Laser-hybrid welding
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2008-04-22T05:55:27Z
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/* Laser Hybrid process */
'''Laser Hybrid welding''' is a type of welding process that combines the principles of [[laser beam welding]] and [[arc welding]].
== Introduction ==
The combination of laser light and an electrical arc into an amalgamated welding process has been
known since the 1970's, but has only recently been used in industrial applications. There are three main types of hybrid welding process, depending on the arc used; TIG, Plasma arc or MIG augmented laser welding. While TIG augmented laser welding was the first to be researched, MIG is the first to go into industry and is commonly known as hybrid laser welding.
Whereas in the early days laser sources still had to
prove their suitability for industrial use, today they are standard equipment in many manufacturing enterprises.
The combination of laser welding with another weld process is called a "hybrid welding
process". This means that a laser beam and an electrical arc act simultaneously in one welding
zone, influencing and supporting each other.
== Laser ==
Laser welding not only requires high laser power but also a high quality beam to
obtain the desired "deep-weld effect". The resulting higher quality of beam can be
exploited either to obtain a smaller focus diameter or a larger focal distance.
A variety of laser types are used for this process, in particular [[Nd:YAG]] where
the laser light can be transmitted via a water cooled glass fiber. The beam is projected onto the workpiece by collimating and focusing [[optics]]. [[Carbon dioxide laser]] can also be used where the beam is transmitted via lens or mirrors.
== Laser Hybrid process ==
For welding metallic objects, the laser beam is focused to obtain
intensities of more than 1 MW/cm<sup>2</sup>. When the laser beam hits the surface of the
material, this spot is heated up to vaporization temperature, and a vapor cavity is
formed in the weld metal due to the escaping metal vapor. This is known as a keyhole. The extraordinary feature
of the weld seam is its high depth-to-width ratio. The energy-flow density of the freely
burning arc is slightly more than 100 kW/cm<sup>2</sup>. Unlike a dual process where two separate weld processes act in succession, hybrid welding may be viewed as a combination of both weld processes acting simultaneously in one and the same process zone. Depending on the kind of arc or laser process used, and depending on the process parameters, the two systems will influence each other in different ways.
The combination of the laser process and the arc process results in an
increase in both weld penetration depth and welding speed (as compared to each
process alone). The metal vapor escaping from the vapor cavity acts upon the arc
plasma. Absorption of the laser radiation in the processing plasma remains
negligible. Depending on the ratio of the two power inputs, the character of the
overall process may be mainly determined either by the laser or by the arc.
Absorption of the laser radiation is substantially influenced by the temperature of the
workpiece surface. Before the laser welding process can start, the initial reflectance
must be overcome, especially on [[aluminum]] surfaces. This can be achieved by
preheating the material. In the hybrid process, the arc heats the metal, helping the laser beam to couple in. After the vaporisation temperature has
been reached, the vapor cavity is formed, and nearly all radiation energy can be put
into the workpiece. The energy required for this is thus determined by the
temperature dependent absorption and by the amount of energy lost by conduction
into the rest of the workpiece. In Laser Hybrid welding, using MIG, vaporisation takes place not
only from the surface of the workpiece but also from the filler wire, so that more metal
vapor is available to facilitate the absorption of the laser radiation.
{{Metalworking - Welding}}
[[Category:Welding]]
[[Category:Laser applications]].