ebenton2ph

[ebenton2ph]

Can anyopne give any pointers on welding iron to cast? I have done this using nickel rods and stainless steel rods and bothe worked of but sometimes a slight bump causes the weld to break loose . Actually the welde holds but some of the cast breaks out behind the weld.

[Jose Gomez]

It's called under-bead cracking, and is very common when attempting to weld any kind of cast. Cast metal does not have the ability to strech and absorb the stress generated by the weld as it contracts while cooling, so the only way to try to avoid cracking is to pre-heat the entire part to be welded to 400-450 degrees F, then weld the part with preferably nickel, or stainless rod if nickel is not available. Peen the weld between passes to relieve some of the shrinkage stress, and ensure that the part remains evenly heated during welding. Immediately after welding re-heat the part to 400-450 degrees F and pack it in vermiculite, or do what ever you can to ensure that it cools as slowly as possible.
Another method that is typically sucesfull is to braze the part together using a torch and brass filler rod. If you chose to braze the piece remember that the slow cool is still part of the secret to sucess, and that the repair will be gold color when completed (kind of cool but sticks out like a sore thumb).

[Travis Covington]

Tig it with nickel.
Travis

[Ten Hammers]

My experience. Cheap Ace hardware vise ( 4" jaw, swivel base ) broke in the rear under the "anvil" section ( both sides). Check fit of break. Remove screw. Heat to good red and get rid of paint and any lube on threads. Area on bench previously prepared of course and shop open to rid the fumes. GI can full of oil dry near and ready. I used Forney X1000 rod ( not by choice but because the business had it on hand). It is a stainless rod of some sort. Read instructions on rod and weld according to mfg suggestion ( by now the weldament has cooled somewhat). Pein if you wish to stress relieve. Re-heat and place in GI can ( buried deep and covered in oil dry). Come back tomorrow. This has worked a couple of times for me and above suggestions work as well. Brazing of course is a superior way to repair as well. The rod I spoke of seems to work well for dissimilar metals ( weld extension on a drill bit or mild to a casting). YMMV.

[drone]

Mr. Gomez did a great job describing the way to get a good cast weld. My 2 cents would be adequete pre-heat, peening with a hammer after welding the cast and adequete and slow post-heat. If the old lady isnt home you can do your post heat than let cool down in oven starting at 500'F and taking it down to warm over a few hours. I have also had luck heating a pot full of sand in oven and after welding, peening and post heat burying the cast in the sand for a slow cool. Oh yeah I used nickel rods as well. Good luck and let us know how it turned out.

[Don A]

I just welded a Canedy Otto blower cover, and it seem to be holding.

I first put it in a bed of coals over night (in my burn barrel). This got rid of all the oil and also got rid of a gob of dried J.B. Weld.

I wire brushed both pieces real good.

Then, I put them together and tacked them.

By the way, I was using

Auralloy

rods for the whole job. Not sure of the composition, but they were recommended (and free).

I put the tacked piece on the bench and trenched a U shaped groove along the crack with a Dremel stone.

I put the piece in my forge and gently brought it up to a black heat... you could almost see a red tint around the cracked area.

Then I would weld a little, pien a little. I tried to distribute the weld so that it would spread the stress. I welded it at the edge of my forge, so that when I wasn't welding, I could push it back over the fire.

When I had welded and piened across the whole crack, I moved it from the forge into another waiting bed of coals, then covered it with coals. I put an old metal tank over the whole works, sealed off any air, then left it over night. After 24 hours, it was still very warm to touch.

I did notice a slight bit of warpage around the outlet (very little, mind you). I figure I over-did the initial heat for burning off the oil and J.B. Weld. I know I got it hotter at one point than I should have.

Everything is holding well so far. Beginner's luck, but I'll take it.

Don

[NateDJ]

I had this same question about 4 days ago and stopped in to see an old friend. He is a machinist by trade and is still running his shop at 87 years old. He has been welding cast iron for ''as long as can be remembered'' and basically described the same process as the rest of these guys, he suggested using an air chisel to peen with and not peen just the weld but the sides as well.

For the jobs that you can't control the cool down cycle such as in a large engine he suggest to pre-heat the area around where you will weld and then only weld about 1/2inch and do it on the lowest setting you can strike and hold an arc. This is done so you never raise the temp of the surrounding metal enough to cause it to expand enough to be more than you can peen the welding rod material back into as it shrinks. I understood him to mean that you would lay down a short bead then peen the bead into the shrinking cast iron. He states that the welded area should be at the ~500f you pre-heated the area to before starting on the next 1/2 inch.
His experience is mostly on large industrial engines that cant be buried or otherwise insulated and usually the customer wanted to start and run the thing when he was finished welding it anyway. He states he hasn't had a weld fail doing it this way since he was shown how when he was a teenager, (did they have welders back that far;)

Hmm this reminds me, he just bought a lathe I need to get a picture of on here.

[Hillbillysmith]

Listen to Jose Gomez!!