The laser beam can be guided by a planar optical element (such as a mirror) and then projected onto the weld by a reflective focusing element or lens.
Laser welding is a kind of non-contact welding, which does not need pressure during operation, but needs inert gas to prevent oxidation of molten pool, and occasionally filler metal is used.
TIG is tungsten inert gas shielded welding.
Main disadvantages of laser welding
(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 to be 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 high reflectivity and high thermal conductivity materials such as aluminum, copper and their alloys;
(5) When welding with medium to 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 than10%;
(7) The weld rapidly solidifies, which may cause porosity and embrittlement;
(8) The equipment is expensive.
In order to eliminate or reduce the defects of laser welding and make better use of this excellent welding method, some composite welding processes with other heat sources and lasers are proposed, including laser and arc, laser and plasma arc, laser and induction heat source composite welding, double laser beam welding and multi-beam laser welding. In addition, various auxiliary technological measures are put forward, such as laser wire filling welding (which can be subdivided into cold wire welding and hot wire welding), laser welding assisted by external magnetic field, laser welding with shielding gas to control the depth of molten pool, laser-assisted friction stir welding and so on.