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The Characteristics of Continuous Waveshape Control for the Suppression of Defects in the Fiber Laser Welding of Pure Titanium Sheet (I) - The Effect According to Applying Slope Up & Down -

순 티타늄 박판의 파이버 레이저 용접시 결함 억제를 위한 연속의 출력 파형제어 특성(I) - 슬롭 업 & 다운 적용에 따른 영향 -

  • Kim, Jong-Do (Division of Marine Engineering, Korea Maritime and Ocean univ.) ;
  • Kim, Ji-Sung (Graduate School, Korea Maritime and Ocean Univ.)
  • 김종도 (한국해양대 해사대학 기관관공학부) ;
  • 김지성 (한국해양대 대학원 기관공학과)
  • Received : 2016.11.11
  • Accepted : 2016.12.12
  • Published : 2016.12.30

Abstract

Laser welding has superior characteristic such as low distortion, high welding speed, easy automation and real time control. But it is easy to occur weld defects such as porosity, crater, humping bead in the area of welding start and end. These weld defects can be suppressed by applying the wave shape control. In this study CW fiber laser was used for welding of $0.5mm^t$ pure titanium. Penetration properties were evaluated with the time of slope up and down. After then the bead shape was observed, and the maximum depth and the area of crater were measured. The bead shape of welding start area changed to be sharp with increase of slope up time and non-weld area of welding start increased. The crater and humping bead were suppressed with slope down time. The cooling rate of crater area was understood through measure of the hardness. Also, The distribution tendency of alloying elements was observed by EPMA and EDS. When wave shape control didn't applied to weld, the hardness of end weld increased due to rapid cooling rate and the hardness of rear part in the crater was higher than that of fore part. On the other hand, when the wave shape control was used for end weld, the increase of hardness in the end weld couldn't be found due to gradual cooling rate.

Keywords

References

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