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김철희(Cheolhee Kim),강민정(Minjung Kang),안영남(Young-nam Ahn) 한국레이저가공학회 2011 한국레이저가공학회지 Vol.14 No.1
Manufacturing technology platform for automotive and mobile industries has been constructed since 2009, for the platform technology project funded by ministry of knowledge and economics. Technology platform in laser welding has also been developed for automotive steel sheets with a strength up to 1GPa. Laser welding technology platform will provide welding characteristics for various laser sources, steel plates and welding conditions. This article shortly explains outline of laser welding technology platform and partially introduces the developed laser welding data base.
강민정,김철희,김준기,김동철,김종훈,Kang, Minjung,Kim, Cheolhee,Kim, Junki,Kim, Dongcheol,Kim, Jonghoon 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.4
The use of light-weight Al alloys in the automotive industry is increasing to meet requirements for fuel efficiency and emission reduction. Joining Al alloy to the conventional steel sheet is also very important issue with the increased use of Al alloy, and several joining processes have been introduced to enhance joining strength between dissimilar metals. This paper deals with a galvanic corrosion in the dissimilar metal joining. Salt spray tests up to 2000 hours were conducted on a self-piercing rivet, spot welded, adhesive bonded and weld-bonded joints, and cross-sections and tensile shear strength according the salt spray duration were analyzed at every 500-hour. Self-piercing rivet joint had relative low initial strength but the joint strength did not change regardless of the salt spray duration. The strength of other joints (spot welded, adhesive bonded and weld-bonded joints) decreased with the increase of salt spray duration and the corrosion behaviour of each joint was discussed.
김정학(Junghak Kim),김철희(Cheolhee Kim),김정한(Jeonghan Kim),이세헌(Sehun Rhee) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
Welding process monitoring is advantageous for maintaining weld quality and numerous sensing techniques have been developed for laser welding. Coaxial image monitoring enables direct monitoring of the weld pool shape and keyhole behavior, but requires the complex optical system and the image processing technique. In this study, we coaxially acquired the weld pool images during laser lap welding by using the camera and special illumination. The welding characteristics ? pool width and length, keyhole shape, etc ? were extracted by using image processing and the relationship between these characteristics and the penetration depth were investigated.
안영남,김철희,이원범,김정한,Ahn, Young-Nam,Kim, Cheolhee,Lee, Wonbeom,Kim, Jeonhan 대한용접접합학회 2013 대한용접·접합학회지 Vol.31 No.6
Gas nitriding is a surface hardening process where nitrogen is introduced into the surface of a ferrous alloy. During fusion welding of nitrided carbon steel, the nitride inside weld metal is dissolved and generates nitrogen gas, which causes porosities - blow holes and pits. In this study, several laser welding processes such as weaving welding, two-pass welding, dual beam welding and laser-arc hybrid welding were investigated to elongate the weld pool to enhance nitrogen gas evacuation. The surface pits were successfully eliminated with elongated weld pool. However blowholes inside the weld metal were effective reduced but not fully disappeared.