On-line Punchless Detection of Laser Welding Part of Cold-rolling Steel Strip

The punchless welding point detection system using laser diagnostics for continuous strip production line has been developed. At the entrance of the steel strip production line, the preceding and following coils are welded for continuous processing. The welding point detection and tracking of the position is essential for the setup change of various important processing facilities according to the specifications of the coil under processing. Conventionally the hole is punched for on-line detection of the welding point by transmission and detection of light. But the punched hole causes several disadvantages such as decrease of productivity, generation of flaws, breaking of high steel strip. There are mainly three types of welding of coils; flash butt, laser and mesh seam welding. The punchless welding point detection system for laser welding has been developed and tested in real production line. The welding point is detected by measuring the change of reflected light distribution due to welding part and high speed temporal analysis of the measured reflectance signal.