Cast Steel Welding

[Olivero]

Sounds really tedious that way, I welded mine pretty much non stop, only stopping to find the next seam. If you keep heating one part and letting another cool, does that not make it more prone to crack as you now have different expansion-contraction across the piece?

I will need to get a Mordor fire pit though.

[ryanjones2150]

which is exactly what you're doing when you weld continuously, heating one part and letting another cool. The difference in the expansion and contraction and the cooler metal around it contributes to the cracking. So pre and post heat aim to even that out. Peening relieves the stresses caused by the weld puddle solidifying.

[fabricator]

I would weld it to a steel plate and be done with it.

[Meltedmetal]

I would weld it to a steel plate and be done with it.

You then might want to cover the slots in the base, or bolt it to the plate or live with the accumulating chips in the base. And I know for me the first thing that would happen is I'd drop some small part that would bounce right into those slots.---Meltedmetal

[ryanjones2150]

Yup, and it would probably be stainless or aluminum too. Now what....that's the kind of stuff that makes a man resort to profanity. By gosh.

[old jupiter]

Welding cast iron right IS tedious, Olivero, no way around that.

My opinion is that the "best" way to weld the usual sorts of grey cast iron is by gas welding, which is REALLY tedious, requiring a long slow preheat to well over a thousand degrees (exact temp depending on the content of the cast iron, if you can find that out). Do the welding with the casting closely surrounded with (also very hot) firebricks and wrapped in forbidden asbestos cloth, with only the actual weld area uncovered. Use cast iron rod dipped in cast iron flux. Rather than dipping rod in a liquid puddle, you stick cast iron rod into the mushy iron puddle with a sort of jabbing action which tends to displace the oxides and glop up to the top of the puddle. Make a big ugly, kind of crusty-looking build-up because you are going to machine off or rotary file off much of it and get down to good new iron. A very slow operation. After welding, completely wrap the very hot part and the firebricks with the asbestos cloth, This method ends up with the most uniform material in your part. A stress-relieving "normalization" operation might also be called for. I'm glad I haven't had to do this in decades, but it was sort of impressive to do at the time (fixing a couple of racing outboard motor cylinder blocks, . . . none of which have been made of cast iron in a looong time).

Generally I prefer to gas-braze cast iron, if I have to do it at all.

There's also a sort-of-quick method I once used to fix a cracked exhaust manifold (Ford 240 six). You can sometimes get away with stick-welding a broken grey iron casting COLD, using NiRod. Vee out the crack after "stop-drilling" holes at the very ends of the crack. I might, as I usually do with any welding, have given the manifold enough heat to drive off any moisture, but that's all, and when I started welding the part was only warm to the touch. I welded a half-inch long bead and STOPPED, did some peening while it cooled, and waited until I could hold my hand on the first bead, then welded another half inch and repeat process. Tedious for sure, and if you try this technique you must NOT be in any hurry or you'll soon hear the faint little pings of the new cracks.

But that poor manifold, which at the time I welded it was already twelve years old and had probably already lost some of its original properties, still held up without further cracking for another twenty years, which amazed me. When I had to do some engine work (those Ford 240s were TOUGH!!), I took a close look at my old repair. The Ni-Rod bead had contracted over the years, pulling away from the sides of my Veed-out crack, and looked like a length of dirty grey clothesline lying in the middle of the V-groove. Yet it still had adhesion at the bottom of the crack, and was still sealing the manifold from any exhaust leaks and noises. Still amazes me!