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 mm.