Parameters of welding with micro-jet cooling

Purpose: of that paper was analysing main welding process with parameters of micro-jet cooling. The main reason of it was investigate possibilities of getting varied amount of acicular ferrite (AF) in WMD (weld metal deposit). High amount of acicular ferrite influences positively impact toughness of weld. For optimal amount of AF it is necessary to determine the parameters (eg. number of clusters, diameter of stream) of the micro-jet.Design/methodology/approach: During research with varied micro-jet parameters the chemical analysis, micrograph tests and Charpy V impact test of the metal weld deposit on pendulum machine were carried out. The Charpy V impact test was prepared according to standard ISO EN 148-1 Metallic materials - Charpy pendulum impact test - Part 1: Test method. Samples for impact testing were prepared according to standard ASTM A370.Findings: Varied amount of acicular ferrite in weld metal deposit (in range 55-75%) in terms of micro-jet cooling parameters (numbers of jet, gas pressure). This high amount of acicular ferrite is unheard in weld metal deposit in another way or other methods of welding like MAG or TIG.Research limitations/implications: That research was made for MIG method (according to PN-EN ISO 4063:2009) only. Another method of welding in this article was not tested. Other methods (for eg. MAG, TIG) have not been tested, but it is suspected that similar phenomena are taking place.Practical implications: Micro-jet cooling it is way to get higher amount of acicular ferrite in weld metal deposit than the usual methods of welding. It is very important because it could be used to steering of weld joint structure and mechanical properties (for example impact toughness).Originality/value: In this research new method of cooling weld joint during welding was used. At the present time use of micro-jet cooling while MIG is in the testing phase and requires an accurate diagnosis.This method is very promising and capable of industrial application, mainly due to the significant improvement of weld quality and reduces costs.