Sqz Cast Alum. 356+Weld=Black Eruptions

By colorado Date 09-07-2001 14:26

We're supplying aluminum 356 squeeze castings to a customer who is subsequently TIG welding a 6061 T6 plate to the base. TIG welding technique is gas tungsten arc using a large shield with a cold wire feed. Heat capacity of the weld is being managed closely. Along the weld bead, they experience regions that weld very well, but then in some regions a black deposit or eruption appears along the weld bead. Sometimes the weld can be ground out and reapplied, other times it just gets worse.

Q1: Anyone experienced this and know the composition/origin of the black, sooty eruptions? Is it die lubricants from the squeeze casting process? Possibly magnesium oxide - or something else?

Q2: Any recommended cleaning/prep solutions for aluminum-silicon 300 series castings?

Thanks in advance for the help.

By Lawrence (*****)

Date 09-07-2001 17:12

Welding aluminum and magnesium castings is similar to fishing in the ocean, one never quite knows what one might hook up with. The *eruptions* sound nasty and your guess about oil sounds best. But what can you do with a temperamental casting beside route out the bad metal and try to fillweld?

Once upon a time, back in the days of old when we we were gleefully killing the Ozone. There was a miraculous (yet evil) thing called a *Vapor degreaser* this device would contain <or try to contain> a heated mist of Trichloroethane. The heated vapor would expand the part (expanding the flaws) allowing the magical mist to find its way into every nook and cranny- making pure what was once sullied by grease or oil. Now we have soap and water. Do I sound bitter?

I have heard of folks preheating the part to burn away the oils and stuff prior to welding but that sounds risky and would most likely run you afoul if your work requires the material to be near its original temper designation.

Long live the Green Knight! Slayer of Vapor Degreasers, and Long live the Butterflies the Snaildarters and the Earthfriends!

we will find solutions despite their *help*

Thinking green thoughts
Lar

By Brett B (*)

Date 09-10-2001 14:59

Colorado,

We are currently welding a die cast 360, currently using Alcotec 4145
filler rod. Prior to welding we use a orbital grinder with a 40 grit disc and
clean the are to be welded ( make sure the disc is only being used on the aluminum ), also sandblasting the area is an option.
I have talked to Tony Anderson at Alcotec and they recommend using
Tri-Clean that is made by LPS ( lubricant manufacturer ) to clean the castings before welding, you can get at most industrial supply houses.
Keeping an eye on your amperage is critical,if you put to much heat into
the casting all of the impurities come up out of the castings. We requested the people that do our casting run our parts through a
vibratory cleaning before being sent to us.
By doing the following we have had good sucess in the welds, as a
side note we pressure test the welds since they have to be airtight.

Good luck Brett B