welding cast aluminium ?

[maddmatt]

i have welded two quad swingarms ,they were both cast aluminium and i had one **** of a time , another guy has the same type of swingarm and he want me to weld it. i tig welded the first two but i'm considering stick welding it (i never stick welded aluminium) the metal is poris and very contaminated!! i put the arc on it and try to get a puddle formed and as soon as the puddle starts it disipates (melts away) it is like when you don't clean the oxide off , the aluminium just melts away. my question is "what should i do?" i'm not new to welding but i deffiniately don't know as much as alot of you guys on this site.

any thoughts on this would be great!!
Thanks,
Matt

[Jerry]

Hello Maddmatt, I understand your problems with this, I too have trouble at times. When I weld on a cast aluminum part I like to first clean it as good as I can, be it with acetone, wire wheel whatever, I hear that some folks even boil the castings in water or ?. One thing I've found is to use 4043 on castings and 5356 for structural aluminum. Have gas coverage down to say 10-15, too much will cause problems when welding. Pre heat casting say 200 or so to help with welding and pulling out of moisture. Keep tungsten clean and clean aluminum when contaminates come out during welding.

Good luck

Here's a couple sites to search on. You'll find good info here.

http://www.alcotec.com/attsaw.htm

http://www.lincolnelectric.com/knowledge/articles/content/tigalum.asp

[chip hayden]

another consideration is that many cycle parts are sand cast and not die cast. this makes them lighter but larger grained internally. many will butter pass and needle hammer to fill in the voids in the first few passes. then it usually finishes up nicely on the last pass and cap. also check to make sure it's aluminum and not magnesium with lemon juice. mag will turn black almost instantly. you can also carve mag with a penknife.

[maddmatt]

thanks for the imput guys