Laser beam welding
Encyclopedia
Laser beam welding 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.
(EBW), laser beam welding has high power density (on the order of 1 MW/cm2) resulting in small heat-affected zone
s 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.
A continuous or pulsed laser beam may be used depending upon the application. Milliseconds long pulses are used to weld thin materials such as razor blades while continuous laser systems are employed for deep welds.
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 laser
s make them especially suitable for high volume applications. LBW is particularly dominant in the automotive industry.
Some of the advantages of LBW in comparison to EBW are as follows: the laser beam can be transmitted through air rather than requiring a vacuum, the process is easily automated with robotic machinery, x-rays are not generated, and LBW results in higher quality welds.
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.
, much shorter than gas lasers, and as a result require that operators wear special eyewear or use special screens to prevent retina
damage. Nd:YAG lasers can operate in both pulsed and continuous mode, but the other types are limited to pulsed mode.
The original and still popular solid-state design is 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. Disk shaped crystals are growing in popularity in the industry, and flashlamps are giving way to diodes due to their high efficiency.
Typical power output for ruby lasers is 10–20 W, while the Nd:YAG laser outputs between 0.04–6,000 W. To deliver the laser beam to the weld area, fiber optics are usually employed.
These lasers can operate in both continuous and pulsed mode, and the wavelength of the laser beam is 10.6 μm.
Fiber optic cable absorbs and is destroyed by this wavelength, so a rigid lens and mirror delivery system is used.
Power outputs for gas lasers can be much higher than solid-state lasers, reaching 25 kW
.
s, the gain medium is the optical fiber itself. They are capable of power up to 50 kW and are increasingly being used for robotic industrial welding.
, so that the robotic arm does not need to follow the seam any more. The advantages of remote laser welding are the higher speed and the higher precision of the welding process.
Welding
Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...
technique used to join multiple pieces of metal through the use of a laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
. 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.
Operation
Like electron beam weldingElectron beam welding
Electron beam welding is a fusion welding process in which a beam of high-velocity electrons is applied to the materials being joined. The workpieces melt as the kinetic energy of the electrons is transformed into heat upon impact, and the filler metal, if used, also melts to form part of the weld...
(EBW), laser beam welding has high power density (on the order of 1 MW/cm2) resulting in small heat-affected zone
Heat-affected zone
The heat-affected zone is the area of base material, either a metal or a thermoplastic, which has had its microstructure and properties altered by welding or heat intensive cutting operations. The heat from the welding process and subsequent re-cooling causes this change in the area surrounding...
s 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
Focus (optics)
In geometrical optics, a focus, also called an image point, is the point where light rays originating from a point on the object converge. Although the focus is conceptually a point, physically the focus has a spatial extent, called the blur circle. This non-ideal focusing may be caused by...
: penetration is maximized when the focal point is slightly below the surface of the workpiece.
A continuous or pulsed laser beam may be used depending upon the application. Milliseconds long pulses are used to weld thin materials such as razor blades while continuous laser systems are employed for deep welds.
LBW is a versatile process, capable of welding carbon steels, HSLA steels, stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....
, aluminum, and titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
. 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 laser
Gas laser
A gas laser is a laser in which an electric current is discharged through a gas to produce coherent light. The gas laser was the first continuous-light laser and the first laser to operate "on the principle of converting electrical energy to a laser light output...
s make them especially suitable for high volume applications. LBW is particularly dominant in the automotive industry.
Some of the advantages of LBW in comparison to EBW are as follows: the laser beam can be transmitted through air rather than requiring a vacuum, the process is easily automated with robotic machinery, x-rays are not generated, and LBW results in higher quality welds.
A derivative of LBW, laser-hybrid welding
Laser-hybrid welding
Laser Hybrid welding is a type of welding process that combines the principles of laser beam welding and arc welding.The combination of laser light and an electrical arc into an amalgamated welding process has existed since the 1970s, but has only recently been used in industrial applications...
, combines the laser of LBW with an arc welding method such as gas metal arc welding
Gas metal arc welding
Gas metal arc welding , sometimes referred to by its subtypes metal inert gas welding or metal active gas welding, is a semi-automatic or automatic arc welding process in which a continuous and consumable wire electrode and a shielding gas are fed through a welding gun...
. 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.
Equipment
- The two types of lasers commonly used are solid-state laserSolid-state laserA solid-state laser is a laser that uses a gain medium that is a solid, rather than a liquid such as in dye lasers or a gas as in gas lasers. Semiconductor-based lasers are also in the solid state, but are generally considered as a separate class from solid-state lasers .-Solid-state...
s and gas lasers (especially ruby laserRuby laserA ruby laser is a solid-state laser that uses a synthetic ruby crystal as its gain medium. The first working laser was a ruby laser made by Theodore H. "Ted" Maiman at Hughes Research Laboratories on May 16, 1960....
s and Nd:YAG lasers). - The first type uses one of several solid media, including synthetic ruby and chromiumChromiumChromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
in aluminum oxide, neodymiumNeodymiumNeodymium is a chemical element with the symbol Nd and atomic number 60. It is a soft silvery metal that tarnishes in air. Neodymium was discovered in 1885 by the Austrian chemist Carl Auer von Welsbach. It is present in significant quantities in the ore minerals monazite and bastnäsite...
in glass (Nd:glass), and the most common type, crystal composed of yttriumYttriumYttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and it has often been classified as a "rare earth element". Yttrium is almost always found combined with the lanthanides in rare earth minerals and is...
aluminum garnetGarnetThe garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives. The name "garnet" may come from either the Middle English word gernet meaning 'dark red', or the Latin granatus , possibly a reference to the Punica granatum , a plant with red seeds...
doped with neodymium (Nd:YAG). - Gas lasers use mixtures of gases like heliumHeliumHelium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
, nitrogenNitrogenNitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
, and carbon dioxideCarbon dioxideCarbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
(CO2 laser) as a medium. - Regardless of type, however, when the medium is excited, it emits photons and forms the laser beam.
Solid state laser
Solid-state lasers operate at wavelengths on the order of 1 micrometerMicrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
, much shorter than gas lasers, and as a result require that operators wear special eyewear or use special screens to prevent retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
damage. Nd:YAG lasers can operate in both pulsed and continuous mode, but the other types are limited to pulsed mode.
The original and still popular solid-state design is 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
Xenon
Xenon is a chemical element with the symbol Xe and atomic number 54. The element name is pronounced or . A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
or krypton
Krypton
Krypton is a chemical element with the symbol Kr and atomic number 36. It is a member of Group 18 and Period 4 elements. A colorless, odorless, tasteless noble gas, krypton occurs in trace amounts in the atmosphere, is isolated by fractionally distilling liquified air, and is often used with other...
.
When flashed, a pulse of light lasting about two milliseconds is emitted by the laser. Disk shaped crystals are growing in popularity in the industry, and flashlamps are giving way to diodes due to their high efficiency.
Typical power output for ruby lasers is 10–20 W, while the Nd:YAG laser outputs between 0.04–6,000 W. To deliver the laser beam to the weld area, fiber optics are usually employed.
Gas laser
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.
Fiber optic cable absorbs and is destroyed by this wavelength, so a rigid lens and mirror delivery system is used.
Power outputs for gas lasers can be much higher than solid-state lasers, reaching 25 kW
Kw
kw or KW may refer to:* Kuwait, ISO 3166-1 country code** .kw, the country code top level domain for Kuwait* Kilowatt* Self-ionization of water Kw* Cornish language's ISO 639 code* Kitchener–Waterloo, Ontario, Canada...
.
Fiber laser
In fiber laserFiber laser
A fiber laser or fibre laser is a laser in which the active gain medium is an optical fiber doped with rare-earth elements such as erbium, ytterbium, neodymium, dysprosium, praseodymium, and thulium. They are related to doped fiber amplifiers, which provide light amplification without lasing...
s, the gain medium is the optical fiber itself. They are capable of power up to 50 kW and are increasingly being used for robotic industrial welding.
Laser beam delivery
Modern laser beam welding machines can be grouped into two types. In the traditional type, the laser output is moved to follow the seam. This is usually achieved with a robot. In many modern applications, remote laser beam welding is used. In this method, the laser beam is moved along the seam with the help of a laser scannerLaser scanning
In modern engineering, the term `laser scanning' is used to described two related, but separate meanings. The first, more general, meaning is the controlled deflection of laser beams, visible or invisible...
, so that the robotic arm does not need to follow the seam any more. The advantages of remote laser welding are the higher speed and the higher precision of the welding process.
External links
- Dual beam laser welding; research article from the 2002 Welding Journal
- Weld morphology and thermal modeling in dual-beam laser welding; research article from the 2002 Welding Journal
- Laser welding articles from the Industrial Laser Solutions Magazine
- Laser-beam welding makes aircraft lighter; Fraunhofer SocietyFraunhofer SocietyThe Fraunhofer Society is a German research organization with 60 institutes spread throughout Germany, each focusing on different fields of applied science . It employs around 18,000, mainly scientists and engineers, with an annual research budget of about €1.65 billion...
Material and Beam Technology - IWS, DresdenDresdenDresden is the capital city of the Free State of Saxony in Germany. It is situated in a valley on the River Elbe, near the Czech border. The Dresden conurbation is part of the Saxon Triangle metropolitan area....
, GermanyGermanyGermany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
(1 January 2005) - Laser Welding Further information about laser welding from JK Lasers.