| The most principal welding method for aluminum alloys is Metal Inert Gas Arc Welding(MIG).MIG welding aluminum alloy can easily produce weld porosity and other defects,which will seriously affect weld quality and reduce the service life of products.The porosity of aluminum alloy MIG welding has been difficult to solve for a long time.This paper adopts MIG welding method to conduct butt welding test of 6mm thick 5083 aluminum alloy and analyzes the generation mechanism of porosity defects in the welding seam and puts forward control measures.The results show that the porosity of the aluminum alloy MIG welding butt test are hydrogen porosities,which are mainly distributed near the weld center and fusion line.The welding process parameters and welding position have a great influence on the weld porosity.In the flat welding position,when the welding pulse current is 200 A,the welding speed is 600mm/min,the welding voltage is 22 V,and the gas flow rate is 15L/min,the porosity of the weld is at the lowest rate of 2.1%;when welding direct current is 190 A,welding voltage is 22 V,welding speed is 600mm/min and protection of gas flow is 15L/min,the porosity of welding seam is 1.2%.The porosity of flat welding and vertical welding is much lower than that of horizontal welding and pitching.When the pulse current is used to weld,the droplet transition is a single drop of the droplet transition,the arc combustion,the droplet transition is more stable,can obtain the lower weld porosity;When the shielding gas flow makes the arc cover the whole molten pool and the welding arc shape is the umbrella shape,it can obtain the small weld porosity.When using a direct current welding,melting transition way to shoot drops transition,voltage raise as much as possible within the range can be adjusted,increase arc height which covers the whole welding molten pool,arc morphology of bell shape,lower weld porosity can be obtained.When the droplet transition is subjet transition,the droplet size is too large,and the droplet formation time is easy to absorb hydrogen,and the transition of the droplet is unstable and prone to bursting,leading to the increase of porosity of the weld.When the droplet transition is the transition of jet flow,the droplet size is small,the surface area of the droplet is larger than the surface area,the melting drop is heavier,and the porosity of the weld is increased.Molten pool temperature time is too long or too short leads to weld porosity increases,should strictly control the welding heat input: using pulse current welding,the welding heat input control in the 2.83 KJ/cm,at this time of high temperature molten pool is beneficial to the air bubbles to escape the gaseous impurities can also control the external invasion,weld porosity is lower;With direct current welding,the welding thermal input is controlled at 4.2KJ/cm ~ 4.4KJ/cm.At this time,the high temperature melting pool is conducive to the external escape of the bubble and can control the invasion of external impurity gas,and the porosity of the welding seam is low.The control measures for the porosity defects of aluminum alloy MIG welding are: the surface and groove of the test plate are strictly cleaned before welding.The wire is removed from the drying cabinet.Try to weld in a dry environment;The protection air flow should be around 15L/min.When welding 5083 aluminum alloy,the lower magnesium content of ER5183 welding wire can be used;Using the mixture of helium gas as the protection gas,50% helium +50% argon can effectively control the generation of welding porosities.Before welding,reasonably plan the welding sequence,avoid welding in horizontal welding and pitching position,and welding as far as possible in flat welding and vertical position;Selecting reasonable welding parameters can effectively control the porosity of the weld. |
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