Welding Cast Aluminum?

[Russell]

Hey guys!

I need to weld my NV4500's bellhousing up. It has a crack running from where the external slave cylinder's upper bolt goes through the bell on the passenger side, and all along up the side to just behind the top right bolt on the passenger side

I was still able to use the clutch on the truck right up until I removed it, so I only really need to stitch it back together. The material is pretty thin the whole way up, less than 1/4" thick.

I have a 110V MIG welder at my place, equipped with a 75% Argon and 25% CO2 shielding gas mixture. I was told that I can just buy a spool of aluminum feed wire and weld the cast iron bellhousing without heating up first, or worrying about the metal around the weld cracking.

Is that true, or is there more to welding cast aluminum? Seeing as the whole bellhousing is covered in grease, is there going to be concerns of a poor weld due to the now impregnated oil?

Any other suggestions?

Thanks!

 

[tRustyK5]

You're screwed.

A) The bell will keep cracking worse and worse the more you weld on it. Cast aluminum is very rigid and does not like the large doses of localized heat.

B) Cast aluminum is porous, and you can count on the oil and grease fouling the weld.

C) you don't have near enough machine to even attempt welding that...

I have welded cast aluminum and had some success, but never on such a rigid shape like that bell.

Rene

 

[Chevy911]

Unfortunatly there is more to it than just stitching it together, cast aluminum itself has impurities in it, and the oil will have soaked in to the casting as well. I repaired a SM465 bellhousing at the slave cylinder, using a miller tig, and had to weld it probably 4 times due to the impurities, even after I cleaned it with degreaser, lacquer thinner, and heating it to sweat the oil out. I had to do a pass then grind out all the impurities, then weld again, until I could do a good pass. In the end it worked great, the bellhousing is still in my truck almost 2 years later.

It might be possible with the mig, but I think that amount of aluminum would be too much for it. Aluminum conducts heat much faster than steel, its hard to get it up to melting temp, most of the heat you put in gets wicked away by the metal, you might end up doing cold welds that don't penetrate the aluminum, and will fail later on. I'm not 100% sure since its variable within the amp range, but I think I was about 160 - 190 amps when I was welding the slave cylinder mount. Thats more than your mig will put out, and I could stay in one spot and heat until the metal would melt, then add filler, you don't have that option with the mig. I would reccomend that you clean the heck out of it and bring it to a competent welding shop, they will have the equipment to do it well. I can't imagine it being too costly either, if you bring them a clean bellhousing out of the vehicle, and maybe a 12 pack!

Let me know how you make out, oh, and have a few pilsner's while you work too! ever since I moved back to Ontario I've been missing those pilsner's that can only be had out west, LOL

 

[Russell]

I also have a big arc welder as well, and I'm fairly good at welding with it as well. My big concern is burning through the bellhousing rather than building it back up. I'm a pretty aggressive welder and tend to burn through thinner metal like this. I figured that the mig would be a bit better for doing a smaller precision weld like this...

I also have a stove I can put the bellhousing into to heat it up to around 350F before I weld on it

 

[Stomis]

Clearly not true after reading this but I thought you could only TIG aluminum

 

[Russell]

I've been told that non-cast aluminum welds just like steel, but you run through rods / wire about 10x faster than with mild steel.

 

[surpip]

I've hear of mig and tig alum. but never arc

 

[misterfnygy]

ive never done it with aluminum but what about brazing?? Works well on cast iron and steel. SHould be plenty strong for the bellhousing....