Temporal evolution of weld pool geometry during multikilowatt conduction mode laser spot welding of steels is examined by conducting over eighty carefully planned experiments and concomitant analysis of the data by numerical simulation of heat transfer and fluid flow. The variables investigated are the concentration of sulfur in steel, laser power, power density and irradiation time. The results show that the mere presence of sulfur is not a guarantee of high weld metal aspect ratio. To achieve a beneficial aspect ratio is steels containing sulfur, processing variables must be controlled carefully so that convective heat transfer in the weld pool is important. Only when convective heat transfer is important, i.e., at high Peclet numbers, concentration of sulfur affects both the temporal evolution and the final shape and size of the weld pool. At a given laser power and concentration of sulfur, power density is an important factor in controlling the temporal evolution of weld pool geometry. In the first few seconds of laser-material interaction, the temperature profiles, fluid flow, and the shape and size of the weld pool change significantly. Heating of the workpiece continues with time much after the weld pool geometry is essentially fully developed. Our current understanding of heat transfer and fluid flow in welding can serve as a basis for improved understanding of the temporal evolution of weld metal shape and size for high-power conduction-mode welding of steels with different sulfur contents.
|Original language||English (US)|
|Journal||Welding Journal (Miami, Fla)|
|State||Published - Mar 1 1996|
All Science Journal Classification (ASJC) codes
- Mechanics of Materials
- Mechanical Engineering
- Metals and Alloys