Effect of laser welding on microstructure and mechanical behaviour of dual phase 600 steel sheets

• Published in: Heliyon 2021-12, Vol.7 (12), p.e08601-e08601, Article e08601
• Main Authors: Mansur, Vinicius Machado, Mansur, Raquel Alvim de Figueiredo, Carvalho, Sheila Medeiros de, Siqueira, Rafael Humberto Mota de, Lima, Milton Sergio Fernandes de
• Format: Article
• Language: English
• Subjects: Dual-phase steels; Formability; Laser beam welding
• ISSN: 2405-8440; 2405-8440
• DOI: 10.1016/j.heliyon.2021.e08601

Dual Phase steels are one of the most used advanced high-strength materials in the industry, due to its combination of a ductile ferritic matrix and disperse hard martensite islands, which provide outstanding mechanical properties for components to be cold stamped. This work investigated fiber laser welding applicability in Dual Phase 600 1.6 mm thick steel sheets, evaluating potential welding impacts on properties of the material for industrial applications. A first set of bead-on-plate welds was generated to define best parameters for subsequent tests. A second set was prepared, consisting of butt joints welded in the optimized condition. Weld microstructure was characterized as 100% martensitic at fusion zone (FZ), with growing fractions of ferrite at Heat Affected Zone (HAZ) as one moves away from fusion line. Hardness is around 60% higher at FZ than at BM, being maximum at supercritical HAZ due to its highly refined microstructure and HAZ softening was not observed. Tensile and Erichsen cupping tests presented similar strength results between welded and non-welded specimens, with slight ductility reduction. Finally, numeric simulations based on Finite Element Analysis were carried out to estimate temperature evolution, phase proportions, residual stresses and distortion levels, achieving excellent agreement with experimental results. •The laser welds are defect-free and presented a major fraction of martensite microconstituent in both fusion and heat-affected zone.•In contrast to what is reported in the literature, the heat-affected zone did not show a decrease in hardness due to the tempering.•The results of the uniaxial tensile tests and Erichsen drawability show that welded sheets are applicable for cold stamping. Laser beam welding; Dual-phase steels; Formability.