Laser Welding
Laser welding involves application of laser beams on the sets of parts to provide a complete union of the parts sets. Laser welding operates by production of the laser beams that are concentrated on the purposed part joint. The welded material is heated up to the boiling point by the laser beam absorbed. Beyond this point, the metal becomes vapor that can be directed on deposition location. The parts section, in vapor form, fuse together to form uniform crossection once deposited in the joint. A filler rod (of matching material type and properties as the parts sets) is added during welding (Miller, 2014). Lasers are electromagnetic waves produced by the excitation of a given atom at a wavelength of about 1.06 micrometers. The surface of the part to be welded should be absorbent, not a reflective profile that would deviate the waves from the joint to be welded (Miller, 2014).
The Heston’s article focuses on the monitoring of the weld quality. The quality of the laser welds depends on variables like the concentration point of the laser beam, the penetration and the optics of the weld (Heston, 2015). The concentration of the laser beam should be invariant as to inhibit variable shift of the welding pool. This produces a uniform strong joint quality weld unlike shifting the laser beam focus. The depth of the weld determines the extent of bonding between the mating parts (Heston, 2015). High penetrability of the material to be welded usually exhibit deep weld depths translating to stronger welds. The penetration by the beam is subject to the optics of the laser beam, for example, the reflectivity of the welded material on the type of beam employed. Laser beams can be categorized into three depending on the wavelength used, infrared, laser, and ultraviolet rays. During welding, the high temperatures of the section welded produces ultraviolet rays, but is unseen to normal eye.
For better quality laser welds, monitoring of the wavelength of the laser beam before, during and after the welding operation is necessary. Destructive tests are carried on the welded sections to check this quality. The data from the welded section is compared with the allowable wavelength properties to appraise the weld quality. Weld depths and penetration are not easily determined by destructive test. The development of the Inline Coherent Imaging (ICI) increased measurement accuracy of the weld depth and the penetration level (Heston, 2015). It operates by directing the laser beam to the bottom of the keyhole (the pool developed when the fusion temperatures are reached) thereby deducing the depth of the weld and the penetration calculated thereof. The ICI technology has reduced the monitoring costs, negating use of destructive testing to appraise the laser weld quality. Accuracy is increased thereby the company can identify possible factors to manipulate to increase weld quality. Unlike destructive tests, the data produced by the monitoring technology are real time making it possible to adjust the weld factors for better quality.
The article provides a good excerpt on producing and maintaining high quality laser welds. It provided appropriate imagery descriptions of monitoring technology and the methodology employed. The succinct language and descriptive annotations make the article easy to understand, particularly technicians in welding industry. It is a good piece and is recommended for the fabrication sector.
References
Heston, T. (2015). Know laser weld penetration—now. The Fabricator, 23-25.
Miller, C. B. (2014). Laser Welding. US Laser Corp, 27-29.