Abstract: The plasma radiation spectrum and the shape of arc are collected by using the spectrometer and the high speed camera in the process of two-pulse laser-arc hybrid welding. The plasma electron temperature and electron density are calculated based on Boltzmann plotting method and Stark broadening method, and the electron temperature and electron density at different pulse durations and different frequencies of pulse arc are investigated. Based on the spectral analysis and the high speed image, the plasma physical properties of laser-arc two-pulse hybrid welding are studied. The results show that the arc shrinks and the brightness increases with the increase in laser pulse duration, the electron temperature decreases and the electron density increases with the increase in laser pulse duration, the penetration depth increases, the intensity of spectrum increases and the nitrogen content in the weld decreases; the arc volume becomes larger than before, the brightness increases with the increase in pulse arc frequency, the electron temperature decreases, the electron density decreases, the penetration depth decreases, and the characteristics of the arc welding at the upper part of the weld zone are obviously enhanced. Key

Key words: manufaturingtechnologyandequipment, highnitrogensteel, laser-archybridwelding, electrontemperature, electrondensity, penetrationdepth