gas in aluminum casting

[ryank]

Hello all im having trouble clearing up this problem ive been welding voids in these aluminum castings and im getting ring of gas around where ive welded the material is .150 im running helium argon mix im cleaning casting with acetone. welder is set up like always i just dont get it unless theres some forgein material in casting id apeciate any in put on this thanks ryan

[TexAg]

I'm not sure I can exactly picture what you've described. But, it kind of sounds like you have described the discoloration from the heat affected zone. There are chemical tools to help clean that and reduce the coloration. It may also be helpful to slowly preheat your casting to get it up to temp prior to welding..(i've never welded al castings so that really is just a guess).

Do you have a pic of the weld with the ring you could post?

[wldrman]

A lot of times, if the casting was heated up at all, the pores open up and allow dirt,grease or whatever to be obsorbed into the metal. Some aluminum castings are just dirty right out of the box. Did you v out the voids before welding? If not, do so. Then take a clean ssteel brush and clean out as much dirt as you can. I like to use isopropyl alcohol for cleaning, but acetone will work fine. Definitly pre-heat, sometimes the contamination will burn out of the void and you will need to re-clean.

Hope this helps.

[garth]

Hi are you tiging or miging it either way you should be using straight argon for aluminum done lots of cast al. and have not had that prob. maybe Im just lucky if you prehaet for a little bit it should leach out any junk left in the pours then clean with the acitone. good luck let us know how it goes.

[ryank]

Just got in and got all your replies im using tig welding and i am pre heating and cleaning but im using argon at 10 cfm and heliem at 35 cfm with gas lense on my torch iwill try to describe this hole better for you all. Its like taking a shot gun and blowing a whole in in 3/16 aluminum. im thinking theres something in the casting causing this gas because im not getting this problem any where else on the casting just where the whole is. if running just argon what cfm would be best. thanks ryan