Investigation of the Laser Welding Process of Brass

Summary and outlook: In our experiment we have measured keyhole length and width for alloy CuZn37 welding with a high-speed camera. According to the ration between length and width, we can quantify the elongation of a keyhole. The bigger a ration is, the more elongated a keyhole is. The high speed video can also confirm with the variation of ratios. It is also interesting to note that keyhole tail and surface wave around a keyhole rim varies with different laser power, welding speed and defocusing combination.

From the welding workpiece point of view, we have analyzed the welding samples from seam surfaces and cross sections. According to the analysis of the initial, middle and end seam surface, we can estimate how much surface waves affect HAZ. Moreover, we can find how much laser penetrates into the smaple with the analysis of top seam width, middle seam width, and root width for full penetration and penetrating depth for partial penetration. We also experimentally confirm the relation between the keyhole elongation and welding seam measurements.

In this thesis, our research into defocusing influences on keyhole dimension and alloy sheet is not complete. There are many other factors which can affect laser welding on CuzN alloy sheet. Shielding gas is one of them that we have not taken into account in this thesis yet. When shielding as is delivered, the pressure of the gas can be applied to balance the closing effects from surface tension pressure especially when the recoil pressure is not big enough to keep a keyhole open in the low welding speed. In addition, variation of a keyhole size is dependent on different percents of Cu and Zn elements in alloys and thickness of alloy sheet. This can also be researched for the future prospect.