The primary advantages of laser welding are a small heat affected zone (HAZ), accurate control of heat input, and the ability to direct the beam precisely to the weld point. The benefits of these factors are reduced thermal distortion, the ability to weld close to heat-sensitive parts, and precision welding capabilities. In part, these applications are successful because the typical focused beam diameter of 100 microns (0.004”) localizes temperature increases around the weld area to fractions of an inch.

Laser welding is typically performed without adding filler material to the weld. This creates a homogenous junction between the two pieces without introducing foreign material in the form of filler alloys. The downside is that part fit up at the weld interface must ideally be zero to prevent undercutting of the weld joint. In actual practice, a slight gap not exceeding 10% of the thinnest piece or the actual weld depth, whichever is less, is acceptable. In addition, the conventional welding technique of creating initial spot welds at intervals along the joint helps to prevent material separation during the actual weld pass.

In this application, we fillet welded a 0.15 mm (0.006”) thin steel cover to a much thicker steel substrate. Our beam delivery setup consisted of a 63.5 mm (2.5”) positive meniscus lens, which provides a 100-micron (0.004”) spot size with a 1.8 mm (0.07”) depth of focus. An argon shield gas was adjusted to flow over the processing area at a rate of 3.9 cubic feet per minute (CFM) to prevent the molten weld pool from reacting with the surrounding atmosphere. Each weld was completed in approximately 1.3 seconds using 200 watts of power at a velocity of 15 inches per minute.

 
This weld was completed in 1.3 seconds
using 200 watts of power at 15 IPM.