MONITORING METHOD OF LASER BEAM WELDING FOR DIE-CAST MATERIAL AND DEVICE THEREFOR

摘要

PROBLEM TO BE SOLVED: To accurately detect a welding failure such as porosities inside of a weld metal when a die-cast material is welded by a YAG laser. SOLUTION: This monitoring device for laser beam welding is equipped with a laser beam source 1 for which the YAG laser is used, a condensing lens 6 for condensing laser light from the laser beam source 1 to the die-cast material, a wavelength selection and permeable mirror 4 which allows only the laser light from the laser beam source 1 to permeate and reflects light other than that, a prism 5 which takes out one part of the laser light and irradiates one part or plural parts of a part from start of solidification to the end thereof in backward of a molten pool of the die-cast material with the light, photodetectors 10 and 12 which reflect the light scattered by irradiating the die-cast material with the laser light by means of the wavelength selection and permeable mirror 4 and photoelectrically convert this reflected light, and a fault detecting means which determines the amount of the porosities and size thereof inside of the weld bead of the die-cast material based on an optical signal detected by the optical detectors 10 and 12.