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Laser welding is growing in importance within metal fabrication industries. Welding using carbon dioxide (CO2) and YAG lasers is increasingly widespread for example. Diode lasers and fiber lasers are also finding more and more applications. High-power CO2 lasers (6-12 kW) are often used to weld car body structures, transmission components, heat exchangers and tailored blanks.
For many years, low-power YAG lasers (100-500 W) have been used for welding of small components, for example medical instruments and electronic packages. Nd:YAG lasers with high powers (in the kW range) are often delivered via fiber optics and manipulated via robots. One significant application area is welding of car components, e.g. roof seems.
The laser beam is focused into a small spot, providing the intensity to melt and evaporate the material. The welding is basically carried out in two ways. In conduction mode welding the heat is transferred from the surface into the material via thermal conduction. This is typical for low-power Nd:YAG laser welding with relatively shallow welds.
High-power laser welding is characterized by keyhole welding. The laser energy then melts and evaporates the metal. The pressure of the vapor displaces the molten metal so that a cavity is formed - the keyhole. The keyhole supports the transfer of the laser energy into the metal and guides the laser beam deep into the material. Keyhole welding thus allows very deep and narrow welds to be obtained and is therefore also called deep penetration welding.
Welding gases must fulfil several demands - shielding of the weld pool and the heat affected area, protection of the optics against fumes and spatter, root protection and 'plasma control' during CO2 laser welding. The plasma is a cloud of ionized metal vapor and gases that can be formed above the keyhole. This cloud affects laser radiation and thus interrupts the welding process. This effect depends on the type of laser and the power applied, for which reason different laser welding gases are used
LINDE’s LASERLINE ® program offers laser users a complete package including appropriate gases, customized gas supply and comprehensive applications support.
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