By: Paul A. Blomquist, Carl Chretien, Applied Thermal Sciences (ATS); Stan Ferree, ESAB Welding and Cutting Products; Dale Anderson and Brian Marx, Concurrent Technologies Corporation
Applied Thermal Sciences has been working to develop the equipment and process technology for Hybrid Laser Arc Welding (HLAW), with the goal of improving the productivity and reducing the cost of shipbuilding in the United States. Recently, as part of a project team led by the Navy Metalworking Center, ATS developed procedures and received qualification approval for the HLAW process as applied to high strength steels for primary structural components of naval surface combatant vessels. For these steels, control of weld metal diffusible hydrogen is critical. The addition of the laser to the traditional Gas Metal Arc Welding (GMAW) process results in a higher total melt volume than that of the GMAW process alone, which could affect hydrogen absorption into the weld pool. A literature search revealed no information relating to diffusible hydrogen characteristics of HLAW. For this reason, comparative measurements were made using HLAW, autogenous Laser Beam Welding (LBW) and conventional GMAW, to determine the diffusible hydrogen content. All testing was performed in accordance with AWS A4.3, the standard for evaluation of diffusible hydrogen in weld metal. Additional work was performed to evaluate diffusible hydrogen results in the context of total melt volume versus merely added weight of weld metal. Results show that the HLAW process results in low levels of diffusible hydrogen in the welds and that the addition of the LBW process contributes very little to the diffusible hydrogen in the welds. These results demonstrate that the HLAW process can be applied to hydrogen-sensitive steels, keeping in mind that all typical “low-hydrogen” practices, such as cleanliness of parts, control of environment, etc., are maintained.
The above brief overview was extracted from its original abstract and paper presented at The International Congress on Applications of Lasers & Electro-Optics (ICALEO) in Orlando, FL. To order a copy of the complete proceedings from this conference click here