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Laser Beam Welding




The laser beam is a coherent (single phase) light of a single Wavelength (monochromatic). The laser beam has low beam divergence and high energy content and thus will create heat when it strikes a surface.

Lasers are utilized in metalworking for:
  • Seam tracking and inspection

  • Surface heat treating

  • Welding

  • Cutting (metallic and non-metallic materials)



LASER TYPES


There are two primary types of lasers used in welding and cutting:

Carbon dioxide lasers use a mixture of high purity Carbon Dioxide with Helium and Nitrogen as the Lasing Medium . Here are some of the key characteristics for CO2 lasers:

  • Infrared (10.6 Micrometre s)

  • Beam transmission by mirror only (not Fibre Optic )

  • Cutting lasers are typically from 0.5 to 10 kW

  • Difficulties in cutting/welding reflective materials (e.g., Aluminum or Copper )

  • Can cut non-metallic materials

  • High cutting speed possible


s use a solid bar of Yttrium aluminum Garnet doped with Neodymium as the lasing medium. Here are some of the key charateristics for Nd:YAG lasers:

  • Infrared (1.06 micrometres)

  • Beam transmission by optical fiber possible

  • Available to 2 kW

  • Wavelength absorbed well by metallic materials (including Al and Cu)

  • Not suitable for cutting non-metallic materials

  • Good for fine work, but cutting speeds are generally lower than CO2


Both CO2 and Nd:YAG lasers can operate in either continuous or pulsed operating modes.


LASER BEAM WELDING (LBW)


Nd:YAG lasers are being more commonly utilized in automotive parts manufacturing using Robot ic delivery. CO2 laser welding using a 10 kW system can produce a single pass autogenous weld in ¾” thick stainless steel at 20 ipm (8 mm/s). Systems producing up to 50 kW have been built. Keyhole welding is a method of laser welding in which a high power continuous-wave laser is focused on the metal to be welded, forming a pocket of ionized metallic gas. This vapor absorbs the laser energy more effectively than the solid material and transfers the heat outward radially from the keyhole, forming a molten region surrounding the vapor.As the beam moves across the work-piece the keyhole is filled in with molten material and solidifies to form a weld.


LASER BEAM CUTTING (LBC)


CO2 Lasers are most popular for 2D profile cutting of Steel plates up to ~3/4” thick (1/2” for stainless, 3/8” for aluminum). Approximate CO2 laser cutting speeds for steel of different thicknesses:
  • 350 ipm (0.15 m/s) - 20 gauge (0.95 mm)

  • 100 ipm (0.04 m/s) - 14 in (6.4 mm) thick

  • 35 ipm (0.015 m/s) - 58 in (15.9 mm) thick


Nd:YAG systems are more common on thinner gauge materials using robotic delivery systems.

Assist gases are used to help expel the molten metal, protect the lenses, and in the case of Oxygen on steels—to provide chemical cutting action.


SEE ALSO


  • American Welding Society, Welding Handbook, Volume 2 (8th Ed.)