The process is frequently used in high volume and precision requiring applications using automation, as in the automotive and aeronautics industries.
Like electron-beam welding (EBW), laser beam welding has high power density (on the order of 1 MW/cm2) resulting in small heat-affected zones and high heating and cooling rates.
The depth of penetration is proportional to the amount of power supplied, but is also dependent on the location of the focal point: penetration is maximized when the focal point is slightly below the surface of the workpiece.
Due to high cooling rates, cracking is a concern when welding high-carbon steels.
The speed of welding is proportional to the amount of power supplied but also depends on the type and thickness of the workpieces.
This combination allows for greater positioning flexibility, since GMAW supplies molten metal to fill the joint, and due to the use of a laser, increases the welding speed over what is normally possible with GMAW.
[9] In 2016 the RepRap project, which historically worked on fused filament fabrication, expanded to development of open source laser welding systems.
[10] Such systems have been fully characterized and can be used in a wide scale of applications while reducing conventional manufacturing costs.
Solid-state lasers operate at wavelengths on the order of 1 micrometer, much shorter than gas lasers used for welding, and as a result require that operators wear special eyewear or use special screens to prevent retina damage.
Disk shaped crystals are growing in popularity in the industry, and flashlamps are giving way to diodes due to their high efficiency.
Fiber optic cable absorbs and is destroyed by this wavelength, so a rigid lens and mirror delivery system is used.
Modern laser beam welding machines can be grouped into two types.
[12] Pulsed-laser welding also has some disadvantages such as causing hot cracking in aluminum alloys.
Due to the complexity of the pulsed laser process, it is necessary to employ a procedure that involves a development cycle.
A methodology combining some of the published models involves:[13][14][15] Not all radiant energy is absorbed and turned into heat for welding.
Some of the radiant energy is absorbed in the plasma created by vaporizing and then subsequently ionizing the gas.
[12] Rosenthal point source assumption leaves an infinitely high temperature discontinuity which is addressed by assuming a Gaussian distribution instead.
[12] A Gaussian energy distribution can be applied by multiplying the power density by a function like this:[14]
Using a temperature distribution instead of a point source assumption allows for easier calculation of temperature-dependent material properties such as absorptivity.
On the irradiated surface, when a keyhole is formed, Fresnel reflection (the almost complete absorption of the beam energy due to multiple reflection within the keyhole cavity) occurs and can be modeled by
, where ε is a function of dielectric constant, electric conductivity, and laser frequency.
Which mode is in operation depends on whether the power density is sufficiently high enough to cause evaporation.
=viscosity, β=thermal expansion coefficient, g=gravity, and F is the volume fraction of fluid in a simulation grid cell.
In order to determine the boundary temperature at the laser impingement surface, you would apply an equation like this.
,[15] where kn=the thermal conductivity normal to the surface impinged on by the laser, h=convective heat transfer coefficient for air, σ is the Stefan–Boltzmann constant for radiation, and ε is the emissivity of the material being welded on, q is laser beam heat flux.
Unlike CW (Continuous Wave) laser welding which involves one moving thermal cycle, pulsed laser involves repetitively impinging on the same spot, thus creating multiple overlapping thermal cycles.
Next, you would apply this boundary condition and solve for Fourier's 2nd Law to obtain the internal temperature distribution.
Results can be validated by specific experimental observations or trends from generic experiments.
[9] The physics of pulsed laser can be very complex and therefore, some simplifying assumptions need to be made to either speed up calculation or compensate for a lack of materials properties.
The temperature-dependence of material properties such as specific heat are ignored to minimize computing time.