Another Cast Aluminum Question

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Is there some secrete in preparing cast aluminum to be tig welded on?  For some reason when i get projects every now and then of cast aluminum i seem to have a hard time with welding it.  I try to clean the area to be welded as best i can and sometimes run my torch over the area on clean setting to bring up any impurities and still have a hard time making good penetration in producing a smooth weld.  I just dont really get it.  Ive sometimes even grind down the area to be welded smooth and still have a hard time welding. I have even tried to torch the part to be welded to warm it up and still have a hard time. Is there a certain temperature to be obtained in preheating cast aluminum? Also what are you guys using to clean the aluminum/ prepping it to be welding?  Im asking because...... well guess what i have another project that requires me welding on cast Al.  The rods I have been using are 4043.  I cant remember if i used a different type or not, but that is what i have now for cast Al.Thanks,Brent
Reply:Pics would help.  So would knowing what exactly you are welding.  Not all cast is created equal.  Some of it welds fairly easily, some of it just isn't even worth messing with.My name's not Jim....
Reply:dont have any pics now, but the cast i am welding on is for a intercooler endtank and a cast aluminum intercooler tubing.  Its all brand new parts, so i wouldnt have to worry about cleaning any type of oil or grime on both the outside and inside of the parts.
Reply:Cast aluminum parts are made using a few different processes.  Sand castings will have silicon sand residue and residue from the binders used in the sand molds embedded into the surface.  These castings can also have sand imbedded in them, if the pouring isn't done properly.  The molten aluminum can also have a variety of contaminants in it, depending on the quality control a the casting plant.  Some cast aluminum alloys are simply difficult to weld because the alloying ingredients used in some alloys segregate like oil and water when they melt and refreeze.  All of these factors will make a cast aluminum part more difficult or impossible to weld.  If the casting plant has bad quality control you can even find parts where some are easy to weld and some are impossible.  Worn, used, dirty parts just add to the problems.Aluminum parts can also be cast into metal molds; either gravity fed or by injecting the molten aluminum under pressure.  Generally speaking, these castings have cleaner surfaces, and if made with welding-compatible alloys, should be easier to weld.  Surface finish on as-cast areas are cleaner/smoother than sand castings, so you can usually tell the difference.  Castings made in metal molds will still have mold-release agents on the surface.  You need to clean the surface of even brand new parts with a wire brush and solvent to guarantee that you have clean metal to weld. Originally Posted by disepyondont have any pics now, but the cast i am welding on is for a intercooler endtank and a cast aluminum intercooler tubing.  Its all brand new parts, so i wouldnt have to worry about cleaning any type of oil or grime on both the outside and inside of the parts.
Reply:Originally Posted by disepyondont have any pics now, but the cast i am welding on is for a intercooler endtank and a cast aluminum intercooler tubing.  Its all brand new parts, so i wouldnt have to worry about cleaning any type of oil or grime on both the outside and inside of the parts.
Reply:I know i have to prep the metal even if its brand new, i meant that i dont have to spend alot more time cleaning it for say if it was dirty with dirt/grime.  Sorry i should have been more informative. thanks for the informative information A_DAB_Will_Do.  Makes me feel a bit better that its not entirely me on why i have so much frustration welding on cast.Im using a Precision TIG 225the end tanks are not polished. here is a link to what they look like. http://www.precisionturbo.net/ART/quartet-b.jpg