restore project gone wrong cast alu weld failure

[vk6zgo]

its loaded with impurities from casting like casting sand, and porosity, possibly oils too.

It will probobly change size when you melt it. Soldering kinda works with the right flux. Brazing Al is crap and super highly dependent on which rods you have.

you can watch TIG welding CAST aluminum videos on youtube to see why its hard/impossible.

a high quality casting you can possibly weld, like a high end engine block. Some POS like a chinese low cost lawn mower takes a grand master.

You need tig, you need the right cleaning setting, you need the intuition and the bare minimum quality of casting to make this possible.

Like, you need to weld dirty, bare minimum cleaning, because the cleaning function upsets it too much (but its still necessary).

Circa 1953, my Uncle got his 1930s Bedford truck engine block brazed.
It lasted another couple of decades.

They did stuff like that back in the day---for another example, rebuilding crank journals on uncommon brands of crankshafts with a surface as good as original.

PS: Sorry, I just "locked in on engine blocks" not realising that we were still referring to aluminium.------ mea culpa!

As to epoxy, a workmate once used the type commonly used at that time to seal joints of massive multicore trunk cables to repair the cracked block on his side valve Morris Oxford.
It outlasted his ownership of the car.

On the other hand, some of the epoxy bought over the counter is pretty much useless.

[coppercone2]

watch Al braze videos on youtube. They compare rods. Some are shit and some are good. Some rods only meant to make a fat bump on top of a severely damaged aluminum radiator tube.

I highly recommend soldering it with the viscous yellow flux and solder. my luck with brazing it is totally fail.

also get a wooden brush with steel bristles, not plastic, so it does not melt if you try to scrub it while keeping it hot and stuff. seriously at your own risk.

I said this before, when you practice brazing, after you braze, file it down a bit, then pick at it with a strong steel pick. You will see sometimes you have something that looks great but if you jab into it and yank on it, chunks come out.

but if its a 1950's engine casting, its probobly good. people actually thought aluminum was amazing and engines were amazing back then so they used to get it right, now its ubiquitous and low cost IMO. I imagine someone actually did everything right and put effort in it because they thought it was some jetsons space age shit

There was a aluminum bit on top of the washington monument because it used to be the worlds most expensive metal. It was like putting a big diamond on the pyramids back then lol


also the braze is really brittle so I don't recommend it for handles. If anything, I would get some thick shim stock and try to just make a big aluminum solder lap joint under the thing to reinforce it after you cosmetically filled in any gaps with stiff braze.

and if aluminum was easy the navy would not have so many problems with their aluminum boats lol

[vk6zgo]

An example of a cast case that was exposed to oil and other solvents during it's entire life.  Then, it's very large.  A heat sink.  Aluminum loves to warp.   

I suspect we are just seeing the effects of a novice.

The all aluminium block in the Leyland P76 was a higher capacity version of the Rover/"GM reject" V8.

It was a nice engine but didn't need a lot of heat to warp----one might even say "at the drop of a hat"!
"Line boring" the main bearings was supposed to be standard procedure.

Nobody told me, & being used to cast iron blocks, I was amazed when my newly machined crankshaft wouldn't fit.

[JJ_023]

I wouldn't consider brazing a process that is brittle, you can make some very strong and ductile joints with that process.  That's too generic of a statement.  What are you specifically brazing?  What filler material are you using?  Is there preheated and post-heat involved?  What brazing rod are you using?  What is the process for brazing?  Oxyacetylene is completely different than tig.

[coppercone2]

aluminum braze is brittle as hell the rods snap like spaghetti

[JJ_023]

Depending on how the casting responds the 1st pass you might not even add any rod.  Just bring things up to a surface as well as import heat to warm the casting.  Then use a carbide burr to cut the top .02" out.  Then go at it with filler wire, repeating that cycle as much as necessary to get a sound weldment.  If it's oil soaked or really dirty sand filled casting it could take a few tries.

[MarkT]

It almost exploded when we tried to welded it together,

Not cast magnesium alloy by any chance?  Or an Al/Mg alloy?

[beanflying]

Mixed in here with this link is a rebuild I did on a HP 740B that arrived with a very broken front handle / side casting. https://www.eevblog.com/forum/testgear/hewlett-packard-740b-dc-standard-digital-voltmeter-(and-740a)/msg1419955/#msg1419955

There was some oddball Aluminiums used in the 50's and 60's one example was the https://en.wikipedia.org/wiki/Birmabright used in making Land Rovers. Apparently you could use some of it to fusion weld itself if needed but I never needed to on my Series 3 when I had it.

[JJ_023]

It almost exploded when we tried to welded it together,

Not cast magnesium alloy by any chance?  Or an Al/Mg alloy?

You could take a few shavings and test it with vinegar.  You should get a reaction if it is magnesium based alloy.

[coppercone2]

I don't mean cleaning the weld like preweld I mean the settings for in-weld cleaning might need to be set lower

but whatever its just something I saw someone on youtube say. I think the little demonstration showed that very high weld cleaning setting (natually what you would want for a dirty casting) caused a problem, but a low setting actually worked nicely, but obviously the weld area was prepped normally.

[langwadt]

I don't mean cleaning the weld like preweld I mean the settings for in-weld cleaning might need to be set lower

but whatever its just something I saw someone on youtube say. I think the little demonstration showed that very high weld cleaning setting (natually what you would want for a dirty casting) caused a problem, but a low setting actually worked nicely, but obviously the weld area was prepped normally.

https://youtu.be/OWG1f5e7HEU?si=MHbNZTgzKazKYzkY&t=197

[coppercone2]

lol @ comments
"I was a field service engineer for GM. At one of our training sessions the guys from the plant informed us that they were adding iron powder to the aluminum used in casting transmission case halves, because aluminum has an affinity to the ferrous based molds, which was transferring material to the molds, which caused a lot of work to clean them more often than they would like, eventually ruining the molds, at a cost of over $650k per half. Adding the iron powder to the molten aluminum made the issue much less of a problem. When I earned this the light went on and then I realized why I was having so much trouble welding these castings, just like you are in this demo. Knowing this also made me understand why some of the castings I was seeing were very smooth, and others were not, and that;s because of the aluminum skin being pulled off and attaching to the molds. That's mt story and I'm sticking to it."

[p.larner]

ive always found no matter what most ali is a pig to weld,used to use oxy accetalyne back in the 1970's,think its nearly up to welding temp next thng its a molten blob on the workshop floor!.I find tig better.

[TimNJ]

I have used aluminum filled epoxy to fix cast aluminum and cast zinc/Zamak parts.

Smooth On MetalSet A4 is what I’ve used.

[cncjerry]

I doubt that is aluminium. It could be a weird alloy and that was why the aluminium filler didn't stick.  Probabky would have had better result with a torch and low temp  metal filler. Why not just use Bondo or JB weld epoxy?  For all the strength that corner needs, that's all it would take to make it perfect after sanding.

I had a friend bring over what looked like an aluminum belt buckle. I asked a few times if he was sure, I scraped it down, looked at it with a binocular scope, etc.  Hit it with a torch with a very fine ruby orifice, and the buckle did a witch of the west.  I could have used TIG but I was worried about the material.  It was pot metal,  so  I cnc milled a small mold, placed the buckle in it and stirred the pieces together with a hot soldering iron. 

Jerry