| The purpose of the study is because the equivalent power can be used to decide the effectiveness of laser power on penetration depth during laser-arc hybrid welding.When laser combined with an arc with less than the equivalent power,the penetration depth would be controlled by laser and as that with an arc with higher than the equivalent power the arc might take the lead on penetration.In this paper,three kinds of base metal with different thermal parameters,aluminum alloy,mild steel and austenite stainless steel, were bead-on-plate welded with 2 kW cw Nd:YAG autogenous laser welding process and pulsed gas metal arc welding(P-GMAW) process. The power needed for P-GMAW to have a same penetration depth as that of 2 kW Nd:YAG laser weld at a same welding speed was tested. The P-GMAW power which achieved a same penetration depth of 2 kW Nd:YAG laser weld was defined as the equivalent power of P-GMA to 2 kW Nd:YAG laser power at that welding speed and when it was divided by the laser power,the quotient was then defined as the equivalent ratio. The equivalent powers of P-GMA for the three materials were determined by experiments.The main factors which influence the equivalent power were analyzed by numerical simulation methods.The tested results showed that,for mild steel and stainless steel,the variation tendency of equivalent power was similar,which increased with the increase of welding speed.For mild steel,with the increase of welding speed from 0.5m/min to 1.75m/min,the equivalent power increased from 9.8 kW to 12.8 kW,equivalent ratio increased from 4.9 to 6.4.For stainless steel,with the increase of welding speed from 0.6m/min to 1.6m/min,equivalent power increased from 8.45 kW to 13.47 kW,and the equivalent ratio increased from 4.2 to 6.7.However, for aluminum alloy,equivalent power and equivalent ratio decreased with the increase of welding speed.While welding speed increased from 0.6m/min to 1.6m/min,the equivalent power decreased from 4.2 kW to 3.7 kW,and the equivalent ratio decreased from 2.1 to 1.85.Analysis revealed that the laser absorption rate,thermal efficiency of arc and the thermal physics parameters of the material were the main factors influencing the variations of equivalent power and equivalent ratio of the three metals.The P-GMAW temperature field and weld formation were numerically simulated by using double ellipsoid body distribution heat source mode,the numerical simulation results showed that welding thermal efficiency changed with welding speed.And the variations were different for different base metals.For Aluminum alloy,the welding thermal efficiency increased with welding speed,but for carbon steel and stainless steel,it is decreased.According to the weld formation of laser deep penetration welding, the cylinder-exponentially decreasing distribution mode of laser heat source was founded.The simulation results of 2 kW Nd:YAG laser welding temperature field showed that laser absorption rate as a part of welding thermal efficiency was one of the important factors for laser weld depth and it varies little with welding speed.The calculated equivalent P-GMA power to 2 kW Nd:YAG laser power indicates that the welding thermal efficiency decides the variation of equivalent power and ratio with welding speed.Thermophysical parameters were also important factors,which had the influence not only on the weld shapes but also on the magnitudes of equivalent power of different materials.The difference on the thermal efficiency of arc with the change of welding speed was indeed a function of thermophysical parameters of different materials. |
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