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.
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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.
The spot size of the laser can vary between 0. 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. Millisecond-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.
In Figures 1 b through Increasing the amount of heat input from The EDS stemless wine glass shape with wider surface bead analysis results, shown in Figures 1 b through d , widths. These results of Nb- and Ti-rich particles verify bases exhibit the partial penetration welds.
In variation of the seam widths as a function of the heat addition, the amount of C and S were determined by CS- input is given in Figure 3. After increasing the heat input to the highest value, Therefore, having optimal weld bead geometry is related to the selection of welding process parameters. As shown seams based on the welding speed.
The tively, were obtained from their calculations where k is cooling rate was calculated according to Wang et al. The Bouse and Mihalisin, and Won et al. Figure 5 shows the relationship between the dendrite arm spacing and the cooling rate. The more extensive liquation of grain boundaries at the highest heat input welding condition Figure 6 d is observed.
Increasing the weld heat input decreases the amount of Fig.
The low heat Fig. Hong et al. The amount of Nb in Laves phase of redistribution. To evaluate the fusion structure and EB welds of Inconel , about Figures 7 a through d show the SEM Vincent, respectively. EDS spectra analysis from the structure Mo, Ti, Si form, and its formation requires a niobium labeled as L in Figure 7 d conformed with the Laves concentration ranging from 10 pct to 30 pct.
Similarly, Ram et al. They reported that the enhanced weld metal cooling rate in GTA pulse current welding PC resulted in a lower Nb concentration Cr Vincent described the Laves morphology as a Low cooling rates in welding structures lead to the coarse dendritic structures, hence, resulting in 0. As a comparison, the compo- sitions of dendrite cores described by previous research- ers[7,8,29—31] also are given in Table IV.
The dendrite core 0.
However, the Nb concentrations in 0. Mo It is shown that these values correspond to the data in 2. In addition, elemental partitioning[29,30,37,38] was used to evaluate the role of the alloying elements for the 3. The parti- Ni tioning behavior of Si previously was reported for Another coef- Major Elements Weight Percent Table VI summarizes the Cr Huseyin Gokcan, Mr. This value of k for Nb is in the range 0. As shown in Table VI, the values of k for pp. Cr, Fe, and Ni calculated in this study are similar to the 2.
Ram, A. Reddy, K. Rao, G. Reddy, and J. Richards and M. Jawwad, M. Strangwood, and C. A, , vol. Hong, J. Park, N. Park, I. Eom, M. Kim, and C. Chen, M. Chaturvedi, and N. In this study, Inconel superalloy with an equaxied 7. Rao, and G. ASTM 9. Masters Thesis, Indian Institute of Technology, Weeter, C. Albright, and W.
The following conclusions can be drawn from this vol. Gobbi, L. Zhang, J. Norris, K. Richter, and J. Sheet, Strip, Foil and Plate, Benyounis, A. Olabi, and M. Pro- both the welding conditions and the characteristics cess. Anawa and A. Optics Laser Technol. Wang, J. Zhang, Y.
Tang, and Z. Bouse and J. Tien and T. Furthermore, the mea- Won, K. Kim, T. Yeo, and K. Pulsed operation produced joints similar to spot welds but with complete penetration. The pulse energy is 1 to Joules.
Pulse time is 1 to 10 milliseconds. Diode lasers Lasers are used for materials that are difficult to weld using other methods, for hard to access areas and for extremely small components. Intert gas shielding is needed for more reactive materials.
Laser Beam Welding Examples Overview Laser Beam Welding Process Video Laser beam welding LBW is a welding process which produces coalescence of materials with the heat obtained from the application of a concentrate coherent light beam impinging upon the surfaces to be joined.
The focused laser beam has the highest energy concentration of any known source of energy. The laser beam is a source of electromagnetic energy or light that can be pro jetted without diverging and can be concentrated to a precise spot. The beam is coherent and of a single frequency. Gases can emit coherent radiation when contained in an optical resonant cavity. Gas lasers can be operated continuously but originally only at low levels of power.
Later developments allowed the gases in the laser to be cooled so that it could be operated continuously at higher power outputs.
The gas lasers are pumped by high radio frequency generators which raise the gas atoms to sufficiently high energy level to cause lasing. Currently, watt carbon dioxide laser systems are in use. Higher powered systems are also being used for experimental and developmental work.
A 6-kw laser is being used for automotive welding applications and a kw laser has been built for research purposes.
There are other types of lasers; however, the continuous carbon dioxide laser now available with watts to 10 kw of power seems the most promising for metalworking applications. The coherent light emitted by the laser can be focused and reflected in the same way as a light beam. The focused spot size is controlled by a choice of lenses and the distance from it to the base metal. The spot can be made as small as 0. A sharply focused spot is used for welding and for cutting.
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.