LASER SHEET METAL WELDING
LASER WELDING offers many advantages over traditional welding techniques. These advantages are, for the most part, based on the ability to deliver energy sufficient for melting metals in a localized area. The result is consistent, reliable welds with minimal distortion, a small heat affected zone (HAZ) and a narrow weld profile with excellent appearance.Laser welding process
Laser welding occurs when a focused 0.008 to 0.04 inch (0.2 - 1 mm) diameter beam from a high power laser is absorbed at the weld joint or surface (in the case of a lap weld joint) of the material being welding. Laser melted material flows to create the weld joint. In most cases, the molten metal is covered with a shield gas such as nitrogen, argon or helium.
Key parameters for laser sheet metal welding are the laser type (CO2 or Nd:YAG are the most common), average power, continuous wave (CW) or pulsed, pulse rate, pulse length (duration), focused beam diameter and welding speed.
The optimum focused beam size for a given weld and joint design is most often achieved by varying the focal length of the foc
using lens, which in turn varies the power density delivered to the weld joint. Having the correct power density is key to the quality of the resulting weld and stability of the process. If the power density is too great, material from the weld joint will be vaporized or expelled, creating a very poor weld. If the power density is too low, the weld will lack penetration. Welding speed is also adjusted to effect penetration, heat input to the material and/or bead size.
Joint designs for laser welding
Laser welding is applied to joint designs similar to electron beam welding, micro-TIG welding and other high energy density welding processes. Where possible, joints are designed to enhance the absorption of the laser beam directing the beam into the joint. Examples from the figure below include the modified corner joint and edge joint. Good joint fitup and the degree to which the fitup is maintained during welding are key to laser welding. For additional information on this subject, download the “Laser Welding” application note.
Typical systems
Laser welding is used with sheet, plate, tubing and a wide range of formed 3D parts. Typical elements of a laser sheet metal welding system are:
· Laser source: CW and pulsed CO2 and Nd:YAG lasers are all used for laser welding. In many cases, the best choice depends upon the type and thickness of the material(s) being welded, required weld penetration, joint design and anticipated fitup and required welding speed (cycle time).
· Beam delivery: The laser beam is delivered from the laser source to the focusing lens using mirrors (CO2 or Nd:YAG lasers) or through an optical fiber (Nd:YAG only).
· Assist gas delivery: Controlling the atmosphere surrounding the molten and heated metal during the welding process is key to consistency of the process.
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Fixturing: Welding fixturing is required to maintain good joint fitup during welding. In some cases, fixturing is design to provide additional heat sinking or insulation to influence the cooling rate of the weld.
For more information, email applications@prima-na.com