welding Aluminum

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I have a lincon mig 140 and have been practicing welding aluminum....well practing might be streaching it...but I have gotten good at throwing aluminum scraps at the wall in my shop.   (starting to get a little expensive) My welds look like a inchworm in a blender and there is splatter everywhere.  Does heating the aluminum help? Any tips would be greatly appreciated.
Reply:One thing that generally helps a bit is knowledge that many other folks also have a pile of aluminum scrap at a nearby wall.If you arent getting good fusion, you probably arent 1) cleaning it good enough, or 2) getting enough heat to the weld.  A 140 amp welder is at the lower end of being capable of welding aluminum well.  This might be overkill, but try first etching the surface of the metal with an acid (I keep some hydroflouric acid around for tough jobs, but I would not start with that, because it is really dangerous, maybe just some aluminum wheel cleaner or air conditioner fin cleaner would be good enough.)  You can rinse with water, but you will need to dry it quickly and brush.  You probably will not need to de-grease after that.  Then use a stainless brush to make the surface bright.  Brush in one direction only.  Turn your welder to its highest setting with an argon flow of about 20 (run a little gas before you start to weld to purge the gun of all air), and run a bead about 2 inches long, pushing, not pulling.  Move pretty quickly once you see the puddle or you will burn through if it's thin.  You dont say how thick your stock is, but...start with the scrap next to the wall, so as not to waste any more money.  Hopefully you have two open inches somewhere.  Once you get 2 inches, go for more, until you a) run out of scrap or, b) run out of money.....Good luck.Last edited by smithboy; 10-16-2005 at 02:02 PM.Smithboy...if it ain't broke, you ain't tryin'.
Reply:I aggre with Smithboy. Unless your work is 1/8" or less I would crank my machine all the way up and adjust the wire speed accordlingy. When it comes to wire speed one tip would be that a hissing sound is a sign of slow wire speed and a weld with a large crown can be a sign of fast wire speed. Try to find something in the middle. A cracklin' sound is about right. What size metal anr you welding and what size wire are you using?