x-ray aluminum

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i'm going to be taking a welding test this week, that nobody seems to be able to pass due to porosity......mig welding aluminum .... i've done some research on the cause of porosity... i don't think they are storing their wire or base material properly....is there anything you can do if they've just left the wire on the machine for who knows how long? or if they don't have acetone to clean material with?any other tips would greatly appreciated.....i'm not the most experienced with aluminum...but i've been reading everything i can find.....i think with the proper knowledge i have a better chance of passing
Reply:take acetone with you.Dynasty 200DXPassport plus w/ spoolmate 100victor 315c oxy/(act and prop)Miller digital elitemilwaukee power tools
Reply:will do....i should probably take a new wire brush to?
Reply:good move take what is needed (except for material and filler)will look like you know what needs to be done as far as prepidealarc 250/250 ac-dc tigidealarc 250/250 ac-dc tig #2 used for sticklincoln sp100hh125dual arbor grinder polisher30 yrs of hand tools52 pitch blocks 6p-26prake gauge -pitch gaugeG&D prop repair 918-207-6938Hulbert,okla 74441
Reply:As far as the wire, take a sheet of green scotchbrite and one of those spring loaded paperclips.    tear off a corner of scotchbrite and fold it over twice and clamp it over the wire when it enters the drive rolls.take your own new stainless wire brush, and brush the hell out of the area then wipe with acetone till the brand new rag comes out spotless.If they are using spool guns with 2lb spools then take your own sealed fresh spool.Vantage 500's LN-25's, VI-400's, cobramatics, Miller migs, synch 350 LX, Powcon inverters, XMT's, 250 Ton Acurrpress 12' brake, 1/4" 10' Atlantic shear,Koikie plasma table W/ esab plasmas. marvel & hyd-mech saws, pirrana & metal muncher punches.
Reply:what does the test consist of?plate ,pipe??thickness.....G
Reply:i dont know what the test consists of......i just know that everyone is failing because of porosity.....the job is welding aluminum pipe
Reply:this is what iv'e got so far....clean with stainless brush and acetone.....and use a short arc length and push angle....should i use a lower heat or run hotter?
Reply:blooddonor,aluminum MIG porosity comes from lots of causes but they all have one thing in common.The puddle is freezing before the gas bubbles are allowed to float up and wash off with the hot argon.If you're welding pipe with MIG there is a real problem smaller than 6" as the speed of MIG and the rate of change of angle is so high that without some extreme prep and preheat I doubt anyone can pass that test?If the fit is open root then there will have to be purge just like SS or the root gap will allow atmosphere into the root and you can't avoid porosity.If the wire is stored cool the oxide will hold humidity and you'd have to work in a pure spray mode to keep the puddle fluid enough for long enough to allow the gas bubbles to float up.  If you're in 6061 T6 pipe then a spray transfer will give a very weak break bend- this is kind of a rock and hard place for quality.I'd put desiccate packets in the wire cabinet and tape it shut for at least 24hours, put up a wiper on the feed rolls as has been noted above,  warm the wire feed cabinet as long as possible. If the power supply has a pulse or pulse with pulse that can allow a near globular transfer to reduce the spray introduction of more gas contaminates and allow the surface oxides and hydrogen to 'gas out', while the puddle is molten instead of trapping.I'd preheat the pipe coupons just to 'hot to the touch' and then use the SS tooth brush to clear and 'groove the oxide' and help the oxide give up its moisture before welding.  I'd make sure the inner pipe ID was cleaned like the beveled weld groove so the inner wall's retained moisture was dried and scrubbed with the SS tooth brush.Of course, the first step after all handling is to wipe with acetone and not use bare hands (oil) and make sure you do the bevel with a carbide tool or finer sander >120 girt not a hard wheel that can leave grit and binder in on the metal surface in the V groove.Those are some of the things normally done to reduce MIG porosity.cheers,Kevin Morin