A.K. Dasgupta

Physics of zinc vaporization and plasma absorption during CO2 laser welding

A number of mathematical models have been developed earlier for single-material laser welding processes considering one-, two-, and three-dimensional heat and mass transfers. However, modeling of laser welding of materials with multiple compositions has been a difficult problem. This paper addresses a specific case of this problem where CO2 laser welding of zinc-coated steel, commonly used in automobile body manufacturing, is mathematically modeled. The physics of a low boiling point material, zinc, is combined with a single-material (steel) welding model, considering multiple physical phenomena such as keyhole formation, capillary and thermocapillary forces, recoil and vapor pressures, etc. The physics of laser beam–plasma interaction is modeled to understand the effect on the quality of laser processing. Also, an adaptive meshing scheme is incorporated in the model for improving the overall computational efficiency. The model, whose results are found to be in close agreement with the experimental observ...

Effect of processing parameters on zero-gap laser welds made on multi-coated steel

We are presenting a study on zero-gap CO2 laser lap welding of multi-coated steel using alloying additives. Steel coated with multiple elements like zinc, nickel, aluminum, epoxy resin etc., being considered for use in fuel tanks for newer alternative fuels, was experimented and the effects of welding parameters on properties like porosity, hardness, bead quality etc. was investigated. An L-9 Taguchi experiment design was used to incorporate multiple multi-level processing factors. The results indicated optimal operating window for the material, which can be further optimized for real-time production.We are presenting a study on zero-gap CO2 laser lap welding of multi-coated steel using alloying additives. Steel coated with multiple elements like zinc, nickel, aluminum, epoxy resin etc., being considered for use in fuel tanks for newer alternative fuels, was experimented and the effects of welding parameters on properties like porosity, hardness, bead quality etc. was investigated. An L-9 Taguchi experiment design was used to incorporate multiple multi-level processing factors. The results indicated optimal operating window for the material, which can be further optimized for real-time production.

New high power in-line, industrial CO2 laser beam instrumentation for real-time monitoring

Beam profiling of high power (1 kW and higher) CO2 lasers has been limited to either antiquated acrylic mode burns or intrusive beam profiling devices. Neither of these devices can show the operator real-time laser beam spatial profiles while processing materials; in most cases, the process needs to be discontinued for the analyzer to be used. II-VI and Spiricon have developed a new in-line, continuous high power CO2 laser beam profiling device that can be used while processing materials, and does not interfere with the process. Using the Active-X® features of the Spiricon Laser Beam Diagnostic software, critical beam parameters can be sent to external process control programs for additional monitoring and even feedback control.Beam profiling of high power (1 kW and higher) CO2 lasers has been limited to either antiquated acrylic mode burns or intrusive beam profiling devices. Neither of these devices can show the operator real-time laser beam spatial profiles while processing materials; in most cases, the process needs to be discontinued for the analyzer to be used. II-VI and Spiricon have developed a new in-line, continuous high power CO2 laser beam profiling device that can be used while processing materials, and does not interfere with the process. Using the Active-X® features of the Spiricon Laser Beam Diagnostic software, critical beam parameters can be sent to external process control programs for additional monitoring and even feedback control.