Laser welding is an efficient and precise welding method which uses high energy density laser beam as heat source. There are two basic modes of laser welding: laser thermal conduction welding and laser deep penetration welding. The former uses a lower laser power density (105-106w / cm2). After the workpiece absorbs the laser, it only melts on the surface, and then forms a molten pool by heat transfer inside the workpiece. This kind of welding mode has the advantages of shallow penetration and small depth width ratio. The latter has a high laser power density (106-107w / cm2). The workpiece melts and even gasifies rapidly after absorbing the laser. The molten metal forms a small hole laser beam under the action of steam pressure, which can directly shine on the hole bottom, making the small hole continuously extend until the steam pressure in the small hole is balanced with the surface tension and gravity of the liquid metal. When the keyhole moves along the welding direction with the laser beam, the molten metal in front of the keyhole flows around the keyhole to the rear, and the weld is formed after solidification. This welding mode has a large penetration depth and a large aspect ratio. In the field of mechanical manufacturing, in addition to those thin parts, deep penetration welding is generally used.

It has the following characteristics:            

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.            

It can 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 wear and deformation of the machine can be minimized.            

The laser beam is easy to focus, align and guided by optical instruments. It can be placed at a proper distance from the workpiece, and can be guided again between the machines and tools or obstacles around the workpiece. Other welding rules cannot play due to the above space restrictions.            

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

The laser beam can be focused in a very small area, and small and close spaced components can be welded.            

The range of weldable materials is large, and various heterogeneous materials can be joined. 

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

When welding thin or fine wire, it will not be easy to have remelting problems like arc welding. 

Not affected by the magnetic field (arc welding and electron beam welding are easy), it can accurately align the weldment.            

No vacuum or X-ray protection is required.            

In case of perforation welding, the depth width ratio of weld bead can reach 10:1.            

The device can be switched to transmit the laser beam to multiple workstations.