Dissimilar resistance spot welding of AISI 1010 carbon steel and AZ31B magnesium alloy
Frederico Vieira Cintra Karklin Tavares1; Guilherme Augusto Ferreira de Macêdo1; Paulo Vitor dos Santos Esteves1; Soraia Sandra Pires1; Thais Roberta Campos1; Leonel Dimas de Abreu1; Pedro Paiva Brito1
1 Pontifical Catholic University of Minas Gerais
doi:10.20906/CPS/COB-2015-2128
Resumo
Weight reduction in automotive components can be achieved by the application of light metals, such as magnesium alloys. In turn, the incorporation of such new materials in the existing steel structures demands research and development of joining manufacturing processes. Currently, the most widely used joining process in the automotive industry is resistance spot welding, in which both a limited amount of fusion and plastic deformation take place at the interface to produce a metallurgical bond between the materials. In the present contribution, dissimilar overlap joints of AISI 1010 carbon steel and AZ31B magnesium alloy were produced by resistance spot welding and the resulting joints were analyzed as a function of the welding conditions. Material thickness in both cases was set to 1 mm and the welding experiments were carried out using a conventional spot welder operating with a 8.5 kA welding current. Characterization of the weld microstructure was performed by analyzing the transverse cross section of the joints by conventional optical microscopy and the mechanical properties of the weld nuggets was evaluated by Vickers microhardness. The shear strength of the welded joints was also determined by applying conventional tensile testing. It was possible to observe that, owing to differences in electric and thermal conductivity between both metals, welding with symmetrical (same diameter) electrodes led to excessive melting of steel, overheating of magnesium and puncturing of the AZ31B side of the joint. In order to counter this problem, larger diameter electrodes were employed at the steel side of the joint, reducing current density and improving heat extraction from the weld nugget.
Palavras-chave: Resistance Spot Welding; AZ31B magnesium alloy; AISI 1010 carbon steel; Dissimilar