Welding Tips and Tricks

Hey y’all. Looking for some advice On tig brazing a differential out of a highway tractor that’s seen salt and all the crud on the road.
First we purchased this truck from Ritchie bros and it was from fort Mac/ oil sands area and from the look of the undercarriage it was on the salt roads not ice roads.
It looks like a previous person has rewelded an airline hanger bracket on the backside of the top of the pumpkin. And it’s spewing gear oil out of a pin hole I believe. I can confirm tomorrow when I cut the hanger out of the way and needle scale off the rust off the back.
First off . Aluminum bronze or silicone bronze ?
I’m a farmer with minimal experience but do have a few cast pieces laying around to practice on.
I’ve got a everlast 210 ext tig welder I was going to use looking for advice on settings
Should I set it just like I were welding aluminum? Thanks
Jonny

Is there a specific reason you want to TIG braze vs welding?
In my very limited experience with cast AL, I found it helpful to preheat the joint with just the TIG torch and then be cautious about not putting too much heat into the part during welding. The preheat helps cook out impurities and gives an idea of what to expect as far as how the arc is going to behave. If the part gets too hot, then it all just goes to hell and falls apart. Of course clean and prep the best you can, but those two pieces seemed to be the most useful to get right.

For settings, I use typical aluminum settings but go pretty gentle on the foot pedal, so probably running a little colder. I have used 4043 as filler. I haven't had good results turning up the cleaning action too high, I stay around 70 on the AC balance.

Take all of this with a grain of salt... this was just from trial and error on practice parts until I was able to make somewhat reliable welds. Hopefully someone with some real knowledge can weigh in, for both our sakes.

Braze it if the condition is as poor as you describe. And I'd use Silicon Bronze if the material is exposed to that harsh environment.

COwelder - brazing introduces less heat than welding, and can be more tolerant of imperfect conditions/materials. For something like this repair, the weld would be demonstrably stronger than the parent material and probably create cracks outside the weld (I'm trying to imagine the repair from the description and my own Heavy Equipment repair trials...). And it sounds like its a small, "plug a hole" weld, not a structural repair.

Welding cast iron isn't an easy operation. You should use high percentage nickel rods, preheat, postheath, you can also weld cold (with special rods), and you should really understand the stress in the weld zone that is caused by welding cast iron. Often times hammering the weld is required.
The other alternative is brazing. Silicon bronze is slightly easier to use compared to aluminum bronze. Aluminum bronze brazes better on AC (-90 +10). Silicon bronze requires DC.
Before you start brazing use some scrap casting to get feel about the "sweet spot" before the base metal liquifies and the bronze flows.
Best regards

CJ7373- I was under the (incorrect?) impression that brazing was less tolerant to contamination, due to the lower heat input but I have never TIG brazed and don't know much about it. I thought that "preheating" along the joint with the TIG torch was allowing me to cook out impurities and then clean the surface to allow better fusion during welding. Seemed like that was what was happening but I could definitely be wrong about that.

As far as just patching a pinhole on a diff, I would bet that it would be quite easy to do with several methods.

Are we talking about cast AL or cast iron? I was under the impression he was asking about aluminum. I have never found cast iron to be as fickle as people say, Aluminum is a different story. Not that I advocate it, but I made several successful cast iron repairs with straight up 7018 before I had any clue about proper procedures. These were things such as bearing housings that would see similar service conditions as a diff.

COwelder wrote:CJ7373- I was under the (incorrect?) impression that brazing was less tolerant to contamination, due to the lower heat input but I have never TIG brazed and don't know much about it. I thought that "preheating" along the joint with the TIG torch was allowing me to cook out impurities and then clean the surface to allow better fusion during welding. Seemed like that was what was happening but I could definitely be wrong about that.

As far as just patching a pinhole on a diff, I would bet that it would be quite easy to do with several methods.

Are we talking about cast AL or cast iron? I was under the impression he was asking about aluminum. I have never found cast iron to be as fickle as people say, Aluminum is a different story. Not that I advocate it, but I made several successful cast iron repairs with straight up 7018 before I had any clue about proper procedures. These were things such as bearing housings that would see similar service conditions as a diff.

I seriously doubt that silicon or aluminum bronze brazing will work on any aluminum.
In the past when I was very young and had no idea about different metal alloys, I welded leak-proof stainless steel exhaust pipe with 6013. I also welded stainless pipe with er70 MIG/MAG (100% CO2). Those welds were ugly, but they still hold on to this day. At that time I wasn't aware what I'm doing, and now I'm wondering how do they still hold?
My point is, you can weld cast iron with 7018, but that's not the smartest thing to do. Differentials are under heavy vibrations, temperature changes, and rolling a dice on these things is not very clever.

Get some ER4943 brilliant for welding cast alloy.

Johnny, what make truck? Is it a tandem? Some of the trucks had inherent problems with differential problems. I"ve seen sand pits in castings that didn't show up til years later. More info will help make the repairs from OUR end.
gramps