Bronze brazing questioni

[camdigger]

I have a broken iron casting needing repair. The broken piece is long gone. I have bashed up a patch from similar thickness scrap steel. Due to the nature of cast iron and dissimilar metals, I think I need to do a braze repair. Many braze repairs I see have a lot of built up re enforcement over the seam. How much is truly necessary?

I have done a pass down both sides that look OK, but have little crown to the bead (1/16” +)
The materials are both 3/16” thick, and one bead is over 3” long, while the other is 1” long.

[camdigger]

Pic of the parts.

[LKeithR]

If you've got good fusion at the joints you shouldn't need much or any buildup. I've done lots of brazing repairs where I had to grind the weld flush when I was finished. Seldom had any issues but, of course, there are exceptions.

Oxyacetylene brazing is becoming a lost art--don't see much of it anymore. Not nearly as much cast iron repair as there used to be and a lot is done with tig and a rod like everdur or something similar. Forty years ago I probably did at least one brazing job a week but at this moment I can't remember the last time I actually brazed something...

[greywynd]

Originally Posted by LKeithR

If you've got good fusion at the joints you shouldn't need much or any buildup. I've done lots of brazing repairs where I had to grind the weld flush when I was finished. Seldom had any issues but, of course, there are exceptions.

Oxyacetylene brazing is becoming a lost art--don't see much of it anymore. Not nearly as much cast iron repair as there used to be and a lot is done with tig and a rod like everdur or something similar. Forty years ago I probably did at least one brazing job a week but at this moment I can't remember the last time I actually brazed something...

I agree with everything Keith said here. I still braze rusty sheet metal on occasion. As an example a while back, I brazed an exhaust for an excavator that had cracked. Was still solid, it had broken where the pipe joined the body of the muffler. Did that before I came west, and it’s still going now.

Even though it’s a rare thing to do, I always try to have some brazing rod around, just because sometimes it’s hard to do things any other way.


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[Norm W]

I picked up some brazing rod that a fellow was throwing away because the flux had come off of it. I didn't tell him that 20 Mule Team Borax is some of the best flux you could use.

[digr]

Originally Posted by Norm W

I picked up some brazing rod that a fellow was throwing away because the flux had come off of it. I didn't tell him that 20 Mule Team Borax is some of the best flux you could use.

Good to know

[camdigger]

Originally Posted by Norm W

I picked up some brazing rod that a fellow was throwing away because the flux had come off of it. I didn't tell him that 20 Mule Team Borax is some of the best flux you could use.

I inherited 5 lbs each of 1/8” and 3/32” flux coated rod. The flux coating is still intact even though the rod has to be over 40 years old.

I see several YouTubers use UNcoated rod and a paste flux. Is the paste borax.? Powder mixed with what to make the paste?

How does one use the borax powder to braze? Is the rod preheated and stuck into the borax, or is the area coated with borax before the actual brazing happens?

I understand borax is the best flux for forge welding too. Something about dissolving the oxidized scale….

[Ironman]

Originally Posted by camdigger

I have a broken iron casting needing repair. The broken piece is long gone. I have bashed up a patch from similar thickness scrap steel. Due to the nature of cast iron and dissimilar metals, I think I need to do a braze repair. Many braze repairs I see have a lot of built up re enforcement over the seam. How much is truly necessary?

I have done a pass down both sides that look OK, but have little crown to the bead (1/16” +)
The materials are both 3/16” thick, and one bead is over 3” long, while the other is 1” long.

This sure looks like a ropemaker tool.
Just for your info....you CAN weld cast and mild steel together with NiRod. Done this on an engine block and a tractor transmission that had a piece missing.

[camdigger]

Originally Posted by Ironman

This sure looks like a ropemaker .

Yes. This is an antique “Wonder Rope Maker” approximately 110 years old. I doubt they have been available new in 8 decades or more. Made in Onterrible. Mostly cast iron with very little machining. These are a hit at antique threshing shows and the like as demo units. Because they are cast iron and old,it is unusual to find one that is not broken somewhere. Due to scarcity and popularity, they tend to be pricey at flea markets, etc.

Ni-rod is magic stuff, but it is expensive ( so I’ve heard ) but I do not have any. I have seen it used to weld dissimilar materials before, like high carbon wear edges to mild steel, for example.

However, I had 10# of brazing rod and a torch set here, so easy choice to make. Besides, I have never run Nirod. At least I had done some brazing before, even if it was decades ago.

Getting close to done. Maybe I’ll take a few pictures and start a thread. There have been a few surprises along the way. Some pleasant, some not so.

[LKeithR]

Back in the "good ol' days" Ni-Rod 55 (55% nickel content) was a fairly popular rod. I believe there was also a version with a higher nickel content--95% seems to stick in my mind. Success using both depended a lot on the quality of the cast iron; poor quality cast was very hard to weld. There was also an even lower grade rod called "Type F", we never had much success with it as it was pretty crude.

Over the years a lot of different manufacturers came up with specialty rods for welding cast iron--and other exotic metals. Eutectic, UTP, Muggyweld and Stoody come to mind but I know there were others as well. The problem with most stick rods was that to get them to flow and fuse properly you had to use more heat than you really wanted to put into the base metal. Preheating and post cooling were critical to success.

The biggest problem encountered when joining a dissimilar metal to cast was not the fusion--any higher nickel content rod, including SS, would bond most together. The problem was the rate of expansion and contraction which often differed substantially between cast iron and whatever else you were welding to. With some materials it didn't matter how good your weld was, it was almost impossible to avoid cracking when the differing parent metals cooled...