Laser welding is a non-contact which requires access to the weld zone from only one side of the parts being welded. The laser weld is formed as the intense laser light rapidly heats the material – typically calculated in milliseconds.
Three types of weld joints can be achieved with laser welding:
1.) Conduction welds are performed at low energy, resulting in wide, shallow weld nuggets.
2.) Conduction/penetration welds utilize a medium energy density and result in a deeper weld nugget.
3.) Penetration or keyhole welds are resultant of direct energy delivery into the material being welded resulting in deep, narrow nuggets.
Since laser welding is a one sided, non-contact process, infinite multi axis weld joint geometries can be achieved with one set-up. Butt, lap and fillet joint geometries can be used to weld seam and spot weld part joints. In addition the laser is able to weld into areas with limited access. The most significant requirement for reliable laser welding is close fit-up at the joint interfaces. Laser spot or seam welding is usually an autogenesis process, meaning that no filler material is added during the welding process. However filler materials can be added into the weld pool if required to improve the weld joint.
There are two of types of laser welding processes; Continuous Wave and Pulsed. As the name suggests continuous wave or CW is either on or off, whereas pulsed lasers create welds by individual pulses. The pulsed laser process utilizes high peak power to create the weld, whereas the CW laser uses average power. High peak pulse power density W/cm2 is an intense precise concentration of the power at the part. This allows the pulsed laser to use less energy to create the weld, with a smaller heat affected zone. This provides the pulsed laser with unrivalled spot welding performance and minimal heat input for seam welding.
Laser welders can join a wide range of steels, nickel alloys, titanium, aluminum, and copper. Pulse shaping capabilities are used to improve weld quality characteristics such as; cracking, reflectivity, effect of high thermal cycling, and the vaporization of volatile alloying elements. Pulse shape programming is also used to enable laser welding of dissimilar materials.