Thermomechanical and Metallurgical Study of Laser-Welded AISI 1018 Steel

Non-conventional welding processes such as laser welding are being widely used by several industries. The great advantages they provide such as high welding speeds, lower thermal affectation and reduced discontinuities in the fusion zone allow its application in different materials. On the other hand, mild-/low-carbon steels such as AISI 1018 are being used by the automotive industry to manufacture different components. However, the properties of these materials are influenced by heat inputs. The softening of the heat-affected zones is the most important problem. Therefore, the aim of this study was to weld 12 coupons by laser beam of AISI 1018 steel of 8 and 16 mm thickness to analyze the mechanical and microstructural properties. The formation of a softening zone in heat-affected zone was determined. The softening zone caused cracking in this area during tensile tests. The cause of cracking in this zone was determined by phase quantification. Tensile and microhardness tests were performed to determine the mechanical properties of the welding joints. Microhardness increased in fusion zone and decreased in heat-affected zone. Tensile tests showed ductile fracture in heat-affected zone of the welding joints. The experimental results were verified with simulations showing a reasonable agreement.