Laser beam welding

Laser Beam Welding is a technique in manufacturing whereby two or more pieces of material (usually metal) are joined by together through use of a laser beam.

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 is 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:

• Gas lasers (CO2 type)
• Solid state lasers (Nd:YAG type)

CO2 lasers use a mixture of high purity carbon dioxide with helium and nitrogen as the lasing medium. Here are some of the key charateristics for CO2 lasers:

• Infrared (10.6 micro-metres)
• Beam transmission by mirror only (not fibre optic)
• Cutting lasers are typically from 0.5 to 2 kw
• Difficulties in cutting/welding reflective materials (e.g., Aluminum or copper)
• Can cut non-metallic materials
• High cutting speed possible

Nd:YAG lasers 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 micro-metres)
• Beam transmission by optical fiber possible
• Available to 2 kw
• Wavelength absorbed well by metallic materials (including Al & 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 robotic delivery. CO2 laser welding using a 10kW system can produce a single pass autogenous weld in ¾” thick stainless steel at ~20ipm. Systems producing up to 25kW have been built. Melt-in or keyhole modes can be utilized, with or without additional filler metal (autogenous welding).

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 steel:

• 350ipm – 20 guage;
• 100ipm – ¼” thick;
• 35ipm – 5/8” 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.

Suggested Additional Reading

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