Types of lasers include gas, liquid and solid. 1. Gas lasers excite the electrons in gases, such as helium, neon, carbon dioxide and nitrogen. 2. In this article you will learn about Laser Beam Welding equipment, principle, working, advantages and disadvantages with its application. A Laser is a device that produces a concentrated coherent light beam by mature laser technology and has been a mainstay of macro laser welding since.
|Language:||English, Spanish, German|
|Distribution:||Free* [*Sign up for free]|
PDF | One of the newest procedures successfully used in machine building Laser Welding claims the laser beam to focus greater energy in a. Laser Beam Welding. The term laser is the abbreviation for,,Light Amplification by Stimulated Emission of Radia- tion”. The laser is the further. Welding (LBW) is a fusion joining process that produces coalescence of materials with welded. In the LBM process, the laser beam is directed by flat optical.
The large spot is used for heat treating. The laser offers a source of concentrated energy for welding; however, there are only a few lasers in actual production use today.
The high-powered laser is extremely expensive. Laser welding technology is still in its infancy so there will be improvements and the cost of equipment will be reduced. Recent use of fiber optic techniques to carry the laser beam to the point of welding may greatly expand the use of lasers in metal-working. Laser Welding vs. Arc Welding Laser beam welding energy transfer is different than arc welding processes.
In laser welding the absorption of energy by a material is affected by many factors such as the type of laser, the incident power density and the base metal's surface condition. Laser output is not electrical in nature and does not require a flow of electrical current.
This eliminates any effect of magnetism, and does not limit the process to electrically conductive materials. Lasers can interact with any material. It doesn't require a vacuum and it does not produce x-rays. How it Works Pump source provides energy to the medium, exciting the laser such that electrons held with in the atoms are elevated temporarily to higher energy states.
The electrons held in this excited state cannot remain there indefinitely and drop down to a lower energy level. The electron looses the excess energy gained from the pump energy by emitting a photon.
This is called spontaneous emission and the photons produced by this method are the seed for laser generation. Photons emitted by spontaneous emission eventually strike other electrons in the higher energy states. The incoming photon "knocks" the electron from the excited state to a lower energy level creating another photon.
These photons are coherent meaning they are in phase, of the same wavelength, and traveling the same direction. A process called stimulated emission. Photons are emitted in all directions, however some travel along the laser medium to strike the resonator mirrors to be reflected back through the medium.
The resonator mirrors define the preferential amplification direction for stimulated emission. In order for the amplification to occur there must be a greater percentage of atoms in the excited state than the lower energy levels. This population inversion of more atoms in the excited state leads to the conditions required for laser generation. The focus spot of the laser is targeted on the workpiece surface which will be welded.
At the surface the concentration of light energy converts into thermal energy heat. The heat causes the surface of the material to melt, which progresses through the surface by a process called surface conductivity. The beam energy level is maintained below the vaporization temperature of the workpiece material. The ideal thickness of the materials to be welded is 20mm. The energy is a laser is concentrated, an advantage when working with materials that have high thermal conductivity.
History Einstein first postulated the quantum-mechanical fundamentals of lasers at the beginning of the 20th century.
Since this time the applications for laser beam sources have evolved. The process gas, Argon-CO2, increases the welding speed and in the case of a diode laser, will support the transition of heat conductivity welding to a deep welding, i. Adding active gas changes the direction of the metal flow within a weld pool and produces narrower, high-quality weld.
CO2 Lasers are used to weld polymers. The Edison Welding Institute is using through-transmission lasers in the nm range to readily form welded joints.
Using silicon carbides embedded in the surfaces of the polymer, the laser is capable of melting the material leaving a near invisible joint line Welding With Lasers Laser Beam Welding Demonstration The laser can be compared to solar light beam for welding.
It can be used in air. The laser beam can be focused and directed by special optical lenses and mirrors. It can operate at considerable distance from the workpiece. When using the laser beam for welding, the electromagnetic radiation impinges on the surface of the base metal with such a concentration of energy that the temperature of the surface is melted vapor and melts the metal below.
One of the original questions concerning the use of the laser was the possibility of reflectivity of the metal so that the beam would be reflected rather than heat the base metal. It was found, however, that once the metal is raised to its melting temperature, the surface conditions have little or no effect. The distance from the optical cavity to the base metal has little effect on the laser. The laser beam is coherent and it diverges very little.
It can be focused to the proper spot size at the work with the same amount of energy available, whether it is close or far away. With laser welding, the molten metal takes on a radial configuration similar to convectional arc welding.
However, when the power density rises above a certain threshold level, keyholing occurs, as with plasma arc welding. Keyholing provides for extremely deep penetration. 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. The first type uses one of several solid media, including synthetic ruby chromium in aluminum oxide , neodymium in glass Nd:glass , and the most common type, neodymium in yttrium aluminum garnet Nd:YAG. Gas lasers use mixtures of gases such as helium , nitrogen , and carbon dioxide CO2 laser as a medium.
Regardless of type, however, when the medium is excited, it emits photons and forms the laser beam. Nd:YAG lasers can operate in both pulsed and continuous mode, but the other types are limited to pulsed mode. 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. To deliver the laser beam to the weld area, fiber optics are usually employed. Gas laser[ edit ] 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 CO2 gas laser beam is Fiber optic cable absorbs and is destroyed by this wavelength, so a rigid lens and mirror delivery system is used. Laser beam delivery[ edit ] 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 scanner , 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. Thermal modeling of pulsed-laser welding[ edit ] Pulsed-laser welding has advantages over continuous wave CW laser welding.
Some of these advantages are lower porosity and less spatter.