hz, the low-frequency pulse has the function of scouring and stirring a molten pool, the welding line stress can be lightened, the welding crack is improved, and meanwhile, the air holes in the middle and lower layers of the welding line are easier to discharge. Selecting the positive and negative polarity time ratio of the power frequency pulse 21: 4, operating frequency 40Hz can make positive polarity electric arc concentrate more, and the punching capability is strong, and electric arc temperature is high during the antipole, has the negative pole cleaning effect to the weld surface, and is comparatively serious to the tungsten utmost point scaling loss when considering the antipole, and the positive and negative polarity time ratio of comprehensive consideration is selected 21: 4.

in the embodiment of the invention, a composite welding system constructed by a pulse variable polarity plasma arc welding system and a fiber laser is adopted to realize the welding process, an MSP430 singlechip is adopted as a microcomputer control core, signals are output to a secondary inversion unit, the pulse variable polarity plasma arc pulse current is controllable in high, medium and low frequency, the high frequency pulse frequency is 200-1000Hz, the power frequency is 40Hz, and the low frequency pulse frequency is 1-5Hz, wherein the microcomputer control unit outputs signals to realize digital control by adopting C language, specifically IAR for MSP430 software is adopted to realize the editing, testing and burning of a welding machine program, the interface is simple, and the man-machine interaction mode is flexible. Specifically, as shown in fig. 1, the welding system adopted mainly includes: the plasma welding machine comprises a pulse polarity-changing plasma welding machine 1, a plasma welding gun 2, a fiber laser 3, a wire feeding system 4 and the like, wherein double-pulse polarity-changing plasma waveform high-low frequency modulation is adopted, and the output waveform of the welding machine is controlled through a C language program based on a microcomputer driving module of a single chip microcomputer of the welding machine. Wherein wire feeding system 4, in order to ensure welding stability, the wire guide mouth material is red copper, and the welding wire diameter on probation is not more than 1.4 mm. The plasma cathode is connected with the plasma welding gun 2, the plasma anode is connected with the workpiece 5 to form a pulse variable polarity plasma welding loop, and the KUKA welding control system is utilized to control the adjustment of welding parameters such as the laser power, the laser on-off and the welding speed and the like, and the adjustment and the pulse variable polarity plasma welding process are cooperatively controlled. FIG. 2 is a schematic diagram of a pulse polarity-changing plasma current waveform in an embodiment of the present invention, where positive and negative polarities of a pulse alternate once to form a power frequency cycle, and a high-low energy pulse alternate once to form a low-frequency pulse cycle.

The specific welding method comprises the following steps:

cleaning oxide films on the front side and the back side of a to-be-welded part of a workpiece, wherein the cleaning method adopts a mechanical cleaning method, polishing is carried out by using sand paper and a steel wire brush, and the workpiece is arranged on a tool fixture for fixing; combining a plasma welding gun 2 and a laser head 6 into a side-axis type composite heat source welding gun, fixing the angles and positions of the two guns, inclining a laser beam to the side of the welding gun by 5-10 degrees, forming an included angle of 45-60 degrees between the welding gun and a workpiece, and enabling the distance between light and tungsten to be 3-6 mm; the welding equipment and the device are connected according to the method shown in fig. 1.

Before welding, setting parameters such as laser power, defocusing amount and the like according to the requirements of a welding process, and adjusting plasma welding current, pulse frequency and positive and negative polarity time; the positions of the two guns are adjusted, the height between the nozzle of the plasma welding gun and the workpiece is 5-6mm, the plasma welding gun is prevented from colliding with the workpiece, laser cannot damage the plasma welding gun, the light tungsten distance and the wire feeding position are further adjusted, and the stable welding process and high welding quality are ensured on the premise that the two heat sources are well compounded.

Step three, according to the process requirement, the angle of the tip of the tungsten electrode is 45 degrees, the internal shrinkage of the tungsten electrode is 2mm, the ionic gas flow is regulated to be 1-2L/min, the protective gas flow is 15-20L/min, the welding speed is 480-1040mm/min, and the wire feeding speed is 4.5-6.5 m/min.

And step four, checking whether the welding equipment normally operates and whether the welding track is safe.

Starting a high-frequency pilot arc power supply of the pulse plasma welding power supply, after pilot arc starting, falling the gun by the robot, starting a plasma main arc after the gun falling is finished, closing the pilot arc, emitting laser, starting wire feeding, and starting to travel at a set welding speed; during welding, laser acts on the bottom of a molten pool formed by plasma arcs to form a laser small hole penetration workpiece, and the plasma arcs mainly play a role in heating the workpiece and melting a welding wire to cover the surface; and (5) after welding, closing the laser, stopping wire feeding, and closing the plasma arc.

The following is a further description of specific examples of the application of the process of the invention: