Application of near infrared pyrometry for continuous Nd:YAG laser welding of stainless steel

The bi-dimensional monochromatic (0.860 mm wavelength, 2:5 2:5 mm2 vision zone, 40 ms acquisition time) and the 1- spot multiwavelengths (in the spectral range 1.3±1.573 mm, 800 mm vision zone, 6 ms acquisition time) pyrometers are applied for surface temperature monitoring in Nd:YAG continuous laser welding. The experiments are performed for stainless steel plates applying variation of: laser power (600±2700 W), welding speed (3±10 m/min), shielding gas ¯ow rate, presence of surface pollution, with ®xed or variable gap and misalignment between the similar and dissimilar plates, etc. The variation of brightness temperature versus modi®cation of operational parameters is found, certain typical welding defects can be detected. # 2000 Elsevier Science B.V. All rights reserved