Journal of Welding and Joining

The Korean Welding and Joining Society (대한용접접합학회)
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Microstructure and Mechanical Properties of Gas Metal Arc Brazed Joint of DP Steel with Cu-Si Filler Metal

Cu-Si 삽입금속을 이용한 DP강의 MIG 아크 브레이징 접합부의 미세조직과 기계적 성질

  • Cho, Wook-Je (Hyundai materials, business environment team) ;
  • Yoon, Tae-Jin (Institute of materials technology, Pusan National University) ;
  • Kwak, Sung-Yun (Dept. of Material Science and Engineering, Pusan National University) ;
  • Lee, Jae-Hyeong (Dept. of Material Science and Engineering, Pusan National University) ;
  • Kang, Chung-Yun (Dept. of Material Science and Engineering, Pusan National University)
  • 조욱제 (현대머티리얼 환경사업팀) ;
  • 윤태진 (부산대학교 소재기술연구소) ;
  • 곽승윤 (부산대학교 재료공학과) ;
  • 이재형 (부산대학교 재료공학과) ;
  • 강정윤 (부산대학교 재료공학과)
  • Received : 2016.09.27
  • Accepted : 2016.10.25
  • Published : 2016.10.31
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Abstract

In this study, Microstructure and tensile properties in arc brazed joints of 1000MPa grade DP steel using Cu-Si insert metal were investigated. The fusion zone was composed of Cu phase which solidified a little Fe and Si. The former phase formed due to dilute the edge of base material by arc, although Fe was not solid solution in Cu at the room temperature. Cu3Si particles formed by crystallization at $1100^{\circ}C$ during faster cooling. After the tensile shear test, there are no differences between the brazed joint efficiencies. The maximum joint efficient was about 37% compared to strength of base metal. It is better than that of arc brazed joint of DP steel using Cu-Sn filler metal. Fracture position of all brazing conditions was in the fusion zone. Crack initiation occurred at three junction point which was a stress singularity point of upper sheet, lower sheet and the fusion zone. And then crack propagated across the fusion zone. The reason why the fracture occurred at fusion zone was that the hardness of fusion zone was lower than that of base material and heat affected zone. The correlation among maximum load and hardness of fusion zone and EST at fractured position was $R^2=0.9338$. Therefore, this means that hardness and EST can have great impact on maximum load.

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References

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