Micro-jet cooling gases for low alloy steel welding

Purpose: of that paper was analysing main gases used in micro-jet cooling after welding. The main reason of it was to 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. Design/methodology/approach: During research varied gases were testes as micro-jet parameters. Further 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 (in that case kind of gas and gas pressure). 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. 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. 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.