2016 №06 (12) DOI of Article
2016 №06 (14)

Automatic Welding 2016 #06
Avtomaticheskaya Svarka (Automatic Welding), #6, 2016, pp. 82-87

Peculiarities of structure of Cu–Cu, Ni–Cu and Steel–Cu joints produced by overlap friction stir welding method

G.M. Grigorenko, M.A. Poleshchuk, L.I. Adeeva, A.Yu. Tunik, E.V. Zelenin And S.N. Stepanyuk
E.O. Paton Electric Welding Institute, NASU 11 Kazimir Malevich Str., 03680, Kiev, Ukraine. E-mail: office@paton.kiev.ua

The work is dedicuted to investigation of overlap friction stir welded joints of sheet billets of homogeneous (Cu–Cu) and dissimilar metals with unlimited (Ni–Cu) and limited solubility (Cu–St.3, Kh18N10–Cu) of the components in solid state. The FSW process is performed due to plastic deformation of metal being heated to recrystallization temperature without melting. The leading role in this process plays mechanical stirring of metals in plastic state. The role of diffusion processes is insignificant. The quality joints are received at optimum welding modes. Plasticization and dynamic recrystallization in FSW of Cu–Cu plates promote for grain refinement (5–30 mm) in the stir zone and develop dense weld microstructure, comparable with the base metal. The weld microhardness reaches 80–107 % of the base metal microhardness. FSW of Cu and Ni resulted in the quality welded joint with mutual penetration of one metal into another at up to 3 mm depth. Interdiffusion of Cu and Ni along the grain boundaries takes place at up to 20 μm depth with formation of solid solution interlayers of these metals. Examination of Cu–St.3 and Kh18N10–Cu joints demonstrated significant grain refining in the recrystallization zone as well as in the HAZ. St.3 and Kh18N10 steels plung in copper at 1000 and 2000 μm depth in form of bands and strips. Large amount of Fe-based inclusions, embedded in form of separate bands and particles, is noted in the stir zone. Thus, applying the welds at specific distance from each other allows producing quality solid welding-up of upper thinner plate to massive lower plate (as in deposition) with overlapping of recrystallization zones at minimum heating and distortion of the parts. The carried investigations allow recommending this method for reconstruction of initial dimensions and development of protective layer (Ni, Kh18N10 steel) on copper plates of CCM mold. 11 Ref., 1 Table, 8 Figures.

Keywords: friction stir welding, lap joint, mechanical stirring of metals, diffusion, solubility in solid phase, microstructure, X-ray spectrum microanalysis, chemical composition, microhardness

Received:                14.04.16
Published:               19.07.16


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