ADJUSTABLE RING MODE (ARM) FIBER LASER IN WELDING OF 304 STAINLESS STEEL SHEETS IN PARTIALLY PENETRATED LAP JOINT CONFIGURATIONS: Macro 901

摘要

An experimental investigation was presented in this paper on partially penetrated laser keyhole welding process of AISI 304 stainless steel sheets in lap joint configuration by means of ARM laser. ARM (Adjustable Ring Mode) is a new generation of fiber laser source that consists of two concentric laser beams with the capability of dynamically adjusting power distribution across inner circle and outer ring beams. The power distribution can go from only ring with a top-hat distribution profile to only circle with a Gaussian like profile. The influence of synergy in laser powers of center and ring mode on mechanical strength, microstructure, geometrical sizes, visual appearance, and internal soundness of welded joints were studied. The proper optimization in power distribution of inner core and outer ring could adjust the weld width and depth of penetration. This modification has increased the maximum load of welded joint by about 125%. The keyhole and molten pool dynamics observations under different arrangements of laser powers have depicted the influential role of ring laser beam. The leading and trailing edges of the outer ring beam acted as the source for preheating and post-heating, adjusting the temperature distribution, stabilizing the flow of molten material, and helping the center laser beam to quickly generate the keyhole and maintain the stable processing conditions. These combinations can be considered as the best fit to have a stable process for joining of highly reflective materials such as stainless steel. From a microstructural point of view, it was observed that ARM welded joints experienced a lower cooling rates of the molten material that influenced the microstructure morphology of the welded joints.