The phenomena of gas shielding in fiber laser welding of low alloy steel was studied by a literature review. Analysis of different shielding gas feeding methods has led to following conclusions:
1. The size of the shielding area depends mainly of welding speed and thickness of the material in keyhole welding.
2. On many occasions one nozzle provides sufficient shielding. An optimal nozzle inclination angle providing the longest shielding area is 15 ° with high density gases. In order to obtain deeper welds a double nozzle with an inner jet provides better penetration and shielding for the weld.
3. By enlarging nozzle diameter and increasing flow rate of the gas a better coverage is achieved. This is especially beneficial with high density gases such as argon.
However for thicker materials the use of multiple nozzles is recommendable to secure the coverage and decrease the gas consumption.
4. Environmental shielding is not a good option for welding of low alloy steels because of unreasonably high manufacturing costs of the setup. It does provide the most secure shielding which, however, is not necessary.
5. A suitable gas feeding method for laser welding can be obtained by designing shielding gas feeding case-specifically. This will lead to better welding results.
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