Abstract:

To study the application of vibratory process on laser welding, the industrial pure iron is selected in this research. Different laser welding parameters and vibratory frequency parameters are carried out to optimize the welding joint forming and to improve the welding quality. The cross-section morphology, microstructure and microhardness of the welding joint are studied by optical microscope, scanning electron microscope and microhardness tester respectively. The results indicate that the depth of fusion is increased by vibration. The grains in weld metal are dramatically refined at a higher vibration frequency. On the other hand, vibration acceleration can be used as an alternative parameter for vibratory amplitude. Under the condition that the applied vibration frequency is close to the inherent vibration frequency of the material, the grain refining effect is not obvious when the vibration acceleration becomes higher. The average value of welding joint microhardness is decreased from 273.3 HV without vibration to 244.6 HV with the parameters of 3 000 W the laser power, -10 mm the defocusing amount, 1.2m/min the welding speed, 118Hz the vibration frequency and 36.1 m/s²the vibration acceleration. At the same time, the conspicuous grain refinement can be observed.

Key words: laser welding, microhardness, microstructure, mechanical vibration