Welding Old Aluminum Castings

By RollieFree Date 05-12-2003 02:57

I have to weld aluminum castings on a regular basis. Specifically old motorcycle engine cases. I am always looking for better ways. The typical trouble is obviously contamination and previous repairs (not to mention junk metal to begin with) as well as some post weld cracking and pinholes at the edge where new meets old.

I am looking for suggestions on precleaning, preheating times and temps, and post weld treatment..or any other advise. Currently I am using a Miller Syncrowave 250, 3/32" tungsten (brown), 4043 rod, pure argon. Preclean with an acid cleaner (Protex) and stainless brush. Preheat to 240 for about an hour, then wrap in a Kevlar blanket while welding. Back in the heat to cool for a few hours.

Also any reference material you can suggest will be appreciated.

Thanks,
RF

By 357max

Date 05-14-2003 01:04

When I have to repair weld castings I boil them in a fifteen gallon army pot. I use a propane brush burner torch for the heat source. Keep boiling and replacing/topping off with fresh water. When no oil continues to rise to the surface it is clean. I then scrub with lacquer thinner, then 50/50 lacquer thinner and acetone. Then finally wiping with acetone. Of course there is filing for groove preparations. Hope this helps.

By jer

Date 05-31-2003 01:25

I too have welded many aluminum castings and have done some cycle cylinders also. I pre-heat to maybe 200-400 and I wire brush. I have used 4043 and 5356 rods and I use pure tungsten.

I seem to find various degrees of contamination in the aluminum. Pre-heating will get any moisture out of casting. I do not wrap an aluminum casting for I feel it is not needed but when I weld cast-iron I'll place back in my oven and bring down slowly.

By brande

Date 06-01-2003 07:06

If you want the repair to last, 5356 or other 5000 alloy is required.
4000 series fillers tend to crack, due to the metallurgical incompatability.
Most common castings are magnesium alloyed. 4000 series fillers are silicon alloyed. The mag-silicide produced in a 5000-4000 weld can easily cause underbead cracking or lack of fusion defects.

Tungsten type, gas flow, etc have nothing to do with this.
Preheat, postheat and the like have little to do with this as well, as long as your machine is big enough for the job. A Syncro 250 should be plemty big for the work you anticipate.

As a cleaning technique, you may consider running your tig torch across the weld area to pre clean, as long as you are on AC current.

Try these suggestions. If you are still having problems, email directly.

Good Luck
brande

By Brett B (*)

Date 06-02-2003 11:29

We weld castings everyday and I would recommend 4145 filler alloy,
if you go to Alcotec website they have recommend filler metal charts for aluminum castings. As a note the filler is pretty spendy but we have had excellent results with it. Also 4008 and 4010 are good choices, we haven't had any cracks or lack of fusion issues or any other problems.

Ask your local welding shop to get you a Alcotec catalogue it is full of information on various aluminum welding alloys and has a breakdown of which alloys alot of your common parts are made out of and helpful information.

Brett B.