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 Steel
In the case of steel, we must bear in mind that the carbon content
contributes significantly to the results of welding. The carbon
content of the material should not exceed 0.2 %.
One significant advantage of laser welding in steel is the high
speed and the relatively small warming zone, so even components
that are susceptible to warping can be laser welded. The speed of
welding is governed by the laser power, the combination of materials,
the geometry, and the type of laser. For example, different wavelengths
in the laser mean different degrees of absorption. In principle,
CO2 and Nd:YAG lasers are suitable for deep penetration
welding in steel. Heat conductivity welding can also be carried
out with diode lasers, however (see the kitchen
sink example).
Typical welding speeds for welds with a depth of 1, 3, 6 mm are
in the region of 14, 6 and 2 meters per minute, respectively (stainless
steel, CO2 laser, 3.5 kW) Too high a concentration of
carbon may call for hybrid applications, if welds are to be made
free of pores and cracks. For example, the material may be preheated
inductively to achieve good welding results in the combination of
the materials C38 / 25Mn5. Automobile drive-shafts with this combination
are today manufactured on an industrial scale. Other hybrid applications
utilize the intensity of plasma arcs to increase the effectiveness
of the application. This can have the disadvantage of a significantly
broader warming zone.
As an example, this illustration shows a low-warp weld on parts
of an automobile gearbox.
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