Advantages and disadvantages of laser welding

Advantages and disadvantages of laser welding

Advantages and disadvantages of laser welding Laser welding is one of the important aspects of the application of laser material processing technology. Laser welding is a welding method that bombards weldments with focused laser beams as energy. The advantages and disadvantages of laser welding are shared below.

Advantages and disadvantages of laser welding 1 advantages and disadvantages of laser welding

Advantages:

(1) can reduce the heat input to the minimum requirements, and the metallographic change range in the heat affected zone is small, and the deformation caused by heat conduction is also the lowest.

(2) The welding process parameters of 32 mm thickness single pass welding have been verified, which can reduce the time required for thick plate welding and even save the use of filler metal.

(3) There is no need to use electrodes, and there is no need to worry about electrode pollution or damage. Moreover, because it is not a contact welding process, the wear and deformation of the machine can be minimized.

(4) The laser beam is easy to focus, align and be guided by optical instruments, and can be placed at a proper distance from the workpiece and redirected between machines or obstacles around the workpiece. Due to the above space constraints, other welding rules can't work.

(5) The workpiece can be placed in a closed space (under the control of vacuum pumping or internal gas environment).

(6) The laser beam can be focused in a small area, and small and dense parts can be welded.

(7) There is a wide range of weldable materials, and various heterogeneous materials can also be bonded to each other.

(8) It is easy to carry out high-speed welding by automation, and it can also be controlled by digital or computer.

(9) When welding thin materials or fine-diameter wires, there will be no remelting problem like arc welding.

(10) is not affected by magnetic field (arc welding and electron beam welding are easy), and the weldment can be aligned accurately.

(1 1) Two metals with different physical properties (such as different resistances) can be welded.

(12) No vacuum or X-ray protection is required.

(13) If perforated welding is adopted, the depth-width ratio of the weld can reach 10: 1.

(14) The equipment can be switched to transmit the laser beam to multiple workstations.

Disadvantages:

(1) The position of the weldment must be very accurate and within the focus range of the laser beam.

(2) When the weldment needs a fixture, it must be ensured that the final position of the weldment is aligned with the solder joint impacted by the laser beam.

(3) The maximum weldable thickness is limited, and the workpiece with penetration thickness far exceeding 19mm is not suitable for laser welding on the production line.

(4) Laser will change the weldability of materials with high reflectivity and high thermal conductivity, such as aluminum, copper and their alloys.

(5) When welding with medium energy and high energy laser beam, plasma controller should be used to drive away ionized gas around the molten pool to ensure the reappearance of weld.

(6) The energy conversion efficiency is too low, usually lower than 10%.

(7) The weld solidifies rapidly, which may lead to porosity and embrittlement.

The equipment is expensive.

Advantages and disadvantages of laser welding 2 advantages and disadvantages of laser welding

① Laser welding can obtain high-quality joint strength and large depth-width ratio, and the welding speed is relatively fast.

② Because laser welding does not need vacuum environment, remote control and automatic production can be realized through lens and optical fiber.

(3) The laser power density is high, and it has a good welding effect on difficult-to-weld materials such as titanium and timely welding, and can weld materials with different properties.

④ Micro-welding can be carried out. After the laser beam is focused, a small light spot can be obtained and accurately positioned, which can be applied to the assembly and welding of small workpieces in mass automatic production.

Disadvantages of laser welding

(1) laser and welding system accessories are relatively expensive, so the initial investment and maintenance costs are higher than those of traditional welding technology, and the economic benefits are poor.

(2) The conversion efficiency of laser welding is generally low (usually 5%~30%), because the absorption rate of laser by solid materials is low, especially after the appearance of plasma (plasma can absorb laser).

(3) Because the focused spot of laser welding is small, the equipment accuracy of workpiece joint is required to be high, and small equipment deviation will produce large machining error.

Is laser welding harmful to people?

The invisibility and energy of the laser emitted by the welding machine are too high, so non-professionals should not touch the laser source, otherwise it is very dangerous. In addition, laser is also an electromagnetic wave, but the laser used in the welding machine has a large wavelength, so there is no radiation hazard of short-wavelength light waves such as ultraviolet rays.

Many gases are produced in the welding process, but most of them are inert gases, which are not toxic, but it also depends on the different treatment of welding materials. It is best to take protective measures to reduce gas inhalation.

The laser emitted by the welding machine has almost no radiation hazard, but there will be ionizing radiation and stimulated radiation during welding, so it is best to stay away from the welding site during welding. This kind of induction radiation is short wave, which has great influence on eyes and body. It is best to stay away from solder joints. When working at close range, protective measures should be taken as far as possible, such as wearing respiratory protective equipment, radiation protection clothing and eye mask.

Advantages and disadvantages of laser welding 3 Compared with other welding technologies, the main advantages of laser welding are:

1, with high speed, large depth and small deformation.

2, welding can be carried out at room temperature or under special conditions, and the welding equipment is simple. For example, when the laser passes through the electromagnetic field, the beam will not deviate; Laser can be welded in vacuum, air and a certain gas environment, and can be welded through glass or materials transparent to the light beam.

3. It can weld refractory materials, such as titanium and timely. It can weld anisotropic materials with good effect.

4. After laser focusing, the power density is high. When welding high-power devices, the depth-width ratio can reach 5: 1, and the highest can reach 10: 1.

5, micro welding can be carried out. After the laser beam is focused, a small light spot can be obtained and accurately positioned, which can be applied to the assembly and welding of small workpieces in mass automatic production. (The minimum spot can reach 0. 1 mm)

6. It can weld inaccessible parts and implement non-contact long-distance welding, which has great flexibility. Especially in recent years, the application of optical fiber transmission technology in YAG laser processing technology and the popularization of fiber continuous laser have made laser welding technology more widely popularized and applied, which is more convenient for automatic integration.

7. The laser beam is easy to divide beams according to time and space, and multiple beams can be processed at multiple stations at the same time, which provides conditions for more accurate welding.

However, laser welding also has some limitations:

1, which requires high assembly accuracy of weldments, and the position of the light beam on the workpiece cannot be obviously shifted. This is because after laser focusing, the spot size is very small and the weld is very narrow, which is full of metal materials. If the workpiece assembly accuracy or beam positioning accuracy can not meet the requirements, it is easy to cause welding defects.

2. The laser and its related systems have high cost and large one-time investment.

Laser welding principle:

Laser welding is to irradiate the metal surface with high-intensity laser beam, and melt the metal to form welding through the interaction between laser and metal.

In the process of interaction between laser and metal, metal melting is only one of the physical phenomena. Sometimes light energy is not mainly converted into metal melting, but expressed in other forms, such as vaporization and plasma formation.

However, in order to achieve good fusion welding, metal melting must be the main form of energy conversion.

Therefore, it is necessary to know what happens in the interaction between laser and metal.

Various physical phenomena and the relationship between these physical phenomena and laser parameters, so that by controlling laser parameters, most laser energy is converted into energy of metal melting, and the purpose of welding is achieved.

Laser welding process parameters

1, power density

Power density is one of the most critical parameters in laser processing. At high power density, the surface layer can be heated to the boiling point in a microsecond time range, resulting in a large amount of vaporization.

Therefore, high power density is beneficial to material removal processing, such as stamping, cutting and engraving.

For low power density, it takes several milliseconds for the surface layer to reach the boiling point, and before the surface layer is vaporized, the bottom layer reaches the melting point, which is easy to form a good welding.

Therefore, in conductive laser welding, the power density is in the range of 104~ 106W/cm2.

2. Laser pulse waveform

Laser pulse waveform is an important problem in laser welding, especially in thin plate welding.

When the high-intensity laser beam hits the material surface, 60~98% of the laser energy on the metal surface will be reflected and lost, and the reflectivity changes with the surface temperature.

In the process of laser pulse, the reflectivity of metal changes greatly.

3. Laser pulse width

Pulse width is one of the important parameters of pulsed laser welding, which is not only different from material removal and material melting, but also a key parameter to determine the cost and volume of processing equipment.

4. The influence of defocusing on welding quality

Laser welding usually needs some attention, because the power density of the spot center at the laser focus is too high, and it is easy to evaporate into holes. The power density distribution on each plane far from the laser focus is relatively uniform.