Research progress on measurement methods of thermal properties of welding arc plasma

Measuring parameters of welding arc plasma,such as temperature and particle density,contributes to deeply understanding and studying physical properties of welding arc plasma,which provides basic data for finding new ways to improve welding quality and welding process. Usage principles and working characteristics of several commonly used contact and non-contact methods were reviewed in this paper,such as Langmuir probe method,thermocouple method,optical interference method and spectral analysis method. The principle of spectral theory of welding arc plasma and several methods of spectral measurement were highlighted. The measurement principles,advantages and disadvantages of three methods,namely normal temperature method,relative intensities method of spectral lines（ two-line intensity correlation method and the Boltzmann plot method） and absolute intensities method of spectral lines,for calculating the temperature field of welding arc are described and analyzed,while the three methods had different application conditions and welding environment between each other. These calculation methods help to measure the temperature field distribution of the welding arc plasma,and help to select appropriate plasma measurement methods and calculation methods in the actual research process.