Deep penetration (or keyhole) laser welding is a line-of-sight, single-sided, non-contact joining process. It is characterised by its high focused energy density, which is capable of producing high aspect ratio welds (narrow weld width: large weld depth) in many metallic materials. It can be performed at atmospheric pressure, although inert gas shielding is required for more reactive materials. Furthermore, laser welding is of a relatively low heat input, especially when compared with arc welding processes.
Laser beams can be focused in to submillimetre-sized diameter spots, enabling power densities in the range 103 - 107 W/mm2 to be applied to the joint. These power densities are sufficient to form a 'keyhole' weld below the laser beam impingement point. Efficient absorption of the laser beam by this keyhole allows low heat-input welds to be produced. High productivity can come from the fast processing speeds that can be used in thinner materials, or the fact that just a single pass is needed to make a deep penetration weld in thicker materials. These productivity advantages combined with the automated nature of laser welding, can be used in reliable, repeatable, autonomous welding operations.
As heat inputs are ordinarily an order of magnitude lower than arc welding processes, deep penetration laser welding is also attractive when welding components requiring minimal thermal distortion, or materials favouring low heat input.
Laser welding is a versatile fusion welding process, which has found a number of applications in industry; from welding of car bodies and aircraft fuselage panels to the welding of shipbuilding structures.
The process can be used to weld a variety of materials including, carbon steels, stainless steels, titanium, aluminium and nickel alloys. The industrial uptake of laser welding is driven by requirements such as high volume production, high quality welds and/or low weld distortion.
TWI has considerable experience in the successful development and qualification of laser welding procedures for a variety of different applications, across numerous industry sectors.