ABSTRACT
	This contribution deals with laser welding of thin steel sheets. As tested materials the low carbon steels of various thicknesses were used ( steel 11 321 - thickness 0,28 mm, Kohal IZ - thickness 0,58 mm and steel 11 305 - thickness 0,7 mm ). The research was carried out on the equipment of type ELA 001A with the laser beam output to 1000 W. For the protection against oxidation of molten weld metal the CO2 protecting atmosphere was applicated. 
	For selected materials the laser welding parameters were optimized. Obtained properties of welded joints were evaluated by mechanical tests - tensile test and microhardness test. The structure of welded joints was investigated by metalographical analysis. 
	Obtained results showed that by welding parameters optimization it is possible to create the high quality welded joints with convenient mechanical properties on used equipment. At given source output ( to 1,0 kW ) it is possible to carry out the single - layer welds for material thickness to 0,5 mm. At higher thicknesses it is more favourable to carry out these welds as double sided. The microhardness measurements confirmed that on the contrary to classical welding the maximum hardness values are in the weld metal at laser welding. The hardness increase is minimal and depends on carbon content and welding parameters. Width of heat affected zone was in the range 0,4 - 1,0 mm at all welded materials. This width increases with the grouth of beam output and with decreasion of welding speed. Metalographical analysis confirmed the formation of favourable structure of weld metal and heat affected zone from the point of view of grains size and type of structural components.