Thin Cast Iron Repair

Try TIG brazing with the Silicon bronze rod. No flux is needed.
Pure nickle is better for cast iron, but bronze can work.
You still need to clean the joint out .

As a bit of an aside, I watched a welder at work repair a cast pump housing using preheat and then using nickel wirefeed (mig) in the cleaned out joint. The welding involved running an inch of weld here and an inch there until the area was filled....kept it from getting too hot in one place. Then some post heat and packed it with insulation to allow it to cool slowly over a few hours. No cracks and it ground out smoooth.
Thought it was interesting and wanted to share it here.
Sean

Splint it with a patch of sheet and bolt or rivet it. Do a job that looks obvious, but neat.
Cast iron is a pain to weld. Large flat sheets especially so, and cast iron that gets heated in service afterwards is even worse. Doing repairs on stoves is one of the worst cases for beginner CI repairs - they're like exhaust mainfolds, but without the thickness to work with.

I may be able to get some nickel rod in time. What's the advantage of nickel? Does it weld better? Anything to help insure sucess is worth pursuing. But, the bronze will be strong enough given the delicate nature of the rest of it.
If I get nickel, do I just weld as usual? I assume argon will work?

Nickle is stronger and has less weld contraction.
Grind out the crack so you have clean edges on both sides, but leave enough of the joint for alignment purposes. Warm the whole piece gently until a drop of oil smokes (around 500-600 degF). Lay in the nickle with a little heat as possible. You don't want to melt the base metal, just get it hot enough for the nickle to stick to it. Do short stitches, working from both ends of the crack to break up the heat. On a delicate piece like this don't worry about peening the stitches as you go. Once welded, pack it in some form of insulation so it cools slowly.

Thanks, I wish I could get away with it! The stove is owned by the historical society and a friend broke it. I need it to look good. I'm going to have to 'v' and weld from the back side.
Fortunately, it's the legs so I have some strength needs, but not a heat cycling issue.
Ed

If I may pick your brain some more, why do you advise TIG over brazing? The foot pedal heat control is one thing that comes to mind, perhaps the nickel has less contraction than the low-fuming bronze?
Also, is it obvious when the nickel is sticking effectively? I'm imagining that at the correct heat the nickel will loose its surface tension and wet the cast iron surface?
Is multi-pass welding risky? It would be nice to build it up a bit.
Thanks,
Ed

TIG puts less overall heat into the piece than brazing so you have a smaller heat affected zone (HAZ). You have much better control and no flux is used so clean up is quicker.
Exactly.
Once you have the parts joined you can do multipass, just don't get in to much of a hurry. Try to keep the whole piece from getting too hot in one spot.
Heat isn't the enemy, it is a heat differential that is the enemy of cast iron, and cast aluminum and cast bronze for that matter. Preheating and slow cooling help keep the heat evenly dispersed over the whole piece.

If they're not going to light it, I'd go with epoxy - seriously.

Okay, I got a line on some nickel TIG filler. (Only one place had it around here.)
I've got a Maxstar 200 (thank Earnie for the help on that selection). Should I use pulse? I'm guessing I should set the amp range at about 110 max (using a pedal)?
My concern with multi-pass and stitch welding too is that I'll be creating little hot zones here and there that then get re-visited for another blast. Is this concern unfounded?
I'm thinking about sandblasting, then heating the parts and my steel shot box in the oven to 500 slowly, then taking the pieces out to the shop in ceramic fiber insulation, warming up a bit more with a rosebud or big bertha, then welding, maybe adding a little heat away from the welded area, then cuddling up in the ceramic fiber again.
If all goes well to that point, what are the chances it's good and not about to crack like glass?

I also have a bunch and I am willing to sell small quantities.
The pulser is perfect for this as it reduces overall heat input
Once the whole part is hot it is less of a problem.
Easier to just heat them with the rosebud, in place, until a drop of oil smokes. Moving them around a lot can be a pain.
I welded up an aluminum intake manifold last year for a friend and that was big enough that I preheated it in the oven and then wrapped it in a welding blanket . It had no trouble staying hot enough during the whole weld repair.
SInce I have no idea exactly what kind of cast iron it is, I can't say. Older castings are usually better made and less likely to crack.

How do you decide the pulse rate and other pulse settings? The Miller manual doesn't give guidance other than defining the terms and that rate affects bead apperance; and percentage at peak and peak amperage affects penetration.
The Miller tech. I talked to knew virtually nothing about it other than that pulse functionality was driven by stainless welding.
I have played with the settings, starting with what you once posted your machine was set at. I found settings that made the bead smooth for decorative welding (about 350 pps, don't remember the other settings and my welder is 40 miles away at the moment). I would guess that with cast, to minimize heat I'd want less than 50% at peak, maybe 20%, and rate would be as required to make the bead sit well?
Do you think I'll have an issue with curling if I just 'v' the back and leave the front untouched? It would look the best, and I could get near 100% penetration...

One of my biggest gripes with the welding manufactures is this very lack of pulser guidelines.
Basic settings to start with: 50% background amperage 50% Percentage ON time 1.2 pulses per second
Tack weld a strong back across the back of the piece to prevent the curling.

Ernie Leimkuhler wrote in message > One of my biggest gripes with the welding manufactures is this very Maybe we should beat it out here! Wow, 1.2 pps. Why does the Maxstar go to 500!?
For weld *appearance* with mild steel I settled in on
80% background amperage 37% Percentage ON time 350 pulses per second
It works but maybe I'm out in left field.
What's the reasoning behind your recommendations? Especially confusing to me is, what is affected if it's 1 pps or 500 when the average (at 50% on time) heat input is the same?

Higher pulse rates, above 4 pps are not used the same way. A really high pulse rate has the affect of super liquifying the weld puddle, which makes for very smooth beads.
It is mostly used with autogenous welds, as in no filler added. It works really well on stainless steel.

Thanks for all the help, Ernie.
I ended up doing it this way:
1). 'v' grooving the cracks except at the ends 2). I pre-heated the smaller broken off pieces then placed a glob of nickel bead at each end where the crack was left alone, then let them cool in air. 3). I took the risk of placing a glob of bead at the crack ends on the main pieces without pre-heat when I realized I'd be better off with a glob on each half of the crack. I thought I'd probably get away with it since I wasn't restraining anything from cooling contraction. I let them cool in air 4). I fitted the pieces back together and hand held them aligned as I fused the corresponding globs of nickel. The pieces remained aligned perfectly after cooling in air. 4). I pre-heated the re-assembled pieces then ran a bead along the v groove. The nickel laid in nicely. Some minimal dripping through the crack occured where I got a little aggressive. I didn't stitch weld it since it was only about 3" long anyway. No problem with curling (after seeing the tack welds didn't budge I didn't expect a contraction issue). 5). I ground off the globs at the ends of the crack and vee'd the bease metal, then welded it. 6). I re-heated the entire assembly until I just started to see some red in a dark room, then laid it between two 1 1/2" thick sheets of ceramic fiber insulation blankets. 7). In the morning I ground them with a stone, then sandblasted to get some texture blending. When it left the shop the color match was perfect.
I'm no fan of welding cast but this was actually fun (barring the fear and stress). Compaired to brazing this was way better with the nickel's strong tendancy not to run and the awesome control with the foot amptrol. Compaired to stick welding it's like the difference between sex and torture. Thanks again, Ernie, for the good advice.
A couple last questions:
Could I have used a carbide burr to grind the welds? I know some cast rods are hard as can be, I didn't want to risk trashing a burr.
Have you had experience with the color match in say, a clear coated part? On the other hand, I wonder if in a rusting situation the nickel would stand-out?
Ed
pre-heating the two smaller broken-off pieces and
Ed

How do you balance peak amperage versus on-time and background amps? It seems like an endless spectrum of possibilites when you think about upping the peak amperage and lowering the on-time and/or the background amperage, and vice-versa, etc.

You start with basic concepts and work from there.
The thinner the metal, the more of a Spike pulse you want.
I have yet to find a great use for a soft pulse, but I will get there eventually.
Try variations of pulser settings on different materials.
The profusiononline.com online pulse calculators will allow you to select an average amperage for the pulsing parameters.
There is so little guidance on pulsers in the welding industry that it is bordering on criminal.

Happy to help
If you used pure nickle filler, then a carbide burr will work fine, just watch out for the tiny metal slivers.
The only way to get a true color match would be to gas weld it with cast iron filler rod. A very involved process.