Journal of Welding and Joining

The Korean Welding and Joining Society (대한용접접합학회)
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Characteristics of $CO_2$ or Nd:YAG Laser Welded 600MPa Grade TRIP Steel

600MPa급 TRIP강의 $CO_2$ 및 Nd:YAG 레이저 용접부의 특성

  • Han, Tae-Kyo (Dept. of Material Science and Engineering, Pusan National University) ;
  • Kim, Seung-Jun (Dept. of Material Science and Engineering, Pusan National University) ;
  • Lee, Bong-Keun (Dept. of Material Science and Engineering, Pusan National University) ;
  • Kim, Dae-Up (Hyundai Mobis Technical Institute) ;
  • Kang, Chung-Yun (Dept. of Material Science and Engineering, Pusan National University)
  • 한태교 (부산대학교 공과대학 재료공학과) ;
  • 김성준 (부산대학교 공과대학 재료공학과) ;
  • 이봉근 (부산대학교 공과대학 재료공학과) ;
  • 김대업 (현대 모비스 기술연구소) ;
  • 강정윤 (부산대학교 공과대학 재료공학과)
  • Published : 2006.02.01
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Abstract

The characteristics of $CO_2$ or Nd:YAG laser welded 600MPa ade TRIP steel was investigated. He or Ar gas was used as a shield gas in case of $CO_2$ laser welding, but the shield gas was not used in case of Nd:YAG laser welding. Bead on plate welding was performed with various welding conditions. Defects in the joints of both welding type occurred at 1.8m/min but were not observed over the welding speed of 2.1m/min in case of Nd:YAG laser welding. However, porosity occurred in $CO_2$ laser welding and the tendency of decreasing with the increase of welding speed. The hardness was the highest at heat affected zone near fusion zone as well as at the fusion zone and decreased on approaching the base metal. In a perpendicular tensile test to the weld line, all specimens that have been welded at optimum conditions were fractured at the base metal, and the tensile properties showed the rather higher than those of raw material. In a parallel tensile test, the strength of the joints was higher than that of the base metal. Elongation was found to be lower than that of the raw material. Forming height by Erichsen test and elongation were deeply related with the ratio of base metal/weld metal and the maximum hardness of the weld metal. Also porosity induced to decrease the strength and the elongation. The maximum formability was recorded at approximately 80% as compared with that of the raw material with the optimum condition.

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References

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