Laser beam welding
From Wikipedia, the free encyclopedia
Laser beam welding (LBW) is a welding technique used to join multiple pieces of metal through the use of a laser. The beam provides a concentrated heat source, allowing for narrow, deep welds and high welding rates. The process is frequently used in high volume applications, such as in the automotive industry.
Contents |
[edit] Operation
Like electron beam welding, laser beam welding has high power density (on the order of 1 MW/cm²), resulting in small heat-affected zones and high heating and cooling rates. The spot size of the laser can vary between 0.2 mm and 13 mm, though only smaller sizes are used for welding. The depth of penetration is proportional to the amount of power supplied, but is also dependent on the location of the focal point: penetration is maximized when the focal point is slightly below the surface of the workpiece.
LBW is a versatile process, capable of welding carbon steels, HSLA steels, stainless steel, aluminum, and titanium. Due to high cooling rates, cracking is a concern when welding high-carbon steels. The weld quality is high, similar to that of electron beam welding. The speed of welding is proportional to the amount of power supplied but also depends on the type and thickness of the workpieces. The high power capability of gas lasers make them especially suitable for high volume applications. LBW is particularly dominant in the automotive industry.[1][2]
A derivative of LBW, laser-hybrid welding, combines the laser of LBW with an arc welding method such as gas metal arc welding. This combination allows for greater positioning flexibility, since GMAW supplies molten metal to fill the joint, and due to the use of a laser, increases the welding speed over what is normally possible with GMAW. Weld quality tends to be higher as well, since the potential for undercutting is reduced.[3]
[edit] Equipment
The two types of lasers commonly used in metalworking are solid-state lasers and gas lasers (especially carbon dioxide lasers). The first uses one of several solid media, including synthetic ruby and chromium in aluminum oxide, neodymium in glass (Nd:glass), and the most common type, crystal composed of yttrium, aluminum, and garnet doped with neodymium (Nd:YAG). Gas lasers use mixtures of gases like helium, nitrogen, and carbon dioxide as a medium. Regardless of type, however, when the medium is excited, it emits photons and forms the laser beam.
Solid-state lasers operate at wavelengths on the order of 1 micrometer, much shorter than gas lasers, and as a result require that operators wear special eyewear to prevent cornea damage. Nd:YAG lasers can operate in both pulsed and continuous mode, but the other types are limited to pulsed mode. All use a single crystal shaped as a rod approximately 20 mm in diameter and 200 mm long, and the ends are ground flat. This rod is surrounded by a flash tube containing xenon or krypton. When flashed, a pulse of light lasting about two milliseconds is emitted by the laser. Typical power output for ruby lasers is 10–20 W, while the Nd:YAG laser outputs between 0.04–600 W. To deliver the laser beam to the weld area, fiber optics are usually employed.
Gas lasers use high-voltage, low-current power sources to supply the energy needed to excite the gas mixture used as a lasing medium. These lasers can operate in both continuous and pulsed mode, and the wavelength of the laser beam is 10.6 μm. As there are no waveguides (i.e. glass fiber) at this, a lens and mirror delivery system is used. Power outputs for gas lasers can be much higher than solid-state lasers, reaching 25 kW.[4]
[edit] See also
[edit] References
- Cary, Howard B. and Scott C. Helzer (2005). Modern Welding Technology. Upper Saddle River, New Jersey: Pearson Education. ISBN 0-13-113029-3.
- Weman, Klas (2003). Welding processes handbook. New York: CRC Press LLC. ISBN 0-8493-1773-8.
[edit] Notes
 Metalworking
|
|
|---|---|
| Welding | |
| Arc welding: Shielded metal (MMA) | Gas metal (MIG) | Flux-cored | Submerged | Gas tungsten (TIG) | Plasma | |
| Other processes: Oxyfuel | Resistance | Spot | Forge | Ultrasonic | Electron beam | Laser beam | |
| Equipment: Power supply | Electrode | Filler metal | Shielding gas | Robot | |
| Related: Heat-affected zone | Weldability | Residual stress | Arc eye | Underwater welding | |
|
See also: Brazing | Soldering | Metalworking | Fabrication | Casting | Machining | Metallurgy | Jewelry |
|
