레이저 용접 냉연고장력 튜브 제조공정 개발

Optimal processing and system to produce the laser welded tube for hydroforming bumper beam are studied. The calculated size of tube is a thickness of 1 .4㎜ , diameter of 105.4㎜ and length of 2000㎜. The tube is shaped from cool rolled high strength steel sheet(tensile strength: 60kgf/㎟ grade). 3 roll bending process, multi-step continuous roll forming method are studied and compared with 2 roll bending method. Weld quality monitoring and seam tracking along the butt-joint lengthwise to the tube axis are also studied. The longitudinal butt-joint is welded by the CO₂ laser welding system equipped with a seam tracker and plasma sensor. The constructed CO₂ laser tube welding system can be used for the precision seam tracking and the real-time monitoring of weld quality. The obtained laser welded tubes were made an investigation by microscopic examination and simplified hydroforming test. Finally, the laser welded tubes are going to make automobile bumper beam.