Laser are now being used in the automotive industry to produce seam or stitch welds, as alternatives to conventional resistance spot welding, which are used extensively for attaching auto body panels to sub-assemblies. The advantages of laser welding over resistance spot welding result from the smallness of the laser spot size, the large penetration depth of the weld into the material and the requirement that only single-sided access to the work piece is necessary. Further, the equipment used to carry out the welds can be easily adapted to new vehicle program changes, unlike that used for resistance spot welding. Potential benefits realized by the application of laser welding includes reduced flange widths, increased structural strength and high speed automated processing. Traditionally CO2 lasers have been used for auto body applications. Recent advances have been made with Nd:YAG lasers, which are now capable of producing beam powers of more than 2 kW or more through a fiber optic cable. This is particularly useful for robotic operations, where it is necessary to manipulate the laser beam about a stationary part. laser are also used in the manufacture of tailored blanks, where suitably prepared sheet metal, including differing thickness and material combinations are butt welded together prior to being pressed into the finished shape. This results in considerable cost and weight savings and increases structural rigidity.
Although at present steel is the main material used in the vehicle manufacturing industry, the use of lighter materials, such as Al, Mg and Ti will in the future become of increasing importance, in order to reduce weight. This, however will require the ability to make satisfactory joins between these materials and steel. Aluminium alloys are invariable less weldable than automotive sheet steels due to its high diffusivity and the presence of passive oxide layers, which have a significantly higher melting temperature than the base alloy and often a poor electrical conductivity. Laser welding of Al alloys is also problematic due to its high thermal conductivity and high reflectivity of the laser light, but progress is being made using Nd:YAG lasers.
There are number of different laser welding systems available. CO2 and Nd:YAG lasers are already in use in industry. Low power Nd:YAG lasers are used in the electronics industry Rapid improvements in technology means that diode lasers of sufficiently high power and power density for the production of good deep penetration welds are now available.
Laser Welding Process
When welding with laser beam, it is necessary to differentiate between two forms of welding: heat conduction welding and deep penetration welding. Conduction welding occurs at lower power densities or higher welding speeds. The absorbed energy is transferred by heat conduction into the volume of the work piece and produced a broad, shallow pool of molten material.
In deep penetration welding, the laser beam is focused to a small spot and the power can exceed 5*10^6 Watts/m^2. Sufficient energy is input to vaporizer the material and a vapour-filled channel is formed through which the laser energy penetrates deep into the work piece. Deep seams are produced which increase the absorption efficiency and make greater use of laser beam. The energy required to melt and vaporize the material depends on the physical properties of the material, the wavelength of the laser light and the properties of the surface of the work piece. These welds typically have deep, narrow weld profiles, a small HAZ and little distortion. As a result of the better energy utilization and large depth to width ratio of weld is attainable with deep penetration welding, this is the prime method of welding used in industry with the conventional laser sources.
Although at present steel is the main material used in the vehicle manufacturing industry, the use of lighter materials, such as Al, Mg and Ti will in the future become of increasing importance, in order to reduce weight. This, however will require the ability to make satisfactory joins between these materials and steel. Aluminium alloys are invariable less weldable than automotive sheet steels due to its high diffusivity and the presence of passive oxide layers, which have a significantly higher melting temperature than the base alloy and often a poor electrical conductivity. Laser welding of Al alloys is also problematic due to its high thermal conductivity and high reflectivity of the laser light, but progress is being made using Nd:YAG lasers.
There are number of different laser welding systems available. CO2 and Nd:YAG lasers are already in use in industry. Low power Nd:YAG lasers are used in the electronics industry Rapid improvements in technology means that diode lasers of sufficiently high power and power density for the production of good deep penetration welds are now available.
Laser Welding Process
When welding with laser beam, it is necessary to differentiate between two forms of welding: heat conduction welding and deep penetration welding. Conduction welding occurs at lower power densities or higher welding speeds. The absorbed energy is transferred by heat conduction into the volume of the work piece and produced a broad, shallow pool of molten material.
In deep penetration welding, the laser beam is focused to a small spot and the power can exceed 5*10^6 Watts/m^2. Sufficient energy is input to vaporizer the material and a vapour-filled channel is formed through which the laser energy penetrates deep into the work piece. Deep seams are produced which increase the absorption efficiency and make greater use of laser beam. The energy required to melt and vaporize the material depends on the physical properties of the material, the wavelength of the laser light and the properties of the surface of the work piece. These welds typically have deep, narrow weld profiles, a small HAZ and little distortion. As a result of the better energy utilization and large depth to width ratio of weld is attainable with deep penetration welding, this is the prime method of welding used in industry with the conventional laser sources.
Very Interesting, Good job and thanks for sharing such a good information..
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