Speaker
Description
Numerical simulations developed to understand high temperature industrial processes, such as welding, need to be fed with thermophysical properties of the matter over temperature and with input parameters such as the absorbed part of the laser power, which is usually used as heating source. Literature mentions values of emissivity, which can be approached as the absorptivity through Kirchhoff’s law for given wavelength and direction, but for the wavelength of 645 nm. Therefore, this presentation deals with the development of a three-colour pyrometer dedicated to the measurement of the normal spectral absorptivity of liquid metal at the wavelength of the heating laser (1 070 nm), which can differ from one laser to the other. The absorptivity is a key parameter when a sample is heated by a laser. Among the three wavelengths (λ1, λ2 and λ3), the central one λ2 corresponds to the one of the laser. Signals from wavelengths λ1 and λ3 are used to evaluate the temperature through calibration with a blackbody, and signal from λ2 allows to get the normal spectral absorptivity during experiment with an aerodynamically levitated liquid sample. Methodology is presented for iron, zirconium, and nickel, materials currently used in high temperature industrial processes.
