Characteristic Of The Vapor/plasmas Induced During Laser Welding Of Typical Aeronautic Materials

Laser welding technology has been applied in the field of aerospace, ship industry, automotive industry, and pressure vessel manufacture, civilian and medical industry for its prominent merits. Such as the high energy density, low heat-affected zone, low weld deformations, and high welding speed. The absorptivity of laser for metal material can reach to more than 80%, and the welding efficiency rises sharply while in the laser deep penetration welding. Therefore laser deep penetration welding is the ideal welding state. The notable characteristic of it is keyhole and plasmas. Plasmas are the potential root of some weld defects, such as unfused, gas porosity, and change of component, and so on. However, the existence of it provided a method of monitor the welding process. It can be sampled and analyzed by light and special sensor. Important physical characteristic of plasmas can be obtained by analyzing the spectral component which gained by the radiation of the plasmas.Three typical aerial materials were studied in this research. There are 5A90 Al-Li alloy, TA15 titanium alloy, and SUS 304 steel. The vapor/plasmas induced in YAG laser welding, CO₂ laser welding, and YAG-MIG hybrid welding of these materials were researched. The process of laser welding was monitored by a spectrometer to obtain the distribution of typical spectral of vapor/plasma. On this basis, the temperature and electron density values of vapor/plasmas were calculated by the methods of relative intensity and the intensity of obtained typical spectral, and influence of process parameters and laser wavelength on them were discussed.For 5A90 Al-Li alloy, the distribution of the spectral and variety of the temperature and electron density of vapor/plasma induced in YAG laser welding, MIG welding, and YAG-MIG hybrid welding were researched. Results were shown that the distribution of the spectral in YAG laser welding, MIG welding, and YAG-MIG hybrid welding are quite different. The average temperature of vapor/plasma in YAG-MIG hybrid welding of 5A90 is about 6554K, which is near to the values in MIG welding, but 1200K higher than that in YAG laser welding. The average electron density was 2.7X10¹² cm^-3, which is also near to the values in MIG welding. However, the average electron density of vapor/plasma in YAG laser welding is about 3.9X10¹⁴cm^-3.For TA15 titanium alloy, the characteristic of vapor/plasma induced in 1.06 micron YAG laser welding and 10.6 micron CO₂ laser welding were compared. Results show that t the distribution of the spectral in YAG laser welding and CO₂ laser welding are different. The temperature of vapor/plasma in CO₂ laser welding is about 1000K higher than that in YAG laser welding, and the electron density is two orders of magnitude more than that in YAG laser welding.For SUS304 steel, the average temperature of vapor/plasma in YAG laser welding under a certain process parameters is 7436K, the average electron density isl.36X10¹⁶ (cm^-3) ; and the value in CO₂ laser welding is 7870K and 2.94X10¹⁶ (cm^-3) .Results of the study above show that the temperature and electron density of vapor/plasmas are not only associated with the materials being welded, but also be connected with laser wavelength and techniques methods. However, welding parameter has little impact on these when under the same techniques method.The related data of vapor/plasmas in laser welding and hybrid welding of typical aerial materials obtained in this research provided the process research and the technical study of laser welding and hybrid welding with base.