A COMPARISON OF METHODS FOR ESTIMATING THE WELD-METAL COOLING RATE INLASER WELDS

Microstructural transformations in 304 L stainless-steel welds as a fu nction of welding parameters were studied using a high-power continuou s CO2 laser. The experimental results can be represented by the relati on lambda1 = 40 V-1/2 where lambda1 is the primary dendrite spacing in mum and V is the welding speed in mm s-1, for different laser powers and two sample thicknesses. The cooling rates estimated by different m ethods have been found to be in the range 10(2) to 3 x 10(3) K s-1, an d the temperature gradients are in the range 10(2) to 9 X 10(2) K cm-1 . The experimental results are shown to be in very good agreement with recent dendrite-growth models. An analogy is presented between the co oling rate during melt spinning and laser welding.