Effect of gas atmosphere on the non-metallic inclusions in laser-welded trip steel with Al and Si additions

The present study aims to characterize the weldability of a multiphase, automotive steel containing Al and Si additions from the point of view of its tendency to form non-metallic inclusions.Laser welding tests of 2-mm-thick sheets were performed using the keyhole-welding mode and a solid-state laser.The tests were carried out in air and with the use of an argon atmosphere.The distribution, type and chemical composition of the non-metallic inclusions formed in the base metal and fusion zones were analysed.The effect of applying the protective gas on the type and amount of non-metallic inclusions was determined using light and scanning electron microscopy.The chemical composition of the identified particles was assessed using the EDS method.It was found that a protective gas has a beneficial effect on reducing the non-metallic inclusions, but only to a limited extent.The boundary between the complex oxides and the pure aluminium oxides was determined to be 2-3 μm.