A high power diode laser was used to perform butt welds, without any filler metal, preheating or postweld treatment, on AISI 1045 steel plate. The influence of the direction of the shielding gas flow on the characteristics of the welds was investigated. For this purpose the shielding gas (Ar) was supplied to the joint by two different ways: coaxial, and transverse to the laser beam. Due to the high carbon content in the AISI 1045 steel and the fast cooling rates produced by the welding process, bainite and martensite microstructures were formed at the heat affected zone of the weld bead. Nevertheless, there is no presence of internal cracks. Moreover, the weld beads have not developed other kind of weld flaws such as centerline cracking or lamelar tearing.

As result of the different gas configurations investigated, the welds have distinct dimensional and microstructural characteristics. The use of the shielding gas flow in transverse configuration leads to the formation of microstructures less liable to promote the formation of cracks and the welds exhibited a larger resistant area, thus better-quality welds are expected with this transverse configuration.

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