ASSESSMENT OF PROPERTIES AND CORROSION RESISTENCE OF GALVANIZED STEEL WELDED WITH LASER BEAM

The paper describes the influence of laser welding parameters on the structure, mechanical properties and corrosion resistance of 1.2 mm thick galvanized sheets made of DC04 low-carbon steel. The tested test joints were made with a disc laser on a robotic laser welding station (TruLaser Robot 5120) with a TruDisk 12002 laser. In the laser welding process, butt welded joints were made without additional material with variable welding speed (linear welding energy from 30 to 45 J/mm). Welded joints were subjected to non-destructive tests (visual, magnetic-particle and radiographic tests), destructive tests (tensile strength, bend test, hardness test) and tests for corrosion resistance (corrosion potential test, using a three-electrode measuring system and a potentiostat-ATLAS 0531 EU galvanostat) by Atlas-Sollich and corrosion test in a salt chamber). The conducted tests have shown that it is possible to make connections that meet the criteria of ISO 15614-11. All made joints, regardless of the applied linear energy of welding, are characterized by high strength and plastic properties. It can be noticed that as the linear energy of welding increases, the weld seam and the heat-affected zone of the welded joints become wider. A joint made with higher linear energy has higher hardness and tensile strength than a joint made with lower linear energy. In the static tensile test, rupture occurred in the base material, regardless of the value of the linear energy of welding. In the bending test, regardless of the value of the linear energy of welding, the bending angle of 180 ° was achieved, without tears and scratches, the values of relative elongation ranged from 29% to 42%, which confirms the high plastic properties. A joint made with lower line energy has greater corrosion resistance than a joint made with higher line energy, but much lower than the native material. It can be assumed that during welding a part of the galvanic coating is removed or damaged.