Journal of Welding and Joining

The Korean Welding and Joining Society (대한용접접합학회)
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A Study on the Formation Mechanism of Discontinuities in $CO_2$ Laser Fusion Zone of Fe-Co-Ni Sintered Segment and Carbon Steel

Pe-Co-Ni 분말 소결 금속과 탄소강의 이종재료간 레이저 용접부의 결함형성기구 연구

  • 신민효 (한양대학교 신소재공학부) ;
  • 김태웅 (이화다이아몬드공업㈜ 기술연구소) ;
  • 박희동 (이화다이아몬드공업㈜ 기술연구소) ;
  • 이창희 (한양대학교 신소재공학부)
  • Published : 2003.06.01
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Abstract

In this study, the formation mechanism of discontinuities in the laser fusion zone of diamond saw blade was investigated. $CO_2$ laser weldings were conducted along the butt between Fe base sintered tip and carbon steel shank with sets of variable welding parameters. The effect of heat input on irregular humps, outer cavity, inner cavity and bond strengh was evaluated. The optimum heat input to have a proper humps was in the range of 10.4~$17.6kJm_{-1}$. With increasing heat input, both outer and inner cavities were reduced. The outer cavity was caused by insufficient refill of keyhole, while inner cavity was caused by trapping of bubble in molten metal. The bubble came from sintered tip and intensive vaporization at bottom tip of the keyhole. A gas formation and low melting point element vaporization were not occurred during welding. We could not find any relationship between bond strength and amount of discontinuities. Because the fracture were occurred in not only sintered tip but also carbon steel shank due to hardness distributions.

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