5 Precious Tips to Help You Get Better at Laser Welding

Laser welding is an efficient and precise welding method using a high energy density laser beam as a heat source. Laser welding is one of the important aspects of the application of laser material processing technology. In the 1970s, it was mainly used for welding thin-walled materials and low-speed welding. The welding process belongs to the heat conduction type, that is, laser radiation heats the surface of the workpiece, and the surface heat diffuses internally through heat transfer. By controlling the parameters such as laser pulse width, energy, peak power, and repetition frequency, the workpiece melts and forms a specific molten pool. Because of its unique advantages, it has been successfully applied to the precision welding of micro and small parts.

1. Technical Principle

Laser welding can be realized by a continuous or pulsed laser beam. The principle of laser welding can be divided into heat conduction welding and laser deep penetration welding. When the power density is less than 104 ~ 105 w / cm2, it is heat conduction welding. At this time, the penetration is shallow and the welding speed is slow; When the power density is greater than 105 ~ 107 w / cm2, the metal surface will be concave into "holes" under the action of heating to form deep penetration welding, which has the characteristics of fast welding speed and large depth width ratio.

1. Classification

There are mainly two kinds of lasers used for welding, namely CO2 laser and Nd: YAG laser.

Both CO2 laser and Nd: YAG laser is infrared light invisible to the naked eye. The beam generated by Nd: YAG laser is mainly near-infrared light with a wavelength of 1.5 nm 06 LM, the thermal conductor has high light absorption at this wavelength, and its reflectivity is 20% - 30% for most metals.

3. Welding Characteristics

It belongs to fusion welding, which uses a laser beam as energy to impact the weldment joint.

The laser beam can be guided by a planar optical element (such as a mirror) and then projected on the weld with a reflective focusing element or lens.

Laser welding belongs to non-contact welding, and pressure is not required during operation, but inert gas is required to prevent oxidation of molten pool, and filler metal is occasionally used.

Laser welding and MIG welding can form laser MIG hybrid welding to realize large penetration welding, and the heat input is greatly reduced compared with MIG welding.

4. Advantages And Aisadvantages

Advantages :

● The heat input can be reduced to the minimum required amount, the metallographic change range of heat-affected zone is small, and the deformation caused by heat conduction is also the lowest;

● The welding process parameters of 32mm thick single pass welding have been verified to be qualified, which can reduce the time required for thick plate welding and even save the use of filler metal;

● There is no need to use electrodes, and there is no concern about electrode contamination or damage. Because it is not a contact welding process, the loss and deformation of machines and tools can be minimized;

● The laser beam is easy to focus, align, and guided by optical instruments, can be placed at an appropriate distance from the workpiece, and can be guided between machines and tools or obstacles around the workpiece. Other welding rules cannot be played due to the above space constraints;

● The workpiece can be placed in a closed space (vacuumized or under the control of internal gas environment);

● The laser beam can focus on a very small area and can weld small and closely spaced parts;

● There are a wide range of weldable materials, and various heterogeneous materials can also be joined to each other;

● It is easy to carry out high-speed welding by automation, and can also be controlled by digital or computer;

● When welding thin materials or fine diameter wires, it will not be easy to have the trouble of remelting like arc welding;

● It is not affected by a magnetic field (arc welding and electron beam welding are easy), and can accurately align weldments;

● It can weld two metals with different physical properties (such as different resistance);

● No vacuum or X-ray protection is required;

● If perforated welding is used, the depth to width ratio of weld bead can reach 10:1;

● The switching device can transfer the laser beam to multiple workstations.

Aisadvantages:

● The position of the weldment shall be very accurate and must be within the focusing range of the laser beam;

● When a fixture is required for the weldment, it must be ensured that the final position of the weldment must be aligned with the welding spots impacted by the laser beam;

● 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;

● The weldability of high reflective and high thermal conductivity materials such as aluminum, copper and their alloys will be changed by laser;

● When medium to high energy laser beam welding is carried out, the plasma controller shall be used to drive away from the ionized gas around the molten pool to ensure the reoccurrence of the weld bead;

● The energy conversion efficiency is too low, usually less than 10%;

● The weld bead solidifies rapidly, and there may be concerns about porosity and embrittlement;

● The equipment is expensive.

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