Diffusion in Electrodes Used for Resistance Spot Welding of Galvannealed Steel

Abstract:

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A study was carried out on Zr-Cr bearing copper electrodes used for resistance spot welding of galvannealed steel strips. One electrode exhibited a series of well-defined layers in which Zn diffused to form β- and γ-brasses; an external layer containing iron was detected in this electrode. Another electrode that exhibited a high degree of damage did not exhibited continuous Zn-diffusion layers in all places, moreover, the Fe-containing layer was either removed, or had it grown to a high extent in some places; the occurrence of Cu-rich particles embedded within the Fe containing layer was observed. Multiple cracks were observed within the γ brass layer in both electrodes. The difference in the observed behaviour of the electrodes can be attributed to a difference in the characteristics of the galvannealed coating of the strips, as the first electrode was used to weld strips in which the layer corresponding to the  phase was well developed, whereas the second electrode was used to weld strips with only an incipient layer. It can be concluded that growth of the  phase changes the thermophysical properties of the zinc coating, affecting the temperature profile during spot welding.

Info:

Periodical:

Defect and Diffusion Forum (Volumes 297-301)

Edited by:

Andreas Öchsner, Graeme E. Murch, Ali Shokuhfar and João M.P.Q. Delgado

Pages:

300-307

DOI:

10.4028/www.scientific.net/DDF.297-301.300

Citation:

M. de la Garza et al., "Diffusion in Electrodes Used for Resistance Spot Welding of Galvannealed Steel", Defect and Diffusion Forum, Vols. 297-301, pp. 300-307, 2010

Online since:

April 2010

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Price:

$35.00

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