Validation of parameters selection of welding with micro-jet cooling by using method of fundamental solutions

摘要

The aim of the paper was analyzing the main welding process with parameters of micro-jet cooling just after the welding process and subjecting this process to verification based on numerical methods. To accomplish this purpose, it was decided to get a varied amount of acicular ferrite (AF) in WMD (weld metal deposit). The high amount of acicular ferrite influences positively impact toughness of weld. During research with different micro-jet parameters the chemical analysis, micrograph tests and Charpy V impact test of the metal weld deposit on pendulum machine were carried out. Independently, it was decided to check the heat distribution in the weld metal deposit using numerical method. The methods allow checking the heat distribution during the use of a new welding process (with micro-jet cooling). A varied amount of acicular ferrite in weld metal deposit (in the range 55–68%) was obtained only because of the possibility of using micro-jet technology. Main micro-jet cooling parameters depend on the number of the jets, micro-jet gas pressure and diameter of cooling jets. This high amount of acicular ferrite is unheard in weld metal deposit in another way or other methods of welding such as MAG or TIG. Micro-jet cooling is the way to steer the microstructure of weld metal deposit. It is important because consequently it could be used to the steering of weld joint structure and mechanical properties (for example impact toughness). The most effective cooling gas is helium. Welding with micro-jet cooling could be treated as a very promising process with a high industrial application. Also, using the Method of Fundamental Solutions, the influence of the heat flow process in WMD after welding with micro-jet cooling was checked. Controlled influence of the heat flow process in the welded joint will allow for proper selection of micro-jet cooling parameters. The first time the possibilities of an innovative and still developing welding process were verified by the Method of Fundamental Solutions.