Lasers were developed in the early 1960s, and by the mid-1960s CO2 lasers were being used to weld. A decade later automated laser welding systems were incorporated into production lines, and the technology has found wide acceptance in many industries. Laser welding systems are capable of delivering a tremendous amount of energy very quickly and with pinpoint accuracy. The beam can be focused to target hard-to-access welds, and, utilizing fiber-optic cables provide a more homogeneous weld (no hot spots).
A laser beam is generated by rapidly raising and lowering the energy state of an “optical gain material,” such as a gas or a crystal, which causes the emission of photons. The photons are subsequently concentrated and made coherent (lined up in phase with each other) and then projected on the surface of a part where radiant heat “couples” with the material, causing it to melt and produce the weld. Unfortunately, the majority of the laser’s power is wasted on heat and reflected off the part’s surface. Thus, by contrast, the depth penetration per unit of power in a laser weld is less than that of an electron beam weld. This problem can be mitigated by pulsing the laser, i.e., varying the power of the laser during the weld cycle. Pulsing the laser lowers the average power during the weld cycle keeping the part relatively cool. This can be particularly beneficial in achieving a strong weld on highly reflective materials such as copper and aluminum.
The power output of a laser can vary from a few watts to hundreds of kilowatts, and different types of lasers have different welding characteristics. As an example, the particular wave- length of light produced by the laser can make it more suitable for some applications and less for others.
Laser welding generally requires the use of a cover gas to keep oxygen out of the weld area improving efficiency and weld purity. The type of gas used depends on the type of laser, the material being welded, and the nuances of the application. Some laser welding applications may require an enclosed environment (i.e, a “glove box”) to assure complete gas coverage when joining parts having complex geometries.
Read more on our Quick Look: Laser Welding Guide.