The Effect of Process Parameters on the Lifetime of Copper Electrodes used in Spot Welding of Interstitial Free Steel Sheets

  • H. R. M. Costa Centro Federal de Educação Tecnológica Celso Suckow da Fonseca, Graduate Program in Mechanical Engineering and Materials Tecnology, Rio de Janeiro, Brazil
  • J. S. Dias Centro Federal de Educação Tecnológica Celso Suckow da Fonseca, Graduate Program in Mechanical Engineering and Materials Tecnology, Rio de Janeiro, Brazil
  • R. A. A. Aguiar Centro Federal de Educação Tecnológica Celso Suckow da Fonseca, Graduate Program in Mechanical Engineering and Materials Tecnology, Rio de Janeiro, Brazil
  • R. A. A. Lima Centro Federal de Educação Tecnológica Celso Suckow da Fonseca, Graduate Program in Mechanical Engineering and Materials Tecnology, Rio de Janeiro, Brazil
  • D. M. Lopes Centro Federal de Educação Tecnológica Celso Suckow da Fonseca, Graduate Program in Mechanical Engineering and Materials Tecnology, Rio de Janeiro, Brazil
Keywords: electrode lifetime, microhardness, spot welding, nugget, Scanning Electon Microscopy (SEM)

Abstract

The purpose of this work is to evaluate the electrode wear behaviour and the distribution of hardness in a joint made by the resistance spot welding process. The lifetime of electrodes was evaluated by examination of the electrode caps after more than 2000 tests with acceptable welds. A microstructural evaluation by optical microscopy (OM) and scanning electron microscopy (SEM) was carried out. The microstructure of the welded joint is primarily composed of ferrite grains. The microhardness testing results indicated a significant increase in hardness in the weld nugget, caused by the formation of martensite in the fusion zone. The hardness results showed lower values in all regions at the end of the useful lifetime of the electrode. The methodology used for selection of welding  parameters  has highlighted an optimal combination of 200 kgf electrode force and 9-cycle (cy) welding time, to increase the lifetime of the electrode and to achieve more weld points. Still, the cover electrode tends to form brass (Zn + Cu) on the indentation obtained by spot welding, subsequently reducing the electrode life. The results indicate the importance of combining and optimizing the welding parameters in order to reduce the wear of the electrode used for resistance spot welding.

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Published
2016-12-15
How to Cite
Issue
Vol 27 (2016)
Section
Articles

Papers accepted for publication become the copyrighted property of the Annals of "Dunarea de Jos" University of Galati, Fascicle XII, Welding Equipment and Technology. No part of the publication may be reproduced or transmitted in any form, or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, except in limited quantities for the non-commercial purposes of scientific or educational advancement, without permission in writing from the Editorial Board.