GTAW Oily Cast Aluminum

admin

I have a request to know the best way to clean impact damage BMW Motorcycle Crrankcase. The impact has  small spider like cracks that radiate out. So I need to get it very clean to weld. What is the best way to do this ?
Reply:Check out some of the threads by castweld.  He did an oil pan a while back that might be a similar situation to what you've got.
Reply:Clean with  stainless steel brush or wire wheel.Acetone area and remove as much oil and let evaporate. I personnaly would make some small gouges with a radius on the ends not to  crack further. Never leave a sharp sqaured end. Try not to over heat componants. If need be, put some wet rags around the area.Becarefull not to get things too wet not to electrocute yourself.That's my take.
Reply:you will porbably clean with solvent and find it didnt work.. may need heat to get the oil out of thepores..
Reply:I'm with weld bead probably gonna need some heat to get it clean.  Also I buy non flammable brake parts cleaner in the spray cans by the case, and it does a great job to clean up grease and oil.I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:"brake parts cleaner"Is great for the cleaning part but the stuff with chlorine in it hurts like hell when you weld over it. and can kill you
Reply:I like the idea of soaking with acetone, but I would go one step further, and soak with methyl hydrate afterwards, and then gently bring up the temp with a torch; and then do it all over again a second time before gouging, grinding and welding.
Reply:Also I would set your wave bal to 65%
Reply:Dremel tool with carbide tip cutter makes for a precise micro gouging tool.
Reply:Fat Bastard. you are correct on the chlorine aspect.  I should have mentioned that, but the non flammable Brake cleaner that I have been getting is "non chlorinated" as well.  I got the last I bought from the local advanced auto parts.I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Id do all of your grinding first, then quick once over with a wire brush.  Then cook it with a torch until you dont see any more oil coming off the pores.  Then hit it with some kind of solvent and wire brush again, and weld away.Have we all gone mad?
Reply:I would die grind crack completely out, wash with jet vat (hot water and soap)= less fumes when welding. Or use acetone, lacquer thinner mineral spirits, or such- and as said before- stay away from anything with chlorine. Wire brush and rewash. Preheat to about 350 and weld then post heat to 350. Some of these castings were vacuum impregnated with plastic resin to seal them. If your casting was really porus when casted and sealed with resin you will see black crud bubling up in the puddle. Keep puddle going and use filler rod to "flick" out crud or keep puddle going untill crud burns off. If here is a lot of resin or trapped oil you may have to grind weld and start over. Have fun!Peter
Reply:Great tips castweld. ty
Reply:Originally Posted by maartyGreat tips castweld. ty
Reply:Castweld said it best! Good piece of info.Thanks!
Reply:I always have good luck with a handle held sandblaster. When ever i am going to do a motorcycle part or crank case, i will use a sandblaster. An old trick a welding instructor showed me.
Reply:I know this sounds weird, but once the excess oil is cleaned off, contaminate your tungsten.   For whatever reason, its easier to weld dirty aluminum with a dirty tungsten.   This has worked for repairing  some very badly cracked Flathead Ford heads (Edelbrock Block Lettered), Harley Heads,  and some dirty aluminum vaporizers on LOX trailers.   Even after washing the dirty aluminum in an etching acid and scrubbed with a new stainless wire brush, it would spatter and refuse to puddle.  Give it to much heat and it'll just drip away.   The dirty tungsten has allowed me to save a few parts that otherwise would have been junk.    Not saying this is for critical structural welds but they have all held up 100% over the years.   JMHO.
Reply:IMore Info..http://weldingweb.com/vbb/showthread.php...ighlight=honda...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by castweldKeep puddle going and use filler rod to "flick" out crud or keep puddle going untill crud burns off. If here is a lot of resin or trapped oil you may have to grind weld and start over. Have fun!Peter
Reply:You could try baking it at a suitable temperature / time to drive of hydrocarbons. It's probably Al-Si or Al-Mg-Si type commonly used for die cast products.Heating to about 350°C for a few hours may drive off oils, etc without sacrificing mechanical properties.Even after this treatment you may still have a porosity problem, however removing porosity and rewelding will improve the repair as stated by others. This is critical, as even a tiny full thickness pore will result in oil leakage.Good luck, would like to know how you went with this one.