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A Study of Weldability for Pure Titanium by Nd:YAG Laser(III) - Weld Properties of Edge Welding -

순티타늄판의 Nd:YAG 레이저 용접성에 관한 연구(III) - 에지 용접 특성 -

  • Kim, Jong-Do (Division of Marine System Engineering, Korea Maritime University) ;
  • Kil, Byung-Lea (Division of Marine System Engineering, Korea Maritime University) ;
  • Kwak, Myung-Sub (Industrial Application R&D Institute, DSME. Co., LTD.) ;
  • Song, Moo-Keun (Graduate School, Korea Maritime University)
  • 김종도 (한국해양대학교 기관시스템공학부) ;
  • 길병래 (한국해양대학교 기관시스템공학부) ;
  • 곽명섭 (대우조선해양(주) 산업기술연구소) ;
  • 송무근 (한국해양대학교 대학원)
  • Published : 2009.12.31

Abstract

Titanium and titanium alloy can be reproduced immediately even if oxide films($TiO_2$) break apart in sea water. Therefore, since titanium demonstrates large specific strength and outstanding resistance to stress corrosion cracking, crevice corrosion, pitting and microbiologically influenced corrosion in sea water environment, it has been widely applied to heat exchanger for ships. In particular, with excellent elongation, pure titanium may be deemed as optimal material for production of heat exchanger plate which is used with wrinkles formed for efficient heat exchange. Conventional plate type heat exchanger prevented leakage of liquid through insertion of gasket between plates and mechanical tightening by bolts and nuts, but in high temperature and high pressure environment, gasket deterioration and leakage occur, so heat exchanger for LPG re-liquefaction device etc do not use gasket but weld heat exchanger plate for use. On the other hand, since welded plate cannot be separated, it is important to obtain high quality reliable welds. In addition, for better workability and production performance, lasers that can obtain weldment with large aspect ratio and demonstrate fast welding speed even in atmospheric condition not in vacuum condition are used in producing products. So far, 1st report and 2nd report compared and analyzed embrittlement degrees by bead colors of weldment through quantitative analysis of oxygen and nitrogen and measurement of hardness as fundamental experiment for the evaluation of titanium laser welding, and evaluated the welding performance and mechanical properties of butt welding. This study welded specimens in various conditions by using laser and GTA welding machine to apply edge welding to heat exchanger, and evaluated the mechanical strength through tensile stress test. As a result of tensile test, laser weldment demonstrated tensile strength 4 times higher than GTA welds, and porosity could be controlled by increasing and decreasing slope of laser power at overlap area.

Keywords

References

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