Fall 2008 (contents):
1. Anatomy of Laser Pulse
2. Hybrid Laser/GMAW Welding - Mixing it up!
3. All that glitters is GOLD
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Anatomy of a Laser Pulse for Welding
Laser welding is finding growing acceptance in field of manufacturing as price of lasers have decreased and capabilities have increased. Laser welding is unique since it offers non-contact autogenous welding process that is not affected by the electrical conductivity or magnetic properties of the materials being welded. Lasers can be used in pulsed or CW (Continuous Wave) mode. In pulsed mode, laser welds are similar to resistance spot welding and in CW mode they are similar to arc welding processes. While CW mode is common for larger structural welds and competes with arc welding processes, pulsed welding is common for welds in smaller components such as pacemakers, microwave enclosures, batteries, and sensors. Lasers can be used in pulsed mode to make seam welds where overlapping pulses are able to produce a hermetic seal.
The laser pulse has many features that need to be understood to fully appreciate and capitalize on the benefits of laser welding. This paper will discuss all aspects of the laser pulse including initial coupling, weld fusion, and cooling. Combination of these features can be effectively used to control weld penetration, weld size, welding mode (conduction vs. keyhole), residual stress, and related defects such as porosity and cracks.
To download the full article, please visit the Publications link on at www.welding-consultant.com
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Hybrid Laser/GMAW Welding - Mixing it up!
Both Laser and GMAW (Gas Metal Arc Welding or MIG welding) have unique capabilities that make them ideally suited for special applications. Laser welding has the capability to produce deep and narrow welds at high speed and with low thermal input. However, they are not capable of bridging big gaps between the parts being welded. Au contraire, GMAW produces a broader and shallower weld with higher heat input but is able to tailor the weld microstructure with choice of filler wire and is able to bridge wider gaps.
Combination of Laser and GMAW is all the rage in large scale ship building world where positive attributes of both processes - good gap bridging capability, high welding speed, and reduced distortion - are required to produce the desired weld. Hybrid Laser/GMAW welding combines both process simultaneously at the weld. Hybrid welding requires a GMAW power supply and a high power continuous wave (CW) laser source, of the order of 5 kW or more; can be CO2, YAG, or fiber laser. However, there are costs associated with having two welding sources along with synchronization and automation for joint tracking. Give the level of complications, the process will find niche applications where the additional expenditures are justifiable.
There might be other process combinations that might work out as well. There is already a published report of combining Electron Beam welding with Brazing. Maybe hybrids are the future for welding too, and not just for automobiles!
(Source: Various articles printed in the Welding Journal)
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All that glitters is GOLD
Gold was perhaps the first metal discovered by humans; probably they came across these shiny rocks in river beds where most of the early gold was discovered. Panning for gold was made famous by the California gold rush of 1849. Gold became part of every human culture; its brilliance, luster, malleability, and resistance to tarnish made it ideal for jewelry and other ornaments. There is also evidence of "cold welding" of gold to form artefacts; possibly the first evidence of mankinds use of welding technology. Gold can be easily cold welded since it is soft and the surface is free of contaminants including oxides; cold welding is a form of solid state bonding except at room temperature.
Due to limited supplies, gold has commanded great value and led to many wars and conquests since ancient times. Gold was first used as currency around 700 B.C. by Lydian merchants who finally figured out that bartering for everything was getting too complicated. Gold has been used as currency or equivalent ever since. Gold finds many uses in industrial applications including gold wire bonding, gold plating, and gold-based braze alloys. Even though other conductive metals such as Platinum, Silver, and Palladium have carved out their own niche, Gold has been able to maintain its luster.
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