Weld or Braze

DaveK OR · Mar 27, 2017

Even a crappy-looking brazing job can be stronger than the part you are fixing. As long as you get good flow through the joint, it should be quite strong enough. The cast iron part is far more likely to fail at a crack (perhaps invisible) near the joint than at the brazed joint itself. People put down brazing as an inferior repair method, but it's still a very strong way to join metal parts, and can be done with just a torch, under field conditions. If done properly, the brazing metal flows across the entire joint, to give you a very strong connection. When you weld a thick piece like that, you probably won't get full penetration unless you are very, very good.

If you do go with brazing as the repair method, you might consider using a silver-based brazing alloy (sometimes called hard-solder). You can get it to flow at lower temperatures than some of the bronze alloys, and it is available in very thin sheets or flat ribbon. You can pre-flux the joint, position pieces of the brazing alloy directly in the joint, and then if you can hold it in position while you heat, you won't have to wick the brazing alloy into the joint. It's a tricky thing, but can result in a joint easily stronger than the metal. Silver-based brazing alloy is expensive, but you really don't need very much.

Shield Arc · Mar 27, 2017

I ordered these Silicon Bronze Tig rod a while back. I was shocked how easy they are to run.

3/32" Silicon Bronze Tig 36" Rod - 1 Lb - AWS A5.7 ERCuSi-A | eBay

yomax4 · Mar 27, 2017

Bunch of different ways to fix this of course. I'm going to have to go with Cast Stick. Couple tacks and then take a die grinder and a carbide burr and eat a bunch of cast to get it beveled a little. Then do what the rod manufacturer suggests. I also like Nickel Free rod for problem cast but you may be ok with just basic 55-95%. keep it cool and multipass. If you did want to try to braze it, i would still tack with something and bevel a bit to get the filler in there a ways. I have some Harris Welco 14FC series Nickel Bronze flux coated rods that I would use for this If I was to braze it. You can braze overhead with this stuff and It has a good tensile strength. Would you be doing the repair yourself?

DaveK OR · Mar 31, 2017

I ran across a link to this stuff, which could do for your repair... The tensile strength isn't as high as a good brazing job, but for your needs it should work. even if it's down around 10,000 psi, you have enough joint area that it should hold under any load you might apply. A stronger brazed joint would be a bit better, but then you probably need to pull the assembly apart for the repair. The heat required for brazing might well be enough that you could damage nearby seals and gasketed joints. This stuff flows at around 400F, and you can fill the joint with the paste, clamp it together, then just heat it gently with a propane torch.

There is other stuff like this with different properties, and you might find one that has a bit more strength without having to heat it too much for the nearby seals and gaskets.

tjflicek · Apr 7, 2017

Shield Arc said:
I ordered these Silicon Bronze Tig rod a while back. I was shocked how easy they are to run.
3/32" Silicon Bronze Tig 36" Rod - 1 Lb - AWS A5.7 ERCuSi-A | eBay

On November 9, 2012 you replied to my 1st post on this forum. I tried to suggest the attributes of Silicon Bronze TIG rod at that time, thought you might have tried it before now.

Arc weld · Apr 8, 2017

A problem with brazing might be the heat involved for proper fusion (for lack of a better term). It might burn seals in the diff.

muddstopper · Apr 8, 2017

Is that where the 3pt hitch arms mount. If so, lots of stress in that area. I did something similar several years ago. Broke both ears off the housing. They way I fixed it has worked for several years now so I will just pass it on. I did remove the diff housing, you just cant get the proper access with it still on the tractor. I bought some nickle99 stick rods and tack welded the ears back on the housing. I then did as was already suggested and ground the pieces down to a fine point, both sides. I would weld a bead on one side, then flip the piece and weld a bead on the other side. I continued to do this until I have the big Vee filled flush. It was tedious work, and I had to stop and hit the weld with a grinder every so often to knockout bird dropping welds and keep everything in proper shape, using some sort of weld backer would have helped a lot to prevent some of the dripping welds, but I didnt know that technique back then. When finished, a little sanding and some paint and you cant tell it was ever broke.

RedNeckGeek · Apr 8, 2017

Just the fact that it broke through such heavy sections shows that the part takes a lot of load. And whatever repair is used needs to be as strong or stronger than the original part or it's just going to break again. You can try a braze, which with the right alloy can be stronger than the original part, but you're going to have to be careful not to cook nearby seals or joint compound. Those heavy sections are going to need to get to near red heat, and you must NOT use water or any kind of forced cooling or you'll end up with a brittle part that will break the first time you shock load it. Nickel rod will work if you decide to weld it, but you'll need to make a full penetration weld by grinding a V on each side of the joint. I'd come in from each side, making a double V, put the root pass in one side then grind the other until I hit weld metal, then weld out from there. Same cautions apply with not force cooling the weld as brazing, so either way you stand a good chance of cooking nearby seals and joint compound. If cooking is gonna be a problem, you might just try the mechanical repair first and see if it holds. If it breaks again, you're going to have to disassemble to weld or braze, and at that point replacing the part with a new one might look pretty good.

Whatever you decide, post a couple shots so we can all see how it turned out, OK?

OH10 · Apr 11, 2017

I want to follow up on this thread since the young man came out with his Thermal Arc 3 in one machine and did a very nice job on my broken casting. Here are some pictures. He told me he used both stick and wire.