Welding cast iron

[darryl]

Ok- I will be asking the guy if he knows what he's doing. Discreetly of course-

[eKretz]

I don't get that "Brazing does not require near the preheat that proper welding does..".
I mean, you have to heat the metal red to get the braze (bronze) to stick,
so not sure what you mean about less heat.

-D

On a small part maybe not much difference, the whole part heats up either way. On a large one the entire part must be brought up to preheat temp for welding. You can get away with a quick braze much, much faster as it only locally stresses the iron over a small area and doesn't put as much local heat in. And not sure what you don't understand about the difference in heat from brazing and welding - there is a very big difference between brazing heat (just into the red heat zone) and the temperature it takes to melt iron.

[Doozer]

You mention brazing heat.... At work I have been experimenting on using silver solder.
Stuff is pretty expensive. I only have to get the iron BARELY RED to get the solver solder
to wet out and flow. I really like that. Only thing, it seems eutectic and lacks a transition zone
like the aluminum bronze braze filler that I am used to. But for tight fit ups and small stuff
I will be trying silver solder again.

--Doozer

[macona]

My dad has always welded cast with Lincoln 91K2H dual shield wire, a lot of wires will work but the thing is between passes you need to peen the weld, either a hammer or a needle scaler. We welded up the covers for my 10ee with that and he has welded all sorts of other stuff for people and never a break.

[nc5a]

As Doc says Muggy weld rod works fairly well. Per Doc's recommendation I bought some for a repair I needed to do. I bought 14 sticks based on the total length of the weld repair 66" that I needed to do, 33" inside and 33" outside. I found as did Doc that porosity is an issue. so grinding and welding out the porosity and re-welding is the name of the game. After welding, grinding, welding grinding etc 66" of cracks I had 1 rod left. Another note, Muggy weld rod is very expensive, I think I paid right at $1 per rod plus shipping.

[Doc Nickel]

Doc, are those parts subject to any significant stress, or more just cosmetic-ish?

-That round boss right above the "back side" crack, is one of the two the collet closer yoke pivots on. There's significant force on that when you close a collet.

Another note, Muggy weld rod is very expensive, I think I paid right at $1 per rod plus shipping.

-Unfortunately, you mean $10 per rod. Yeah, it's expensive, but compared to a certain amount of oxygen and acetylene, some brass or bronze rod (you priced silicon bronze recently: ) and the hassle of all the pre-and-post-heat processes, it's a frickin' bargain.

Back when I stuck the Springfield levers back together, I'd have it veed out, welded and be grinding it smooth before a conventional technique would have had it hot enough to braze.

Doc.

[barracudajoe]

One thing nobody seems to mention. The quality of the material used in the casting! I've seen some pretty bad inclusions in cheap castings both Iron & Aluminum that I wouldn't want to try to weld.
When the casting is of good quality it's not too hard of a job to do.

[JRouche]

(you priced silicon bronze recently: )
Doc.

Heck Doc, that stuff has always been expensive.

I got turned on to it from my friend Del. He could TIG weld and O/A gas weld cast iron just like me.

So, he showed me a large cast iron fix that was TIG welded , by him as I watched. He used SB. JR

[BWS]

Silicon bronze,and Tig it. Like all mentioned above,pre and post heat is critical. I weld the part while it sits on a large,electric griddle set wide open.

Gotta really draw out the post welding "cool down". I usually throw a piece of foil type HVAC blanket insulation over the whole shebang and the ramp heat down over several hours.

There's more to it,actually much more but.... I just don't think you're going to "get away with" any methods without the griddle?

[challenger]

So do these methods actually make a puddle or do they all simply make a joint? Is the filler and the casting integrated on a molecular level?

[JoeLee]

Oh brother, this again.
Welding iron is not so much about the filler material.
It is about the pre-heat and post-cool.
Both need to be slow, especially the post-cool.
One reason (not the only reason) that brazing works so well,
is that if you want to pre-heat for welding, you are dragging
out the torch anyways, so you might as well keep using the
torch and braze it or even torch weld it. This is not vodoo.
It is established physics. It is all about the critical-cooling-curve
of the material being welded, whether it will get too hard and crack.
If you don't pre-heat and slow-cool when welding cast iron,
it is not going to work. People are so lazy and try to short cut
everything. Then they wonder why shlt don't work. They have
too large of an ego to possibly think THEY could be the problem.
And life goes on, and history repeats it self.

-Doozer

Yes, a lot of it is that but the results depend on how good the cast iron is. I used to weld a lot of cracked exhaust manifolds for inboard boat motors. Water pumps too. People never properly drained them completely for winter storage and the water would freeze and crack the outer water jacket which wasn't very thick, maybe 3/16" in thickness if that. I tried various methods. Pre-heat was a PIA, time consuming and didn't yield any better results than just going at it with nickel rod and TIG. I found I could pre-heat it with the arc from the TIG torch easier than I could trying to heat it with oxy acet.
Being thin also presented a problem with pre-heat and post cool. Most of these manifolds were such garbage cast that it would disintegrate under the arc. Nickel rod worked the best with TIG. I would just pre-heat with the TIG torch and let it cool. Don't remember anything cracking during or after cooling but pin holes in the crap cast were a big problem.
Then I went to spray weld with Eutectic spray powders. I got much better and cleaner looking results. That was the way to go, wish I had discovered that process sooner.

JL................

[loose nut]

Oh brother, this again.
Welding iron is not so much about the filler material.

Got to argue that. Could be the covid is making me bitchy.

For welding cast the rod or process makes all the difference. Nirod will do the job is slow and more work but cheap. Rods from Exergon or Sodel are much better, easier to weld and don't really need a preheat but will give your poor heart a beating when you see the price. Tig does have some advantages but not everyone has tig gear. If you have a torch then just braze it Cheaper then welding and a good braze job is just as strong as cast iron. You still need to let it cool down slow.

[Doozer]

Got to argue that back.
If you do proper preheat and very slow cool,
you can MIG weld freaking cast iron.
Seriously.

-Doozer

[nickel-city-fab]

Pro welder/fabricator here; I do stuff like that for a living.
There are more than one reason why cast iron welding is "brittle"
One is the sudden temperature changes that Doozer mentions --
When the iron cools, it needs time for the carbon to precipitate out.
Else you'll get a very brittle part.
The carbon in iron carbides all precipitate out on a line that becomes a crack as it cools.
Hence the slow and even pre and post heat, or wrap it in a blanket, or similar.

Another factor is chemistry.
I tell new guys that welding is just high temperature chemistry and physics.
I prefer nickel 99 for a base layer because the nickel won't react with the carbon in the iron.
It's also stretchy like silly putty. The new stuff is the muggyweld.
Haven't tried it yet, but lots of people seem to like it.
You might still need some preheat with these methods, but you can get away with an ordinary propane torch for that.

The third factor to consider is constraint: is the part held rigidly, or allowed to "float"
If parts are held rigidly, then the warm up and cool down becomes critical.
A part that is held solidly can pull itself in half after welding, as it cools. See above regarding carbide precipitation.
If the part is allowed to "float" and move around as it needs to, the job becomes much easier, less danger of cracking.
Peening can help in this regard, I like to peen with a dull air hammer.

Finally, what does the job actually need? I like the TIG brazing for most industrial applications, or Nickel 99 stick rod.
BUT, this person isn't doing big industrial stuff. It probably won't have much load on it if any.
Here is where economy comes into play: I would do this job with oxy-acetylene brass brazing, old style.
Not much preheat or postheat required, no need to constrain the parts, they can "float"
I would probably tie the pieces into position with some baling wire and braze away. Then toss a welding blanket over it to cool off. The clean up the part with a bur in the die grinder.

In a pinch, one can use Stainless TIG on cast iron. Its kinda barnyard hack but it works. Reason why it works is because the chromium in the SS filler gets picked up by the carbon in the iron, and the resulting chromium carbide remains diffused throughout the area. I would still peen it and cool down slow. It's a good way to put now tips on log splitters and mower sections.

[JRouche]

Pro welder/fabricator here; I do stuff like that for a living.
I prefer nickel 99 for a base layer because the nickel won't react with the carbon in the iron..

I have some Ni-rod left over here from a job. Love the stuff. I cant afford it Thats why I still have it from 25 years ago. Waiting for that "special" job. JR

Edit: Id like to say, my preference is to use the ni-rod (or similar) for heavy castings and the sil-bronze for thinner stuff. Sil-bronze with OA is a dream, flows like butter and is very strong. TIG with SB is doable, I have done both several times. The OA is my go to.