Abstract
It is thought that porosity in a laser spot weld metal is due to a remnant of gas produced by closing of the top surface mouth of the keyhole generated during welding, and that the pulse shape influences the porosity formation tendency. Therefore, the formation of porosity was examined in welds made with rectangular pulse shapes. Cobalt-chromium alloy and CP titanium were used for this study. Spot welds were formed by irradiation with single pulsed YAG laser under various parameters of output power, pulse width and defocused distance. Then, the penetration geometry and porosity were observed and measured. Porosity was more easily formed in spot welds of cobalt-chromium alloy than CP titanium. It was confirmed that if the penetration depth was 1.5mm or less in the CP titanium, the formation of weld metals without porosity was possible. However, it was difficult to obtain a deeply penetrated weld metal without porosity in the cobalt-chromium alloy.
