Journal of Welding and Joining

The Korean Welding and Joining Society (대한용접접합학회)
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A Comparative Study of Weldable Current Range on AC and MFDC Resistance Spot Welding for 440 MPa Grade Steel Sheet

440 MPa급 도금강판의 저항 점 용접 시 AC 및 MFDC전원에 따른 가용전류구간 비교 연구

  • Ji, Changwook (Advanced Manufacturing Process R &d Group, KITECH) ;
  • Park, Chansu (School of Materials Science and Engineering, Pusan National University) ;
  • Kim, Chiho (School of Materials Science and Engineering, Pusan National University) ;
  • Cho, Yongjoon (Materials Manufacturing Engineering R&D Team, Hyundai Motor Company) ;
  • Oh, Dongjin (Department of Naval Architecture and Ocean Engineering, Pusan National University) ;
  • Kim, Myung-Hyun (Department of Naval Architecture and Ocean Engineering, Pusan National University) ;
  • Kim, Yang-Do (School of Materials Science and Engineering, Pusan National University) ;
  • Park, Yeong-Do (Department of Advanced Materials Engineering, Dong-Eui University)
  • 지창욱 (한국생산기술연구원 울산지역본부 첨단제조공정그룹) ;
  • 박찬수 (부산대학교 재료공학과) ;
  • 김치호 (부산대학교 재료공학과) ;
  • 조용준 (현대자동차 재료생기개발팀) ;
  • 오동진 (부산대학교 조선해양공학과) ;
  • 김명현 (부산대학교 조선해양공학과) ;
  • 김양도 (부산대학교 재료공학과) ;
  • 박영도 (동의대학교 신소재공학과)
  • Received : 2016.04.04
  • Accepted : 2016.07.04
  • Published : 2017.02.28
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Abstract

This paper presents a comparative study of the AC and MFDC resistance spot welding process with consideration of sheet thickness. The previous studies have confirmed that there is difference in the optimum welding current and expulsion current with AC and MFDC. The aim of this study was revealing the effect of sheet thickness on weldable current range and expulsion behavior for AC and MFDC welding processes. The optimum welding current of AC was lower (1.6 kA) than MFDC welding process in 0.8 mm sheet thickness. Early nugget growth being caused by the peak current of AC developed weld interface deformation, which resulted in suppressing the growth of corona bond and occurrence of low current expulsion. The resistance spot welding for thicker sheet (1.4 mm) required lower current of 0.6 kA for the expulsion on the MFDC welding process. The growth of contact diameter (size of corona bond) and button diameter was linear up to the expulsion current with MFDC welding process. Therefore, more attention is required when the AC and MFDC resistance spot welding process is applied for different thickness of steel sheet combination for automotive application.

Keywords

References

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