P. I. Petrov, Institute of Electronics, Sofia, Bulgaria
This paper reports result from study weldability of low alloyed steels 18MND5 by CO2 laser beam welding. The laser beam power P and the welding speed V were varied systematically between 9 to 32 kW and 1 m/min to 5 m/min, respectively. The observed weld depth penetration h is up to 10 mm and the width of weld seams is between 0.8 and 1.25 mm. As the welding speed increases, the size of weld seam decreases. The optimum welding parameters give the higher joining efficiency, that is defined as Vh/P [mm2/kJ]. The influence of technological processing conditions on the defects related to the heat and mass transport characteristics of the welding seam formation are investigated too. There were made investigations of structural changes of metal in welds and heat affected zones to determine influence of welding thermal cycle (microstructural analysis and microhardness testing of the welds). Defect structures are quantified by comparison with an existing European standard for electron and laser beam welding, EN ISO 13919-1. To qualify the mechanical properties of the welds un-notched static bend test, hardness and standard Charpy-V type test specimens are used.
Summary: In this study are investigated the influence of technological processing conditions on the microstructure and defects related to the heat and mass transport characteristics of the welding seam formation during laser beam welding of low alloy steels.
