Material, component design and bond stress are a few factors that determine the joining method. Laser welding is often the ideal solution for joining metals that require relatively fast processing speed, low heat input, low heat affected zone (HAZ) and minimal distortion. There are four common laser welding processes.
Metal Welding Techniques
Hybrid welding combines laser welding with other welding processes, typically MIG (metal inert gas) welding.
Conduction welding is similar to spot welding but allows the laser beam to move after the melt pool is produced. This method can use either modulated or pulsed lasers to create a seam weld that can be structurally hermetic. Weld penetration depths are typically less than 2 mm.
Laser spot welding is a non-contact process which uses a laser to create a single weld spot to join metals together. When the laser is focused, the light is absorbed by the substrate and melts the metal. The liquefied metal flows, solidifies and creates a small spot weld. This entire process occurs within milliseconds and may be repeated depending on material thickness and required bond strength.
Deep penetration welding requires extremely high power densities to create a laser weld. The focused laser beam both melts and vaporizes the substrate. The vapor pressure displaces the molten metal and creates a deep and narrow “keyhole”. As the laser beam moves, the molten metal flows around the keyhole and solidifies in a deep and narrow seam along its path.
Types of Metals
||Gold & Silver
||Brass & Copper
AMB Adjustable Mode Beam Lasers
|Fiber lasers are now widely used for welding of a very wide range of thicker metals. The near infrared 1070 nm wavelength has definite advantages over the incumbent CO2 laser technology due to the lower reflectivity of metals at this wavelength. This is particularly true for high reflectivity metals such as aluminum and copper where high power fiber lasers are used to weld up to 15 mm, these thicknesses have not previously been welded with other lasers. Using high average power lasers and relatively small spot sizes to weld thicker metals requires a technique known as keyhole welding. The keyhole produced by the laser very effectively traps the laser beam inside the joint leading to deep penetration and quality welds at high speeds. The high brightness of fiber lasers allows longer focal length lenses with more depth of focus to be used for keyhole welding. This means less sensitivity to focus position which greatly improves the ease with which high quality welds can be achieved. Other examples of fiber laser welding thick metals include full penetration of transmission components and deep penetration welding of thick section steels for ships and pipelines.
AMB Adjustable Mode Beam Lasers
Laser welding is often the ideal solution for joining metals that require relatively fast processing speed, low heat input, low heat affected zone (HAZ) and minimal distortion. The good beam quality of kW class fiber lasers coupled with medium to high average powers offer a wide range of laser welding mechanisms from narrow high aspect ratio keyhole welding to shallow wide conduction welding. Low to medium power CW fiber lasers (up to 1 kW) are used for welding a very wide range of thin sheet materials up to 1.5 mm thick at very high speed.
Low to medium power CW fiber lasers can be focused to small spots with galvanometers and long focal length lenses allowing remote laser welding. There are many advantages to using longer focal length lenses with a larger stand off as it increases the work area significantly. For example, remote welding stations equipped with fiber lasers can weld complete door panels. When combined with robots, lap or seam welds can be made over a complete auto body. Other examples also include hermetic welding of battery packs and pressure seals.
IPG’s unique modulating Quasi-CW fiber lasers offer pulsed laser welding capabilities with high peak and low average power for low heat input applications. Fiber delivery allows easy integration into conventional direct optics weld heads or galvanometer heads. Typical spot welding applications may employ either direct optics for medical device welding such as heart pacemakers. Galvanometer based beam delivery systems may be used for high speed spot welding of cellphone and tablet casings, razor blades or under the hood automotive components.